It has been suggested that the cytokine vascular endothelial growth factor (VEGF) has an important role in the pathogenesis of diabetic retinopathy, but its role in nephropathy has not been clearly demonstrated. Assessment of VEGF, 125I-VEGF binding, and vascular endothelial growth factor receptor-2 (VEGFR-2) in the kidney was performed after 3 and 32 weeks of streptozotocin-induced diabetes. Gene expression of both VEGF and VEGFR-2 was assessed by Northern blot analysis and the localization of the ligand and receptor was examined by in situ hybridization. VEGF and VEGFR-2 protein were also evaluated by immunohistochemistry. Binding of the radioligand 125I-VEGF was evaluated by in vitro and in vivo autoradiography. Diabetes was associated with increased renal VEGF gene expression. VEGF mRNA and protein were localized to the visceral epithelial cells of the glomerulus and to distal tubules and collecting ducts in both diabetic and nondiabetic rats. Renal VEGFR-2 mRNA was increased after 3 weeks of diabetes but not in long-term diabetes. In situ hybridization and immunohistochemical studies revealed that glomerular endothelial cells were the major site of VEGFR-2 expression. In addition, VEGFR-2 gene expression was detected in cortical and renomedullary interstitial cells and on endothelial cells of peritubular capillaries. There was an increase in 125I-VEGF binding sites after 3 but not 32 weeks of diabetes. The major VEGF binding sites were in the glomeruli. 125I-VEGF binding was also observed in medullary rays and in the renal papillae. These studies indicate an early and persistent increase in renal VEGF gene expression in association with experimental diabetes. In addition, an early and transient increase in renal VEGF receptors was also observed in diabetic rats. These findings are consistent with a role for VEGF in mediating some of the changes observed in the diabetic kidney.

Long-term Ang (1-7) treatment caused both vasoprotection, via improvement in endothelial function, and atheroprotection, with a reduction in lesion progression in a model of atherosclerosis. These effects appear to be mediated by the restoration of nitric oxide bioavailability and involve a complex interaction of both Mas and AT(2) receptors.

Ang-(1-7) (angiotensin-1-7), a peptide product of the recently described ACE (angiotensin-converting enzyme) homologue ACE2, opposes the harmful actions of AngII (angiotensin II) in cardiovascular tissues, but its role in liver disease is unknown. The aim of the present study was to assess plasma levels of Ang-(1-7) in human liver disease and determine its effects in experimental liver fibrosis. Angiotensin peptide levels were measured in cirrhotic and non-cirrhotic patients with hepatitis C. The effects of Ang-(1-7) on experimental fibrosis were determined using the rat BDL (bile-duct ligation) model. Liver histology, hydroxyproline quantification and expression of fibrosis-related genes were assessed. Expression of RAS (renin-angiotensin system) components and the effects of Ang-(1-7) were examined in rat HSCs (hepatic stellate cells). In human patients with cirrhosis, both plasma Ang-(1-7) and AngII concentrations were markedly elevated (P<0.001). Non-cirrhotic patients with hepatitis C had elevated Ang-(1-7) levels compared with controls (P<0.05), but AngII concentrations were not increased. In BDL rats, Ang-(1-7) improved fibrosis stage and collagen Picrosirius Red staining, and reduced hydroxyproline content, together with decreased gene expression of collagen 1A1, alpha-SMA (smooth muscle actin), VEGF (vascular endothelial growth factor), CTGF (connective tissue growth factor), ACE and mas [the Ang-(1-7) receptor]. Cultured HSCs expressed AT1Rs (AngII type 1 receptors) and mas receptors and, when treated with Ang-(1-7) or the mas receptor agonist AVE 0991, produced less alpha-SMA and hydroxyproline, an effect reversed by the mas receptor antagonist A779. In conclusion, Ang-(1-7) is up-regulated in human liver disease and has antifibrotic actions in a rat model of cirrhosis. The ACE2/Ang-(1-7)/mas receptor axis represents a potential target for antifibrotic therapy in humans.

These findings indicate that there is significant expression of the AT2R in the adult kidney, and that the AT2R has a role in mediating Ang II-induced proliferation and apoptosis in proximal tubular epithelial cells and expression of osteopontin.

OBJECTIVE -Diabetic subjects have a high prevalence of hypertension, increased total body exchangeable sodium levels, and an impaired ability to excrete a sodium load. This study assessed the effect of dietary sodium restriction on the efficacy of losartan in hypertensive subjects with type 2 diabetes and albumin excretion rates of 10 -200 g/min.RESEARCH DESIGN AND METHODS -In this study, 20 subjects were randomized to losartan 50 mg/day (n ϭ 10) or placebo (n ϭ 10). Drug therapy was given in two 4-week phases separated by a washout period. In the last 2 weeks of each phase, patients were assigned to low-or regular-sodium diets, in random order. In each phase, 24-h ambulatory blood pressure, urinary albumin-to-creatinine ratio (ACR), and renal hemodynamics were measured.RESULTS -Achieved urinary sodium on a low-sodium diet was 85 Ϯ 14 and 80 Ϯ 22 mmol/day in the losartan and placebo groups, respectively. In the losartan group, the additional blood pressureϪlowering effects of a low-sodium diet compared with a regularsodium diet for 24-h systolic, diastolic, and mean arterial blood pressures were 9.7 mmHg (95% confidence interval [CI], 2.2Ϫ17.2; P ϭ 0.002), 5.5 mmHg (2.6Ϫ8.4; P ϭ 0.002), and 7.3 mmHg (3.3Ϫ11.3; P ϭ 0.003), respectively. In the losartan group, the ACR decreased significantly on a low-sodium diet versus on a regular-sodium diet (Ϫ29% [CI Ϫ50.0 to Ϫ8.5%] vs. ϩ14% [Ϫ19.4 to 47.9%], respectively; P ϭ 0.02). There was a strong correlation between fall in blood pressure and percent reduction in the ACR (r ϭ 0.7, P ϭ 0.02). In the placebo group, there were no significant changes in blood pressure or ACR between regularand low-sodium diets. There were no significant changes in renal hemodynamics in either group.CONCLUSIONS -These data demonstrated that a low-sodium diet potentiates the antihypertensive and antiproteinuric effects of losartan in type 2 diabetes. The blood pressure reduction resulting from the addition of a low-sodium diet to losartan was of similar magnitude to that predicted from the addition of a second antihypertensive agent. Diabetes Care 25:663-671, 2002H igh blood pressure is an important modifiable risk factor in preventing diabetic micro-and macrovascular complications. Subjects with diabetes have a high prevalence of hypertension and often require multiple antihypertensive agents to achieve blood pressure targets (1).The role of ACE inhibitors in the prevention and treatment of diabetic nephropathy is well established in patients with type 2 (2) and type 1 diabetes (3). More recently, blockade of the reninangiotensin system (RAS) with angiotensin (ANG)-II receptor antagonists has been shown to attenuate the rate of progression of renal dysfunction in patients with type 2 diabetes (4,5).In nondiabetic subjects with renal disease, the antiproteinuric effects of ACE inhibitors strongly depend on dietary sodium intake (6). Furthermore, the antihypertensive effects of ANG-II receptor antagonists have shown dependence on the baseline activation of the RAS in nondiabetic patients (7). In...

The expression and cellular localization of angiotensin II (Ang II) and AT(1) receptor proteins were examined in the normal human prostate and benign prostatic hyperplasia (BPH) by immunohistochemistry. In the normal prostate, Ang II immunoreactivity was localized to the basal layer of the epithelium and AT(1) receptor immunostaining was found predominantly on stromal smooth muscle and also on vascular smooth muscle of prostatic blood vessels. Ang II immunoreactivity was markedly increased in hyperplastic acini in BPH compared with acini in the normal prostate (normal: 7.4+/-0.2%, n=5 vs. BPH: 22.7+/-1.9%, n=5, p<0.001). However, AT(1) receptor immunoreactivity was significantly decreased in BPH compared with the normal prostate [normal: 16.4+/-2.2%, n=4 vs. BPH: 9.4+/-1.3%, n=5, p<0.05 (p=0.025)]. The present study demonstrates the presence of Ang II peptide in the basal layer of the epithelium and AT(1) receptors on stromal smooth muscle, suggesting that Ang II may mediate paracrine functions on cellular growth and smooth muscle tone in the human prostate. Furthermore, AT(1) receptor down-regulation in BPH may be due to receptor hyperstimulation by increased local levels of Ang II in BPH. These data extend previous findings in support of the novel concept that overactivity of the renin-angiotensin system (RAS) may be involved in the pathophysiology of BPH.

Abstract-The aim of this study was to explore the regulation of angiotensin receptors after chronic infusion with angiotensin II (Ang II) and to clarify the relative roles of the angiotensin type 1 (AT 1 ) and type 2 (AT 2 ) receptors in the mediation of Ang II-induced mesenteric vascular hypertrophy. In male Sprague-Dawley rats, Ang II infusion at a dose of 58.3 ng/min by subcutaneous osmotic minipumps for 14 days led to increased mesenteric weight and wall:lumen ratio of the vessels and proliferation of smooth muscle cells. Key Words: angiotensin II Ⅲ receptors, angiotensin Ⅲ vascular proliferation Ⅲ proliferating cell nuclear antigen T he function of angiotensin receptors in vascular proliferation and hypertrophy has been an area of ongoing debate. 1 Contradictory functions of angiotensin type 1 (AT 1 ) and type 2 (AT 2 ) receptors have been documented by several investigators both in vivo and in vitro. Angiotensin II (Ang II) may play a dual role in cultured smooth muscle and endothelial cells, 2 with the growth promoting effects of Ang II mediated by the AT 1 receptor, whereas the antiproliferative effects of Ang II occur via the AT 2 receptor. 3-5 However, several recent studies have suggested that the AT 2 receptor may act in a different manner in certain contexts. For example, Ang II-induced increase in RNA synthesis in cultured A10 smooth muscle cells, a cell line without AT 1 receptors, could be blocked by PD123319, an AT 2 receptor antagonist, but not by losartan, an AT 1 receptor antagonist, which suggests a potential trophic action of the AT 2 receptor on smooth muscle cell growth. 6 In vivo, the AT 2 receptor antagonist CGP 42112A, has been reported to be more effective at the prevention of neointima formation in an injured carotid artery model than the AT 1 receptor antagonist losartan. 7 This finding was interpreted as an indicator that the AT 2 receptor plays a predominant role in neointima formation after vascular injury. 7 However, with a transgenic technique, overexpression of the AT 2 receptor attenuates neointimal formation after balloon injury in the rat carotid artery. 8In the rat administered Ang II chronically, the relative roles of the AT 1 and AT 2 receptor in the mediation of vascular hypertrophy have been explored by several groups. Ang II-induced aortic hypertrophy and fibrosis was prevented by the AT 2 receptor antagonist PD123319 but not by the AT 1 receptor antagonist valsartan. 9 However, the opposite results have been reported by another group. 10 The difference in results between these studies is unexplained. In none of these chronic Ang II infusion studies was regulation of angiotensin receptors and in particular the AT 2 receptor explored. Therefore, the aim of the present study was to assess the regulation of angiotensin receptors after chronic infusion of Ang II alone or with either an AT 1 or AT 2 receptor antagonist. In addition, the effects of these angiotensin receptor antagonists on Ang II-associated mesenteric vascular proliferation and hypertrophy were directly eva...

Angiotensin converting enzyme (ACE) 2 activity and angiotensin-(1-7) [Ang-(1-7)] levels are increased in experimental cirrhosis; however, the pathways of hepatic Ang-(1-7) production have not been studied. This study investigated the role of ACE2, ACE, and neutral endopeptidase (NEP) in the hepatic formation of Ang-(1-7) from angiotensin I (Ang I) and Ang II and their effects on portal resistance. Ang I or Ang II were administered to rat bile duct ligated (BDL) and control livers alone and in combination with the ACE inhibitor lisinopril, the ACE and NEP inhibitor omapatrilat, or the ACE2 inhibitor MLN4760 (n = 5 per group). BDL markedly upregulated ACE, ACE2, and NEP. Ang-(1-7) was produced from Ang II in healthy and in BDL livers and was increased following ACE inhibition and decreased by ACE2 inhibition. In contrast, Ang-(1-7) production from Ang I was minimal and not affected by ACE or NEP inhibition. Surprisingly, ACE2 inhibition in BDLs dramatically increased Ang-(1-7) production from Ang I, an effect abolished by ACE2/NEP inhibition. Ang II and Ang I induced greater portal pressure increases in BDL livers than controls. The effects of Ang I were closely correlated with Ang II production and were strongly attenuated by both ACE and ACE/NEP inhibition. These findings show that the major substrate for hepatic production of Ang-(1-7) is Ang II and this is catalyzed by ACE2. Ang I is largely converted to Ang II by ACE, and net conversion of Ang I to Ang-(1-7) is small. NEP has the ability to generate large amounts of Ang-(1-7) in the BDL liver from Ang I only when ACE2 activity is greatly decreased or inhibited.