Sulphatides trigger polymorphonuclear granulocyte spreading on collagen-coated surfaces and inhibit subsequent activation of 5-lipoxygenase

Sulphatides are sulphate esters of galactocerebrosides that are present on the surfaces of many cell types and act as specific ligands to selectins. T he present study was undertaken to investigate the effect of sulphatides on polymorphonuclear granulocyte (PMN) attachment, spreading and 5-lipoxygena se(5-LO) metabolism. Sulphatides, but not non-sulphated galactocerebrosides , dose-dependently enhanced attachment to collagen, as measured by the myel operoxidase assay. Studies with blocking antibodies indicated that the incr eased attachment was mediated by CD 11b/CD18 (Mac-1) beta2 integrin. Scanni ng electron microscopy indicated that sulphatides also greatly enhanced the degree of cell spreading. In PMNs treated in suspension, sulphatides had n o effect on the ionophore A23187-stimulated release of arachidonic acid and the synthesis of 5-LO metabolites. In contrast, in PMNs attached to collag en, the enzymic conversion of arachidonic acid by 5-LO was inhibited by sul phatides. Inhibition of 5-LO metabolism by sulphatides was observed even in the presence of exogenous substrate, suggesting that sulphatides directly inhibited 5-LO action. Consistent with this, sulphatides interfered with io nophore-induced translocation of the 5-LO to the nuclear envelope. Substanc es competing with sulphatide binding to cells, like dextran sulphate, or a strong inhibitor of cell spreading, like the actin-polymerizing agent jaspl akinolide, prevented the effects of sulphatides on PMN attachment and sprea ding and leukotriene synthesis. We conclude that shape changes occurring in response to sulphatides specifically impair PMN leukotriene synthesis by i nhibiting translocation of 5-LO.