Angiotensin (1‐7) exerts antioxidant effects, inhibits mTOR signaling and protects against endoplasmic reticulum stress and apoptosis in HK2 cells

Abstract

Angiotensin (Ang) 1‐7, a bioactive heptapeptide of the renin‐angiotensin aldosterone system is known to exert antioxidant and nephroprotective effects. However, the cellular mechanisms involved in the beneficial effect of Ang 1‐7 is not entirely understood. Here, we studied the effect of Ang 1‐7 on H2O2‐mediated oxidative damage, endoplasmic reticulum (ER) stress and apoptosis in the human proximal tubular (HK2) cells and the specific mechanisms. HK2 cells were incubated with H2O2 (500 µM) and pre‐treated without and with Ang 1‐7 (100 nM). We measured reactive oxygen species (ROS) generation, ER stress, apoptosis and mTOR signaling in these cells. H2O2 treatment resulted in an increased oxidative stress in HK2 cells. Increased in the expression ER stress marker, binding immunoglobulin protein (BiP) and C/EBP homologous protein (CHOP), and cellular apoptosis was also observed after H2O2treatment. Moreover, H2O2 treatment resulted in the activation of mTOR complexes (mTORC1 and mTORC2) in these cells. Ang 1‐7 pre‐treatment to H2O2incubated cells significantly attenuated ROS generation, ER stress and apoptosis. These effects of Ang 1‐7 were blocked by co‐treatment with A779 (Mas receptor antagonist). Additionally, prior treatment of Ang 1‐7 inhibited the H2O2mediated mTOR activation. However, A779 treatment and transfection of HK2 cells with Mas receptor siRNA reversed the inhibitory effect of Ang 1‐7 on mTOR activities. In conclusion, our study suggests that Ang 1‐7 acting via Mas receptor could protect HK2 cells from H2O2‐induced oxidative damage through inhibition of oxidative stress, ER stress and ultimately cell apoptosis by suppressing mTOR activation.