Intestinal CCL25 expression is increased in colitis and correlates with inflammatory activity

Area of Science:

• Gastroenterology
• Immunology
• Hepatology

Background:

• The CCR9/CCL25 axis is crucial for lymphocyte homing to the gut.
• This pathway's role in colonic inflammation and its link to liver disease, specifically primary sclerosing cholangitis (PSC), is not well understood.
• While CCL25 is typically found in the small intestine, its expression in the colon during inflammation needs further investigation.

Purpose of the Study:

• To investigate the role of the CCR9/CCL25 pathway in colonic inflammation associated with inflammatory bowel disease (IBD).
• To determine if this pathway contributes to lymphocyte recruitment in the colon and potentially links to liver inflammation in PSC.
• To assess the correlation between CCL25 expression, disease activity, and T-cell infiltration in the colon.

Main Methods:

• Analysis of colonic CCL25 expression in patients with active colitis compared to healthy controls.
• Correlation of CCL25 levels with endoscopic Mayo score and mucosal TNFα expression.
• Quantification of CCR9(+) T-cells (CD4+ and CD8+) in inflamed colonic tissue versus normal colon.
• Assessment of CCR9(+) lymphocyte adhesion to stimulated hepatic sinusoidal endothelium under flow conditions.

Main Results:

• Colonic CCL25 expression is upregulated in active colitis and correlates with disease severity and TNFα levels.
• A significant proportion of infiltrating T-cells in colitis are CCR9(+) effector lymphocytes (approx. 90% CD4+, 30% CD8+), compared to <10% in normal colon.
• CCR9(+) lymphocytes exhibit enhanced adhesion to liver sinusoidal endothelial cells, suggesting a mechanism for liver recruitment.

Conclusions:

• The CCR9/CCL25 pathway is implicated in the pathogenesis of ulcerative colitis.
• This pathway correlates with colonic inflammatory burden and may contribute to overlapping lymphocyte recruitment between the inflamed colon and liver.
• Findings support the CCR9/CCL25 axis as a potential therapeutic target in IBD and related liver diseases like PSC.