title: Differential Roles of the NADPH-Oxidase 1 and 2 in Platelet Activation and Thrombosis.
abstract: Reactive oxygen species (ROS) are known to regulate platelet activation; however, the mechanisms of ROS production during platelet activation remain unclear. Platelets express different isoforms of nicotinamide adenine dinucleotide (phosphate) (NAD(P)H) oxidases (NOXs). Here, we investigated the role of NOX1 and NOX2 in ROS generation and platelet activation using NOX1 and NOX2 knockout mice.
  
  
  
  NOX1(-/Y) platelets showed selective defects in G-protein-coupled receptor-mediated platelet activation induced by thrombin and thromboxane A2 analog U46619, but were not affected in platelet activation induced by collagen-related peptide, a glycoprotein VI agonist. In contrast, NOX2(-/-) platelets showed potent inhibition of collagen-related peptide-induced platelet activation, and also showed partial inhibition of thrombin-induced platelet activation. Consistently, production of ROS was inhibited in NOX1(-/Y) platelets stimulated with thrombin, but not collagen-related peptide, whereas NOX2(-/-) platelets showed reduced ROS generation induced by collagen-related peptide or thrombin. Reduced ROS generation in NOX1/2-deficient platelets is associated with impaired activation of Syk and phospholipase Cγ2, but minimally affected mitogen-activated protein kinase pathways. Interestingly, laser-induced arterial thrombosis was impaired but the bleeding time was not affected in NOX2(-/-) mice. Wild-type thrombocytopenic mice injected with NOX2(-/-) platelets also showed defective arterial thrombosis, suggesting an important role for platelet NOX2 in thrombosis in vivo but not hemostasis.
  
  
  
  NOX1 and NOX2 play differential roles in different platelet activation pathways and in thrombosis. ROS generated by these enzymes promotes platelet activation via the Syk/phospholipase Cγ2/calcium signaling pathway.
authors.affiliation: From the Departments of Pharmacology (M.K.D., K.K., B.E., Z.X., A.S.-T., B.S., M.U.-F., J.C., X.D.) and Anesthesiology (J.C.), University of Illinois at Chicago.
authors.forename: M Keegan
authors.initials: MK
authors.lastname: Delaney
authors.affiliation: From the Departments of Pharmacology (M.K.D., K.K., B.E., Z.X., A.S.-T., B.S., M.U.-F., J.C., X.D.) and Anesthesiology (J.C.), University of Illinois at Chicago.
authors.forename: Kyungho
authors.initials: K
authors.lastname: Kim
authors.affiliation: From the Departments of Pharmacology (M.K.D., K.K., B.E., Z.X., A.S.-T., B.S., M.U.-F., J.C., X.D.) and Anesthesiology (J.C.), University of Illinois at Chicago.
authors.forename: Brian
authors.initials: B
authors.lastname: Estevez
authors.affiliation: From the Departments of Pharmacology (M.K.D., K.K., B.E., Z.X., A.S.-T., B.S., M.U.-F., J.C., X.D.) and Anesthesiology (J.C.), University of Illinois at Chicago.
authors.forename: Zheng
authors.initials: Z
authors.lastname: Xu
authors.affiliation: From the Departments of Pharmacology (M.K.D., K.K., B.E., Z.X., A.S.-T., B.S., M.U.-F., J.C., X.D.) and Anesthesiology (J.C.), University of Illinois at Chicago.
authors.forename: Aleksandra
authors.initials: A
authors.lastname: Stojanovic-Terpo
authors.affiliation: From the Departments of Pharmacology (M.K.D., K.K., B.E., Z.X., A.S.-T., B.S., M.U.-F., J.C., X.D.) and Anesthesiology (J.C.), University of Illinois at Chicago.
authors.forename: Bo
authors.initials: B
authors.lastname: Shen
authors.affiliation: From the Departments of Pharmacology (M.K.D., K.K., B.E., Z.X., A.S.-T., B.S., M.U.-F., J.C., X.D.) and Anesthesiology (J.C.), University of Illinois at Chicago.
authors.forename: Masuko
authors.initials: M
authors.lastname: Ushio-Fukai
authors.affiliation: From the Departments of Pharmacology (M.K.D., K.K., B.E., Z.X., A.S.-T., B.S., M.U.-F., J.C., X.D.) and Anesthesiology (J.C.), University of Illinois at Chicago.
authors.forename: Jaehyung
authors.initials: J
authors.lastname: Cho
authors.affiliation: From the Departments of Pharmacology (M.K.D., K.K., B.E., Z.X., A.S.-T., B.S., M.U.-F., J.C., X.D.) and Anesthesiology (J.C.), University of Illinois at Chicago. xdu@uic.edu.
authors.forename: Xiaoping
authors.initials: X
authors.lastname: Du
mesh_terms: D000818:Animals; D001792:Blood Platelets / Q000187:drug effects / Q000201:enzymology*; D039481:CD11b Antigen / Q000097:blood; D020013:Calcium Signaling; D004195:Disease Models, Animal; D004789:Enzyme Activation; D020022:Genetic Predisposition to Disease; D006487:Hemostasis; D008297:Male; D008562:Membrane Glycoproteins / Q000097:blood* / Q000172:deficiency / Q000235:genetics; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009247:NADH, NADPH Oxidoreductases / Q000097:blood* / Q000172:deficiency / Q000235:genetics; D000074624:NADPH Oxidase 1; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases / Q000097:blood* / Q000172:deficiency / Q000235:genetics; D010641:Phenotype; D051966:Phospholipase C gamma / Q000097:blood; D010766:Phosphorylation; D015539:Platelet Activation / Q000187:drug effects; D010974:Platelet Aggregation; D010980:Platelet Membrane Glycoproteins / Q000819:agonists / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000097:blood*; D043562:Receptors, G-Protein-Coupled / Q000819:agonists / Q000097:blood; D000072377:Syk Kinase / Q000097:blood; D013917:Thrombin / Q000378:metabolism; D013927:Thrombosis / Q000097:blood* / Q000201:enzymology* / Q000235:genetics; D013997:Time Factors
chemical_list: D039481:CD11b Antigen; D008562:Membrane Glycoproteins; D010980:Platelet Membrane Glycoproteins; D017382:Reactive Oxygen Species; D043562:Receptors, G-Protein-Coupled; C098341:platelet membrane glycoprotein VI; D009247:NADH, NADPH Oxidoreductases; C488842:Cybb protein, mouse; D000074624:NADPH Oxidase 1; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases; C000614711:NOX1 protein, mouse; D000072377:Syk Kinase; C000606897:Syk protein, mouse; D020928:Mitogen-Activated Protein Kinases; D051966:Phospholipase C gamma; D013917:Thrombin
keywords: NADPH oxidase; blood platelets; platelet activation; reactive oxygen species; thrombosis