Increased Angiotensin II–Induced Hypertension and Inflammatory Cytokines in Mice Lacking Angiotensin-Converting Enzyme N Domain Activity

Abstract

Angiotensin converting enzyme (ACE) is composed of the N- and C-terminal catalytic domains. To study the role of the ACE domains in the inflammatory response, N-KO and C-KO mice, models lacking one of the two ACE domains, were analyzed during angiotensin II-induced hypertension. At 2 weeks, N-KO mice have systolic blood pressures that averaged 173 ± 4.6 mm Hg, which is more than 25 mm Hg higher than the blood pressures observed in wild-type or C-KO mice (146 ± 3.2 and 147 ± 4.2 mm Hg). After 3 weeks, blood pressure differences between N-KO, C-KO and WT were even more pronounced. Macrophages from N-KO mice have increased expression of tumor necrosis factor α after stimulation with either lipopolysaccharide (about 4-fold) or angiotensin II (about 2-fold), as compared to C-KO or wild-type mice. Inhibition of the enzyme prolyl oligopeptidase, responsible for the formation of acetyl SDKP and other peptides, eliminated the blood pressure difference and the difference in tumor necrosis factor α expression between angiotensin II treated N-KO and wild-type mice. However, this appears independent of acetyl SDKP. These data establish significant differences in the inflammatory response as a function of ACE N- or C-domain catalytic activity. They also indicate a novel role of prolyl oligopeptidase in the cytokine regulation and in the blood pressure response to experimental hypertension.

Enhanced Angiotensin Receptor-Associated Protein in Renal Tubule Suppresses Angiotensin-Dependent Hypertension

“…In this study, chronic Ang II infusion was performed at 1000 and 2000 ng/kg per min to examine the effects of distal tubule–dominant overexpression of ATRAP on the Ang II–mediated BP increase. Although the higher dose of Ang II (2000 ng/kg per min) is reported to provoke a reduction in food intake and to cause Ang II–induced wasting and skeletal muscle atrophy, 17 the lower dose of Ang II (1000 ng//kg per min) has been used in many previously performed experiments in mice, 18,19 and suppression of the Ang II–induced BP increase by the distal tubule–dominant overexpression of ATRAP was observed with both the lower and higher doses of Ang II in the present study.…”

Rediscovering ACE: novel insights into the many roles of the angiotensin-converting enzyme

“…These data come from an analysis of the NKO mice discussed above [82, 85]. Figure 2 shows data from an experiment in which thioglycollate-elicited peritoneal macrophages were collected and exposed in vitro to lipopolysaccharide (LPS) for 18 hours.…”

“…Further, increased TNFα production was found in peritoneal macrophages from N-KO mice made hypertensive by angiotensin II infusion. In vitro, N-KO macrophages over produce the pro-inflammatory cytokine IL-12 in response to LPS but produce less of the anti-inflammatory cytokine IL-10 [85]. While these findings clearly show an effect of the ACE N-domain on cytokine production, what is not clear is whether this is a direct effect on the biochemistry of cytokine production, or whether the biochemical milieu within the ACE N-KO mice somehow instructs macrophages along a developmental program leading to changes in differentiation state and an intrinsically higher inflammatory response to pro-inflammatory stimuli.…”

Angiotensin-converting enzyme and the tumor microenvironment: mechanisms beyond angiogenesis

“…A study of angiotensin II-induced hypertension in the NH 2 -terminus inactivated mice (called N-KO) showed augmented hypertension compared with WT (107). Interestingly, ex vivo studies showed that macrophages from the N-KO had augmented pro-inflammatory cytokine profile, suggesting that accumulated Ac-SDKP may impact macrophage polarization toward the M1 phenotype (107). By contrast, several other models of inflammation, including experimental autoimmune myocarditis, found reduced pro-inflammatory cytokine markers in the presence of Ac-SDKP (100).…”

“…Whether this tetrapeptide confounds the generally beneficial impact of ACE on tumor immunology remains an interesting area of investigation. The availability of the N-KO mouse model (50,107) should not only provide answers to these important questions but also enable evaluation of the role Ac-SDKP on immune cells without the potential complicated effects of other ACE susbtrates and peptides that accumulate in the setting of routine ACE inhibitors, which block both termini of the ACE protein.…”