Down-regulation Of Growth Factor Receptor-bound Protein2by Britanin In Experimental Autoimmune Myocarditis

Plants of the genus Inula(Asteraceae family) have been used as traditional herbal medicines throughout the world for a long period, and have previously been reported to yield a variety of sesquiterpenes, which accounting for their bioactivities such as anti-inflammatory, antitumor and bactericidal effects.Britanin, a sequiterpenoid from the the aerial parts of Inμla lineariifolia, was examined with respect to its inhibitory activities against LPS-induced NO production in RAW264.7macrophages. britanin exhibited potent inhibitory activities against NO production with not significantly cytotoxic at the concentrations required for inhibiting NO production.Myocarditis is an acute inflammatory disease of the heart and is often a precursor of dilated cardiomyopathy. Experimental autoimmune myocarditis (EAM) has been used as a model for human myocarditis.In this study, we sought to further characterize the anti-inflammatory effect of britanin for the treatment of EAM and investigate the potential drug target for the treatment of EAM. Experimental autoimmune myocarditis was induced in BALB/c mice by immunization with porcine cardiac myosin(PCM).4doses (20mg/kg/day,10mg/kg/day,5mg/kg/day,2.5mg/kg/day) britanin was administered by intraperitoneal injection to mice with EAM from0to21after immunization. britanin treatment significantly reduced the severity of myocarditis、as detected by histopathological evaluation. Britanin treatment decreased the serum levels of cytokines tumor necrosis fator (TNF)-a and interferon (IFN)-y. Comparative proteomic analysis by two-dimensinal gel electrophoresis of mice immunized with PCM showed20mg/kg britanin caused broad changes in protein expression in lymphocytes including down-regμlation of growth factor receptor-bound protein2(Grb2). Immunoblotting studies showed that20mg/kg britanin attenuated the rise in GRB2level in lymphocytes of mice with EAM. Moreover, we demonstrated that blockade of GRB2with monoclonal antibody significantly reduced severity of myocarditis in EAM mice. Overall, these findings indicated that GRB2is important in the induction of EAM and might be a potential drug target of britanin for the treatment of EAM.