Effect of hyperbaric oxygen on intercellular adhesion molecule-1 (ICAM-1) expression in murine lung

Background: The lung is one of the most susceptible organs to the toxic effect of high pressure oxygen. However, the contribution of the cellular adhesion molecules and inflammatory leukocytes in the pulmonary oxygen toxicity, especially in an acute exudative phase, is not well understood. In the present study we have investigated the toxic effect of hyperbaric oxygen (HBO) expressed by the analysis of the intercellular adhesion molecule-1 (ICAM-1) on the pulmonary vascular endothelial cells and leukocyte function. Methods: Mice were exposed to HBO at 3 ATA of PO2 for 3, 4, or 6 h. Expression of ICAM-1 was serially observed by immunohistochemical analysis. The oxidative metabolic activity of the leukocytes was measured after HBO exposure. Results: After HBO exposure an increase in the number of pulmonary interstitial leukocytes (PIL) and bronchoalveolar lavage (BAL) was observed at 72 h and 48 h, respectively. The expression of ICAM-1 was strongly enhanced immediately after HBO exposure and this enhancement lasted for 24 h. This suggests the importance of enhanced expression of adhesion molecules in the generation of pulmonary oxygen toxicity. However, we could not detect increased chemiluminescence activity in the early phase in the BAL cells and PIL. Conclusion: Expression of ICAM-1 was enhanced from the very early stage after HBO, but neither accumulation of leukocytes in the lung nor increase in the chemiluminescence activity were observed in this phase. Therefore, activation of inflammatory leukocytes in the pulmonary oxygen toxicity may occur only after prolonged (more than 4 h) or repetitive exposures to HBO.