RO-32-0432, A SELECTIVE AND ORALLY-ACTIVE INHIBITOR OF PROTEIN-KINASE-C PREVENTS T-CELL ACTIVATION

Several lines of circumstantial evidence support the assumption that p rotein kinase C (PKC) activation together with elevated levels of cyto solic Ca++ are necessary for T-cell activation and proliferation in re sponse to a physiological stimulus, i.e., MHC class II restricted anti gen presentation. By using a potent, cell-permeable and selective inhi bitor of PKC, Ro 32-0432, we have tested this hypothesis. Ro 32-0432 i nhibits interleukin-2 (IL-2) secretion, IL-2 receptor expression in, a nd proliferation of, peripheral human T-cells stimulated with phorbol ester together with phytohemagglin or anti-CD3, but does not inhibit I L-2 induced proliferation in cells already stimulated to express IL-2 receptors. Proliferation of the influenza peptide antigen HA 307-319-s pecific human T-cell clone (HA27) after exposure to anti-gen-pulsed au tologous presenting cells was also inhibited by Ro 32-0432. Oral admin istration of Ro 32-0432 inhibited subsequent phorbol ester-induced ede ma in rats demonstrating the systemic efficacy of the compound to inhi bit PKC-driven responses. Induction of more physiologically T-cell dri ven responses such as host vs. graft responses and the secondary paw s welling in adjuvant-induced arthritis were also inhibited by Ro 32-043 2. These data demonstrate the crucial role for PKC in T-cell activatio n and that selective p.o. bioavailable PKC inhibitors are efficacious in preventing T-cell driven chronic inflammatory responses in vivo. In hibition of PKC represents an important mechanistic approach to preven t T-cell activation and compounds of this class may have important the rapeutic applicability to chronic inflammatory and autoimmune diseases .