Antioxidant and vasorelaxant activities induced by northeastern Brazilian fermented grape skins.

BACKGROUND: In northeastern Brazil, grape pomace has become a potential alternative byproduct because of the recover phenolic compounds from the vinification process. Comparative analyses were performed between lyophilized extract of grape skins from pomace, described as fermented (FGS), and fresh, unfermented (UGS) grape skins to show the relevant brand's composition upon the first maceration in winemaking. METHODS: The use of in vitro testing such as Folin-Ciocalteu's, DPPH free radical scavenger and HPLC methods were performed to evidence antioxidant effect and phenolic compounds. Additionally, vascular reactivity studies were performed in third-order branches of rat superior mesenteric arteries, which were obtained and placed in organ baths containing Krebs-Henseleit solution, maintained at 37 °C, gassed with a mixture of 95% O2 and 5% CO2, and maintained at pH 7.4. The in situ formation of reactive oxygen species (ROS) was evaluated in small mesenteric rings using oxidative fluorescent dihydroethidium dye. RESULTS: We found higher phenolic content and antioxidant activity in FGS when compared to UGS. HPLC analyses identified a significant number of phenolic compounds with antioxidant potential in both samples. The vasorelaxant effect induced by FGS was more potent than that induced by UGS, and the activity was attenuated after removal of vascular endothelium or by blockade of endothelium-derived relaxing factors, such as NO and EDHF. CONCLUSIONS: The FGS extract may be a great source of natural polyphenol products with potent antioxidant effects and endothelium-dependent vasodilatory actions involving NO and EDHF pathways.

The 2-nitrate-1,3-dibuthoxypropan, a new nitric oxide donor, induces vasorelaxation in mesenteric arteries of the rat.

The reduced availability of nitric oxide (NO) is associated with cardiovascular diseases. Therefore, NO donors such as organic nitrates are useful for the treatment of these disorders. The 2-nitrate-1,3-dibuthoxypropan (NDBP) is an organic nitrate synthesized from glycerin, which the pharmacological effects have not been investigated. In this study we evaluated the vasorelaxant effect induced by NDBP in superior mesenteric artery from rats. In phenylephrine pre-contracted artery rings, NDBP (10(-8)-10(-4)M) elicited concentration-dependent and endothelium-independent relaxation, which were attenuated by hydroxocobalamin-HDX (30 µM), a NO extracellular scavenger, and 1-H-[1,2,4] oxadiazolo [4,3-a] quinoxalin-1-one-ODQ (10 µM), an inhibitor of soluble guanylyl cyclase (sGC). In addition, the NDBP-induced relaxation was reduced by non-selective K(+) channels blocker KCl (20 mM) or selective K(+) channels blockers such as tetraethylammonium-TEA (B(KCa), 1 mM), charybdotoxin-ChTX (B(KCa), 100 nM), glibenclamide (K(ATP), 1µM) and 4-aminopyridine-4-AP (K(V), 1mM). In preparations with ODQ (10 µM) plus TEA (1 mM), the response was virtually abolished. In rat smooth muscle cells culture, NDBP (10(-6)-10(-4)M) caused concentration-dependent increases in NO levels. These findings suggest that NDBP causes vasorelaxation through NO generation and activation of the sCG/cGMP/PKG pathway.

Uncovering the vasorelaxant effect induced by Vale do São Francisco red wine: a role for nitric oxide.

The aim of this study was to investigate the mechanisms underlying the vasorelaxant effect induced by the polyphenolic compounds found in red wine from Vale do São Francisco. In phenylephrine (10 µM) precontracted mesenteric artery rings, the red wine caused a concentration-dependent relaxation (maximum response to phenylephrine 10 µM = 87.5% ± 6.5%, n = 10). After endothelium removal, the vasorelaxant effect elicited by red wine was attenuated (28.4% ± 4.9%, n = 10). In addition, the vasorelaxant effect induced by red wine in rings pretreated with 100 µM of N(w)-nitro-l-arginine methyl ester and 10 µM of 1H-[1,2,4] oxadiazolo-[4,3-a]-quinoxalin-1-one was attenuated (23.4% ± 5.1%, n = 7 and 11.8% ± 2.7%, n = 6, respectively). Pretreatment with atropine did not affect the vasorelaxant effect induced by red wine (81% ± 3.9%, n = 6). Furthermore, in rabbit aortic endothelial cell line, red wine 100 and 300 µg/mL caused concentration-dependent increases in nitric oxide levels (58 ± 1; 82 ± 7.9; Δ% of fluorescence, n = 5, respectively). In conclusion, we suggest that the alcohol free-lyophilized red wine induces an endothelium-dependent vasorelaxant effect due, at least in part, to a secondary increase in the concentration of nitric oxide and that this effect might be associated with phenolic compounds found in the red wine.

Experimental evidence for a direct cytotoxicity of Loxosceles intermedia (brown spider) venom in renal tissue.

Brown spider (Loxosceles genus) venom causes necrotic lesions often accompanied by fever, hemolysis, thrombocytopenia, and acute renal failure. Using mice exposed to Loxosceles intermedia venom, we aimed to show whether the venom directly induces renal damage. The experimental groups were composed of 50 mice as controls and 50 mice that received the venom. Light microscopic analysis of renal biopsy specimens showed alterations including hyalinization of proximal and distal tubules, erythrocytes in Bowman's space, glomerular collapse, tubule epithelial cell blebs and vacuoles, interstitial edema, and deposition of eosinophilic material in the tubule lumen. Electron microscopic findings indicated changes including glomerular epithelial and endothelial cell cytotoxicity as well as disorders of the basement membrane. Tubule alterations include epithelial cell cytotoxicity with cytoplasmic membrane blebs, mitochondrial changes, increase in smooth endoplasmic reticulum, presence of autophagosomes, and deposits of amorphous material in the tubules. We also found that the venom caused azotemia with elevation of blood urea levels but did not decrease C3 complement concentration or cause hemolysis in vivo. Confocal microscopy with antibodies against venom proteins showed direct binding of toxins to renal structures, confirmed by competition assays. Double-staining immunofluorescence reactions with antibodies against type IV collagen or laminin, antibodies to venom toxins, and fluorescent cytochemistry with DAPI revealed deposition of toxins in glomerular and tubule epithelial cells and in renal basement membranes. Two-dimensional electrophoresis showed venom rich in low molecular mass and cationic toxins. By immunoblotting with antibodies to venom toxins on renal extracts from venom-treated mice, we detected a renal binding toxin at 30 kD. The data provide experimental evidence that L. intermedia venom is directly involved in nephrotoxicity.