The Prostaglandin Agonist Beraprost Aggravates Doxorubicin-mediated Apoptosis by Increasing iNOS Expression in Cardiomyocytes

Wei-Shiung      Lian; Herng-Cheng      Chiou; Heng      Lin; Jin-Jer      Chen; Ching-Feng      Cheng

doi:10.2174/15701611113119990124

Abstract

Doxorubicin (DOX) is widely used as an anti-cancer agent although it causes irreversible cardiomyopathy by increasing oxidative stress and deregulating nitric oxide production. Beraprost (BPS), a stable prostacyclin (PGI₂) analog, is a potent vasodilator that has beneficial effects on myocardial ischemia. The objectives of the present study were to delineate the uncertain effects of prostcyclin therapy on DOX induced cardiomyopathy and to explore the mechanisms underlying PGI₂ and DOX interaction. For this reason, we stimulated endogenous PGI₂ production using bicistronic COX-1/PGIS gene transfer and BPS supplementation, and investigated the effects on DOX-induced cardiomyopathy. Caspase-dependent protein content, lactate dehydrogenase (LDH), DNA fragmentation, and TUNEL positive cells were elevated in DOX-treated cardiomyocytes. These indicators were further elevated by adenovirus-COX- 1/PGIS transfection or BPS supplementation. In addition, PGI₂ overexpression further increased iNOS expression and superoxide accumulation in cardiomyocytes compared with DOX alone, which may be the reason for aggravated cytotoxicity. Moreover, BPS can induce cAMP response elements (CRE) binding to the iNOS promoter and phospho- cAMP response element binding protein (CREB) expression in a cyclic AMP-dependent manner. Our in vivo studies show that MnTBAP and aminoguanidine treatment of DOX and BPS co-administered in mice can attenuate caspase-3 and PARP-1 protein expression, and improve mouse survival, as observed in the iNOS gene-deleted mice. In conclusion, we demonstrated that BPS or adv-COX-1/PGIS increases PGI₂ levels through iNOS expression and peroxynitrite production, via CREB protein phosphorylation; thereby aggravating DOX-mediated cardiotoxicity.

Keywords: Beraprost, doxorubicin, cardiomyocytes, cAMP response element binding protein (CREB), inducible nitric oxide synthase (iNOS), prostacyclin (PGI₂).

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