Class III PI3‐Kinase in Angiotensin II‐Induced Cardiac Hypertrophy

Abstract

Pathological cardiac hypertrophy could lead to heart failure and sudden cardiac death. Our previous study demonstrated that Class I PI3‐kinase (PI3KC1) contributes to the development of cardiac hypertrophy by elevating intracellular reactive oxygen species (ROS) levels. In the current study, we evaluated the role of Class III PI3‐kinase (PI3KC3) in Ang II‐induced cardiac hypertrophy. Treatment of cultured cardiomyocytes with Ang II (10−6 M) significantly increased the cellular surface area, which was measured under a fluorescence microscope after staining with anti‐alpha‐sarcomeric actin antibodies. In cardiomyocytes, Ang II (10−9‐10−5 M) induced a dose‐dependent activation of PI3KC3, detected using an ELISA kit. More interestingly, Ang II‐induced cardiac hypertrophy was dramatically exacerbated by co‐treatment with 3‐Methyladenine (3‐MA, 10−6 M), a PI3KC3 inhibitor, suggesting that activation of PI3KC3 may play a protective role in Ang II‐induced cardiac hypertrophy. To identify the intracellular signaling pathway involved in the PI3KC3‐mediated protective effect, mitochondrial ROS was measured using MitoSOX in cardiomyocytes treated with control, Ang II (10−6 M), Ang II plus 3‐MA (10−6 M), and 3‐MA alone. The results demonstrated that Ang II treatment significantly increased mitochondrial ROS production and that Ang II‐induced increases in ROS generation were potentiated by co‐treatment with 3‐MA. It is well known that the major intracellular source of ROS is the damaged mitochondria, which is scavenged by autophagy (also called mitophagy) in cardiomyocytes. Thus, we measured autophagy activity by detection of autophagosomes using staining method with MAP‐LC3 antibodies in cardiomyocytes treated with Ang II. Treatment of cardiomyocytes with Ang II (10−9 to 10−5 M) significantly increased autophagy activity with two phases (increased activity at low doses, decreased activity at high doses, peaked at 10−7 M). More interestingly, Ang II (10−6 M)‐induced increases in autophagy were dramatically attenuated by 3‐MA (10−6 M). Taken together, these data suggest that activation of PI3KCIII has a protective effect on Ang II‐induced hypertrophy by enhancing autophagy activity and decreasing mitochondrial ROS generation in cardiomyocytes.Support or Funding InformationNIH HL143519