Ghrelin prevents doxorubicin-induced cardiotoxicity through TNF-alpha/NF-κB pathways and mitochondrial protective mechanisms

We had reported that increased levels of endogenous ghrelin during the progression of doxorubicin-induced cardiomyopathy and heart failure might provide a compensatory self-protective effect. We investigated which pathway(s) produced these protective effects in vitro. Primary cultured cardiomyocytes were induced with doxorubicin in the presence or absence of ghrelin or a tumor necrosis factor-alpha (TNF-alpha) antagonist (etanercept). Ghrelin up-regulated TNF-alpha in a time- and dose-dependent manner. It significantly reduced cell apoptosis and markers of oxidative stress, such as malondialdehyde (MDA) content and lactate dehydrogenase (LDH) activity; it also increased anti-oxidative enzyme activity such as superoxide dismutase (MnSOD) and catalase (CAT), retained mitochondrial membrane potential and energy metabolism compared with doxorubicin alone. Moreover, ghrelin increased mitochondrial anti-apoptosis related gene protein expression such as bcl-2 and MnSOD, reduced cytoplasmic cytochrome C (Cyt C) release and strengthened the activation of NF-κB. All these effects were abrogated by etanercept. This suggests ghrelin affects the TNF-alpha/NF-κB activation pathways, up-regulating TNF-alpha, to produce anti-oxidative and anti-apoptotic effects that protected cardiomyocytes from doxorubicin-induced cytotoxicity.