CISPLATIN-INDUCED ACTIVATION OF MURINE BONE-MARROW-DERIVED MACROPHAGES REQUIRE PROTEIN-TYROSINE PHOSPHORYLATION

The aim of the present study is to evaluate the involvement of tyrosin e phosphorylation in the signal transduction mechanism of cisplatin-in duced macrophage activation in vivo. Stimulation of bone marrow-derive d macrophages (BMDM) with cisplatin (CP) resulted in a time- and dose- dependent phosphorylation of several proteins having estimated molecul ar weights of approximately 18, 20, 21, 30, 33, 35, 39, 41, 44, 58 and 123 kD, detected by immunoblot using anti-phosphotyrosine antibody. C P-induced tyrosine phosphorylation was inhibited by the tyrosine kinas e inhibitor genistein. Using this inhibitor, we were able to correlate tyrosine phosphorylation with several functional effects of CP on mur ine bone marrow-derived macrophages (BMDM). Treatment of macrophages w ith genistein before incubation with CP completely inhibited the CP-in duced tumoricidal activation of macrophages as well as production of T NF and NO, whereas pre-treatment of macrophages with phosphatase inhib itor sodium vanadate upregulated macrophage activation in addition to enhanced protein tyrosine phosphorylation. Taken together, these data suggest that tyrosine phosphorylation play a critical regulatory role in the activation of macrophages with CP. (C) 1998 International Socie ty for Immunopharmacology.