Expression of interleukin-6 in hippocampus of rat with febrile seizures and the effect of valproic acid administration on its methylation level

Objective To investigate the level of interleukin-6 (IL-6) and the effect of valproic acid(VPA) administration on IL-6 promoter methylation, further to explore the epigenetic mechanism in febrile seizures. Methods Sprague-Dawley (SD) rats (21 day) were randomly divided into control group (n=12) and febrile seizure (FS) group (n=12), and seizures were generated using hot bath methods and evaluated by racine score and electroencephalogram (EEG). The IL-6 protein and mRNA levels were detected using ELISA and quantitative reverse transcription polymerase chain reaction (qRT-PCR), respectively.Rat C6 cell line was cultured and randomly divided into control, VPA(0.2 mol/L), hyperthermia(43.5 ℃, 1 h), hyperthermia (43.5 ℃, 1 h)+VPA (0.2 mol/L) groups.The methylation status of IL-6 promoter in FS rats and the effect of VPA on IL-6 methylation in C6 cell line were examined by bisulfite sequencing polymerase chain reaction (BSP) to determine the epigenetic regulation of IL-6 level in FS. Results Racine score and EEG results showed that the frequency and amplitude of neuronal discharge increased after hot water bath in rats, and the latency of convulsion was shorter.The expression levels of IL-6 mRNA and protein were significantly increased in Fs group compared with those in control group(mRNA: Control: 0.98±0.34; FS: 2.85±0.39, P<0.05; Protein: Control: (2 824.33±169.20)pg/ml; FS: (3 514.58±86.4)pg/ml, P<0.01). The methylation of IL-6 promoter in FS group (84% (21/25)) was lower than that in control group (100% (25/25)) (P<0.05). A significant increase in methylation of IL-6 promoter was observed in C6 cell line from VPA combined with hyperthermia (96% (24/25)) but no change was showed in that from VPA alone (100% (25/25)) compared with that from control(100% (25/25)). Conclusion IL-6 level is up-regulated in FS rats, and the hypomethylation or demethylation of the IL-6 promoter region might increase the IL-6 level.VPA administration can elevate its methylation level, which provides a strong experimental basis for the future study of the epigenetic mechanism in FS. Key words: Febrile seizures; Interleukin-6; DNA methylation; Valproic acid; Bisulfite sequencingpolymerase chain reaction