Angiotensin-(1–7) abolishes AGE-induced cellular hypertrophy and myofibroblast transformation via inhibition of ERK1/2

Abstract

Angiotensin-(1–7) (Ang-(1–7))/AT7-Mas receptor axis is an alternative pathway within the renin–angiotensin system (RAS) that generally opposes the actions of Ang II/AT1 receptor pathway. Advanced glycated end product (AGEs) including glucose- and methylglyoxal-modified albumin (MGA) may contribute to the development and progression of diabetic nephropathy in part through activation of the Ang II/AT1 receptor system; however, the influence of AGE on the Ang-(1–7) arm of the RAS within the kidney is unclear. The present study assessed the impact of AGE on the Ang-(1–7) axis in NRK-52E renal epithelial cells. MGA exposure for 48h significantly reduced the intracellular levels of Ang-(1–7) approximately 50%; however, Ang I or Ang II expression was not altered. The reduced cellular content of Ang-(1–7) was associated with increased metabolism of the peptide to the inactive metabolite Ang-(1–4) [MGA: 175±9 vs. Control: 115±11fmol/min/mg protein, p<0.05, n=3] but no change in the processing of Ang I to Ang-(1–7). Treatment with Ang-(1–7) reversed MGA-induced cellular hypertrophy and myofibroblast transition evidenced by reduced immunostaining and protein expression of α-smooth muscle actin (α-SMA) [0.4±0.1 vs. 1.0±0.1, respectively, n=3, p<0.05]. Ang-(1–7) abolished AGE-induced activation of the MAP kinase ERK1/2 to a similar extent as the TGF-β receptor kinase inhibitor SB58059; however, Ang-(1–7) did not attenuate the MGA-stimulated release of TGF-β. The AT7-Mas receptor antagonist D-Ala7-Ang-(1–7) abolished the inhibitory actions of Ang-(1–7). In contrast, AT1 receptor antagonist losartan did not attenuate the MGA-induced effects. We conclude that Ang-(1–7) may provide an additional therapeutic approach to the conventional RAS blockade regimen to attenuate AGE-dependent renal injury.