Human cardiac myosin (HCM) activates Toll-like receptors 2, 7 and 8 (B87)

Abstract

Abstract Toll-like receptor (TLR) activation has been implicated as a link between innate immunity and adaptive immunity in autoimmune diseases including myocarditis. Human cardiac myosin (HCM) has long been known as an autoantigen in myocarditis. The role of HCM on innate immunity has not been studied. To test the hypothesis that HCM activates TLRs, HEK 293 cells transfected with human (h) TLR2, 3, 4, 5, 7, 8, and 9 were treated with HCM or a cryptic HCM peptide S2-16 for 72h. IL-8 levels in supernatants were measured by ELISA. HCM or S2-16 treatment resulted in 2–4 times more IL-8 from hTLR2, 7 and 8 transfected cell lines compared with media. HEK control cells treated with HCM or S2-16 showed same level of IL-8 as media. In addition, skeletal muscle myosin treated hTLR transfected cell lines showed no difference in IL-8 levels from media. To confirm this observation, human monocytes were isolated and treated with HCM and S2-16. Supernatant was harvested 24 h later and IL-8 was measured by ELISA. Both HCM and S2-16 treatment resulted in a dose-dependent increase of IL-8. Similar increase in IL-8 in human monocytic THP-1 cell line was also observed. The finding that HCM activates innate immunity through TLR 2, 7, and 8 is novel, and links innate and adaptive immunity in autoimmune myocarditis. Exposure of HCM during viral infection or after apoptosis or necrosis in the heart may lead to chronic stimulation of TLRs and autoimmune heart disease.