DEXAMETHASONE SUPPRESSION OF IL-1-BETA-INDUCED CYCLOOXYGENASE-2 EXPRESSION IS NOT MEDIATED BY LIPOCORTIN-1 IN A549 CELLS

A549 cells grown under serum free conditions do not express cyclooxyge nase 2 (cox 2). However, addition of IL-1 beta results in the inductio n of cox 2 in a time and dose dependent manner; actinomycin D complete ly blocks this induction. Dexamethasone completely suppressed the indu ction of cox 2 only if present during the first 3.5h of IL-1 beta trea tment but not if added after 3.5h. Treatment with a neutralising monoc lonal antibody (1A, Biogen) specific to lipocortin-1 failed to reverse this inhibition by dexamethasone. However, using this same antibody w e were able to reverse completely the effects of dexamethasone on the suppression of PGE(2) release. These observations support the idea tha t glucocorticoids directly regulate cox 2 expression at the transcript ional level and this phenomenon is not not mediated by lipocortin-1. ( C) 1994 Academic Press, Inc.