The human blood monocyte is a significant source of oxygenated metabolites of arachidonic acid termed eicosanoids. Monocytes produce thromboxane in quantities (per microgram cell protein) which are equivalent to the platelet, as well as leukotrienes B4 and C4 (LTB4 and LTC4). The biologic activities of these eicosanoids pertinent to inflammation are intimately involved with vascular tone, permeability, and the recruitment of circulating leukocytes to intra- and extra-vascular sites. Other human inflammatory cells are quantitative sources of some, but not all three of these products. The regulation of eicosanoid synthesis by mononuclear phagocytes has been most extensively studied using differentiated macrophages of animal origin. However, important species differences exist. For example, the metabolic profile of murine (prostacyclin, PGE2, LTC4) and human (thromboxane, PGE2, LTB4, and LTC4) mononuclear phagocytes differ significantly. Also, the blood monocyte and not the tissue macrophage is the most accessible for study in human systems. The primary objective of this study is to better characterize the regulation of eicosanoid synthesis by human blood monocytes within settings relevant to their function in vivo. Techniques for cell purification and culture as well as eicosanoid analysis have been established. There are four specific aims. First, we will explore the functional regulation of eicosanoid synthesis by interaction with defined biologic substrates (fibronectin, collagen, endothelial cell extracellular matrix). Secondly, direct comparisons will be made between monocytes and neutrophils regarding the role of substrate interactions. Preliminary evidence indicates that adhesion to surfaces produces significant quantitative and qualitative metabolic changes in both cells. We also will characterize the monocyte's secretory responses to three differing categories of physiologic triggers: fixed ligands (complement and immune complexes), soluble or fluid phase agents, and factors which may enhance other agonists but do not elicit direct secretory responses. Finally, we will extend our study of monocyte interaction with biologic substrates to the endothelium. Using coordinated morphological studies within a newly developed model for the maturation of human endothelial cells (EC), the functional relationships between eicosanoid synthesis and the process of transendothelial migration will be examined directly.
| Pawlowski, N A; Kaplan, G; Abraham, E et al. (1988) The selective binding and transmigration of monocytes through the junctional complexes of human endothelium. J Exp Med 168:1865-82 |
