Caudal type homeobox 2 expression induced by leukocytapheresis might be associated with mucosal healing in ulcerative colitis

The transcription factor Cdx2 regulates inflammasome activity through expression of the NLRP3 suppressor TRIM31 to maintain intestinal homeostasis

The intestine-specific transcription factor Cdx2 is essential for intestinal homeostasis and has been implicated in the pathogenesis of disorders including inflammatory bowel disease. However, the mechanism by which Cdx2 influences intestinal disease is not clear. Here, we present evidence supporting a novel Cdx2–TRIM31–NLRP3 (NLR family, pyrin domain containing 3) signaling pathway, which may represent a mechanistic means by which Cdx2 impacts intestinal inflammation. We found that conditional loss of Cdx function resulted in an increase in proinflammatory cytokines, including tumor necrosis factor alpha, interleukin (IL)-1β, and IL-6, in the mouse colon. We further show that TRIM31, which encodes a suppressor of NLRP3 (a central component of the NLRP3 inflammasome complex) is a novel Cdx2 target gene and is attenuated in the colon of Cdx conditional mutants. Consistent with this, we found that attenuation of TRIM31 in Cdx mutant intestine occurs concomitant with elevated levels of NLRP3 and an increase in inflammasome products. We demonstrate that specific inhibition of NLRP3 activity significantly reduced IL-1β and IL-6 levels and extended the life span of Cdx conditional mutants, reflecting the therapeutic potential of targeting NLRP3. Tumor necrosis factor-alpha levels were also induced independent of NLRP3, potentially via elevated activity of the proinflammatory NF-κB signaling pathway in Cdx mutants. Finally, in silico analysis of ulcerative colitis patients revealed attenuation of CDX2 and TRIM31 expression coincident with enhanced expression of proinflammatory cytokines. We conclude that the novel Cdx2–TRIM31–NLRP3 signaling pathway promotes proinflammatory cytokine expression, and its inhibition may have therapeutic potential in human intestinal diseases.

Immunological Mechanisms of Adsorptive Cytapheresis in Inflammatory Bowel Disease

Ulcerative colitis and Crohn's disease are the two main forms of inflammatory bowel disease (IBD). The study of immunological pathways involved in the onset of IBD is of fundamental importance to identify potential biological markers of disease activity and specific targets for therapy. Removing excess and activated circulating leukocytes with adsorptive cytapheresis has been shown to be a potentially effective treatment for patients with an inflamed bowel. Adsorptive cytapheresis is a non-pharmacological approach for active IBD, in which known sources of inflammatory cytokines such as activated myeloid lineage leucocytes are selectively depleted from the circulatory system. The decrease in inflammatory load caused by removing these cells is thought to enhance drug therapy and thereby promote disease remission. The benefit of cytapheresis appears to rest upon its ability to reduce levels of certain immune cell populations; however, whether this depletion results in further changes in lymphocyte populations and cytokine production needs further clarification. In this review, we aim to summarize existing evidence on the role of cytapheresis in patients with IBD, its effect on cytokine levels and cellular populations, and to discuss its potential impact on disease activity.