Pleiotropic role of lyn kinase in leukotriene B₄-induced eosinophil activation

The authors have examined the role of the src-family of protein tyrosine kinases in leukotriene B₄ (LTB₄)-induced activation of guinea-pig eosinophils. Western blot analysis identified the src-like protein tyrosine kinases p53(lyn) p56(lyn), p56/59(hck), p55(fgr) and p56(lck) whereas p60(src) p62(yes), p55(blk) and p59(fyn) were not detected. LTB₄ promoted a rapid increase in p53/56(lyn) activity in eosinophils, which peaked at 5 seconds and remained elevated at 60 seconds; hck, fgr, and lck were not activated. A role for p53/56(lyn) in eosinophil activation was investigated with the use of the src-selective inhibitor PP1 (1 μmol/L to 10 μmol/L), which attenuated LTB₄-stimulated p53/56(lyn) activity and the phosphorylation of extracellular signal-regulated kinase-2 in intact cells. At comparable concentrations, PP1 was also shown to attenuate LTB₄-induced nicotinamide adenine dinucleotide phosphate (reduced form) (NADPH) oxidase activation, chemotaxis, and Ca⁺⁺- dependent [³H]arachidonic acid (AA) release. Moreover, an inhibitor of mitogen-activated protein kinase kinase-1, PD 098059, significantly inhibited LTB₄-induced chemotaxis but had no effect on oxidant production or [³H]AA release. Collectively, these results implicate lyn kinase in LTB₄-induced eosinophil activation through the recruitment of divergent cell-signaling pathways. (C) 2000 American Society of Hematology.