Adriamycin inhibits inositol 1,4,5-trisphosphate 3-kinase activity in vitro and blocks formation of inositol 1,3,4,5-tetrakisphosphate in stimulated Jurkat T-lymphocytes. Does inositol 1,3,4,5-tetrakisphosphate play a role in Ca(2+)-entry?

Effects of the cytostatic drug adriamycin on inositol polyphosphate metabolism were analyzed in a human T-cell line (Jurkat) using a recently developed anion-exchange high performance liquid chromatography/post-column complexometric dye system. Treatment of intact T-cells with adriamycin prior to stimulation with an anti-CD3 monoclonal antibody induced a dose- and time-dependent decrease in the intracellular level of inositol 1,3,4,5-tetrakisphosphate (complete inhibition after 2 h at 10 microM adriamycin) and an increase in the level of inositol 1,3,4-trisphosphate without significantly changing the levels of other inositol phosphates. A marked inhibition of the inositol 1,4,5-trisphosphate 3-kinase activity and a slight activation of the inositol 1,3,4,5-tetrakisphosphate 5-phosphatase activity were observed in cytosolic extracts in the presence of adriamycin, providing an explanation for the drug-induced metabolic effect. Adriamycin thus seems to be an extremely valuable tool for further dissecting inositol polyphosphate metabolism, as well as signaling pathways. Along these lines, we observed that adriamycin did not change the free cytosolic Ca2+ concentration of Jurkat T-lymphocytes and, in particular, did not modulate Ca2+ influx upon T-cell receptor stimulation. We conclude that (i) inositol phosphate signaling pathways constitute an as yet undescribed target for the action of adriamycin and that (ii) an increase of inositol 1,3,4,5-tetrakisphosphate is not necessary for sustained Ca(2+)-entry in stimulated T-cells.