Tea catechins improve left ventricular dysfunction, suppress myocardial inflammation and fibrosis, and alter cytokine expression in rat autoimmune myocarditis

Background: Myocarditis is a clinically serious disease. Tea catechins have been shown to reduce inflammation; however the effects of catechins on the development of myocarditis have not been well studied. Aims: To clarify the role of catechins, using an experimental autoimmune myocarditis (EAM) model. Methods and results: Lewis rats were immunized with porcine cardiac myosin to establish EAM. Tea catechins were administered orally from day 0 to day 21 (Group A, n=12), from day 14 to day 21 (Group B, n=8), or saline (Group C, n=9) daily. Rats were killed on day 21. Echocardiograms indicated that Group A showed significantly improved cardiac function compared to Group C. Pathologically, non-treated EAM hearts showed severe myocardial cell infiltration and fibrosis; however Group A showed significantly less area. Immunohistochemistry revealed enhanced expression of NF-κB and ICAM-1 in non-treated EAM hearts, which was suppressed by catechin administration in Group A. mRNA levels of TNF-α were decreased and Th2 cytokines were markedly enhanced in Group A compared with the control group. Late catechin administration (Group B) showed limited effects on EAM. Conclusion: The catechins suppressed ventricular remodelling in EAM; thus catechin treatment might be a promising option for the prevention of EAM myocarditis.