Erythropoietin attenuates hypertrophy of neonatal rat cardiac myocytes induced by angiotensin-II in vitro.

Objective: Erythropoietin (EPO) is a haematopoietic hormone that has been confirmed as a novel cardioprotective agent. In this study, we test the hypothesis that EPO inhibits angiotensin-II (Ang-II)-induced hypertrophy in cultured neonatal rat cardiomyocytes.

Material And Methods: Cultured neonatal rat cardiomyocytes were used to evaluate the effects of EPO on Ang-II-induced hypertrophy in vitro. The surface area and mRNA expression of atrial natriuretic (ANF) myocytes were employed to detect cardiac hypertrophy. A phosphatidylinositol 3'-kinase (PI3K) inhibitor LY294002 and an endothelial nitric oxide synthase (eNOS) inhibitor L-NAME were also employed to detect the underlying mechanism of EPO. Intracellular signal molecules, such as Akt (PKB), phosphorylated Akt, eNOS and transforming growth factor-beta1 (TGF-beta1) protein expression were determined by Western blot. Nitric oxide (NO) levels in the supernatant of cultured cardiomyocytes were assayed using an NO assay kit.

Results: The results indicate that EPO significantly attenuates Ang-II-induced hypertrophy shown as inhibition of increases in cell surface area and ANF mRNA levels. NO production was also increased proportionally in the EPO-treated group. EPO enhanced Akt activation and eNOS protein expression, whereas LY294002 or L-NAME partially abolished the anti-hypertrophic effect of EPO, accompanied by a decrease in Akt activation, eNOS protein expression and/or a reduction of NO production. EPO also down-regulated the protein expression of TGF-beta1.

Conclusion: We conclude that EPO attenuates cardiac hypertrophy via activation of the PI3K-Akt-eNOS-NO pathway and the down-regulation of TGF-beta1.