Activating transcription factor 5 (ATF5) controls intestinal tuft and goblet cell expansion upon succinate-induced type 2 immune responses in mice

Dietary succinate supplementation alleviates DSS-induced colitis via the IL-4Rα/Hif-1α Axis

Inflammatory bowel disease (IBD) remains a pressing global health challenge, necessitating novel therapeutic strategies. Succinate, a metabolite known for its role in type 2 immunity and tuft cell activation in the small intestine, presents its potential in IBD management. However, its impact on colonic inflammation has not been explored. Here, we demonstrate that succinate administration induces a type 2 immune response, significantly alleviating dextran sulfate sodium (DSS)-induced colonic inflammation. Succinate enhances antibacterial capacity, reduces intestinal permeability, and reshapes the colonic cytokine milieu. Mechanistically, succinate promotes myeloid cell expansion in peripheral blood, mesenteric lymph nodes, and the colonic lamina propria. The protective effects of succinate were abolished in Ccr2-/- mice, confirming the role of monocyte recruitment, but persisted in Rag1-/- mice, indicating independence from adaptive immunity. Adoptive transfer of monocytes from succinate-treated donors mitigated intestinal inflammation in recipient mice. Transcriptomic analysis revealed heightened expression of Il1b and Il6, and higher lactate production in monocytes upon lipopolysaccharide (LPS) stimulation, highlighting a reprogrammed pro-inflammatory trained immunity phenotype. Finally, we identify the IL-4Rα/Hif-1α axis is critical for succinate-mediated protection. These findings reveal the ability of succinate to reprogram monocytes into protective intestinal macrophages via induction of type 2 response, restoring homeostasis through enhanced barrier function and immune modulation. Our study positions thus uncover succinate as a promising therapeutic candidate for IBD.

The potential of orally exposed risk factors and constituents aggravating food allergy: Possible mechanism and target cells

Food allergy is a significant concern for the health of humans worldwide. In addition to dietary exposure of food allergens, genetic and environmental factors also play an important role in the development of food allergy. However, only the tip of the iceberg of risk factors in food allergy has been identified. The importance of food allergy caused by orally exposed risk factors and constituents, including veterinary drugs, pesticides, processed foods/derivatives, nanoparticles, microplastics, pathogens, toxins, food additives, dietary intake of salt/sugar/total fat, vitamin D, and therapeutic drugs, are highlighted and discussed in this review. Moreover, the epithelial barrier hypothesis, which is closely associated with the occurrence of food allergy, is also introduced. Additionally, several orally exposed risk factors and constituents that have been reported to disrupt the epithelial barrier are elucidated. Finally, the possible mechanisms and key immune cells of orally exposed risk factors and constituents in aggravating food allergy are overviewed. Further work should be conducted to define the specific mechanism by which these risk factors and constituents are driving food allergy, which will be of central importance to the targeted therapy of food allergy.

G protein subunit Gγ13-mediated signaling pathway is critical to the inflammation resolution and functional recovery of severely injured lungs

Tuft cells are a group of rare epithelial cells that can detect pathogenic microbes and parasites. Many of these cells express signaling proteins initially found in taste buds. It is, however, not well understood how these taste signaling proteins contribute to the response to the invading pathogens or to the recovery of injured tissues. In this study, we conditionally nullified the signaling G protein subunit Gγ13 and found that the number of ectopic tuft cells in the injured lung was reduced following the infection of the influenza virus H1N1. Furthermore, the infected mutant mice exhibited significantly larger areas of lung injury, increased macrophage infiltration, severer pulmonary epithelial leakage, augmented pyroptosis and cell death, greater bodyweight loss, slower recovery, worsened fibrosis and increased fatality. Our data demonstrate that the Gγ13-mediated signal transduction pathway is critical to tuft cells-mediated inflammation resolution and functional repair of the damaged lungs.To our best knowledge, it is the first report indicating subtype-specific contributions of tuft cells to the resolution and recovery.

Possible connection between intestinal tuft cells, ILC2s and obesity

Intestinal tuft cells (TCs) are defined as chemosensory cells that can "taste" danger and induce immune responses. They play a critical role in gastrointestinal parasite invasion, inflammatory bowel diseases and high-fat diet-induced obesity. Intestinal IL-25, the unique product of TCs, is a key activator of type 2 immunity, especially to promote group 2 innate lymphoid cells (ILC2s) to secret IL-13. Then the IL-13 mainly promotes intestinal stem cell (ISCs) proliferation into TCs and goblet cells. This pathway formulates the circuit in the intestine. This paper focuses on the potential role of the intestinal TC, ILC2 and their circuit in obesity-induced intestinal damage, and discussion on further study and the potential therapeutic target in obesity.