Butyrate transcriptionally enhances peptide transporter PepT1 expression and activity.
BACKGROUND
PepT1, an intestinal epithelial apical di/tripeptide transporter, is normally expressed in the small intestine and induced in colon during chronic inflammation. This study aimed at investigating PepT1 regulation by butyrate, a short-chain fatty acid produced by commensal bacteria and accumulated inside inflamed colonocyte.


RESULTS
We found that butyrate treatment of human intestinal epithelial Caco2-BBE cells increased human PepT1 (hPepT1) promoter activity in a dose- and time-dependent manner, with maximal activity observed in cells treated with 5 mM butyrate for 24 h. Under this condition, hPepT1 promoter activity, mRNA and protein expression levels were increased as assessed by luciferase assay, real-time RT-PCR and Western blot, respectively. hPepT1 transport activity was accordingly increased by approximately 2.5-fold. Butyrate did not alter hPepT1 mRNA half-life indicating that butyrate acts at the transcriptional level. Molecular analyses revealed that Cdx2 is the most important transcription factor for butyrate-induced increase of hPepT1 expression and activity in Caco2-BBE cells. Butyrate-activated Cdx2 binding to hPepT1 promoter was confirmed by gel shift and chromatin immunoprecipitation. Moreover, Caco2-BBE cells overexpressing Cdx2 exhibited greater hPepT1 expression level than wild-type cells. Finally, treatment of mice with 5 mM butyrate added to drinking water for 24 h increased colonic PepT1 mRNA and protein expression levels, as well as enhanced PepT1 transport activity in colonic apical membranes vesicles.


CONCLUSIONS
Collectively, our results demonstrate that butyrate increases PepT1 expression and activity in colonic epithelial cells, which provides a new understanding of PepT1 regulation during chronic inflammation.
Department of Medicine, Division of Digestive Diseases, Emory University School of Medicine, Atlanta, Georgia, United States of America.
Guillaume
G
Dalmasso
Hang Thi Thu
HT
Nguyen
Yutao
Y
Yan
Laetitia
L
Charrier-Hisamuddin
Shanthi V
SV
Sitaraman
Didier
D
Merlin
D000107:Acetylation; D001665:Binding Sites; D015153:Blotting, Western; D020148:Butyric Acid / Q000494:pharmacology*; D000071616:CDX2 Transcription Factor; D018938:Caco-2 Cells; D047369:Chromatin Immunoprecipitation; D004742:Enhancer Elements, Genetic; D006657:Histones / Q000378:metabolism; D018398:Homeodomain Proteins / Q000378:metabolism; D006801:Humans; D000074011:Peptide Transporter 1; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D027981:Symporters / Q000235:genetics* / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects*
D000071616:CDX2 Transcription Factor; C491270:CDX2 protein, human; D006657:Histones; D018398:Homeodomain Proteins; D000074011:Peptide Transporter 1; D012333:RNA, Messenger; C082186:SLC15A1 protein, human; D027981:Symporters; D020148:Butyric Acid