Vol. 285, Issue 2, 862-868, May 1998

Tyrosine Phosphatase-Dependent/Tyrosine Kinase-Independent Induction of Nuclear Factor-B by Tumor Necrosis Factor-: Effects on Prostaglandin Endoperoxide Synthase-2 mRNA Accumulation

Keyvan Mahboubi, Wilson Young and Nicholas R. Ferreri

Department of Pharmacology, New York Medical College, Valhalla, New York

We previously have demonstrated that tumor necrosis factor- (TNF-) increases prostaglandin endoperoxide synthase-2 (PGHS-2) mRNA accumulation and tyrosine phosphorylation in the fibrosarcoma cell line, MCA-101. Tyrosine kinase inhibitor, genistein, and tyrosine phosphatase inhibitor, phenylarsine oxide (PAO), blocked TNF--mediated induction of PGHS-2 mRNA in these cells. Because the PGHS-2 promoter has a nuclear factor-B (NF-B) binding motif, which is important for PGHS-2 gene transcription in some cell types, we have evaluated the effects of tyrosine kinase inhibitors and PAO on TNF--induced NF-B activation. TNF- (1 nM) rapidly induced translocation of NF-B, an event accompanied by degradation of inhibitory protein IB-. N-tosyl-L-phenylalanine chloromethyl ketone (TPCK), a serine protease inhibitor, inhibited IB- degradation and NF-B activation in response to TNF- in a dose-dependent manner (25, 50, 100 µM). TPCK also inhibited PGHS-2 mRNA accumulation. These data suggest that NF-B contributed to PGHS-2 mRNA accumulation in MCA-101 cells stimulated with TNF-. PAO (2.4 µM) completely abolished activation of NF-B and degradation of IB- induced by TNF- at a concentration that blocked PGHS-2 mRNA accumulation. However, four tyrosine kinase inhibitors, genistein, tyrphostin 47, herbimycin A and erbstatin, failed to block translocation of NF-B and degradation of IB-. These data demonstrate that tyrosine kinase pathways are not required for TNF--induced NF-B activation in MCA-101 cells and suggest that signaling via these pathways mediates TNF--induced PGHS-2 mRNA accumulation via an NF-B-independent mechanism. Moreover, an upstream tyrosine phosphatase pathway may mediate PGHS-2 mRNA accumulation by TNF- via an NF-B-dependent mechanism.