Autophagy, a cytoprotective mechanism in intestinal epithelial cells, plays a crucial role in maintaining intestinal homeostasis. Beyond its cell-autonomous effects, the significance of autophagy in these cells is increasingly acknowledged in the dynamic interplay between the microbiota and the immune response. In the context of colon cancer, intestinal epithelium disruption of autophagy has been identified as a critical factor influencing tumor development. This disruption modulates the composition of the gut microbiota, eliciting an anti-tumoral immune response. Here, we report that Atg7 deficiency in intestinal epithelial cells shapes the intestinal microbiota leading to an associated limitation of colitis induced by Citrobacter rodentium infection. Mice with an inducible, intestinal epithelial-cell-specific deletion of the autophagy gene, Atg7, exhibited enhanced clearance of C. rodentium, mitigated hyperplasia, and reduced pathogen-induced goblet cell loss. This protective effect is linked to a higher proportion of neutrophils and phagocytic cells in the early phase of infection. At later stages, it is associated with the downregulation of pro-inflammatory pathways and an increase in Th17 and Treg responses-immune responses known for their protective roles against C. rodentium infection, modulated by specific gut microbiota. Fecal microbiota transplantation and antibiotic treatment approaches revealed that the Atg7-deficiency-shapped microbiota, especially Gram-positive bacteria, playing a central role in driving resistance to C. rodentium infection. In summary, our findings highlight that inhibiting autophagy in intestinal epithelial cells contributes to maintaining homeostasis and preventing detrimental intestinal inflammation through microbiota-mediated colonization resistance against C. rodentium. This underscores the central role played by autophagy in shaping the microbiota in promoting immune-mediated resistance against enteropathogens.
© 2025. The Author(s).

Phosphatase and tensin homolog (PTEN) is vital for B cell development, acting as a key negative regulator in the PI3K signaling pathway. We used CD23-cre to generate PTEN-conditional knockout mice (CD23-cKO) to examine the impact of PTEN mutation on peripheral B cells. Unlike mb1-cre-mediated PTEN deletion in early B cells, CD23-cKO mutants exhibited systemic inflammation with increased IL-6 production in mature B cells upon CpG stimulation. Inflammatory B cells in CD23-cKO mice showed elevated phosphatidylinositol 3-phosphate [PI(3)P] levels and increased TLR9 endosomal localization. Pharmacological inhibition of PI(3)P synthesis markedly reduced TLR9-mediated IL-6. Single-cell RNA-sequencing (RNA-seq) revealed altered endocytosis, BANK1, and NF-κB1 expression in PTEN-deficient B cells. Ectopic B cell receptor (BCR) expression on non-inflammatory mb1-cKO B cells restored BANK1 and NF-κB1 expression, enhancing TLR9-mediated IL-6 production. Our study highlights PTEN as a crucial inflammatory checkpoint, regulating TLR9/IL-6 axis by fine-tuning PI(3)P homeostasis. Additionally, BCR downregulation prevents the differentiation of inflammatory B cells in PTEN deficiency.
© 2024 The Author(s).

Phosphatase and tensin homolog (PTEN) is a negative regulator for PI3K signaling essential for B cell development. To explore the physiological effects of PTEN mutation on peripheral B cells, we generated CD23/cre-PTEN Flox/Flox (CD23-cKO) mice in this study to avoid the developmental arrest. The mutant mice develop systemic inflammation associated with B cell expansion in the early phase followed with a severe immune cell-infiltration in multiple vital organs. PTEN deficiency leads to an accumulation of PI(3)P, an increase of lysosomal recruitment of TLR9/p38 complex, and an aberrant activation of TLR9/IL-6 axis in B cells. Interestingly, cholesterol biosynthesis pathway is upregulated in mutant cells upon TLR9 engagement. A blockade of cholesterol biosynthesis by targeting SQLE greatly reduces the level of PI(3)P and the interaction between TLR9 and p38, which lowers the level of TLR9-induced IL-6. Thus, PTEN represents a critical metabolic checkpoint that fine-tunes lipid and cholesterol homeostasis to control TLR9-driven inflammation.

Invariant natural killer T (iNKT) cell development in the thymus depends on T cell receptor recognition of CD1d ligand on CD4/CD8 double-positive thymocytes. We previously reported that B7-CD28 co-stimulation is required for thymic iNKT cell development, but the cellular and molecular mechanisms underlying this co-stimulatory requirement are not understood. Here we report that CD28 expression on CD1d-expressing antigen-presenting T cells is required for thymic iNKT cell development. Mechanistically, antigen-presenting T cells provide co-stimulation through an unconventional mechanism, acquiring B7 molecules via CD28-dependent trogocytosis from B7-expressing thymic epithelial cells, dendritic cells, and B cells and providing critical B7 co-stimulation to developing iNKT cells. Thus, the present study demonstrates a mechanism of B7 co-stimulation in thymic T cell development by antigen-presenting T cells.
Published by Elsevier Inc.

Axin1 is a negative regulator of wingless-type MMTV integration site family, member 1 (Wnt)/β-catenin signaling with tumor-suppressor function. The Wnt pathway has a critical role in the intestine, both during homeostasis and cancer, but the role of Axin1 remains elusive.
We assessed the role of Axin1 in normal intestinal homeostasis, with control, epithelial-specific, Axin1-knockout mice (Axin1ΔIEC) and Axin2-knockout mice. We evaluated the tumor-suppressor function of Axin1 during chemically induced colorectal tumorigenesis and dextran sulfate sodium-induced colitis, and performed comparative gene expression profiling by whole-genome RNA sequencing. The clinical relevance of the Axin1-dependent gene expression signature then was tested in a database of 2239 clinical colorectal cancer (CRC) samples.
We found that Axin1 was dispensable for normal intestinal homeostasis and redundant with Axin2 for Wnt pathway down-regulation. Axin1 deficiency in intestinal epithelial cells rendered mice more susceptible to chemically induced colon carcinogenesis, but reduced dextran sulfate sodium-induced colitis by attenuating the induction of a proinflammatory program. RNA-seq analyses identified an interferon γ/T-helper1 immune program controlled by Axin1 that enhances the inflammatory response and protects against CRC. The Axin1-dependent gene expression signature was applied to human CRC samples and identified a group of patients with potential vulnerability to immune checkpoint blockade therapies.
Our study establishes, in vivo, that Axin1 has redundant function with Axin2 for Wnt down-regulation and infers a new role for Axin1. Physiologically, Axin1 stimulates gut inflammation via an interferon γ/Th1 program that prevents tumor growth. Linked to its T-cell-mediated effect, the colonic Axin1 signature offers therapeutic perspectives for CRC.
Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.