Lead activates nuclear transcription factor-kappa beta, activator protein-1 and amino-terminal c-Jun kinase in pheochromocytoma cells

Lead (Pb) is a ubiquitous environmental contaminant that produces variety o f effects on the central and peripheral nervous system, induces inflammator y response, and modulates immune functions. Though increase in lipid peroxi dation and reactive oxygen intermediates (ROI) have been observed in Pb-ind uced toxicity, the molecular mechanism underlying these effects is largely unknown. Since nuclear factor kappa B (NF-kappa B) and activator protein (A P-1) are known to be activated by oxidative stress, we hypothesized that Pb -induced effects may be modulated via these transcription factors. The effe cts of Pb on NF-kappa B, AP-1, and related kinases were studied in pheochro mocytoma cells (PC-12). Our results showed that treatment of murine PC-12 c ells with Pb resulted in activation of NF-kappa B and degradation of I kapp a B alpha (the inhibitory subunit of NF-kappa B). Pb-induced NF-kappa B dep endent gene expression was also enhanced. The binding of Pb-induced NF-kapp a B to DNA was blocked by antibodies for p65 and p50 but not by c-Rel or no nspecific antibodies such as cyclin D-1 and preimmune serum, suggesting tha t NF-kappa B consisted of p65 and p50 subunits. Similar to its effects on N F-kappa B, Pb also activated AP-1 in a time- and dose-dependent manner. Bes ides activating these transcription factors, Pb was also found to upregulat e the related kinases such as mitogen activated protein kinase kinase (MEK) and c-Jun N-terminal kinase (JNK) (also known as stress-activated protein kinase) in a dose- and time-dependent manner. Thus, these results suggest t hat NF-kappa B, AP-1, MEK, and JNK may be important mediators of Pb-induced signaling in gene expression mediating inflammatory response and immunomod ulation. (C) 1999 Academic Press.