title: Mechanisms involved in the inhibitory effect of chronic alcohol exposure on pancreatic acinar thiamin uptake.
abstract: Pancreatic acinar cells (PAC) obtain thiamin from the circulation via a carrier-mediated process that involves thiamin transporters 1 and 2 (THTR-1 and THTR-2; products of SLC19A2 and SLC19A3, respectively). Chronic alcohol exposure of PAC inhibits thiamin uptake, and, on the basis of in vitro studies, this inhibition appears to be transcriptionally mediated. The aim of this study was to confirm the involvement of a transcriptional mechanism in mediating the chronic alcohol effect in in vivo settings and to delineate the molecular mechanisms involved. Using transgenic mice carrying full-length SLC19A2 and SLC19A3 promoters, we found that chronic alcohol feeding led to a significant reduction in the activity of SLC19A2 and SLC19A3 promoters (as well as in thiamin uptake and expression of THTR-1 and -2). Similar findings were seen in 266-6 cells chronically exposed to alcohol in vitro. In the latter studies, the alcohol inhibitory effect was found to be mediated via the minimal SLC19A2 and SLC19A3 promoters and involved the cis-regulatory elements stimulating protein 1 (SP1)/gut-enriched Kruppel-like factor and SP1-GG-box and SP1/GC, respectively. Chronic alcohol exposure of PAC also led to a significant reduction in the expression of the SP1 transcription factor, which upon correction (via expression) led to the prevention of alcohol inhibitory effects on not only the activity of SLC19A2 and SLC19A3 promoters but also on the expression of THTR-1 and -2 mRNA and thiamin uptake. These results demonstrate that the inhibitory effect of chronic alcohol exposure on physiological/molecular parameters of thiamin uptake by PAC is mediated via specific cis-regulatory elements in SLC19A2 and SLC19A3 minimal promoters.
authors: Department of Medical Research, VA Medical Center, Long Beach; Departments of Medicine and Physiology/Biophysics, University of California, Irvine, California.
authors: Padmanabhan
authors: P
authors: Srinivasan
authors: Veedamali S
authors: VS
authors: Subramanian
authors: Hamid M
authors: HM
authors: Said
mesh_terms: D061354:Acinar Cells / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D000818:Animals; D001665:Binding Sites; D001692:Biological Transport; D002478:Cells, Cultured; D000431:Ethanol / Q000633:toxicity*; D005786:Gene Expression Regulation; D017930:Genes, Reporter; D006801:Humans; D000090062:Kruppel-Like Factor 4; D051741:Kruppel-Like Transcription Factors / Q000378:metabolism; D049409:Luciferases, Firefly / Q000096:biosynthesis / Q000235:genetics; D026901:Membrane Transport Proteins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D046790:Pancreas, Exocrine / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D011401:Promoter Regions, Genetic; D016329:Sp1 Transcription Factor / Q000378:metabolism; D013831:Thiamine / Q000378:metabolism*; D013997:Time Factors; D014158:Transcription, Genetic
chemical_list: D000090062:Kruppel-Like Factor 4; D051741:Kruppel-Like Transcription Factors; D026901:Membrane Transport Proteins; C120043:SLC19A2 protein, human; C492291:SLC19A3 protein, human; C492292:Slc19a2 protein, mouse; C492290:Slc19a3 protein, mouse; D016329:Sp1 Transcription Factor; D000431:Ethanol; D049409:Luciferases, Firefly; D013831:Thiamine
keywords: SLC19A2; SLC19A3; alcohol feeding; cis-regulatory elements; thiamin transport