STING regulates the transformation of the proinflammatory macrophage phenotype by HIF1A into autoimmune myocarditis

Macrophages play an essential role in the pathogenesis of autoimmune myocarditis, but the molecular mechanism remains largely unknown. Here, the role of Stimulator of interferon gene (Sting) in autoimmune myocarditis was investigated. Six-week-old male BALB/c mice received two subcutaneous injections of 250 μg α-MyHC peptide to establish experimental autoimmune myocarditis (EAM). With single-cell RNA sequencing analysis of cardiac immune (Cd45⁺) cells, Sting was found to initiate proinflammatory macrophage differentiation related to the acute EAM phase. Furthermore, proinflammatory macrophages contribute to the pathogenesis of EAM via hypoxia-inducible factor-1α (Hif1α). A higher expression level of Sting was detected in macrophages from myocarditis, which was positively correlated with Hif1α expression. Single-stranded DNA (ssDNA) accumulation in macrophages in myocarditis was observed in the hearts of EAM mice. Pharmacological blockade of STING by C-176 (a specific inhibitor) ameliorated the inflammatory response of EAM and reduced proinflammatory molecule (Ifn-β, Tnf-α, Ccl2, and F4/80) expression and Hif1α expression. In vitro studies revealed that ssDNA activated the expression of Sting; in turn, Sting accelerated proinflammatory molecule expression in mouse macrophages. Inhibition of Hif1α expression could reduce Sting-associated cardiac inflammation and proinflammatory molecule expression. In addition, the expression of STING and ssDNA accumulation in macrophages were observed in human autoimmune myocarditis heart samples. STING activated proinflammatory macrophage via HIF1A, promoting the development of autoimmune myocarditis. The STING signaling pathway might provide a novel mechanism of autoimmune myocarditis and serve as a potential therapeutic target for autoimmune myocarditis patients.