ACTIVATION OF C-JUN N-TERMINAL KINASE IN BACTERIAL LIPOPOLYSACCHARIDE-STIMULATED MACROPHAGES

Activation of macrophages by bacterial lipopolysaccharide (LPS) induce s transcription of genes that encode for proinflammatory regulators of the immune response. Previous work has suggested that activation of t he transcription factor activator protein 1 (AP-1) is one LPS-induced event that mediates this response. Consistent with this notion, we fou nd that LPS stimulated AP-l-mediated transcription of a transfected re porter gene in the murine macrophage cell line RAW 264.7, As AP-1 acti vity is regulated in part by activation of the c-Jun N-terminal kinase (JNK), which phosphorylates and subsequently increases the transcript ional activity of c-Jun, we examined whether LPS treatment of macropha ges resulted in activation of this kinase. LPS treatment of RAW 264.7 cells, murine bone marrow-derived macrophages, and the human monocyte cell line THP-1 resulted in rapid activation of the p46 and p54 isofor ms of JNK, Treatment with wild-type and rough mutant forms of LPS and synthetic lipid A resulted in JNK activation, while pretreatment with the tyrosine kinase inhibitor herbimycin A inhibited this response, Bi nding of LPS-LPS binding protein (LBP) complexes to CD14, a surface re ceptor that mediates many LPS responses, was found to be crucial, as p retreatment of THP-I cells with the monoclonal antibody 60b, which blo cks this binding, inhibited JNK activation, These results suggest that LPS activation of JNK in monocyte/macrophage cells is a CD14- and pro tein tyrosine phosphorylation-dependent event that may mediate the ear ly activation of AP-1 in regulating LPS-triggered gene induction.