Vol. 289, Issue 3, 1465-1471, June 1999

Tepoxalin Enhances the Activity of an Antioxidant, Pyrrolidine Dithiocarbamate, in Attenuating Tumor Necrosis Factor -Induced Apoptosis in WEHI 164 Cells

Daniel H.S. Lee, J. Philip Macintyre, Gareth R. Taylor, Elizabeth Wang, Richard K. Plante, Susanna S.C. Tam, Barbara L. Pope and Catherine Y. Lau

The R.W. Johnson Pharmaceutical Research Institute, Toronto, Canada

The nuclear transcription factor-B (NF-B) and free radicals are known to be involved in apoptosis. We studied the effects of a series of di-aryl-substituted pyrazole NF-B inhibitors including tepoxalin on tumor necrosis factor  (TNF)-induced apoptosis in murine fibrosarcoma WEHI 164 cells. We found that potent inhibitors of NF-B were also effective in attenuating apoptosis. WEHI 164 cells that had been dually treated with tepoxalin and the antioxidant pyrrolidine dithiocarbamate (PDTC) were significantly protected from TNF-induced killing. To study the role of free radicals in mediating TNF-induced apoptosis, stable WEHI 164 cells overexpressing Bcl-2, an antioxidant protein, were generated. These cells were protected from TNF-induced apoptosis and neither tepoxalin nor PDTC provided further significant protection. These results suggest that Bcl-2, PDTC, and tepoxalin may attenuate apoptosis in this system by affecting the same signaling pathway or converging pathways. Because tepoxalin suppresses the release of free radicals, PDTC scavenges free radicals and Bcl-2 is an antioxidant protein, free radicals are among the key mediators of this TNF-induced killing event. Tepoxalin and antioxidants may be useful in developing new therapeutics for treating neurodegenerative diseases, autoimmune deficiency syndrome, and ischemia-reperfusion injuries.