[show abstract][hide abstract] ABSTRACT: Parkinson's disease (PD) is associated with a massive loss of dopaminergic cells in the substantia nigra leading to dopamine hypofunction and alteration of the basal ganglia circuitry. These neurons, are under the control, among others, of the excitatory glutamatergic and inhibitory γ-aminobutyric acid (GABA) systems. An imbalance between these systems may contribute to excitotoxicity and dopaminergic cell death. Neurosteroids, a group of steroid hormones synthesized in the brain, modulate the function of several neurotransmitter systems. The substantia nigra of the human brain expresses high concentrations of allopregnanolone (3α, 5αtetrahydroprogesterone), a neurosteroid that positively modulates the action of GABA at GABAA receptors and of 5α dehydroprogesterone, a neurosteroid acting at the genomic level. This article reviews the roles of NS acting as neuroprotectants and as GABAA receptor agonists in the physiology and pathophysiology of the basal ganglia, their impact on dopaminergic cell activity and survival, and potential therapeutic application in PD.
Frontiers in Neuroendocrinology 04/2013; · 7.99 Impact Factor
[show abstract][hide abstract] ABSTRACT: Loss of huntingtin-mediated BDNF gene transcription has been shown to occur in HD and thus contribute to the degeneration of the striatum. Several studies have indicated that an increase in BDNF levels is associated with neuroprotection and amelioration of neurological signs in animal models of HD. In a recent study, an increase in BDNF mRNA and protein levels was recorded in mice administered recombinant BDNF peripherally. Chronic, indwelling osmotic mini-pumps containing either recombinant BDNF or saline were surgically placed in R6/2 or wild-type mice from 4 weeks of age until euthanasia. Neurological evaluation (paw clasping, rotarod performance, locomotor activity in an open field) was performed. After transcardial perfusion, histological and immunohistochemical studies were performed. We found that BDNF- treated R6/2 mice survived longer and displayed less severe signs of neurological dysfunction than the vehicle treated ones. Primary outcome measures such as brain volume, striatal atrophy, size and morphology of striatal neurons, neuronal intranuclear inclusions and microglial reaction confirmed a neuroprotective effect of the compound. BDNF was effective in increasing significantly the levels of activated CREB and of BDNF the striatal spiny neurons. Moreover, systemically administered BDNF increased the synthesis of BDNF as demonstrated by RT-PCR, and this might account for the beneficial effects observed in this model.
PLoS ONE 01/2013; 8(5):e64037. · 3.73 Impact Factor
[show abstract][hide abstract] ABSTRACT: Abnormal use-dependent synaptic plasticity is universally accepted as the main physiological correlate of memory deficits in neurodegenerative disorders. It is unclear whether synaptic plasticity deficits take place during neuroinflammatory diseases, such as multiple sclerosis (MS) and its mouse model, experimental autoimmune encephalomyelitis (EAE). In EAE mice, we found significant alterations of synaptic plasticity rules in the hippocampus. When compared to control mice, in fact, hippocampal long-term potentiation (LTP) induction was favored over long-term depression (LTD) in EAE, as shown by a significant rightward shift in the frequency-synaptic response function. Notably, LTP induction was also enhanced in hippocampal slices from control mice following interleukin-1β (IL-1β) perfusion, and both EAE and IL-1β inhibited GABAergic spontaneous inhibitory postsynaptic currents (sIPSC) without affecting glutamatergic transmission and AMPA/NMDA ratio. EAE was also associated with selective loss of GABAergic interneurons and with reduced gamma-frequency oscillations in the CA1 region of the hippocampus. Finally, we provided evidence that microglial activation in the EAE hippocampus was associated with IL-1β expression, and hippocampal slices from control mice incubated with activated microglia displayed alterations of GABAergic transmission similar to those seen in EAE brains, through a mechanism dependent on enhanced IL-1β signaling. These data may yield novel insights into the basis of cognitive deficits in EAE and possibly of MS.
PLoS ONE 01/2013; 8(1):e54666. · 3.73 Impact Factor
[show abstract][hide abstract] ABSTRACT: 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 that PDE10A decline in R6/2 mice. These findings raise the issue of how PDE10A inhibition is beneficial in HD if such enzyme is lost. R6/2 mice and their wild type littermates were treated with the PDE10A inhibitor TP10 (a gift from Pfizer) or saline, sacrificed at 5, 9, 13 weeks of age, and single and double label immunohistochemistry and western blotting were performed. PDE10A increased dramatically in the spiny neurons of R6/2 compared to the wild type mice. Conversely, in the striatal cholinergic interneurons, PDE10A was lower and it did not change significantly with disease progression. In the other subsets of striatal interneurons (namely, parvalbuminergic, somatostatinergic, and calretininergic interneurons) PDE10A immunoreactivity was higher in the R6/2 compared to the wild-type mice. In the TP10 treated R6/2, PDE10A levels were lower than in the saline treated mice in the medium spiny neurons, whereas they were higher in all subsets of striatal interneurons except for the cholinergic ones. However, in the whole striatum densitometry studies, PDE10A immunoreactivity was lower in the R6/2 compared to the wild-type mice. Our study demonstrates that PDE10A is increased in the spiny neurons of R6/2 mice striatum. Thus, the accumulation of PDE10A in the striatal projection neurons, by hydrolyzing greater amounts of cyclic nucleotides, is likely to contribute to cell damage in HD. Consequently, the beneficial effect of TP10 in HD models (Giampà et al, 2009, 2010) is explained by the efficiency of such compound in counteracting this phenomenon and therefore increasing the availability of cyclic nucleotides.
Neurobiology of Disease 12/2012; · 5.62 Impact Factor
[show abstract][hide abstract] ABSTRACT: Interleukin-1β (IL-1β) is involved in mood alterations associated with inflammatory illnesses and with stress. The synaptic basis of IL-1β-induced emotional disturbances is still unknown. To address the possible involvement of the endocannabinoid system in IL-1β-induced anxiety, we performed behavioral and neurophysiological studies in mice exposed to stress or to intracerebroventricular injections of this inflammatory cytokine or of its antagonist. We found that a single intracerebroventricular injection of IL-1β caused anxiety in mice, and abrogated the sensitivity of cannabinoid CB1 receptors (CB1Rs) controlling GABA synapses in the striatum. Identical behavioral and synaptic results were obtained following social defeat stress, and intracerebroventricular injection of IL-1 receptor antagonist reverted both effects. IL-1β-mediated inhibition of CB1R function was secondary to altered cholesterol composition within membrane lipid rafts, and required intact function of the transient receptor potential vanilloid 1 (TRPV1) channel, another element of the endocannabinoid system. Membrane lipid raft disruption and inhibition of cholesterol synthesis, in fact, abrogated IL-1β-CB1R coupling, and TRPV1-/- mice were indeed insensitive to the synaptic and behavioral effects of both IL-1β and stress. On the other hand, cholesterol enrichment of striatal slices mimicked the synaptic effects of IL-1β on CB1Rs only in control mice, while the same treatment was ineffective in slices prepared from TRPV1-/- mice. The present investigation identifies a previously unrecognized interaction between a major proinflammatory cytokine and the endocannabinoid system in the pathophysiology of anxiety.
Journal of Neuroscience 10/2012; 32(40):13896-13905. · 6.91 Impact Factor
[show abstract][hide abstract] ABSTRACT: Projections from thalamic intralaminar nuclei convey sensory signals to striatal cholinergic interneurons. These neurons respond with a pause in their pacemaking activity, enabling synaptic integration with cortical inputs to medium spiny neurons (MSNs), thus playing a crucial role in motor function. In mice with the DYT1 dystonia mutation, stimulation of thalamostriatal axons, mimicking a response to salient events, evoked a shortened pause and triggered an abnormal spiking activity in interneurons. This altered pattern caused a significant rearrangement of the temporal sequence of synaptic activity mediated by M(1) and M(2) muscarinic receptors in MSNs, consisting of an increase in postsynaptic currents and a decrease of presynaptic inhibition, respectively. Consistent with a major role of acetylcholine, either lowering cholinergic tone or antagonizing postsynaptic M(1) muscarinic receptors normalized synaptic activity. Our data demonstrate an abnormal time window for synaptic integration between thalamostriatal and corticostriatal inputs, which might alter the action selection process, thereby predisposing DYT1 gene mutation carriers to develop dystonic movements.
Journal of Neuroscience 08/2012; 32(35):11991-2004. · 6.91 Impact Factor
[show abstract][hide abstract] ABSTRACT: Dysautonomia can occur in early stages of Parkinson's disease (PD) influencing tolerance to dopaminergic therapies. Rotigotine, a non-ergot dopamine agonist, has recently been developed as an effective alternative antiparkinsonian drug, but its influence on the autonomic nervous system was not investigated. Twenty subjects out of 34 consecutive de novo PD patients were submitted to full assessment of cardiovascular autonomic function before and after reaching a stable rotigotine regimen [6 mg/24 h (n = 3) or 8 mg/24 h (n = 17)]. Patients reached significant clinical improvement (-27% on the Unified Parkinson's Disease Rating Scale part III) and did not show significant differences in cardiovascular tests compared to baseline data. However, an unexpected trend towards increasing systolic blood pressure after head-up tilt test was detected. Our study demonstrates that rotigotine does not influence cardiovascular autonomic responses in early de novo PD patients. Consequently, it may represent a well-tolerated and efficacious therapeutic option in newly diagnosed PD subjects.
European Neurology 08/2012; 68(3):187-92. · 1.50 Impact Factor
[show abstract][hide abstract] ABSTRACT: Dopamine is a neurotransmitter involved in several brain functions ranging from emotions control, movement organization to memory formation. It is also involved in the regulation of mechanisms of synaptic plasticity. However, its role in Alzheimer's disease (AD) pathogenesis is still puzzling. Several recent line of research instead indicates a clear role for dopamine in both amyloid β formation as well as in cognitive decline progression. In particular it has been shown that dopamine D(2)-like receptors (namely D(3) and D(2)) could be mostly responsible for dopamine dysfunction in AD. Here we aimed to study the effects of the dopamine agonist Rotigotine on cortical excitability and on central cholinergic transmission in cases of AD. Rotigotine is a dopamine agonist with a pharmacological profile with high affinity for D(3) and D(2) receptors. We used paired pulse protocols assessing short intracortical inhibition (SICI) and intracortical facilitation (ICF) to asses cortical excitability over the primary motor cortex and Short Latency Afferent Inhibition (SLAI) protocols, to verify the effects of the drug on central cholinergic transmission in a group of AD patients compared to age-matched controls. We observed that rotigotine induces unexpected changes in both cortical excitability (increased) and central cholinergic transmission (restored) of AD patients. These unexpected effects might depend on the dopamine D(2)-like receptors dysfunction previously described in AD brains. The current findings could indicate that future strategies aimed to ameliorate symptoms of the related AD cognitive decline could also involve some dopaminergic drugs. This article is part of a Special Issue entitled 'Cognitive Enhancers'.
[show abstract][hide abstract] ABSTRACT: Multiple sclerosis (MS) causes a variety of motor and sensory deficits and it is also associated with mood disturbances. It is unclear if anxiety and depression in MS entirely reflect a subjective reaction to a chronic disease causing motor disability or rather depend on specific effects of neuroinflammation in neuronal circuits. To answer this question, behavioral, electrophysiological, and immunofluorescence experiments were performed in mice with experimental autoimmune encephalomyelitis (EAE), which models MS in mice. First, we observed high anxiety indexes in EAE mice, preceding the appearance of motor defects. Then, we demonstrated that tumor necrosis factor α (TNF-α) has a crucial role in anxiety associated with neuroinflammation. In fact, intracerebroventricular (icv) administration of etanercept, an inhibitor of TNF-α signaling, resulted in anxiolytic-like effects in EAE-mice. Accordingly, icv injection of TNF-α induced per se overt anxious behavior in control mice. Moreover, we propose the striatum as one of the brain regions potentially involved in EAE anxious behavior. We observed that before disease onset EAE striatum presents elevated TNF-α levels and strong activated microglia, early signs of inflammation associated with alterations of striatal excitatory postsynaptic currents (EPSCs). Interestingly, etanercept corrected the synaptic defects of pre-symptomatic EAE mice while icv injection of TNF-α in non-EAE mice altered EPSCs, thus mimicking the synaptic effects of EAE. In conclusion, anxiety characterizes EAE course since the very early phases of the disease. TNF-α released from activated microglia mediates this effect likely through the modulation of striatal excitatory synaptic transmission.
[show abstract][hide abstract] ABSTRACT: Amyloid-β (Aβ) oligomers are heterogeneous and instable compounds of variable molecular weight. Flow cytometry and fluorescence resonance energy transfer (FRET)-based methods allow the simultaneous detection of Aβ oligomers with low and high molecular weight in their native form. We evaluated whether an estimate of different species of Aβ oligomers in the cerebrospinal fluid (CSF) with or without dilution with RIPA buffer could be more useful in the diagnosis of Alzheimer's disease (AD) than the measurement of Aβ42 monomers, total tau (t-tau), and phosphorylated tau (p-tau). Increased t-tau (p < 0.01) and p-tau (p < 0.01), and decreased Aβ42 (p < 0.01), were detected in the CSF of patients with AD (n = 46), compared to patients with other dementia (OD) (n = 35) or with other neurological disorders (OND) (n = 56). In native CSF (n = 137), the levels of Aβ oligomers were lower (p < 0.05) in AD than in OD and OND patients; in addition, the ratio Aβ oligomers/p-tau was lower in AD than in OD (p < 0.01) and OND (p < 0.05) patients, yielding a sensitivity of 75% and a specificity of 64%. However, in CSF diluted with RIPA (n = 30), Aβ oligomers appeared higher (p < 0.05) in AD than in OND patients, suggesting they become partially disaggregated and more easily detectable after RIPA. In conclusion, FRET analysis in native CSF is essential to correctly determine the composition of Aβ oligomers. In this experimental setting, the simultaneous estimate of low and high molecular weight Aβ oligomers is as useful as the other biomarkers in the diagnosis of AD. The low amount of Aβ oligomers detected in native CSF of AD may be inversely related to their levels in the brain, as occurs for Aβ monomers, representing a biomarker for the amyloid pathogenic cascade.
[show abstract][hide abstract] ABSTRACT: Background: Multiple sclerosis (MS) patients discontinuing natalizumab treatment are at risk of disease reactivation. No clinical or surrogate parameters exist to identify patients at risk of post-natalizumab MS reactivation.Objective: To determine the role of natalizumab-induced lymphocytosis and of Akt polymorphisms in disease reactivation after natalizumab discontinuation.Methods: Peripheral leukocyte count and composition were monitored in 93 MS patients during natalizumab treatment, and in 56 of these subjects who discontinued the treatment. Genetic variants of the anti-apoptotic protein Akt were determined in all subjects because natalizumab modulates the apoptotic pathway and lymphocyte survival is regulated by the apoptotic cascade.Results: Natalizumab-induced peripheral lymphocytosis protected from post-natalizumab MS reactivation. Subjects who relapsed or had magnetic resonance imaging (MRI) worsening after treatment cessation, in fact, had milder peripheral lymphocyte increases during the treatment, largely caused by less marked T cell increase. Furthermore, subjects carrying a variant of the gene coding for Akt associated with reduced anti-apoptotic efficiency (rs2498804T) had lower lymphocytosis and higher risk of disease reactivation.Conclusion: This study identified one functionally meaningful genetic variant within the Akt signaling pathway that is associated with both lymphocyte count and composition alterations during natalizumab treatment, and with the risk of disease reactivation after natalizumab discontinuation.
[show abstract][hide abstract] ABSTRACT: Alzheimer's disease (AD) is a multifactorial neurodegenerative disorder characterized by the extracellular deposit of Amyloid beta (Aβ), mainly of the Amyloid beta(1-42) (Aβ(1-42)) peptide in the hippocampus and neocortex leading to progressive cognitive decline and dementia. The possible imbalance between the Aβ production/degradation process was suggested to contribute to the pathogenesis of AD. Among others, the serine protease plasmin has shown to be involved in Aβ(1-42) clearance, a hypothesis strengthened by neuropathological studies on AD brains. To explore whether there is a change in plasmin system in CSF of AD patients, we analyzed CSF samples from AD and age-matched controls, looking at plasminogen, tissue plasminogen activator (t-PA) and plasminogen activator inhibitor (PAI-1) protein levels and t-PA and urokinase plasminogen activator (u-PA) enzymatic activities. We also measured Aβ(1-42), total-tau and phospho-tau (181) CSF levels and sought for a possible relationship between them and plasmin system values. Our findings showed that t-PA, plasminogen and PAI-1 levels, as t-PA enzymatic activity, remained unchanged in AD with respect to controls; u-PA activity was not detected. We conclude that CSF analysis of plasminogen system does not reflect changes observed post-mortem. Unfortunately, the CSF detection of plasmin system could not be a useful biomarker for either AD diagnosis or disease progression. However, these findings do not exclude the possible involvement of the plasmin system in AD.
Journal of Neural Transmission 03/2012; 119(7):763-9. · 3.05 Impact Factor
[show abstract][hide abstract] ABSTRACT: Abnormal glutamate-dependent synaptic excitation contributes to neuronal damage in multiple sclerosis (MS). Little is known about the involvement of the GABA system in this disorder. Here we found that cerebrospinal fluid (CSF) from MS patients with enhanced brain lesions on magnetic resonance imaging inhibited GABA transmission in mouse brain slices. Enhanced IL-1β neuronal action was responsible for this effect, because IL-1β receptor antagonist blocked, and exogenous IL-1β mimicked the synaptic effect of inflamed CSF. Our results provide evidence that focal inflammation in MS perturbs the cytokine milieu within the circulating CSF, resulting in diffuse GABAergic alteration in neurons.
[show abstract][hide abstract] ABSTRACT: The dysfunction of cholinergic neurons is a typical hallmark in Alzheimer's disease (AD). In animal models of AD, fragments of amyloid beta protein (Aβ) and Tau protein are thought to interfere with central cholinergic transmission, specifically with synthesis and release of acetylcholine. Thus, we aimed to investigate whether the cerebrospinal fluid (CSF) levels of Aβ42 and Tau proteins in AD patients could influence physiological central cholinergic activity. In AD patients (n = 19), central cholinergic function was evaluated in vivo by using short afferent latency inhibition (SLAI), and compared to age-matched healthy controls. In the same AD patients, CSF samples were collected through lumbar puncture to obtain individual levels of Aβ42, total Tau (t-Tau) and phosphorylated Tau (p-Tau) (Thr181). SLAI was decreased in AD patients in comparison to age-matched healthy controls. We found that in patients there was a negative correlation between the individual amount of cholinergic activity assessed by SLAI and the CSF levels of Aβ42. On the other hand, there was a positive correlation between the levels of SLAI and CSF p-Tau. No correlation was found when SLAI was analysed together with t-Tau. These results demonstrate that mechanisms of cortical cholinergic activity are altered in patients bearing a pathological CSF hallmark of AD, suggesting that these peptides may have some influence on the cholinergic dysfunction in AD. We suggest that coupling of CSF biomarkers with neurophysiological parameters of central cholinergic function could be important to better detect ongoing mechanisms of neural degeneration in vivo.
Journal of Neural Transmission 03/2012; 119(7):771-8. · 3.05 Impact Factor
[show abstract][hide abstract] ABSTRACT: BACKGROUND: The Expanded Disability Status Scale (EDSS) is the most widely used measure of disability in MS, however because of its limitations surrogate markers of clinical disability progression are of high interest. Transcranial magnetic stimulation (TMS) measures of demyelination and cortical excitability correlate with disability levels in MS. OBJECTIVE: Aim of this study was testing whether paired pulse (pp) TMS represents a reliable surrogate marker to measure clinical disability in MS. METHODS: ppTMS measures of intracortical synaptic transmission such as short interval intracortical inhibition (SICI), long interval intracortical inhibition (LICI), short interval intracortical facilitation (SICF) and intracortical facilitation (ICF) were collected from 74 patients affected by MS. Correlation of EDSS scores with ppTMS measures was analyzed. RESULTS: EDSS scores correlated with patient's age, disease duration, Motor Evoked Potentials latency and thresholds and SICF measures but not with age of onset, SICI, ICF and LICI. CONCLUSIONS: These findings support a possible use of SICF and MEP latency as surrogate markers of disability in MS. Further research is warranted to determine the role of SICF in the follow up of disease progression and to validate its use as an endpoint in multiple sclerosis clinical trials.
[show abstract][hide abstract] ABSTRACT: The role of N-methyl-D-aspartate receptors (NMDARs) in the generation and maintenance of epileptic seizures has been widely investigated, however, little is known of possible separate roles played by NMDARs that contain different NR2 subunits. A better comprehension of how distinct NMDARs subtypes participate in seizure generation and/or diffusion may lead to the development of more targeted pharmacologic strategies to treat epilepsy. Therefore, we have performed an electrophysiologic investigation using a multielectrode array device, on slices comprising entorhinal cortex (EC) and hippocampus, continuously perfused in a Mg(2+) -free medium, with added 4-aminopiridine (4AP; 10-15 μm). Two separate rhythmic patterns of interictal-like activity were generated in EC and hippocampus, with EC seizures entrained to those in CA3, so that a significant degree of cross-correlation occurred. Perfusion with the NR2A-containing NMDAR antagonist [(R)-[(S)-1-(4-bromo-phenyl)-ethylamino]-(2,3-dioxo-1,2,3,4-tetrahydroquinoxalin-5-yl)-methyl]-phosphonic acid (NVP-AAM077; 50 nm) or Zn(2+) (200 nm), did not affect the rate of interictal-like events in EC and hippocampus; however, it significantly reduced their cross-correlation, causing a substantial decoupling of the two rhythm generators. The same effect was observed with (αR,βS)-α-(4-hydroxyphenyl)-β-methyl-4-(phenylmethyl)-1-piperidinepropanol maleate (Ro25-6981; 1 μm), when coapplied with a subthreshold dose of NVP-AAM077. Our results suggest that NR2 subunits may be crucial in entraining cortical networks, leading to recruitment of wider range oscillations during epilepsy. Therefore, a pharmacologic strategy directed onto NR2 subunits may help to limit seizure diffusion and recruitment of potentially entrained oscillatory networks.
[show abstract][hide abstract] ABSTRACT: A significant proportion of multiple sclerosis (MS) patients have functionally relevant cerebellar deficits, which significantly contribute to disability. Although clinical and experimental studies have been conducted to understand the pathophysiology of cerebellar dysfunction in MS, no electrophysiological and morphological studies have investigated potential alterations of synaptic connections of cerebellar Purkinje cells (PC). For this reason we analyzed cerebellar PC GABAergic connectivity in mice with MOG((35-55))-induced experimental autoimmune encephalomyelitis (EAE), a mouse model of MS. We observed a strong reduction in the frequency of the spontaneous inhibitory post-synaptic currents (IPSCs) recorded from PCs during the symptomatic phase of the disease, and in presence of prominent microglia activation not only in the white matter (WM) but also in the molecular layer (ML). The massive GABAergic innervation on PCs from basket and stellate cells was reduced and associated to a decrease of the number of these inhibitory interneurons. On the contrary no significant loss of the PCs could be detected. Incubation of interleukin-1beta (IL-1β) was sufficient to mimic the electrophysiological alterations observed in EAE mice. We thus suggest that microglia and pro-inflammatory cytokines, together with a degeneration of basket and stellate cells and their synaptic terminals, contribute to impair GABAergic transmission on PCs during EAE. Our results support a growing body of evidence that GABAergic signaling is compromised in EAE and in MS, and show a selective susceptibility to neuronal and synaptic degeneration of cerebellar inhibitory interneurons.
Neurobiology of Disease 02/2012; 46(2):414-24. · 5.62 Impact Factor