[Effects of mTOR inhibitor rapamycin on Smad 3 protein and collagen type I expression in rat myocardial fibroblasts infected with coxsackie virus B 3].
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 infected with coxsackievirus 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/beta-actin ratio was dose-dependently reduced (1 nmol/L, 0.381 +/- 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-dependently 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, all P < 0.05 vs.0 h) in CVB 3 infected myocardial fibroblasts. (2) Smad 3/beta-actin ratio of myocardial 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/beta-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).


CONCLUSIONS
Rapamycin 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.
Chen
Chun-yuan
CY
Department of Paediatric, Third Xiangya Hospital, Central South University, Changsha 410003, China.
Sun
Yue-Nü
YN
Yang
Zuo-cheng
ZC
Cai
Zi-li
ZL
D000818:Animals; D002478:Cells, Cultured; D024042:Collagen Type I / Q000378:metabolism*; D003384:Coxsackievirus Infections / Q000378:metabolism; D004770:Enterovirus; D005260:Female; D005347:Fibroblasts / Q000378:metabolism*; D008297:Male; D032386:Myoblasts, Cardiac / Q000378:metabolism* / Q000821:virology; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction; D020123:Sirolimus / Q000494:pharmacology*; D051900:Smad3 Protein / Q000378:metabolism*
D024042:Collagen Type I; D051900:Smad3 Protein; D020123:Sirolimus