Publications (20)76.45 Total impact
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Article: Upregulation of the angiotensin-converting enzyme 2/angiotensin-(1-7)/Mas receptor axis in the heart and the kidney of growth hormone receptor knock-out mice.
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ABSTRACT: OBJECTIVE: Growth hormone (GH) resistance leads to enhanced insulin sensitivity, decreased systolic blood pressure and increased lifespan. The aim of this study was to determine if there is a shift in the balance of the renin-angiotensin system (RAS) towards the ACE2/Ang-(1-7)/Mas receptor axis in the heart and the kidney of a model of GH resistance and retarded aging, the GH receptor knockout (GHR-/-) mouse. DESIGN: RAS components were evaluated in the heart and the kidney of GHR-/- and control mice by immunohistochemistry and Western blotting (n=12 for both groups). RESULTS: The immunostaining of Ang-(1-7) was increased in both the heart and the kidney of GHR-/- mice. These changes were concomitant with an increased immunostaining of the Mas receptor and ACE2 in both tissues. The immunostaining of AT1 receptor was reduced in heart and kidney of GHR-/- mice while that of AT2 receptor was increased in the heart and unaltered in the kidney. Ang II, ACE and angiotensinogen levels remained unaltered in the heart and the kidney of GH resistant mice. These results were confirmed by Western blotting and correlated with a significant increase in the abundance of the endothelial nitric oxide synthase in both tissues. CONCLUSIONS: The shift within the RAS towards an exacerbation of the ACE2/Ang-(1-7)/Mas receptor axis observed in GHR-/- mice could be related to a protective role in cardiac and renal function; and thus, possibly contribute to the decreased incidence of cardiovascular diseases displayed by this animal model of longevity.Growth hormone & IGF research: official journal of the Growth Hormone Research Society and the International IGF Research Society 09/2012; · 2.35 Impact Factor -
Article: The Mas receptor mediates modulation of insulin signaling by angiotensin-(1-7).
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ABSTRACT: Angiotensin (Ang)-(1-7) stimulates proteins belonging to the insulin signaling pathway and ameliorates the Ang II negative effects at this level. However, up to date, receptors involved and mechanisms behind these observations remain unknown. Accordingly, in the present study, we explored the in vivo effects of antagonism of the Ang-(1-7) specific Mas receptor on insulin signal transduction in rat insulin-target tissues. We evaluated the acute modulation of insulin-stimulated phosphorylation of Akt, GSK-3β (Glycogen synthase kinase-3β) and AS160 (Akt substrate of 160kDa) by Ang-(1-7) and/or Ang II in the presence and absence of the selective Mas receptor antagonist A-779 in insulin-target tissues of normal rats. Also using A-779, we determined whether the Mas receptor mediates the improvement of insulin sensitivity exerted by chronic Ang-(1-7) treatment in fructose-fed rats (FFR), a model of insulin resistance, dyslipidemia and mild hypertension. The two major findings of the present work are as follows; 1) Ang-(1-7) attenuates acute Ang II-mediated inhibition of insulin signaling components in normal rats via a Mas receptor-dependent mechanism; and 2). The Mas receptor appears to be involved in beneficial effects of Ang-(1-7) on the phosphorylation of crucial insulin signaling mediators (Akt, GSK-3β and AS160), in liver, skeletal muscle and adipose tissue of FFR. These results shed light into the mechanism by which Ang-(1-7) exerts its positive physiological modulation of insulin actions in classical metabolic tissues and reinforces the central role of Akt in these effects.Regulatory Peptides 05/2012; 177(1-3):1-11. · 2.11 Impact Factor -
Article: Long-term treatment with nebivolol attenuates renal damage in Zucker diabetic fatty rats.
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ABSTRACT: Atenolol, a first-generation β-blocker, effectively reduces blood pressure, although its use in metabolic syndrome remains controversial. Accordingly, this study evaluated the renal effects of nebivolol, a third-generation β-blocker with additional vasodilating activity, versus those of atenolol in an animal model of diabetic nephropathy. Zucker diabetic fatty (ZDF) rats and control lean Zucker rats (LZRs) were treated for 6 months with either nebivolol or atenolol. Blood pressure, circulating insulin, triglycerides, cholesterol and glucose, as well as proteinuria and creatinine clearance were evaluated. Thiobarbituric acid-reactive species, reduced glutathione (GSH)/oxidized glutathione (GSSG) ratio, CuZn superoxide dismutase, catalase and glutathione peroxidase were determined as biomarkers of oxidative stress in kidney homogenates. Expression of transforming growth factor-β1 (TGF-β1), α-smooth muscle actin (α-SMA), collagen type I and III, plasminogen activator inhibitor-1 (PAI-1), vascular and platelet endothelial cell adhesion molecule-1 (VCAM-1 and PECAM-1, respectively) were determined by immunohistochemistry. Fibrosis was evaluated by light microscopy. Both drugs induced a similar control of blood pressure throughout the study. Contrary to atenolol, nebivolol showed a beneficial impact on lipid profile, preserved glomerular filtration rate, reduced proteinuria and induced a positive regulation of structural podocyte proteins (nephrin and podocin) expression. Additionally nebivolol decreased oxidative stress biomarkers, induced a substantial reduction in the accumulation of extracellular matrix proteins, down-regulated the renal expression of VCAM-1, monocyte chemotactic protein-1 (MCP-1), ED1, α-SMA, TGF-β1 and PAI-1 and up-regulated the expression of PECAM-1. Our current finding underscores the importance of this therapy in hypertensive states concomitant with altered lipid and glucose metabolism.Journal of hypertension 06/2011; 29(8):1613-23. · 4.02 Impact Factor -
Article: Novel roles of galectin‐1 in hepatocellular carcinoma cell adhesion, polarization, and in vivo tumor growth
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ABSTRACT: Galectin-1 (Gal-1), a widely expressed β-galactoside–binding protein, exerts pleiotropic biological functions. Gal-1 is up-regulated in hepatocarcinoma cells, although its role in liver pathophysiology remains uncertain. We investigated the effects of Gal-1 on HepG2 hepatocellular carcinoma (HCC) cell adhesion and polarization. Soluble and immobilized recombinant Gal-1 (rGal-1) promoted HepG2 cell adhesion to uncoated plates and also increased adhesion to laminin. Antibody-mediated blockade experiments revealed the involvement of different integrins as critical mediators of these biological effects. In addition, exposure to rGal-1 markedly accelerated the development of apical bile canaliculi as shown by TRITC-phalloidin labeling and immunostaining for multidrug resistance associated-protein 2 (MRP2). Notably, rGal-1 did not interfere with multidrug resistance protein 1/P-glycoprotein or MRP2 apical localization, neither with transfer nor secretion of 5-chloromethylfluorescein diacetate through MRP2. Stimulation of cell adhesion and polarization by rGal-1 was abrogated in the presence of thiodigalactoside, a galectin-specific sugar, suggesting the involvement of protein–carbohydrate interactions in these effects. Additionally, Gal-1 effects were abrogated in the presence of wortmmanin, PD98059 or H89, suggesting involvement of phosphoinositide 3-kinase (PI3K), mitogen-activated protein kinase and cyclic adenosine monophosphate–dependent protein kinase signaling pathways in these functions. Finally, expression levels of this endogenous lectin correlated with HCC cell adhesion and polarization and up-regulation of Gal-1–favored growth of hepatocarcinoma in vivo. Conclusion: Our results provide the first evidence of a role of Gal-1 in modulating HCC cell adhesion, polarization, and in vivo tumor growth, with critical implications in liver pathophysiology. (HEPATOLOGY 2011;)Hepatology 05/2011; 53(6):2097 - 2106. · 11.66 Impact Factor -
Article: Novel roles of galectin-1 in hepatocellular carcinoma cell adhesion, polarization, and in vivo tumor growth.
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ABSTRACT: Galectin-1 (Gal-1), a widely expressed β-galactoside-binding protein, exerts pleiotropic biological functions. Gal-1 is up-regulated in hepatocarcinoma cells, although its role in liver pathophysiology remains uncertain. We investigated the effects of Gal-1 on HepG2 hepatocellular carcinoma (HCC) cell adhesion and polarization. Soluble and immobilized recombinant Gal-1 (rGal-1) promoted HepG2 cell adhesion to uncoated plates and also increased adhesion to laminin. Antibody-mediated blockade experiments revealed the involvement of different integrins as critical mediators of these biological effects. In addition, exposure to rGal-1 markedly accelerated the development of apical bile canaliculi as shown by TRITC-phalloidin labeling and immunostaining for multidrug resistance associated-protein 2 (MRP2). Notably, rGal-1 did not interfere with multidrug resistance protein 1/P-glycoprotein or MRP2 apical localization, neither with transfer nor secretion of 5-chloromethylfluorescein diacetate through MRP2. Stimulation of cell adhesion and polarization by rGal-1 was abrogated in the presence of thiodigalactoside, a galectin-specific sugar, suggesting the involvement of protein-carbohydrate interactions in these effects. Additionally, Gal-1 effects were abrogated in the presence of wortmmanin, PD98059 or H89, suggesting involvement of phosphoinositide 3-kinase (PI3K), mitogen-activated protein kinase and cyclic adenosine monophosphate-dependent protein kinase signaling pathways in these functions. Finally, expression levels of this endogenous lectin correlated with HCC cell adhesion and polarization and up-regulation of Gal-1-favored growth of hepatocarcinoma in vivo. CONCLUSION: Our results provide the first evidence of a role of Gal-1 in modulating HCC cell adhesion, polarization, and in vivo tumor growth, with critical implications in liver pathophysiology.Hepatology 03/2011; 53(6):2097-106. · 11.66 Impact Factor -
Article: Centrally administered insulin potentiates the pressor response to angiotensin II.
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ABSTRACT: The aim of the present study was to determine if insulin can modulate the pressor response to angiotensin II at brain level in normotensive rats. Anaesthetized male rats were intracerebroventricularly infused with insulin (12 mU/h, n=15) or Ringer's solution as vehicle (n=15) for 2 h. Immediately, changes in mean arterial pressure (MAP) in response to an intracerebroventricular subpressor dose of angiotensin II (5 pmol, n=10) or vehicle (n=5) were measured for 10 min. Then, hypothalami were removed and Akt and ERK1/2 phosphorylation levels were determined. In other subset of animals, PD98059 (MAPK inhibitor) or vehicle were intracerebroventricularly administered previously to insulin perfusion for 2 h and changes in MAP in response to intracerebroventricular angiotensin II (5 pmol) injection were evaluated for 10 min (n=6 for each group). Angiotensin II did not modify MAP in vehicle pre-treated rats, but increased MAP in insulin pre-treated animals. Insulin significantly increased Akt phosphorylation, but no changes were observed after angiotensin II injection in vehicle-pretreated animals. Angiotensin II or insulin infusion increased in more than two fold phospho-ERK 1/2 hypothalamic levels. Animals that received insulin infusion followed by Ang II injection presented 4.5 higher values than those which received vehicle, and nearly twice than those who received Ang II without insulin pre-treatment. PD98059 administration abolished the blood pressure response exerted by angiotensin II in insulin pre-treated rats. In conclusion, centrally administered insulin potentiates the pressor effects to angiotensin II, suggesting a novel mechanism, possibly involving MAPK activation, by which insulin influences blood pressure control at central level.Regulatory Peptides 04/2010; 163(1-3):57-61. · 2.11 Impact Factor -
Article: Angiotensin-(1-7) improves cardiac remodeling and inhibits growth-promoting pathways in the heart of fructose-fed rats.
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ABSTRACT: The present study examined whether chronic treatment with angiotensin (ANG)-(1-7) reduces cardiac remodeling and inhibits growth-promoting signaling pathways in the heart of fructose-fed rats (FFR), an animal model of insulin resistance. Sprague-Dawley rats were fed either normal rat chow (control) or the same diet plus 10% fructose in drinking water. For the last 2 wk of a 6-wk period of the corresponding diet, control and FFR were implanted with osmotic pumps that delivered ANG-(1-7) (100 ng.kg(-1).min(-1)). A subgroup of each group of animals (control or FFR) underwent a sham surgery. We determined heart weight, myocyte diameter, interstitial fibrosis, and perivascular collagen type III deposition as well as the phosphorylation degree of ERK1/2, JNK1/2, and p38MAPK. FFR showed a mild hypertension that was significantly reduced after ANG-(1-7) treatment. Also, FFR displayed higher ANG II circulating and local levels in the heart that remained unaltered after chronic ANG-(1-7) infusion. An increased heart-to-body weight ratio, myocyte diameter, as well as left ventricular fibrosis and perivascular collagen type III deposition were detected in the heart of FFR. Interestingly, significant improvements in these cardiac alterations were obtained after ANG-(1-7) treatment. Finally, FFR that received ANG-(1-7) chronically displayed significantly lower phosphorylation levels of ERK1/2, JNK1/2, and p38MAPK. The beneficial effects obtained by ANG-(1-7) were associated with normal values of Src-homology 2-containing protein-tyrosine phosphatase-1 (SHP-1) activity in the heart. In conclusion, chronic ANG-(1-7) treatment ameliorated cardiac hypertrophy and fibrosis and attenuated the growth-promoting pathways in the heart. These findings show an important protective role of ANG-(1-7) in the heart of insulin-resistant rats.AJP Heart and Circulatory Physiology 03/2010; 298(3):H1003-13. · 3.71 Impact Factor -
Article: Angiotensin-(1-7) stimulates the phosphorylation of Akt in rat extracardiac tissues in vivo via receptor Mas.
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ABSTRACT: The in vivo effect of angiotensin (ANG)-(1-7) on the activation of insulin signaling transduction in rat extracardiac tissues is unknown. Thus, in the present study, we evaluated the ability of ANG-(1-7) to stimulate the phosphorylation of Akt, a main mediator of insulin action in rat extracardiac tissues (adipose tissue, liver and skeletal muscle). We proved that ANG-(1-7) induces the phosphorylation of Akt at both threonine 308 and serine 473 in all tissues analyzed. Selective antagonism of the Mas receptor with A779 blocked the ANG-(1-7)-induced Akt phosphorylation in extracardiac tissues. Reinforcing this evidence, we determined that ANG-(1-7) induces the in vivo activation of the downstream target of Akt, glycogen synthase kinase-3beta in liver and skeletal muscle. Moreover, in every tissue analyzed, the presence of the Mas receptor was detected by immunohistochemical analysis. Based on the current results, we postulate that ANG-(1-7) could be a positive physiological contributor to the actions of insulin in extracardiac tissues. Therefore, our findings extend the possibilities for new approaches in the study of ANG-(1-7)/Mas receptor axis and show the therapeutic potential of ANG-(1-7) in the treatment of metabolic disorders such as insulin resistance as well as other disorders associated with diminished Akt activity.Regulatory Peptides 02/2010; 161(1-3):1-7. · 2.11 Impact Factor -
Article: Ames dwarf (Prop1(df)/Prop1(df)) mice display increased sensitivity of the major GH-signaling pathways in liver and skeletal muscle.
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ABSTRACT: Growth hormone (GH) is an anabolic hormone that regulates growth and metabolism. Ames dwarf mice are natural mutants for Prop1, with impaired development of anterior pituitary and undetectable levels of circulating GH, prolactin and TSH. They constitute an endocrine model of life-long GH-deficiency. The main signaling cascades activated by GH binding to its receptor are the JAK2/STATs, PI-3K/Akt and the MAPK Erk1/2 pathways. We have previously reported that GH-induced STAT5 activation was higher in Ames dwarf mice liver compared to non-dwarf controls. The aim of this study was to evaluate the principal components of the main GH-signaling pathways under GH-deficiency in liver and skeletal muscle, another GH-target tissue. Ames dwarf mice and their non-dwarf siblings were assessed. Animals were injected i.p. with GH or saline 15min before tissue removal. Protein content and phosphorylation of signaling mediators were determined by immunoblotting of tissue solubilizates. GH was able to induce STAT5 and STAT3 tyrosine phosphorylation in both liver and muscle, but the response was higher for Ames dwarf mice than for non-dwarf controls. When Erk1/2 activation was assessed in liver, only dwarf mice showed GH-induced phosphorylation, while in muscle no response to the hormone was found in either genotype. GH-induced Akt phosphorylation at Ser473 in liver was only detected in dwarf mice. In skeletal muscle, both normal and dwarf mice responded to a GH stimulus, although dwarf mice presented higher GH activation levels. The phosphorylation of GSK-3, a substrate of Akt, increased upon hormone stimulation only in dwarf mice in both tissues. In contrast, no differences in the phosphorylation of mTOR, another substrate of Akt, were observed after GH stimulus, either in normal or dwarf mice in liver, while we were unable to determine mTOR in muscle. Protein content of GH-receptor and of the signaling mediators studied did not vary between normal and dwarf animals in the assessed tissues. These results show that several components of the main GH-signaling pathways exhibit enhanced sensitivity to the hormone in liver and muscle of Ames dwarf mice.Growth hormone & IGF research: official journal of the Growth Hormone Research Society and the International IGF Research Society 12/2009; 20(2):118-26. · 2.35 Impact Factor -
Article: Insulin signaling cascade in the hearts of long-lived growth hormone receptor knockout mice: effects of calorie restriction.
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ABSTRACT: Calorie restriction (CR) improves insulin sensitivity and increases life span in normal but not in long-lived growth hormone-resistant knockout (GHRKO) mice. In this study, we examined interactive effects of GH resistance and long-term CR on cardiac insulin action. GHRKO mice exhibited marked increases in the insulin-induced phosphorylation of the insulin receptor (IR), insulin receptor substrate-1 (IRS-1), Akt, and ERK1/2 along with elevated insulin-stimulated IRS-1-associated regulatory subunit of phosphatidylinositol 3-kinase in the heart. These changes were associated with elevated protein levels of IR, IRS-1, and Akt and with a down-regulation of cardiac glucose transporter 4 (GLUT4). In normal mice, CR induced an important increase in the phosphorylation of cardiac Akt without elevation of Akt protein, reaching activation levels similar to those seen in GHRKO mice. This change may be cardioprotective and thus contribute to increased longevity in response to CR. Interestingly, the insulin signaling cascade in the heart of GHRKO mice was unaffected by CR.The Journals of Gerontology Series A Biological Sciences and Medical Sciences 09/2008; 63(8):788-97. · 4.60 Impact Factor -
Article: Angiotensin-(1-7) has a dual role on growth-promoting signalling pathways in rat heart in vivo by stimulating STAT3 and STAT5a/b phosphorylation and inhibiting angiotensin II-stimulated ERK1/2 and Rho kinase activity.
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ABSTRACT: Angiotensin (ANG) II contributes to cardiac remodelling by inducing the activation of several signalling molecules, including ERK1/2, Rho kinase and members of the STAT family of proteins. Angiotensin-(1-7) is produced in the heart and inhibits the proliferative actions of ANG II, although the mechanisms of this inhibition are poorly understood. Accordingly, in the present study we examined whether ANG-(1-7) affects the ANG II-mediated activation of ERK1/2 and Rho kinase, STAT3 and STAT5a/b in rat heart in vivo. We hypothesized that ANG-(1-7) inhibits these growth-promoting pathways, counterbalancing the trophic action of ANG II. Solutions of normal saline (0.9% NaCl) containing ANG II (8 pmol kg(-1)) plus ANG-(1-7) in increasing doses (from 0.08 to 800 pmol kg(-1)) were administered via the inferior vena cava to anaesthetized male Sprague-Dawley rats. After 5 min, hearts were removed and ERK1/2, Rho kinase, STAT3 and STAT5a/b phosphorylation was determined by Western blotting using phosphospecific antibodies. Angiotensin II stimulated ERK1/2 and Rho kinase phosphorylation (2.3 +/- 0.2- and 2.1 +/- 0.2-fold increase over basal values, respectively), while ANG-(1-7) was without effect. The ANG II-mediated phosphorylation of ERK1/2 and Rho kinase was prevented in a dose-dependent manner by ANG-(1-7) and disappeared in the presence of the Mas receptor antagonist d-Ala7-ANG-(1-7). Both ANG II and ANG-(1-7) increased STAT3 and STAT5a/b phosphorylation to a similar extent (130-140% increase). The ANG-(1-7)-stimulated STAT phosphorylation was blocked by the AT(1) receptor antagonist losartan and not by d-Ala7-ANG-(1-7). Our results show a dual action of ANG-(1-7), that is, a stimulatory effect on STAT3 and 5a/b phosphorylation through AT(1) receptors and a blocking action on ANG II-stimulated ERK1/2 and Rho kinase phosphorylation through Mas receptor activation. The latter effect could be representative of a mechanism for a protective role of ANG-(1-7) in the heart by counteracting the effects of locally generated ANG II.Experimental Physiology 06/2008; 93(5):570-8. · 3.21 Impact Factor -
Article: ACE inhibition and AT1 receptor blockade prevent fatty liver and fibrosis in obese Zucker rats.
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ABSTRACT: Non-alcoholic steatohepatitis (NASH), which is a common liver disease in industrialized countries, is associated with obesity, hypertension, and type-2 diabetes (metabolic syndrome). Since angiotensin II (ANG II) has been suggested to play an important role in liver inflammation and fibrosis, the purpose of this study was to investigate whether therapy against renin-angiotensin system (RAS) may provide some beneficial effect in liver of an animal model of metabolic syndrome. For 6 months, obese Zucker rats (OZRs) were treated as follows: OZR-group, OZR + Perindopril (P) group, OZR + Irbesartan (IRB) group, OZR + Amlodipine (AML) group, and lean Zucker rats (LZRs) group as a control. Livers were evaluated by immunohistochemistry techniques using corresponding antibodies. All treated groups showed a similar reduction in blood pressure compared to untreated OZR. Therapy either with IRB or P improves insulin sensitivity and reduces hepatic enzyme level with respect to untreated OZR. Conversely, AML failed to modify both parameters. Untreated OZR displayed higher hepatic ANG II levels and steatosis together with a marked increase in tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6) and transforming growth factor-beta1 (TGF-beta1) level compared to LZR. Following RAS inhibition either by P or IRB, a significant reduction (P < 0.01) in the immunostaining of TNF-alpha, IL-6 and TGF-beta1 compared to untreated OZR was observed. These results indicate that ANG II expression is increased in the liver of these animals with steatohepatitis. Furthermore, RAS control by either angiotensin-converting enzyme inhibition or AT1 receptor blockade seems to provide a beneficial modulation concerning the inflammatory response to liver injury in this model. Consequently, blockade of RAS could be a new approach to prevent or to treat patients with NASH.Obesity 04/2008; 16(4):770-6. · 4.28 Impact Factor -
Article: Angiotensin (ANG)-(1-7) elicits a dual role on growth-promoting signaling pathways in rat heart in vivo by stimulating STAT3 and 5a/b phosphorylation and inhibiting ANG II-stimulated ERK1/2 and Rho-kinase activity.
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ABSTRACT: Angiotensin (ANG) II contributes to cardiac remodeling by inducing the activation of several signaling molecules including ERK1/2, Rho-kinase and members of the STAT family of proteins. ANG-(1-7) is produced in the heart and inhibits the proliferative actions of ANG II, although the mechanisms of this inhibition are poorly understood. Accordingly, in the current study we examined whether ANG-(1-7) affects the ANG II-mediated ERK1/2, STAT3 and 5a/b as well as Rho-kinase activation in the rat heart in vivo. We hypothesize that ANG-(1-7) inhibits these growth promoting pathways, counterbalancing the trophic action of Ang II. Solutions of normal saline (0,9% NaCl) containing ANG II (8 pmol/Kg) plus ANG-(1-7) in increasing doses (0.08-800 pmol/Kg) were administered via vena cava to male Sprague-Dawley rats. After 5 min, hearts were isolated and ERK1/2, Rho-kinase, STAT 3 and 5a/b phosphorylation was determined by Western Blotting using phosphospecific antibodies. ANG II stimulated ERK1/2 and Rho-kinase phosphorylation (2.3 +/- 0.2-fold increase and 2.1 +/- 0.2-fold increase over basal, respectively), while Ang-(1-7) was without effect. The ANG II-mediated phosphorylation of ERK 1/2 and Rho-kinase was dose-dependently prevented by Ang-(1-7) and disappeared in the presence of the mas receptor antagonist D-Ala7-ANG-(1-7). Both ANG II and ANG-(1-7) increased STAT3 and STAT5a/b phosphorylation to a similar extent (130-140 % increase). The Ang-(1-7)-stimulated STAT phosphorylation was blocked by the AT1 receptor antagonist losartan and not by D-Ala7-ANG-(1-7). Our results show a dual action of Ang-(1-7), that is, a stimulatory effect on STAT3 and a/b phosphorylation through AT1 receptors and a blocking action on ANG II-stimulated ERK1/2 and Rho kinase phosphorylation through mas receptor activation. This last effect could be representative of a mechanism for a protective role of ANG-(1-7) in the heart by counteracting the effects of locally generated ANG II.Experimental Physiology 02/2008; · 3.21 Impact Factor -
Article: Angiotensin-(1 7) stimulates the phosphorylation of JAK2, IRS-1 and Akt in rat heart in vivo: role of the AT1 and Mas receptors.
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ABSTRACT: Angiotensin (ANG) II exerts a negative modulation on insulin signal transduction that might be involved in the pathogenesis of hypertension and insulin resistance. ANG-(1-7), an endogenous heptapeptide hormone formed by cleavage of ANG I and ANG II, counteracts many actions of ANG II. In the current study, we have explored the role of ANG-(1-7) in the signaling crosstalk that exists between ANG II and insulin. We demonstrated that ANG-(1-7) stimulates the phosphorylation of Janus kinase 2 (JAK2) and insulin receptor substrate (IRS)-1 in rat heart in vivo. This stimulating effect was blocked by administration of the selective ANG type 1 (AT(1)) receptor blocker losartan. In contrast to ANG II, ANG-(1-7) stimulated cardiac Akt phosphorylation, and this stimulation was blunted in presence of the receptor Mas antagonist A-779 or the phosphatidylinositol 3-kinase (PI3K) inhibitor wortmannin. The specific JAK2 inhibitor AG-490 blocked ANG-(1-7)-induced JAK2 and IRS-1 phosphorylation but had no effect on ANG-(1-7)-induced phosphorylation of Akt, indicating that activation of cardiac Akt by ANG-(1-7) appears not to involve the recruitment of JAK2 but proceeds through the receptor Mas and involves PI3K. Acute in vivo insulin-induced cardiac Akt phosphorylation was inhibited by ANG II. Interestingly, coadministration of insulin with an equimolar mixture of ANG II and ANG-(1-7) reverted this inhibitory effect. On the basis of our present results, we postulate that ANG-(1-7) could be a positive physiological contributor to the actions of insulin in heart and that the balance between ANG II and ANG-(1-7) could be relevant for the association among insulin resistance, hypertension, and cardiovascular disease.AJP Heart and Circulatory Physiology 09/2007; 293(2):H1154-63. · 3.71 Impact Factor -
Article: Irbesartan restores the in-vivo insulin signaling pathway leading to Akt activation in obese Zucker rats.
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ABSTRACT: Angiotensin II (AII) has been shown to contribute to the pathogenesis of hypertension and insulin resistance. In addition, the administration of selective AII type 1 receptor blockers has been shown to improve insulin sensitivity. However, only a few studies have addressed the molecular mechanisms involved in this association. Furthermore, in a previous study we illustrated that obese Zucker rats (OZR) present increased serine 994 (Ser994) phosphorylation of hepatic insulin receptor, and this event seems to be implicated in the regulation of the intrinsic IRK in this model of insulin resistance. We examined the effects of chronic treatment with irbesartan (50 mg/kg a day for 6 months) on the hepatic insulin signaling system of OZR. The extent of phosphorylation of several components of the insulin signaling system was assessed by immunoprecipitation, followed by immunoblotting with phosphospecific antibodies. In addition, liver AII levels and fat deposits were determined by immunohistochemistry and Oil red O, respectively. OZR displayed a marked attenuation in the in-vivo phosphorylation of several components of the insulin signaling pathways in the liver, together with significantly higher hepatic AII levels and hepatic steatosis when compared with lean Zucker rats. We found that in the livers of OZR long-term administration of irbesartan is associated with: (i) increased insulin-stimulated insulin receptor tyrosine phosphorylation; (ii) decreased insulin receptor Ser994 phosphorylation; (iii) augmented insulin receptor substrate (IRS) 1 and 2 abundance and tyrosine phosphorylation; (iv) augmented association between IRS and the p85 regulatory subunit of phosphatidylinositol 3-kinase; (v) increased insulin-induced Akt phosphorylation; and (vi) decreased hepatic steatosis. The present study provides substantial information that demonstrates that long-term selective AII blockade by irbesartan improves insulin signaling and is associated with decreased insulin receptor Ser994 phosphorylation in the liver of a representative animal model of the human metabolic syndrome.Journal of Hypertension 09/2006; 24(8):1607-17. · 4.02 Impact Factor -
Article: Behaviour of the anti-oxidant defence system and heme oxygenase-1 protein expression in fructose-hypertensive rats.
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ABSTRACT: 1. Addition of fructose to a rat diet for various periods of time leads to hypertension, hyperinsulinaemia and dyslipidaemia and provides a model for testing oxidative stress parameters in the animals. 2. In the present study, oxidative stress generation, the soluble and enzymatic defence system and heme oxygenase-1 (HO-1) protein expression were investigated in the heart, liver and kidney of rats fed fructose for a period of 1 or 8 months. 3. Compared with the control group, fructose-hypertensive rats showed increased in lipid peroxidation only in the heart after both 1 and 8 months of fructose treatment. Changes in the behaviour of the soluble and enzymatic defence system and HO-1 protein expression were different depending on the organ. Increased or unaltered activities of anti-oxidant enzymes were found in the liver and kidney, respectively. Induction of HO-1 prevented the generation of oxidative stress in the liver, where the activity of anti-oxidant defence enzymes was not reduced. Increased expression of HO-1 protein was not able to prevent the generation of oxidative stress in the heart, where fructose treatment diminished the activity of anti-oxidant enzymes. 4. The results of the present study demonstrate that upregulation of HO-1 may prevent the generation of oxidative stress only when the anti-oxidant defence system is still operative.Clinical and Experimental Pharmacology and Physiology 09/2006; 33(8):734-9. · 1.85 Impact Factor -
Article: Influence of the crosstalk between growth hormone and insulin signalling on the modulation of insulin sensitivity.
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ABSTRACT: Growth hormone (GH) is an important modulator of insulin sensitivity. Multiple mechanisms appear to be involved in this modulatory effect. GH does not interact directly with the insulin receptor (IR), but conditions of GH excess are associated in general with hyperinsulinemia that induces a reduction of IR levels and impairment of its kinase activity. Several post-receptor events are shared between GH and insulin. This signaling crosstalk could be involved in the diabetogenic effects of GH. The utilization of animal models of GH excess, deficiency or resistance provided evidence that the signaling pathway leading to stimulation of the phosphatidylinositol 3-kinase (PI3K)/Akt cascade is an important site of regulation, and pointed to the liver as the major site of GH-induced insulin resistance. In skeletal muscle, GH-induced insulin resistance might involve an increase in the amount of the p85 subunit of PI3K that plays a negative role in insulin signalling. GH also reduces insulin sensitivity by enhancing events that negatively modulate insulin signaling such as stimulation of serine phosphorylation of IRS-1, which prevents its recruitment to the IR and induction of the suppressor of cytokine signalling (SOCS)-1 and SOCS-3 which modulate the signalling potential of the IRS proteins. In addition, GH has been shown to decrease the expression of the insulin-sensitizing adipo-cytokines adiponectin and visfatin. Finally, genetic manipulation of mice indicated that whereas GH plays a major role in reducing insulin sensitivity, circulating IGF-I also participates in the control of insulin sensitivity and plays an important role in the hormonal balance between GH and insulin.Growth Hormone & IGF Research 11/2005; 15(5):324-36. · 2.16 Impact Factor -
Article: Increased in vivo phosphorylation of insulin receptor at serine 994 in the liver of obese insulin-resistant Zucker rats.
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ABSTRACT: Serine phosphorylation of the insulin receptor (IR) has been proposed to exert an inhibitory influence on its tyrosine kinase activity. Previous works using site-directed mutagenesis suggested that serine 994 of the IR (IR Ser 994) might be part of an inhibitory domain of the receptor. In this study we examined whether this residue is subjected to phosphorylation in vivo. We used a site-phosphospecific antibody to determine the extent of phosphorylation of IR Ser 994 in insulin target tissues from two animal models of insulin resistance with different IR kinase (IRK) activity: obese (fa/fa) Zucker rats and transgenic mice overexpressing bovine growth hormone (PEPCK-bGH mice). Phosphorylation at IR Ser 994 was markedly increased in liver of obese rats. This alteration appeared to be tissue-selective since no phosphorylation on Ser 994 was detected in IRs isolated from skeletal muscle of these animals. On the other hand, the phosphorylation level of IR Ser 994 was very low in liver of PEPCK-bGH mice and did not differ from that of the control group. We have also demonstrated that protein kinase (PK) C isoforms alpha, betaI and zeta are able to promote the in vitro phosphorylation of the IR on Ser 994. Differential findings in these two models of insulin resistance might thus reflect increased PKC activity resulting from increased lipid availability in obese Zucker rats. Our results suggest that Ser 994 is a novel in vivo IR phosphorylation site that might be involved in the regulation of the IRK in some states of insulin resistance.Journal of Endocrinology 10/2004; 182(3):433-44. · 3.55 Impact Factor -
Article: Use of a purified Trypanosoma cruzi antigen and CpG oligodeoxynucleotides for immunoprotection against a lethal challenge with trypomastigotes.
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ABSTRACT: The crucial role played by Ag163B6/cruzipain, the major cystein proteinase of Trypanosoma cruzi, in the process of parasite internalization into mammalian cells and IgG hydrolysis, signals this antigen as a potential target for raising a protective immune response against Chagas' disease. On the other hand, synthetic oligodeoxynucleotides containing CpG-motifs (CpG-ODN) are capable of driving immunity toward a Th1 bias. Considering the importance of Th1 mechanisms in resistance against this intracellular parasite, we analyzed the ability of Ag163B6/cruzipain plus CpG-ODN to induce immunoprotection against a lethal challenge with trypomastigotes. Mice were immunized with Ag163B6+CpG-ODN showing high specific antibody titers, mostly IgG2a. Spleen cells from these mice strongly proliferated and presented significant increase of IL-2 and IFN-gamma concentrations in their supernatant upon antigen stimulation. Trypomastigote challenge rendered elevated parasitemia and mortality in all control groups, meanwhile Ag163B6+CpG-ODN mice displayed the lowest level of blood parasites and 100% survival to acute infection. Besides, we demonstrated that other parasite antigens introduced into mice when challenged, and consequently never seen before by the immune system, also elicited a Th1 immune response. Taken together, these results plus others provide the basis for the design of a multicomponent anti-T. cruzi vaccine which may ultimately be used not only to protect humans at risk of infection, but also may alleviate or prevent the pathogenic responses characteristic of chronic Chagas' disease by reducing or perhaps eliminating tissue parasites from infected patients.Vaccine 01/2004; 22(1):77-86. · 3.77 Impact Factor -
Article: Ames dwarf (Prop1df/Prop1df) mice display increased sensitivity of the major GH-signaling pathways in liver and skeletal muscle
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ABSTRACT: ContextGrowth hormone (GH) is an anabolic hormone that regulates growth and metabolism. Ames dwarf mice are natural mutants for Prop1, with impaired development of anterior pituitary and undetectable levels of circulating GH, prolactin and TSH. They constitute an endocrine model of life-long GH-deficiency. The main signaling cascades activated by GH binding to its receptor are the JAK2/STATs, PI-3K/Akt and the MAPK Erk1/2 pathways.ObjectivesWe have previously reported that GH-induced STAT5 activation was higher in Ames dwarf mice liver compared to non-dwarf controls. The aim of this study was to evaluate the principal components of the main GH-signaling pathways under GH-deficiency in liver and skeletal muscle, another GH-target tissue.MethodsAmes dwarf mice and their non-dwarf siblings were assessed. Animals were injected i.p. with GH or saline 15 min before tissue removal. Protein content and phosphorylation of signaling mediators were determined by immunoblotting of tissue solubilizates.ResultsGH was able to induce STAT5 and STAT3 tyrosine phosphorylation in both liver and muscle, but the response was higher for Ames dwarf mice than for non-dwarf controls. When Erk1/2 activation was assessed in liver, only dwarf mice showed GH-induced phosphorylation, while in muscle no response to the hormone was found in either genotype. GH-induced Akt phosphorylation at Ser473 in liver was only detected in dwarf mice. In skeletal muscle, both normal and dwarf mice responded to a GH stimulus, although dwarf mice presented higher GH activation levels. The phosphorylation of GSK-3, a substrate of Akt, increased upon hormone stimulation only in dwarf mice in both tissues. In contrast, no differences in the phosphorylation of mTOR, another substrate of Akt, were observed after GH stimulus, either in normal or dwarf mice in liver, while we were unable to determine mTOR in muscle. Protein content of GH-receptor and of the signaling mediators studied did not vary between normal and dwarf animals in the assessed tissues.ConclusionThese results show that several components of the main GH-signaling pathways exhibit enhanced sensitivity to the hormone in liver and muscle of Ames dwarf mice.Growth Hormone & IGF Research.
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Institutions
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2008–2012
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University of Buenos Aires
- • Instituto de Química y Fisicoquímica Biológicas - IQUIFIB
- • Facultad de Farmacia y Bioquímica
Buenos Aires, Buenos Aires F.D., Argentina
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2011
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Hospital Alemán
Buenos Aires, Buenos Aires F.D., Argentina
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2007
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National Council of Scientific and Technical Research
Buenos Aires, Buenos Aires F.D., Argentina
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