Redox regulation of NF-kappa B DNA binding activity by dihydrolipoate

NF-kappa B transcription factor regulates a wide variety of cellular and viral genes including the human immunodeficiency virus type 1. Here, we demonstrate that dihydrolipoate/alpha-lipoate redox couple which is a cofactor for mitochondrial dehydrogenases reactions, influences the DNA binding activity of NF-kappa B. The elimination of dithiothreitol in the electrophoretic mobility shift assay protocol resulted in the inability to detect DNA binding activity of activated NF-kappa B. The DNA binding activity was restored by the addition of dihydrolipoate in the binding reaction mixture. Inhibition of NF-kappa B DNA binding activity by in vitro exposure to a sulfhydryl oxidizing agent, diamide was also blocked by dihydrolipoate. In contrast, the addition of the oxidized form, alpha-lipoate inhibited the NF-kappa B DNA binding activity. Coincidentally, preincubation of Jurkat cells with dihydrolipoate potentiated and alpha-lipoate inhibited the okadaic acid-induced NF-kappa B activation as detected by assessing its DNA binding activity. These results suggest the redox exchange between lipoate and NF-kappa B molecules. Furthermore, since the inhibition of AP-1 DNA binding activity by diamide was also blocked by dihydrolipoate, this natural reductant may participate in the redox regulation of transcription factors by enhancing the DNA-protein interactions.