LIPOXYGENASE PRODUCT FORMATION AND CELL-ADHESION DURING NEUTROPHIL GLOMERULAR ENDOTHELIAL-CELL INTERACTION

Leukotriene (LT) and lipoxin (LX) levels were monitored in ionophore-s timulated coincubations of polymorphonuclear neutrophils (PMN) and mic rovascular kidney glomerular endothelial cells (GEN) to determine the profile of Lipoxygenase (LO) products generated during cell-cell inter actions and the relative contributions of transcellular pathways to LO product biosynthesis in this setting. LTB(4) and LTC(4) were the majo r products formed, as determined by reverse-phase high-performance liq uid chromatography and radioimmunoassay. LTB(4) and LTC(4) levels were increased by 23 and 185%, respectively, in coincubations of PMN and G EN, compared with incubations of PMN alone. In contrast, LXA(4) and LX B(4) levels were not changed in the presence of GEN. These data sugges ted that GEN utilize PMN-derived LTA(4) to generate LT. In keeping wit h this hypothesis, LT biosynthesis was enhanced if PMN were primed wit h human granulocyte-macrophage colony-stimulating factor (GM-CSF), a c ytokine that augments LTA(4) biosynthesis by activated PMN. The influe nce of LT on PMN adhesion to GEN was also assessed, since adhesion app ears to be a pivotal event in recruitment of PMN in acute glomerulonep hritis. Under basal conditions, LTB(4) provoked low levels of adhesion via a PMN-directed CD11/CD18-dependent mechanism. The level of adhesi on was markedly enhanced by prior priming of PMN with GM-CSF or activa tion of GEN with tumor necrosis factor-alpha (TNF). LTB(4) was as pote nt in this regard as the complement component C5a, platelet-activating factor (PAF), and interleukin-8 (IL-8), other mediators that contribu te to the entrapment of PMN in inflamed glomeruli. LTC(4) also provoke d PMN-GEN adhesion via a CD11/CD18-dependent mechanism, but, in contra st to LTB(4), via actions with GEN. This action of LTC(4) appeared to be mediated, at least in part, by induction of PAF synthesis by GEN. I nterestingly, LT-induced PMN-GEN adhesion was markedly attenuated foll owing remodeling of PMN phospholipids with 15(S)-hydroxyeicosatetraeno ic acid, a product of 15-LO, which has been implicated as an anti-infl ammatory eicosanoid in some experimental and human inflammatory diseas es. Taken together, these results provide further evidence that 1) tra nscellular biosynthetic pathways may amplify the profiles of inflammat ory mediators and thereby contribute to leukocyte recruitment in acute glomerulonephritis and 2) that products of the 5-LO and 15-LO pathway s may exert opposing actions on PMN trafficking during glomerular infl ammation in vivo.