Cytokine tuning of intestinal epithelial function

The intestine serves as both our largest single barrier to the external environment and the host of more immune cells than any other location in our bodies. Separating these potential combatants is a single layer of dynamic epithelium composed of heterogeneous epithelial subtypes, each uniquely adapted to carry out a subset of the intestine’s diverse functions. In addition to its obvious role in digestion, the intestinal epithelium is responsible for a wide array of critical tasks, including maintaining barrier integrity, preventing invasion by microbial commensals and pathogens, and modulating the intestinal immune system. Communication between these epithelial cells and resident immune cells is crucial for maintaining homeostasis and coordinating appropriate responses to disease and can occur through cell-to-cell contact or by the release or recognition of soluble mediators. The objective of this review is to highlight recent literature illuminating how cytokines and chemokines, both those made by and acting on the intestinal epithelium, orchestrate many of the diverse functions of the intestinal epithelium and its interactions with immune cells in health and disease. Areas of focus include cytokine control of intestinal epithelial proliferation, cell death, and barrier permeability. In addition, the modulation of epithelial-derived cytokines and chemokines by factors such as interactions with stromal and immune cells, pathogen and commensal exposure, and diet will be discussed

IL-7 promotes T cell proliferation through destabilization of p27Kip1

Interleukin (IL)-7 is required for survival and homeostatic proliferation of T lymphocytes. The survival effect of IL-7 is primarily through regulation of Bcl-2 family members; however, the proliferative mechanism is unclear. It has not been determined whether the IL-7 receptor actually delivers a proliferative signal or whether, by promoting survival, proliferation results from signals other than the IL-7 receptor. We show that in an IL-7–dependent T cell line, cells protected from apoptosis nevertheless underwent cell cycle arrest after IL-7 withdrawal. This arrest was accompanied by up-regulation of the cyclin-dependent kinase inhibitor p27Kip1 through a posttranslational mechanism. Overexpression of p27Kip1 induced G1 arrest in the presence of IL-7, whereas knockdown of p27Kip1 by small interfering RNA promoted S phase entry after IL-7 withdrawal. CD4 or CD8 T cells transferred into IL-7–deficient hosts underwent G1 arrest, whereas 27Kip1-deficient T cells underwent proliferation. We observed that IL-7 withdrawal activated protein kinase C (PKC)θ and that inhibition of PKCθ with a pharmacological inhibitor completely blocked the rise of p27Kip1 and rescued cells from G1 arrest. The conventional pathway to breakdown of p27Kip1 is mediated by S phase kinase-associated protein 2; however, our evidence suggests that PKCθ acts via a distinct, unknown pathway inducing G1 arrest after IL-7 withdrawal from T cells. Hence, IL-7 maintains T cell proliferation through a novel pathway of p27Kip1 regulation

Interleukin 7 Receptor Control of T Cell Receptor γ Gene Rearrangement: Role of Receptor-associated Chains and Locus Accessibility

VDJ recombination of T cell receptor and immunoglobulin loci occurs in immature lymphoid cells. Although the molecular mechanisms of DNA cleavage and ligation have become more clear, it is not understood what controls which target loci undergo rearrangement. In interleukin 7 receptor (IL-7R)α−/− murine thymocytes, it has been shown that rearrangement of the T cell receptor (TCR)-γ locus is virtually abrogated, whereas other rearranging loci are less severely affected. By examining different strains of mice with targeted mutations, we now observe that the signaling pathway leading from IL-7Rα to rearrangement of the TCR-γ locus requires the γc receptor chain and the γc-associated Janus kinase Jak3. Production of sterile transcripts from the TCR-γ locus, a process that generally precedes rearrangement of a locus, was greatly repressed in IL-7Rα−/− thymocytes. The repressed transcription was not due to a lack in transcription factors since the three transcription factors known to regulate this locus were readily detected in IL-7Rα−/− thymocytes. Instead, the TCR-γ locus was shown to be methylated in IL-7Rα−/− thymocytes. Treatment of IL-7Rα−/− precursor T cells with the specific histone deacetylase inhibitor trichostatin A released the block of TCR-γ gene rearrangement. This data supports the model that IL-7R promotes TCR-γ gene rearrangement by regulating accessibility of the locus via demethylation and histone acetylation of the locus

Interleukin-27 regulates the function of the gastrointestinal epithelial barrier in a human tissue derived organoid model

Funding: This research was funded by CICRA (CICRA: better lives for children with crohns and colitis. Available online: https://www.cicra.org (last accessed on 23 January 2022); Ph.D. studentship to DBP) and an NHS Grampian Endowment project grant. Acknowledgments: We wish to acknowledge the Grampian Tissue Biorepository for assistance in tissue preparation. Organoids were stored at −80 ◦C at the University of Aberdeen. Graphical abstract was created using Biorender with a licence for use in publication (agreement number AD22YOD1N6). DBP now at Lydia Becker Institute of Immunology and Inflammation and Wellcome Centre for Cell-Matrix Research, University of Manchester, UKPeer reviewedPublisher PD

Cytokine-driven cell cycling is mediated through Cdc25A

Lymphocytes are the central mediators of the immune response, requiring cytokines for survival and proliferation. Survival signaling targets the Bcl-2 family of apoptotic mediators, however, the pathway for the cytokine-driven proliferation of lymphocytes is poorly understood. Here we show that cytokine-induced cell cycle progression is not solely dependent on the synthesis of cyclin-dependent kinases (Cdks) or cyclins. Rather, we observe that in lymphocyte cell lines dependent on interleukin-3 or interleukin-7, or primary lymphocytes dependent on interleukin 7, the phosphatase Cdc25A is the critical mediator of proliferation. Withdrawal of IL-7 or IL-3 from dependent lymphocytes activates the stress kinase, p38 MAPK, which phosphorylates Cdc25A, inducing its degradation. As a result, Cdk/cyclin complexes remain phosphorylated and inactive and cells arrest before the induction of apoptosis. Inhibiting p38 MAPK or expressing a mutant Cdc25A, in which the two p38 MAPK target sites, S75 and S123, are altered, renders cells resistant to cytokine withdrawal, restoring the activity of Cdk/cyclin complexes and driving the cell cycle independent of a growth stimulus

Oral delivery of il-27 recombinant bacteria attenuates immune colitis in mice

BACKGROUND & AIMS: Treatment of inflammatory bowel disease (IBD) would benefit from specific targeting of therapeutics to the intestine. We developed a strategy for localized delivery of the immunosuppressive cytokine IL27, which is actively synthesized in situ by the food-grade bacterium Lactococcuslactis (LL-IL-27), and tested its ability to reduce colitis in mice. METHODS: The 2 genes encoding mouse IL27 were synthesized with optimal codon usage for L lactis and joined with a linker; a signal sequence was added to allow for secretion of the product. The construct was introduced into L lactis. Colitis was induced via transfer of CD4(+)CD45RB(hi) T cells into Rag(−/−) mice to induce colitis; 7.5 weeks later, LL-IL-27 was administered to mice via gavage. Intestinal tissues were collected and analyzed. RESULTS: LL-IL-27 administration protected mice from T-cell transfer-induced enterocolitis and death. LL-IL-27 reduced disease activity scores, pathology features of large and small bowel, and levels of inflammatory cytokines in colonic tissue. LL-IL-27 also reduced numbers of CD4(+) and IL17(+) T cells in gut-associated lymphoid tissue. The effects of LL-IL-27 required production of IL10 by the transferred T cells. LL-IL-27 was more effective than either LL-IL-10 or systemic administration of recombinant IL27 in reducing colitis in mice. LL-IL-27 also reduced colitis in mice following administration of dextran sodium sulfate. CONCLUSIONS: L lactis engineered to express IL27 (LL-IL-27) reduces colitis in mice, by increasing production of IL10. Mucosal delivery of LL-IL-27 could be a more effective and safer therapy for IBD

Interleukin-27 Is a Potential Rescue Therapy for Acute Severe Colitis Through Interleukin-10-Dependent, T-Cell-Independent Attenuation of Colonic Mucosal Innate Immune Responses

Background: If treatment with intravenous steroids fail, inflammatory bowel disease patients with acute severe colitis face systemic anti–tumor necrosis factor biologic rescue therapy or colectomy. Interleukin (IL)-27 is a cytokine with an immunosuppressive role in adaptive immune responses. However, the IL-27 receptor complex is also expressed on innate immune cells, and there is evidence that IL-27 can impact the function of innate cell subsets, although this particular functionality in vivo is not understood. Our aim was to define the efficacy of IL-27 in acute severe colitis and characterize novel IL-27–driven mechanisms of immunosuppression in the colonic mucosa. Methods: We assessed oral delivery of Lactococcus lactis expressing an IL-27 hyperkine on the innate immune response in vivo in a genetically intact, noninfective, acute murine colitis model induced by intrarectal instillation of 2,4,6-trinitrobenzenesulfonic acid in SJL/J mice. Results: IL-27 attenuates acute severe colitis through the reduction of colonic mucosal neutrophil infiltrate associated with a decreased CXC chemokine gradient. This suppression was T cell independent and IL-10 dependent, initially featuring enhanced mucosal IL-10. IL-27 was associated with a reduction in colonic proinflammatory cytokines and induced a multifocal, strong, positive nuclear expression of phosphorylated STAT-1 in mucosal epithelial cells. Conclusion: We have defined novel mechanisms of IL-27 immunosuppression toward colonic innate immune responses in vivo. Mucosal delivery of IL-27 has translational potential as a novel therapeutic for inflammatory bowel disease, and it is a future mucosal directed rescue therapy in acute severe inflammatory bowel disease

The Artificial Sweetener Splenda Promotes Gut Proteobacteria, Dysbiosis, and Myeloperoxidase Reactivity in Crohn’s Disease–Like Ileitis

We thank John D. Ward and Lindsey N. Kaydo for their technical support and Dr. Wei Xin for the histological scoring of ileitis severity. ARP is an Assistant Professor of Medicine at CWRU School of Medicine. Metagenomic sequencing was conducted in the laboratory of Dr. Skip Virgin at Washington University, School of Medicine, St. Louis, MO. Raw sequencing data files will be available upon request.Peer reviewedPostprin

Cytokine-driven cell cycling is mediated through Cdc25A

Lymphocytes are the central mediators of the immune response, requiring cytokines for survival and proliferation. Survival signaling targets the Bcl-2 family of apoptotic mediators, however, the pathway for the cytokine-driven proliferation of lymphocytes is poorly understood. Here we show that cytokine-induced cell cycle progression is not solely dependent on the synthesis of cyclin-dependent kinases (Cdks) or cyclins. Rather, we observe that in lymphocyte cell lines dependent on interleukin-3 or interleukin-7, or primary lymphocytes dependent on interleukin 7, the phosphatase Cdc25A is the critical mediator of proliferation. Withdrawal of IL-7 or IL-3 from dependent lymphocytes activates the stress kinase, p38 MAPK, which phosphorylates Cdc25A, inducing its degradation. As a result, Cdk/cyclin complexes remain phosphorylated and inactive and cells arrest before the induction of apoptosis. Inhibiting p38 MAPK or expressing a mutant Cdc25A, in which the two p38 MAPK target sites, S75 and S123, are altered, renders cells resistant to cytokine withdrawal, restoring the activity of Cdk/cyclin complexes and driving the cell cycle independent of a growth stimulus