The MAP kinase inhibitors, PD098059, UO126 and SB203580, inhibit IL‐1β‐dependent PGE 2 release via mechanistically distinct processes

In common with human bronchial epithelial cells, pulmonary A549 cells release prostaglandin (PG) E 2 in response to pro‐inflammatory cytokines. We have therefore used these cells to examine the effect of the selective mitogen activated protein (MAP) kinase inhibitors; PD098059, a m itogen activated and e xtracellular r egulated k inase kinase (MEK) 1 inhibitor, UO126, a dual MEK1 & MEK2 inhibitor, and SB203580, a p38 MAP kinase inhibitor in the IL‐1β‐dependent release of PGE 2 . Following IL‐1β treatment the extracellular regulated kinases (ERKs) and the p38 MAP kinases were rapidly phosphorylated. PD09059, UO126 and SB203580 prevented IL‐1β‐induced PGE 2 release at doses that correlated closely with published IC 50 values. Small or partial effects at the relevant doses were observed on induction of cyclo‐oxygenase (COX) activity or COX‐2 protein suggesting that the primary effects were at the level of arachidonate availability. Neither PD098059 nor SB203580 showed any effect on IL‐1β‐induced arachidonate release. We therefore speculate that the MEK1/ERK and p38 kinase cascades play a role in the functional coupling of arachidonate release to COX‐2. In contrast, UO126 was highly effective at inhibiting IL‐1β‐dependent arachidonate release, implicating MEK2 in the activation of the PLA 2 that is involved in IL‐1β‐dependent PGE 2 release. We conclude that the MEK1, MEK2 and p38 MAP kinase inhibitors, PD098059, UO126 and SB203580, are highly potent in respect of inflammatory PG release. Finally, we conclude that these inhibitors act via mechanistically distinct processes, which may have anti‐inflammatory benefits.British Journal of Pharmacology (2000) 130 , 1353–1361; doi: 10.1038/sj.bjp.0703431