Dexamethasone alters arachidonate release from human epithelial cells by induction of p11 protein synthesis and inhibition of phospholipase A(2) activity

The effect of the glucocorticosteroid, dexamethasone, on arachidonic acid ( AA) release and on protein levels of p11 and cytosolic phospholipase A(2) ( cPLA(2)) was studied in two epithelial cell lines, HeLa cells and BEAS-2B c ells. Dexamethasone treatment of HeLa cells and BEAS-2B cells increased cel lular pll protein and mRNA levels in a time- and dose-dependent manner. It had little effect on levels of cPLA(2) protein. In order to determine if in creased pll protein expression resulted in increased interaction between p1 1 and cPLA(2), anti-cPLA(2) antibodies were used to immunoprecipitate p11.c PLA(2) complexes and Western blots of the immunoprecipitate were used to de tect p11, In cells treated with dexamethasone, more p11 was detected in the anti-cPLA(2) immunoprecipitate compared with control cells. Dexamethasone treatment of HeLa cells prelabeled with [H-3]AA decreased the release of [H -3]AA under basal conditions and after stimulation with the calcium ionopho re A23187 (10(-6) M). In order to determine if altering the p11 protein lev els in HeLa cells independent of glucocorticosteroid treatment could also p roduce an effect on [H-3]AA release, cells were stably transfected with pla smids expressing either p11 antisense mRNA or p11 mRNA Cloned HeLa cells ex pressing p11 antisense mRNA exhibited less cellular p11 protein compared wi th control cells and greater [H-3]AA release compared with cells transfecte d with a control vector. Cloned HeLa cells stably transfected with a p11 ex pression vector exhibited increased p11 cellular protein and diminished [H- 3]AA release under basal conditions and in response to A23187, Therefore, d examethasone alteration of epithelial cell AA release may be due in part to induction of p11 protein expression.