Animals ; Cell Proliferation ; Cells, Cultured ; Coxsackievirus Infections ; metabolism ; Enterovirus B, Human ; Myocytes, Cardiac ; cytology ; metabolism ; virology ; Osteopontin ; metabolism ; Rats

Objective Mammalian target of rapamycin(mTOR)plays a central role in controlling cell proliferation.survival and growth.We investigated the role of mTOR signal transduction on viral myocarditis by observing the effect of mTOR inhibitor rapamycin on Smad 3 and collagen type Ⅰ expression in rat myocardial fibroblasts infeeted with coxsaekievirus B 3(CVB 3).Methods Primary cultured myocardial fibroblasts of SD rats infected with CVB 3 were treated with or without rapamycin.The Smad 3 and collagen type Ⅰ expression of the cells were determined by RT-PCR and Western blot.Results (1) mTOR/β-actin ratio was dose-dependenfly reduced(1 nmol/L,0.38 ±0.022:10 nmol/L,0.282±0.014;100 nmol/L,0.263±0.012 vs.control 1.45±0.04．all P＜0.05 vs.control)after 48 hours rapamycin treatments and time-dependendy reduced after 10 nmol/L rapamycin treatment(24 h,0.203±0.021;48 h,0.163±0.022;72 h,0.144±0.013 vs.0 h,0.341±0.022,allP＜0.05 vs.0 h)in CVB 3 infected myocardial fibroblasts.(2)Smad 3/β-actin ratio of myocardiol fibroblasts was significantly increased in CVB 3 infected cardial fibroblasts and this increase could be significantly attenuated by rapamycin(control,0.63±0.06;CVB 3,1.18±0.03;CVB 3+Rapamycin,0.77±0.08 by RT-PCR and 0.89±0.07,2.27±0.13 and 0.131±0.013 by Western blot).Collagen type Ⅰ/β-actin ratio was also significantly increased by CVB 3 and this increase could be reversed by rapamycin(1.13±0.06,1.303±0.012,0.82±0.03 by RT-PCR).Conclusion Rapamyein can inhibit the Smad 3 and collagen type Ⅰ expressions in CVB 3 infected myocardial fibroblasts suggesting that the mTOR signal pathway may play an important role in the pathogenesis of CVB 3 induced myocardial fibrosis.