Rodrigo Yokota

Alternative pathways for angiotensin II production as an important determinant of kidney damage in endotoxemia

Sepsis is an uncontrolled systemic inflammatory response against an infection and a major public health issue worldwide. This condition affects several organs, and, when caused by Gram-negative bacteria, kidneys are particularly damaged. Due to the importance of renin-angiotensin system (RAS) in regulating renal function, in the present study, we aimed to investigate the effects of endotoxemia over the renal RAS. Wistar rats were injected with Escherichia coli lipopolysaccharide (LPS) (4 mg/kg), mimicking the endotoxemia induced by Gram-negative bacteria. Three days after treatment, body mass, blood pressure, and plasma nitric oxide (NO) were reduced, indicating that endotoxemia triggered cardiovascular and metabolic consequences and that hypotension was maintained by NO-independent mechanisms. Regarding the effects in renal tissue, inducible NO synthase (iNOS) was diminished, but no changes in the renal level of NO were detected. RAS was also highly affected by endotoxemia, since renin, angiotensin-converting enzyme (ACE), and ACE2 activities were altered in renal tissue. Although these enzymes were modulated, only angiotensin (ANG) II was augmented in kidneys; ANG I and ANG 1-7 levels were not influenced by LPS. Cathepsin G and chymase activities were increased in the endotoxemia group, suggesting alternative pathways for ANG II formation. Taken together, our data suggest the activation of noncanonical pathways for ANG II production and the presence of renal vasoconstriction and tissue damage in our animal model. In summary, the systemic administration of LPS affects renal RAS, what may contribute for several deleterious effects of endotoxemia over kidneys.

Diabetic Nephropathy Induced by Increased Ace Gene Dosage Is Associated with High Renal Levels of Angiotensin (1-7) and Bradykinin.

Population studies have shown an association between diabetic nephropathy (DN) and insertion/deletion (I/D) polymorphism of the angiotensin-converting enzyme (ACE) gene (ACE in humans, Ace in mice). The aim was to evaluate the modulation of Ace copies number and diabetes mellitus (DM) on renal RAS and correlate it with indicators of kidney function. Increased number of copies of the Ace gene, associated with DM, induces renal dysfunction. The susceptibility to the development of DN in 3 copies of animals is associated with an imbalance in activity of RAS enzymes leading to increased synthesis of Ang II and Ang-(1–7). Increased concentration of renal Ang-(1–7) appears to potentiate the deleterious effects triggered by Ang II on kidney structure and function. Results also show increased bradykinin concentration in 3 copies diabetic group. Taken together, results indicate that the deleterious effects described in 3 copies diabetic group are, at least in part, due to a combination of factors not usually described in the literature. Thus, the data presented here show up innovative and contribute to understanding the complex mechanisms involved in the development of DN, in order to optimize the treatment of patients with this complication.

Intra-Renal Angiotensin Levels Are Increased in High-Fructose Fed Rats in the Extracorporeal Renal Perfusion Model

Overconsumption of fructose leads to metabolic syndrome as a result of hypertension, insulin resistance, and hyperlipidemia. In this study, the renal function of animals submitted to high fructose intake was analyzed from weaning to adulthood using in vivo and ex vivo methods, being compared with a normal control group. We investigated in ex vivo model of the role of the renin Angiotensin system (RAS) in the kidney. The use of perfused kidney from animals submitted to 8-week fructose treatment showed that high fructose intake caused metabolic and cardiovascular alterations that were consistent with other studies. Moreover, the isolated perfused kidneys obtained from rats under high fructose diet showed a 33% increase in renal perfusion pressure throughout the experimental period due to increased renal vascular resistance and a progressive fall in the glomerular filtration rate, which reached a maximum of 64% decrease. Analysis of RAS peptides in the high fructose group showed a threefold increase in the renal concentrations of angiotensin I (Ang I) and a twofold increase in angiotensin II (Ang II) levels, whereas no change in angiotensin 1-7 (Ang 1-7) was observed when compared with the control animals. We did not detect changes in angiotensin converting enzyme (ACE) activity in renal tissues, but there is a tendency to decrease. These observations suggest that there are alternative ways of producing Ang II in this model. Chymase the enzyme responsible for Ang II formation direct from Ang I was increased in renal tissues in the fructose group, confirming the alternative pathway for the formation of this peptide. Neprilysin (NEP) the Ang 1-7 forming showed a significant decrease in activity in the fructose vs. control group, and a tendency of reduction in ACE2 activity. Thus, these results suggest that the Ang 1-7 vasodilator peptide formation is impaired in this model contributing with the increase of blood pressure. In summary, rats fed high fructose affect renal RAS, which may contribute to several deleterious effects of fructose on the kidneys and consequently an increase in blood pressure.

Nebivolol prevents vascular oxidative stress and hypertension in rats chronically treated with ethanol

BACKGROUND AND AIMS Chronic ethanol consumption is associated with hypertension and atherosclerosis. Vascular oxidative stress is described as an important mechanism whereby ethanol predisposes to atherosclerosis. We hypothesized that nebivolol would prevent ethanol-induced hypertension and vascular oxidative stress. METHODS Male Wistar rats were treated with ethanol 20% (vol./vol.) or nebivolol (10 mg/kg/day, p. o., gavage), a selective β1-adrenergic receptor antagonist. RESULTS Ethanol-induced increase in blood pressure and in the circulating levels of adrenaline and noradrenaline was prevented by nebivolol. Similarly, nebivolol prevented ethanol-induced increase in plasma levels of renin, angiotensin I and II. Chronic ethanol consumption increased the aortic levels of superoxide anion (O2-), thiobarbituric acid reactive species (TBARS) as well as the expression of Nox1 and nitrotyrosine immunostaining in the rat aorta. Treatment with nebivolol prevented these responses. The decrease in aortic levels of nitrate/nitrite (NOx) induced by ethanol was prevented by the treatment with nebivolol. Finally, nebivolol attenuated ethanol-induced increase in phenylephrine- and noradrenaline-induced contraction of endothelium-intact and endothelium-denuded aortic rings. CONCLUSIONS The novelty of our study is that nebivolol prevented ethanol-induced hypertension and vascular oxidative stress. Additionally, we showed that the sympathetic nervous system (SNS) and the renin-angiotensin system (RAS) are important endogenous mediators of the cardiovascular effects of ethanol.

196 EFFECTS ON SYMPATHETIC ACTIVITY AND RENIN ANGIOTENSIN SYNTEM IN EXPERIMENTAL METABOLIC SYNDROME MODEL

Introduction: Administration of a diet rich in fructose initiates a series of metabolic events resulting in hypertriglyceridemia, hypertension and glucose intolerance. Objectives: The purpose of this study was to evaluate the role of the renin angiotensin system on cardiovascular function induced by fructose intake during 8 weeks. Desing and Methods: Weaned (21 days old) male Wistar rats (50-60 g) were divided in 2 groups and they were followed for 8 weeks: Control (CG) and Fructose (FG, 10% in drinking water). The participation of the renin-angiotensin system has been evaluated by receptor blockade AT1a with losartan (10 mg/kg iv) and by angiotensin-converting enzyme (ACE) in serum by fluorimetric measurements. Ganglionic blockade (hexamethonium, 20 mg/kg, iv) was used to determine vascular activity of sympathetic nervous system. Arterial pressure (AP) and heart rate (HR) were directly recorded using a data acquisition system (Windaq, 2 KHz) in conscious and awake rats. Results: FG showed an increase of mean AP (120±3.1 mmHg) when compared to CG (98±1.6 mmHg). No changes in heart rate were observed. Blocking with losartan showed an increased depressor response in FG (-18 ± 1.7 mm Hg) compared to the GC (-7 ± 1.5 mmHg) likewise after hexamethonium administration. ACE serum in FG (153±2,7 mU/mL) was higher than CG (103±14,3 mU/mL). Conclusions: In conclusion, these data suggest that metabolic changes induced by frutose-rich diet during life spam in rats are accompanied by hypertension associated with increase of renin angiotensin system and sympathetic overactivity.

729 RENAL AND METABOLIC EVALUATIONS IN RATS WITH METABOLIC SYNDROME INDUCED BY FRUCTOSE

Introduction and objectives: High fructose fed rats has previously been described as an animal model of impaired glucose tolerance. The aim of this study was to evaluate the contribution of overloading of fructose on metabolic and renal function in rats. Design and methods: Male Wistar rats (50–60 g) were divided into control group (CG, n = 6) and Fructose Group (FG, 10% fructose, drinking water, 8 weeks, n = 7). Renal Angiotensin I Converting Enzyme activity (ACE) was evaluated by fluorimetry. Angiotensins Quantification were analyzed by HPLC. The kidney was collected for histological glomerular analysis (5 &mgr;m, Picrosirius Red) to evaluate the collagen deposition at Glomerular Tuft (CGT) and Bowman[Combining Acute Accent]s Capsule (CBC). Blood was collected to biochemical assays (Labtest, BR). Results: There was no difference in Lee Index between groups, however the adiposity was increased in FG (8 ± 0,5 g/kg) when compared with CG (6 ± 1 g/kg). Basal glycemia and Triglycerides were augmented in FG when compared with CG. Renal ANG II was increased in FG (63 ± 8,4 pmol/g) when compared with CG (29 ± 2,5 pmol/g). However, there was no changes in renal ACE activity (CG: 5 ± 0,7 vs 4,6 ± 0,7 mU/mg prot). The CGT was higher (25%) in FG when compared with CG. The CBC was also increased in FG (29%) when compared with CG. Conclusions: In conclusion, our data suggest that fructose is related metabolic alterations associated with an increased renal collagen deposition. Moreover, the elevated renal AngII induced by fructose could be involved in tissue damage and contribute to decrease in renal function.