The Role of Constitutive Nitric Oxide Synthase in Ultraviolet B Light-Induced Nuclear Factor kappa B Activity [Gene Regulation]

August 11th, 2014 by Tong, L., Wu, S.

NF-κB is a transcription factor involved in many signaling pathways, which also plays an important role in UV-induced skin tumorigenesis. UV radiation can activate NF-κB, but the detailed mechanism remains unclear. In this report, we provided evidence that the activation of constitutive nitric oxide synthase (s) plays a role in regulation of IκB reduction and NF-κB activation in human keratinocyte HaCaT cells in early phase (within 6 h) post-UVB. Treating the cells with L-NAME, a selective inhibitor of cNOS, can partially reverse the IκB reduction and inhibit the DNA-binding activity as well as nuclear translocation of NF-κB after UVB radiation. A luciferase reporter assay indicates that UVB-induced NF-κB activation is totally diminished in cNOS null cells. The cNOS mediated reduction of IκB is likely due to the imbalance of nitric oxide/peroxynitrite since treating the cells with lower (50 μM), but not higher (100-500 μM), concentration of SNAP can reverse the effect of L-NAME in partial restore IκB level post-UVB. Our data also showed that NF-κB activity was required for maintaining a stable IKKα level since treating the cells with NF-κB or cNOS inhibitors could reduce IKKα level upon UVB radiation. In addition, our data demonstrated that while NF-κB protects cells from UVB induced death, its pro-survival activity was likely neutralized by pro-death activity of peroxynitrite after UVB radiation.