PI3K Signaling Pathway Mediates Apelin-13-induced H9c2 Rat Cardiomyocytes Hypertrophy

Aim:APJ is an orphan G protein-coupled receptor and its endogenous ligand is apelin. Our laboratory reported that, in the stroke-prone renovascular hypertensive rats, the expression of apelin increased, following cardiac hypertrophy, in myocardium of left ventricular hypertrophy SD rats, the expression of APJ also increased. These suggested that apelin may induce cardiac hypertrophy. The purpose of this work is to study G protein-coupled receptor and endogenous ligand apelin-APJ involved in H9c2 rat cardiomyocytes hypertrophy, and to explore the specific molecular mechanism how PI3K signal pathway mediates apelin-13-induced H9c2 rat cardiomyocytes hypertrophy.Methods:Use inverted microscope observing the morphology of H9c2 rat cardiomyocytes, use phase contrast microscope measuring the diameter of H9c2 rat cardiomyocytes, use Multisizer 3 measuring the volume of H9c2 rat cardiomyocytes and use BCA method measuring the protein content in H9c2 rat cardiomyocytes, use western blot measuring the expression of PI3K, p-PI3K, Akt, p-Akt, ERK1/2, p-ERK1/2, p70S6K, p-p70S6K and caveolin-1 in H9c2 rat cardiomyocytes.Results:The measurement results by Phase contrast microscope, Multisizer 3 and BCA method show that, compared with control group, apelin-13(2μM, treated for 96h) can significantly increase the diameter, the volume and the protein content of H9c2 rat cardiomyocytes. Pre-incubation separately specific PI3K inhibitor LY294002(25μM), specific Akt inhibitor 1701-1(10μM), specific ERK inhibitor PD98059(10μM), can significantly inhibit apelin-13-induced the diameter, the volume and the protein content increase in H9c2 rat cardiomyocytes. The measurement results by western blot show that, compared with control group, apelin-13(2μM, treated for 4h) can significantly increase the expression of PI3K, p-PI3K, p-Akt, p-ERK1/2 and p-p70S6K, and significantly decrease the expression of caveolin-1; Compared with apelin-13 group, pre-incubation specific PI3K inhibitor LY294002(25μM), the expression of p-PI3K, p-Akt, p-ERK1/2 and p-p70S6K decreased; Pre-incubation specific Akt inhibitor 1701-1(10μM), the expression of p-Akt, p-ERK1/2 and p-p70S6K decreased; Pre-incubation specific ERK inhibitor PD98059(10μM), the expression of p-ERK1/2 and p-p70S6K decreased; the expression of PI3K, Akt, p70S6K, ERK1/2 and caveolin-1 were not changed.Conclusion:Apelin-13 induces H9c2 rat cardiomyocytes hypertrophy mediated by PI3K-Akt-ERK1/2-p70S6K signaling pathway.