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Etazolate, an α-secretase activator, reduces neuroinflammation and offers persistent neuroprotection following traumatic brain injury in mice
... The usefulness of such models is also to test the pharmacological compounds with potential therapeutic activity on cerebellar injury and myelin protection/repair. To validate our model, we used etazolate, a pyrazolopyridine derivative, shown to be an α-secretase activator with neuroprotective and remyelinating effects in vitro and in vivo (Llufriu-Dabén et al., 2018;Marcade et al., 2008;Siopi et al., 2013). In previous studies, Marcade and collaborators have shown that etazolate, at low micromolar ranges, is able to protect neurons against Aβ neurotoxicity by enhancing the release of a soluble neuroprotective protein, sAPPα (Marcade et al., 2008), through α-secretase cleavage of amyloid precursor protein (APP) (Nalivaeva and Turner, 2013). ...
... In previous studies, Marcade and collaborators have shown that etazolate, at low micromolar ranges, is able to protect neurons against Aβ neurotoxicity by enhancing the release of a soluble neuroprotective protein, sAPPα (Marcade et al., 2008), through α-secretase cleavage of amyloid precursor protein (APP) (Nalivaeva and Turner, 2013). Our group has also shown that etazolate promotes neuroprotection and improves histological and functional outcomes in a model of closed-head injury in vivo (Siopi et al., 2013). Recently, we have also shown that etazolate is protective of myelin sheaths and exerts remyelinating effects after chemical-induced demyelination ex vivo and in vivo (Llufriu-Dabén et al., 2018). ...
... In fact, besides neurons and oligodendrocytes, other cell types in the cerebellum could be also affected after traumatic injury. Overall, our present data including our previous reports provide evidence that etazolate is beneficial in cerebral lesions in vivo (Llufriu-Dabén et al., 2018;Siopi et al., 2013) and ex vivo (Llufriu-Dabén et al., 2018), suggesting that the same pathways underlying the lesion might be involved in these models. In fact, our previous study showed for the first time the neuroprotective effect of etazolate, as an α-secretase activator, in a weight-drop model of TBI in mice (Siopi et al., 2013). ...
Background:
Traumatic brain injury (TBI) induces significant cognitive deficits correlated with white matter injury (WMI), involving both axonal and myelin damage. Several models of TBI ex vivo are available to mimic focal impact on brain tissue. However, none of them addressed the study of trauma-induced myelin damage.
New method:
The aim of this study was to set up a novel ex vivo weight-drop model on organotypic cultures obtained from mouse cerebellum, a highly myelinated structure, in order to study the temporal evolution of cerebellar lesion and demyelination. The extent of injury was measured by propidium iodide (PI) fluorescence and demyelination was evaluated by loss of GFP-fluorescence in cerebellar slices from PLP-eGFP mice.
Results:
Live imaging of slices showed an increase of PI-fluorescence and a significant loss of GFP-fluorescence at 6 h, 24 h and 72 h post-injury. At the impact site, we observed a loss of Purkinje cells and myelin sheaths with a marked loss of myelin protein MBP at 72 h following injury. Etazolate, a known protective compound, was able to reduce both the PI-fluorescence increase and the loss of GFP-fluorescence, emphasizing its protective effect on myelin loss.
Comparison with existing methods and conclusions:
In line with the existing models of focal injury, we characterized trauma-induced cerebellar lesion with an increase of PI fluorescence by live imaging. Our findings describe a novel tool to study trauma-induced myelin damage in cerebellar slices and to test biomolecules of therapeutic interest for myelin protection.
... In our previous report, we have shown that enhancing the release of the endogenous soluble protein sAPPα, has a therapeutic potential resulting in histological and functional improvements following TBI in mice (Siopi et al., 2013). sAPPα is released by α-secretase processing of β amyloid precursor protein (βAPP) and is known to be neurotrophic and neuroprotective (Chasseigneaux et al., 2011;Hefter and Draguhn, 2017;Mockett et al., 2017). ...
... Therefore, the purpose of this study was to investigate the protective and remyelination potential of a pharmacological strategy able to promote sAPPα release following demyelination. Etazolate, a pyrazolopyridine derivative, is known to enhance the α-secretase processing of βAPP to sAPPα and also promotes neuroprotection from Aβ peptide neurotoxicity in vitro (Marcade et al., 2008) and post-TBI complications in vivo (Siopi et al., 2013). Nevertheless, the therapeutic potential of etazolate in myelin sheath protection and remyelination remains unknown. ...
... Our work highlights the role of α-secretases in etazolate-induced sAPPα release and myelin repair. In addition, etazolate presents a good tolerability and safety profile in humans (Vellas et al., 2011) and exerts other benefits such as anti-inflammatory (Guo et al., 2014;Siopi et al., 2013), pro-cognitive (Drott et al., 2010), antidepressant and anxiolytic (Ankur et al., 2013;Jindal et al., 2012) activities in animal models. Our work provides an additional evidence that etazolate-induced sAPPα release protects myelinated axons from demyelination and enhances remyelination, highlighting the therapeutic potential of strategies to enhance sAPPα release in demyelinating disorders. ...
Remyelination is an endogenous regenerative process of myelin repair in the central nervous system (CNS) with limited efficacy in demyelinating disorders. As strategies enhancing endogenous remyelination become a therapeutic challenge, we have focused our study on α-secretase-induced sAPPα release, a soluble endogenous protein with neuroprotective and neurotrophic properties. However, the role of sAPPα in remyelination is not known. Therefore, we investigated the remyelination potential of α-secretase-induced sAPPα release following CNS demyelination in mice. Acute demyelination was induced by feeding mice with cuprizone (CPZ) for 5weeks. To test the protective effect and the remyelination potential of etazolate, we designed two treatment protocols. Etazolate was administrated either during the last two weeks or at the end of the CPZ intoxication. In both protocols, etazolate restored the number of myelinated axons in corpus callosum with a corresponding increase in the amount of MBP, one of the major myelin proteins in the brain. We also performed ex vivo studies to decipher etazolate's mechanism of action in a lysolecithin-induced demyelination model using organotypic culture of cerebellar slices. Etazolate treatment was able to i) enhance the release of sAPPα in the culture media of demyelinated slices, ii) protect myelinated axons from demyelination, iii) increase the number of mature oligodendrocytes, iv) promote the reappearance of the paired Caspr(+) adjacent to the nodes of Ranvier and v) increase the percentage of myelinated axons with short internodes, an indicator of remyelination. Etazolate failed to promote all the aforementioned effects in the presence of GI254023X, an α-secretase inhibitor. Moreover, the protective effects of etazolate in demyelinated slices were mimicked by sAPPα treatment in a dose-dependent manner. In conclusion, etazolate-induced sAPPα release protects myelinated axons from demyelination while also promoting remyelination. This work, thus, highlights the therapeutic potential of strategies that enhance sAPPα release in demyelinating disorders.
... Approximately 85-89% of TBI patients show nonopen trauma injuries caused by traffic accidents (Masson et al. 2001;Wu et al. 2008), so, closed-head trauma animal models provide useful tools of clinical relevance to mimic and investigate the majority of TBI cases in humans. In the present study, we have used the weight-drop method which is a direct, nonpenetrating, impact acceleration model (Cernak 2005) that causes a controlled closed-head trauma (Hellal et al. 2003;Homsi et al. 2009Homsi et al. , 2010Siopi et al. 2011;Siopi, Calabria, et al. 2012;Siopi, Llufriu-Dabén, et al. 2012;Siopi et al. 2013). The weigh-drop method is one of the most frequently used rodent models of head injury (Cernak 2005). ...
... Closed-head trauma was induced by a 50-g weight dropped from a 36-cm height along a stainless steel rod, on the right frontal side of the head. This experimental paradigm creates DAI in the corpus callosum and a limited contra-coup lesion in the right hemisphere (orbitofrontal cortex and perirhinal cortex), accompanied with functional deficits and a 5-15% mortality rate within the first 5 min following the impact (Homsi et al. 2009(Homsi et al. , 2010Siopi et al. 2013). Initially, we used a total of 60 animals and 49 of them sustained TBI. ...
... The functional outcome was assessed by a person that was blind to the experimental groups. A cumulative score was designed based on a previous study (Flierl et al. 2009) and was performed at the peak of acute neurological impairment 24 h post-TBI (Girgis et al. 2013;Siopi et al. 2013). Five phenotypical cues (5 points) were evaluated, as well as the capacity of the animal to exit a circular arena within 2 min (3 points), adding up to a total score of 8 points (Girgis et al. 2013;Siopi et al. 2013). ...
Traumatic brain injury (TBI) and its consequences represent one of the leading causes of death in young adults. This lesion
mediates glial activation and the release of harmful molecules and causes brain edema, axonal injury, and functional impairment.
Since glial activation plays a key role in the development of this damage, it seems that controlling it could be beneficial
and could lead to neuroprotective effects. Recent studies show that minocycline suppresses microglial activation, reduces
the lesion volume, and decreases TBI-induced locomotor hyperactivity up to 3 months. The endocannabinoid system (ECS) plays
an important role in reparative mechanisms and inflammation under pathological situations by controlling some mechanisms that
are shared with minocycline pathways. We hypothesized that the ECS could be involved in the neuroprotective effects of minocycline.
To address this hypothesis, we used a murine TBI model in combination with selective CB1 and CB2 receptor antagonists (AM251
and AM630, respectively). The results provided the first evidence for the involvement of ECS in the neuroprotective action
of minocycline on brain edema, neurological impairment, diffuse axonal injury, and microglial activation, since all these
effects were prevented by the CB1 and CB2 receptor antagonists.
... These include antiviral [1], antibacterial [2], antimalarial [3], antitrypanosomal [4], anti-inflammatory [5], anti-hypertension and pulmonary hypertension [6,7] and anti-tumour activity with various mechanisms of action [8][9][10][11][12][13][14]. Interestingly, some structurally related pyrazolo [3,4-b]pyridines were reported to exhibit neuroprotective, antidepressant, anxiolytic and anti-Alzheimer's properties [15][16][17][18]. ...
Three novel pyrazolo[3,4-b]pyridines were synthesized via the cyclization of 5-amino-1-phenylpyrazole with the corresponding unsaturated ketone in the catalytic presence of ZrCl4. The ketones were afforded by modifying a stabilized ylide facilitated Wittig reaction in fairly high yields. The novel compounds exhibited exciting photophysical properties with the dimethylamine phenyl-bearing pyrazolopyridine showing exceptionally large Stoke’s shifts. Finally, both the dimethylamino- and the pyrene-substituted compounds demonstrated high and selective binding to amyloid plaques of Alzheimer’s disease (AD) patient brain slices upon fluorescent confocal microscopy observation. These results reveal the potential application of pyrazolo[3,4-b]pyridines in the development of AD amyloid plaque probes of various modalities for AD diagnosis.
... Etazolate is a pyrazolopyridine-derived compound that exhibits a wide range of pharmacological properties Megat et al., 2021;Siopi et al., 2013). Etazolate enhances GABAergic signaling through positive allosteric modifications of GABA(A) receptors, which could explain its anxiolytic activity (Marcade et al., 2008;Thompson et al., 2002). ...
... Rights reserved. exhibit a relief in AD symptoms [59,63]. Acitretin also enhances the α-secretase secretion and is thought to help in the non-amyloidogenic APP pathway [64]. ...
Alzheimer’s disease (AD) is a neurodegenerative old age disease that is complex, multifactorial, unalterable, and progressive in nature. The currently approved therapy includes cholinesterase inhibitors, NMDA-receptor antagonists and their combination therapy provides only temporary symptomatic relief. Sincere efforts have been made by the researchers globally to identify new targets, discover, and develop novel therapeutic agents for the treatment of AD. This brief review article is intended to cover the recent advances in drug development and emerging therapeutic agents for AD acting at different targets. The article is compiled using various scientific online databases and by referring to clinicaltrials.gov and ALZFORUM (alzforum.org) websites. The upcoming therapies act on one or more targets including amyloids (secretases, Aβ42 production, amyloid deposition, and immunotherapy), tau proteins (tau phosphorylation/aggregation and immunotherapy) and neuroinflammation in addition to other miscellaneous targets. Despite the tremendous improvement in our understanding of the underlying pathophysiology of AD, only aducanumab was approved by FDA for the treatment of AD in 18 years i.e., since 2003. Hence, it is concluded that novel therapeutic strategies are required to discover and develop therapeutic agents to fight against the century old AD.
Graphic Abstract
... W październiku 2020 r. miały się zakończyć badania fazy I/II dapagliflozyny, która reprezentuje najnowszą klasę leków przeciwcukrzycowych -inhibitorów kotransportera 2 glukozy zależnego od jonów sodowych (SGLT2, sodium-glucose co-transporter 2). Dapagliflozyna poza inhibicją SGLT2, zmniejsza insulinooporność i hamuje acetylocholinoesterazę [56]. ...
Streszczenie
Choroba Alzheimera (AD, Alzheimer’s disease) opisywana jako przewlekłe i nieodwracalne schorzenie neurodegeneracyjne pozostaje najczęstszą przyczyną demencji. Ze względu na obserwowane od dłuższego czasu zjawisko starzenia się populacji, nieuleczalność AD stała się narastającym problem medycyny XXI w. Obecne metody leczenia mają wyłącznie charakter objawowy, zapewniają minimalne, czasowe usprawnienie funkcji poznawczych pacjentów. W pracy przedstawiono najnowsze kierunki poszukiwań skutecznej farmakoterapii zdolnej do zapobieżenia lub zahamowania progresji AD. Ze względu na to, iż nie jest znana dokładna patogeneza choroby Alzheimera główne strategie terapeutyczne opierają się jedynie na hipotezach: kaskady amyloidowej, białka tau, stresu oksydacyjnego, neurozapalenia oraz tych związanych z dysfunkcją układu cholinergicznego, jak również glutaminianergicznego. Większość związków obecnie testowanych w badaniach klinicznych nakierowana jest na patologiczny amyloid β (Aβ), będący narzędziem sprawczym neurodegeneracji, według opisywanej dotychczas najszerzej teorii kaskady amyloidowej. Z toksycznym Aβ próbuje się walczyć za pośrednictwem: immunoterapii (szczepionki, przeciwciała monoklonalne), związków hamujących jego powstanie: inhibitorów/modulatorów γ-sekretazy i inhibitorów β-sekretazy. Immunoterapię próbuje się wykorzystać również do nasilenia klirensu hiperfosforylowanego białka tau, którego obecność jest nieodzowną cechą choroby Alzheimera. Oprócz przedstawicieli immunoterapii, przedmiotem prac badawczych stały się również związki o działaniu przeciwzapalnym, metabolicznym i neuroprotekcyjnym. W fazę badań klinicznych zostały wprowadzone ponadto związki działające objawowo, które wyrównując deficyty cholinergiczne, noradrenergiczne i glutaminianergiczne poprawiają funkcje poznawcze.
... The protein can enhance long-term potentiation and memory and is both neurotrophic and neuroprotective against a range of pro-apoptotic and disease-associated insults including A toxicity [3][4][5]. This protection is also observed in models of traumatic brain injury and stroke [6,7]. Indeed, increasing evidence now suggests that there is a reduction in sAPP␣ production in the AD brain and the loss of this neuroprotective agent contributes to AD pathogenesis [8][9][10][11]. ...
Background:
Secreted amyloid precursor protein-alpha (sAPPα) can enhance memory and is neurotrophic and neuroprotective across a range of disease-associated insults, including amyloid-β toxicity. In a significant step toward validating sAPPα as a therapeutic for Alzheimer's disease (AD), we demonstrated that long-term overexpression of human sAPPα (for 8 months) in a mouse model of amyloidosis (APP/PS1) could prevent the behavioral and electrophysiological deficits that develop in these mice.
Objective:
To explore the underlying molecular mechanisms responsible for the significant physiological and behavioral improvements observed in sAPPα-treated APP/PS1 mice.
Methods:
We assessed the long-term effects on the hippocampal transcriptome following continuous lentiviral delivery of sAPPα or empty-vector to male APP/PS1 mice and wild-type controls using Affymetrix Mouse Transcriptome Assays. Data analysis was carried out within the Affymetrix Transcriptome Analysis Console and an integrated analysis of the resulting transcriptomic data was performed with Ingenuity Pathway analysis (IPA).
Results:
Mouse transcriptome assays revealed expected AD-associated gene expression changes in empty-vector APP/PS1 mice, providing validation of the assays used for the analysis. By contrast, there were specific sAPPα-associated gene expression profiles which included increases in key neuroprotective genes such as Decorin, betaine-GABA transporter, and protocadherin beta-5, subsequently validated by qRT-PCR. An integrated biological pathways analysis highlighted regulation of GABA receptor signaling, cell survival, and inflammatory responses. Furthermore, upstream gene regulatory analysis implicated sAPPα activation of Interleukin-4, which can counteract inflammatory changes in AD.
Conclusion:
This study identified key molecular processes that likely underpin the long-term neuroprotective and therapeutic effects of increasing sAPPα levels in vivo.
... Etazolate (EHT0202) is an α-secretase activator and modulator of the GABA receptor. In a model of closed-head injury in Swiss mice, a dose of 1, 3, or 10 mg/kg of etazolate was associated with an anti-inflammatory effect, memory improvement, and restoration of sAβPPα levels (Siopi et al., 2013). In a rat model, etazolate (20 nM-2 μM) showed dose-dependent neuroprotection against fibrillar Aβ (Marcade et al., 2008), and in aged rats, etazolate prevented age-related cognitive deficits, including a reduction in memory upon oral administration of up to 2.37 mg/kg (0.5 mL/kg for 7 days) (Drott et al., 2010). ...
Amyloid-β (Aβ) senile plaques and neurofibrillary tangles of tau are generally recognized as the culprits of Alzheimer's disease (AD) and related dementia. About 25 years ago, the amyloid cascade hypotheses postulated a direct correlation of plaques with the development of AD, and it has been the dominant theory since then. In this period, more than 200 clinical trials focused mainly on targeting components of the Aβ cascade have dramatically failed, some of them in Phase III. With a greater than 99.6% failure rate at a cost of several billion from governments, industry, and private funders, therapeutic strategies targeting amyloid and tau are now under scrutiny. Therefore, it is time to reevaluate alternatives to targeting Aβ and tau as effective therapeutic strategies for AD. The diagnosis of AD is currently based on medical examination of symptoms including tests to assess memory impairment, attention, language, and other thinking skills. This is complemented with brain scans, such as computed tomography, magnetic resonance imaging, or positron emission tomography with the help of imaging probes targeting Aβ or tau deposits. This approach has contributed to the tunnel vision focus on Aβ and tau as the main culprits of AD. However, events upstream of these proteopathies (age-related impaired neuronal bioenergetics, lysosome function, neurotrophic signaling, and neuroinflammation, among others) are almost surely where the development of alternative therapeutic interventions should be targeted. Here, we present the current status of therapeutic candidates targeting diverse mechanisms and strategies including Aβ and tau, proteins involved in Aβ production and trafficking (ApoE, α/β/γ-secretases), neuroinflammation, neurotransmitters, neuroprotective agents antimicrobials, and gene and stem cell therapy. There are currently around 33 compounds in Phase III, 78 in Phase II, and 32 more in Phase I trials. With the current world health crisis of increased dementia in a rapidly aging population, effective AD therapies are desperately needed.
... sAPPα is neurotrophic [74][75][76][77][78][79][80][81][82] . The intraventricular administration of sAPPα enhances memory function of mice 83 , and sAPPα mediates numerous APP-mediated actions on brain development and cognition 68,74,[84][85][86] . ...
Rivastigmine (or Exelon) is a cholinesterase inhibitor, currently used as a symptomatic treatment for mild-to-moderate Alzheimer’s disease (AD). Amyloid-β peptide (Aβ) generated from its precursor protein (APP) by β-secretase (or BACE1) and γ-secretase endoproteolysis. Alternative APP cleavage by α-secretase (a family of membrane-bound metalloproteases– Adamalysins) precludes the generation of toxic Aβ and yields a neuroprotective and neurotrophic secreted sAPPα fragment. Several signal transduction pathways, including protein kinase C and MAP kinase, stimulate α-secretase. We present data to suggest that rivastigmine, in addition to anticholinesterase activity, directs APP processing away from BACE1 and towards α-secretases. We treated rat neuronal PC12 cells and primary human brain (PHB) cultures with rivastigmine and the α-secretase inhibitor TAPI and assayed for levels of APP processing products and α-secretases. We subsequently treated 3×Tg (transgenic) mice with rivastigmine and harvested hippocampi to assay for levels of APP processing products. We also assayed postmortem human control, AD, and AD brains from subjects treated with rivastigmine for levels of APP metabolites. Rivastigmine dose-dependently promoted α-secretase activity by upregulating levels of ADAM-9, -10, and -17 α-secretases in PHB cultures. Co-treatment with TAPI eliminated rivastigmine-induced sAPPα elevation. Rivastigmine treatment elevated levels of sAPPα in 3×Tg mice. Consistent with these results, we also found elevated sAPPα in postmortem brain samples from AD patients treated with rivastigmine. Rivastigmine can modify the levels of several shedding proteins and directs APP processing toward the non-amyloidogenic pathway. This novel property of rivastigmine can be therapeutically exploited for disease-modifying intervention that goes beyond symptomatic treatment for AD.
... In the OF, a test that assesses exploration and general motor abilities, mice that sustained rCBI ambulated greater distances overall than sham-treated animals. Hyperactivity has been previously reported in translational TBI studies employing severe contusive injury models such as controlled cortical impact (CCI) (e.g., [25,76,77]), more severe closed-head methods [78,79], or repetitive mild closed-head injuries [10,80,81]. These injuries may result in either gross lesions or more subtle damage to the hippocampus, and discrete hippocampal lesions result in OF hyperactivity [82][83][84], However, this is only one of many experimental manipulations resulting in an increase in general locomotor activity [85], and as most experimental models of TBI induce diffuse as well as focal injuries, changes in arousal and activity could be the outcome of insult to many regions, including parietal cortex. ...
There is strong evidence to suggest a link between repeated head trauma and cognitive and emotional disorders, and Repetitive concussive brain injuries (rCBI) may also be a risk factor for depression and anxiety disorders. Animal models of brain injury afford the opportunity for controlled study of the effects of injury on functional outcomes. In this study, male and cycling female C57BL/6J mice sustained rCBI (3x) at 24-hr intervals and were tested in a context and cued fear conditioning paradigm, open field (OF), elevated zero maze and tail suspension test. All mice with rCBI showed less freezing behavior than sham control mice during the fear conditioning context test. Injured male, but not female mice also froze less in response to the auditory cue (tone). Injured mice were hyperactive in an OF environment and spent more time in the open quadrants of the elevated zero maze, suggesting decreased anxiety, but there were no differences between injured mice and sham-controls in depressive-like activity on the tail suspension test. Pathologically, injured mice showed increased astrogliosis in the injured cortex and white matter tracts (optic tracts and corpus callosum). There were no changes in the number of parvalbumin-positive interneurons in the cortex or amygdala, but injured male mice had fewer parvalbumin-positive neurons in the hippocampus. Parvalbumin-reactive interneurons of the hippocampus have been previously demonstrated to be involved in hippocampal-cortical interactions required for memory consolidation, and it is possible memory changes in the fear-conditioning paradigm following rCBI are the result of more subtle imbalances in excitation and inhibition both within the amygdala and hippocampus, and between more widespread brain regions that are injured following a diffuse brain injury.
... Microglia, as the main immunoeffectors in the CNS, play a critical role in the occurrence and development of neuroinflammation [3,6]. By sensing inflammatory stimuli, microglia can be activated, and morphological changes and the production of inflammatory cytokines, chemokines, and reactive oxygen species (ROS) [7][8][9], which further induce the activation of astrocytes and cause neuroinflammatory damage [10][11][12], can occur. Thus, the suppression of microglial activation has been recognized as an attractive option for the alleviation of neuroinflammation-related diseases. ...
Neuroinflammation is one of the critical events in neurodegenerative diseases, whereas microglia play an important role in the pathogenesis of neuroinflammation. In this study, we investigated the effects of a natural sesquiterpene lactone, 6-O-angeloylplenolin (6-OAP), isolated from the traditional Chinese medicine Centipeda minima (L.) A.Br., on neuroinflammation and the underlying mechanisms. We showed that treatment with lipopolysaccharide (LPS) caused activation of BV2 and primary microglial cells and development of neuroinflammation in vitro, evidenced by increased production of inflammatory cytokines TNF-α and IL-1β, the phosphorylation and nuclear translocation of NF-κB, and the transcriptional upregulation of COX-2 and iNOS, leading to increased production of proinflammatory factors NO and PGE2. Moreover, LPS treatment induced oxidative stress through increasing the expression levels of NOX2 and NOX4. Pretreatment with 6-OAP (0.5−4 μM) dose-dependently attenuated LPS-induced NF-κB activation and oxidative stress, thus suppressed neuroinflammation in the cells. In a mouse model of LPS-induced neuroinflammation, 6-OAP (5−20 mg·kg−1·d−1, ip, for 7 days before LPS injection) dose-dependently inhibited the production of inflammatory cytokines, the activation of the NF-κB signaling pathway, and the expression of inflammatory enzymes in brain tissues. 6-OAP pretreatment significantly ameliorated the activation of microglia and astrocytes in the brains. 6-OAP at a high dose caused a much stronger antineuroinflammatory effect than dexamethansone (DEX). Furthermore, we demonstrated that 6-OAP pretreatment could inhibit LPS-induced neurite and synaptic loss in vitro and in vivo. In conclusion, our results demonstrate that 6-OAP exerts antineuroinflammatory effects and can be considered a novel drug candidate for the treatment of neuroinflammatory diseases.
... Epigallocatechin-gallate (EGCG) is a green tea polyphenol that is suggested to have neuroprotective properties in neurodegenerative diseases [127,128], and has completed phase II and III clinical trials (NCT00951834) for early stage AD. Etazolate (EHT0202) as a γ-aminobutyric acid (GABA) A receptor modulator and α-secretase activator is proven to present neuroprotective functions [129,130]. Its phase II clinical trial in AD treatment (NCT00880412) was completed in 2009, although no results or further studies have been published since then. ...
Alzheimer’s disease (AD) is one of the most common causes of dementia. Its pathogenesis is characterized by the aggregation of the amyloid-β (Aβ) protein in senile plaques and the hyperphosphorylated tau protein in neurofibrillary tangles in the brain. Current medications for AD can provide temporary help with the memory symptoms and other cognitive changes of patients, however, they are not able to stop or reverse the progression of AD. New medication discovery and the development of a cure for AD is urgently in need. In this review, we summarized drugs for AD treatments and their recent updates, and discussed the potential of microglia induced neuroinflammation as a target for anti-AD drug development.
... In another study, etazolate was also found to improve cognitive performance in aged rats (Drott et al. 2010). More recently, Siopi et al. showed that etazolate treatment was associated with reduced inflammation in mice following brain injury, as well as improved performance in behavioural tasks (Siopi et al. 2013). Vellas and colleagues were the first to investigate the effect of etazolate in combination with an acetycholinesterase (AChE) inhibitor in a sample of 159 AD patients (ClinicalTrials.gov ...
Glutamatergic and cholinergic dysfunction are well‐attested features of Alzheimer's disease (AD), progressing with other pathological indices of the disorder and exacerbating neuronal and network dysfunction. However, relatively little attention has been paid to the inhibitory component of the excitatory/inhibitory (E/I) network, particularly dysfunction in the gamma‐aminobutyric acid (GABA) signaling system. There is growing evidence in support of GABAergic remodeling in the AD brain, potentially beginning in early stages of disease pathogenesis, and this could thus be a valid molecular target for drug development and pharmacological therapies. Several GABAergic drugs have been tested for efficacy in attenuating or reversing various features and symptoms of AD, and this could represent a novel path by which we might address the growing need for more effective and benign therapies.
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... Additionally, proinflammatory cytokines derived from microglia can activate receptor-dependent apoptotic pathways via recruitment of adaptor molecules and caspase-8 or -10 activation [7,8]. Accordingly, inhibition of microglial activation and, therefore, production of inflammatory mediators has been suggested to be a potential therapeutic strategy for protecting the damaged brain in TBI [9,10]. ...
Traumatic brain injury (TBI) induces a series of inflammatory processes that contribute to neuronal damage. The present study investigated the involvement of soluble epoxide hydrolase (sEH) in neuroinflammation and brain damage in mouse TBI and in microglial cultures. The effects of genetic deletion of sEH and treatment with an sEH inhibitor, 12-(3-adamantan-1-yl-ureido)-dodecanoic acid (AUDA), on brain damage and inflammatory responses were evaluated in mice subjected to controlled cortical impact. The anti-inflammatory mechanism of sEH inhibition/deletion was investigated in vitro. TBI-induced an increase in sEH protein level in the injured cortex from 1 h to 4 days and sEH was expressed in microglia. Genetic deletion of sEH significantly attenuated functional deficits and brain damage up to 28 days post-TBI. Deletion of sEH also reduced neuronal death, apoptosis, brain edema, and BBB permeability at 1 and 4 day(s). These changes were associated with markedly reduced microglial/macrophage activation, neutrophil infiltration, matrix metalloproteinase-9 activity, inflammatory mediator expression at 1 and 4 day(s), and epoxyeicosatrienoic acid (EET) degradation at 1 and 4 day(s). Administration of AUDA attenuated brain edema, apoptosis, inflammatory mediator upregulation and EET degradation at 4 days. In primary microglial cultures, AUDA attenuated both LPS- or IFN-γ-stimulated nitric oxide (NO) production and reduced LPS- or IFN-γ-induced p38 MAPK and NF-κB signaling. Deletion of sEH also reduced IFN-γ-induced NO production. Moreover, AUDA attenuated N2A neuronal death induced by BV2 microglial-conditioned media. Our results suggest that inhibition of sEH may be a potential therapy for TBI by modulating the cytotoxic functions of microglia.
... Drugs targeting extrasynaptic GABA A Rs are currently being explored, with some being tested in pre-clinical and clinical studies for their potential to improve cognition [336][337][338]; these might offer a promising route in the symptomatic treatment of the disease. The possibility of targeting other GABA-mediated pathways is also being explored, with the GABA A R-targeting drug etazolate having been tested in Phase II clinical trials for its neuroprotective and anti-amyloidogenic effects in AD patients [336,[339][340][341][342]. Attention is also increasingly being paid to the relationship between BZ use and the risk of developing AD [343,344]. ...
Gamma-aminobutyric acid (GABA) is the primary inhibitory neurotransmitter in the vertebrate brain. In the past, there has been a major research drive focused on the dysfunction of the glutamatergic and cholinergic neurotransmitter systems in Alzheimer's disease (AD). However, there is now growing evidence in support of a GABAergic contribution to the pathogenesis of this neurodegenerative disease. Previous studies paint a complex, convoluted and often inconsistent picture of AD-associated GABAergic remodeling. Given the importance of the GABAergic system in neuronal function and homeostasis, in the maintenance of the excitatory/inhibitory balance, and in the processes of learning and memory, such changes in GABAergic function could be an important factor in both early and later stages of AD pathogenesis. Given the limited scope of currently available therapies in modifying the course of the disease, a better understanding of GABAergic remodeling in AD could open up innovative and novel therapeutic opportunities.
... Upregulation of α-secretase activity was reported for etazolate, an allosteric activator of GABA A receptors, which increased APPsα in rat cortical neurons and guinea pig brain (Marcade et al., 2008), improved memory in aged rats (Drott et al., 2010) and proved protective against traumatic brain injury (Siopi et al., 2013). The neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP) potently increased APPsα levels, an effect that was abrogated by an antagonist of the GPCR PAC1, by a hydroxamate-based ADAM inhibitor and by inhibitors of MAP kinases and PI3 kinases (Kojro et al., 2006). ...
Cleavage of the amyloid precursor protein (APP) by α-secretase generates an extracellularly released fragment termed secreted APP-alpha (APPsα). Not only is this process of interest due to the cleavage of APP within the amyloid-beta sequence, but APPsα itself has many physiological properties that suggest its great potential as a therapeutic target. For example, APPsα is neurotrophic, neuroprotective, neurogenic, a stimulator of protein synthesis and gene expression, and enhances long-term potentiation (LTP) and memory. While most early studies have been conducted in vitro, effectiveness in animal models is now being confirmed. These studies have revealed that either upregulating α-secretase activity, acutely administering APPsα or chronic delivery of APPsα via a gene therapy approach can effectively treat mouse models of Alzheimer’s disease (AD) and other disorders such as traumatic head injury. Together these findings suggest the need for intensifying research efforts to harness the therapeutic potential of this multifunctional protein.
... A variety of potential strategies may shift the balance towards non-amyloidogenic cleavage of APP, including modulation of expression, trafficking and regulation of ADAM10 (Postina, 2012). Direct activation of α-secretases by etazolate has been shown to be beneficial in TBI in mice (Siopi et al., 2013). As an indirect mechanism, activation of muscarinic M1 acetylcholine receptors has been reported to increase α-secretase cleavage of APP and decrease Aß levels (Beach et al., 2001). ...
Despite its key role in the molecular pathology of Alzheimer’s disease (AD), the physiological function of amyloid precursor protein (APP) is unknown. Increasing evidence, however, points towards a neuroprotective role of this membrane protein in situations of metabolic stress. A key observation is the up-regulation of APP following acute (stroke, cardiac arrest) or chronic (cerebrovascular disease) hypoxic-ischemic conditions. While this mechanism may increase the risk or severity of AD, APP by itself or its soluble extracellular fragment APPsα can promote neuronal survival. Indeed, different animal models of acute hypoxia-ischemia, traumatic brain injury (TBI) and excitotoxicity have revealed protective effects of APP or APPsα. The underlying mechanisms involve APP-mediated regulation of calcium homeostasis via NMDA receptors (NMDAR), voltage-gated calcium channels (VGCC) or internal calcium stores. In addition, APP affects the expression of survival- or apoptosis-related genes as well as neurotrophic factors. In this review, we summarize the current understanding of the neuroprotective role of APP and APPsα and possible implications for future research and new therapeutic strategies.
... Scientific study also reported decreased generation of A and enhanced sAPP␣ formation through upregulation of ␣-secretase activity [56]. Several ␣-secretase activity enhancing compounds such as exebryl-1, bryostatin-1, etazolate/EHT-0202 have also been reported in the literature that works through a different mechanism [57][58][59]. ...
Alzheimer’s disease (AD) is a well-known cause of memory loss and dementia in elderly people all across the world. It is pathophysiologically characterized by the extracellular deposition of amyloid beta (Aβ) proteins and retention of intracellular neurofibrillary tangles (NFTs) of hyperphosphorylated tau proteins. Several enzymes, such as lipoxygenases, acetylcholinesterases, secretases, glycogen synthase kinase 3, caspases, sirtuins have been reported to actively participate in the pathogenesis of AD. Due to the limited drug approval by US-FDA for the management of AD till now (only memantine and four other acetylcholinesterase inhibitors), there is an urgent need to find out the novel inhibitors that could specifically act against these enzymes or therapeutically important targets, and barricade or decelerate AD progression. In this current review, we aim to unravel various enzymes and their potential inhibitors that could be exploited against AD pathogenesis. We have also covered several other important miscellaneous targets which could be used as AD therapeutics.
... Etazolate produced a dose-dependent anti-inflammatory and anti-edematous effect in conjunction with improved cognitive performance in the mouse model of TBI. These effects were correlated with reinstated levels of sAPPa after TBI [131]. ...
Alzheimer’s disease (AD) is an age-related neurodegenerative disease of the central nervous system correlated with the progressive loss of cognition and memory. β-Amyloid plaques, neurofibrillary tangles and the deficiency in cholinergic neurotransmission constitute the major hallmarks of the AD. Two major hypotheses have been implicated in the pathogenesis of AD namely the cholinergic hypothesis which ascribed the clinical features of dementia to the deficit cholinergic neurotransmission and the amyloid cascade hypothesis which emphasized on the deposition of insoluble peptides formed due to the faulty cleavage of the amyloid precursor protein. Current pharmacotherapy includes mainly the acetylcholinesterase inhibitors and N-methyl-d-aspartate receptor agonist which offer symptomatic therapy and does not address the underlying cause of the disease. The disease-modifying therapy has garnered a lot of research interest for the development of effective pharmacotherapy for AD. β and γ-Secretase constitute attractive targets that are focussed in the disease-modifying approach. Potentiation of α-secretase also seems to be a promising approach towards the development of an effective anti-Alzheimer therapy. Additionally, the ameliorative agents that prevent aggregation of amyloid peptide and also the ones that modulate inflammation and oxidative damage associated with the disease are focussed upon. Development in the area of the vaccines is in progress to combat the characteristic hallmarks of the disease. Use of cholesterol-lowering agents also is a fruitful strategy for the alleviation of the disease as a close association between the cholesterol and AD has been cited. The present review underlines the major therapeutic strategies for AD with focus on the new developments that are on their way to amend the current therapeutic scenario of the disease.
... On days 1, 3, and 7 post-TBI, C57BL/6 mice and APOE-KO mice from vehicle group (n = 5 for each group) and bexarotene group (n = 5) were anesthetized and then sacrificed by decapitation. The brain tissue around the injury site was orderly harvested and washed with phosphate-buffered saline (PBS) as described by Siopi et al. (2013). The RIPA lysate was used to extract the total protein and then the protein concentration was measured by BCA method. ...
Bexarotene has been proved to have neuroprotective effects in many animal models of neurological diseases. However, its neuroprotection in traumatic brain injury (TBI) is still unknown. This study aims to explore the neuroprotective effects of bexarotene on TBI and its possible mechanism. Controlled cortical impact (CCI) model was used to simulate TBI in C57BL/6 mice as well as APOE gene knockout (APOE-KO) mice. After CCI, mice were daily dosed with bexarotene or vehicle solution intraperitoneally. The motor function, learning and memory, inflammatory factors, microglia amount, apoptosis condition around injury site and main side-effects were all measured. The results showed that, after CCI, bexarotene treatment markedly improved the motor function and spatial memory in C57BL/6 compare to APOE-KO mice which showed no improvement. The inflammatory cytokines, microglia amount, cell apoptosis rate, and protein of cleaved caspase-3 around the injury site were markedly upregulated after TBI in both C57BL/6 and APOE-KO mice, and all these upregulation were significantly mitigated by bexarotene treatment in C57BL/6 mice, but not in APOE-KO mice. No side-effects were detected after consecutive administration. Taken together, bexarotene inhibits the inflammatory response as well as cell apoptosis and improves the neurological function of mice after TBI partially through apolipoprotein E. This may make it a promising candidate for the therapeutic treatment after TBI.
... Therefore sAPPα may act as a modulator of inflammation. Siopi et al., [98] studied the effects of the α-secretase activator etazolate on acute and post-TBI outcome in a mouse model. Within a therapeutic window of two hours, a single dose of etazolate reduced inflammation and edema, and improved memory and locomotion, with these effects closely associated with restoration of sAPPα levels. ...
Soluble, secreted Amyloid Precursor Protein- (sAPP), a product of -secretase (ADAM10) cleavage of Full Length-APP (FL-APP), is a trophic factor critical for synaptic complexity and maintenance. As cleavage at the -site of APP precludes the -site cleavage that is the first step in Amyloid (A) production, enhancing sAPP production may not only support and restore neuronal health, but may also decrease the generation of anti-trophic A. Over-production or reduced clearance of A is a hallmark of Alzheimer’s Disease (AD), and recent findings suggest it also plays a role in other neurodegenerative diseases and neurological conditions, such as Amyotrophic Lateral Sclerosis (ALS), Cerebral Amyloid Angiopathy (CAA), and Traumatic Brain Injury (TBI). Yet decades of focus on A-lowering strategies alone including passive and active immunotherapy and γ-secretase and BACE1 (BACE) inhibition have yet to yield positive clinical results. Clinical trials of several BACE inhibitors are underway in AD patients, and although there is optimism about this strategy, there are also concerns about mechanism-based side-effects of these drugs. A truly effective therapy would not only slow the degenerative process underlying onset and progression of the disease, it should also restore healthy neuronal function. It is very likely this will comprise combination therapy utilizing more than one drug or intervention. Molecules that enhance sAPP may be a safe, effective component of a multi-modal therapeutic approach to AD and other neurodegenerative diseases, and have the potential to increase neuronal health by providing trophic support and disrupting neurodegenerative mechanisms.
... Although the data from the preclinical studies have shown that the secondary pathophysiological cascades provide a large therapeutic window for pharmacological intervention, clinical trials have failed to approve the preclinical neuroprotective treatments [249]. Given the multifactorial consequences of brain injury, it is likely that simultaneous targeting of several targets with multipotential drugs may be the most promising therapeutic approach to improve outcome following TBI [249][250][251][252][253][254][255]. One of these potential drugs is lithium. ...
Wnt signaling is required for neurogenesis, the fate of neural progenitors, the formation of neuronal circuits during development, neuron positioning and polarization, axon and dendrite development and finally for synaptogenesis. This signaling pathway is also implicated in the generation and differentiation of glial cells. In this review, we describe the mechanisms of action of Wnt signaling pathways and their implication in the development and correct functioning of the nervous system. We also illustrate how a dysregulated Wnt pathway could lead to psychiatric, neurodegenerative and demyelinating pathologies. Lithium, used for the treatment of bipolar disease, inhibits GSK3β, a central enzyme of the Wnt/β-catenin pathway. Thus, lithium could, to some extent, mimic Wnt pathway. We highlight the possible dialogue between lithium therapy and modulation of Wnt pathway in the treatment of the diseases of the nervous system.
... Scientific study also reported decreased generation of A and enhanced sAPP␣ formation through upregulation of ␣-secretase activity [56]. Several ␣-secretase activity enhancing compounds such as exebryl-1, bryostatin-1, etazolate/EHT-0202 have also been reported in the literature that works through a different mechanism [57][58][59]. ...
Atta-ur-Rahman / M. Iqbal Choudhary (Eds.) All rights reserved-Abstract: Accompanying the gradual rise in the average age of the population of most industrialized countries is a regrettable escalation in individuals afflicted with progressive neurodegenerative disorders, epitomized by Alzheimer's disease (AD). The development of effective new treatment strategies for AD has therefore become one of the most critical challenges in current neuroscience. Cholinesterase inhibitors (ChEIs) remain the primary therapeutic strategy for AD, and act by amplifying residual cholinergic activity, a neurotransmitter system central in cognitive processing that is reported to be depleted in the AD brain. With the recent failure of current drug classes focused towards the molecular events known to underpin AD, including the generation of amyloid-β peptide (Aβ) containing plaques and neurofibrillary tangles (hyper-phosphorylated tau). The development of new generation of cholinergic drugs has been accomplished to take advantage of the known modulatory action of the cholinergic system on Aβ, tau production as well as the maintenance synapses, which are known to be lost in AD. Following upon the development of acetylcholinesterase inhibitors (AChE-Is), phenserine, that additionally possessed amyloid precursor protein (APP) synthesis inhibitory actions to lower the generation of Aβ. Selective butyrylcholinesterase inhibitors (BuChE-Is), cymserine analogues, have been developed on the same chemical backbone during further anti-AD research advancement. The above mentioned inhibitors retain actions on APP as well as Aβ and amplify central cholinergic actions without the classical dose-limiting adverse effect profile; therefore, these current BuChE-Is are now moving into AD clinical trials.
Alzheimer's disease (AD) is a complicated, multifaceted, irreversible, and incurable neurotoxic old age illness. Although NMDA (N-methyl D-aspartate)-receptor antagonists, cholinesterase repressors, and their pairings have been approved for the treatment, they are useful for short symptomatic relief. Researchers throughout the globe have been constantly working to uncover the therapy of Alzheimer's disease as new candidates must be determined, and newer treatment medicines must be developed. The aim of this review is to address recent advances in medication research along with new Alzheimer's disease therapy for diverse targets. Information was gathered utilizing a variety of internet resources as well as websites, such as ALZFORUM (alzforum.org) and clinicaltrials.gov. In contrast to other domains, the proposed medicines target amyloids (secretases, A42 generation, neuroinflammation, amyloid precipitation, and immunization), tau proteins (tau phosphorylation/aggregation and immunotherapy), and amyloid deposition. Despite tremendous advancement in our understanding of the underlying pathophysiology of Alzheimer's disease, the FDA (Food and Drug Administration) only approved aducanumab for diagnosis and treatment in 2003. Hence, novel treatment tactics are needed to find and develop therapeutic medicines to combat Alzheimer's disease.
Traumatic brain injury (TBI) is an important global health concern that represents a leading cause of death and disability. It occurs due to direct impact or hit on the head caused by factors such as motor vehicles, crushes, and assaults. During the past decade, an abundance of new evidence highlighted the importance of inflammation in the secondary damage response that contributes to neurodegenerative and neurological deficits after TBI. It results in disruption of the blood–brain barrier (BBB) and initiates the release of macrophages, neutrophils, and lymphocytes at the injury site. A growing number of researchers have discovered various signalling pathways associated with the initiation and progression of inflammation. Targeting different signalling pathways (NF-κB, JAK/STAT, MAPKs, PI3K/Akt/mTOR, GSK-3, Nrf2, RhoGTPase, TGF-β1, and NLRP3) helps in the development of novel anti-inflammatory drugs in the management of TBI. Several synthetic and herbal drugs with both anti-inflammatory and neuroprotective potential showed effective results. This review summarizes different signalling pathways, associated pathologies, inflammatory mediators, pharmacological potential, current status, and challenges with anti-inflammatory drugs.
Traumatic brain injury (TBI) is a major cause of disability and death. However, despite increased attention due to explosive detonations in warzones and discussions of the long-term effects of mild TBI on athletes, there are no clinically accepted therapies. Although several drugs have been tested in clinical trials, none have been approved. Because testing of compounds begins in vitro, it is practical to model the in vivo environment as closely as possible to avoid late-stage failures. Advancements in 3D organoids, cultures that maintain in vivo structure, and utilization of organotypic slices are creating more complex and physiologically relevant in vitro models of brain tissue to be injured in in vitro models of blast, stretch, and indentation to reduce the socioeconomic cost of TBI.
Objective
Sepsis-associated encephalopathy (SAE) is characterized by diffuse cerebral and central nervous system (CNS) dysfunction. Microglia play a vital role in protecting the brain from neuronal damage, which is closely related to inflammatory responses. The Nrf2 signaling pathway has an impact on microglial and neuronal injury. Here, we mainly explored the molecular mechanism by which H2 regulates neuroinflammation in SAE and the role of Nrf2 in this process.
Methods
An in vivo model of SAE was generated by cecal ligation and puncture (CLP). Primary microglia and neurons were cultured to establish an in vitro model. Microglia, neurons and brain tissue were obtained to detect Nrf2 expression, inflammation, cell injury, apoptosis, and microglial polarization. Escape latency, the number of platform crossings and the time spent in the target quadrant were measured to assess cognitive function.
Results
H2 attenuated microglial polarization from the M1 to the M2 phenotype, cytokine release and TLR/NF-κb activation and protected neurons from LPS-activated microglia-induced injury via the Nrf2 pathway. SAE activated Nrf2 expression, and H2 further improved Nrf2 expression in SAE mice. H2 alleviated microglial polarization from the M1 to the M2 phenotype and cytokine release in the cerebral cortex and improved neuronal injury or cognitive dysfunction in SAE mice and wild-type mice but not in Nrf2-/- mice.
Conclusion
H2 exerts antineuroinflammatory effects associated with TLR4/NF-κB signaling activation and neuroprotective effects by inhibiting the excessive release of proinflammatory cytokines, neuronal loss and apoptosis in vitro and in vivo through the Nrf2 pathway.
Late Onset Alzheimer’s Disease is the most common cause of dementia, characterized by extracellular deposition of plaques primarily of amyloid-β (Aβ) peptide and tangles primarily of hyperphosphorylated tau protein. We present data to suggest a noninvasive strategy to decrease potentially toxic Aβ levels, using repeated electromagnetic field stimulation (REMFS) in primary human brain (PHB) cultures. We examined effects of REMFS on Aβ levels (Aβ40 and Aβ42, that are 40 or 42 amino acid residues in length, respectively) in PHB cultures at different frequencies, powers, and specific absorption rates (SAR). PHB cultures at day in vitro 7 (DIV7) treated with 64 MHz, and 1 hour daily for 14 days (DIV 21) had significantly reduced levels of secreted Aβ40 (p = 001) and Aβ42 (p = 0.029) peptides, compared to untreated cultures. PHB cultures (DIV7) treated at 64 MHz, for 1 or 2 hour during 14 days also produced significantly lower Aβ levels. PHB cultures (DIV28) treated with 64 MHz 1 hour/day during 4 or 8 days produced a similar significant reduction in Aβ40 levels. 0.4 W/kg was the minimum SAR required to produce a biological effect. Exposure did not result in cellular toxicity nor significant changes in secreted Aβ precursor protein-α (sAPPα) levels, suggesting the decrease in Aβ did not likely result from redirection toward the α-secretase pathway. EMF frequency and power used in our work is utilized in human magnetic resonance imaging (MRI, thus suggesting REMFS can be further developed in clinical settings to modulate Aβ deposition.
Demyelination is a well-known pathological process in CNS disorders such as multiple sclerosis (MS). It provokes progressive axonal degeneration and functional impairments and no efficient therapy is presently available to combat such insults. Recently, we have shown that etazolate, a pyrazolopyridine compound and an α-secretase activator, was able to promote myelin protection and remyelination after cuprizone (CPZ)-induced acute demyelination in C57Bl/6 mice. In continuation of this work, here we have further investigated the effects of etazolate treatment after acute cuprizone-induced demyelination at the molecular level (expression of myelin genes Plp, Mbp and Mag and inflammatory markers Il-1β, Tnf-α) and at the functional level (locomotor and spatial memory skills) in vivo. To this end, we have employed two protocols which consists of administering etazolate (10 mg/kg/d) for a period of 2 weeks either during (Protocol #1) or after (Protocol #2) 5-weeks of CPZ-induced demyelination. At the molecular level, we observed that CPZ intoxication altered inflammatory and myelin gene expression and it was not restored with either of the etazolate treatment protocols. At the functional level, the locomotor activity was impaired after 3-weeks of CPZ intoxication (Protocol #1) and our data indicates a modest but beneficial effect of etazolate treatment. Spatial memory evaluated was not affected either by CPZ intake or etazolate treatment in both protocols. Altogether, this study shows that the beneficial effect of etazolate upon demyelination does not occur at the gene expression level. Furthermore, our results also highlight the difficulty in revealing functional sequelae following CPZ intoxication.
Mild TBI (mTBI) is a significant health concern. Animal models of mTBI are essential for understanding mechanisms, and pathological outcomes, as well as to test therapeutic interventions. A variety of closed head models of mTBI that incorporate different aspects (i.e., biomechanics) of the mTBI have been reported. The aim of the current review was to compile a comprehensive list of the closed head mTBI rodent models, along with the common data elements, and outcomes, with the goal to summarize the current state of the field. Publications were identified from a search of PubMed and Web of Science and screened for eligibility following PRISMA guidelines. Articles were included that were closed head injuries in which the authors classified the injury as mild in rats or mice. Injury model and animal-specific common data elements, as well as behavioral and histological outcomes, were collected and compiled from a total of 402 articles. Our results outline the wide variety of methods used to model mTBI. We also discovered that female rodents and both young and aged animals are under-represented in experimental mTBI studies. Our findings will aid in providing context comparing the injury models and provide a starting point for the selection of the most appropriate model of mTBI to address a specific hypothesis. We believe this review will be a useful starting place for determining what has been done and what knowledge is missing in the field to reduce the burden of mTBI.
The continual increase of the aging population worldwide renders Alzheimer's disease (AD) a global prime concern. Several attempts have been focused on understanding the intricate complexity of the disease's development along with the on‐ andgoing search for novel therapeutic strategies. Incapability of existing AD drugs to effectively modulate the pathogenesis or to delay the progression of the disease leads to a shift in the paradigm of AD drug discovery. Efforts aimed at identifying AD drugs have mostly focused on the development of disease‐modifying agents in which effects are believed to be long lasting. Of particular note, the secretase enzymes, a group of proteases responsible for the metabolism of the β‐amyloid precursor protein (βAPP) and β‐amyloid (Aβ) peptides production, have been underlined for their promising therapeutic potential. This review article attempts to comprehensively cover aspects related to the identification and use of drugs targeting the secretase enzymes. Particularly, the roles of secretases in the pathogenesis of AD and their therapeutic modulation are provided herein. Moreover, an overview of the drug development process and the contribution of computational (in silico) approaches for facilitating successful drug discovery are also highlighted along with examples of relevant computational works. Promising chemical scaffolds, inhibitors, and modulators against each class of secretases are also summarized herein. Additionally, multitarget secretase modulators are also taken into consideration in light of the current growing interest in the polypharmacology of complex diseases. Finally, challenging issues and future outlook relevant to the discovery of drugs targeting secretases are also discussed.
Traumatic brain injury (TBI) is a risk factor for development of chronic neurodegenerative disorders later in life. This review summarizes the current knowledge and concepts regarding the connection between long-term consequences of TBI and aging-associated neurodegenerative disorders including Alzheimer's disease (AD), chronic traumatic encephalopathy (CTE), and Parkinsonism, with implications for novel therapy targets. Several aggregation-prone proteins such as the amyloid-beta (Aβ) peptides, tau proteins, and α-synuclein protein are involved in secondary pathogenic cascades initiated by a TBI and are also major building blocks of the hallmark pathological lesions in chronic human neurodegenerative diseases with dementia. Impaired metabolism and degradation pathways of aggregation-prone proteins are discussed as potentially critical links between the long-term aftermath of TBI and chronic neurodegeneration. Utility and limitations of previous and current preclinical TBI models designed to study the link between TBI and chronic neurodegeneration, and promising intervention pharmacotherapies and non-pharmacologic strategies to break this link, are also summarized. Complexity of long-term neuropathological consequences of TBI is discussed, with a goal of guiding future preclinical studies and accelerating implementation of promising therapeutics into clinical trials.
This article is part of the Special Issue entitled “Novel Treatments for Traumatic Brain Injury”.
Traumatic brain injury (TBI) results in white matter injury (WMI) that is associated with neu-rological deficits. Neuroinflammation originating from microglial activation may participate in WMI and associated disorders. To date, there is little information on the time courses of these events after mild TBI. Therefore we investigated (i) neuroinflammation, (ii) WMI and (iii) behavioral disorders between 6 hours and 3 months after mild TBI. For that purpose, we used experimental mild TBI in mice induced by a controlled cortical impact. (i) For neuroin-flammation, IL-1b protein as well as microglial phenotypes, by gene expression for 12 micro-glial activation markers on isolated CD11b + cells from brains, were studied after TBI. IL-1b protein was increased at 6 hours and 1 day. TBI induced a mixed population of microglial phenotypes with both pro-inflammatory, anti-inflammatory and immunomodulatory markers from 6 hours to 3 days post-injury. At 7 days, microglial activation was completely resolved. (ii) Three myelin proteins were assessed after TBI on ipsi-and contralateral corpus callo-sum, as this structure is enriched in white matter. TBI led to an increase in 2',3'-cyclic-nucleotide 3'-phosphodiesterase, a marker of immature and mature oligodendrocyte, at 2 days post-injury; a bilateral demyelination, evaluated by myelin basic protein, from 7 days to 3 months post-injury; and an increase in myelin oligodendrocyte glycoprotein at 6 hours and 3 days post-injury. Transmission electron microscopy study revealed various myelin sheath abnormalities within the corpus callosum at 3 months post-TBI. (iii) TBI led to sensorimotor deficits at 3 days post-TBI, and late cognitive flexibility disorder evidenced by the reversal learning task of the Barnes maze 3 months after injury. These data give an overall invaluable overview of time course of neuroinflammation that could be involved in demyelination and late cognitive disorder over a timescale of 3 months in a model of mild TBI. This model could help to validate a pharmacological strategy to prevent post-traumatic WMI and behav-ioral disorders following mild TBI.
Amyloid precursor protein (APP) gives rise to the amyloid-? peptide and thus has a key role in the pathogenesis of Alzheimer disease. By contrast, the physiological functions of APP and the closely related APP-like proteins (APLPs) remain less well understood. Studying these physiological functions has been challenging and has required a careful long-term strategy, including the analysis of different App-knockout and Aplp-knockout mice. In this Review, we summarize these findings, focusing on the in vivo roles of APP family members and their processing products for CNS development, synapse formation and function, brain injury and neuroprotection, as well as ageing. In addition, we discuss the implications of APP physiology for therapeutic approaches.
Traumatic brain injury (TBI) is one of the leading cause of psychiatric conditions in patients, amongst which, depression and anxiety are more frequent. Despite the preclinical antidepressant-like effects, clinical development of Phospodiesterase-4 (PDE4) enzyme inhibitors has been hampered due to serious side effect profiles, such as nausea and vomiting. Etazolate (ETZ) is a new generation PDE4 inhibitor with encouraging safety and tolerance profiles. In our previous studies we have addressed that ETZ produces antidepressant-like effects in animal models of depression, however, the underlying mechanism(s) following TBI have not been completely explored. Impact accelerated TBI by weight drop method causes depression-like behavioral deficits in modified open field exploration, hyper-emotionality and sucrose consumption paradigms. TBI not only causes immediate mechanical damage to the brain, but also induces biochemical changes that lead to delayed neural cell loss leading to a secondary injury. The present study examines the antidepressant effects of ETZ on the TBI-induced depression-like behavior deficits and attempts to explore the underlying mechanism. In order to understand the underlying pathology of TBI and mechanism(s) of ETZ in TBI molecular markers namely, brain cAMP, cAMP response element binding protein (pCREB) and brain-derived neurotrophic factor (BDNF) were estimated. Additionally, the level of oxidative (lipid peroxidation) & nitrosative (nitrite) stress markers, along with antioxidant enzymes markers, such as, reduced glutathione (GSH), superoxide dismutase (SOD) and catalase (CAT) were measured. Furthermore, the involvement of hypothalamic-pituitary adrenal (HPA) axis activity in underlying mechanism was also investigated by measuring serum corticosterone (CORT) level. The results revealed that TBI significantly altered cAMP, pCREB and BDNF levels. Moreover, a significant increase in oxidative-nitrosative stress markers levels, while, significant decreases in antioxidant enzymes markers level were observed. However, no significant change was observed in serum CORT level. Chronic ETZ (0.5 and 1 mg/kg) treatment significantly attenuated TBI-induced behavioral deficits and restored the TBI induced derangements in molecular and biochemical markers. This study indicates that ETZ modulates cAMP signaling and oxidative/antioxidant markers in the TBI model suggesting its prospect as a potential candidate for the pharmacotherapy of depression.
Alzheimer’s disease (AD) is characterized pathologically by the deposition of -amyloid peptides (A) and the accumulation of neurofibrillary tangles (NFTs) composed of hyper-phosphorylated tau. Regardless of the pathological hallmarks, synaptic dysfunction is widely accepted as a causal event in AD. Of the two major types of synapses in the CNS: glutamatergic and GABAergic, which provide excitatory and inhibitory outputs respectively, abundant data implicate an impaired glutamatergic system during disease progression. However, emerging evidence supports the notion that disrupted default neuronal network underlies impaired memory, and that alterations of GABAergic circuits, either plays a primary role or as a compensatory response to excitotoxicity, may also contribute to AD by disrupting the overall network function. The goal of this review is to provide an overview of the involvement of A, tau and apoE4, the major genetic risk factor in late-onset AD, in GABAergic neurotransmission and the potential of modulating the GABAergic function as AD therapy.
Rationale:
Olfactory bulbectomy (OBX) is a widely used model for antidepressant screening and known to induce neurodegeneration in several brain areas. Our earlier studies demonstrated that etazolate produced antidepressant-like effects in behavioral despair models of depression; however, the potential role of etazolate on behavior and morphological changes in the hippocampus region along with its underlying mechanism(s) following OBX has not been adequately addressed.
Objectives:
We evaluated if etazolate could protect against OBX-induced depression-like behavioral deficits and neurodegeneration. The possible underlying mechanism of etazolate in OBX model was also investigated.
Methods:
The effects of etazolate were measured in a battery of behavioral paradigms, including the forced swim test (FST), sucrose consumption, open arm activity in elevated plus maze (EPM), and hyperemotionality tests. The underlying mechanisms were investigated by measuring serum corticosterone (CORT), cyclic adenosine monophosphate (cAMP), cAMP response element binding protein (CREB), brain-derived neurotrophic factor (BDNF), and oxidative/nitrosative stress (lipid peroxidation and nitrite) levels and antioxidant enzymes, like reduced glutathione (GSH), superoxide dismutase (SOD), and catalase (CAT) levels in the hippocampus.
Result:
OBX rats showed depression-like behavior anomalies in behavioral paradigms. OBX rats also showed high CORT and decreased cAMP, phosphorylated CREB (pCREB), and BDNF levels. Additionally, we found increased oxidative/nitrosative stress and reduced antioxidant enzyme levels in the hippocampus. Histopathological analysis showed morphological changes and neuronal loss in the hippocampus. Etazolate (0.5 and 1 mg/kg) attenuated the OBX-induced behavioral, biochemical, neurobiological, and histopathological alterations.
Conclusion:
The aforesaid results suggest that etazolate produces an antidepressant-like effect and neuroprotection in OBX, which is possibly mediated by modulating biochemical and neurobiological markers in the hippocampus.
Pseudoginsenoside-F11 (PF11), an ocotillol-type ginsenoside, has been shown to possess significant neuroprotective activity. Since microglia-mediated inflammation is critical for induction of neurodegeneration, this study was designed to investigate the effect of PF11 on activated microglia. PF11 significantly suppressed the release of ROS and proinflammatory mediators induced by LPS in a microglial cell line N9 including NO, PGE2, IL-1β, IL-6 and TNF-α. Moreover, PF11 inhibited interaction and expression of TLR4 and MyD88 in LPS-activated N9 cells, resulting in an inhibition of the TAK1/IKK/NF-κB signaling pathway. PF11 also inhibited the phosphorylation of Akt and MAPKs induced by LPS in N9 cells. Importantly, PF11 significantly alleviated the death of SH-SY5Y neuroblastoma cells and primary cortical neurons induced by the conditioned-medium from activated microglia. At last, the effect of PF11 on neuroinflammation was confirmed in vivo: PF11 mitigated the microglial activation and proinflammatory factors expression obviously in both cortex and hippocampus in mice injected intrahippocampally with LPS. These findings indicate that PF11 exerts anti-neuroinflammatory effects on LPS-activated microglial cells by inhibiting TLR4-mediated TAK1/IKK/NF-κB, MAPKs and Akt signaling pathways, suggesting its therapeutic implication for neurodegenerative disease associated with neuroinflammation.
Etazolate abrogates the lipopolysaccharide (LPS)-induced downregulation of the cAMP/pCREB/BDNF signaling, neuroinflammatory response and depressive-like behavior in mice, Neuroscience (2014), doi: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Traumatic brain injury (TBI) and its consequences represent one of the leading causes of death in young adults. This lesion mediates glial activation and the release of harmful molecules and causes brain edema, axonal injury, and functional impairment. Since glial activation plays a key role in the development of this damage, it seems that controlling it could be beneficial and could lead to neuro-protective effects. Recent studies show that minocycline suppresses microglial activation, reduces the lesion volume, and decreases TBI-induced locomotor hyperactivity up to 3 months. The endocannabi-noid system (ECS) plays an important role in reparative mechanisms and inflammation under pathological situations by controlling some mechanisms that are shared with minocycline pathways. We hypothesized that the ECS could be involved in the neuroprotective effects of minocycline. To address this hypothesis, we used a murine TBI model in combination with selective CB1 and CB2 receptor antagonists (AM251 and AM630, respectively). The results provided the first evidence for the involvement of ECS in the neuroprotective action of minocycline on brain edema, neurological impairment, diffuse axonal injury, and microglial activation, since all these effects were prevented by the CB1 and CB2 receptor antagonists.
Objective: To examine the performance characteristics of two forms of the University of Pennsylvania Smell Identification Test (UPSIT) in a sample of persons with traumatic brain injury (TBI). Design: Analysis of consecutive admissions into a brain injury rehabilitation program. Setting: Midwestern medical center. Participants: One hundred twenty-two adults diagnosed with TBI (49% severe TBI, 16% moderate TBI, 35% mild TBI). Main Outcome Measures: University of Pennsylvania Smell Identification Test (UPSIT; 3- and 40-item versions). Results: Fifty-six percent of sample exhibited impaired olfaction on the full UPSIT; 40% of these patients were unaware of their deficits. Contrary to expectation, TBI patients detected dangerous odors (natural gas, gasoline, smoke) with high accuracy. Usefulness of a 3-item screening measure was examined: Missing even one item related to a 2:1 likelihood of being anosmic. Conclusions: These findings support past investigations indicating that anosmia, and unawareness of olfactory dysfunction, are common in persons with TBI and related to injury severity. The use of the 3-item screening measure as a gross indicator was supported, although caution is advised, because nearly 20% of patients performing perfectly on the 3-item screen scored in the anosmic range on the full UPSIT.
Biochemical, epidemiological, and genetic findings demonstrate a link between cholesterol levels, processing of the amyloid precursor protein (APP), and Alzheimer's disease. In the present report, we identify the alpha-secretase ADAM 10 (a disintegrin and metalloprotease) as a major target of the cholesterol effects on APP metabolism. Treatment of various peripheral and neural cell lines with either the cholesterol-extracting agent methyl-beta-cyclodextrin or the hydroxymethyl glutaryl-CoA reductase inhibitor lovastatin resulted in a drastic increase of secreted alpha-secretase cleaved soluble APP. This strong stimulatory effect was in the range obtained with phorbol esters and was further increased in cells overexpressing ADAM 10. In cells overexpressing APP, the increase of alpha-secretase activity resulted in a decreased secretion of Abeta peptides. Several mechanisms were elucidated as being the basis of enhanced alpha-secretase activity: increased membrane fluidity and impaired internalization of APP were responsible for the effect observed with methyl-beta-cyclodextrin; treatment with lovastatin resulted in higher expression of the alpha-secretase ADAM 10. Our results demonstrate that cholesterol reduction promotes the nonamyloidogenic alpha-secretase pathway and the formation of neuroprotective alpha-secretase cleaved soluble APP by several mechanisms and suggest approaches to prevention of or therapy for Alzheimer's disease.
Cognitive impairment after traumatic brain injury (TBI) is correlated with decreased cholinergic markers of neuronal viability. The purpose of this experiment was to test the hypothesis that pharmacological activation of the muscarinic cholinergic system during the recovery period after TBI will improve cognitive performance. LU 25-109-T is a partial muscarinic M1 agonist that also acts as an antagonist at presynaptic M2 autoreceptors (thus, increasing ACh release). Injured rats were injected subcutaneously daily for 15 days with either 0.0, 3.6, or 15 μmol/kg of LU 25-109-T beginning 24 h after a receiving a moderate (2.1 ± 0.1 atm) level of central fluid percussion brain injury. Cognitive performance was assessed on days 11–15 postinjury in a Morris water maze (MWM). Injured rats treated with 15 μmol/kg, but not those treated with 3.6 μmol/kg, showed a significant improvement ( p < 0.01) in MWM performance as compared with injured vehicle-treated rats. This result supports the hypotheses that a decrease in posttraumatic cholinergic neurotransmission contributes to TBI-induced cognitive deficits and that increasing cholinergic tone during the recovery period following TBI will improve cognitive performance.
The combination of diffuse brain injury with a hypoxic insult is associated with poor outcomes in patients with traumatic brain injury. In this study, we investigated the impact of post-traumatic hypoxia in amplifying secondary brain damage using a rat model of diffuse traumatic axonal injury (TAI). Rats were examined for behavioral and sensorimotor deficits, increased brain production of inflammatory cytokines, formation of cerebral edema, changes in brain metabolism and enlargement of the lateral ventricles.
Adult male Sprague-Dawley rats were subjected to diffuse TAI using the Marmarou impact-acceleration model. Subsequently, rats underwent a 30-minute period of hypoxic (12% O2/88% N2) or normoxic (22% O2/78% N2) ventilation. Hypoxia-only and sham surgery groups (without TAI) received 30 minutes of hypoxic or normoxic ventilation, respectively. The parameters examined included: 1) behavioural and sensorimotor deficit using the Rotarod, beam walk and adhesive tape removal tests, and voluntary open field exploration behavior; 2) formation of cerebral edema by the wet-dry tissue weight ratio method; 3) enlargement of the lateral ventricles; 4) production of inflammatory cytokines; and 5) real-time brain metabolite changes as assessed by microdialysis technique.
TAI rats showed significant deficits in sensorimotor function, and developed substantial edema and ventricular enlargement when compared to shams. The additional hypoxic insult significantly exacerbated behavioural deficits and the cortical production of the pro-inflammatory cytokines IL-6, IL-1β and TNF but did not further enhance edema. TAI and particularly TAI+Hx rats experienced a substantial metabolic depression with respect to glucose, lactate, and glutamate levels.
Altogether, aggravated behavioural deficits observed in rats with diffuse TAI combined with hypoxia may be induced by enhanced neuroinflammation, and a prolonged period of metabolic dysfunction.
Permanent olfactory dysfunction can often arise after traumatic brain injury (TBI) and while one of the main causes is the immediate loss of neurons in the olfactory bulb (OB), the emergent neuroinflammatory environment following TBI may further promote OB deterioration. Therefore, we examined the effects of acute anti-inflammatory treatment with minocycline on post-TBI olfactory behavior and on OB surface. The mouse model of closed-head injury by mechanical percussion was applied to anesthetized Swiss mice. The treatment protocol included three injections of minocycline (i.p.) at 5 min (90 mg/kg), 3 h, and 9 h (45 mg/kg) post-TBI. An olfactory avoidance test was run up to 12 weeks post-TBI. The mice were then sacrificed and their OB surface was measured. Our results demonstrated a post-TBI olfactory behavior deficit that was significant up to at least 12 weeks post-TBI. Additionally, substantial post-TBI OB atrophy was observed that was strongly correlated with the behavioral impairment. Minocycline was able to attenuate both the olfactory lesions and corresponding functional deficit in the short and long term. These results emphasize the potential role of minocycline as a promising neuroprotective agent for the treatment of TBI-related olfactory bulb lesions and deficits.
Traumatic brain injury (TBI) induces both focal and diffuse lesions that are concurrently responsible for the ensuing morbidity and mortality and for which no established treatment is available. It has been recently reported that an endogenous neuroprotector, the soluble form α of the amyloid precursor protein (sAPPα), exerts neuroprotective effects following TBI. However, the emergent post-traumatic neuroinflammatory environment compromises sAPPα production and may promote neuronal degeneration and consequent brain atrophy. Hence, the aim of this study was to examine the effects of the anti-inflammatory drug minocycline on sAPPα levels, as well as on long-term histological consequences post-TBI. The weight-drop model was used to induce TBI in mice. Minocycline or its vehicle were administered three times: at 5 min (90 mg/kg, i.p.) and at 3 and 9 h (45 mg/kg, i.p.) post-TBI. The levels of sAPPα, the extent of brain atrophy, and reactive gliosis were evaluated by ELISA, cresyl violet, and immunolabeling of GFAP and CD11b, respectively. Our results revealed a post-TBI sAPPα decrease that was significantly attenuated by minocycline. Additionally, corpus callosum and striatal atrophy, ventriculomegaly, astrogliosis, and microglial activation were observed at 3 months post-TBI. All the above consequences were significantly reduced by minocycline. In conclusion, inhibition of the acute phase of post-TBI neuroinflammation was associated with the sparing of sAPPα and the protection of brain tissue in the long-term, emphasizing the potential role of minocycline as an effective treatment for TBI.
The heterogeneity of traumatic brain injury (TBI) is considered one of the most significant barriers to finding effective therapeutic interventions. In October, 2007, the National Institute of Neurological Disorders and Stroke, with support from the Brain Injury Association of America, the Defense and Veterans Brain Injury Center, and the National Institute of Disability and Rehabilitation Research, convened a workshop to outline the steps needed to develop a reliable, efficient and valid classification system for TBI that could be used to link specific patterns of brain and neurovascular injury with appropriate therapeutic interventions. Currently, the Glasgow Coma Scale (GCS) is the primary selection criterion for inclusion in most TBI clinical trials. While the GCS is extremely useful in the clinical management and prognosis of TBI, it does not provide specific information about the pathophysiologic mechanisms which are responsible for neurological deficits and targeted by interventions. On the premise that brain injuries with similar pathoanatomic features are likely to share common pathophysiologic mechanisms, participants proposed that a new, multidimensional classification system should be developed for TBI clinical trials. It was agreed that preclinical models were vital in establishing pathophysiologic mechanisms relevant to specific pathoanatomic types of TBI and verifying that a given therapeutic approach improves outcome in these targeted TBI types. In a clinical trial, patients with the targeted pathoanatomic injury type would be selected using an initial diagnostic entry criterion, including their severity of injury. Coexisting brain injury types would be identified and multivariate prognostic modeling used for refinement of inclusion/exclusion criteria and patient stratification. Outcome assessment would utilize endpoints relevant to the targeted injury type. Advantages and disadvantages of currently available diagnostic, monitoring, and assessment tools were discussed. Recommendations were made for enhancing the utility of available or emerging tools in order to facilitate implementation of a pathoanatomic classification approach for clinical trials.
White matter disruption is an important determinant of cognitive impairment after brain injury, but conventional neuroimaging underestimates its extent. In contrast, diffusion tensor imaging provides a validated and sensitive way of identifying the impact of axonal injury. The relationship between cognitive impairment after traumatic brain injury and white matter damage is likely to be complex. We applied a flexible technique-tract-based spatial statistics-to explore whether damage to specific white matter tracts is associated with particular patterns of cognitive impairment. The commonly affected domains of memory, executive function and information processing speed were investigated in 28 patients in the post-acute/chronic phase following traumatic brain injury and in 26 age-matched controls. Analysis of fractional anisotropy and diffusivity maps revealed widespread differences in white matter integrity between the groups. Patients showed large areas of reduced fractional anisotropy, as well as increased mean and axial diffusivities, compared with controls, despite the small amounts of cortical and white matter damage visible on standard imaging. A stratified analysis based on the presence or absence of microbleeds (a marker of diffuse axonal injury) revealed diffusion tensor imaging to be more sensitive than gradient-echo imaging to white matter damage. The location of white matter abnormality predicted cognitive function to some extent. The structure of the fornices was correlated with associative learning and memory across both patient and control groups, whilst the structure of frontal lobe connections showed relationships with executive function that differed in the two groups. These results highlight the complexity of the relationships between white matter structure and cognition. Although widespread and, sometimes, chronic abnormalities of white matter are identifiable following traumatic brain injury, the impact of these changes on cognitive function is likely to depend on damage to key pathways that link nodes in the distributed brain networks supporting high-level cognitive functions.
Prospective memory (PM) is one of the most important cognitive domains in everyday life. The neuronal basis of PM has been examined by a large number of neuroimaging and neuropsychological studies, and it has been suggested that several cerebral domains contribute to PM. For these activation studies, a constellation of experimental PM trials was developed and adopted to healthy subjects. In the present study, we used a widely used clinical PM assessment battery to determine the lesions attributable to PM failure, with the hypothesis that lesion-symptom analysis using diffusion tensor imaging (DTI) in subjects with diffuse axonal injury (DAI) can reveal the neuronal basis of PM in everyday life.
Fourteen DAI patients (age: range of 18-36, median 24) participated in this study. PM failure was scored in the range of 0-6 using three sub-tests of the Rivermead Behavioural Memory Test. The PM scores of DAI patients were in the range of 2-6 (median 4.5, inter-quartile range 2.25). The severity of axonal injury following DAI was examined using fractional anisotropy (FA), one of the DTI parameters, at voxel level in each subject. We then obtained clusters correlated with PM failure by conducting voxel-based regression analysis between FA values and PM scores. Three clusters exhibited significant positive correlation with PM score, the left parahippocampal gyrus, left inferior parietal lobe, and left anterior cingulate.
This is the first lesion-symptom study to reveal the neuronal basis of PM using DTI on subjects with DAI. Our findings suggest that the neuronal basis of PM is in the left parahippocampal gyrus, left inferior parietal lobe, and/or left anterior cingulate. These findings are similar to those of previous activation studies with loading experimental PM tasks.
Microglia are the primary mediators of the immune defense system of the CNS and are integral to the subsequent inflammatory response. The role of microglia in the injured CNS is under scrutiny, as research has begun to fully explore how postinjury inflammation contributes to secondary damage and recovery of function. Whether microglia are good or bad is under debate, with strong support for a dual role or differential activation of microglia. Microglia release a number of factors that modulate secondary injury and recovery after injury, including pro- and anti-inflammatory cytokines, chemokines, nitric oxide, prostaglandins, growth factors, and superoxide species. Here we review experimental work on the complex and varied responses of microglia in terms of both detrimental and beneficial effects. Addressed in addition are the effects of microglial activation in two examples of CNS injury: spinal cord and traumatic brain injury. Microglial activation is integral to the response of CNS tissue to injury. In that light, future research is needed to focus on clarifying the signals and mechanisms by which microglia can be guided to promote optimal functional recovery.
Traumatic brain injury (TBI) causes a wide spectrum of consequences, such as microglial activation, cerebral inflammation, and focal and diffuse brain injury, as well as functional impairment. In this study we aimed to investigate the effects of acute treatment with minocycline as an inhibitor of microglial activation on cerebral focal and diffuse lesions, and on the spontaneous locomotor activity following TBI. The weight-drop model was used to induce TBI in mice. Microglial activation and diffuse axonal injury (DAI) were detected by immunohistochemistry using CD11b and ss-amyloid precursor protein (ss-APP) immunolabeling, respectively. Focal injury was determined by the measurement of the brain lesion volume. Horizontal and vertical locomotor activities were measured for up to 12 weeks post-injury by an automated actimeter. Minocycline or vehicle were administered three times post-insult, at 5 min (90 mg/kg i.p.), 3 h, and 9 h post-TBI (45 mg/kg i.p.). Minocycline treatment attenuated microglial activation by 59% and reduced brain lesion volume by 58%, yet it did not affect DAI at 24 h post-TBI. More interestingly, minocycline significantly decreased TBI-induced locomotor hyperactivity at 48 h post-TBI, and its effect lasted for up to 8 weeks. Taken together, the results indicate that microglial activation appears to play an important role in the development of TBI-induced focal injury and the subsequent locomotor hyperactivity, and its short-term inhibition provides long-lasting functional recovery after TBI. These findings emphasize the fact that minocycline could be a promising new therapeutic strategy for head-injured patients.
Traumatic brain injury represents the leading cause of death in young individuals. Various animal models have been developed to mimic human closed head injury (CHI). Widely used models induce head injury by lateral fluid percussion, a controlled cortical impact or impact acceleration. The presented model induces a CHI by a standardized weight-drop device inducing a focal blunt injury over an intact skull without pre-injury manipulations. The resulting impact triggers a profound neuroinflammatory response within the intrathecal compartment with high consistency and reproducibility, leading to neurological impairment and breakdown of the blood-brain barrier. In this protocol, we define standardized procedures for inducing CHI in mice and determine various severity grades of CHI through modulation of the weight falling height. In experienced hands, this CHI model can be carried out in as little as 30 s per animal, with additional time required for subsequent posttraumatic analysis and data collection.
One of the severe complications following traumatic brain injury (TBI) is cerebral edema and its effective treatment is of great interest to prevent further brain damage. This study investigated the effects of minocycline, known for its anti-inflammatory properties, on cerebral edema and its respective inflammatory markers by comparing different dose regimens, on oxidative stress and on neurological dysfunction following TBI. The weight drop model was used to induce TBI in mice. The brain water content was measured to evaluate cerebral edema. Inflammatory markers were detected by ELISA (IL-1beta), zymography and Western blot (MMP-9). The oxidative stress marker (glutathione levels) and neurological function were measured by Griffith technique and string test, respectively. Minocycline was administered i.p. once (5 min), twice (5 min and 3 h) or triple (5 min, 3 h and 9 h) following TBI. The first dose of minocycline only varied (45 or 90 mg/kg), whereas the following doses were all at 45 mg/kg. The single and double administrations of minocycline reduced the increase of inflammatory markers at 6 h post-TBI. Minocycline also reduced cerebral edema at this time point, only after double administration and at the high dose regimen, although with no effect on the TBI-induced oxidized glutathione increase. The anti-edematous effect of minocycline persisted up to 24 h, upon a triple administration, and accompanied by a neurological recovery. In conclusion, we reported an anti-edematous effect of minocycline after TBI in mice according to a specific treatment regimen. These findings emphasize that the beneficial effects of minocycline depend on the treatment regimen following a brain injury.
Traumatic brain injury (TBI) remains one of the leading causes of mortality and morbidity worldwide in individuals under the age of 45 years, and, despite extensive efforts to develop neuroprotective therapies, there has been no successful outcome in any trial of neuroprotection to date. In addition to recognizing that many TBI clinical trials have not been optimally designed to detect potential efficacy, the failures can be attributed largely to the fact that most of the therapies investigated have been targeted toward an individual injury factor. The contemporary view of TBI is that of a very heterogenous type of injury, one that varies widely in etiology, clinical presentation, severity, and pathophysiology. The mechanisms involved in neuronal cell death after TBI involve an interaction of acute and delayed anatomic, molecular, biochemical, and physiological events that are both complex and multifaceted. Accordingly, neuropharmacotherapies need to be targeted at the multiple injury factors that contribute to the secondary injury cascade, and, in so doing, maximize the likelihood of a successful outcome. This review focuses on a number of such multifunctional compounds that have shown considerable success in experimental studies and that show maximum promise for success in clinical trials.
The role of tumor necrosis factor (TNF) as an immune mediator has long been appreciated but its function in the brain is still unclear. TNF receptor 1 (TNFR1) is expressed in most cell types, and can be activated by binding of either soluble TNF (solTNF) or transmembrane TNF (tmTNF), with a preference for solTNF; whereas TNFR2 is expressed primarily by microglia and endothelial cells and is preferentially activated by tmTNF. Elevation of solTNF is a hallmark of acute and chronic neuroinflammation as well as a number of neurodegenerative conditions including ischemic stroke, Alzheimer's (AD), Parkinson's (PD), amyotrophic lateral sclerosis (ALS), and multiple sclerosis (MS). The presence of this potent inflammatory factor at sites of injury implicates it as a mediator of neuronal damage and disease pathogenesis, making TNF an attractive target for therapeutic development to treat acute and chronic neurodegenerative conditions. However, new and old observations from animal models and clinical trials reviewed here suggest solTNF and tmTNF exert different functions under normal and pathological conditions in the CNS. A potential role for TNF in synaptic scaling and hippocampal neurogenesis demonstrated by recent studies suggest additional in-depth mechanistic studies are warranted to delineate the distinct functions of the two TNF ligands in different parts of the brain prior to large-scale development of anti-TNF therapies in the CNS. If inactivation of TNF-dependent inflammation in the brain is warranted by additional pre-clinical studies, selective targeting of TNFR1-mediated signaling while sparing TNFR2 activation may lessen adverse effects of anti-TNF therapies in the CNS.
The actions of etazolate (SQ20009) on cultured cortical neurons have been examined in electrophysiological experiments and in receptor binding studies. Etazolate (0.3 to 100 microM) prolongs the duration of spontaneously occurring IPSPs. Higher concentrations of etazolate produce an increase in membrane chloride conductance, an effect which is picrotoxinin and bicuculline sensitive. Etazolate potentiates the response to exogenously applied GABA and acts synergistically with diazepam to enhance GABA-mediated conductance. Etazolate does not increase glycine-mediated conductance changes. Etazolate increases [3H]flunitrazepam binding and stimulates the GABA enhancement of [3H]flunitrazepam binding. In addition, GABA stimulates the etazolate enhancement of [3H]flunitrazepam binding. The etazolate-mediated increases in binding are Cl- dependent and picrotoxinin and bicuculline sensitive. The dose response relationships for etazolate-mediated effects are similar in physiological experiments and in binding studies. These data suggest that etazolate interacts with the postsynaptic GABA receptor complex at a site distinct from either the GABA recognition site or the benzodiazepine binding site to enhance GABA-mediated inhibition and to increase benzodiazepine binding.
We have investigated the possible effect of estrogen on the metabolism of the Alzheimer amyloid precursor protein (APP). Using a cell line that contains high levels of estrogen receptors, we have found that treatment with physiological concentrations of 17 beta-estradiol is associated with accumulation in the conditioned medium of an amino-terminal cleavage product of APP (soluble APP or protease nexin-2), indicative of non-amyloidogenic processing. There were no obvious changes in the levels of intracellular immature or mature APP holoproteins, suggesting that estrogen may increase the secretory metabolism of APP.
This chapter highlights the controversies concerning the role of brain inflammation elicited after brain trauma. In clinical practice, classification of primary brain injury is determined by neuroimaging scans that reveal specific types of damage, including skull fractures, tissue lacerations, subdural or epidural hemorrhages, and contusions, which constitute the hallmarks of focal Traumatic brain injury (TBI). The pathological alterations resulting from brain injury trigger multiple biochemical cascades that lead to the release of neurotoxic substances that ultimately exacerbate neuronal cell death. Much research effort has been dedicated to establishing the roles of excitotoxicity, the oxidative pathway, and cerebral inflammation after brain injury. Cellular and molecular responses to TBI, including inflammation, may vary according to genetic patterns, use of animal strains, and the methods used to produce brain injuries. It is clear that cryolesion can hardly be compared to fluid percussion injury or diffuse axonal damage. Also, individual laboratories use distinctly different behavioral tests to assess outcomes, making the comparison of studies almost impossible. Despite this experimental variability, the common consensus today remains: Inflammation possesses both beneficial and detrimental properties, as complete ablation of cytokines and cytokine receptors generates exacerbated tissue and neurological damage after TBI.
Background: EHT0202 (etazolate hydrochloride) is a new compound exhibiting both potential disease-modifying and symptomatic treatment properties in Alzheimer's Disease increasing alpha-secretase activity and sAPP alpha secretion, as well as acting as a GABA-A receptor modulator and as a PDE-4 inhibitor. Methods: This pilot, random-ized, double-blind, placebo-controlled, parallel group, multicentre, Phase IIA study was conducted in 159 randomized patients suffering from mild to moderate Alzheimer's Disease. EHT0202 (40 or 80mg bid) or placebo was administered as adjunctive therapy to one acetylcholinesterase inhibitor over a 3-month period. This study was designed to assess the clinical safety and tolerability of EHT0202 as a primary objective, with secondary endpoints (cognitive function, daily living activities, behaviour, caregiver burden and global functioning) included to explore clinical efficacy of EHT0202 versus placebo. Results: EHT0202 was shown to be safe and generally well tolerated. Dose-dependent numbers of early withdrawal and central nervous system related adverse events were observed. As expected, since the study was not powered and not designed to show drug efficacy, and except for ratings on the ADCS-ADL scale, no significant differences were seen between treatment groups. Conclusions: These first encouraging safety results do support further development of EHT0202 in order to assess its clinical efficacy and to confirm its tolerability in a larger cohort of Alzheimer patients and for a longer period.
gamma-Aminobutyric acid_A (GABA_A) receptors are ligand-gated ion channels that mediate inhibitory synaptic transmission in the central nervous system. The role of protein phosphorylation in the modulation of GABA_A receptor function was examined with cells transiently transfected with GABA_A receptor subunits. GABA_A receptors consisting of the alpha_1 and beta_1 or the alpha_1, beta_1, and gamma_2 subunits were directly phosphorylated on the beta_1 subunit by adenosine 3',5'-monophosphate (cAMP)-dependent protein kinase (PKA). The phosphorylation decreased the amplitude of the GABA response of both receptor types and the extent of rapid desensitization of the GABA_A receptor that consisted of the alpha_1 and beta_1 subunits. Site-specific mutagenesis of the serine residue phosphorylated by PKA completely eliminated the PKA phosphorylation and modulation of the GABA_A receptor. In primary embryonic rat neuronal cell cultures, a similar regulation of GABA_A receptors by PKA was observed. These results demonstrate that the GABA_A receptor is directly modulated by protein phosphorylation and suggest that neurotransmitters or neuropeptides that regulate intracellular cAMP levels may modulate the responses of neurons to GABA and consequently have profound effects on synaptic excitability.
The implication of cyclooxygenase (COX) type 2 in post-traumatic consequences is so far controversial. In experimental models of traumatic brain injury (TBI), genetic disruption or pharmacological inhibition of COX-2 has been shown to be neuroprotective, deleterious or without effect. Therefore, the aim of our study was to investigate the effect of COX-2 inhibition against neurological deficit and brain œdema after TBI that was induced by mechanical percussion in male Swiss mice. Despite the increased level and activity of COX-2, its inhibition either with nimesulide (12mg/kg) or meloxicam (2mg/kg) modified neither the neurological score nor the brain water content that were evaluated at 6 and 24h after injury. Interestingly, the non-selective COX inhibition with indomethacin (5mg/kg) significantly promoted neurological recovery at 6 and 24h after trauma, without improving brain œdema. In conclusion, the present study yields considerable evidence that COX-2 may not solely constitute an interesting target for the treatment of TBI consequences. Our data point to a potentially deleterious role of COX-1 in the development of neurological impairment in brain-injured mice. However, the neuroprotective mechanism of indomethacin remains to be clarified.
Inhibition of the bradykinin B2 receptor type (B2R) has been shown to improve neurological outcome in models of focal traumatic brain injury. However, the involvement of B2R in trauma-induced diffuse injury has not yet been explored. This is an important point, since in humans a pattern of diffuse injury is commonly found in severely injured patients and has been associated with a poor neurological outcome and prognosis. Using the non-peptide B2R antagonist LF 16-0687 Ms and B2R null (B2R-/-) mice, we investigated the role of B2R in a model of closed head trauma (CHT). LF 16-0687 Ms given 30 min after injury reduced the neurological deficit by 26% and the cerebral edema by 22% when evaluated 4 h after CHT. Neurological function after CHT was improved in B2R-/- mice compared to B2R+/+ mice, although there was no difference in the development of brain edema. Treatment with LF 16-0687 Ms and B(2)R gene deletion decreased the accumulation of neutrophils at 24 h after CHT (50% and 36%, respectively). In addition, the inducible NO synthase (iNOS) mRNA level increased markedly, and this was reduced by LF 16-0687 Ms. Taken together, these data support a detrimental role of B2R in the development of the neurological deficit and of the inflammatory secondary damage resulting from diffuse traumatic brain injury. Therefore, blockade of bradykinin B2 receptors might represent an attractive therapeutic approach in the pharmacological treatment of traumatic brain injury.
Treatment with sAPPα, the product of non-amyloidogenic processing of the amyloid precursor protein (APP) has been shown to be protective following diffuse traumatic brain injury (TBI), by improving motor outcome and reducing axonal injury. However the effects of treatment with sAPPα following a focal TBI have yet to be determined. To investigate this, mice were subjected to a controlled cortical impact injury and treated with either sAPPα or its vehicle at 30 min post-injury. Following treatment with sAPPα the mice showed a significant improvement in motor and cognitive function early following injury, as determined on the ledged beam and Barnes Maze, respectively, relating to a more rapid rate of recovery. However the effect of treatment with sAPPα was not as dramatic as that seen previously following a diffuse injury. Nonetheless, these improvements in functional outcome were acompanied by a small but significant improvement in the amount of cortical and hippocampal at 7 days post-injury, and provide further support for the efficacy of sAPPα as a potential neuroprotective agent following TBI.
Comorbidity of cognitive and stress disorders is a common clinical sequel of traumatic brain injury (TBI) that is essentially determined by the site and severity of the insult, but also by the extent of the ensuing neuroinflammatory response. The present study sought to examine the late effects of closed-head TBI on memory function and anxiety in mice, in order to further examine the potential efficacy of an acute anti-inflammatory treatment with minocycline. The mouse model of closed-head injury by mechanical percussion was applied on anesthetized Swiss mice. The treatment protocol included three injections of minocycline (i.p.) at 5 min (90 mg/kg), 3 h and 9 h (45 mg/kg) post-TBI. The Novel Object Recognition Test as well as the Elevated Plus Maze (EPM) and Elevated Zero Maze (EZM) tasks were employed to assess post-TBI memory and anxiety respectively. Our results revealed a recognition memory deficit that was significant up to at least 13 weeks post-TBI. However, neither EPM nor EZM revealed any alteration in post-TBI anxiety levels albeit some mild disinhibition. Most importantly, minocycline was able to attenuate the memory impairment in an effective and lasting manner, highlighting its therapeutic potential in TBI.
J. Neurochem. (2012) 120 (Suppl. 1), 46–54.
Alpha-secretase-mediated cleavage of the amyloid precursor protein (APP) releases the neuroprotective APP fragment sαAPP and prevents amyloid β peptide (Aβ) generation. Moreover, α-secretase-like cleavage of the Aβ transporter ‘receptor for advanced glycation end products’ counteracts the import of blood Aβ into the brain. Assuming that Aβ is responsible for the development of Alzheimer’s disease (AD), activation of α-secretase should be preventive. α-Secretase-mediated APP cleavage can be activated via several G protein-coupled receptors and receptor tyrosine kinases. Protein kinase C, mitogen-activated protein kinases, phosphatidylinositol 3-kinase, cAMP and calcium are activators of receptor-induced α-secretase cleavage. Selective targeting of receptor subtypes expressed in brain regions affected by AD appears reasonable. Therefore, the PACAP receptor PAC1 and possibly the serotonin 5-HT6 receptor subtype are promising targets. Activation of APP α-secretase cleavage also occurs upon blockade of cholesterol synthesis by statins or zaragozic acid A. Under physiological statin concentrations, the brain cholesterol content is not influenced. Statins likely inhibit Aβ production in the blood by α-secretase activation which is possibly sufficient to inhibit AD development. A disintegrin and metalloproteinase 10 (ADAM10) acts as α-secretase on APP. By targeting the nuclear retinoic acid receptor β, the expression of ADAM10 and non-amyloidogenic APP processing can be enhanced. Excessive activation of ADAM10 should be avoided because ADAM10 and also ADAM17 are not APP-specific. Both ADAM proteins cleave various substrates, and therefore have been associated with tumorigenesis and tumor progression.
J. Neurochem. (2011) 118, 1032–1042.
Mild traumatic brain injury (mTBI) patients do not show clear structural brain defects and, in general, do not require hospitalization, but frequently suffer from long-lasting cognitive, behavioral and emotional difficulties. Although there is no current effective treatment or cure for mTBI, tumor necrosis factor-alpha (TNF-α), a cytokine fundamental in the systemic inflammatory process, represents a potential drug target. TNF-α levels increase after mTBI and may induce or exacerbate secondary damage to brain tissue. The present study evaluated the efficacy of the experimental TNF-α synthesis inhibitor, 3,6′-dithiothalidomide, on recovery of mice from mTBI in a closed head weight-drop model that induces an acute elevation in brain TNF-α and an impairment in cognitive performance, as assessed by the Y-maze, by novel object recognition and by passive avoidance paradigms at 72 h and 7 days after injury. These impairments were fully ameliorated in mice that received a one time administration of 3,6′-dithiothalidomide at either a low (28 mg/kg) or high (56 mg/kg) dose provided either 1 h prior to injury, or at 1 or 12 h post-injury. Together, these results implicate TNF-α as a drug target for mTBI and suggests that 3,6′-dithiothalidomide may act as a neuroprotective drug to minimize impairment.
The large number of transgenic mice realized thus far with different purposes allows addressing new questions, such as which animals, over the entire set of transgenic animals, show a specific behavioural abnormality. In the present study, we have used a metanalytical approach to organize a database of genetic modifications, brain lesions and pharmacological interventions that increase locomotor activity in animal models. To further understand the resulting data set, we have organized a second database of the alterations (genetic, pharmacological or brain lesions) that reduce locomotor activity. Using this approach, we estimated that 1.56% of the genes in the genome yield to hyperactivity and 0.75% of genes produce hypoactivity when altered.
Traumatic brain injury (TBI) is a major health and socioeconomic problem that affects all societies. In recent years, patterns of injury have been changing, with more injuries, particularly contusions, occurring in older patients. Blast injuries have been identified as a novel entity with specific characteristics. Traditional approaches to the classification of clinical severity are the subject of debate owing to the widespread policy of early sedation and ventilation in more severely injured patients, and are being supplemented with structural and functional neuroimaging. Basic science research has greatly advanced our knowledge of the mechanisms involved in secondary damage, creating opportunities for medical intervention and targeted therapies; however, translating this research into patient benefit remains a challenge. Clinical management has become much more structured and evidence based since the publication of guidelines covering many aspects of care. In this Review, we summarise new developments and current knowledge and controversies, focusing on moderate and severe TBI in adults. Suggestions are provided for the way forward, with an emphasis on epidemiological monitoring, trauma organisation, and approaches to management.
Increasing evidence suggests that interleukin-1β (IL-1β) is a key mediator of the inflammatory response following traumatic brain injury (TBI). Recently, we showed that intracerebroventricular administration of an IL-1β-neutralizing antibody was neuroprotective following TBI in mice. In the present study, an anti-IL-1β antibody or control antibody was administered intraperitoneally following controlled cortical injury (CCI) TBI or sham injury in 105 mice and we extended our histological, immunological and behavioral analysis. First, we demonstrated that the treatment antibody reached target brain regions of brain-injured animals in high concentrations (> 11 nm) remaining up to 8 days post-TBI. At 48 h post-injury, the anti-IL-1β treatment attenuated the TBI-induced hemispheric edema (P < 0.05) but not the memory deficits evaluated using the Morris water maze (MWM). Neutralization of IL-1β did not influence the TBI-induced increases (P < 0.05) in the gene expression of the Ccl3 and Ccr2 chemokines, IL-6 or Gfap. Up to 20 days post-injury, neutralization of IL-1β was associated with improved visuospatial learning in the MWM, reduced loss of hemispheric tissue and attenuation of the microglial activation caused by TBI (P < 0.05). Motor function using the rotarod and cylinder tests was not affected by the anti-IL-1β treatment. Our results suggest an important negative role for IL-1β in TBI. The improved histological and behavioral outcome following anti-IL-1β treatment also implies that further exploration of IL-1β-neutralizing compounds as a treatment option for TBI patients is warranted.
Previous animal and human studies have demonstrated that chronic treatment with several different antidepressants can stimulate neurogenesis, neural remodeling, and synaptic plasticity in the normal hippocampus. Imipramine is a commonly used tricyclic antidepressant (TCA). We employed a controlled cortical impact (CCI) mouse model of traumatic brain injury (TBI) to assess the effect of imipramine on neurogenesis and cognitive and motor function recovery after TBI. Mice were given daily imipramine injections for either 2 or 4 weeks after injury. Bromodeoxyuridine (BrdU) was administered 3-7 days post-brain injury to label the cells that proliferated as a result of the injury. We assessed the effects of imipramine on post-traumatic motor function using a beam-walk test and an assessment of cognitive function: the novel object recognition test (NOR). Histological analyses were performed at 2 and 4 weeks after CCI. Brain-injured mice treated with imipramine showed significantly improved cognitive function compared to a saline-treated group (p<0.001). However, there was no significant difference in motor function recovery between imipramine-treated and saline-treated mice. Histological examination revealed increased preservation of proliferation of Ki-67- and BrdU-positive cells in the hippocampal dentate gyrus (DG) at 2 and 4 weeks after TBI. Immunofluorescence double-labeling with BrdU and neuron-specific markers at 4 weeks after injury showed that most progenitors became neurons in the DG and astrocytes in the hilus. Notably, treatment with imipramine increased preservation of the total number of newly-generated neurons. Our findings provide direct evidence that imipramine treatment contributes to cognitive improvement after TBI, perhaps by enhanced hippocampal neurogenesis.
EHT0202 (etazolate hydrochloride) is a new compound exhibiting both potential disease-modifying and symptomatic treatment properties in Alzheimer's Disease increasing alpha-secretase activity and sAPP alpha secretion, as well as acting as a GABA-A receptor modulator and as a PDE-4 inhibitor.
This pilot, randomized, double-blind, placebo-controlled, parallel group, multicentre, Phase IIA study was conducted in 159 randomized patients suffering from mild to moderate Alzheimer's Disease. EHT0202 (40 or 80 mg bid) or placebo was administered as adjunctive therapy to one acetylcholinesterase inhibitor over a 3-month period. This study was designed to assess the clinical safety and tolerability of EHT0202 as a primary objective, with secondary endpoints (cognitive function, daily living activities, behaviour, caregiver burden and global functioning) included to explore clinical efficacy of EHT0202 versus placebo.
EHT0202 was shown to be safe and generally well tolerated. Dose-dependent numbers of early withdrawal and central nervous system related adverse events were observed. As expected, since the study was not powered and not designed to show drug efficacy, and except for ratings on the ADCS-ADL scale, no significant differences were seen between treatment groups.
These first encouraging safety results do support further development of EHT0202 in order to assess its clinical efficacy and to confirm its tolerability in a larger cohort of Alzheimer patients and for a longer period.
Traumatic brain injury (TBI) causes secondary biochemical changes that contribute to subsequent tissue damage and associated neuronal cell death. Neuroprotective treatments that limit secondary tissue loss and/or improve behavioral outcome have been well established in multiple animal models of TBI. However, translation of such neuroprotective strategies to human injury have been disappointing, with the failure of more than thirty controlled clinical trials. Both conceptual issues and methodological differences between preclinical and clinical injury have undoubtedly contributed to these translational difficulties. More recently, changes in experimental approach, as well as altered clinical trial methodologies, have raised cautious optimism regarding the outcomes of future clinical trials. Here we critically review developing experimental neuroprotective strategies that show promise, and we propose criteria for improving the probability of successful clinical translation.
Etazolate is a phosphodiesterase 4 (PDE4) inhibitor and GABAA receptor modulator that also stimulates alpha-secretase activity and neurotrophic soluble amyloid precursor protein (sAPPalpha) production, currently developed as a possible Alzheimer's disease therapeutic. In this study two doses of etazolate were tested for cognitive effects in normally aged rats, using a complex spatial learning and memory task that emphasized two naturally occurring behaviors in rodents, foraging for food and returning large pieces of found food to a safe home location. Both etazolate doses completely prevented both (1) a foraging deficit that developed in untreated aged rats over the course of the test, as well as (2) a trial-specific deficit in memory for previously visited food locations that also developed over the course of the test in untreated aged rats. Both doses also significantly reduced a separate memory deficit for changing locations of the animals' home box, plus completely prevented a significant tendency for untreated aged animals to attempt entry into similar-appearing but incorrect home boxes. The combined behavioral data demonstrate positive effects of etazolate on separate age-related cognitive deficits, using a complex task based on naturally occurring rodent behaviors.
We present the photochemically induced olfactory bulbectomy (P-bulbectomy) as a novel method to ablate the olfactory bulb thus inducing an animal model of depression. The photosensitizer Rose Bengal was injected through the tail vein and then the cool halogen light illuminated the skull region overlying of the olfactory bulb for 10 min. Two weeks after surgery, P-bulbectomy had completely removed olfactory bulb uniformly in all animals. P-bulbectomy induced typical depression-related behaviors such as hyperactivity in the open field test and an enhancement of immobility time and in the forced swimming test. Depression-related neurohistological phenomenon was also seen; reduction of choline-acetyltransferase-positive cell numbers in the medial septum and a decline in cell proliferation in the dentate gyrus of hippocampus. This study shows that P-bulbectomy may be a convenient and reproducible experimental method to produce an animal model of depression.
Olfactory functions are not systematically evaluated following traumatic brain injury (TBI). This study aimed at comparing two smell tests that are used in a clinical setting.
The University of Pennsylvania Smell Identification Test (UPSIT) and the Alberta Smell Test were compared in terms of assessment time, cost and diagnosis. Parameters associated with olfactory loss such as injury severity, type of cerebral lesion and depressive data were considered. Forty-nine TBI patients admitted to an outpatient rehabilitation programme took part in this experiment.
The scores of the two smell tests were significantly correlated. Both tests indicated that patients with frontal lesion performed significantly worse than patients with other types of lesion. Mood and injury severity were not associated with olfactory impairment when age was taken into account. Between 40-44% of the patients showing olfactory impairments were not aware of their deficit.
Since a significant proportion of the patients showing olfactory impairments were not aware of their deficit, it is recommended than clinicians systematically evaluate olfactory functions using the Alberta Smell test. To refine their diagnosis, the UPSIT can also be used.
Neuroinflammatory conditions such as traumatic brain injury, aging, Alzheimer's disease, and Down syndrome are often associated with cognitive dysfunction. Much research has targeted inflammation as a causative mediator of these deficits, although the diverse cellular and molecular changes that accompany these disorders obscure the link between inflammation and impaired memory. Therefore, we used a transgenic mouse model with a dormant human IL-1beta excisional activation transgene to direct overexpression of IL-1beta with temporal and regional control. Two weeks of hippocampal IL-1beta overexpression impaired long-term contextual and spatial memory in both male and female mice, while hippocampal-independent and short-term memory remained intact. Human IL-1beta overexpression activated glia, elevated murine IL-1beta protein and PGE(2) levels, and increased pro-inflammatory cytokine and chemokine mRNAs specifically within the hippocampus, while having no detectable effect on inflammatory mRNAs in the liver. Sustained neuroinflammation also reduced basal and conditioning-induced levels of the plasticity-related gene Arc.
Glial activation and neuroinflammation occur in neurodegenerative disease and brain injury, however their presence in normal brain aging suggests that chronic neuroinflammation may be a factor in age-related dementia. Few studies have investigated the impact of sustained elevation of hippocampal interleukin-1beta, a pro-inflammatory cytokine upregulated during aging and Alzheimer's disease, on cognition in mice. We utilized the IL-1beta(XAT) transgenic mouse to initiate bilateral hippocampal overexpression of interleukin-1beta to determine the influence of sustained neuroinflammation independent of disease pathology. Fourteen days following transgene induction, adult male and female IL-1beta(XAT) mice were tested on non-spatial and spatial versions of the Morris water maze. For the spatial component, one retention trial was conducted 48 h after completion of a 3 day acquisition protocol (eight trials per day). Induction of IL-1beta did not impact non-spatial learning, but was associated with delayed acquisition and decreased retention of the spatial task. These behavioral impairments were accompanied by robust reactive gliosis and elevated mRNA expression of inflammatory genes in the hippocampus. Our results suggest that prolonged neuroinflammation response per se may impact mnemonic processes and support the future application of IL-1beta(XAT) transgenic mice to investigate chronic neuroinflammation in age- and pathology-related cognitive dysfunction.
Traumatic brain injury (TBI) -induced brain edema can be reduced by acute progesterone (PROG) treatment in young adult males and females, and in aged males. To extend these findings we tested these hypotheses: 1. Acute PROG treatment post-TBI will reduce cortical edema in aged females as much as in young adults. 2. TBI will induce edema in sub-cortical structures (SCS): the thalamus (TH), hypothalamus (HT), brain stem (BS) and anterior pituitary (AP). 3. Acute, systemic PROG treatment post-TBI will reduce edema in SCS.
Young adult (n = 42) and aged (n = 40), bilaterally ovariectomized rats were given medial frontal cortical (MFC) contusion injury, treated with PROG (16 mg/kg body weight) or vehicle at 1, 6 and 24 hours post-injury and killed at 6, 24 and 48 hours post-injury. Their brains were removed and the target areas isolated and measured for water content.
TBI induced cortical and delayed sub-cortical edema. Acute PROG treatment decreased this edema. At 6 hours post-TBI serum PROG levels were substantially elevated in both young and aged, PROG-treated, groups, but were higher in the latter.
Acute PROG treatment post-TBI could prove an effective intervention to prevent or attenuate systemic, post-injury cortical and sub-cortical edema in young and aged females.
This study was designed to investigate the long-term effects of simvastatin treatment after traumatic brain injury (TBI) in rats.
Adult female Wistar rats (n = 24) were injured with controlled cortical impact and divided into 3 groups. The first 2 groups were treated with simvastatin (0.5 or 1.0 mg/kg) administered orally for 14 days starting 1 day after TBI. The third group (control) received phosphate-buffered saline orally for 14 days. Neurological functional outcome was measured with modified neurological severity scores performed 1 day before TBI; on days 1, 4, 7, 14 after TBI; and biweekly thereafter. All animals were sacrificed 3 months after TBI. Brain tissues of half of the animals were processed for preparation of paraffin-embedded sections for immunohistological studies. The remaining half were frozen for enzyme-linked immunosorbent assay studies for quantification of brain-derived neurotrophic factor (BDNF) in the hippocampus and cortex.
The results showed that both doses of simvastatin significantly improved functional outcome compared with the control, with no difference between the 2 doses. Simvastatin treatment of 1.0 mg/kg increased the number of morphologically intact neurons in the hippocampus, but treatment of 0.5 mg/kg had no significant effect. Enzyme-linked immunosorbent assay studies showed that 0.5 mg/kg simvastatin significantly increased BDNF levels within the hippocampus, but 1.0 mg/kg had no significant effect. Neither dose had any effect on BDNF levels within the cortex.
Simvastatin treatment provides long-lasting functional improvement after TBI in rats. It also enhances neuronal survival in the hippocampus and increases BDNF levels in the hippocampus secondary to simvastatin treatment.
The presumed pathogenesis of posttraumatic anosmia is stretching or shearing of the olfactory nerves in a coup-contracoup head contusion. Direct injury to the brain is an alternate mechanism of injury. In this study we report a case where direct injury to the brain is the probable mechanism of injury.
A case report was performed.
A 55-year-old man presented with loss of smell beginning 1 month after a closed head injury with loss of consciousness. The MRI showed posttraumatic scarring in the region of the olfactory bulbs.
This case suggests that central nervous system injury to the olfactory bulbs and tracts may be a mechanism of posttraumatic anosmia.
Although the concepts of secondary injury and neuroprotection after neurotrauma are experimentally well supported, clinical trials of neuroprotective agents in traumatic brain injury or spinal cord injury have been disappointing. Most strategies to date have used drugs directed toward a single pathophysiological mechanism that contributes to early necrotic cell death. Given these failures, recent research has increasingly focused on multifunctional (i.e., multipotential, pluripotential) agents that target multiple injury mechanisms, particularly those that occur later after the insult. Here we review two such approaches that show particular promise in experimental neurotrauma: cell cycle inhibitors and small cyclized peptides. Both show extended therapeutic windows for treatment and appear to share at least one important target.
To determine the incidence of olfactory dysfunction after head trauma using clinical and radiologic findings, quantitative assessment, and electro-physiologic methods.
A total of 190 patients with head trauma of different severity (n = 32 with mild traumatic brain injury (TBI), n = 94 with signs of moderate TBI, and n = 64 with severe TBI) 6 to 32 months prior to the study.
Patients were selected retrospectively, surveyed by telephone (n = 190), and screened for olfactory function with Brief Smell Identification Test (n = 82). Those with olfactory dysfunction were assessed as outpatients using the Sniffin' Sticks (n = 19) and olfactory-evoked potential recording (n = 16).
Twenty-one participants (11%) reported a decreased sense of smell after trauma. The incidence of olfactory dysfunction after head injury was 12.8%. The results of the odor-evoked potentials were heterogeneous. A significant correlation was found between olfactory dysfunction and the appearance of skull base fractures and intracranial hemorrhage or hematoma.
The site of trauma may be more relevant to prognosis than a simple probability (of olfactory loss) based on incidence. Odor-evoked potentials indicate that functional anosmia can occur even when there is some evidence of intact olfactory nerve function.
Altered processing of the amyloid precursor protein (APP) is a central event in the formation of amyloid deposits in the brains
of individuals with Alzheimer's disease. To investigate whether cellular APP processing is controlled by cell-surface neurotransmitter
receptors, human embryonic kidney (293) cell lines were transfected with the genes for human brain muscarinic acetylcholine
receptors. Stimulation of m1 and m3 receptor subtypes with carbachol increased the basal release of APP derivatives within
minutes of treatment, indicating that preexisting APP is released in response to receptor activation. Receptor-activated APP
release was blocked by staurosporine, suggesting that protein kinases mediate neurotransmitter receptor-controlled APP processing.
All of the principal types of brain damage that occur in man as a result of a non-missile head injury, viz. cerebral contusions, intracranial haematoma, raised intracranial pressure, diffuse axonal injury, diffuse hypoxic damage, and diffuse swelling have been produced in subhuman primates subjected to inertial, i.e. non-impact, controlled angular acceleration of the head through 60 degrees in the sagittal, oblique and lateral planes.
In addition to being the major excitatory neurotransmitter in the mammalian brain, glutamate is believed to play a key role in the regulation of neurite outgrowth and synaptogenesis during development. In cultured embryonic hippocampal pyramidal neurons, glutamate inhibits dendrite outgrowth by a mechanism involving elevation of intracellular-free calcium levels ([Ca2+]i). In the present study, secreted forms of the beta-amyloid precursor protein (APPss) counteracted the inhibitory effect of glutamate on dendrite outgrowth in cultured embryonic hippocampal neurons. The prolonged elevation of [Ca2+]i normally induced by glutamate was significantly attenuated in neurons that had been pretreated with 2-10 nM of APPs695 or APPs751. Immunocytochemistry with beta-amyloid precursor protein antibodies showed that immunoreactivity was concentrated in axons and, particularly, in their growth cones. Because beta-amyloid precursor proteins are axonally transported, and APPss can be released from axon terminals/growth cones in response to electrical activity, the present findings suggest that APPss may play a role in developmental and synaptic plasticity by modulating dendritic responses to glutamate.
Alternative processing of the beta-amyloid precursor protein (beta APP) can result in liberation of either secreted forms of beta APP (APPSs), which may play roles in neuronal plasticity and survival, or amyloid beta-peptide (A beta), which can be neurotoxic. In rat hippocampal cell cultures A beta 1-40 caused a time- and concentration-dependent reduction in neuronal survival. APPS695 and APPS751 significantly reduced A beta-induced injury in a concentration-dependent manner. A beta caused an elevation of intracellular calcium levels ([Ca2+]i) which was significantly attenuated by APPSs. A beta also caused induction of reactive oxygen species (measured using the oxidation-sensitive fluorescent dye 2,7-dichlorofluorescein) which was also attenuated by APPSs. A beta-induced neurotoxicity and elevations of [Ca2+]i were attenuated by vitamin E, suggesting the involvement of free radicals in A beta-induced loss of calcium homeostasis and neuronal injury. The APPSs protected neurons against oxidative injury caused by exposure to iron. Taken together, the data indicate that A beta kills neurons by causing free radical production and increased [Ca2+]i. APPSs can protect neurons against such free radical- and Ca(2+)-mediated injury. These findings support the hypothesis that altered processing of beta APP contributes to neuronal injury in Alzheimer's disease.
One function of Alzheimer amyloid protein precursor (APP) is the regulation of growth and differentiation in several types of cells, including fibroblasts, PC12 cells, and neurons. This activity is represented by a small stretch of amino acids in the center of the molecule around RERMS. The APP 17-mer peptide containing the RERMS domain supported survival and neurite extension of rat cortical neurons in a dose-dependent and sequence-specific manner. The APP fragment synthesized in Escherichia coli supported the survival and neurite extension of rat cortical neurons, whereas the mutant APP fragment lacking the 30 amino acids around the RERMS domain had drastically reduced activity to support the survival and neurite extension. The current study established APP as a neuron survival factor and determined that the sequence around RERMS is important for this function.
The beta-amyloid precursor protein (beta APP) is a membrane-spanning glycoprotein that is the source of the beta-amyloid peptide (beta AP) which accumulates as senile plaques in the brains of patients with Alzheimer's disease. beta APP is normally processed such that a cleavage occurs within the beta AP, liberating secreted forms of beta APP (APPss) from the cell. The neuronal functions of these forms are unknown. We now report that APPss have a potent neuroprotective action in cultured rat hippocampal and septal neurons and in human cortical neurons. APPs695 and APPs751 protected neurons against hypoglycemic damage, and the neuroprotection was abolished by antibodies to a specific region common to both APPs695 and APPs751. APPss caused a rapid and prolonged reduction in [Ca2+]i and prevented the rise in [Ca2+]i that normally mediated hypoglycemic damage. APPss also protected neurons against glutamate neurotoxicity, effectively raising the excitotoxic threshold. APPss may normally play excitoprotective and neuromodulatory roles. Alternative processing of APPss in Alzheimer's disease may contribute to neuronal degeneration by compromising the normal function of APPss and by promoting the deposition of beta AP.