Role of Interleukin-22 in chronic liver injury

Opportunities and challenges: interleukin-22 comprehensively regulates polycystic ovary syndrome from metabolic and immune aspects

Polycystic ovary syndrome (PCOS) is known as a prevalent but complicated gynecologic disease throughout the reproductive period. Typically, it is characterized by phenotypic manifestations of hyperandrogenism, polycystic ovary morphology, and persistent anovulation. For now, the therapeutic modality of PCOS is still a formidable challenge. Metabolic aberrations and immune challenge of chronic low-grade inflammatory state are significant in PCOS individuals. Recently, interleukin-22 (IL-22) has been shown to be therapeutically effective in immunological dysfunction and metabolic diseases, which suggests a role in the treatment of PCOS. In this review, we outline the potential mechanisms and limitations of IL-22 therapy in PCOS-related metabolic disorders including its regulation of insulin resistance, gut barrier, systemic inflammation, and hepatic steatosis to generate insights into developing novel strategies in clinical practice.

Interleukin-22 promotes the proliferation and migration of hepatocellular carcinoma cells via the phosphoinositide 3-kinase (PI3K/AKT) signaling pathway

BACKGROUND

Interleukin-22 (IL-22) is a pro-inflammatory cytokine released during the immune response in chronic liver injury. Although IL-22 mediates tissue regeneration, its uncontrolled production may generate a carcinogenic environment resulting in hepatocellular carcinoma (HCC). This study aims to identify the effect of IL-22 on anti-apoptotic and metastatic genes and the molecular pathways responsible for IL-22-mediated hepatic carcinogenesis.

METHODS AND RESULTS

Three cancerous liver lines, HepG2, SNU-387, Huh7, and one normal liver line, THLE2, were treated with IL-22. RT-qPCR analysis was conducted to study the role of IL-22 in altering the expression levels of anti-apoptotic genes, MCL-1 and BCL-2, and metastatic genes, MMP-7 and MMP-9. A significant increase in expression levels of these genes was observed after IL-22 treatment. Furthermore, to explore the major pathways involved in IL-22-mediated upregulation of anti-apoptotic and metastatic genes, cells were treated with inhibitors of JAK/STAT and PI3K/AKT pathways along with IL-22. Resultantly, a significant decrease in expression levels of target genes was observed, indicating the involvement of JAK/STAT and PI3K/AKT signaling cascades in IL-22-mediated oncogenesis. Finally, Cell Scratch assay was performed to check the effect of IL-22 and inhibitors of JAK/STAT and PI3K/AKT on the metastatic potential of liver cells. While migration was observed in Huh7 and THLE2 cells treated with IL-22, no migration was observed in cells treated with IL-22 along with JAK/STAT and PI3K/AKT inhibitors. Results indicate that IL-22 encourages metastasis in HCC cells via the JAK/STAT and PI3K/AKT pathways.

CONCLUSION

Results showed that IL-22 upregulates anti-apoptotic and metastatic genes in HCC through JAK/STAT and PI3K/AKT signaling pathways.

Polystyrene microplastics exacerbate experimental colitis in mice tightly associated with the occurrence of hepatic inflammation

The potential health effects of microplastics (MPs) have become a public concern due to their ubiquitousness in the environment and life. Numerous studies have demonstrated that a high dose of MPs can adversely affect gastrointestinal health. However, few studies have focused on the impact of microplastics on patients' health with respect to gastrointestinal diseases. Inflammatory bowel disease (IBD) has emerged as a global disease with a rapidly increasing incidence. IBD, a specific gastrointestinal illness characterized by acute, chronic inflammation and intestinal barrier dysfunction, might increase sensitivity to MPs exposure. Herein, we investigated the impact and mechanism of PS-MPs on dextran sodium sulfate (DSS)-induced colitis. The results demonstrated that gavage with PS-MPs alone caused minimal effects on the intestinal barrier and liver status of mice. For mice with colitis, additional PS-MPs exposure caused a shorter colon length, aggravated histopathological damage and inflammation, reduced mucus secretion, and increased the colon permeability. Furthermore, PS-MPs exposure also increased the risk of secondary liver injury associated with inflammatory cell infiltration. These findings provide more histopathological evidence and suggest a need for more research on the health risk of MPs for sensitive individuals.

Lack of Association of Polymorphisms in IL22 and IL22RA1 Genes with Fibrosis Severity in Patients with Chronic Hepatitis C

The IL-22 pathway has been shown to play an important role in the pathogenesis of liver fibrosis. However, little is known about the role of single-nucleotide polymorphisms (SNPs) in IL-22-related genes in relation to the severity of liver fibrosis. This study aimed to investigate the association of polymorphisms in IL22 and IL22RA1 genes with the severity of liver fibrosis in patients with chronic hepatitis C. A total of 326 patients (165 with mild fibrosis and 161 with severe fibrosis) were included. Four SNPs in IL22 (rs1179251, rs2227473, rs1012356, and rs2227485) and two in IL22RA1 (rs4648936 and rs3795299) were evaluated by real-time PCR. No significant association was observed between the polymorphisms studied and the severity of liver fibrosis. The SNPs rs1179251, rs2227473, rs1012356, and rs2227485 in IL22 and rs4648936 and rs3795299 in IL22RA1 may not be involved in the pathogenesis of liver fibrosis in patients with chronic hepatitis C.

Liver expression of IL-22, IL-22R1 and IL-22BP in patients with chronic hepatitis C with different fibrosis stages

AIMS

Liver fibrosis is the result of an exacerbated wound-healing response associated with chronic liver injury. Interleukin-22 (IL-22) plays a key role in liver disease, through either a protective or an adverse role, depending on the context. The relationship between IL-22 and its receptors IL-22R1 and IL-22BP (soluble inhibitor) in liver fibrosis is unknown. In this study, we assessed the presence and quantity of IL-22, IL-22R1, and IL-22BP-producing cells in liver tissues of patients with chronic hepatitis C.

METHODS AND RESULTS

The number of IL-22-producing cells was significantly higher in stages F1, F2, and F3 when compared to F0 or F4 (p < 0.05). The immunostaining of IL-22R1 decreased as liver fibrosis increased from F1 to F4. On the other hand, the concentration of IL-22BP-producing cells was higher in patients with cirrhosis (F4). Furthermore, the IL-22BP:IL-22 ratio was highest in patients with cirrhosis.

CONCLUSIONS

Our results suggest that IL-22, IL-22R1 and IL-22BP may be involved in the mechanisms of liver fibrosis in patients with chronic hepatitis C.

Therapeutic Opportunities of IL-22 in Non-Alcoholic Fatty Liver Disease: From Molecular Mechanisms to Clinical Applications

Nonalcoholic fatty liver disease (NAFLD) represents one of the most common liver disorders and can progress into a series of liver diseases, including nonalcoholic steatohepatitis (NASH), fibrosis, cirrhosis, and even liver cancer. Interleukin-22 (IL-22), a member of the IL-10 family of cytokines, is predominantly produced by lymphocytes but acts exclusively on epithelial cells. IL-22 was proven to favor tissue protection and regeneration in multiple diseases. Emerging evidence suggests that IL-22 plays important protective functions against NAFLD by improving insulin sensitivity, modulating lipid metabolism, relieving oxidative and endoplasmic reticulum (ER) stress, and inhibiting apoptosis. By directly interacting with the heterodimeric IL-10R2 and IL-22R1 receptor complex on hepatocytes, IL-22 activates the Janus kinase 1 (JAK1)/ signal transducer and activator of transcription 3 (STAT3), c-Jun N-terminal kinase (JNK) and extracellular-signal regulated kinase (ERK) pathways to regulate the subsequent expression of genes involved in inflammation, metabolism, tissue repair, and regeneration, thus alleviating hepatitis and steatosis. However, due to the wide biodistribution of the IL-22 receptor and its proinflammatory effects, modifications such as targeted delivery of IL-22 expression and recombinant IL-22 fusion proteins to improve its efficacy while reducing systemic side effects should be taken for further clinical application. In this review, we summarized recent progress in understanding the physiological and pathological importance of the IL-22-IL-22R axis in NAFLD and the mechanisms of IL-22 in the protection of NAFLD and discussed the potential strategies to maneuver this specific cytokine for therapeutic applications for NAFLD.

The multifactorial mechanisms of bacterial infection in decompensated cirrhosis

Infections, due to a dysfunctional immune response, pose a great risk to patients with decompensated cirrhosis and herald the beginning of the terminal phase of this disease. Infections typically result from breaches in innate immune barriers and inadequate clearance by immune cells. This leads to bacterial and bacterial product translocation to the systemic circulation, which is already primed by ongoing hepatic inflammation in patients with cirrhosis, who are particularly prone to developing organ failure in the presence of an infection. Early identification of bacterial infection, along with the prompt use of appropriate antibiotics, have reduced the mortality associated with certain infections in patients with decompensated cirrhosis. Judicious use of antibiotic therapy remains imperative given the emergence of multidrug-resistant infections in the cirrhotic population. Important research over the last few years has identified molecular targets on immune cells that may enhance their function, and theoretically prevent infections. Clinical trials are ongoing to delineate the beneficial effects of targeted molecules from their off-target effects. Herein, we review the mechanisms that predispose patients with cirrhosis to bacterial infections, the clinical implications of infections and potential targets for the prevention or treatment of infections in this vulnerable population.

Extracellular vesicles-derived miR-150-5p secreted by adipose-derived mesenchymal stem cells inhibits CXCL1 expression to attenuate hepatic fibrosis

Hepatic fibrosis (HF) is involved in aggravated wound‐healing response as chronic liver injury. Extracellular vesicles (EVs) carrying microRNA (miR) have been reported as therapeutic targets for liver diseases. In this study, we set out to explore whether adipose‐derived mesenchymal stem cells (ADMSCs)‐derived EVs containing miR‐150‐5p affect the progression of HF. Carbon tetrachloride (CCl₄) was firstly used to induce HF mouse models in C57BL/6J mice, and activation of hepatic stellate cells (HSCs) was achieved using transforming growth factor β (TGF‐β). EVs were then isolated from ADMSCs and co‐cultured with HSCs. The relationship between miR‐150‐5p and CXCL1 was identified using dual luciferase gene reporter assay. Following loss‐ and gain‐function experimentation, HSC proliferation was examined by MTT assay, and levels of fibrosis‐, HSC activation‐ and apoptosis‐related genes were determined in vitro. Additionally, pathological scores, collagen volume fraction (CVF) as well as levels of inflammation‐ and hepatic injury‐associated genes were determined in in vivo. Down‐regulated miR‐150‐5p and elevated CXCL1 expression levels were detected in HF tissues. ADMSCs‐derived EVs transferred miR‐150‐5p to HSCs. CXCL1 was further verified as the downstream target gene of miR‐150‐5p. Moreover, ADMSCs‐EVs containing miR‐150‐5p markedly inhibited HSC proliferation and activation in vitro. Meanwhile, in vivo experiments also concurred with the aforementioned results as demonstrated by inhibited CVF, reduced inflammatory factor levels and hepatic injury‐associated indicators. Both experiments results were could be reversed by CXCL1 over‐expression. Collectively, our findings indicate that ADMSCs‐derived EVs containing miR‐150‐5p attenuate HF by inhibiting the CXCL1 expression.

Targeted treatment of alcoholic liver disease based on inflammatory signalling pathways

Targeted therapy is an emerging treatment strategy for alcoholic liver disease (ALD). Inflammation plays an important role in the occurrence and development of ALD, and is a key choice for its targeted treatment, and anti-inflammatory treatment has been considered beneficial for liver disease. Surprisingly, immune checkpoint inhibitors have become important therapeutic agents for hepatocellular carcinoma (HCC). Moreover, studies have shown that the combination of inflammatory molecule inhibitors and immune checkpoint inhibitors can exert better effects than either alone in mouse models of HCC. This review discusses the mechanism of hepatic ethanol metabolism and the conditions under which inflammation occurs. In addition, we focus on the potential molecular targets in inflammatory signalling pathways and summarize the potential targeted inhibitors and immune checkpoint inhibitors, providing a theoretical basis for the targeted treatment of ALD and the development of new combination therapy strategies for HCC.

Angelica sinensis polysaccharide attenuates CCl4-induced liver fibrosis via the IL-22/STAT3 pathway

Angelica sinensis polysaccharide (ASP) has hepatoprotective effects in liver injury models. However, its role and mechanism in chronic liver fibrosis have not been fully elucidated. In this study, a carbon tetrachloride (CCl4)-induced chronic liver fibrosis mouse model was established. The results showed that ASP treatment reduced serum alanine aminotransferase by approximately 50% and liver fibrosis areas by approximately 70%. Hepatic stellate cell (HSC) activation was inhibited in ASP-treated mice. Furthermore, the mechanism was studied in-depth, focusing on the interleukin 22/signal transducer and activator of transcription 3 (IL-22/STAT3) axis. Concentrations of 50 μg/ml and 100 μg/ml ASP induced the secretion of IL-22 in vitro, which further increased at a concentration of 200 μg/ml. Moreover, in vivo data showed that ASP significantly promoted IL-22 production in splenocytes and liver tissues. The antifibrotic effects of ASP were abolished after IL-22 neutralization. In addition, ASP activated the STAT3 pathway in the liver, as demonstrated by a 2-fold increase compared to that of the CCl4 group, which was abrogated by the IL-22 antibody. Subsequently, we showed that the antifibrotic effects of ASP were abrogated by blocking STAT3 with S3I-201. In conclusion, ASP effectively alleviates chronic liver fibrosis by inhibiting HSC activation through the IL-22/STAT3 pathway.

A Double Edged Sword Role of Interleukin-22 in Wound Healing and Tissue Regeneration

Wound healing and tissue regeneration is an intricate biological process that involves repair of cellular damage and maintenance of tissue integrity. Cascades involved in wound healing and tissue regeneration highly overlap with cancer causing pathways. Usually, subsequent tissue damage events include release of a number of cytokines to accomplish post-trauma restoration. IL-22 is one of the cytokines that are immediately produced to initiate immune response against several tissue impairments. IL-22 is a fundamental mediator in inflammation, mucous production, protective role against pathogens, wound healing, and tissue regeneration. However, accumulating evidence suggests pivotal role of IL-22 in instigation of various cancers due to its pro-inflammatory and tissue repairing activity. In this review, we summarize how healing effects of IL-22, when executed in an uncontrollable fashion can lead to carcinogenesis.

Cellular Interplay as a Consequence of Inflammatory Signals Leading to Liver Fibrosis Development

Inflammation has been known to be an important driver of fibrogenesis in the liver and onset of hepatic fibrosis. It starts off as a process meant to protect the liver from further damage, but it can become the main promoter of liver fibrosis. There are many inflammation-related pathways activated during liver fibrosis that lead to hepatic stellate cells (HSCs) activation and collagen-deposition in the liver. Such events are mostly modulated upstream of HSCs and involve signals from hepatocytes and innate immune cells. One particular event is represented by cell death during liver injury that generates multiple inflammatory signals that further trigger sterile inflammation and enhancement of inflammatory response. The assembly of inflammasome that responds to danger-associated molecular patterns (DAMPs) stimulates the release of pro-inflammatory cytokines and at the same time, initiates programmed cell death called pyroptosis. This review focuses on cellular and molecular mechanisms responsible for initiation and progress of inflammation in the liver.

Effect of folate supplementation on immunological and autophagy markers in experimental nonalcoholic fatty liver disease

BACKGROUND AND AIMS

Chronic hepatic inflammation is an important pathogenic mediator of nonalcoholic fatty liver disease (NAFLD) that contributes to disease severity. It is commonly suggested that autophagy dysfunction may be an underlying cause of nonalcoholic fatty liver disease. However, the exact role of autophagy in lipid metabolism remains controversial. There has been a growing interest in the role of folate supplementation for the treatment and/or prevention of NAFLD. We aimed in this study to investigate the effects of different doses of folate supplementation on several immune markers and autophagy trying to explore the complex role of IL-22 and autophagy in NAFLD.

METHODS

Fifty Wistar rats were randomly separated into experimental (n = 40) and control groups (n = 10), which were fed for eight weeks with a high-fat diet (HFD) containing 40% fats or a standard diet, respectively. The experimental group was further subdivided into four subgroups where the first subgroup was left untreated while the other three were treated with different doses of folate (50, 100, and 150 μg/kg of body weight, respectively). At the end of the experimental period, animals from each group were sacrificed for blood and tissue analyses.

RESULTS

NAFLD rats showed decreased IL-22 serum levels and increased LC3B expression as compared to controls. Folate treatment was significantly associated with improvement in disease parameters, reduced presence of the pro-inflammatory cytokines TNF-α and CXCL8 and LC3B expression, and increased IL-22 levels in a dose-dependent manner.

CONCLUSION

These results highlight the capacity of folate to modulate the production of several pro-inflammatory cytokines and autophagy thereby having a favorable impact disease progression.

Torularhodin Ameliorates Oxidative Activity in Vitro and d-Galactose-Induced Liver Injury via the Nrf2/HO-1 Signaling Pathway in Vivo

Torularhodin is a natural product extracted from Sporidiobolus pararoseus and has a similar chemical structure to β-carotene. The antioxidative effects of torularhodin were investigated using DPPH, ABTS, a cell oxidative damage model in vitro, and a d-galactose-induced liver-injured mouse model in vivo. Cell experiments demonstrated that torularhodin had a powerful effect on oxidative damage caused by H₂O₂ to AML12 cells. Torularhodin significantly reduced inflammatory cytokines and increased the activity of antioxidant enzymes both in mouse serum and the liver. The inhibition of d-galactose-induced oxidative damage in the liver was correlated with the torularhodin-mediated effects on improving the activity of Nrf2/HO-1, reducing the expression of Bax and NF-κB p65 by western blot analysis. RT-PCR results demonstrated torularhodin upregulated the antioxidative mRNA expression of Nrf2, NQO1, and HO-1 in the liver. In summary, torularhodin significantly scavenged free radicals and prevented oxidative damage in vitro and reduced d-galactose-induced liver oxidation via promotion of the Nrf2/HO-1 pathways in vivo.

The role of sphingosine kinase 2 in alcoholic liver disease

Alcoholic liver disease (ALD) is one of the most common liver diseases worldwide. However, the exact mechanisms underlying ALD remain unclear. Previous studies reported that sphingosine kinase 2 (SphK2) plays an essential role in regulating hepatic lipid metabolism. In the current study, we demonstrate that compared to wild-type (WT) mice, SphK2 deficient (SphK2^-/-) mice exhibited a greater degree of liver injury and hepatic lipid accumulation after feeding with an alcohol diet for 60 days. This is accompanied by a down-regulation of steroid 7-alpha-hydroxylase (Cyp7b1) and an up-regulation of pro-inflammatory mediators (Tnfα, F4/80, Il-1β). In vitro experiments showed that alcohol induced SphK2 expression in mouse primary hepatocytes and cultured mouse macrophages. Furthermore, alcohol feeding induced a more severe intestinal barrier dysfunction in SphK2^-/- mice than WT mice. Deficiency of SphK2 impaired the growth of intestinal organoids. Finally, SphK2 expression levels were down-regulated in the livers of human patients with alcoholic cirrhosis and hepatocellular carcinoma compared to healthy controls. In summary, these findings suggest that SphK2 is a crucial regulator of hepatic lipid metabolism and that modulating the SphK2-mediated signaling pathway may represent a novel therapeutic strategy for the treatment of ALD and other metabolic liver diseases.

IL13Rα2 expression identifies tissue-resident IL-22-producing PLZF+ innate T cells in the human liver

Innate lymphocytes are selectively enriched in the liver where they have important roles in liver immunology. Murine studies have shown that type I NKT cells can promote liver inflammation, whereas type II NKT cells have an anti-inflammatory role. In humans, type II NKT cells were found to accumulate in the gut during inflammation and IL13Rα2 was proposed as a marker for these cells. In the human liver, less is known about type I and II NKT cells. Here, we studied the phenotype and function of human liver T cells expressing IL13Rα2. We found that IL13Rα2 was expressed by around 1% of liver-resident memory T cells but not on circulating T cells. In support of their innate-like T-cell character, the IL13Rα2+ T cells had higher expression of promyelocytic leukaemia zinc finger (PLZF) compared to IL13Rα2- T cells and possessed the capacity to produce IL-22. However, only a minority of human liver sulfatide-reactive type II NKT cells expressed IL13Rα2. Collectively, these findings suggest that IL13Rα2 identifies tissue-resident intrahepatic T cells with innate characteristics and the capacity to produce IL-22.

The Interleukin-20 Cytokine Family in Liver Disease

The three main causes of inflammation and chronic injury in the liver are viral hepatitis, alcohol consumption, and non-alcoholic steatohepatitis, all of which can lead to liver fibrosis, cirrhosis, and hepatocellular carcinoma, which in turn may prompt the need for liver transplant. The interleukin (IL)-20 is a subfamily part of the IL-10 family of cytokines that helps the liver respond to damage and disease, they participate in the control of tissue homeostasis, and in the immunological responses developed in this organ. The best-studied member of the family in inflammatory balance of the liver is the IL-22 cytokine, which on the one hand may have a protective role in fibrosis progression but on the other may induce liver tissue susceptibility in hepatocellular carcinoma development. Other members of the family might also carry out this dual function, as some of them share IL receptor subunits and signal through common intracellular pathways. Investigators are starting to consider the potential for targeting IL-20 subfamily members in liver disease. The recently explored role of miRNA in the transcriptional regulation of IL-22 and IL-24 opens the door to promising new approaches for controlling the local immune response and limiting organ injury. The IL-20RA cytokine receptor has also been classified as being under miRNA control in non-alcoholic steatohepatitis. Moreover, researchers have proposed combining anti-inflammatory drugs with IL-22 as a hepatoprotective IL for alcoholic liver disease (ALD) treatment, and clinical trials of ILs for managing severe alcoholic-derived liver degeneration are ongoing. In this review, we focus on exploring the role of the IL-20 subfamily of cytokines in viral hepatitis, ALD, non-alcoholic steatohepatitis, and hepatocellular carcinoma, as well as delineating the main strategies explored so far in terms of therapeutic possibilities of the IL-20 subfamily of cytokines in liver disease.

The role of IL-22 in the resolution of sterile and nonsterile inflammation

In a broad sense, inflammation can be conveniently characterised by two phases: the first phase, which is a pro-inflammatory, has evolved to clear infection and/or injured tissue; and the second phase concerns regeneration of normal tissue and restitution of normal physiology. Innate immune cell-derived pro-inflammatory cytokines and chemokines activate and recruit nonresident immune cells to the site of infection, thereby amplifying the inflammatory responses to clear infection or injury. This phase is followed by a cytokine milieu that promotes tissue regeneration. There is no absolute temporal distinction between these two phases, and cytokines may have dual pleiotropic effects depending on the timing of release, inflammatory microenvironment or concentrations. IL-22 is a cytokine with reported pro- and anti-inflammatory roles; in this review, we contend that this protein has primarily a function in restitution of normal tissue and physiology.

IL-22 inactivates hepatic stellate cells via downregulation of the TGF-β1/Notch signaling pathway

Interleukin-22 (IL-22) inhibits liver fibrosis by inducing hepatic stellate cell (HSC) senescence, primarily through the activation of signal transducer and activator of transcription 3 signaling. However, whether other signaling pathways are involved remains unknown. The present study assessed the regulatory mechanism between IL‑22 and the Notch signaling pathway in vitro. The results revealed that IL‑22 had anti‑proliferative effects on HSC‑T6 cells, and cellular inactivation was reflected by simultaneous inhibition of α‑smooth muscle actin, transforming growth factor-β1 (TGF‑β1), tumor necrosis factor-α and intercellular adhesion molecule 1. Treatment with TGF‑β1 resulted in significant Notch3 upregulation and activation of its downstream effectors Hes family basic helix‑loop‑helix (bHLH) transcription factor (Hes)-1, Hes‑5 and Hes related family BHLH transcription factor with YRPW motif 1. Furthermore, this effect was markedly reversed by further treatment with IL‑22, indicating there may be regulatory cascades of IL‑22/TGF‑β1/Notch signaling in HSC‑T6 cells. The results of the present study demonstrated an inhibitory function of IL‑22 towards Notch signaling in hepatic cells, providing evidence that Notch may serve as a novel target for liver fibrosis.

Immune response of Th17-associated cytokines by peripheral blood mononuclear cells from patients with chronic hepatitis C virus infection

Hepatitis C virus (HCV) chronic infection causes severe cellular immune dysfunction. Here, we investigated the production of Th17-associated cytokines by peripheral blood mononuclear cells (PBMCs) of untreated patients with HCV, patients presenting an early virologic response (EVR) after 12weeks of treatment with interferon-α plus ribavirin with or without HCV protease inhibitors, and patients who were nonresponders to HCV therapy. PBMCs were stimulated with HCV core and nonstructural antigens, and the production of Th17-associated cytokines was measured with a Milliplex MAP immunoassay. Core-stimulated PBMCs from both untreated and nonresponder patients produced interleukin (IL)-17A, and vigorous production of IL-17A in response to NS3 antigen was only verified in the untreated group. Nonresponder patients also produced IL-17F after core antigen stimulation. IL-21 production was unaltered in the three groups of patients, whereas IL-17E and IL-22 were not detected. The production of Th17 cytokines by cells from patients showing an EVR was insignificant. IL-17A and IL-17F levels were not correlated with alanine aminotransferase levels or viremia. However, advanced fibrosis was associated with higher IL-17A production in T0 cells stimulated with core antigen. Untreated patients with HCV and patients who were nonresponders to antiviral treatment differed in their PBMC immune responses of Th17-associated cytokines. The early virological response to antiviral treatment dramatically decreased Th17 immune responses to HCV antigens.

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.