Doxorubicin is a highly effective antineoplastic drug, but its clinical use is limited by its adverse side effects on the heart. We investigated possible protective effects of erythropoietin against doxorubicin-induced cardiomyopathy.Cardiomyopathy was induced in mice by a single intraperitoneal injection of doxorubicin (15 mg/kg). In some cases, human recombinant erythropoietin (5000 U/kg) was started simultaneously. Two weeks later, left ventricular dilatation and dysfunction were apparent in mice given doxorubicin but were significantly attenuated by erythropoietin treatment. Erythropoietin also protected hearts against doxorubicin-induced cardiomyocyte atrophy and degeneration, myocardial fibrosis, inflammatory cell infiltration, and downregulation of expression of GATA-4 and 3 sarcomeric proteins, myosin heavy chain, troponin I, and desmin. Cyclooxygenase-2 expression was upregulated in doxorubicin-treated hearts, and that, too, was attenuated by erythropoietin. No doxorubicin-induced apoptotic effects were seen, nor were any changes seen in the expression of tumor necrosis factor-alpha or transforming growth factor-beta1. Antiatrophic and GATA-4 restoring effects of erythropoietin were demonstrated in the in vitro experiments with cultured cardiomyocytes exposed to doxorubicin, which indicated the direct cardioprotective effects of erythropoietin beyond erythropoiesis. Cardiac erythropoietin receptor expression was downregulated in doxorubicin-induced cardiomyopathy but was restored by erythropoietin. Among the downstream mediators of erythropoietin receptor signaling, activation of extracellular signal-regulated kinase was reduced by doxorubicin but restored by erythropoietin. By contrast, erythropoietin was ineffective when administered after cardiac dysfunction was established in the chronic stage.The present study indicates a protective effect of erythropoietin against doxorubicin-induced cardiomyopathy.
Backgrounds: Cardiac hypertrophy is an adaptive response of the injured heart, but usually results in heart failure and sudden death. Tachycardia is accompanied with various cardiovascular diseases and is a cause of sudden death. Although many studies of cardiac gene therapy were previously reported, none of them directly targeted cardiac hypertrophy nor tachycardia, and therapeutic genes used in them mainly targeted to enhance the angiogenesis rather than to directly modulate pathologic conditions of cardiomyocytes. On the other hand, a definitive biological function of CD9, a member of transmembrane 4 superfamily, remains elusive although its multifunctional characteristics have been reported; knockout mouse studies by us and others solely revealed the crucial role of CD9 in gamete membrane fusion (Science 287, 321-324; 2000). Here we present a novel biological function of CD9, by which we develop an innovative cardiac gene therapy.
