[Show abstract][Hide abstract] ABSTRACT: CEACAM1, CEACAM5, and CEACAM6 represent 3 of the CEACAM (carcinoembryonic antigen-related cell adhesion molecule) subfamily members expressed on intestinal epithelial cells (IECs). Deficiency in their expression, as seen in inflammatory bowel disease (IBD), results in the lack of activation of CD8+ regulatory T cells in the mucosa. Since CEACAM expression was shown to be regulated by the transcription factor SOX9, we sought to determine whether the defect in CEACAM expression in IBD was related to aberrant SOX9 expression.
IECs and lamina propria lymphocytes (LPLs) were freshly isolated from colonic tissues. T84 and HT29 16E cells were cocultured with LPLs. SOX9 and CEACAM subfamily member expression was assessed by real-time polymerase chain reaction (PCR), Western blot, immunohistochemistry, and immunofluorescence.
In Crohn's disease (CD) but not in ulcerative colitis (UC), a significant reduction in mRNA and protein expression for CEACAM1 and 5 was noted; in contrast, no difference in SOX9 mRNA expression was seen. However, nuclear SOX9 immunostaining was increased in CD IECs. Furthermore, SOX9 protein was reduced in the cytoplasm of LPL-stimulated T84 and HT29 16E cells, while CEACAM5 expression was increased.
The defect in CEACAM family members in CD IECs appears to be related to the aberrant nuclear localization of SOX9. Changes in SOX9 expression in the CD mucosa relate to the local microenvironment and altered IEC:LPL crosstalk.
[Show abstract][Hide abstract] ABSTRACT: Intestinal lymphoepithelial interactions occur in the epithelium and the subepithelial space. We asked whether normal, Crohn's disease (CD), or ulcerative colitis (UC) lamina propria lymphocytes (LPL) could promote intestinal epithelial cell (IEC) growth and differentiation.
T84 cells were cocultured with isolated LPL. IECs were then lysed and subjected to measurement of intestinal alkaline phosphatase (IAP) activity; Western blot analysis for MAPK and Akt activation; and real-time polymerase chain reaction to assess caudal-related homeoprotein 2 (CDX2) messenger RNA (mRNA) levels. Tissue sections were immunostained for evidence of mitogen-activated protein kinase (MAPK) and phosphatidylinositol 3-kinase (PI3K) activation, CDX2, and IAP; and CDX2 mRNA expression was assessed in human colonic biopsy specimens.
IAP activity was increased in T84 cells cocultured for 8 days with normal LPL (P < .05) and even greater with CD LPL (P < .001). Crypt IECs in active CD mucosa expressed IAP ex vivo. Phospho-MAPK (extracellular signal-regulated kinase 1/2, p38, and c-Jun-N-terminal kinase) and phospho-Akt were seen as early as 30 minutes after coculture. MAPK activation was greatest in T84 cells cocultured with CD LPL. There was a specific increase in Phospho-p38 MAPK and Phospho-Akt staining in the nuclei of crypt IECs in active vs inactive CD, normal mucosa, and UC mucosa. CDX2 mRNA expression was increased in CD LPL cocultured T84 cells, which did not correlate with CDX2 protein localization ex vivo.
There is cross talk between LPL and IECs, which leads to IEC differentiation. The differentiation is accelerated in CD mucosa.