Production of PGE2 by bovine cultured airway smooth muscle cells and its inhibition by cyclo‐oxygenase inhibitors

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Abstract
1 Prostaglandin E2 (PGE2) is thought to be an important inhibitory modulator of inflammatory processes in the airway. It inhibits inflammatory cell function and cholinergic neurotransmission in vitro and roles have been postulated in vivo in refractoriness and in the mechanism of action of the diuretic agent, frusemide. 2 The production of PGE2 by bovine cultured airway smooth muscle cells has been studied under a range of conditions. The effects of cyclo-oxygenase inhibitors (flurbiprofen, indomethacin, acetyl salicylic acid) on serum-induced production of PGE2 were assessed over a range of concentrations (10−7–10−4 m). 3 Serum-stimulated production of PGE2 in control wells ranged from 350 to 800 ng PGE2 ml−1 in cells from different animals. All three cyclo-oxygenase inhibitors inhibited PGE2 production with an order of potency, flurbiprofen > indomethacin > acetyl salicylic acid. Log IC50 values were − 6.24 for flurbiprofen, − 5.23 for indomethacin and − 3.50 for acetyl salicylic acid. 4 PGE2 production was stimulated by arachidonic acid (10−5 m) or addition of the proinflammatory mediator, bradykinin (10−8–10−5 m). 5 Incubation of cells for 24 h with 5 bromo deoxyuridine (BRDU) (10−4 m) to prevent DNA synthesis did not alter PGE2 production in response to serum, suggesting that it was not a function of proliferation per se. 6 Our study suggests that airway smooth muscle may be an important source of PGE2. Production of PGE2 may be a novel feedback mechanism whereby airway smooth muscle cells can negatively modulate airways inflammation. The differing potencies of the cyclo-oxygenase inhibitors may explain the contrasting effect of these drugs in recent studies in asthma.