The current study assessed whether activation of the novel estrogen receptor GPR30 ameliorates salt-dependent renal damage in intact mRen2.Lewis (mRen2) females. Hemizygous mRen2 were maintained on either a normal salt (NS, 0.5% Na) or high salt (HS, 4% Na) diet for 10 wks (5 to 15 wks of age), and HS animals were treated with the GPR30 agonist G-1 or vehicle for two weeks. Systolic blood pressure markedly increased with HS [149 ± 3 to 219 ± 5 mmHg, P<0.01], but G-1 did not influence pressure [P=0.42]. G-1 and estradiol induced relaxation of pre-constricted mesenteric vessels from NS mRen2, but both responses were attenuated in the HS group. Despite the lack of an effect on blood pressure, G-1 decreased renal hypertrophy, proteinuria, urinary 8-isoprostane excretion, and tubular 4-HNE staining. HS significantly increased GPR30 mRNA [1.01 ± 0.04 vs. 1.59 ± 0.13; P<0.01] and protein [0.60 ± 0.31 vs. 3.99 ± 0.75; P<0.01] in the renal cortex. GPR30 was highly expressed in the brush border of proximal tubules and co-localized with megalin. Finally, megalin expression was reduced by HS and restored with G-1. We conclude that GPR30-mediated beneficial effects in salt-sensitive mRen2 females occurred independent of changes in systolic blood pressure. The failure of G-1 to influence pressure may reflect a salt-induced impairment in GPR30-mediated vasorelaxation. The renoprotective actions of GPR30 may involve attenuation of tubular oxidative stress and activation of megalin-mediated protein reabsorption.

Yamaleyeva LM, Gilliam-Davis S, Almeida I, Brosnihan KB, Lindsey SH, Chappell MC. Differential regulation of circulating and renal ACE2 and ACE in hypertensive mRen2.Lewis rats with early-onset diabetes. Am J Physiol Renal Physiol 302: F1374 -F1384, 2012. First published February 29, 2012 doi:10.1152/ajprenal.00656.2011We examined the impact of early diabetes on the circulating and kidney renin-angiotensin system (RAS) in male and female mRen2.Lewis (mRen2) hypertensive rats. Diabetes (DB) was induced by streptozotocin (STZ; 65 mg/kg) at 11 wk of age for 4 wk without insulin replacement. Systolic blood pressures were not increased in DB males or females compared with controls (CON). Circulating angiotensinconverting enzyme 2 (ACE2) increased ninefold (P Ͻ 0.05) in DB females and threefold (P Ͻ 0.05) in DB males, but circulating ACE and ANG II were higher in the DB groups. Serum C-reactive protein was elevated in DB females but not DB males, and the vascular responses to acetylcholine and estradiol were attenuated in the DB females. Proteinuria, albuminuria, and angiotensinogen excretion increased to a similar extent in both DB females and males. Glomerular VEGF expression also increased to a similar extent in both DB groups. Renal inflammation (CD68 ϩ cells) increased only in DB females although males exhibited greater inflammation that was not different with DB. Cortical ACE2 did not change in DB females but was reduced (30%) in DB males. Renal neprilysin activity (Ͼ75%, P Ͻ 0.05) was markedly reduced in the DB females to that in the DB and CON males. ACE activity was significantly lower in both female (75%, P Ͻ 0.05) and male (50%; P Ͻ 0.05) DB groups, while cortical ANG II and Ang-(1-7) levels were unchanged. In conclusion, female mRen2 rats are not protected from vascular damage, renal inflammation, and kidney injury in early STZ-induced diabetes despite a marked increase in circulating ACE2 and significantly reduced ACE within the kidney.angiotensin; kidney; neprilysin; hypertension; proteinuria ANGIOTENSIN-CONVERTING ENZYME 2 (ACE2), a homolog of ACE, is recognized as an important enzymatic component of the renin-angiotensin system (RAS) that may regulate functional output of this hormonal system (5,7,8,14,28,30,51,50). Although ACE2 was originally characterized for its ability to hydrolyze ANG I to Ang-(1-9), subsequent studies revealed a very high catalytic activity to convert ANG II to Ang-(1-7) (41,44,45,56,58). Indeed, ACE2 inhibition or genetic knockout studies reveal a heightened sensitivity to ANG II-induced increases in blood pressure, as well as an exacerbation of end-organ damage in these experimental models (31,32,46,48,52,60). In contrast to ACE, circulating ACE2 is low to nondetectable in rodents and humans, and tissue sources of the enzyme are more likely to influence the local RAS (12, 40). Diabetic renal injury is generally associated with a reduction in the activity and/or expression of renal tissue ACE2, which may contribute to a deleterious imbalance in the relative expression of ANG I...

The present study determined whether early loss of estrogen influences salt-sensitive changes in blood pressure, renal injury, and cardiac hypertrophy as well as the effects on the circulating renin-angiotensin-aldosterone system (RAAS) in the hypertensive female mRen(2). Lewis strain. Ovariectomy (OVX) of heterozygous mRen(2). Lewis rats on a normal salt (NS) diet (0.5% sodium) increased systolic blood pressure from 137+/-3 to 177+/-5 mmHg (P<0.01) by 15 wk but did not show any changes in cardiac-to-body weight index (CI), proteinuria, or creatinine clearance. Maintenance with a high-sodium (HS) diet (4%) increased blood pressure (203+/-4 mmHg, P<0.01), proteinuria (3.5+/-0.3 vs. 6.4+/-0.7 mg/day, P<0.05), and CI (4.0+/-0.1 vs. 5.2+/-0.1 mg/kg, P<0.01) but decreased creatinine clearance (0.89+/-0.15 vs. 0.54+/-0.06 ml/min, P<0.05). OVX exacerbated the effects of salt on the degree of hypertension (230+/-5 mmHg), CI (5.6+/-0.2 mg/kg), and proteinuria (13+/-3.0 mg/day). OVX increased the urinary excretion of aldosterone approximately twofold in animals on the NS diet (3.8+/-0.5 vs. 6.6+/-0.5 ng.mg creatinine-1.day-1, P<0.05) and HS diet (1.4+/-0.2 vs. 4.5+/-1.0 ng.mg creatinine-1.day-1, P<0.05). Circulating renin, angiotensin-converting enzyme, and angiotensin II were also significantly increased in the OVX group fed a HS diet. These results reveal that the protective effects of estrogen apart from the increase in blood pressure were only manifested in the setting of a chronic HS diet and suggest that the underlying sodium status may have an important influence on the overall effect of reduced estrogen.

Angiotensin converting enzyme 2 (ACE2) is a key enzyme of the renin-angiotensin system (RAS) that influences the relative expression of angiotensin (Ang) II and Ang-(1–7). Although ACE2 expression increases in normal pregnancy, the impact of ACE2 deficiency in pregnancy has not been elucidated. We determined the influence of ACE2 deficiency on circulating and tissue RAS components, fetal and maternal growth characteristics, and maternal hemodynamics (mean blood pressure (MBP) and cardiac output (CO)) at day 18 of gestation. Gestational body weight gain was lower in the ACE2 knock out (KO) vs C57BL/6 (WT) mice (30.3 ± 4.7 vs 38.2 ± 1.0 g, p<0.001). Fetal weight (0.94 ± 0.1 vs 1.24 ± 0.01 g, p<0.01) and length (19.6 ± 0.2 vs 22.2 ± 0.2 mm, p<0.001) were less in KO. MBP was significantly reduced in WT with pregnancy; it was elevated (p<0.05) in the KO virgin and pregnant mice, and this was associated with an increased CO in both WT and KO pregnant mice (p<0.05). Plasma Ang-(1–7) was reduced in pregnant KO mice (p<0.05). Placenta Ang II levels were higher in KO mice (52.9 ± 6.0 vs 22.0 ± 3.3 fmol/mg protein, p<0.001). Renal Ang II levels were greater in KO virgin mice (30.0 ± 1.7 vs 23.7 ± 1.1 fmol/mg protein, p<0.001). There was no change in the Ang-(1–7) levels in the KO placenta and virgin kidney. These results suggest that ACE2 deficiency and associated elevated placenta Ang II levels impact pregnancy by impairing gestational weight gain and restricting fetal growth.