The Labdane Ent-3-Acetoxy-Labda-8(17), 13-Dien-15-Oic Decreases Blood Pressure In Hypertensive Rats

Abstract Background: Labdane-type diterpenes induce lower blood pressure via relaxation of vascular smooth muscle; however, there are no studies describing the effects of labdanes in hypertensive rats. Objective: The present study was designed to investigate the cardiovascular actions of the labdane-type diterpene ent-3-acetoxy-labda-8(17), 13-dien-15-oic acid (labda-15-oic acid) in two-kidney 1 clip (2K-1C) renal hypertension. Methods: Vascular reactivity experiments were performed in aortic rings isolated from 2K-1C and normotensive (2K) male Wistar rats. Nitrate/nitrite (NOx) measurement was performed in aortas by colorimetric assay. Blood pressure measurements were performed in conscious rats. Results: Labda-15-oic acid (0.1-300 µmol/l) and forskolin (0.1 nmol/l - 1 µmol/l) relaxed endothelium-intact and endothelium-denuded aortas from both 2K-1C and 2K rats. Labda-15-oic acid was more effective at inducing relaxation in endothelium-intact aortas from 2K pre-contracted with phenylephrine when compared to the endothelium-denuded ones. Forskolin was more potent than labda-15-oic acid at inducing vascular relaxation in arteries from both 2K and 2K-1C rats. Labda-15-oic acid-induced increase in NOx levels was lower in arteries from 2K-1C rats when compared to 2K rats. Intravenous administration of labda-15-oic acid (0.3-3 mg/kg) or forskolin (0.1-1 mg/kg) induced hypotension in conscious 2K-1C and 2K rats. Conclusion: The present findings show that labda-15-oic acid induces vascular relaxation and hypotension in hypertensive rats

Data on the effects of losartan on protein expression, vascular reactivity and antioxidant capacity in the aorta of ethanol-treated rats

We describe the effects of losartan, a selective AT1 receptor antagonist on the alterations induced by treatment with ethanol in the rat aorta. The data shown here are related to the article entitled “Angiotensin type 1 receptor mediates chronic ethanol consumption-induced hypertension and vascular oxidative stress” (P. Passaglia, C.S. Ceron, A.S. Mecawi, J. Antunes-Rodrigues, E.B. Coelho, C.R. Tirapelli, 2015) [1]. Here we include new data on the protective effect of losartan against ethanol-induced oxidative stress. Male Wistar rats treated for 2 weeks with ethanol (20%, vol./vol.) exhibited increased aortic production of reactive oxygen species (ROS) and losartan (10 mg/kg/day; p.o. gavage) prevented this response. Ethanol did not alter the expression of eNOS in the rat aorta. Losartan prevented ethanol-induced increase in the aortic expression of nNOS. Neither ethanol nor losartan affected superoxide dismutase (SOD) or catalase (CAT) activities in the rat aorta. Treatment with ethanol increased the contraction induced by phenylephrine in both endothelium-intact and endothelium-denuded aortas and these responses were prevented by losartan. Conversely, neither ethanol nor losartan affected the endothelium-dependent relaxation induced by acetylcholine

Vitamin C prevents the endothelial dysfunction induced by acute ethanol intake

Aims: Investigate the effect of ascorbic acid (vitamin C) on the endothelial dysfunction induced by acute ethanol intake. Main methods: Ethanol (1 g/kg; p.o. gavage) effects were assessed within 30 min in male Wistar rats. Key findings: Ethanol intake decreased the endothelium-dependent relaxation induced by acetylcholine in the rat aorta and treatment with vitamin C (250 mg/kg; p.o. gavage, 5 days) prevented this response. Ethanol increased superoxide anion (O2−) generation and decreased aortic nitrate/nitrite levels and these responses were not prevented by vitamin C. Superoxide dismutase (SOD) and catalase (CAT) activities as well as hydrogen peroxide (H2O2) and reduced glutathione (GSH) levels were not affected by ethanol. RhoA translocation as well as the phosphorylation levels of protein kinase B (Akt), eNOS (Ser1177 or Thr495 residues), p38MAPK, SAPK/JNK and ERK1/2 was not affected by ethanol intake. Vitamin C increased SOD activity and phosphorylation of Akt, eNOS (Ser1177 residue) and p38MAPK in aortas from both control and ethanol-treated rats. Incubation of aortas with tempol prevented ethanol-induced decrease in the relaxation induced by acetylcholine. Ethanol (50 mM/1 min) increased O2− generation in cultured aortic vascular smooth muscle cells (VSMC) and vitamin C did not prevent this response. In endothelial cells, vitamin C prevented the increase on ROS generation and the decrease in the cytosolic NO content induced by ethanol. Significance: Our study provides novel evidence that vitamin C prevents the endothelial dysfunction induced by acute ethanol intake by a mechanism that involves reduced ROS generation and increased NO availability in endothelial cells

Pharmacological characterization of the mechanisms underlying the vascular effects of succinate

We investigated the mechanisms underlying the vascular effects of succinate. Vascular reactivity experiments were performed in aortic rings isolated from male Wistar rats and C57BL/6 wild type (WT) or GPR91-/- mice. Nitrate/nitrite (NOx) was measured colorimetrically whereas 6-keto-prostaglandin F1α (stable product of prostacyclin) was measured by enzyme immunoassay (EIA). Phosphorylation of endothelial nitric oxide synthase (eNOS) was assessed by western immunoblotting. Functional assays revealed that the direct effect of succinate in the vasculature is biphasic. At lower concentrations succinate induced relaxation while at higher concentrations succinate induced vascular contraction. Succinate concentration-dependently relaxed rat aortic rings with intact endothelium. Endothelial removal reduced, but not abolished succinate-induced relaxation in Wistar rats and WT mice. In contrast, aortic rings from GPR91-/- mice only exhibited moderated responses, which were not modified by the absence of endothelium. Pre-incubation of endothelium-intact, but not endothelium-denuded rat aortic rings with L-NAME, indomethacin and tetraethylammonium (TEA) reduced succinate-induced relaxation. In endothelium-intact rings, succinate-induced relaxation was attenuated by ODQ, haemoglobin, Rp-8-Br-Pet-cGMPS, thapsigargin and SC-560. Blockade of K+ channels with 4-aminopyridine, apamin and charybdotoxin, reduced succinate-induced relaxation. Succinate increased the concentration of NOx and 6-keto-prostaglandin F1α in endothelium-intact aortas. Succinate increased eNOS phosphorylation at ser1177 residue. CaCl2-induced contraction of endothelium-intact or endothelium-denuded aortas was not affected by succinate. The major new finding of our study is that it first demonstrates a direct effect of succinate in the vasculature. Succinate displays a biphasic and concentration-dependent effect. The vascular relaxation induced by succinate is partially mediated by endothelial GPR91 receptors via NO-cGMP pathway, a vasodilator cyclooxygenase (COX) product(s) and the opening of K+ channels

Data on the mechanisms underlying succinate-induced aortic contraction

AbstractWe describe the mechanisms underlying the vascular contraction induced by succinate. The data presented here are related to the article entitled “Pharmacological characterization of the mechanisms underlying the vascular effects of succinate” (L.N. Leite, N.A. Gonzaga, J.A. Simplicio, G.T. Vale, J.M. Carballido, J.C. Alves-Filho, C.R. Tirapelli, 2016) [1]. Succinate acts as a signaling molecule by binding to a G-protein-coupled receptor termed GPR91, “Citric acid cycle intermediates as ligands for orphan G-protein-coupled receptors” (W. He, F.J. Miao, D.C. Lin, R.T. Schwandner, Z. Wang, J. Gao, J.L. Chen, H. Tian, L. Ling, 2004) [2]. Here we include data on the contractile effect of succinate in the aorta. Succinate contracted both endothelium-intact and endothelium-denuded aortic rings isolated from male Wistar rats or C57BL/6 mice. Succinate was less effective at inducing contraction in arteries isolated from GPR91-deficient mice, when compared to its vascular effect in aortas from wild type mice. SB203508 (p38MAK inhibitor), SP600125 (JNK inhibitor) and Y27632 (Rho-kinase inhibitor) reduced succinate-induced contraction in both endothelium-intact and endothelium-denuded rat aortic rings, while PD98059 (ERK1/2 inhibitor) did not affect succinate-induced contraction. The contractile response induced by succinate on endothelium-intact and endothelium-denuded rat aortic rings was reduced by indomethacin (non-selective cyclooxygenase inhibitor), H7 (protein kinase C inhibitor), verapamil (Ca2+ channel blocker) and tiron (superoxide anion scavenger)