PAF is involved in the Mycoplasma arthritidis superantigen-triggering pathway for iNOS and COX-2 expression in murine peritoneal cells.
We investigated the capacity of Mycoplasma arthritidis mitogen (MAM) to induce (a) expression of the inducible enzymes cyclo-oxygenase (COX-2) and nitric oxide synthase (iNOS), (b) production of prostaglandin E2 (PGE2) and nitric oxide (NO), and (c) involvement of platelet-activating factor (PAF) in the MAM-induced activation pathway. Resident peritoneal cells from C3H/HePas mice were incubated with MAM in the presence or absence of a PAF-antagonist (WEB2170) or COX-2 inhibitors (nimesulide or NS398). Enzyme expression was evaluated by immunoblotting, PGE2 by EIA, and NO by Griess reaction. Following MAM-stimulation of peritoneal cells, expression of COX-2 was detected at 3 h (peak levels at 12 h) and of iNOS at 6 h (peak levels at 20 h). PGE2 increased till 20 h, decreasing thereafter, whereas NO increased with time. WEB2170 (5 x 10(-5) M) treatment caused 44% inhibition of NO output and reduced iNOS expression (48% at the peak of expression). Concomitant treatment with WEB2170 and nimesulide (10(-5) M) reversed these inhibitory effects. WEB2170 reduced COX-2 expression (43% at the peak of expression) and prevented the decline in PGE2 levels after 20 h. These results suggest the involvement of PAF in the signaling pathway triggered by MAM that leads to expression of iNOS and COX-2, and show that PAF regulates the production of NO, possibly by controlling levels of PGE2.
Shio
Marina Tiemi
MT
Department of Immunology, Institute of Biomedical Sciences, University of São Paulo, Brazil.
Ribeiro-Dias
Fátima
F
Timenetsky
Jorge
J
Jancar
Sonia
S
D000818:Animals; D000941:Antigens; D000942:Antigens, Bacterial; D001172:Arthritis, Rheumatoid / Q000276:immunology / Q000378:metabolism; D002478:Cells, Cultured; D051546:Cyclooxygenase 2; D015232:Dinoprostone / Q000096:biosynthesis; D004195:Disease Models, Animal; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007527:Isoenzymes / Q000187:drug effects / Q000378:metabolism*; D008262:Macrophage Activation / Q000187:drug effects / Q000276:immunology*; D008264:Macrophages / Q000187:drug effects / Q000201:enzymology* / Q000276:immunology; D008297:Male; D051379:Mice; D008809:Mice, Inbred C3H; D008934:Mitogens / Q000276:immunology* / Q000494:pharmacology; D009569:Nitric Oxide / Q000096:biosynthesis; D019001:Nitric Oxide Synthase / Q000187:drug effects / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II; D010537:Peritoneum / Q000166:cytology / Q000276:immunology / Q000378:metabolism; D010972:Platelet Activating Factor / Q000378:metabolism*; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology; D011451:Prostaglandin-Endoperoxide Synthases / Q000187:drug effects / Q000378:metabolism*; D011506:Proteins; D015398:Signal Transduction / Q000187:drug effects / Q000276:immunology; D018089:Superantigens / Q000276:immunology / Q000494:pharmacology; D015854:Up-Regulation / Q000187:drug effects / Q000276:immunology
D000941:Antigens; D000942:Antigens, Bacterial; D004791:Enzyme Inhibitors; D007527:Isoenzymes; D008934:Mitogens; C052996:Mycoplasma arthritidis mitogen; D010972:Platelet Activating Factor; D010975:Platelet Aggregation Inhibitors; D011506:Proteins; D018089:Superantigens; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse; D051546:Cyclooxygenase 2; D011451:Prostaglandin-Endoperoxide Synthases; D015232:Dinoprostone