The mmu_circ_0000335 inhibits M1 microglial-induced hippocampal neuronal apoptosis via the miR-19b-3p/SOCS1 axis in a mouse epilepsy model

Background : Increasing evidence has demonstrated that circular RNAs (circRNAs) participate in epileptogenesis, but the expression profile and role of circRNAs in epilepsy remain unknown. A circRNA microarray was performed to examine epilepsy-related circRNAs. Bioinformatics analyses, luciferin reporter experiments and real-time quantitative PCR (Rt-qPCR) in vitro experiments were performed to demonstrate the mechanism of circRNA-mediated gene regulation of the microglial phenotype under epileptic conditions. Then, to further confirm the effect of circRNAs on nerve damage in the hippocampus, a mouse model of epilepsy was established by intraperitoneal injection of lithium chloride and pilocarpine. Results: The data indicated that 364 circRNAs were differentially expressed comparing epilepsy and control tissues. In particular, mmu_circ_0000335 expression was significantly downregulated in epileptic mice which was confirmed by Rt-qPCR. Overexpression of mmu_circ_0000335 promoted BV2 cell transformation into the M2 macrophage phenotype by increasing expression of CD206, Arg1, Ym1 and IL-10 while decreasing M1 macrophage markers IL-1β, IL-6, TNF-α and IFN-γ expressions under epileptic conditions. mmu_circ_0000335 expression triggered upregulation of Suppressor of Cytokine Signaling 1 (SOCS1) by decreasing miR-19b-3p levels, as determined by luciferase reporter assay. In vivo studies found that mmu_circ_0000335 overexpression decreased epilepsy-induced neural cell apoptosis in the hippocampus by reducing inflammatory cytokine expression. Immunofluorescence detection showed that mmu_circ_0000335 overexpression promoted microglial transformation into the M2 phenotype which had an anti-inflammatory effect. Conclusions: These results collectively indicated that mmu_circ_0000335 was involved in epilepsy progression by functioning as a miR-19b-3p sponge to enhance SOCS1 expression. Thus, mmu_circ_0000335 may be a candidate therapeutic target for epilepsy patients.