Hydroxychloroquine cures autoimmune myocarditis by inhibiting innate immune via the CXCL16-CXCR6 axis between macrophages and T cells

Abstract Background Myocarditis is a life-threatening inflammatory disease of the heart, with a lack of effective treatment options. Hydroxychloroquine (HCQ), a well-established antimalarial agent, has been widely used in the management of rheumatic disorders. This research aims to evaluate the efficacy of HCQ in the treatment of myocarditis. Methods A mouse model of experimental autoimmune myocarditis (EAM) was used to evaluate the therapeutic effects of HCQ on cardiac function, inflammation, and fibrosis. Echocardiography, histology and cytokine assays were performed to assess cardiac function and inflammatory responses. Single-cell RNA sequencing was employed to analyze immune cell populations and chemotactic activity. CXCL16 levels were measured in cardiac tissue and serum, while YY1 expression was measured by Western blotting in macrophages and cardiac tissue. Additionally, flow cytometry was used to evaluate immune cell infiltration and migration. Results HCQ improved cardiac function in acute and chronic myocarditis. Histological analysis showed that HCQ treatment reduced inflammation, fibrosis, and immune cell infiltration in myocarditis models. Single-cell RNA sequencing revealed that HCQ lowered inflammatory cell proportions and suppressed macrophage chemotaxis. Mechanistically, HCQ reduced YY1 levels, which led to the downregulation of CXCL16 expression in macrophages and the inhibition of CXCL16-mediated chemotaxis to Th17 and NKT cells. The use of CXCL16 neutralizing antibodies improved cardiac function and reduced inflammation in myocarditis. Conclusions HCQ improves cardiac function and reduces inflammation in myocarditis by inhibiting CXCL16 expression in macrophages through the suppression of its transcription factor YY1, which in turn reduces the chemotaxis of Th17 and NKT cells. These findings suggest that HCQ is a promising therapeutic agent for myocarditis.