TNF-α-induced down-regulation of CDX2 suppresses MEP1A expression in colitis

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Abstract

Background/aims: High levels of pro-inflammatory cytokines are linked to inflammatory bowel disease (IBD). The transcription factor Caudal-related homeobox transcription factor 2 (CDX2) plays a crucial role in differentiation of intestinal epithelium and regulates IBD-susceptibility genes, including meprin 1A (MEP1A). The aim was to investigate the expression of CDX2 and MEP1A in colitis; to assess if they are regulated by tumor necrosis factor-α (TNF-α), and finally to reveal if CDX2 is involved in a TNF-α-induced down-regulation of MEP1A. Methods: Expression of CDX2 and MEP1A was investigated in colonic biopsies of ulcerative colitis (UC) patients and in dextran sodium sulfate (DSS)-induced colitis. CDX2 protein expression was investigated by immunoblotting and immunohistochemical procedures. CDX2 and MEP1A regulation was examined in TNF-α-treated Caco-2 cells by reverse transcription-polymerase chain reaction and with reporter gene assays, and the effect of anti-TNF-α treatment was assessed using infliximab. Finally, in vivo CDX2–DNA interactions were investigated by chromatin immunoprecipitation. Results: The CDX2 and MEP1A mRNA expression was significantly decreased in active UC patients and in DSS-colitis. Colonic biopsy specimens from active UC showed markedly decreased CDX2 staining. TNF-α treatment diminished the CDX2 and MEP1A mRNA levels, a decrease which, was counteracted by infliximab treatment. Reporter gene assays showed significantly reduced CDX2 and MEP1A activity upon TNF-α stimulation. Finally, TNF-α impaired the ability of CDX2 to interact and activate its own, as well as the MEP1A expression. Conclusions: The present results indicate that a TNF-α-mediated down-regulation of CDX2 can be related to suppressed expression of MEP1A during intestinal inflammation.

Highlights

► CDX2 regulates MEP1A expression in intestinal epithelial cells. ► CDX2 and MEP1A expression are correlatively decreased in intestinal inflammation. ► High levels of TNF-α suppresses the ability of CDX2 to activate MEP1A expression. ► A dysfunction of CDX2 is a key contributor in the pathogenesis of IBD.

Abbreviations

CD
Crohn's disease
CDX2
Caudal-related homeobox transcription factor 2
ChIP
chromatin immunoprecipitation
CK20
cytokeratin 20
CLDN2
claudin-2
DAI
disease activity index
DSS
dextran sodium sulfate
GAPDH
glyceraldehyde 3-phosphate dehydrogenase
GSK3β
glycogen synthase kinase-3β
HA
hemagglutinin
HNF4α
hepatocyte nuclear factor 4 alpha
IBD
inflammatory bowel disease
IEC
intestinal epithelial cell
IFX
infliximab
IHC
immunohistochemistry
INF-γ
interferon-γ
MEP1A
meprin 1A
MUC2
mucin 2
NF
nuclear factor
PEPT1
peptide transporter 1
qRT-PCR
quantitative reverse-transcription polymerase chain reaction
RPLP0
ribosomal protein large p0
TNF-α
tumor necrosis factor-α
UC
ulcerative colitis

Keywords

DSS-colitis
Inflammatory bowel disease
Infliximab
Intestine
Tumor necrosis factor
Ulcerative colitis

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