Novitskiy Gennadiy, Potter James J, Rennie-Tankersley Lynda, Mezey Esteban
Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205-2195, USA.
J Biol Chem. 2004 Apr 9;279(15):15639-44. doi: 10.1074/jbc.M311499200. Epub 2004 Jan 13.
Hepatic fibrosis is due to the increased synthesis and deposition of type I collagen. Acetaldehyde activates type I collagen promoters. Nuclear factor kappaB (NF-kappaB) was previously shown to inhibit expression of murine alpha(1)(I) and human alpha(2)(I) collagen promoters. The present study identifies binding of NF-kappaB, present in nuclear extracts of stellate cells, to a region between -553 and -537 of the murine alpha(2)(I) collagen promoter. The NF-kappaB (p65) expression vector inhibited promoter activity. Mutation of the promoter at the NF-kappaB-binding site increased basal promoter activity and abrogated the activating and inhibitory effects of transforming growth factor beta and tumor necrosis factor alpha, respectively, on promoter activity. Acetaldehyde increased IkappaB-alpha kinase activity and phosphorylated IkappaB-alpha, NF-kappaB 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-kappaB to the murine alpha(2)(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-kappaB to the nucleus with increased DNA binding activity may be important in mediating the effects of acetaldehyde on other genes.
肝纤维化是由于I型胶原的合成和沉积增加所致。乙醛可激活I型胶原启动子。先前研究表明，核因子κB（NF-κB）可抑制小鼠α(1)(I)和人α(2)(I)胶原启动子的表达。本研究鉴定了星状细胞核提取物中的NF-κB与小鼠α(2)(I)胶原启动子-553至-537区域的结合。NF-κB（p65）表达载体抑制启动子活性。在NF-κB结合位点处对启动子进行突变可增加基础启动子活性，并分别消除转化生长因子β和肿瘤坏死因子α对启动子活性的激活和抑制作用。乙醛可增加IκB-α激酶活性，并使IκB-α、NF-κB核蛋白磷酸化，以及其与启动子的结合。然而，乙醛的激活作用不受启动子突变的影响。总之，虽然乙醛可增加NF-κB与小鼠α(2)(I)胶原启动子的结合，但这种结合并不介导乙醛对启动子活性的激活作用。乙醛增加NF-κB向细胞核的转位并增强DNA结合活性的作用，可能在介导乙醛对其他基因的作用中具有重要意义。
