Butyrate enhances intestinal epithelial barrier function via up-regulation of tight junction protein Claudin-1 transcription.
BACKGROUND
Barrier function is essential for the maintenance of normal intestinal function. Dysregulation of the intestinal barrier underlies a wide range of disorders.


OBJECTIVE
Previously, we found that sodium butyrate (NaB) decreased the molecular permeability of intestinal barrier in vivo model, but the mechanism by which NaB facilitated the tightness of tight junctions (TJs) in small intestinal epithelium needed further studies.


METHODS
In vitro culture of the cdx2-IEC monolayer was used to mimic barrier function. The TJs were assessed by transepithelial electrical resistance (TEER) and paracellular flux of fluorescein isothiocyanate-conjugated dextran 40,000 (FD-40), Western blot, Q-RT-PCR, and immunofluorescence. Promoter and chromatin immunoprecipitation (ChIP) assays were also done to analyze the Claudin-1 gene.


RESULTS
NaB decreased FD-40 flux, increased TEER and TJ protein Claudin-1 expression, induced ZO-1 and Occludin redistribution in cellular membrane, and reversed the damage effect after calcium (Ca(2+)) switch assay. Silencing Claudin-1 prevented protective function of NaB from enhancing intestinal barrier integrity. Further studies demonstrated that NaB increased Claudin-1 transcription by facilitating the interaction between transcription factor SP1 and a specific motif within the promoter region of Claudin-1. This SP1 binding motif was located upstream of the coding region (-138 to -76 bp) and indispensable for the transcription of Claudin-1 following NaB treatment. ChIP assay confirmed the association between SP1 and Claudin-1 promoter, and the elimination of the SP1 binding site by point mutation resulted in a significant loss of Claudin-1 transcription after NaB dealing.


CONCLUSIONS
NaB enhanced intestinal barrier function through increasing Claudin-1 transcription via facilitating the association between SP1 and Claudin-1 promoter.
Division of General Surgery, Peking University First Hospital, Peking University, 8 Xi ShiKu Street, Beijing, 100034, People's Republic of China. wang12hong3bo@126.com
Hong-Bo
HB
Wang
Peng-Yuan
PY
Wang
Xin
X
Wang
Yuan-Lian
YL
Wan
Yu-Cun
YC
Liu
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D002087:Butyrates / Q000494:pharmacology*; D002460:Cell Line; D047369:Chromatin Immunoprecipitation; D062445:Claudin-1 / Q000235:genetics / Q000378:metabolism*; D007413:Intestinal Mucosa / Q000187:drug effects* / Q000502:physiology*; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D034622:RNA Interference; D051381:Rats; D016329:Sp1 Transcription Factor / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic; D015854:Up-Regulation / Q000187:drug effects*
D002087:Butyrates; D062445:Claudin-1; C568114:Cldn1 protein, rat; D016329:Sp1 Transcription Factor