Nicotinic Agonist Inhibits Cardiomyocyte Apoptosis in CVB3-Induced Myocarditis via α3β4-nAChRPI3KAkt-Dependent Survivin Upregulation

الملخص EN

Background.

Cardiomyocyte apoptosis is critical for the development of coxsackievirus B3- (CVB3-) induced myocarditis, which is a common cardiac disease that may result in heart failure or even sudden death.

Previous studies have associated CVB3-induced apoptosis with the downregulation of antiapoptotic proteins.

Here, attempts were made to examine whether nicotinic acetylcholine receptors (nAChRs), especially α3β4-nAChRs, were a novel therapeutic antiapoptotic target via the activation of survivin, a strong antiapoptotic protein, in viral myocarditis (VMC).

Methods and Results.

In the present study, we demonstrated that nAChRs, α3β4-nAChR subunits in particular, were present and upregulated in CVB3-infected neonatal rat cardiomyocytes (NRC) and H9c2 cells by RT-qPCR.

The function of α3β4-nAChRs was next examined using its specific blocker α-CTX AuIB in vitro.

The results of the TUNEL assay and western blot experiments showed that the block of α3β4-nAChRs abrogated nicotine-mediated protection of NRC from CVB3-induced apoptosis, and this effect displayed a substantial correlation with the protein expressions of pAkt, survivin, and Cleaved Caspase-3.

Hence, the involvement of the PI3K/Akt pathway was further verified by LY294002, a selective inhibitor of PI3K.

As a result, nicotine-mediated induction of pAkt and survivin was abolished by LY294002; meanwhile, apoptotic NRC were increased accompanied by an increase of Cleaved Caspase-3 expression.

Regarding CVB3-infected BALB/c mice, the α-CTX AuIB- and LY294002-treated groups had a lower survival rate, deteriorative ventricular systolic function, and more severe inflammation than the nicotine-treated group and the modulation of pAkt, survivin, and Cleaved Caspase-3 protein expressions was similar to that in CVB3-infected NRC.

In addition, we found that a nicotinic agonist reduced CVB3 replication in a dose-dependent manner in vitro, which indicates that nAChR activation may serve as a possible protection mechanism of CVB3-induced myocarditis.

Conclusions.

Our study demonstrated that α3β4-nAChR subunits are essential in the nicotine-mediated antiapoptotic effect of protecting cardiomyocytes from CVB3-induced apoptosis in vivo and in vitro.

This protection correlated with the PI3K/Akt pathway and the inducement of the antiapoptotic protein survivin.

A combination of these mechanisms serves as a novel protective response to treat viral myocarditis.