Dimethyl fumarate ameliorates autoimmune hepatitis in mice by blocking NLRP3 inflammasome activation

Dimethyl fumarate (DMF) is a fumaric acid derivative clinically approved for the treatment of some inflammatory diseases, but the underlying mechanism for its therapeutic effects remains incompletely understood. NLR family pyrin domain containing 3 (NLRP3) inflammasome activation has critical roles in innate immune responses to various infections and sterile inflammations. In this study, we aimed to explore whether DMF affects auto-immune hepatitis (AIH) in mice induced by concanavalin A (Con A) by modulating NLRP3 inflammasome activation. The results showed that DMF suppressed the activation of NLRP3 inflammasome activation in lipopolysaccharide-primed murine bone marrow-derived macrophages upon ATP or nigericin treatment, as evidenced by reduced cleavage of pro-caspase-1, release of mature interleukin-1β (IL-1β) and generation of gasdermin D N-terminal fragment (GSDMD-NT). DMF also greatly reduced ASC speck formation upon the stimulation of nigericin or ATP, indicating its inhibitory effect on NLRP3 inflammasome assembly. Consistent with reduced generation of GSDMD-NT, ATP or nigericin-induced pyroptosis was markedly suppressed by DMF. Moreover, DMF treatment alleviated mitochondrial damage induced by ATP or nigericin. Interestingly, all these effects were reversed by the protein kinase A (PKA) pathway inhibitors (H89 and MDL-12330A). Mechanistically, DMF enhanced PKA signaling and thus increased NLRP3 phosphorylation at PKA-specific sites to attenuate its activation. Importantly, DMF decreased serum levels of inflammatory cytokines and ameliorated liver injury in Con A-induced AIH of mice, concomitant with reduced the generation of caspase-1p10 and GSDMD-NT and alleviating mitochondrial aggregation in the liver. Collectively, DMF displayed anti-inflammatory effects by inhibiting NLRP3 inflammasome activation likely through regulating PKA signaling, highlighting its potential application in treating AIH.