The activity of cytosolic phospholipase A2 is required for the lysis of adenovirus-infected cells by tumor necrosis factor.

Abstract

Most cell types are resistant to apoptosis induced by tumor necrosis factor (TNF) unless the cells are treated with a sensitizing agent. Inhibitors of transcription or translation act as sensitizing agents, as do adenoviruses lacking one or more resistance genes. We have reported recently that the activity of cytosolic phospholipase A2 (cPLA2) is necessary for the TNF-induced lysis of cells that are sensitized by inhibitors of transcription or translation (C. Voelkel-Johnson, T. E. Thorne, and S. M. Laster, J. Immunol. 156:201-207, 1996). In this report we have asked whether the lysis of cells infected by the adenovirus dl758 (which lacks the E3 14.7-kDa resistance gene product) also involves the activity of cPLA2. We report that a phosphorothioate-modified antisense oligonucleotide specific for cPLA2, but not the control oligonucleotide, inhibited the TNF-induced release of both [3H]arachidonic acid and 51Cr from infected cells. Arachidonyltrifluoromethyl ketone (AA COCF3), an inhibitor of cPLA2, also inhibited the release of 51Cr, and we found that the release of [3H]arachidonic acid was highly selective and was preferred over the release of [3H]palmitic acid. Taken together, these results suggest strongly that cPLA2 is indeed the phospholipase responsible for the release of [3H]arachidonic acid during the lysis of infected cells and that its activity is necessary for cell death. Finally, since arachidonic acid serves as the substrate for the synthesis of inflammatory lipids, our results suggest a possible link between the TNF-induced lysis of infected cells and inflammation. The E3 14.7-kDa resistance protein may, therefore, play two roles: preventing TNF-induced cell death and, as our results show, preventing the TNF-induced release of arachidonic acid.