Background—Hyperbaric oxygen (HBO) decreases ischemia-reperfusion (IR) induced neutrophil-ICAM adhesion by blocking CD18 polarization. The purpose of this study was to evaluate whether this HBO effect is nitric oxide (NO) dependent and to determine if NO synthase (NOS) is required.
Methods—A gracilis muscle flap was raised in 9 groups of male Wistar rats. Global ischemic injury was induced by clamping the gracilis muscle pedicle artery and vein for 4 hours. The HBO treatment consisted of 100% O2 at 2.5 ATA during the last 90 minutes of ischemia. Groups were repeated with and without various NOS inhibitors and C-PTIO, a NO scavenger. Normalneutrophils (PMNs) were exposed to activated plasma on ICAM coated coverslips (% adherent) and labeled with FITC-anti-rat-CD11b for confocal microscopy (% polarized). The percent of adherent and polarized cells was reported as mean ± SEM. Statistical Analysis was by ANOVA. Ap ≤ 0.05 was considered significant.
Results—C-PTIO treated IR-HBO plasma showed a significant increase in the percent polarization of CD18 compared to IR-HBO untreated plasma from 4.1±2.5 to 33.7±7.7 (p ≤ 0.05). The NO scavenger, C-PTIO, also increased the percent of adherent cells from 1.6±0.4 to 20.3±5.9(p ≤ 0.05). Administration of LNAME and other NOS inhibitors prior to HBO treatment restored neutrophil adhesion and CD18 polarization to IR control values, significantly greater than IR HBO alone.
Conclusions—These results suggest that the HBO reduction of IR induced neutrophil polarization of CD18 and adherence to ICAM is mediated through a nitric oxide mechanism that requires NOS.