Renal Angiotensin-converting Enzyme 2 Research Articles

Angiotensin-converting enzyme 2 mediates hyperfiltration associated with diabetes

The degradation of ANG II by angiotensin-converting enzyme 2 (ACE2), leading to the formation of ANG(1-7), is an important step in the regulation of the renin-angiotensin-aldosterone system (RAAS), and one that is significantly altered in the diabetic kidney. This study examined the role of ACE2 in the hyperfiltration associated with diabetes. Streptozotocin diabetes was induced in male C57BL6 mice and ACE2 knockout (KO) mice. C57BL6 mice were further randomized to receive the selective ACE2 inhibitor MLN-4760. After 2 wk of study, animals were subjected to micropuncture experiments. The renal reserve was further assessed in C57BL6 mice and ACE2 KO mice after exposure to a high-protein diet. The induction of diabetes in wild-type mice was associated with increased renal ACE2 activity, hyperfiltration, and renal hypertrophy. On micropuncture, diabetes was associated with increased tubular free flow and stop-flow pressure, enhanced tubuloglomerular feedback reactivity, and an increased maximal response indicative of increased glomerular hydrostatic capillary pressure. Each of these increases were prevented in diabetic ACE2 KO mice and diabetic mice treated with a selective ACE2 inhibitor for 2 wk. However, unlike chronically treated animals, ACE2 inhibition with MLN-4760 had no acute effect on stop-flow pressure or tubuloglomerular feedback reactivity. ACE2 KO mice also failed to increase their creatinine clearance in response to a high-protein diet. The results of our study suggest that ACE2 plays a key role in the recruitment of the renal reserve and hyperfiltration associated with diabetes.

Insulin treatment attenuates renal ADAM17 and ACE2 shedding in diabetic Akita mice

Angiotensin-converting enzyme 2 (ACE2) is located in several tissues and is highly expressed in renal proximal tubules, where it degrades the vasoconstrictor angiotensin II (ANG II) to ANG-(1-7). Accumulating evidence supports protective roles of ACE2 in several disease states, including diabetic nephropathy. A disintegrin and metalloprotease (ADAM) 17 is involved in the shedding of several transmembrane proteins, including ACE2. Our previous studies showed increased renal ACE2, ADAM17 expression, and urinary ACE2 in type 2 diabetic mice (Chodavarapu H, Grobe N, Somineni HK, Salem ES, Madhu M, Elased KM. PLoS One 8: e62833, 2013). The aim of the present study was to determine the effect of insulin on ACE2 shedding and ADAM17 in type 1 diabetic Akita mice. Results demonstrate increased renal ACE2 and ADAM17 expression and increased urinary ACE2 fragments (≈70 kDa) and albumin excretion in diabetic Akita mice. Immunostaining revealed colocalization of ACE2 with ADAM17 in renal tubules. Renal proximal tubular cells treated with ADAM17 inhibitor showed reduced ACE2 shedding into the media, confirming ADAM17-mediated shedding of ACE2. Treatment of Akita mice with insulin implants for 20 wk normalized hyperglycemia and decreased urinary ACE2 and albumin excretion. Insulin also normalized renal ACE2 and ADAM17 but had no effect on tissue inhibitor of metalloproteinase 3 (TIMP3) protein expression. There was a positive linear correlation between urinary ACE2 and albuminuria, blood glucose, plasma creatinine, glucagon, and triglycerides. This is the first report showing an association between hyperglycemia, cardiovascular risk factors, and increased shedding of urinary ACE2 in diabetic Akita mice. Urinary ACE2 could be used as a biomarker for diabetic nephropathy and as an index of intrarenal ACE2 status.

Autocrine and Paracrine Function of Angiotensin 1-7 in Tissue Repair During Hypertension

Angiotensin-converting enzyme 2 (ACE2) cleaves angiotensin (Ang) II to generate Ang1-7, which mediates cellular actions through Mas receptors (MasR). Hypertension is accompanied by high or low circulating AngII levels and cardiac/renal injury. The purpose of this study is to explore (i) whether circulating AngII affects ACE2/MasR expressions in the hypertensive heart and kidney; and (ii) whether Ang1-7 regulates cardiac repair/remodeling responses through MasR during hypertension. In the first portion of the study, rats received either an AngII infusion (400ng/kg/min) for 4 weeks, leading to hypertension with high circulating AngII, or an aldosterone (ALDO, 0.75 μg/h) infusion for 4 weeks, leading to hypertension with low/normal circulating AngII. Cardiac and renal ACE2/MasR expressions were examined. We found that cardiac ACE2 was increased and MasR attenuated in both AngII and ALDO groups. However, renal ACE2 and MasR remained unchanged in both AngII- and ALDO-treated animals. In the second portion, rats received AngII infusion with/without MasR antagonist (A779, 1mg/kg/day) for 4 weeks. The roles of MasR blockade in cardiac inflammation, fibrosis, apoptosis, and ventricular function were examined. Chronic AngII infusion caused scattered cardiac injuries, and A779 cotreatment exacerbated cardiac injury, resulting in aggravated inflammatory, fibrogenic, and apoptotic responses compared with the AngII group. Cardiac function, however, was unaltered in the AngII and A779 groups. ACE2 and MasR expressions in the hypertensive heart and kidney are not regulated by circulating AngII levels. Ang1-7 is involved in multiple repair responses, suggesting that therapeutic strategies aimed at administering Ang1-7 hold potential for the management of cardiac remodeling.

ACE2 alterations in kidney disease.

Angiotensin-converting enzyme 2 (ACE2) is a monocarboxypeptidase that degrades angiotensin (Ang) II to Ang-(1-7). ACE2 is highly expressed within the kidneys, it is largely localized in tubular epithelial cells and less prominently in glomerular epithelial cells and in the renal vasculature. ACE2 activity has been shown to be altered in diabetic kidney disease, hypertensive renal disease and in different models of kidney injury. There is often a dissociation between tubular and glomerular ACE2 expression, particularly in diabetic kidney disease where ACE2 expression is increased at the tubular level but decreased at the glomerular level. In this review, we will discuss alterations in circulating and renal ACE2 recently described in different renal pathologies and disease models as well as their possible significance.

Rosiglitazone Treatment of Type 2 Diabetic db/db Mice Attenuates Urinary Albumin and Angiotensin Converting Enzyme 2 Excretion

Alterations within the renal renin angiotensin system play a pivotal role in the development and progression of cardiovascular and renal disease. Angiotensin converting enzyme 2 (ACE2) is highly expressed in renal tubules and has been shown to be renoprotective in diabetes. The protease, a disintegrin and metalloprotease (ADAM) 17, is involved in the ectodomain shedding of several transmembrane proteins including ACE2. Renal ACE2 and ADAM17 were significantly increased in db/db mice compared to controls. We investigated the effect of the insulin sensitizer, rosiglitazone, on albuminuria, renal ADAM17 protein expression and ACE2 shedding in db/db diabetic mice. Rosiglitazone treatment of db/db mice normalized hyperglycemia, attenuated renal injury and decreased urinary ACE2 and renal ADAM17 protein expression. Urinary excreted ACE2 is enzymatically active. Western blot analysis of urinary ACE2 demonstrated two prominent immunoreactive bands at approximately 70 & 90 kDa. The predominant immunoreactive band is approximately 20 kDa shorter than the one demonstrated for kidney lysate, indicating possible ectodomain shedding of active renal ACE2 in the urine. Therefore, it is tempting to speculate that renoprotection of rosiglitazone could be partially mediated via downregulation of renal ADAM17 and ACE2 shedding. In addition, there was a positive correlation between blood glucose, urinary albumin, plasma glucagon, and triglyceride levels with urinary ACE2 excretion. In conclusion, urinary ACE2 could be used as a sensitive biomarker of diabetic nephropathy and for monitoring the effectiveness of renoprotective medication.

Abstract 379: Insulin Attenuated Albuminuria by Upregulating Angiotensin Converting Enzyme 2 (ACE2) in Type 1 Diabetic Akita Mice

Diabetic nephropathy (DN) is a microvascular complication of diabetes that is clinically diagnosed by a progressive increase in albuminuria. Alterations within renin angiotensin system balance contribute to the pathogenesis of diabetic kidney disease. Angiotensin converting enzyme 2 (ACE2), a metallocarboxypetidase, has a renoprotective role due to its ability to form Angiotensin (1-7) [Ang-(1-7)] by degrading Angiotensin II (Ang II). Accumulating evidence shows that strict glycemic control attenuates diabetic kidney damage. Therefore, the aim of this study is to test the hypothesis that normalizing hyperglycemia with insulin will reduce albuminuria by increasing ACE2 in Akita diabetic mice. Type 1 diabetic Akita mice (C57BL/6-Ins2Akita/J) and their wild type (WT) littermates were used. Metabolic parameters were monitored weekly. Urine was collected over 24 hours to measure the urinary albumin, total protein and ACE2 activity. Akita mice developed significant hyperglycemia (Akita: 452±6; WT: 118±2 mg/dL), hypoinsulinemia (Akita: 0.5; WT: 1.5 ng/mL) and hypoadiponectinemia (Akita: 3.0; WT: 6.0 μg/mL) compared to WT mice. There was a significant increase in urinary albumin excretion (Akita: 2.1±0.2; WT: 0.2±0.06 mg/day) in Akita mice compared to WT mice. In addition, Akita mice demonstrated a significant decrease in renal (Akita: 3±0.3; WT: 4.1±0.1 pmol/hr/μg protein) and urinary (Akita: 0.2±0.03; WT: 0.7±0.1 pmol/hr/μg protein) ACE2 activity compared to WT mice (P<0.05). Western blot & immunohistochemistry revealed downregulation of renal ACE2 & nephrin protein expression in Akita mice compared to WT mice. Treatment with insulin implants (LinβitR) for 10 weeks significantly decreased hyperglycemia in Akita mice (treated: 135±21; untreated: 452±6 mg/dL). Insulin treatment significantly decreased urinary albumin excretion (treated: 0.18±0.2; untreated: 2.1±0.2 mg/day) and increased urinary ACE2 activity (treated: 1.3±0.3; untreated: 0.2±0.03 pmol/hr/μg protein) in Akita mice. In conclusion, normalizing hyperglycemia in Akita mice with insulin increased ACE2 activity and attenuated albuminuria.

Abstract 381: Upregulation of Tumor Necrosis Factor α-converting Enzyme (TACE) Protein Expression in db/db Mice is Reversed by Rosiglitazone

TACE, also known as ADAM17, is involved in the ectodomain shedding of several membrane bound proteins. Angiotensin converting enzyme 2 (ACE2), homologue of angiotensin converting enzyme (ACE), is known to be renoprotective by increasing the degradation of vasoactive peptide Angiotensin II (Ang II) to vasodilator peptide Ang - (1-7). It has been shown before that TACE mediates regulated ectodomain shedding of ACE2. PPARγ agonist, rosiglitazone, is known to impart renoprotection by attenuating albuminuria. However, the exact mechanism of renoprotection is not clear. Our previous results and others showed that renal ACE2 protein expression is increased during early stages of diabetes in db/db mice. We also demonstrated increased urinary ACE2 excretion in db/db mice. The goal of this study is to test the hypothesis that TACE is upregulated in db/db diabetic mice and treatment with rosiglitazone imparts renoprotection by attenuating the shedding of renal ACE2 via downregulating TACE protein expression. Male 6 week db/db mice were fed rosiglitazone (20mg/kg/day) for 10 weeks. Metabolic and urinary parameters were monitored weekly. Kidney lysate and urine was used to perform western blot and ACE2 activity (pmols/h/μg protein) respectively. db/db mice demonstrated glucose intolerance, hyperglycemia (348.2±29.9 mg/dL), and albuminuria (0.3±0.05 mg/day) at a very early age. Chronic rosiglitazone treatment normalized blood glucose levels (142.0±12.2 mg/dL), improved glucose tolerance and decreased albuminuria (0.17±0.03 mg/day) in treated db/db mice. Western blot showed increased renal TACE protein expression of db/db mice compared to controls (p<0.05). Treatment with rosiglitazone significantly decreased renal TACE protein expression in treated db/db mice compared to untreated mice (p<0.05). In addition, db/db mice demonstrated a 7 fold increase in urinary ACE2 activity (15.1±4.5) compared to controls (1.74±0.9). Treatment with rosiglitazone significantly attenuated and normalized ACE2 activity in treated db/db mice (0.1±0.06). In conclusion, TACE is upregulated in db/db mice and normalizing hyperglycemia with rosiglitazone could impart renoprotection by decreasing renal TACE protein expression and shedding of renal ACE2.

Differential regulation of circulating and renal ACE2 and ACE in hypertensive mRen2.Lewis rats with early-onset diabetes

We 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 angiotensin-converting enzyme 2 (ACE2) increased ninefold (P < 0.05) in DB females and threefold (P < 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(+)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 (>75%, P < 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 < 0.05) and male (50%; P < 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.

Urinary angiotensin‐converting enzyme 2 in patients with CKD

Angiotensin-converting enzyme 2 (ACE2) is a type I membrane protein that antagonizes the action of angiotensin II. Because of the need for invasive kidney biopsy, little is known about the role of renal ACE2 in human kidney diseases. The authors studied if urinary ACE2 could provide a novel clue to renal ACE2 in chronic kidney disease (CKD). Subjects were 190 patients with CKD including 38 patients with diabetic nephropathy and 36 healthy subjects. Parameters were urinary ACE2 by enzyme-linked immunosorbent assay, blood pressure, casual plasma glucose, proteinuria, microalbuminuria, serum creatinine and estimated glomerular filtration rate. Urine and serum samples were also subjected to western blotting of ACE2. Western blotting confirmed increased urinary ACE2 levels in patients with CKD. Urinary ACE2 was significantly higher in patients with CKD than healthy subjects (median 9.64 (interquartile range, 4.41-16.89) vs 1.50 (0.40-2.33) mg/g·creatinine, P < 0.001) and in patients with diabetic nephropathy than patients without diabetic nephropathy (median 13.16 (interquartile range 6.81-18.70) vs 8.90 (4.19-16.67) mg/g·creatinine, P < 0.05). No significant difference in urinary ACE2 was observed by the use of angiotensin-converting enzyme inhibitor and angiotensin receptor blocker. Urinary ACE2 could be used as a non-invasive marker to understand the role of renal ACE2 in CKD.

Corrigendum

CorrigendumCorrigendumPublished Online:01 Dec 2010https://doi.org/10.1152/ajprenal.zh2-6109-corr.2010Original articleMoreSectionsPDF (387 KB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInEmailWeChat Volume 298, June 2010Volume 67, June 2010Pages F1297–F1305. Ferrario CM, Varagic J. The ANG-(1-7)/ACE2/mas axis in the regulation of nephron function. Am J Physiol Renal Physiol 298: , 2010.On p. F1300, the presentation of the data in Fig. 1 showing the decrease in the expression and activity of renal ACE2 in mRen2.Lewis congenics is erroneous. The error arises from inappropriate comparisons of ACE2 mRNA from different assays and a mistaken comparison of activities in the Lewis kidney and the mRen2.Lewis heart. Evidence supporting the original hypothesis for reduced renal cortical ACE2 activity was reported in both male and female mRen2.Lewis hypertensive rats and is shown in the corrected version of Fig. 1 and its revised legend below.Fig. 1.Composite of the expression of angiotensin-converting enzyme 2 (ACE2) activity in the rat kidney. In the renal cortex of a male Lewis rat, significant staining is evident in proximal tubules while there is minimal immunoreactive ACE2 in the glomerulus (left). In comparison to the Lewis normotensive rats, ACE2 activity in the renal cortex is significantly lower in both male and female hypertensive mRen2.Lewis (mRen2) rats (right). Values are means ± SE (*P < 0.05 vs. Lewis) for renal cortical ACE2 activity as adapted from Ref. 109.Download figureDownload PowerPointThis article has no references to display. Download PDF Previous Back to Top FiguresReferencesRelatedInformationRelated ArticlesThe ANG-(1–7)/ACE2/mas axis in the regulation of nephron function 01 Jun 2010American Journal of Physiology-Renal PhysiologyCited ByAngiotensin-converting enzyme 2 is reduced in Alzheimer’s disease in association with increasing amyloid-β and tau pathology25 November 2016 | Alzheimer's Research & Therapy, Vol. 8, No. 1 More from this issue > Volume 299Issue 6December 2010Pages F1515-F1515 Copyright & PermissionsCopyright © 2010 the American Physiological Societyhttps://doi.org/10.1152/ajprenal.zh2-6109-corr.2010History Published online 1 December 2010 Published in print 1 December 2010 Metrics

Effect of ACE2 and angiotensin-(1–7) in a mouse model of early chronic kidney disease

Angiotensin-converting enzyme 2 (ACE2) is expressed at high levels in the kidney and converts angiotensin II (ANG II) to ANG-(1-7). We studied the effects of ACE2 inhibition and ANG-(1-7) in the (5/6) nephrectomy ((5/6) Nx) mouse model of chronic kidney disease (CKD). Male FVB mice underwent sham surgery (Sham) or (5/6) Nx and were administered either vehicle, the ACE2 inhibitor MLN-4760 (MLN), the AT(1) receptor antagonist losartan, MLN plus losartan, or ANG-(1-7) for 4 wk. In (5/6) Nx mice with or without MLN, kidney cortical ACE2 protein expression was significantly decreased at 4 wk, compared with Sham. Inhibition of ACE2 caused a decrease in renal cortical ACE2 activity. Kidney cortical ACE expression and activity did not differ between groups of mice. In (5/6) Nx mice treated with MLN, kidney levels of ANG II were significantly increased, compared with Sham. (5/6) Nx induced a mild but insignificant increase in blood pressure (BP), a 50% reduction in FITC-inulin clearance, and a significant increase in urinary albumin excretion. ACE2 inhibition in (5/6) Nx mice did not affect BP or FITC-inulin clearance but significantly increased albuminuria compared with (5/6) Nx alone, an effect reversed by losartan. Treatment of (5/6) Nx mice with ANG-(1-7) increased kidney and plasma levels of ANG-(1-7) but did not alter BP, FITC-inulin clearance, or urinary albumin excretion, and it increased relative mesangial area. These data indicate that kidney ACE2 is downregulated in the early period after (5/6) Nx. Inhibition of ACE2 in (5/6) Nx mice increases albuminuria via an AT(1) receptor-dependent mechanism, independent of BP. In contrast, ANG-(1-7) does not affect albuminuria after (5/6) Nx. We propose that endogenous ACE2 is renoprotective in CKD.

Reduction in renal ACE2 expression in subtotal nephrectomy in rats is ameliorated with ACE inhibition

Alterations within the RAS (renin–angiotensin system) are pivotal for the development of renal disease. ACE2 (angiotensin-converting enzyme 2) is expressed in the kidney and converts the vasoconstrictor AngII (angiotensin II) into Ang-(1–7), a peptide with vasodilatory and anti-fibrotic actions. Although the expression of ACE2 in the diabetic kidney has been well studied, little is known about its expression in non-diabetic renal disease. In the present study, we assessed ACE2 in rats with acute kidney injury induced by STNx (subtotal nephrectomy). STNx and Control rats received vehicle or ramipril (1 mg·kg−1 of body weight·day−1), and renal ACE, ACE2 and mas receptor gene and protein expression were measured 10 days later. STNx rats were characterized by polyuria, proteinuria, hypertension and elevated plasma ACE2 activity (all P<0.01) and plasma Ang-(1–7) (P<0.05) compared with Control rats. There was increased cortical ACE binding and medullary mas receptor expression (P<0.05), but reduced cortical and medullary ACE2 activity in the remnant kidney (P<0.05 and P<0.001 respectively) compared with Control rats. In STNx rats, ramipril reduced blood pressure (P<0.01), polyuria (P<0.05) and plasma ACE2 (P<0.01), increased plasma Ang-(1–7) (P<0.001), and inhibited renal ACE (P<0.001). Ramipril increased both cortical and medullary ACE2 activity (P<0.01), but reduced medullary mas receptor expression (P<0.05). In conclusion, our results show that ACE2 activity is reduced in kidney injury and that ACE inhibition produced beneficial effects in association with increased renal ACE2 activity. As ACE2 both degrades AngII and generates the vasodilator Ang-(1–7), a decrease in renal ACE2 activity, as observed in the present study, has the potential to contribute to the progression of kidney disease.

Fructose/losartan interactions: Effects on renal ACE2

Fructose diet enhances losartan's hypotensive effect in mice. Angiotensin‐converting enzyme 2 (ACE2) has emerged as an important component of the renin angiotensin system. We examined the interactions between fructose diet and losartan on renal ACE/ACE2 balance. Male C57BL mice were fed a 60% fructose diet for 10 weeks and losartan (Los, 30mg/kg/day) was given in the drinking water for the last wk. Renal ACE and ACE2 activity were measured by radiofluorescent and fluorogenic assays, respectively. Renal Ang II levels were measured by RIA. Renal ACE and ACE2 protein expression were measured by Western blots. There was no alteration in renal ACE activity or protein expression between groups. Renal Ang II, ACE2 activity and ACE2 protein expression were increased in fructose group (Ang II: 112 ± 40 vs. 440 ± 114 pg/μg protein; ACE2 activity: 2.8 ± 0.2 vs. 3.9 ± 0.2 pmol/hr/ ?g protein; ACE2 protein expression: 0.6 ± 0.1 vs. 1.3 ± 0.1 AU). Los had no effect on renal Ang II or ACE protein or activity. Los increased ACE2 protein in controls (0.7 ± 0.1 vs. 1.4 ± 0.2, AU) with no change in activity. In fructose mice, Los decreased renal Ang II (440 ± 114 vs. 190 ± 85 pg/µg protein). Fructose produced consistent activation of the renal ACE2 system while Los produced no additional effects. Results suggest that interaction between Los and fructose is not mediated by changes in the renal ACE/ACE2 balance.

Role of angiotensin‐converting enzyme 2 and angiotensin(1–7) in 17β‐oestradiol regulation of renal pathology in renal wrap hypertension in rats

17beta-Oestradiol (E2)-mediated inhibition of angiotensin-converting enzyme (ACE) protects the E2-replete kidney from the progression of hypertensive renal disease. Angiotensin-converting enzyme 2 (ACE2), a homologue of ACE, counters the actions of ACE by catalysing the conversion of angiotensin II (Ang II) to angiotensin(1-7) [Ang(1-7)]. We investigated E2 regulation of ACE2 in the renal wrap (RW) model of hypertension in rats. After 6 weeks on a high-sodium diet (4% NaCl), the activity of ACE2 was reduced in the renal cortex by 31%, which was mirrored by similar decreases in ACE2 protein (30%) and mRNA expression (36%) in the ovariectomized RW rat (RW-OVX); E2 replacement prevented these effects. The RW-OVX rats exhibited greater renal injury, including 1.7-fold more tubulointerstitial fibrosis and 1.6-fold more glomerulosclerosis than E2-replete females (RW-Intact and RW-OVX+E2). Angiotensin(1-7) infusion prevented these exacerbating effects of ovariectomy on renal pathology; no differences in indicators of renal injury were observed between RW-OVX-Ang(1-7) and RW-Intact rats. These renal protective effects of Ang(1-7) infusion were not attributable to increased ACE2 activity or to changes in heart rate or body weight, since these parameters were unchanged by Ang(1-7) infusion. Furthermore, Ang(1-7) infusion did not attenuate renal injury by reducing mean arterial pressure (MAP), since infusion of the peptide did not lower MAP but rather caused a slight increase during a 6 week chronic treatment for Ang(1-7). These results suggest that E2-mediated upregulation of renal ACE2 and the consequent increased Ang(1-7) production contribute to E2-mediated protection from hypertensive renal disease. These findings have implications for E2-deficient women with hypertensive renal disease and suggest that therapeutics targeted towards increasing ACE2 activity and Ang(1-7) levels will be renal protective.

Expression of ACE and ACE2 in Individuals With Diabetic Kidney Disease and Healthy Controls

Angiotensin-converting enzyme (ACE) 2 (ACE2) is expressed mainly in the heart and kidney and forms angiotensin-1-7 from angiotensin II. ACE2 might act in a counterregulatory manner to ACE. There is little information about renal ACE and ACE2 expression in human diabetic nephropathy. Cross-sectional study. Kidney tissue from 20 patients with type 2 diabetes and overt nephropathy and 20 healthy kidney donors. Diabetes status. Renal expression of ACE and ACE2 assessed by means of immunohistochemistry and in situ hybridization. Correlation between ACE and ACE2 expression and levels of various biochemical parameters. Decreased ACE2 and increased ACE expression in both the tubulointerstitium and glomeruli resulted in a significant (P < 0.001) increase in ACE/ACE2 ratio in patients with diabetes with overt nephropathy compared with controls, although ACE messenger RNA in the tubulointerstitium did not significantly increase. ACE/ACE2 ratio correlated positively with values for mean blood pressure, fasting blood glucose, serum creatinine, proteinuria, and hemoglobin A(1c) and inversely with estimated glomerular filtration rate (P < 0.001). Inclusion of small number of human renal biopsy specimens with structural distortion of cortical tissue. The high ACE/ACE2 ratio in kidneys of patients with type 2 diabetes with overt nephropathy may contribute to renal injury.

ANGIOTENSIN CONVERTING ENZYME 2 IN THE KIDNEY

SUMMARY 1Angiotensin converting enzyme 2 (ACE2) is an important homeostatic component of the renin angiotensin system (RAS). ACE2 both degrades the vasoconstrictor, angiotensin II and generates the potent vasodilator peptide, angiotensin 1–7. These actions counterbalance those of ACE.2ACE2 is highly expressed in the healthy kidney, particularly in the proximal tubules, where it colocalizes with ACE and angiotensin receptors.3Kidney disease and subtotal nephrectomy is associated with a reduction in renal ACE2 expression, possibly facilitating the damaging effects of angiotensin II in the failing kidney. Acquired or genetic ACE2 deficiency also appears to exacerbate renal damage and albuminuria in experimental models, supporting this hypothesis.4ACE2 also has an important role in blood pressure control. Many models of hypertension are associated with reduced ACE2 expression. Although ACE2 KO animals are normotensive, in states associated with activation of the RAS, ACE2 overexpression improves blood pressure control and reduces angiotensin responsiveness.

ACE and ACE2: their role to balance the expression of angiotensin II and angiotensin-(1–7)

The discovery of angiotensin-converting enzyme 2 (ACE-2) has revealed a far more complex enzymatic cascade that may influence the renin-angiotensin system within the kidney, specifically the expression of the functional products angiotensin II (Ang II) and Ang-(1-7). The regulation of this critical system involved in blood pressure control must now encompass the integral relationship of ACE and ACE-2 activities.

Loss of Angiotensin-Converting Enzyme-2 Leads to the Late Development of Angiotensin II-Dependent Glomerulosclerosis

Angiotensin-converting enzyme-2 (ACE2), a membrane-bound carboxymonopeptidase highly expressed in the kidney, functions as a negative regulator of the renin-angiotensin system. Here we report early accumulation of fibrillar collagen in the glomerular mesangium of male ACE2 mutant (ACE2−/y) mice followed by development of glomerulosclerosis by 12 months of age whereas female ACE2 mutant (ACE2−/−) mice were relatively protected. Progressive kidney injury was associated with increased deposition of collagen I, collagen III and fibronectin in the glomeruli and increased urinary albumin excretion compared to age-matched control mice. These structural and functional changes in the glomeruli of male ACE2 mutant mice were prevented by treatment with the angiotensin II type-1 receptor antagonist irbesartan. Loss of ACE2 was associated with a marked increase in renal lipid peroxidation product formation and activation of mitogen-activated protein kinase and extracellular signal-regulated kinases 1 and 2 in glomeruli, events that are also prevented by angiotensin II type-1 receptor blockade. We conclude that deletion of the ACE2 gene leads to the development of angiotensin II-dependent glomerular injury in male mice. These findings have important implications for our understanding of ACE2, the renin-angiotensin system, and gender in renal injury, with ACE2 likely to be an important therapeutic target in kidney disease.

Renal ACE2 expression in human kidney disease

Angiotensin-converting enzyme 2 (ACE2) is a recently discovered homologue of angiotensin-converting enzyme (ACE) that is thought to counterbalance ACE. ACE2 cleaves angiotensin I and angiotensin II into the inactive angiotensin 1-9, and the vasodilator and anti-proliferative angiotensin 1-7, respectively. ACE2 is known to be present in human kidney, but no data on renal disease are available to date. Renal biopsies from 58 patients with diverse primary and secondary renal diseases were studied (hypertensive nephropathy n = 5, IgA glomerulopathy n = 8, minimal change nephropathy n = 7, diabetic nephropathy n = 8, focal glomerulosclerosis n = 5, vasculitis n = 7, and membranous glomerulopathy n = 18) in addition to 17 renal transplants and 18 samples from normal renal tissue. Immunohistochemical staining for ACE2 was scored semi-quantitatively. In control kidneys, ACE2 was present in tubular and glomerular epithelium and in vascular smooth muscle cells and the endothelium of interlobular arteries. In all primary and secondary renal diseases, and renal transplants, neo-expression of ACE2 was found in glomerular and peritubular capillary endothelium. There were no differences between the various renal disorders, or between acute and chronic rejection and control transplants. ACE inhibitor treatment did not alter ACE2 expression. In primary and secondary renal disease, and in transplanted kidneys, neo-expression of ACE2 occurs in glomerular and peritubular capillary endothelium. Further studies should elucidate the possible protective mechanisms involved in the de novo expression of ACE2 in renal disease.