Overexpression Of Angiotensinogen Research Articles

Angiotensinogen - A Potential Diagnostic and Prognostic Candidate Gene  for Adenocarcinomas of Rectum and Stomach

<p>The Angiotensinogen (AGT) gene encodes for angiotensinogen protein that mainly regulates blood pressure and maintains the fluid and salt balance in the body. AGT expression variations have been documented earlier in only a few subtypes of human cancers, the multi-omics profiling of AGT as a shared biomarker in different other subtypes of human cancers remains to be uncovered. In the current study, AGT multi-omics analysis in 24 major subtypes of human cancer were performed using different authentic online databases and bioinformatics analysis including UALCAN, Kaplan Meier (KM) plotter, Human protein Atlas (HPA), GENT2, MEXPRESS, cBioportal, STRING, DAVID, TIMER., and CTD database. AGT is found commonly up-regulated in most human cancers. Overexpression of AGT is significantly correlated with the poor overall survival (OS) of only rectum adenocarcinoma (READ) and Stomach Adenocarcinoma (STAD). This implies that AGT plays a significant role in the development and progression of these cancers. We further noticed that AGT is also overexpressed in READ and STAD patients of different clinicopathological features. Pathways enrichment analysis revealed that AGT is involved in various diverse pathways. While, a few interesting correlations were also documented between AGT expression and its promoter methylation level, CD8+ T immune cells level, and CNVs. Moreover, we also predicted a few drugs through gene-drug interaction analysis that could be used in the treatment of READ and STAD by regulating the AGT expression. Our findings suggest that AGT alone might be helpful in predicting the diagnosis and prognosis of READ and STAD patients commonly.</p>

Role of microRNA 690 in Mediating Angiotensin II Effects on Inflammation and Endoplasmic Reticulum Stress.

Overactivation of the renin–angiotensin system (RAS) during obesity disrupts adipocyte metabolic homeostasis and induces endoplasmic reticulum (ER) stress and inflammation; however, underlying mechanisms are not well known. We propose that overexpression of angiotensinogen (Agt), the precursor protein of RAS in adipose tissue or treatment of adipocytes with Angiotensin II (Ang II), RAS bioactive hormone, alters specific microRNAs (miRNA), that target ER stress and inflammation leading to adipocyte dysfunction. Epididymal white adipose tissue (WAT) from B6 wild type (Wt) and transgenic male mice overexpressing Agt (Agt-Tg) in adipose tissue and adipocytes treated with Ang II were used. Small RNA sequencing and microarray in WAT identified differentially expressed miRNAs and genes, out of which miR-690 and mitogen-activated protein kinase kinase 3 (MAP2K3) were validated as significantly up- and down-regulated, respectively, in Agt-Tg, and in Ang II-treated adipocytes compared to respective controls. Additionally, the direct regulatory role of miR-690 on MAP2K3 was confirmed using mimic, inhibitors and dual-luciferase reporter assay. Downstream protein targets of MAP2K3 which include p38, NF-κB, IL-6 and CHOP were all reduced. These results indicate a critical post-transcriptional role for miR-690 in inflammation and ER stress. In conclusion, miR-690 plays a protective function and could be a useful target to reduce obesity.

Comparison of adipose tissue derived genes in endogenous Cushing's syndrome versus diet-induced obesity.

Dysregulation of adipokine secretion and action is a characteristic feature of obesity and a key clinical feature of Cushing's syndrome (CS). We have investigated whether endogenous glucocorticoid excess influences adipose tissue-derived gene expression. mRNA expression of adipokines; adiponectin, resistin, tumour necrosis factor-a, interleukin-6 (IL-6), angiotensinogen (AGT), plasminogen activator inhibitor type 1, retinol binding protein 4, visfatin, and cystatin C was assessed by quantitative real-time RT-PCR in visceral adipose tissue removed during abdominal surgery of eight patients with CS, and six control patients. We did not find any significant difference in the investigated genes; however, the almost significant overexpression of AGT and underexpression of IL-6 might be noteworthy (p = 0.06 in both cases). No significant differences were found in the expression of the investigated genes known as cardiometabolic risk factors. This indicates that there are no major differences between endogenous hypercortisolism or diet-induced obesity regarding the expression of adipokines involved in cardiometabolic disorders. However, the difference in AGT and IL-6 expression might be included in pathways affecting fat distribution in CS.

Local activation of the pulmonary extravascular angiotensin system induces epithelial apoptosis and lung fibrosis.

Previous work suggests that a local extravascular angiotensin system plays an important role in the development of pulmonary fibrosis through stimulation of alveolar epithelial cell (AEC) apoptosis and collagen deposition. To demonstrate a causative role for the local tissue angiotensin (ANG) system in lung fibrosis, we hypothesize that overexpression of the angiotensinogen (AGT) gene or pharmacologic elevation of lung tissue ANG II levels might cause apoptosis of AECs and lung fibrosis. ANGII levels were elevated in rat or mouse lung tissue by intratracheal instillation of either purified ANGII or an adenovirus expressing AGT, or by ubiquitous overexpression of AGT in transgenic mice. Intratracheal instillation of purified ANGII caused significant collagen accumulation in lung tissue, both ex vivo and in vivo. Ubiquitous overexpression of AGT enhanced the profibrotic effect of bleomycin given at suboptimal doses. Intratracheal delivery of an adenoviral vector expressing mouse AGT (Ad-AGT) overexpressed AGT primarily in AECs and caused both apoptosis of AECs and pulmonary fibrosis. The lung collagen accumulation and AEC apoptosis caused by Ad-AGT was blocked by the caspase inhibitor ZVAD-fmk, by the ANG receptor AT1 antagonist Losartan or by the non-selective ANGII receptor antagonist Saralasin. Together, these data support the hypothesis that elevated pulmonary expression of AGT and its conversion to angiotensin II plays a causative role in the development of lung fibrosis through its induction of AEC apoptosis.

Overexpression of AGT promotes bronchopulmonary dysplasis via the JAK/STAT signal pathway.

Angiotensinogen (AGT) is involved in the production of angiotensin II which is the main mediator of action of the rennin-angiotensin system (RAS), whereas the RAS mediates the regulation of sodium homeostasis, blood pressure, and inflammation. The present study aimed to investigate the roles of the AGT in the progression of broncopulmonary dysplasia in premature newborns. By bioinformatics analysis, AGT was found to be the major node in molecular interaction networks of BPD mouse model. Quantitative PCR and western blot analyses were applied to examine AGT expression in A549 cells which were treated with the hyperoxic condition. The AGT inhibitor Valsartan and the AGT agonist ANGII were employed to investigate the roles of AGT in cell growth and the inflammation. Results show that hyperoxic treatment induced upregulation of AGT expression in A549 cells. Overexpression of AGT resulted in the inflammation via the JAK/STAT signal pathway, ultimately suppressed the proliferation of the A549 cell. In conclusion, increased expression of AGT was demonstrated to be associated with the development and progression of BPD, and may be regarded as a promising therapeutic target for BPD.

Abstract 042: Selective Maternal Hepatic Silencing of Angiotensinogen in Reduced Uterine Placental Perfusion Pressure Rats Improves Blood Pressure and Fetal Weights

Women with Preeclampsia (PE), a form of new onset hypertension during pregnancy, exhibit alterations in the renin angiotension system (RAS). These differences include angiotensin II type 1 receptor agonistic autoantibodies (AT1-AA), ANG II sensitivity, and increased oxidation and levels of angiotensinogen (AGT). While antihypertensive drugs are used in pregnancy, their use is associated with reduced fetal growth, and RAS blockade is specifically contraindicated due to fetotoxicity. AGT is the precursor to ANG II and the initial substrate of the RAS pathway. Genetic mutations that result in an over-expression of AGT are strongly associated with hypertension. We have previously shown that siRNA targeting maternal hepatic AGT in a transgenic model of preeclampsia (hAGT x hREN) resulted in lower blood pressure, a 90% reduction in AT1-AA activity, and normalized IUGR. The purpose of the present study is to examine the effect of silencing maternal hepatic AGT on maternal blood pressure and fetal growth in the reduced uterine placental perfusion pressure (RUPP) model of PE. Methods: Pregnant Sprague Dawley rats were divided into 4 groups: normal pregnant (NP, n=7); RUPP (n= 6); RUPP + siRNA (n =7); NP + siRNA (n=7). On day 12 of gestation (GD), siRNA was subcutaneously injected into rats (10mg/kg), GD14 the RUPP surgery was performed, GD18 carotid catheters inserted, and GD19 conscious blood pressure (MAP) and fetal weight was recorded. Results: MAP was elevated in RUPP vs. NP (134±6 vs. 101±4 mmHg, p< 0.05), but was lower in RUPP + siRNA (117±4 mmHg) and unchanged in the NP+siRNA (92±3 mmHg) group compared to NP. Average fetal weights by group were 2.30±0.09 g (NP), 1.89±0.10 g (RUPP), 2.38±0.09 g (NP+siRNA), and 2.12±0.06 (RUPP+siRNA). A one-way ANOVA indicates a significant reduction in pup weights between NP and RUPP, but not NP+siRNA and RUPP+siRNA, indicating administration of siRNA to RUPP rats prevented the decrease in fetal weight. Conclusion: Administration of AGT siRNA to RUPP rats blunts the increase in blood pressure and prevents a decrease in fetal weights in response to placental ischemia and thus could be a potential therapy for management of preeclampsia and other hypertensive disorders of pregnancy. Research Supported by Alnylam & T32HL105324,

Possible role for nephron-derived angiotensinogen in angiotensin-II dependent hypertension.

The role of intranephron angiotensinogen (AGT) in blood pressure (BP) regulation is not fully understood. Previous studies showed that proximal tubule-specific overexpression of AGT increases BP, whereas proximal tubule-specific deletion of AGT did not alter BP. The latter study may not have completely eliminated nephron AGT production; in addition, BP was only assessed on a normal salt diet. To evaluate this issue in greater detail, we developed mice with inducible nephron-wide AGT deletion. Mice were generated which were hemizygous for the Pax8-rtTA and LC-1 transgenes and homozygous for loxP-flanked AGT alleles to achieve nephron-wide AGT disruption after doxycycline induction. Compared to controls, AGT knockout (KO) mice demonstrated markedly reduced renal AGT immunostaining, mRNA, and protein levels; unexpectedly AGT KO mice had reduced AGT mRNA levels in the liver along with 50% reduction in plasma AGT levels. BP was significantly lower in the AGT KO mice compared to controls fed a normal, low, or high Na(+) intake, with the highest BP reduction on a low Na(+) diet. Regardless of Na(+) intake, AGT KO mice had higher plasma renin concentration (PRC) and markedly reduced urinary AGT levels compared to controls. Following angiotensin-II (Ang-II) infusion, AGT KO mice demonstrated an attenuated hypertensive response despite similar suppression of PRC in the two groups. Taken together, these data suggest that nephron-derived AGT may be involved in Ang-II-dependent hypertension, however, a clear role for nephron-derived AGT in physiological BP regulation remains to be determined.

InactivationofAdiposeAngiotensinogen Reduces inflammatory Adipokines and Adipose Tissue Macrophages

Adiposerennin-angiotensin systemhasbeen linked to obesity and metabolic syndrome. Previously we showed that overexpression of Angiotensinogen(Agt) in adipose tissue increased insulin resistance, adipose and systemic inflammation in mice fed a low fat(LF)diet. To further dissect the direct role of adipose Agt in metabolic disorders,we have created an adipose specific Agt knockout (Agt-KO)mice using the Cre-LoxPsystem.Agt-KO and control(WT) littermates were fed either a low-fat (LF) or high-fat (HF) diet to assess metabolic changes. Surprisingly, most metabolic parameters (body weight and fat mass, glucose and insulin tolerance tests) were comparable between the WT and Agt-KO littermates in both diets. Analyses of adipose tissue gene expression indicated shifts in angiogenesis and insulin signaling in the Agt-KO mice fed LF diets when compared to the WT mice. MCP1 gene expression was also downregulated in adipose tissue of the Agt-KO vs. WT littermates. These changes correlated with MCP-1 and Leptin protein expression, both of which were downregulated in the Agt-KO. Moreover,targeted inactivation of adipose Agt reduced total macrophage infiltration in both the LF and HF fed Agt-KO mice. This was in contrast to the total adipocyte area,which did not change between the two genotypes. In conclusion, despite the lack of an obvious phenotype in adipose Agt deficient mice, cellular and molecular changes observed are consistent with previously reported functions of RAS in insulin resistance, and inflammation.

Abstract 308: Nephron Specific Deletion Of Angiotensinogen Modulates Blood Pressure

It is unknown if intrarenal generation of angiotensinogen (AGT) is important in blood pressure (BP) regulation. Previous studies showed that proximal tubule-specific overexpression of AGT increases BP, while proximal tubule-specific deletion of AGT using the KAP promoter-Cre transgene did not alter BP. The latter study may not have completely eliminated nephron AGT production; in addition, BP was only assessed on a normal salt diet. To evaluate this issue in greater detail, we developed mice with inducible nephron-wide AGT deletion. Mice were generated which were hemizygous for the Pax8-rtTA and LC-1 transgenes and homozygous for loxP flanked AGT alleles to achieve nephron-specific AGT disruption after doxycycline induction. Adult Pax8-rtTA/LC-1/floxed AGT mice at 3 months of age were treated with doxycycline 2 mg/ml in drinking water for 11 days and studied 4 weeks after treatment. Blood pressure (recorded via telemetry) and metabolic balance studies were determined during 5 days of normal, high and low Na diets. Compared to controls, AGT knockout (KO) mice demonstrated significantly lower systolic, diastolic, and mean BPs on all three diets (N=4 each group). The BP reduction was most evident on a low Na diet (mean BP 107 ± 2 mmHg in controls and 88 ± 13 mmHg in AGT KO). Plasma renin concentration was higher in the AGT KO mice as compared to controls on all three diets. There were no detectable differences in weight, urine volume, urine osmolality or urine Na excretion between the controls and KO mice on all three diets, however due to variability, small differences in these parameters may not have been detected. Taken together, these data suggest that nephron AGT may contribute to BP regulation and this is most evident during low Na intake.

Abstract 233: Evidence for an Interaction Between Systemic and Renal Angiotensinogen in the Control of Arterial Pressure

Both the liver and proximal tubule make angiotensinogen (AGT), and overexpression of AGT in either region increases blood pressure (BP). To determine the relative contributions of renal and systemic AGT in modulating BP, mice were used with AGT overexpression in kidney (K), liver (L) or both sites (KL). Male transgenic and wildtype (WT) controls aged 24 weeks underwent BP recording via telemetry and metabolic cage studies on normal (0.25%) and high (3.2%) sodium diets. Mean BP (MAP) was higher in K and KL vs L and WT mice fed normal salt, while MAP in L mice was higher than controls. High salt intake did not alter MAP in WT, K or KL mice but increased it in L mice. Plasma AGT levels, plasma renin concentration, urine Na excretion and urine volume were similar between groups regardless of sodium intake. Urinary AGT (ng/day) on normal sodium intake was: WT: 5±1, L: 4±1, K: 20±5 and KL: 34±9. High salt increased urine AGT in all groups (WT: 19±4, L: 42±8, K: 290±75, KL: 407± 72). High salt did not alter plasma AGT levels but reduced plasma renin concentration in all groups. Taken together, these data show a correlation between urinary AGT and BP. Mice with renal AGT overexpression may be maximally hypertensive on a normal sodium diet since renal AGT is already high. Mice with liver AGT overexpression have mild hypertension on a normal sodium diet that is exacerbated by high sodium intake; this is associated with a significant increase in urinary AGT as compared to WT animals. Thus, systemic AGT may have the potential to regulate renal AGT and this effect may be a key determinant of BP.

Differential effects of high-fat diet on myocardial lipid metabolism in failing and nonfailing hearts with angiotensin II-mediated cardiac remodeling in mice

Normal myocardium adapts to increase of nutritional fatty acid supply by upregulation of regulatory proteins of the fatty acid oxidation pathway. Because advanced heart failure is associated with reduction of regulatory proteins of fatty acid oxidation, we hypothesized that failing myocardium may not be able to adapt to increased fatty acid intake and therefore undergo lipid accumulation, potentially aggravating myocardial dysfunction. We determined the effect of high-fat diet in transgenic mice with overexpression of angiotensinogen in the myocardium (TG1306/R1). TG1306/R1 mice develop ANG II-mediated left ventricular hypertrophy, and at one year of age approximately half of the mice present heart failure associated with reduced expression of regulatory proteins of fatty acid oxidation and reduced palmitate oxidation during ex vivo working heart perfusion. Hypertrophied hearts from TG1306/R1 mice without heart failure adapted to high-fat feeding, similarly to hearts from wild-type mice, with upregulation of regulatory proteins of fatty acid oxidation and enhancement of palmitate oxidation. There was no myocardial lipid accumulation or contractile dysfunction. In contrast, hearts from TG1306/R1 mice presenting heart failure were unable to respond to high-fat feeding by upregulation of fatty acid oxidation proteins and enhancement of palmitate oxidation. This resulted in accumulation of triglycerides and ceramide in the myocardium, and aggravation of contractile dysfunction. In conclusion, hearts with ANG II-induced contractile failure have lost the ability to enhance fatty acid oxidation in response to increased fatty acid supply. The ensuing accumulation of lipid compounds may play a role in the observed aggravation of contractile dysfunction.

Overproduction of Angiotensinogen from Adipose Tissue Induces Adipose Inflammation, Glucose Intolerance, and Insulin Resistance

Although obesity is associated with overactivation of the white adipose tissue (WAT) renin-angiotensin system (RAS), a causal link between the latter and systemic insulin resistance is not established. We tested the hypothesis that overexpression of angiotensinogen (Agt) from WAT causes systemic insulin resistance via modulation of adipose inflammation. Glucose tolerance, systemic insulin sensitivity, and WAT inflammatory markers were analyzed in mice overexpressing Agt in the WAT (aP2-Agt mice). Proteomic studies and in vitro studies using 3T3-L1 adipocytes were performed to build a mechanistic framework. Male aP2-Agt mice exhibited glucose intolerance, insulin resistance, and lower insulin-stimulated glucose uptake by the skeletal muscle. The difference in glucose tolerance between genotypes was normalized by high-fat (HF) feeding, and was significantly improved by treatment with angiotensin-converting enzyme (ACE) inhibitor captopril. aP2-Agt mice also had higher monocyte chemotactic protein-1 (MCP-1) and lower interleukin-10 (IL-10) in the WAT, indicating adipose inflammation. Proteomic studies in WAT showed that they also had higher monoglyceride lipase (MGL) and glycerol-3-phosphate dehydrogenase levels. Treatment with angiotensin II (Ang II) increased MCP-1 and resistin secretion from adipocytes, which was prevented by cotreating with inhibitors of the nuclear factor-κB (NF-κB) pathway or nicotinamide adenine dinucleotide phosphate (NADPH) oxidase. In conclusion, we show for the first time that adipose RAS overactivation causes glucose intolerance and systemic insulin resistance. The mechanisms appear to be via reduced skeletal muscle glucose uptake, at least in part due to Ang II-induced, NADPH oxidase and NFκB-dependent increases in WAT inflammation.

Adipocyte-specific deficiency of angiotensinogen decreases plasma angiotensinogen concentration and systolic blood pressure in mice

Previous studies demonstrated that overexpression of angiotensinogen (AGT) in adipose tissue increased blood pressure. However, the contribution of endogenous AGT in adipocytes to the systemic renin-angiotensin system (RAS) and blood pressure control is undefined. To define a role of adipocyte-derived AGT, mice with loxP sites flanking exon 2 of the AGT gene (Agt(fl/fl)) were bred to transgenic mice expressing Cre recombinase under the control of an adipocyte fatty acid-binding protein 4 promoter (aP2) promoter to generate mice with adipocyte AGT deficiency (Agt(aP2)). AGT mRNA abundance in adipose tissue and AGT secretion from adipocytes were reduced markedly in adipose tissues of Agt(aP2) mice. To determine the contribution of adipocyte-derived AGT to the systemic RAS and blood pressure control, mice were fed normal laboratory diet for 2 or 12 mo. In males and females of each genotype, body weight and fat mass increased with age. However, there was no effect of adipocyte AGT deficiency on body weight, fat mass, or adipocyte size. At 2 and 12 mo of age, mice with deficiency of AGT in adipocytes had reduced plasma concentrations of AGT (by 24-28%) compared with controls. Moreover, mice lacking AGT in adipocytes exhibited reduced systolic blood pressures compared with controls (Agt(fl/fl), 117 ± 2; Agt(aP2), 110 ± 2 mmHg; P < 0.05). These results demonstrate that adipocyte-derived AGT contributes to the systemic RAS and blood pressure control.

Tumor necrosis factor-α: a reno-protective cytokine? Focus on “Tumor necrosis factor-α suppresses angiotensinogen expression through formation of a p50/p50 homodimer in human renal proximal tubular cells”

<i>Tumor necrosis factor-α: a reno-protective cytokine?</i> Focus on “Tumor necrosis factor-α suppresses angiotensinogen expression through formation of a p50/p50 homodimer in human renal proximal tubular cells”

Angiotensin II downregulates the fatty acid oxidation pathway in adult rat cardiomyocytes via release of tumour necrosis factor-α

Advanced heart failure is often associated with reduced myocardial fatty acid oxidation capacity. We have previously observed that failing hearts of mice with overexpression of angiotensinogen in the myocardium exhibit marked reduction of key regulatory proteins of fatty acid oxidation. In the present study, we determined whether exposure of adult rat cardiac (ARC) myocytes to angiotensin II (Ang II) influences expression of fatty acid translocase, muscle-type carnitine palmitoyl transferase-I, and medium-chain acyl-CoA dehydrogenase. Ang II reduced mRNA expression of the three regulatory proteins in ARC myocytes during the entire 14-days culture period. However, protein expression and palmitate oxidation rate remained unaltered for 7 days, but subsequently markedly decreased. The decrease of protein expression and of fatty acid oxidation coincided with the onset of increased protein expression of tumour necrosis factor-alpha (TNF-alpha). The effect of Ang II was completely abolished by either blocking TNF-alpha formation through inhibition of reactive oxygen species-mediated activation of nuclear factor-kappaB or by neutralizing TNF-alpha with a specific antibody. Activation of peroxisome proliferator-activated receptor-alpha (PPARalpha) and PPARbeta/delta counteracted Ang II-mediated reduction of the fatty acid oxidation pathway. Prolonged exposure of cardiac myocytes to Ang II elicits downregulation of the fatty acid oxidation pathway mediated by enhanced synthesis of TNF-alpha.

Deficiency of Angiotensin Type 2 Receptor Rescues Obesity But Not Hypertension Induced by Overexpression of Angiotensinogen in Adipose Tissue

Increased angiotensinogen (AGT) production by white adipose tissue has been related to not only obesity but also hypertension. Several studies have highlighted the importance of the angiotensin II type 2 receptor (AT2) in the regulation of blood pressure and fat mass, but the relevance of this transporter in a physiopathological model of increased AGT production, as it occurs in obesity, has not yet been investigated. We used transgenic mice that display either a deletion of AT2 (AT2 KO), an overexpression of AGT (OVEX), or both compound mutants (KOVEX). Results demonstrated that adipocyte hypertrophy and increased lipogenic gene expression induced by adipose AGT overproduction was rescued by deletion of AT2. In line with AGT overexpression, KOVEX and OVEX mice have similar increased plasma AGT levels. However, KOVEX mice display a higher blood pressure than OVEX mice. In kidney, renin expression was clearly reduced in OVEX mice, and its expression was normalized in KOVEX mice. Taken together, we demonstrated that the loss of AT2 expression was sufficient to rescue obesity induced by adipose tissue AGT overexpression and confirmed the necessary role of AT2 for the onset of obesity in this model. Furthermore, despite a reduction of adipose mass in KOVEX, AT2 deficiency caused increased renin production, further worsening the hypertension caused by AGT overexpression.

Overexpression of angiotensinogen and AT1 receptors amplified by insulin in vascular smooth muscle cells of diabetic type 2 subjects

Foudi, Nabil; Legedz, Liliana; Hodroj, Wassim; Randon, Jacques; Feugier, Patrick; Bricca, Giampiero Author Information

Mechanisms Mediating the Renal Profibrotic Actions of Vasoactive Peptides in Transgenic Mice

Abstract. Transgenic mice are useful tools to investigate the mechanisms of the renal profibrotic actions of endothelin and angiotensin II. The overexpression of angiotensinogen and renin genes induces renal sclerosis independently of changes in systemic hemodynamics. The same results are observed when the endothelin-1 gene is overexpressed. Transgenic mice harboring the luciferase gene, under the control of the collagen I α2 chain promoter, and made hypertensive by induction of a nitric oxide (NO) deficiency have been studied. In this strain of mice, luciferase activity is an early index of renal and vascular fibrosis. Luciferase activity was increased in preglomerular arterioles and glomeruli when mice were treated with Nω-nitro-L-arginine methyl ester, an inhibitor of NO synthases. Bosentan (an endothelin receptor antagonist) was as efficient as losartan (an AT1 receptor antagonist) in preventing renal fibrosis, although it did not decrease BP. In short-term experiments, angiotensin II produced an increase in luciferase activity that was entirely prevented by losartan but also by bosentan. It can be concluded that, during chronic inhibition of NO, the collagen I gene is activated, which contributes to the development of nephroangiosclerosis and glomerulosclerosis. Angiotensin II plays a major role in this fibrogenic process, and its effect is at least partly independent of systemic hemodynamics and mediated by the profibrotic action of endothelin-1.