Temporal lobe epilepsy is the most common form of epilepsy in humans. Caspase activation is a mechanism of cell death induced by seizures. Tellurium (IV) compounds present antitumoral, immunomodulatory and neuroprotective effects due to their ability to inhibit cysteine proteases. We studied the activity of caspase-1, -3 and -8 in the hippocampus of rats exhibiting status epilepticus induced by pilocarpine. All three caspases were activated. Tellurium (IV) compounds RF-07, RF-03 and AS-101 inhibited caspases in vitro, showing high second-order inhibition rate constants. The intraperitoneal injection of RF-07 prior to pilocarpine suppressed the behavioral and electroencephalographic seizure occurrence. According to our results, the caspases are activated as early as 90 min following SE. Tellurium (IV) compounds exerted anticonvulsant effects associated with the inhibition of caspases. These results suggest a promising therapeutic potential of organotellurium (IV) compounds as antiepileptogenic agents.
The identification of novel molecular targets crucially involved in motor neuron degeneration/survival is a necessary step for the development of hopefully more effective therapeutic strategies for amyotrophic lateral sclerosis (ALS) patients. In this view, S1R, an endoplasmic reticulum (ER)-resident receptor with chaperone-like activity, has recently attracted great interest. S1R is involved in several processes leading to acute and chronic neurodegeneration, including ALS pathology. Treatment with the S1R agonist PRE-084 improves locomotor function and motor neuron survival in presymptomatic and early symptomatic mutant SOD1-G93A ALS mice. Here, we tested the efficacy of PRE-084 in a model of spontaneous motor neuron degeneration, the wobbler mouse (wr) as a proof of concept that S1R may be regarded as a key therapeutic target also for ALS cases not linked to SOD1 mutation. Increased staining for S1R was detectable in morphologically spared cervical spinal cord motor neurons of wr mice both at early (6th week) and late (12th week) phases of clinical progression. S1R signal was also detectable in hypertrophic astrocytes and reactive microglia of wr mice. Chronic treatment with PRE-084 (three times a week, for 8weeks), starting at symptom onset, significantly increased the levels of BDNF in the gray matter, improved motor neuron survival and ameliorated paw abnormality and grip strength performance. In addition, the treatment significantly reduced the number of reactive astrocytes whereas, that of CD11b+ microglial cells was increased. A deeper evaluation of microglial markers revealed significant increased number of cells positive for the pan-macrophage marker CD68 and of CD206+ cells, involved in tissue restoration, in the white matter of PRE-084-treated mice. The mRNA levels of TNF-α and IL-1β were not affected by PRE-084 treatment. Thus, our results support pharmacological manipulation of S1R as a promising strategy to cure ALS and point to increased availability of growth factors and modulation of astrocytosis and of macrophage/microglia as part of the mechanism involved in S1R-mediated neuroprotection.
Neuropathic pain is a devastating neurological disease that seriously affects quality of life in patients. The mechanisms leading to the development and maintenance of neuropathic pain are still poorly understood. However, recent evidence points towards a role of spinal microglia in the modulation of neuronal mechanisms. In this context, cannabinoids are thought to modulate synaptic plasticity as well as glial functions. Here, we have investigated the effect of chronic treatment with a selective agonist of cannabinoid type 2 receptor (CB2), 1-(2',4'-dichlorophenyl)-6-methyl-N-cyclohexylamine-1,4-dihydroindeno[1,2-c]pyrazole-3 carboxamide (NESS400), on pain thresholds in the spared nerve injury (SNI) model in the mouse and on the distribution and activation of spinal microglia. Repeated treatment with NESS400 (4 mg/kg) significantly alleviated neuropathic mechanical allodynia and thermal hyperalgesia. In the dorsal horn (L4-L6) of neuropathic mice microglia activation (quantification of the length of microglial processes) and astrocytosis were associated with CB2 receptor over-expression on both cell types. Treatment with NESS400 significantly reduced the number of hypertrophic microglia while leaving microglial cell number unaffected and reduced astrogliosis. Moreover, prolonged administration of NESS400 reduced mRNA expression of pro-inflammatory markers and enhanced anti-inflammatory marker gene expression in dorsal horn extracts. In conclusion, we show that selective CB2 receptor stimulation prevents thermal hyperalgesia, alleviates mechanical allodynia and facilitates the proliferation of anti-inflammatory microglial phenotype in the ipsilateral dorsal horn of the spinal cord in SNI mice.
Promethazine (PMZ) is an FDA-approved antihistaminergic drug that was identified as a potentially neuroprotective compound in the NINDS screening program. PMZ accumulates in brain mitochondria in vivo and inhibits Ca2+-induced mitochondrial permeability transition pore (PTP) in rat liver mitochondria in vitro. We hypothesized that PMZ may have a protective effect in a mitochondrial toxin model of Parkinson's disease (PD). Mice treated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) sustained a significant loss of dopaminergic neurons within the SNpc that was strongly attenuated by PMZ treatment. However, neither striatal MPP+ concentrations nor MPTP-induced inhibition of mitochondrial complex I were affected by PMZ treatment. In isolated mouse brain mitochondria, PMZ partially prevented and reversed MPP+-induced depolarization of membrane potential and inhibited the Ca2+-induced PTP in brain mitochondria. The sum of data indicates that PMZ is a strong neuroprotective agent capable of protecting dopaminergic neurons against MPTP toxicity in vivo.
Exercise has been shown to be beneficial for Parkinson's disease (PD). A major interest in our lab has been to investigate how exercise modulates basal ganglia function and modifies disease progression. Dopamine (DA) depletion leads to loss of dendritic spines within the caudate nucleus and putamen (striatum) in PD and its animal models and contributes to motor impairments. Striatal medium spiny neurons (MSNs) can be delineated into two populations, the dopamine D1 receptor (DA-D1R)-containing MSNs of the direct pathway and dopamine D2 receptor (DA-D2R)-containing MSNs of the indirect pathway. There is evidence to suggest that the DA-D2R-indirect pathway MSNs may be preferentially affected after DA-depletion with a predominate loss of dendritic spine density when compared to MSNs of the DA-D1R-direct pathway in rodents; however, others have reported that both pathways may be affected in primates. The purpose of this study was to investigate the effects of intensive exercise on dendritic spine density and arborization in MSNs of these two pathways in the MPTP mouse model of PD. We found that MPTP led to a decrease in dendritic spine density in both DA-D1R- and DA-D2R-containing MSNs and 30days of intensive treadmill exercise led to increased dendritic spine density and arborization in MSNs of both pathways. In addition, exercise increased the expression of synaptic proteins PSD-95 and synaptophysin. Taken together these findings support the potential effect of exercise in modifying synaptic connectivity within the DA-depleted striatum and in modifying disease progression in individuals with PD.
Emerging evidence points to reactive glia as a pivotal factor in Parkinson's disease (PD) and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-lesioned mouse model of basal ganglia injury, but whether astrocytes and microglia activation may exacerbate dopaminergic (DAergic) neuron demise and/or contribute to DAergic repair is presently the subject of much debate. Here, we have correlated the loss and recovery of the nigrostriatal DAergic functionality upon acute MPTP exposure with extensive gene expression analysis at the level of the ventral midbrain (VM) and striata (Str) and found a major upregulation of pro-inflammatory chemokines and wingless-type MMTV integration site1 (Wnt1), a key transcript involved in midbrain DAergic neurodevelopment. Wnt signaling components (including Frizzled-1 [Fzd-1] and β-catenin) were dynamically regulated during MPTP-induced DAergic degeneration and reactive glial activation. Activated astrocytes of the ventral midbrain were identified as candidate source of Wnt1 by in situ hybridization and real-time PCR in vitro. Blocking Wnt/Fzd signaling with Dickkopf-1 (Dkk1) counteracted astrocyte-induced neuroprotection against MPP(+) toxicity in primary mesencephalic astrocyte-neuron cultures, in vitro. Moreover, astroglial-derived factors, including Wnt1, promoted neurogenesis and DAergic neurogenesis from adult midbrain stem/neuroprogenitor cells, in vitro. Conversely, lack of Wnt1 transcription in response to MPTP in middle-aged mice and failure of DAergic neurons to recover were reversed by pharmacological activation of Wnt/β-catenin signaling, in vivo, thus suggesting MPTP-reactive astrocytes in situ and Wnt1 as candidate components of neuroprotective/neurorescue pathways in MPTP-induced nigrostriatal DAergic plasticity.
GABA and enkephalin-utilizing efferents from the striatum to the external segment of the pallidal complex (GPe) are thought to be overactive in Parkinson's disease (PD). This overactivity is generally held to play a major role in the genesis of parkinsonian symptoms, which are thought to appear when dopaminergic neuronal death exceeds a critical threshold. Little is known, however, regarding the activity of this pathway during disease progression and more particularly, prior to the emergence of parkinsonian symptoms. In order to test the hypothesis that an upregulation of striatal preproenkephalin-A (PPE-A) mRNA levels occurs before the appearance of parkinsonian motor disabilities, the present study assessed PPE-A mRNA expression and striatal dopamine (DA) content following a chronic 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) administration protocol in monkeys that produces a progressive parkinsonian state. Groups ranged from normal to full parkinsonian through asymptomatic lesioned monkeys. The key finding of this study is that PPE-A expression is already upregulated in asymptomatic-lesioned monkeys showing a marked DA depletion (56%). Importantly, this up-regulation is restricted to motor regions of the basal ganglia circuitry. The increased PPE-A mRNA expression observed in asymptomatic, but DA-depleted animals, supports our initial hypothesis of such an upregulation occurring before the appearance of parkinsonian motor disabilities. Furthermore, when considered with recent electrophysiological and histochemical data, these findings question the functional significance of upregulated enkephalin transmission in the indirect striatopallidal pathway.
The 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-lesioned mouse serves as a model of basal ganglia injury and Parkinson's disease. The present study investigated the effects of MPTP-induced lesioning on associative memory, conditioned fear, and affective behavior. Male C57BL/6 mice were administered saline or MPTP and separate groups were evaluated at either 7 or 30 days post-lesioning. In the social transmission of food preference test, mice showed a significant decrease in preference for familiar food 30 days post-MPTP compared to controls. Mice at both 7 and 30 days post-MPTP lesioning had increased fear extinction compared to controls. High Performance Liquid Chromatography analysis of tissues homogenates showed dopamine and serotonin were depleted in the striatum, frontal cortex, and amygdala. No changes in anxiety or depression were detected by the tail suspension, sucrose preference, light-dark preference, or hole-board tests. In conclusion, acute MPTP lesioning regimen in mice causes impairments in associative memory and conditioned fear, no mood changes, and depletion of dopamine and serotonin throughout the brain.
Environmental enrichment has been shown to be both neuroprotective and neurorestorative in 1-methyl-2-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse models of Parkinson's disease (PD). However, whether social interaction or novel physical stimulation is responsible for this recovery is controversial. In the current study, we have investigated the effects of only social enrichment (SocE) in progressively MPTP-lesioned mice. After mice were lesioned using a progressively increased dose (4 mg/kg, 8 mg/kg, 16 mg/kg and 32 mg/kg; each dose daily for 5 days), the MPTP-induced behavioral deficits, after the 32 mg/kg dose, were reversed with acute L-DOPA. This acute behavioral recovery suggests that this progressive MPTP-induced neurodegeneration is an appropriate murine model of PD. Mice were housed four per cage for the first 2 weeks of progressive lesioning or vehicle treatment. After the 8 mg/kg MPTP dose (prior to SocE intervention) mice showed a significant decrease in rearing and foot fault behaviors (FF/BB) compared to the vehicle group. Additionally, there was a 38% decrease in mean number of tyrosine hydroxylase immunoreactive (TH-ir) substantia nigra pars compacta (SNpc) neurons/section, and a 50% decrease in the optical density of TH-ir dorsolateral caudate putamen (CPu) terminals compared to the vehicle group. Mice were then housed either two (socially limited environment; SLE) or twelve (SocE) mice per cage during continued MPTP lesioning for the next 2 weeks at 16 mg/kg and 32 mg/kg MPTP. MPTP treatment was then discontinued, while mice remained in the SLE or SocE cages for an additional week. Rearing behavior was further impaired in SLE-MPTP mice following progressive MPTP, accompanied by additional decreases in the mean number of TH-ir SNpc neurons/section and CPu TH-ir terminals. CPu TH and dopamine transporter (DAT) protein expression, as well as dopamine tissue and TH protein levels was significantly decreased compared to either vehicle group. However, the deficit in rearing behavior in SLE-MPTP mice was reversed with acute L-DOPA following the intervention period. SocE-MPTP mice showed rearing and FF/BB behaviors similar to vehicle levels, although FF/BB was not significantly different from pre-intervention levels. The reversal from pre-intervention rearing deficits was correlated with an attenuated decrease in the mean number of SNpc TH-ir neurons/section and CPu TH and DAT protein, and with a blocked decrease in CPu TH-ir terminals compared to pre-intervention levels. Our findings show that SocE mice not only resist further nigrostriatal lesioning and FF/BB deficit, but rearing behavior is recovered to the level of the vehicle group despite continued MPTP treatment. In contrast, SLE mice showed continued loss of nigrostriatal TH-ir and decline of motor behaviors with progressive MPTP. The data suggest that non-pharmacological intervention that started at an early stage of dopamine loss is effective at slowing or blocking further nigrostriatal degeneration.
The diazoxide derivative 7-chloro-3-methyl-3,4-dihydro-2H-1,2,4-benzothiadiazine-S,S-dioxide (IDRA21) enhances memory and learning in rodents, most likely by potentiating AMPAergic synaptic activity. We examined IDRA21's effect upon AMPAergic synaptic currents and whole-cell glutamate currents in cultured rat hippocampal neurons to determine whether IDRA21 was a partial modulator of AMPA receptor desensitization and deactivation. Comparable to cyclothiazide, IDRA21 prolonged AMPAergic autaptic currents (5.6 times control, EC50 150 microM) and slowed the rate of AMPA deactivation (3 times control) following 1-ms applications of 1 mM glutamate to excised, outside-out membrane patches. IDRA21 also augmented autaptic GABA currents by 27 +/- 8.1%, although it had two opposing effects, reducing the peak amplitude versus prolonging autaptic GABA currents. IDRA21 (200 microM) inhibited whole-cell GABA currents elicited by exogenously applied 1 mM GABA by 41 +/- 11%. At sufficient concentrations, IDRA21 reduced AMPA receptor desensitization and slowed the rate of deactivation, most consistent with full agonist activity with lower potency compared to cyclothiazide. IDRA21 slightly augments GABAergic synaptic currents.
In human disease, channelopathies involving functional reduction of the delayed rectifier potassium channel α-subunit Kv1.1 - either by mutation or autoimmune inhibition - result in temporal lobe epilepsy. Kv1.1 is prominently expressed in the axons of the hippocampal tri-synaptic pathway, suggesting its absence will result in widespread effects on normal network oscillatory activity. Here, we performed in vitro extracellular recordings using a multielectrode array to determine the effects of loss of Kv1.1 on spontaneous sharp waves (SPWs) and high frequency oscillations (HFOs). We found that Kcna1-null hippocampi generate SPWs and ripples (80-200 Hz bandwidth) with a 50% increased rate of incidence and 50% longer duration, and that epilepsy-associated pathologic HFOs in the fast ripple bandwidth (200-600 Hz) are also present. Furthermore, Kcna1-null CA3 has enhanced coupling of excitatory inputs and population spike generation and CA3 principal cells have reduced spike timing reliability. Removing the influence of mossy fiber and perforant path inputs by micro-dissecting the Kcna1-null CA3 region mostly rescued the oscillatory behavior and improved spike timing. We found that Kcna1-null mossy fibers and medial perforant path axons are hyperexcitable and produce greater pre- and post-synaptic responses with reduced paired-pulse ratios suggesting increased neurotransmitter release at these terminals. These findings were recapitulated in wild-type slices exposed to the Kv1.1 inhibitor dendrotoxin-κ. Collectively, these data indicate that loss of Kv1.1 enhances synaptic release in the CA3 region, which reduces spike timing precision of individual neurons leading to disorganization of network oscillatory activity and promotes the emergence of fast ripples.
Dravet syndrome is an intractable epileptic encephalopathy characterized by early onset epileptic seizures followed by cognitive decline, hyperactivity, autistic behaviors and ataxia. Most Dravet syndrome patients possess heterozygous mutations of SCN1A gene encoding voltage-gated sodium channel α(I) subunit (Na(v)1.1). We have previously reported that mice heterozygous for a nonsense mutation in Scn1a developed early onset epileptic seizures. However, the learning ability and sociability of the mice remained to be investigated. In the present study, we subjected heterozygous Scn1a mice to a comprehensive behavioral test battery. We found that while heterozygous Scn1a mice had lowered spontaneous motor activity in home cage, they were hyperactive in novel environments. Moreover, the mice had low sociability and poor spatial learning ability that correspond to the autistic behaviors and cognitive decline seen in Dravet syndrome patients. These results suggest that Na(v)1.1 haploinsufficiency intrinsically contributes to not only epileptic seizures but also lowered sociability and learning impairment in heterozygous Scn1a mutant mice, as it should also be the case in patients with Dravet syndrome.
In the present study, we prepared a SCA3 animal model by generating transgenic mice expressing polyglutamine-expanded ataxin-3-Q79. Ataxin-3-Q79 was expressed in brain areas implicated in SCA3 neurodegeneration, including cerebellum, pontine nucleus and substantia nigra. Ataxin-3-Q79 transgenic mice displayed motor dysfunction with an onset age of 5-6 months, and neurological symptoms deteriorated in the following months. A prominent neuronal loss was not found in the cerebellum of 10 to 11-month-old ataxin-3-Q79 mice displaying pronounced ataxic symptoms, suggesting that instead of neuronal demise, ataxin-3-Q79 causes neuronal dysfunction of the cerebellum and resulting ataxia. To test the involvement of transcriptional dysregulation in ataxin-3-Q79-induced cerebellar malfunction, microarray analysis and real-time RT-PCR assays were performed to identify altered cerebellar mRNA expressions of ataxin-3-Q79 mice. Compared to non-transgenic mice or mice expressing wild-type ataxin-3-Q22, 10 to 11-month-old ataxin-3-Q79 mice exhibited downregulated mRNA expressions of proteins involved in glutamatergic neurotransmission, intracellular calcium signaling/mobilization or MAP kinase pathways, GABA(A/B) receptor subunits, heat shock proteins and transcription factor regulating neuronal survival and differentiation. Upregulated expressions of Bax, cyclin D1 and CDK5-p39, which may mediate neuronal death, were also observed in ataxin-3-Q79 transgenic mice. The involvement of transcriptional abnormality in initiating the pathological process of SCA3 was indicated by the finding that 4 to 5-month-old ataxin-3-Q79 mice, which did not display neurological phenotype, exhibited downregulated mRNA levels of genes involved in glutamatergic signaling and signal transduction. Our study suggests that polyglutamine-expanded ataxin-3 causes cerebellar dysfunction and ataxia by disrupting the normal pattern of gene transcriptions.
Alzheimer's disease (AD) is characterized by accumulation and deposition of Abeta peptides in the brain. Abeta deposition in cerebral vessels occurs in many AD patients and results in cerebral amyloid angiopathy (AD/CAA). Abeta deposits evoke neuro- and neurovascular inflammation contributing to neurodegeneration. In this study, we found that exposure of cultured human brain endothelial cells (HBEC) to Abeta(1-40) elicited expression of inflammatory genes MCP-1, GRO, IL-1beta and IL-6. Up-regulation of these genes was confirmed in AD and AD/CAA brains by qRT-PCR. Profiling of 54 transcription factors indicated that AP-1 was strongly activated not only in Abeta-treated HBEC but also in AD and AD/CAA brains. AP-1 complex in nuclear extracts from Abeta-treated HBEC bound to AP-1 DNA-binding sequence and activated the reporter gene of a luciferase vector carrying AP-1-binding site from human MCP-1 gene. AP-1 is a dimeric protein complex and supershift assay identified c-Jun as a component of the activated AP-1 complex. Western blot analyses showed that c-Jun was activated via JNK-mediated phosphorylation, suggesting that as a result of c-Jun phosphorylation, AP-1 was activated and thus up-regulated MCP-1 expression. A JNK inhibitor SP600125 strongly inhibited Abeta-induced c-Jun phosphorylation, AP-1 activation, AP-1 reporter gene activity and MCP-1 expression in cells stimulated with Abeta peptides. The results suggested that JNK-AP1 signaling pathway is responsible for Abeta-induced neuroinflammation in HBEC and Alzheimer's brain and that this signaling pathway may serve as a therapeutic target for relieving Abeta-induced inflammation.
Alzheimer's disease and prion diseases (e.g., Creutzfeldt-Jakob disease) display profound neural lesions associated with aberrant protein processing and extracellular amyloid deposits. However, the intracellular events in prion diseases and their relation with the processing of the amyloid precursor protein (APP) and beta-amyloid generation are unknown. The adaptor protein Dab1 may regulate intracellular trafficking and secretase-mediated proteolysis in APP processing. However, a putative relationship between prion diseases and Dab1/APP interactions is lacking. Thus, we examined, in inoculated animals, whether Dab1 and APP processing are targets of the intracellular events triggered by extracellular exposure to PrP(106-126) peptide. Our in vitro results indicate that PrP(106-126) peptide induces tyrosine phosphorylation of Dab1 by activated members of the Src family of tyrosine kinases (SFK), which implies further Dab1 degradation. We also corroborate these results in Dab1 protein levels in prion-inoculated hamsters. Finally, we show that fibrillar prion peptides have a dual effect on APP processing and beta-amyloid production. First, they block APP trafficking at the cell membrane, thus decreasing beta-amyloid production. In parallel, they reduce Dab1 levels, which also alter APP processing. Lastly, neuronal cultures from Dab1-deficient mice showed severe impairment of APP processing with reduced sAPP secretion and A beta production after prion peptide incubation. Taken together, these data indicate a link between intracellular events induced by exposure to extracellular fibrillar peptide or PrP(res), and APP processing and implicate Dab1 in this link.
Prion diseases are neurodegenerative pathologies characterized by the accumulation, in the brain, of altered forms of the prion protein (PrP), named PrP(Sc). A synthetic peptide homologous to residues 106-126 of PrP (PrP106-126) was reported to maintain the neurodegenerative characteristics of PrP(Sc). We investigated the intracellular mechanisms involved in PrP106-126-dependent degeneration of primary cultures of cerebellar granule neurons. Prolonged exposure of such neurons to PrP106-126 induced apoptotic cell death. The L-type voltage-sensitive calcium channel blocker nicardipine reproduced this effect, suggesting that blockade of Ca(2+) entry through this class of calcium channels may be responsible for the granule cell degeneration. Microfluorometric analysis showed that PrP106-126 caused a reduction in cytosolic calcium levels, elicited by depolarizing K(+) concentrations in these neurons. Electrophysiological studies demonstrated that PrP106-126 and nicardipine selectively reduce the L-type calcium channel current. These data demonstrate that PrP106-126 alters the activity of L-type voltage-sensitive calcium channels in rat cerebellar granule cells and suggest that this phenomenon is related to the cell death induced by the peptide.
In Huntington's disease (HD) mutant huntingtin protein impairs the function of several transcription factors, in particular the cAMP response element-binding protein (CREB). CREB activation can be increased by targeting phosphodiesterases such as phospohodiesterase 4 (PDE4) and phosphodiesterase 10A (PDE10A). Indeed, both PDE4 inhibition (DeMarch et al., 2008) and PDE10A inhibition (Giampà et al., 2010) proved beneficial in the R6/2 mouse model of HD. However, Hebb et al. (2004) reported PDE10A decline in R6/2 mice. These findings raise the issue of how PDE10A inhibition is beneficial in HD if such enzyme is lost.
Dopaminergic depletion in the nigrostriatal system is the neurochemical hallmark of Parkinson's disease (PD). Although numerous efforts have been made to determine the evolution of dopaminergic depletion in PD, "in vivo" data concerning the stages of this process are still scarce. We evaluated 6-[18F]-fluoro-l-DOPA ((18)F-DOPA) and 11C-(+)-alpha-dihydrotetrabenazine ((11)C-DTBZ) using PET in a model of chronically MPTP-induced parkinsonism in non-human primates.
Sixty-seven cynomolgus monkeys (Macacafascicularis) were included in the study. Progressive parkinsonism was induced by repeated administration of small doses of MPTP (iv) over several months. Animals were classified as controls, asymptomatic, recovered (having exhibited parkinsonian features transiently) and stable parkinsonian, according to their motor status. Analysis of striatal dopaminergic activity was conducted by regions of interest (ROI) and statistical parametric mapping (SPM) over normalized parametric images.
A progressive loss of striatal uptake was evident among groups for both radiotracers, which correlated significantly with the clinical motor status. Changes occurred earlier, i.e. in the less affected stages, with (11)C-DTBZ. Similar results were achieved by ROI and SPM analysis. Uptake was similar with both radiotracers for the asymptomatic and recovered groups.
Serial assessment with (18)F-DOPA and (11)C-DTBZ PETs provides an effective approach to evaluate evolution of dopaminergic depletion in monkeys with MPTP-induced parkinsonism. This approach could be useful to perform studies aiming to test the effect of early therapeutic intervention and putative neuroprotective treatments.
Leucine-rich repeat kinase 2 (LRRK2) is a recently identified gene that, when mutated at specific locations, results in the onset of parkinsonian symptoms with clinical features indistinguishable from idiopathic Parkinson's disease. Based on structural and domain analysis, LRRK2 is predicted to function as a stress-responsive protein scaffold mediating the regulation of mitogen activating protein kinase (MAPK) pathways. Consistent with this notion, our results supported the notion that expression of wild-type LRRK2 but not Y1699C or G2019S mutants enhanced the tolerance of HEK293 and SH-SY5Y cells towards H(2)O(2)-induced oxidative stress. This increase in stress tolerance was dependent on the presence of the kinase domain of the LRRK2 gene and manifested through the activation of the ERK pathway. Collectively, our results indicated that cells expressing LRRK2 mutants suffer a loss of protection normally derived from wild-type LRRK2, making them more vulnerable to oxidative stress.
Leber's hereditary optic neuropathy (LHON) is a retinal neurodegenerative disorder caused by mitochondrial DNA point mutations. Complex I of the respiratory chain affected by the mutation results in a decrease in ATP and an increase of reactive oxygen species production. Evaluating the efficacy of minocycline in LHON, the drug increased the survival of cybrid cells in contrast to the parental cells after thapsigargin-induced calcium overload. Similar protection was observed by treatment with cyclosporine A, a blocker of the mitochondrial permeability transition pore (mPTP). Ratiometric Ca(2+) imaging reveals that acetylcholine/thapsigargin triggered elevation of the cytosolic calcium concentration is alleviated by minocycline and cyclosporine A. The mitochondrial membrane potential of LHON cybrids was significantly conserved and the active-caspase-3/procaspase-3 ratio was decreased in both treatments. Our observations show that minocycline inhibits permeability transition induced by thapsigargin in addition to its antioxidant effects. In relation with its high safety profile, these results would suggest minocycline as a promising neuroprotective agent in LHON.
Impulse control disorders such as pathological gambling (PG) are a serious and common adverse effect of dopamine (DA) replacement medication in Parkinson's disease (PD). Patients with PG have increased impulsivity and abnormalities in striatal DA, in common with behavioural and substance addictions in the non-PD population. To date, no studies have investigated the role of extrastriatal dopaminergic abnormalities in PD patients with PG. We used the PET radiotracer, [11C] FLB-457, with high-affinity for extrastriatal DA D2/3 receptors. 14 PD patients on DA agonists were imaged while they performed a gambling task involving real monetary reward and a control task. Trait impulsivity was measured with the Barratt Impulsivity Scale (BIS). Seven of the patients had a history of PG that developed subsequent to DA agonist medication. Change in [11C] FLB-457 binding potential (BP) during gambling was reduced in PD with PG patients in the midbrain, where D2/D3 receptors are dominated by autoreceptors. The degree of change in [11C] FLB-457 binding in this region correlated with impulsivity. In the cortex, [11C] FLB-457 BP was significantly greater in the anterior cingulate cortex (ACC) in PD patients with PG during the control task, and binding in this region was also correlated with impulsivity. Our findings provide the first evidence that PD patients with PG have dysfunctional activation of DA autoreceptors in the midbrain and low DA tone in the ACC. Thus, altered striatal and cortical DA homeostasis may incur vulnerability for the development of PG in PD, linked with the impulsive personality trait.
Microglial activation is implicated in the pathogenesis of ALS and can be detected in animal models of the disease that demonstrate increased survival when treated with anti-inflammatory drugs. PK11195 is a ligand for the "peripheral benzodiazepine binding site" expressed by activated microglia. Ten ALS patients and 14 healthy controls underwent [(11)C](R)-PK11195 PET of the brain. Volumes of interest were defined to obtain [(11)C](R)-PK11195 regional binding potential values for motor and "extra-motor" regions. Significantly increased binding was found in motor cortex (P = 0.003), pons (P = 0.004), dorsolateral prefrontal cortex (P = 0.010) and thalamus (P = 0.005) in the ALS patients, with significant correlation between binding in the motor cortex and the burden of upper motor neuron signs clinically (r = 0.73, P = 0.009). These findings indicate that cerebral microglial activation can be detected in vivo during the evolution of ALS, and support the previous observations that cerebral pathology is widespread. They also argue for the development of therapeutic strategies aimed at inflammatory pathways.
[11C](R)PK11195-PET is a marker of activated microglia while [11C]PIB-PET detects raised amyloid load. Here we studied in vivo the distributions of amyloid load and microglial activation in Alzheimer's disease (AD) and their relationship with cognitive status. Thirteen AD subjects had [11C](R)PK11195-PET and [11C]PIB-PET scans. Ten healthy controls had [11C](R)PK11195-PET and 14 controls had [11C]PIB-PET scans. Region-of-interest analysis of [11C](R)PK11195-PET detected significant 20-35% increases in microglial activation in frontal, temporal, parietal, occipital and cingulate cortices (p<0.05) of the AD subjects. [11C]PIB-PET revealed significant two-fold increases in amyloid load in these same cortical areas (p<0.0001) and SPM (statistical parametric mapping) analysis confirmed the localisation of these increases to association areas. MMSE scores in AD subjects correlated with levels of cortical microglial activation but not with amyloid load. The inverse correlation between MMSE and microglial activation is compatible with a role of microglia in neuronal damage.
Idiopathic Parkinson's disease (PD) is a neurodegenerative disorder associated with akinesia, tremor and rigidity. While the characteristic Lewy body pathology targets pigmented and other brainstem nuclei at post-mortem, activated microglia are found in both subcortical and cortical areas. [11C](R)-PK11195 is a positron emission tomography (PET) marker of peripheral benzodiazepine sites (PBBS), which are selectively expressed by activated microglia. We examined 18 PD patients clinically and with [11C](R)-PK11195 and [18F]-dopa PET. Compared to 11 normal controls, the PD patients showed significantly increased mean levels of [11C](R)-PK11195 binding in the pons, basal ganglia and frontal and temporal cortical regions. Eight PD patients were examined longitudinally, and their [11C](R)-PK11195 signal remained stable over 2 years. Levels of microglial activation did not correlate with clinical severity or putamen [18F]-dopa uptake. Our in vivo findings confirm that widespread microglial activation is associated with the pathological process in PD. The absence of significant longitudinal changes suggests that microglia are activated early in the disease process, and levels then remain relatively static, possibly driving the disease via cytokine release.
Thirty Parkinson's disease (PD) patients were divided into three equal groups according to their disease duration while 10 normal healthy volunteers matched for age and sex served as a control group. Striatal and extrastriatal serotonergic function was studied with (11)C-DASB PET, a marker of serotonin transporter availability. (11)C-DASB binding was correlated with disease disability and exposure to dopaminergic therapy. We found significant (11)C-DASB binding reductions in striatal, brainstem, and cortical regions in PD but no correlations were evident between (11)C-DASB binding and UPDRS scores, Hoehn &Yahr staging, disease duration and level of exposure to dopaminergic therapy. Our results suggest that progressive non-linear serotonergic dysfunction occurs in PD but it does not determine levels of disability. Additionally, chronic exposure to dopaminergic therapy does not appear to influence SERT binding.
Neurturin (NTN) is a neurotrophic factor with known potential to protect and restore the function of dopaminergic substantia nigra neurons whose degeneration has been most closely linked to the major motor deficits in Parkinson's disease (PD). CERE-120, an adeno-associated virus serotype 2 (AAV2)-based gene delivery vector encoding human NTN, is being developed as a potential therapeutic for PD. In a series of preclinical studies reported herein, CERE-120 delivery to the striatum produced a dose-related neuroprotection of nigrostriatal neurons in the rat 6-hydroxydopamine (6-OHDA) lesion model. Long-lasting efficacy of CERE-120 was evidenced by substantia nigra cell protection, preserved fiber innervation of the striatum, and behavioral recovery for at least 6 months. In addition, striatal infusion of CERE-120 was found to have a safety and tolerability profile devoid of side effects or toxicological responses, for at least 12 months post-treatment, even at dose multiples 125 times that of the lowest efficacious dose tested. These results support the ongoing CERE-120 clinical program in PD patients.
This paper reassesses the currently accepted viewpoint that targeting the terminal fields (i.e. striatum) of degenerating nigrostriatal dopamine neurons with neurotrophic factors in Parkinson's disease (PD) is sufficient for achieving an optimal neurotrophic response. Recent insight indicating that PD is an axonopathy characterized by axonal transport deficits prompted this effort. We tested whether a significantly greater neurotrophic response might be induced in SN neurons when the neurotrophic factor neurturin (NRTN) is also targeted to the substantia nigra (SN), compared to the more conventional, striatum-only target. While recognizing the importance of maintaining the integrity of nigrostriatal fibers and terminals (especially for achieving optimal function), we refocused attention to the fate of SN neurons. Under conditions of axonal degeneration and neuronal transport deficits, this component of the nigrostriatal system is most vulnerable to the lack of neurotrophic exposure following striatal-only delivery. Given the location of repair genes induced by neurotrophic factors, achieving adequate neurotrophic exposure to the SN neurons is essential for an optimal neurotrophic response, while the survival of these neurons is essential to the very survival of the fibers. Two separate studies were performed using the 6-OHDA model of nigrostriatal degeneration, in conjunction with delivery of the viral vector AAV2-NRTN (CERE-120) to continuously express NRTN to either striatum or nigra alone or combined striatal/nigral exposure, including conditions of ongoing axonopathy. These studies provide additional insight for reinterpreting past animal neurotrophic/ 6-OHDA studies conducted under conditions where axon transport deficiencies were generally not accounted for, which suggested that targeting the striatum was both necessary and sufficient. The current data demonstrate that delivering NRTN directly to the SN produces 1) expanded NRTN distribution within the terminal field and cell bodies of targeted nigrostriatal neurons, 2) enhanced intracellular neurotrophic factor signaling in the nigrostriatal neurons, and 3) produced greater numbers of surviving dopamine neurons against 6-OHDA-induced toxicity, particularly under the conditions of active axonopathy. Thus, these data provide empirical support that targeting the SN with neurotrophic factors (in addition to striatum) may help enhance the neurotrophic response in midbrain neurons, particularly under conditions of active neurodegeneration which occurs in PD patients.
Prion diseases are neurodegenerative pathologies characterized by the accumulation in the brain of a protease-resistant form of the prion protein (PrP(c)), named PrP(Sc). A synthetic peptide homologous to residues 106-126 of PrP (PrP106-126) maintains many PrP(Sc) characteristics. We investigated the intracellular signaling responsible for the PrP106-126-dependent cell death of SH-SY5Y, a cell line derived from a human neuroblastoma. In this cell line, PrP106-126 induced apoptotic cell death and caused activation of caspase-3, although the blockade of this enzyme did not inhibit cell death. The p38 MAP kinase blockers, SB203580 and PD169316, prevented the apoptotic cell death evoked by PrP106-126 and Western blot analysis revealed that the exposure of the cells to the peptide induced p38 phosphorylation. Taken together, our data suggest that the p38 MAP kinase pathway can mediate the SH-SY5Y cell death induced by PrP106-126.
The role of IL-12 in excitotoxic neurodegeneration of brain is largely unknown. To address this issue, we used the model of kainic acid (KA)-induced hippocampal injury in IL-12p35 knockout (KO) mice, a well-characterized model for human neurodegenerative diseases. After KA treatment, hippocampal neurodegeneration was significantly less severe in the IL-12p35 KO mice than in wild-type mice as demonstrated by reduced pathological changes and astrogliosis. One day after KA treatment, levels of F4/80 and CD86 expression on microglia were significantly lower in IL-12p35 KO mice than in wild-type mice analyzed by flow cytometry, indicating that IL-12p35 deficiency resulted in lower levels of microglial activation. Five days after KA treatment, CD86 expression on microglia of wild-type mice was still higher, whereas F4/80 expression in wild-type mice decreased and was similar to that in IL-12p35 KO mice. Because microglial activation is necessary for KA-induced neurodegeneration, the lower level of microglial activation in the absence of IL-12p35 may alleviate hippocampal injury in KO mice. In summary, this study indicates that IL-12 may play a critical role in excitotoxin-induced brain injury.
Oculopharyngeal muscular dystrophy (OPMD) is a late-onset disorder caused by a (GCG)n trinucleotide repeat expansion in the poly(A) binding protein nuclear-1 (PABPN1) gene, which in turn leads to an expanded polyalanine tract in the protein. We generated transgenic mice expressing either the wild type or the expanded form of human PABPN1, and transgenic animals with the expanded form showed clear signs of abnormal limb clasping, muscle weakness, coordination deficits, and peripheral nerves alterations. Analysis of mitotic and postmitotic tissues in those transgenic animals revealed ubiquitinated PABPN1-positive intranuclear inclusions (INIs) in neuronal cells. This latter observation led us to test and confirm the presence of similar INIs in postmortem brain sections from an OPMD patient. Our results indicate that expanded PABPN1, presumably via the toxic effects of its polyalanine tract, can lead to inclusion formation and neurodegeneration in both the mouse and the human.
Huntington's disease (HD) is an inherited progressive neurological disorder for which there is no effective therapy. It is caused by a CAG/polyglutamine repeat expansion that leads to abnormal protein aggregation and deposition in the brain. Several compounds have been shown to disrupt the aggregation process in vitro, including a number of benzothiazoles. To further explore the therapeutic potential of the benzothiazole aggregation inhibitors, we assessed PGL-135 and riluzole in hippocampal slice cultures derived from the R6/2 mouse, confirming their ability to inhibit aggregation with an EC50 of 40 microM in this system. Preliminary pharmacological work showed that PGL-135 was metabolically unstable, and therefore, we conducted a preclinical trial in the R6/2 mouse with riluzole. At the maximum tolerated dose, we achieved steady-state riluzole levels of 100 microM in brain. However, this was insufficient to inhibit aggregation in vivo and we found no improvement in the disease phenotype.
Human growth transformation dependent protein (HGTD-P) is a newly identified protein that promotes neuronal apoptosis in hypoxia-ischemia brain damage (HIBD) in neonatal rats. However, the mechanisms regulating HGTD-P expression are not clear. Here we describe microRNAs targeted to HGTD-P and examine their effects on regulating neuronal apoptosis in HIBD. We use samples from cultured neurons after oxygen-glucose deprivation (OGD) and postnatal day 10 rat brains after hypoxia-ischemia (HI). RT-PCR, western blotting, and immunostaining are used to detect the expression of HGTD-P and cleaved caspase 3, as well as real-time PCR detect microRNA expression. MicroRNA agomir is used to inhibit the expression of HGTD-P, and DAPI, TUNEL, and TTC staining are employed to detect cell apoptosis and brain damage. Moreover, in vitro processing assay is used to examine the mechanism by which HI down-regulates miR-139-5p expression. We found that miR-139-5p is down-regulated in neurons and rat brains after HI treatment. The expression pattern of miR-139-5p correlates inversely with that of HGTD-P. Furthermore, miR-139-5p agomir inhibits neuronal apoptosis and attenuates HIBD, which is concurrent with down-regulation of HGTD-P. Moreover, pre-miR-139 processing activity decreases in extracts from OGD neurons, and OGD neuronal extracts attenuates the processing of pre-miR-139 by Dicer. In conclusion, HI induces inhibitors which block the processing step of pre-miR-139, resulting in down-regulation of mature miR-139-5p. The down-regulation of miR-139-5p plays a critical role in up-regulation of HGTD-P expression. MiR-139-5p agomir attenuates brain damage when used 12h after HI, providing a longer therapeutic window than anti-apoptosis compounds currently available.
Poly(ADP-ribose) polymerase-1 (PARP-1) is the guardian of the genome acting as a sentinel for genomic damage. However, PARP-1 is also mediator of cell death after ischemia-reperfusion injury, glutamate excitotoxicity, and various inflammatory processes. The biochemistry underlying PARP-1-mediated cell death has remained elusive, although NAD(+) consumption and energy failure have been thought to be one of the possible molecular mechanisms. Recent observations link PARP-1 activation with translocation of apoptosis-inducing factor (AIF) to the nucleus and indicate that AIF is an essential downstream effector of PARP-1-mediated cell death. PARP-1 activation signals AIF release from the mitochondria, resulting in a novel, caspase-independent pathway of programmed cell death. These recent findings suggest that AIF maybe a target for development of future therapeutic treatment for many neurological disorders involving excitotoxicity.
Spinocerebellar ataxia 27 (SCA27) is a recently described syndrome characterized by impaired cognitive abilities and a slowly progressive ataxia. SCA27 is caused by an autosomal dominant missense mutation in Fibroblast Growth Factor 14 (FGF14). Mice lacking FGF14 (Fgf14(-/-) mice) have impaired sensorimotor functions, ataxia and paroxysmal dyskinesia, a phenotype that led to the discovery of the human mutation. Here we extend the similarities between Fgf14(-/-) mice and FGF14(F145S) humans by showing that Fgf14(-/-) mice exhibit reliable acquisition (place learning) deficits in the Morris water maze. This cognitive deficit appears to be independent of sensorimotor disturbances and relatively selective since Fgf14(-/-) mice performed similarly to wild type littermates during cued water maze trials and on conditioned fear and passive avoidance tests. Impaired theta burst initiated long-term synaptic potentiation was also found in hippocampal slices from Fgf14(-/-) mice. These results suggest a role for FGF14 in certain spatial learning functions and synaptic plasticity.
Missense mutations in protein kinase Cgamma (gammaPKC) gene have been found in spinocerebellar ataxia type 14 (SCA14), an autosomal dominant neurodegenerative disease. We previously demonstrated that mutant gammaPKC found in SCA14 is susceptible to aggregation and induces apoptosis in cultured cell lines. In the present study, we investigated whether mutant gammaPKC formed aggregates and how mutant gammaPKC affects the morphology and survival of cerebellar Purkinje cells (PCs), which are degenerated in SCA14 patients. Adenovirus-transfected primary cultured PCs expressing mutant gammaPKC-GFP also had aggregates and underwent apoptosis. Long-term time-lapse observation revealed that PCs have a potential to eliminate aggregates of mutant gammaPKC-GFP. Mutant gammaPKC-GFP disturbed the development of PC dendrites and reduced synapse formation, regardless of the presence or absence of its aggregates. In PCs without aggregates, mutant gammaPKC-GFP formed soluble oligomers, resulting in reduced mobility and attenuated translocation of mutant gammaPKC-GFP upon stimulation. These molecular properties of mutant gammaPKC might affect the dendritic morphology in PCs, and be involved in the pathogenesis of SCA14.
It has been shown that the reversed operation of glutamate transporters when ATP levels fall accounts for most glutamate release induced by severe cerebral ischemia. Nitric oxide (NO) is formed after ischemia and causes ATP depletion. Our purpose is to test if NO release from inducible NO synthase (iNOS) after stroke may cause a delayed glutamate release due to ATP depletion that might underlie progression of the ischemic infarct. We have studied the effect of the highly selective inhibitor of iNOS activity 1400W on brain ATP levels, extracellular glutamate, and stroke outcome after transient focal cerebral ischemia in rats.
To induce focal ischemia, the middle cerebral artery (MCA) was occluded by using the intraluminal thread technique (tMCAO). 1400W was administered, after tMCAO, by using an Alzet osmotic pump to yield a drug delivery rate of 2.5 mg/kg/h. Results. Postischemic treatment with 1400W induced a reduction in the neurofunctional impairment and in the total volume of brain infarct. Western blot analysis showed ischemia-induced expression of iNOS. Treatment with 1400W partially prevented delayed ATP reduction and produced inhibition of the subsequent delayed increase in glutamate levels caused by the ischemic insult.
Our data indicate that 1400W improves stroke outcome, an effect concomitant to the inhibition of both ischemia-induced decrease in brain ATP levels and increase in glutamate release. These results provide evidence indicating that the expression of iNOS induced by ischemia may contribute to the progression of the ischemic infarct and have important therapeutic implications for the management of stroke.
Prions are transmissible pathogens that cause neurodegenerative diseases, although the mechanisms behind the nervous system dysfunctions are unclear. To study the effects of a prion infection on voltage-gated calcium channels, scrapie-infected gonadotropin-releasing hormone neuronal cells (ScGT1-1) in culture were depolarized by KCl and calcium responses recorded. Lower calcium responses were observed in infected compared to uninfected cells. This effect was still observed when L-type calcium channels were blocked by nimodipine. After inhibition of N-type calcium channels with omega-conotoxin GVIA, there was no difference in calcium responses. The calcium responses after nimodipine treatment became progressively lower during infection, but there was no major loss of the cellular prion protein (PrP(C)) or marked increase in accumulation of the abnormal prion protein (PrP(Sc)) in the cultures. These results indicate that scrapie infection causes a dysfunction of voltage-gated N-type calcium channels, which is exacerbated slowly over time. Quinacrine treatment cleared PrP(Sc) and restored calcium responses in the ScGT1-1 cultures.
Repetitive behaviors (such as circling) are one of the defining features of autism. The substantia nigra (SN) is involved in circling. We used unilateral SN pars reticulata (SNR) infusions of the GABA agonist muscimol to induce circling and deoxyglucose autoradiography mapping in adult and postnatal day (PN) 15 male and female rats to determine its substrates. In adults, muscimol infusions in posterior SNR induced a higher circling rate than in anterior SNR, after which males displayed faster circling than females. In contrast, PN15 female rats circled faster than PN15 male rats. Autoradiograms demonstrated age- and sex-specific alterations of deoxyglucose uptake in the SN pars compacta (SNC) associated with highest circling rates. The data suggest that there is a close relationship of the GABAergic SNR and dopaminergic SNC in the induction of circling; there is a topographic organization of the SNR in terms of circling behavior and associated deoxyglucose uptake, which is dependent on age and sex.
Machado-Joseph disease (MJD) is an autosomal dominant neurodegenerative disorder in families of Portuguese-Azorean ancestry. The gene responsible for MJD has been assigned to a 29-cM interval on chromosome 14q. A large Brazilian family with MJD was genotyped with six new microsatellite markers spanning 19 cM on chromosome 14q. Linkage analysis and haplotype reconstruction reduced the MJD candidate region to a 3-cM interval between markers D14S280 and D14S81, permitting positional cloning. This interval also contains the spinal cerebellar ataxia 3 (SCA3) gene, responsible for a genetic subtype of the type I autosomal dominant cerebellar ataxias, clinically related to MJD. This result supports the hypothesis that abnormalities in the same gene may be responsible for both disorders. The minor clinical differences between the two diseases may result from allelic heterogeneity.
Glial cell line-derived neurotrophic factor (GDNF) is a potent survival agent for neurons, however, its effect on A beta-evoked neuronal death has not been examined. We show that the injection of A beta into New Zealand white rabbit brain activates the endoplasmic reticulum (ER) chaperones, grp 78 and grp 94, and the transcription factor, gadd 153. These effects correlate with the activation of JNK and ERK as well as of microglia and with the phosphorylation of tau protein. Treatment with GDNF inhibits the activation of gadd 153, reduces the phosphorylation of JNK, abolishes the phosphorylation of ERK, prevents microglial activation, greatly reduces apoptotic cells, and does not affect the phosphorylation of tau. Our data suggest that the tau hyperphosphorylation and apoptosis triggered by A beta are two independent events, and that the neuroprotective effect of GDNF against A beta may result either directly by the inhibition of ER stress or indirectly through the inhibition of JNK and ERK activation.
The purpose of this study was to use black blood magnetic resonance imaging (BB-MRI) to assess delayed cerebral vasospasm (DCV) after subarachnoid hemorrhage (SAH) in rats, and evaluate whether delayed treatment with the anti-platelet agent cilostazol was effective on DCV. BA vasospasm was sequentially assessed at 1, 2, and 3 h, and 1-6 days after SAH by BB-MRI. BB-MRI clearly visualized biphasic vasospasm; early vasospasm at 1 h later and the maximal DCV at day 2. Cilostazol was perorally administered twice at day 1 after having confirmed significant DCV using BB-MRI. The effect of cilostazol on DCV was evaluated at day 2. Cilostazol significantly attenuated DCV and suppressed the levels of malondialdehide and 8-isoprostane in CSF after SAH. This study shows that BB-MRI is a useful and less invasive method for the evaluation of DCV, and cilostazol may be effective on DCV.
Human chromosome 15q11-q13 is subject to regulation by genomic imprinting, an epigenetic process by which genes are expressed in a parent-of-origin specific manner. Three neurodevelopmental disorders, Prader-Willi syndrome, Angelman syndrome, and 15q duplication syndrome, result from aberrant expression of imprinted genes in this region. Here, we review the current literature pertaining to mouse models and recently identified patients with atypical deletions, which shed light on the epigenetic regulation of the chromosome 15q11-q13 subregion and the genes that are responsible for the phenotypic outcomes of these disorders.
A cluster of low copy repeats on the proximal long arm of chromosome 15 mediates various forms of stereotyped deletions and duplication events that cause a group of neurodevelopmental disorders that are associated with autism or autism spectrum disorders (ASD). The region is subject to genomic imprinting and the behavioral phenotypes associated with the chromosome 15q11.2-q13 disorders show a parent-of-origin specific effect that suggests that an increased copy number of maternally derived alleles contributes to autism susceptibility. Notably, nonimprinted, biallelically expressed genes within the interval also have been shown to be misexpressed in brains of patients with chromosome 15q11.2-q13 genomic disorders, indicating that they also likely play a role in the phenotypic outcome. This review provides an overview of the phenotypes of these disorders and their relationships with ASD and outlines the regional genes that may contribute to the autism susceptibility imparted by copy number variation of the region.
Sandhoff disease is a severe neurodegenerative glycosphingolipid (GSL) lysosomal storage disorder, currently without treatment options. One therapeutic approach under investigation is substrate reduction therapy (SRT). By partially inhibiting GSL biosynthesis, the impaired rate of GSL catabolism is balanced by a slower rate of influx of GSLs into the lysosome. In a previous study, we reported the beneficial effects of treating Sandhoff disease mice with the glucose analogue N-butyldeoxynojirimycin (NB-DNJ), a compound that inhibits the first step of GSL biosynthesis catalysed by the ceramide specific glucosyltransferase. NB-DNJ, however, exhibits adverse effects at high doses such as weight loss and GI tract distress (due to glucosidase inhibition). This might limit the therapeutic potential of NB-DNJ for treating diseases affecting the CNS where high dose therapy may be required to achieve therapeutic levels of the drug in the brain. In the present study, a more selective compound, the galactose analogue N-butyldeoxygalactonojirimycin (NB-DGJ), was evaluated in the Sandhoff disease mouse model. Treatment with NB-DGJ showed greater therapeutic efficacy than NB-DNJ with no detectable side effects. The ability to escalate the dose of NB-DGJ, leading to extended life expectancy and increased delay in symptom onset, demonstrates the greater therapeutic potential of NB-DGJ for the treatment of the human gangliosidoses.
Macroautophagy is a dynamic process whereby cytoplasmic molecules are sequestered within autophagosomes. Based on amino acid similarity, there exist two groups of mammalian autophagy-related gene (Atg) 8 homologues [microtubule-associated protein 1 light chain 3 (LC3) and γ-aminobutyric-acid type A receptor associated proteins (GABARAPs)], which play essential role in autophagosomal formation. Despite recent progress in studies on LC3, the other Atg8 homologues remain to be poorly understood, especially in pathological condition. In this study, we determined whether Atg8 homologues are affected in Lewy body disease, including Parkinson's disease (PD) and dementia with Lewy bodies (DLB). Our findings indicated that biochemical and pathological properties of LC3 were altered and that the level of LC3 was increased in an insoluble fraction from the brain of patients with DLB, whereas the level of GABARAPs was decreased in DLB. Furthermore, immunohistochemical staining revealed that both LC3 and GABARAPs were localized in Lewy bodies in PD and DLB. These findings suggest that autophagic function is impaired through alteration of Atg8 homologues in Lewy body disease.