Erythropoietin inhibits angiotensin II induced cardiomyocyte hypertrophy in vitro via activating PI3K/Akt-eNOS pathway / 中华心血管病杂志

<p><b>OBJECTIVE</b>To explore the effect of erythropoietin (EPO) on angiotensin II (AngII) induced neonatal rat cardiomyocyte hypertrophy and the association with PI3K/Akt-eNOS signaling pathway.</p><p><b>METHODS</b>Cardiomyocytes were isolated from new-born Sprague-Dawley rats and stimulated by AngII in vitro. The cell surface area and mRNA expression of atrial natriuretic factor (ANF) of cardiomyocytes were determined in the presence and absence of various concentrations of EPO, phosphatidylinositol 3'-kinase (PI3K) inhibitor LY294002 and nitric oxide synthase (NOS) inhibitor L-NAME. Intracellular signal molecules, such as Akt, phosphorylated Akt, eNOS and phosphorylated eNOS protein expressions were detected by western blot. Nitric oxide (NO) level in the supernatant of cultured cardiomyocytes was assayed by NO assay kit.</p><p><b>RESULTS</b>EPO (20 U/ml) significantly inhibited AngII induced cardiomyocyte hypertrophy as shown by decreased cell surface area and ANF mRNA expression (all P < 0.05). EPO also activated Akt and enhanced the expression of eNOS and its phosphorylation (all P < 0.05), increased the NO production (P < 0.01). These effects could be partially abolished by cotreatment with LY294002 or L-NAME (all P < 0.05).</p><p><b>CONCLUSION</b>EPO attenuates AngII induced cardiomyocytes hypertrophy via activating PI3K-Akt-eNOS pathway and promoting NO production.</p>

Erythropoietin suppresses the expressions of TGF-beta1 and collagen in rat cardiac fibroblasts induced by angiotensin II / 中华心血管病杂志

<p><b>OBJECTIVE</b>Recent studies have shown cardiac protection effects of erythropoietin (EPO). The present experiment was designed to investigate the effects of EPO on TGF-beta1, nitric oxide synthase (NOS), collagen contents induced by angiotensin II (Ang II) in rat cardiac fibroblasts (CFs) and explore the roles of PI3-K/Akt signaling pathway on related effects.</p><p><b>METHODS</b>Neonatal rat CFs was isolated by collagenase and trypsinase digestion methods. PBS, EPO, Ang II in the absence or presence of LY294002, an inhibitor of PI3-K, or L-NAME, an inhibitor of NOS, were added to CFs and cultured for 24 hours. The concentration of collagen I and collagen III in culture medium were quantitated by ELISA. The levels of nitric oxide (NO) and the activities of NOS as well as NOS isoforms were measured by chemical enzymic method. Western blot was applied to detecting the protein expressions of Akt, p-Akt, eNOS, iNOS, and TGF-beta1.</p><p><b>RESULTS</b>The concentrations of collagen I and collagen III in CFs culture medium were significantly increased while the level of NO was significantly decreased by Ang II and these changes were significantly suppressed by EPO in a dose dependent manner. The effects of EPO on eNOS and NO could be blocked by LY294002. L-NAME could block EPO's effect on NO but not on the eNOS expression. The suppression effects on expressions of TGF-beta1 and collagen by Ang II in CFs were blocked by both LY294002 and L-NAME.</p><p><b>CONCLUSION</b>EPO suppresses the upregulated expressions of TGF-beta1 and increased production of collagen induced by Ang II through activating the PI3-K/Akt signaling pathway in neonatal rat CFs.</p>