Epithelial IL-23R Signaling Licenses Protective IL-22 Responses in Intestinal Inflammation

Targeting the Interleukin 23 Pathway in Inflammatory Bowel Disease

Interleukin (IL) 23, a member of the IL12 family of cytokines, maintains intestinal homeostasis, but is also implicated in the pathogenesis of inflammatory bowel diseases (IBDs). IL23 is a heterodimer composed of disulfide-linked p19 and p40 subunits. Humanized monoclonal antibodies selectively targeting the p19 subunit of IL23 are poised to become prominent drugs in IBDs. In this review, we discuss the pharmacodynamic and pharmacokinetic properties of the currently available IL23p19 inhibitors and discuss the mechanistic underpinnings of their therapeutic effects, including the mechanism of action, epitope affinity, potency, and downstream signaling. Furthermore, we address available data on the efficacy, safety, and tolerability of IL23p19 inhibitors in the treatment of IBDs and discuss important studies performed in other immune-mediated inflammatory diseases. Finally, we evaluate the potential for combining classes of biological therapies and provide future directions on the development of precision medicine-guided positioning of IL23p19 inhibitors in IBD.

Crosstalk Within the Intestinal Epithelium: Aspects of Intestinal Absorption, Homeostasis, and Immunity

Gut health is crucial in many ways, such as in improving human health in general and enhancing production in agricultural animals. To maximize the effect of a healthy gastrointestinal tract (GIT), an understanding of the regulation of intestinal functions is needed. Proper intestinal functions depend on the activity, composition, and behavior of intestinal epithelial cells (IECs). There are various types of IECs, including enterocytes, Paneth cells, enteroendocrine cells (EECs), goblet cells, tuft cells, M cells, and intestinal epithelial stem cells (IESCs), each with unique 3D structures and IEC distributions. Although the communication between IECs and other cell types, such as immune cells and neurons, has been intensively reviewed, communication between different IECs has rarely been addressed. The present paper overviews the networks among IECs that influence intestinal functions. Intestinal absorption is regulated by incretins derived from EECs that induce nutrient transporter activity in enterocytes. EECs, Paneth cells, tuft cells, and enterocytes release signals to activate Notch signaling, which modulates IESC activity and intestinal homeostasis, including proliferation and differentiation. Intestinal immunity can be altered via EECs, goblet cells, tuft cells, and cytokines derived from IECs. Finally, tools for investigating IEC communication have been discussed, including the novel 3D intestinal cell model utilizing enteroids that can be considered a powerful tool for IEC communication research. Overall, the importance of IEC communication, especially EECs and Paneth cells, which cover most intestinal functional regulating pathways, are overviewed in this paper. Such a compilation will be helpful in developing strategies for maintaining gut health.

IL-23 exerts dominant pathogenic functions in Crohn's disease-ileitis

Crohn's disease (CD), a main form of Inflammatory Bowel Disease (IBD) is a chronic inflammatory disorder, mainly affecting the ileum. Interleukin (IL)-12 and IL-23 are both targeted by Ustekinumab, a commonly used monoclonal antibody for IBD treatment. However, their specific roles in ileitis have not been extensively explored. Here, we utilized the TnfΔΑRE model of CD-ileitis to probe the functions of IL-12 and IL-23 by employing genetically deficient mice for their respective subunits. Our findings highlight that IL-23, rather than IL-12, plays a pivotal role in the progression of ileitis. IL-23 deficiency resulted in reduced immune cell infiltration in the ileum, and decreased expression of effector cytokines downstream of IL-23 signaling. Interestingly, expanding CD14+ neutrophils were highly expressing Il23a in the inflamed ileum. Furthermore, the deletion of IL-12 conferred modest additional protection only in the absence of IL-23, suggesting potential compensatory mechanisms between these cytokines. Furthermore, our study suggests that IL-23 may function independently of IL-17, as Il17a deletion exacerbated murine ileitis, consistent with clinical studies in human CD patients using anti-IL-17 inhibitors. This research underscores the significance of targeting IL-23 in CD-ileitis, while the concurrent targeting of both IL-12 and IL-23 should be also considered as an advantageous therapeutic approach.

Ablation of Atp5if1 impairs metabolic reprogramming and proliferation of T lymphocytes and compromises mouse survival

T cells experience metabolic reprogramming to an enhanced glycolysis upon activation. Herein, we have investigated whether ATPase Inhibitory Factor 1 (IF1), the physiological inhibitor of mitochondrial ATP synthase, participates in rewiring T cells to a particular metabolic phenotype. We show that the activation of naive CD4+ T lymphocytes both in vitro and in vivo is accompanied by a sharp upregulation of IF1, which is expressed only in Th1 effector cells. T lymphocytes of conditional CD4+-IF1-knockout mice display impaired glucose uptake and flux through glycolysis, reducing the biogenesis of mitochondria and cellular proliferation after activation. Consequently, mice devoid of IF1 in T lymphocytes cannot mount an effective Th1 response against bacterial infection compromising their survival. Overall, we show that the inhibition of a fraction of ATP synthase by IF1 regulates metabolic reprogramming and functionality of T cells, highlighting the essential role of IF1 in adaptive immune responses.

Interleukin-1 family cytokines at the crossroads of microbiome regulation in barrier health and disease

Recent advances in understanding how the microbiome can influence both the physiology and the pathogenesis of disease in humans have highlighted the importance of gaining a deeper insight into the complexities of the host-microbial dialogue. In tandem with this progress, has been a greater understanding of the biological pathways which regulate both homeostasis and inflammation at barrier tissue sites, such as the skin and the gut. In this regard, the Interleukin-1 family of cytokines, which can be segregated into IL-1, IL-18 and IL-36 subfamilies, have emerged as important custodians of barrier health and immunity. With established roles as orchestrators of various inflammatory diseases in both the skin and intestine, it is now becoming clear that IL-1 family cytokine activity is not only directly influenced by external microbes, but can also play important roles in shaping the composition of the microbiome at barrier sites. This review explores the current knowledge surrounding the evidence that places these cytokines as key mediators at the interface between the microbiome and human health and disease at the skin and intestinal barrier tissues.

Identification of the grass carp interleukin-23 receptor and its proinflammatory role in intestinal inflammation

The interleukin 23 receptor (IL-23R) is associated with a variety of inflammatory diseases in humans and other mammals. However, whether IL-23R is involved in inflammatory diseases in teleost fish is less understood. Thus, to investigate the potential involvement of IL-23R in fish inflammatory diseases, the full-length cDNA of IL-23R from grass carp Ctenopharyngodon idella was cloned and used to generate a recombinant protein (rgcIL-23R) containing the extracellular domain of IL-23R, against which a polyclonal antibody (rgcIL-23R pAb) was then developed. qPCR analysis revealed that IL-23R mRNA was significantly upregulated in most grass carp tissues in response to infection with Gram-negative Aeromonas hydrophila. Treatment with rgcIL-23R significantly induced IL-17A/F1 expression in C. idella kidney (CIK) cells. By contrast, knockdown of IL-23R caused significant decreases in IL-23R, STAT3, and IL-17N expression in CIK cells after lipopolysaccharide (LPS) stimulation. Similarly, rgcIL-23R pAb treatment effectively inhibited the LPS-induced increase in the expression of IL-23 subunit genes and those of the IL-23/IL-17 pathway in CIK cells. Furthermore, intestinal symptoms identical to those caused by A. hydrophila were induced by anal intubation with rgcIL-23R, but suppressed by rgcIL-23R pAb. Therefore, these results suggest that IL-23R has a crucial role in the regulation of intestinal inflammation and, thus, is a promising target for controlling inflammatory diseases in farmed fish.

IL-23 stabilizes an effector Treg cell program in the tumor microenvironment

Interleukin-23 (IL-23) is a proinflammatory cytokine mainly produced by myeloid cells that promotes tumor growth in various preclinical cancer models and correlates with adverse outcomes. However, as to how IL-23 fuels tumor growth is unclear. Here, we found tumor-associated macrophages to be the main source of IL-23 in mouse and human tumor microenvironments. Among IL-23-sensing cells, we identified a subset of tumor-infiltrating regulatory T (Treg) cells that display a highly suppressive phenotype across mouse and human tumors. The use of three preclinical models of solid cancer in combination with genetic ablation of Il23r in Treg cells revealed that they are responsible for the tumor-promoting effect of IL-23. Mechanistically, we found that IL-23 sensing represents a crucial signal driving the maintenance and stabilization of effector Treg cells involving the transcription factor Foxp3. Our data support that targeting the IL-23/IL-23R axis in cancer may represent a means of eliciting antitumor immunity.

The Role of IL-23 Inhibitors in Crohn's Disease

Promoting a Th17 pathogenic response, the interleukin (IL)-23 pathway is crucial in the pathophysiology of inflammatory bowel disease (IBD). With a favorable safety profile, ustekinumab, a monoclonal antibody targeting the shared p40 component of IL-12/23, is currently approved for the treatment of IBD in patients with disease refractory to corticosteroids and biologic drugs. Risankizumab, mirikizumab, and guselkumab are specific IL-23p19 antagonists tested for the treatment of Crohn's disease (CD). However, only risankizumab currently has been approved for its treatment. Trials with guselkumab and mirikizumab are currently ongoing, with promising preliminary efficacy and safety results. In this review, we provide a summary of the current knowledge about selective IL-23 inhibitors, focusing on their positioning in the therapeutic algorithm of patients with moderate to severe CD.

Proline uptake promotes activation of lymphoid tissue inducer cells to maintain gut homeostasis

Metabolic regulation is integral to the proper functioning of innate lymphoid cells, yet the underlying mechanisms remain elusive. Here, we show that disruption of exogenous proline uptake, either through dietary restriction or by deficiency of the proline transporter Slc6a7, in lymphoid tissue inducer (LTi) cells, impairs LTi activation and aggravates dextran sodium sulfate-induced colitis in mice. With an integrative transcriptomic and metabolomic analysis, we profile the metabolic characteristics of various innate lymphoid cell subsets and reveal a notable enrichment of proline metabolism in LTi cells. Mechanistically, defective proline uptake diminishes the generation of reactive oxygen species, previously known to facilitate LTi activation. Additionally, LTi cells deficient in Slc6a7 display downregulation of Cebpb and Kdm6b, resulting in compromised transcriptional and epigenetic regulation of interleukin-22. Furthermore, our study uncovers the therapeutic potential of proline supplementation in alleviating colitis. Therefore, these findings shed light on the role of proline in facilitating LTi activation and ultimately contributing to gut homeostasis.

The role of IL-17 in lung cancer growth

Interleukin 17 (IL-17) is an inflammatory cytokine with multiple roles in immune protection, immunopathology, and inflammation-related tumors. Lung cancer is inflammation-related cancer, and a large number of studies have shown that IL-17 contributes to the metastasis and progression of lung cancer. However, some studies have shown that IL17 inhibits the occurrence of lung cancer. At present, there is still some controversy about the role of IL17 in the occurrence and development of lung cancer. This review introduces the basic characteristics of IL-17 and focuses on its role in lung cancer, in order to provide a certain theoretical basis for the prevention, diagnosis, and treatment of lung cancer.

IL-12 and IL-23 pathway inhibition in inflammatory bowel disease

Interleukin-12 (IL-12) and interleukin-23 (IL-23), which belong to the IL-12 family of cytokines, have a key role in intestinal homeostasis and inflammation and are implicated in the pathogenesis of inflammatory bowel disease. Upon their secretion by antigen-presenting cells, they exert both pro-inflammatory and anti-inflammatory receptor-mediated effects. An increased understanding of these biological effects, particularly the pro-inflammatory effects mediated by IL-12 and IL-23, has led to the development of monoclonal antibodies that target a subunit common to IL-12 and IL-23 (p40; targeted by ustekinumab and briakinumab), or the IL-23-specific subunit (p19; targeted by risankizumab, guselkumab, brazikumab and mirikizumab). This Review provides a summary of the biology of the IL-12 family cytokines IL-12 and IL-23, discusses the role of these cytokines in intestinal homeostasis and inflammation, and highlights IL-12- and IL-23-directed drug development for the treatment of Crohn's disease and ulcerative colitis.

The Role of IL-23 in the Pathogenesis and Therapy of Inflammatory Bowel Disease

Interleukin-23 (IL-23) is a proinflammatory cytokine produced mainly by macrophages and antigen-presenting cells (APCs) after antigenic stimulation. IL-23 plays a significant role as a mediator of tissue damage. Indeed, the irregularities in IL-23 and its receptor signaling have been implicated in inflammatory bowel disease. IL-23 interacts with both the innate and adaptive immune systems, and IL-23/Th17 appears to be involved in the development of chronic intestinal inflammation. The IL-23/Th17 axis may be a critical driver of this chronic inflammation. This review summarizes the main aspects of IL-23's biological function, cytokines that control cytokine production, effectors of the IL-23 response, and the molecular mechanisms associated with IBD pathogenesis. Although IL-23 modulates and impacts the development, course, and recurrence of the inflammatory response, the etiology and pathophysiology of IBD are not completely understood, but mechanism research shows huge potential for clinical applications as therapeutic targets in IBD treatment.

Targeting IL-23 for IBD: Rationale and Progress to Date

Inflammatory bowel disease, including Crohn's disease and ulcerative colitis, comprises multiple complex immune-mediated disorders. Early diagnosis and prompt disease control may prevent long-term complications and hospitalization. The therapeutic options have expanded in the last two decades, with the development of biologics and small molecules targeting specific pathways implicated in inflammatory bowel disease pathogenesis. The interleukin (IL)-23/Th-17 axis is one such example. Targeting IL-12/23 is effective for the treatment of both moderate-to-severe Crohn's disease and ulcerative colitis, and ustekinumab (an IL-12/23p40 antagonist) is approved for both indications. In patients with psoriasis, improved clinical outcomes were observed with agents that more selectively targeted IL-23 (IL-23p19 antagonists) compared with those that target both IL-12 and IL-23. Many specific IL-23p19 antagonists are currently being investigated in Crohn's disease and ulcerative colitis, and risankizumab has been recently approved for moderate-to-severely active Crohn's disease. In this review, we summarize the mechanisms of action and the evidence from clinical trials supporting the efficacy and safety of IL-23p19 antagonists for the treatment of inflammatory bowel disease.

Microbiota-derived short-chain fatty acids and modulation of host-derived peptides formation: Focused on host defense peptides

The byproducts of bacterial fermentation known as short-chain fatty acids (SCFAs) are chemically comprised of a carboxylic acid component and a short hydrocarbon chain. Recent investigations have demonstrated that SCFAs can affect intestinal immunity by inducing endogenous host defense peptides (HDPs) and their beneficial effects on barrier integrity, gut health, energy supply, and inflammation. HDPs, which include defensins, cathelicidins, and C-type lectins, perform a significant function in innate immunity in gastrointestinal mucosal membranes. SCFAs have been demonstrated to stimulate HDP synthesis by intestinal epithelial cells via interactions with G protein-coupled receptor 43 (GPR43), activation of the Jun N-terminal kinase (JNK) and Mitogen-activated protein kinase kinase (MEK)/extracellular signal-regulated kinase (ERK) pathways, and the cell growth pathways. Furthermore, SCFA butyrate has been demonstrated to enhance the number of HDPs released from macrophages. SCFAs promote monocyte-to-macrophage development and stimulate HDP synthesis in macrophages by inhibiting histone deacetylase (HDAC). Understanding the etiology of many common disorders might be facilitated by studies into the function of microbial metabolites, such as SCFAs, in the molecular regulatory processes of immune responses (e.g., HDP production). This review will focus on the current knowledge of the role and mechanism of microbiota-derived SCFAs in influencing the synthesis of host-derived peptides, particularly HDPs.

Kernel-based genetic association analysis for microbiome phenotypes identifies host genetic drivers of beta-diversity

BACKGROUND

Understanding human genetic influences on the gut microbiota helps elucidate the mechanisms by which genetics may influence health outcomes. Typical microbiome genome-wide association studies (GWAS) marginally assess the association between individual genetic variants and individual microbial taxa. We propose a novel approach, the covariate-adjusted kernel RV (KRV) framework, to map genetic variants associated with microbiome beta-diversity, which focuses on overall shifts in the microbiota. The KRV framework evaluates the association between genetics and microbes by comparing similarity in genetic profiles, based on groups of variants at the gene level, to similarity in microbiome profiles, based on the overall microbiome composition, across all pairs of individuals. By reducing the multiple-testing burden and capturing intrinsic structure within the genetic and microbiome data, the KRV framework has the potential of improving statistical power in microbiome GWAS.

RESULTS

We apply the covariate-adjusted KRV to the Hispanic Community Health Study/Study of Latinos (HCHS/SOL) in a two-stage (first gene-level, then variant-level) genome-wide association analysis for gut microbiome beta-diversity. We have identified an immunity-related gene, IL23R, reported in a previous microbiome genetic association study and discovered 3 other novel genes, 2 of which are involved in immune functions or autoimmune disorders. In addition, simulation studies show that the covariate-adjusted KRV has a greater power than other microbiome GWAS methods that rely on univariate microbiome phenotypes across a range of scenarios.

CONCLUSIONS

Our findings highlight the value of the covariate-adjusted KRV as a powerful microbiome GWAS approach and support an important role of immunity-related genes in shaping the gut microbiome composition. Video Abstract.

Helicobacter pylori promotes colorectal carcinogenesis by deregulating intestinal immunity and inducing a mucus-degrading microbiota signature

OBJECTIVE

Helicobacter pylori infection is the most prevalent bacterial infection worldwide. Besides being the most important risk factor for gastric cancer development, epidemiological data show that infected individuals harbour a nearly twofold increased risk to develop colorectal cancer (CRC). However, a direct causal and functional connection between H. pylori infection and colon cancer is lacking.

DESIGN

We infected two Apc-mutant mouse models and C57BL/6 mice with H. pylori and conducted a comprehensive analysis of H. pylori-induced changes in intestinal immune responses and epithelial signatures via flow cytometry, chip cytometry, immunohistochemistry and single cell RNA sequencing. Microbial signatures were characterised and evaluated in germ-free mice and via stool transfer experiments.

RESULTS

H. pylori infection accelerated tumour development in Apc-mutant mice. We identified a unique H. pylori-driven immune alteration signature characterised by a reduction in regulatory T cells and pro-inflammatory T cells. Furthermore, in the intestinal and colonic epithelium, H. pylori induced pro-carcinogenic STAT3 signalling and a loss of goblet cells, changes that have been shown to contribute-in combination with pro-inflammatory and mucus degrading microbial signatures-to tumour development. Similar immune and epithelial alterations were found in human colon biopsies from H. pylori-infected patients. Housing of Apc-mutant mice under germ-free conditions ameliorated, and early antibiotic eradication of H. pylori infection normalised the tumour incidence to the level of uninfected controls.

CONCLUSIONS

Our studies provide evidence that H. pylori infection is a strong causal promoter of colorectal carcinogenesis. Therefore, implementation of H. pylori status into preventive measures of CRC should be considered.

IL-22 alters gut microbiota composition and function to increase aryl hydrocarbon receptor activity in mice and humans

BACKGROUND

IL-22 is induced by aryl hydrocarbon receptor (AhR) signaling and plays a critical role in gastrointestinal barrier function through effects on antimicrobial protein production, mucus secretion, and epithelial cell differentiation and proliferation, giving it the potential to modulate the microbiome through these direct and indirect effects. Furthermore, the microbiome can in turn influence IL-22 production through the synthesis of L-tryptophan (L-Trp)-derived AhR ligands, creating the prospect of a host-microbiome feedback loop. We evaluated the impact IL-22 may have on the gut microbiome and its ability to activate host AhR signaling by observing changes in gut microbiome composition, function, and AhR ligand production following exogenous IL-22 treatment in both mice and humans.

RESULTS

Microbiome alterations were observed across the gastrointestinal tract of IL-22-treated mice, accompanied by an increased microbial functional capacity for L-Trp metabolism. Bacterially derived indole derivatives were increased in stool from IL-22-treated mice and correlated with increased fecal AhR activity. In humans, reduced fecal concentrations of indole derivatives in ulcerative colitis (UC) patients compared to healthy volunteers were accompanied by a trend towards reduced fecal AhR activity. Following exogenous IL-22 treatment in UC patients, both fecal AhR activity and concentrations of indole derivatives increased over time compared to placebo-treated UC patients.

CONCLUSIONS

Overall, our findings indicate IL-22 shapes gut microbiome composition and function, which leads to increased AhR signaling and suggests exogenous IL-22 modulation of the microbiome may have functional significance in a disease setting. Video Abstract.

Interleukin-23 receptor signaling impairs the stability and function of colonic regulatory T cells

The cytokine interleukin-23 (IL-23) is involved in the pathogenesis of inflammatory and autoimmune conditions including inflammatory bowel disease (IBD). IL23R is enriched in intestinal Tregs, yet whether IL-23 modulates intestinal Tregs remains unknown. Here, investigating IL-23R signaling in Tregs specifically, we show that colonic Tregs highly express Il23r compared with Tregs from other compartments and their frequency is reduced upon IL-23 administration and impairs Treg suppressive function. Similarly, colonic Treg frequency is increased in mice lacking Il23r specifically in Tregs and exhibits a competitive advantage over IL-23R-sufficient Tregs during inflammation. Finally, IL-23 antagonizes liver X receptor pathway, cellular cholesterol transporter Abca1, and increases Treg apoptosis. Our results show that IL-23R signaling regulates intestinal Tregs by increasing cell turnover, antagonizing suppression, and decreasing cholesterol efflux. These results suggest that IL-23 negatively regulates Tregs in the intestine with potential implications for promoting chronic inflammation in patients with IBD.

Mechanical bacterial lysate enhances antimicrobial barrier mechanisms in human airway epithelial cells

Polyvalent mechanical bacterial lysate is effective in the prevention of respiratory tract infections, although its mechanism of action is not entirely elucidated. Because epithelial cells constitute the frontline defense against infections, we investigated the molecular mechanisms of innate response exerted by bronchial epithelial cells in the presence of polyvalent mechanical bacterial lysate. By using primary human bronchial epithelial cells, we observed that polyvalent mechanical bacterial lysate was able to increase the expression of cellular adhesion molecules such as ICAM-1 and E-cadherin, as well as the expression of amphiregulin, a growth factor able to support human bronchial epithelial cell proliferation. Remarkably, polyvalent mechanical bacterial lysate promoted in human bronchial epithelial cells the de novo expression of human β-defensin-2, a major antimicrobial peptide, conferring them a direct antimicrobial activity. Moreover, polyvalent mechanical bacterial lysate-stimulated human bronchial epithelial cells provided signals for increased IL-22 production by innate lymphoid cells via IL-23, which could further contribute to the release of antimicrobial peptides by epithelial cells. In agreement with these in vitro data, the concentration of both IL-23 and antimicrobial peptides (human β-defensin-2 and LL-37) increased in the saliva of healthy volunteers after sublingual administration of polyvalent mechanical bacterial lysate. Altogether, these results indicate that polyvalent mechanical bacterial lysate administration might support mucosal barrier integrity and promote mechanisms of antimicrobial activity in airway epithelial cells.

AKR1B8 deficiency drives severe DSS-induced acute colitis through invasion of luminal bacteria and activation of innate immunity

Background

Dysfunction of intestinal epithelial cells (IECs) promotes inflammatory bowel disease (IBD) and associated colorectal cancer (CRC). AKR1B8 deficiency impairs the IEC barrier function, leading to susceptibility to chronic colitis induced by dextran sulfate sodium (DSS), yet it remains unclear how acute colitic response is in AKR1B8 deficient mice.

Methods

AKR1B8 knockout (KO) and littermate wild type mice were exposed to oral 1.5% DSS in drinking water for 6 days. Disease activity index and histopathological inflammation scores by H&E staining were calculated for colitic severity; permeability was assessed by fluorescein isothiocyanate dextran (FITC-Dextran) probes and bacterial invasion and transmission were detected by in situ hybridization in mucosa or by culture in blood agar plates. Immunofluorescent staining and flow cytometry were applied for immune cell quantification. Toll-like receptor 4 (TLR4) and target gene expression was analyzed by Western blotting and qRT-PCR.

Results

AKR1B8 KO mice developed severe acute colitis at a low dose (1.5%) of DSS in drinking water compared to wild type controls. In AKR1B8 KO mice, FITC-dextran was penetrated easily and luminal bacteria invaded to the surface of IEC layer on day 3, and excessive bacteria translocated into the colonic mucosa, mesenteric lymph nodes (MLNs) and liver on day 6, which was much mild in wild type mice. Hyper-infiltration of neutrophils and basophils occurred in AKR1B8 KO mice, and monocytes in spleen and macrophages in colonic mucosa increased markedly compared to wild type mice. TLR4 signaling in colonic epithelial cells of AKR1B8 KO mice was activated to promote great IL-1β and IL-6 expression compared to wild type mice.

Conclusions

AKR1B8 deficiency in IECs drives severe acute colitis induced by DSS at a low dose through activation of the innate immunity, being a novel pathogenic factor of colitis.

Inflammatory Bowel Disease: A Review of Pre-Clinical Murine Models of Human Disease

Crohn’s disease (CD) and ulcerative colitis (UC) are both highly inflammatory diseases of the gastrointestinal tract, collectively known as inflammatory bowel disease (IBD). Although the cause of IBD is still unclear, several experimental IBD murine models have enabled researchers to make great inroads into understanding human IBD pathology. Here, we discuss the current pre-clinical experimental murine models for human IBD, including the chemical-induced trinitrobenzene sulfonic acid (TNBS) model, oxazolone and dextran sulphate sodium (DSS) models, the gene-deficient I-kappa-B kinase gamma (Iκκ-γ) and interleukin(IL)-10 models, and the CD4⁺ T-cell transfer model. We offer a comprehensive review of how these models have been used to dissect the etiopathogenesis of disease, alongside their limitations. Furthermore, the way in which this knowledge has led to the translation of experimental findings into novel clinical therapeutics is also discussed.

Longitudinal monitoring of STAT3 phosphorylation and histologic outcome of tofacitinib therapy in patients with ulcerative colitis

BACKGROUND

Tofacitinib is the first in class, pan-JAK inhibitor approved for ulcerative colitis (UC). Clinical efficacy has been shown, but long-term real-life endoscopic and histologic data are lacking.

AIM

To investigate the effects of tofacitinib in patients with refractory UC focussing on endoscopic, histologic and molecular outcomes, including STAT3 phosphorylation (pSTAT3) detection in the spatial context of mucosal inflammation METHODS: We prospectively monitored 59 highly refractory patients (96.7% anti-TNF exposure, 91.7% vedolizumab exposure) initiating tofacitinib at two IBD referral centres and assessed outcome at the end of induction and after 48 weeks of therapy. Endoscopic improvement was defined as a Mayo endoscopic subscore ≤1, endoscopic and histologic remission as Mayo endoscopic subscore 0 and Nancy histologic score 0. Multiplex immunohistochemistry with multispectral imaging was used to assess pSTAT3.

RESULTS

Endoscopic improvement was achieved by 24.4% and 30.5% of patients at weeks 8 and 48, respectively. Endoscopic and histologic remission rates were 11.1%, 23.7 and 16.7%, 21.4%, respectively. Endoscopic improvement at week 8 was significantly associated with treatment continuation in the long-term (72.7% vs 20.6%, p = 0.003). Although we observed a gradual decrease of mucosal pSTAT3 levels in both remitters and non-remitters (p < 0.05), no association with treatment outcome could be demonstrated. However, lamina propria pSTAT3 was significantly associated with the Nancy Histologic index (p = 0.004).

CONCLUSION

Tofacitinib can induce and maintain endoscopic and histologic remission in up to one-quarter of highly refractory UC patients. Longitudinal monitoring of nuclear pSTAT3 in mucosal tissue compartments reflects distinctive on-target effects, independently of long-term treatment outcomes.

Interleukin-23 in the Pathogenesis of Inflammatory Bowel Disease and Implications for Therapeutic Intervention

The interleukin-23 [IL-23] cytokine, derived predominantly from macrophages and dendritic cells in response to microbial stimulation, has emerged as a critical promoter of chronic intestinal inflammation. Genome-wide association studies linking variants in IL23R to disease protection, bolstered by experimental evidence from colitis models, and the successful application of therapies against the IL-12/IL-23 shared p40 subunit in the treatment of inflammatory bowel disease [IBD] all provide compelling evidence of a crucial role for IL-23 in disease pathogenesis. Moreover, targeting the p19 subunit specific for IL-23 has shown considerable promise in recent phase 2 studies in IBD. The relative importance of the diverse immunological pathways downstream of IL-23 in propagating mucosal inflammation in the gut, however, remains contentious. Here we review current understanding of IL-23 biology and explore its pleiotropic effects on T cells, and innate lymphoid, myeloid and intestinal epithelial cells in the context of the pathogenesis of IBD. We furthermore discuss these pathways in the light of recent evidence from clinical trials and indicate emerging targets amenable to therapeutic intervention and translation into clinical practice.

Antibody-mediated blockade of the IL23 receptor destabilizes intratumoral regulatory T cells and enhances immunotherapy

Regulatory T cells (Treg) can impede antitumor immunity and currently represent a major obstacle to effective cancer immunotherapy. Targeting tumor-infiltrating regulatory Treg while sparing systemic Treg represents an optimal approach to this problem. Here, we provide evidence that the interleukin 23 receptor (IL23R) expressed by tumor-infiltrating Treg promotes suppressive activity. Disruption of the IL23R results in increased responsiveness of destabilized Treg to the IL12 cytokine, the production of γ-interferon, and the recruitment of CD8 T cells that inhibit tumor growth. Since the Treg destabilization pathway that is initiated by IL23R blockade is distinct and independent from the destabilization pathway coupled to glucocorticoid-induced TNFR-related protein (GITR) activation, we examined the impact of the coordinate induction of the two destabilization pathways on antitumor immune responses. Combined GITR and IL23R antibody treatment of mice inoculated with MC38 tumors resulted in robust and synergistic antitumor responses. These findings indicate that the delineation of independent Treg destabilization pathways may allow improved approaches to the development of combination immunotherapy for cancers.

Pattern Recognition Receptor Signaling and Cytokine Networks in Microbial Defenses and Regulation of Intestinal Barriers: Implications for Inflammatory Bowel Disease

Inflammatory bowel disease is characterized by defects in epithelial function and dysregulated inflammatory signaling by lamina propria mononuclear cells including macrophages and dendritic cells in response to microbiota. In this review, we focus on the role of pattern recognition receptors in the inflammatory response as well as epithelial barrier regulation. We explore cytokine networks that increase inflammation, regulate paracellular permeability, cause epithelial damage, up-regulate epithelial proliferation, and trigger restitutive processes. We focus on studies using patient samples as well as speculate on pathways that can be targeted to more holistically treat patients with inflammatory bowel disease.

TH Cells and Cytokines in Encephalitogenic Disorders

The invasion of immune cells into the central nervous system (CNS) is a hallmark of the process we call neuroinflammation. Diseases such as encephalitides or multiple sclerosis (MS) are characterised by the dramatic influx of T lymphocytes and monocytes. The communication between inflammatory infiltrates and CNS resident cells is primarily mediated through cytokines. Over the years, numerous cytokine networks have been assessed to better understand the development of immunopathology in neuroinflammation. In MS for instance, many studies have shown that CD4+ T cells infiltrate the CNS and subsequently lead to immunopathology. Inflammatory CD4+ T cells, such as TH1, TH17, GM-CSF-producing helper T cells are big players in chronic neuroinflammation. Conversely, encephalitogenic or meningeal regulatory T cells (TREGs) and TH2 cells have been shown to drive a decrease in inflammatory functions in microglial cells and thus promote a neuroprotective microenvironment. Recent studies report overlapping as well as differential roles of these cells in tissue inflammation. Taken together, this suggests a more complex relationship between effector T cell subsets in neuroinflammation than has hitherto been established. In this overview, we review the interplay between helper T cell subsets infiltrating the CNS and how they actively contribute to neuroinflammation and degeneration. Importantly, in this context, we will especially focus on the current knowledge regarding the contribution of various helper cell subsets to neuroinflammation by referring to their helper T cell profile in the context of their target cell.

Immune translational control by CPEB4 regulates intestinal inflammation resolution and colorectal cancer development

Upon tissue injury, cytokine expression reprogramming transiently remodels the inflammatory immune microenvironment to activate repair processes and subsequently return to homeostasis. However, chronic inflammation induces permanent changes in cytokine production which exacerbate tissue damage and may even favor tumor development. Here, we address the contribution of post-transcriptional regulation, by the RNA-binding protein CPEB4, to intestinal immune homeostasis and its role in inflammatory bowel diseases (IBD) and colorectal cancer (CRC) development. We found that intestinal damage induces CPEB4 expression in adaptive and innate immune cells, which is required for the translation of cytokine mRNA(s) such as the one encoding interleukin-22. Accordingly, CPEB4 is required for the development of gut-associated lymphoid tissues and to maintain intestinal immune homeostasis, mediating repair and remodeling after acute inflammatory tissue damage and promoting the resolution of intestinal inflammation. CPEB4 is chronically overexpressed in inflammatory cells in patients with IBD and in CRC, favoring tumor development.

•

CPEB4 is overexpressed in Th17 and ILC3 cells upon intestinal barrier damage

•

CPEB4 is required for Il-22 mRNA translation and IL-22 expression

•

CPEB4 promotes tissue repair in acute transient inflammation

•

In chronic inflammation CPEB4 exacerbates intestinal pathology and promotes tumor growth

Upregulation of antimicrobial peptide expression in slc26a3-/- mice with colonic dysbiosis and barrier defect

Genetic defects in SLC26A3 (DRA), an intestinal Cl-/HCO3- exchanger, result in congenital chloride diarrhea (CLD), marked by lifelong acidic diarrhea and a high risk of inflammatory bowel disease. Slc26a3-/- mice serve as a model to understand the pathophysiology of CLD and search for treatment options. This study investigates the microbiota changes in slc26a3-/- colon, the genotype-related causes for the observed microbiota alterations, its inflammatory potential, as well as the corresponding host responses. The luminal and the mucosa-adherent cecal and colonic microbiota of cohoused slc26a3-/- and wt littermates were analyzed by 16S rRNA gene sequencing. Fecal microbiota transfer from cohoused slc26a3-/- and wt littermates to germ-free wt mice was performed to analyze the stability and the inflammatory potential of the communities.The cecal and colonic luminal and mucosa-adherent microbiota of slc26a3-/- mice was abnormal from an early age, with a loss of diversity, of short-chain fatty acid producers, and an increase of pathobionts. The transfer of slc26a3-/- microbiota did not result in intestinal inflammation and the microbial diversity in the recipient mice normalized over time. A strong increase in the expression of Il22, Reg3β/γ, Relmβ, and other proteins with antimicrobial functions was observed in slc26a3-/- colon from juvenile age, while the mucosal and systemic inflammatory signature was surprisingly mild. The dysbiotic microbiota, low mucosal pH, and mucus barrier defect in slc26a3-/- colon are accompanied by a stark upregulation of the expression of a panel of antimicrobial proteins. This may explain the low inflammatory burden in the gut of these mice.

Sodium butyrate alleviates intestinal injury and microbial flora disturbance induced by lipopolysaccharides in rats

Sodium butyrate alleviates LPS-induced intestinal inflammation in rats by regulating intestinal injury, inflammatory cytokine levels, and intestinal flora.

The Role of Immune and Epithelial Stem Cells in Inflammatory Bowel Disease Therapy

BACKGROUND

Inflammatory Bowel Disease (IBD) is categorized as Crohn's disease (CD) and Ulcerative colitis (UC) and is characterized by chronic inflammation in the gastrointestinal (GI) tract. Relapsing symptoms, including abdominal pain, increased stool frequency, loss of appetite as well as anemia contribute to significant deterioration of quality of life. IBD treatment encompasses chemotherapy (e.g. corticosteroids, thiopurines) and biological agents (e.g. antibodies targeting tumour necrosis factor α, interleukin 12/23) and surgery. However, efficacy of these therapies is not satisfactory. Thus, scientists are looking for new options in IBD treatment that could induce and maintain remission.

OBJECTIVE

To summarize previous knowledge about role of different intestinal cells in IBD pathophysiology and application of stem cells in the IBD treatment.

RESULTS

Recent studies have emphasized an important role of innate lymphoid cells (ILCs) as well as intestinal epithelial cells (IECs) in the IBD pathophysiology suggesting that these types of cells can be new targets for IBD treatment. Moreover, last studies show that stem cells transplantation reduces inflammation in patients suffering from IBD, which are resistant to conventional therapies.

CONCLUSION

Both hematopoietic stem cells (HSCs) and mesenchymal stem cells (MSCs) are able to restore damaged tissue and regulate the immune system. Autologous HSCs transplantation eliminates autoreactive cells and replace them with new T-cells resulting a long-time remission. Whereas MSCs transplantation is effective therapy in one of the major complications of IBD, perianal fistulas.

IL23R on myeloid cells is involved in murine pulmonary granuloma formation

PURPOSE OF THE STUDY

The involvement of the IL-23/IL23R pathway is well known in the disease pathogenesis of sarcoidosis and other inflammatory diseases. To date, the pathogenic mechanism of IL-23 is most notably described on CD4⁺ Th17 lymphocytes. However, the function of the IL23R on myeloid cells in sarcoidosis is poorly understood. Thus, the aim of the study is to investigate the role of the IL23R on myeloid cell in pulmonary granuloma formation. Methods: We generated IL23RLysMCre mice lacking the IL23R gene in myeloid cells. The importance of IL23R in myeloid cells for the development of sarcoidosis was studied in a mouse model of inflammatory lung granuloma formation through embolization of PPD from Mycobacterium bovis-coated Sepharose beads into previously PPD-immunized mice. In addition the function of IL23R on myeloid cells was studied in LPS or IFNγ stimulated BMDMs and BMDCs. The mRNA and protein expression levels of relevant cytokines were analyzed by RT-PCR (TaqMan) and ELISA. The composition of immune cells in BALF was quantified by flow cytometry and alteration in granuloma sizes were observed by H&E stained lung sections. Results: Mycobacterium Ag-elicted pulmonary granulomas tend to be smaller in IL23RLysMCre mice and NF-κB dependent Th1 cytokines in the murine lungs are reduced compared to wildtype mice. In line, we observed that IL23R-deficient bone marrow-derived macrophages show a reduced production of Th1 cytokines after LPS stimulation. Conclusion: We here for the first time demonstrate a role for IL23R on myeloid cells in pulmonary inflammation and granuloma formation. Our findings provide essential insights in the pathogenesis of inflammatory lung diseases like sarcoidosis, which might be useful for the development of novel therapeutics targeting distinct immunological pathways like IL-23/IL23R.

Milk-derived extracellular vesicles alleviate ulcerative colitis by regulating the gut immunity and reshaping the gut microbiota

Rationale: Bovine milk constitutes an essential part of human diet, especially for children, due to its enrichment of various nutrients. We recently developed an effective protocol for the isolation of extracellular vesicles from milk (mEVs) and discovered that mEVs contained large amounts of immune-active proteins and modulated the gut immunity and microbiota in healthy mice. Here, we aimed to explore the therapeutic effects of mEVs on inflammatory bowel disease. Methods: MicroRNAs and protein content in mEVs were analyzed by RNA sequencing and proteomics, respectively, followed by functional annotation. Ulcerative colitis (UC) was induced by feeding mice with dextran sulfate sodium. Intestinal immune cell populations were phenotyped by flow cytometry, and the gut microbiota was analyzed via 16S rRNA sequencing. Results: We showed that abundant proteins and microRNAs in mEVs were involved in the regulation of immune and inflammatory pathways and that oral administration of mEVs prevented colon shortening, reduced intestinal epithelium disruption, inhibited infiltration of inflammatory cells and tissue fibrosis in a mouse UC model. Mechanistically, mEVs attenuated inflammatory response via inhibiting TLR4-NF-κB signaling pathway and NLRP3 inflammasome activation. Furthermore, mEVs were able to correct cytokine production disorder and restore the balance between T helper type 17 (Th17) cells and interleukin-10+Foxp3+ regulatory T (Treg) cells in the inflamed colon. The disturbed gut microbiota in UC was also partially recovered upon treatment with mEVs. The correlation between the gut microbiota and cytokines suggests that mEVs may modulate intestinal immunity via influencing the gut microbiota. Conclusions: These findings reveal that mEVs alleviate colitis by regulating intestinal immune homeostasis via inhibiting TLR4-NF-κB and NLRP3 signaling pathways, restoring Treg/Th17 cell balance, and reshaping the gut microbiota.

IκB Kinase-β Regulates Neutrophil Recruitment Through Activation of STAT3 Signaling in the Esophagus

BACKGROUND & AIMS

The epithelial barrier is the host's first line of defense against damage to the underlying tissue. Upon injury, the epithelium plays a critical role in inflammation. The IκB kinase β (IKKβ)/nuclear factor-κB pathway was shown to be active in the esophageal epithelium of patients with esophageal disease. However, the complex mechanisms by which IKKβ signaling regulates esophageal disease pathogenesis remain unknown. Our prior work has shown that expression of a constitutively active form of IKKβ specifically in esophageal epithelia of mice (Ikkβca^{Esophageal Epithelial Cell-Knockin (EEC-KI)}) is sufficient to cause esophagitis.

METHODS

We generated ED-L2/Cre;Rosa26-Ikkβca^+/L;Stat3^L/L (Ikkβca^EEC-KI;Stat3^{Esophageal Epithelial Cell Knockout (EEC-KO)}) mice, in which the ED-L2 promoter activates Cre recombinase in the esophageal epithelium, leading to constitutive activation of IKKβ and loss of Stat3. Esophageal epithelial tissues were collected and analyzed by immunostaining, RNA sequencing, quantitative real-time polymerase chain reaction assays, flow cytometry, and Western blot. Ikkβca^EEC-KI mice were treated with neutralizing antibodies against interleukin (IL)23p19 and IL12p40.

RESULTS

Here, we report that Ikkβca^EEC-KI mice have increased activation of epithelial Janus kinase 2/STAT3 signaling. Stat3 deletion in Ikkβca^EEC-KI mice attenuated the neutrophil infiltration observed in Ikkβca^EEC-KI mice and resulted in decreased expression of genes related to immune cell recruitment and activity. Blocking experiments in Ikkβca^EEC-KI mice showed that STAT3 activation and subsequent neutrophil recruitment are dependent on IL23 secretion.

CONCLUSIONS

Our study establishes a novel interplay between IKKβ and STAT3 signaling in epithelial cells of the esophagus, where IKKβ/IL23/STAT3 signaling controls neutrophil recruitment during the onset of inflammation. GEO accession number: GSE154129.

IL-23 reshapes kidney resident cell metabolism and promotes local kidney inflammation

Interstitial kidney inflammation is present in various nephritides in which serum interleukin 23 (IL-23) is elevated. Here we showed that murine and human renal tubular epithelial cells (TECs) expressing the IL-23 receptor (IL-23R) responded to IL-23 by inducing intracellular calcium flux, enhancing glycolysis, and upregulating calcium/calmodulin kinase IV (CaMK4), which resulted in suppression of the expression of the arginine-degrading enzyme arginase 1 (ARG1), thus increasing in situ levels of free L-arginine. Limited availability of arginine suppressed the ability of infiltrating T cells to proliferate and produce inflammatory cytokines. TECs from humans and mice with nephritis expressed increased levels of IL-23R and CaMK4 but reduced levels of ARG1. TEC-specific deletion of Il23r or Camk4 suppressed inflammation, whereas deletion of Arg1 exacerbated inflammation in different murine disease models. Finally, TEC-specific delivery of a CaMK4 inhibitor specifically curbed renal inflammation in lupus-prone mice without affecting systemic inflammation. Our data offer the first evidence to our knowledge of the immunosuppressive capacity of TECs through a mechanism that involves competitive uptake of arginine and signify the importance of modulation of an inflammatory cytokine in the function of nonlymphoid cells, which leads to the establishment of an inflammatory microenvironment. New approaches to treat kidney inflammation should consider restoring the immunosuppressive capacity of TECs.

G-protein coupled receptor 35 (GPR35) regulates the colonic epithelial cell response to enterotoxigenic Bacteroides fragilis

G protein-coupled receptor (GPR)35 is highly expressed in the gastro-intestinal tract, predominantly in colon epithelial cells (CEC), and has been associated with inflammatory bowel diseases (IBD), suggesting a role in gastrointestinal inflammation. The enterotoxigenic Bacteroides fragilis (ETBF) toxin (BFT) is an important virulence factor causing gut inflammation in humans and animal models. We identified that BFT signals through GPR35. Blocking GPR35 function in CECs using the GPR35 antagonist ML145, in conjunction with shRNA knock-down and CRISPRcas-mediated knock-out, resulted in reduced CEC-response to BFT as measured by E-cadherin cleavage, beta-arrestin recruitment and IL-8 secretion. Importantly, GPR35 is required for the rapid onset of ETBF-induced colitis in mouse models. GPR35-deficient mice showed reduced death and disease severity compared to wild-type C57Bl6 mice. Our data support a role for GPR35 in the CEC and mucosal response to BFT and underscore the importance of this molecule for sensing ETBF in the colon.

Crossing the boundaries: IL-23 and its role in linking inflammation of the skin, gut and joints

Several lines of evidence point towards the central role of IL-23 as a crucial inflammatory mediator in the pathogenesis of SpA—a group of inflammatory arthritic diseases whose symptoms span the skin, gastrointestinal tract and joints. While therapeutic blockade of IL-23 proved successful in the treatment of IBD, psoriatic skin disease and peripheral SpA, it failed in patients suffering from SpA with predominantly axial involvement. Here we review state-of-the-art discoveries on IL-23 signalling pathways across target tissues involved in SpA. We discuss the discrepancies in resident IL-23–responding cells and their downstream activities across skin, gut and joint that shape the unique immunological landscape of SpA.

Act Locally, Act Globally-Microbiota, Barriers, and Cytokines in Atherosclerosis

Atherosclerosis is a lipid-driven chronic inflammatory disease that is characterized by the formation and progressive growth of atherosclerotic plaques in the wall of arteries. Atherosclerosis is a major predisposing factor for stroke and heart attack. Various immune-mediated mechanisms are implicated in the disease initiation and progression. Cytokines are key mediators of the crosstalk between innate and adaptive immune cells as well as non-hematopoietic cells in the aortic wall and are emerging players in the regulation of atherosclerosis. Progression of atherosclerosis is always associated with increased local and systemic levels of pro-inflammatory cytokines. The role of cytokines within atherosclerotic plaque has been extensively investigated; however, the cell-specific role of cytokine signaling, particularly the role of cytokines in the regulation of barrier tissues tightly associated with microbiota in the context of cardiovascular diseases has only recently come to light. Here, we summarize the knowledge about the function of cytokines at mucosal barriers and the interplay between cytokines, barriers, and microbiota and discuss their known and potential implications for atherosclerosis development.

IL-12 Family Cytokines in Cancer and Immunotherapy

The IL-12 family cytokines are a group of unique heterodimeric cytokines that include IL-12, IL-23, IL-27, IL-35 and, most recently, IL-39. Recent studies have solidified the importance of IL-12 cytokines in shaping innate and adaptive immune responses in cancer and identified multipronged roles for distinct IL-12 family members, ranging from effector to regulatory immune functions. These cytokines could serve as promising candidates for the development of immunomodulatory therapeutic approaches. Overall, IL-12 can be considered an effector cytokine and has been found to engage anti-tumor immunity by activating the effector Th1 response, which is required for the activation of cytotoxic T and NK cells and tumor clearance. IL-23 and IL-27 play dual roles in tumor immunity, as they can both activate effector immune responses and promote tumor growth by favoring immune suppression. IL-35 is a potent regulatory cytokine and plays a largely pro-tumorigenic role by inhibiting effector T cells. In this review, we summarize the recent findings on IL-12 family cytokines in the control of tumor growth with an emphasis primarily on immune regulation. We underscore the clinical implications for the use of these cytokines either in the setting of monotherapy or in combination with other conventional therapies for the more effective treatment of malignancies.

Enteropathogenic Escherichia coli Infection Induces Diarrhea, Intestinal Damage, Metabolic Alterations, and Increased Intestinal Permeability in a Murine Model

Enteropathogenic E. coli (EPEC) are recognized as one of the leading bacterial causes of infantile diarrhea worldwide. Weaned C57BL/6 mice pretreated with antibiotics were challenged orally with wild-type EPEC or escN mutant (lacking type 3 secretion system) to determine colonization, inflammatory responses and clinical outcomes during infection. Antibiotic disruption of intestinal microbiota enabled efficient colonization by wild-type EPEC resulting in growth impairment and diarrhea. Increase in inflammatory biomarkers, chemokines, cellular recruitment and pro-inflammatory cytokines were observed in intestinal tissues. Metabolomic changes were also observed in EPEC infected mice with changes in tricarboxylic acid (TCA) cycle intermediates, increased creatine excretion and shifts in gut microbial metabolite levels. In addition, by 7 days after infection, although weights were recovering, EPEC-infected mice had increased intestinal permeability and decreased colonic claudin-1 levels. The escN mutant colonized the mice with no weight loss or increased inflammatory biomarkers, showing the importance of the T3SS in EPEC virulence in this model. In conclusion, a murine infection model treated with antibiotics has been developed to mimic clinical outcomes seen in children with EPEC infection and to examine potential roles of selected virulence traits. This model can help in further understanding mechanisms involved in the pathogenesis of EPEC infections and potential outcomes and thus assist in the development of potential preventive or therapeutic interventions.

Diet Rich in Simple Sugars Promotes Pro-Inflammatory Response via Gut Microbiota Alteration and TLR4 Signaling

Diet is a strong modifier of microbiome and mucosal microenvironment in the gut. Recently, components of western-type diets have been associated with metabolic and immune diseases. Here, we studied how high-sugar diet (HSD) consumption influences gut mucosal barrier and immune response under steady state conditions and in a mouse model of acute colitis. We found that HSD significantly increased gut permeability, spleen weight, and neutrophil levels in spleens of healthy mice. Subsequent dextran sodium sulfate administration led to severe colitis. In colon, HSD significantly promoted neutrophil infiltration and increased the levels of IL-6, IL-1β, and TNF-α. Moreover, HSD-fed mice had significantly higher abundance of pathobionts, such as Escherichia coli and Candida, in fecal samples. Although germ-free mice colonized with microbiota of conventionally reared mice that consumed different diets had equally severe colitis, mice colonized with HSD microbiota showed markedly increased infiltration of neutrophils to the gut. The induction of colitis in Toll-like receptor 4 (TLR4)-deficient HSD-fed mice led to significantly milder colitis than in wild-type mice. In conclusion, our results suggested a significant role of HSD in disruption of barrier integrity and balanced mucosal and systemic immune response. In addition, these processes seemed to be highly influenced by resident potentially pathogenic microbiota or metabolites via the TLR4 signaling pathway.

All are Equal, Some are More Equal: Targeting IL 12 and 23 in IBD - A Clinical Perspective

Chronic inflammatory diseases like inflammatory bowel diseases (IBD) or psoriasis represents a worldwide health burden. Researchers provided great achievements in understanding the origin of these diseases leading to improved therapeutic options. The discovery of cytokines like tumor necrosis factor-α or transforming growth factor-β are examples for these efforts. Interleukin 12 (IL 12) and interleukin 23 (IL 23) represent different important cytokines in this regard. They both belong to the interleukin 12 family and are related by sharing the subunit p40. Ustekinumab is an antibody that blocks p40 and thereby interleukins 12 and 23. Trials showed promising results in treating IBD patients with this drug. Consequently, new questions arose about the distinct features of IL 12 and 23. This review focuses on these interleukins regarding their functions in the healthy and inflamed gut and provides an overview about the results from in vitro and in vivo studies as well as clinical trials.

IL-23/IL-17 Axis in Inflammatory Rheumatic Diseases

In inflammatory rheumatic disorders, the immune system attacks and damages the connective tissues and invariably internal organs. During the past decade, remarkable advances having been made towards our understanding on the cellular and molecular mechanisms involved in rheumatic diseases. The discovery of IL-23/IL-17 axis and the delineation of its important role in the inflammation led to the introduction of many needed new therapeutic tools. We will present an overview of the rationale for targeting therapeutically the IL-23/IL-17 axis in rheumatic diseases and the clinical benefit which has been realized so far. Finally, we will discuss the complex interrelationship between IL-23 and IL-17 and the possible uncoupling in certain disease settings.

Gut Microbiota-Derived Propionate Regulates the Expression of Reg3 Mucosal Lectins and Ameliorates Experimental Colitis in Mice

BACKGROUND AND AIMS

Regenerating islet-derived protein type 3 [Reg3] lectins are antimicrobial peptides at mucosal surfaces of the gut, whose expression is regulated by pathogenic gut microbes via interleukin-22- or Toll-like receptor signalling. In addition to antimicrobial effects, tissue protection is hypothesized, but has been poorly investigated in the gut.

METHODS

We applied antibiotic-induced microbiota perturbations, gnotobiotic approaches and a dextran-sodium sulfate [DSS] colitis model to assess microbial Reg3 regulation in the intestines and its role in colitis. We also used an intestinal organoid model to investigate this axis in vitro.

RESULTS

First, we studied whether gut commensals are involved in Reg3 expression in mice, and found that antibiotic-mediated reduction of Clostridia downregulated intestinal Reg3B. A loss in Clostridia was accompanied by a significant reduction of short-chain fatty acids [SCFAs], and knock-out [KO] mice for SCFA receptors GPR43 and GPR109 expressed less intestinal Reg3B/-G. Propionate was found to induce Reg3 in intestinal organoids and in gnotobiotic mice colonized with a defined, SCFA-producing microbiota. Investigating the role of Reg3B as a protective factor in colitis, we found that Reg3B-KO mice display increased inflammation and less crypt proliferation in the DSS colitis model. Propionate decreased colitis and increased proliferation. Treatment of organoids exposed to DSS with Reg3B or propionate reversed the chemical injury with a loss of expression of the stem-cell marker Lgr5 and Olfm4.

CONCLUSIONS

Our results suggest that Clostridia can regulate Reg3-associated epithelial homeostasis through propionate signalling. We also provide evidence that the Reg3-propionate axis may be an important mediator of gut epithelial regeneration in colitis.

Interleukin-22 drives a metabolic adaptive reprogramming to maintain mitochondrial fitness and treat liver injury

Rationale: Interleukin 22 (IL-22) is an epithelial survival cytokine that is at present being explored as therapeutic agents for acute and chronic liver injury. However, its molecular basis of protective activities remains poorly understood. Methods: Here we demonstrate that IL-22 inhibits the deteriorating metabolic states induced by stimuli in hepatocytes. Utilizing cell biological, molecular, and biochemical approaches, we provide evidence that IL-22 promotes oxidative phosphorylation (OXPHOS) and glycolysis and regulates the metabolic reprogramming related transcriptional responses. Results: IL-22 controls metabolic regulators and enzymes activity through the induction of AMP-activated protein kinase (AMPK), AKT and mammalian target of rapamycin (mTOR), thereby ameliorating mitochondrial dysfunction. The upstream effector lncRNA H19 also participates in the controlling of these metabolic processes in hepatocytes. Importantly, amelioration of liver injury by IL-22 through activation of metabolism relevant signaling and regulation of mitochondrial function are further demonstrated in cisplatin-induced liver injury and steatohepatitis. Conclusions: Collectively, our results reveal a novel mechanism underscoring the regulation of metabolic profiles of hepatocytes by IL-22 during liver injury, which might provide useful insights from the bench to the clinic in treating and preventing liver diseases.

Th17 Cells in Inflammatory Bowel Disease: An Update for the Clinician

Studies in humans strongly implicate Th17 cells in the pathogenesis of inflammatory bowel disease. Thus, Th17 cells are major targets of approved and emerging biologics. Herein, we review the role of Th17 in IBD with a clinical focus.

BATF2 prevents T-cell-mediated intestinal inflammation through regulation of the IL-23/IL-17 pathway

Inappropriate activation of the IL-23 signaling pathway causes chronic inflammation through the induction of immunopathological Th17 cells in several tissues including the intestine, whereas adequate Th17 responses are essential for host defense against harmful organisms. In the intestinal lamina propria, IL-23 is primarily produced by innate myeloid cells including dendritic cells (DCs) and macrophages (Mϕs). However, the molecular mechanisms underlying the regulation of IL-23 production by these cells remains poorly understood. In this study, we demonstrated that BATF2 regulates intestinal homeostasis by inhibiting IL-23-driven T-cell responses. Batf2 was highly expressed in intestinal innate myeloid subsets, such as monocytes, CD11b+ CD64+ Mϕs and CD103+ DCs. Batf2-/- mice spontaneously developed colitis and ileitis with altered microbiota composition. In this context, IL-23, but not TNF-α and IL-10, was produced in high quantities by intestinal CD11b+ CD64+ Mϕs from Batf2-/- mice compared with wild-type mice. Moreover, increased numbers of IFN-γ+, IL-17+ and IFN-γ+ IL-17+ CD4+ T cells, but not IL-10+ CD4+ T cells, accumulated in the colons and small intestines of Batf2-/- mice. In addition, RORγt-expressing innate lymphoid cells were increased in Batf2-/- mice. Batf2-/-Rag2-/- mice showed a reduction in intestinal inflammation present in Batf2-/- mice. Furthermore, the high numbers of intestinal IL-17+ and IFN-γ+ IL-17+ CD4+ T cells were markedly reduced in Batf2-/- mice when introducing Il23a deficiency, which was associated with the abrogation of intestinal inflammation. These results indicated that BATF2 in innate myeloid cells is a key molecule for the suppression of IL-23/IL-17 pathway-mediated adaptive intestinal pathology.

Interleukin 23 and autoimmune diseases: current and possible future therapies

PURPOSE

IL-23 is a central proinflammatory cytokine with a wide range of influence over immune response. It is implicated in several autoimmune diseases due to the infinite inflammatory loops it can create through the positive feedbacks of both IL-17 and IL-22 arms. This made IL-23 a key target of autoimmune disorders therapy, which indeed was proven to inhibit inflammation and ameliorate diseases. Current autoimmune treatments targeting IL-23 are either by preventing IL-23 ligation to its receptor (IL-23R) via antibodies or inhibiting IL-23 signaling by signaling downstream mediators' inhibitors, with each approach having its own pros and cons.

METHODS

Literature review was done to further understand the biology of IL-23 and current therapies.

RESULTS

In this review, we discuss the biological features of IL-23 and its role in the pathogenesis of autoimmune diseases including psoriasis, rheumatoid arthritis and inflammatory bowel diseases. Advantages, limitations and side effects of each concept will be reviewed, suggesting several advanced IL-23-based bio-techniques to generate new and possible future therapies to overcome current treatments problems.

Role of the IL-23 pathway in the pathogenesis and treatment of enthesitis in psoriatic arthritis

INTRODUCTION

Enthesitis is a key feature of spondyloarthritis (SpA). Several studies have underlined the role of interleukin (IL)-23 in SpA development as a crucial cytokine in the pathogenesis of enthesitis.

AREA COVERED

This review summarizes recent evidence of the role of IL-23 in the pathogenesis of and as a target of the treatment of enthesitis. We review the definition, diagnosis and clinical impact of enthesitis and its connection with microbial infections, gut dysbiosis, and mechanical stress. We also review clinical trials and real-life studies of drugs targeting the p19 or p40 subunits of IL-23.

EXPERT OPINION

Novel therapies targeting the p19 or p40 subunit of IL-23 appear to be promising treatment options for patients with enthesitis. Although we are currently unable to identify the best therapeutic window to target IL-23 in SpA disease evolution, the promising ability of this therapy to control the gut-entheseal axis is increasing our knowledge of SpA pathogenesis.

Human β-Defensin 2 Mediated Immune Modulation as Treatment for Experimental Colitis

Defensins represents an integral part of the innate immune system serving to ward off potential pathogens and to protect the intestinal barrier from microbial encroachment. In addition to their antimicrobial activities, defensins in general, and human β-defensin 2 (hBD2) in particular, also exhibit immunomodulatory capabilities. In this report, we assessed the therapeutic efficacy of systemically administered recombinant hBD2 to ameliorate intestinal inflammation in three distinct animal models of inflammatory bowel disease; i.e., chemically induced mucosal injury (DSS), loss of mucosal tolerance (TNBS), and T-cell transfer into immunodeficient recipient mice. Treatment efficacy was confirmed in all tested models, where systemically administered hBD2 mitigated inflammation, improved disease activity index, and hindered colitis-induced body weight loss on par with anti-TNF-α and steroids. Treatment of lipopolysaccharide (LPS)-activated human peripheral blood mononuclear cells with rhBD2 confirmed the immunomodulatory capacity in the circulatory compartment. Subsequent analyzes revealed dendritic cells (DCs) as the main target population. Suppression of LPS-induced inflammation was dependent on chemokine receptor 2 (CCR2) expression. Mechanistically, hBD2 engaged with CCR2 on its DC target cell to decrease NF-κB, and increase CREB phosphorylation, hence curbing inflammation. To our knowledge, this is the first study showing in vivo efficacy of a systemically administered defensin in experimental disease.