Interleukin-22: immunobiology and pathology

Recent Progress in Multiple Sclerosis Treatment Using Immune Cells as Targets

Multiple sclerosis (MS) is an autoimmune-mediated demyelinating disease of the central nervous system. The main pathological features are inflammatory reaction, demyelination, axonal disintegration, reactive gliosis, etc. The etiology and pathogenesis of the disease have not been clarified. The initial studies believed that T cell-mediated cellular immunity is the key to the pathogenesis of MS. In recent years, more and more evidence has shown that B cells and their mediated humoral immune and innate immune cells (such as microglia, dendritic cells, macrophages, etc.) also play an important role in the pathogenesis of MS. This article mainly reviews the research progress of MS by targeting different immune cells and analyzes the action pathways of drugs. The types and mechanisms of immune cells related to the pathogenesis are introduced in detail, and the mechanisms of drugs targeting different immune cells are discussed in depth. This article aims to clarify the pathogenesis and immunotherapy pathway of MS, hoping to find new targets and strategies for the development of therapeutic drugs for MS.

PTPN2 regulates bacterial clearance in a mouse model of enteropathogenic and enterohemorrhagic E. coli infection

Macrophages intimately interact with intestinal epithelial cells, but the consequences of defective macrophage-epithelial cell interactions for protection against enteric pathogens are poorly understood. Here, we show that in mice with a deletion in protein tyrosine phosphatase nonreceptor type 2 (PTPN2) in macrophages, infection with Citrobacter rodentium, a model of enteropathogenic and enterohemorrhagic E. coli infection in humans, promoted a strong type 1/IL-22-driven immune response, culminating in accelerated disease but also faster clearance of the pathogen. In contrast, deletion of PTPN2 specifically in epithelial cells rendered the epithelium unable to upregulate antimicrobial peptides and consequently resulted in a failure to eliminate the infection. The ability of PTPN2-deficient macrophages to induce faster recovery from C. rodentium was dependent on macrophage-intrinsic IL-22 production, which was highly increased in macrophages deficient in PTPN2. Our findings demonstrate the importance of macrophage-mediated factors, and especially macrophage-derived IL-22, for the induction of protective immune responses in the intestinal epithelium, and show that normal PTPN2 expression in the epithelium is crucial to allow for protection against enterohemorrhagic E. coli and other intestinal pathogens.

Interleukin-22 alleviates alcohol-associated hepatic fibrosis, inhibits autophagy, and suppresses the PI3K/AKT/mTOR pathway in mice

BACKGROUND

Alcohol-associated hepatic fibrosis is a widespread liver disease with no effective treatment. Recent studies have indicated that interleukin-22 (IL-22) can ameliorate alcohol-associated liver disease. However, the mechanism underlying the role of IL-22 in alcohol-associated hepatic fibrosis remains unclear. Therefore, we investigated the effect of IL-22 in a mouse model of alcohol-associated hepatic fibrosis and its underlying mechanisms.

METHODS

Alcohol-associated hepatic fibrosis was induced by feeding male C57BL/6J mice with a Lieber-DeCarli liquid diet containing 4% ethyl alcohol for 8 weeks and injecting them with 5% tetrachloromethane (CCl₄ ) intraperitoneally for the last 4 weeks. During the last 4 weeks, IL-22 was also administered. We investigated the role of IL-22 in autophagy and the PI3K/AKT/mTOR signaling pathway using a 3-methyladenine intraperitoneal injection in the mice treated with IL-22. The effects of IL-22 on alcohol-associated hepatic fibrosis, autophagy-related gene expression, and PI3K/AKT/mTOR activity were assessed using histopathology, biochemical analysis, transmission electron microscopy, quantitative real-time PCR, immunohistochemistry, and western blotting.

RESULTS

Mice treated with ethanol and CCl₄ displayed distinct liver injuries, including hepatocyte necrosis, inflammatory cell infiltration, and hepatic fibrosis, which were substantially attenuated by IL-22 treatment. In addition, we found that IL-22 regulated the expression of autophagy-related genes and inhibited the PI3K/AKT/mTOR pathway, as evidenced by the reduction in p-PI3K, p-AKT, and p-mTOR expression after IL-22 treatment.

CONCLUSIONS

IL-22 exerts a marked protective effect against alcohol-associated hepatic fibrosis. Its effect may be partly related to the alteration of autophagy-related gene expression and inhibition of the PI3K/AKT/mTOR pathway in the liver.

Choline supplementation regulates gut microbiome diversity, gut epithelial activity, and the cytokine gene expression in gilts

Choline is an essential nutrient that is necessary for both fetal development and maintenance of neural function, while its effect on female ovarian development is largely unexplored. Our previous study demonstrated that choline supplementation promotes ovarian follicular development and ovulation, although its underlying mechanism was unclear. To uncover the potential regulation pathway, eighteen female Yorkshire × Landrace gilts were fed with either standard commercial diet (Control group, n = 9) or choline supplemented diet (Choline group, additional 500 mg/kg of control diet, n = 9) from day 90 of age to day 186. At day 186, feces samples were analyzed for effects on the gut microbiome using 16S ribosomal RNA gene V3-V4 region sequencing with Illumina MiSeq, serum samples were analyzed for trimethylamine (TMA) and trimethylamine-N-oxide (TMAO) using HILIC method, and jejunum tissues were analyzed for immune related gene expression using qRT-PCR. Our results show that choline supplementation did not alter the circulating level of TMA and TMAO (P > 0.05), but rather increased gut microbiome alpha diversity (P < 0.05). Beta diversity analysis results showed that the choline diet mainly increased the abundance of Firmicutes, Proteobacteria, and Actinobacteria, but decreased the abundance of Bacteroidetes, Spirochaetes, and Euryarchaeota at the phyla level. Meta-genomic analysis revealed that choline supplementation activated pathways in the gut microbiota associated with steroid hormone biosynthesis and degradation of infertility-causing environmental pollutants (bisphenol, xylene, and dioxins). To further verify the effect of choline on intestinal activity, a porcine intestine cell line (IPEC-J2) was treated with serial concentrations of choline chloride in vitro. Our data demonstrated that choline promoted the proliferation of IPEC-J2 while inhibiting the apoptotic activity. qRT-PCR results showed that choline significantly increased the expression level of Bcl2 in both IPEC-J2 cells and jejunum tissues. The expression of IL-22, a cytokine that has been shown to impact ovarian function, was increased by choline treatment in vitro. Our findings reveal the beneficial effect of choline supplementation on enhancing the gut microbiome composition and intestinal epithelial activity, and offer insights into how these changes may have contributed to the ovarian development-promoting effect we reported in our previous study.

Current Knowledge of Th22 Cell and IL-22 Functions in Infectious Diseases

T helper 22 (Th22) cells, a newly defined CD4+ T-cell lineage, are characterized by their distinct cytokine profile, which primarily consists of IL-13, IL-22 and TNF-α. Th22 cells express a wide spectrum of chemokine receptors, such as CCR4, CCR6 and CCR10. The main effector molecule secreted by Th22 cells is IL-22, a member of the IL-10 family, which acts by binding to IL-22R and triggering a complex downstream signaling system. Th22 cells and IL-22 have been found to play variable roles in human immunity. In preventing the progression of infections such as HIV and influenza, Th22/IL-22 exhibited protective anti-inflammatory characteristics, and their deleterious proinflammatory activities have been demonstrated to exacerbate other illnesses, including hepatitis B and Helicobacter pylori infection. Herein, we review the current understanding of Th22 cells, including their definition, differentiation and mechanisms, and the effect of Th22/IL-22 on human infectious diseases. According to studies on Th22 cells, Th22/IL-22 may be a promising therapeutic target and an effective treatment strategy for various infections.

Immunology of Giant Cell Arteritis

Giant cell arteritis is an autoimmune disease of medium and large arteries, characterized by granulomatous inflammation of the three-layered vessel wall that results in vaso-occlusion, wall dissection, and aneurysm formation. The immunopathogenesis of giant cell arteritis is an accumulative process in which a prolonged asymptomatic period is followed by uncontrolled innate immunity, a breakdown in self-tolerance, the transition of autoimmunity from the periphery into the vessel wall and, eventually, the progressive evolution of vessel wall inflammation. Each of the steps in pathogenesis corresponds to specific immuno-phenotypes that provide mechanistic insights into how the immune system attacks and damages blood vessels. Clinically evident disease begins with inappropriate activation of myeloid cells triggering the release of hepatic acute phase proteins and inducing extravascular manifestations, such as muscle pains and stiffness diagnosed as polymyalgia rheumatica. Loss of self-tolerance in the adaptive immune system is linked to aberrant signaling in the NOTCH pathway, leading to expansion of NOTCH1+CD4+ T cells and the functional decline of NOTCH4+ T regulatory cells (Checkpoint 1). A defect in the endothelial cell barrier of adventitial vasa vasorum networks marks Checkpoint 2; the invasion of monocytes, macrophages and T cells into the arterial wall. Due to the failure of the immuno-inhibitory PD-1 (programmed cell death protein 1)/PD-L1 (programmed cell death ligand 1) pathway, wall-infiltrating immune cells arrive in a permissive tissues microenvironment, where multiple T cell effector lineages thrive, shift toward high glycolytic activity, and support the development of tissue-damaging macrophages, including multinucleated giant cells (Checkpoint 3). Eventually, the vascular lesions are occupied by self-renewing T cells that provide autonomy to the disease process and limit the therapeutic effectiveness of currently used immunosuppressants. The multi-step process deviating protective to pathogenic immunity offers an array of interception points that provide opportunities for the prevention and therapeutic management of this devastating autoimmune disease.

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.

Assessment of the Relationship Between Inflammation and Glomerular Filtration Rate

Background

Chronic kidney disease (CKD) is a global health problem. As it progresses to end stages, renal replacement therapy is required but ultimately, the best treatment is transplantation. Decreased renal function has been associated with an inflammatory state associated to primary CKD and in kidney transplant recipients (KTRs).

Objective

To establish how the serum concentrations of some cytokines, such as interleukin (IL)-2, IL-8, IL-22, IL-17α, interferon-gamma, IL-4, and transforming growth factor-β, correlate with various CKD stages.

Methods

One hundred and forty-one KTRs between the ages of 18 and 75 years were included in the study. We also included 112 live kidney donors, 37 CKD PG_CKD+3, and 76 GP_healthy. Participants were grouped according to their glomerular filtration rate (GFR) and their circulating cytokine levels, previously quantified by ELISA.

Results

By linear regression analysis, we established the relation of each cytokine with the GFR. Transforming growth factor-β correlated positively with the GFR in the study population, except in healthy individuals. A negative correlation of IL-8 and IL-17α and GFR was found in all cases.

Conclusions

Whether these cytokines (IL-8 and IL-17α) could be used as inflammatory biomarkers indicating CKD progression, regardless of the type of population, remains to be prospectively determined.

T cell-derived interleukin-22 drives the expression of CD155 by cancer cells to suppress NK cell function and promote metastasis

Although T cells can exert potent anti-tumor immunity, a subset of T helper (Th) cells producing interleukin-22 (IL-22) in breast and lung tumors is linked to dismal patient outcome. Here, we examined the mechanisms whereby these T cells contribute to disease. In murine models of lung and breast cancer, constitutional and T cell-specific deletion of Il22 reduced metastases without affecting primary tumor growth. Deletion of the IL-22 receptor on cancer cells decreases metastasis to a degree similar to that seen in IL-22-deficient mice. IL-22 induced high expression of CD155, which bound to the activating receptor CD226 on NK cells. Excessive activation led to decreased amounts of CD226 and functionally impaired NK cells, which elevated the metastatic burden. IL-22 signaling was also associated with CD155 expression in human datasets and with poor patient outcomes. Taken together, our findings reveal an immunosuppressive circuit activated by T cell-derived IL-22 that promotes lung metastasis.

Two faces: IL-22 effects prevail over defense against metastasis

Interleukin-22 (IL-22) is a cytokine with pleotropic and opposing roles in physiological and pathological states. In this issue of Immunity, Giannou et al. and Briukhovetska et al. demonstrate how IL-22 is involved in promoting cancer metastasis formation.

The Role of Inflammation in the Pathogenesis of Psoriasis

"Psoriasis is a chronic inflammatory skin condition with genetic determinism characterized by the presence of welldefined, erythematous plaques, covered by white, pearly, stratified scales, located on the extension areas, the skin of the scalp, intertriginous regions. The origin of psoriasis is multifactorial, involving hereditary and environmental pathogenic mechanisms. It is triggered by various risk factors involving a variety of processes, such as inflammation, antigen presentation, cell signaling, and transcriptional regulation. "

Evolution of developmental and comparative immunology in poultry: The regulators and the regulated

Avian has a unique immune system that evolved in response to environmental pressures in all aspects of innate and adaptive immune responses, including localized and circulating lymphocytes, diversity of immunoglobulin repertoire, and various cytokines and chemokines. All of these attributes make birds an indispensable vertebrate model for studying the fundamental immunological concepts and comparative immunology. However, research on the immune system in birds lags far behind that of humans, mice, and other agricultural animal species, and limited immune tools have hindered the adequate application of birds as disease models for mammalian systems. An in-depth understanding of the avian immune system relies on the detailed studies of various regulated and regulatory mediators, such as cell surface antigens, cytokines, and chemokines. Here, we review current knowledge centered on the roles of avian cell surface antigens, cytokines, chemokines, and beyond. Moreover, we provide an update on recent progress in this rapidly developing field of study with respect to the availability of immune reagents that will facilitate the study of regulatory and regulated components of poultry immunity. The new information on avian immunity and available immune tools will benefit avian researchers and evolutionary biologists in conducting fundamental and applied research.

Advances in Current Drugs and Formulations for the Management of Atopic Dermatitis

Atopic dermatitis (AD) is a chronic, relapsing inflammatory skin disease with a complex pathophysiology. Treatment of AD remains challenging owing to the presence of a wide spectrum of clinical phenotypes and limited response to existing therapies. However, recent genetic, immunological, and pathophysiological insights into the disease mechanism resulted in the invention of novel therapeutic drug candidates. This review provides a comprehensive overview of current therapies and assesses various novel drug delivery strategies currently under clinical investigation. Further, this review majorly emphasizes on various topical treatments including emollient therapies, barrier repair agents, topical corticosteroids (TCS), phosphodiesterase 4 (PDE4) inhibitors, calcineurin inhibitors, and Janus kinase (JAK)-signal transducer and activator of transcription (STAT) pathway inhibitors. It also discusses biological and systemic therapies, upcoming treatments based on ongoing clinical trials. Additionally, this review scrutinized the use of pharmaceutical inactive ingredients in the approved topical dosage forms for AD treatment.

Vitamin D influences gut microbiota and acetate production in zebrafish (Danio rerio) to promote intestinal immunity against invading pathogens

Although evidence has shown that vitamin D (VD) influences gut homeostasis, limited knowledge is available how VD regulates intestinal immunity against bacterial infection. In the present study, cyp2r1 mutant zebrafish, lacking the capacity to metabolize VD, and zebrafish fed a diet devoid of VD, were utilized as VD-deficient animal models. Our results confirmed that the expression of antimicrobial peptides (AMPs) and IL-22 was restrained and the susceptibility to bacterial infection was increased in VD-deficient zebrafish. Furthermore, VD induced AMP expression in zebrafish intestine by activating IL-22 signaling, which was dependent on the microbiota. Further analysis uncovered that the abundance of the acetate-producer Cetobacterium in VD-deficient zebrafish was reduced compared to WT fish. Unexpectedly, VD promoted the growth and acetate production of Cetobacterium somerae under culture in vitro. Importantly, acetate treatment rescued the suppressed expression of β-defensins in VD-deficient zebrafish. Finally, neutrophils contributed to VD-induced AMP expression in zebrafish. In conclusion, our study elucidated that VD modulated gut microbiota composition and production of short-chain fatty acids (SCFAs) in zebrafish intestine, leading to enhanced immunity.

Increased serum interleukin 22 levels in patients with axial spondyloarthritis

OBJECTIVES

The role of IL-22 in radiographic axial spondyloarthritis is not fully elucidated. Thus, there is a need for new insights into this cytokine in this disease. We aimed to compare interleukin (IL)-22 level between spondyloarthritis, nonspecific-low back pain patients, and pain-free controls, and to evaluate associations between this cytokine and spondyloarthritis characteristics.

METHODS

We conducted a case-control study including 62 patients with radiographic axial spondyloarthritis (G1), 46 with nonspecific low back pain (G2), and 42 healthy volunteers (G3). IL-22 was measured using Enzyme-linked immunosorbent assay. We evaluate disease activity and structural damage of spondyloarthritis.

RESULTS

IL-22 level was higher in G1 than in G2 and G3 (38±40 versus14.42±8.17 versus14.3±18.67 pg/mL, p<0.01). IL-22 discriminated patients in G1 from G2 with a cutoff of 22.28pg/mL (Sensitivity: 62.9%, Specificity: 97.8%, area under the curve (AUC): 0.808). IL-22 cutoff of 19.27pg/mL discriminated patients in G1 from G3 (Sensitivity: 67%, Specificity: 94.3%, AUC: 0.855). No associations were found between IL-22 levels and disease activity and structural damage.

CONCLUSIONS

Our study showed that IL-22 level was higher in radiographic axial spondyloarthritis patients compared to controls. It was also able to differentiate G1 patients from G2 and G3. This finding suggests that the IL-22 pathway showed to play a pathological role in spondyloarthritis.

Emerging principles of cytokine pharmacology and therapeutics

Cytokines are secreted signalling proteins that play essential roles in the initiation, maintenance and resolution of immune responses. Although the unique ability of cytokines to control immune function has garnered clinical interest in the context of cancer, autoimmunity and infectious disease, the use of cytokine-based therapeutics has been limited. This is due, in part, to the ability of cytokines to act on many cell types and impact diverse biological functions, resulting in dose-limiting toxicity or lack of efficacy. Recent studies combining structural biology, protein engineering and receptor pharmacology have unlocked new insights into the mechanisms of cytokine receptor activation, demonstrating that many aspects of cytokine function are highly tunable. Here, we discuss the pharmacological principles underlying these efforts to overcome cytokine pleiotropy and enhance the therapeutic potential of this important class of signalling molecules.

Supplemental wheat germ modulates phosphorylation of STAT3 in the gut and NF-κBp65 in the adipose tissue of mice fed a Western diet

Background

Commensal gut bacteria, including Lactobacillus, can produce metabolites that stimulate the release of gut antimicrobial peptides (AMPs) via the signal transducer and activator of transcription (STAT)3 pathway and prevent obesity-associated leaky gut and chronic inflammation. We have previously reported that wheat germ (WG) selectively increased cecal Lactobacillus in obese mice.

Objectives

This study investigated the effects of WG on gut STAT3 activation and AMPs (Reg3γ and Reg3β) as well as the potential of WG to inhibit nuclear Nf-κB-activation and immune cell infiltration in the visceral adipose tissue (VAT) of mice fed a Western diet (i.e., high-fat and sucrose diet [HFS]).

Methods

Six-wk-old male C57BL/6 mice were randomly assigned to 4 groups (n = 12/group): control (C, 10% fat and sucrose kcal) or HFS (45% fat and 26% sucrose kcal) diet with or without 10% WG (wt/wt) for 12 wk. Assessments include serum metabolic parameters jejunal AMPs genes, inflammatory markers, and phosphorylation of STAT3 as well as VAT NF-κBp65. Independent and interaction effects of HFS and WG were analyzed with a 2-factor ANOVA.

Results

WG significantly improved markers of insulin resistance and upregulated jejunal Il10 and Il22 genes. The HFS + WG group had a 15-fold increase in jejunal pSTAT3 compared with the HFS group. Consequently, WG significantly upregulated jejunal mRNA expression of Reg3γ and Reg3β. The HFS group had a significantly higher VAT NF-κBp65 phosphorylation than the C group, while the HFS + WG group suppressed this to the level of C. Moreover, VAT Il6 and Lbp genes were downregulated in the HFS + WG group compared with HFS. Genes related to macrophage infiltration in the VAT were repressed in the WG-fed mice.

Conclusion

These findings show the potential of WG to influence vital regulatory pathways in the gut and adipose tissue which may reduce the chronic inflammatory burden on these tissues that are important targets in obesity and insulin resistance.

Disease tolerance: a protective mechanism of lung infections

Resistance and tolerance are two important strategies employed by the host immune response to defend against pathogens. Multidrug-resistant bacteria affect the resistance mechanisms involved in pathogen clearance. Disease tolerance, defined as the ability to reduce the negative impact of infection on the host, might be a new research direction for the treatment of infections. The lungs are highly susceptible to infections and thus are important for understanding host tolerance and its precise mechanisms. This review focuses on the factors that induce lung disease tolerance, cell and molecular mechanisms involved in tissue damage control, and the relationship between disease tolerance and sepsis immunoparalysis. Understanding the exact mechanism of lung disease tolerance could allow better assessment of the immune status of patients and provide new ideas for the treatment of infections.

Activation of mucosal immunity as a novel therapeutic strategy for combating brucellosis

Brucellosis is a disease of livestock that is commonly asymptomatic until an abortion occurs. Disease in humans results from contact of infected livestock or consumption of contaminated milk or meat. Brucella zoonosis is primarily caused by one of three species that infect livestock, Bacillus abortus in cattle, B. melitensis in goats and sheep, and B. suis in pigs. To aid in disease prophylaxis, livestock vaccines are available, but are only 70% effective; hence, improved vaccines are needed to mitigate disease, particularly in countries where disease remains pervasive. The absence of knowing which proteins confer complete protection limits development of subunit vaccines. Instead, efforts are focused on developing new and improved live, attenuated Brucella vaccines, since these mimic attributes of wild-type Brucella, and stimulate host immune, particularly T helper 1-type responses, required for protection. In considering their development, the new mutants must address Brucella's defense mechanisms normally active to circumvent host immune detection. Vaccination approaches should also consider mode and route of delivery since disease transmission among livestock and humans is believed to occur via the naso-oropharyngeal tissues. By arming the host's mucosal immune defenses with resident memory T cells (TRMs) and by expanding the sources of IFN-γ, brucellae dissemination from the site of infection to systemic tissues can be prevented. In this review, points of discussion focus on understanding the various immune mechanisms involved in disease progression and which immune players are important in fighting disease.

Role of IL-22 in acute asthma mouse model

Introduction: Allergic asthma is often associated with eosinophilic inflammation, which is related to the T-helper cell type 2 (Th2) cytokines and responsive to corticosteroids. However, there are also phenotypes of non-Th2-mediated asthma, which have poor responsivity to corticosteroids. The leading phenotype of non-Th2-mediated asthma is neutrophilic asthma, which is considered difficult to treat. Recently, IL-22 has been found to be involved in neutrophilic inflammation in asthma. However, studies on the role of IL-22 in asthma are still controversial as IL-22 has both pro-inflammatory and anti-inflammatory roles in asthma. This study examined whether the IL-22 level increased in acute neutrophilic asthma in the mouse model. Herein, we aimed to demonstrate increased IL-22 levels in neutrophilic asthma and elucidate the pathways leading to elevated neutrophil counts.Methods: Six-week old female BALB/c mice were sensitized and challenged with PBS, ovalbumin (OVA) or OVA + lipopolysaccharide (LPS). The mice were then assigned to one of the following five groups: (1) control (PBS/ PBS), (2) OVA/PBS, (3) OVA/OVA, (4) OVA+LPS/PBS, (5) OVA+LPS/OVA+LPS.Results: The levels of Th2 cytokines, IL-17, and IL-22 were assessed, with investigation of the neutrophil chemokines. This study showed that in the acute neutrophilic asthma, the levels of IL-17 and IL-22 were significantly higher than those in the OVA/OVA group, which represents acute eosinophilic asthma. Moreover, the level of CCL20 increased in the neutrophilic asthma group.Conclusion: Thus, this study suggests that in the acute neutrophilic asthma mouse model, IL-17 and IL-22 may increase with CCL20, resulting in neutrophilic inflammation.

JAK-STAT signaling pathway in the pathogenesis of atopic dermatitis: An updated review

Atopic dermatitis (AD) is a chronic, inflammatory, pruritic form of dermatosis with heterogeneous manifestations that can substantially affect patients' quality of life. AD has a complex pathogenesis, making treatment challenging for dermatologists. The Janus kinase (JAK)-signal transducer and activator of transcription (STAT) pathway plays a central role in modulating multiple immune axes involved in the immunopathogenesis of AD. In particular, Th2 cytokines, including interleukin (IL)-4, IL-5, IL-13, IL-31, and thymic stromal lymphopoietin, which contribute to the symptoms of chronic inflammation and pruritus in AD, are mediated by JAK-STAT signal transduction. Furthermore, JAK-STAT is involved in the regulation of the epidermal barrier and the modulation of peripheral nerves related to the transduction of pruritus. Targeting the JAK-STAT pathway may attenuate these signals and show clinical efficacy through the suppression of various immune pathways associated with AD. Topical and oral JAK inhibitors with variable selectivity have emerged as promising therapeutic options for AD. Notably, topical ruxolitinib, oral upadacitinib, and oral abrocitinib were approved by the U.S. Food and Drug Administration for treating patients with AD. Accordingly, the present study reviewed the role of JAK-STAT pathways in the pathogenesis of AD and explored updated applications of JAK inhibitors in treating AD.

Interleukin (IL)-22 in common carp (Cyprinus carpio L.): Immune modulation, antibacterial defense, and activation of the JAK-STAT signaling pathway

Interleukin (IL)-22 is an IL-10 family cytokine secreted by CD4⁺ T cells and plays an important role in regulating inflammation and infection elimination. IL-22 homologues have been reported in the teleost, but the functions of IL-22 are still unclear. In this study, we identified two duplicated IL-22 genes in common carp (Cyprinus carpio L.), termed Cc_IL-22A and Cc_IL-22B. Sequence analysis showed that Cc_IL-22A and Cc_IL-22B had four conserved cysteine residues, which could form two intra-chain disulfide bridges. The Cc_IL-22A and Cc_IL-22B were constitutively expressed in various tissues, with the highest expression in the gill. The mRNA expression levels of Cc_IL-22A and Cc_IL-22B were significantly up-regulated in the gill, intestine, head kidney, and spleen of common carp challenged with Aeromonas. hydrophila. In vivo study showed that the expression levels of pro-inflammatory cytokines were significantly up-regulated in the head kidney and spleen when Cc_IL-22A or Cc_IL-22B were over-expressed. Furthermore, the over-expression of Cc_IL-22A and Cc_IL-22B indicated a protective effect on tissues, with only lymphocytic infiltration observed in comparison to the control and pcN3 groups, without obvious change in tissue morphology. Similar stimulatory effects of rIL-22A and rIL-22B were observed in vitro. When HKLs were stimulated with rIL-22A or rIL-22B, the expression levels of critical signaling molecules in the Janus kinase (JAK) and signal transducer and activator of transcription (STAT) pathway were significantly induced, including JAK1, JAK3, STAT1, and STAT3, as well as pro-inflammatory cytokines (IL-1β and TNF-α). Together, these results suggest that Cc_IL-22A and Cc_IL-22B may regulate inflammatory responses through the JAK-STAT signaling pathway and have a significant impact on the immune defense of common carp against bacterial infection. Therefore, our study provides a new perspective on the functions of Cc_IL-22A and Cc_IL-22B in the immune defense mechanism of fish.

Metabolic control of innate lymphoid cells in health and disease

Innate lymphoid cells (ILCs) are a family of predominantly tissue-resident lymphocytes that critically orchestrate immunity, inflammation, tolerance and repair at barrier surfaces of the mammalian body. Heterogeneity among ILC subsets is comparable to that of adaptive CD4⁺ T helper cell counterparts, and emerging studies demonstrate that ILC biology is also dictated by cellular metabolism that adapts bioenergetic requirements during activation, proliferation or cytokine production. Accumulating evidence in mouse models and human samples indicates that ILCs exhibit profound roles in shaping states of metabolic health and disease. Here we summarize and discuss our current knowledge of the cell-intrinsic and cell-extrinsic metabolic factors controlling ILC responses, as well as highlight contributions of ILCs to organismal metabolism. It is expected that continued research in this area will advance our understanding of how to manipulate ILCs or their metabolism for therapeutic strategies that benefit human health.

Vitamin D Receptor Gene Polymorphism ApaI as a Predisposing Factor for Psoriasis and Its Relation With Serum Vitamin D Levels and Psoriasis Severity

BACKGROUND AND AIM

Psoriasis is a chronic, relapsing and inflammatory multisystemic disease with both genetic predisposition and autoimmune pathogenic traits. Several types of vitamin D receptor (VDR) polymorphisms have been investigated as a predisposing factor for psoriasis susceptibility with controversial results. However, the exact pathophysiological effect of the VDR gene on psoriasis susceptibility remains poorly understood. We aimed to determine whether VDR gene polymorphisms, specifically rs7975232 (ApaI), afford psoriasis susceptibility in a given community in Saudi Arabia. Also, to assess its possible relation with disease severity.

SUBJECTS AND METHODS

In a comparative case-control study comprising 53 psoriatic patients and 41 matched healthy controls, we measured serum ApaI levels, and the PCR-RFLEP technique detected ApaI genetic polymorphism (rs7975232) for both groups. Serum vitamin D level was measured in both groups.

RESULT

Our results revealed that A/A genotype of ApaI was significantly more predominant in patients than controls, while A/a genotype was more common in healthy subjects. Furthermore, A allele was significantly over-represented in the patients' group compared to the controls (P≤0.001). Serum vitamin D levels were significantly higher in mild psoriatic patients than in those with moderate and severe types (P=0.002). Mild psoriatic patients with a/a genotypes have higher vitamin D levels than severe patients with A/A genotypes and A/a moderate patients (P≤0.001).

CONCLUSION

Our data indicated clearly that VDR gene polymorphism, namely ApaI, is associated with psoriasis susceptibility. Furthermore, serum vitamin D level in psoriatic patients varies among different ApaI genotypes, where it is lowest in AA genotype.

IL-22 and Lactobacillus delbrueckii mitigate alcohol-induced exacerbation of DSS-induced colitis

Ulcerative colitis (UC) is characterized by cycles of active disease flare and inactive disease remission. During UC remission, IL-22 is up-regulated, acting as a hallmark of entrance into UC remission. Recently, we found that in our mouse model of binge alcohol and dextran sodium sulfate (DSS)-induced colitis, alcohol increases severity of UC pathology. In this study, we assessed not only whether alcohol influenced IL-22 expression and thereby perpetuates UC, but also whether recombinant IL-22 (rIL-22) or treatment with a probiotic could alleviate exacerbated symptoms of UC. Levels of large intestine IL-22 were significantly decreased ∼6.9-fold in DSS ethanol compared with DSS vehicle. Examination of lamina propria (LP) cells in the large intestine revealed IL-22+ γδ T cells in DSS vehicle-treated mice were significantly increased, while IL-22+ γδ T cells in DSS ethanol mice were unable to mount this IL-22 response. We administered rIL-22 and found it restored weight loss of DSS ethanol-treated mice. Colonic shortening and increased Enterobacteriaceae were also attenuated. Administration of Lactobacillus delbrueckii attenuated weight loss (p < 0.01), colon length (p < 0.001), mitigated increases in Enterobacteriaceae, increased levels of IL-22, and increased levels of p-STAT3 back to that of DSS vehicle group in DSS ethanol mice. In contrast, sole administration of L. delbrueckii supernatant was not sufficient to reduce UC exacerbation following alcohol. Our findings suggest L. delbrueckii contributes to repair mechanisms by increasing levels of IL-22, resulting in phosphorylation of STAT3, thus attenuating the alcohol-induced increases in intestinal damage after colitis.

Cytokine Profiling in Different SARS-CoV-2 Genetic Variants

This study is a successor of our previous work concerning changes in the chemokine profile in infection that are associated with different SARS-CoV-2 genetic variants. The goal of our study was to take into account both the virus and the host immune system by assessing concentrations of cytokines in patients infected with different SARS-CoV-2 variants (ancestral Wuhan strain, Alpha, Delta and Omicron). Our study was performed on 340 biological samples taken from COVID-19 patients and healthy donors in the timespan between May 2020 and April 2022. We performed genotyping of the virus in nasopharyngeal swabs, which was followed by assessment of cytokines' concentration in blood plasma. We noted that out of nearly 30 cytokines, only four showed stable elevation independently of the variant (IL-6, IL-10, IL-18 and IL-27), and we believe them to be 'constant' markers for COVID-19 infection. Cytokines that were studied as potential biomarkers lose their diagnostic value as the virus evolves, and the specter of potential targets for predictive models is narrowing. So far, only four cytokines (IL-6, IL-10, IL-18, and IL-27) showed a consistent rise in concentrations independently of the genetic variant of the virus. Although we believe our findings to be of scientific interest, we still consider them inconclusive; further investigation and comparison of immune responses to different variants of SARS-CoV-2 is required.

The Future of Targeted Treatment of Primary Sjögren's Syndrome: A Focus on Extra-Glandular Pathology

Primary Sjögren's syndrome (pSS) is a chronic, systemic autoimmune disease defined by exocrine gland hypofunction resulting in dry eyes and dry mouth. Despite increasing interest in biological therapies for pSS, achieving FDA-approval has been challenging due to numerous complications in the trials. The current literature lacks insight into a molecular-target-based approach to the development of biological therapies. This review focuses on novel research in newly defined drug targets and the latest clinical trials for pSS treatment. A literature search was conducted on ClinicalTrials.gov using the search term "Primary Sjögren's syndrome". Articles published in English between 2000 and 2021 were included. Our findings revealed potential targets for pSS treatment in clinical trials and the most recent advances in understanding the molecular mechanisms underlying the pathogenesis of pSS. A prominent gap in current trials is in overlooking the treatment of extraglandular symptoms such as fatigue, depression, and anxiety, which are present in most patients with pSS. Based on dryness and these symptom-directed therapies, emerging biological agents targeting inflammatory cytokines, signal pathways, and immune reaction have been studied and their efficacy and safety have been proven. Novel therapies may complement existing non-pharmacological methods of alleviating symptoms of pSS. Better grading systems that add extraglandular symptoms to gauge disease activity and severity should be created. The future of pSS therapies may lie in gene, stem-cell, and tissue-engineering therapies.

Exposure to dechlorane 602 induces perturbation of gut immunity and microbiota in female mice

The homeostasis of gut immunity and microbiota are associated with the health of the gut. Dechlorane 602 (Dec 602) with food web magnification potential has been detected in daily food. People who were orally exposed to Dec 602 may encounter increased risk of health problems in the gut. In order to reveal the influence of short-term exposure of Dec 602 on gut immunity and microbiota, adult female C57BL/6 mice were administered orally with Dec 602 (low/high doses: 1.0/10.0 μg/kg body weight per day) for 7 days. Lymphocytes were examined by flow cytometry. Gut microbiota was measured by 16S rRNA gene sequencing. Results showed that fecal IgA was upregulated after exposure to the high dose of Dec 602, suggesting that there might be inflammation in the gut. Then, changes of immune cells in mesenteric lymph nodes and colonic lamina propria were examined. We found that exposure to the high dose of Dec 602 decreased the percentages of the anti-inflammatory T regulatory cells in mesenteric lymph nodes. In colonic lamina propria, the production of gut protective cytokine interleukin-22 by CD4⁺ T cells was decreased, and a decreased trend of interleukin-22 production was also observed in type 3 innate lymphoid cells in the high dose group. Furthermore, an altered microbiota composition toward inflammation in the gut was observed after exposure to Dec 602. Additionally, the altered microbiota correlated with changes of immune parameters, suggesting that there were interactions between influenced microbiota and immune parameters after exposure to Dec 602. Taken together, short-term exposure to Dec 602 induced gut immunity and microbiota perturbations, and this might be the mechanisms for Dec 602 to elicit inflammation in the gut.

Down-regulating Interleukin-22/Interleukin-22 binding protein axis promotes inflammation and aggravates diet-induced metabolic disorders

The prevalence of metabolic diseases has become a severe public health problem. Previously, we reported that Interleukin-22 (IL-22) was independently associated with type 2 diabetes mellitus and cardiovascular disease, and could protect endothelial cells from glucose- and lysophosphatidylcholine-induced injury. The activity of IL-22 is strongly regulated by IL-22-binding protein (IL-22BP). The aim of this investigation was to determine the effect of IL-22/IL-22BP axis on glucolipid metabolism. Serum IL-22 and IL-22BP expression in metabolic syndrome (MetS) patients and healthy controls was examined. IL-22BP-knockout (IL-22ra2^-/-) and wild-type (WT) mice were fed with control diet (CTD) and high-fat diet (HFD) for 12 weeks. The IL-22 related pathway expression, the glucolipid metabolism, and inflammatory markers in mice were examined. Serum IL-22 and IL-22BP levels were found significantly increased in MetS patients (p < 0.001). IL-22BP deficiency down-regulated IL-22-related pathway, aggravated glucolipid metabolism disorder, and promoted inflammation in mice. Collectively, this work deepens the understanding of the relationship between IL-22/IL-22BP axis and metabolism disorders, and identified that down-regulation of IL-22/IL-22BP axis promotes metabolic disorders in mice.

Troxerutin attenuates insulin resistance via pancreatic IL-22/JAK1/STAT3 signaling activation in dihydrotestosterone-induced polycystic ovary syndrome rats

Polycystic ovary syndrome (PCOS) is an extremely common endocrine-metabolic disorder and the main cause of infertility in premenopausal women, thus targeted treatments are sorely needed. Accumulative evidence showed that exogenous supplementation of IL-22 in PCOS mice may be of significant positive effect on insulin resistance (IR), a root causative factor for this condition, but much remained unknown about its mechanism. According to our previous study, troxerutin, a common anticoagulant and thrombolytic agent in clinic, alleviated various PCOS-like phenotypes in dihydrotestosterone (DHT)-treated rat model with unclear mechanism. Here, glucose tolerance tests (GTTs), insulin tolerance tests (ITTs), and homeostatic model assessment of insulin resistance (HOMA-IR) analyses revealed that troxerutin treatment in DHT-treated rats also significantly improved insulin resistance and enhanced serum IL-22 levels, which thereby activated IL-22R1/Janus kinase 1 (JAK1)/signal transducer and activator of transcription-3 (STAT3) signaling pathway in pancreatic islet. This protective effect of troxerutin on insulin resistance improvement was blocked by an inhibitor of p-STAT3, S3I-201. Troxerutin administration to DHT rats decreased the relative abundance of Bifidobacterium and enhanced secondary bile acid profiles, which were positively correlated with serum IL-22 concentration. Conclusively, the present study reported that troxerutin is an endogenous enhancer of IL-22 and the effect of troxerutin on insulin resistance improvement was via IL-22R1/JAK1/STAT3 signaling activation in a DHT-induced PCOS rat model. These insights may be translated into a primary therapeutic agent for PCOS with insulin resistance and hyperandrogenism.NEW & NOTEWORTHY Troxerutin decreased the relative abundance of Bifidobacterium, along with enhancement of secondary bile acids/IL-22 system, which thereby activated its downstream IL-22R1/JAK1/STAT3 signaling pathway in pancreatic β cells, subsequently attenuated insulin resistance (IR), hyperandrogenism and PCOS-like phenotypes in DHT-induced PCOS rat models. Troxerutin is an endogenous IL-22 enhancer and may be of therapeutic value for PCOS with insulin resistance.

Transcriptome analysis of the spleen provides insight into the immunoregulation of Scortum barcoo under Streptococcus agalactiae infection

Jade perch (Scortum barcoo) is a freshwater fish with substantial economic value, which has been widely cultivated all over the world. However, with the intensification and expansion of farming, several bacterial and viral diseases have occurred in jade perch. To understand the immune response of jade perch against Streptococcus agalactiae (Group B Streptococcus, GBS), we performed a histopathological examination and transcriptome sequencing of jade perch spleen after artificial bacterial infection. GBS infection can cause structural changes and even necrosis of the jade perch spleen, which may affect the survival of infected individuals. A total of 144,458 unigenes were obtained through de novo assembly of spleen transcriptome. Among them, 1821 unigenes were identified as DEGs, including 1415 up-regulated and 406 down-regulated unigenes in the infection group. Moreover, the analysis of GO and KEGG revealed that many GO terms and pathways were involved in the host immune response, such as Toll-like receptor signaling pathway, Cytokine-cytokine receptor interaction, and TNF signaling pathway. In addition, according to transcriptome data and qRT-PCR analysis, the expression levels of many cytokines that participate in the inflammatory response changed a lot after GBS infection. Overall, this transcriptomic analysis provided valuable information for studying the immune response of jade perch against bacterial infection.

IL-22BP production is heterogeneously distributed in Crohn’s disease

Crohn’s disease (CD), a form of inflammatory bowel disease (IBD), is characterized by impaired epithelial barrier functions and dysregulated mucosal immune responses. IL-22 binding protein (IL-22BP) is a soluble inhibitor regulating IL-22 bioactivity, a cytokine proposed to play protective roles during CD. We and others have shown that IL-22BP is produced in IBD inflamed tissues, hence suggesting a role in CD. In this work, we extended the characterization of IL-22BP production and distribution in CD tissues by applying enzyme-linked immunosorbent assays to supernatants obtained from the culture of endoscopic biopsies of patients, and reverse transcription-quantitative polymerase chain reaction on sorted immune cell subsets. We reveal that IL-22BP levels are higher in inflamed ileums than colons. We observe that in a cell-intrinsic fashion, populations of mononuclear phagocytes and eosinophils express IL-22BP at the highest levels in comparison to other sources of T cells. We suggest the enrichment of intestinal eosinophils could explain higher IL-22BP levels in the ileum. In inflamed colon, we reveal the presence of increased IL-22/IL22BP ratios compared to controls, and a strong correlation between IL-22BP and CCL24. We identify monocyte-derived dendritic cells (moDC) as a cellular subtype co-expressing both cytokines and validate our finding using in vitro culture systems. We also show that retinoic acid induces the secretion of both IL-22BP and CCL24 by moDC. Finally, we report on higher IL-22BP levels in active smokers. In conclusion, our work provides new information relevant to therapeutic strategies modulating IL-22 bioactivity in CD, especially in the context of disease location.

Th22 cells induce Müller cell activation via the Act1/TRAF6 pathway in diabetic retinopathy

T helper 22 (Th22) cells have been implicated in diabetic retinopathy (DR), but it remains unclear whether Th22 cells involve in the pathogenesis of DR. To investigate the role of Th22 cells in DR mice, the animal models were established by intraperitoneal injection of STZ and confirmed by fundus fluorescein angiography and retinal haematoxylin-eosin staining. IL-22BP was administered by intravitreal injection. IL-22 level was measured by ELISA in vivo and in vitro. The expression of IL-22Rα1 in the retina was assessed by immunofluorescence. We assessed GFAP, VEGF, ICAM-1, inflammatory-associated factors and the integrity of blood-retinal barrier in control, DR, IL-22BP, and sham group. Müller cells were co-cultured with Th22 cells, and the expression of the above proteins was measured by immunoblotting. Plasmid transfection technique was used to silence Act1 gene in Müller cells. Results in vivo and in vitro indicated that Th22 cells infiltrated into the DR retinal and IL-22Rα1 expressed in Müller cells. Th22 cells promoted Müller cells activation and inflammatory factor secretion by secreting IL-22 compared with high-glucose stimulation alone. In addition, IL-22BP ameliorated the pathological alterations of the retina in DR. Inhibition of the inflammatory signalling cascade through Act1 knockdown alleviated DR-like pathology. All in all, the results suggested that Th22 cells infiltrated into the retina and secreted IL-22 in DR, and then IL-22 binding with IL-22Rα1 activated the Act1/TRAF6 signal pathway, and promoted the inflammatory of Müller cells and involved the pathogenesis of DR.

Organoids as a Model System for Studying Notch Signaling in Intestinal Epithelial Homeostasis and Intestinal Cancer

Organoid culture is an approach that allows three-dimensional growth for stem cells to self-organize and develop multicellular structures. Intestinal organoids have been widely used to study cellular or molecular processes in stem cell and cancer research. These cultures possess the ability to maintain cellular complexity as well as recapitulate many properties of the human intestinal epithelium, thereby providing an ideal in vitro model to investigate cellular and molecular signaling pathways. These include, but are not limited to, the mechanisms required for maintaining balanced populations of epithelial cells. Notch signaling is one of the major pathways of regulating stem cell functions in the gut, driving proliferation and controlling cell fate determination. Notch also plays an important role in regulating tumor progression and metastasis. Understanding how Notch pathway regulates epithelial regeneration and differentiation by using intestinal organoids is critical for studying both homeostasis and pathogenesis of intestinal stem cells that can lead to discoveries of new targets for drug development to treat intestinal diseases. In addition, use of patient-derived organoids can provide effective personalized medicine. This review summarizes the current literature regarding epithelial Notch pathways regulating intestinal homeostasis and regeneration, highlighting the use of organoid cultures and their potential therapeutic applications.

Preventive Effect of Vitamin C on Dextran Sulfate Sodium (DSS)-Induced Colitis via the Regulation of IL-22 and IL-6 Production in Gulo(−/−) Mice

Reactive oxygen species (ROS), which are exceptionally high in IBD lesions, are known to cause abnormal immune responses to inflammatory reactions in inflammatory bowel diseases (IBD) through damage to the intestinal mucosal linings. Moreover, they are theorized to be an agent of IBD development. Vitamin C is widely known to be an effective antioxidant for its ability to regulate inflammatory responses through its ROS scavenging effect. Therefore, we examined vitamin C’s influence on the development and progression of IBD in Gulo(−/−) mice, which cannot synthesize vitamin C like humans due to a defect in the expression of L-gulono-γ–lactone oxidase, an essential enzyme for vitamin C production. First, we found extensive oxidative stress and an inflammation increase in the colon of vitamin C-insufficient Gulo(−/−) mice. We also found decreased IL-22 production and NKp46(+) cell recruitment and the impaired activation of the p38MAPK pathway. Additionally, comparing vitamin C-insufficient Gulo(−/−) mice to vitamin C-sufficient Gulo(−/−) mice and wild-type mice, the insufficient group faced a decrease in mucin-1 expression, accompanied by an increase in IL-6 production, followed by the activation of the STAT3 and Akt pathways. The results suggest that vitamin C insufficiency induces severe colitis, meaning vitamin C could also take on a preventative role by regulating the production of cytokines and the induction of inflammation.

Activated T cells are the cellular source of IL-22 that enhances proliferation and survival of lymphocytes in Nile tilapia

As a pleiotropic cytokine mainly secreted by CD4⁺ T cells, interleukin (IL)-22 plays an important role in immune regulation and infection elimination. Despite IL-22 homologues have been identified in non-mammal, whether and how IL-22 participates in the adaptive immune response of early vertebrates have not been fully addressed. In this study, we identified an evolutionarily conserved IL-22 from Nile tilapia Oreochromis niloticus (defined as OnIL-22), proved by its properties regarding sequence, gene structure, functional domain, tertiary structure and phylogeny. IL-22 was broadly expressed in lymphoid-related tissues of tilapia, and with relatively higher levels in skin, gill, intestine and liver. The expression of OnIL-22 in spleen lymphocytes was markedly induced at the adaptive immune stage after Streptococcus agalactiae infection. Moreover, once lymphocytes were activated by PMA plus ionomycin or T-cell specific mitogen PHA in vitro, OnIL-22 expression was obviously up-regulated at both mRNA and protein levels. These results thus suggest that activated T cells produce IL-22 to take part in the adaptive immune response of tilapia. Furthermore, treatment of lymphocytes with recombinant OnIL-22 increased the expression of genes related to proliferation and survival, and further promoted the proliferation and reduced the apoptosis of lymphocytes during bacterial infection or T-cell activation. These cellular effects of IL-22 seem to be associated with JAK1/STAT3 axis downstream of IL-22, because IL-22 application not only elevated the mRNA expression of JAK1 and STAT3, but also enhanced their phosphorylation in lymphocytes. Altogether, we suggest that activated T cells produce IL-22 to promote lymphocyte proliferation and survival probability via JAK1/STAT3 signaling pathway, thus participating in adaptive immune response of Nile tilapia. Our study therefore provides helpful perspective for understanding the function and mechanism of adaptive immune system in teleost.

ZBTB46 defines and regulates ILC3s that protect the intestine

RORγt is a lineage-specifying transcription factor that is expressed by immune cells that are enriched in the gastrointestinal tract and promote immunity, inflammation and tissue homeostasis1-15. However, fundamental questions remain with regard to the cellular heterogeneity among these cell types, the mechanisms that control protective versus inflammatory properties and their functional redundancy. Here we define all RORγt+ immune cells in the intestine at single-cell resolution and identify a subset of group 3 innate lymphoid cells (ILC3s) that expresses ZBTB46, a transcription factor specifying conventional dendritic cells16-20. ZBTB46 is robustly expressed by CCR6+ lymphoid-tissue-inducer-like ILC3s that are developmentally and phenotypically distinct from conventional dendritic cells, and its expression is imprinted by RORγt, fine-tuned by microbiota-derived signals and increased by pro-inflammatory cytokines. ZBTB46 restrains the inflammatory properties of ILC3s, including the OX40L-dependent expansion of T helper 17 cells and the exacerbated intestinal inflammation that occurs after enteric infection. Finally, ZBTB46+ ILC3s are a major source of IL-22, and selective depletion of this population renders mice susceptible to enteric infection and associated intestinal inflammation. These results show that ZBTB46 is a transcription factor that is shared between conventional dendritic cells and ILC3s, and identify a cell-intrinsic function for ZBTB46 in restraining the pro-inflammatory properties of ILC3s and a non-redundant role for ZBTB46+ ILC3s in orchestrating intestinal health.

Multi-omics analyses of airway host-microbe interactions in chronic obstructive pulmonary disease identify potential therapeutic interventions

The mechanistic role of the airway microbiome in chronic obstructive pulmonary disease (COPD) remains largely unexplored. We present a landscape of airway microbe-host interactions in COPD through an in-depth profiling of the sputum metagenome, metabolome, host transcriptome and proteome from 99 patients with COPD and 36 healthy individuals in China. Multi-omics data were integrated using sequential mediation analysis, to assess in silico associations of the microbiome with two primary COPD inflammatory endotypes, neutrophilic or eosinophilic inflammation, mediated through microbial metabolic interaction with host gene expression. Hypotheses of microbiome-metabolite-host interaction were identified by leveraging microbial genetic information and established metabolite-human gene pairs. A prominent hypothesis for neutrophil-predominant COPD was altered tryptophan metabolism in airway lactobacilli associated with reduced indole-3-acetic acid (IAA), which was in turn linked to perturbed host interleukin-22 signalling and epithelial cell apoptosis pathways. In vivo and in vitro studies showed that airway microbiome-derived IAA mitigates neutrophilic inflammation, apoptosis, emphysema and lung function decline, via macrophage-epithelial cell cross-talk mediated by interleukin-22. Intranasal inoculation of two airway lactobacilli restored IAA and recapitulated its protective effects in mice. These findings provide the rationale for therapeutically targeting microbe-host interaction in COPD.

Interleukin-22 Ameliorates Dextran Sulfate Sodium-Induced Colitis through the Upregulation of lncRNA-UCL to Accelerate Claudin-1 Expression via Sequestering miR-568 in Mice

Background

Bioactive compound such as interleukin-22 (IL-22) treatment is regarded as a sufficient treatment for ulcerative colitis (UC). It has been found that long noncoding RNAs (lncRNAs) expressed in many inflammatory diseases, including UC. We aimed to verify the treatment effect of bioactive compounds including IL-22 and lncRNAs in UC on colitis mice.

Methods

UC mice were induced using DSS, followed by IL-22 or PBS intraperitoneally (i.p.) injection. Then, the histopathological parameters of the mice were determined. Then, RNA sequencing was performed to screen the differential lncRNAs. Quantitative real-time PCR (qRT-PCR) and lentivirus identified lncRNA-Ulcerative Colitis lncRNA (lncRNA-UCL) were regarded as the molecular regulator of the colitis mice. The correlation with lncRNA-UCL and mmu-miR-568 was validated using RNA-pulldown. Meanwhile, claudin-1 was predicted and confirmed as the target molecule of mmu-miR-568 using dual-luciferase assay.

Results

IL-22 could significantly improve the histopathological features and decrease proinflammatory cytokine production in UC mice induced by DSS. It also can stimulate intestinal epithelial cell (IEC) reproduction and prevention of apoptosis. lncRNA-UCL was significantly downregulated in UC mice caused by DSS, while IL-22 treatment effectively reversed this effect. In terms of mechanism, lncRNA-UCL regulates intestinal epithelial homeostasis by sequestering mmu-miR-568 and maintaining close integrated protein expression, such as claudin-1.

Conclusions

We have demonstrated the incredible role of bioactive compound, such as IL-22, in alleviating DSS-induced colitis symptoms via enhancing lncRNA-UCL expression. It can be regulated using tight junction (TJ) protein.

Role of Nutrient-sensing Receptor GPRC6A in Regulating Colonic Group 3 Innate Lymphoid Cells and Inflamed Mucosal Healing

BACKGROUND AND AIMS

Group 3 innate lymphoid cells [ILC3s] sense environmental signals and are critical in gut homeostasis and immune defence. G-protein-coupled receptors [GPCRs] mediate cellular responses to diverse environmental signals. However, the GPCRs' regulation mechanisms of ILC3s is largely unknown.

METHODS

We used wild-type [WT] and GPRC6A-/- mice to investigate the role of GPRC6A in the population and the function of ILC3s. We then purified ILC3s from WT and GPRC6A-/- mice. Colitis was induced in WT mice and GPRC6A-/- mice through dextran sodium sulphate [DSS] administration or C. rodentium infection. Furthermore L-arginine, a selective GPRC6A agonist, was administered to mice with colitis.

RESULTS

We found that colonic ILC3s expressed GPRC6A. The deficiency of GPRC6A decreased ILC3-derived interleukin-22 [IL-22] production and the number of proliferating ILC3s, which led to increased susceptibility to colon injury and pathogen infection and impaired inflamed mucosal healing. Further studies showed that L-arginine, a GPRC6A agonist, promoted colonic ILC3 expansion and function via the mammalian target of rapamycin complex 1 [mTORC1] signalling in vitro. In addition, L-arginine attenuated DSS-induced colitis in vivo. This was associated with a significant increase in IL-22 secretion by ILC3s.

CONCLUSIONS

Our findings unveil a role for the nutrient-sensing receptor GPRC6A in colonic ILC3 function and identify a novel ILC3 receptor signalling pathway modulating inflamed mucosal healing.

IL-22 regulates endometrial regeneration by enhancing tight junctions and orchestrating extracellular matrix

The uterine endometrium uniquely regenerates after menses, postpartum, or after breaks in the uterine layer integrity throughout women’s lives. Direct cell–cell contacts ensured by tight and adherens junctions play an important role in endometrial integrity. Any changes in these junctions can alter the endometrial permeability of the uterus and have an impact on the regeneration of uterine layers. Interleukin 22 (IL-22) is a cytokine that is recognized for its role in epithelial regeneration. Moreover, it is crucial in controlling the inflammatory response in mucosal tissues. Here, we studied the role of IL-22 in endometrial recovery after inflammation-triggered abortion. Fecundity of mice was studied in consecutive matings of the same animals after lipopolysaccharide (LPS) (10 µg per mouse)-triggered abortion. The fecundity rate after the second mating was substantially different between IL-22 knockout (IL-22^−/−) (9.1%) and wild-type (WT) (71.4%) mice (p < 0.05), while there was no difference between the groups in the initial mating, suggesting that IL-22 deficiency might be associated with secondary infertility. A considerable difference was observed between IL-22^−/− and WT mice in the uterine clearance following LPS-triggered abortion. Gross examination of the uteri of IL-22^−/− mice revealed non-viable fetuses retained inside the horns (delayed clearance). In contrast, all WT mice had completed abortion with total clearance after LPS exposure. We also discovered that IL-22 deficiency is associated with a decreased expression of tight junctions (claudin-2 and claudin-10) and cell surface pathogen protectors (mucin-1). Moreover, IL-22 has a role in the remodeling of the uterine tissue in the inflammatory environment by regulating epithelial–mesenchymal transition markers called E- and N-cadherin. Therefore, IL-22 contributes to the proper regeneration of endometrial layers after inflammation-triggered abortion. Thus, it might have a practical significance to be utilized as a treatment option postpartum (enhanced regeneration function) and in secondary infertility caused by inflammation (enhanced barrier/protector function).

Steviol glycosides as an alternative osmotic agent for peritoneal dialysis fluid

Background: Peritoneal dialysis (PD) is a renal replacement technique that requires repeated exposure of the peritoneum to hyperosmolar PD fluids (PDFs). Unfortunately, it promotes alterations of the peritoneal membrane (PM) that affects its functionality, including mesothelial-mesenchymal transition (MMT) of mesothelial cells (MCs), inflammation, angiogenesis, and fibrosis. Glucose is the most used osmotic agent, but it is known to be at least partially responsible, together with its degradation products (GDP), for those changes. Therefore, there is a need for more biocompatible osmotic agents to better maintain the PM. Herein we evaluated the biocompatibility of Steviol glycosides (SG)-based fluids.

Methods: The ultrafiltration and transport capacities of SG-containing and glucose-based fluids were analyzed using artificial membranes and an in vivo mouse model, respectively. To investigate the biocompatibility of the fluids, Met-5A and human omental peritoneal MCs (HOMCs) were exposed in vitro to different types of glucose-based PDFs (conventional 4.25% glucose solution with high-GDP level and biocompatible 2.3% glucose solution with low-GDP level), SG-based fluids or treated with TGF-β1. Mice submitted to surgery of intraperitoneal catheter insertion were treated for 40 days with SG- or glucose-based fluids. Peritoneal tissues were collected to determine thickness, MMT, angiogenesis, as well as peritoneal washings to analyze inflammation.

Results: Dialysis membrane experiments demonstrated that SG-based fluids at 1.5%, 1%, and 0.75% had a similar trend in weight gain, based on curve slope, as glucose-based fluids. Analyzing transport capacity in vivo, 1% and 0.75% SG-based fluid-exposed nephrectomized mice extracted a similar amount of urea as the glucose 2.3% group. In vitro, PDF with high-glucose (4.25%) and high-GDP content induced mesenchymal markers and angiogenic factors (Snail1, Fibronectin, VEGF-A, FGF-2) and downregulates the epithelial marker E-Cadherin. In contrast, exposition to low-glucose-based fluids with low-GDP content or SG-based fluids showed higher viability and had less MMT. In vivo, SG-based fluids preserved MC monolayer, induced less PM thickness, angiogenesis, leukocyte infiltration, inflammatory cytokines release, and MMT compared with glucose-based fluids.

Conclusion: SG showed better biocompatibility as an osmotic agent than glucose in vitro and in vivo, therefore, it could alternatively substitute glucose in PDF.

Sex-Dependent Hepatoprotective Role of IL-22 Receptor Signaling in Non-Alcoholic Fatty Liver Disease-Related Fibrosis

BACKGROUND & AIMS

Nonalcoholic fatty liver disease (NAFLD) is a major health problem with complex pathogenesis. Although sex differences in NAFLD pathogenesis have been reported, the mechanisms underlying such differences remain understudied. Interleukin (IL)22 is a pleiotropic cytokine with both protective and/or pathogenic effects during liver injury. IL22 was shown to be hepatoprotective in NAFLD-related liver injury. However, these studies relied primarily on exogenous administration of IL22 and did not examine the sex-dependent effect of IL22. Here, we sought to characterize the role of endogenous IL22-receptor signaling during NAFLD-induced liver injury in males and females.

METHODS

We used immunofluorescence, flow cytometry, histopathologic assessment, and gene expression analysis to examine IL22 production and characterize the intrahepatic immune landscape in human subjects with NAFLD (n = 20; 11 men and 9 women) and in an in vivo Western high-fat diet-induced NAFLD model in IL22RA knock out mice and their wild-type littermates.

RESULTS

Examination of publicly available data sets from 2 cohorts with NAFLD showed increased hepatic IL22 gene expression in females compared with males. Furthermore, our immunofluorescence analysis of liver sections from NAFLD subjects (n = 20) showed increased infiltration of IL22-producing cells in females. Similarly, IL22-producing cells were increased in wild-type female mice with NAFLD and the hepatic IL22/IL22 binding protein messenger RNA ratio correlated with expression of anti-apoptosis genes. The lack of endogenous IL22-receptor signaling (IL22RA knockout) led to exacerbated liver damage, inflammation, apoptosis, and liver fibrosis in female, but not male, mice with NAFLD.

CONCLUSIONS

Our data suggest a sex-dependent hepatoprotective antiapoptotic effect of IL22-receptor signaling during NAFLD-related liver injury in females.

Conventional and pathogenic Th2 cells in inflammation, tissue repair, and fibrosis

Type 2 helper T (Th2) cells, a subset of CD4⁺ T cells, play an important role in the host defense against pathogens and allergens by producing Th2 cytokines, such as interleukin-4 (IL-4), IL-5, and IL-13, to trigger inflammatory responses. Emerging evidence reveals that Th2 cells also contribute to the repair of injured tissues after inflammatory reactions. However, when the tissue repair process becomes chronic, excessive, or uncontrolled, pathological fibrosis is induced, leading to organ failure and death. Thus, proper control of Th2 cells is needed for complete tissue repair without the induction of fibrosis. Recently, the existence of pathogenic Th2 (Tpath2) cells has been revealed. Tpath2 cells produce large amounts of Th2 cytokines and induce type 2 inflammation when activated by antigen exposure or tissue injury. In recent studies, Tpath2 cells are suggested to play a central role in the induction of type 2 inflammation whereas the role of Tpath2 cells in tissue repair and fibrosis has been less reported in comparison to conventional Th2 cells. In this review, we discuss the roles of conventional Th2 cells and pathogenic Th2 cells in the sequence of tissue inflammation, repair, and fibrosis.

Characterization of Mycobacterium tuberculosis-Specific Th22 Cells and the Effect of Tuberculosis Disease and HIV Coinfection

The development of a highly effective tuberculosis (TB) vaccine is likely dependent on our understanding of what constitutes a protective immune response to TB. Accumulating evidence suggests that CD4+ T cells producing IL-22, a distinct subset termed "Th22" cells, may contribute to protective immunity to TB. Thus, we characterized Mycobacterium tuberculosis-specific Th22 (and Th1 and Th17) cells in 72 people with latent TB infection or TB disease, with and without HIV-1 infection. We investigated the functional properties (IFN-γ, IL-22, and IL-17 production), memory differentiation (CD45RA, CD27, and CCR7), and activation profile (HLA-DR) of M. tuberculosis-specific CD4+ T cells. In HIV-uninfected individuals with latent TB infection, we detected abundant circulating IFN-γ-producing CD4+ T cells (median, 0.93%) and IL-22-producing CD4+ T cells (median, 0.46%) in response to M. tuberculosis The frequency of IL-17-producing CD4+ T cells was much lower, at a median of 0.06%. Consistent with previous studies, IL-22 was produced by a distinct subset of CD4+ T cells and not coexpressed with IL-17. M. tuberculosis-specific IL-22 responses were markedly reduced (median, 0.08%) in individuals with TB disease and HIV coinfection compared with IFN-γ responses. M. tuberculosis-specific Th22 cells exhibited a distinct memory and activation phenotype compared with Th1 and Th17 cells. Furthermore, M. tuberculosis-specific IL-22 was produced by conventional CD4+ T cells that required TCR engagement. In conclusion, we confirm that Th22 cells are a component of the human immune response to TB. Depletion of M. tuberculosis-specific Th22 cells during HIV coinfection may contribute to increased risk of TB disease.

The role of interleukin-22 in lung health and its therapeutic potential for COVID-19

Although numerous clinical trials have been implemented, an absolutely effective treatment against coronavirus disease 2019 (COVID-19) is still elusive. Interleukin-22 (IL-22) has attracted great interest over recent years, making it one of the best-studied cytokines of the interleukin-10 (IL-10) family. Unlike most interleukins, the major impact of IL-22 is exclusively on fibroblasts and epithelial cells due to the restricted expression of receptor. Numerous studies have suggested that IL-22 plays a crucial role in anti-viral infections through significantly ameliorating the immune cell-mediated inflammatory responses, and reducing tissue injury as well as further promoting epithelial repair and regeneration. Herein, we pay special attention to the role of IL-22 in the lungs. We summarize the latest progress in our understanding of IL-22 in lung health and disease and further discuss maneuvering this cytokine as potential immunotherapeutic strategy for the effective manage of COVID-19.

Gut Microbiota-Derived Tryptophan Metabolites Maintain Gut and Systemic Homeostasis

Tryptophan is an essential amino acid from dietary proteins. It can be metabolized into different metabolites in both the gut microbiota and tissue cells. Tryptophan metabolites such as indole-3-lactate (ILA), indole-3-acrylate (IAC), indole-3-propionate (IPA), indole-3-aldehyde (IAID), indoleacetic acid (IAA), indole-3-acetaldehyde and Kyn can be produced by intestinal microorganisms through direct Trp transformation and also, partly, the kynurenine (Kyn) pathway. These metabolites play a critical role in maintaining the homeostasis of the gut and systematic immunity and also potentially affect the occurrence and development of diseases such as inflammatory bowel diseases, tumors, obesity and metabolic syndrome, diseases in the nervous system, infectious diseases, vascular inflammation and cardiovascular diseases and hepatic fibrosis. They can not only promote the differentiation and function of anti-inflammatory macrophages, Treg cells, CD4⁺CD8αα⁺ regulatory cells, IL-10⁺ and/or IL-35⁺B regulatory cells but also IL-22-producing innate lymphoid cells 3 (ILC3), which are involved in maintaining the gut mucosal homeostasis. These findings have important consequences in the immunotherapy against tumor and other immune-associated diseases. We will summarize here the recent advances in understanding the generation and regulation of tryptophan metabolites in the gut microbiota, the role of gut microbiota-derived tryptophan metabolites in different immune cells, the occurrence and development of diseases and immunotherapy against immune-associated diseases.