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.


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.


CONCLUSIONS
We conclude that EPO attenuates cardiac hypertrophy via activation of the PI3K-Akt-eNOS-NO pathway and the down-regulation of TGF-beta1.
Department of Cardiology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.
Yuan
Y
Wen
Xin-Jin
XJ
Zhang
Ye-Xin
YX
Ma
Xue-Jing
XJ
Xu
Li-Feng
LF
Hong
Zhen-Hua
ZH
Lu
D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D000831:Animals, Newborn; D009320:Atrial Natriuretic Factor / Q000235:genetics; D001483:Base Sequence; D015153:Blotting, Western; D006332:Cardiomegaly / Q000139:chemically induced*; D002478:Cells, Cultured; D017931:DNA Primers; D004921:Erythropoietin / Q000494:pharmacology*; D006321:Heart / Q000187:drug effects*; D066298:In Vitro Techniques; D009206:Myocardium / Q000166:cytology / Q000201:enzymology / Q000473:pathology*; D009569:Nitric Oxide / Q000096:biosynthesis; D052250:Nitric Oxide Synthase Type III / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D016133:Polymerase Chain Reaction; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D012333:RNA, Messenger; D051381:Rats
D017931:DNA Primers; D012333:RNA, Messenger; D004921:Erythropoietin; D000804:Angiotensin II; D009569:Nitric Oxide; D009320:Atrial Natriuretic Factor; D052250:Nitric Oxide Synthase Type III; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt