SCN9A Epileptic Encephalopathy Mutations Display a Gain-offunction Phenotype and Distinct Sensitivity to Oxcarbazepine

Genetic mutants of voltage-gated sodium channels(VGSCs)are considered to be responsible for the increasing number of epilepsy syndromes.Previous research has indicated that mutations of one of the VGSC genes,SCN9A(Navl.7),result in febrile seizures and Dravet syndrome in humans.Despite these recent efforts,the electrophysiological basis of SCN9A mutations remains unclear.Here,we performed a genetic screen of patients with febrile seizures and identified a novel missense mutation of SCN9A(W1150R).Electrophysiological characterization of different SCN9A mutants in HEK293T cells,the previously-reported N641Y and K655R variants,as well as the newly-found W1150R variant,revealed that the current density of the W1150R and N641Y variants was significantly larger than that of the wild-type(WT)channel.The time constants of recovery from fast inactivation of the N641Y and K655R variants were markedly lower than in the WT channel.The W1150R variant caused a negative shift of the G-V curve in the voltage dependence of steady-state activation.All mutants displayed persistent currents larger than the WT channel.In addition,we found that oxcarbazepine(OXC),one of the antiepileptic drugs targeting VGSCs,caused a significant shift to more negative potential for the activation and inactivation in WT and mutant channels.OXC-induced inhibition of currents was weaker in the W1150R variant than in the WT.Furthermore,with administering OXC the time constant of the N641Y variant was longer than those of the other two SCN9A mutants.In all,our results indicated that the point mutation W1150R resulted in a novel gain-of-function variant.These findings indicated that SCN9A mutants contribute to an increase in seizure,and show distinct sensitivity to OXC.

Efficacy and mechanisms of Dingxian pill(定痫丸)combined with valproic acid on pentylenetetrazol-induced chronic epilepsy in rats

OBJECIVE:To investigate the efficacy and mechanisms of Dingxian pill(定痫丸)combined with valproic acid(VPA)on pentylenetetrazol-induced chronical epilepsy in rats.METHODS:A rat model of epilepsy was established by administering pentylenetetrazol(PTZ)water solution(35 mg/kg).Rats were divided into 4 groups,among which three groups were treated with different drugs once a day for 28 d including Dingxian pill(2.4 g/kg),VPA(0.2 g/kg),or a combination of Dingxian pill(2.4 g/kg)and VPA(0.2 g/kg)respectively,and the control group was given the same volume of saline.Rats in different groups were compared based on animal behavior,electroencephalograms,Morris water maze,immunohistochemistry,transcriptomics and real-time polymerase chain reaction.RSULTS:The combination therapy of Dingxian pill and VPA inhibited PTZ-induced seizure-like behavior and reduced seizure grades more significantly than VPA alone.Compared with the control group,the learning and memory ability of chronic PTZ-induced epileptic rats was improved in all the drug treatment groups,especially in the group that received both Dingxian pill and VPA.Similar to the results of MWM tests,expression of the neuroexcitability marker gene c-Fos was reduced after Dingxian pill and/or VPA treatment,and the effect was most pronounced in the combined treatment group.Transcriptomic analysis revealed that gene expression in the rodent hippocampus,which is involved in epilepsy,was upregulated by combined treatment with Dingxian pill and VPA,compared with VPA treatment alone.CONCLUSION:Our results not only highlight the antiepileptic effects of combined Dingxian pill and VPA treatment,but also shed light on the underlying molecular mechanisms and provide a way to apply Traditional Chinese Medicine in the treatment of epilepsy.