title: TNF-alpha decreases ABCA1 expression and attenuates HDL cholesterol efflux in the human intestinal cell line Caco-2.
abstract: HDL cholesterol levels are decreased in Crohn's disease, a tumor necrosis factor-alpha (TNF-alpha)-driven chronic inflammatory condition involving the gastrointestinal tract. ATP-binding cassette transporter A1 (ABCA1), one of several liver X receptor (LXR) target genes, is a cell surface transporter that mediates the rate-controlling step in HDL synthesis. The regulation of ABCA1 and HDL cholesterol efflux by TNF-alpha was investigated in the human intestinal cell line Caco-2. In response to cholesterol micelles or T0901317, an LXR nonsterol agonist, TNF-alpha decreased the basolateral efflux of cholesterol to apolipoprotein A1 (apoA1). TNF-alpha, by attenuating ABCA1 promoter activity, markedly decreased ABCA1 gene expression without attenuating the expression of LXR-alpha, LXR-beta, and most other LXR target genes, such as ABCG1, FAS, ABCG8, scavenger receptor-B1 (SR-B1), and apoC1. TNF-alpha also decreased ABCA1 mass by markedly enhancing the rate of ABCA1 degradation and modestly inhibiting its rate of synthesis. Inhibitors of the nuclear factor-kappaB (NF-kappaB) pathway, which is activated by TNF-alpha, partially reverse the effect of TNF-alpha on ABCA1 protein expression. The results suggest that TNF-alpha, the major cytokine implicated in the inflammation of Crohn's disease, decreases HDL cholesterol levels by attenuating the expression of intestinal ABCA1 and cholesterol efflux to apoA1.
authors.affiliation: Department of Internal, Medicine University of Iowa, Iowa City, IA 52242, USA. f-jeffrey-fi eld@uiowa.edu
authors.forename: F Jeffrey
authors.initials: FJ
authors.lastname: Field
authors.forename: Kim
authors.initials: K
authors.lastname: Watt
authors.forename: Satya N
authors.initials: SN
authors.lastname: Mathur
mesh_terms: D064286:ATP Binding Cassette Transporter 1; D018528:ATP-Binding Cassette Transporters / Q000235:genetics*; D000818:Animals; D018938:Caco-2 Cells; D008076:Cholesterol, HDL / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000187:drug effects*; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism; D007422:Intestines / Q000166:cytology*; D000071518:Liver X Receptors; D016328:NF-kappa B / Q000378:metabolism; D057093:Orphan Nuclear Receptors / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
chemical_list: C577836:ABCA1 protein, human; D064286:ATP Binding Cassette Transporter 1; D018528:ATP-Binding Cassette Transporters; D008076:Cholesterol, HDL; D000071518:Liver X Receptors; D016328:NF-kappa B; C000605213:NR1H3 protein, human; D057093:Orphan Nuclear Receptors; D014409:Tumor Necrosis Factor-alpha