Cysteinyl leukotrienes mediate the enhancing effects of indomethacin and aspirin on eosinophil production in murine bone marrow cultures.
BACKGROUND
Prostaglandin E(2) (PGE(2)) suppresses, while indomethacin and aspirin enhance, eosinophil production in murine liquid bone-marrow cultures. Because cysteinyl leukotrienes (cys-LTs) enhance human eosinophil colony formation, we investigated whether the effects of indomethacin and aspirin on murine bone-marrow were due to blockade of PGE(2) production alone, or involved further promotion of cys-LTs production/signalling.


METHODS
BALB/c liquid bone-marrow cultures were established with IL-5, alone or associated with indomethacin, aspirin, or cys-LTs. The effects of preventing cys-LT production or signalling were assessed.


RESULTS
Indomethacin and aspirin counteracted the suppression of eosinophil production by exogenous PGE(2). LTD(4), LTC(4) and LTE(4) enhanced IL-5-dependent eosinophil production and further counteracted the effect of exogenous PGE(2). The 5-lipoxygenase activating protein (FLAP) inhibitor, MK886, a leukotriene synthesis inhibitor, zileuton, the CysLT(1) receptor antagonists, MK571 and montelukast, or inactivation of the LTC(4) synthase gene, abolished effects of indomethacin and aspirin. MK886 and zileuton were ineffective but MK571 and montelukast were effective, against LTD(4). Indomethacin, aspirin and LTD(4) failed to enhance eosinophil production in bone-marrow from CysLT1 receptor-deficient mice. Indomethacin, aspirin and LTD(4) no longer counteracted the effects of exogenous PGE(2) in the presence of MK571 and montelukast. MK886, MK571 and montelukast had no effect by themselves, or in association with PGE(2).


CONCLUSIONS
Dependence on the FLAP/5-lipoxygenase/LTC(4) synthase pathway and receptor signalling shows that cyclo-oxygenase inhibitors act here through endogenous cys-LTs. While PGE(2) does not act by suppressing cys-LT production, cys-LTs override PGE(2) signalling. Eosinophil production is therefore coordinately regulated by both pathways.
Elsas
P X
PX
Department of Immunology, IMPPG, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil. pxelsas@yahoo.com.br
Queto
T
T
Mendonça-Sales
S C
SC
Elsas
M I G
MI
Kanaoka
Y
Y
Lam
B K
BK
D058927:5-Lipoxygenase-Activating Proteins; D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology*; D001241:Aspirin / Q000494:pharmacology*; D001854:Bone Marrow Cells / Q000187:drug effects / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism; D002478:Cells, Cultured; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology; D003545:Cysteine / Q000187:drug effects / Q000378:metabolism*; D015232:Dinoprostone / Q000378:metabolism; D004804:Eosinophils / Q000187:drug effects / Q000378:metabolism; D005260:Female; D005982:Glutathione Transferase / Q000378:metabolism; D007213:Indomethacin / Q000494:pharmacology*; D015289:Leukotrienes / Q000378:metabolism*; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D015398:Signal Transduction
D058927:5-Lipoxygenase-Activating Proteins; C548592:ALOX5AP protein, human; C548593:Alox5ap protein, mouse; D000894:Anti-Inflammatory Agents, Non-Steroidal; D002352:Carrier Proteins; D016861:Cyclooxygenase Inhibitors; D015289:Leukotrienes; D008565:Membrane Proteins; C112381:cysteinyl-leukotriene; D005982:Glutathione Transferase; C041116:leukotriene-C4 synthase; D015232:Dinoprostone; D003545:Cysteine; D001241:Aspirin; D007213:Indomethacin