Regulation of the development of acute hepatitis by IL-23 through IL-22 and IL-17 production

Pharmacokinetic/Pharmacodynamic Assessment of Selective Phosphodiesterase Inhibitors in a Mouse Model of Autoimmune Hepatitis

Autoimmune hepatitis (AIH) is a life-threatening disorder currently treated with nonspecific immunosuppressive drugs. It is postulated that phosphodiesterase (PDE) inhibitors, as agents exerting anti-inflammatory and immunomodulatory activities, may constitute a possible treatment of autoimmune disorders. This study develops a pharmacokinetic/pharmacodynamic (PK/PD) model to assess the effects of PDE-selective inhibitors, namely, cilostazol (PDE3), rolipram (PDE4), and BRL-50481 (PDE7), in a mouse model of AIH. The pharmacokinetics of the PDE inhibitors (PDEi) were assessed in male BALB/c mice after intraperitoneal administration. In pharmacodynamic studies, mice received PDEi and AIH was induced in these animals by intravenous injection of concanavalin A (ConA). Serum drug concentrations, tumor necrosis factor α (TNFα), interleukin 17 (IL-17), and aminotransferase activities were quantified. The PK/PD analysis was performed using ADAPT5 software. The PK/PD model assumes inhibition of cAMP hydrolysis in T cells by PDEi, ConA-triggered formation of TNFα and IL-17, suppression of TNFα and IL-17 production by cAMP, and stimulatory effects of TNFα and IL-17 on the hepatic release of aminotransferases. Selective blockage of PDE4 leads to the highest inhibition of cAMP degradation in T cells and amelioration of disease outcomes. However, inhibition of both PDE3 and PDE7 also contribute to this effect. The proposed PK/PD model may be used to assess and predict the activities of novel PDEi and their combinations in ConA-induced hepatitis. A balanced suppression of different types of PDE appears to be a promising treatment option for AIH; however, this hypothesis warrants testing in humans based on translation of the PK/PD model into clinical settings. SIGNIFICANCE STATEMENT: A novel PK/PD model of PDE inhibitor effects in mice with ConA-induced autoimmune hepatitis was developed involving a mechanistic component describing changes in cAMP concentrations in mouse T cells. According to model predictions, inhibition of PDE4 in T cells causes the highest cAMP elevation in T cells, but suppression of PDE3 and PDE7 also contribute to this effect. A balanced inhibition of PDE3, PDE4, and PDE7 appears to be a promising treatment strategy for AIH.

Th17 cells in the liver: balancing autoimmunity and pathogen defense

In addition to carcinogenesis, T helper 17 (Th17) cells (a subtype of CD4 + T lymphocytes) are involved in the acute, chronic, and cirrhotic phases of liver diseases; however, their role in the development and progression of liver diseases remains unclear. It is difficult to elucidate the role of Th17 cells in liver diseases due to their dichotomous nature, i.e., plasticity in terms of pathogenic or host protective function depending on environmental and time phase factors. Moreover, insufficient depletion of Th17 cells by inhibiting the cytokines and transcription factors involved in their production causes difficulties in analyzing their specific role in vitro and in vivo murine models, partially due to complex interaction. This review summarizes the recent progress in understanding the plasticity and function of hepatic Th17 cells and type 3 cytokines.

The aryl hydrocarbon receptor in liver inflammation

The aryl hydrocarbon receptor (AHR) is a ubiquitously expressed ligand-activated transcription factor with multifaceted physiological functions. In the immune system, AHR has been unequivocally identified as a key regulatory factor that can integrate environmental, dietary, or microbial signals into innate and adaptive immune responses. Correspondingly, AHR activity seems to be most important at barrier organs, such as the gut, skin, and lung. The liver is likewise prominently exposed to gut-derived dietary or microbial AHR ligands and, moreover, generates plenty of AHR ligands itself. Yet, surprisingly little is known about the role of AHR in the regulation of hepatic immune responses, which are normally biased towards tolerance, preventing harmful inflammation in response to innocuous stimuli. In this review, we summarize the current knowledge about the role of AHR in hepatic immune responses in the healthy liver as well as in inflammatory liver disease. Moreover, we discuss AHR as a potential therapeutic target in hepatic disorders, including autoimmune liver disease, liver fibrosis, and liver cancer.

Mesenchymal stem cell-based treatment in autoimmune liver diseases: underlying roles, advantages and challenges

Autoimmune liver disease (AILD) is a series of chronic liver diseases with abnormal immune responses, including autoimmune hepatitis (AIH), primary biliary cholangitis (PBC), and primary sclerosing cholangitis (PSC). The treatment options for AILD remain limited, and the adverse side effects of the drugs that are typically used for treatment frequently lead to a low quality of life for AILD patients. Moreover, AILD patients may have a poor prognosis, especially those with an incomplete response to first-line treatment. Mesenchymal stem cells (MSCs) are pluripotent stem cells with low immunogenicity and can be conveniently harvested. MSC-based therapy is emerging as a promising approach for treating liver diseases based on their advantageous characteristics of immunomodulation, anti-fibrosis effects, and differentiation to hepatocytes, and accumulating evidence has revealed the positive effects of MSC therapy in AILD. In this review, we first summarize the mechanisms, safety, and efficacy of MSC treatment for AILD based on work in animal and clinical studies. We also discuss the challenges of MSC therapy in clinical applications. In summary, although promising data from preclinical studies are now available, MSC therapy is currently far for being applied in clinical practice, thus developing MSC therapy in AILD is still challenging and warrants further research.

Systemic effects of IL-17 in inflammatory arthritis

Inflammatory arthritis occurs in many diseases and is characterized by joint inflammation and damage. However, the inflammatory state in arthritis is commonly associated with systemic manifestations, which are generally linked to a poor prognosis. The pro-inflammatory cytokine IL-17 functions within a complex network of cytokines and contributes to the pathogenesis of various inflammatory diseases. Three IL-17 inhibitors have already been approved for the treatment of psoriasis, psoriatic arthritis, and ankylosing spondylitis. After a brief description of IL-17 and its local effects on joints, this Review focuses on the systemic effects of IL-17 in inflammatory arthritis. Increased circulating concentrations of bioactive IL-17 mediate changes in blood vessels, liver and cardiac and skeletal muscles. The effects of IL-17 on vascular and cardiac cells might contribute to the increased risk of cardiovascular events that occurs in all patients with inflammatory disorders. In the liver, IL-17 contributes to the high circulating concentrations of acute-phase proteins, such as C-reactive protein, and the appearance of liver lesions. In skeletal muscle, IL-17 contributes to muscle contractibility defects and weakness. Thus, targeting IL-17 might have beneficial effects at both local and systemic levels, and could also be proposed for the treatment of a wider range of inflammatory diseases.

The roles of IL-17C in T cell-dependent and -independent inflammatory diseases

IL-17C, which is a member of the IL-17 family of cytokines, is preferentially produced by epithelial cells in the lung, skin and colon, suggesting that IL-17C may be involved in not only host defense but also inflammatory diseases in those tissues. In support of that, IL-17C was demonstrated to contribute to development of T cell-dependent imiquimod-induced psoriatic dermatitis and T cell-independent dextran sodium sulfate-induced acute colitis using mice deficient in IL-17C and/or IL-17RE, which is a component of the receptor for IL-17C. However, the roles of IL-17C in other inflammatory diseases remain poorly understood. Therefore, we investigated the contributions of IL-17C to development of certain disease models using Il17c^−/− mice, which we newly generated. Those mice showed normal development of T cell-dependent inflammatory diseases such as FITC- and DNFB-induced contact dermatitis/contact hypersensitivity (CHS) and concanavalin A-induced hepatitis, and T cell-independent inflammatory diseases such as bleomycin-induced pulmonary fibrosis, papain-induced airway eosinophilia and LPS-induced airway neutrophilia. On the other hand, those mice were highly resistant to LPS-induced endotoxin shock, indicating that IL-17C is crucial for protection against that immunological reaction. Therefore, IL-17C neutralization may represent a novel therapeutic approach for sepsis, in addition to psoriasis and acute colitis.

IL-17 and IL-17-producing cells and liver diseases, with focus on autoimmune liver diseases

The pro-inflammatory cytokine interleukin(IL)-17 and IL-17-producing cells are important players in the pathogenesis of many autoimmune / inflammatory diseases. More recently, they have been associated with liver diseases. This review first describes the general knowledge on IL-17 and IL-17 producing cells. The second part describes the in vitro and in vivo effects of IL-17 on liver cells and the contribution of IL-17 producing cells to liver diseases. IL-17 induces immune cell infiltration and liver damage driving to hepatic inflammation and fibrosis and contributes to autoimmune liver diseases. The circulating levels of IL-17 and the frequency of IL-17-producing cells are elevated in a variety of acute and chronic liver diseases. The last part focuses on the effects of IL-17 deletion or neutralization in various murine models. Some of these observed beneficial effects suggest that targeting the IL-17 axis could be a new therapeutic strategy to prevent chronicity and progression of various liver diseases.

Ambiguous roles of innate lymphoid cells in chronic development of liver diseases

Innate lymphoid cells (ILCs) are defined as a distinct arm of innate immunity. According to their profile of secreted cytokines and lineage-specific transcriptional factors, ILCs can be categorized into the following three groups: group 1 ILCs (including natural killer (NK) cells and ILC1s) are dependent on T-bet and can produce interferon-γ; group 2 ILCs (ILC2s) are dependent on GATA3 and can produce type 2 cytokines, including interleukin (IL)-5 and IL-13; and, group 3 ILCs (including lymphoid tissue-like cells and ILC3s) are dependent on RORγt and can produce IL-22 and IL-17. Collaborative with adaptive immunity, ILCs are highly reactive innate effectors that promptly orchestrate immunity, inflammation and tissue repair. Dysregulation of ILCs might result in inflammatory disorders. Evidence regarding the function of intrahepatic ILCs is emerging from longitudinal studies of inflammatory liver diseases wherein they exert both physiological and pathological functions, including immune homeostasis, defenses and surveillance. Their overall effect on the liver depends on the balance of their proinflammatory and antiinflammatory populations, specific microenvironment and stages of immune responses. Here, we review the current data about ILCs in chronic liver disease progression, to reveal their roles in different stages as well as to discuss their therapeutic potency as intervention targets.

Association of STAT4 and PTPN22 polymorphisms and their interactions with type-1 autoimmune hepatitis susceptibility in Chinese Han children

AIMS

To investigate the impact of signal transducer and activator of transcription 4 (STAT4) and the protein tyrosine phosphatase N22 (PTPN22) gene single nucleotide polymorphisms (SNPs), gene-gene interactions and haplotype on type-1 Autoimmune Hepatitis (AIH) risk.

RESULTS

Logistic regression analysis showed that type 1 AIH was significantly higher in carriers of T allele of rs7574865 than those with GG genotype (P- value less than 0.001), higher in carriers of C allele of rs7582694 than those with GG genotype (P- value < 0.001), and lower in carriers of T allele of rs2476601 than those with CC genotype (P- value < 0.001). GMDR model indicated a significant two-locus model (p = 0.0100) involving rs7582694 and rs2476601. Participants with GC or CC of rs7582694 and CC of rs2476601 genotype have the highest type 1 AIH risk (P- value < 0.001), after covariates adjustment. Haplotype containing the rs7582694-C and rs7574865-T alleles were associated with a statistically increased type 1 AIH risk (P < 0.001).

MATERIALS AND METHODS

Logistic regression was performed to investigate association between SNPs within STAT4 and PTPN22 gene and susceptibility to type 1 AIH. Generalized multifactor dimensionality reduction (GMDR) was used to screen the best interaction combinations among the 4 SNPs.

CONCLUSIONS

We conclude that rs7574865 and rs7582694 in STAT4 gene minor alleles, interaction between rs7582694 and rs2476601, and haplotype containing the rs7582694-C and rs7574865-T alleles are associated with increased type 1 AIH risk, but rs2476601 in PTPN22 gene minor allele is associated with decreased type 1 AIH risk.

γδ T cells are indispensable for interleukin-23-mediated protection against Concanavalin A-induced hepatitis in hepatitis B virus transgenic mice

Hepatitis B virus surface antigen (HBsAg) carriers are highly susceptible to liver injury triggered by environmental biochemical stimulation. Previously, we have reported an inverse correlation between γδ T cells and liver damage in patients with hepatitis B virus (HBV). However, whether γδ T cells play a role in regulating the hypersensitivity of HBsAg carriers to biochemical stimulation-induced hepatitis is unknown. In this study, using HBV transgenic (HBs-Tg) and HBs-Tg T-cell receptor-δ-deficient (TCR-δ^-/- ) mice, we found that mice genetically deficient in γδ T cells exhibited more severe liver damage upon Concanavalin A (Con A) treatment, as indicated by substantially higher serum alanine aminotransferase levels, further elevated interferon-γ (IFN-γ) levels and more extensive necrosis. γδ T-cell deficiency resulted in elevated IFN-γ in CD4⁺ T cells but not in natural killer or natural killer T cells. The depletion of CD4⁺ T cells and neutralization of IFN-γ reduced liver damage in HBs-Tg and HBs-Tg-TCR-δ^-/- mice to a similar extent. Further investigation revealed that HBs-Tg mice showed an enhanced interleukin-17 (IL-17) signature. The administration of exogenous IL-23 enhanced IL-17A production from Vγ4 γδ T cells and ameliorated liver damage in HBs-Tg mice, but not in HBs-Tg-TCR-δ^-/- mice. In summary, our results demonstrated that γδ T cells played a protective role in restraining Con A-induced hepatitis by inhibiting IFN-γ production from CD4⁺ T cells and are indispensable for IL-23-mediated protection against Con A-induced hepatitis in HBs-Tg mice. These results provided a potential therapeutic approach for treating the hypersensitivity of HBV carriers to biochemical stimulation-induced liver damage.

A Functional IL22 Polymorphism (rs2227473) Is Associated with Predisposition to Childhood Cerebral Malaria

Cerebral malaria (CM) is a severe complication of Plasmodium falciparum infection. This encephalopathy is characterized by coma and is thought to result from mechanical microvessel obstruction and an excessive activation of immune cells leading to pathological inflammation and blood-brain barrier alterations. IL-22 contributes to both chronic inflammatory and infectious diseases, and may have protective or pathogenic effects, depending on the tissue and disease state. We evaluated whether polymorphisms (n = 46) of IL22 and IL22RA2 were associated with CM in children from Nigeria and Mali. Two SNPs of IL22, rs1012356 (P = 0.016, OR = 2.12) and rs2227476 (P = 0.007, OR = 2.08) were independently associated with CM in a sample of 115 Nigerian children with CM and 160 controls. The association with rs2227476 (P = 0.01) was replicated in 240 nuclear families with one affected child from Mali. SNP rs2227473, in linkage disequilibrium with rs2227476, was also associated with CM in the combined cohort for these two populations, (P = 0.004, OR = 1.55). SNP rs2227473 is located within a putative binding site for the aryl hydrocarbon receptor, a master regulator of IL-22 production. Individuals carrying the aggravating T allele of rs2227473 produced significantly more IL-22 than those without this allele. Overall, these findings suggest that IL-22 is involved in the pathogenesis of CM.

IL-38 alleviates concanavalin A-induced liver injury in mice

Interleukin (IL)-38 is a poorly characterized cytokine of the IL-1 family with anti-inflammatory activity. The role of IL-38 in liver injury remains unknown. We have investigated the potential effect of hydrodynamic-based gene delivery to express human IL-38 in mice with concanavalin A (Con A)-induced liver injury. Transfer of plasmid DNA encoding IL-38 significantly reduced hepatic toxicity and serum levels of aspartate aminotransferase and alanine aminotransferase compared with administration of a control plasmid. Moreover, IL-38 expression dramatically reduced serum levels of several pro-inflammatory cytokines, such as tumor necrosis factor-α, interferon-γ, IL-6, IL-17, and IL-22, but not levels of the anti-inflammatory cytokine IL-10. These results suggest that in vivo expression of human IL-38 in mice has hepatoprotective effects against Con A-induced liver injury by inhibition of inflammatory cytokine production.

VEGF and LPS synergistically silence inflammatory response to Plasmodium berghei infection and protect against cerebral malaria

Malaria infection induces, alongside endothelial damage and obstruction hypoxia, a potent inflammatory response similar to that observed in other systemic diseases caused by bacteria and viruses. Accordingly, it is increasingly recognised that cerebral malaria (CM), the most severe and life threatening complication of Plasmodium falciparum infection, bears a number of similarities with sepsis, an often fatal condition associated with a misregulated inflammatory response triggered by systemic microbial infections. Using a Plasmodium berghei ANKA mouse model, histology, immunohistochemistry and gene expression analysis, we showed that lipopolysaccharide S (LPS), at doses that normally induce inflammation tolerance, protects P. berghei infected mice against experimental CM (ECM). Vascular endothelial growth factor (VEGF) preserved blood vessel integrity, and the combination with LPS resulted in a strong synergistic effect. Treated mice did not develop ECM, showed a prolonged survival and failed to develop a significant inflammatory response and splenomegaly in spite of normal parasite loads. The protective role of VEGF was further confirmed by the observation that the treatment of P. berghei infected C57BL/6 and Balb/c mice with the VEGF receptor inhibitor axitinib exacerbates cerebral pathology and aggravates the course of infection. Infected mice treated with VEGF and LPS showed an induction of the anti-inflammatory genes Nrf2 and HO-1 and a suppression to basal levels of the genes IFN-γ and TNF-α. These results provide the rationale for developing new therapeutic approaches against CM and shed new light on how the inflammatory process can be modulated in the presence of systemic infectious diseases.

The Aryl Hydrocarbon Receptor: A Key Bridging Molecule of External and Internal Chemical Signals

The aryl hydrocarbon receptor (AhR) is a highly evolutionary conserved, ligand-activated transcription factor that is best known to mediate the toxicities of dioxins and dioxin-like compounds. Phenotype of AhR-null mice, together with the recent discovery of a variety of endogenous and plant-derived ligands, point to the integral roles of AhR in normal cell physiology, in addition to its roles in sensing the environmental chemicals. Here, we summarize the current knowledge about AhR signaling pathways, its ligands and AhR-mediated effects on cell specialization, host defense and detoxification. AhR-mediated health effects particularly in liver, immune, and nervous systems, as well as in tumorgenesis are discussed. Dioxin-initiated embryotoxicity and immunosuppressive effects in fish and birds are reviewed. Recent data demonstrate that AhR is a convergence point of multiple signaling pathways that inform the cell of its external and internal environments. As such, AhR pathway is a promising potential target for therapeutics targeting nervous, liver, and autoimmune diseases through AhR ligand-mediated interventions and other perturbations of AhR signaling. Additionally, using available laboratory data obtained on animal models, AhR-centered adverse outcome pathway analysis is useful in reexamining known and potential adverse outcomes of specific or mixed compounds on wildlife.

Interleukin-22: immunobiology and pathology

Interleukin-22 (IL-22) is a recently described IL-10 family cytokine that is produced by T helper (Th) 17 cells, γδ T cells, NKT cells, and newly described innate lymphoid cells (ILCs). Knowledge of IL-22 biology has evolved rapidly since its discovery in 2000, and a role for IL-22 has been identified in numerous tissues, including the intestines, lung, liver, kidney, thymus, pancreas, and skin. IL-22 primarily targets nonhematopoietic epithelial and stromal cells, where it can promote proliferation and play a role in tissue regeneration. In addition, IL-22 regulates host defense at barrier surfaces. However, IL-22 has also been linked to several conditions involving inflammatory tissue pathology. In this review, we assess the current understanding of this cytokine, including its physiologic and pathologic effects on epithelial cell function.

Mesenchymal stem cells ameliorate experimental autoimmune hepatitis by activation of the programmed death 1 pathway

Previous studies have shown beneficial effects of mesenchymal stem cells (MSCs) transplantation in many autoimmune diseases. However, few studies have focused on the effects of MSCs on autoimmune hepatitis. In our study, we investigated the therapeutic effects of BMSCs (bone mesenchymal stem cells) transplantation in mouse experimental autoimmune hepatitis (EAH) and explored the potential mechanism. BMSCs were injected intravenously into EAH mice. Then, serum levels of ALT and AST, and pathologic alteration of liver tissue were measured to evaluate the liver function and inflammation degree. The expressions of programmed death ligand 1, IL-17 and IL-23 were detected by enzyme-linked immunosorbent assay (ELISA), reverse transcription-polymerase chain reaction (RT-PCR), and western blotting. Upon serum biochemical levels and pathological examination, the BMSCs-treated mice especially with multiple dosing administration showed significantly reduction of liver damage. Moreover, the expression of IL-17 was down-regulated by BMSCs intervention as compared to the model group, whereas the PD-L1 and IL-23 were up-regulated following the administration of MSCs. In conclusion, the results of this study suggest that BMSCs transplantation, especially on multiple dosing, may exert immunosuppression effect to ameliorate EAH through the inhibition of IL-17 and up-regulation of PD-L1.

CD49a promotes T-cell-mediated hepatitis by driving T helper 1 cytokine and interleukin-17 production

It is becoming increasingly clear that the T-cell-mediated immune response is important in many diseases. In this study, we used concanavalin A (Con A) -induced hepatitis to investigate the role of CD49a in the molecular and cellular mechanism of the T-cell-mediated immune response. We found that CD49a(-/-) mice had significantly reduced levels of serum alanine aminotransferase and were protected from Con A-induced hepatitis. CD49a deficiency led to decreased production of interferon-γ (IFN-γ) and interleukin-17A (IL-17A) after Con A injection. Furthermore, we found that hepatic CD4(+) T cells and invariant natural killer T cells up-regulated CD49a expression, along with enhanced activation after Con A injection, leading to production of inflammatory cytokines by these T cells. Blockade of CD49a in vivo ameliorated Con A-induced hepatitis with reduced production of IFN-γ and IL-17A. Hence, CD49a promoted Con A-induced hepatitis through enhancing inflammatory cytokine production (IFN-γ and IL-17A) by CD4(+) T and invariant natural killer T cells. The protective effect of CD49a blockade antibody suggested a new target therapeutic molecule for intervention of T-cell-mediated liver injury.

Aryl hydrocarbon receptor plays protective roles in ConA-induced hepatic injury by both suppressing IFN-γ expression and inducing IL-22

The aryl hydrocarbon receptor (AhR), a ligand-activated nuclear transcription factor, is known to mediate the toxic and carcinogenic effects of various environmental pollutants, while AhR has been shown to protect animals from various types of tissue injury. ConA-induced hepatitis is known as a mouse model of acute liver injury. Here, we found a protective role of AhR in ConA-induced hepatitis. AhR is induced in the liver during ConA-induced hepatitis, and Ahr (-/-) mice were highly sensitive to this model. Bone marrow chimera experiments indicate that Ahr (-/-) hematopoietic cells are responsible for hypersensitivity to ConA-induced hepatitis. We found that IFN-γ from invariant NKT cells was up-regulated and IL-22 from innate lymphoid cells (ILCs) was abolished in Ahr (-/-) mice. In addition, IL-22 production was still observed in Rag2 (-/-) mice but it was severely reduced in Ahr (-/-) Rag2 (-/-) mice. ConA-induced IL-22 production was also dependent on retinoic acid-related orphan receptor γt. These results show that AhR has crucial protective roles in ConA-induced liver injury via promoting IL-22 production from ILCs and suppressing IFN-γ expression from NKT cells.

Emerging Role of Interleukin 22 in Hepatitis B Virus Infection: a Double-edged Sword

Hepatitis B virus (HBV) infection remains a worldwide health problem, and is the major cause of hepatitis, liver cirrhosis, and hepatocellular carcinoma. The innate and adaptive immune responses of the HBV-infected host contribute greatly to the development and pathogenesis of chronic HBV infection, and often affect the efficacy of anti-HBV drugs. Interleukin (IL)-22 is a newly identified cytokine that is involved in the pathogenesis of liver disease, but its role in liver inflammation in patients with HBV infection remains controversial. In this report, we summarize the production and function of IL-22 in inflammatory environments, and review the current research into IL-22 biology in HBV infection. A better understanding of the intrahepatic microenvironments that directly influence the activity of IL-22 will be important for the development of new immunotherapeutic approaches that target IL-22-producing cells or IL-22 itself.

Interleukin-22 as a molecular adjuvant facilitates IL-17-producing CD8+ T cell responses against a HBV DNA vaccine in mice

Interleukin-22 (IL-22) is mainly produced by activated Th1 cells, Th17 cells and NK cells and promotes anti-microbial defense, pro-inflammatory and tissue remodeling responses. However, its potential use as a vaccine adjuvant has not been tested. In this study, we tested if a DNA construct expressing IL-22 (pVAX-IL-22) could be used as a molecular adjuvant to enhance host immune responses induced by HBV DNA vaccination (pcD-S2). After immunizing mice with pcD-S2 combined with pVAX-IL-22, we didn't find enhancement of HBsAg-specific antibody responses in comparison to mice immunized with pcD-S2 alone. However, there was an enhancement of the level of IL-17 expression in antigen specific CD8(+) cytotoxic T lymphocytes (Tc17). By using CD8 T-cell knockout (KO) and IL-17 KO mice, Tc17 cells were found to be a dominant population driving cytotoxicity. Importantly, there was a correlation between pVAX-IL-22 enhancement of T lymphocytes and a reduction of HBsAg-positive hepatocytes in HBsAg transgenic mice. These results demonstrate that IL-22 might be used as an effective adjuvant to enhance cellular immune responses during HBsAg DNA vaccination since it can induce Tc17 cells to break tolerance in HBsAg transgenic mice.

Association of STAT4 polymorphisms with susceptibility to type-1 autoimmune hepatitis in the Japanese population

Background/Aims

Recent studies demonstrated an association of STAT4 polymorphisms with autoimmune diseases including systemic lupus erythematosus and rheumatoid arthritis, indicating multiple autoimmune diseases share common susceptibility genes. We therefore investigated the influence of STAT4 polymorphisms on the susceptibility and phenotype of type-1 autoimmune hepatitis in a Japanese National Hospital Organization (NHO) AIH multicenter cohort study.

Methodology/Principal Findings

Genomic DNA from 460 individuals of Japanese origin including 230 patients with type-1 autoimmune hepatitis and 230 healthy controls was analyzed for two single nucleotide polymorphisms in the STAT4 gene (rs7574865, rs7582694). The STAT4 rs7574865T allele conferred risk for type-1 autoimmune hepatitis (OR = 1.61, 95% CI = 1.23–2.11; P = 0.001), and patients without accompanying autoimmune diseases exhibited an association with the rs7574865T allele (OR = 1.50, 95%CI = 1.13–1.99; P = 0.005). Detailed genotype-phenotype analysis of type-1 autoimmune hepatitis patients with (n = 44) or without liver cirrhosis (n = 186) demonstrated that rs7574865 was not associated with the development of liver cirrhosis and phenotype (biochemical data and the presence of auto-antibodies).

Conclusions/Significance

This is the first study to show a positive association between a STAT4 polymorphism and type-1 autoimmune hepatitis, suggesting that autoimmune hepatitis shares a gene commonly associated with risk for other autoimmune diseases.

Pivotal roles of T-helper 17-related cytokines, IL-17, IL-22, and IL-23, in inflammatory diseases

T-helper 17 (Th17) cells are characterized by producing interleukin-17 (IL-17, also called IL-17A), IL-17F, IL-21, and IL-22 and potentially TNF- α and IL-6 upon certain stimulation. IL-23, which promotes Th17 cell development, as well as IL-17 and IL-22 produced by the Th17 cells plays essential roles in various inflammatory diseases, such as experimental autoimmune encephalomyelitis, rheumatoid arthritis, colitis, and Concanavalin A-induced hepatitis. In this review, we summarize the characteristics of the functional role of Th17 cells, with particular focus on the Th17 cell-related cytokines such as IL-17, IL-22, and IL-23, in mouse models and human inflammatory diseases.

Hepatitis B virus induces IL-23 production in antigen presenting cells and causes liver damage via the IL-23/IL-17 axis

IL-23 regulates myriad processes in the innate and adaptive immune systems, and is a critical mediator of the proinflammatory effects exerted by Th17 cells in many diseases. In this study, we investigated whether and how hepatitis B virus (HBV) causes liver damage directly through the IL-23 signaling pathway. In biopsied liver tissues from HBV-infected patients, expression of both IL-23 and IL-23R was remarkably elevated. In vivo observations also indicated that the main sources of IL-23 were myeloid dendritic cells (mDCs) and macrophages. Analysis of in vitro differentiated immature DCs and macrophages isolated from healthy donors revealed that the HBV surface antigen (HBsAg) efficiently induces IL-23 secretion in a mannose receptor (MR)-dependent manner. Culture with an endosomal acidification inhibitor and the dynamin inhibitor showed that, upon binding to the MR, the HBsAg is taken up by mDCs and macrophages through an endocytosis mechanism. In contrast, although the HBV core antigen (HBcAg) can also stimulate IL-23 secretion from mDCs, the process was MR- and endocytosis-independent. In addition, IL-23 was shown to be indispensible for HBsAg-stimulated differentiation of naïve CD4(+) T cells into Th17 cells, which were determined to be the primary source of IL-17 in HBV-infected livers. The cognate receptor, IL-17R, was found to exist on the hepatic stellate cells and mDCs, both of which might represent the potential target cells of IL-17 in hepatitis B disease. These data provide novel insights into a yet unrecognized mechanism of HBV-induced hepatitis, by which increases in IL-23 expression, through an MR/endocytosis-dependent or -independent manner, produce liver damage through the IL-23/IL-17 axis.

High susceptibility to liver injury in IL-27 p28 conditional knockout mice involves intrinsic interferon-γ dysregulation of CD4+ T cells

Interleukin (IL)-27, a newly discovered IL-12 family cytokine, is composed of p28 and EBI3. In this study, CD11c-p28(f/f) conditional knockout mice were generated to delete p28 specifically in dendritic cells (DCs). We demonstrated that in the absence of DC-derived p28, these mice were highly susceptible to both low and higher concentrations of concanavalin A (ConA) (5 mg/kg or 10 mg/kg), with extremely early and steady high levels of interferon-γ (IFN-γ) in sera. Neutralizing IFN-γ prevented ConA-induced liver damage in these mice, indicating a critical role of IFN-γ in this pathological process. Interestingly, the main source of the increased IFN-γ in CD11c-p28(f/f) mice was CD4+ T cells, but not natural killer T (NKT) cells. Depletion of CD4+ , but not NK1.1+ , cells completely abolished liver damage, whereas transferring CD4+ T cells from CD11c-p28(f/f) mice, but not from wild-type mice or CD11c-p28(f/f) -IFN-γ(-/-) double knockout mice to CD4(-/-) mice, restored the increased liver damage. Further studies defined higher levels of IFN-γ and T-bet messenger RNA in naïve CD4+ T cells from CD11c-p28(f/f) mice, and these CD4+ T cells were highly responsive to both low and higher concentrations of anti-CD3, indicating a programmed functional alternation of CD4+ T cells.

CONCLUSION

We provide a unique model for studying the pathology of CD4+ T cell-mediated liver injury and reveal a novel function of DC-derived p28 on ConA-induced fulminant hepatitis through regulation of the intrinsic ability for IFN-γ production by CD4+ T cells.

IL-22: An Evolutionary Missing-Link Authenticating the Role of the Immune System in Tissue Regeneration

Tissue regeneration is a critical component of organ maintenance. The ability of lymphocytes to kill pathogen-infected cells has been well-studied. However, the necessity for lymphocytes to participate in reconstruction of destroyed tissues has not been explored until recently. Interleukin (IL)-22, a newly defined cytokine exclusively produced by subsets of lymphocytes, provides the strongest proof yet for the tissue regenerative potentials of the immune system. IL-22 plays an obligatory role in epithelial homeostasis in the gut, liver and lung. The receptor for IL-22 (IL-22R1 and IL-10R2) is predominantly expressed by epithelial cells. While the pro-inflammatory effect is questioned, the pro-constructive potential of IL-22 is well established. It is evident from the response to IL-22, that epithelial cells not only produce anti-microbial peptides but also actively proliferate. Aryl hydrocarbon receptor (AhR) and retinoic acid-related orphan receptor (RORγt) transcription factor are required for IL-22 generation from Lymphoid Tissue inducer cells LTi, Th22 and NK-like cells. However, IL-22 production from conventional NK cells is independent of AhR and RORγt. In this review, we present a case for a paradigm shift in how we define the function of the immune system. This would include tissue regeneration as a legitimate immune function.

Increased Th17 cells and interleukin-17 contribute to immune activation and disease aggravation in patients with chronic hepatitis B virus infection

T helper17 (Th17) cells have been demonstrated to participate in the pathogenesis of hepatitis B virus (HBV) associated liver damage. However, the contribution of Th17 cells to immune activation and disease aggravation in patients with HBV infection is not fully clear. In this study, we investigated the Th17 cells frequencies and interleukin-17 (IL-17) mRNA expressions in peripheral blood mononuclear cells (PBMCs), intrahepatic IL-17-positive cells accumulation, as well as serum IL-17 levels in asymptomatic chronic HBV carriers (AsC), and patients with chronic hepatitis B (CHB) and HBV related acute-on-chronic liver failure (ACLF). Furthermore, the dynamic changes of Th17 cells frequencies and IL-17 concentration in different prognostic ACLF patients were observed. As result, the intrahepatic and peripheral Th17 cells and serum IL-17 concentration were both significantly higher in CHB and HBV related ACLF patients than that in AsC and normal control groups, and increased gradually with immune inflammation aggravation from AsC, CHB to ACLF. Moreover, in ACLF patients, peripheral Th17 cells frequencies were positively correlated with international normalized ratio (INR) and model of end-stage liver disease (MELD) score. Especially the survival patients had an initially lower Th17 cells frequencies and IL-17 levels which gradually decreased following condition improvement as compared with higher baseline level followed by gradually increasing trend in the non-survivals. In conclusion, Th17 cells can be contributed to the immune activation and disease aggravation in patients with chronic HBV infection. This may places Th17 cells as a potential blocking target for controlling CHB and ACLF.

IL-33/ST2 axis in inflammation and immunopathology

Interleukin-33 (IL-33), a member of the IL-1 family of cytokines, binds to its plasma membrane receptor, heterodimeric complex consisted of membrane-bound ST2L and IL-1R accessory protein, inducing NFkB and MAPK activation. IL-33 exists as a nuclear precursor and may act as an alarmin, when it is released after cell damage or as negative regulator of NFκB gene transcription, when acts in an intracrine manner. ST2L is expressed on several immune cells: Th2 lymphocytes, NK, NKT and mast cells and on cells of myeloid lineage: monocytes, dendritic cells and granulocytes. IL-33/ST2 axis can promote both Th1 and Th2 immune responses depending on the type of activated cell and microenvironment and cytokine network in damaged tissue. We previously described and discuss here the important role of IL-33/ST2 axis in experimental models of type 1 diabetes, experimental autoimmune encephalomyelitis, fulminant hepatitis and breast cancer. We found that ST2 deletion enhance the development of T cell-mediated autoimmune disorders, EAE and diabetes mellitus type I. Disease development was accompanied by dominantly Th1/Th17 immune response but also higher IL-33 production, which suggest that IL-33 in receptor independent manner could promote the development of inflammatory autoreactive T cells. IL-33/ST2 axis has protective role in Con A hepatitis. ST2-deficient mice had more severe hepatitis with higher influx of inflammatory cells in liver and dominant Th1/Th17 systemic response. Pretreatment of mice with IL-33 prevented Con A-induced liver damage through prevention of apoptosis of hepatocytes and Th2 amplification. Deletion of IL-33/ST2 axis enhances cytotoxicity of NK cells, production of IFN-γ in these cells and systemic production of IFN-γ, IL-17 and TNF-α, which leads to attenuated tumor growth. IL-33 treatment of tumor-bearing mice suppresses activity of NK cells, dendritic cell maturation and enhances alternative activation of macrophages. In conclusion, we observed that IL-33 has attenuated anti-inflammatory effects in T cell-mediated responses and that both IL-33 and ST2 could be further explored as potential therapeutic targets in treatment of immune-mediated diseases.

Experimental Pneumocystis lung infection promotes M2a alveolar macrophage-derived MMP12 production

Among several bacterial and viral pathogens, the atypical fungal organism Pneumocystis jirovecii has been implicated as a contributor to the pathogenesis of chronic obstructive pulmonary disease (COPD). In a previous study, we reported that Pneumocystis-colonized HIV-positive subjects had worse obstruction of airways and higher sputum levels of macrophage elastase/matrix metalloproteinase 12 (MMP12), a protease strongly associated with the development of COPD. Here, we examined parameters of Pneumocystis-induced MMP12 in the lungs of mice and its role in the lung immune response to murine Pneumocystis. Initial studies demonstrated that P. murina exposure induced Mmp12 mRNA expression in whole lungs and alveolar macrophages (AMs), which was dependent on the presence of CD4+ T cells as well as signal transducer and activator of transcription 6. Mmp12 mRNA expression was upregulated in AMs by interleukin (IL)-4 treatment, but downregulated by interferon (IFN)-γ, indicating preferential expression in alternatively activated (M2a) macrophages. IL-4 treatment induced the 54-kDa proenzyme form of MMP12 and the 22-kDa fully processed and active form, whereas IFN-γ failed to induce either. Despite a reported antimicrobial role in macrophage phagolysosomes, mice deficient in MMP12 were not found to be more susceptible to lung infection with P. murina. Collectively, our data indicate that MMP12 induction is a component of the P. murina-induced M2 response and thus provides insight into the link between Pneumocystis colonization/infection and exacerbations in COPD.

Decreased serum LL-37 and vitamin D3 levels in atopic dermatitis: relationship between IL-31 and oncostatin M

BACKGROUND

Skin lesions with atopic dermatitis (AD) are associated with dysregulated expression of LL-37 and enhanced expression of IL-22, thymic stromal lymphopoietin (TSLP), IL-25, IL-31, and oncostatin M. Vitamin D3 enhances LL-37 production in keratinocytes. This study aimed to examine the serum levels of LL-37 and vitamin D3 and their regulation of cytokine production in patients with AD.

METHODS

Serum levels of LL-37 and 25-hydroxyvitamin D3 were analyzed by ELISA. The effects of 1,25-dihydroxyvitamin D3 or LL-37 on cytokine production in T cells or keratinocytes were analyzed by ELISA and real-time PCR.

RESULTS

Serum levels of LL-37 and 25-hydroxyvitamin D3 were decreased in patients with AD compared to normal donors and were correlated in both groups. Serum levels of LL-37 correlated with those of oncostatin M and IL-31 in normal donors and patients with AD, while 25-hydroxyvitamin D3 levels did so only in normal donors. 1,25-dihydroxyvitamin D3 increased LL-37 production in human keratinocytes and neutrophils. 1,25-dihydroxyvitamin D3 and LL-37 enhanced the oncostatin M and IL-31 production in CD3/28-stimulated T cells, but did not alter IL-25 and TSLP production in TNF-α-stimulated keratinocytes. In CD3/28-stimulated T cells, 1,25-dihydroxyvitamin D3 reduced the IL-22 production, while LL-37 enhanced it. These effects of 1,25-dihydroxyvitamin D3 and LL-37 were suppressed by vitamin D receptor antagonist and pertussis toxin, respectively.

CONCLUSIONS

Systemic vitamin D3 levels are reduced in patients with AD, which may contribute to decreased systemic LL-37 levels. LL-37 may systemically potentiate the oncostatin M and IL-31 production in normal donors and patients with AD, while vitamin D3 may do so only in normal donors.

IL-22 Protects Against Liver Pathology and Lethality of an Experimental Blood-Stage Malaria Infection

The host response following malaria infection depends on a fine balance between levels of pro-inflammatory and anti-inflammatory mediators resulting in the resolution of the infection or immune-mediated pathology. Whilst other components of the innate immune system contribute to the pro-inflammatory milieu, T cells play a major role. For blood-stage malaria, CD4(+) and γδ T cells are major producers of the IFN-γ that controls parasitemia, however, a role for TH17 cells secreting IL-17A and other cytokines, including IL-17F and IL-22 has not yet been investigated in malaria. TH17 cells have been shown to play a role in some protozoan infections, but they also are a source of pro-inflammatory cytokines known to be involved in protection or pathogenicity of infections. In the present study, we have investigated whether IL-17A and IL-22 are induced during a Plasmodium chabaudi infection in mice, and whether these cytokines contribute to either protection or to pathology induced during the infection. Although small numbers of IL-17- and IL-22-producing CD4 T cells are induced in the spleens of infected mice, a more pronounced induction is observed in the liver, where increases in mRNA for IL-17A and, to a lesser extent, IL-22 were observed and CD8(+) T cells, rather than CD4 T cells, are a major source of these cytokines in this organ. Although the lack of IL-17 did not affect the outcome of infection or pathology, lack of IL-22 resulted in 50% mortality within 12 days after infection with significantly greater weight loss at the peak of infection and significant increase in alanine transaminase in the plasma in the acute infection. As parasitemias and temperature were similar in IL-22 KO and wild-type control mice, our observations support the idea that IL-22 but not IL-17 provides protection from the potentially lethal effects of liver damage during a primary P. chabaudi infection.

Inflammasome-IL-1-Th17 response in allergic lung inflammation

Allergic asthma has increased dramatically in prevalence and severity over the last three decades. Both clinical and experimental data support an important role of Th2 cell response in the allergic response. Recent investigations revealed that airway exposure to allergen in sensitized individuals causes the release of ATP and uric acid, activating the NLRP3 inflammasome complex and cleaving pro-IL-1β to mature IL-1β through caspase-1. The production of pro-IL-1β requires a toll-like receptor (TLR) 4 signal which is provided by the allergen. IL-1β creates a pro-inflammatory milieu with the production of IL-6 and chemokines which mobilize neutrophils and enhance Th17 cell differentiation in the lung. Here, we review our results showing that NLRP3 inflammasome activation is required to develop allergic airway inflammation in mice and that IL-17 and IL-22 production by Th17 cells plays a critical role in established asthma. Therefore, inflammasome activation leading to IL-1β production contributes to the control of allergic asthma by enhancing Th17 cell differentiation.