Functional inhibition of rat polymorphonuclear leukocyte B2 integrins by hyperbaric oxygen is associated with impaired cGMP synthesis

Abstract

We hypothesized that hyperbaric oxygen caused a metabolic derangement in polymorphonuclear leukocytes that impaired the function of B2 integrins. Isolated neutrophils from rats that had been exposed to 3 atm oxygen for 45 min failed to exhibit B2 integrin-dependent adherence to nylon columns or to fibrinogen-coated plates. Adherence was restored after cells were incubated with 8-bromo-cGMP, phorbol 12-myristate 13-acetate (PMA) or the reducing agent dithioerythritol. Hyperbaric oxygen was found to inhibit cGMP synthesis that normally occurred when cells were stimulated by passage through nylon columns, and exposure to PMA or dithioerythritol reestablished cGMP synthesis. Cells adherent to plastic plates synthesized cGMP when they were exposed to N-formyl-methionyl-leucine-phenylalanine (FMLP) or PMA. Neutrophils from rats exposed to hyperbaric oxygen synthesized cGMP in response to PMA but failed to respond to FMLP, although hyperbaric oxygen did not alter the affinity of the FMLP receptor or its associated G protein. Dithioerythritol restored the cGMP synthetic ability of adherent neutrophils in response to FMLP. We conclude that hyperbaric oxygen inhibits B2 integrin-dependent adherence because it impairs cGMP synthesis by activated neutrophils.