miR-340-5p/IRF1/USP18 Axis Regulates Neuroinflammation, Seizure Severity in Experimental Epilepsy

Epilepsy is a widespread neurological disorder where maladaptive neuroinflammation significantly drives epileptogenesis. Current therapeutic strategies often fall short in addressing the underlying inflammatory mechanisms, leaving a substantial portion of patients with drug-resistant forms. Understanding the specific molecular pathways that link inflammation to seizure activity is crucial for developing disease-modifying treatments. This study investigates a previously unrecognized signaling axis that controls inflammatory responses and inflammatory cell death in experimental models of epilepsy.

Researchers identified a novel signaling axis through integrated bioinformatic analyses of GSE73878 and GSE18740 datasets, combined with transcription factor and microRNA prediction. Functional and mechanistic validations were conducted using lipopolysaccharide-stimulated BV2 microglia and pentylenetetrazole-induced mouse seizure models. Seizure severity and epileptic phenotypes were assessed via Racine scale assessments and EEG recordings. The study investigated the effects of silencing USP18 to understand its role in neuroinflammation and seizure activity.

Under epileptic conditions, USP18 was markedly upregulated, accompanied by increased pro-inflammatory cytokine release, apoptosis, and pyroptosis. Silencing USP18 attenuated neuroinflammation and reduced seizure severity in the experimental models. Mechanistically, interferon regulatory factor 1 (IRF1) was identified as a direct transcriptional activator of USP18. > miR-340-5p was found to suppress USP18 expression by directly targeting IRF1, thereby mitigating inflammatory signaling and neuronal injury. This revealed a novel regulatory pathway linking microRNA-mediated control, interferon-responsive transcription, and inflammatory effector mechanisms.