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ABSTRACT: OBJECTIVE: To investigate diabetes mellitus (DM)-induced oxidative DNA damage, putative involvement of angiotensin (Ang) II, and possible modulatory effects of Ang-(1-7) in rat corpus cavernosum (CC). DESIGN: In vivo study. SETTING: Research laboratory. ANIMAL(S): Adult male Wistar rats. INTERVENTION(S): Streptozotocin-induced diabetic rats received either captopril, losartan (both 300 mg/L in drinking water), or Ang-(1-7) (576 μg/kg/d IP) for a 3-week period immediately before sacrifice at 6 weeks of DM. MAIN OUTCOME MEASURE(S): Histopathological changes in CC were examined in Masson's trichrome-stained tissue sections. Oxidative stress was evaluated by measuring total oxidant status and antioxidant status. The DNA damage was estimated by measuring 8-hydroxy-2'-deoxyguanosine by immunohistochemistry and ELISA. RESULT(S): The CC smooth muscle degeneration was observed in association with an increase in total oxidant status and a decrease in total antioxidant status in rats with DM. Oxidative DNA damage was significantly increased in both cytoplasm and nuclei of CC in DM. Treatment with captopril, losartan, or Ang-(1-7) inhibited these changes in rats with DM. CONCLUSION(S): The data indicate that Ang II signaling is involved in DM-induced structural changes and oxidative DNA damage in the CC and that modulation of the signaling by captopril, losartan, and Ang-(1-7) restores the effects of DM. Thus, Ang-(1-7)/MAS1 axis may be a novel therapeutic target for erectile dysfunction in DM.
Fertility and sterility 03/2013; · 3.97 Impact Factor
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ABSTRACT: Polyamidoamine (PAMAM) dendrimers are cationic branch-like macromolecules that may serve as drug delivery systems for gene-based therapies such as RNA interference. For their safe use in the clinic, they should ideally only enhance drug delivery to target tissues and exhibit no adverse effects. However, little is known about their toxicological profiles in terms of their interactions with cellular signal transduction pathways such as the epidermal growth factor receptor (EGFR). The EGFR is an important signaling cascade that regulates cell growth, differentiation, migration, survival and apoptosis. Here, we investigated the impact of naked, unmodified Superfect (SF), a commercially available generation 6 PAMAM dendrimer, on the epidermal growth factor receptor (EGFR) tyrosine kinase -Extracellular-regulated kinase 1/2 (ERK1/2) signaling pathway in human embryonic kidney (HEK-293) cells. At concentrations routinely used for transfection, SF exhibited time and dose-dependent stimulation of EGFR and ERK1/2 phosphorylation whereas AG1478, a selective EGFR tyrosine kinase antagonist, inhibited EGFR-ERK1/2 signaling. SF-induced phosphorylation of EGFR for 1h was partly reversible upon removal of the dendrimer and examination of cells 24 later. Co-treatment of SF with epidermal growth factor (EGF) ligand resulted in greater EGFR stimulation than either agent alone implying that the stimulatory effects of SF and the ligand are synergistic. Dendrimer-induced stimulation of EGFR-ERK1/2 signaling could be attenuated by the antioxidants apocynin, catalase and tempol implying that an oxidative stress dependent mechanism was involved. These results show for the first time that PAMAM dendrimers, aside from their ability to improve drug delivery, can modulate the important EGFR-ERK1/2 cellular signal transduction pathway- a novel finding that may have a bearing on their safe application as drug delivery systems.
International journal of pharmaceutics 03/2013; · 2.96 Impact Factor
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ABSTRACT: Diabetes is associated with increased incidence of cardiovascular disease. Mechanisms that contribute to development of diabetic cardiopathy are not well understood. Phosphatidylinositol 3-kinase (PI3K) is a family of protein kinases that play an important role in regulation of cardiac function. It has been shown that inhibition of certain PI3K enzymes may produce cardiovascular protection. The aim of the present study was to determine whether chronic treatment with LY294002, an inhibitor of PI3K, can attenuate diabetes-induced cardiac dysfunction in isolated hearts obtained from normotensive and hypertensive rats. Recovery of cardiac function after 40 min of global ischemia and 30 min of reperfusion, measured as left ventricular developed pressure, left ventricular end-diastolic pressure, coronary flow and coronary vascular resistance, was worse in hearts obtained from diabetic and/or hypertensive animals compared to their respective controls. Treatment with LY294002 (1.2 mg/kg/day) for 4 weeks significantly prevented diabetes-induced cardiac dysfunction in both normotensive and hypertensive rats. Treatment with LY294002 did not significantly alter blood pressure or blood glucose levels. These results suggest that inhibition of PI3K signaling pathways can prevent ischemia/reperfusion-induced cardiac dysfunction in normotensive and hypertensive rats without correcting hyperglycemia or high blood pressure.
Molecular and Cellular Biochemistry 11/2012; · 2.06 Impact Factor
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ABSTRACT: Although exogenous administration of Angiotensin-(1-7) [Ang-(1-7)] can prevent development of diabetes induced end-organ damage, little is known about the role of endogenous Ang-(1-7) in diabetes and requires further characterization. Here, we studied the effects of chronically inhibiting endogenous Ang-(1-7) formation with DX600, a selective angiotensin converting enzyme-2 (ACE2) inhibitor, on renal and cardiac NADPH oxidase (NOX) activity, vascular reactivity and cardiac function in a model of Type-1 diabetes. The contribution of endogenous Ang-(1-7) to the protective effects of Losartan and Captopril and that of prostaglandins to the cardiovascular effects of exogenous Ang-(1-7) were also examined. Cardiac and renal NOX activity, vascular reactivity to endothelin-1 (ET-1) and cardiac recovery from ischemia/reperfusion (I/R) injury were evaluated in streptozotocin-treated rats. Chronic treatment with DX600 exacerbated diabetes-induced increase in cardiac and renal NOX activity. Diabetes-induced abnormal vascular reactivity to ET-1 and cardiac dysfunction were improved by treatment with Ang-(1-7) and worsened by treatment with DX600 or A779, a Mas receptor antagonist. Ang-(1-7)-mediated improvement in cardiac recovery or vascular reactivity was attenuated by Indomethacin. Captopril and Losartan-induced improvement in cardiovascular function was attenuated when these drugs were co-administered with A779. Ang-(1-7)-mediated decrease in renal NOX activity was prevented by indomethacin. Losartan also decreased renal NOX activity that could be attenuated with A779 co-treatment. In conclusion, endogenous Ang-(1-7) inhibits diabetes-induced cardiac/renal NOX activity and end-organ damage, and mediates the actions of Captopril and Losartan. Further, prostaglandins are important intermediaries in the beneficial effects of Ang-(1-7) in diabetes. Combining either Losartan or Captopril with Ang-(1-7) had additional beneficial effects in preventing diabetes-induced cardiac dysfunction and this may represent a novel therapeutic strategy. Collectively, these data shed new insights into the likely mechanism of action through which the ACE2/Ang-(1-7)/Mas receptor axis prevents Type 1 diabetes-induced cardiovascular dysfunction.
Pharmacological Research 05/2012; 66(3):269-75. · 4.44 Impact Factor
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ABSTRACT: This study characterized the effects of diabetes and/or ischemia on epidermal growth factor receptor, EGFR, and/or erbB2 signaling pathways on cardiac function. Isolated heart perfusion model of global ischemia was used to study the effect of chronic inhibition or acute activation of EGFR/erbB2 signaling on cardiac function in a rat model of type-1 diabetes. Induction of diabetes with streptozotocin impaired recovery of cardiac function (cardiac contractility and hemodynamics) following 40 minutes of global ischemia in isolated hearts. Chronic treatment with AG825 or AG1478, selective inhibitors of erbB2 and EGFR respectively, did not affect hyperglycemia but led to an exacerbation whereas acute administration of the EGFR ligand, epidermal growth factor (EGF), led to an improvement in cardiac recovery in diabetic hearts. Diabetes led to attenuated dimerization and phosphorylation of cardiac erbB2 and EGFR receptors that was associated with reduced signaling via extracellular-signal-regulated kinase 1/2 (ERK1/2), p38 mitogen activated protein (MAP) kinase and AKT (protein kinase B). Ischemia was also associated with reduced cardiac signaling via these molecules whereas EGF-treatment opposed diabetes and/or ischemia induced changes in ERK1/2, p38 MAP kinase, and AKT-FOXO signaling. Losartan treatment improved cardiac function in diabetes but also impaired EGFR phosphorylation in diabetic heart. Co-administration of EGF rescued Losartan-mediated reduction in EGFR phosphorylation and significantly improved cardiac recovery more than with either agent alone. EGFR/erbB2 signaling is an important cardiac survival pathway whose activation, particularly in diabetes, ischemia or following treatment with drugs that inhibit this cascade, significantly improves cardiac function. These findings may have clinical relevance particularly in the treatment of diabetes-induced cardiac dysfunction.
PLoS ONE 01/2012; 7(6):e39066. · 4.09 Impact Factor
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ABSTRACT: The transactivation of the epidermal growth factor (EGF) receptor appears to be an important central transduction mechanism in mediating diabetes-induced vascular dysfunction. Angiotensin-(1-7) [Ang-(1-7)] via its Mas receptor can prevent the development of hyperglycaemia-induced cardiovascular complications. Here, we investigated whether Ang-(1-7) can inhibit hyperglycaemia-induced EGF receptor transactivation and its classical signalling via ERK1/2 and p38 MAPK in vivo and in vitro.
Streptozotocin-induced diabetic rats were chronically treated with Ang-(1-7) or AG1478, a selective EGF receptor inhibitor, for 4 weeks and mechanistic studies performed in the isolated mesenteric vasculature bed as well as in primary cultures of vascular smooth muscle cells (VSMCs).
Diabetes significantly enhanced phosphorylation of EGF receptor at tyrosine residues Y992, Y1068, Y1086, Y1148, as well as ERK1/2 and p38 MAPK in the mesenteric vasculature bed whereas these changes were significantly attenuated upon Ang-(1-7) or AG1478 treatment. In VSMCs grown in conditions of high glucose (25 mM), an Src-dependent elevation in EGF receptor phosphorylation was observed. Ang-(1-7) inhibited both Ang II- and glucose-induced transactivation of EGF receptor. The inhibition of high glucose-mediated Src-dependant transactivation of EGF receptor by Ang-(1-7) could be prevented by a selective Mas receptor antagonist, D-Pro7-Ang-(1-7).
These results show for the first time that Ang-(1-7) inhibits EGF receptor transactivation via a Mas receptor/Src-dependent pathway and might represent a novel general mechanism by which Ang-(1-7) exerts its beneficial effects in many disease states including diabetes-induced vascular dysfunction.
British Journal of Pharmacology 08/2011; 165(5):1390-400. · 4.41 Impact Factor
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ABSTRACT: We assessed the contribution of angiotensin-(1-7) [Ang-(1-7)] to captopril-induced cardiovascular protection in spontaneously hypertensive rats (SHRs) chronically treated with the nitric oxide synthesis inhibitor NG-nitro-L-arginine methyl ester (SHR-l). NG-nitro-L-arginine methyl ester (80 mg/L) administration for 3 weeks increased mean arterial pressure (MAP) from 196 ± 6 to 229 ± 3 mm Hg (P < 0.05). Treatment of SHR-l with Ang-(1-7) antagonist [d-Ala7]-Ang-(1-7) (A779; 744 μg·kg(-1)·d(-1) ip) further elevated MAP to 253 ± 6 mm Hg (P < 0.05 vs SHR-l or SHR). Moreover, A779 treatment attenuated the reduction in MAP and proteinuria by either captopril (300 mg/L in drinking water) or hydralazine (1.5 mg·kg(-1)·d(-1) ip). In isolated perfused hearts, the recovery of left ventricular function from global ischemia was enhanced by captopril or hydralazine treatment and was exacerbated with A779. The Ang-(1-7) antagonist attenuated the beneficial effects of captopril and hydralazine on cardiac function. Recovery from global ischemia was also improved in isolated SHR-l hearts acutely perfused with captopril during both the perfusion and reperfusion periods. The acute administration of A779 reduced the beneficial actions of captopril to improve recovery after ischemia. We conclude that during periods of reduced nitric oxide availability, endogenous Ang-(1-7) plays a protective role in effectively buffering the increase in blood pressure and renal injury and the recovery from cardiac ischemia. Moreover, Ang-(1-7) contributes to the blood pressure lowering and tissue protective actions of captopril and hydralazine in a model of severe hypertension and end-organ damage.
Journal of cardiovascular pharmacology 02/2011; 57(5):559-67. · 2.83 Impact Factor
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ABSTRACT: The mechanisms by which angiotensin-(1-7) [Ang-(1-7)] exerts its beneficial effects on end-organ damage associated with diabetes and hypertension are not well understood. The purpose of this study was A) to compare the effects of apocynin with Ang-(1-7) on renal vascular dysfunction and NADPH oxidase activity in a combined model of diabetes and hypertension and B) to further determine whether chronic treatment with Ang-(1-7) can modulate renal catalase, and peroxisome proliferator activated receptor- gamma (PPAR-gamma) levels in streptozotocin-induced diabetes in both normotensive Wistar Kyoto rats (WKY) and in spontaneously hypertensive rats (SHR). Apocynin or Ang-(1-7) treatment for one month starting at the onset of diabetes similarly attenuated elevation of renal NADPH oxidase activity in the diabetic SHR kidney and reduced the degree of proteinuria and hyperglycemia, but had little or modest effect on reducing mean arterial pressure. Both drugs also attenuated the diabetes-induced increase in renal vascular responsiveness to endothelin-1. Induction of diabetes in WKY and SHR animals resulted in significantly reduced renal catalase activity and in PPAR-gamma mRNA and protein levels. Treatment with Ang-(1-7) significantly prevented diabetes-induced reduction in catalase activity and the reduction in PPAR-gamma mRNA and protein levels in both animal models. Taken together, these data suggest that activation of Ang-(1-7)-mediated signaling could be an effective way to prevent the elevation of NADPH oxidase activity and inhibition of PPAR-gamma and catalase activities in diabetes and/or hypertension.
European journal of pharmacology 07/2010; 638(1-3):108-14. · 2.59 Impact Factor
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ABSTRACT: Peroxisomes are known to play a role in cellular oxidative stress during pathogenesis of diabetes and hypertension. We reported earlier that FPTIII (a farnesyl protein transferase inhibitor) attenuates ischemia-reperfusion injury and renal dysfunction in diabetic hypertensive (DH) rats. In this study, we have examined the effect of FPTIII on peroxisomal enzymes in relation to oxidative stress in kidneys of DH rats.
Male Wistar-Kyoto (WKY) and spontaneously hypertensive (SHR) rats were treated with streptozotocin (STZ) and/or FPTIII. Activities of key peroxisomal enzymes, catalase, acyl-CoA oxidase and beta-oxidation of lignoceric acid were measured in kidney homogenates. Lipid peroxidation in kidney was measured by malondialdehyde (MDA) assay.
Catalase activity was significantly (p < 0.01) reduced in diabetic WKY or SHR, and FPTIII markedly attenuated (p < 0.01) diabetes-induced inhibition of catalase. FPTIII also reduced STZ-induced increase in acyl-CoA oxidase activity. Fatty acid beta-oxidation and lipid peroxides were significantly increased in kidneys of DH rats. FPTIII reduced (p < 0.01) diabetes and hypertension-induced increase in fatty acid oxidation and lipid peroxides.
Our results suggest that farnesyl transferase inhibition modulates peroxisome enzyme activities and alleviates oxidative stress, thus providing a possible mechanism for reported FPTIII-mediated protection against renal dysfunction in DH rats.
Kidney and Blood Pressure Research 03/2010; 33(1):60-5. · 1.46 Impact Factor
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ABSTRACT: The objective of this study was to determine if acute inhibition of 20-hydroxyeicosatetraenoic acid (20-HETE) synthesis or reduced inactivation of epoxyeicosatrienoic acids (EETs) can correct L-N(G)-nitro-arginine-methyl-ester (L-NAME)-induced abnormal vascular reactivity in the perfused mesenteric bed and the carotid artery of spontaneously hypertensive rats (SHR). Administration of L-NAME in drinking water (80 mg/l) to SHR for 3 weeks resulted in abnormal vascular reactivity to norepinephrine and carbachol in the perfused mesenteric vascular bed and carotid artery, and significantly elevated mean arterial blood pressure (244 +/- 9 mm Hg) as compared to SHR controls drinking regular water (176 +/- 3 mm Hg). In the perfused mesenteric vascular bed, the impaired vascular responsiveness to norepinephrine was corrected by acute treatment with N-hydroxy-N'-(4-butyl-2-methylphenyl)formamidine (HET0016), an inhibitor of 20-HETE formation, but not by 1-cyclohexyl-3-dodecyl urea (CDU), an inhibitor of soluble epoxide hydrolase. Treatment with either HET0016 or CDU did not improve impaired carbachol-induced vasodilation in the perfused mesenteric vascular bed. In the isolated carotid artery, treatment with HET0016 corrected the L-NAME-induced increase in norepinephrine-induced vasoconstriction, whereas only CDU treatment could improve impaired carbachol-induced vasodilation. Results of this study indicate that vascular function in a state of compromised nitric oxide formation is differentially modulated by 20-HETE and EETs, and that treatment with HET0016 or CDU may improve vascular function in a state of high blood pressure and endothelial dysfunction.
Pharmacology 01/2010; 86(3):149-56. · 1.79 Impact Factor
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ABSTRACT: Diabetes mellitus is associated with vascular complications including an impairment of vascular function and alterations in the reactivity of blood vessels to vasoactive hormones. However, the signaling mechanisms leading to vascular dysfunction in diabetes are not fully understood. This microarray-based study was designed to identify differential gene expression between the normal and diabetic mesenteric vasculature and to investigate the effect of inhibiting epidermal growth factor receptor (EGFR) signaling on global gene expression in the mesenteric bed of streptozotocin (STZ)-induced diabetic rats. Transcriptome analysis was performed in triplicate using oligonucleotide microarrays housing 10,000 rat genes on the mesenteric bed of normal, diabetic, and diabetic rats treated with AG1478, a selective inhibitor of EGFR. Four weeks of diabetes led to a profound alteration in gene expression within the mesenteric bed with 1167 of the 3074 annotated genes being up-regulated and 141 genes down-regulated by at least 2-fold. The up-regulated gene ontologies included receptor tyrosine kinases, G-protein coupled receptors and ion channel activity. In particular, significant overexpressions of colipase, phospholipase A2, carboxypeptidases, and receptor tyrosine kinases such as EGFR, erbB2 and fibroblast growth factor receptor were observed in diabetes mesenteric vasculature. A 4-week intraperitoneal treatment of diabetic animals with AG1478 (1.2 mg/kg/alt diem) beginning on the same day as STZ injection prevented up-regulation of the majority (approximately 95%) of the genes associated with STZ diabetes including those apparently "unrelated" to the known EGFR pathway without correction of hyperglycemia. These results suggest that activation of EGFR signaling is a key initiating step that leads to induction of multiple signaling pathways in the development of diabetes-induced vascular dysfunction. Thus, therapeutic targeting of EGFR may represent a novel strategy for the prevention and/or treatment of vascular dysfunction in diabetes.
Vascular Pharmacology 08/2009; 51(4):236-45. · 1.99 Impact Factor
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ABSTRACT: Renal dysfunction is a major cause of morbidity and mortality in patients with hypertension. In an attempt to understand the molecular mechanisms leading to renal dysfunction and in particular that of epidermal growth factor receptor (EGFR) and RasGTPase signaling, we analyzed global gene expression changes in the kidneys of deoxycorticosterone acetate (DOCA)-salt-induced hypertensive rats with and without treatment with AG1478, a selective inhibitor of EGFR tyrosine kinase, or FPTIII, a farnesyl transferase inhibitor known to inhibit RasGTPase. Microarray-based global gene expression analysis was performed in triplicate for each rat kidney taken from normotensive Wistar rats, DOCA-salt hypertensive (DH) rats, DH rats treated with AG1478, or DH rats treated with FPTIII. From the initial data set of 10,163 gene spots per group, upregulation of 2398 genes and downregulation of only 50 genes by more than 2-fold was observed in hypertensive rat kidneys compared to non-diseased controls. Interestingly, treatment of animals with AG1478 or FPTIII prevented upregulation of more than 97% of genes associated with hypertension in the rat kidney. Analysis of proteinuria, renal artery responsiveness and histopathology studies confirmed that DOCA-salt hypertensive rats had developed kidney damage over the study period and that this kidney dysfunction could be significantly prevented upon AG1478 or FPTIII treatment without normalising blood pressure. Taken together, our data imply that signaling cascades involving EGFR and/or RasGTPase pathways are key contributors to the induction of renal damage in hypertension and these and potentially other downstream effector molecules may serve as novel targets for therapeutic intervention.
Vascular Pharmacology 06/2009; 51(2-3):101-9. · 1.99 Impact Factor
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ABSTRACT: This study examined the role of epidermal growth factor receptor (EGFR) signalling on the organization and remodelling of collagen fibrils (CFs) and proteoglycans (PGs) in the stroma of diabetic rat cornea.
Diabetes was induced in female Wistar rats (n = 5) by streptozotocin (STZ) injection (55 mg/kg). Treatment with a selective inhibitor of EGFR tyrosine kinase, AG1478, was started on the same day as the induction of diabetes and administered every other day for 4 weeks. Corneas were fixed in 4% paraformaldehyde at 4 degrees to allow for analysis of CF diameters and in 2.5% glutaraldehyde in sodium acetate buffer containing cuprolinic blue to enable the study of PG distribution. AnalySIS soft imaging software was used to analyse CFs and PGs.
Epithelial thickness, and median diameter and area fraction of CF in corneal stroma were decreased in diabetic rat cornea compared with normal cornea (p < 0.001), whereas the median PG area and area fractions were significantly increased (p < 0.001). Treatment with AG1478, although it had no action on normal cornea, prevented these diameter and area fraction changes in CFs and PGs. The cornea of AG1478-treated diabetic rats showed a slight increase in CF diameter and area fraction and a decreased number density.
These data show that the distribution of corneal stroma CFs and PGs was altered after 4 weeks of diabetes and that, furthermore, treatment with an EGFR signalling inhibitor normalized these abnormalities. The data suggest that EGFR plays an important role in the development of diabetes-induced corneal remodelling.
Acta ophthalmologica 03/2009; 87(8):881-9. · 2.44 Impact Factor
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ABSTRACT: We studied the effect an inhibitor of Ras-GTPase (FPTIII, 1.5 mg/kg alt diem for 4 weeks) on mean arterial pressure (MAP), urine protein, vascular reactivity and cardiac function in streptozotocin (STZ)-induced diabetes in control normotensive (WKY) and spontaneously hypertensive rats (SHR). The increased urinary protein in STZ-treated WKY (D-WKY) and STZ-treated SHR (D-SHR) were significantly lower in FPTIII treated D-WKY and D-SHR. The abnormal vascular responsiveness to endothelin-1, angiotensin II, carbachol or histamine in isolated carotid artery from D-WKY and D-SHR was improved by chronic treatment with FPTIII. In isolated perfused hearts, recovery of left ventricular function from 40 min of global ischemia was significantly improved in FPTIII treated D-WKY and D-SHR. These results show that treatment with FPTIII can attenuate development of abnormal vascular reactivity and renal/cardiac dysfunction during simultaneous occurrence of hypertension and diabetes.
Vascular Pharmacology 08/2008; 49(4-6):151-7. · 1.99 Impact Factor
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ABSTRACT: We examined the influence of chronic treatment with angiotensin-(1-7) [Ang-(1-7)] on renox (renal NADPH oxidase, NOX-4) and the development of renal dysfunction in streptozotocin-treated spontaneously hypertensive rats (diabetic SHR).
Mean arterial pressure, urinary protein and vascular responsiveness of the isolated renal artery to vasoactive agonists were studied in vehicle- or Ang-(1-7)-treated SHR and diabetic SHR.
Ang-(1-7) decreased the elevated levels of renal NADPH oxidase (NOX) activity and attenuated the activation of NOX-4 gene expression in the diabetic SHR kidney. Ang-(1-7) treatment increased sodium excretion but did not affect mean arterial pressure in diabetic SHR. There was a significant increase in urinary protein (266 +/- 22 mg/24 h) in the diabetic compared to control SHR (112 +/- 13 mg/24 h) and treatment of diabetic SHR with Ang-(1-7) reduced the degree of proteinuria (185 +/- 23 mg/24 h, p < 0.05). Ang-(1-7) treatment also attenuated the diabetes-induced increase in renal vascular responsiveness to endothelin-1, norepinephrine, and angiotensin II in SHR, but significantly increased the vasodilation of the renal artery of SHR and diabetic SHR to the vasodilator agonists.
These results suggest that treatment with Ang-(1-7) constitutes a potential therapeutic strategy to alleviate NOX-mediated oxidative stress and to reduce renal dysfunction in diabetic hypertensive rats.
American Journal of Nephrology 01/2008; 28(1):25-33. · 2.54 Impact Factor
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ABSTRACT: We evaluated the ability of angiotensin-(1-7) [Ang-(1-7)] to produce relaxation of the corpus cavernosum of New Zealand White rabbits. The reactivity of corpus cavernosal strips isolated from young rabbits (8-10 months old) was assessed in organ-bath chambers. Cumulative concentration response curves for Ang-(1-7), angiotensin II (Ang II), carbachol and sodium nitroprusside (SNP) were established. Ang-(1-7) (10(-12) to 10(-5)M) produced a concentration-dependent relaxation of the corpus cavernosal strips with a pD(2) value of 9.8+/-0.3. Ang-(1-7)-induced maximal relaxant response was reduced by 48+/-2%, 57+/-3% and 76+/-2% in the presence of A-779 (10(-6)M), a selective Ang-(1-7) receptor (AT(1-7)) antagonist, nitro-l-arginine methyl ester (l-NAME) (10(-4)M), an inhibitor of nitric oxide (NO) synthase, or iberiotoxin (5 x 10(-8)M), an inhibitor of calcium-activated potassium (BK) channels, respectively. In contrast, Ang II-induced contraction was increased in the presence of A-779. Carbachol-, SNP- and Ang-(1-7)-induced relaxations were significantly reduced whereas Ang-II induced contraction was significantly increased in the cavernosum strips from older (18-24 months old) and diabetic rabbits compared to the young. Pre-incubation of the cavernosum strips obtained from young, older or diabetic rabbits with Ang-(1-7) resulted in a significant attenuation of Ang II-induced contraction. In conclusion, these results demonstrate that Ang-(1-7) can produce nitric oxide-dependent relaxation of the corpus cavernosum through activation of AT(1-7) and BK channels. Older and diabetic animals showed impaired Ang-(1-7)-mediated relaxation suggesting that aging and diabetes related erectile dysfunction (ED) may be partly due to decreased Ang-(1-7)-mediated relaxation of the corpus cavernosum. Acute pre-incubation with Ang-(1-7) was effective in attenuating Ang II-induced contraction of rabbit corpus cavernosum suggesting that the possible role of Ang-(1-7) in treatment of ED should be investigated.
Pharmacological Research 10/2007; 56(3):209-16. · 4.44 Impact Factor
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ABSTRACT: The aim of this study was to test the hypothesis that treatment with angiotensin-(1-7) [ANG-(1-7)] or ANG-(1-7) nonpeptide analog AVE-0991 can produce protection against diabetes-induced cardiovascular dysfunction. We examined the influence of chronic treatment (4 wk) with ANG-(1-7) (576 microg.kg(-1).day(-1) ip) or AVE-0991 (576 microg.kg(-1).day(-1) ip) on proteinuria, vascular responsiveness of isolated carotid and renal artery ring segments and mesenteric bed to vasoactive agonists, and cardiac recovery from ischemia-reperfusion in streptozotocin-treated rats (diabetes). Animals were killed 4 wk after induction of diabetes and/or treatment with ANG-(1-7) or AVE-0991. There was a significant increase in urine protein (231 +/- 2 mg/24 h) in diabetic animals compared with controls (88 +/- 6 mg/24 h). Treatment of diabetic animals with ANG-(1-7) or AVE-0991 resulted in a significant reduction in urine protein compared with vehicle-treated diabetic animals (183 +/- 16 and 149 +/- 15 mg/24 h, respectively). Treatment with ANG-(1-7) or AVE-0991 also prevented the diabetes-induced abnormal vascular responsiveness to norepinephrine, endothelin-1, angiotensin II, carbachol, and histamine in the perfused mesenteric bed and isolated carotid and renal arteries. In isolated perfused hearts, recovery of left ventricular function from 40 min of global ischemia was significantly better in ANG-(1-7)- or AVE-0991-treated animals. These results suggest that activation of ANG-(1-7)-mediated signal transduction could be an important therapeutic strategy to reduce cardiovascular events in diabetic patients.
AJP Heart and Circulatory Physiology 02/2007; 292(1):H666-72. · 3.71 Impact Factor
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ABSTRACT: We examined the influence of chronic treatment with ANG-(1-7) on development of hypertension and end-organ damage in spontaneously hypertensive rats (SHR) chronically treated with the nitric oxide synthesis inhibitor L-NAME (SHR-L-NAME). L-NAME administered orally (80 mg/l) for 4 wk significantly elevated mean arterial pressure (MAP) compared with SHR controls drinking regular water (269 +/- 10 vs. 196 +/- 6 mmHg). ANG-(1-7) (24 microg x kg(-1) x h(-1)) or captopril (300 mg/l) significantly attenuated the elevation in MAP due to L-NAME (213 +/- 7 and 228 +/- 8 mmHg, respectively), and ANG-(1-7) + captopril completely reversed the L-NAME-dependent increase in MAP (193 +/- 5 mmHg). L-NAME-induced increases in urinary protein were significantly lower in ANG-(1-7)-treated animals (226 +/- 6 vs. 145 +/- 12 mg/day). Captopril was more effective (96 +/- 12 mg/day), and there was no additional effect of captopril + ANG-(1-7) (87 +/- 5 mg/day). The abnormal vascular responsiveness to endothelin-1, carbachol, and sodium nitroprusside in perfused mesenteric vascular bed of SHR-L-NAME was improved by ANG-(1-7) or captopril, with no additive effect of ANG-(1-7) + captopril. In isolated perfused hearts, recovery of left ventricular function from 40 min of global ischemia was significantly better in ANG-(1-7)- or captopril-treated SHR-L-NAME, with additive effects of combined treatment. The beneficial effects of ANG-(1-7) on MAP and cardiac function were inhibited when indomethacin was administered with ANG-(1-7), but indomethacin did not reverse the protective effects on proteinuria or vascular reactivity. The protective effects of the ANG-(1-7) analog AVE-0991 were qualitatively comparable to those of ANG-(1-7) but were not improved over those of captopril alone. Thus, during reduced nitric oxide availability, ANG-(1-7) attenuates development of severe hypertension and end-organ damage; prostaglandins participate in the MAP-lowering and cardioprotective effects of ANG-(1-7); and additive effects of captopril + ANG-(1-7) on MAP, but not proteinuria or endothelial function, suggest common, as well as different, mechanisms of action for the two treatments. Together, the results provide further evidence of a role for ANG-(1-7) in protective effects of angiotensin-converting enzyme inhibition and suggest dissociation of factors influencing MAP and those influencing end-organ damage.
AJP Heart and Circulatory Physiology 03/2006; 290(2):H684-91. · 3.71 Impact Factor
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ABSTRACT: The purpose of this study was to examine the effect of inhibition of Ras-GTPase mediated signalling on the development of hypertension and end-organ damage in spontaneously hypertensive rats chronically treated with nitric oxide synthesis inhibitor L-NAME (SHR-L-NAME). Administration of L-NAME in drinking water (80 mg/L) for 3 weeks significantly elevated mean arterial blood pressure (MABP) (223+/-4 mmHg) as compared to that of SHR controls (165+/-3 mmHg). The administration of Ras-GTPase inhibitor FPTIII (232 ng/min) to SHR-L-NAME during the last 6 days significantly attenuated high blood pressure (192+/-4 mmHg). Morphological studies of the kidneys and hearts showed that treatment with FPTIII minimized the extensive arterial fibrinoid necrosis, arterial thrombosis, narrowing of arterial lumen with marked arterial hyperplastic arterial changes that were observed in vehicle treated SHR-L-NAME. L-NAME-induced increase in urine volume and protein was also significantly lower in FPTIII-treated animals. The impaired vascular responsiveness to isoprenaline in the perfused mesenteric vascular bed of SHR-L-NAME-treated animals was significantly attenuated by FPTIII treatment. In isolated perfused hearts, recovery of left ventricular function from a 40 min of global ischemia was significantly better in FPTIII-treated SHR-L-NAME. Treatment with FPTIII also significantly reduced expression of cardiac sodium-hydrogen exchanger-1 (NHE-1) which was elevated in SHR-L-NAME. These data indicate that inhibition of Ras-GTPase-mediated signalling can attenuate end-organ damage during severe hypertension and endothelial dysfunction.
Pharmacological Research 12/2005; 52(5):401-12. · 4.44 Impact Factor
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ABSTRACT: Diabetes causes accelerated vascular dysfunction through mechanisms that are poorly understood. This study examined the role of Ca2+/calmodulin-dependent protein kinase II (CaMKII), Ras-GTPase and 20-hydroxyeicosatetraenoic acid (20-HETE) in the development of abnormal reactivity to vasoactive agents in the carotid artery of diabetic rats. The vasoconstrictor response induced by endothelin-1 (ET-1) was significantly increased, whereas vasodilator response to carbachol was significantly reduced in the carotid artery segments of the STZ-diabetic rats. In contrast, the vasoconstrictor response to depolarization of the carotid arterial rings with 50mM KCl was similar in control and diabetic animals. Chronic intraperitoneal administration of KN-93 (5 mg/kg/alt diem), an inhibitor of CaMKII, FPTIII (1.5 mg/kg/alt diem), an inhibitor of Ras-GTPase, and inhibitors of 20-HETE formation 1-aminobenzotriazole (ABT, 50 mg/kg/alt diem) and N-hydroxy-N'-(4-butyl-2-methylphenyl)formamidine (HET0016, 2.5mg/kg/day), produced significant normalization of the altered agonist-induced vasoconstrictor and vasodilator responses without affecting blood glucose levels. All the inhibitors were administered for 4 weeks starting from the day 1 of diabetes induction. Inhibition of CaMKII, Ras-GTPase or 20-HETE formation did not affect the agonist-induced vasoconstrictor and vasodilator responses in the non-diabetic control animals. These data indicate that chronic blockade of CaMKII, Ras-GTPase or the production of 20-HETE normalizes the altered vascular reactivity to ET-1 and carbachol in the carotid artery of STZ-induced diabetic rats.
Pharmacological Research 10/2005; 52(3):252-7. · 4.44 Impact Factor
