PROLYL‐OLIGOPEPTIDASE INHIBITION AMELIORATES EXPERIMENTAL HYPERTENSION AND DECREASES INFLAMMATORY CYTOKINES IN MICE LACKING ANGIOTENSIN CONVERTING ENZYME N DOMAIN ACTIVITY

Abstract

Using gene targeting, ACE domain‐specific knockout mouse lines N‐KO & C‐KO were created. After 14 day Ang II infusion, BP was 27 mm Hg (p<0.0001) higher in N‐KO vs. WT/C‐KO. N‐KO kidney Ang II levels were 1.5‐fold those of WT/C‐KO (p<0.015). Peritoneal macrophage cytokine expression in response to Ang II, measured as percentage of F4/80+/TNFαhigh cells vs total F4/80+, was 40.3% ± 4.7% for N‐KO and 19.8% ± 2.8% for WT (p<0.005). In response to LPS, N‐KO macrophages made 4‐fold the TNFα as C‐KO/WT cells (p<0.001). AcSDKP, a substrate specifically cleaved by the N‐domain, is made by the enzyme prolyl‐oligopeptidase (POP). Daily injections of the POP inhibitor S‐17092 were given to N‐KO and WT mice. This reduced the LPS‐mediated N‐KO macrophage production of TNFα to that of cells from WT. The hypertensive response to Ang II was also tested in N‐KO and WT mice treated with daily S‐17092. POP inhibition had no effect on the BP of WT, but reduced the BP of N‐KO to that of WT (p<0.01). Furthermore, FACS analysis of peritoneal macrophages showed a decreased percentage of F4/80+/TNFαhigh cells in N‐KO mice treated with daily S‐17092. The lack of N domain activity in ACE exhibited a pro‐inflammatory role in experimental hypertension via cytokine regulation, accumulation of renal Ang II, and increased BP response. Inhibition of POP eliminated the differences in macrophage TNFα expression and blood pressure response between N‐KO and WT mice.