Involvement of phosphatidic acid in both degranulation and oxidative activity in fMet-Leu-Phe stimulated polymorphonuclear leukocytes.

Polymorphonuclear leukocytes (neutrophils) release a variety of toxic agents--proteins and reactive oxygen species (ROS)--that are used to inactivate foreign microorganisms in the non-specific immune response. This study was undertaken to compare intracellular signalling pathways that lead to the ROS production as well as degranulation of azurophilic granules of human fMet-Leu-Phe/cytochalasin B stimulated neutrophils. Luminol-amplified chemiluminescence was used for monitoring the oxidative activity of human neutrophils in the presence of various inhibitors. The elastase activity was assessed in the neutrophil supernatant as a marker for degranulation of azurophilic granules. Tested inhibitors of enzymes of signalling cascades showed the same effect on the ROS production and on the activity of elastase released from neutrophils. The only difference was obtained with staurosporine: it inhibited the chemiluminescence response, but increased the elastase release. Early signalling pathways leading to the ROS production and the degranulation are ubiquitous in human neutrophils. They are branching most probably at the point of the phosphatidic acid production by phospholipase D. A protein kinase activated by this lipid second messenger might play a central regulatory role in human neutrophils.