Interleukin-22 protects against acute alcohol-induced hepatotoxicity in mice

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.

Emerging Role of Interleukins for the Assessment and Treatment of Liver Diseases

BACKGROUND

The most common liver diseases are fibrosis, alcoholic liver disease, non-alcoholic fatty disease, viral hepatitis, and hepatocellular carcinoma. These liver diseases account for approximately 2 million deaths per year worldwide, with cirrhosis accounting for 2.1% of the worldwide burden. The most widely used liver function tests for diagnosis are alanine transaminase, aspartate transaminase, serum proteins, serum albumin, and serum globulins, whereas antivirals and corticosteroids have been proven to be useful for the treatment of liver diseases. A major disadvantage of these diagnostic measures is the lack of specificity to a particular tissue or cell type, as these enzymes are common to one or more tissues. The major adverse effect of current treatment methods is drug resistance. To overcome these issues, interleukins have been investigated. The balance of these interleukins determines the outcome of an immune response. Interleukins are considered interesting therapeutic targets for the treatment of liver diseases. In this review, we summarize the current state of knowledge regarding interleukins in the diagnosis, treatment, and pathogenesis of different acute and chronic liver diseases.

OBJECTIVE

To understand the role of interleukins in the assessment and treatment of different types of liver diseases.

METHODS

A literature search was conducted using PubMed, Science Direct, and NCBI with the following keywords: Interleukins, Acute Liver Failure, Alcoholic Liver Disease, Non-Alcoholic Fatty Liver Disease, Liver Fibrosis, Hepatocellular Carcinoma, Inflammation, Liver injury, Hepatoprotective effect. Clinical trial data on these interleukins have been searched on Clinicaltrials.gov.

RESULTS

Existing literature and preclinical and clinical trial data demonstrate that interleukins play a crucial role in the pathogenesis of liver diseases.

CONCLUSION

Our findings indicate that IL-1, IL-6, IL-10, IL-17, IL-22, IL-35, and IL-37 are involved in the progression and control of various liver conditions via the regulation of cell signaling pathways. However, further investigation on the involvement of these interleukins is necessary for their use as a targeted therapy in liver diseases.

Acetaminophen-Induced Liver Injury Exposes Murine IL-22 as Sex-Related Gene Product

Gaining detailed knowledge about sex-related immunoregulation remains a crucial prerequisite for the development of adequate disease models and therapeutic strategies enabling personalized medicine. Here, the key parameter of the production of cytokines mediating disease resolution was investigated. Among these cytokines, STAT3-activating interleukin (IL)-22 is principally associated with recovery from tissue injury. By investigating paradigmatic acetaminophen-induced liver injury, we demonstrated that IL-22 expression is enhanced in female mice. Increased female IL-22 was confirmed at a cellular level using murine splenocytes stimulated by lipopolysaccharide or αCD3/CD28 to model innate or adaptive immunoactivation. Interestingly, testosterone or dihydrotestosterone reduced IL-22 production by female but not by male splenocytes. Mechanistic studies on PMA/PHA-stimulated T-cell-lymphoma EL-4 cells verified the capability of testosterone/dihydrotestosterone to reduce IL-22 production. Moreover, we demonstrated by chromatin immunoprecipitation that testosterone impairs binding of the aryl hydrocarbon receptor to xenobiotic responsive elements within the murine IL-22 promoter. Overall, female mice undergoing acute liver injury and cultured female splenocytes upon inflammatory activation display increased IL-22. This observation is likely related to the immunosuppressive effects of androgens in males. The data presented concur with more pronounced immunological alertness demonstrable in females, which may relate to the sex-specific course of some immunological disorders.

The good and the bad about separation anxiety: roles of IL-22 and IL-22BP in liver pathologies

The human liver fulfills several vital tasks daily and possesses an impressive ability to self-regenerate. However, the capacity of this self-healing process can be exhausted by a variety of different liver diseases, such as alcoholic liver damage, viral hepatitis, or hepatocellular carcinoma. Over time, all these diseases generally lead to progressive liver failure that can become fatal if left untreated. Thus, a great effort has been directed towards the development of innovative therapies. The most recently discovered therapies often involve modifying the patient's immune system to enhance a beneficial immune response. Current data suggest that, among others, the cytokine IL-22 might be a promising therapeutical candidate. IL-22 and its endogenous antagonist, IL-22BP, have been under thorough scientific investigation for nearly 20 years. While IL-22 is mainly produced by TH22 cells, ILC3s, NKT cells, or γδ T cells, sources of IL-22BP include dendritic cells, eosinophils, and CD4+ cells. In many settings, IL-22 was shown to promote regenerative potential and, thus, could protect tissues from pathogens and damage. However, the effects of IL-22 during carcinogenesis are more ambiguous and depend on the tumor entity and microenvironment. In line with its capabilities of neutralizing IL-22 in vivo, IL-22BP possesses often, but not always, an inverse expression pattern compared to its ligand. In this comprehensive review, we will summarize past and current findings regarding the roles of IL-22 and IL-22BP in liver diseases with a particular focus on the leading causes of advanced liver failure, namely, liver infections, liver damage, and liver malignancies.

The double-edged role of IL-22 in organ fibrosis

Fibrosis is unregulated tissue repair in damaged or diseased organs, and the accumulation of excess extracellular matrix (ECM) impacts the structure and functions of organs, leading to death. Fibrosis is usually triggered by inflammation and tissue damage, and inflammatory mediators stimulate the proliferation of myofibroblasts and the excessive production of ECM. The IL-10 family cytokines play important roles in the development of fibrosis, and its member IL-22 has recently attracted specific attention. IL-22 plays great roles in preventing pathogens invasion and tissue damage, as well as making a contribution to pathogenic processes. Increasing evidence suggested that IL-22 is a key molecule in tissue repair, proliferation and mucosal barrier defense, and it has also been suggested to play both pro-fibrotic and anti-fibrotic roles in tissues. In this review, we summarized the pro-fibrotic and anti-fibrotic functions of IL-22 in various organs which may be of great significance for the development of potential therapeutic strategies for fibrosis-related diseases.

From intestinal dysbiosis to alcohol-associated liver disease

Alcohol-associated intestinal dysbiosis and bacterial overgrowth can lead to a dysregulation of tryptophan metabolism and lower production of indoles. Several of these indole derivatives are aryl hydrocarbon receptor ligands that, in turn, are involved in antimicrobial defense via induction of interleukin-22 (IL-22). IL-22 increases the expression of intestinal regenerating islet-derived 3 (Reg3) lectins, which maintain low bacterial colonization of the inner mucus layer and reduce bacterial translocation to the liver. Chronic alcohol consumption is associated with reduced intestinal expression of Reg3β and Reg3γ, increased numbers of mucosa-associated bacteria and bacterial translocation. Translocated microbial products and viable bacteria reach the liver and activate the innate immune system. Release of inflammatory molecules promotes inflammation, contributes to hepatocyte death and results in a fibrotic response. This review summarizes the mechanisms by which chronic alcohol intake changes the gut microbiota and contributes to alcohol-associated liver disease by changing microbial-derived metabolites.

Incidence and Risk Factors Associated With 30-Day Readmission for Alcoholic Hepatitis

BACKGROUND

Alcohol abuse and liver disease are associated with high rates of 30-day hospital readmission, but factors linking alcoholic hepatitis (AH) to readmission are not well understood. We aimed to determine the incidence rate of 30-day readmission for patients with AH and to evaluate potential predictors of readmission.

METHODS

We used the Nationwide Readmissions Database to determine the 30-day readmission rate for recurrent AH between 2010 and 2014 and examined trends in readmissions during the study period. We also identified the 20 most frequent reasons for readmission. Multivariate survey logistic regression analysis was used to identify factors associated with 30-day readmission.

RESULTS

Of the 61,750 index admissions for AH, 23.9% were readmitted within 30-days. The rate of readmission did not change significantly during the study period. AH, alcoholic cirrhosis, and hepatic encephalopathy were the most frequent reasons for readmission. In multivariate analysis female sex, leaving against medical advice, higher Charlson comorbidity index, ascites, and history of bariatric surgery were associated with earlier readmissions, whereas older age, payer type (private or self-pay/other), and discharge to skilled nursing-facility reduced this risk.

CONCLUSIONS

The 30-day readmission rate in patients with AH was high and stable during the study period. Factors associated with readmission may be helpful for development of consensus-based expert guidelines, treatment algorithms, and policy changes to help decrease readmission in AH.

Protective effects of Lactobacillus plantarum against chronic alcohol-induced liver injury in the murine model

Long-term alcohol consumption causes liver injuries such as alcoholic hepatitis, fatty liver, and endotoxemia. Some probiotics were demonstrated to exert beneficial effects in the gastrointestinal tract. The present study was aimed to evaluate the protective effects of Lactobacillus plantarum CMU995 against alcohol-induced liver injury. The mice were orally administered L. plantarum CMU995 for 1 week, followed by the administration of alcohol and different tested substances daily for 6 weeks. The liver injury was examined by measuring the levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT), malondialdehyde (MDA), anti-oxidative enzyme, endotoxin, inflammatory cytokines, and lipid accumulation in the liver or serum among different groups. L. plantarum CMU995 exhibited beneficial effects on alcohol-induced liver injury via reduction in the serum concentration of AST, ALT, cholesterol, triglycerides, endotoxin, TNF-α, IL-1β, and oxidative stress. Furthermore, we also found that the levels of glutathione (GSH), superoxide dismutase (SOD), and intestinal tight junction protein zonula occludens-1 (ZO-1) were considerably higher in L. plantarum CMU995-fed groups when compared with placebo group. Meanwhile, the protective effects were demonstrated biological gradients as controversial dose-dependent. We speculate that L. plantarum CMU995 inhibited the migration of alcohol-derived endotoxin into the blood and liver, thereby improving the intestinal barrier. The present evidence may provide a novel microbiota-based strategy to prevent the alcohol-induced liver injury.

Bacteria engineered to produce IL-22 in intestine induce expression of REG3G to reduce ethanol-induced liver disease in mice

OBJECTIVE

Antimicrobial C-type lectin regenerating islet-derived 3 gamma (REG3G) is suppressed in the small intestine during chronic ethanol feeding. Our aim was to determine the mechanism that underlies REG3G suppression during experimental alcoholic liver disease.

DESIGN

Interleukin 22 (IL-22) regulates expression of REG3G. Therefore, we investigated the role of IL-22 in mice subjected to chronic-binge ethanol feeding (NIAAA model).

RESULTS

In a mouse model of alcoholic liver disease, we found that type 3 innate lymphoid cells produce lower levels of IL-22. Reduced IL-22 production was the result of ethanol-induced dysbiosis and lower intestinal levels of indole-3-acetic acid (IAA), a microbiota-derived ligand of the aryl hydrocarbon receptor (AHR), which regulates expression of IL-22. Importantly, faecal levels of IAA were also found to be lower in patients with alcoholic hepatitis compared with healthy controls. Supplementation to restore intestinal levels of IAA protected mice from ethanol-induced steatohepatitis by inducing intestinal expression of IL-22 and REG3G, which prevented translocation of bacteria to liver. We engineered Lactobacillus reuteri to produce IL-22 (L. reuteri/IL-22) and fed them to mice along with the ethanol diet; these mice had reduced liver damage, inflammation and bacterial translocation to the liver compared with mice fed an isogenic control strain and upregulated expression of REG3G in intestine. However, L. reuteri/IL-22 did not reduce ethanol-induced liver disease in Reg3g-/- mice.

CONCLUSION

Ethanol-associated dysbiosis reduces levels of IAA and activation of the AHR to decrease expression of IL-22 in the intestine, leading to reduced expression of REG3G; this results in bacterial translocation to the liver and steatohepatitis. Bacteria engineered to produce IL-22 induce expression of REG3G to reduce ethanol-induced steatohepatitis.

Increased interleukin-23 receptor (IL-23R) expression is associated with disease severity in acute-on-chronic liver failure

BACKGROUND

Th17 cells mediated immune response is important in chronic hepatitis B (CHB) infection and inflammation associated diseases; however, little is known about their immunopathogenic role in acute-on-chronic liver failure (ACLF). Interleukin-23 receptor (IL-23R) is essential for the generation of pathogenic Th17 cells; therefore, we aimed to evaluate IL-23R expression and its correlation with disease severity in ACLF.

METHODS

Forty-two patients with ACLF (HBV and alcohol-related), thirty-two with CHB and twenty healthy controls (HC) were studied. Circulating and intrahepatic profile of Th17 cells and IL-23R was investigated. Association of IL-23R with disease severity was determined.

RESULTS

Circulating Th17 cells were significantly increased in both ACLF groups (P = 0.03, P = 0.006) than CHB and HC. Percentage of Th17 cells was higher in liver than peripheral blood of ACLF patients (P = 0.04). Expression of IL-23R was immensely up-regulated on Th17 cells of ACLF patients. Importantly, IL-23R not only correlated with the increased percentage of Th17 cells but also had significant association with inflammation (P = 0.03) and clinical disease severity indices including Child-Turcotte-Pugh (P = 0.001) and Model for End-Stage Liver Disease (P = 0.002) scores. The ACLF non-survivors showed higher IL-23R expression (P = 0.01). Transcription factor retinoic acid receptor-related orphan nuclear receptor gamma-t (ROR-γt) was also high in circulation and in liver of ACLF patients and it positively correlated with ALT levels (P = 0.03). Surface receptors, including CCR6, IL-17R and pro-inflammatory cytokines IL-17A, IL-22, CXCL8 and GM-CSF were highly augmented in ACLF.

CONCLUSION

ACLF patients express high IL-23R on Th17 cells which induces inflammation and strongly correlates with liver disease severity.

Targeting IL-10 Family Cytokines for the Treatment of Human Diseases

Members of the interleukin (IL)-10 family of cytokines play important roles in regulating immune responses during host defense but also in autoimmune disorders, inflammatory diseases, and cancer. Although IL-10 itself primarily acts on leukocytes and has potent immunosuppressive functions, other family members preferentially target nonimmune compartments, such as tissue epithelial cells, where they elicit innate defense mechanisms to control viral, bacterial, and fungal infections, protect tissue integrity, and promote tissue repair and regeneration. As cytokines are prime drug targets, IL-10 family cytokines provide great opportunities for the treatment of autoimmune diseases, tissue damage, and cancer. Yet no therapy in this space has been approved to date. Here, we summarize the diverse biology of the IL-10 family as it relates to human disease and review past and current strategies and challenges to target IL-10 family cytokines for clinical use.

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.

Tethering Interleukin-22 to Apolipoprotein A-I Ameliorates Mice from Acetaminophen-induced Liver Injury

Increasing evidence indicates that interleukin-22 (IL-22) holds tremendous potential as a protective agent in preventing liver injury, but its pleiotropic effects and pathogenic role in carcinogenesis, rheumatoid arthritis and psoriasis restrict its systemic application. Here, we first developed a nanoparticle (liposIA) as a liver-targeted agent through IL-22 tethered to apolipoprotein A-I (ApoA-I) in a gene therapy vector. LiposIA was prepared using thin film dispersion method and the complexes exhibited desirable nanoparticle size, fine polydisperse index, highly efficient transfection, and excellent serum and storage stability. Biodistribution and hepatic STAT3 phosphorylation studies revealed that IL-22 tethered to ApoA-I led to highly efficient liver targeting. More importantly, our studies showed that a single-dose of liposIA was able to protect mice against acetaminophen-induced liver injury and did not initiate inflammatory response or systemic toxicity in vivo. During this process, activated STAT3/Erk and Akt/mTOR signaling transductions were observed, as well as inhibition of reactive oxygen species (ROS) generation, which prevented mitochondrial dysfunction. These studies demonstrated that IL-22 tethered to apolipoprotein A-I could target and ameliorate acetaminophen-induced acute liver injury, which highlighted that a targeted strategy for IL-22 delivery might have broad utility for the protection of hepatocellular damage.

Targeting inflammation for the treatment of alcoholic liver disease

Alcoholic liver disease (ALD) is a leading cause of chronic liver disease with a wide spectrum of manifestations including simple steatosis to steatohepatitis, cirrhosis, and hepatocellular carcinoma. Liver injury in ALD is caused by chronic inflammation, which has been actively investigated as a therapeutic target for the treatment of ALD for over the last four decades. In this review, we summarize a wide variety of inflammatory mediators that have been shown to contribute to the pathogenesis of ALD, and discuss the therapeutic potential of these mediators for the treatment of ALD.

Crosstalk of liver immune cells and cell death mechanisms in different murine models of liver injury and its clinical relevance

BACKGROUND

Liver inflammation or hepatitis is a result of pluripotent interactions of cell death molecules, cytokines, chemokines and the resident immune cells collectively called as microenvironment. The interplay of these inflammatory mediators and switching of immune responses during hepatotoxic, viral, drug-induced and immune cell-mediated hepatitis decide the fate of liver pathology. The present review aimed to describe the mechanisms of liver injury, its relevance to human liver pathology and insights for the future therapeutic interventions.

DATA SOURCES

The data of mouse hepatic models and relevant human liver diseases presented in this review are systematically collected from PubMed, ScienceDirect and the Web of Science databases published in English.

RESULTS

The hepatotoxic liver injury in mice induced by the metabolites of CCl₄, acetaminophen or alcohol represent necrotic cell death with activation of cytochrome pathway, formation of reactive oxygen species (ROS) and mitochondrial damage. The Fas or TNF-alpha induced apoptotic liver injury was dependent on activation of caspases, release of cytochrome c and apoptosome formation. The ConA-hepatitis demonstrated the involvement of TRAIL-dependent necrotic/necroptotic cell death with activation of RIPK1/3. The alpha-GalCer-induced liver injury was mediated by TNF-alpha. The LPS-induced hepatitis involved TNF-alpha, Fas/FasL, and perforin/granzyme cell death pathways. The MHV3 or Poly(I:C) induced liver injury was mediated by natural killer cells and TNF-alpha signaling. The necrotic ischemia-reperfusion liver injury was mediated by hypoxia, ROS, and pro-inflammatory cytokines; however, necroptotic cell death was found in partial hepatectomy. The crucial role of immune cells and cell death mediators in viral hepatitis (HBV, HCV), drug-induced liver injury, non-alcoholic fatty liver disease and alcoholic liver disease in human were discussed.

CONCLUSIONS

The mouse animal models of hepatitis provide a parallel approach for the study of human liver pathology. Blocking or stimulating the pathways associated with liver cell death could unveil the novel therapeutic strategies in the management of liver diseases.

Impact of An Soup of Miao nationality on expression of Occludin in intestinal mucosa and content of IL-22 in hepatic tissue in mice with acute liver failure

AIM

To evaluate the effect of An Soup of Miao nationality on acute hepatic failure by detecting the expression of Occludin in the intestinal mucosa and the content of interleukin-22 (IL-22) in liver tissue.

METHODS

Forty male SD rats were randomly and equally divided into four groups, namely, normal control group, acute liver failure model group, bifid triple viable bacteria group, and An Soup group. The bifid triple viable bacteria group and An Soup group were gavaged with bifid triple viable bacteria and An Soup once a day for 9 d; the normal control group and acute liver failure model group were gavaged with equal volume of normal saline. At the 8^th day, all groups except the normal control group were subcutaneously injected with 300 mg/kg thioacetamide (prepared with TAA and normal saline) once a day for two consecutive days to induce acute hepatic failure. At the 10^th day, the rats were killed, serum samples were taken to detect the levels of alanine aminotransferase and aspartate aminotransferase, and ileal tissue that was 3 cm away from the ileocecal junction and hepatic tissue were taken to detect the expression of Occludin in the intestinal mucosa and the content of IL-22 in hepatic tissue, respectively.

RESULTS

Except for the normal control group, the levels of serum transaminase and content of IL-22 in hepatic tissue increased significantly in the other three groups (P < 0.01). Compared with the model group, the levels of serum transaminase decreased significantly in the bifid triple viable bacteria group and An Soup group (P < 0.05), but the difference between the bifid triple viable bacteria group and An Soup group was not significant (P > 0.05). Compared with the model group, the content of IL-22 in hepatic tissue increased significantly in the bifid triple viable bacteria group and An Soup group (P < 0.05), but there was no significant difference between the bifid triple viable bacteria group and An Soup group (P > 0.05). Except the normal control group, the expression level of Occludin in the intestinal mucosa decreased in other three groups (P < 0.01). Compared with the model group, the expression of Occludin in the intestinal mucosa increased significantly in the bifid triple viable bacteria group and An Soup group (P < 0.05), although the difference between the bifid triple viable bacteria group and An Soup group was not significant (P > 0.05).

CONCLUSION

An Soup has dietary effects on acute hepatic failure by protecting intestinal mucosal barrier and up-regulating IL-22 expression.

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.

Hepatoprotective effects of hoveniae semen cum fructus extracts in ethanol intoxicated mice

[Purpose]

The objective of this study was to evaluate the hepatoprotective effects of Hoveniae Semen Cum Fructus extract in ethanol induced hepatic damages.

[Methods]

Hepatic damages were induced by oral administration of ethanol and then Hoveniae Semen Cum Fructus extract was administered.

[Results]

Following Hoveniae Semen Cum Fructus extract administration, body and liver weights were increased, while aspartate aminotransferase, alanine aminotransferase, albumin, γ-glutamyl transferase, and triglyceride levels in the serum, triglyceride contents, tumor necrosis factor -α level, cytochrome (CY) P450 2E1 activity in the liver and mRNA expression of hepatic lipogenic genes, and Nitrotyrosine and 4-HNE-immunolabelled hepatocytes were decreased. However, mRNA expression of genes involved in fatty acid oxidation was increased. Also, as a protective mechanism for hepatic antioxidant defense systems, decreased liver MDA contents, increased glutathione contents, increased dismutase and catalase activities were observed when compared to the ethanol control.

[Conclusion]

Hoveniae Semen Cum Fructus extract favorably protected against liver damages, mediated by its potent anti-inflammatory and anti-steatosis properties through the augmentation of the hepatic antioxidant defense system by NF-E2-related factor-2 activation, and down-regulation of the mRNA expression of hepatic lipogenic genes or up-regulation of the mRNA expression of genes involved in fatty acid oxidation.

Though Active on RINm5F Insulinoma Cells and Cultured Pancreatic Islets, Recombinant IL-22 Fails to Modulate Cytotoxicity and Disease in a Protocol of Streptozotocin-Induced Experimental Diabetes

Interleukin (IL)-22 is a cytokine displaying tissue protective and pro-regenerative functions in various preclinical disease models. Anti-bacterial, pro-proliferative, and anti-apoptotic properties mediated by activation of the transcription factor signal transducer and activator of transcription (STAT)-3 are key to biological functions of this IL-10 family member. Herein, we introduce RINm5F insulinoma cells as rat β-cell line that, under the influence of IL-22, displays activation of STAT3 with induction of its downstream gene targets Socs3, Bcl3, and Reg3b. In addition, IL-22 also activates STAT1 in this cell type. To refine those observations, IL-22 biological activity was evaluated using ex vivo cultivated murine pancreatic islets. In accord with data on RINm5F cells, islet exposure to IL-22 activated STAT3 and upregulation of STAT3-inducible Socs3, Bcl3, and Steap4 was evident under those conditions. As these observations supported the hypothesis that IL-22 may exert protective functions in toxic β-cell injury, application of IL-22 was investigated in murine multiple-low-dose streptozotocin (STZ)-induced diabetes. For that purpose, recombinant IL-22 was administered thrice either immediately before and at disease onset (at d4, d6, d8) or closely thereafter (at d8, d10, d12). These two IL-22-treatment periods coincide with two early peaks of β-cell injury detectable in this model. Notably, none of the two IL-22-treatment strategies affected diabetes incidence or blood glucose levels in STZ-treated mice. Moreover, pathological changes in islet morphology analyzed 28 days after disease induction were not ameliorated by IL-22 administration. Taken together, despite being active on rat RINm5F insulinoma cells and murine pancreatic islets, recombinant IL-22 fails to protect pancreatic β-cells in the tested protocols from toxic effects of STZ and thus is unable to ameliorate disease in the widely used model of STZ-induced diabetes.

Therapeutic Role of Interleukin 22 in Experimental Intra-abdominal Klebsiella pneumoniae Infection in Mice

Interleukin 22 (IL-22) is an IL-10-related cytokine produced by T helper 17 (Th17) cells and other immune cells that signals via IL-22 receptor alpha 1 (IL-22Ra1), which is expressed on epithelial tissues, as well as hepatocytes. IL-22 has been shown to have hepatoprotective effects that are mediated by signal transducer and activator of transcription 3 (STAT3) signaling. However, it is unclear whether IL-22 can directly regulate antimicrobial programs in the liver. To test this hypothesis, hepatocyte-specific IL-22Ra1 knockout (Il22Ra1(Hep-/-)) and Stat3 knockout (Stat3(Hep-/-)) mice were generated and subjected to intra-abdominal infection with Klebsiella pneumoniae, which results in liver injury and necrosis. We found that overexpression of IL-22 or therapeutic administration of recombinant IL-22 (rIL-22), given 2 h postinfection, significantly reduced the bacterial burden in both the liver and spleen. The antimicrobial activity of rIL-22 required hepatic Il22Ra1 and Stat3. Serum from rIL-22-treated mice showed potent bacteriostatic activity against K. pneumoniae, which was dependent on lipocalin 2 (LCN2). However, in vivo, rIL-22-induced antimicrobial activity was only partially reduced in LCN2-deficient mice. We found that rIL-22 also induced serum amyloid A2 (SAA2) and that SAA2 had anti-K. pneumoniae bactericidal activity in vitro. These results demonstrate that IL-22, through IL-22Ra1 and STAT3 singling, can induce intrinsic antimicrobial activity in the liver, which is due in part to LCN2 and SAA2. Therefore, IL-22 may be a useful adjunct in treating hepatic and intra-abdominal infections.

Alcoholic hepatitis: The pivotal role of Kupffer cells

Kupffer cells play a central role in the pathogenesis of alcoholic hepatitis (AH). It is believed that alcohol increases the gut permeability that results in raised levels of serum endotoxins containing lipopolysaccharides (LPS). LPS binds to LPS-binding proteins and presents it to a membrane glycoprotein called CD14, which then activates Kupffer cells via a receptor called toll-like receptor 4. This endotoxin mediated activation of Kupffer cells plays an important role in the inflammatory process resulting in alcoholic hepatitis. There is no effective treatment for AH, although notable progress has been made over the last decade in understanding the underlying mechanism of alcoholic hepatitis. We specifically review the current research on the role of Kupffer cells in the pathogenesis of AH and the treatment strategies. We suggest that the imbalance between the pro-inflammatory and the anti-inflammatory process as well as the increased production of reactive oxygen species eventually lead to hepatocyte injury, the final event of alcoholic hepatitis.

Update on Alcoholic Hepatitis

Alcoholic liver disease is one of the most prevalent liver diseases worldwide, and a major cause of morbidity and mortality. Alcoholic hepatitis is a severe form of liver injury in patients with alcohol abuse, can present as an acute on chronic liver failure associated with a rapid decline in liver synthetic function, and consequent increase in mortality. Despite therapy, about 30%-50% of patients with severe alcoholic hepatitis eventually die. The pathogenic pathways that lead to the development of alcoholic hepatitis are complex and involve oxidative stress, gut dysbiosis, and dysregulation of the innate and adaptive immune system with injury to the parenchymal cells and activation of hepatic stellate cells. As accepted treatment approaches are currently limited, a better understanding of the pathophysiology would be required to generate new approaches that improve outcomes. This review focuses on recent advances in the diagnosis, pathogenesis of alcoholic hepatitis and novel treatment strategies.

Role of interleukin-22 in liver diseases

Interleukin (IL)-22, which is discovered by the Dumoutier team during the stimulation of murine BW5147 T lymphoma cells with IL-9, is a member of the IL-10 cytokine family because of the similarity of structure and encoding genes. IL-22 is involved in many inflammatory diseases and autoimmune diseases, such as psoriasis, ulcerative colitis, and systemic lupus erythematosus. Recently it has been found that IL-22 can protect against liver injury and promote hepatocytes proliferation. This paper will make a brief introduction of the role of IL-22 in liver diseases.

T-helper cell-mediated factors in drug-induced liver injury

Drug-induced liver injury (DILI) leads to a large burden on the healthcare system due to its potential morbidity and mortality. The key for predicting and preventing DILI is to understand the underlying mechanisms. Hepatic inflammation is one of the most common features of DILI. The inflammation can be attributed to the innate immune response. The adaptive immune system is also affected by the innate immune response resulting in liver damage. T-helper cells are important regulators of acquired immunity. T-helper cell-mediated immune responses play pivotal roles in the pathogenesis of a variety of liver disorders. This review summarizes recent advances in the T-helper cell-mediated factors in DILI and potential mechanisms, which may lead to a better understanding of DILI.

Pathogenesis of alcoholic liver disease: Role of oxidative metabolism

Alcohol consumption is a predominant etiological factor in the pathogenesis of chronic liver diseases, resulting in fatty liver, alcoholic hepatitis, fibrosis/cirrhosis, and hepatocellular carcinoma (HCC). Although the pathogenesis of alcoholic liver disease (ALD) involves complex and still unclear biological processes, the oxidative metabolites of ethanol such as acetaldehyde and reactive oxygen species (ROS) play a preeminent role in the clinical and pathological spectrum of ALD. Ethanol oxidative metabolism influences intracellular signaling pathways and deranges the transcriptional control of several genes, leading to fat accumulation, fibrogenesis and activation of innate and adaptive immunity. Acetaldehyde is known to be toxic to the liver and alters lipid homeostasis, decreasing peroxisome proliferator-activated receptors and increasing sterol regulatory element binding protein activity via an AMP-activated protein kinase (AMPK)-dependent mechanism. AMPK activation by ROS modulates autophagy, which has an important role in removing lipid droplets. Acetaldehyde and aldehydes generated from lipid peroxidation induce collagen synthesis by their ability to form protein adducts that activate transforming-growth-factor-β-dependent and independent profibrogenic pathways in activated hepatic stellate cells (HSCs). Furthermore, activation of innate and adaptive immunity in response to ethanol metabolism plays a key role in the development and progression of ALD. Acetaldehyde alters the intestinal barrier and promote lipopolysaccharide (LPS) translocation by disrupting tight and adherent junctions in human colonic mucosa. Acetaldehyde and LPS induce Kupffer cells to release ROS and proinflammatory cytokines and chemokines that contribute to neutrophils infiltration. In addition, alcohol consumption inhibits natural killer cells that are cytotoxic to HSCs and thus have an important antifibrotic function in the liver. Ethanol metabolism may also interfere with cell-mediated adaptive immunity by impairing proteasome function in macrophages and dendritic cells, and consequently alters allogenic antigen presentation. Finally, acetaldehyde and ROS have a role in alcohol-related carcinogenesis because they can form DNA adducts that are prone to mutagenesis, and they interfere with methylation, synthesis and repair of DNA, thereby increasing HCC susceptibility.

The crystal structure of zebrafish IL-22 reveals an evolutionary, conserved structure highly similar to that of human IL-22

The class II cytokine family consists of small α-helical signaling proteins including the interleukin-10 (IL-10)/IL-22 family, as well as interferons (IFNs). They regulate the innate immune response and in addition have an important role in protecting epithelial tissues. Teleost fish possess a class II cytokine system surprisingly similar to that of humans, and thus zebrafish offers an attractive model organism for investigating the role of class II cytokines in inflammation. However, the evolution of class II cytokines is critical to understand if we are to take full advantage of zebrafish as a model system. The small size and fast evolution of these cytokines obscure phylogenetic analyses based purely on sequences, but one can overcome this obstacle by using information contained within the structure of those molecules. Here we present the crystal structure of IL-22 from zebrafish (zIL-22) solved at 2.1 Å, which displays a typical class II cytokine architecture. We generated a structure-guided alignment of vertebrate class II cytokines and used it for phylogenetic analysis. Our analysis suggests that IL-22 and IL-26 arose early during the evolution of the IL-10-like cytokines. Thus, we propose an evolutionary scenario of class II cytokines in vertebrates, based on genomic and structural data.

Therapy with interleukin-22 alleviates hepatic injury and hemostasis dysregulation in rat model of acute liver failure

The therapeutic efficacy of interleukin-22 (IL-22) on liver injury and hematological disturbances was studied in rat model of acute liver failure (ALF) induced by D-galactosamine/lipopolysaccharide (D-GalN/LPS). The following parameters were investigated: (1) survival rate, (2) serum levels of liver function enzymes (aspartate aminotransferase (AST), alanine aminotransferase (ALT), and alkaline phosphatase (ALP)), total bilirubin (TBILI), and total albumen (ALB), (3) blood clotting tests (prothrombin time (PT), activated partial thromboplastin time (aPTT), and fibrinogen level (FIB)) and white blood cells (WBCs), red blood cells (RBCs), and platelet counts, (4) hepatic levels of tumor necrosis factor- α (TNF- α ) and cyclooxygenase-2 (COX-2), and (5) liver histopathology. After 48 hours of D-GalN/LPS, the rats exhibited 20% mortality, significant increases in AST, ALT, ALP, TBILI, PT, and aPTT, TNF- α , and COX-2 and significant decreases in FIB, WBCs, and RBCs. By contrast, therapy with IL-22 prevented the lethal effect of D-GalN/LPS by 100% and efficiently alleviated all the biochemical and hematological abnormalities that were observed in ALF untreated group. Furthermore, IL-22 treatment decreased the hepatic contents of TNF- α and COX-2. The histopathological findings also supported the hepatoprotective effect of IL-22. Taken together, therapy with IL-22 can represent a promising therapeutic tool against liver injury and its associated hemostasis disturbances.

Therapeutic opportunities of the IL-22-IL-22R1 system

Interleukin-22 (IL-22) is a key effector molecule that is produced by activated T cells, including T helper 22 (TH22) cells, TH17 cells and TH1 cells, as well as subsets of innate lymphoid cells. Although IL-22 can act synergistically with IL-17 or tumour necrosis factor, some important functions of IL-22 are unique to this cytokine. Data obtained over the past few years indicate that the IL-22-IL-22 receptor subunit 1 (IL-22R1) system has a high potential clinical relevance in psoriasis, ulcerative colitis, graft-versus-host disease, certain infections and tumours, as well as in liver and pancreas damage. This Review highlights current knowledge of the biology of the IL-22-IL-22R1 system, its role in inflammation, tissue protection, regeneration and antimicrobial defence, as well as the positive and potentially negative consequences of its therapeutic modulation.

Hepatoprotective and anti-fibrotic functions of interleukin-22: therapeutic potential for the treatment of alcoholic liver disease

Interleukin-22 (IL-22) plays a key role in promoting antimicrobial immunity and tissue repair at barrier surfaces by binding to the receptors IL-22R1, which is generally thought to be expressed exclusively in epithelial cells, and IL-10R2. Our laboratory previously demonstrated that IL-22 plays an important role in ameliorating liver injury in many rodent models by targeting hepatocytes that express high levels of IL-22R1 and IL-10R2. Recently, we have identified high expression levels of IL-22R1 and IL-10R2 in liver progenitor cells and hepatic stellate cells (HSCs). Overexpression of IL-22 in vivo or treatment with IL-22 in vitro promotes proliferation of liver progenitor cells via a signal transducer and activator of transcription 3 (STAT3)-dependent mechanism. IL-22 treatment also prevents HSC apoptosis in vitro and in vivo. Surprisingly, overexpression of IL-22, via either gene targeting or exogenous administration of adenovirus expressing IL-22, reduces liver fibrosis and accelerates the resolution of liver fibrosis during recovery. The anti-fibrotic effects of IL-22 are mediated via the activation of STAT3 in HSCs and subsequent induction of suppressor of cytokine signaling 3, which induces HSC senescence. Taken together, the hepatoprotective, mitogenic, and anti-fibrotic effects of IL-22 are beneficial in ameliorating alcoholic liver injury. Importantly, due to the restricted expression of IL-22R1, IL-22 therapy is expected to have few side effects, thus making IL-22 a potential candidate for treatment of alcoholic liver disease.

Interleukin-22 is frequently expressed in small- and large-cell lung cancer and promotes growth in chemotherapy-resistant cancer cells

INTRODUCTION

In lung cancer, interleukin-22 (IL-22) expression within primary tissue has been demonstrated, but the frequency and the functional consequence of IL-22 signaling have not been addressed. This study aims at analyzing the cellular effects of IL-22 on lung carcinoma cell lines and the prognostic impact of IL-22 tissue expression in lung cancer patients.

METHODS

Biological effects of IL-22 signaling were investigated in seven lung cancer cell lines by Western blot, flow cytometry, real-time polymerase chain reaction, and proliferation assays. Tumor tissue specimens of two cohorts with a total of 2300 lung cancer patients were tested for IL-22 expression by immunohistochemistry. IL-22 serum concentrations were analyzed in 103 additional patients by enzyme-linked immunosorbent assay.

RESULTS

We found the IL-22 receptor 1 (IL-22-R1) to be expressed in six of seven lung cancer cell lines. However IL-22 signaling was functional in only four cell lines, where IL-22 induced signal transducer activator of transcription 3 phosphorylation and increased cell proliferation. Furthermore, IL-22 induced the expression of antiapoptotic B-cell lymphoma 2, but did not rescue tumor cells from carboplatin-induced apoptosis. Cisplatin-resistant cell lines showed a significant up-regulation of IL-22-R1 along with a stronger proliferative response to IL-22 stimulation. IL-22 was preferentially expressed in small- and large-cell lung carcinoma (58% and 46% of cases, respectively). However, no correlation between IL-22 expression by immunohistochemistry and prognosis was observed.

CONCLUSION

IL-22 is frequently expressed in lung cancer tissue. Enhanced IL-22-R1 expression and signaling in chemotherapy-refractory cell lines are indicative of a protumorigenic function of IL-22 and may contribute to a more aggressive phenotype.

IL-22 in tissue-protective therapy

IL-22, a member of the IL-10 cytokine family, has recently gained significant attention as a protective agent in murine models of diseases driven by epithelial injury. Like its biochemical and functional sibling IL-10, IL-22 elicits cellular activation primarily by engaging the STAT3 signalling pathway. Exclusively produced by leukocytes, but targeting mostly cells of epithelial origin, IL-22 has been proposed as a specialized cytokine messenger acting between leukocytic and non-leukocytic cell compartments. A lack of response in leukocytes to IL-22 mirrors tightly controlled IL-22 receptor expression and probably explains the apparent lack of instant adverse effects after systemic IL-22 administration to mice. Anti-apoptotic, pro-proliferative and pro-regenerative characteristics the major biological properties of this cytokine. Specifically, application of IL-22 is associated with tissue protection and/or regeneration in murine models of infection/microbe-driven inflammation at host/environment interfaces, ventilator-induced lung injury, pancreatitis and liver damage. Overall, preclinical studies would support therapeutic administration of seemingly well-tolerated recombinant IL-22 for treatment of an array of acute diseases manifested in epithelial tissues. However, the feasibility of prolonged administration of this cytokine is expected to be restricted by the tumourigenic potential of the IL-22/STAT3 axis. IL-22, moreover, apparently displays an inherent context-specific capacity to amplify distinct aspects of autoimmune inflammation. Here, the prospects, expectations and restrictions of IL-22 administration in tissue-protective therapy are discussed.

Application of interleukin-22 mediates protection in experimental acetaminophen-induced acute liver injury

Acetaminophen (APAP, paracetamol)-induced hepatotoxicity, although treatable by timely application of N-acetylcysteine, can be fatal. Because it is among the common causes of acute liver failure in intensive care units and in light of its gradually increasing incidence, the need for novel therapeutic strategies aimed at severe intoxication is apparent. Recently, it has been shown that IL-22, a STAT3-activating cytokine, has the capability to mediate liver protection. Herein, the protective potential of IL-22 in murine APAP-induced hepatotoxicity was assessed. Intravenous administration of prophylactic IL-22 significantly reduced serum alanine aminotransferase levels and histopathologic damage in APAP-induced liver injury, a process that coincided with increased hepatocyte proliferation in vivo. Concomitant gene expression analysis revealed hepatic induction of genes prototypically up-regulated by the IL-22/STAT3 axis, among others suppressor of cytokine signaling-3, lipocalin-2, and α1-antichymotrypsin. Notably, in a translational setting of therapeutic treatment 2 hours after APAP, IL-22 supported protection in the context of suboptimal N-acetylcysteine dosing. IL-22 likewise connected to augmented hepatocyte proliferation in this experimental setting. As detected by analysis of inflammatory cytokine production, systemically applied IL-22 did not display acute immunomodulation/stimulation in otherwise untreated or endotoxemic mice. Those latter observations clearly confirm acute tolerability of systemically applied IL-22. Observations presented altogether suggest that therapeutic IL-22 administration is a conceivable tissue-protective regimen aimed at hard-to-treat patients with severe APAP-induced hepatotoxicity.

Pro-Inflammatory Signaling by IL-10 and IL-22: Bad Habit Stirred Up by Interferons?

Interleukin (IL)-10 and IL-22 are key members of the IL-10 cytokine family that share characteristic properties such as defined structural features, usage of IL-10R2 as one receptor chain, and activation of signal transducer and activator of transcription (STAT)-3 as dominant signaling mode. IL-10, formerly known as cytokine synthesis inhibitory factor, is key to deactivation of monocytes/macrophages and dendritic cells. Accordingly, pre-clinical studies document its anti-inflammatory capacity. However, the outcome of clinical trials assessing the therapeutic potential of IL-10 in prototypic inflammatory disorders has been disappointing. In contrast to IL-10, IL-22 acts primarily on non-leukocytic cells, in particular epithelial cells of intestine, skin, liver, and lung. STAT3-driven proliferation, anti-apoptosis, and anti-microbial tissue protection is regarded a principal function of IL-22 at host/environment interfaces. In this hypothesis article, hidden/underappreciated pro-inflammatory characteristics of IL-10 and IL-22 are outlined and related to cellular priming by type I interferon. It is tempting to speculate that an inherent inflammatory potential of IL-10 and IL-22 confines their usage in tissue protective therapy and beyond that determines in some patients efficacy of type I interferon treatment.

IFNα converts IL-22 into a cytokine efficiently activating STAT1 and its downstream targets

Besides their antiviral activity, type I Interferons (IFN) display context-specific immunomodulation. In contrast to long-known IFNα/β, Interleukin (IL)-22 is an anti-bacterial, largely tissue protective cytokine that recently gained attention. Herein, cellular IFNα/IL-22 interactions are investigated. We report that pre-conditioning of epithelial cells with IFNα initiated dramatic changes in IL-22 signaling normally dominated by signal transducer and activator of transcription (STAT)-3. Specifically, by using human DLD1 colon epithelial/carcinoma cells we demonstrate that, upon IFNα, IL-22 converts into a cytokine robustly activating STAT1 and its downstream pro-inflammatory targets CXCL9, CXCL10, and inducible nitric oxide synthase (iNOS). Accordingly, only after IFNα pre-incubation was IL-22-induced STAT1 binding to the CXCL10 promoter detectable. Using the viral mimic polyinosinic:polycytidylic acid and the IFNα/β antagonist B18R we furthermore demonstrate the capability of endogenous IFN to promote IL-22-induced STAT1 activation and expression of CXCL10. IL-22-induced STAT1 activation subsequent to IFNα priming became likewise apparent in human Caco2 colon epithelial/carcinoma cells, HepG2 hepatoma cells, and primary keratinocytes. Current observations may relate to characteristics of IFNα/β in clinical therapy and expose margins of tissue protection by IL-22 application.

Inflammation in alcoholic liver disease

Frank Burr Mallory's landmark observation in 1911 on the histopathology of alcoholic liver disease (ALD) was the first identification of a link between inflammation and ALD. In this review, we summarize recent advances regarding the origins and roles of various inflammatory components in ALD. Metabolism of ethanol generates a number of metabolites, including acetate, reactive oxygen species, acetaldehyde, and epigenetic changes, that can induce inflammatory responses. Alcohol and its metabolites can also initiate and aggravate inflammatory conditions by promoting gut leakiness of microbial products, by sensitizing immune cells to stimulation, and by activating innate immune pathways, such as complement. Chronic alcohol consumption also sensitizes nonimmune cells, e.g., hepatocytes, to inflammatory signals and impairs their ability to respond to protective signals. Based on these advances, a number of inflammatory targets have been identified with potential for therapeutic intervention in ALD, presenting new opportunities and challenges for translational research.

Hepatoprotective and anti-inflammatory cytokines in alcoholic liver disease

The activation of innate immunity by various factors (e.g. lipopolysaccharide and complements) plays an important role in initiating and promoting alcoholic liver injury via the stimulation of Kupffer cells to induce oxidative stress and to produce pro-inflammatory cytokines (e.g. tumor necrosis factor [TNF]-α) that cause hepatocellular damage. Accumulating evidence suggests that the activation of innate immunity also stimulates Kupffer cells to produce the hepatoprotective cytokine interleukin-6 (IL-6) and the anti-inflammatory cytokine IL-10 during alcoholic liver injury. IL-6 protects against alcoholic liver injury via the activation of signal transducer and activator of transcription 3 (STAT3) and the subsequent induction of a variety of hepatoprotective genes in hepatocytes. IL-10 inhibits alcoholic liver inflammation via the activation of STAT3 in Kupffer cells/macrophages and the subsequent inhibition of liver inflammation. Recent studies have suggested that IL-10 may play a dual role in controlling ethanol-induced steatosis and liver injury via the inhibition of the pro-inflammatory cytokine TNF-α, thereby ameliorating alcoholic liver injury, or via the inhibition of the hepatoprotective cytokine IL-6, thereby potentiating alcoholic liver injury. IL-22 is another important hepatoprotective cytokine that protects against acute and chronic alcoholic liver injury by binding to a receptor complex composed of IL-10R2 and IL-22R chains on the surfaces of hepatocytes. Finally, IL-22 treatment is a potential therapeutic option for treating severe forms of alcoholic liver disease because of its antioxidant, antiapoptotic, antisteatotic, proliferative, and antimicrobial effects, as well as the potential added benefit of few side effects.