Angiotensin 1-7 Exerts Antioxidant Effects, Suppresses Mammalian Target of Rapamycin (mTOR) Signaling, and Inhibits Apoptosis in Renal Proximal Tubular Cells

Oxidative stress is one of the crucial pathogenic factors involved in the progression of renal injury. Angiotensin (ANG) 1-7, a bioactive heptapeptide of the renin-angiotensin-aldosterone system is known to exert antioxidant and nephroprotective effects. However, the cellular mechanism involved in the beneficial effect of ANG 1-7 is not clear. Here, we assessed ANG 1-7's effect on H₂O₂-mediated oxidative damage in the human proximal tubular (HK2) cells and the underlying mechanisms. HK2 cells were incubated with H₂O₂ (500µM, 4h) pre-treated with and without ANG 1-7 (100nM, 24h), and Reactive Oxygen Species (ROS) generation, mitochondrial dysfunction, endoplasmic reticulum (ER) stress, Apoptosis and mammalian target of rapamycin (mTOR) signaling were determined. H₂O₂ induced an increase in oxidative and ER stress together with loss of mitochondrial membrane potential, decreased ATP levels, and induced Apoptosis in HK2 cells. Moreover, H₂O₂ treatment resulted in the activation of mTOR complexes (mTORC1 and mTORC2) in these cells. ANG 1-7 significantly attenuated H₂O₂-induced ROS generation, ER stress and Apoptosis, and also improved mitochondrial function. Additionally, pre-treatment of ANG 1-7 inhibited the H₂O₂-mediated mTOR activation. These effects of ANG 1-7 were blocked by co-treatment with the Mas receptor (MasR) inhibitor, A779. Furthermore, transfection of HK2 cells with Mas receptor siRNA also abolished the inhibitory effect of ANG 1-7 on mTOR activities. In conclusion, ANG 1-7 via MasR mitigates oxidative stress, suppresses mTOR signaling, and protects HK2 cells from ER stress, mitochondrial dysfunction, and Apoptosis, suggesting ANG 1-7-MasR renoprotective effects.

Angiotensin 1-7; Apoptosis; HK2 cells; Oxidative stress; mTOR.