Epilepsy and innate immune system: A possible immunogenic predisposition and related therapeutic implications

GAD65 autoantibody characteristics in patients with co-occurring type 1 diabetes and epilepsy may help identify underlying epilepsy etiologies

BACKGROUND

Autoantibodies against the smaller isoform of glutamate decarboxylase (GAD65Ab) reflect autoimmune etiologies in Type 1 diabetes (T1D) and several neurological disorders, including Stiff Person Syndrome (SPS). GAD65Ab are also reported in cases of epilepsy, indicating an autoimmune component. GAD65Ab in patients with co-occurring T1D, epilepsy or SPS may be part of either autoimmune pathogenesis. To dissect the etiologies associated with GAD65Ab, we analyzed GAD65Ab titer, epitope specificity and enzyme inhibition in GAD65Ab-positive patients diagnosed with epilepsy (n = 28), patients with epilepsy and T1D (n = 10), patients with SPS (n = 20), and patients with T1D (n = 42).

RESULTS

GAD65Ab epitope pattern in epilepsy differed from T1D and SPS patients. Four of 10 patients with co-occurring T1D and epilepsy showed GAD65Ab profiles similar to T1D patients, while lacking GAD65Ab characteristics found in GAD65Ab-positive epilepsy patients. One of these patients responded well to anti-epileptic drugs (AEDs), while another patient did not require medication for seizure control. The third patient was refractory due to a diagnosis of meningioma. The response of the remaining patient to AEDs was unknown. GAD65Ab in the remaining six patients with T1D and epilepsy showed profiles similar to those in epilepsy patients.

CONCLUSIONS

Different autoimmune responses associated with T1D, epilepsy and SPS are reflected by disease-specific GAD65Ab patterns. Moreover, the epileptic etiology in patients diagnosed with both T1D and epilepsy may present two different etiologies regarding their epileptic condition. In one group T1D co-occurs with non-autoimmune epilepsy. In the other group GAD65Ab are part of an autoimmune epileptic condition.

TRIF contributes to epileptogenesis in temporal lobe epilepsy during TLR4 activation

Increasing evidence indicates that inflammatory processes play a crucial role in the etiopathology of epilepsy and seizure disorders. The Toll/IL-1R domain-containing adapter-inducing IFN-β (TRIF) activated several transcriptions leading to the production of pro-inflammatory cytokines in the central nervous system, which suggests a potential role for TRIF in the epileptogenesis of epilepsy. In this study, we investigated the roles of TRIF in human and mice epileptogenic tissues. Western blot and immunohistochemistry assays showed that the expression of TRIF was significantly upregulated in neurons and glial cells in both human epileptic tissues and mouse models, and positively correlated with seizure frequency. TRIF expression positively correlated with high-mobility group box 1 (HMGB1) expression. In TRIF-deficient mice, electroencephalograms displayed a significant decrease in seizure frequency and duration time, while KA induced seizures compared with wild-type (WT) mice. The number and duration time of spontaneous seizures were also decreased in the chronic KA-induced TRIF-deficient mouse models. In TLR4-deficient hippocampal neurons and mouse models, TRIF expression was lower compared with WT mice during HMGB1 and KA stimulation. Meanwhile, in KA-induced TRIF-deficient mouse models, microglia activation was significantly suppressed; pro-inflammatory factors including IL-1β, TNF-α, iNOS, HMGB1 and IFN-β were reduced; and the survival of the neurons in the hippocampus increased compared with WT mice. Our findings suggested that TRIF may be involved in the epileptogenesis of temporal lobe epilepsy, which would make it a potential therapeutic target for the treatment of epilepsy.

CD36 Deficiency Suppresses Epileptic Seizures

Cluster of differentiation 36 (CD36) belongs to the class B scavenger receptor family. CD36 is a glycoprotein found on the surface of various cell types and has been implicated in the mechanism of numerous central nervous system (CNS) diseases. However, the relationship between CD36 and epilepsy remains unknown. In this study, we aimed to detect the expression of CD36 in two different chronic epileptic mouse models and determine whether CD36 deficiency leads to suppressive neuronal hyperexcitability and decreased susceptibility of epileptic seizures. Here, we found that CD36 was expressed in the neurons and that CD36 expression was significantly elevated in epileptic mice induced by pentylenetetrazol (PTZ) and kainic acid (KA). Behavioral studies revealed that CD36 deletion in mice (CD36-/- mice) resulted in an attenuated progression of chronic epilepsy compared with wild-type (WT) mice. Whole-cell patch-clamp technique exhibited a decreased frequency of action potentials (APs) in the hippocampal slices of CD36-/- mice. In addition, local field potential (LFP) analysis further indicated that CD36 deletion reduced the frequency and duration of epileptiform-like discharges. These results revealed that CD36 deficiency could produce an antiepileptic effect and could provide new insight into antiepileptic treatment.

Anterior thalamic nuclei deep brain stimulation reduces disruption of the blood-brain barrier, albumin extravasation, inflammation and apoptosis in kainic acid-induced epileptic rats

Objective The therapeutic efficacy of anterior thalamic nuclei deep brain stimulation (ATN-DBS) against seizures has been largely accepted; however, the effects of ATN-DBS on disruption of the blood-brain barrier (BBB), albumin extravasation, inflammation and apoptosis still remain unclear. Methods Rats were distributed into four treatment groups: physiological saline (PS, N = 12), kainic acid (KA, N = 12), KA-sham-DBS (N = 12) and KA-DBS (N = 12). Seizures were monitored using video-electroencephalogram (EEG). One day after surgery, all rats were sacrificed. Then, samples were prepared for quantitative real-time PCR (qPCR), western blot, immunofluorescence (IF) staining, and transmission electron microscopy to evaluate the disruption of the BBB, albumin extravasation, inflammation, and apoptosis. Result Because of the KA injection, the disruption of the BBB, albumin extravasation, inflammation and apoptosis were more severe in the KA and the KA-sham-DBS groups compared to the PS group (all Ps < 0.05 or < 0.01). The ideal outcomes were observed in the KA-DBS group. ATN-DBS produced a 46.3% reduction in seizure frequency and alleviated the disruption of the BBB, albumin extravasation, inflammatory reaction and apoptosis in comparison to the KA-sham-DBS group (all Ps < 0.05 or < 0.01). Conclusion (1) Seizures can be reduced using ATN-DBS in the epileptogenic stage. (2) ATN-DBS can reduce the disruption of the BBB and albumin extravasation. (3) ATN-DBS has an anti-inflammatory effect in epileptic models.

Elevated expression of EBV and TLRs in the brain is associated with Rasmussen's encephalitis

Rasmussen's encephalitis (RE) is a rare pediatric neurological disorder, the etiology of which remains unclear. It has been speculated that the immunopathogenesis of RE involves damage to neurons, which eventually leads to the occurrence of RE. Viral infection may be a critical factor in triggering RE immunopathogenesis. In this study, we analyzed the expression of Epstein-Barr virus (EBV) antigens as well as of Toll-like receptor 3 (TLR3), TLR9, and downstream adapter TIRdomain-containing adapter-inducing interferon-β (TRIF) in the brain tissues of 26 patients with RE and 16 control individuals using immunohistochemistry (IHC). In the RE group, EBV antigens were detected in 53% of individuals at various expression levels. In contrast, there was no detectable EBV antigen expression in control brain tissues. Moreover, we found marked increases in the expression of TLR3, TLR9, and TRIF in the brain tissues of RE patients compared with levels in the control group. Furthermore, among RE cases, EBV expression and high TLR3 expression were associated with more severe brain atrophy. Our results suggest that the elevated expression of EBV and TLRs may be involved in RE occurrence through the activation of downstream molecules.

Regulation of kindling epileptogenesis by hippocampal Toll-like receptors 2

This study examined whether Toll-like receptors 2 (TLR2) contribute to rapid kindling epileptogenesis. A TLR2 agonist, lipoteichoic acid (LTA), LTA antibody (LTA-A), or normal saline (control) was administered daily over 3 consecutive days, unilaterally into ventral hippocampus of adult male Wistar rats. Thirty minutes after the last injection, the animals were subjected to a rapid kindling procedure. The ictogenesis was gauged by comparing afterdischarge threshold (ADT) and afterdischarge duration (ADD) before the treatments, after the treatments prior to kindling, and 24 h after kindling. Kindling progression and retention were analyzed using video recording. The results showed that before kindling, LTA produced an ADT reduction. Neither LTA nor LTA-A affected baseline ADD. On kindling progression, LTA accelerated occurrence of generalized seizures, whereas LTA-A delayed this effect. Treatment with LTA-A reduced the number of secondary generalized complex partial seizures. Twenty-four hours after kindling, the rats of both the saline and LTA groups showed increased hippocampal excitability as compared with prekindling parameters. Administration of LTA-A prevented kindling-induced increase of hippocampal excitability. Immunostaining revealed that LTA-A attenuated the inflammatory response produced by seizures. These findings suggest that the activation of TLR2 in the hippocampus may facilitate limbic epileptogenesis.

The watch-pat in pediatrics sleep disordered breathing: Pilot study on children with negative nocturnal pulse oximetry

OBJECTIVES

The main purpose of this study was to determine the efficacy of Watch-PAT in Pediatric Sleep Disordered Breathing (PSDB) diagnosis in children with symptoms suggestive of PSDB, in which the nocturnal pulse oximetry was negative according to the Brouilette criteria.

METHODS

We enrolled 28 patients aged between 5 and 12 years (mean age: 7.75 ± 1.69), who underwent the registration with Watch-PAT, that utilizes the Peripheral Arterial Tone (PAT), AHI, RDI, body position, snoring, pulse oximetry and actigraphy.

RESULTS

Recording Watch-PAT was indicative of PSDB in 10/28 (35.7%) patients; when it was placed the threshold of AHI > 1 the number of positive patients for PSDB increased to 17/28 (60.7%). Exists a positive correlation between pat-RDI (rho = 0.798, p = 0.005) and the snoring > 40% of the time (rho = 0.656, p < 0.001) were correlated with the pat-AHI values.

CONCLUSION

The recording Watch-PAT appears to permit the defection of a certain number of SDB that might escape to the clinical evaluation and pulse oximetry only.

Seizures and risk of epilepsy in autoimmune and other inflammatory encephalitis

PURPOSE OF REVIEW

The aim of this study was to assess the seizure manifestations and risk of epilepsy in encephalitis associated with antibodies against neuronal cell-surface (autoimmune encephalitis) or myelin-associated antigens, and to review several chronic epileptic disorders, including Rasmussen's encephalitis, fever-induced refractory epileptic syndromes (FIRES) and new-onset refractory status epilepticus (NORSE).

RECENT FINDINGS

Seizures are a frequent manifestation of autoimmune encephalitis. Some autoimmune encephalitis may associate with characteristic features: faciobrachial dystonic seizures (anti-LGI1 encephalitis), electroencephalogram extreme delta brush (anti-NMDAR) or multifocal FLAIR-MRI abnormalities (anti-GABAAR). In anti-LGI1 encephalitis, cortical, limbic and basal ganglia dysfunction results in different types of seizures. Autoimmune encephalitis or myelin-antibody associated syndromes are often immunotherapy-responsive and appear to have a low risk for chronic epilepsy. In contrast patients with seizures related to GAD65-antibodies (an intracellular antigen) frequently develop epilepsy and have suboptimal response to treatment (including surgery). Rasmussen's encephalitis or FIRES may occur with autoantibodies of unclear significance and rarely respond to immunotherapy. A study of patients with NORSE showed that 30% developed chronic epilepsy.

SUMMARY

Although seizures are frequent in all types of autoimmune encephalitis, the risk for chronic epilepsy is dependent on the antigen: lower if located on the cell-surface, and higher if intracellular. For other disorders (Rasmussen's encephalitis, FIRES, NORSE), the prognosis remains poor.

Breaking the cycle: A comparison between intravenous immunoglobulins and high dosage prednisone in the treatment of medically intractable epilepsy in children

PURPOSE

Because immune mediated mechanisms are suspected in epileptogenesis, IVIg and corticosteroids have been used as alternatives to treat refractory seizures. We present our experience treating intractable epileptic children with IVIg and prednisone.

METHODS

Children with intractable epilepsy treated with prednisone or IVIg between 2005-2016 were reviewed retrospectively. Children with infantile spasms and autoimmune epilepsy were excluded. Data analyzed include epilepsy type and etiology, duration of epilepsy prior to treatment, seizure outcome, time to best seizure outcome, and adverse effects.

RESULTS

Fifty-one patients were included: 26 received IVIg; 25 received prednisone. Etiologies were similar between cohorts: genetic (13 IVIg; 10 prednisone), lesional (8 IVIg; 7 prednisone), and unknown (5 IVIg; 8 prednisone). In the prednisone cohort, 92.0% had generalized epilepsy compared to 61.5% for IVIg. Among the IVIg treated, 84.6% responded (10 genetic, 4 unknown, and 8 lesional) with mean seizure reduction of 77.3% and mean time to best response of 9.8 weeks. With prednisone, 24.0% responded (2 genetic, 3 unknown, and 1 lesional) with a mean seizure reduction of 95.0% and mean time to best response of 2.7 weeks. Adverse effects occurred in 2 and 16 patients treated with IVIg and prednisone, respectively. The difference in responders and seizure reduction was statistically significant (p<0.0001 and p=0.001, respectively).

CONCLUSION

IVIg had greater responders and lower adverse effects and honeymoon effect. This response was independent of epilepsy type, etiology, and duration suggesting different mechanisms of action between prednisone and IVIg and a common, reversible, immune-mediated pathway to intractability.

Autoimmune Ear Disease: Clinical and Diagnostic Relevance in Cogan's Sydrome

The autoimmune inner ear disease is a clinical syndrome with uncertain pathogenesis that is often associated to rapidly progressive hearing loss that, especially at the early stages of disease, may be at monoaural localization, although more often it is at binaural localization. It usually occurs as a sudden deafness, or a rapidly progressive sensorineural hearing loss. In this study a particular form of autoimmune inner ear disease is described, Cogan’s syndrome. Cogan’s syndrome is a chronic inflammatory disorder that most commonly affects young adults. Clinical hallmarks are interstitial keratitis, vestibular and auditory dysfunction. Associations between Cogan’s syndrome and systemic vasculitis, as well as aortitis, also exist. We report a case of a young woman who presented audiological and systemic characteristics attributable to Cogan’s syndrome. In the description of the case we illustrate how the appearance and evolution of the disease presented.

Levetiracetam in Neonatal Seizures as First-line Treatment: A Prospective Study

AIM OF THE STUDY

The aim of this study is to evaluate the efficacy and safety of levetiracetam (LEV) as first-line treatment of neonatal seizures.

MATERIALS AND METHODS

This study was conducted in patients of Neonatal Intensive Care Unit of Santo Bambino Hospital, University of Catania, Italy, from January to August 2016. A total of 16 neonates with convulsions not associated with major syndromes, which required anticonvulsant therapy, were included and underwent IV LEV at standard doses.

RESULTS

All patients responded to treatment, with a variety range of seizure resolution period (from 24 h to 15 days; mean hours: 96 ± 110.95). No patient required a second anticonvulsant therapy. Regarding safety of LEV, no major side-effects were observed.

CONCLUSIONS

To our knowledge, it is one of the few studies confirming the efficiency of LEV as first-line treatment in seizures of this age group. LEV was effective in resolving seizures and was safely administered in the current study.

Seizures and Epilepsies due to Channelopathies and Neurotransmitter Receptor Dysfunction: A Parallel between Genetic and Immune Aspects

Despite intensive research activity leading to many important discoveries, the pathophysiological mechanisms underlying seizures and epilepsy remain poorly understood. An important number of specific gene defects have been related to various forms of epilepsies, and autoimmunity and epilepsy have been associated for a long time. Certain central nervous system proteins have been involved in epilepsy or acute neurological diseases with seizures either due to underlying gene defects or immune dysfunction. Here, we focus on 2 of them that have been the object of particular attention and in-depth research over the past years: the N-methyl-D-aspartate receptor and the leucin-rich glioma-inactivated protein 1 (LGI1). We also describe illustrative examples of situations in which genetics and immunology meet in the complex pathways that underlie seizures and epilepsy.

Histone deacetylase inhibitor SAHA attenuates post-seizure hippocampal microglia TLR4/MYD88 signaling and inhibits TLR4 gene expression via histone acetylation

BACKGROUND

Epilepsy is a common neurological disorder characterized by recurrent unprovoked seizures. Seizure-induced TLR4/MYD88 signaling plays a critical role in activating microglia and triggering neuron apoptosis. SAHA is a histone deacetylase inhibitor that regulates gene expression by increasing chromatin histone acetylation. In this study, we investigated the role of SAHA in TLR4/MYD88 signaling in a rat seizure model.

RESULTS

Sprague-Dawley rats with kainic acid (KA)-induced seizures were treated with SAHA. The expression of TLR4, MYD88, NF-κB P65 and IL-1β in hippocampus was detected at hour 2 and 6 and day 1, 2, and 3 post seizure. SAHA pretreatment increased seizure latency and decreased seizure scores. The expression levels of TLR4, MYD88, NF-κB and IL-1β increased significantly in both activated microglia and apoptotic neurons after KA treatment. The effects were attenuated by SAHA. Chromatin immunoprecipitation assays indicated that the H3 histone acetylation levels significantly decreased while H3K9 levels significantly increased in the KA treatment group. The H3 and H3K9 acetylation levels returned to control levels after SAHA (50 mg/kg) pretreatment. There was a positive correlation between the expression of TLR4 and the acetylation levels of H3K9.

CONCLUSIONS

Histone deacetylase inhibitor SAHA can suppress seizure-induced TLR4/MYD88 signaling and inhibit TLR4 gene expression through histone acetylation regulation. This suggests that SAHA may protect against seizure-induced brain damage.