Phospholipase A2-mediated superoxide production of murine peritoneal macrophages induced by chrysotile stimulation.
In the present study, we investigated how chrysotile-stimulated macrophages generate superoxide using murine peritoneal macrophages, with special attention to the modulatory role of phospholipase A(2) (PLA(2)). We examined the effects of the following inhibitors and antagonists for signaling molecules on the superoxide anion (O(2)(-)) production of chrysotile-stimulated macrophages: p-bromophenacyl bromide (pBPB) and mepacrine for PLA(2); islet-activating protein (IAP) for G-protein; H-7 for protein kinase C (PKC); AA861 for 5-lipoxygenase (5-LO); indomethacin for cyclo-oxygenase (COX); ETYA for both 5-LO and COX; hexanolamine PAF for platelet-activating factor (PAF). The PLA(2) and PKC inhibitors effectively inhibited the chrysotile-induced superoxide anion production of macrophages, but not the G-protein inhibitor, the 5-LO and COX inhibitors, and the PAF antagonist. We also examined the effects of the PLA(2) inhibitors on macrophages stimulated by phorbol 12-myristate 13-acetate (PMA) which directly activates PKC. The two structurally different PLA(2) inhibitors showed differential effects on the PMA-induced superoxide generation: pBPB inhibited it but mepacrine did not. These results suggested that (1) PLA(2) and PKC modulate the chrysotile-induced O(2) production, and (2) two different kinds of PLA(2) work upstream and downstream of PKC, but (3) G-protein, 5-LO and COX metabolites, and PAF have no modulatory role in the reaction.
Nakajima
T
T
Division of Environmental Health Research, Osaka Prefectural Institute of Public Health, 69-3, 1-chome, 537-0025, Osaka, Japan.
Ito
M
M
Tchoua
U
U
Tojo
H
H
Hashimoto
M
M
D000818:Animals; D017632:Asbestos, Serpentine / Q000633:toxicity*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D017737:Macrophages, Peritoneal / Q000187:drug effects* / Q000201:enzymology; D008297:Male; D051379:Mice; D008813:Mice, Inbred ICR; D064801:Phospholipase A2 Inhibitors; D054467:Phospholipases A2 / Q000378:metabolism*; D010972:Platelet Activating Factor / Q000494:pharmacology; D011493:Protein Kinase C / Q000378:metabolism; D013481:Superoxides / Q000037:antagonists & inhibitors / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D017632:Asbestos, Serpentine; D004791:Enzyme Inhibitors; D064801:Phospholipase A2 Inhibitors; D010972:Platelet Activating Factor; D013481:Superoxides; D011493:Protein Kinase C; D054467:Phospholipases A2; D013755:Tetradecanoylphorbol Acetate