Katsuhide Okunishi

The intestinal epithelium relies on rapid regeneration to maintain homeostasis after injury, and dysregulation of this process contributes to the pathogenesis of inflammatory bowel disease and colorectal cancer. Interleukin-11 (IL-11), a fibroblast-derived cytokine elevated in these diseases, has well-documented effects on stromal cells, but its direct action on intestinal epithelial cells remains poorly characterized. Here, we used mouse colon organoids as an isolated epithelial system to directly examine the effects of IL-11 on epithelial cells. IL-11 stimulation activated the canonical JAK/STAT3 pathway, as evidenced by increased STAT3 phosphorylation and Socs3 induction in a concentration-dependent manner. In a pipetting-based mechanical disruption model, IL-11 significantly enhanced organoid regeneration, increasing the number recovered. Although mechanical disruption dominated the overall transcriptional landscape, RNA-seq analysis identified coordinated upregulation of STAT3 target genes and proliferation-related pathways specifically in response to IL-11. Pharmacological inhibition of STAT3 attenuated the IL-11-induced promotion of organoid regeneration, confirming the requirement for STAT3-dependent signaling downstream of IL-11. Together, these findings demonstrate that IL-11 directly promotes intestinal epithelial regeneration after mechanical disruption through STAT3-dependent signaling, providing a mechanistic basis for its protective role in acute colonic injury.

A common variant in the RAB27A gene in adults was recently found to be associated with the fractional exhaled nitric oxide level, a marker of eosinophilic airway inflammation. The small GTPase Rab27 is known to regulate intracellular vesicle traffic, although its role in allergic responses is unclear. We demonstrated that exophilin-5, a Rab27-binding protein, was predominantly expressed in both of the major IL-33 producers, lung epithelial cells, and the specialized IL-5 and IL-13 producers in the CD44^hiCD62L^loCXCR3^lo pathogenic Th2 cell population in mice. Exophilin-5 deficiency increased stimulant-dependent damage and IL-33 secretion by lung epithelial cells. Moreover, it enhanced IL-5 and IL-13 production in response to TCR and IL-33 stimulation from a specific subset of pathogenic Th2 cells that expresses a high level of IL-33 receptor, which exacerbated allergic airway inflammation in a mouse model of asthma. Mechanistically, exophilin-5 regulates extracellular superoxide release, intracellular ROS production, and phosphoinositide 3-kinase activity by controlling intracellular trafficking of Nox2-containing vesicles, which seems to prevent the overactivation of pathogenic Th2 cells mediated by IL-33. This is the first report to our knowledge to establish the significance of the Rab27-related protein exophilin-5 in the development of allergic airway inflammation, and provides insights into the pathophysiology of asthma.

Previous genetic studies in mice have shown that functional loss of activin receptor–like kinase 7 (ALK7), a type I transforming growth factor-β receptor, increases lipolysis to resist fat accumulation in adipocytes. Although growth/differentiation factor 3 (GDF3) has been suggested to function as a ligand of ALK7 under nutrient-excess conditions, it is unknown how GDF3 production is regulated. Here, we show that a physiologically low level of insulin converts CD11c⁻ adipose tissue macrophages (ATMs) into GDF3-producing CD11c⁺ macrophages ex vivo and directs ALK7-dependent accumulation of fat in vivo. Depletion of ATMs by clodronate upregulates adipose lipases and reduces fat mass in ALK7-intact obese mice, but not in their ALK7-deficient counterparts. Furthermore, depletion of ATMs or transplantation of GDF3-deficient bone marrow negates the in vivo effects of insulin on both lipolysis and fat accumulation in ALK7-intact mice. The GDF3-ALK7 axis between ATMs and adipocytes represents a previously unrecognized mechanism by which insulin regulates both fat metabolism and mass.

Peripheral tolerance can be induced after the feeding of Ag, which is referred to as oral tolerance. We demonstrated in this study that the oral administration of OVA induced tolerance in an experimental model of asthma in mice, and investigated which cells function as the regulatory cells in the transfer of this oral tolerance. In OVA-fed mice, the percentage of eosinophils in bronchoalveolar lavage fluid, serum IgE levels, airway hyperresponsiveness, and mRNA levels of IL-13 and eotaxin were significantly lower than found in nonfed mice. Histological examination of lung tissue showed a suppression of the accumulation of inflammatory cells in the peribronchial area of OVA-fed mice. Feeding after the first immunization or between the first and the second immunization suppressed these findings, whereas feeding just before the airway Ag challenge did not. The suppression of disease in OVA-fed mice was successfully transferred by injection of whole spleen cells of OVA-fed mice. When CD11c⁺ dendritic cells (DCs) were removed from splenocytes, this transfer of suppression was completely abolished. The injection of splenic DCs purified from OVA-fed mice alone transferred the suppression, whereas the injection of splenic DCs from naive mice that were cocultured with OVA in vitro did not. These data suggest that not only CD4⁺ T cells, but also CD11c⁺ DCs induced by Ag feeding are important for the active transfer of oral tolerance in this murine experimental model of asthma.