BACKGROUND: Previously, it has been suggested that lipopolysaccaride (LPS) stimulates the activation of the transcriptional factor activator protein (AP-1) which is in part regulated by activation of the c-Jun N-terminal kinase (JNK) / stress-activated protein kinase (SAPK) in the murine macrophage cell line RAW 264.7. METHODS: Consistent with this notion, we find that treatment of LPS on RAW 264.7 cells induces the generation of nitric oxide (NO) and results in the activation of JNK and treated with NO donors and NO inhibitors. RESULTS: NO donors including sodium nitroprusside (1 mM), GSNO (0.2 mM), or SNAP (0.5 mM) treatment of the macrophage cell line markedly induces the activation of JNK. However NGMMA (2 mM), a competitive inhibitor of NO, does not inhibit the activation of JNK induced by LPS. SIN-1, NO, and superoxide donor induce an activation of JNK that is slightly decreased by treatment with sodium dismutase whereas the activation of JNK is significantly augmented by adding sodium dismutase with catalase. C2 ceramide suppresses the generation of NO induced by LPS, but significantly increases the activity of JNK in vivo. LPS can induce the activation of JNK at 30 min after stimulation in RAW 264.7 cells. Exposure to SNP does not affect the enzymatic activity of JNK, immunoprecipitates, JNK, and c-Jun N-terminal proteins. CONCLUSIONS: These data suggest that even though NO is one of the major activators of JNK induced by LPS, there is, at least, an NO-independent JNK activation, signaling a pathway for LPS. Also, there may be an undefined NO-sensitive JNK-regulator (s) in vivo.