ALDH1A Inhibition Suppresses Colitis and Alters α4β7 Integrin Expression on Activated T Cells in Mdr1a^-/- Mice

Area of Science:

• Immunology
• Gastroenterology
• Pharmacology

Background:

• Limited oral treatment options exist for inflammatory bowel disease (IBD).
• Aldehyde dehydrogenase 1A (ALDH1A) enzymes regulate immune cells and retinoic acid production in the gut, impacting intestinal diseases.
• Previous studies showed oral ALDH1A inhibitor WIN 18,446 suppressed acute colitis in mice.

Purpose of the Study:

• To evaluate the efficacy of ALDH1A inhibition using an oral drug (WIN 18,446) in a chronic mouse model of inflammatory bowel disease (IBD).
• To investigate the effects of ALDH1A inhibition on immune cell populations in the colon-draining lymph nodes (cMLN) during chronic colitis.

Main Methods:

• Chronic colitis was induced in *Mdr1a*^-/- mice via *H. bilis* inoculation.
• Mice received a diet containing the ALDH1A inhibitor WIN 18,446 starting one week before colitis induction and continuing throughout the study.
• Clinical symptoms, histological scores, and immune cell phenotypes (T cells, dendritic cells, B cells) in cMLN were analyzed.

Main Results:

• WIN 18,446 treatment significantly reduced clinical symptoms and improved histological scores of chronic colitis.
• Treatment led to decreased expression of the gut homing integrin α4β7 on T cells in cMLN.
• Increased expression of CD103 and alterations in dendritic cells, plasmacytoid dendritic cells, and B cells were observed in inhibitor-treated mice.

Conclusions:

• ALDH1A inhibition, using the oral agent WIN 18,446, demonstrates therapeutic potential for chronic inflammatory bowel disease (IBD) by modulating immune cell responses.
• This approach offers a potential new, orally administered treatment strategy for IBD.
• Further research is warranted to assess efficacy on active colitis and compare it with existing therapies.