This research project will explore the role of leukotriene B4(LTB4) and platelet activating factor (PAF), two potent proinflammatory lipids, in the regulation of neutrophil oxidative metabolism. Studies have demonstrated that LTB4 and PAF, though relatively weak direct stimulants of neutrophil superoxide production, markedly enhance the cell's oxidative response to certain soluble stimuli. The goal of this proposal is to further delineate the characteristics and control of lipid-mediated oxidative enhancement and to define the subcellular mechanisms through which augmentation of oxidative reponsiveness is accomplished. Experiments detailed herein will examine the effects of LTB4 and PAF on both the affinity and number of chemotactic peptide receptors expressed on the cell surface. Also studied will be the effects of the lipids on the distribution and activity of protein kinase C, an intracellular mediator recently implicated in neutrophil activation by chemotactic peptides and phorbol diesters. Prior exposure to the lipids may not only increase the oxidative killing capacity of cells arriving at inflammatory foci but also may result in premature, potentially damaging release of reactive oxygen metabolites if the enhancing effect is not closely regulated. The project will therefore explore potential mechanisms which may curb oxidative enhancement in vivo. Gradual exposure of neutrophils to LTB4 and PAF by slow infusions, as would occur in vivo as cells migrate along physiologic chemoattractant concentration gradients, will be utilized to determine the importance of exposure rate to oxidative enhancement. The potential role of oxidative metabolites produced by neutrophils in the inactivation of extracellular LTB4 and PAD will also be evaluated. These studies will attempt to define the biochemical basis for oxidative enhancement and to promote a better understanding of cellular mechanisms involved in the control of inflammation. It is hoped that inflammatory control mechanisms may then be exploited for rational approaches to the control of abnormal inflammatory responses.
| Gay, J C; Stitt, E S (1988) Platelet-activating factor induces protein kinase activity in the particulate fraction of human neutrophils. Blood 71:159-65 |
