title: Endothelium negatively modulates the vascular relaxation induced by nitric oxide donor, due to uncoupling NO synthase.
abstract: Nitrosyl ruthenium complexes have been characterized as nitric oxide (NO) donors that induce relaxation in the denuded rat aorta. There are some differences in their vascular relaxation mechanisms compared with sodium nitroprusside. This study investigates whether the endothelium could interfere with the [Ru(terpy)(bdq)NO](3+)-TERPY-induced vascular relaxation, by analyzing the maximal relaxation (Emax) and potency (pD(2)) of TERPY. Vascular reactivity experiments showed that the endothelium negatively modulates (pD(2): 6.17+/-0.07) the TERPY relaxation in intact rat aortic rings compared with the denuded rat aorta (pD(2): 6.65+/-0.07). This effect is abolished by a non-selective NO-synthase (NOS) inhibitor L-NAME (pD(2): 6.46+/-0.10), by the superoxide anion (O(2)(-)) scavenger TIRON (pD(2): 6.49+/-0.08), and by an NOS cofactor BH(4) (pD(2): 6.80+/-0.10). The selective dye for O(2)(-) (DHE) shows that TERPY enhances O(2)(-) concentration in isolated endothelial cells (intensity of fluorescence (IF):11258.00+/-317.75) compared with the basal concentration (IF: 7760.67+/-381.50), and this enhancement is blocked by L-NAME (IF: 8892.33+/-1074.41). Similar results were observed in vascular smooth muscle cells (concentration of superoxide after TERPY: 2.63+/-0.17% and after TERPY+L-NAME: -4.63+/-0.14%). Considering that TERPY could induce uncoupling NOS, thus producing O(2)(-), we have also investigated the involvement of prostanoids in the negative modulation of the endothelium. The non-selective cyclooxygenase (COX) inhibitor indomethacin and the selective tromboxane (TXA(2)) receptor antagonist SQ29548 reduce the effect of the endothelium on TERPY relaxation (pD(2) INDO: 6.80+/-0.17 and SQ29548: 6.85+/-0.15, respectively). However, a selective prostaglandin F(2alpha) receptor antagonist (AH6809) does not change the endothelium effect. Moreover, TERPY enhances the concentration of TXA(2) stable metabolite (TXB(2)), but this effect is blocked by L-NAME and TIRON. The present findings indicate that TERPY induces uncoupling of eNOS, enhancing O(2)(-) concentration. This enhancement in O(2)(-) concentration induces COX activation, producing TXA(2), which negatively modulates the rat aorta relaxation induced by the NO donor TERPY.
authors.affiliation: Departamento de Farmacologia, Instituto de Ciências Biologicas, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil.
authors.forename: Daniella
authors.initials: D
authors.lastname: Bonaventura
authors.forename: Claure N
authors.initials: CN
authors.lastname: Lunardi
authors.forename: Gerson J
authors.initials: GJ
authors.lastname: Rodrigues
authors.forename: Mário A
authors.initials: MA
authors.lastname: Neto
authors.forename: Juliana A
authors.initials: JA
authors.lastname: Vercesi
authors.forename: Renata G
authors.initials: RG
authors.lastname: de Lima
authors.forename: Roberto S
authors.initials: RS
authors.lastname: da Silva
authors.forename: Lusiane M
authors.initials: LM
authors.lastname: Bendhack
mesh_terms: D000818:Animals; D001011:Aorta / Q000201:enzymology*; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000201:enzymology*; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000201:enzymology; D032389:Myocytes, Smooth Muscle / Q000201:enzymology; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000378:metabolism*; D020030:Nitric Oxide Donors / Q000737:chemistry / Q000494:pharmacology*; D052250:Nitric Oxide Synthase Type III / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009599:Nitroprusside / Q000494:pharmacology; D009603:Nitroso Compounds / Q000737:chemistry / Q000494:pharmacology*; D011451:Prostaglandin-Endoperoxide Synthases / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D012428:Ruthenium / Q000737:chemistry / Q000494:pharmacology*; D013481:Superoxides / Q000378:metabolism; D014664:Vasodilation / Q000187:drug effects*
chemical_list: D004791:Enzyme Inhibitors; D020030:Nitric Oxide Donors; D009603:Nitroso Compounds; D013481:Superoxides; D009599:Nitroprusside; D009569:Nitric Oxide; D012428:Ruthenium; D052250:Nitric Oxide Synthase Type III; C496316:Nos3 protein, rat; D011451:Prostaglandin-Endoperoxide Synthases; D019331:NG-Nitroarginine Methyl Ester