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Background: Many transversal mechanisms act synergistically at different time-points in the cascade of Alzheimer’s disease (AD), since amyloid-β (Aβ) deposition, tau pathology, and neuroinflammation influence each other. Objective: We explored the contributions of microglia and astrocytes in patients with symptomatic sporadic AD stratified according to AT(N) system and APOE genotype. Methods: We compared the cerebrospinal fluid (CSF) levels of sTREM-2 and markers of astrocytic activation (GFAP; β-S100) from 71 patients with AD (23 A+T–,48 A+T+; 38 APOE ɛ3, 33 APOE ɛ4) and 30 healthy controls (HC). With multivariate analyses we investigated associations between glial biomarkers, Aβ42, and p-tau in all subgroups. Results: CSF sTREM-2 was higher in A+T+ [1.437 (0.264)] and A+T– [1.355 (0.213)] than in HC [1.042 (0.198); both p

Although the cerebellum is not among the most renowned brain structures affected in Alzheimer`s disease (AD), recent evidence suggest that it undergoes degenerative changes during the course of the disease. A main neurophysiological feature of AD patients is the remarkable impairment of long term potentiation (LTP)-like cortical plasticity assessed in the primary motor cortex (M1) using theta burst stimulation (TBS) protocols. In healthy conditions, continuous (cTBS) and intermittent TBS (iTBS) of the cerebellum induce respectively long term depression (LTD)-like and LTP-like after effects in the contralateral M1. Here we aimed at examining the effects of cerebellar TBS on contralateral M1 excitability in a sample of 15 AD patients and 12 healthy age matched controls (HS). Motor evoked potentials (MEPs) were obtained in the contralateral M1 before and after cerebellar cTBS and iTBS protocols. As compared to HS, AD patients showed an impairment of LTP-like cortical plasticity mechanisms following cerebellar iTBS. No difference was observed for the cTBS protocol, in which both populations exhibited the expected LTD-like after effect. This study shows that mechanisms of cerebellar-cortical plasticity are impaired in AD. Given its role in high order cognitive functions, new potential therapeutic strategies could be built up in the future to modulate neural activity in the cerebellum in AD.

Multiple sclerosis (MS) is a chronic disease of the central nervous system (CNS) characterized by persistent inflammation orchestrated by cluster of differentiation (CD) 4 T helper (Th) cells. In particular, Th1 and Th17 cells amplify, whereas T regulatory (Treg) cells moderate inflammation. The role of other Th subsets in MS is not clear. In the present study, we investigated the generation of different Th responses by human dendritic cells (DCs) in MS. We compared the production of several Th cytokines by naive CD4+ T-cells polarized with myeloid and plasmacytoid DCs (mDCs and pDCs) in healthy donors (HD) and relapsing–remitting (RR)-MS patients. We found that resiquimod-stimulated mDCs were able to activate Th17 differentiation, whereas pDCs induced interleukin (IL)-10-producing Th cells. Surprisingly, resiquimod-stimulated pDCs from MS patients also significantly induced the differentiation of Th9 cells, which produce IL-9 and are known to be involved in allergic diseases. We investigated the potential role of IL-9 in MS. We found that IL-9 activated signal transducer and activator of transcription (STAT) 1 and STAT5 phosphorylation and interfered with IL-17 and interferon (IFN) regulatory transcription factor (IRF)-4 expression in Th17-polarized cells. Moreover, in the cerebrospinal fluid (CSF) of 107 RR-MS patients, IL-9 inversely correlated with indexes of inflammatory activity, neurodegeneration and disability progression of MS. High levels of IL-9 were associated with the absence of IL-17 in the CSF of RR-MS patients. Our results demonstrate a Th9-inducing potential of pDCs in MS, suggesting an immunoregulatory role leading to attenuation of the exaggerated Th17 inflammatory response.

Background: Subtle diffuse intrathecal inflammation is undetectable by conventional neuroimaging, and could influence multiple sclerosis (MS) disease course. Objective: To explore the role of subclinical persisting intrathecal inflammation in radiologically isolated syndrome (RIS) or clinically isolated syndrome (CIS) conversion to MS, and in early MS disease reactivation. Methods: One-hundred ninety-three subjects with RIS, CIS, relapsing–remitting (RR), or primary progressive (PP) MS were included, along with 76 matched controls. Cerebrospinal fluid (CSF) levels of interleukin-8 (IL-8), a major proinflammatory cytokine, were measured as a biomarker of intrathecal inflammation. Patients were followed up for 2 years. Clinical and imaging measures of disease progression were recorded. Results: High central contents of IL-8 were associated to clinical progression in subjects with RIS, and to the risk of conversion to MS in subjects with CIS. Asymptomatic intrathecal inflammation placed subjects at risk for MS conversion, even regardless lesion load. CSF IL-8 levels were higher in RR MS with high disease activity. Higher number of relapses in the first two years since diagnosis and shorter first inter-attack intervals were observed in patients with high levels of IL-8. Conclusion: IL-8 might provide utility in determining the presence of active intrathecal inflammation, and could be important in diagnostically undefined cases.

During multiple sclerosis (MS) inflammatory attacks, and in subsequent clinical recovery phases, immune cells contribute to neuronal and oligodendroglial cell survival and tissue repair by secreting growth factors. Animal studies showed that growth factors also play a substantial role in regulating synaptic plasticity, and namely in long-term potentiation (LTP). LTP could drive clinical recovery in relapsing patients by restoring the excitability of denervated neurons. We recently reported that maintenance of synaptic plasticity reserve is crucial to contrast clinical deterioration in MS and that the platelet-derived growth factor (PDGF) may play a key role in its regulation. We also reported that a Hebbian form of LTP-like cortical plasticity, explored by paired associative stimulation (PAS), correlates with clinical recovery from a relapse in MS. Here, we explored the role of PDGF in clinical recovery and in adaptive neuroplasticity in relapsing-remitting MS (RR-MS) patients. We found a correlation between the cerebrospinal fluid (CSF) PDGF concentrations and the extent of clinical recovery after a relapse, as full recovery was more likely observed in patients with high PDGF concentrations and poor recovery in subjects with low PDGF levels. Consistently with the idea that PDGF-driven synaptic plasticity contributes to attenuate the clinical consequences of tissue damage in RR-MS, we also found a striking correlation between CSF levels of PDGF and the amplitude of LTP-like cortical plasticity explored by PAS. CSF levels of fibroblast growth factor, granulocyte colony-stimulating factor and granulocyte-macrophage colony-stimulating factor did not correlate with clinical recovery nor with measures of synaptic transmission and plasticity.

BACKGROUND AND PURPOSE Alterations of glutamate-mediated synaptic transmission occur early during neuroinflammatory insults, and lead to degenerative neuronal damage in multiple sclerosis (MS) and also in experimental autoimmune encephalomyelitis (EAE), which is a murine model of MS. Fingolimod is an effective orally active agent for the treatment of MS, affecting lymphocyte invasion of the brain. However, it is still unclear if fingolimod can be neuroprotective in this disorder. EXPERIMENTAL APPROACH Using neurophysiological recordings and morphological evaluation of dendritic integrity, we evaluated the effects of oral fingolimod on the clinical score of EAE mice in order to determine whether the compound was associated with preservation of synaptic transmission. KEY RESULTS Oral fingolimod prevented and reversed the pre- and postsynaptic alterations of glutamate transmission in EAE mice. These effects were associated with a clear amelioration of the clinical deterioration seen in EAE mice, and with a significant inhibition of neuronal dendritic pathology. Fingolimod did not alter the spontaneous excitatory postsynaptic currents in control animals, suggesting that only the pathological processes behind the inflammation-induced defects in glutamate transmission were modulated by this compound. CONCLUSIONS AND IMPLICATIONS The beneficial effects of fingolimod on the clinical, synaptic and dendritic abnormalities of murine EAE might correlate with the neuroprotective actions of this agent, as observed in MS patients. LINKED ARTICLE This article is commented on by Gillingwater, pp. 858–860 of this issue. To view this commentary visit http://dx.doi.org/10.1111/j.1476-5381.2011.01612.x

Objective: The frequency of inflammatory episodes in the early stages of multiple sclerosis (MS) has been correlated with late neurodegeneration, but the mechanism by which inflammation gives rise to delayed neuronal damage is unknown. Increased activity of the neurotransmitter glutamate is thought to play a role in the inflammation-driven neurodegenerative process of MS, and therefore we tested whether inflammatory cytokines released during acute MS attacks have the property of enhancing glutamate-mediated transmission and excitotoxicity in central neurons. Methods: We compared the effect of cerebrospinal fluid (CSF) from active and quiescent MS patients on glutamate-mediated excitatory postsynaptic currents (EPSCs) and excitotoxic damage in rodent brain slices. We also measured CSF concentrations of tumor necrosis factor-α, of interleukin-1β (IL-1β), and of IL-1 receptor antagonist (IL-1ra), and correlated cytokine levels with cortical excitability assessed in MS patients by means of paired-pulse transcranial magnetic stimulation (TMS). Results: CSF from MS patients with enhanced brain lesions at magnetic resonance imaging was able to increase spontaneous EPSC frequency and glutamate-mediated neuronal swelling in vitro, through a mechanism dependent on enhanced IL-1β signaling and increased glutamate α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptor stimulation. Furthermore, IL-1β/IL-1ra ratio was significantly higher in the CSF of active MS subjects, and correlated with intracortical facilitation, an accredited TMS measure of glutamate transmission. Finally, we identified for the first time transient receptor potential vanilloid 1 channels as essential intermediates for the synaptic action of IL-1β on central glutamatergic synapses. Interpretation: Our results provide compelling evidence of the synaptic mechanism linking inflammation and excitotoxic neurodegeneration in MS. ANN NEUROL 2012;71:76–83

Abnormal dopamine (DA) transmission in the striatum plays a pivotal role in attention-deficit/hyperactivity disorder (ADHD). As striatal DA signalling modulates the endocannabinoid system (ECS), the present study was aimed at investigating cannabinoid CB1 receptor (CB1R) function in a model of ADHD obtained by triple point-mutation in the dopamine transporter (DAT) gene in mice, making them insensitive to cocaine [DAT cocaine-insensitive (DAT-CI) mice]. DAT-CI mice had a marked hyperactive phenotype, and neurophysiological recordings revealed that the sensitivity of CB1Rs controlling GABA-mediated synaptic currents [CB1Rs((GABA)) ] in the striatum was completely lost. In contrast, CB1Rs modulating glutamate transmission [CB1Rs((Glu)) ], and GABA(B) receptors were not affected in this model of ADHD. In DAT-CI mice, the blockade of CB1R((GABA)) function was complete even after cocaine or environmental manipulations activating the endogenous DA-dependent reward system, which are known to sensitize these receptors in control animals. Conversely, the hedonic property of sucrose was intact in DAT-CI mice, indicating normal sweet perception in these animals. Our results point to CB1Rs as novel molecular players in ADHD, and suggest that therapeutic strategies aimed at interfering with the ECS might prove effective in this disorder.

Objective: It is still unclear whether chronic cerebrospinal venous insufficiency (CCSVI) is associated with multiple sclerosis (MS), because substantial methodological differences have been claimed by Zamboni to account for the lack of results of other groups. Furthermore, the potential role of venous malformations in influencing MS severity has not been fully explored. This information is particularly relevant, because uncontrolled surgical procedures are increasingly offered to MS patients to treat their venous stenoses. Methods: In the present study, CCSVI was studied in 84 MS patients and in 56 healthy subjects by applying the Zamboni method for CCSVI identification. Results: We found no significant differences (p = 0.12) in CCSVI frequency between MS and control subjects. Furthermore, no differences were found between CCSVI-positive and CCSVI-negative patients in terms of relevant clinical variables such as disease duration, time between onset and first relapse, relapsing or progressive disease course, and risk of secondary progression course. Statistically significant differences were not found between CCSVI-positive and CCSVI-negative MS subjects by analyzing direct measures of disability such as mean Expanded Disability Status Scale (EDSS) (p = 0.07), mean progression index (p > 0.1), and mean MS severity score (p > 0.1). The percentage of subjects who reached EDSS 4.0 and 6.0 milestones was not different among CCSVI-negative and CCSVI-positive subjects, and no significant correlation was found between severity of disability and number of positive CCSVI criteria. Interpretation: Our results indicate that CCSVI has no role in either MS risk or MS severity. Ann Neurol 2011

Our aim is to establish the predictive value of LTP-like cortical plasticity as a prognostic biomarker of disease progression in terms of cognitive decline. We applied different neurophysiological protocols in a sample of 60 AD patients and 30 age matched healthy controls. Results: We found that area under curve (AUC) was 0.90 for LTP, indicating an excellent diagnostic accuracy of this biomarker, but only 0.64 for SAI. We performed univariate regression analyses for LTP, SAI, CSF biomarkers, APOE4 genotype, neuropsychological evaluation, disease duration, education and demographic factors. Results showed that LTP was the only significant predictor of disease progression ( p = 0.02), while there was no effect for SAI ( p = 0.84), CSF total tau ( p = 0.10), CSF p-tau ( p = 0.21), CSF A β ( p = 0.54), APOE4 genotype ( p = 0.32), neuropsychological battery and other demographic factors. The probability of disease progression significantly decreased with every point increase of LTP ( p = 0.04). ROC curve was also performed to evaluate the sensitivity and specificity of LTP biomarker in predicting cognitive decline in AD patients. We found an AUC = 0.71 indicating a fair prognostic accuracy of this biomarker in discriminating among AD patients those with faster disease progression. LTP impairment can be considered as a biomarker of progression in AD patients.

Proinflammatory cytokines such as tumor necrosis factor-α and interleukin-1β (IL1β) regulate both excitatory and inhibitory synaptic transmission in the central nervous system. The interaction between IL1β and endocannabinoid system (ECS) is also emerging, based on the evidence that IL1β effects on striatal spontaneous excitatory and inhibitory postsynaptic currents are regulated by transient receptor potential vanilloid 1 (TRPV1) channels, members of the ECS. Furthermore, IL1β has also been shown to control the sensitivity of cannabinoid CB1 receptors controlling GABA transmission (CB1Rs(GABA)) in the striatum. To better detail the synaptic action of IL1β, and to clarify its complex interaction with the ECS, here we investigated the possible interplay between IL1β and CB1Rs controlling glutamate transmission (CB1Rs(glu)), other critical elements of the ECS. Our results show that the sensitivity of CB1Rs(glu) is fully blocked in the presence of IL1β in corticostriatal brain slices, and that the protein kinase C/TRPV1 pathway is involved in this effect. IL1β failed to modulate the sensitivity of glutamate synapses to the stimulation of GABAB receptors. We also provided evidence that IL1β-CB1Rs(GABA) but not IL1β-CB1Rs(glu) interaction is under the control of the brain-derived neurotrophic factor (BDNF)/trkB signaling and of lipid raft composition, because BDNF gene partial deletion, pharmacological blockade of trkB and membrane cholesterol removal with methyl-β-cyclodextrin all blocked IL1β-mediated inhibition of CB1Rs(GABA) but left unaltered the sensitivity of CB1Rs(glu) to this cytokine. Our results provide further evidence that synaptic transmission and the ECS are regulated by IL1β in the striatum.

Introduction APOE E4 allele associates not only with AD risk and a lower age onset, but also with faster cognitive decline and greater cerebral atrophy, suggesting a key role of this polymorphism in modulating both disease risk and clinical outcome. Objectives In this study we investigated the correlation between cognitive decline, motor cortical plasticity and cerebrospinal fluid (CSF) biomarkers profile of AD patients divided by APOE polymorphism in E4 allele carriers (E4) and homozygous E3 carriers. Materials and methods A monophasic Magstim 200 device was used to deliver intermitted/continuous theta burst stimulation (iTBS/cTBS) protocols. ELISA was used for determination of CSF biomarkers level. Forty-one AD patients underwent lumbar puncture for CSF withdrawal, blood screening for APOE polymorphism, stimulation protocols applied over the primary motor cortex and mini mental state examination (MMSE) at baseline and at 6-, 12- and 18-months. Results No difference was found in CSF biomarkers profile within the APOE variants group. I-TBS after-effects were significantly reduced in E3 in comparison with E4 AD patients. Correlation analyses revealed that the individual amount of iTBS induced plasticity correlated with delta-MMSE and total Tau showing that a less pronounced LTP-like plasticity and higher total-Tau CSF levels were associated with a higher delta-MMSE. Only in apoE4 patients Tau pathology correlates with cortical plasticity impairment and cognitive decline. A multivariate analysis showed that APOE polymorphism and LTP-like plasticity, but not t-Tau levels, are independently able to predict delta-MMSE in AD patients. Conclusions APOE variants show different level of cortical plasticity and are independently associated with clinical progression in AD patients. Tau pathology is specific for ApoE4 group driving cortical plasticity impairment and cognitive decline. ApoE4 patients represent a pure model of TAU-driven AD pathology. ApoE3 patients are characterized by different mechanisms of cortical plasticity impairment and clinical symptoms. LTP impairment is a marker of pathophysiological dysfunction in AD and, as such, it should be taken in account also for the adoption of new pharmacological strategies, considering AD as a disorder of synaptic plasticity.

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.

Abnormal dopamine (DA) transmission in the striatum plays a pivotal role in attention-deficit/hyperactivity disorder (ADHD). As striatal DA signalling modulates the endocannabinoid system (ECS), the present study was aimed at investigating cannabinoid CB1 receptor (CB1R) function in a model of ADHD obtained by triple point-mutation in the dopamine transporter (DAT) gene in mice, making them insensitive to cocaine [DAT cocaine-insensitive (DAT-CI) mice]. DAT-CI mice had a marked hyperactive phenotype, and neurophysiological recordings revealed that the sensitivity of CB1Rs controlling GABA-mediated synaptic currents [CB1Rs((GABA)) ] in the striatum was completely lost. In contrast, CB1Rs modulating glutamate transmission [CB1Rs((Glu)) ], and GABA(B) receptors were not affected in this model of ADHD. In DAT-CI mice, the blockade of CB1R((GABA)) function was complete even after cocaine or environmental manipulations activating the endogenous DA-dependent reward system, which are known to sensitize these receptors in control animals. Conversely, the hedonic property of sucrose was intact in DAT-CI mice, indicating normal sweet perception in these animals. Our results point to CB1Rs as novel molecular players in ADHD, and suggest that therapeutic strategies aimed at interfering with the ECS might prove effective in this disorder.