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Background-We previously identified the G-protein-coupled receptor Mas, encoded by the Mas proto-oncogene, as an endogenous receptor for the heptapeptide angiotensin-(1-7); however, the receptor is also suggested to be involved in actions of angiotensin II. We therefore tested whether this could be mediated indirectly through an interaction with the angiotensin II type 1 receptor, AT 1 . Methods and Results-In transfected mammalian cells, Mas was not activated by angiotensin II; however, AT 1 receptor-mediated, angiotensin II-induced production of inositol phosphates and mobilization of intracellular Ca 2ϩ was diminished by 50% after coexpression of Mas, despite a concomitant increase in angiotensin II binding capacity. Mas and the AT 1 receptor formed a constitutive hetero-oligomeric complex that was unaffected by the presence of agonists or antagonists of the 2 receptors. In vivo, Mas acts as an antagonist of the AT 1 receptor; mice lacking the Mas gene show enhanced angiotensin II-mediated vasoconstriction in mesenteric microvessels.Conclusions-These results demonstrate that Mas can hetero-oligomerize with the AT 1 receptor and by so doing inhibit the actions of angiotensin II. This is a novel demonstration that a G-protein-coupled receptor acts as a physiological antagonist of a previously characterized receptor. Consequently, the AT 1 -Mas complex could be of great importance as a target for pharmacological intervention in cardiovascular diseases.

Biochemical analysis revealed that angiotensin-converting enzyme related carboxy-peptidase (ACE2) cleaves angiotensin (Ang) II to Ang-(1-7), a heptapeptide identified as an endogenous ligand for the G protein-coupled receptor Mas. No data are currently available that systematically describe ACE2 distribution and activity in rodents. Therefore, we analyzed the ACE2 expression in different tissues of mice and rats on mRNA (RNase protection assay) and protein levels (immunohistochemistry, ACE2 activity, western blot). Although ACE2 mRNA in both investigated species showed the highest expression in the ileum, the mouse organ exceeded rat ACE2, as also demonstrated in the kidney and colon. Corresponding to mRNA, ACE2 activity was highest in the ileum and mouse kidney but weak in the rat kidney, which was also confirmed by immunohistochemistry. Contrary to mRNA, we found weak activity in the lung of both species. Our data demonstrate a tissue- and species-specific pattern for ACE2 under physiological conditions.

. The SGLT2 inhibitor empagliflozin ameliorates early features of diabetic nephropathy in BTBR ob/ob type 2 diabetic mice with and without hypertension. Am J Physiol Renal Physiol 307: F317-F325, 2014. First published June 18, 2014 doi:10.1152/ajprenal.00145.2014.-Diabetic nephropathy is the leading cause of end-stage renal disease in humans in the Western world. The recent development of Na ϩ -glucose cotransporter 2 (SGLT2) inhibitors offers a new antidiabetic therapy via enhanced glucose excretion. Whether this strategy exerts beneficial effects on the development of type 2 diabetic nephropathy is still largely unclear. We investigated the effects of the specific SGLT2 inhibitor empagliflozin in BTBR.Cg-LepϽobϾ/WiscJ (BTBR ob/ob) mice, which spontaneously develop type 2 diabetic nephropathy. In the first experiment, BTBR ob/ob mice received either a diet containing 300 ppm empagliflozin or equicaloric placebo chow for 12 wk. In the second experiment, BTBR ob/ob mice received 1 g·kg body wt Ϫ1 ·day Ϫ1ANG II to induce arterial hypertension and were separated into the same two diet groups for 6 wk. In both experiments, empagliflozin treatment enhanced glucosuria, thereby lowering blood glucose. Independently of hypertension, empagliflozin reduced albuminuria in diabetic mice. However, empagliflozin treatment affected diabetesrelated glomerular hypertrophy, markers of renal inflammation, and mesangial matrix expansion only in BTBR ob/ob mice without hypertension. In summary, empagliflozin demonstrated significant antihyperglycemic effects, differentially ameliorating early features of diabetic nephropathy in BTBR ob/ob mice with and without hypertension.