title: Dual pathways of carbon monoxide-mediated vasoregulation: modulation by redox mechanisms.
abstract: BACKGROUND
  Vascular tissues produce carbon monoxide (CO) via HO-dependent and HO-independent mechanisms; the former in tandem with biliverdin and iron and the latter as a lone product. CO has been shown to function as both a vasoconstrictor and vasodilator; however, factors that dictate the vasoregulatory phenotype of this gas are unknown.
  
  
  OBJECTIVE
  We investigated whether CO-mediated vasoconstriction is mechanistically linked to enhanced reactive oxygen species production that masks vasodilatory pathways.
  
  
  RESULTS
  Sprague-Dawley rat interlobar and interlobular arteries were examined in terms of superoxide (O2*-) generation and vascular reactivity in the absence and presence of antioxidants. Both authentic CO and the CO-releasing molecule (CORM)-3 constricted renal arteries and increased O2*- production in a dose-dependent manner. The antioxidants tempol, ebselen, and deferoxamine inhibited CO-induced O2*- production and converted CO from constrictor to dilator. CO-induced O2*- generation was found to involve the activity of multiple oxidases including nitric oxide synthase, NADPH oxidase, xanthine oxidase, and complex IV of the mitochondrial electron chain. Furthermore, inhibition of these enzymes converted CO from constrictor to dilator. Similarly, biliverdin and bilirubin inhibited CO-induced O2*- production and vasoconstriction, allowing for a vasodilatory response to CO to be expressed. CO-induced vasoconstriction was dependent on a non-thromboxane agonist of the thromboxane receptor, whereas vasodilatory mechanisms of CO relied on the activation of soluble guanylate cyclase and calcium-gated potassium channels.
  
  
  CONCLUSIONS
  CO-induced vasoconstriction involves the generation of reactive oxygen species, which, when negated, allows for the expression of vasodilatory pathways which are masked by the primary oxidative stress response to this gas.
authors.affiliation: Department of Pharmacology, New York Medical College, Valhalla, NY, USA. bdlamon@aol.com
authors.forename: Brian D
authors.initials: BD
authors.lastname: Lamon
authors.forename: Frank F
authors.initials: FF
authors.lastname: Zhang
authors.forename: Nitin
authors.initials: N
authors.lastname: Puri
authors.forename: Sergey V
authors.initials: SV
authors.lastname: Brodsky
authors.forename: Michael S
authors.initials: MS
authors.lastname: Goligorsky
authors.forename: Alberto
authors.initials: A
authors.lastname: Nasjletti
mesh_terms: D000818:Animals; D000963:Antimetabolites / Q000378:metabolism / Q000494:pharmacology*; D001158:Arteries / Q000378:metabolism*; D002248:Carbon Monoxide / Q000378:metabolism / Q000494:pharmacology*; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D006162:Guanylate Cyclase / Q000378:metabolism; D007668:Kidney / Q000378:metabolism*; D008297:Male; D009942:Organometallic Compounds / Q000494:pharmacology; D018384:Oxidative Stress / Q000187:drug effects*; D010088:Oxidoreductases / Q000378:metabolism; D024681:Potassium Channels, Calcium-Activated; D051381:Rats; D017207:Rats, Sprague-Dawley; D013481:Superoxides / Q000378:metabolism; D014661:Vasoconstriction / Q000187:drug effects*
chemical_list: D000963:Antimetabolites; D009942:Organometallic Compounds; D024681:Potassium Channels, Calcium-Activated; C476530:tricarbonylchloro(glycinato)ruthenium(II); D013481:Superoxides; D002248:Carbon Monoxide; D010088:Oxidoreductases; D006162:Guanylate Cyclase