Neuromodulatory properties of inflammatory cytokines and their impact on neuronal excitability

Neuroprotection mediated by inhibition of calpain during acute viral encephalitis

Neurologic complications associated with viral encephalitis, including seizures and cognitive impairment, are a global health issue, especially in children. We previously showed that hippocampal injury during acute picornavirus infection in mice is associated with calpain activation and is the result of neuronal death triggered by brain-infiltrating inflammatory monocytes. We therefore hypothesized that treatment with a calpain inhibitor would protect neurons from immune-mediated bystander injury. C57BL/6J mice infected with the Daniel's strain of Theiler's murine encephalomyelitis virus were treated with the FDA-approved drug ritonavir using a dosing regimen that resulted in plasma concentrations within the therapeutic range for calpain inhibition. Ritonavir treatment significantly reduced calpain activity in the hippocampus, protected hippocampal neurons from death, preserved cognitive performance, and suppressed seizure escalation, even when therapy was initiated 36 hours after disease onset. Calpain inhibition by ritonavir may be a powerful tool for preserving neurons and cognitive function and preventing neural circuit dysregulation in humans with neuroinflammatory disorders.

Independent impact of infections on the course and outcome of status epilepticus: a 10-year cohort study

Infections are frequent in patients with status epilepticus (SE). It remains unclear if infections merely reflect severity of the underlying illness or if they independently predict unfavourable course and outcome. We sought to determine if infections diagnosed within 48 h from SE onset are independent predictors of poor course and outcome and if their effect is modified by clinical characteristics. From 2005 to 2014, pertinent clinical data, microbiology, death, return to functional baseline, and unfavourable outcome in survivors were assessed in SE patients treated in the intensive care units (ICU) of an academic medical care center. Among 352 consecutive patients, 81 (23 %) were diagnosed with infections at SE onset. In-hospital mortality was higher in patients with infections (26 %) compared to 10 % in patients without infections (p < 0.001). Infections at SE onset increased the odds ratios (OR) for prolonged ICU (OR = 4.1, 95 %CI 1.87-6.74) and hospital stay (OR = 5.4, 95 %CI 1.24-9.63), refractory SE (OR = 3.1, 95 %CI 1.79-5.34), prolonged mechanical ventilation (OR = 3.8, 95 %CI 2.15-6.79), no return to functional baseline (OR = 2.1, 95 %CI 1.10-4.02), unfavourable outcome in survivors (OR = 2.0, 95 %CI 1.02-3.81), and death (OR = 2.5, 95 %CI 1.28-4.99). All associations were independent of confounders and without significant effect modification by age, level of consciousness, types and severity of SE, and etiologies. In addition, the number of infections increased the probability of unfavourable course and outcome. Infections at SE onset are frequent and associated with prolonged medical care, treatment refractory SE, higher morbidity and mortality independently of potential confounders calling for the evaluation of treatment strategies.

Anti-Inflammatory Small Molecules To Treat Seizures and Epilepsy: From Bench to Bedside

As a crucial component of brain innate immunity, neuroinflammation initially contributes to neuronal tissue repair and maintenance. However, chronic inflammatory processes within the brain and associated blood-brain barrier (BBB) impairment often cause neurotoxicity and hyperexcitability. Mounting evidence points to a mutual facilitation between inflammation and epilepsy, suggesting that blocking the undesired inflammatory signaling within the brain might provide novel strategies to treat seizures and epilepsy. Neuroinflammation is primarily characterized by the upregulation of proinflammatory mediators in epileptogenic foci, among which cyclooxygenase-2 (COX-2)/prostaglandin E2 (PGE2), interleukin-1β (IL-1β), transforming growth factor-β (TGF-β), toll-like receptor 4 (TLR4), high-mobility group box 1 (HMGB1), and tumor necrosis factor-α (TNF-α) have been extensively studied. Small molecules that specifically target these key proinflammatory perpetrators have been evaluated for antiepileptic and antiepileptogenic effects in animal models. These important preclinical studies provide new insights into the regulation of inflammation in epileptic brains and guide drug discovery efforts aimed at developing novel anti-inflammatory therapies for seizures and epilepsy.

Impact of rapamycin on status epilepticus induced hippocampal pathology and weight gain

Growing evidence implicates the dentate gyrus in temporal lobe epilepsy (TLE). Dentate granule cells limit the amount of excitatory signaling through the hippocampus and exhibit striking neuroplastic changes that may impair this function during epileptogenesis. Furthermore, aberrant integration of newly-generated granule cells underlies the majority of dentate restructuring. Recently, attention has focused on the mammalian target of rapamycin (mTOR) signaling pathway as a potential mediator of epileptogenic change. Systemic administration of the mTOR inhibitor rapamycin has promising therapeutic potential, as it has been shown to reduce seizure frequency and seizure severity in rodent models. Here, we tested whether mTOR signaling facilitates abnormal development of granule cells during epileptogenesis. We also examined dentate inflammation and mossy cell death in the dentate hilus. To determine if mTOR activation is necessary for abnormal granule cell development, transgenic mice that harbored fluorescently-labeled adult-born granule cells were treated with rapamycin following pilocarpine-induced status epilepticus. Systemic rapamycin effectively blocked phosphorylation of S6 protein (a readout of mTOR activity) and reduced granule cell mossy fiber axon sprouting. However, the accumulation of ectopic granule cells and granule cells with aberrant basal dendrites was not significantly reduced. Mossy cell death and reactive astrocytosis were also unaffected. These data suggest that anti-epileptogenic effects of mTOR inhibition may be mediated by mechanisms other than inhibition of these common dentate pathologies. Consistent with this conclusion, rapamycin prevented pathological weight gain in epileptic mice, suggesting that rapamycin might act on central circuits or even peripheral tissues controlling weight gain in epilepsy.

Geranylgeraniol and Neurological Impairment: Involvement of Apoptosis and Mitochondrial Morphology

Deregulation of the cholesterol pathway is an anomaly observed in human diseases, many of which have in common neurological involvement and unknown pathogenesis. In this study we have used Mevalonate Kinase Deficiency (MKD) as a disease-model in order to investigate the link between the deregulation of the mevalonate pathway and the consequent neurodegeneration. The blocking of the mevalonate pathway in a neuronal cell line (Daoy), using statins or mevalonate, induced an increase in the expression of the inflammasome gene (NLRP3) and programmed cell death related to mitochondrial dysfunction. The morphology of the mitochondria changed, clearly showing the damage induced by oxidative stress and the decreased membrane potential associated with the alterations of the mitochondrial function. The co-administration of geranylgeraniol (GGOH) reduced the inflammatory marker and the damage of the mitochondria, maintaining its shape and components. Our data allow us to speculate about the mechanism by which isoprenoids are able to rescue the inflammatory marker in neuronal cells, independently from the block of the mevalonate pathway, and about the fact that cell death is mitochondria-related.

Proteomic profiling of epileptogenesis in a rat model: Focus on inflammation

Detailed knowledge about the patterns of molecular alterations during epileptogenesis is a presupposition for identifying targets for preventive or disease-modifying approaches, as well as biomarkers of the disease. Large-scale differential proteome analysis can provide unique and novel perspectives based on comprehensive data sets informing about the complex regulation patterns in the disease proteome. Thus, we have completed an elaborate differential proteome analysis based on label-free LC-MS/MS in a rat model of epileptogenesis. Hippocampus and parahippocampal cortex tissues were sampled and analyzed separately at three key time points chosen for monitoring disease development following electrically-induced status epilepticus, namely, the early post-insult phase, the latency phase, and the chronic phase with spontaneous recurrent seizures. We focused the bioinformatics analysis on proteins linked to immune and inflammatory responses, because of the emerging evidence of the specific pathogenic role of inflammatory signalings during epileptogenesis. In the early post-insult and the latency phases, pathway enrichment analysis revealed an extensive over-representation of Toll-like receptor signaling, pro-inflammatory cytokines, heat shock protein regulation, and transforming growth factor beta signaling and leukocyte transendothelial migration. The inflammatory response in the chronic phase proved to be more moderate with differential expression in the parahippocampal cortex exceeding that in the hippocampus. The data sets provide novel information about numerous differentially expressed proteins, which serve as interaction partners or modulators in key disease-associated inflammatory signaling events. Noteworthy, a set of proteins which act as modulators of the ictogenic Toll-like receptor signaling proved to be differentially expressed. In addition, we report novel data demonstrating the regulation of different Toll-like receptor ligands during epileptogenesis. Taken together, the findings deepen our understanding of modulation of inflammatory signaling during epileptogenesis providing an excellent and comprehensive basis for the identification of target and biomarker candidates.

Transient increase of interleukin-1β after prolonged febrile seizures promotes adult epileptogenesis through long-lasting upregulating endocannabinoid signaling

It remains unclear how infantile febrile seizures (FS) enhance adult seizure susceptibility. Here we showed that the transient increase of interleukin-1β (IL-1β) after prolonged FS promoted adult seizure susceptibility, which was blocked by interleukin-1 receptor antagonist (IL-1Ra) within a critical time window. Postnatal administered IL-1β alone mimicked the effect of FS on adult seizure susceptibility. IL-1R1 knockout mice were not susceptible to adult seizure after prolonged FS or IL-1β treatment. Prolonged FS or early-life IL-1β treatment increased the expression of cannabinoid type 1 receptor (CB1R) for over 50 days, which was blocked by IL-1Ra or was absent in IL-1R1 knockout mice. CB1R antagonist, knockdown and endocannabinoid synthesis inhibitor abolished FS or IL-1β-enhanced seizure susceptibility. Thus, this work identifies a pathogenic role of postnatal IL-1β/IL-1R1 pathway and subsequent prolonged prominent increase of endocannabinoid signaling in adult seizure susceptibility following prolonged FS, and highlights IL-1R1 as a potential therapeutic target for preventing the development of epilepsy after infantile FS.

Inflammatory mediators in human epilepsy: A systematic review and meta-analysis

BACKGROUND

Accumulating evidence suggests a role for inflammation in the pathophysiology of epilepsy.

METHODS

We performed a systematic review and meta-analysis of studies that investigated inflammatory mediators in human epilepsy. Studies reporting on inflammatory mediators in serum, cerebrospinal fluid or brain tissue of epilepsy patients were included. Studies comparing patients to controls were included in a meta-analysis.

RESULTS

66 articles reporting on 1934 patients were included. IL-1ra, IL-1β, IL-6, IL-10, IFN-γ and TNF-α were the most extensively investigated proteins. Elevated levels for IL-1ra, IL-1β, IL-6 and CXCL8/IL-8 were reported in several different epilepsy etiologies and media, while other proteins were specifically increased for one etiology. IL-1α, IL-7 and IL-13, as well as the chemokines CCL2-5, -19 and -22, were increased exclusively in brain tissue. In an aggregate meta-analysis, we found significantly different protein levels for serum IL-6, IL-17 and CSF IL-1β and IL-10.

CONCLUSION

Inflammatory pathways are involved in epilepsy. Future studies may further clarify their role, and prove potential of targeted anti-inflammatory treatment.

Infections, inflammation and epilepsy

Epilepsy is the tendency to have unprovoked epileptic seizures. Anything causing structural or functional derangement of brain physiology may lead to seizures, and different conditions may express themselves solely by recurrent seizures and thus be labelled "epilepsy." Worldwide, epilepsy is the most common serious neurological condition. The range of risk factors for the development of epilepsy varies with age and geographic location. Congenital, developmental and genetic conditions are mostly associated with the development of epilepsy in childhood, adolescence and early adulthood. Head trauma, infections of the central nervous system (CNS) and tumours may occur at any age and may lead to the development of epilepsy. Infections of the CNS are a major risk factor for epilepsy. The reported risk of unprovoked seizures in population-based cohorts of survivors of CNS infections from developed countries is between 6.8 and 8.3 %, and is much higher in resource-poor countries. In this review, the various viral, bacterial, fungal and parasitic infectious diseases of the CNS which result in seizures and epilepsy are discussed. The pathogenesis of epilepsy due to brain infections, as well as the role of experimental models to study mechanisms of epileptogenesis induced by infectious agents, is reviewed. The sterile (non-infectious) inflammatory response that occurs following brain insults is also discussed, as well as its overlap with inflammation due to infections, and the potential role in epileptogenesis. Furthermore, autoimmune encephalitis as a cause of seizures is reviewed. Potential strategies to prevent epilepsy resulting from brain infections and non-infectious inflammation are also considered.

Value of Functionalized Superparamagnetic Iron Oxide Nanoparticles in the Diagnosis and Treatment of Acute Temporal Lobe Epilepsy on MRI

Purpose. Although active targeting of drugs using a magnetic-targeted drug delivery system (MTDS) with superparamagnetic iron oxide nanoparticles (SPIONs) is a very effective treatment approach for tumors and other illnesses, successful results of drug-resistant temporal lobe epilepsy (TLE) are unprecedented. A hallmark in the neuropathology of TLE is brain inflammation, in particular the activation of interleukin-1β (IL-1β) induced by activated glial cells, which has been considered a new mechanistic target for treatment. The purpose of this study was to determine the feasibility of the functionalized SPIONs with anti-IL-1β monoclonal antibody (mAb) attached to render MRI diagnoses and simultaneously provide targeted therapy with the neutralization of IL-1β overexpressed in epileptogenic zone of an acute rat model of TLE. Experimental Design. The anti-IL-1β mAb-SPIONs were studied in vivo versus plain SPIONs and saline. Lithium-chloride pilocarpine-induced TLE models (n = 60) were followed by Western blot, Perl's iron staining, Nissl staining, and immunofluorescent double-label staining after MRI examination. Results. The magnetic anti-IL-1β mAb-SPION administered intravenously, which crossed the BBB and was concentrated in the astrocytes and neurons in epileptogenic tissues, rendered these tissues visible on MRI and simultaneously delivered anti-IL-1β mAb to the epileptogenic focus. Conclusions. Our study provides the first evidence that the novel approach enhanced accumulation and the therapeutic effect of anti-IL-1β mAb by MTDS using SPIONs.

Modulation of neuronal excitability by immune mediators in epilepsy

A complex set of inflammatory molecules and their receptors has been described in epileptogenic foci in different forms of pharmacoresistant epilepsies. By activating receptor-mediated pathways in neurons, these molecules have profound neuromodulatory effects that are distinct from their canonical activation of immune functions. Importantly, the neuromodulatory actions of some inflammatory molecules contribute to hyperexcitability in neural networks that underlie seizures. This review summarizes recent findings related to the role of cytokines (IL-1beta and TNF-alpha) and danger signals (HMGB1) in decreasing seizure threshold, thereby contributing to seizure generation and the associated neuropathology. We will discuss preclinical studies suggesting that pharmacological inhibition of specific inflammatory signals may be useful to treat drug-resistant seizures in human epilepsy, and possibly arrest epileptogenesis in individuals at risk of developing the disease.

Lipopolysaccharide preconditioning prevents acceleration of kindling epileptogenesis induced by traumatic brain injury

10-20% of symptomatic epilepsies are post-traumatic. We examined effect of LPS preconditioning on epileptogenesis after controlled cortical impact (CCI). LPS (0.01, 0.1 and 0.5 mg/kg) was injected i.p. to rats 5 days before induction of CCI to parieto-temporal cortex. Kindling started 24h after CCI by i.p. injection of 30 mg/kg of pentylenetetrazole every other day until manifestation of 3 consecutive generalized seizures. CCI injury accelerated the rate of kindled seizures acquisition. LPS (0.1 and 0.5 mg/kg) prevented the acceleration of kindling. LPS preconditioning significantly decreased IL-1β and TNF-α over-expression and the number of damaged neurons in the hippocampus of traumatic rats.

Neuroinflammatory paradigms in lysosomal storage diseases

Lysosomal storage diseases (LSDs) include approximately 70 distinct disorders that collectively account for 14% of all inherited metabolic diseases. LSDs are caused by mutations in various enzymes/proteins that disrupt lysosomal function, which impairs macromolecule degradation following endosome-lysosome and phagosome-lysosome fusion and autophagy, ultimately disrupting cellular homeostasis. LSDs are pathologically typified by lysosomal inclusions composed of a heterogeneous mixture of various proteins and lipids that can be found throughout the body. However, in many cases the CNS is dramatically affected, which may result from heightened neuronal vulnerability based on their post-mitotic state. Besides intrinsic neuronal defects, another emerging factor common to many LSDs is neuroinflammation, which may negatively impact neuronal survival and contribute to neurodegeneration. Microglial and astrocyte activation is a hallmark of many LSDs that affect the CNS, which often precedes and predicts regions where eventual neuron loss will occur. However, the timing, intensity, and duration of neuroinflammation may ultimately dictate the impact on CNS homeostasis. For example, a transient inflammatory response following CNS insult/injury can be neuroprotective, as glial cells attempt to remove the insult and provide trophic support to neurons. However, chronic inflammation, as seen in several LSDs, can promote neurodegeneration by creating a neurotoxic environment due to elevated levels of cytokines, chemokines, and pro-apoptotic molecules. Although neuroinflammation has been reported in several LSDs, the cellular basis and mechanisms responsible for eliciting neuroinflammatory pathways are just beginning to be defined. This review highlights the role of neuroinflammation in select LSDs and its potential contribution to neuron loss.

Procalcitonin and mortality in status epilepticus: an observational cohort study

INTRODUCTION

Acute-phase proteins, such as procalcitonin (PCT), C-reactive protein (CRP) and albumin, may relate with course and outcome in status epilepticus (SE), as seizures bring about inflammation, changes of cytokine levels and blood-brain barrier breakdown. We aimed to determine the predictive value of serum levels of PCT at SE onset for the emergence of infections and unfavorable outcome in adult patients with SE. Furthermore, we sought to compare the predictive value of PCT, CRP and albumin for death.

METHODS

This observational cohort study was performed in the intensive care units of the University Hospital Basel (Switzerland), a university-affiliated tertiary care center. Adult patients with SE admitted from 2005 to 2012 were included. Serum levels of PCT, CRP and albumin were assessed at SE onset. Unfavorable outcome (i.e., death and a Glasgow Outcome Score of 1 to 3) during hospital stay and mortality after 30 days were considered the primary and infections as the secondary outcome measures.

RESULTS

In 91 SE patients, mortality was 23.1 % during hospital stay and at 30-days follow-up. Infections emerged in 30.8 % of patients. In the multivariable analysis, PCT predicted unfavorable outcome independently from possible confounders such as acute etiology, infections during SE, the Charlson Comorbidity Index, and the Status Epilepticus Severity Score (hazard ratio 1.44 per every increasing ug/L, 95 % confidence interval 1.11-1.87). Additional multivariable analysis including serum levels of PCT, CRP and albumin revealed PCT as the only biomarker independently associated with an increased hazard for unfavorable outcome. PCT levels at SE onset were not related to infections during SE.

CONCLUSIONS

Serum PCT levels measured at SE onset are independently associated with unfavorable outcome but do not predict the emergence of infections during SE. Procalcitonin may increase the predictive value of clinical scoring systems allowing for rapid risk stratification early in the course of SE.

Astrocyte pathology in Alexander disease causes a marked inflammatory environment

Astrocytes and microglia are commonly involved in a wide variety of CNS pathologies. However, they are typically involved in a secondary response in which many cell types are affected simultaneously and therefore it is difficult to know their contributions to the pathology. Here, we show that pathological astrocytes in a mouse model of Alexander disease (AxD; GFAP (Tg);Gfap (+/R236H)) cause a pronounced immune response. We have studied the inflammatory response in the hippocampus and spinal cord of these mice and have found marked microglial activation, which follows that of astrocytes in a spatial pathological progression, as shown by increased levels of Iba1 and microglial cell (Iba1+) density. RNA sequencing and subsequent gene ontology (GO) analysis revealed that a majority of the most upregulated genes in GFAP (Tg);Gfap (+/R236H) mice are directly associated with immune function and that cytokine and chemokine GO attributes represent nearly a third of the total immune attributes. Cytokine and chemokine analysis showed CXCL10 and CCL2 to be the most and earliest increased molecules, showing concentrations as high as EAE or stroke models. CXCL10 was localized exclusively to astrocytes while CCL2 was also present in microglia. Despite the high levels of CXCL10 and CCL2, T cell infiltration was mild and no B cells were found. Thus, mutations in GFAP are sufficient to trigger a profound inflammatory response. The cellular stress caused by the accumulation of GFAP likely leads to the production of inflammatory molecules and microglial activation. Examination of human AxD CNS tissues also revealed microglial activation and T cell infiltrates. Therefore, the inflammatory environment may play an important role in producing the neuronal dysfunction and seizures of AxD.

Modulation of inflammatory mediators in the trigeminal ganglion by botulinum neurotoxin type A: an organ culture study

Background

Onabotulinumtoxin type A (BoNT-A) has been found to reduce pain in chronic migraine. The aim of the present study was to ask if BoNT-A can interact directly on sensory mechanisms in the trigeminal ganglion (TG) using an organ culture method.

Methods

To induce inflammation, rat TGs were incubated for 24 hrs with either the mitogen MEK1/2 inhibitor U0126, BoNT-A or NaCl. After this the TGs were prepared for immunohistochemistry. Sections of the TG were then incubated with primary antibodies against CGRP (neuronal transmitter), iNOS (inflammatory marker), IL-1β (Interleukin 1β), SNAP-25 (synaptic vesicle docking protein) or SV2-A (Botulinum toxin receptor element).

Results

We report that CGRP, iNOS, IL-1β, SNAP-25 and SV2-A were observed in fresh TG with a differential distribution. Interestingly, NaCl organ culture of the TG resulted in enhanced expression of CGRP and SNAP-25 in neurons and iNOS in SGCs. Co-incubation with U0126 or BoNT-A retained the increased expression of SNAP-25, while it decreased the IL-1β immunoreactivity in neurons. The iNOS expression in SGCs returned to levels observed in fresh specimens. Moreover, we observed no alteration SV2-A expression in SGCs. Thus, the overall picture is that both U0126 and BoNT-A have the ability to modify the expression of certain molecules in the TG.

Conclusion

We hypothesize that chronic migraine might be associated with some degree of inflammation in the TG that could involve both neurons and SGCs. It is clinically well recognized that treatment with corticosteroids will reduce the symptoms of chronic migraine; however this remedy is associated with long-term side effects. Understanding the mechanisms involved in the expressional alterations may suggest novel ways to modify the changes and indicate novel therapeutics. The results of the present work illustrate one way by which BoNT-A may modify these expressional alterations.

GABAA currents are decreased by IL-1β in epileptogenic tissue of patients with temporal lobe epilepsy: implications for ictogenesis

Temporal lobe epilepsy (TLE) is the most prevalent form of adult focal onset epilepsy often associated with drug-resistant seizures. Numerous studies suggest that neuroinflammatory processes are pathologic hallmarks of both experimental and human epilepsy. In particular, the interleukin (IL)-1β/IL-1 receptor type 1 (R1) axis is activated in epileptogenic tissue, where it contributes significantly to the generation and recurrence of seizures in animal models. In this study, we investigated whether IL-1β affects the GABA-evoked currents (I(GABA)) in TLE tissue from humans. Given the limited availability of fresh human brain specimens, we used the "microtransplantation" method of injecting Xenopus oocytes with membranes from surgically resected hippocampal and cortical tissue from 21 patients with TLE and hippocampal sclerosis (HS), hippocampal tissue from five patients with TLE without HS, and autoptic and surgical brain specimens from 15 controls without epilepsy. We report the novel finding that pathophysiological concentrations of IL-1β decreased the I(GABA) amplitude by up to 30% in specimens from patients with TLE with or without HS, but not in control tissues. This effect was reproduced by patch-clamp recordings on neurons in entorhinal cortex slices from rats with chronic epilepsy, and was not observed in control slices. In TLE specimens from humans, the IL-1β effect was mediated by IL-1R1 and PKC. We also showed that IL-1R1 and IRAK1, the proximal kinase mediating the IL-1R1 signaling, are both up-regulated in the TLE compared with control specimens, thus supporting the idea that the IL-1β/IL-R1 axis is activated in human epilepsy. Our findings suggest a novel mechanism possibly underlying the ictogenic action of IL-1β, thus suggesting that this cytokine contributes to seizure generation in human TLE by reducing GABA-mediated neurotransmission.

Differential TGF-β Signaling in Glial Subsets Underlies IL-6-Mediated Epileptogenesis in Mice

TGF-β1 is a master cytokine in immune regulation, orchestrating both pro- and anti-inflammatory reactions. Recent studies show that whereas TGF-β1 induces a quiescent microglia phenotype, it plays a pathogenic role in the neurovascular unit and triggers neuronal hyperexcitability and epileptogenesis. In this study, we show that, in primary glial cultures, TGF-β signaling induces rapid upregulation of the cytokine IL-6 in astrocytes, but not in microglia, via enhanced expression, phosphorylation, and nuclear translocation of SMAD2/3. Electrophysiological recordings show that administration of IL-6 increases cortical excitability, culminating in epileptiform discharges in vitro and spontaneous seizures in C57BL/6 mice. Intracellular recordings from layer V pyramidal cells in neocortical slices obtained from IL-6 -: treated mice show that during epileptogenesis, the cells respond to repetitive orthodromic activation with prolonged after-depolarization with no apparent changes in intrinsic membrane properties. Notably, TGF-β1 -: induced IL-6 upregulation occurs in brains of FVB/N but not in brains of C57BL/6 mice. Overall, our data suggest that TGF-β signaling in the brain can cause astrocyte activation whereby IL-6 upregulation results in dysregulation of astrocyte -: neuronal interactions and neuronal hyperexcitability. Whereas IL-6 is epileptogenic in C57BL/6 mice, its upregulation by TGF-β1 is more profound in FVB/N mice characterized as a relatively more susceptible strain to seizure-induced cell death.

Enrichment pathway analysis. The inflammatory genetic background in Bipolar Disorder

INTRODUCTION

The pathophysiology of Bipolar Disorder (BD) is yet to be fully characterized. In the last years attention was focused on neurodevelopment or neurodegenerative events. In this context, hyper- and hypo- activation of inflammatory cascades may play a role in modulating the architecture and function of neuronal tissues. In the present paper we tested the enrichment of molecular pathways related to inflammatory cascades (IL-1, IL-2, IL-6, IL-8, TNF and INF) testing whether genes related to these systems hold more variations associated with the risk for BD than expected.

METHODS

~7000 bipolar patients and controls with genome-wide data available from NIMH dataset were analyzed. SNPs were imputed, checked for quality control, pruned and tested for association (0.01<p). Fisher test was conducted to test the enrichment within the pathways and the association was permutated (10(5) times) to limit false positive findings.

RESULTS

As a result, IL-6, IL-8 and IFN related pathways held twice to thrice the number of expected variants associated with BD. These tests resisted the permutation analysis.

LIMITATIONS

The restricted number of inflammatory components included in the analysis and the lack of functional consequences for some of the SNPs analyzed may be biased; however, these choices helped the authors to lighten the statistical computational load for the analyses and at the same time included possibly hidden SNPs in linkage disequilibrium with the analyzed variations.

CONCLUSIONS

We bring evidence that the inflammatory cascades may be genetically varied in Bipolar patients. This genetic background may explain part of the pathophysiology of the disorder.