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 some of the tumor necrosis factor (TNF) induced cellular responses including cytotoxicity. We evaluated the induction of both the 85-kDa cytosolic phospholipase A(2) (cPLA(2)) and non-pancreatic group IT PLA(2) gene 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 incubation. 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 PLA(2) activity which was blocked by the cPLA(2) inhibitor AACOCF(3). Treatment with TNF-alpha for 4-24 h increased the cPLA(2) protein and mRNA levels which were blocked by the broad inhibitor of protein kinases staurosporine, the protein kinase C (PKC) inhibitor calphostin C, and to a lesser extent the calcium/calmodulin-dependent protein kinase inhibitor W-7. Reverse transcription and polymerase chain reaction amplification of the group II PLA(2) mRNA showed that it is expressed in human lung but not in the bronchial epithelial cell line. TNF-alpha failed 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-regulated by TNF-alpha and this effect may contribute to the TNF-alpha stimulated AA release in airway epithelial cells.