Direct Evidence for Intrarenal Chymase-Dependent Angiotensin II Formation on the Diabetic Renal Microvasculature
Our previous work supports a major role for angiotensin-converting enzyme (ACE)-independent intrarenal angiotensin (ANG) II formation on microvascular function in type 2 diabetes mellitus. We tested the hypothesis that there is a switch from renal vascular ACE-dependent to chymase-dependent ANGII formation in diabetes mellitus. The in vitro juxtamedullary afferent arteriole (AA) contractile responses to the intrarenal conversion of the ACE-specific, chymase-resistant ANGI peptide ([Pro10]ANGI) to ANGII were significantly reduced in kidneys of diabetic (db/db) compared with control (db/m) mice. AA responses to the intrarenal conversion of the chymase-specific, ACE-resistant ANGI peptide ([Pro11, D-Ala12]ANGI) to ANGII were significantly enhanced in kidneys of diabetic compared with control mice. AA diameters were significantly reduced by 9±2, 15±3, and 24±3% of baseline in diabetic kidneys in response to 10, 100, and 1000 nmol/L [Pro11, D-Ala12]ANGI, respectively, and the responses were significantly attenuated by angiotensin type 1 receptor or chymase-specific (JNJ-18054478) inhibition. [Pro11, D-Ala12]ANGI did not produce a significant AA vasoconstriction in control kidneys. Chymase inhibition significantly attenuated ANGI-induced AA vasoconstriction in diabetic, but not control kidneys. Renal vascular mouse mast cell protease-4 or chymase/β-actin mRNA expression was significantly augmented by 5.1±1.4 fold; while ACE/β-actin mRNA expression was significantly attenuated by 0.42±0.08 fold in diabetic compared with control tissues. In summary, intrarenal formation of ANGII occurs primarily via ACE in the control, but via chymase in the diabetic vasculature. In conclusion, chymase-dependent mechanisms may contribute to the progression of diabetic kidney disease.
- afferent arteriole
- juxtamedullary nephron
- db/db mouse
- angiotensin-converting enzyme
- chymase inhibitor
- Received July 17, 2012.
- Revision received October 2, 2012.
- Accepted November 6, 2012.
- © 2012 American Heart Association, Inc.