Immunological perspectives of temporal lobe seizures

Elevated IL-6 plasma levels are associated with GAD antibodies-associated autoimmune epilepsy

Background

Antibodies against glutamic acid decarboxylase (GADA) are present in multiple neurological manifestations, such as stiff-person syndrome, cerebellar ataxia, limbic encephalitis, and epilepsy. Increasing data support the clinical significance of GADA as an autoimmune etiology of epilepsy, however, there is not yet definitive evidence to confirm the pathogenic link between GADA and epilepsy.

Objective

Interleukin-6 (IL-6), a pro-convulsive and neurotoxic cytokine, and interleukin-10 (IL-10), an anti-inflammatory and neuroprotective cytokine, are crucial inflammatory mediators in the brain. Increased production of IL-6 and its association with epileptic disease profiles are well established, suggesting the presence of chronic systemic inflammation in epilepsy. Therefore, in this study, we investigated the association of plasma cytokine concentrations of IL-6 and IL-10 and their ratio with GADA in patients with drug-resistant epilepsy.

Methods

Interleukin-6 and IL-10 concentrations were measured by ELISA in plasma, and the IL-6/IL-10 ratio was calculated in a cross-sectional cohort of 247 patients with epilepsy who had their GADA titers measured previously for their clinical significance in epilepsy. Based on GADA titers, patients were grouped as GADA negative (n = 238), GADA low positive (antibody titers < 1,000 RU/mL, n = 5), and GADA high positive (antibody titers ≥ 1,000 RU/mL, n = 4).

Results

Median IL-6 concentrations were significantly higher in patients with high GADA positivity [2.86 pg/mL, interquartile range (IQR) = 1.90-5.34 pg/mL] than in GADA-negative patients [1.18 pg/mL, interquartile range (IQR) = 0.54-2.32 pg/mL; p = 0.039]. Similarly, IL-10 concentrations were also higher in GADA high-positive patients [1.45 pg/mL, interquartile range (IQR) = 0.53-14.32 pg/mL] than in GADA-negative patients [0.50 pg/mL, interquartile range (IQR) = 0.24-1.00 pg/mL], however, the difference was not statistically significant (p = 0.110). Neither IL-6 nor IL-10 concentrations were different between GADA-negative and GADA low-positive patients (p > 0.05) or between GADA low-positive or GADA high-positive patients (p > 0.05). The IL-6/IL-10 ratio was also similar among all the study groups.

Conclusion

Increased circulatory concentrations of IL-6 are associated with high GADA titers in patients with epilepsy. These data provide additional pathophysiological significance of IL-6 and help to further describe the immune mechanisms involved in the pathogenesis of GADA-associated autoimmune epilepsy.

Late-onset seizures and epilepsy: Electroclinical features suggestive of autoimmune etiology

Introduction

Late-onset epilepsy (LOE) has recently become a topic of intense research. Besides stroke, tumors, and dementia, autoimmune encephalitis (AE) has emerged as another possible cause of recurrent seizures in the elderly, and may account for a proportion of cases of LOE of unknown origin (LOEUO). This 24-h ambulatory electroencephalography (AEEG)-based study compared patients with LOEUO and AE to identify features suggestive of immune-mediated seizures in the elderly.

Materials and methods

We retrospectively reviewed 232 AEEG examinations performed in patients over 55 years with ≥6-month follow-up, and selected 21 subjects with AE and 25 subjects with LOEUO. Clinical charts and AEEG recordings were carefully analyzed.

Results

Twenty-five patients with LOEUO (12 women, mean age at onset 67.9 years) and 21 AE subjects (8 women, mean age at onset 65.7 years) were enrolled. High-frequency seizures were reported in 20/21 AE and 7/25 LOEUO cases (p < 0.00001). Focal aware seizures were more common in AE (14/21 vs. 6/25, p = 0.00058), whereas “isolated” focal-to-bilateral tonic-clonic seizures occurred in 5/25 patients with LOEUO only (p = 0.053). AE subjects reported ictal autonomic manifestations more frequently (p = 0.0033). Three-hundred-seventy and 24 seizures were recorded in 13/21 patients with AE and 3/25 patients with LOEUO, respectively (p = 0.0006). Interictal epileptiform discharges were observed in 70% of both groups, but their sleep activation was more common in AE (p = 0.06).

Conclusion

Our study shows that high-frequency focal seizures with autonomic manifestations should raise the suspicion of AE in the elderly with new-onset seizures. It also highlights the relevant contribution of AEEG, which might reduce the diagnostic delay and provide useful clues to recognize AE.

A 1-year follow-up study on immunological changes following deep brain stimulation in patients with epilepsy

The aim of this study was to evaluate the effects of deep brain stimulation of the anterior nucleus of the thalamus (ANT-DBS) on systemic inflammatory responses in patients with drug-resistant epilepsy (DRE). Twenty-two Finnish patients with ANT-DBS implantation were enrolled in this pilot study. Changes in plasma interleukin-6 (IL-6) and interleukin-10 (IL-10) levels were examined using generalized estimating equation models at seven time points (before DBS surgery and 1, 2, 3, 6, 9 and 12 months after implantation). In the whole group, the IL-6/IL-10 ratio decreased significantly over time following ANT-DBS, while the decrease in IL-6 levels and increase in IL-10 levels were not significant. In the responder and nonresponder groups, IL-6 levels remained unchanged during the follow-up. Responders had significantly lower pre-DBS IL-10 levels before the ANT-DBS treatment than nonresponders, but the levels significantly increased over time after the treatment. In addition, responders had a higher pre-DBS IL-6/IL-10 ratio than nonresponders, and the ratio decreased for both groups after treatment, but the decrease did not reach the level of statistical significance. The rate of decrease in the ratio per month tended to be higher in responders than in nonresponders. These results may highlight the anti-inflammatory properties of ANT-DBS treatment associated with its therapeutic effectiveness in patients with DRE. Additional studies are essential to evaluate the potential of the proinflammatory cytokine IL-6, the anti-inflammatory cytokine IL-10, and their ratio as biomarkers to evaluate the therapeutic response to DBS treatment, which could facilitate treatment optimization.

PI3K, mTOR and GSK3 modulate cytokines' production in peripheral leukocyte in temporal lobe epilepsy

INTRODUCTION

Epilepsy is a common pathological condition that predisposes individuals to seizures, as well as cognitive and emotional dysfunctions. Different studies have demonstrated that inflammation contributes to the pathophysiology of epilepsy. Indeed, seizures change the peripheral inflammatory pattern, which, in turn, could contribute to seizures. However, the cause of the altered production of peripheral inflammatory mediators is not known. The PI3K/mTOR/GSK3β pathway is important for different physiological and pharmacological phenomena. Therefore, in the present study, we tested the hypothesis that the PI3K/mTOR/GSK3β pathway is deregulated in immune cells from patients with epilepsy and contributes to the abnormal production of inflammatory mediators.

METHODS

Patients with temporal lobe epilepsy presenting hippocampal sclerosis and controls aged between 18 and 65 years-old were selected for this study. Peripheral blood was collected for the isolation of peripheral mononuclear blood cells (PBMC). Cells were pre-incubated with different PI3K, mTOR and GSK-3 inhibitors for 30 min and further stimulated with phytohaemaglutinin (PHA) or vehicle for 24 h. The supernatant was used to evaluate the production of IL-1β, IL-6, IL-10, TNF e IL-12p70.

RESULTS

Non-selective inhibition of PI3K, as well as inhibition of PI3Kγ and GSK-3, reduced the levels of TNF and IL-10 in PHA-stimulated cells from TLE individuals. This stimulus increased the production of IL-12p70 only in cells from TLE individuals, while the inhibition of PI3K and mTOR enhanced the production of this cytokine. On the other hand, inhibition of GSK3 reduced the PHA-induced production of IL-12p70.

CONCLUSIONS

Herein we demonstrated that the production of cytokines by immune cells from patients with TLE differs from non-epileptic patients. This differential regulation may be associated with the altered activity and responsiveness of intracellular molecules, such as PI3K, mTOR and GSK-3, which, in turn, might contribute to the inflammatory state that exists in epilepsy and its pathogenesis.

Immunomodulatory and protective effects of interleukin-4 on the neuropathological alterations induced by a potassium channel blocker

The pathophysiology of neurological diseases related to potassium-channel dysfunction such as epilepsy is increasingly linked to immune system modulation. However, there are limited reports of which interleukin-4 (IL-4) can act on the neuroinflammatory response after seizure. Hence, we evaluated the effect of IL-4 in murine model of neuroexcitotoxcity using kaliotoxin (KTx), a potassium-channel blocker. Results showed that IL-4 treatment can significantly reduce the neuronal death induced by KTx. Probably by decreasing mitochondria swelling, reversing oxidative damage and enhancing Bcl-2 expression. Furthermore, IL-4 treatment significantly reduced TNF-α expression and enhanced GFAP and IL-10 expressions in the brain. IL-4 can be neuroprotective in epileptogenesis.

Chronically reduced IL-10 plasma levels are associated with hippocampal sclerosis in temporal lobe epilepsy patients

Background

Increasing evidence supports the role of soluble inflammatory mediators in the pathogenesis of refractory temporal lobe epilepsy (TLE). Hippocampal sclerosis (HS) is a well-described pathohistological abnormality in TLE. The association of proinflammatory cytokines with epileptic disease profiles is well established; however, the potential significance of circulating interleukin 10 (IL-10), particularly in TLE-associated HS, is still poorly understood. Therefore, taking into consideration the neuroprotective and anticonvulsive effects of IL-10, we performed this study to examine the role of the plasma levels of IL-10 in patients with TLE with HS (TLE + HS), TLE without HS (TLE-HS) and with other types of epilepsy.

Methods

This study included 270 patients with refractory epilepsy who were classified into four groups: i) 34 patients with TLE + HS, ii) 105 patients with TLE-HS, iii) 95 patients with extra-TLE (XLE) and iv) 36 patients with idiopathic generalized epilepsy (IGE). The plasma IL-10 levels were quantified using a commercially available enzyme-linked immunosorbent assay (ELISA).

Results

IL-10 levels were significantly lower in TLE + HS than in TLE-HS (p = 0.013). In a subgroup of TLE-HS patients who had seizures 1 month before sampling, patients with seizures had significantly higher IL-10 levels than patients who were seizure-free (p = 0.039). Among a small group (n = 15) of non-refractory TLE-HS patients, IL-10 levels showed a moderate negative correlation with the duration of epilepsy (r = − 0.585, p = 0.023).

Conclusions

This study demonstrated that chronically reduced levels of plasma IL-10 were associated with HS in TLE patients, suggesting that there was an inadequate systemic anti-inflammatory immune response. These results could provide new biological insights into the pathophysiology of HS in TLE. We also found that the production of IL-10 could be affected by the seizure frequency and declined concomitantly with increased disease durations. Therefore, the measurement of plasma IL-10 may have diagnostic value as a biomarker for stratifying TLE + HS from other epilepsy types or as a marker of disease progression towards a progressive form of epilepsy.

Immune-mediated epilepsy with GAD65 antibodies

Anti-GAD65 antibodies have been identified in both acute/subacute seizures (limbic encephalitis and extralimbic encephalitis) and chronic isolated epilepsy. The evidence of high serum titers and intrathecal synthesis play a fundamental role in diagnosis but poorly correlate with disease severity or response to therapies. It remains controversial whether anti-GAD65 Abs are the pathogenic entity or only serve as a surrogate marker for autoimmune disorders mediated by cytotoxic T cells. Unlike other immune-mediated epilepsy, although multiple combinations of therapeutics are used, the efficacy and prognosis of patients with GAD65-epilepsy patients are poor. Besides, GAD65-epilepsy is more prone to relapse and potentially evolve into a more widespread CNS inflammatory disorder. This article reviews the recent advances of GAD65-epilepsy, focusing on the diagnosis, epidemiology, pathophysiology, clinical features, and treatment, to better promote the recognition and provide proper therapy for this condition.

Risk of epilepsy in rheumatoid arthritis: a meta-analysis of population based studies and bioinformatics analysis

Background:

An increasing number of studies support an association between rheumatoid arthritis (RA) and brain disorders. This study aims to determine the association between RA and epilepsy.

Methods:

A comprehensive search of databases in both English and Chinese was performed. Data from the selected studies were extracted and analyzed independently by two authors. Genes associated with epilepsy and RA were also collected and analyzed.

Results:

We included six nationwide population based studies (n = 7,094,113 cases in total) for the meta-analysis. The risk of epilepsy was increased in RA patients [risk ratio (RR) = 1.601; 95% confidence interval (CI): 1.089–2.354; p = 0.017; n = 3,803,535 cases] and children born to mothers with RA (RR = 1.475; 95% CI: 1.333–1.633; p < 0.001, n = 3,290,578 cases). Subgroup analysis and meta-regression showed the RR of epilepsy in RA was negatively correlated with age. Furthermore, we found that 433 identified genes in a coexpression network from the hippocampi of 129 epileptic patients were enriched in the RA and related Kyoto Encyclopedia of Genes and Genomes pathways, while 13 genes (mainly related to inflammatory cytokines and chemokines) were identified as potential key genes bridging the RA and epilepsy.

Conclusions:

Our study, utilizing meta-analysis and bioinformatical data, highlights a close association between epilepsy and RA. Further studies are still warranted to expand these findings, especially for a population that is exposed to RA during fetal and childhood periods.

Innate Immunity in the Central Nervous System: A Missing Piece of the Autoimmune Encephalitis Puzzle?

The autoimmune encephalitides are a group of autoimmune conditions targeting the central nervous system and causing severe clinical symptoms including drug-resistant seizures, cognitive dysfunction and psychiatric disturbance. Although these disorders appear to be antibody mediated, the role of innate immune responses needs further clarification. Infiltrating monocytes and microglial proliferation at the site of pathology could contribute to the pathogenesis of the disease with resultant blood brain barrier dysfunction, and subsequent activation of adaptive immune response. Both innate and adaptive immune cells can produce pro-inflammatory molecules which can perpetuate ongoing neuroinflammation and drive ongoing seizure activity. Ultimately neurodegenerative changes can ensue with resultant long-term neurological sequelae that can impact on ongoing patient morbidity and quality of life, providing a potential target for future translational research.

Mycophenolate mofetil contributes to downregulation of the hippocampal interleukin type 2 and 1β mediated PI3K/AKT/mTOR pathway hyperactivation and attenuates neurobehavioral comorbidities in a rat model of temporal lobe epilepsy

The role of neuroinflammatory mediators has been well established in the pathogenesis of temporal lobe epilepsy (TLE) and associated neurobehavioral comorbidities. Mycophenolate mofetil (MMF) is commonly used as an immunosuppressant in organ transplantations. Its neuroprotective effect is well explored in different preclinical and clinical studies. The present study was designed to investigate the effect of MMF in rat model of lithium pilocarpine (LiPc)-induced spontaneous recurrent seizures and its associated neurobehavioral comorbidities. MMF treatment showed a dose-dependent decrease in seizure severity and reduced aggression in epileptic rats. There was marked improvement in spatial and recognition memory functions, along with substantial decrease in depression-like behavior in MMF treated epileptic rats. There was considerable decrease in mossy fiber sprouting in the dentate gyrus and the cornu ammonis 3 regions of the hippocampus, along with reduction in neuronal death in the treated groups. Furthermore, the hippocampal mRNA level of IL-1β, IL-2, PI3K, AKT, HIF-1α, RAPTOR, mTOR, Rps6kb1 and Rps6 was found to be decreased in MMF treated animals. mTOR, S6, pS6 and GFAP protein expression was decreased, whereas NeuN was increased in the rat hippocampus of the treated animals. The results concluded that MMF suppress recurrent seizures, and improves its associated behavioral impairments and cognitive deficit in rat model of TLE. The observed effects of MMF be correlated with the inhibition of IL-2 and IL-1β linked PI3K/AKT/mTOR signaling pathway hyperactivation.

Effects of carbamazepine on the P-gp and CYP3A expression correlated with PXR or NF-κB activity in the bEnd.3 cells

Drug-resistant epilepsy (DRE) is present in 20-30% of all patients who develop epilepsy. Growing evidences demonstrated that glutamate released during seizures to increase the brain P-glycoprotein (P-gp) expression. Carbamazepine (CBZ) is known to influence the P-gp and cytochrome P450 (CYP) expression. However, the exact molecular mechanism is still unknown. We investigated that the effects of NF-κB and pregnane X receptor (PXR) activity on P-gp and CYP3A expression in mouse brain endothelial (bEnd.3) cells treated with l-glutamate (mimicking the seizure conditions), CBZ (mimicking the AED treating conditions) or both (l-glutamate plus CBZ) through qPCR and Western blotting assay. Mean fluorescence intensity was used to observe P-gp efflux function by analysis of intracellular Rhodamine123 (Rho123) accumulation. P-gp, CYP3A, PXR and NF-κB p65 were elevated in bEnd.3 cells incubated with l-glutamate, CBZ or CBZ pretreated by l-glutamate for 30 min. Both the mRNA and protein levels of P-gp and CYP3A were remarkably reduced by PXR or NF-κB p65 knock-down by siRNA transfections. The decreased intracellular accumulation of Rho123 suggested that the expression of P-gp was enhanced in bEnd.3 cells. These data suggested that overexpression of P-gp and CYP3A during seizures and treated with CBZ may be regulated by PXR or NF-κB p65 activity and expression, which revealed a mechanism underlying the development of DRE.

Clinical Management of Epilepsy With Glutamic Acid Decarboxylase Antibody Positivity: The Interplay Between Immunotherapy and Anti-epileptic Drugs

Background: There is scanty guidance in the literature on the management of patients with glutamic acid decarboxylase (GAD65) antibody associated autoimmune epilepsy (GAD-epilepsy). GAD-epilepsy is a rare distinct neurological syndrome with a wide clinical spectrum. We describe six GAD-epilepsy patients with special emphasis on the treatment timing and the relationship between immunologic and anti-epileptic therapy.

Methods: Six patients diagnosed with GAD-epilepsy in Tampere University Hospital who had received immunotherapy from 2013 to 2017 were retrospectively analyzed from patient records. Data about symptom onset, including antibody levels, magnetic resonance imaging (MRI), electroencephalograms, immunotherapy and anti-epileptic treatment timing and treatment responses were collected and analyzed. Kruskall-Wallis test was used in the statistical evaluation.

Results: All patients were female aged 9–54 at symptom onset. Three had hypothyroidism, none had diabetes, two had migraine. Five patients had very high (>2,000 IU/ml) and one had high (52–251 IU/ml) GAD65 antibody titers. All patients presented with seizure disorders. Patients who received early initiation of immunotherapy (3–10 months) responded well to treatment; patients in whom the immunotherapy was started later (15–87 months) did not respond (p = 0.0495). The first patient was seizure-free after 1 year of regular intravenous immunoglobulin and one antiepileptic drug (AED). The second patient developed unilateral temporal lobe T2 signal changes in MRI; she responded well to immunotherapy, experiencing a significant reduction in seizure frequency and resolution of MRI abnormalities. However, seizures continued despite trials with several AEDs. The third patient responded well to immunoadsorption and rituximab with one AED, with lowering of GAD65 titers (from >2,000 to 300). There was a long delay in the diagnosis of GAD-epilepsy in the three patients who had developed refractory epilepsy, one with hippocampal sclerosis. They all received immunotherapy but none responded. However, AED modification or vagus nerve stimulation reduced the seizure frequency in two patients. Epilepsy surgery was ineffective.

Conclusions: These results highlight the importance of early detection of GAD65 antibodies in refractory epilepsy as immunotherapy can be effective if administered in the early stages of the disease when it can prevent permanent brain tissue damage.

Immunity and inflammation in status epilepticus and its sequelae: possibilities for therapeutic application

Status epilepticus (SE) is a life-threatening neurological emergency often refractory to available treatment options. It is a very heterogeneous condition in terms of clinical presentation and causes, which besides genetic, vascular and other structural causes also include CNS or severe systemic infections, sudden withdrawal from benzodiazepines or anticonvulsants and rare autoimmune etiologies. Treatment of SE is essentially based on expert opinions and antiepileptic drug treatment per se seems to have no major impact on prognosis. There is, therefore, urgent need of novel therapies that rely upon a better understanding of the basic mechanisms underlying this clinical condition. Accumulating evidence in animal models highlights that inflammation ensuing in the brain during SE may play a determinant role in ongoing seizures and their long-term detrimental consequences, independent of an infection or auto-immune cause; this evidence encourages reconsideration of the treatment flow in SE patients.

Anticonvulsant effect of cannabidiol in the pentylenetetrazole model: Pharmacological mechanisms, electroencephalographic profile, and brain cytokine levels

Cannabidiol (CBD), the main nonpsychotomimetic compound from Cannabis sativa, inhibits experimental seizures in animal models and alleviates certain types of intractable epilepsies in patients. Its pharmacological profile, however, is still uncertain. Here we tested the hypothesis that CBD anticonvulsant mechanisms are prevented by cannabinoid (CB₁ and CB₂) and vanilloid (TRPV1) receptor blockers. We also investigated its effects on electroencephalographic (EEG) activity and hippocampal cytokines in the pentylenetetrazole (PTZ) model. Pretreatment with CBD (60mg/kg) attenuated seizures induced by intraperitoneal, subcutaneous, and intravenous PTZ administration in mice. The effects were reversed by CB₁, CB₂, and TRPV1 selective antagonists (AM251, AM630, and SB366791, respectively). Additionally, CBD delayed seizure sensitization resulting from repeated PTZ administration (kindling). This cannabinoid also prevented PTZ-induced EEG activity and interleukin-6 increase in prefrontal cortex. In conclusion, the robust anticonvulsant effects of CBD may result from multiple pharmacological mechanisms, including facilitation of endocannabinoid signaling and TRPV1 mechanisms. These findings advance our understanding on CBD inhibition of seizures, EEG activity, and cytokine actions, with potential implications for the development of new treatments for certain epileptic syndromes.

Increased expression of interleukin 17 in the cortex and hippocampus from patients with mesial temporal lobe epilepsy

Mesial temporal lobe epilepsy (MTLE) is the most common form of focal epilepsies in adults and proinflammatory cytokines have long been thought to play an important role in pathogenesis and epileptogenicity. In the present study, we investigated the levels and expression patterns of the interleukin 17 (IL-17) system in temporal neocortex and hippocampus from 24 patients with MTLE and 8 control (Ctr) samples. We found that IL-17 and IL-17 receptor (IL-17R) were clearly upregulated in MTLE at both mRNA and protein levels, compared with Ctr. Immunostaining indicated that neurons, astrocytes, microglia and endothelial cells of blood vessels are the major sources of IL-17. These findings suggest that IL-17 system may be involved in the pathogenesis and epileptogenicity of MTLE.

Peripheral leukocyte profile in people with temporal lobe epilepsy reflects the associated proinflammatory state

INTRODUCTION

Markers of low-grade peripheral inflammation have been reported amongst people with epilepsy. The mechanisms underlying this phenomenon are unknown. We attempted to characterize peripheral immune cells and their activation status in people with temporal lobe epilepsy (TLE) and healthy controls.

METHODS AND RESULTS

Twenty people with TLE and 19 controls were recruited, and peripheral blood lymphocyte and monocyte subsets evaluated ex vivo by multi-color flow cytometry. People with TLE had higher expression of HLA-DR, CD69, CTLA-4, CD25, IL-23R, IFN-γ, TNF and IL-17 in CD4(+) lymphocytes than controls. Granzyme A, CTLA-4, IL-23R and IL-17 expression was also elevated in CD8(+) T cells from people with TLE. Frequency of HLA-DR in CD19(+) B cells and regulatory T cells CD4(+)CD25(+)Foxp3(+) producing IL-10 was higher in TLE when compared with controls. A negative correlation between CD4(+) expressing co-stimulatory molecules (CD69, CD25 and CTLA-4) with age at onset of seizures was found. The frequency of CD4(+)CD25(+)Foxp3(+) cells was also positively correlated with age at onset of seizures.

CONCLUSION

Immune cells of people with TLE show an activation profile, mainly in effector T cells, in line with the low-grade peripheral inflammation.

Chronotypes in Patients with Epilepsy: Does the Type of Epilepsy Make a Difference?

Circadian rhythms govern all biological functions. Circadian misalignment has a major impact on health. Late chronotype is a risk factor for circadian misalignment which in turn can affect the control of seizures in epilepsy patients. We compared a group of 87 confirmed epilepsy patients regardless of subtypes with age- and sex-matched healthy controls. We compared generalized epilepsy patients with localization related epilepsy patients and with healthy controls. We found that primary generalized epilepsy patients were 5 times more likely to have a late chronotype than healthy controls. We did not find any significant differences between localization related epilepsy patients and healthy controls or between the overall epilepsy cohort and healthy controls. Generalized epilepsy patients are more likely to be evening types as compared to those with focal epilepsy or subjects without epilepsy. Epilepsy patients do not experience the same age related increase in morningness as do age-matched healthy controls. This is important in regard to timing of AED, identifying and preventing sleep deprivation, and integrating chronotype evaluations and chronotherapy in comprehensive epilepsy care. Further studies, using objective phase markers or the impact of chronotherapy on seizure control, are necessary.

What Elements of the Inflammatory System Are Necessary for Epileptogenesis In Vitro?

The inflammatory and central nervous systems share many signaling molecules, compromising the utility of traditional pharmacological and knockout approaches in defining the role of inflammation in CNS disorders such as epilepsy. In an in vitro model of post-traumatic epileptogenesis, the development of epilepsy proceeded in the absence of the systemic inflammatory system, and was unaffected by removal of cellular mediators of inflammation, including macrophages and T-lymphocytes.

Epileptogenesis in vivo can be altered by manipulation of molecules such as cytokines and complement that subserve intercellular signaling in both the inflammatory and central nervous systems. Because of the dual roles of these signaling molecules, it has been difficult to precisely define the role of systemic inflammation in epileptogenesis. Organotypic hippocampal brain slices can be maintained in culture independently of the systemic inflammatory system, and the rapid course of epileptogenesis in these cultures supports the idea that inflammation is not necessary for epilepsy. However, this preparation still retains key cellular inflammatory mediators. Here, we found that rodent hippocampal organotypic slice cultures depleted of T lymphocytes and microglia developed epileptic activity at essentially the same rate and to similar degrees of severity as matched control slice cultures. These data support the idea that although the inflammatory system, neurons, and glia share key intercellular signaling molecules, neither systemic nor CNS-specific cellular elements of the immune and inflammatory systems are necessary components of epileptogenesis.

Paroxetine prevented the down-regulation of astrocytic L-Glu transporters in neuroinflammation

The extracellular L-glutamate (L-Glu) concentration is elevated in neuroinflammation, thereby causing excitotoxicity. One of the mechanisms is down-regulation of astrocyte L-Glu transporters. Some antidepressants have anti-inflammatory effects. We therefore investigated effects of various antidepressants on the down-regulation of astrocyte L-Glu transporters in the in vitro neuroinflammation model. Among these antidepressants, only paroxetine was effective. We previously demonstrated that the down-regulation of astrocyte L-Glu transporters was caused by L-Glu released from activated microglia. We here clarified that only paroxetine inhibited L-Glu release from microglia. This is the novel action of paroxetine, which may bring advantages on the therapy of neuroinflammation.

Focal epilepsies: immunologic and inflammatory mechanisms

There is increasing evidence documenting activation of inflammatory processes in focal epilepsies. This review article summarizes current data regarding immune mediated inflammatory processes in patients with symptomatic partial epilepsies such as mesial temporal sclerosis, focal cortical dysplasia, and Rasmussen's encephalitis. We have also reviewed several neuronal surface antibody-associated syndromes, which have been recently described with focal seizures as an important part of clinical presentation, such as antibody-associated limbic encephalitis and N-methyl-D-aspartic acid receptor antibody syndrome. An autoimmune mechanism may be one pathogenic factor in some symptomatic epilepsies acting as a triggering event in the process leading to the development of epilepsy.

Targeting inflammation as a therapeutic strategy for drug-resistant epilepsies: an update of new immune-modulating approaches

An increasing body of literature data suggests that inflammation, and in particular neuroinflammation, is involved in the pathophysiology of particular forms of epilepsy and convulsive disorders. Animal models have been used to identify inflammatory triggers in epileptogenesis and inflammation has recently been shown to enhance seizures. For example, pharmacological blockade of the IL-1beta/IL-1 receptor type 1 axis during epileptogenesis has been demonstrated to provide neuroprotection in temporal lobe epilepsy. Furthermore, experimental models have suggested that neural damage and the onset of spontaneous recurrent seizures are modulated via complex interactions between innate and adaptive immunity. However, it has also been suggested that inflammation can occur as a result of epilepsy, since animal models have also shown that seizure activity can induce neuroinflammation, and that recurrent seizures maintain chronic inflammation, thereby perpetuating seizures. On the basis of these observations, it has been suggested that immune-mediated therapeutic strategies may be beneficial for treating some drug resistant epilepsies with an underlying demonstrable inflammatory process. Although the potential mechanisms of immunotherapeutic strategies in drug-resistant seizures have been extensively discussed, evidence on the efficacy of such therapy is limited. However, recent research efforts have been directed toward utilizing the potential therapeutic benefits of anti-inflammatory agents in neurological disease and these are now considered prime candidates in the ongoing search for novel anti-epileptic drugs. The objective of our review is to highlight the immunological features of the pathogenesis of seizures and to analyze possible immunotherapeutic approaches for drug resistant epilepsies that can alter the immune-mediated pathogenesis.

Peripherally restricted acute phase response to a viral mimic alters hippocampal gene expression

We have previously shown that peripherally restricted acute phase response (APR) elicited by intraperitoneal (i.p.) injection of a viral mimic, polyinosinic-polycytidylic acid (PIC), renders the brain hypersusceptible to excitotoxic insult as seen from profoundly exacerbated kainic acid (KA)-induced seizures. In the present study, we found that this hypersusceptibility was protracted for up to 72 h. RT-PCR profiling of hippocampal gene expression revealed rapid upregulation of 23 genes encoding cytokines, chemokines and chemokine receptors generally within 6 h after PIC challenge. The expression of most of these genes decreased by 24 h. However, two chemokine genes, i.e., Ccl19 and Cxcl13 genes, as well as two chemokine receptor genes, Ccr1 and Ccr7, remained upregulated for 72 h suggesting their possible involvement in the induction and sustenance of seizure hypersusceptibility. Also, 12 genes encoding proteins related to glutamatergic and GABAergic neurotransmission featured initial upregulation or downregulation followed by gradual normalization. The upregulation of the Gabrr3 gene remained upregulated at 72 h, congruent with its plausible role in the hypersusceptible phenotype. Moreover, the expression of ten microRNAs (miRs) was rapidly affected by PIC challenge, but their levels generally exhibited oscillating profiles over the time course of seizure hypersusceptibility. These results indicate that protracted seizure susceptibility following peripheral APR is associated with a robust polygenic response in the hippocampus.