Involvement of the calcium-sensing receptor in cyclosporin A-induced cardiomyocyte apoptosis in rats

In this study, we sought to determine whether the calcium-sensing receptor (CaSR) is involved in Cyclosporin A (CsA)-induced cardiomyocyte apoptosis and identify its signal transduction pathway. Forty Wistar rats were randomly divided into four groups: the control group, the CsA group (CsA 15 mg/kg/day intraperitoneally, i.p.), the GdCl(3) group (GdCl(3) 10 mg/kg, every other day, i.p.), and the CsA + GdCl(3) group (CsA 15 mg/kg/day, i.p. and GdCl(3) 10 mg/kg, every other day, i.p.). The groups were treated for two weeks. Cardionnyocyte apoptosis and injury were observed by light microscopy, electron microscopy and TUNEL staining. CaSR mRNA expression was determined by RT-PCR, and CaSR protein expression was detected by western blot and immunohistochemistry. The protein expression levels of cytochrome c, cleaved caspase-9, cleaved caspase-3, Bax, and Bcl-2 were detected by western blot and immunohistochemistry. CsA increased the expression of CaSR mRNA and protein and enhanced cardiomyocyte apoptosis. GdCl(3), a specific activator of CaSR, further enhanced CaSR expression and cardiomyocyte apoptosis and led to the upregulation of cytochrome c, cleaved caspase-9, cleaved caspase-3, and Bax, as well as the down-regulation of Bcl-2. The present in vivo study provides further information on CsA-induced cardiomyocyte apoptosis. We determined for the first time that CaSR is involved in CsA-induced cardiomyocyte apoptosis in the rat through the activation of downstream cytochrome c-caspase-3 pathways. Furthermore, we offer evidence that the Bcl-2 family is involved in this process. These findings could provide novel strategies for the prevention and cure of CsA-induced cardiotoxicity.