Mechanisms involved in the augmentation of arachidonic acid-induced free-radical generation from rat neutrophils following hypoxia-reoxygenation

Abstract

Polymorphonuclear leukocytes are known to play an important role in hypoxia/ischemia and reoxygenation injury. The present study was undertaken to investigate the involvement of protein kinase C, calmodulin, and cyclic adenosine monophosphate in the augmentation of the free-radical generation observed after hypoxia-reoxygenation (H-R). Free-radical generation from the rat polymorphonuclear leukocytes was measured as the arachidonic acid (1-5× 10^-5 M)-induced luminol-dependent chemiluminescence response, which was augmented following H-R. The increase in free-radical generation after H-R was completely blocked by the pretreatment of cells with PKC inhibitor H₇, whereas indomethacin (a cyclo-oxygenase inhibitor) or forskolin (an adenylate cyclase activator) failed to modulate the H-R-dependent response. However, W₇-a calcium/calmodulin (Ca²⁺/CaM) antagonist-partially reduced the augmented free-radical generation observed in the H-R cells. Results obtained thus suggest the possible involvement of protein kinase C and calcium in the augmentation of the free-radical generation response following H-R.