title: Electron spin resonance spectroscopic demonstration of the generation of reactive oxygen species by diseased human synovial tissue following ex vivo hypoxia-reoxygenation.
abstract: OBJECTIVE
  To apply an electron spin resonance (ESR) spectroscopic technique as a means of determining the oxidising capacity of reactive oxygen species produced during hypoxia and reoxygenation of diseased human synovial tissue.
  
  
  METHODS
  Twenty four specimens of fresh synovial tissue were obtained from patients undergoing primary total knee joint replacement and graded according to the degree of inflammation present. Tissue samples were subjected to an ex vivo hypoxia-reoxygenation cycle in the presence of the nitroso based spin trap, 3,5-dibromo-4-nitrosobenzene sulphonate. The degree of oxidation of the spin trap to a stable free radical was determined and followed with time. Control samples were subjected to hypoxia only.
  
  
  RESULTS
  The results indicate that the oxidising capacity of reactive oxygen species produced by human synovial tissue varies with the degree of inflammation present. Only the more inflamed specimens, from both rheumatoid arthritis and osteoarthritis patients, demonstrated increased production of reactive oxygen species when subjected to a hypoxia-reoxygenation cycle. This change was reduced by both competitive and non-competitive inhibitors of the endothelial based enzyme xanthine oxidase. The relative concentration of reactive oxygen species generated by the synovial tissue samples correlated with the mean capillary density of the specimens.
  
  
  CONCLUSIONS
  This study supports the hypothesis of movement induced hypoxicreperfusion injury of the chronically inflamed joint by demonstrating the generation of reactive oxygen species within inflamed human synovium following an ex vivo hypoxia-reoxygenation cycle. Evidence is presented that the microvascular endothelial based enzyme xanthine oxidase is the predominant source of ESR detectable oxidising species in inflamed synovial specimens exposed to hypoxia-reoxygenation.
authors.affiliation: Inflammation Research Group, London Hospital Medical College, United Kingdom.
authors.forename: D
authors.initials: D
authors.lastname: Singh
authors.forename: N B
authors.initials: NB
authors.lastname: Nazhat
authors.forename: K
authors.initials: K
authors.lastname: Fairburn
authors.forename: T
authors.initials: T
authors.lastname: Sahinoglu
authors.forename: D R
authors.initials: DR
authors.lastname: Blake
authors.forename: P
authors.initials: P
authors.lastname: Jones
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001172:Arthritis, Rheumatoid / Q000473:pathology; D046508:Culture Techniques; D004578:Electron Spin Resonance Spectroscopy; D006801:Humans; D007719:Knee Joint; D008875:Middle Aged; D010003:Osteoarthritis / Q000473:pathology; D010117:Oxypurinol / Q000494:pharmacology; D017382:Reactive Oxygen Species / Q000032:analysis / Q000378:metabolism*; D015427:Reperfusion Injury / Q000378:metabolism*; D013583:Synovial Membrane / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D013844:Thiazoles / Q000494:pharmacology; D014969:Xanthine Oxidase / Q000037:antagonists & inhibitors
chemical_list: D017382:Reactive Oxygen Species; D013844:Thiazoles; C046749:amflutizole; D014969:Xanthine Oxidase; D010117:Oxypurinol