title: [Role of cyclic adenosine monophosphate(cAMP) in the regulation of intestinal epithelial barrier function under hypoxia].
abstract: OBJECTIVE
  To investigate the role of cyclic adenosine monophosphate(cAMP) in the regulation of intestinal epithelial barrier function under hypoxia.
  
  
  METHODS
  Intestinal epithelial barrier was established by Caco-2 monolayers. Cells were divided into four groups: normoxia (Nx), normoxia plus Forskolin(Nx+FSK), hypoxia(Hx), hypoxia plus SQ22536(Hx+SQ22536). cAMP concentrations of different groups were assessed by cAMP enzyme immunoassay kit. RT-PCR and Western blotting were used to detect the mRNA and protein expressions of claudin-1 and occludin under normoxic and hypoxic condition. Caco-2 monolayers were grown on Millicell filters, and transepithelial electrical resistance(TER) was measured using a Millipore electric resistance system.
  
  
  RESULTS
  The concentration of cAMP under hypoxic conditions(Hx group) was higher compared with Nx group [(6.30±0.50) pmol/L vs. (2.38±0.18) pmol/L, P<0.01]. At the same time, both mRNA and protein expressions of claudin-1 and occluding were lower in Hx group than those in Nx group(all P<0.05). TER decreased by 76.30±0.64(P<0.01). When the monolayers were exposed to hypoxia plus SQ22536 (Hx+SQ22536 group), the concentration of cAMP was(2.12±0.23) pmol/L, which was lower than that under hypoxic conditions(Hx group, P<0.01). Both mRNA and protein expressions of claudin-1 and occludin were higher compared to Hx group (all P<0.01). TER increased by 32.96±2.16 (P<0.05).
  
  
  CONCLUSIONS
  When Caco-2 cells are exposed to hypoxia, barrier function, claudin-1 and occludin expression are diminished in parallel with a high level of intracellular cAMP compared with the normoxic condition. Inhibition of the intracellular cAMP level under hypoxia can maintain the intestinal epithelial function through regulating the claudin-1 and occludin expression and attenuate the permeability of intestinal mucosa.
authors.affiliation: Department of General Surgery, Xinqiao Hospital, The Third Military Medical University, Chongqing 400037, China. hwbyang@126.com.
authors.forename: Yang
authors.initials: Y
authors.lastname: Yang
authors.forename: Wen-Sheng
authors.initials: WS
authors.lastname: Wang
authors.forename: Yuan
authors.initials: Y
authors.lastname: Qiu
authors.forename: Li-Hua
authors.initials: LH
authors.lastname: Sun
authors.forename: Hua
authors.initials: H
authors.lastname: Yang
mesh_terms: D000249:Adenosine Monophosphate; D018938:Caco-2 Cells; D062445:Claudin-1 / Q000378:metabolism; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism; D007422:Intestines; D062793:Occludin / Q000378:metabolism
chemical_list: D062445:Claudin-1; D062793:Occludin; D000249:Adenosine Monophosphate