title: Reactive oxygen and nitrogen species modulate the ex-vivo effects of LPS on platelet adhesion to fibrinogen.
abstract: OBJECTIVE
  Excessive production of nitric oxide (NO) and reactive oxygen species (ROS) in sepsis modulates different cell functions. Since the sepsis severity is associated with the degree of platelet activation, we decided to investigate the role of systemic generation of NO and ROS in modulating the platelet adhesion of lipopolysaccharide (LPS)-treated rats.
  
  
  METHODS
  Platelet adhesion was evaluated using fibrinogen-coated 96-well microtiter plates. Cyclic GMP levels were measured using enzyme immunoassay kit.
  
  
  RESULTS
  Treatment of rats with LPS significantly increased spontaneous platelet adhesion, but reduced the thrombin-activated platelet adhesion when compared with control rats. Chronic treatment of rats with the NO synthase inhibitor L-NAME (20 mg/rat/day, 7 days) prior to LPS injection normalized the increased adhesion in non-activated platelets, but failed to affect the adhesion in thrombin-activated platelets. The cGMP levels were modified neither in non-activated nor in thrombin-activated platelets of LPS-treated rats when compared with control rats. The incubation of non-activated platelets with the O2- scavenger PEG-SOD reversed the stimulatory effect of LPS on spontaneous adhesion, but had no effect in stimulated-platelet adhesion of non-treated or LPS-treated groups. Moreover, pretreatment of rats with the antioxidant N-acetylcysteine (NAC; 150 mg/kg) prevented the increase of non-activated platelet adhesion, and significantly reduced the inhibitory effect of LPS on thrombin-stimulated adhesion.
  
  
  CONCLUSIONS
  Our findings suggest that in LPS-treated rats, NO plays an important modulatory role only in non-stimulated platelet adhesion through cGMP-independent mechanisms, while ROS, directly or by affecting the redox state of the animals, modulates both non-activated and thrombin-activated platelet adhesion.
authors.affiliation: Department of Pharmacology, Faculty of Medical Sciences, University of Campinas, Campinas (SP), Brazil.
authors.forename: André Luis
authors.initials: AL
authors.lastname: Casarin
authors.forename: Maria Elisa
authors.initials: ME
authors.lastname: Lopes-Pires
authors.forename: Rafael Prada
authors.initials: RP
authors.lastname: Morganti
authors.forename: Edson
authors.initials: E
authors.lastname: Antunes
authors.forename: Sisi
authors.initials: S
authors.lastname: Marcondes
mesh_terms: D000111:Acetylcysteine / Q000494:pharmacology; D000818:Animals; D001792:Blood Platelets / Q000187:drug effects*; D006152:Cyclic GMP / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005340:Fibrinogen / Q000502:physiology*; D016166:Free Radical Scavengers / Q000494:pharmacology; D066298:In Vitro Techniques; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008297:Male; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D010973:Platelet Adhesiveness / Q000187:drug effects*; D011092:Polyethylene Glycols / Q000494:pharmacology; D051381:Rats; D026361:Reactive Nitrogen Species / Q000378:metabolism*; D017382:Reactive Oxygen Species / Q000378:metabolism*; D013482:Superoxide Dismutase / Q000494:pharmacology; D013917:Thrombin / Q000494:pharmacology
chemical_list: D004791:Enzyme Inhibitors; D016166:Free Radical Scavengers; D008070:Lipopolysaccharides; D026361:Reactive Nitrogen Species; D017382:Reactive Oxygen Species; D011092:Polyethylene Glycols; D005340:Fibrinogen; D013482:Superoxide Dismutase; C063471:polyethylene glycol-superoxide dismutase; D013917:Thrombin; D006152:Cyclic GMP; D019331:NG-Nitroarginine Methyl Ester; D000111:Acetylcysteine