Abstract
Advanced glycation end products (AGEs) and their receptor (RAGE) system are involved
in diabetic nephropathy. Angiotensin-converting enzyme 2 (ACE 2) plays a protective
role against cardiovascular and renal injury by stimulating the production of angiotensin-(1–7)
[Ang-(1–7)], an antagonist of angiotensin II (Ang II). However, effects of the AGEs-RAGE
axis on ACE 2 expression in mesangial cells remain unknown. We examined here the role
of ACE 2 in the AGEs-RAGE-induced mesangial cell damage and investigated whether olmesartan,
one of the Ang II type 1 receptor blockers (ARB), prevented the deleterious effects
of AGEs via restoration of ACE 2 and Ang-(1–7) level. AGEs significantly increased
superoxide generation, upregulated RAGE mRNA level, and decreased ACE 2 gene expression
and Ang-(1–7) production in mesangial cells, all of which were blocked by olmesartan,
but not by a different type of ARB, azilsartan. An antioxidant, N-acetylcysteine or RAGE-antibodies also restored the decrease in ACE 2 mRNA level
in AGEs-exposed mesangial cells. Moreover, olmesartan, but not azilsartan completely
inhibited the AGEs-induced increase in vascular cell adhesion molecule-1 (VCAM-1)
mRNA level in mesangial cells, which was abolished by the treatment with A-779, an
antagonist of Ang-(1–7) receptor, Mas receptor. Our present study suggests that olmesartan
could block the AGEs-induced VCAM-1 gene induction in mesangial cells by restoring
the downregulated ACE 2 levels and subsequently stimulating the Ang-(1–7)-Mas receptor
axis. Restoration of ACE 2 levels and blockade of renin-angiotensin system by olmesartan
might be a promising strategy for the treatment of diabetic nephropathy.
Key words
AGEs - ACE 2 - Ang-(1–7) - mas receptor