Identification of a Novel NF-κB-binding Site with Regulation of the Murine α₂(I) Collagen Promoter

Hepatic fibrosis is due to the increased synthesis and deposition of type I collagen. Acetaldehyde activates type I collagen promoters. Nuclear factor κB (NF-κB) was previously shown to inhibit expression of murine α₁(I) and human α₂(I) collagen promoters. The present study identifies binding of NF-κB, present in nuclear extracts of stellate cells, to a region between -553 and -537 of the murine α ₂(I) collagen promoter. The NF-κB (p65) expression vector inhibited promoter activity. Mutation of the promoter at the NF-κB-binding site increased basal promoter activity and abrogated the activating and inhibitory effects of transforming growth factor β and tumor necrosis factor α, respectively, on promoter activity. Acetaldehyde increased IκB-α kinase activity and phosphorylated IκB-α, NF-κB nuclear protein, and its binding to the promoter. However, the activating effect of acetaldehyde was not affected by the mutation of the promoter. In conclusion, although acetaldehyde increases the binding of NF-κB to the murine α₂(I) collagen promoter, this binding does not mediate the activating effect of acetaldehyde on promoter activity. The effects of acetaldehyde in increasing the translocation of NF-κB to the nucleus with increased DNA binding activity may be important in mediating the effects of acetaldehyde on other genes.