Angiotensin-(1-7) decreases glycated albumin-induced endothelial interleukin-6 expression via modulation of miR-146a.

The presence of glycated albumin (GA) is associated with increased diabetic complications. This study investigated the effect of angiotensin-(1-7) on the expression of GA-induced endothelial interleukin-6 (IL-6) in human aortic endothelial cells (HAECs). We also evaluated whether miR-146a is involved in the post-transcriptional regulation of angiotensin-(1-7). HAECs were stimulated with GA with or without angiotensin-(1-7) pretreatment. Inflammatory cytokine screening approach identified that angiotensin-(1-7) (10(-7) M) potently inhibited GA (200 μg/mL)-stimulated endothelial IL-6 expression in conditioned medium. ELISA confirmed this finding. Real-time PCR showed that angiotensin-(1-7) decreased GA-induced intracellular IL-6 mRNA expression and western blotting showed that angiotensin-(1-7) decreased GA-induced intracellular IL-6 protein expression. Bioinformatics' miR target analysis identified homology between miR-146a and the 3'-UTR of the human IL-6 mRNA, suggesting a potential regulation of IL-6 by miR-146a. Treatment with GA decreased endothelial miR-146a expression to 37.2% of the albumin control, while angiotensin-(1-7) increased endothelial miR-146a expression to 1.9-times that of the medium control. Pretreatment with angiotensin-(1-7) inhibited the GA-mediated downregulation of miR-146a to 78.9% of the albumin control levels. Furthermore, the inhibitory effect of angiotensin-(1-7) on IL-6 expression was abolished in GA-treated, miR-146a inhibitor-transfected HAECs. In conclusion, these results suggest that angiotensin-(1-7) exerted an endothelial protective effect through IL-6 downregulation, and miR-146a modulation is involved in this protective effect.