Butyrate suppresses hypoxia-inducible factor-1 activity in intestinal epithelial cells under hypoxic conditions.
Interaction between the products of intestinal bacteria and the intestinal epithelial cells is a key event in understanding the biological, physiological, and pathological functions of the intestinal epithelium. Here, we examined the effect of butyrate, one of the major intestinal bacterial products, on hypoxia-inducible factor-1 (HIF-1) activity under hypoxic conditions in intestinal epithelial cells. HIF-1 activity was assessed by luciferase assay using cytoplasmic extracts of intestinal epithelial cells, Caco-2, and IEC-6 cells. These cells were transiently transfected with hypoxia response element (HRE)-luciferase reporter plasmids and cultured under hypoxic conditions in the presence or absence of sodium butyrate (NaB). The effect of NaB on HRE DNA binding activity in Caco-2 cells under hypoxic conditions was assessed by electrophoretic mobility shift assay. Expression of a hypoxia-responsive gene encoding intestinal trefoil factor (ITF) in Caco-2 cells after NaB treatment was assessed using reverse-transcription PCR. The barrier function of Caco-2 cells under hypoxic conditions was also evaluated by transepithelial electrical resistance measurement. NaB suppressed up-regulation of HIF-1 transcriptional activity under hypoxic conditions in Caco-2 and IEC-6 cells. In parallel, NaB reduced HRE DNA binding activity under the same conditions. Furthermore, NaB down-regulated enhanced transcription of ITF gene. Addition of NaB under hypoxic conditions delayed recovery of transepithelial electrical resistance of the monolayers after hypoxia-reoxygenation treatment. These findings indicate that NaB suppresses HIF-1 transcriptional activity on hypoxia-responsive genes by reducing the HRE DNA binding activity under hypoxic conditions in intestinal epithelial cells.
Miki
Keita
K
Second Department of Surgery, Hamamatsu University School of Medicine, Hamamatsu 431-3192, Japan. k-miki3@mug.biglobe.ne.jp
Unno
Naoki
N
Nagata
Toshi
T
Uchijima
Masato
M
Konno
Hiroyuki
H
Koide
Yukio
Y
Nakamura
Satoshi
S
D000818:Animals; D002087:Butyrates / Q000494:pharmacology*; D018938:Caco-2 Cells; D002460:Cell Line; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D015536:Down-Regulation; D004594:Electrophysiology; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism*; D005227:Fatty Acids / Q000737:chemistry; D006801:Humans; D000860:Hypoxia; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D007413:Intestinal Mucosa / Q000378:metabolism*; D007422:Intestines / Q000187:drug effects; D008156:Luciferases / Q000378:metabolism; D009077:Mucins / Q000378:metabolism; D009124:Muscle Proteins / Q000378:metabolism; D010455:Peptides / Q000378:metabolism; D010957:Plasmids / Q000378:metabolism; D051381:Rats; D020218:Response Elements; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012978:Sodium Oxybate / Q000494:pharmacology; D013997:Time Factors; D014157:Transcription Factors / Q000378:metabolism*; D014162:Transfection; D000071164:Trefoil Factor-2; D015854:Up-Regulation
D002087:Butyrates; D005227:Fatty Acids; C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D009077:Mucins; D009124:Muscle Proteins; D010455:Peptides; D014157:Transcription Factors; D000071164:Trefoil Factor-2; D012978:Sodium Oxybate; D008156:Luciferases