Angiotensin II Promotes Anti-Apoptosis Via Akt-Kinase Phosphorylation, an Effect Ameliorated by High Dose Aspirin
The balance between cell proliferation and apoptosis is essential for physiological function. We tested the hypothesis that angiotensin II (ANG II) has anti-apoptotic effects via the activation of AKT kinase in rats overexpressing the human renin and angiotensinogen genes (dTGR). dTGR are hypertensive (182±8 mm Hg) with severe renal damage (150-fold increased albuminuria), perivascular and interstitial fibrosis and vasculopathy, and die at 7 weeks. Renal NF-κB DNA binding activity is increased. We studied the time course of the pathogenesis from week 5 to week 7. Blood pressure, albuminuria, fibrosis, vasculopathy and monocyte infiltration increased over time. In contrast, KI-67 proliferating cells were more abundant in week 5 compared to week 7 as well as compared to non-transgenic rats. Phosphorylation of AKT kinase increased with the severity of the disease. Immunostaining of p-AKT and the activated NF-κB subunit p65 were observed in the glomeruli and endothelium. While Bcl-2 and phosphorylated Bad was predominantly expressed in the endothelium in week 7, the strongest bax immunostaining in the vessel wall media was observed in week 5. We then investigated the effect of chronic high dose aspirin (ASA; 600 mg/kg/d) on remodeling. While ASA did not change blood pressure, albuminuria and fibrosis were similar to non-transgenic controls. ASA completely normalized AKT protein synthesis as well as AKT phosphorylation and NF-κB DNA binding activity. Bax immunostaining at week 7 increased in the media, while Bcl-2 decreased. Western blot in dTGR kidney homogenates showed increased Bcl-2 levels compared ASA-treated and non-transgenic rats. We then confirmed the effect of ASA on p-AKT stimulating endothelial cells in vitro with ANG II (10-7 M; 10 min). Western blot showed reduced p-AKT in ASA pretreated cells. These results show that ANG II is anti-apoptotic by activating AKT kinase. ASA is able to restore the impaired balance of tissue remodeling. Finally, in addition to inhibiting I-κB kinase, ASA may exert a part of its ameliorating effects in this model by inhibiting AKT phosphorylation.