IL-22 induces lipopolysaccharide-binding protein in hepatocytes: a potential systemic role of IL-22 in Crohn's disease

Effect of Herb-Partitioned Moxibustion on Autophagy and Immune-Associated Gene Expression Profiles in a Rat Model of Crohn's Disease

Objective

To investigate the immune regulation mechanism of herb-partitioned moxibustion in rats with Crohn's disease (CD) focusing on autophagy.

Methods

Rats were randomly divided into normal (N) group, CD model (M) group, CD model with herb-partitioned moxibustion (MM) group, normal with herb-partitioned moxibustion (NM) group, CD model with mesalazine (western medicine, Med ) group, and normal saline (NS) group, with 10 rats in each group. The CD model rats were prepared by trinitrobenzene sulphonic expect for the N group and NM group. After the CD rats model were established, the rats in the MM and NM groups were treated with herb-partitioned moxibustion at Tianshu (ST25) and Qihai (CV6) acupoints once daily for 7 days, and rats in the Med and NS groups were respectively treated with mesalazine enteric coated tablet and normal saline once daily for 7 days. After intervention, hematoxylin-eosin staining was used to observe the histological changes of colon; RNA sequencing was used to observe the changes in autophagy- and immune-associated gene expression profiles. In addition, autophagy- and immune-associated cytokines and signaling pathways in CD rats were also screened.

Results

HPM significantly increased the body weight of CD rats (P<0.01) and improved the pathological injury of colon in CD rats (P<0.01). HPM also changed the expression of many autophagy- and immune-associated genes, especially downregulating the expression of autophagy-associated Nod2, Irgm genes as well as the receptor of immune-associated Il12b, Il22 (Il12rb1, Il22ra2) genes in the colon of CD rats. HPM also changed the enrichment levels of differentially expressed genes in the human T-cell leukemia virus type-1 infection pathway, the Epstein-Barr virus infection pathway, and the cell adhesion molecule pathway. In addition, the expression levels of Nod2, Irgm, IL-12b, and IL-22 mRNA were increased (all P< 0.01) in the M group compared to the N group, while the expression levels of Nod2, Irgm, IL-12b, and IL-22 mRNA were decreased (P<0.05 or P<0.01) in the MM and Med groups compared to the M group.

Conclusion

Herb-partitioned moxibustion may effectively attenuate intestinal inflammation and promote the repair of colon mucosal injury of CD rats through the regulation of autophagy- and immune-associated gene expression and signaling pathways.

Bacteria-related Events and the Immunological Response of Onset and Relapse Adult Crohn's Disease Patients

BACKGROUND AND AIMS

Crohn's disease [CD] is a chronic, systemic inflammatory disease characterised by periods of remission and flare-ups. It has been associated with a disturbed gastrointestinal barrier function, an increase in the transport of luminal contents into the tissue, and lower immune tolerance.

METHODS

Peripheral blood samples were collected from healthy controls and 33 adult active flare-up CD patients. We classified patients as onset or relapse flare-up subjects, according to the days of disease evolution. Plasma levels of lipopolysaccharide-binding protein [LBP], fatty acid-binding proteins [FABP], and antibodies against bacterial lysates, interferons [IFN] and interleukin-6 [IL6] were measured by enzyme-linked immunosorbent assay [ELISA] in each group of patients.

RESULTS

Onset CD patients had higher plasma levels of LBP [57.32 ± 38.86 vs 30.22 ± 9.80 µg/ml] and IFNα [1.25 ± 0.23 vs 0.95 ± 0.36 log10pg/ml] and lower levels of immunoglobulins G and A [IgG and IgA] antibodies against bacterial lysates than relapse CD patients. We also observed a subgroup of onset patients with the highest levels of LBP. In this subgroup, LBP correlated negatively with C-reactive protein [CRP]. Onset and relapse CD patients had similar levels of FABP6 and FABP2, though LBP and FABP6 correlated positively only in relapse patients. In relapse patients, anti-E coli IgG antibodies correlated positively with systemic IL6 and IFNα levels.

CONCLUSIONS

Our findings suggest that onset and relapse flare-ups in adult CD patients are related to different systemic immune-related bacterial events. Characterising these differences may provide insights into the aetiology of Crohn's disease, and would help in the selection of appropriate therapies.

Long Interleukin-22 Binding Protein Isoform-1 Is an Intracellular Activator of the Unfolded Protein Response

The human IL22RA2 gene co-produces three protein isoforms in dendritic cells [IL-22 binding protein isoform-1 (IL-22BPi1), IL-22BPi2, and IL-22BPi3]. Two of these, IL-22BPi2 and IL-22BPi3, are capable of neutralizing the biological activity of IL-22. The function of IL-22BPi1, which differs from IL-22BPi2 through an in-frame 32-amino acid insertion provided by an alternatively spliced exon, remains unknown. Using transfected human cell lines, we demonstrate that IL-22BPi1 is secreted detectably, but at much lower levels than IL-22BPi2, and unlike IL-22BPi2 and IL-22BPi3, is largely retained in the endoplasmic reticulum (ER). As opposed to IL-22BPi2 and IL-22BPi3, IL-22BPi1 is incapable of neutralizing or binding to IL-22 measured in bioassay or assembly-induced IL-22 co-folding assay. We performed interactome analysis to disclose the mechanism underlying the poor secretion of IL-22BPi1 and identified GRP78, GRP94, GRP170, and calnexin as main interactors. Structure-function analysis revealed that, like IL-22BPi2, IL-22BPi1 binds to the substrate-binding domain of GRP78 as well as to the middle domain of GRP94. Ectopic expression of wild-type GRP78 enhanced, and ATPase-defective GRP94 mutant decreased, secretion of both IL-22BPi1 and IL-22BPi2, while neither of both affected IL-22BPi3 secretion. Thus, IL-22BPi1 and IL-22BPi2 are bona fide clients of the ER chaperones GRP78 and GRP94. However, only IL-22BPi1 activates an unfolded protein response (UPR) resulting in increased protein levels of GRP78 and GRP94. Cloning of the IL22RA2 alternatively spliced exon into an unrelated cytokine, IL-2, bestowed similar characteristics on the resulting protein. We also found that CD14++/CD16+ intermediate monocytes produced a higher level of IL22RA2 mRNA than classical and non-classical monocytes, but this difference disappeared in immature dendritic cells (moDC) derived thereof. Upon silencing of IL22RA2 expression in moDC, GRP78 levels were significantly reduced, suggesting that native IL22RA2 expression naturally contributes to upregulating GRP78 levels in these cells. The IL22RA2 alternatively spliced exon was reported to be recruited through a single mutation in the proto-splice site of a Long Terminal Repeat retrotransposon sequence in the ape lineage. Our work suggests that positive selection of IL-22BPi1 was not driven by IL-22 antagonism as in the case of IL-22BPi2 and IL-22BPi3, but by capacity for induction of an UPR response.

The IL-1 Pathway Is Hyperactive in Hidradenitis Suppurativa and Contributes to Skin Infiltration and Destruction

Hidradenitis suppurativa (HS) (also designated acne inversa) is a chronic inflammatory disease characterized by painful purulent skin lesions and progressive destruction of skin architecture. Despite the high burden for the patients, pathogenetic pathways underlying HS alterations remain obscure. When we examined the HS cytokine pattern, IL-1β turned out to be a highly prominent cytokine, overexpressed even compared with psoriatic lesions. Analyses of IL-1β-induced transcriptome in various cell types showed overlapping profiles, with upregulations of molecules causing immune cell infiltration and extracellular matrix degradation, and of specific cytokines including IL-6, IL-32, and IL-36. Matching cellular IL-1 receptor levels, dermal fibroblasts showed both the strongest and broadest IL-1β response, which was not clearly shared or strengthened by other cytokines. The IL-1β signature was specifically present in HS lesions and could be reversed by application of IL-1 receptor antagonist. Search for blood parameters associated with IL-1β pathway activity in HS identified serum amyloid A, which was synergistically induced by IL-1β and IL-6 in hepatocytes. Consequently, strongly elevated blood serum amyloid A levels in HS correlated positively with the extent of inflammatory skin alterations. In summary, the IL-1β pathway represents a pathogenetic cascade, whose activity may be therapeutically targeted and monitored by blood SAA levels.

Marital distress, depression, and a leaky gut: Translocation of bacterial endotoxin as a pathway to inflammation

BACKGROUND

Marital distress and depression work in tandem to escalate risks for inflammation-related disorders. Translocation of bacterial endotoxin (lipopolysaccharide, LPS) from the gut microbiota to blood circulation stimulates systemic inflammatory responses.

METHODS

To investigate increased gut permeability (a "leaky gut") as one potential mechanistic pathway from marital distress and depression to heightened inflammation, this secondary analysis of a double-blind, randomized crossover study examined serial assessments of two endotoxin biomarkers, LPS-binding protein (LBP) and soluble CD14 (sCD14), as well as C-reactive protein (CRP), interleukin 6 (IL-6), and tumor necrosis factor alpha (TNF-α) during two separate 9.5 h visits. The 43 (N = 86) healthy married couples, ages 24-61 (mean = 38.22), discussed a marital disagreement during both visits; behavioral coding of these interactions provided data on hostile marital behaviors, a hallmark of marital distress. The Structured Diagnostic Interview for DSM-IV assessed participants' mood disorder history.

RESULTS

Participants with more hostile marital interactions had higher LBP than those who were less hostile. Additionally, the combination of more hostile marital interactions with a mood disorder history was associated with higher LBP/sCD14 ratios. Higher LBP and LBP/sCD14 were associated with greater CRP production; for example, only 21% of low LBP participants (lowest quartile) had average CRP across the day > 3, compared to 79% of those in the highest quartile. Higher sCD14 was associated with higher IL-6.

CONCLUSIONS

These bacterial LPS translocation data illustrate how a distressed marriage and a mood disorder history can promote a proinflammatory milieu through increased gut permeability, thus fueling inflammation-related disorders.

Nonclinical safety assessment of a human interleukin-22FC IG fusion protein demonstrates in vitro to in vivo and cross-species translatability

Although Interleukin-22 (IL-22) is produced by various leukocytes, it preferentially targets cells with epithelial origins. IL-22 exerts essential roles in modulating various tissue epithelial functions, such as innate host defense against extracellular pathogens, barrier integrity, regeneration, and wound healing. Therefore, IL-22 is thought to have therapeutic potential in treating diseases associated with infection, tissue injury or chronic tissue damage. A number of in vitro and in vivo nonclinical studies were conducted to characterize the pharmacological activity and safety parameters of UTTR1147A, an IL-22 recombinant fusion protein that links the human cytokine IL-22 with the Fc portion of a human immunoglobulin. To assess the pharmacological activity of UTTR1147A, STAT3 activation was evaluated in primary hepatocytes isolated from human, cynomolgus monkey, minipig, rat, and mouse after incubation with UTTR1147A. UTTR1147A activated STAT3 in all species evaluated, demonstrating that all were appropriate nonclinical species for toxicology studies. The nonclinical safety profile of UTTR1147A was evaluated in rats, minipigs, and cynomolgus monkeys to establish a safe clinical starting dose for humans in Phase I trials and to support clinical intravenous, subcutaneous and/or topical administration treatment regimen. Results demonstrate the cross-species translatability of the biological response in activating the IL-22 pathway as well as the translatability of findings from in vitro to in vivo systems. UTTR1147A was well tolerated in all species tested and induced the expected pharmacologic effects of epidermal hyperplasia and a transient increase in on-target acute phase proteins. These effects were all considered to be clinically predictable, manageable, monitorable, and reversible.

Roles of IL-22 in allergic airway inflammation in mice and humans

Asthma is a chronic inflammatory disease of the airways that is characterized by eosinophilic inflammation, mucus hypersecretion and airway remodeling that leads to airway obstruction. Although these pathognomonic features of asthma are primarily mediated by allergen-specific T helper type 2 cells (Th2 cells) and their cytokines, recent studies have revealed critical roles of lung epithelial cells in the pathogenesis of asthma. Lung epithelial cells not only form physical barriers by covering the surfaces of the airways but also sense inhaled allergens and initiate communication between the environment and the immune system. The causative involvement of lung epithelium in the pathogenesis of asthma suggests that some molecules that modulate epithelial function have a regulatory role in asthma. IL-22, an IL-10-family cytokine produced by IL-17A-producing T helper cells (Th17 cells), γδ T cells and group 3 innate lymphoid cells (ILC3s), primarily targets epithelial cells and promotes their proliferation. In addition, IL-22 has been shown to induce epithelial production of various molecules that regulate local immune responses. These findings indicate that IL-22 plays crucial roles in the pathogenesis of asthma by regulating epithelial function. Here, we review the current understanding of the molecular and cellular mechanisms underlying IL-22-mediated regulation of airway inflammation in asthma.

Atorvastatin, losartan and captopril may upregulate IL-22 in hypertension and coronary artery disease; the role of gene polymorphism

AIMS

Interleukin-22 (IL-22) may be considered as an important cytokine in maintenance and progression of hypertension and coronary artery disease (CAD). The aim of the present study was to investigate the effect of treatment of hypertension and CAD on serum levels of IL-22 and the possible association of IL-22-rs1179251 gene polymorphism with hypertension and CAD.

MATERIALS AND METHODS

A total of 286 subjects with suspected CAD were enrolled. Serum levels and gene polymorphism of IL-22 were investigated in hypertensive patients with no CAD (H-Tens), hypertensive patients with CAD (CAD + H-Tens); 3), CAD patients with no hypertension (CAD); and non-hypertensive with no CAD subjects as a control group (Ctr). The patients received routine medications for hypertension and CAD. Serum IL-22 levels and IL-22-rs1179251 gene polymorphism were evaluated using ELISA and RFLP-/PCR techniques, respectively.

KEY FINDINGS

Findings demonstrated that there were significantly higher levels of IL-22 in case groups (H-Tens, CAD + H-Tens, and CAD) compared to the Ctr group (P = 0.001, P = 0.014, and P < 0.001, respectively). Moreover, atorvastatin, losartan and captopril were administered significantly more in patients compared to the Ctr group. The results indicated a decreased risk of CAD + H-Tens of rs1179251 dominant genetic model (OR = 0.324; 95% CI = 0.121-0.873; P = 0.026).

SIGNIFICANCE

Atorvastatin, losartan and captopril may be led to upregulation of IL-22 in CAD and hypertensive patients. Meanwhile, higher levels of circulating IL-22 could contribute to alleviating the hypertension and CAD conditions. The G allele of IL-22 rs1179251 may be a protective factor for concomitant hypertension and CAD.

IL22 Inhibits Epithelial Stem Cell Expansion in an Ileal Organoid Model

Background & Aims

Crohn's disease is an inflammatory bowel disease that affects the ileum and is associated with increased cytokines. Although interleukin (IL)6, IL17, IL21, and IL22 are increased in Crohn's disease and are associated with disrupted epithelial regeneration, little is known about their effects on the intestinal stem cells (ISCs) that mediate tissue repair. We hypothesized that ILs may target ISCs and reduce ISC-driven epithelial renewal.

Methods

A screen of IL6, IL17, IL21, or IL22 was performed on ileal mouse organoids. Computational modeling was used to predict microenvironment cytokine concentrations. Organoid size, survival, proliferation, and differentiation were characterized by morphometrics, quantitative reverse-transcription polymerase chain reaction, and immunostaining on whole organoids or isolated ISCs. ISC function was assayed using serial passaging to single cells followed by organoid quantification. Single-cell RNA sequencing was used to assess Il22ra1 expression patterns in ISCs and transit-amplifying (TA) progenitors. An IL22-transgenic mouse was used to confirm the impact of increased IL22 on proliferative cells in vivo.

Results

High IL22 levels caused decreased ileal organoid survival, however, resistant organoids grew larger and showed increased proliferation over controls. Il22ra1 was expressed on only a subset of ISCs and TA progenitors. IL22-treated ISCs did not show appreciable differentiation defects, but ISC biomarker expression and self-renewal-associated pathway activity was reduced and accompanied by an inhibition of ISC expansion. In vivo, chronically increased IL22 levels, similar to predicted microenvironment levels, showed increases in proliferative cells in the TA zone with no increase in ISCs.

Conclusions

Increased IL22 limits ISC expansion in favor of increased TA progenitor cell expansion.

Interleukin-22-deficiency and microbiota contribute to the exacerbation of Toxoplasma gondii-induced intestinal inflammation

Upon oral infection with Toxoplasma gondii cysts (76 K strain) tachyzoites are released into the intestinal lumen and cross the epithelial barrier causing damage and acute intestinal inflammation in C57BL/6 (B6) mice. Here we investigated the role of microbiota and IL-22 in T.gondii-induced small intestinal inflammation. Oral T.gondii infection in B6 mice causes inflammation with IFNγ and IL-22 production. In IL-22-deficient mice, T.gondii infection augments the Th1 driven inflammation. Deficiency in either IL-22bp, the soluble IL-22 receptor or Reg3γ, an IL-22-dependent antimicrobial lectin/peptide, did not reduce inflammation. Under germ-free conditions, T.gondii-induced inflammation was reduced in correlation with parasite load. But intestinal inflammation is still present in germ-free mice, at low level, in the lamina propria, independently of IL-22 expression. Exacerbated intestinal inflammation driven by absence of IL-22 appears to be independent of IL-22 deficiency associated-dysbiosis as similar inflammation was observed after fecal transplantation of IL-22-/- or WT microbiota to germ-free-WT mice. Our results suggest cooperation between parasite and intestinal microbiota in small intestine inflammation development and endogenous IL-22 seems to exert a protective role independently of its effect on the microbiota. In conclusion, IL-22 participates in T.gondii induced acute small intestinal inflammation independently of microbiota and Reg3γ.

Pivotal Role of IL-22 Binding Protein in the Epithelial Autoregulation of Interleukin-22 Signaling in the Control of Skin Inflammation

Disruption of skin homeostasis can lead to inflammatory cutaneous diseases resulting from the dysregulated interplay between epithelial keratinocytes and immune cells. Interleukin (IL)-22 signaling through membrane-bound IL-22 receptor 1 (IL-22R1) is crucial to maintain cutaneous epithelial integrity, and its malfunction mediates deleterious skin inflammation. While IL-22 binding protein (IL-22BP) binds IL-22 to suppress IL-22 signaling, how IL-22BP controls epithelial functionality to prevent skin inflammation remains unclear. Here, we describe the pivotal role of IL-22BP in mediating epithelial autoregulation of IL-22 signaling for the control of cutaneous pathogenesis. Unlike prominent expression of IL-22BP in dendritic cells in lymphoid tissues, epidermal keratinocytes predominantly expressed IL-22BP in the skin in the steady state, whereas its expression decreased during the development of psoriatic inflammation. Deficiency in IL-22BP aggravates psoriasiform dermatitis, accompanied by abnormal hyperproliferation of keratinocytes and excessive cutaneous inflammation as well as enhanced dermal infiltration of granulocytes and γδT cells. Furthermore, IL-22BP abrogates the functional alternations of keratinocytes upon stimulation with IL-22. On the other hand, treatment with IL-22BP alleviates the severity of cutaneous pathology and inflammation in psoriatic mice. Thus, the fine-tuning of IL-22 signaling through autocrine IL-22BP production in keratinocytes is instrumental in the maintenance of skin homeostasis.

Effector T Helper Cell Subsets in Inflammatory Bowel Diseases

The gastrointestinal tract is a site of high immune challenge, as it must maintain a delicate balance between tolerating luminal contents and generating an immune response toward pathogens. CD4⁺ T cells are key in mediating the host protective and homeostatic responses. Yet, CD4⁺ T cells are also known to be the main drivers of inflammatory bowel disease (IBD) when this balance is perturbed. Many subsets of CD4⁺ T cells have been identified as players in perpetuating chronic intestinal inflammation. Over the last few decades, understanding of how each subset of Th cells plays a role has dramatically increased. Simultaneously, this has allowed development of therapeutic innovation targeting specific molecules rather than broad immunosuppressive agents. Here, we review the emerging evidence of how each subset functions in promoting and sustaining the chronic inflammation that characterizes IBD.

Pre-clinical and translational pharmacology of a human interleukin-22 IgG fusion protein for potential treatment of infectious or inflammatory diseases

Interleukin (IL)-22 plays protective roles in infections and in inflammatory diseases that have been linked to its meditation of innate immunity via multiple mechanisms. IL-22 binds specifically to its heterodimeric receptor, which is expressed on a variety of epithelial tissues. UTTR1147A is a recombinant fusion protein that links the human cytokine IL-22 with the Fc portion of human immunoglobulin (Ig) G4. Here, we report extensive in vitro and in vivo nonclinical studies that were conducted to characterize the pharmacological activity of UTTR1147A. The in vitro activity and potency of UTTR1147A were analyzed using primary human hepatocytes and human colonic epithelial cell lines. Assessment of in vivo efficacy was performed in a mouse colitis model and by measuring relevant pharmacodynamic biomarkers, including antimicrobial peptides REG3A/β, serum amyloid protein A (SAA) and lipopolysaccharide binding protein (LBP). The pharmacokinetic and pharmacodynamic characteristics of UTTR1147A were assessed in healthy mice, rats and cynomolgus monkeys. UTTR1147A induced STAT3 activation through binding to IL-22 receptor expressed in primary human hepatocytes and human colon cell lines. In both, activation occurred in a concentration-dependent manner with similar potencies. In the mouse colitis model, murine IL-22Fc- (muIL-22Fc) treated groups at doses of 1.25 μg and above had statistically lower average histologic colitis scores compared to the control treated group. Administration of muIL-22Fc or UTTR1147A was associated with a dose-dependent induction of PD markers REG3β and SAA in rodents as well as REG3A, SAA and LBP in cynomolgus monkeys. The combined data confirm pharmacological activity of IL-22Fc and support potential regenerative and protective mechanisms in epithelial tissues.

Absence of specific alternatively spliced exon of CD44 in macrophages prevents colitis

CD44 is a transmembrane molecule appearing in numerous isoforms generated by insertions of alternatively spliced variant exons (CD44v) and having various binding partners. CD44v7 on T cells was proposed to promote colitis by preventing T-cell apoptosis. Here we demonstrate that Cd44v7-deficient T cells - like Cd44 wild-type (Cd44^WT) T cells - provoked disease in two different colitis models: the model induced by CD4⁺CD45RB^high T-cell transfer into Rag2-deficient mice and a new model based on ovalbumin (OVA)-specific T-cell transfer into Rag-sufficient, OVA-challenged mice. In contrast, CD44v7 absence on macrophages in recipient mice prevented colitis. Prevention was associated with the downregulation of signal transducer and activator of transcription 3 (STAT3)-activating and Foxp3-counteracting interleukin-6 (IL-6), lower numbers of phospho-STAT3-containing lymphocytes, and higher Foxp3⁺ T-cell counts in the colon. Consequently, the protected colons showed lower IL-12, IL-1β expression, and decreased interferon-γ levels. Importantly, stimulation of T cells by Cd44v7-deficient macrophages induced upregulation of Foxp3 in vitro, while cotransfer of Cd44^WT macrophages into Cd44v7-deficient mice reduced Foxp3⁺ T-cell counts and caused colitis. Accordingly, the CD44v7 ligand osteopontin, whose levels were elevated in Crohn's disease, specifically induced IL-6 in human monocytes, a cytokine also increased in these patients. We suggest macrophage-specific targeting of the CD44v7 pathway as a novel therapeutic option for Crohn's disease.

Clinical importance of IL-22 cascade in IBD

IL-22 is a relatively new cytokine that is characterized by several unique biological properties. In the intestines, the effect of IL-22 is restricted mainly to non-lymphoid cells such as epithelial cells. Interestingly, the expression pattern and major cellular source of IL-22 have distinct difference between large and small intestines. IL-22 possesses an ability to constitutively activate STAT3 for promoting epithelial cell regeneration and reinforcing mucosal barrier integrity through stimulating the expression of anti-bacterial peptide and mucins. Of note, IL-22 is characterized as a two-faced cytokine that can play not only protective but also deleterious roles in the intestinal inflammation depending on the cytokine environment such as the expression levels of IL-23, T-bet, and IL-22 binding protein. Most importantly, clinical relevance of IL-22 to inflammatory bowel disease has been well highlighted. Mucosal healing, which represents the current therapeutic goal for IBD, can be induced by IL-22. Indeed, indigo naturalis, which can activate IL-22 pathway through Ahr, has been shown in a clinical trial to exhibit a strong therapeutic effect on ulcerative colitis. Despite the beneficial effect of IL-22, continuous activation of the IL-22 pathway increases the risk of colitis-associated cancer, particularly in patients with an extended history of IBD. This review article discusses how IL-22 regulates colitis, how beneficial versus deleterious effects of IL-22 is determined, and why IL-22 represents a promising target for IBD therapy.

Regulatory mechanisms of collagen expression by interleukin-22 signaling in scleroderma fibroblasts

BACKGROUND

Various cytokines have been indicated to be involved in the pathogenesis of systemic sclerosis (SSc). IL-22 is one of the member of IL-10 cytokine family, and several studies have implicated IL-22 signaling in the pathogenesis of autoimmune diseases.

OBJECTIVES

To clarify the role of IL-22 in the regulatory mechanism of ECM expression and to determine the contribution of IL-22 to the phenotype of SSc.

METHODS

The effect of IL-22 on ECM expression in normal fibroblasts was determined by using PCR array, real-time PCR and immunoblotting. microRNA expression was evaluated by real-time PCR. The expression levels of IL-22 in the skin and sera were determined by using immunohistochemical staining and ELISA.

RESULTS

IL-22 significantly increased the expression of type I collagen protein without changing its mRNA levels in cultured normal human dermal fibroblast. The expression of let-7a, one of the microRNAs which have negative effect on type I collagen expression, was significantly decreased by the treatment with IL-22 in dermal fibroblasts. There was no significant difference in the serum levels of IL-22 between SSc patients and control subjects. However, the expression of IL-22 was detected in the infiltrated lymphocytes in the SSc dermis, but not in normal dermis. IL-22 receptors were expressed in both normal and SSc dermal fibroblasts to the similar extent.

CONCLUSION

IL-22 expressed in infiltrated lymphocytes may stimulate the up-regulation of type I collagen protein in dermal fibroblasts via let-7a down-regulation in SSc skin.

Regulation of IL-22BP in psoriasis

IL-22 is a potent pro-inflammatory cytokine upregulated in psoriasis and in other inflammatory diseases. The function of IL-22 is regulated by the soluble scavenging receptor, IL-22 binding protein (IL-22BP or IL-22RA2). However, the role and regulation of IL-22BP itself in the pathogenesis of inflammatory disease remain unclear. We used the TLR7 agonist Imiquimod (IMQ) to induce a psoriasis-like skin disease in mice and found a strong downregulation of IL-22BP in the affected skin as well as in the lymph nodes of animals treated with IMQ. We also analysed psoriatic skin of patients and compared this to skin of healthy donors. Interestingly, IL-22BP expression was similarly downregulated in skin biopsies of psoriasis patients compared to the skin of healthy donors. Since IL-22BP is expressed foremost in dendritic cells, we characterized its expression in monocyte-derived dendritic cells (MoDC) during maturation. In this way, we found Prostaglandin E2 (PGE₂) to be a potent suppressor of IL-22BP expression in vitro. We conclude that regulation of IL-22BP by inflammatory mediators is an important step for the progression of inflammation in the skin and possibly also in other autoimmune diseases.

The Mycobiome: A Neglected Component in the Microbiota-Gut-Brain Axis

In recent years, the gut microbiota has been considered as a full-fledged actor of the gut-brain axis, making it possible to take a new step in understanding the pathophysiology of both neurological and psychiatric diseases. However, most of the studies have been devoted to gut bacterial microbiota, forgetting the non-negligible fungal flora. In this review, we expose how the role of the fungal component in the microbiota-gut-brain axis is legitimate, through its interactions with both the host, especially with the immune system, and the gut bacteria. We also discuss published data that already attest to a role of the mycobiome in the microbiota-gut-brain axis, and the impact of fungi on clinical and therapeutic research.

A catch-22: Interleukin-22 and cancer

Barrier surfaces of multicellular organisms are in constant contact with the environment and infractions to the integrity of epithelial surfaces is likely a frequent event. Interestingly, components of the immune system, that can be activated by environmental compounds such as the microbiota or nutrients, are interspersed among epithelial cells or directly underlie the epithelium. It is now appreciated that immune cells continuously receive and integrate signals from the environment. Curiously, such continuous reception of stimulation does not normally trigger an inflammatory response but mediators produced by immune cells in response to such signals seem to rather promote barrier integrity and repair. The molecular mediators involved in this process are poorly understood. In recent years, the cytokine interleukin-22, produced mainly by group 3 innate lymphoid cells (ILCs), has been studied as a paradigm for how immune cells can control various aspects of epithelial cell function because expression of its receptor is restricted to non-hematopoietic cells. We will summarize here the diverse roles of IL-22 for the malignant transformation of epithelial cells, for tumor growth, wound healing and tissue repair. Furthermore, we will discuss IL-22 as a potential therapeutic target.

A Protective Function of IL-22BP in Ischemia Reperfusion and Acetaminophen-Induced Liver Injury

Acute liver injury can be secondary to a variety of causes, including infections, intoxication, and ischemia. All of these insults induce hepatocyte death and subsequent inflammation, which can make acute liver injury a life-threatening event. IL-22 is a dual natured cytokine which has context-dependent protective and pathogenic properties during tissue damage. Accordingly, IL-22 was shown to promote liver regeneration upon acute liver damage. However, other studies suggest pathogenic properties of IL-22 during chronic liver injury. IL-22 binding protein (IL-22BP, IL-22Ra2) is a soluble inhibitor of IL-22 that regulates IL-22 activity. However, the significance of endogenous IL-22BP in acute liver injury is unknown. We hypothesized that IL-22BP may play a role in acute liver injury. To test this hypothesis, we used Il22bp-deficient mice and murine models of acute liver damage induced by ischemia reperfusion and N-acetyl-p-aminophenol (acetaminophen) administration. We found that Il22bp-deficient mice were more susceptible to acute liver damage in both models. We used Il22 × Il22bp double-deficient mice to show that this effect is indeed due to uncontrolled IL-22 activity. We could demonstrate mechanistically increased expression of Cxcl10 by hepatocytes, and consequently increased infiltration of inflammatory CD11b+Ly6C+ monocytes into the liver in Il22bp-deficient mice upon liver damage. Accordingly, neutralization of CXCL10 reversed the increased disease susceptibility of Il22bp-deficient mice. In conclusion, our data indicate that IL-22BP plays a protective role in acute liver damage, via controlling IL-22-induced Cxcl10 expression.

Role of Interleukin-22 in chronic liver injury

Liver fibrosis is the result of an exacerbated wound-healing response associated with chronic liver injury. Advanced liver fibrosis results in cirrhosis, liver failure, and portal hypertension and frequently requires liver transplantation. The host immune response has an important role driving fibrosis deposition by activating hepatic stellate cells (HSCs). Interleukin-22 (IL-22) is a cytokine that plays a key role in promoting antimicrobial immunity and tissue repair at barrier surfaces. Data from literature suggest that IL-22 has a protective role in the liver by reducing fibrosis in some pathological conditions, however the results are contradictory. This review highlights current knowledge of IL-22' role in chronic liver injury, as well as its therapeutic potential for the treatment of chronic liver injury.

Modified apple polysaccharide prevents colitis through modulating IL-22 and IL-22BP expression

Chronic intestinal inflammation enhances cell proliferation, angiogenesis, and migration, then promotes the development of colorectal cancer (CRC). Many ingredients of apples have been proven to have anti-inflammatory properties, and show benefits for colitis treatment. In our previous studies, we found modified apple polysaccharide (MAP) could prevent colitis associated colorectal carcinogenesis effectively. Herein, we further our study to observe the effect of MAP on dextran sodium sulfate (DSS)-induced colitis and to investigate the possible mechanisms. IL-22 has both pathogenic and protective effects during intestinal tissue damage. It could be neutralized by the soluble IL-22 receptor, known as the IL-22 binding protein (IL-22BP). A DSS-induced colitis mouse model, a mouse CRC cell line MCA-38 and a mouse dendritic cell line DC2.4 were treated with MAP. Western blot, ELISA, BrdU staining and a co-culture system were used to detect the expression of IL-22 and IL-22BP. MAP significantly protected ICR mice against DSS-induced colitis, and inhibited the growth of MCA-38 cells. The mechanisms may be that MAP down-regulated IL-22 level and up-regulated expression of IL-22BP. These data may provide another molecular basis for understanding how apples act to prevent colitis and suggest that MAP has a potential to treat colitis and prevent CRC.

Copy number variations of the IL-22 gene are associated with ankylosing spondylitis: A case-control study in Chinese Han population

IL-22 provides a new insight into the mechanisms of autoimmunity, and copy number variations (CNVs) are associated with autoimmune diseases. This study aims to explore the association of IL-22 gene CNVs with ankylosing spondylitis (AS) susceptibility. The copy numbers of IL-22 gene (2 fragments: IL-22_1, IL-22_2) were examined by AccuCopy™ methods in a cohort of 649 AS patients and 628 controls. Association of IL-22 CNVs and AS susceptibility was analyzed, and AS risk was estimated by Odds Ratio (ORs) and 95% confidence intervals (CIs), and the Benjamini-Hochberg method was applied to regulate the false discovery rate (FDR). We found one copy of IL-22 gene was significantly associated with AS [OR=0.345, 95%CI (0.144, 0.827), P=0.013, PFDR=0.026] in the IL-22_2 fragment, and this association still exist after adjustment of age and sex [OR=0.344, 95%CI (0.143, 0.825), P=0.017, PFDR=0.034]. In the stratification analysis by gender, the statistical difference was detected in males in the IL-22_2 fragment [OR=0.306, 95%CI (0.121, 0.778), P=0.009, PFDR=0.018; adjusted OR=0.306, 95%CI (0.120, 0.777), P=0.013, PFDR=0.026]. We suggest that IL-22 CNVs are associated with AS and that lower copy number might be a protective factor for AS, especially in male patients.

Oral Administration of Lactobacillus rhamnosus GG Ameliorates Salmonella Infantis-Induced Inflammation in a Pig Model via Activation of the IL-22BP/IL-22/STAT3 Pathway

The high rate of Salmonella enterica serovar Infantis (S. Infantis) infection poses significant risk for the development of non-typhoidal Salmonella gastroenteritis. However, efficient strategies to prevent or treat the infection remain elusive. Here, we explored the effect of the probiotic Lactobacillus rhamnosus GG (LGG) administration in preventing S. Infantis infection in a pig model. Probiotic LGG (1.0 × 1010 CFU/day) was orally administered to newly weaned piglets for 1 week before S. Infantis challenge. LGG pretreatment reduced the severity of diarrhea and alleviated intestinal inflammation caused by S. Infantis. Pre-administration of LGG excluded Salmonella from colonization of the jejunal mucosa but increased the abundance of Bifidobacterium in the feces. LGG promoted the expansion of CD4+ T-bet+ IFNγ+ T cells but attenuated S. Infantis-induced increases in the percentage of CD4+ IFNγ+ T cells and serum interleukin (IL)-22 levels in peripheral blood after S. Infantis challenge. In the small intestine, LGG pretreatment upregulated expression of the transcription factor T-bet but downregulated the S. Infantis-induced increase of CD4+ IFNγ+ T cells in Peyer's patches and IL-7Rα expression in the jejunum. Notably, LGG-treated pigs had enhanced expression of IL-22 and activated STAT3 in the ileum in response to S. Infantis infection. Pretreatment of pigs with LGG also elevated intestinal IL-22-binding protein production in response to S. Infantis challenge. In contrast, LGG consumption reduced the S. Infantis-induced increase in the number of CCL20-expressing cells in the jejunum. Our results suggest that the mechanism by which LGG ameliorates the intestinal inflammation caused by S. Infantis involves the upregulation of T-bet, activation of STAT3, and downregulation of CCL20.

IL-22BP dictates characteristics of Peyer's patch follicle-associated epithelium for antigen uptake

Interleukin-22 (IL-22) acts protectively and harmfully on intestinal tissue depending on the situation; therefore, IL-22 signaling needs to be tightly regulated. IL-22 binding protein (IL-22BP) binds IL-22 to inhibit IL-22 signaling. It is expressed in intestinal and lymphoid tissues, although its precise distribution and roles have remained unclear. In this study, we show that IL-22BP is highly expressed by CD11b+CD8α- dendritic cells in the subepithelial dome region of Peyer's patches (PPs). We found that IL-22BP blocks IL-22 signaling in the follicle-associated epithelium (FAE) covering PPs, indicating that IL-22BP plays a role in regulating the characteristics of the FAE. As expected, FAE of IL-22BP-deficient (Il22ra2-/-) mice exhibited altered properties such as the enhanced expression of mucus and antimicrobial proteins as well as prominent fucosylation, which are normally suppressed in FAE. Additionally, Il22ra2-/- mice exhibited the decreased uptake of bacterial antigens into PPs without affecting M cell function. Our present study thus demonstrates that IL-22BP promotes bacterial uptake into PPs by influencing FAE gene expression and function.

Eosinophils in Autoimmune Diseases

Eosinophils are multifunctional granulocytes that contribute to initiation and modulation of inflammation. Their role in asthma and parasitic infections has long been recognized. Growing evidence now reveals a role for eosinophils in autoimmune diseases. In this review, we summarize the function of eosinophils in inflammatory bowel diseases, neuromyelitis optica, bullous pemphigoid, autoimmune myocarditis, primary biliary cirrhosis, eosinophilic granulomatosis with polyangiitis, and other autoimmune diseases. Clinical studies, eosinophil-targeted therapies, and experimental models have contributed to our understanding of the regulation and function of eosinophils in these diseases. By examining the role of eosinophils in autoimmune diseases of different organs, we can identify common pathogenic mechanisms. These include degranulation of cytotoxic granule proteins, induction of antibody-dependent cell-mediated cytotoxicity, release of proteases degrading extracellular matrix, immune modulation through cytokines, antigen presentation, and prothrombotic functions. The association of eosinophilic diseases with autoimmune diseases is also examined, showing a possible increase in autoimmune diseases in patients with eosinophilic esophagitis, hypereosinophilic syndrome, and non-allergic asthma. Finally, we summarize key future research needs.

The Microbiota and Epigenetic Regulation of T Helper 17/Regulatory T Cells: In Search of a Balanced Immune System

Immune cells not only affect tissue homeostasis at the site of inflammation but also exert systemic effects contributing to multiple chronic conditions. Recent evidence clearly supports an altered T helper 17/regulatory T cell (Th17/Treg) balance leading to the development and progression of inflammatory diseases that not only affect the gastrointestinal tract but also have whole-body manifestations, including insulin resistance. Epigenetic mechanisms are amenable to both environmental and circulating factors and contribute to determining the T cell landscape. The recently identified participation of the gut microbiota in the remodeling of the epigenome of immune cells has triggered a paradigm shift in our understanding of the etiology of various inflammatory diseases and opened new paths toward therapeutic strategies. In this review, we provide an overview of the contribution of the Th17/Treg balance in the development and progression of inflammatory bowel diseases and metabolic diseases. We discuss the involvement of epigenetic mechanisms in the regulation of T cell function in the particular context of dysbiosis. Finally, we examine the potential for nutritional interventions affecting the gut microbiota to reshape the T cell epigenome and address the inflammatory component of various diseases.

A pathogenic role for T cell-derived IL-22BP in inflammatory bowel disease

Intestinal inflammation can impair mucosal healing, thereby establishing a vicious cycle leading to chronic inflammatory bowel disease (IBD). However, the signaling networks driving chronic inflammation remain unclear. Here we report that CD4⁺ T cells isolated from patients with IBD produce high levels of interleukin-22 binding protein (IL-22BP), the endogenous inhibitor of the tissue-protective cytokine IL-22. Using mouse models, we demonstrate that IBD development requires T cell-derived IL-22BP. Lastly, intestinal CD4⁺ T cells isolated from IBD patients responsive to treatment with antibodies against tumor necrosis factor-α (anti-TNF-α), the most effective known IBD therapy, exhibited reduced amounts of IL-22BP expression but still expressed IL-22. Our findings suggest that anti-TNF-α therapy may act at least in part by suppressing IL-22BP and point toward a more specific potential therapy for IBD.

Hypoxic modulation of hepatocyte responses to the cytokine interleukin-22

The cytokine interleukin-22 (IL-22) is a potent regulator of tissue responses during inflammation. Depending on the context of inflammation, IL-22 can have protective or inflammatory effects on epithelial cells. This dual nature of IL-22 leads us to hypothesize that its activity must be exquisitely regulated to prevent host tissue damage. Environmental factors may act as a cellular cue as to how cells respond to IL-22. Inflammatory environments are characterized by low oxygen and thus we examined whether cells respond differently to IL-22 hypoxia compared with normoxia. In this study, we show that hepatocyte responses to IL-22 stimulation are reduced in hypoxic environments. IL-22 stimulation of hepatocytes incubated in low oxygen led to reduced levels of activated signal transducer and activator of transcription 3 and further downstream effects such as reduced induction of the anti-microbial protein, lipocalin-2. This modulation appears to be independent of the hypoxia-inducible factor-1α signaling pathway. Thus, hypoxia that accompanies chronic inflammation may be a mechanism to regulate the bioactivity of the dual-natured IL-22 cytokine.

How Does Interleukin-22 Mediate Liver Regeneration and Prevent Injury and Fibrosis?

Interleukin-22 (IL-22) is a pluripotent T cell-derived cytokine which is a member of IL-10 cytokine family. It is the only interleukin produced by immune cells but does not target immune system components. IL-22 is mainly produced by dendritic cells (DCs) and TH17, TH22, NK, and NKT cells and targets a number of body tissues including liver, pancreas, and other epithelial tissues. It provokes a series of downstream signaling pathways upon binding with IL-22R complex which protects liver damage through STAT3 activation. IL-22BP is an inhibitor of IL-22 which has 20-1000x more affinity to bind with IL-22 compared to IL-22R1 that inhibits IL-22 activity. Its level was found to be positively correlated with the severity of liver damage and fibrosis. So, the present review is an effort to reveal the exact mechanism lying in the hepatoprotective activity of IL-22 and some of its future therapeutic implications.

Cytokines IL-17 and IL-22 in the host response to infection

Cytokines IL-17 and IL-22 play pivotal roles in host defense against microbes and in the development of chronic inflammatory diseases. These cytokines are produced by cells that are often located in epithelial barriers, including subsets of T cells and innate lymphoid cells. In general, IL-17 and IL-22 can be characterized as important cytokines in the rapid response to infectious agents, both by recruiting neutrophils and by inducing the production of antimicrobial peptides. Although each cytokine induces an innate immune response in epithelial cells, their functional spectra are generally distinct: IL-17 mainly induces an inflammatory tissue response and is involved in the pathogenesis of several autoimmune diseases, whereas IL-22 is largely protective and regenerative. In this review, we compare IL-17 and IL-22, describing overlaps and differences in their cellular sources as well as their regulation, signaling, biological functions and roles during disease, with a focus on the contribution of these cytokines to the gut mucosal barrier during bacterial infection.

Human IL-22 binding protein isoforms act as a rheostat for IL-22 signaling

The cytokine interleukin-22 (IL-22), which is a member of the IL-10 family, is produced exclusively by immune cells and activates signal transducer and activator of transcription 3 (STAT3) in nonimmune cells, such as hepatocytes, keratinocytes, and colonic epithelial cells, to drive various processes central to tissue homeostasis and immunosurveillance. Dysregulation of IL-22 signaling causes inflammatory diseases. IL-22 binding protein (IL-22BP; encoded by IL22RA2) is a soluble IL-22 receptor, which antagonizes IL-22 activity and has genetic associations with autoimmune diseases. Humans have three IL-22BP isoforms, IL-22BPi1 to IL-22BPi3, which are generated by alternative splicing; mice only have an IL-22BPi2 homolog. We showed that, although IL-22BPi3 had less inhibitory activity than IL-22BPi2, IL-22BPi3 was more abundant in various human tissues under homeostatic conditions. IL-22BPi2 was more effective than IL-22BPi3 at blocking the contribution of IL-22 to cooperative gene induction with the inflammatory cytokine IL-17, which is often present with IL-22 in autoimmune settings. In addition, we found that IL-22BPi1 was not secreted and therefore failed to antagonize IL-22 signaling. Furthermore, IL-22BPi2 was the only isoform that was increased in abundance when myeloid cells were activated by Toll-like receptor 2 signaling or retinoic acid, a maturation factor for myeloid cells. These data suggest that the human IL-22BP isoforms have distinct spatial and temporal roles and coordinately fine-tune IL-22-dependent STAT3 responses in tissues as a type of rheostat.

Role of group 3 innate lymphoid cells during experimental otitis media in a rat model

The objective of this study was to evaluate the role of group 3 innate lymphoid cells (ILC3) in the middle ear (ME) mucosal response to bacterial infection in a rat model. To confirm the role of ILC3 in bacterially induced otitis media (OM), the serum concentrations of IL-17 and IL-22 were determined by ELISA, and the tissue expression of IL-17 and IL-22 in infected ME mucosa was assessed by immunohistochemical staining. Immunohistochemical staining of specific cell surface markers was also assessed to confirm the origin of the cells expressing IL-17 and IL-22. Twenty Sprague-Dawley rats were used in the surgically-induced animal model of OM. OM was induced by inoculation of non-typeable Haemophilus influenzae into the ME cavity of the rats. The rats were divided into four experimental groups: three infected groups and one control group. Infected groups were subdivided into sets of 5 rats, one for each of the three time points (1, 4 and 7 days post-inoculation). For determination of rat IL-17 and IL-22 levels in infected rats and control rats, infected or control ME mucosa sections were analyzed by immunohistochemistry with specific antibodies directed against IL-17 and IL-22. Immunohistochemical staining for CD3, RORγt, and NKp46 were also conducted on the samples to confirm the origin of cells expressing IL-17 and IL-22. IL-17 and IL-22 serum concentrations were significantly increased in the infected rats compared to control rats. Immunohistochemical staining revealed increased IL-17 and IL-22 expressions in all infected ME mucosae from the first day after inoculation. In addition, the results of tissue staining for the specific surface markers were negative for CD3 and NKp46, but were highly positive for RORγt. IL-17 and IL-22 revealed their association with the bacterially induced proliferative and hyperplastic responses of ME mucosa, which are characteristic features in pathogenesis of OM. Surface marker examination showed that the source cells for IL-17 and IL-22 seemed to be lymphoid tissue inducer (LTi) cells. The results suggest that LTi cells release IL-17 and IL-22, and play a significant role in both the early phase of OM induction and recovery from it.

The role of barrier function, autophagy, and cytokines in maintaining intestinal homeostasis

Intestinal homeostasis is maintained through the interplay of the intestinal mucosa, local and systemic immune factors, and the microbial content of the gut. The cellular processes of autophagy, endoplasmic reticulum stress, the unfolded protein response and regulation of reactive oxygen species production are required to maintain a balance between pro-inflammatory responses against potential pathogens and a tolerogenic response towards commensal bacteria. Intestinally active cytokines regulate innate immune pathways and cellular pathways within the gut mucosa. Disruption of these processes, or alterations in the cytokine milieu, can result in an improper response to the commensal gut microbial community leading to inappropriate inflammation characteristic of conditions such as inflammatory bowel disease.

Lipopolysaccharide-binding protein is efficient in biodosimetry during radiotherapy of lung cancer

The aim of the present study was to determine if the serum levels of early markers of inflammation, such as interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), C-reactive protein (CRP), and lipopolysaccharide-binding protein (LBP) were correlated with the radiation dose received by the pulmonary and mediastinal structures of patients with non-small cell lung cancer (NSCLC). This pilot study included 26 patients with NSCLC who received total radiation doses ranging from 54 to 74 Gy (2.0 Gy/fraction). Cytokines were measured at baseline by enzyme-linked immunosorbant assay, and following administration of total doses of 20 and 40 Gy. A control group of 26 participants was sampled for comparisons with patient baseline cytokine levels. Only data from the 40-Gy cytokine blood levels of patients with NSCLC were identified to be correlated with histograms of the parameters of each patient's radiotherapy protocol. The IL-6, TNF-α and CRP median baseline levels of the patients with NSCLC were significantly higher than those of the controls (all P≤0.01). No differences were observed between the LBP levels of the patients and controls [median, 36.34 (25-75%; 31.35-39.27) vs. 36.92 (30.20-44.05) µg/ml, respectively; P=0.42]. No significant differences in the levels of the four cytokines between baseline, and at 20 and 40 Gy were observed [IL-6 (P=0.19); TNF-α (P=0.68); CRP (P=0.44) and LBP (P=0.29)]. LBP was significantly and positively correlated with the mean radiation dose to the lung (r=0.409; P=0.038), and showed a positive correlation with the percentage of lung volume exposed to at least 20 Gy of the planned radiation dose (r=0.3536; P=0.0764). CRP levels were positively correlated with the mean radiation dose to the esophagus (r=0.404; P=0.041); however, IL-6, TNF-α and CRP were not significantly associated with other lung dosimetry parameters. Thus, LBP levels were correlated with radiation exposure of pulmonary tissues, and LBP may be a marker that warrants further investigation on radiotoxicity in NSCLC patients.

Influence of orally fed a select mixture of Bacillus probiotics on intestinal T-cell migration in weaned MUC4 resistant pigs following Escherichia coli challenge

Efficient strategies for treating enteritis caused by F4⁺ enterotoxigenic Escherichia coli (ETEC)/verocytotoxigenic Escherichia coli (VTEC)/enteropathogenic E. coli (EPEC) in mucin 4 resistant (MUC4 RR; supposed to be F4ab/ac receptor–negative [F4ab/acR⁻]) pigs remain elusive. A low (3.9 × 10⁸ CFU/day) or high (7.8 × 10⁸ CFU/day) dose of Bacillus licheniformis and Bacillus subtilis spore mixture (BLS-mix) was orally administered to MUC4 RR piglets for 1 week before F4⁺ ETEC/VTEC/EPEC challenge. Orally fed BLS-mix upregulated the expression of TLR4, NOD2, iNOS, IL-8, and IL-22 mRNAs in the small intestine of pigs challenged with E. coli. Expression of chemokine CCL28 and its receptor CCR10 mRNAs was upregulated in the jejunum of pigs pretreated with high-dose BLS-mix. Low-dose BLS-mix pretreatment induced an increase in the proportion of peripheral blood CD4⁻CD8⁻ T-cell subpopulations and high-dose BLS-mix induced the expansion of CD4⁻CD8⁻ T cells in the inflamed intestine. Immunostaining revealed that considerable IL-7Rα–expressing cells accumulated at the lamina propria of the inflamed intestines after E. coli challenge, even in pigs pretreated with either low- or high-dose BLS-mix, although Western blot analysis of IL-7Rα expression in the intestinal mucosa did not show any change. Our data indicate that oral administration of the probiotic BLS-mix partially ameliorates E. coli-induced enteritis through facilitating upregulation of intestinal IL-22 and IκBα expression, and preventing loss of intestinal epithelial barrier integrity via elevating ZO-1 expression. However, IL-22 also elicits an inflammatory response in inflamed intestines as a result of infection with enteropathogenic bacteria.

Association between CXCR2 and IL-22BP expression indicate a poor outcome for gastric adenocarcinoma progression

C-X-C motif chemokine receptor type 2 (CXCR2), a key regulatory protein, has been associated with multiple roles in the progression of numerous tumors, including gastric adenocarcinoma (GA). However, the mechanism of CXCR2 in the development of tumors remains controversial and unclear. In a previous study, the expression of CXCR2 and interleukin-22 receptor 2 (IL-22BP) was observed in GA. This promoted the present study, which aimed to explore the association between the two proteins, and to further analyze their roles in GA. CXCR2 and IL-22BP protein expression was analyzed by immunohistochemistry and reverse transcription-quantitative polymerase chain reaction assays in gastric cancer (GC) tissue, additionally confirmed via western blotting and immunocytochemical analysis in the MKN-45, BGC-823 and SGC-7901 cell lines. The association between expression levels and clinicopathological characteristics was evaluated by the Mann-Whitney U and Kruskal-Wallis tests. Using Kaplan-Meier plots and Cox proportional hazard models, overall survival (OS) was analyzed. Compared with non-cancerous tissue, CXCR2 and IL-22BP were over expressed (P<0.001 and P<0.001, respectively), and were observed mainly in the cytoplasm (P=0.022 and P=0.014, respectively) in GA. The associated protein and messenger RNA levels were analyzed, and coexpression was identified. Increased expression and more positive cases of CXCR2 and IL-22BP were observed with advanced pathological tumor-node-metastasis (p-TNM) stage in GC (P<0.001 and P<0.001, respectively), as well as the presence and absence of lymph node metastasis (LNM) (P=0.003 and P=0.041, respectively) and deep or superficial muscular invasion (P=0.002 and P=0.004, respectively). In addition, an association between IL-22BP and tumor diameter was indicated (P=0.021). In a Kaplan-Meier analysis, compared with negative expression, the two proteins identified a group of patients with the shortest OS. Cox proportional hazard models revealed that the two proteins, in addition to p-TNM stage, LNM and depth of invasion, predicted a short time to OS. The coexpression of CXCR2 and IL-22BP was demonstrated in GA, which may indicate that CXCR2 is involved in more complex mechanisms and roles, and indicate a poor outcome in GA progression.

Reduced diversity and altered composition of the gut microbiome in individuals with myalgic encephalomyelitis/chronic fatigue syndrome

BACKGROUND

Gastrointestinal disturbances are among symptoms commonly reported by individuals diagnosed with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). However, whether ME/CFS is associated with an altered microbiome has remained uncertain. Here, we profiled gut microbial diversity by sequencing 16S ribosomal ribonucleic acid (rRNA) genes from stool as well as inflammatory markers from serum for cases (n = 48) and controls (n = 39). We also examined a set of inflammatory markers in blood: C-reactive protein (CRP), intestinal fatty acid-binding protein (I-FABP), lipopolysaccharide (LPS), LPS-binding protein (LBP), and soluble CD14 (sCD14).

RESULTS

We observed elevated levels of some blood markers for microbial translocation in ME/CFS patients; levels of LPS, LBP, and sCD14 were elevated in ME/CFS subjects. Levels of LBP correlated with LPS and sCD14 and LPS levels correlated with sCD14. Through deep sequencing of bacterial rRNA markers, we identified differences between the gut microbiomes of healthy individuals and patients with ME/CFS. We observed that bacterial diversity was decreased in the ME/CFS specimens compared to controls, in particular, a reduction in the relative abundance and diversity of members belonging to the Firmicutes phylum. In the patient cohort, we find less diversity as well as increases in specific species often reported to be pro-inflammatory species and reduction in species frequently described as anti-inflammatory. Using a machine learning approach trained on the data obtained from 16S rRNA and inflammatory markers, individuals were classified correctly as ME/CFS with a cross-validation accuracy of 82.93 %.

CONCLUSIONS

Our results indicate dysbiosis of the gut microbiota in this disease and further suggest an increased incidence of microbial translocation, which may play a role in inflammatory symptoms in ME/CFS.

Loss of IL-22 inhibits autoantibody formation in collagen-induced arthritis in mice

Interleukin 22 (IL-22) expression is associated with increased joint destruction and disease progression in rheumatoid arthritis (RA). Although IL-22 is considered a pro-inflammatory cytokine, its mechanism of action in RA remains incompletely understood. Here, we used the collagen-induced arthritis model in IL-22 deficient (IL-22(-/-) ) mice to study the role of IL-22 in RA. In spite of normal disease incidence, disease severity is significantly diminished in IL-22(-/-) mice. Moreover, pathogenicity of Th17 cells and development and function of B cells are unaffected. In contrast, splenic plasma cells, as well as serum autoantibody titers, are reduced in the absence of IL-22. At the peak of disease, germinal centers (GCs) are severely reduced in the spleens of IL-22(-/-) mice, correlating with a decline in GC B-cell numbers. Within the GC, we identified IL-22R1 expressing follicular dendritic cell-like stromal cells. Human lymphoid stromal cells respond to IL-22 ex vivo by inducing transcription of CXCL12 and CXCL13. We therefore postulate IL-22 as an important enhancer of the GC reaction, maintaining chemokine levels for the persistence of GC reactions, essential for the production of autoantibody-secreting plasma cells. Blocking IL-22 might therefore prevent immune-complex deposition and destruction of joints in RA patients.

The enigmatic role of IL-22 in asthma

Asthma is a complex, heterogeneous disorder with increasing prevalence. It is now recognized that several asthma phenotypes exist, including type 2-high and type 2-low (or non-type 2) subsets. As current research strives to identify subgroups of asthmatics that share disease pathobiology to establish endotypes, efforts to clarify the underlying molecular mechanisms of disease are needed and essential. IL-22 is thought to be a mediator of asthma pathogenesis, but whether this cytokine has a pathologic or beneficial role in the lung during severe disease is still debated. Studies focused on the regulation of this cytokine by its receptors and other inflammatory mediators during allergic airway responses are necessary to clarify its role in disease. Here, we discuss the ambiguity surrounding the role of IL-22 in asthma and considerations for targeting IL-22 therapeutically.

Effects of bamboo vinegar powder on growth performance and mRNA expression levels of interleukin-10, interleukin-22, and interleukin-25 in immune organs of weaned piglets

The aim of this study was to explore the effects of bamboo vinegar powder on growth performance, diarrhea situation and mRNA expression levels of cytokines i.e., interleukin-10 (IL-10), interleukin-22 (IL-22), and interleukin-25 (IL-25) in immune organs of weaned piglets, and to accumulate theoretical data for the application of bamboo vinegar powder in weaned piglet production. Forty-five crossbred (Duroc × Landrace × Yorkshire, all male) weaned piglets with similar body weight (6.74 ± 0.17 kg) at 31 days of age were randomly assigned to 5 treatments with 3 replicates per treatment and 3 piglets in each replicate. The five treatments were as follows: CON (a basal diet), ANT (the basal diet + 0.12% antibiotics), BV1 (the basal diet + 0.1% bamboo vinegar powder), BV5 (the basal diet + 0.5% bamboo vinegar powder), BV10 (the basal diet + 1.0% bamboo vinegar powder). This experiment lasted 35 days. The growth performance and diarrhea situation were recorded. The relative mRNA expression levels of IL-10, IL-22 and IL-25 in liver, spleen, duodenum and mesenteric lymph nodes were detected by real-time PCR. Feed: gain of BV5 was significantly lower than that of CON (P < 0.05). In comparison with CON, diarrhea rate and diarrhea index of BV1 and BV5 all tended to decrease (P < 0.1). Compared with CON, mRNA expression level of IL-10 in liver of ANT tended to be lower (P < 0.1) and these of BV1, BV5 and BV10 were significantly reduced (P < 0.05). The mRNA expression levels of IL-10 in duodenum of ANT, BV1, BV5 and BV10 were all lower than those of CON, of which BV10 had significantly decreased IL-10 mRNA expression in duodenum (P < 0.05). The mRNA expression levels of IL-22 in duodenum of ANT, BV1, BV5 and BV10 all tended to be inhibited compared with CON (P < 0.1). With the increase of bamboo vinegar powder dosage, mRNA expression levels of IL-25 in spleen and mesenteric lymph nodes of BV1, BV5 and BV10 tended to be up-regulated. Overall, bamboo vinegar powder could improve growth performance, and regulate mRNA expression levels of IL-10, IL-22 and IL-25 in immune organs of weaned piglets. The dosage at 0.5% showed optimum effects.

Microbiota-specific Th17 Cells: Yin and Yang in Regulation of Inflammatory Bowel Disease

Multiple mechanisms are involved in regulation of host response to microbiota to maintain the intestinal homeostasis. Th17 cells are enriched in the intestinal lamina propria under steady conditions. Many studies have demonstrated that microbiota-reactive Th17 cells in the intestines mediate the pathogenesis of inflammatory bowel diseases. However, clinical trials of anti-interleukin-17A or anti-interleukin-17RA antibodies in patients with Crohn's Disease show no improvement or even exacerbation of disease. Accumulating data has also indicated that Th17 cells may provide a protective effect as well to the intestines from inflammatory insults under homeostasis regulation, even under inflammatory conditions. Thus both proinflammatory and anti-inflammatory functions of intestinal Th17 cells have emerged under various conditions. In this review article, we will summarize recent progresses of Th17 cells in regulation of intestinal homeostasis and in the pathogenesis of inflammatory bowel diseases.

The Role of IL-22 in Viral Infections: Paradigms and Paradoxes

Interleukin-22 (IL-22) is a member of the IL-10 family of cytokines. Hematopoietic cells express IL-22, and this cytokine signals through the heterodimeric IL-22 receptor expressed by non-hematopoietic cells. A growing body of evidence points toward a role for IL-22 in a diverse array of biological functions ranging from cellular proliferation, tissue protection and regeneration, and inflammation. In recent years, the role that IL-22 plays in antiviral immune responses has been examined in a number of infection models. Herein, we assess our current understanding of how IL-22 determines the outcome of viral infections and define common mechanisms that are evident from, sometimes paradoxical, findings derived from these studies. Finally, we discuss the potential therapeutic utility of IL-22 manipulation in the treatment and prevention of viral infections and associated pathologies.

Biological and pathological activities of interleukin-22

Interleukin (IL)-22, a member of the IL-10 family, is a cytokine secreted by several types of immune cells including IL-22(+)CD4(+) T cells (Th22) and IL-22 expressing innate leukocytes (ILC22). Recent studies have demonstrated that IL-22 is a key component in mucosal barrier defense, tissue repair, epithelial cell survival, and proliferation. Furthermore, accumulating evidence has defined both protective and pathogenic properties of IL-22 in a number of conditions including autoimmune disease, infection, and malignancy. In this review, we summarize the expression and signaling pathway and functional characteristics of the IL-22 and IL-22 receptor axis in physiological and pathological scenarios and discuss the potential to target IL-22 signaling to treat human diseases.

Interleukin-22 in Graft-Versus-Host Disease after Allogeneic Stem Cell Transplantation

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a potential curative treatment for hematologic malignancies and non-malignant diseases. Because of the lower toxicity of reduced intensity conditioning, the number of transplants is in constant increase. However, allo-HSCT is still limited by complications, such as graft-versus-host disease (GVHD), which is associated with important morbidity and mortality. Acute GVHD is an exacerbated inflammatory response that leads to the destruction of healthy host tissues by donor immune cells. Recently, the contribution of innate immunity in GVHD triggering has been investigated by several groups and resulted in the identification of new cellular and molecular effectors involved in GVHD pathogenesis. Interleukin-22 (IL-22) is produced by both immune and adaptive cells and has both protective and inflammatory properties. Its role in GVHD processes has been investigated, and the data suggest that its effect depends on the timing, the target tissue, and the origin of the producing cells (donor/host). In this review, we discuss the role of IL-22 in allo-HSCT and GVHD.

The Role of T-Cell Subsets in Chronic Inflammation in Celiac Disease and Inflammatory Bowel Disease Patients: More Common Mechanisms or More Differences?

Background

Chronic intestinal inflammation due to noninfectious causes represents a growing health issue all over the world. Celiac disease as well as inflammatory bowel diseases (IBD) like Crohn's disease and ulcerative and microscopic colitis involve uncontrolled T-cell activation and T-cell-mediated damage as common denominators. Therefore, diagnosis and treatment decisions clearly benefit from the knowledge of the intricacies of the systemic and the local T-cell activity.

Summary

Depending on the cytokine milieu, CD4⁺ T cells can differentiate into proinflammatory T helper 1 (Th1), anti-inflammatory Th2, antimicrobial Th17, pleiotropic Th9, tissue-instructing Th22 cells, and in the regulatory compartment forkhead box protein 3⁺ Treg, suppressive Tr1 or Th3 cells. Additionally, follicular Th cells provide B-cell help in antibody class switching; cytotoxic CD8⁺ T cells target virus-infected or tumor cells. This review discusses our current knowledge on the contribution of defined T-cell subpopulations to establishing and maintaining chronic intestinal inflammation in either of the above entities. It also puts emphasis on the differences in the prevalence of these diseases between Eastern and Western countries.

Key Messages

In celiac disease, the driving role of T cells in the lamina propria and in the epithelium mainly specific for two defined antigens is well established. Differences in genetics and lifestyle between Western and Eastern countries were instrumental in understanding underlying mechanisms. In IBD, the vast amount of potential antigens and the corresponding antigen-specific T cells makes it unlikely to find universal triggers. Increased mucosal CD4⁺ regulatory T cells in all four entities fail to control or abrogate local inflammatory processes. Thus, prevailing differences in the functional T-cell subtypes driving chronic intestinal inflammation in celiac disease and IBD at best allow some overlap in the treatment options for either disease.

Interleukin-22-Induced Antimicrobial Phospholipase A2 Group IIA Mediates Protective Innate Immunity of Nonhematopoietic Cells against Listeria monocytogenes

Listeria monocytogenes is a bacterial pathogen which establishes intracellular parasitism in various cells, including macrophages and nonhematopoietic cells, such as hepatocytes. It has been reported that several proinflammatory cytokines have pivotal roles in innate protection against L. monocytogenes infection. We found that a proinflammatory cytokine, interleukin 22 (IL-22), was expressed by CD3(+) CD4(+) T cells at an early stage of L. monocytogenes infection in mice. To assess the influence of IL-22 on L. monocytogenes infection in hepatocytes, cells of a human hepatocellular carcinoma line, HepG2, were treated with IL-22 before L. monocytogenes infection in vitro. Gene expression analysis of the IL-22-treated HepG2 cells identified phospholipase A2 group IIA (PLA2G2A) as an upregulated antimicrobial molecule. Addition of recombinant PLA2G2A to the HepG2 culture significantly suppressed L. monocytogenes infection. Culture supernatant of the IL-22-treated HepG2 cells contained bactericidal activity against L. monocytogenes, and the activity was abrogated by a specific PLA2G2A inhibitor, demonstrating that HepG2 cells secreted PLA2G2A, which killed extracellular L. monocytogenes. Furthermore, colocalization of PLA2G2A and L. monocytogenes was detected in the IL-22-treated infected HepG2 cells, which suggests involvement of PLA2G2A in the mechanism of intracellular killing of L. monocytogenes by HepG2 cells. These results suggest that IL-22 induced at an early stage of L. monocytogenes infection enhances innate immunity against L. monocytogenes in the liver by stimulating hepatocytes to produce an antimicrobial molecule, PLA2G2A.

Interleukin-22 Signaling in the Regulation of Intestinal Health and Disease

Interleukin (IL)-22 is a member of the IL-10 family of cytokines that has been extensively studied since its discovery in 2000. This review article aims to describe the cellular sources and signaling pathways of this cytokine as well as the functions of IL-22 in the intestine. In addition, this article describes the roles of IL-22 in the pathogenesis of several gastrointestinal diseases, including inhibition of inflammation and barrier defense against pathogens within the intestine. Since many of the functions of IL-22 in the intestine are incompletely understood, this review is meant to assess our current understanding of the roles of IL-22 and provide new opportunities for inquiry to improve human intestinal health and disease.

RORγt(+) IL-22-producing NKp46(+) cells protect from hepatic ischemia reperfusion injury in mice

BACKGROUND & AIMS

NKp46(+) cells are major effector cells in the pathogenesis of hepatic ischemia reperfusion injury (IRI). Nevertheless, the precise role of unconventional subsets like the IL-22-producing NKp46(+) cells (NK22) remains unknown. The purpose of this study was to examine the role of NK22 cells in IRI in transplantation, particularly with respect to regulation by the transcription factor ROR-gamma-t (RORγt).

METHODS

To explore the role of NK22 cells in IRI in the absence of adaptive immunity, B6.RORγt-(gfp/wt)-reporter and B6.RORγt-(gfp/gfp)-knockout (KO) mice on a Rag KO background underwent 90min partial warm ischemia, followed by 24h of reperfusion.

RESULTS

Rag KO mice that possess fully functional NKp46(+) cells, and Rag-common-γ-chain-double-KO (Rag-γc-DKO) mice that lack T, B and NKp46(+) cells, were used as controls. We found that Rag-γc-DKO mice lacking NK22 cells show more severe levels of hepatocellular damage (GPT, histological injury) when compared to both Rag-RORγt-reporter and Rag KO mice that possess NK22 cells. Importantly, Rag-RORγt-reporter and Rag KO mice undergoing IRI expressed high protein levels of both IL-22 and GFP (RORγt), suggesting a protective role for RORγt(+) NK22 cells in IRI. Therefore, we tested the hypothesis that RORγt critically protects from IRI through the induction of hepatic NK22 cells by studying Rag-Rorγt-DKO mice under IRI conditions. We found that the lack of RORγt(+) NK22 cells in Rag-Rorγt-DKO mice significantly enhanced IR-induced hepatocellular injury, a phenotype that could be reversed upon adoptive transfer of Rag-Rorγt-reporter NK22 cells into DKO mice.

CONCLUSIONS

RORγt(+) NK22 cells play an important protective role in IRI in mice.