Scorpion polypeptide BmK IT2 alleviates epileptic seizures and neuronal pyroptosis by regulating sodium channel...

Epilepsy is the fourth most common neurological disorder, and nearly 30 % of patients develop seizures that are refractory to conventional anticonvulsant drugs. The etiology of epilepsy is diverse and includes a variety of genetic channelopathies that result in neuronal hyperexcitability, seizure generation, maladaptive circuit plasticity, intracellular calcium dysregulation, and neurodegeneration. For instance, mutations in SCN8A encoding the voltage-gated sodium channel Nav1.6 are known to disrupt calcium homeostasis in neurons, induce neuronal death, and cause persistent epilepsy. The traditional Chinese medicine Scorpion has a history of treating epilepsy for thousands of years, but its pharmacodynamic active ingredients and specific mechanism are still unclear.

This study explored the anti-epileptic effect of BmK IT2 and its potential molecular mechanism.

In the present study, we investigated the ameliorative effect of the scorpion -extract peptide BmK IT2 on epilepsy in vivo experiments, and its possible molecular mechanism by immunohistochemistry, immunofluorescence, and calcium imaging experiments. The inhibitory effects of BmK IT2 on the current density of different sodium channel subtypes in hippocampal pyramidal neurons were detected by whole-cell patch-clamp, and molecular docking and in vitro experiments predicted the key residues that might act on sodium channels.

Here we show that intracerebroventricular administration of BmK IT2 can reduce behavioral seizure frequency, including the incidence of clonic grand seizures by 67 %, and seizure-associated mortality in mouse models of acute and chronic epilepsy. Further, BmK IT2 treatment reversed seizure-induced deficits in spatial learning and memory, and mitigated depression- and anxiety-like behaviors. These therapeutic effects were associated with marked reductions in total voltage-activated sodium current, high-frequency burst firing, and c-Fos expression by hippocampal neurons as well as decreased hippocampal neuron loss following status epilepticus. In vitro and in silico experiments identified 588D and 598 F in Nav1.6 domain II and 1187 E in domain III as key recognition sites for BmK IT2. Additionally, treatment with BmK IT2 also suppressed reversal of the sodium-calcium exchanger 1 (NCX1) and concomitant calcium influx.

These findings suggest that BmK IT2 alleviate potentially epileptic seizures, potentially prevent pyroptosis of neurons by voltage-gating the Nav1.6 channel of hippocampal pyramidal neurons and inhibiting the NLRP1/caspase-1/GSDMD signaling pathway. BmK IT2 is a potential molecular template for the design of anti-epileptogenic drugs targeting Nav1.6.