OBJECTIVE: To observe the effeet of rapamycin, an inhibitor of mammalian target of rapamycin (mTOR), on mTOR and eukaryotic initiation factor-4E(eIF-4E)expression in coxsac-kievirus B3 (CVB3)-induced rat myocardial cells and to investigate the role of mTOR/eIF-4E signal pathway in viral myocarditis. METHODS: To construct a cell model of viral myocarditis with primary cultured myocardial cells. Myocardial cells infected by CVB3 were treated with 10 nmol/L rapamycin according to the cell toxicity test. The mTOR and eIF-4E expressions of cells were determined by RT-PCR and Western Blot. RESULTS: Rapamycin inhibited the degeneration of CVB3-induced myocardial cells. Expressions of mTOR and eIF-4E mRNA or protein in CVB3-induced myocardial cells were significantly upregulated compared with the control group (P < 0.05), and rapamycin (10 nmol/L) inhibited the upregulation (P < 0.05). CONCLUSION Rapamycin can downregulate the expressions of mTOR and eIF-4E in CVB3-induced myocardial cells, suggesting that mTOR/eIF-4E signal transduction may play an important role in viral myocarditis.
Animals ; Animals, Newborn ; Coxsackievirus Infections ; Enterovirus B, Human ; Eukaryotic Initiation Factor-4E ; biosynthesis ; Myocarditis ; metabolism ; virology ; Myocytes, Cardiac ; metabolism ; Protein Kinases ; biosynthesis ; Rats ; Rats, Sprague-Dawley ; Signal Transduction ; Sirolimus ; pharmacology ; TOR Serine-Threonine Kinases

OBJECTIVEThis study examined the effect of rapamycin, an inhibitor of mammalian target of rapamycin (mTOR), on eukaryotic initiation factor (eIF- 4E) expression in rat myocardial fibroblasts infected by Coxsackievirus B3 (CVB3) in order to identify the drug target for treatment of viral myocarditis.

METHODSPrimary cultured rat myocardial fibroblasts were treated with CVB3 with multiplicity of infection (MOI=0.5 PFU/cell). The experiment consisted of four groups in which the cultured rat fibroblasts cells were treated with CVB3, rapamycin (10 nM) and CVB3 + rapamycin or placebo (control). Experimental model of CVB3-infected myocardial fibroblasts was confirmed by detection of CVB3 mRNA expression with RT-PCR and observation of morphological changes of the infected cells with microscopy. eIF-4E expression was determined by both RT-PCR and Western Blot methods.

RESULTSMorphological changes were found in the fibroblasts treated with MOI 0.5 PFU/cell of CVB3 by transmission electron microscope and the viral particles were found in the cytoplasm. CVB3 mRNA was expressed in CVB3-infected fibroblasts after 1, 2, and 3 days after infection and 2 days after passage. The gray scale values of the eIF- 4E /beta -actin in the control, the CVB3, the rapamycin and the CVB3+rapamycin groups were 0.73 +/- 0.07, 0.87 +/- 0.03, 0.32 +/- 0.03 and 0.56 +/- 0.04 respectively detected by RT-PCR, and were 0.79 +/- 0.09, 1.35 +/- 0.12, 0.55 +/- 0.04, and 0.62 +/- 0.07 respectively detected by Western blot. EIF- 4E expression in the CVB3 group was higher than that in the control group. Both the rapamycin and the CVB3+rapamycin groups had lower eIF- 4E expression than the control and the CVB3 groups.

CONCLUSIONSCVB3 can infect myocardial fibroblasts and up-regulate the eIF- 4E expression in rat myocardial fibroblasts. Rapamycin can inhibit eIF- 4E expression and may be a potential medicine for treatment of viral myocarditis. It was suspected that mTOR/eIF- 4E signal pathway in rat myocardial fibroblasts might play an important role in the pathogenesis of viral myocarditis.

Animals ; Cells, Cultured ; Enterovirus B, Human ; Enterovirus Infections ; drug therapy ; metabolism ; Eukaryotic Initiation Factor-4E ; genetics ; Fibroblasts ; metabolism ; virology ; Gene Expression Regulation ; drug effects ; Myocarditis ; drug therapy ; etiology ; metabolism ; Myocardium ; metabolism ; Rats ; Sirolimus ; pharmacology ; therapeutic use