Stimulation of protein kinase C redistribution and inhibition of leukotriene B-4-induced inositol 1,4,5-trisphosphate generation in human neutrophils by lipoxin A(4)

1 To test the hypothesis that protein kinase C (PKC) is involved in the inhibitory actions of lipoxin A(4) (LXA(4)) on second messenger generation, we studied the effects of LXA(4) on PKC in human neutrophils and on leukotriene B-4 (LTB(4))-stimulated inositol-1,4,5-trisphosphate (Ins(1,4,5)P-3) generation. 2 LXA(4), 1 mu M, caused a fall in cytosolic PKC-dependent histone phosphorylating activity to 23.5% of basal levels. 3 LXA(4), caused an increase in particulate PKC-dependent histone phosphorylating activity with a bell-shaped dose-response fashion; maximal stimulation was observed at 10 nM LXA(4). 4 Western blot analysis with affinity-purified antibodies to alpha- and beta-PKC showed that only the beta-PKC isotype was translocated by LXA(4). 5 LXA(4) inhibited LTB(4)-stimulated Ins(1,4,5)P-3 generation in a bell-shaped fashion with maximal inhibition at 1 nM LXA(4). The observed inhibition was dose-dependently removed by pre-incubation with a PKC inhibitor (Ro-31-8220). 6 These results show that LXA(4) activates PKC in whole cells and supports a role for PKC activation in the inhibitory action of LXA(4) On LTB(4)-induced Ins(1,4,5)P-3 generation. 7 LXA(4) (1-1000 nM) pre-incubation did not affect specific binding of [H-3]-LTB(4) to neutrophils. Thus, the inhibitory effect of LXA(4) on LTB(4)-stimulated Ins(1,4,5)P-3 generation could not be attributed to an effect on LTB(4) receptors.