title: Synergism between nitric oxide and hydrogen peroxide in the inhibition of platelet function: the roles of soluble guanylyl cyclase and vasodilator-stimulated phosphoprotein.
abstract: In previous studies, a strong synergism between low concentrations of hydrogen peroxide and nitric oxide in the inhibition of agonist-induced platelet aggregation has been established and may be due to enhanced formation of cyclic GMP. In this investigation, hydrogen peroxide and NO had no effect on the activity of pure soluble guanylyl cyclase or its activity in platelet lysates and cytosol. H(2)O(2) was found to increase the phosphorylation of vasodilator-stimulated phosphoprotein (VASP), increasing the amount of the 50-kDa form that results from phosphorylation at serine(157). This occurs both in the presence and in the absence of low concentrations of NO, even at submicromolar concentrations of the peroxide, which alone was not inhibitory to platelets. These actions of H(2)O(2) were inhibited to a large extent by an inhibitor of cyclic AMP-dependent protein kinase, even though H(2)O(2) did not increase cyclic AMP. This inhibitor reversed the inhibition of platelets induced by combinations of NO and H(2)O(2) at low concentrations. The results suggest that the action on VASP may be one site of action of H(2)O(2) but that this event alone does not lead to inhibition of platelets; another unspecified action of NO is required to complete the events required for inhibition.
authors.affiliation: Department of Biochemistry and Molecular Biology, Royal Free and University College Medical School (University College London), Rowland Hill Street, London, NW3 2PF, United Kingdom.
authors.forename: M
authors.initials: M
authors.lastname: Sabetkar
authors.forename: K M
authors.initials: KM
authors.lastname: Naseem
authors.forename: J M
authors.initials: JM
authors.lastname: Tullett
authors.forename: A
authors.initials: A
authors.lastname: Friebe
authors.forename: D
authors.initials: D
authors.lastname: Koesling
authors.forename: K R
authors.initials: KR
authors.lastname: Bruckdorfer
mesh_terms: D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000470:Alkaloids / Q000494:pharmacology; D001792:Blood Platelets / Q000187:drug effects / Q000502:physiology*; D001798:Blood Proteins / Q000378:metabolism; D002227:Carbazoles; D015815:Cell Adhesion Molecules / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000097:blood; D006152:Cyclic GMP / Q000097:blood*; D017869:Cyclic GMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000097:blood; D003600:Cytosol / Q000201:enzymology; D004357:Drug Synergism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006162:Guanylate Cyclase / Q000097:blood*; D006801:Humans; D006834:Hydrazines / Q000494:pharmacology; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D066298:In Vitro Techniques; D007191:Indazoles / Q000494:pharmacology; D007211:Indoles; D007700:Kinetics; D008840:Microfilament Proteins; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000494:pharmacology*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D009589:Nitrogen Oxides; D010750:Phosphoproteins / Q000378:metabolism*; D010768:Phosphoserine / Q000097:blood; D010974:Platelet Aggregation / Q000187:drug effects* / Q000502:physiology; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology; D013347:Subcellular Fractions / Q000378:metabolism; D013917:Thrombin / Q000494:pharmacology; D000098662:Vasodilator-Stimulated Phosphoprotein
chemical_list: D000470:Alkaloids; D001798:Blood Proteins; D002227:Carbazoles; D015815:Cell Adhesion Molecules; D004791:Enzyme Inhibitors; D006834:Hydrazines; D007191:Indazoles; D007211:Indoles; D008840:Microfilament Proteins; D020030:Nitric Oxide Donors; D009589:Nitrogen Oxides; D010750:Phosphoproteins; D010975:Platelet Aggregation Inhibitors; D000098662:Vasodilator-Stimulated Phosphoprotein; C073601:KT 5823; C090937:3-(5'-hydroxymethyl-2'-furyl)-1-benzylindazole; D010768:Phosphoserine; D009569:Nitric Oxide; C084012:1,1-diethyl-2-hydroxy-2-nitrosohydrazine; D006861:Hydrogen Peroxide; D017868:Cyclic AMP-Dependent Protein Kinases; D017869:Cyclic GMP-Dependent Protein Kinases; D013917:Thrombin; D006162:Guanylate Cyclase; D006152:Cyclic GMP; D015056:1-Methyl-3-isobutylxanthine; D019331:NG-Nitroarginine Methyl Ester