NLRP3 inflammasome regulates Th17/Treg cell balance in experimental autoimmune myocarditis

This study aimed to investigate whether the NLRP3 inflammasome modulates the Th17/Treg cell balance in experimental autoimmune myocarditis (EAM).

BALB/c mice were immunized subcutaneously with purified cardiac myosin heavy chain-α to induce EAM, injected NLRP3 inhibitor (MCC950) or PBS into the EAM mice by intraperitoneal injection. Splenic CD4⁺ T cells were isolated for in vitro culture. Myocardial inflammation was evaluated by HE staining. Th17/Treg ratios were analyzed by flow cytometry in cardiac tissue and cultured cells. RORγt and Foxp3 mRNA expression was measured by RT-PCR and IL-17/IL-10 levels by ELISA.

Our study demonstrates that NLRP3 inhibition significantly attenuates myocardial inflammatory cell infiltration and preserves cardiac architecture in EAM mice. The EAM group exhibited significantly increased Th17/Treg ratios and RORγt mRNA expression in myocardial tissue compared to both MCC950-treated and control groups while demonstrating markedly decreased Foxp3 mRNA levels. In vitro experiments using cultured CD4⁺ T cells revealed substantially higher Th17 cell proportions, RORγt expression, and IL-17 secretion in the EAM group versus MCC950-treated cells, accompanied by significantly reduced Treg cell frequencies, Foxp3 mRNA levels, and IL-10 production.

During the pathogenesis of experimental autoimmune myocarditis (EAM), the NLRP3 inflammasome promotes Th17 cell differentiation while suppressing Treg cell development. Inhibition of the NLRP3 inflammasome restores the Th17/Treg balance and mitigates myocardial injury. These findings suggest that the NLRP3 inflammasome is a critical signaling hub in modulating immune responses in EAM. Targeting NLRP3 may represent a novel immunotherapeutic strategy for myocarditis.