title: Role of intestinal circadian genes in alcohol-induced gut leakiness.
abstract: BACKGROUND
  Several studies have indicated that endotoxemia is the required co-factor for alcoholic steatohepatitis (ASH) that is seen in only about 30% of alcoholics. Recent studies have shown that gut leakiness that occurs in a subset of alcoholics is the primary cause of endotoxemia in ASH. The reasons for this differential susceptibility are not known. Since disruption of circadian rhythms occurs in some alcoholics and circadian genes control the expression of several genes that are involved in regulation of intestinal permeability, we hypothesized that alcohol induces intestinal hyperpermeability by stimulating expression of circadian clock gene proteins in the intestinal epithelial cells.
  
  
  METHODS
  We used Caco-2 monolayers grown on culture inserts as an in vitro model of intestinal permeability and performed Western blotting, permeability, and siRNA inhibition studies to examine the role of Clock and Per2 circadian genes in alcohol-induced hyperpermeability. We also measured PER2 protein levels in intestinal mucosa of alcohol-fed rats with intestinal hyperpermeability.
  
  
  RESULTS
  Alcohol, as low as 0.2%, induced time dependent increases in both Caco-2 cell monolayer permeability and in CLOCK and PER2 proteins. SiRNA specific inhibition of either Clock or Per2 significantly inhibited alcohol-induced monolayer hyperpermeability. Alcohol-fed rats with increased total gut permeability, assessed by urinary sucralose, also had significantly higher levels of PER2 protein in their duodenum and proximal colon than control rats.
  
  
  CONCLUSIONS
  Our studies: (i) demonstrate a novel mechanism for alcohol-induced intestinal hyperpermeability through stimulation of intestinal circadian clock gene expression, and (ii) provide direct evidence for a central role of circadian genes in regulation of intestinal permeability.
authors.affiliation: Department of Medicine, Division of Digestive Diseases and Nutrition, Rush University Medical Center, 1725 W. Harrison, Chicago, IL 60612, USA.
authors.forename: Garth
authors.initials: G
authors.lastname: Swanson
authors.forename: Christopher B
authors.initials: CB
authors.lastname: Forsyth
authors.forename: Yueming
authors.initials: Y
authors.lastname: Tang
authors.forename: Maliha
authors.initials: M
authors.lastname: Shaikh
authors.forename: Lijuan
authors.initials: L
authors.lastname: Zhang
authors.forename: Fred W
authors.initials: FW
authors.lastname: Turek
authors.forename: Ali
authors.initials: A
authors.lastname: Keshavarzian
mesh_terms: D000818:Animals; D056926:CLOCK Proteins / Q000235:genetics* / Q000502:physiology; D018938:Caco-2 Cells; D002463:Cell Membrane Permeability / Q000187:drug effects / Q000235:genetics*; D002940:Circadian Rhythm / Q000187:drug effects / Q000235:genetics*; D000431:Ethanol / Q000494:pharmacology*; D041981:Gastrointestinal Tract / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D007408:Intestinal Absorption / Q000187:drug effects / Q000235:genetics*; D008297:Male; D056950:Period Circadian Proteins / Q000235:genetics* / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: C421902:PER2 protein, human; D056950:Period Circadian Proteins; D000431:Ethanol; D056926:CLOCK Proteins; C538943:CLOCK protein, human