mln-4760 and Albuminuria

Angiotensin-converting enzyme 2 (ACE2) is expressed at high levels in the kidney and converts angiotensin II (ANG II) to ANG-(1-7). We studied the effects of ACE2 inhibition and ANG-(1-7) in the (5/6) nephrectomy ((5/6) Nx) mouse model of chronic kidney disease (CKD). Male FVB mice underwent sham surgery (Sham) or (5/6) Nx and were administered either vehicle, the ACE2 inhibitor MLN-4760 (MLN), the AT(1) receptor antagonist losartan, MLN plus losartan, or ANG-(1-7) for 4 wk. In (5/6) Nx mice with or without MLN, kidney cortical ACE2 protein expression was significantly decreased at 4 wk, compared with Sham. Inhibition of ACE2 caused a decrease in renal cortical ACE2 activity. Kidney cortical ACE expression and activity did not differ between groups of mice. In (5/6) Nx mice treated with MLN, kidney levels of ANG II were significantly increased, compared with Sham. (5/6) Nx induced a mild but insignificant increase in blood pressure (BP), a 50% reduction in FITC-inulin clearance, and a significant increase in urinary albumin excretion. ACE2 inhibition in (5/6) Nx mice did not affect BP or FITC-inulin clearance but significantly increased albuminuria compared with (5/6) Nx alone, an effect reversed by losartan. Treatment of (5/6) Nx mice with ANG-(1-7) increased kidney and plasma levels of ANG-(1-7) but did not alter BP, FITC-inulin clearance, or urinary albumin excretion, and it increased relative mesangial area. These data indicate that kidney ACE2 is downregulated in the early period after (5/6) Nx. Inhibition of ACE2 in (5/6) Nx mice increases albuminuria via an AT(1) receptor-dependent mechanism, independent of BP. In contrast, ANG-(1-7) does not affect albuminuria after (5/6) Nx. We propose that endogenous ACE2 is renoprotective in CKD.

Topics: Albuminuria; Angiotensin I; Angiotensin II; Angiotensin II Type 1 Receptor Blockers; Angiotensin-Converting Enzyme 2; Angiotensin-Converting Enzyme Inhibitors; Animals; Blood Pressure; Body Weight; Chronic Disease; Disease Models, Animal; Glomerular Filtration Rate; Hematocrit; Imidazoles; Infusion Pumps; Injections, Subcutaneous; Inulin; Kidney; Kidney Diseases; Leucine; Losartan; Male; Mice; Nephrectomy; Organ Size; Peptide Fragments; Peptidyl-Dipeptidase A; Proto-Oncogene Mas; Proto-Oncogene Proteins; Receptor, Angiotensin, Type 1; Receptors, G-Protein-Coupled; Time Factors