TUMOR-NECROSIS-FACTOR-ALPHA INDUCES THE 85-KDA CYTOSOLIC PHOSPHOLIPASE A(2) GENE-EXPRESSION IN HUMAN BRONCHIAL EPITHELIAL-CELLS

Phospholipase A(2) (PLA(2)) activity has been suggested to mediate som e of the tumor necrosis factor (TNF) induced cellular responses includ ing cytotoxicity. We evaluated the induction of both the 85-kDa cytoso lic phospholipase A(2) (cPLA(2)) and non-pancreatic group IT PLA(2) ge ne expression by TNF-alpha in a human bronchial epithelial cell line ( BEAS 2B cell). TNF-alpha (20 ng/ml) induced a significantly increased release of prelabeled [H-3]arachidonic acid (AA) following 4-24 h incu bation. Calcium ionophore A23187 (10(-5) M) further increased the [H-3 ]AA release from the TNF-alpha-treated cells. In vitro activity assay revealed that TNF-alpha increased the dithiothreitol (DTT)-resistant P LA(2) activity which was blocked by the cPLA(2) inhibitor AACOCF(3). T reatment with TNF-alpha for 4-24 h increased the cPLA(2) protein and m RNA levels which were blocked by the broad inhibitor of protein kinase s staurosporine, the protein kinase C (PKC) inhibitor calphostin C, an d to a lesser extent the calcium/calmodulin-dependent protein kinase i nhibitor W-7. Reverse transcription and polymerase chain reaction ampl ification of the group II PLA(2) mRNA showed that it is expressed in h uman lung but not in the bronchial epithelial cell line. TNF-alpha fai led to induce the expression of group II PLA(2) in the BEAS 2B cells. These results demonstrate that the cPLA(2) gene expression is up-regul ated by TNF-alpha and this effect may contribute to the TNF-alpha stim ulated AA release in airway epithelial cells.