Differential activation and inhibition of lymphocyte proliferation by modulators of protein kinase C: Diacylglycerols, "rationally designed" activators and inhibitors of protein kinase C

The tumor promoter 12-O-tetradecanoylphorbol 13-acetate (TPA) can enhance or inhibit lymphocyte proliferation. Enhancement correlated with increased interleukin 2 (IL-2) production and activation of protein kinase C while inhibition correlated with decreased IL-2 and downregulation of protein kinase C activity (D. S. Grove and A. M. Mastro, Cancer Res. 51, 82-88). In this study, various activators and inhibitors of protein kinase C were used in order to try to separate the effects of TPA on this enzyme from its effects on IL-2 production and determine if protein kinase C activity was directly or indirectly related to IL-2 production. 1,2-Dioctanoylglycerol, 1-oleoyl-2-acetylglycerol, phospholipase C, and two "rationally designed" activators, 6-(N-decylamino)-4-hydroxymethylindole and 3-(N-acetylamino)-5-(N-decyl-N-methylamino)-benzyl alcohol, were tested. Some activators enhanced proliferation in the presence of a Ca²⁺ ionophore, ionomycin, but not concanavalin A. Some activators suppressed proliferation and downregulated protein kinase C. Others neither downregulated protein kinase C nor inhibited IL-2 production and proliferation. However, inhibition or downregulation of protein kinase C activity always correlated with decreased IL-2 and depressed proliferation. Thus, the evidence in this and the previous study suggests that activation of protein kinase C is directly related to IL-2 production in activated T cells.