Stimulation of protein kinase C redistribution and inhibition of leukotriene B4-induced inositol 1,4,5-trisphosphate generation in human neutrophils by lipoxin A4.
1. To test the hypothesis that protein kinase C (PKC) is involved in the inhibitory actions of lipoxin A4 (LXA4) on second messenger generation, we studied the effects of LXA4 on PKC in human neutrophils and on leukotriene B4 (LTB4)-stimulated inositol-1,4,5-trisphosphate (Ins(1,4,5)P3) generation. 2. LXA4, 1 microM, caused a fall in cytosolic PKC-dependent histone phosphorylating activity to 23.5% of basal levels. 3. LXA4, caused an increase in particulate PKC-dependent histone phosphorylating activity with a bell-shaped dose-response fashion; maximal stimulation was observed at 10 nM LXA4. 4. Western blot analysis with affinity-purified antibodies to alpha- and beta-PKC showed that only the beta-PKC isotype was translocated by LXA4. 5. LXA4 inhibited LTB4-stimulated Ins(1,4,5)P3 generation in a bell-shaped fashion with maximal inhibition at 1 nM LXA4. The observed inhibition was dose-dependently removed by pre-incubation with a PKC inhibitor (Ro-31-8220). 6. These results show that LXA4 activates PKC in whole cells and supports a role for PKC activation in the inhibitory action of LXA4 on LTB4-induced Ins(1,4,5)P3 generation. 7. LXA4 (1-1000 nM) pre-incubation did not affect specific binding of [3H]-LTB4 to neutrophils. Thus, the inhibitory effect of LXA4 on LTB4-stimulated Ins(1,4,5)P3 generation could not be attributed to an effect on LTB4 receptors.
Chung-a-on
K O
KO
Department of Allergy and Respiratory Medicine, UMDS, Guy's Hospital, London.
Soyombo
O
O
Spur
B W
BW
Lee
T H
TH
D015153:Blotting, Western; D004305:Dose-Response Relationship, Drug; D004336:Drug Antagonism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D006893:Hydroxyeicosatetraenoic Acids / Q000494:pharmacology*; D007211:Indoles / Q000494:pharmacology; D015544:Inositol 1,4,5-Trisphosphate / Q000096:biosynthesis*; D007975:Leukotriene B4 / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D044045:Lipoxins; D009504:Neutrophils / Q000187:drug effects* / Q000378:metabolism; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D018102:Receptors, Leukotriene B4 / Q000187:drug effects* / Q000378:metabolism
D004791:Enzyme Inhibitors; D006893:Hydroxyeicosatetraenoic Acids; D007211:Indoles; D044045:Lipoxins; D018102:Receptors, Leukotriene B4; C040527:lipoxin A4; D007975:Leukotriene B4; D015544:Inositol 1,4,5-Trisphosphate; D011493:Protein Kinase C; C064758:Ro 31-8220