Macrophages In Inflamed Mucosa Research Articles

A breakthrough in probiotics: Clostridium butyricum regulates gut homeostasis and anti-inflammatory response in inflammatory bowel disease.

Intestinal immune homeostasis is regulated by gut microbiota, including beneficial and pathogenic microorganisms. Imbalance in gut bacterial constituents provokes host proinflammatory responses causing diseases such as inflammatory bowel disease (IBD). The development of next-generation sequencing technology allows the identification of microbiota alterations in IBD. Several studies have shown reduced diversity in the gut microbiota of patients with IBD. Advances in gnotobiotic technology have made possible analysis of the role of specific bacterial strains in immune cells in the intestine. Using these techniques, we have shown that Clostridium butyricum as a probiotic induces interleukin-10-producing macrophages in inflamed mucosa via the Toll-like receptor 2/myeloid differentiation primary response gene 88 pathway to prevent acute experimental colitis. In this review, we focus on the new approaches for the role of specific bacterial strains in immunological responses, as well as the potential of bacterial therapy for IBD treatments.

A Single Strain of Clostridium butyricum Induces Intestinal IL-10-Producing Macrophages to Suppress Acute Experimental Colitis in Mice

Imbalance in gut bacterial composition provokes host proinflammatory responses causing diseases such as colitis. Colonization with a mixture of Clostridium species from clusters IV and XIVa was shown to suppress colitis through the induction of IL-10-producing regulatory T (Treg) cells. We demonstrate that a distinct Clostridium strain from cluster I, Clostridium butyricum (CB), prevents acute experimental colitis in mice through induction of IL-10, ananti-inflammatory cytokine. However, while CBtreatmenthad no effect on IL-10 production byTcells,IL-10-producing F4/80(+)CD11b(+)CD11c(int) macrophages accumulated in the inflamed mucosa after CB treatment. CB directly triggered IL-10 production by intestinal macrophages in inflamed mucosa via the TLR2/MyD88 pathway. The colitis-preventing effect of CB was negated in macrophage-specific IL-10-deficient mice, suggesting that induction of IL-10 by intestinal macrophages is crucial for the probiotic action of CB. Collectively, CB promotes IL-10 production by intestinal macrophages in inflamed mucosa, thereby preventing experimental colitis in mice.

The MUC13 cell-surface mucin protects against intestinal inflammation by inhibiting epithelial cell apoptosis

Background and AimsThe MUC13 transmembrane mucin is highly and constitutively expressed in the small and large intestine. Although MUC13 polymorphisms have been associated with human inflammatory bowel diseases and susceptibility...

Mucosal IL-8 and TGF-β recruit blood monocytes: evidence for cross-talk between the lamina propria stroma and myeloid cells

The lamina propria of the gastrointestinal mucosa contains the largest population of mononuclear phagocytes in the body, yet little is known about the cellular mechanisms that regulate mononuclear cell recruitment to noninflamed and inflamed intestinal mucosa. Here, we show that intestinal macrophages do not proliferate. We also show that a substantial proportion of intestinal macrophages express chemokine receptors for interleukin (IL)-8 and transforming growth factor-beta (TGF-beta), and a smaller proportion expresses receptors for N-formylmethionyl-leucyl-phenylalanine and C5a, but, surprisingly, they do not migrate to the corresponding ligands. In contrast, autologous blood monocytes, which express the same receptors, do migrate to the ligands. Blood monocytes also migrate to conditioned medium (CM) derived from lamina propria extracellular matrix, which we show contains IL-8 and TGF-beta that are produced by epithelial cells and lamina propria mast cells. This migration is specific to IL-8 and TGF-beta, as preincubation of the stroma-CM with antibodies to IL-8 and TGF-beta significantly blocked monocyte chemotaxis to the stromal products. Together, these findings indicate that blood monocytes are the exclusive source of macrophages in the intestinal mucosa and underscore the central role of newly recruited blood monocytes in maintaining the macrophage population in noninflamed mucosa and in serving as the exclusive source of macrophages in inflamed mucosa.

IL-15 is highly expressed in inflammatory bowel disease and regulates local T cell-dependent cytokine production.

IL-15 shares biological activities but no significant sequence homology with IL-2. It induces T cell recruitment to sites of inflammation, T cell proliferation, and cytokine production and rescue from apoptosis. The aim of this study was to investigate expression of IL-15 and its effects on proinflammatory cytokine production in inflammatory bowel disease (IBD). Immunohistochemistry demonstrated local IL-15 production by macrophages in inflamed mucosa from IBD patients. Isolated lamina propria mononuclear cells from these patients but not from controls produced IL-15 when stimulated with LPS or IFN-gamma. Moreover, lamina propria T cells (LP-T) from IBD patients were more responsive to IL-15 as compared with controls, and IL-15 alone without a primary T cell stimulus induced IFN-gamma and TNF production by isolated IBD LP-T cells, especially by LP-T cells from patients with Crohn's disease. LP-T cells from IBD patients could induce CD40-CD40 ligand (CD40L) interaction-dependent TNF and IL-12 production by monocytes in a coculture system. This capacity of LP-T cells was strongly enhanced by preincubation in IL-15 and was the result of higher CD40L expression after culture in IL-15. These data indicate that IL-15 is overexpressed in the inflamed mucosa in IBD and that IL-15 enhances local T cell activation, proliferation, and proinflammatory cytokine production by both T cells and macrophages, the latter via a CD40-CD40L interaction-dependent mechanism. Treatment directed against IL-15 may have therapeutic potential in IBD.