The effects of losartan or angiotensin II receptor antagonists on cartilage: a systematic review

OBJECTIVE

The aim of this study is to analyze the latest evidence on the effects of losartan or Ang II receptor antagonists on cartilage repair, with a focus on their clinical relevance.

DESIGN

The PubMed, Embase, and Cochrane Library databases were searched up to November 12th 2021 to evaluate the effects of losartan or Ang II receptor antagonists on cartilage repair in in vitro studies and in vivo animal studies. Study design, sample characteristics, treatment type, duration, and outcomes were analyzed. The risk of bias and the quality of the eligible studies were assessed using the Systematic Review Centre for Laboratory Animal Experimentation (SYRCLE) risk of bias assessment tool and Collaborative Approach to Meta-Analysis and Review of Animal Data from Experimental Studies (CAMARADES).

RESULTS

A total of 12 studies were included in this systematic review. Of the 12 eligible studies, two studies were in vitro human studies, three studies were in vitro animal studies, one study was an in vitro human and animal study, and six studies were in vivo animal studies. The risk bias and quality assessments were predominantly classified as moderate. Since meta-analysis was difficult due to differences in treatment type, dosage, route of administration, and method of outcome assessment among the eligible studies, qualitative evaluation was conducted for each study.

CONCLUSIONS

Both in vitro and in vivo studies provide evidence to demonstrate beneficial effects of Ang II receptor antagonists on osteoarthritis and cartilage defect models across animal species.

Synthesis, Characterization and Application of a MIP-polyHIPE for Selective Extraction of Angiotensin II Receptor Antagonists Residues in Natural Waters

Polymers via high internal phase emulsion (polyHIPEs) were molecularly imprinted with Irbesartan, an antihypertensive drug belonging to the class of angiotensin II receptor antagonists (sartan drugs), chosen for the proof-of-concept extraction of hazardous emerging contaminants from water. Different analyte-functional monomer molar ratios (1:100, 1:30 and 1:15) were investigated, and the MIP polyHIPEs have been characterized, parallel to the not imprinted polymer (NIP), by batch sorption experiments. The material with the highest template-functional monomer ratio was the best for Irbesartan removal, showing a sorption capacity fivefold higher than the NIP. Regarding the adsorption kinetics, the analyte-sorbent equilibrium was reached after about 3 h, and the film diffusion model best fitted the kinetic profile. Selectivity was further demonstrated by testing Losartan, another sartan drug, observing a fourfold lower sorption capacity, but still higher than that of NIP. The polymers were also synthesized in cartridges for solid-phase extraction (SPE), which was helpful for evaluating the breakthrough curves and performing pre-concentrations. These have been done in tap and river water samples (100-250 mL, 15-500 µg L^-1 Irbesartan), obtaining quantitative sorption/desorption on the MIP-polyHIPE (RSD < 14%, n = 3). The NIP provided a recovery of just around 30%, evidence of partial uptake of the target from water.

Renin-angiotensin-aldosterone system inhibitors and SARS-CoV-2 infection: an analysis from the veteran's affairs healthcare system

BACKGROUND

Angiotensin-converting enzyme inhibitors (ACEI) and angiotensin receptor blockers (ARB) are known to impact the functional receptor for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The association between chronic therapy with these medications and infection risk remains unclear.

OBJECTIVES

The objective was to determine the association between prior ACEI or ARB therapy and SARS-CoV-2 infection among patients with hypertension in the U.S. Veteran's Affairs health system.

METHODS

We compared the odds of SARS-CoV-2 infection among three groups: patients treated with ACEI, treated with ARB, or treated with alternate first-line anti-hypertensives without ACEI/ARB. We excluded patients with alternate indications for ACEI or ARB therapy. We performed an augmented inverse propensity weighted analysis with adjustment for demographics, region, comorbidities, vitals, and laboratory values.

RESULTS

Among 1,724,723 patients with treated hypertension, 659,180 were treated with ACEI, 310,651 with ARB, and 754,892 with neither. Before weighting, patients treated with ACEI or ARB were more likely to be diabetic and use more anti-hypertensives. There were 13,278 SARS-CoV-2 infections (0.8%) between February 12, 2020 and August 19, 2020. Patients treated with ACEI had lower odds of SARS-CoV-2 infection (odds ratio [OR] 0.93; 95% CI: 0.89-0.97) while those treated with ARB had similar odds (OR 1.02; 95% CI: 0.96-1.07) compared with patients treated with alternate first-line anti-hypertensives without ACEI/ARB. In falsification analyses, patients on ACEI did not have a difference in their odds of unrelated outcomes.

CONCLUSIONS

Our results suggest the safety of continuing ACEI and ARB therapy. The association between ACEI therapy and lower odds of SARS-CoV-2 infection requires further investigation.

Blockade of bradykinin receptors or angiotensin II type 2 receptor prevents paclitaxel-associated acute pain syndrome in mice

BACKGROUND

Paclitaxel (PCX) is the first-line choice for the treatment of several types of cancer, including breast, ovarian, and lung cancers. However, patients who receive even a single dose with PCX commonly develop mechanical and cold allodynia, a symptom known as PCX-associated acute pain syndrome (P-APS). Here, we assessed possible involvement of kinin-kallikrein and renin-angiotensin systems in P-APS in mice.

METHODS

Male mice C57Bl/6 wild type (WT) and knockouts for bradykinin receptors, B1 (B1^-/- ) and B2 (B2^-/- ), were used. Mechanical and cold allodynia were evaluated by using von Frey filaments and acetone test, respectively. P-APS was induced by administration of PCX 4 mg/kg, i.v.. ACE inhibitors (captopril and enalapril), antagonists for angiotensin II type 1 (losartan) and type 2 ([AT2R]; PD123319 and EMA 401) receptors were administrated prior the treatment with PCX. RT-PCR was used to analyse the expression of mRNA for B1, B2 and AT2R receptors.

RESULTS

Administration of PCX in B1^-/- and B2^-/- mice induced lower mechanical and cold allodynia compared to the WT. However, the pre-treatment with ACE inhibitors reduced the development of mechanical and cold allodynia in P-APS. Surprisingly, we found that mice pre-treatment with the PD123319 or EMA401, but not losartan, prevented the development of mechanical and cold allodynia induced by PCX.

CONCLUSION

Our results demonstrated the involvement of bradykinin receptors B1 and B2 as well as AT2R in the induction of P-APS in mice, and suggest the use of AT2R antagonists as a potential therapy for the prevention of P-APS in humans.

SIGNIFICANCE

Kinin-kallikrein and renin-angiotensin systems, through B1, B2 and AT2 receptors, potentiates paclitaxel-associated acute pain syndrome (P-APS) in mice. Antagonists for AT2R are potential alternatives to prevent P-APS.

Biphasic effects of angiotensin II and receptor antagonism on aggregability and protein kinase C phosphorylation in human platelets

In order to define the role of angiotensin II (AngII) receptor subtypes, AT1 and AT2, in platelet activation, we examined the effects of AngII and receptor antagonists on both aggregability and phosphorylation status of protein kinase C (PKC) isoforms in human platelets obtained from 56 healthy volunteers. AngII promoted both spontaneous and agonist (collagen and ADP) stimulated platelet aggregation at concentrations of 10 nM or less, but the promotion effects were lost at 100 nM. Antagonism of AT1 receptor inhibited the promotion effects of AngII at 10 nM or less. On the other hand, antagonism of AT2 receptor enhanced platelet aggregability modestly with AngII at 10 nM or less, and markedly with 100 nM AngII. Furthermore, with 10 nM AngII, phospho-PKCα/βII expression in platelets was increased after collagen stimulation and was inhibited by antagonism of AT1 receptor. With 100 nM AngII, expression levels of phospho-PKCα/ βII remained low even after collagen stimulation but were markedly enhanced by antagonism of AT2 receptor. These findings suggest that at 10 nM or below, AngII promotes aggregability and PKC phosphorylation in human platelets through the AT1 receptor, which can be inhibited by AT1 receptor antagonists, but at higher concentrations, the promotion effects were lost through the opposing action of the AT2 receptor. The present study may provide an additional mechanism for AT1 receptor antagonism, which would provide clinical benefit to patients with stroke or cardiovascular disease accompanied by hypertension.

Chronic Allograft Nephropathy: Pathogenesis and Management of an Important Posttransplant Complication

Chronic allograft nephropathy is a devastating complication of kidney transplantation that is responsible for a significant proportion of graft loss. This complication is characterized by a progressive decline in kidney function, which is not attributable to a specific cause. Many risk factors exist for the development of chronic allograft nephropathy, including donor-, recipient-, and transplant-related factors (eg, use of calcineurin inhibitors and acute rejection episodes), as well as comorbid conditions such as hypertension and hyperlipidemia. There is no definitive treatment for this complication; management has focused on minimization or withdrawal of calcineurin inhibitors in conjunction with addition of sirolimus or mycophenolate mofetil. Alterations in the immunosuppressive regimen must be done cautiously, as precipitating acute rejection will cause further damage to the allograft. Optimal control of blood pressure, particularly with the use of agents such as angiotensin II receptor blockers, in conjunction with management of dyslipidemia may be effective concurrent therapies in patients with chronic allograft nephropathy.

Upregulation of Angiotensin II Type 2 Receptor and Limitation of Myocardial Stunning by Angiotensin II Type 1 Receptor Blockers during Reperfused Myocardial Infarction in the Rat

Background: We have previously shown that angiotensin II type 1 receptor blockers induce cardioprotection and upregulate angiotensin II type 2 receptor during in vivo postischemicreperfusion in dogs. Whether angiotensin II type 1 receptor blockers upregulate angiotensin II type 2 receptors in rats is controversial, and whether surmountable and insurmountable angiotensin II type 1 receptor blockers exert similar protective effects during reperfused myocardial infarction is not known.

Methods: We assessed the effects of the surmountable angiotensin receptor blocker valsartan, and the insurmountable angiotensin receptor blocker irbesartan, on hemodynamics and left ventricular systolic and diastolic function (echocardiography/Doppler) in vivo and infarct size (triphenyl tetrazolium chloride method), and regional angiotensin II type 1 receptor and angiotensin II type 2 receptor expression (immunoblots) ex vivo, after anterior reperfused myocardial infarction in rats. The rats were randomized to four groups: intravenous valsartan (10 mg/kg, n = 8), irbesartan (10 mg/kg, n = 8), or saline vehicle (controls, n = 14) over 30 minutes before reperfused myocardial infarction, and sham (n = 8). Angiotensin II type 1 receptor blockade was assessed by the inhibition of angiotensin II pressor responses.

Results: Compared with the control group, both angiotensin receptor blockers significantly decreased infarct size, limited the increase in left atrial pressure, improved positive left ventricular dP/dtm,x and dP/dtm,,, improved left ventricular ejection fraction and diastolic function, and limited infarct expansion after reperfused myocardial infarction. Both angiotensin receptor blockers increased angiotensin II type 2 receptor protein in the postischemic-reperfused zone, with no change in angiotensin II type 1 receptor protein. There were no changes in the sham group.

Conclusion: The overall results indicate that the angiotensin receptor blockers valsartan and irbesartan both induce cardioprotection, limit myocardial stunning, and upregulate angiotensin II type 2 receptor protein expression after reperfused myocardial infarction in the rat. Patients who are already receiving angiotensin receptor blockers and develop acute coronary syndromes might benefit from these cardioprotective effects during reperfusion therapy.

Multiple cross talk between angiotensin II, bradykinin, and insulin signaling in the cortical thick ascending limb of rat kidney

Cortical thick ascending limb (CTAL) naturally expresses the angiotensin II (AngII) receptor type 1A (AT(1)-R), the bradykinin (BK) receptor type 2 (B(2)-R), and the insulin receptor. This segment is made of a single morphologically distinct cell type. AngII and BK are involved in same transduction pathways but differ markedly in their physiological actions on Na(+) transport. Besides, the insulin signaling intersects with those of AngII and BK at multiple levels and especially by stimulation on Na(+) reabsorption. Thus, the CTAL is a biologically suitable model to study the cross talk between G protein-coupled receptors or G protein-coupled receptors and receptor tyrosine kinase. In this work, the cross talks between AngII, BK, and insulin signaling are studied in rat CTAL by measuring changes in [Ca(2+)](i). We show that BK exerts negative modulatory effects on AngII-induced [Ca(2+)](i) responses dependent on tyrosine kinase and MAPK pathways. Moreover, in the presence of BK, AngII-induced Na(+) transport is suppressed. These effects suggest an interaction between AT(1)-R and B(2)-R. We show a positive interaction between the insulin receptor and the AT(1)-R through a protein kinase A-dependent mechanism that involves MAPK cascade, leading to the stimulation of the Ca(2+) influx induced by AngII. The presence of such interactions brings additional arguments for a complex and fine regulation of CTAL functions and puts forward the potentially beneficial effect of BK across this segment, in case of hyperinsulinemia or insulin resistance, by its negative feedback on AngII actions.

Angiotensin II regulates NOS expression in afferent arterioles of the developing porcine kidney

NO protection is crucial against angiotensin II (ANG II) mediated vasoconstriction in postnatal preglomerular resistance vessels. Although whole kidney NOS is developmentally regulated, NOS regulation in developing renal resistance vessels is unknown. The hypothesis was NOS expression and function in developing afferent arterioles are regulated by ANG II through AT1 and AT2 receptors. Afferent arterioles from porcine kidneys, ages newborn, 7, 21 d, and adult, were dissected using a polybead perfusion technique. Dissected afferent arterioles were treated with ANG II and with either the AT1 receptor inhibitor candesartan or the AT2 receptor inhibitor PD 123319 and evaluated for NOS isoform expression and NOS enzymatic activity. Although NOS activity and neuronal NOS (nNOS) expression were greater in the newborn than in the adult, endothelial NOS (eNOS) expression was greater in the adult. ANG II increased NOS activity and eNOS expression at all ages, but nNOS expression only in developing afferents. AT1 and AT2 receptor blockade significantly attenuated NOS activity and eNOS expression at all ages, but nNOS expression only in developing afferents. ANG II regulates nNOS and eNOS expression and NOS activity in afferent arterioles of the developing kidney via AT1 and AT2 receptors.

The renin-angiotensin system mediates hyperoxia-induced collagen production in human lung fibroblasts

A high concentration of oxygen can cause lung injury and lead to pulmonary fibrosis. Angiotensin (Ang) II induces human lung fibroblast proliferation and stimulates collagen synthesis. However, the role of the renin-angiotensin system (RAS) in the pathogenesis of hyperoxia-induced collagen production is unclear. The aims of this study were to investigate the effects of hyperoxia on the components of the RAS and collagen expression in human lung fibroblasts (MRC-5). Hyperoxia increased total collagen, collagen type I, and alpha-smooth muscle actin (alpha-SMA) mRNA and protein expression. RAS components and Ang II production were also significantly increased after hyperoxic exposure. Hyperoxia induced Ang II type 1 receptor (AT1R) expression but did not alter AT2R expression, furthermore, silencing of AT1R signaling with small interfering RNA suppressed hyperoxia-induced phosphorylated-ERK (p-ERK) 1/2, alpha-SMA, and collagen type I expression. Ang II increased p-ERK 1/2 and collagen type I expression, and these increases were inhibited by the AT1R inhibitor, losartan, but not by the AT2R inhibitor, PD123319 under both normoxic and hyperoxic conditions. These data suggest Ang II-mediated signaling transduction via AT1R is involved in hyperoxia-induced collagen synthesis in human lung fibroblasts.

[The effect of angiotensin II on phosphoinositide-3 kinase/Akt cascade in cultured fibroblasts derived from patients with hypertrophic scars]

OBJECTIVE

To study the effect of angiotensin II on phosphoinositide-3 kinase/Akt cascade in cultured fibroblasts derived from patients with hypertrophic scars.

METHODS

The expression of AT1 and AT2 receptor was detected by immunofluorescence staining. Cultured human skin fibroblasts were treated with Ang II (10(-9) - 10(-7) mol/L), with or without an AT1 receptor blocker, valsartan or an AT2 receptor antagonist, PD123319. The phosphorylation of Akt was detected by western blotting, and PI3K activity was measured by Assay of PI3-K activity.

RESULTS

Immunofluorescence staining showed that cultured fibroblasts derived from hypertrophic scars expressed both AT1 and AT2 receptors. Ang II increased Akt phosphorylation and PI3K activity in cultured hypertrophic scar fibroblasts in a dose- and time-dependent manner. Additionally, Ang II-induced Akt phosphorylation was blocked by wortmannin, a PI3-K inhibitor. This Ang II-activated PI3-K/Akt cascade was significantly inhibited by valsartan, an AT1 receptor specific blocker (P<0.05), whereas enhanced by PD123319, an AT2 receptor antagonist (P<0.05).

CONCLUSION

These results indicate that Ang II receptors regulates PI3-K/Akt cascade of hypertrophic scars fibroblasts via AT1 and AT2.

Acute modulation of myocardial function by angiotensin 1-7

Angiotensin 1-7 is a bioactive heptapeptide of the renin-angiotensin system. Its cardiovascular actions have recently acquired growing relevance, mainly due to its counter-regulatory actions in the angiotensin cascade. The aim of the present study was to evaluate the actions of angiotensin 1-7 on myocardial function. Increasing concentrations of angiotensin 1-7 (10(-9) to 10(-5)M) were added to rabbit right papillary muscles: (1) in baseline conditions with intact endocardial endothelium (EE); (2) after selective removal of the EE with Triton X-100 (1s, 0.01%); (3) with intact EE in the presence of the Mas receptor antagonist A-779, the AT(1) receptor antagonist ZD-7155, the AT(2) receptor antagonist PD-123,319 or the nitric oxide synthesis inhibitor NG-nitro-l-arginine (l-NA). Concerning the effects on contractility, we observed a significant decrease on active tension, dT/dt(max), peak shortening and dL/dt(max) of -10.5+/-3.6%, -8.0+/-3.0%, -5.3+/-2.6% and -5.7+/-2.3%, respectively. There was no change on relaxation parameters, namely dT/dt(min) or dL/dt(min). Time to half relaxation was significantly decreased. The presence of ZD-7155 or PD-123,319 did not change these effects. However, angiotensin 1-7 effects on myocardial properties were abolished after selective EE removal and in the presence of A-779 or l-NA. In conclusion, in this animal species, angiotensin 1-7 through its binding to Mas receptor induces a negative inotropic effect modulated by the EE and nitric oxide and independent of AT(1) or AT(2) receptors activation. As the effects described in the present work were influenced by the endocardial endothelium, they may be disrupted in situations associated to endothelial dysfunction, as in heart failure or myocardial ischemia.

Angiotensin II up-regulates PAX2 oncogene expression and activity in prostate cancer via the angiotensin II type I receptor

BACKGROUND

Paired homeobox 2 gene (PAX2) is a transcriptional regulator, aberrantly expressed in prostate cancer cells and its down-regulation promotes cell death in these cells. The molecular mechanisms of tumor progression by PAX2 over-expression are still unclear. However, it has been reported that angiotensin-II (A-II) induces cell growth in prostate cancer via A-II type 1 receptor (AT1R) and is mediated by the phosphorylation of mitogen activated protein kinase (MAPK) as well as signal transducer and activator of transcription 3 (STAT3).

METHODS

Here we have demonstrated that A-II up-regulates PAX2 expression in prostate epithelial cells and prostate cancer cell lines resulting in increased cell growth. Furthermore, AT1R receptor antagonist losartan was shown to inhibit A-II induced PAX2 expression in prostate cancer. Moreover, analysis using pharmacological inhibitors against MEK1/2, ERK1/2, JAK-II, and phospho-STAT3 demonstrated that AT1R-mediated stimulatory effect of A-II on PAX2 expression was regulated in part by the phosphorylation of ERK1/2, JAK II, and STAT3 pathways. In addition, we have showed that down-regulation of PAX2 by an AT1R antagonist as well as JAK-II and STAT3 inhibitors suppress prostate cancer cell growth.

RESULTS

Collectively, these findings show for the first time that the renin-angiotensin system (RAS) may promote prostate tumorigenesis via up-regulation of PAX2 expression.

CONCLUSIONS

Therefore, PAX2 may be a novel therapeutic target for the treatment of carcinomas such as prostate cancer via the down-regulation of its expression by targeting the AT1R signaling pathways.

Guanylyl cyclase-A inhibits angiotensin II type 2 receptor-mediated pro-hypertrophic signaling in the heart

Angiotensin II plays a key role in the development of cardiac hypertrophy. The contribution of the angiotensin II type 1 receptor (AT1) in angiotensin II-induced cardiac hypertrophy is well established, but the role of AT2 signaling remains controversial. Previously, we have shown that natriuretic peptide receptor/guanylyl cyclase-A (GCA) signaling protects the heart from hypertrophy at least in part by inhibiting AT1-mediated pro-hypertrophic signaling. Here, we investigated the role of AT2 in cardiac hypertrophy observed in mice lacking GCA. Real-time RT-PCR and immunoblotting approaches indicated that the cardiac AT2 gene was overexpressed in GCA-deficient mice. Mice lacking AT2 alone did not exhibit an abnormal cardiac phenotype. In contrast, GCA-deficiency-induced increases in heart to body weight ratio, cardiomyocyte cross-sectional area, and collagen accumulation as evidenced by van Gieson staining were attenuated when AT2 was absent. Furthermore, the up-regulated cardiac expression of hypertrophy-related genes in GCA-null animals was also suppressed. Pharmacological blockade of AT2 with PD123319 similarly attenuated cardiac hypertrophy in GCA-deficient mice. In addition, whereas the AT1 antagonist olmesartan attenuated cardiac hypertrophy in GCA-deficient mice, this treatment was without effect on cardiac hypertrophy in GCA/AT2-double null mice, notwithstanding its potent antihypertensive effect in these animals. These results suggest that the interplay of AT2 and AT1 may be important in the development of cardiac hypertrophy. Collectively, our findings support the assertion that GCA inhibits AT2-mediated pro-hypertrophic signaling in heart and offer new insights into endogenous cardioprotective mechanisms during disease pathogenesis.

Increase in systemic blood pressure during intra‐arterial PD123319 Infusion: Evidence for functional expression of angiotensin type 2 receptors in normal volunteers

The functional existence of angiotensin type 2 (AT2) receptors in healthy humans is uncertain. A double-blind, randomized, crossover study was performed comparing forearm vascular responses to intrabrachial arterial PD123319 (a selective AT2 receptor antagonist, 10 microg/min) in healthy young, non-smoking volunteers following 1 week of telmisartan therapy (40-80 mg once daily) and 1 week of placebo therapy. No significant difference was found in baseline mean arterial pressure between telmisartan and placebo treatment. Baseline forearm blood flow (FBF) was significantly higher during telmisartan (2.69 +/- 1.28 ml/s) therapy than during placebo (1.86 +/- 0.75 ml/s). PD123319 did not alter FBF on either telmisartan or placebo therapy. However, significant increases in mean arterial pressure were observed during intra-brachial arterial infusions of PD123319 (p=0.003) during both placebo (80 +/- 9 to 92 +/- 17 mmHg) and telmisartan (80 +/- 11 to 90 +/- 14 mmHg) therapy suggesting the presence of functional AT2 receptors, possibly in locations other than the forearm resistance vessels. Intra-brachial arterial infusion of PD123319 (10 microg/min) has significant systemic effects, which appear more prominent than local changes in FBF and which are not influenced by angiotensin type 1 receptor blockade.

Angiotensin II type 2 receptor blockade increases bone mass

Renin angiotensin system (RAS) regulates circulating blood volume and blood pressure systemically, whereas RAS also plays a role in the local milieu. Previous in vitro studies suggested that RAS may be involved in the regulation of bone cells. However, it was not known whether molecules involved in RAS are present in bone in vivo. In this study, we examined the presence of RAS components in adult bone and the effects of angiotensin II type 2 (AT2) receptor blocker on bone mass. Immunohistochemistry revealed that AT2 receptor protein was expressed in both osteoblasts and osteoclasts. In addition, renin and angiotensin II-converting enzyme were expressed in bone cells in vivo. Treatment with AT2 receptor blocker significantly enhanced the levels of bone mass, and this effect was based on the enhancement of osteoblastic activity as well as the suppression of osteoclastic activity in vivo. These results indicate that RAS components are present in adult bone and that blockade of AT2 receptor results in alteration in bone mass.

A peripherally administered, centrally acting angiotensin II AT2 antagonist selectively increases brain AT1 receptors and decreases brain tyrosine hydroxylase transcription, pituitary vasopressin and ACTH

The physiological actions of brain Angiotensin II AT(2) receptors and their relationship to Angiotensin II AT(1) receptors remain controversial. To further clarify their role, we determined to what extent systemic administration of an AT(2) receptor antagonist affected AT(2) receptor binding within the brain and the expression of AT(1) receptors. For this purpose, we subcutaneously administered the AT(2) receptor antagonist PD123319 (1 mg/kg/day) to adult male rats for two weeks via osmotic minipumps. We also studied the content of pituitary adrenocorticotropic hormone and vasopressin, representative of hypothalamic-pituitary-adrenal axis activation, and the tyrosine hydroxylase gene expression in the locus coeruleus as a measure of central norepinephrine function. We found significant decreases in AT(2) receptor binding in brain areas inside the blood brain barrier, the inferior olive and the locus coeruleus. AT(2) receptor blockade increased AT(1) receptor binding and mRNA expression not only in the subfornical organ and the median eminence, situated outside the blood brain barrier, but also in the hypothalamic paraventricular nucleus, located inside the blood brain barrier. These changes paralleled decreased expression of tyrosine hydroxylase mRNA in the locus coeruleus and decreased pituitary adrenocorticotropic and vasopressin content. Our results demonstrate that sustained peripheral administration of an AT(2) antagonist decreases binding to brain AT(2) receptors, indicating that this drug is a useful tool for the study of their central role. AT(2) receptor activity inhibition up-regulates AT(1) receptor expression in specific brain areas. Blockade of brain AT(2) receptors is compatible with enhanced hypothalamic-pituitary-adrenal axis and decreased central sympathetic system activity.

Adherence to guidelines in people with screen-detected type 2 diabetes, ADDITION, Denmark

OBJECTIVE

In people with screen-detected type 2 diabetes in primary care, (1) to assess adherence to guidelines, recommending consultation with the GP every three months and treatment initiation with an ACE inhibitor or an angiotensin-II receptor antagonist when systolic BP was > 120 mmHg and/or diastolic BP was > 80 mmHg, and (2) to identify predictors for adherence.

DESIGN

Prospective follow-up of a fixed cohort of patients.

SETTING

Fifty-four Danish general practices.

SUBJECTS AND MAIN OUTCOME MEASURES

A total of 361 people with screen-detected type 2 diabetes were followed up for 410 days to assess planned consultations with their GP and recording of BP. Some 226 people, with BP recorded above guideline threshold(s) and where treatment was not already initiated, were followed for up to 410 days to monitor prescription redemption.

RESULTS

At 3, 6, 9 and 12 months 80%, 77%, 74%, and 73% of the cohort attended a consultation. A total of 89% of the cohort attended two of the four planned consultations. The probability of redeemed prescriptions for an ACE inhibitor or an angiotensin-II receptor antagonist according to the guideline during the first year following diagnosis was 51%. High initial BP was associated with prescription redemption. No other analysed individual or organisational characteristics were found to be associated with treatment initiation.

CONCLUSION

The consultation attendance was reasonably high, and treatment initiation with an ACE inhibitor or an angiotensin-II receptor antagonist according to the guideline was found in half of the cases. High initial BP increased the probability of treatment initiation.

Renin-angiotensin system inhibitors in proteinuric chronic kidney disease

Renin-angiotensin inhibitors are effective in slowing the progression of chronic proteinuric kidney disease. These medicines should be used in preference to anti-hypertensives that do not provide renoprotection.

[Inhibition of platelet aggregation and angiotensin II-receptor blockade following TIA; the unexpected results of the Prevention Regimen For Effectively Avoiding Second Strokes (PROFESS) trial]

In the Prevention Regimen for Effectively Avoiding Second Strokes (PROFESS) trial, the combination of acetylsalicylic acid (50 mg) and extended-release dipyridamole (400 mg) (ASA+Dip) was compared with clopidogrel (75 mg) in patients with a recent transient ischaemic attack (TIA) or minor disabling stroke. In the same patients, the selective type I angiotensin II-receptor blocker telmisartan (80 mg) was compared with placebo. Both comparisons did not show any benefit or harm from any of the treatments evaluated. Therefore, ASA+Dip and clopidogrel should be considered effective in secondary stroke prevention following TIA or minor disabling stroke. ASA+Dip caused headache in 6% of patients. Clopidogrel can cause severe haematological side effects in rare cases; its use is hampered mainly by its high cost. Telmisartan was well tolerated in patients with a recent TIA or minor disabling stroke but should not be used for indications other than lowering blood pressure.

Estrogen elicits dorsal root ganglion axon sprouting via a renin-angiotensin system

Many painful conditions occur more frequently in women, and estrogen is a predisposing factor. Estrogen may contribute to some pain syndromes by enhancing axon outgrowth by sensory dorsal root ganglion (DRG) neurons. The objective of the present study was to define mechanisms by which estrogen elicits axon sprouting. The estrogen receptor-alpha agonist propyl pyrazole triol induced neurite outgrowth from cultured neonatal DRG neurons, whereas the estrogen receptor-beta agonist diarylpropionitrile was ineffective. 17beta-Estradiol (E2) elicited sprouting from peripherin-positive unmyelinated neurons, but not larger NF200-positive myelinated neurons. Microarray analysis showed that E2 up-regulates angiotensin II (ANGII) receptor type 2 (AT2) mRNA in vitro, and studies in adult rats confirmed increased DRG mRNA and protein in vivo. AT2 plays a central role in E2-induced axon sprouting because AT2 blockade by PD123,319 eliminated estrogen-mediated sprouting in vitro. We assessed whether AT2 may be responding to locally synthesized ANGII. DRG from adult rats expressed mRNA for renin, angiotensinogen, and angiotensin converting enzyme (ACE), and protein products were present and occasionally colocalized within neurons and other DRG cells. We determined if locally synthesized ANGII plays a role in estrogen-mediated sprouting by blocking its formation using the ACE inhibitor enalapril. ACE inhibition prevented estrogen-induced neuritogenesis. These findings support the hypothesis that estrogen promotes DRG nociceptor axon sprouting by up-regulating the AT2 receptor, and that locally synthesized ANGII can induce axon formation. Therefore, estrogen may contribute to some pain syndromes by enhancing the pro-neuritogenic effects of AT2 activation by ANGII.

Angiotensin II relaxations of bovine adrenal cortical arteries: role of angiotensin II metabolites and endothelial nitric oxide

Angiotensin (Ang) II regulates adrenal steroidogenesis and adrenal cortical arterial tone. Vascular metabolism could decrease Ang II concentrations and produce metabolites with vascular activity. Our goals were to study adrenal artery Ang II metabolism and to characterize metabolite vascular activity. Bovine adrenal cortical arteries were incubated with Ang II (100 nmol/L) for 10 and 30 minutes. Metabolites were analyzed by mass spectrometry. Ang (1-7), Ang III, and Ang IV concentrations were 146+/-21, 173+/-42 and 58+/-11 pg/mg at 10 minutes and 845+/-163, 70+/-14, and 31+/-3 pg/mg at 30 minutes, respectively. Concentration-related relaxations of U46619-preconstricted cortical arteries to Ang II (maximum relaxation=29+/-3%; EC(50)=3.4 pmol/L) were eliminated by endothelium removal and inhibited by the NO synthase inhibitor, nitro-L-arginine (30 micromol/L; maximum relaxation=14+/-7%). Ang II relaxations were enhanced by the angiotensin type-1 receptor antagonist losartan (1 micromol/L; maximum relaxation=41+/-3%; EC(50)=11 pmol/L). Losartan-enhanced Ang II relaxations were inhibited by nitro-L-arginine (maximum relaxation=18+/-5%) and the angiotensin type-2 receptor antagonist PD123319 (10 micromol/L; maximum relaxation=27+/-5%). Ang (1-7) and Ang III caused concentration-related relaxations with less potency (EC(50)=43 and 24 nmol/L, respectively) but similar efficacy (maximum relaxations=39+/-3% and 48+/-5%, respectively) as losartan-enhanced Ang II relaxations. Ang (1-7) relaxations were inhibited by nitro-L-arginine (maximum relaxation=16+/-4%) and the Ang (1-7) receptor antagonist 7(D)-Ala-Ang (1-7) (1 micromol/L; maximum relaxation=10+/-3%) and eliminated by endothelium removal. Thus, Ang II metabolism by adrenal cortical arteries to metabolites with decreased vascular activity represents an inactivation pathway possibly decreasing Ang II presentation to adrenal steroidogenic cells and limits Ang II vascular effects.

Hypotensive activity of novokinin, a potent analogue of ovokinin(2-7), is mediated by angiotensin AT(2) receptor and prostaglandin IP receptor

Novokinin (Arg-Pro-Leu-Lys-Pro-Trp) is a potent hypotensive peptide previously designed based on the structure of ovokinin(2-7) (Arg-Ala-Asp-His-Pro-Phe), a vasorelaxing and hypotensive peptide derived from ovalbumin. Novokinin exhibited an affinity for the angiotensin AT(2) receptor (Ki=7.35 microM). Novokinin significantly lowered systolic blood pressure at a dose of 0.03 and 0.1 mg/kg after intravenous and oral administration, respectively, in spontaneously hypertensive rats (SHRs), and the hypotensive activity was blocked by PD123319, an antagonist of the AT(2) receptor. Novokinin lowered blood pressure in C57BL/6J mice after oral administration at a dose of 50 mg/kg. However, in AT(2) receptor-deficient mice, novokinin did not reduce blood pressure. These results demonstrate that the hypotensive activity of novokinin is mediated by the AT(2) receptor. The hypotensive activity of novokinin in SHRs was completely blocked by indomethacin and CAY10441, an inhibitor of cyclooxygenase and an antagonist of the prostaglandin IP receptor, respectively. These suggest that the hypotensive activity is mediated by prostacyclin and the IP receptor downstream of the AT(2) receptor.

Anti-cancer actions of a recombinant antibody (R6313/G2) against the angiotensin II AT1 receptor

Although several tumour types express both AT1 and AT2 angiotensin II receptors, and angiotensin II stimulates cell proliferation, angiotensin-converting enzyme inhibitors and angiotensin receptor blockers are not effective anti-cancer agents. Development of a biologically active monoclonal antibody (6313/G2) against the AT1 receptor prompted the testing of a recombinant short-chain variable fragment form (R6313/G2) against breast cancer cells in vitro and in vivo. Cell lines MCF-7, MDA-MB-231 and T47D all expressed both receptor subtypes. In vitro, R6313/G2 suppressed cell proliferation in the presence of 100 nM angiotensin II, with IC50s of 30 nM, 153 nM and 2.8 microM for the three cell types respectively; in contrast, the AT1 receptor blocker losartan was effective only in T47D cells, at 25 microM. Studies on MCF-7 and T47D cells showed R6313/G2 also opposed the angiotensin II-induced inhibition of caspase-3/7 activity. In vivo, hollow fibres containing the cell lines were implanted in nu/nu balb-c mice at two sites, s.c. and i.p. Treatments of R6313/G2 at 2.5 nmol/kg and 25 nmol/kg twice per day for 7 days dose dependently reduced cell numbers for all three cell lines, but here MCF-7 cells responded most sensitively and MDA-MB-231 cells least. Although T47D cells were refractory at the s.c. site, growth was inhibited at the i.p. location, and otherwise results were similar at the two sites. In xenografts, MCF-7 cell tumours were dose dependently reduced by R6313/G2, and 13 and 27 nmol/kg R6313/G2 twice/day gave means of 74 and 76% tumour regression after 7 days. The data suggest that the anti-cancer action of R6313/G2 is considerably more effective than AT1 antagonists.

Angiotensin II type 1 receptor antagonist improves the prognosis in rats displaying liver cirrhosis induced by a choline-deficient diet

BACKGROUND

Angiotensin II type 1 receptor (AT1) antagonists are known to suppress TGFbeta and lipid peroxidation. An experimental rat model made by feeding rats a choline-deficient diet (CDD) showed severe steatosis, fibrosis and infiltration of inflammatory cells in the liver resembling nonalcoholic steatohepatitis (NASH). NASH causes fibrosis by lipid peroxidation. In this study, we assess whether AT1 antagonists and angiotensin II type 2 receptor (AT2) antagonists can suppress the hepatic fibrosis and lipid peroxidation in CDD rats that lead to the development of NASH.

METHODS

Both study groups received subcutaneously aqueous solutions of AT2 antagonist (PD123319 - 1 mg/kg/day) and AT1 antagonist (L158809 - 1 mg/kg/day), respectively, 6 times per week. On day 90, some rats (5 /group) were sacrificed by excision of the liver under anesthesia, in order to assess the hepatic hydroxyproline (HP), malondialdehyde (MDA), total glutathione, superoxide dismutase (SOD) activity and TGFbeta-1. The remaining rats were maintained to observe the survival rate.

RESULTS

All CDD rats developed liver cirrhosis. However, the tissue TGF and HP decreased in AT1 antagonist group in comparison with the other two groups. All groups of CDD rats showed strong adipose hyperoxidation. The AT1 antagonist group demonstrated a markedly improved survival rate in comparison to the other two groups.

CONCLUSION

Hepatic fibrosis progression in the AT1 antagonist group was slower than that in the other groups. This observation suggests that AT1 antagonists delayed the progression of liver failure, which thus led to an improved survival rate.

[Angiotensin II-receptor antagonists compared to other antihypertensives: still insufficient evidence for reducing the risk of cerebrovascular incidents]

--There is growing evidence that angiotensin II-receptor antagonists may have protective effects for preventing cerebrovascular incidents. --It is unlikely that these effects are due only to a decrease in blood pressure. --One hypothesis is that high concentrations ofangiotensin II result in improved cerebral perfusion ofangiotensin type 2-receptor mediated mechanisms such as local vasodilatation and angiogenesis. --Several clinical and preclinical studies support this hypothesis. --The results of these studies are discussed in this overview. There is still insufficient evidence that a protective effect on the brain occurs.

Distribution of the non-AT1, non-AT2 angiotensin-binding site in the rat brain: preliminary characterization

The discovery of a novel, non-AT1, non-AT2 binding site for angiotensin II (Ang II) in the brain adds a new dimension to the brain angiotensin system. The distribution of the non-AT1, non-AT2 binding site in the rat brain was determined using radioligand-binding assays and in vitro receptor autoradiography. There is a marked rostral to caudal gradient of the density of this binding site from the olfactory bulbs to the cervical spinal cord, with a consistent binding affinity, K(d) approximately 1-3 nM. Binding is widespread throughout the brain, however, areas of very intense binding are present in a large number of brain regions. The olfactory nerve layer of the olfactory bulb has the highest binding site density. Very high binding site density is also seen in the cerebral cortex with highest binding density in pyriform, insular and entorhinal cortex. Very high binding occurs in brain regions associated with dopaminergic reward (nucleus accumbens, ventral tegmental area) and motor (substantia nigra, caudate/putamen) systems. Very high to high binding also occurs in brain regions associated with the development of Alzheimer's disease (nucleus basalis of Meynert, substantia innominata). Very high to high binding is also seen in brain regions associated with cardiovascular regulation (subfornical organ, median, medial and anteroventral preoptic nucleus, paraventricular nucleus of the hypothalamus, solitary tract nucleus), areas that harbor high densities of the AT1 Ang II receptor subtype. High non-AT1, non-AT2 binding site density is present in brain regions containing high levels of the AT2 Ang II receptor subtype (amygdala, several thalamic nuclei, superior colliculus). Very high binding is also present in the choroid plexus, peri-third ventricular ependyma, and the subcommissural organ. The widespread, yet discrete distribution of high levels of this binding site suggests that it could function as a component of the blood-brain barrier, as a highly specific angiotensinase, or as a receptor for Ang II that mediates known and novel functions of this peptide, or that it serves as a clearance receptor for Ang II.

Arterial stiffness and haemodynamic response to vasoactive medication in subjects with insulin-resistance syndrome

INSR (insulin-resistance syndrome) affects 25% of the Australian population and is associated with increased cardiovascular risk. In the present study, we postulated that early cardiovascular changes in these individuals may be associated with an activated RAS (renin–angiotensin system). We studied 26 subjects: 13 with INSR [waist circumference, 99±6 cm; HOMA (homoeostasis model assessment) score, 2.5±0.3] and 13 NCs (normals controls; waist circumference, 77±2 cm; HOMA score, 1.4±0.2). All received intravenous GTN (glyceryl trinitrate; 10, 20 and 40 μg/min), L-NMMA (NG-monomethyl-L-arginine; 3 mg/kg of body weight), AngII (angiotensin II; 8 and 16 ng/min), the selective AT2R (AngII type 2 receptor) inhibitor PD123319 (10 and 20 μg/min) and AngII (16 ng/min)+PD123319 (20 μg/min). At the end of each infusion, arterial stiffness indices [SI (stiffness index) and RI (reflection index)] and haemodynamic parameters were measured. There was a significantly higher RI response to AngII (P=0.0004 for both 8 and 16 ng/min doses) and to PD123319 (P=0.004 and P=0.03 for 10 and 20 μg/min doses respectively) in subjects with INSR compared with NCs. Co-infusion of AngII and PD123319 did not lead to additive changes in RI. RI responses to L-NMMA and GTN were not significantly different in both groups. No significant differences in SI and haemodynamic responses were detected. In conclusion, AT1R (AngII type 1 receptor) and AT2R activity produce arterial stiffness changes in subjects with INSR. Evidence of increased AT1R- and AT2R-mediated responses in small-to-medium-sized arteries in INSR was found, and may play an early role in the pathogenesis of vascular changes in INSR before haemodynamic changes become apparent.

Angiotensin II regulates adipocyte apolipoprotein E expression

CONTEXT

Obesity is increasing in prevalence and it is important to understand factors that regulate adipose tissue lipid metabolism. Recently, endogenous expression of apolipoprotein E (apoE) in adipose tissue has been shown to have important effects on adipocyte lipid flux and gene expression. Adipose tissue is also a physiological target of angiotensin II (AII).

OBJECTIVE

The aim of the current study was to evaluate a potential regulatory effect for AII on adipose tissue apoE expression.

RESULTS

Infusion of AII into mice for 3 d significantly reduced apoE expression in adipocytes from freshly isolated adipose tissue. ApoE expression was unchanged by the AII infusion in the stromovascular fraction. In isolated human adipocytes, treatment with AII significantly reduced cellular and secreted apoprotein E (by 20-60%). Suppression of apoE expression was observed in sc adipocytes obtained from nonobese (body mass index < 30 kg/m(2)) donors, and in sc and omental adipocytes obtained from obese (body mass index > 30 kg/m(2)) donors. Evaluation of the effect of AII in matched sets of sc and omental adipocytes from three separate donors showed lower overall apoE expression in omental adipocytes in two of the donors, and a concordant down-regulation of apoE expression in sc and omental adipocytes from all three subjects. The specific AT(1) receptor blocker, valsartan, eliminated the effect of AII on adipocyte apoE expression.

CONCLUSION

Both apoE and components of the renin-angiotensin system are expressed in adipose tissue, and each has important effects on adipocyte lipid metabolism and gene expression. The regulatory interaction we have identified between these two pathways has important implications for a complete understanding of adipose tissue lipid homeostasis.

Angiotensin II Induces Capillary Formation From Endothelial Cells Via the LOX-1–Dependent Redox-Sensitive Pathway

Angiotensin II (Ang II) induces angiogenesis by stimulating reactive oxygen species–dependent vascular endothelial growth factor (VEGF) expression. Ang II via type 1 receptor upregulates the expression of LOX-1, a lectin-like receptor for oxidized low-density lipoprotein. LOX-1 activation, in turn, upregulates Ang II type 1 receptor expression. We postulated that interruption of the feedback loop between Ang II and LOX-1 might attenuate Ang II–induced VEGF expression and capillary formation. In vitro experiments showed that Ang II (1 nmol/L) induced the expression of LOX-1 and VEGF and enhanced capillary formation from human coronary endothelial cells in Matrigel assay. Ang II–mediated expression of LOX-1 and VEGF, capillary formation, intracellular reactive oxygen species generation, and phosphorylation of p38 as well as p44/42 mitogen-activated protein kinases, were suppressed by anti–LOX-1 antibody, nicotinamide-adenine dinucleotide phosphate oxidase inhibitor apocynin and the Ang II type 1 receptor blocker losartan, but not by the Ang II type 2 receptor blocker PD123319. Expression of VEGF and capillary formation induced by Ang II were also inhibited by the p44/42 mitogen-activated protein kinase inhibitor U0126 and the p38 mitogen-activated protein kinase inhibitor SB203580. In ex vivo experiments, Ang II stimulated capillary sprouting from aortic rings from wild-type mice, and this phenomenon was significantly attenuated by pretreatment of aortic rings with anti–LOX-1 antibody, apocynin, and losartan, but not by PD123319. Importantly, Ang II–induced capillary sprouting was minimal from aortic rings from LOX-1 null mice compared with wild-type mice. These findings suggest that small concentrations of Ang II promote capillary formation by inducing the expression of VEGF via Ang II type 1 receptor/LOX-1–mediated stimulation of the reactive oxygen species-mitogen-activated protein kinase pathway.

Suppression of diabetes-induced retinal inflammation by blocking the angiotensin II type 1 receptor or its downstream nuclear factor-kappaB pathway

PURPOSE

To investigate the involvement of the renin-angiotensin system (RAS) and the nuclear factor (NF)-kappaB pathway with diabetes-induced retinal inflammation.

METHODS

Six weeks after induction of diabetes, C57BL/6 mice were treated with the angiotensin II type 1 receptor (AT1-R) blocker (ARB) telmisartan or valsartan, the AT2-R blocker PD123319, or the NF-kappaB inhibitor dehydroxymethylepoxyquinomicin (DHMEQ) daily for 1 week. Retinal mRNA and protein levels of the RAS components were examined by RT-PCR and Western blot, respectively. Leukocyte adhesion to the retinal vasculature was evaluated with a concanavalin A lectin perfusion-labeling technique. Retinal expression levels of intercellular adhesion molecule (ICAM)-1 and vascular endothelial growth factor (VEGF) were examined by RT-PCR and ELISA. ARB or DHMEQ was applied to murine capillary endothelial (b-End3) cells stimulated with a high concentration of glucose to analyze nuclear translocation of NF-kappaB via immunohistochemistry for p65 and mRNA and protein levels of ICAM-1 and monocyte chemotactic protein (MCP)-1.

RESULTS

Induction of diabetes led to a significant increase in retinal expression and production of the RAS components including angiotensin II, AT1-R, and AT2-R. Retinal adherent leukocytes were significantly suppressed by AT1-R, but not by AT2-R, blockade. Administration of the ARB, but not of PD123319, inhibited diabetes-induced retinal expression of ICAM-1 and VEGF. DHMEQ also suppressed these cellular and molecular inflammatory parameters in the diabetic retina to the levels obtained with ARB treatment. In vitro, glucose-induced nuclear translocation of NF-kappaB p65 and upregulation of ICAM-1 and MCP-1 were significantly suppressed by application of the ARB. The in vivo treatment with the ARB, as well as DHMEQ, attenuated the diabetes-induced retinal expression of angiotensin II and AT1-R, per se.

CONCLUSIONS

The present data revealed significant a contribution of the AT1-R/NF-kappaB pathway to diabetes-induced retinal inflammation, providing a mechanistic reason for targeting AT1-R or NF-kappaB in the treatment of diabetic retinopathy.

Unintentional paediatric ingestions of angiotensin converting enzyme inhibitors and angiotensin II receptor antagonists

AIMS

There is limited information on safety of angiotensin converting enzyme (ACE) inhibitors and angiotensin II (AII) receptor antagonists in unintentional paediatric ingestions. This study was conducted with the aim of developing referral guidelines for poison information centres.

METHODS

Calls to the NSW poison information centre from January 2002 to July 2004 regarding paediatric ingestion of ACE inhibitors and AII receptor antagonists were recruited and prospectively followed up. Information collected included: demographics (age, gender, weight), type of exposure (unintentional, therapeutic error), ingested dose and clinical effects. Dose was reported in defined daily doses (DDD) to compare across and within the two drug classes with respect to the normal adult dose.

RESULTS

Nineteen cases of paediatric ingestion of ACE inhibitors and AII receptor antagonists were included. The median age was 2 years (Interquartile range (IQR): 20-33 months) and the median dose ingested was 1 DDD (IQR: 1-2). There were nine ACE inhibitor ingestions and 10 AII receptor antagonist ingestions. One of nine children (11%) observed in hospital developed transient hypotension but required no treatment and recovered without complication. This child ingested an ACE inhibitor and ingested >3 DDD.

CONCLUSION

Unintentional paediatric ingestions of ACE inhibitors and AII receptor antagonists resulted in the majority of children remaining asymptomatic. ACE inhibitor ingestions under 2 DDD can be observed at home provided the child is asymptomatic and there is a responsible adult to observe the child. The dose required for observation in AII receptor antagonist ingestions is less clear.

Association of increased plasma cardiotrophin-1 with inappropriate left ventricular mass in essential hypertension

Inappropriate left ventricular mass is present when the value of left ventricular mass exceeds individual needs to compensate hemodynamic load imposed by increased blood pressure. The goal of this study was to investigate whether plasma concentration of cardiotrophin-1, a cytokine that induces exaggerated hypertrophy in cardiomyocytes with hypertensive phenotype, is related to inappropriate left ventricular mass in patients with essential hypertension. The study was performed in 118 patients with never-treated hypertension and without prevalent cardiac disease. The left ventricular mass prediction from stroke work (systolic blood pressurexDoppler stroke volume), sex, and height (in meters(2.7)) was derived. An observed left ventricular mass/predicted left ventricular mass value >128% defined inappropriate left ventricular mass. Plasma cardiotrophin-1 was measured by an enzyme-linked immunosorbent assay. The studies were repeated in a group of 45 patients after 1 year of antihypertensive treatment. At baseline 67 and 51 patients presented with appropriate and inappropriate left ventricular mass, respectively. Plasma cardiotrophin-1 was higher (P<0.001) in patients with inappropriate mass than in patients with appropriate mass and normotensive controls. A direct correlation was found between cardiotrophin-1 and observed left ventricular mass/predicted left ventricular mass ratio (r=0.330, P<0.001) in all hypertensive patients. After treatment, plasma cardiotrophin-1 decreased and increased in patients in which inappropriate left ventricular mass regressed and persisted, respectively, despite a similar reduction of blood pressure in the 2 subgroups of patients. Albeit descriptive in nature, these results suggest the hypothesis that an excess of cardiotrophin-1 may contribute to inappropriate left ventricular growth in hypertensive patients.

On the mechanism of coronary vasodilation induced by angiotensin-(1-7) in the isolated guinea pig heart

Various mechanisms have been postulated to be involved in angiotensin-(1-7)-induced endothelium-dependent vasodilation. Here, we characterized the vasodilator action of angiotensin-(1-7) in the isolated guinea pig heart. Angiotensin-(1-7) (1-10 nmol, bolus) induced dose-dependent increase in the coronary flow. The coronary vasodilation induced by angiotensin-(1-7) was significantly reduced by the nitric oxide synthase inhibitor, L-N(G)-nitroarginine methyl ester (L-NAME) (100 microM) and abolished by a B(2) receptor antagonist, icatibant (100 nM). Coronary vasodilation induced by bradykinin (3 pmol, bolus) was inhibited by L-NAME and icatibant to similar extent as that induced by angiotensin-(1-7). Neither the selective AT(2) angiotensin receptor antagonist, PD123319 (1 microM), nor the antagonist of a putative angiotensin-(1-7) receptors, [D-alanine-7]-angiotensin-(1-7) (A-779, 1 microM), influenced the response to angiotensin-(1-7). In conclusion, in the isolated guinea pig heart angiotensin-(1-7) induces coronary vasodilation that is mediated by endogenous bradykinin and subsequent stimulation of nitric oxide release through endothelial B(2) receptors. In contrast to other vascular beds, AT(2) angiotensin receptors and specific angiotensin-(1-7) receptors do not appear involved in angiotensin-(1-7)-induced coronary vasodilation in the isolated guinea pig heart.

ACE-I/ARB treatment in type 1 diabetes patients with albuminuria is associated with lower odds of progression of coronary artery calcification

AIMS

The objective of this study was to determine whether baseline albuminuria predicts coronary artery calcification (CAC) progression in subjects with type 1 diabetes and whether angiotensin-converting enzyme inhibitor (ACE-I) or angiotensin II type I receptor blocker (ARB) treatment is associated with lower odds of CAC progression.

METHODS

In 2000-2002, the Coronary Artery Calcification in Type 1 Diabetes study enrolled 652 subjects with type 1 diabetes who were between 19 and 56 years old and had no known history of coronary artery disease (CAD). In this analysis, CAC progression over 2.5+/-0.4 years was evaluated in 478 subjects (age=37+/-9 years; male=45%; diabetes duration=23+/-9 years) at a follow-up visit. Albuminuria was defined by American Diabetes Association criteria, and microalbuminuria and macroalbuminuria were combined for the analysis. Logistic regression was used to evaluate the relationship between baseline categorical presence of albuminuria and CAC progression.

RESULTS

At baseline, of the 478 subjects, 157 (33%) were on ACE-I/ARB treatment and 83 (17%) had albuminuria, with 114 (24%) having CAC progression at follow-up. In backward logistic regression, presence of albuminuria at baseline predicted progression of CAC among subjects not treated with ACE-I/ARB [odds ratio=4.06; 95% confidence interval (CI)=1.45-11.35; P=.008]. Among the subjects with albuminuria, the odds of progression was 62% lower (95% CI=88% decrease to 23% increase; P=.106) in those treated with ACE-I/ARB.

CONCLUSIONS

Albuminuria is a significant independent risk factor for CAC progression in young type 1 diabetes patients asymptomatic for CAD, and ACE-I/ARB treatment is associated with substantially lower odds of CAC progression.

Persistent Use of Evidence-Based Pharmacotherapy in Heart Failure Is Associated With Improved Outcomes

Background— Undertreatment with recommended pharmacotherapy is a common problem in heart failure and may influence prognosis. We studied initiation and persistence of evidence-based pharmacotherapy in 107 092 patients discharged after first hospitalization for heart failure in Denmark from 1995 to 2004.

Methods and Results— Prescriptions of dispensed medication and mortality were identified by an individual-level linkage of nationwide registers. Inclusion was irrespective of left ventricular function. Treatment with renin-angiotensin inhibitors (eg, angiotensin-converting enzyme inhibitors and angiotensin-2 receptor blockers), β-blockers, spironolactone, and statins was initiated in 43%, 27%, 19%, and 19% of patients, respectively. Patients who did not initiate treatment within 90 days of discharge had a low probability of later treatment initiation. Treatment dosages were in general only 50% of target dosages and were not increased during long-term treatment. Short breaks in therapy were common, but most patients reinitiated treatment. Five years after initiation of treatment, 79% patients were still on renin-angiotensin inhibitors, 65% on β-blockers, 56% on spironolactone, and 83% on statins. Notably, multiple drug treatment and increased severity of heart failure was associated with persistence of treatment. Nonpersistence with renin-angiotensin inhibitors, β-blockers, and statins was associated with increased mortality with hazard ratios for death of 1.37 (95% CI, 1.31 to 1.42), 1.25 (95% CI, 1.19 to 1.32), 1.88 (95% CI, 1.67 to 2.12), respectively.

Conclusions— Persistence of treatment was high once medication was started, but treatment dosages were below recommended dosages. Increased severity of heart failure or increased number of concomitant medications did not worsen persistence, but nonpersistence identified a high-risk population of patients who required special attention. A focused effort on early treatment initiation, appropriate dosages, and persistence with the regimen is likely to provide long-term benefit.

NO and cGMP mediate angiotensin AT2 receptor-induced renal renin inhibition in young rats

We hypothesized that angiotensin subtype-2 receptor (AT(2)R) inhibits renal renin biosynthesis in young rats via nitric oxide (NO). We monitored changes in renal NO, cGMP, renal renin content (RRC), and ANG II in 4-wk-old rats in response to low sodium (LNa(+)) intake alone and combined with 8-h direct renal cortical administration of AT(1) receptor blocker valsartan (VAL), AT(2)R blocker PD123319 (PD), NO synthase inhibitor N(G)-nitro-l-arginine methyl ester (l-NAME), NO donor S-nitroso-N-acetyl penicillamine (SNAP), or guanylyl cyclase inhibitor 1H-[1,2,4] oxadiazolo[4,2-alpha] quinoxaline-1-one (ODQ). In addition, we monitored renal endothelial nitric oxide synthase (eNOS) and neuronal nitric oxide synthase (nNOS) in response to VAL or PD. LNa(+), VAL, PD, l-NAME, and ODQ increased RRC, ANG II, and renin mRNA. PD and l-NAME decreased NO and cGMP, while SNAP reduced RRC, ANG II, renin mRNA, and reversed the effects of PD. PD also reduced eNOS and nNOS protein and mRNA. Combined treatment with PD, l-NAME, or ODQ and VAL reversed the effects of VAL and caused further increase in RRC, ANG II, renin mRNA, and protein. ODQ reversed the effects of SNAP. These data demonstrate that the renal AT(2) receptor decreases renal renin biosynthesis and ANG II production in young rats. Reversal of the PD effects by SNAP and SNAP effects by ODQ confirms that NO and cGMP mediate the AT(2) receptor inhibition of renal renin production.

Role of the angiotensin II type-2 receptor in radiation nephropathy

Experimental studies have shown that blockade of the angiotensin II type-1 (AT(1)) receptor is effective in the mitigation and treatment of radiation-induced chronic renal failure. Also, blockade of the angiotensin II type-2 (AT(2)) receptor with PD-123319 also had a modest, but reproducible, beneficial effect in experimental radiation nephropathy, and it might augment the efficacy of an AT(1) blocker (L-158,809). Those studies could not exclude the possibility that the effects of AT(2) blockade were nonspecific. The current studies confirm the efficacy of AT(2) blockade for mitigation of experimental radiation nephropathy but paradoxically find no detectable level of AT(2) receptor binding in renal membranes. However, the results of a bioassay showed that the circulating levels of the AT(2) blocker were orders-of-magnitude too low to block AT(1) receptors. The effect of AT(2) blockade in radiation nephropathy cannot be explained by binding to the AT(1) receptor, and the efficacy of the AT(1) blockade in the same model cannot be explained by unopposed overstimulation of the AT(2) receptor.

Angiotensin II type 1 and type 2 receptors play opposite roles in regulating the barrier function of kidney glomerular capillary wall

Although angiotensin II (Ang II) type 1 receptor antagonist ameliorates proteinuria, its pharmacological mechanism and the differential roles of Ang II type 1 receptor (AT1R) and type 2 receptor (AT2R) are not well understood. We analyzed the effect of Ang II type 1 receptor antagonist on proteinuria caused by antibody against nephrin, a functional molecule of glomerular slit diaphragm and dysfunction of which is involved in the development of proteinuria in several glomerular diseases. We show here that AT1R antagonist ameliorated proteinuria by preventing a reduction in the functional molecules of the slit diaphragm. We also analyzed the role of AT1R- or AT2R-mediated actions on the expression of the slit diaphragm molecules in an in vivo study of normal rat and in an in vitro study of cultured podocytes. AT1R-mediated action hampered the mRNA expression of the slit diaphragm molecules, whereas AT2R-mediated action enhanced it. These findings indicate that Ang II receptor subtypes play opposite roles in regulating the barrier function of glomerular capillary wall and that the enhancement of AT2R stimulation may serve as a potential therapeutic strategy for proteinuria.

The angiotensin II receptor 2 is expressed and mediates angiotensin II signaling in lung fibrosis

Idiopathic pulmonary fibrosis (IPF) is a severe interstitial lung disease unresponsive to currently available therapies. In IPF, initial alveolar epithelial cell damage leads to activation of fibroblast-(myo)fibroblasts, which deposit an increased amount of a collagen-rich extracellular matrix. Angiotensin II (ANGII) signaling, mediated via angiotensin II receptor type 1 (AGTR1) or type 2 (AGTR2), controls tissue remodeling in fibrosis, but the relevance of AGTR2 remains elusive. In the present study, we demonstrated increased expression of AGTR1 und AGTR2 in human and rodent lung tissues from patients with IPF and mice subjected to bleomycin-induced fibrosis, respectively. Both AGTR1 und AGTR2 localized to interstitial fibroblasts. Quantitative analysis of cell surface expression in primary mouse fibroblasts revealed a significant increase of AGTR2 surface expression in fibrotic fibroblasts, whereas AGTR1 surface expression levels remained similar. ANGII treatment of normal fibroblasts led to enhanced migration and proliferation, which was abrogated after pretreatment with losartan (LOS), an AGTR1 inhibitor. In contrast, in fibrotic fibroblasts, migration and proliferation was modified only by AGTR2, but not AGTR1 inhibition (using PD123319). ANGII-induced effects were mediated via phosphorylation of the mitogen-activated protein kinases p38 and p42/44, which was blocked via LOS and PD123319, respectively. Similar effects of AGTR1 and AGTR2 inhibition were observed using conditioned media of alveolar epithelial cells, a prominent source of ANGII in the lung in vivo. In summary, we conclude that ANGII signaling occurs primarily via AGTR1 in normal fibroblasts, while AGTR2-mediated effects are dominant on activated (myo)-fibroblasts, a receptor switch that may perturb epithelial-mesenchymal interaction, thereby further perpetuating fibrogenesis.

Evidence for a role of AT(2) receptors at the CVLM in the cardiovascular changes induced by low-intensity physical activity in renovascular hypertensive rats

In the present study, we evaluated the involvement of the rennin-angiotensin system (RAS) in the control of the blood pressure (BP), baroreceptor-mediated bradycardia and the reactivity of caudal ventrolateral medulla (CVLM) neurons to Ang II and to AT(2) receptor antagonist in sedentary or trained renovascular hypertensive rats. Physical activity did not significantly change the baseline mean arterial pressure (MAP), heart rate (HR) or the sensitivity of the baroreflex bradycardia in normotensive Sham rats. However, in 2K1C hypertensive rats, physical activity induced a significant fall in baseline MAP and HR and produced an improvement of the baroreflex function (bradycardic component). The microinjections of Ang II into the CVLM produced similar decreases in MAP in all groups, Sham and 2K1C, sedentary and trained rats. The hypotensive effect of Ang II at the CVLM was blocked by previous microinjection of the AT(2) receptors antagonist, PD123319, in all groups of rats. Unexpectedly, microinjection of PD123319 at the CVLM produced a depressor effect in 2K1C sedentary that was attenuated in 2K1C trained rats. No significant changes in MAP were observed after PD123319 in Sham rats, sedentary or trained. These data showed that low-intensity physical activity is effective in lowering blood pressure and restoring the sensitivity of the baroreflex bradycardia, however these cardiovascular effects are not accompanied by changes in the responsiveness to Ang II at CVLM in normotensive or hypertensive, 2K1C rats. In addition, the blood pressure changes observed after AT(2) blockade in 2K1C rats suggest that hypertension may trigger an imbalance of AT(1)/AT(2) receptors at the CVLM that may be restored, at least in part, by low-intensity physical activity.

Development of CoMFA models of affinity and selectivity to angiotensin II type-1 and type-2 receptors

The renin-angiotensin system (RAS) is of major importance in cardiovascular and renal regulation and has been an attractive target in drug discovery for a long time. The main receptors involved in the RAS are the Angiotensin type-1 (AT(1)) and type-2 (AT(2)) receptors, which are both activated by the endogenous octapeptide angiotensin II (AngII). This study describes the development of 3D-QSAR models for AT(1) and AT(2) receptor affinity and AT(1)/AT(2) receptor selectivity using CoMFA. A data set of 244 compounds, based on the triazolinone and quinazolinone structural classes was compiled from the literature. Before CoMFA could be performed, an alignment rule for the two structural classes was defined using the pharmacophore-searching program DISCOtech. Models were validated using a test set obtained by dividing the data set into a training set and test set using hierarchical clustering, based on the CoMFA fields, AT(1)-, AT(2)-receptor affinities, and AT(1)/AT(2) selectivity values. Predictive models with good statistics could be developed both for AT(1) and AT(2) receptor affinity as well as selectivity towards these receptors.

Angiotensin II plays a role in acute murine experimental autoimmune cystitis

OBJECTIVES

To investigate whether angiotensin II (AII) receptor antagonism decreases the inflammation and oedema in acute murine experimental autoimmune cystitis (EAC), as interstitial cystitis (IC) might have an autoimmune component and AII has been implicated in autoimmune-mediated vascular congestion, oedema and scarring.

MATERIALS AND METHODS

Female Balb/cAN mice were divided into three treatment groups (eight in each group) that were autoimmunized with bladder homogenate to induce EAC. One group received an AII type 1 receptor (AT(1)) antagonist, one group an AII type 2 receptor (AT(2)) antagonist, and one group remained untreated (EAC). A control and sham-injected group were also included. After 10 weeks, bladders were removed, sectioned, and stained with haematoxylin and eosin.

RESULTS

Grossly, there was no thickening or adhesions in the bladders of the control or sham-injected mice. In five of seven surviving EAC bladders, there were dense adhesions to surrounding peritoneal structures. There were also adhesions and bladder thickening in all of the AT(2) antagonist-treated mice (though in a milder form) but in only two of seven surviving AT(1) antagonist-treated mice. There was no inflammation or oedema in the sham and control groups. All the EAC bladders were inflamed, with submucosal oedema and urothelial detachment from the lamina propria. In the AT(1) antagonist-treated mice there was no inflammation or oedema. By contrast, all AT(2) antagonist-treated mice had moderate inflammation and minor detachment of the urothelium from the lamina propria.

CONCLUSIONS

AT(1) receptor blockade ameliorated the inflammatory infiltration, submucosal oedema, and urothelial detachment associated with EAC in mice. This was achieved to a lesser extent by AT(2) receptor blockade. If some patients with IC have a pathophysiology similar to that of EAC mice, there might be potential benefit from AII receptor blockade.

Angiotensin II mediates postischemic leukocyte-endothelial interactions: role of calcitonin gene-related peptide

Vascular inflammation and enhanced production of angiotensin II (ANG II) are involved in the pathogenesis of hypertension and diabetes, disease states that predispose the afflicted individuals to ischemic disorders. In light of these observations, we postulated that ANG II may play a role in promoting leukocyte rolling (LR) and adhesion (LA) in postcapillary venules after exposure of the small intestine to ischemia-reperfusion (I/R). Using an intravital microscopic approach in C57BL/6J mice, we showed that ANG II type I (AT1) or type II (AT2) receptor antagonism (with valsartan or PD-123319, respectively), inhibition of angiotensin-converting enzyme (ACE) with captopril, or calcitonin gene-related peptide (CGRP) receptor blockade (CGRP8-37) prevented postischemic LR but did not influence I/R-induced LA. However, both postischemic LR and LA were largely abolished by concomitant AT1 and AT2 receptor blockade or chymase inhibition (with Y-40079). Additionally, exogenously administered ANG II increased LR and LA, effects that were attenuated by pretreatment with a CGRP receptor antagonist or an NADPH oxidase inhibitor (apocynin). Our work suggests that ANG II, formed by the enzymatic activity of ACE and chymase, plays an important role in inducing postischemic LR and LA, effects that involve the engagement of both AT1 and AT2 receptors and may be mediated by CGRP and NADPH oxidase.

Valsartan reverses post-translational modifications of the δ-subunit of ATP synthase duringin vivo canine reperfused myocardial infarction

To determine whether reperfused myocardial infarction (RMI) induces PTM of the delta-subunit of the mitochondrial metabolic enzyme ATP synthase (ATP/delta) in the ischemic zone (IZ) and whether this can be reversed by the angiotensin II type 1 receptor (AT(1)R) blocker valsartan, we applied a pharmaco-proteomics approach in canine RMI hearts with or without valsartan pretreatment. Using the 2-DE technique, we identified differential regional expression of ATP/delta in the IZ compared to the non-ischemic zone (NIZ), with an approximately 2-fold increase in the IZ that was normalized by valsartan. Furthermore in the IZ, RMI triggered S-nitrosylation of cysteine-100, nitration of the two tyrosines 88 and 225, and hydroxylation of lysine-182 in ATP/delta followed by its myristoylation. Importantly, valsartan abolished these modifications of ATP/delta in the IZ, triggered phosphorylation of serine-76 in both the IZ and NIZ, and decreased necrosis, apoptosis, left ventricular dysfunction and remodeling. Thus, AT(1)R-blocker-induced cardioprotection during RMI is associated with phosphorylation of ATP/delta and inhibition of nitric oxide-related chemical modifications such as S-nitrosylation, nitration and hydroxylation. Targeting specific PTMs during RMI, such as those of ATP/delta with AT(1)R blockade, might be a potentially powerful novel therapeutic approach. However, the identification of S-nitrosylation was putative and requires MS/MS verification.

Effects of dexamethasone exposure on rat metanephric development: in vitro and in vivo studies

Maternal administration of dexamethasone (DEX) for 48 h early in rat kidney development results in offspring with a reduced nephron endowment. However, the mechanism through which DEX inhibits nephrogenesis is unknown. In this study, we hypothesized that DEX may indirectly inhibit nephrogenesis by inhibiting ureteric branching morphogenesis. Whole metanephroi from embryonic day 14.5 (E14.5) rat embryos were cultured in the presence of DEX. DEX (10(-5) M) exposure for 2 days significantly inhibited ureteric branching compared with metanephroi grown in control media or DEX (10(-7) M). Culturing metanephroi for a further 3 days (in control media only) reduced total glomerular number in metanephroi previously exposed to DEX (10(-5) M) or (10(-7) M) compared with control cultures. Expression of genes known to regulate ureteric branching morphogenesis was determined by real-time PCR in metanephroi after 2 days in culture. DEX exposure in vitro decreased expression of glial cell line-derived neurotrophic factor (GDNF) and increased expression of bone morphogenetic protein-4 (BMP-4) and transforming growth factor-beta1 (TGF-beta1). Similar gene expression changes were found in E16.5 metanephroi in which the dam had been exposed to 2 days of DEX (0.2 mg.kg(-1).day(-1)) at E14.5/15.5 in vivo. However, in kidneys collected at E20.5 after in vivo exposure for 2 days, GDNF expression was increased and BMP-4 and TGF-beta1 expression decreased suggesting a biphasic response in gene expression to DEX exposure. These results show for the first time that inhibition of ureteric branching morphogenesis may be a key mechanism through which DEX exposure results in a reduced nephron endowment.

Angiotensin AT1-receptor inhibition exacerbates renal injury resulting from partial unilateral ureteral obstruction in the neonatal rat

The renin-angiotensin system is activated in the developing kidney and is necessary for normal renal development, but is further activated by unilateral ureteral obstruction (UUO). During nephrogenesis, there is a switch from a preponderance of angiotensin AT(2) to AT(1) receptors in the rat. We examined the renal cellular response to angiotensin II receptor inhibition in the neonatal rat subjected to partial UUO under anesthesia within 48 h of birth. Group I ("early") received saline vehicle, losartan (AT(1) inhibitor), or PD-123319 (AT(2) inhibitor) during the completion of nephrogenesis in the first 10 days of life. Group II ("late") received each of the three treatments throughout the subsequent 10 days of life. Kidneys were harvested at 21 days, and the distribution of renin, apoptosis, macrophages, alpha-smooth muscle actin, and collagen was determined. Losartan and PD-123319 each increased vascular renin distribution in both kidneys. Partial UUO reduced growth and increased apoptosis, macrophages, alpha-smooth muscle actin, and collagen in the obstructed kidney. Early losartan treatment further increased alpha-smooth muscle actin and collagen in the obstructed kidney and induced apoptosis, macrophages, and collagen in the contralateral kidney. Late losartan treatment had no effect on any of the parameters in either kidney, and PD-123319 had no effect on either kidney. We conclude that selective inhibition of AT(1) receptors during nephrogenesis (but not during subsequent renal maturation) exacerbates injury to the obstructed kidney and also injures the contralateral kidney. These results suggest that angiotensin II receptor blockers should be avoided in the developing hydronephrotic kidney.

The role of angiotensin II in stress urinary incontinence: A rat model

AIMS

Pharmacological treatment for stress urinary incontinence (SUI) is limited to the use of non-selective alpha-agonists, which are often ineffective. Non-adrenergic mechanisms have also been implicated in urethral closure, including angiotensin II (Ang-II), which has been demonstrated throughout the urinary tract. We investigate the role of Ang-II in urethral tone in a rat model of SUI.

METHODS

Abdominal leak point pressure (ALPP) and retrograde urethral pressure profilometry (RLPP) were measured in 70 female virgin rats. Thirty rats underwent pudendal nerve injury (PNT), 30 had circumferential urethrolysis (U-Lys), and 10 had sham surgery. Rats received daily doses of Angiotensin Type 1 (AT-1) receptor inhibitor (20 mg/kg), Angiotensin Type 2 (AT-2) receptor antagonist (10 mg/kg), or Ang-II (2 mg/kg).

RESULTS

Following U-Lys, RLPP and ALPP decreased from 21.4 +/- 2.0 and 39.2 +/- 3.3 mm Hg, to 13.1 +/- 1.5 and 21.6 +/- 1.9 mmHg, respectively (P < 0.01). After PNT, RLPP, and ALPP decreased from 21.0 +/- 1.6 and 41.9 +/- 3.0 mmHg to 13.1 +/- 1.5 and 24.7 +/- 3.3 mmHg, respectively (P < 0.01). AT-1 inhibitor caused significant decrease in RLPP and ALPP from 21.0 +/- 6.2 and 41.8 +/- 9.4 mmHg, to 12.0 +/- 3.8 and 25.6 +/- 6.6 mmHg, respectively (P < 0.01). Likewise, AT-2 treatment reduced RLPP and ALPP from 21.4 +/- 6.3 and 40.1 +/- 1.7 mmHg, to 13.5 +/- 5.7 and 31.0 +/- 7.2 mmHg, respectively (P < 0.01). Following surgery, Ang-II administration restored RLPP and ALPP to baseline presurgical values.

CONCLUSIONS

AT-1 and AT-2 receptor inhibition significantly lowers urethral resistance, comparable to either neurogenic or urethrolytic injury. Ang-II treatment restored urethral tone in rats with intrinsic sphincter dysfunction. Ang II appears to serve a functional role in the maintenance of urethral tone and stress continence.

Role of angiotensin II type-1 and type-2 receptors on vascular smooth muscle cell growth and glucose metabolism in diabetic rats

This study investigates the mechanisms whereby angiotensin II (Ang II) signaling contributes to cell growth and glucose metabolism in cultured vascular smooth muscle cells (VSMCs) from male Wistar fatty rats (WF) and their littermates (Wistar lean rats, WL). The levels of the medial outgrowth rate of VSMCs and Ang II type-1 receptors (AT1R) in aortae from WF were more enhanced than those in aortae from WL, but the level of Ang II type-2 receptors (AT2R) was not different. A mixture of insulin and Ang II additively increased the values of [(3)H]-thymidine incorporation in WF and WL, which was inhibited by olmesartan, an AT1 receptor blockade (ARB), but not by PD123,319, an AT2 receptor blockade. Similarly, insulin and Ang II phosphorylated extracellular-regulated protein kinase 1/2, retinoblastoma tumor suppressor protein, and cyclic AMP response element binding protein, and these levels were higher in WF than in WL. In contrast, the phosphorylation was suppressed by olmesartan but not PD123,319. Insulin-stimulated Akt phosphorylation and 2-deoxy-d-glucose uptake in WF were significantly reduced by Ang II, and the reduction was ameliorated by olmesartan but not PD123,319. Differently from the result of Akt, the phosphorylation of the insulin-stimulated insulin receptor beta-subunit was not affected by Ang II, olmesartan, or PD123,319. However, the phosphorylation of insulin-stimulated insulin-related substrate (IRS)-1 was suppressed by Ang II, and the suppression was ameliorated by olmesartan, but not PD123,319, in both WF and WL. In contrast, the phosphorylation of IRS-1 on Ser(307) was elevated by the Ang II, and the elevation was suppressed by olmesartan, but not by PD123,319, in both WF and WL. These findings demonstrated that Ang II signaling contributes to cell proliferation and inhibition of the insulin signaling pathways through AT1R, but not trough AT2R, in both non-diabetic and diabetic VSMCs.