Paclitaxel (taxol)-induced NF-κB translocation in murine macrophages

Interaction of bacterial lipopolysaccharide (LPS) with macrophages results in the induction of a cascade of cytokines that mediate the varied effects of LPS. An early intracellular signaling event that follows receptor engagement is the activation of transcription factor NF- Kappa B. NF- Kappa B has been shown to be important for the induction of many LPS-inducible cytokine genes, including tumor necrosis factor alpha, interleukin-1 beta , and interleukin-6. Previously, we and others have shown that the antitumor agent paclitaxel (Taxol) is able to mimic bacterial LPS in its ability to activate murine macrophages. In this report, we have extended these findings by demonstrating that paclitaxel, like LPS, is able to stimulate the translocation of primarily p50-p65 heterodimers of NF- Kappa B to the nucleus. This activation is dose dependent and requires a concentration of greater than or equal to 5 mu m paclitaxel. The kinetics of NF- Kappa B activation by paclitaxel are slower than those of LPS: by 15 min poststimulation, LPS-induced NF- Kappa B activation was readily detected, whereas the paclitaxel-induced NF- Kappa B activation was minimal. Moreover, paclitaxel- and protein-free LPS-induced translocation of NF- Kappa B was seen only in macrophages derived from LPS-responsive C3H/OuJ mice and not from the LPS-hyporesponsive C3H/HeJ mice, a finding that is consistent with those of previous genetic studies linking paclitaxel responsiveness to the Lps gene. Finally, the LPS structural antagonist Rhodobacter sphaeroides diphosphoryl lipid A inhibited both LPS- and paclitaxel-induced NF- Kappa B activation, suggesting a common receptor component in this activation.