title: The effect of hyperbaric oxygen on nitric oxide synthase activity and expression in ischemia-reperfusion injury.
abstract: BACKGROUND
  Hyperbaric oxygen (HBO) mitigates ischemia-reperfusion (IR) injury via a nitric oxide mechanism that is nitric oxide synthase (NOS) dependent. The purpose of this study was to investigate this NOS-dependent mechanism by examining isoform-specific, tissue-specific, and time-specific upregulation of NOS mRNA, protein, and enzymatic activity.
  
  
  METHODS
  We raised a gracilis flap in Wistar rats that were separated into early and late phases. Treatment groups included nonischemic control, IR, HBO-treated ischemia-reperfusion (IR-HBO), and nonischemic HBO control. We harvested tissue-specific samples from gracilis, rectus femoris, aorta, and pulmonary tissues and processed them by reverse transcription polymerase chain reaction and Western blot to determine upregulation of isoform-specific NOS mRNA and protein. We also harvested tissue for NOS activity to investigate upregulation of enzymatic activity. Data are presented as mean ± standard error of the mean with statistics performed by analysis of variance. P ≤ 0.05 was considered significant.
  
  
  RESULTS
  There was no increase in NOS mRNA in the early phase. In the late phase, there was a significant increase in endothelial-derived NOS (eNOS) mRNA in IR-HBO compared with IR in gracilis muscle (79.4 ± 22.3 versus 36.1 ± 4.5; P < 0.05) and pulmonary tissues (91.0 ± 31.2 versus 30.2 ± 3.1; P < 0.01). There was a significant increase in the late-phase eNOS pulmonary protein IR-HBO group compared with IR (235.5 ± 46.8 versus 125.2 ± 14.7; P < 0.05). Early-phase NOS activity was significantly increased in IR-HBO compared with IR in pulmonary tissue only (0.049 ± 0.009 versus 0.023 ± 0.003; P < 0.05).
  
  
  CONCLUSIONS
  The NOS-dependent effects of HBO on IR injury may result from a systemic effect involving an early increase in eNOS enzymatic activity followed by a late-phase increase in eNOS protein expression within the pulmonary tissues.
authors.affiliation: Division of Plastic Surgery, Department of Surgery, University of Nevada School of Medicine, Las Vegas, Nevada 89102, USA. rbaynosa@medicine.nevada.edu
authors.forename: Richard C
authors.initials: RC
authors.lastname: Baynosa
authors.forename: Anna L
authors.initials: AL
authors.lastname: Naig
authors.forename: Patrick S
authors.initials: PS
authors.lastname: Murphy
authors.forename: Xin Hua
authors.initials: XH
authors.lastname: Fang
authors.forename: Linda L
authors.initials: LL
authors.lastname: Stephenson
authors.forename: Kayvan T
authors.initials: KT
authors.lastname: Khiabani
authors.forename: Wei Z
authors.initials: WZ
authors.lastname: Wang
authors.forename: William A
authors.initials: WA
authors.lastname: Zamboni
mesh_terms: D000818:Animals; D001012:Aorta, Abdominal / Q000201:enzymology; D006931:Hyperbaric Oxygenation; D008168:Lung / Q000201:enzymology; D008297:Male; D018482:Muscle, Skeletal / Q000098:blood supply / Q000201:enzymology; D019001:Nitric Oxide Synthase / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D015427:Reperfusion Injury / Q000201:enzymology / Q000517:prevention & control*
chemical_list: D019001:Nitric Oxide Synthase