Angiotensin-(3-4) counteracts the Angiotensin II inhibitory action on renal Ca2+-ATPase through a cAMP/PKA pathway.

We recently demonstrated that Angiotensin-(3-4) [Ang-(3-4)], an Ang II-derived dipeptide, overcomes inhibition of plasma membrane Ca(2+)-ATPase promoted by nanomolar concentrations of Ang II in basolateral membranes of renal proximal tubule cells, with involvement of a so far unknown AT(2)R-dependent and NO-independent mechanism. The present study investigates the signaling pathway triggered by Ang-(3-4) that is responsible for counteracting the inhibitory effect of Ang II, and attempts to elucidate the functional interaction of the dipeptide with Ang II at the level of AT(2)R. Stimulation by cholera toxin of G(s)α protein structurally linked to AT(2)R--as revealed by their co-immunoprecipitation--mimicked the effect of Ang-(3-4) on Ca(2+)-ATPase activity. Furthermore, addition of dibutyril-cAMP (db-cAMP) mimicked Ang-(3-4), whereas the specific PKA inhibitor, PKAi(5-24) peptide, suppressed the counter-regulatory effect of Ang-(3-4) and the AT(2)R agonist, CGP42112A. Membrane-associated PKA activity was stimulated by Ang-(3-4) or CGP42112A to comparable levels as db-cAMP, and the Ang-(3-4) effect was abrogated by the AT(2)R antagonist PD123319, whereas the AT(1)R antagonist Losartan had no effect. Ang-(3-4) stimulated PKA-mediated phosphorylation of Ca(2+)-ATPase and activated PKA to comparable levels. Binding assays demonstrated that Ang-(3-4) could not displace (3)H-Ang II from HEK 293T cells expressing AT(2)R, but 10(-10) mol/L Ang-(3-4) resulted in the appearance of a probable higher-affinity site (picomolar range) for Ang II. The results presented herein demonstrate that Ang-(3-4), acting as an allosteric enhancer, suppresses Ang II-mediated inhibition of Ca(2+)-ATPase through an AT(2)R/cAMP/PKA pathway, after inducing conformational changes in AT(2)R that results in generation of higher-affinity sites for Ang II.

The role of reactive oxygen species in the modulation of the contraction induced by angiotensin II in carotid artery from diabetic rat.

The modulation played by reactive oxygen species on the angiotensin II-induced contraction in type I-diabetic rat carotid was investigated. Concentration-response curves for angiotensin II were obtained in endothelium-intact or endothelium-denuded carotid from control or streptozotocin-induced diabetic rats, pre-treated with tiron (superoxide scavenger), PEG-catalase (hydrogen peroxide scavenger), dimethylthiourea (hydroxyl scavenger), apocynin [NAD(P)H oxidase inhibitor], SC560 (cyclooxygenase-1 inhibitor), SC236 (cyclooxygenase-2 inhibitor) or Y-27632 (Rho-kinase inhibitor). Reactive oxygen species were measured by flow cytometry in dihydroethidium (DHE)-loaded endothelial cells. Cyclooxygenase and AT(1)-receptor expression was assessed by immunohistochemistry. Diabetes increased the angiotensin II-induced contraction but reduced the agonist potency in rat carotid. Endothelium removal, tiron or apocynin restored the angiotensin II-induced contraction in diabetic rat carotid to control levels. PEG-catalase, DMTU or SC560 reduced the angiotensin II-induced contraction in diabetic rat carotid at the same extent. SC236 restored the angiotensin II potency in diabetic rat carotid. Y-27632 reduced the angiotensin II-induced contraction in endothelium-intact or -denuded diabetic rat carotid. Diabetes increased the DHE-fluorescence of carotid endothelial cells. Apocynin reduced the DHE-fluorescence of endothelial cells from diabetic rat carotid to control levels. Diabetes increased the muscular cyclooxygenase-2 expression but reduced the muscular AT(1)-receptor expression in rat carotid. In summary, hydroxyl radical, hydrogen peroxide and superoxide anion-derived from endothelial NAD(P)H oxidase mediate the hyperreactivity to angiotensin II in type I-diabetic rat carotid, involving the participation of cyclooxygenase-1 and Rho-kinase. Moreover, increased muscular cyclooxygenase-2 expression in type I-diabetic rat carotid seems to be related to the local reduced AT(1)-receptor expression and the reduced angiotensin II potency.

Atenuação da remodelação ventricular após infarto agudo do miocárdio / Attenuation of ventricular remodeling after myocardial acute infarction

Após o infarto agudo do miocárdio podem ocorrer complexas alterações da arquitetura ventricular, envolvendo tanto a região infartada como a região não infartada. Há alguns anos, essas alterações passaram a ser designadas como remodelação ventricular pós-infarto. Do ponto de vista clínico, a remodelação está associada ao pior prognóstico após a oclusão coronária. Assim, a remodelação predispõe o coração infartado à ruptura ventricular e é o substrato fisiopatológico para a posterior formação do aneurisma ventricular. Cronicamente, a remodelação está associada com maior prevalência de arritmias malignas, principalmente a taquicardia ventricular sustentada e a fibrilação ventricular. O aspecto mais relevante da remodelação pós-infarto, no entanto, é que esse processo desempenha papel fundamental na fisiopatologia da disfunção ventricular. Aspecto a ser considerado refere-se ao fato de que a evolução do processo de remodelação pode ser modificado por meio de diversas intervenções terapêuticas. Entre as estratégias para atenuar a remodelação ventricular destacam-se: terapia de reperfusão, inibidores da enzima conversora da angiotensina e antagonistas da angiotensina II, betabloqueadores, antagonistas da aldosterona e dispositivos de assistência circulatória.

After acute myocardial infarction (AMI), complex changes in ventricular architecture may occur involving the infarcted and the non-infarcted region. This set of adaptations, which includes changes in the composition, mass, volume and geometry of the heart, is known as myocardial remodeling. In relation to clinical significance, the intensity of the ventricular remodeling process is directly associated with worse prognosis, due to the higher incidence of aneurysm formation, ventricular rupture and arrhythmia, and is also associated with the progression of ventricular dysfunction. A relevant aspect to be considered is that a number of strategies have been employed to prevent or mitigate the process of ventricular remodeling following AMI, for instance: reperfusion therapy, angiotensin converting enzyme inhibitors and angiotensin II antagonists, beta-adrenergic receptor blockade, aldosterone antagonists, and left ventricular assist devices.

Angiotensin II blockade: a strategy to slow ageing by protecting mitochondria?

Protein and lipid oxidation-mainly by mitochondrial reactive oxygen species (mtROS)-was proposed as a crucial determinant of health and lifespan. Angiotensin II (Ang II) enhances ROS production by activating NAD(P)H oxidase and uncoupling endothelial nitric oxide synthase (NOS). Ang II also stimulates mtROS production, which depresses mitochondrial energy metabolism. In rodents, renin-angiotensin system blockade (RAS blockade) increases survival and prevents age-associated changes. RAS blockade reduces mtROS and enhances mitochondrial content and function. This suggests that Ang II contributes to the ageing process by prompting mitochondrial dysfunction. Since Ang II is a pleiotropic peptide, the age-protecting effects of RAS blockade are expected to involve a variety of other mechanisms. Caloric restriction (CR)-an age-retarding intervention in humans and animals-and RAS blockade display a number of converging effects, i.e. they delay the manifestations of hypertension, diabetes, nephropathy, cardiovascular disease, and cancer; increase body temperature; reduce body weight, plasma glucose, insulin, and insulin-like growth factor-1; ameliorate insulin sensitivity; lower protein, lipid, and DNA oxidation, and mitochondrial H(2)O(2) production; and increase uncoupling protein-2 and sirtuin expression. A number of these overlapping effects involve changes in mitochondrial function. In CR, peroxisome proliferator-activated receptors (PPARs) seem to contribute to age-retardation partly by regulating mitochondrial function. RAS inhibition up-regulates PPARs; therefore, it is feasible that PPAR modulation is pivotal for mitochondrial protection by RAS blockade during rodent ageing. Other potential mechanisms that may underlie RAS blockade's mitochondrial benefits are TGF-ß down-regulation and up-regulation of Klotho and sirtuins. In conclusion, the available data suggest that RAS blockade deserves further research efforts to establish its role as a potential tool to mitigate the growing problem of age-associated chronic disease.

Central nitrergic system regulation of neuroendocrine secretion, fluid intake and blood pressure induced by angiotensin-II.

BACKGROUND: Nitric oxide (NO) synthesis has been described in several circumventricular and hypothalamic structures in the central nervous system that are implicated in mediating central angiotensin-II (ANG-II) actions during water deprivation and hypovolemia. Neuroendocrine and cardiovascular responses, drinking behavior, and urinary excretions were examined following central angiotensinergic stimulation in awake freely-moving rats pretreated with intracerebroventricular injections of Nω-nitro-L-arginine methyl ester (L-NAME, 40 µg), an inhibitor of NO synthase, and L-arginine (20 ug), a precursor of NO. RESULTS: Injections of L-NAME or ANG-II produced an increase in plasma vasopressin (VP), oxytocin (OT) and atrial natriuretic peptide (ANP) levels, an increase in water and sodium intake, mean arterial blood pressure and sodium excretion, and a reduction of urinary volume. L-NAME pretreatment enhanced the ANG-II response, while L-arginine attenuated VP and OT release, thirst, appetite for sodium, antidiuresis, and natriuresis, as well as pressor responses induced by ANG-II. DISCUSSION AND CONCLUSION: Thus, the central nitrergic system participates in the angiotensinergic responses evoked by water deprivation and hypovolemia to refrain neurohypophysial secretion, hydromineral balance, and blood pressure homeostasis.

Centrally administered insulin potentiates the pressor response to angiotensin II.

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.

Antihypertensive activity of Salvia elegans Vahl. (Lamiaceae): ACE inhibition and angiotensin II antagonism.

ETHNOPHARMACOLOGICAL RELEVANCE: Salvia elegans Vahl. (Lamiaceae), recognized with the popular name of "mirto" is widely used in Mexico for healing purposes, and also them as antihypertensive treatment. AIM OF THE STUDY: The high prevalence of this illness and the side effects of antihypertensive drugs conducted us to the evaluation of the Salvia elegans extract on angiotensin II action. MATERIALS AND METHODS: The acute response of blood pressure to angiotensin II administration was measured in mice. We also tested in vitro the inhibitory effect on angiotensin convertase enzyme. Additionally, characterization of the pharmacological effect of the extract fraction was obtained. RESULTS: We obtained dose-response curve for the administration of complete extract and extract fractions. Due to the hydroalcoholic extract (SeHA) treatment blood pressure decreased significantly from systolic dose of 0.75 mg kg(-1) (p<0.05) and even had an antihypertensive effect that was greater than that treatment with losartan. SeHA extract decreased the E(max) of the AG II hypertensive effect by about 20% in both systolic and diastolic pressures, treatment with losartan also decreased the same parameter between 6% and 8% for systolic and diastolic pressures, respectively. Fractions SeF8 and SeF8-8 showed similar levels of AG II ED(50) for both pressures compared with losartan, these fractions showed major compounds with maximum absorbance peaks at 221, 289 and 330 nm typical of flavonoids. In the inhibition assay the activity of angiotensin converting enzyme (ACE), the extract SeHA showed percentage inhibition (%IACE) of 50.27+/-5.09% (n=5). SeBuOH fraction is found to have greater inhibitory capacity of achieving a IACE 78.40+/-2.24% (n=5), which was similar to the values obtained in the presence of the SeF8-22 fraction (82.61+/-1.74%) and lisinopril (87.18+/-1.16%). The changes in the value of K(M) suggest that components of the extracts and fractions were recognized by the enzyme's active site. The main compounds of the fractions SeBuOH, SeF8-22 were by flavonoid and phenyl propanoid types, according to UV absorption spectra of the fractions. CONCLUSIONS: The experimental results demonstrated the antihypertensive effect of Salvia elegans and it was due to the AG II antagonism and inhibition of angiotensin converting enzyme.

Effect of acute stress on sexual behavior in female rats: participation of the central angiotensinergic system.

Stress might influence the reproductive behavior in females, and central angiotensin II (Ang II) is a peptide that plays a role in stress response and in the modulation of sexual behavior. The medial amygdala (MeA), an important structure that regulates this behavior, is strongly involved in stress response. The aim of the present study was to evaluate the effect of acute restraint stress on the night of proestrus on sexual receptivity in female rats and the participation of Ang II and MeA in this effect. Adult female Wistar rats with regular estrous cycles were utilized. The acute stress protocol utilized was the restraint stress for 15 min on the night of proestrus. The participation of Ang II was evaluated by injecting Ang II and Ang II receptor antagonists (losartan and PD12319) into the MeA. The lordosis quotient was recorded. The stress or the microinjection of Ang II into the MeA significantly reduced sexual behavior. The blockade of AT(1) or AT(2) receptors in the MeA prevented the effect of stress and the effect of Ang II microinjection into this nucleus on sexual receptivity. We concluded that acute restraint stress on the night of proestrus reduces sexual behavior in rats, and this effect is mediated by both AT(1) and AT(2) receptors in the MeA.

Garlic components inhibit angiotensin II-induced cell-cycle progression and migration: Involvement of cell-cycle inhibitor p27(Kip1) and mitogen-activated protein kinase.

Garlic has been used for prevention and treatment of hypertension; however, the molecular mechanisms of garlic's effects remain to be elucidated. In this study, the mechanisms of the in vitro effect of organosulphur compounds derived from garlic on growth and migration of cultured aortic smooth muscle cells isolated from spontaneously hypertensive rats were investigated. We demonstrated that allyl methyl sulphide (AMS) and diallyl sulphide (DAS) inhibited aortic smooth muscle cell angiotensin II-stimulated cell-cycle progression and migration. Neither cell viability nor annexin-V-binding analysis revealed cytotoxic effects of both organosulphur compounds at the used concentrations. Instead, their inhibitory effects were associated to the prevention of the cell-cycle inhibitor p27(Kip1) (p27) downregulation and the reduction of extracellular signal-regulated kinase 1/2 phosphorylation. When we assessed the antioxidant activity of AMS and DAS, we found that both organosulphur compounds inhibited angiotensin II-reactive oxygen species generation. Our findings show that AMS and DAS, compounds derivate from garlic, could be effective antioxidants targeted at the arterial remodelling seen in hypertension.

Endogenous angiotensin II modulates nNOS expression in renovascular hypertension.

Nitric oxide (NO) influences renal blood flow mainly as a result of neuronal nitric oxide synthase (nNOS). Nevertheless, it is unclear how nNOS expression is modulated by endogenous angiotensin II, an inhibitor of NO function. We tested the hypothesis that the angiotensin II AT1 receptor and oxidative stress mediated by NADPH oxidase contribute to the modulation of renal nNOS expression in two-kidney, one-clip (2K1C) hypertensive rats. Experiments were performed on male Wistar rats (150 to 170 g body weight) divided into 2K1C (N = 19) and sham-operated (N = 19) groups. nNOS expression in kidneys of 2K1C hypertensive rats (N = 9) was compared by Western blotting to that of 2K1C rats treated with low doses of the AT1 antagonist losartan [10 mg x kg(-1) x day(-1); N = 5] or the superoxide scavenger tempol [0.2 mmol x kg(-1) x day(-1); N = 5], which still remain hypertensive. After 28 days, nNOS expression was significantly increased by 1.7-fold in the clipped kidneys of 2K1C rats and by 3-fold in the non-clipped kidneys of 2K1C rats compared with sham rats, but was normalized by losartan. With tempol treatment, nNOS expression increased 2-fold in the clipped kidneys and 1.4-fold in the non-clipped kidneys compared with sham rats. The changes in nNOS expression were not followed by changes in the enzyme activity, as measured indirectly by the cGMP method. In conclusion, AT1 receptors and oxidative stress seem to be primary stimuli for increased nNOS expression, but this up-regulation does not result in higher enzyme activity.

Endogenous angiotensin II modulates nNOS expression in renovascular hypertension

Nitric oxide (NO) influences renal blood flow mainly as a result of neuronal nitric oxide synthase (nNOS). Nevertheless, it is unclear how nNOS expression is modulated by endogenous angiotensin II, an inhibitor of NO function. We tested the hypothesis that the angiotensin II AT1 receptor and oxidative stress mediated by NADPH oxidase contribute to the modulation of renal nNOS expression in two-kidney, one-clip (2K1C) hypertensive rats. Experiments were performed on male Wistar rats (150 to 170 g body weight) divided into 2K1C (N = 19) and sham-operated (N = 19) groups. nNOS expression in kidneys of 2K1C hypertensive rats (N = 9) was compared by Western blotting to that of 2K1C rats treated with low doses of the AT1 antagonist losartan (10 mg·kg-1·day-1; N = 5) or the superoxide scavenger tempol (0.2 mmol·kg-1·day-1; N = 5), which still remain hypertensive. After 28 days, nNOS expression was significantly increased by 1.7-fold in the clipped kidneys of 2K1C rats and by 3-fold in the non-clipped kidneys of 2K1C rats compared with sham rats, but was normalized by losartan. With tempol treatment, nNOS expression increased 2-fold in the clipped kidneys and 1.4-fold in the non-clipped kidneys compared with sham rats. The changes in nNOS expression were not followed by changes in the enzyme activity, as measured indirectly by the cGMP method. In conclusion, AT1 receptors and oxidative stress seem to be primary stimuli for increased nNOS expression, but this up-regulation does not result in higher enzyme activity.

Evidence that the effect of angiotensin II on bovine oocyte nuclear maturation is mediated by prostaglandins E2 and F2alpha.

Angiotensin II (AngII) prevents the inhibitory effect of follicular cells on oocyte maturation, but its involvement in LH-induced meiotic resumption remains unknown. The aim of this study was to assess the involvement of AngII in LH-induced meiotic resumption and of prostaglandins (PGs) in the action of AngII. In the experiment I, seven cows were superovulated, intrafollicularly injected with 10 muM saralasin (a competitive AngII antagonist) or saline when the follicles reached a diameter larger than 12 mm, and challenged with a GnRH agonist to induce an LH surge. Fifteen hours after GnRH, the animals were ovariectomized and the oocytes were recovered to determine the stage of meiosis. The oocytes from follicles that received saline were in germinal vesicle (GV) breakdown (30.8%) or metaphase I (MI; 69.2%) stage while those that received saralasin were in the GV stage (100%; P<0.001) 15 h after GnRH agonist. In another experiment, oocytes were co-cultured with follicular hemisections for 15 h to determine whether PGs mediate the effect of AngII on meiotic resumption. Indomethacin (10 microM) inhibited AngII-induced meiotic resumption (13.4 vs 77.5% MI without indomethacin; P<0.001). Furthermore, the GV oocytes progressed to MI at a similar rate when PGE(2), PGF(2alpha) or AngII was present in the co-culture system with follicular cells (PGE(2) 77.4%, PGF(2alpha) 70.0%, and AngII 75.0% MI). In conclusion, our results provide strong evidence that AngII mediates the resumption of meiosis induced by an LH surge in bovine oocytes and that this event is dependent on PGE(2) or PGF(2alpha) produced by follicular cells.

The positive inotropic effect of endothelin-1 is mediated by mitochondrial reactive oxygen species.

We have previously demonstrated the participation of reactive oxygen species (ROS) in the positive inotropic effect of a physiological concentration of Angiotensin II (Ang II, 1 nM). The objective of the present work was to evaluate the role and source of ROS generation in the positive inotropic effect produced by an equipotent concentration of endothelin-1 (ET-1, 0.4 nM). Isolated cat ventricular myocytes were used to measure sarcomere shortening with a video-camera, superoxide anion (()O(2)(-)) with chemiluminescence, and ROS production and intracellular pH (pH(i)) with epifluorescence. The ET-1-induced positive inotropic effect (40.4+/-3.1%, n=10, p<0.05) was associated to an increase in ROS production (105+/-29 fluorescence units above control, n=6, p<0.05). ET-1 also induced an increase in ()O(2)(-) production that was inhibited by the NADPH oxidase blocker, apocynin, and by the blockers of mitochondrial ATP-sensitive K(+) channels (mK(ATP)), glibenclamide and 5 hydroxydecanoic acid. The ET-1-induced positive inotropic effect was inhibited by apocynin (0.3 mM; 6.3+/-6.6%, n=13), glibenclamide (50 microM; 8.8+/-3.5%, n=6), 5 hydroxydecanoic acid (500 microM; 14.1+/-8.1, n=9), and by scavenging ROS with MPG (2 mM; 0.92+/-5.6%, n=8). ET-1 enhanced proton efflux (J(H)) carried by the Na(+)/H(+) exchanger (NHE) after an acid load, effect that was blocked by MPG. Consistently, the ET-induced positive inotropic effect was also inhibited by the NHE selective blocker HOE642 (5 microM; 9.37+/-6.07%, n=7). The data show that the effect of a concentration of ET-1 that induces an increase in contractility of about 40% is totally mediated by an intracellular pathway triggered by mitochondrial ROS formation and stimulation of the NHE.

Inhibition of Angiotensin II receptors during pregnancy induces malformations in developing rat kidney.

Evidence suggests that Angiotensin II plays an important role in the complex process of renal organogenesis. Rat kidney organogenesis starts between E13-14 and lasts up to 2 weeks after birth. The present study demonstrates histologic modifications and changes in receptor localisation in animals born from mothers treated with Angiotensin II, Losartan or PD123319 (1.0 mg/kg/day) during late pregnancy. Angiotensin II-treated animals exhibited very well developed tubules in the renal medulla in coincidence with higher AT(1) binding. Control animals exhibited angiotensin AT(2) binding in the outer stripe of the outer medulla, while in the Angiotensin II-treated animals binding was observed to the inner stripe. In Angiotensin II-treated 1-week-old animals, the nephrogenic zone contained fewer immature structures, and more developed collecting tubules than control animals. Treatment with Losartan resulted in severe renal abnormalities. For newborn and 1-week-old animals, glomeruli exhibited altered shape and enlarged Bowman spaces, in concordance with a loss of [(125)I]Angiotensin II binding in the cortex. Blockade with PD123319 led to an enlarged nephrogenic zone with increased number of immature glomeruli, and less glomeruli in the juxtamedullary area. Autoradiography showed a considerable loss of AT(1) binding in the kidney cortex of PD123319-treated animals at both ages. The present results show for the first time histomorphological and receptor localisation alterations following treatment with low doses of Losartan and PD123319 during pregnancy. These observations confirm previous assumptions that in the developing kidney Angiotensin II exerts stimulatory effects through AT(1) receptors that might be counterbalanced by angiotensin AT(2) receptors.

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.

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.

Renal interstitial adenosine is increased in angiotensin II-induced hypertensive rats.

Since marked renal vasoconstriction is observed in angiotensin II (ANG II)-mediated hypertensive rats, we studied the possible interaction between ANG II and adenosine in this model. ANG II was infused into male Wistar rats through osmotic minipumps (435 ng x kg(-1) x min(-1)) for 14 days. In sham and ANG II groups, renal tissue and interstitial adenosine were measured; both increased to a similar twofold extent in the ANG II-treated rats (31.40 +/- 4 vs. 62.0 +/- 8.4 nM, sham vs. ANG II, interstitial adenosine; P< 0.001). The latter decreased by 47% with the specific blockade of 5'-nucleotidase. Glomerular hemodynamics demonstrated marked renal vasoconstriction in the angiotensin-treated group, which was reverted by an adenosine A(1)-receptor antagonist (8-cyclopentyl-1,3-dipropylxanthine, 10 mug.kg(-1) x min(-1)). 5'-Nucleotidase and adenosine deaminase (ADA) activities were measured in the cytosolic and membrane fractions. Only the membrane ADA activity decreased from 1,202 +/- 80 to 900 +/- 50 mU/mg protein in the ANG II-treated rats (P< 0.05), as well as in their protein and mRNA expression. Despite the adenosine elevation, A(1) and A(2b) receptor protein did not change; in contrast, downregulation was observed in A(2a) receptor and upregulation in A(3) receptor. A similar pattern was found in the cortex and in the medulla; mRNA significantly decreased only in the A(3) receptor in both segments. These results suggest that the elevation of renal tissue and interstitial adenosine contributes to the renal vasoconstriction observed in the ANG II-induced hypertension and that it is mediated by a decrease in the activity and expression of ADA, increased production of adenosine, and an induced imbalance in adenosine receptors.

[Drugs for heart rate control and non-antiarrhythmic drugs in atrial fibrillation]. / Fármacos para control de la frecuencia ventricular y fármacos no-antiarrítmicos en fibrilación auricular.

Multiple drugs are helpful for rate control in different tachyarrhythmias, in particular atrial fibrillation (AF). Betablockers (betaB) and calcium channel blockers have been used as monotherapy or as adjunctive therapy to antiarrhythmics for mantaining an acceptable ventricular rate. In recent years new concepts about auricular remodelation process as a consequence of AF has shown benefits with drugs as angiotensin-renin system blockers (ARSB) like angiotensin conversing enzime inhibitors (ACEI) and angiotensin receptor blockers (ARB). In this article it will be reviewed the benefits of rate control in AF by using betaB and calcium channel blockers and also the benefits in atrial remodelation process and the prevention of AF with ARSB drugs.

Angiotensin-(1-7) counterregulates angiotensin II signaling in human endothelial cells.

Angiotensin (Ang)-(1-7), acting through the Mas receptor, opposes the actions of Ang II. Molecular mechanisms for this are unclear. Here we sought to determine whether Ang-(1-7) influences Ang II signaling in human endothelial cells, focusing specifically on Src homology 2-containing inositol phosphatase 2 (SHP-2) and its interaction with c-Src. Ang II-induced phosphorylation of c-Src, extracellular signal regulated kinase (ERK)1/2, and SHP-2 and activation of NAD(P)H oxidase were assessed in the absence and presence of Ang-(1-7) (10(-6) mol/L, 15 minutes) by immunoblotting and lucigenin-enhanced chemiluminescence, respectively. (D-Ala(7))-Ang I/II (1-7) (Ang fragment 1-7 receptor antagonist) was used to block Ang-(1-7) effects. Association between SHP-2 and c-Src was assessed by immunoprecipitation/immunoblotting studies. Ang II significantly increased activation of c-Src, ERK1/2, and NAD(P)H oxidase and reduced phosphorylation of SHP-2 (P<0.05) in human endothelial cells. These effects were abrogated in cells pre-exposed to Ang-(1-7). Ang fragment 1-7 receptor antagonist pretreatment blocked the negative modulatory actions of Ang-(1-7) on Ang II-induced signaling. Ang-(1-7) alone did not significantly alter phosphorylation of c-Src, ERK1/2, and SHP-2 and had no effect on basal activity of NAD(P)H oxidase. SHP-2 and c-Src were physically associated in the basal state. This association was increased by Ang-(1-7) and blocked by Ang fragment 1-7 receptor antagonist. Our findings demonstrate that, in human endothelial cells, Ang-(1-7) negatively modulates Ang II/Ang II type 1 receptor-activated c-Src and its downstream targets ERK1/2 and NAD(P)H oxidase. We also show that SHP-2-c-Src interaction is enhanced by Ang-(1-7). These phenomena may represent a protective mechanism in the endothelium whereby potentially deleterious effects of Ang II are counterregulated by Ang-(1-7).

Protective effect of long-term angiotensin II inhibition.

Experimental studies indicate that angiotensin II (ANG II) through its type 1 receptor (AT(1)) promotes cardiovascular hypertrophy and fibrosis. Therefore, the aim of this study was to analyze whether chronic long-term inhibition of the renin-angiotensin system (RAS) can prevent most of the deleterious effects due to aging in the cardiovascular system of the normal rat. The main objective was to compare two strategies of ANG II blockade: a converting enzyme inhibitor (CEI) and an AT(1) receptor blocker (AT(1)RB). A control group remained untreated; treatment was initiated 2 wk after weaning. A CEI, enalapril (10 mg.kg(-1).day(-1)), or an AT(1)RB, losartan (30 mg.kg(-1).day(-1)), was used to inhibit the RAS. Systolic blood pressure, body weight, and water and food intake were recorded over the whole experimental period. Heart, aorta, and mesenteric artery weight as well as histological analysis of cardiovascular structure were performed at 6 and 18 mo. Twenty animals in each of the three experimental groups were allowed to die spontaneously. The results demonstrated a significant protective effect on the function and structure of the cardiovascular system in all treated animals. Changes observed at 18 mo of age in the hearts and aortas were quite significant, but each treatment completely abolished this deterioration. The similarity between the results detected with either enalapril or losartan treatment clearly indicates that most of the effects are exerted through AT(1) receptors. An outstanding finding was the significant and similar prolongation of life span in both groups of treated animals compared with untreated control animals.

Avances en el tratamiento de la insuficiencia cardíaca / Advances in heart failure treatment

El síndrome de insuficiencia cardíaca tiene alta prevalencia e incidencia en el mundo desarrollado, como también en los países con un nivel de desarrollo intermedio, como Chile. Se cree que este fenómeno obedece, en gran medida, al progresivo envejecimiento de la población. Además, las principales causas del síndrome son muy prevalentes (cardiopatía coronaria e hipertensión arterial sistémica). Esta situación ha impuesto una enorme carga económica sobre los sistemas de salud de las diversas naciones, ya que la insuficiencia cardiaca se ha convertido en la principal causa de hospitalización en personas mayores de 65 años. La cardiología preventiva tiene un rol importante que jugar en disminuir la incidencia de nuevos casos del síndrome. En esta revisión se tratan brevemente los siguientes aspectos: 1) avances en la comprensión fisiopatológica de esta condición; 2) insuficiencia cardiaca con función sistólica preservada; 3) algunos avances farmacológicos; 4) anemia e insuficiencia cardíaca; 5) dispositivos e insuficiencia cardíaca; 6) rol de la cirugía en la insuficiencia cardíaca.