5-HYDROXYICOSATETRAENOATE STIMULATES NEUTROPHILS BY A STEREOSPECIFIC,G-PROTEIN-LINKED MECHANISM

We examined how 5-hydroxyicosatetraenoate (5-HETE) activates human neu trophils (PMN). 5-HETE stimulates PMN to mobilize Ca2+ but has little effect on degranulation or superoxide anion production. It nonetheless stereospecifically induced these responses in cells primed with tumor necrosis factor-alpha and likewise induced PMN plasma membranes to bi nd S-35-labeled guanosine 5'-O-(thiotriphosphate) (GTPgammaS) and phos phohydrolyze [gamma-P-32]GTP. Pertussis toxin blocked GTPgammaS bindin g responses. Scatchard analyses of GTPgammaS binding data indicated th at 5-HETE raised the K(a) of high affinity GTPgammaS binding sites wit hout altering these sites' numbers or the parameters of low affinity G TPgammaS binding. Since N-formyl-Met-Leu-Phe, platelet-activating fact or, and leukotriene (LT) B4 have these same bioactions, receptors for the latter agents might mediate responses to 5-HETE. However, 5-HETE d esensitized degranulation responses to itself but not to the receptor agonists, the receptor agonists desensitized to themselves but not 5-H ETE, and a LTB4 antagonist inhibited LTB4 but not 5-HETE in all assays . Finally, PMN and their membranes took up [H-3] 5-HETE at 4 or 37-deg rees-C but, at both temperatures, also acylated the radiolabel into gl ycerolipids. Acylation nullified assessment of 5-HETE binding and ques tions reports that measure the cell binding, but not metabolism, of va rious HETEs. Our studies thus indicate 5-HETE acts by a down-regulatab le, G protein-linked mechanism and represent the best available eviden ce that 5-HETE does not operate through, for example, LTB4 receptors.