Inhibition of T3 mediated T-cell proliferation by Ca2+-channel blockers and inhibitors of Ca2+/phospholipid-dependent kinase.
The potential roles of Ca2+ ions in the response of T lymphocytes to stimulation with monoclonal antisera to the T3 antigen were investigated by means of pharmacological agents that predominantly inhibit the flux of Ca2+ ions into cells (verapamil, nifedipine) or the activity of Ca2+-dependent kinases (trifluoperazine, polymyxin B). As assessed by uptake of [3H]thymidine, proliferation induced with anti-T3 +/- recombinant IL-2 at 72 h was inhibited by greater than 80% in the presence of nifedipine at 50 microM, and almost completely arrested (greater than 95% inhibition) with the other agents at the same concentration. Further quantitative assays of the effects of polymyxin B and trifluoperazine on C-kinase labelling of exogenous substrate showed a major reduction with both agents, but inhibition was substantially greater with polymyxin B that with trifluoperazine (IC50 = 14 and 70 microM respectively). These results were confirmed by qualitative assessment of Ca2+/phospholipid-dependent phosphorylation of endogenous substrates, which demonstrated major phosphoproteins of MW 56,000, 52,000, 43,000, and 20,000, and dose-dependent reduction in labelling in the presence of polymyxin B. Similar results were obtained under more physiological conditions in intact cells labelled with 32P orthophosphate. These findings indicate several possible roles for Ca2+ in T-cell activation, and several possible levels of activity, including modulation of calmodulin-dependent kinases and effects on Ca2+/phospholipid-dependent kinases and Ca2+ channels.
D000911:Antibodies, Monoclonal; D002118:Calcium / Q000502:physiology*; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D006801:Humans; D007376:Interleukin-2 / Q000276:immunology; D008213:Lymphocyte Activation / Q000187:drug effects*; D010750:Phosphoproteins / Q000378:metabolism; D011112:Polymyxin B / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors*; D011948:Receptors, Antigen, T-Cell / Q000276:immunology*; D013601:T-Lymphocytes / Q000276:immunology*; D014268:Trifluoperazine / Q000494:pharmacology
D000911:Antibodies, Monoclonal; D002121:Calcium Channel Blockers; D007376:Interleukin-2; D010750:Phosphoproteins; D011948:Receptors, Antigen, T-Cell; D014268:Trifluoperazine; D011493:Protein Kinase C; D011112:Polymyxin B; D002118:Calcium