Biliverdin inhibits activation of NF-kappaB: reversal of inhibition by human biliverdin reductase.
hBVR functions in the cell as a reductase and as a kinase. In the first capacity, it reduces biliverdin, the product of HO activity, to the effective intracellular antioxidant, bilirubin; as a dual-specificity kinase (S/T/Y) it activates the MAPK and IGF/IRK receptor signal transduction pathways. NF-kappaB and the MAPK pathway are activated by ROS, which results in the activation of stress-inducible genes, including ho-1. Presently, we report on the negative effect of biliverdin on NF-kappaB activation and the converse effect of hBVR. Biliverdin, in a concentration- and time-dependent manner, inhibited transcriptional activity of NF-kappaB in HEK293A cells. Nuclear extracts from biliverdin-treated cells show reduced DNA binding of NF-kappaB in an electromobility shift assay, whereas extracts from cells treated with TNF-alpha showed enhanced binding. Coimmunoprecipitation data show hBVR binds to the 65 kDa subunit of NF-kappaB, and that this is dependent on activation by TNF-alpha. Overexpression of hBVR enhanced both the basal and TNF-alpha-mediated activation of NF-kappaB and also that of the NF-kappaB-activated iNOS gene. Also, overexpression of hBVR arrested the cell cycle in the G(1)/G(0) phase and reduced the number of cells in S phase. Similar results were observed with MCF-7 cells. Because of the Janus nature of NF-kappaB activity in the cell and the inhibitory action of biliverdin, the present findings provide a foundation for therapeutic intervention in inflammatory diseases and cancer that may be attained by preventing reduction of biliverdin. On the other hand, by increasing BVR levels beneficial functions of NF-kappaB might be augmented.
Gibbs
Peter E M
PE
Department of Biochemistry and Biophysics, University of Rochester Medical Center, Rochester, NY 14642, USA.
Maines
Mahin D
MD
D001664:Biliverdine / Q000378:metabolism*; D001943:Breast Neoplasms / Q000201:enzymology / Q000378:metabolism*; D002453:Cell Cycle; D045744:Cell Line, Tumor; D024202:Electrophoretic Mobility Shift Assay; D005260:Female; D015971:Gene Expression Regulation, Enzymologic; D006801:Humans; D047468:Immunoprecipitation; D052002:NF-kappa B p50 Subunit / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II / Q000378:metabolism; D044925:Oxidoreductases Acting on CH-CH Group Donors / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014158:Transcription, Genetic; D014162:Transfection; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D015854:Up-Regulation
D052002:NF-kappa B p50 Subunit; C489548:NFKB1 protein, human; D014409:Tumor Necrosis Factor-alpha; D052247:Nitric Oxide Synthase Type II; D044925:Oxidoreductases Acting on CH-CH Group Donors; C019789:biliverdin reductase; D001664:Biliverdine