Short-chain fatty acids abrogate Japanese encephalitis virus-induced inflammation in microglial cells via miR200a-3p/ZBTB20/Ikβα axis

Japanese encephalitis virus (JEV), a member of the Flaviviridae family, is a leading cause of viral encephalitis in humans. Survivors of this infection often develop life-long neurological sequelae. Short-chain fatty acids (SCFAs) produced in the gut are vital mediators of the gut-brain axis. We aimed to study microRNA-based mechanisms of SCFAs in an in vitro model of JEV infection. N9 microglial cells were pre-treated with SCFA cocktail before JEV infection. Cytokine bead analysis (CBA), immunoblotting and PCR were performed to analyse relevant inflammatory markers. microRNA sequencing was performed using Illumina Hiseq and Bioinformatical tools were used for differentially expressed (DE) miRNAs and Weighted gene co-expression network analysis (WGCNA). microRNA mimic/inhibitor experiments and luciferase assay were performed to study miRNA-target interaction. A significant reduction in MCP1 and TNFα along with reduced expression of phospho-NF-κB was observed in SCFA conditions. Significant attenuation of HDAC activity and protein expression was recorded. miRNA sequencing revealed 160 DE miRNAs in SCFA+JEV treated cells at 6 hours post infection (HPI). WGCNA revealed miR-200a-3p, a hub miRNA significantly upregulated in SCFA conditions. Transcription factor ZBTB20 was bioinformatically predicted and validated as a gene target for miR200a-3p. Further miRNA mimic/inhibitor assay demonstrated that miR-200-3p regulated ZBTB20 along with Iκβα that possibly dampened NF-κB signal activation downstream. N9 microglial cells were pre-treated with SCFA for 12 hours followed by JEV infection for 6hours and 24 hours. There were 4 groups in both the infection timeline namely, Control, SCFAControl, JEVcontrol, SCFAJEV. Total RNA extraction was performed using phenol chloroform method. Differential expression analysis in all 24 conditions was performed by small RNA sequencing (Illumina) according to the manufacturer's instructions.