3-nitrotyrosine and Hypertension--Portal

To evaluate the antioxidant effect of N-acetylcysteine (NAC) on the stomach of rats with portal hypertension.. Twenty-four male Wistar rats weighing ± 250 g were divided into four experimental groups (n = 6 each): Sham-operated (SO), SO + NAC, partial portal vein ligation (PPVL), and PPVL + NAC. Treatment with NAC in a dose of 10 mg/kg (i.p.) diluted in 0.6 mL of saline solution was administered daily for 7 d starting 8 d after the surgery. Animals from the PPVL and SO group received saline solution (0.6 mL) for the same period of time as the PPVL + NAC and SO + NAC group. On the 15(th) day the animals were anesthetized and we evaluated portal pressure by cannulating mesenteric artery. After, we removed the stomach for further analysis. We performed immunohistochemical analysis for endothelial nitric oxide synthase (eNOS), vascular endothelial growth factor (VEGF), and nitrotirosine (NTT) proteins in stomach. We also evaluated eNOS and VEGF by Western blot analysis and assessed DNA damage in blood samples by the comet assay.. The portal hypertension group exhibited increases in portal pressure when compared to SO group (29.8 ± 1.8 vs 12.0 ± 0.3 mmHg) (P < 0.001). The same was observed when we compared the eNOS (56.8 ± 3.7 vs 13.46 ± 2.8 pixels) (P < 0.001), VEGF (34.9 ± 4.7 vs 17.46 ± 2.6 pixels) (P < 0.05), and NTT (39.01 ± 4.0 vs 12.77 ± 2.3 pixels) (P < 0.05) expression by immunohistochemistry of the PPVL animals with the SO group. The expression of eNOS (0.39 ± 0.03 vs 0.25 ± 0.03 a.μ) (P < 0.01) and VEGF (0.38 ± 0.04 vs 0.26 ± 0.04 a.μ) (P < 0.01) were also evaluated by Western blot analysis, and we observed an increase of both proteins on PPVL animals. We also evaluated the DNA damage by comet assay, and observed an increase on damage index and damage frequency on those animals. NAC decreased portal pressure values in PPVL + NAC animals (16.46 ± 2 vs 29.8 ± 1.8 mmHg) (P < 0.001) when compared to PPVL. The expression of eNOS (14.60 ± 4.1 vs 56.8 ± 3.7 pixels) (P < 0.001), VEGF (19.53 ± 3.2 vs 34.9 ± 4.7 pixels) (P < 0.05) and NTT (21.84 ± 0.7 vs 39.01 ± 4.0 pixels) (P < 0.05) evaluated by immunohistochemistry were also reduced in PPVL + NAC animals. Also, when evaluated by Western blot eNOS expression (0.32 ± 0.03 vs 0.39 ± 0.03 a.μ) (P < 0.05) and VEGF expression (0.31 ± 0.09 vs 0.38 ± 0.04 a.μ) (P < 0.01). Furthermore, NAC modulated DNA damage in PPVL + NAC animals.. In view of these results, we believe NAC is able to protect the stomach from the alterations induced by the PPVL procedure.

Topics: Acetylcysteine; Animals; Antioxidants; Blotting, Western; Comet Assay; Disease Models, Animal; DNA Damage; Gastric Mucosa; Hypertension, Portal; Immunohistochemistry; Male; Neovascularization, Pathologic; Nitric Oxide Synthase Type III; Portal Pressure; Rats, Wistar; Stomach; Tyrosine; Vascular Endothelial Growth Factor A; Vasodilation

To investigate the effects of glutamine on oxidative/nitrosative stress and the vascular endothelial growth factor (VEGF)-Akt-endothelial nitric oxide synthase (eNOS) signaling pathway in an experimental model of portal hypertension induced by partial portal vein ligation (PPVL).. Portal hypertension was induced by PPVL. The PPVL model consists of a partial obstruction of the portal vein, performed using a 20 G blunt needle as a guide, which is gently removed after the procedure. PPVL model was performed for 14 d beginning treatment with glutamine on the seventh day. On the fifteenth day, the mesenteric vein pressure was checked and the stomach was removed to test immunoreactivity and oxidative stress markers. We evaluated the expression and the immunoreactivity of proteins involved in the VEGF-Akt-eNOS pathway by Western blotting and immunohistochemical analysis. Oxidative stress was measured by quantification of the cytosolic concentration of thiobarbituric acid reactive substances (TBARS) as well as the levels of total glutathione (GSH), superoxide dismutase (SOD) activity, nitric oxide (NO) production and nitrotyrosine immunoreactivity.. All data are presented as the mean ± SE. The production of TBARS and NO was significantly increased in PPVL animals. A reduction of SOD activity was detected in PPVL + G group. In the immunohistochemical analyses of nitrotyrosine, Akt and eNOS, the PPVL group exhibited significant increases, whereas decreases were observed in the PPVL + G group, but no difference in VEGF was detected between these groups. Western blotting analysis detected increased expression of phosphatidylinositol-3-kinase (PI3K), P-Akt and eNOS in the PPVL group compared with the PPVL + G group, which was not observed for the expression of VEGF when comparing these groups. Glutamine administration markedly alleviated oxidative/nitrosative stress, normalized SOD activity, increased levels of total GSH and blocked NO overproduction as well as the formation of peroxynitrite.. Glutamine treatment demonstrated to reduce oxidative damage but does not reduce angiogenesis induced by PH in gastric tissue, demonstrating a beneficial role for the PI3K-Akt-eNOS pathway.

Topics: Animals; Antioxidants; Disease Models, Animal; Esophageal and Gastric Varices; Glutamine; Glutathione; Hypertension, Portal; Male; Neovascularization, Pathologic; Nitric Oxide; Nitric Oxide Synthase Type III; Oxidative Stress; Phosphatidylinositol 3-Kinase; Proto-Oncogene Proteins c-akt; Rats; Rats, Wistar; Signal Transduction; Stomach; Superoxide Dismutase; Thiobarbituric Acid Reactive Substances; Time Factors; Tyrosine; Vascular Endothelial Growth Factor A

In the gastric mucosa of portal hypertensive rats, adaptive cytoprotection against ethanol-induced damage is impaired. The aim of this study was to determine relation between impaired adaptive cytoprotection and oxidative stress.. Portal hypertension was produced in male Sprague-Dawley rats by inducing staged portal vein occlusion. Oxidative stress levels were evaluated by measuring malondialdehyde and nitrotyrosine levels in the rat gastric mucosa with or without 10% ethanol pretreatment. Inhibition of oxidative stress by an anti-oxidant agent was estimated, and glutathione levels were also measured. Adaptive cytoprotection to 70% ethanol treatment was evaluated by measuring the gastric mucosal injury index in the presence or absence of the anti-oxidant.. The portal hypertensive gastric mucosa pretreated with 10% ethanol had significantly higher oxidative stress levels than the mucosa not pretreated with 10% ethanol. However, the sham-operated gastric mucosa pretreated with 10% ethanol had significantly lower oxidative stress levels than the mucosa not pretreated with 10% ethanol. Pretreatment with 10% ethanol increased glutathione levels in the sham-operated but not in the portal hypertensive gastric mucosa. Administration of the anti-oxidant agent prior to 10% ethanol pretreatment significantly reduced oxidative stress levels, increased glutathione levels, and decreased the injury index in response to 70% ethanol in the portal hypertensive gastric mucosa.. Increased oxidative stress may lead to impaired adaptive cytoprotection in the gastric mucosa of portal hypertensive rats, probably through damage to the system of endogenous anti-oxidant production.

Topics: Adaptation, Physiological; Animals; Cytoprotection; Ethanol; Gastric Mucosa; Glutathione; Histidine; Hypertension, Portal; Male; Malondialdehyde; Oxidative Stress; Rats; Rats, Sprague-Dawley; Thioctic Acid; Tyrosine