Interleukin-1alpha, interleukin-1beta, and interleukin-1Ra polymorphisms in febrile seizures

IL-1β-31/IL1-RA genetic markers association with idiopathic generalized epilepsy and treatment response in a cohort of Egyptian population

Background: Neuroinflammation is an important feature of epileptogenesis.Objectives: To investigate the association of Interleukin-1beta-31 (IL-1β-31) and Interleukin-1 receptor antagonist (IL1-RA) genetic polymorphisms with idiopathic generalized epilepsy and demonstrate their influence on drug resistance in children.Materials and Methods: One hundred children with idiopathic generalized epilepsy were age and gender-matched with apparently healthy controls. Both groups were genotyped for IL-1β-31, and IL1-RA gene variants, analysis of these single nucleotide polymorphisms (SNPs) was done through restriction digestion of the corresponding polymerase chain reaction (PCR) products by restriction fragment length polymorphism (RFLP) assay.Results: Genotype frequency of rs1143627 TT of IL-1β-31 and the homozygous IL1RN*I were found to be more prevalent in epileptic patients (p < .05, OR 0.12 and 5.27respectively). Also observed, T allele of IL-1β-31 and IL1-RAI/I were substantially positively correlated with drug resistance against those who responded well to antiepileptic drugs (AEDs).Conclusions: The significant association with IL-1β-31T and IL1-RAN*I alleles potentiated their useful role as predictive markers for the development of epilepsy and response to medical therapy.

Anakinra Therapy for Non-cancer Inflammatory Diseases

Interleukin-1 (IL-1) is the prototypical inflammatory cytokine: two distinct ligands (IL-1α and IL-1β) bind the IL-1 type 1 receptor (IL-1R1) and induce a myriad of secondary inflammatory mediators, including prostaglandins, cytokines, and chemokines. IL-1α is constitutively present in endothelial and epithelial cells, whereas IL-1β is inducible in myeloid cells and released following cleavage by caspase-1. Over the past 30 years, IL-1-mediated inflammation has been established in a broad spectrum of diseases, ranging from rare autoinflammatory diseases to common conditions such as gout and rheumatoid arthritis (RA), type 2 diabetes, atherosclerosis, and acute myocardial infarction. Blocking IL-1 entered the clinical arena with anakinra, the recombinant form of the naturally occurring IL-1 receptor antagonist (IL-1Ra); IL-1Ra prevents the binding of IL-1α as well as IL-1β to IL-1R1. Quenching IL-1-mediated inflammation prevents the detrimental consequences of tissue damage and organ dysfunction. Although anakinra is presently approved for the treatment of RA and cryopyrin-associated periodic syndromes, off-label use of anakinra far exceeds its approved indications. Dosing of 100 mg of anakinra subcutaneously provides clinically evident benefits within days and for some diseases, anakinra has been used daily for over 12 years. Compared to other biologics, anakinra has an unparalleled record of safety: opportunistic infections, particularly Mycobacterium tuberculosis, are rare even in populations at risk for reactivation of latent infections. Because of this excellent safety profile and relative short duration of action, anakinra can also be used as a diagnostic tool for undefined diseases mediated by IL-1. Although anakinra is presently in clinical trials to treat cancer, this review focuses on anakinra treatment of acute as well as chronic inflammatory diseases.

Polymorphisms in the interleukin-1β (IL-1B) and interleukin-1α (IL-1A) genes on risk of febrile seizures: a meta-analysis

The aim of the current study was to clarify the role of four common genetic polymorphisms in the interleukin-1β (IL-1B) and interleukin-1α (IL-1A) genes on risk of febrile seizures (FS) by means of meta-analyses. We searched for studies published until February 2018 using ISI Web of Science, Pubmed, Wanfang, and Chinese National Knowledge Infrastructure databases. The pooled odds ratios (ORs) and 95% confidence intervals (CIs) were calculated using MetaAnalyst version Beta 3.13. Seventeen case-control studies were included for meta-analysis. For the IL-1B rs16944 polymorphism, the summary analysis of studies conducted among Caucasian populations showed a significant association in the CT+TT versus CC contrast (OR 1.434, 95% CI 1.153-1.785), while the pooled analysis for Asian populations yielded a significant estimate in the TT versus CC+CT comparison (OR 1.393, 95% CI 1.051-1.846). No association was observed between the IL-1B rs1143627, IL-1B rs1143634, and IL-1A rs1800587 polymorphisms and FS risk. Sensitivity analyses excluding studies showing deviation from Hardy-Weinberg equilibrium did not alter conclusions. The findings of our meta-analysis suggest that the IL-1B rs16944 polymorphism may be an important genetic determinant for FS in Caucasian and Asian populations.

Treatment of Inflammatory Diseases with IL-1 Blockade

Background

Autoinflammatory diseases are distinct from autoimmune diseases. Whereas autoinflammatory diseases are due to dysfunctional T-cells and B-cells, autoinflammatory diseases are due to overproduction of macrophage cytokines particularly interleukin-1 beta (IL-1β). A causative role for IL-1 in autoinflammatory diseases is derived from clinical studies blocking the IL-1 receptor or neutralizing monoclonal antibodies or soluble receptors.

Methods

A review was performed of clinical trials in autoinflammatory diseases using the IL-1 receptor antagonist (anakinra), the soluble IL-1 receptor (rilonacept), antibodies to IL-1β (canakinumab, gevokizumab) and anti-IL-1α (xilonix).

Findings

Anakinra blocks the IL-1 Receptor type 1 (IL-1R1) and therefore blocks the activities of both IL-1α and IL-1β. Off-label use of anakinra is common for a broad spectrum of inflammatory diseases. Neutralization of IL-1β is used to treat hereditary autoinflammatory diseases but also atherosclerosis. Rilonacept reduces arterial wall inflammation in patients with chronic kidney disease. Neutralization of IL-1α has prolonged life in patients with advanced metastatic colorectal cancer. Compared to other cytokine blocking therapies, reducing the activities of IL-1 has an excellent safety record.

Conclusions

Blocking IL-1 therapies can be used to treat a wide-spectrum of acute and chronic inflammatory diseases.

Inflammatory cytokine-induced changes in neural network activity measured by waveform analysis of high-content calcium imaging in murine cortical neurons

During acute neuroinflammation, increased levels of cytokines within the brain may contribute to synaptic reorganization that results in long-term changes in network hyperexcitability. Indeed, inflammatory cytokines are implicated in synaptic dysfunction in epilepsy and in an array of degenerative and autoimmune diseases of the central nervous system. Current tools for studying the impact of inflammatory factors on neural networks are either insufficiently fast and sensitive or require complicated and costly experimental rigs. Calcium imaging offers a reasonable surrogate for direct measurement of neuronal network activity, but traditional imaging paradigms are confounded by cellular heterogeneity and cannot readily distinguish between glial and neuronal calcium transients. While the establishment of pure neuron cultures is possible, the removal of glial cells ignores physiologically relevant cell-cell interactions that may be critical for circuit level disruptions induced by inflammatory factors. To overcome these issues, we provide techniques and algorithms for image processing and waveform feature extraction using automated analysis of spontaneous and evoked calcium transients in primary murine cortical neuron cultures transduced with an adeno-associated viral vector driving the GCaMP6f reporter behind a synapsin promoter. Using this system, we provide evidence of network perturbations induced by the inflammatory cytokines TNFα, IL1β, and IFNγ.

Interleukin-1β and interleukin-1receptor antagonist polymorphisms in Egyptian children with febrile seizures: A case-control study

Febrile seizure is the most common seizure disorder of childhood. Of the pro-inflammatory cytokines, interleukin-1 is defined as the first endogenous pyrogen.We designed this study to investigate single-nucleotide polymorphisms (SNPs) situated at positions -31 (C/T), and -511 (C/T) of interleukin-1beta (IL-1β) gene promoter and interleukin-1receptor antagonist (IL-1RA) gene variable number of tandem repeats in intron 2 (VNTR); to determine whether these polymorphisms could be a marker of susceptibility to febrile seizures in Egyptian children and we also measured the serum level of IL-1β to assess its relation to such polymorphisms.This was a case-control study included 155 patients with febrile seizure, and matched with age, sex, ethnicity 155 healthy control subjects. IL-1β promoter at positions -31 (C/T), -511 (C/T), and IL-1RA gene VNTR polymorphisms were genotyped by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP), while the serum IL-1β levels were measured by enzyme-linked immunosorbent assay (ELISA) method.The frequency of the IL-1β-511 TT genotype and T allele at the same position were observed to be increased in patients with febrile seizures (FS) compared with the control group (odds ratio [OR]: 3.96; 95% confidence interval [CI]: 1.68-9.5; P = 0.001 for the TT genotype and OR: 1.65; 95% CI: 1.18-2.3; P = 0.003 for the T allele, respectively). The IL-1 RA II/II homozygous variant and IL-1 RA allele II were overrepresented in patients with FS than control group (OR: 4.02; 95% CI: 1.78-9.15; P = 0.001and OR: 1.73; 95% CI: 1.24-2.4; P = 0.001, respectively). We found a significant positive association between the IL-1 RA II/II genotype and susceptibility to FS in sporadic cases as did allele II at the same position (OR: 5.04; 95% CI: 2.1-12.5 for the IL-1 RA II/II genotype; P = 0.001) and (OR: 1.94; 95% CI: 1.3-2.8 for the allele II; P = 0.001, respectively). Carriers of the IL-1RA II/II homozygous variant and allele II had significantly higher serum levels of IL-1β compared with those with other genotypes and alleles.We demonstrate for the first time that the presence of a T allele or TT genotype at -511 of IL-1β promoter and IL-1RA II/II genotype constitute risk factors for developing FS in Egyptian children.

Inflammation in epileptogenesis after traumatic brain injury

Background

Epilepsy is a common and debilitating consequence of traumatic brain injury (TBI). Seizures contribute to progressive neurodegeneration and poor functional and psychosocial outcomes for TBI survivors, and epilepsy after TBI is often resistant to existing anti-epileptic drugs. The development of post-traumatic epilepsy (PTE) occurs in a complex neurobiological environment characterized by ongoing TBI-induced secondary injury processes. Neuroinflammation is an important secondary injury process, though how it contributes to epileptogenesis, and the development of chronic, spontaneous seizure activity, remains poorly understood. A mechanistic understanding of how inflammation contributes to the development of epilepsy (epileptogenesis) after TBI is important to facilitate the identification of novel therapeutic strategies to reduce or prevent seizures.

Body

We reviewed previous clinical and pre-clinical data to evaluate the hypothesis that inflammation contributes to seizures and epilepsy after TBI. Increasing evidence indicates that neuroinflammation is a common consequence of epileptic seizure activity, and also contributes to epileptogenesis as well as seizure initiation (ictogenesis) and perpetuation. Three key signaling factors implicated in both seizure activity and TBI-induced secondary pathogenesis are highlighted in this review: high-mobility group box protein-1 interacting with toll-like receptors, interleukin-1β interacting with its receptors, and transforming growth factor-β signaling from extravascular albumin. Lastly, we consider age-dependent differences in seizure susceptibility and neuroinflammation as mechanisms which may contribute to a heightened vulnerability to epileptogenesis in young brain-injured patients.

Conclusion

Several inflammatory mediators exhibit epileptogenic and ictogenic properties, acting on glia and neurons both directly and indirectly influence neuronal excitability. Further research is required to establish causality between inflammatory signaling cascades and the development of epilepsy post-TBI, and to evaluate the therapeutic potential of pharmaceuticals targeting inflammatory pathways to prevent or mitigate the development of PTE.

Association of Interleukin-1 Gene Cluster and Interleukin-1 Receptor Polymorphisms With Febrile Seizures

Interleukin-1 (IL-1) plays a key role in inflammation, has an effect on a wide variety of cells, and often leads to tissue destruction. While the ratio between IL-1 and IL-1Ra could influence the development of different diseases of the central nervous system, its gene polymorphisms were investigated in a group of patients with febrile seizures. Ninety patients with febrile seizures were enrolled and compared with 140 controls. The allele and genotype frequency of single nucleotide polymorphisms within the IL-1α, β, IL-1 R and IL-1Ra gene were determined. The frequency of the IL-1Ra/C allele at position Mspa-I 11100 was decreased significantly (P= .002) and the IL-1Ra/T frequency was significantly increased in patients (P= .002). In addition, the CT genotype frequency at the same position was significantly overrepresented in controls compared to patients (P= .001). Certain alleles and genotypes in the IL-1 gene were overrepresented in patients with febrile seizures, which possibly could predispose individuals to this disease.

Serum adiponectin, leptin, and interleukin 6 levels as adipocytokines in children with febrile seizures: The role of adipose tissue in febrile seizures

Proinflammatory and anti-inflammatory cytokines have an important role in the pathogenesis of febrile seizures (FS). Adipocytokines like interleukin 6 (IL-6), leptin, and adiponectin released from adipose tissue play a role in inflammation. This study aimed to assess the probable role of adipose tissue in children with FS. We measured serum IL-6, leptin, and adiponectin levels and evaluated clinical and laboratory findings in children with FS (n = 32) and compared the results with the values of children of the same age with febrile illness without seizures (febrile control, FC; n = 26) and healthy control group (HC; n = 29). The serum levels of white blood cells, C-reactive protein, IL-6, leptin, and adiponectin were found to be significantly higher, while serum hemoglobin (Hb) levels were found to be significantly lower in FS and FC groups than in the HC group (p < 0.001). When we compared the FS with the FC group, the serum Hb levels were significantly lower in the FS group than those in the FC group (p = 0.001). There was no significant difference between the FS and FC group with regard to the serum levels of these adipocytokines (p > 0.05). Our data showed that elevated levels of these adipocytokines as acute phase reactants in FS and FC groups did not contribute to the development of FS.

Risk of subsequent asthma in children with febrile seizures: a nationwide population-based retrospective cohort study

BACKGROUND

No study has reported a relationship between febrile seizures and asthma; thus, we examined the association between these two disorders.

METHODS

We identified 991 cases of children with febrile seizures as the case cohort, and the control group was matched according to age, sex, urbanization level, and their parents' occupation at a 1:4 ratio. We applied the Cox proportional hazards regression model to estimate the hazard ratios and 95% confidence intervals for asthma among the children with febrile seizures.

RESULTS

After 11 years of follow-up, the asthma incidence in the febrile seizure group was approximately 5% higher than that in the control group (log-rank test, P < 0.0001). The risk of asthma in the febrile seizure group was 1.41 times higher than that in the control group (95% confidence interval, 1.21-1.65; P < 0.001). Furthermore, the risk of asthma development increased (0.96 vs 3.62) in conjunction with the frequency of febrile seizure-related medical visits (one to two visits vs more than four visits; P < 0.0001).

CONCLUSION

Febrile seizures may be associated with an increase in the risk of future asthma occurrence in children. We observed a significantly higher cumulative incidence of asthma occurrence in children with more febrile seizure-related medical visits.

Genetic background of febrile seizures

Febrile seizures (FSs) occur in children older than 1 month and without prior afebrile seizures in the absence of a central nervous system infection or acute electrolyte imbalance. Their pathogenesis is multifactorial. The most relevant familial studies evidence an occurrence rate ranging from 10% to 46% and median recurrence rate of 36% in children with positive familial history for FS. The main twin studies demonstrated a higher concordance rate in monozygotic twins with FS than in dizygotic ones. Linkage studies have proposed 11 chromosomal locations responsible to FS attributed to FEB1 to FEB11. Population-based association studies have shown at least one positive association for 14 of 41 investigated genes with FS. The proinflammatory cytokine interleukin 1β (IL-1β) was the most investigated and also gene associated with susceptibility to FS. A possible role in the overlapping of epilepsy and FS was found for 16 of 36 investigated genes. SCN1A, IL-1β, CHRNA4, and GABRG2 were the most commonly involved genes in this context. The genetic background of FS involves the regulation of different processes, including individual and familial susceptibility, modulation of immune response, and neuronal excitability and interactions with exogenous agents such as viruses.

IL-1β: an important cytokine associated with febrile seizures?

Febrile seizures (FSs) are the most common convulsions in childhood. Studies have demonstrated a significant relationship between a history of prolonged FSs during early childhood and temporal sclerosis, which is responsible for intractable mesial temporal lobe epilepsy. It has been shown that interleukin-1β (IL-1β) is intrinsically involved in the febrile response in children and in the generation of FSs. We summarize the gene polymorphisms, changes of IL-1β levels and the putative role of IL-1β in the generation of FSs. IL-1β could play a role either in enhancing or in reducing neural excitability. If the enhancing and reducing effects are balanced, an FS does not occur. When the enhancing effect plays the leading role, an FS is generated. A mild imbalance can cause simple FSs while a severe imbalance can cause complex FSs and febrile status epilepticus. Therefore, anti-IL-1β therapy may help to treat FSs.

Increased association between febrile convulsion and allergic rhinitis in children: a nationwide population-based retrospective cohort study

BACKGROUND AND OBJECTIVES

Febrile convulsions and allergic rhinitis are both common childhood disorders and both are considered as generally benign disorders. Yet, especially in the case of allergic rhinitis, adverse effects on school performance and limited socialization are found. The relationship between febrile convulsions and allergic rhinitis has not been previously reported; thus, this article seeks to explore the association between these two disorders by collecting data from the Taiwanese nationwide cohort database.

METHODS

A total of 1304 children with febrile convulsions were identified as the case cohort, and controls were matched based on age, sex, urbanization levels, and parents' occupation on a 1 to 4 ratio. Cox's proportional hazards regression model was used to estimate the hazard ratio and confidence interval of allergic rhinitis disorder among children with febrile convulsions.

RESULTS

During an average 6.7 years follow-up period, the incidence of allergic rhinitis in the febrile convulsions case group was higher (65.16 vs 51.45 per 1000 person-years). After 11 years of follow-up, the allergic rhinitis incidence in the febrile convulsion patients was approximate 4% higher than controls (log-rank test P < 0.0001). Risk of allergic rhinitis in the febrile convulsions group was found to be 1.21 times higher than in the control group (95% confidence interval, 1.08-1.36). This risk of allergic rhinitis development is further increased (0.94 vs 18.9) with frequency of febrile convulsions-related medical visits (one to three visits vs more than three visits, P < 0.0001).

CONCLUSION

Febrile convulsions may be associated with allergic rhinitis occurrence in children. Children with more than three febrile convulsion-related medical visits had a significantly higher cumulative incidence of allergic rhinitis. Both disorders have previously been reported to have similar cytokine profiles and specific viral infection association. More studies are required to explore a possible link between the two disorders.

Do gene polymorphism in IL-1β, TNF-α and IL-6 influence therapeutic response in patients with drug refractory epilepsy?

PURPOSE

Pro-inflammatory cytokines may play an important pathophysiological role in patients with epilepsy. To understand the role of genes encoding pro-inflammatory cytokines in epilepsy, this study aimed to evaluate the polymorphisms of the promoter regions of IL-1β-511C>T (rs16944), TNF-α-308G>A (rs1800629) and IL-6-174G>C (rs1800795) genes and to look into the interaction between these genes in influencing seizure susceptibility, seizure frequency and response to therapy.

METHODS

The comparative frequency of polymorphism was determined in rs16944, rs1800629 and rs1800795 using PCR-RFLP in a group of 120 persons with epilepsy (PWE) and 110 ethnically matched healthy subjects of comparable age and sex in the North Indian population.

RESULTS

Alleles and genotypes of rs16944, rs1800629 and rs1800795 were not found to influence the odds ratio of having susceptibility to epilepsy. Also gene-gene interaction of possible nine combinations of these genes did not show any positive association with epilepsy. The genotype and allelic frequency of rs1800795 showed a significant association (p<0.05) in seizure frequency (number of seizures/6-months) and drug refractory epilepsy. However, the genotype and allelic frequency of rs16944 and rs1800629 were not found to have such effect.

CONCLUSION

This study demonstrates that the rs16944, rs1800629 and rs1800795 polymorphism does not act as a strong susceptibility factor for epilepsy in North Indian population. The genotypic association of rs1800795 with seizure frequency and drug-refractory epilepsy raises the issue that a specific set of polymorphic genes can influence seizures and therapeutic response in epilepsy.

Lack of association between TNF-α gene polymorphisms at position -308 A, -850T and risk of simple febrile convulsion in pediatric patients

Background:

Febrile convulsions (FCs), occurring between 6 months and 6 years of age is the most common seizure disorder during childhood. The febrile response is thought to be mediated by the release of pyrogenic cytokines, such as tumor necrosis factor and interleukin-1 (IL-1). There is a significant relationship between genetic components for susceptibility of FCs and different report mutation. We investigated association between two polymorphisms in the tumor necrosis factor (TNF)-α promoter region (G-308A, C-850T) and FCs in the southwest area of Iran.

Materials and Methods:

In this matched case–control study, 100 patients with febrile convulsion as case group and 130 healthy children as control group were enrolled in the study. Peripheral blood samples were collected and DNA was extracted by standard phenol–chloroform method. The genotype and allele frequencies of TNF- α polymorphisms in case and control groups were determined by using PCR-RFLP (polymerase chain reaction restriction fragment length polymorphism) method. Statistical analysis was done using Chi-square test.

Results:

The average age of case and control groups were 3.4 ± 1.4 and 3.4 ± 1.2 years, respectively. There was no significant difference between age and sex in both the groups (P > 0.05). A family history of febrile convulsion was detected in 44% of patients. Moreover, the simple febrile convulsion was detected in 85% of the case group.

Conclusion:

RFLP analysis of TNF- α promoter region polymorphisms, considering P = 0.146 and P = 0.084 for G-308A and C-850T, respectively, showed no correlation between TNF- α polymorphisms and predisposition to simple febrile, based on the kind of convulsion (atypical and simple febrile convulsion). We found a significant relation between genotype distribution of G-308A and atypical febrile convulsion in case group (P = 0.04). A significant correlation between genotype distribution of G-308A and atypical febrile convulsion in the case group was found, but there was no correlation between TNF- α polymorphisms at positions of -308A, and 850T and predisposition to simple febrile convulsion. Further studies are needed to understand clinical usefulness of this correlation.

Interleukin-6 gene polymorphism in febrile seizures

Febrile seizures comprise a common type of pediatric convulsion. Inflammation and genetics may be involved in their pathogenesis. Regarding the role of cytokines (especially interleukin-6) in febrile responses, we performed a case control study of interleukin-6 gene (-174, -572, and -597) single-nucleotide polymorphisms to learn if correlations existed between these particular polymorphisms and febrile seizures. We isolated the genomic DNA of 92 children with febrile seizures and 98 healthy control subjects. We genotyped individuals for their polymorphisms, using polymerase chain reaction-restriction fragment length polymorphism. In our study, the frequencies of -174 G alleles and of the -174 and -572 GG genotypes were observed to be significantly higher in patients than in control subjects. The -174 GG genotype frequency was significantly higher in children with a family history of febrile seizures.

Genetic and environmental factors in complex neurodevelopmental disorders

Complex neurodevelopmental disorders, such as schizophrenia, autism, attention deficit (hyperactivity) disorder, (manic) depressive illness and addiction, are thought to result from an interaction between genetic and environmental factors. Association studies on candidate genes and genome-wide linkage analyses have identified many susceptibility chromosomal regions and genes, but considerable efforts to replicate association have been surprisingly often disappointing. Here, we summarize the current knowledge of the genetic contribution to complex neurodevelopmental disorders, focusing on the findings from association and linkage studies. Furthermore, the contribution of the interaction of the genetic with environmental and epigenetic factors to the aetiology of complex neurodevelopmental disorders as well as suggestions for future research are discussed.

Interleukin (IL)-1beta, IL-1 receptor antagonist, IL-6, IL-8, IL-10, and tumor necrosis factor alpha gene polymorphisms in patients with febrile seizures

Inflammation and genetics may play a role in the pathogenesis of febrile seizures (FSs). We aimed to test whether interleukin-1beta (IL-1beta), IL-1 receptor antagonist (IL-1 Ra), IL-6 promoter, IL-8, IL-10, or tumor necrosis factor (TNF) gene polymorphisms could be used as markers of susceptibility to FSs. An association study was performed among a cohort of 104 patients with FSs and 143 normal control subjects. There was no significant difference between patients and controls in the distribution of allele frequencies of the IL-1beta promoter, IL-1beta exon 5, IL-6 promoter, IL-8, IL-10, or TNF-alpha gene polymorphisms. In contrast, the IL-1 Ra-I homozygote was more frequent in patients with FSs than in healthy controls (93.2% vs. 83.92%, chi(2)=4.51, P=0.034). In addition, individuals homozygous for the IL-1 Ra-I genotype were more than twice as likely to develop FSs than individuals heterozygous for the IL-1 Ra-I/II genotype (OR, 2.63, 95% CI: 1.08-6.39; chi(2)=4.55, P=0.033). We conclude that the IL-1 Ra gene might be one of the useful markers for predicting susceptibility to FSs.

Respiratory alkalosis: "basic" mechanism of febrile seizures?

Experimental Febrile Seizures Are Precipitated by a Hyperthermia-Induced Respiratory Alkalosis. Schuchmann S, Schmitz D, Rivera C, Vanhatalo S, Salmen B, Mackie K, Sipila ST, Voipio J, Kaila K. Nat Med 2006;12:817–823. Febrile seizures are frequent during early childhood, and prolonged (complex) febrile seizures are associated with an increased susceptibility to temporal lobe epilepsy. The pathophysiological consequences of febrile seizures have been extensively studied in rat pups exposed to hyperthermia. The mechanisms that trigger these seizures are unknown, however. A rise in brain pH is known to enhance neuronal excitability. Here we show that hyperthermia causes respiratory alkalosis in the immature brain, with a threshold of 0.2–0.3 pH units for seizure induction. Suppressing alkalosis with 5% ambient CO2 abolished seizures within 20 s. CO2 also prevented two long-term effects of hyperthermic seizures in the hippocampus: the upregulation of the Ih current and the upregulation of CB1 receptor expression. The effects of hyperthermia were closely mimicked by intraperitoneal injection of bicarbonate. Our work indicates a mechanism for triggering hyperthermic seizures and suggests new strategies in the research and therapy of fever-related epileptic syndromes.

Genetic susceptibility to febrile seizures: case-control association studies

OBJECTIVE

A genetic predisposition to febrile seizures (FS) has long been recognized. The inheritance appears to be polygenic in small families or sporadic cases of FS encountered in daily clinical practice. To determine whether candidate genes are responsible for the susceptibility to FS, we have performed genetic association studies in FS patients and controls.

METHODS

The single-nucleotide polymorphisms (SNPs) of genes involved in immune response (interleukin (IL) 1B), endocannabinoid signaling (CNR1), acid-base balance (SLC4A3, SLC9A1, SLC9A3), gap junction channel (CX43), and GABA(A) receptor trafficking (PRIP1) were examined in 249 FS patients (186 simple and 63 complex FS) and 225 controls.

RESULTS

There were no significant differences in the allele frequencies of the SNPs between controls and all FS, simple FS, and complex FS patients. When the simple FS patients were divided into two groups according to either having (familial) or not having a family history of FS in close relatives (sporadic), there was a significant association between IL1B -511 SNP and sporadic simple FS (p=0.003).

CONCLUSIONS

These data suggest that cytokine genes may act as enhancers or attenuators of FS susceptibility. Genetic association study may be an effective approach to understanding the molecular basis of FS at least in a subgroup of patients.

Febrile seizures: characterization of double-stranded RNA-induced gene expression

An association has long been suspected between febrile seizures and interleukin-1beta, the most potent endogenous pyrogen. Interleukin-1beta production increases after double-stranded RNA stimulation in leukocytes of febrile seizure patients. To elucidate the genetics of the immune response, the gene expression pattern after double-stranded RNA stimulation was investigated using DNA microarray. Compared with the control group, expression of the genes ACCN4 (sodium channel), KCNC3 (potassium channel), GABRE (gamma-aminobutyric acid receptor epsilon subunit), RIPK2 (receptor interacting protein kinase-2), TLR4 (toll-like receptor-4), IL26 (interleukin-26), and TNF (tumor necrosis factor), and CASP1 (caspase-1) was increased in the febrile seizure group (P < 0.01). Because RIPK2 and CASP1 are associated with interleukin-1beta production, increased expression might cause increased interleukin-1beta production in the febrile seizure patients. The induced expression of several ion channel genes by double-stranded RNA may affect neuronal excitability which leads to seizure susceptibility during infection.

Progress in searching for the febrile seizure susceptibility genes

Febrile seizures (FS) represent the most common form of childhood seizures. They affect 2-5% of infants in the Caucasian population and are even more common in the Japanese population, affecting 6-9% of infants. Some familial FS are associated with a wide variety of afebrile seizures. Generalized epilepsy with febrile seizures plus (GEFS+) is a familial epilepsy syndrome with a spectrum of phenotypes including FS, atypical FS (FS+) and afebrile seizures. A significant genetic component exists for susceptibility to FS and GEFS+: extensive genetic studies have shown that at least nine loci are responsible for FS. Furthermore, mutations in the voltage-gated sodium channel subunit genes (SCN1A, SCN2A and SCN1B) and the GABA(A) receptor subunit genes (GABRG2 and GABRD) have been identified in GEFS+. However, the causative genes have not been identified in most patients with FS or GEFS+. Common forms of FS are genetically complex disorders believed to be influenced by variations in several susceptibility genes. Recently, several association studies on FS have been reported, but the results vary among different groups and no consistent or convincing FS susceptibility gene has emerged. Herein, we review the genetic data reported in FS, including the linkage analysis, association studies, and genetic abnormalities found in the FS-related disorders such as GEFS+ and severe myoclonic epilepsy in infancy.

Febrile seizures: interleukin 1beta and interleukin-1 receptor antagonist polymorphisms

In order to investigate the association between IL-1beta -511 C-->T and IL-1 receptor antagonist intron 2 variable tandem repeat polymorphisms, and febrile seizures in children, 90 children (mean age, 19.7 +/- 11.2 months) diagnosed with febrile seizure and 106 healthy controls (mean age, 14.2 +/- 3.6 months) with no seizure or neurologic events were included in the study. The polymorphisms were analyzed using restriction fragment length polymorphism and agarose gel electrophoresis methods. In the patient group, the frequencies of IL-1beta genotypes CC, CT, and TT were 24.4%, 52.2%, and 23.3%, respectively, compared with 38.7%, 50.95%, and 10.4%, respectively, in the control group. The TT genotype was significantly more common in the patient group than in the control group (P = 0.044), and the T allele frequency was significantly higher in the patient group (0.50 vs 0.36, P = 0.040). Among the three genotypes (RN1/1, RN1/2, and RN2/2) of the IL receptor antagonist gene variable tandem repeat polymorphisms, the frequency of both the RN2/2 genotype and the RN2 allele were significantly higher in the patient group (P = 0.007). Also RN2 allele frequency was found higher in patient group than controls (0.29 vs 0.15, P = 0.020). IL-1beta -511 and IL-1 receptor antagonist intron 2 variable tandem repeat polymorphisms may be involved in susceptibility to febrile convulsions in children.

Antagonism of peripheral inflammation reduces the severity of status epilepticus

Status epilepticus (SE) is one of the most serious manifestations of epilepsy. Systemic inflammation and damage of blood-brain barrier (BBB) are etiologic cofactors in the pathogenesis of pilocarpine SE while acute osmotic disruption of the BBB is sufficient to elicit seizures. Whether an inflammatory-vascular-BBB mechanism could apply to the lithium-pilocarpine model is unknown. LiCl facilitated seizures induced by low-dose pilocarpine by activation of circulating T-lymphocytes and mononuclear cells. Serum IL-1beta levels increased and BBB damage occurred concurrently to increased theta EEG activity. These events occurred prior to SE induced by cholinergic exposure. SE was elicited by lithium and pilocarpine irrespective of their sequence of administration supporting a common pathogenetic mechanism. Since IL-1beta is an etiologic trigger for BBB breakdown and its serum elevation occurs before onset of SE early after LiCl and pilocarpine injections, we tested the hypothesis that intravenous administration of IL-1 receptor antagonists (IL-1ra) may prevent pilocarpine-induced seizures. Animals pre-treated with IL-1ra exhibited significant reduction of SE onset and of BBB damage. Our data support the concept of targeting systemic inflammation and BBB for the prevention of status epilepticus.

The role of interleukin-1 in seizures and epilepsy: a critical review

Interleukin-1 (IL-1) has a multitude of functions in the central nervous system. Some of them involve mechanisms that are related to epileptogenesis. The role of IL-1 in seizures and epilepsy has been investigated in both patients and animal models. This review aims to synthesize, based on the currently available literature, the consensus role of IL-1 in epilepsy. Three lines of evidence suggest a role for IL-1: brain tissue from epilepsy patients and brain tissue from animal models shows increased IL-1 expression after seizures, and IL-1 has proconvulsive properties when applied exogeneously. However, opposing results have been published as well. More research is needed to fully establish the role of IL-1 in seizure generation and epilepsy, and to explore possible new treatment strategies that are based on interference with intracellular signaling cascades that are initiated when IL-1 binds to its receptor.

Association study between interleukin 1 beta gene and epileptic disorders: a HuGe review and meta-analysis

Previous studies have examined the association of a single nucleotide polymorphism at the promoter region of interleukin 1B (IL-1 beta-511T) with temporal lobe epilepsy and febrile seizures susceptibility, but those studies have been inconclusive. Published studies up to March 2007 of temporal lobe epilepsy, febrile seizures and the IL-1 beta-511T single nucleotide polymorphism were identified by searches of Medline and Embase databases. Meta-analysis of temporal lobe epilepsy and febrile seizures case-control data were performed to assess the association of IL-1 beta-511T with temporal lobe epilepsy, temporal lobe epilepsy with hippocampal sclerosis, febrile seizures, and other epileptic disorders. Pooled odds ratios (OR) were estimated by means of a genetic-model-free approach. The quality of the included studies was assessed by a score. The results show a modest association (OR, 1.48; 95% confidence interval, 1.09-2.00; P = 0.01) between the IL-1 beta-511T polymorphism and temporal lobe epilepsy with hippocampal sclerosis.

Role of viral infections in the etiology of febrile seizures

The role of viral infection in the etiology of febrile seizures is a relatively neglected field of neurologic research. A National Institutes of Health Consensus Conference (1981) omitted reference to causes of infections and the role of fever in febrile seizures, and emphasized outcome and anticonvulsant treatment. In an earlier review of the world literature (1924-1964), except for roseola infantum, viral infections as a cause of febrile seizures were rarely diagnosed. The present review includes reports of viruses most commonly associated with febrile seizures in the last decade, especially human herpesvirus-6 and influenza. The specificity and neurotropic properties of some viruses in the febrile seizure mechanism, a possible encephalitic or encephalopathic pathology, and the essential role of fever and height of the body temperature as a measure of the febrile seizure threshold are discussed. Cytokine and immune response to infection, and a genetic susceptibility to febrile seizures are additional etiologic factors. Future research should emphasize early detection of causative viruses, the nature of viral neurotropism, and the role of cytokines in fever induction. Trials of antiviral agents and vaccines, with attention to safety concerns, and more effective antipyretics would address the febrile seizure mechanism more specifically than anticonvulsant therapies.

Lack of association between IL-1β/α gene polymorphisms and temporal lobe epilepsy with hippocampal sclerosis

Mesial temporal lobe epilepsy with hippocampal sclerosis (MTLE-HS) is one of the most common medically intractable epilepsy syndromes and the pathogenesis of HS remains highly obscure. Recent studies demonstrated controversial results about the relationship between interleukin (IL) gene polymorphism and epilepsy in different ethnic groups. This correlation was investigated in Turkish patients with MTLE-HS. The allele distribution of IL-1alpha and IL-1beta in 47 patients of Turkish ancestry was determined and compared with 99 ethnically matched control subjects. Analysis of genotype frequencies between patients and controls showed no statistically significant difference (p>0.05). Our data suggest that IL-1alpha and IL-1beta gene polymorphisms do not act as a strong susceptibility factor for MTLE-HS in individuals of Turkish ancestry.