COMPOUND 21 IMPROVES VASCULAR FUNTION IN THE THORACIC AORTA FROM OBESE MICE: IMPLICATION OF AT2, MAS AND B2 RECEPTORS

Abstract

Objective: The angiotensin AT2 Receptor (AT2R) is known to form heterodimers with either the Mas (MasR) or the bradykinin B2 receptor (B2R). Compound 21 (C21), a highly selective AT2R agonist, induces vascular relaxation through stimulation of nitric oxide (NO). Since AT2R is overexpressed in obese models, we hypothesize that C21 might prevent the development of vascular alterations associated with obesity. The aim of this study was to assess the effect of C21 on endothelial function in a model of diet-induced obesity and the potential crosstalk between AT2R, MasR and/or B2R in this response. Design and method: Eleven-week-old male C57BL6J mice (n = 20/group) were fed a standard (Chow) or a very high-fat diet (HF) for 6 weeks. Half of mice per group were simultaneously treated with C21 (1 mg/kg/day in drinking water, Chow-C21, HF-C21). Vascular reactivity experiments were performed in rings from thoracic aorta. NO production was determined in human endothelial cells (EA.hy926) using DAF-2DA (10-5 M). Results: Thoracic aortas from HF mice exhibited impaired relaxations to acetylcholine (Ach) compared to the Chow group. This alteration was prevented by treatment with C21 [Ach, ChowEmax = 85,6 ± 1,7%; HFEmax = 63,8 ± 3,0% vs HF-C21Emax = 86,0 ± 1,8%, P < 0.001]. In addition, NO availability calculated from the area under the Ach curve in presence and absence of L-NAME (NO synthase inhibitor) was significantly lower in HF mice and increased by C21 treatment [Chow = 237 arbitrary units (AU), HF = 168 AU vs HF-C21 = 239 AU; P < 0.001]. Aortic rings from HF mice exhibited stronger contractions to angiotensin II (Ang II, 10-9-10-6 M). PD123177 (AT2R antagonist, 10-7 M), A779 (MasR antagonist, 10-6 M) or HOE-140 (B2R antagonist, 10-7 M) significantly enhanced Ang II-induced contractions in Chow- but not in HF-rings. HF-C21 aortas exhibited similar responses to Chow rings. In EA.hy926 cells, C21 (10-6 M) significantly increased levels of phosphorylated eNOS and NO production. Both effects were abolished by PD123177, A779 or HOE-140, respectively. Conclusions: In conclusion, our data suggest that C21 improves endothelial dysfunction induced by HF-feeding due to an increase in endothelial NO availability via AT2R activation. In addition, both MasR and B2R are implicated in this response and seem necessary for mediating C21 effects.