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

The Role of Cytokines in the Pathogenesis and Treatment of Alcoholic Liver Disease

Alcoholic liver disease (ALD) is a major cause of chronic liver disease. This term covers a broad spectrum of liver lesions, from simple steatosis to alcoholic hepatitis and cirrhosis. The pathogenesis of ALD is multifactorial and not fully elucidated due to complex mechanisms related to direct ethanol toxicity with subsequent hepatic and systemic inflammation. The accumulation of pro-inflammatory cytokines and the reduction of anti-inflammatory cytokines promote the development and progression of ALD. To date, there are no targeted therapies to counter the progression of chronic alcohol-related liver disease and prevent acute liver failure. Corticosteroids reduce mortality by acting on the hepatic-systemic inflammation. On the other hand, several studies analyzed the effect of inhibiting pro-inflammatory cytokines and stimulating anti-inflammatory cytokines as potential therapeutic targets in ALD. This narrative review aims to clarify the role of the main cytokines involved in the pathogenesis and treatment of ALD.

Novel treatment of acute and acute-on-chronic liver failure: Interleukin-22

Acute liver failure (ALF) is a life-threatening medical condition, characterized by rapidly progressive hepatic dysfunction, coagulopathy and hepatic encephalopathy in patients without chronic liver disease, while acute-on-chronic liver failure (ACLF) occurs in patients with existing chronic liver disease. ALF and ACLF are often associated with multiple organ failure and a high short-term mortality. In this review, we briefly discuss the causes and pathogenesis of ALF and ACLF, the current options available for the treatment of both deadly maladies and interleukin-22 (IL-22), a novel promising drug that may have great therapeutic potential for ALF and ACLF treatment. IL-22 is a cytokine produced by immune cells but mainly targets epithelial cells including hepatocytes. IL-22 has been shown to protect against organ damage and reduce bacterial infection in many preclinical models and several clinical trials including alcohol-associated hepatitis. The potential application of IL-22 for the treatment of ALF and ACLF is also elaborated.

The immunological mechanisms and therapeutic potential in drug-induced liver injury: lessons learned from acetaminophen hepatotoxicity

Acute liver failure caused by drug overdose is a significant clinical problem in developed countries. Acetaminophen (APAP), a widely used analgesic and antipyretic drug, but its overdose can cause acute liver failure. In addition to APAP-induced direct hepatotoxicity, the intracellular signaling mechanisms of APAP-induced liver injury (AILI) including metabolic activation, mitochondrial oxidant stress and proinflammatory response further affect progression and severity of AILI. Liver inflammation is a result of multiple interactions of cell death molecules, immune cell-derived cytokines and chemokines, as well as damaged cell-released signals which orchestrate hepatic immune cell infiltration. The immunoregulatory interplay of these inflammatory mediators and switching of immune responses during AILI lead to different fate of liver pathology. Thus, better understanding the complex interplay of immune cell subsets in experimental models and defining their functional involvement in disease progression are essential to identify novel therapeutic targets for the treatment of AILI. Here, this present review aims to systematically elaborate on the underlying immunological mechanisms of AILI, its relevance to immune cells and their effector molecules, and briefly discuss great therapeutic potential based on inflammatory mediators.

Oxidative stress mediates end-organ damage in a novel model of acetaminophen-toxicity in Drosophila

Acetaminophen is the most common cause of acute drug-induced liver injury in the United States. However, research into the mechanisms of acetaminophen toxicity and the development of novel therapeutics is hampered by the lack of robust, reproducible, and cost-effective model systems. Herein, we characterize a novel Drosophila-based model of acetaminophen toxicity. We demonstrate that acetaminophen treatment of Drosophila results in similar pathophysiologic alterations as those observed in mammalian systems, including a robust production of reactive oxygen species, depletion of glutathione, and dose-dependent mortality. Moreover, these effects are concentrated in the Drosophila fat body, an organ analogous to the mammalian liver. Utilizing this system, we interrogated the influence of environmental factors on acetaminophen toxicity which has proven difficult in vertebrate models due to cost and inter-individual variability. We find that both increasing age and microbial depletion sensitize Drosophila to acetaminophen toxicity. These environmental influences both alter oxidative stress response pathways in metazoans. Indeed, genetic and pharmacologic manipulations of the antioxidant response modify acetaminophen toxicity in our model. Taken together, these data demonstrate the feasibility of Drosophila for the study of acetaminophen toxicity, bringing with it an ease of genetic and microbiome manipulation, high-throughput screening, and availability of transgenic animals.

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

BACKGROUND & AIMS

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Molecular pathogenesis of acetaminophen-induced liver injury and its treatment options

Acetaminophen, also known as N-acetyl-p-aminophenol (APAP), is commonly used as an antipyretic and analgesic agent. APAP overdose can induce hepatic toxicity, known as acetaminophen-induced liver injury (AILI). However, therapeutic doses of APAP can also induce AILI in patients with excessive alcohol intake or who are fasting. Hence, there is a need to understand the potential pathological mechanisms underlying AILI. In this review, we summarize three main mechanisms involved in the pathogenesis of AILI: hepatocyte necrosis, sterile inflammation, and hepatocyte regeneration. The relevant factors are elucidated and discussed. For instance, N-acetyl-p-benzoquinone imine (NAPQI) protein adducts trigger mitochondrial oxidative/nitrosative stress during hepatocyte necrosis, danger-associated molecular patterns (DAMPs) are released to elicit sterile inflammation, and certain growth factors contribute to liver regeneration. Finally, we describe the current potential treatment options for AILI patients and promising novel strategies available to researchers and pharmacists. This review provides a clearer understanding of AILI-related mechanisms to guide drug screening and selection for the clinical treatment of AILI patients in the future.

3'mRNA sequencing reveals pro-regenerative properties of c5ar1 during resolution of murine acetaminophen-induced liver injury

Murine acetaminophen-induced acute liver injury (ALI) serves as paradigmatic model for drug-induced hepatic injury and regeneration. As major cause of ALI, acetaminophen overdosing is a persistent therapeutic challenge with N-acetylcysteine clinically used to ameliorate parenchymal necrosis. To identify further treatment strategies that serve patients with poor N-acetylcysteine responses, hepatic 3′mRNA sequencing was performed in the initial resolution phase at 24 h/48 h after sublethal overdosing. This approach disclosed 45 genes upregulated (≥5-fold) within this time frame. Focusing on C5aR1, we observed in C5aR1-deficient mice disease aggravation during resolution of intoxication as evidenced by increased liver necrosis and serum alanine aminotransferase. Moreover, decreased hepatocyte compensatory proliferation and increased caspase-3 activation at the surroundings of necrotic cores were detectable in C5aR1-deficient mice. Using a non-hypothesis-driven approach, herein pro-regenerative/-resolving effects of C5aR1 were identified during late acetaminophen-induced ALI. Data concur with protection by the C5a/C5aR1-axis during hepatectomy and emphasize the complex role of inflammation during hepatic regeneration and repair.

Autophagy plays a double-edged sword role in liver diseases

As a highly evolutionarily conserved process, autophagy can be found in all types of eukaryotic cells. Such a constitutive process maintains cellular homeostasis in a wide variety of cell types through the encapsulation of damaged proteins or organelles into double-membrane vesicles. Autophagy not only simply eliminates materials but also serves as a dynamic recycling system that produces new building blocks and energy for cellular renovation and homeostasis. Previous studies have primarily recognized the role of autophagy in the degradation of dysfunctional proteins and unwanted organelles. However, there are findings of autophagy in physiological and pathological processes. In hepatocytes, autophagy is not only essential for homeostatic functions but also implicated in some diseases, such as viral hepatitis, alcoholic hepatitis, and hepatic failure. In the present review, we summarized the molecular mechanisms of autophagy and its role in several liver diseases and put forward several new strategies for the treatment of liver disease.

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.

Exogenous activation of toll-like receptor 5 signaling mitigates acetaminophen-induced hepatotoxicity in mice

Acetaminophen (APAP) poisoning is the most common cause of drug-induced acute liver injury (ALI). Our results showed that toll-like receptor 5 (TLR5) was abundantly expressed in hepatocytes and dramatically downregulated in the toxic mouse livers. Hence, we herein investigated the role of TLR5 signaling after APAP overdose. Mice were intraperitoneally (i.p.) injected with APAP to induce ALI, and then injected with flagellin at one hour after APAP administration. Flagellin attenuated APAP-induced ALI based on decreased histopathologic lesions, serum biochemical, oxidative stress, and inflammation. Furthermore, the protective effects of flagellin were abolished by TH1020 (a TLR5 antagonist) treatment. These results suggest that flagellin exerted protective effects on ALI via TLR5 activation. Mechanistically, flagellin injection promoted the translocation of nuclear factor erythroid 2-related factor 2 (Nrf2) to the nucleus in hepatocytes. Consistent with the in vivo results, flagellin increased the activation of Nrf2 in hepatocytes, resulting in decreased APAP toxicity. ML385, a selective inhibitor of Nrf2, abolished the flagellin-mediated hepatoprotective effects in damaged livers and hepatocytes. Additionally, the flagellin-induced Nrf2 translocation was dependent upon the activation of TLR5-JNK/p38 pathways. These findings suggest that TLR5 signaling-induced Nrf2 activation, at least partially, contributed to the protection against APAP-induced ALI by flagellin treatment.

Immunopathobiology and therapeutic targets related to cytokines in liver diseases

Chronic liver injury with any etiology can progress to fibrosis and the end-stage diseases cirrhosis and hepatocellular carcinoma. The progression of liver disease is controlled by a variety of factors, including liver injury, inflammatory cells, inflammatory mediators, cytokines, and the gut microbiome. In the current review, we discuss recent data on a large number of cytokines that play important roles in regulating liver injury, inflammation, fibrosis, and regeneration, with a focus on interferons and T helper (Th) 1, Th2, Th9, Th17, interleukin (IL)-1 family, IL-6 family, and IL-20 family cytokines. Hepatocytes can also produce certain cytokines (such as IL-7, IL-11, and IL-33), and the functions of these cytokines in the liver are briefly summarized. Several cytokines have great therapeutic potential, and some are currently being tested as therapeutic targets in clinical trials for the treatment of liver diseases, which are also described.

IL-22 ameliorates LPS-induced acute liver injury by autophagy activation through ATF4-ATG7 signaling

Uncontrollable inflammatory response acts as a driver of sepsis-associated liver injury (SALI). IL-22 plays an important role in regulating inflammatory responses, but its role in SALI remains unknown. The aim of the study was to assess the association of serum IL-22 with SALI in pediatric patients and to enclose the underlying mechanisms of IL-22 involved in lipopolysaccharide (LPS) - induced acute liver injury (ALI) in mice. Serum IL-22 levels in patients with SALI were significantly lower than in septic patients without liver injury, and the area under receiver operating characteristic (ROC) curve of IL-22 for discriminating SALI was 0.765 (95% CI: 0.593-0.937). Pre-administration of recombinant murine IL-22 alleviated LPS-induced ALI in mice, and serum IL-6 levels and the mRNA levels of TNF-α, IL-1β, and IL-6 in livers were decreased in response to IL-22 pre-treatment in mice. More importantly, IL-22 pre-treatment activated hepatic autophagy mediated by activating transcription factor 4 (ATF4)-autophagy-related gene 7 (ATG7) signaling in vivo and in vitro in response to LPS administration. Moreover, knockdown of ATF4 in mice aggravated LPS-induced ALI, which was associated with suppressed ATG7-related autophagy. In addition, the protective effects of IL-22 on LPS-induced ALI was partially blocked by ATF4 knockdown, which was associated with lower expression of LC3II/I in the livers of ATF4 knockdown (HT or Atf4+/-) mice compared with wild-type mice (WT or Atf4+/+) mice. In conclusion, low serum IL-22 level is associated with SALI occurrence, and IL-22 pre-administration activates autophagy in hepatocytes and protects mice against LPS-induced ALI partially related to ATF4-ATG7 signaling pathway.

GLT25D2 Is Critical for Inflammatory Immune Response to Promote Acetaminophen-Induced Hepatotoxicity by Autophagy Pathway

Acetaminophen (APAP) overdose induces hepatocyte necrosis and causes liver hepatotoxicity. Currently, the role of galactosyltransferase in APAP-induced liver injury is still unclear. This study assessed the contribution of the GLT25D2 gene, a kind of collagen galactosyltransferase, to the development of APAP-induced liver injury. This study found that the expression of GLT25D2 markedly increased first and then decreased in the liver of mice treated with APAP, however, it downregulated in the liver of APAP overdose-patients compared with normal controls. Knockout of GLT25D2 significantly ameliorated the liver injury, meanwhile, it downregulated the proinflammatory cytokines (IL-6, TNF-α) and chemokines (CXCL-10, MIG and CXCL-1) levels, however, and upregulated the anti-inflammatory cytokines (IL-22, IL-10) levels. Mechanistic explorations showed that (1) GLT25D2 knockout promoted autophagy pathway; and (2) the GLT25D2 knockout-induced autophagy selected to clear damaged mitochondria in APAP-induced liver injury by mitophagy; and (3) the autophagy intervention by Atg 7 siRNA cancelled liver protection by knockout of GLT25D2 through regulating liver inflammation. In conclusion, our study proves that the upregulated expression of GLT25D2 decreased autophagy contributing to APAP-induced hepatotoxicity by mediating the inflammatory immune regulatory mechanism.

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.

Interleukin-22 in alcoholic hepatitis and beyond

Alcoholic hepatitis (AH) is a clinical syndrome characterized by jaundice and progressive inflammatory liver injury in patients with a history of prolonged periods of excess alcohol consumption and recent heavy alcohol abuse. Severe AH is a life-threatening form of alcohol-associated liver disease with a high short-term mortality rate around 30-50% at one month from the initial presentation. A large number of pro-inflammatory mediators, metabolic pathways, transcriptional factors and epigenetic factors have been suggested to be associated with the development and progression of AH. Several factors may contribute to liver failure and mortality in patients with severe AH including hepatocyte death, inflammation, and impaired liver regeneration. Although the pathogeneses of AH have been extensively investigated and many therapeutic targets have been identified over the last five decades, no new drugs for AH have been successfully developed. In this review, we discuss interleukin-22 (IL-22) biology and its roles of anti-apoptosis, anti-fibrosis, anti-oxidation, anti-bacterial infection and regenerative stimulation in protecting against liver injury in many preclinical models including several recently developed models such as chronic-plus-binge ethanol feeding, acute-on-chronic liver failure, C-X-C motif chemokine ligand 1 plus high-fat diet-induced nonalcoholic steatohepatitis. Finally, clinical trials of IL-22 for the treatment of AH are also discussed, which showed some promising benefits for AH patients.

Interleukin-22 acts as a mitochondrial protector

Interleukin (IL)-22 has been increasingly recognized as a promising therapeutic option for various types of diseases. This commentary summarizes the novel mechanistic aspects of IL-22 for the treatment of liver diseases including the study by Chen et al. published in the recent issue of the Theranostics that elucidated the novel function of IL-22 as a mitochondrial protector for the adaptive defense against liver injury.

Autophagy: a promising process for the treatment of acetaminophen-induced liver injury

Toxicity from drugs has become an important cause of acute liver failure. Acetaminophen, a commonly used analgesic, can cause severe acute liver injury that can worsen into acute liver failure. Autophagy, a protective cell programme, has been reported to have protective effects in a variety of diseases such as cancer, immune diseases, neurodegenerative diseases, and inflammatory diseases. In this review, we describe how an excess of acetaminophen causes liver injury step by step, from the formation of the initial protein adduct to the final hepatocyte necrosis, as well as the induction of autophagy and its beneficial effects on diseases. Emphasis is placed on the potential effect of autophagy on improving the damage of acetaminophen to hepatocytes. Finally, we are committed to providing insights into the treatment of acute liver failure through the mechanism of acetaminophen induced liver injury, the mechanism of autophagy, and the link between autophagy and liver injury.

Janus kinase-dependent regulation of drug detoxifying protein expression by interleukin-22 in human hepatic cells

Interleukin (IL)-22 is a cytokine up-regulated in inflammatory situations and known to exert various hepatic effects. The potential impact of IL-22 towards liver drug detoxifying proteins remains nevertheless unknown, but may be important to determine owing to the well-established alterations of liver detoxification occuring during inflammation. The present study was therefore designed to analyze the effects of IL-22 towards drug metabolizing enzyme and drug transporter expression and activity in cultured human hepatic cells. Exposure of differentiated hepatoma HepaRG cells or primary human hepatocytes to 10 ng/mL IL-22 was found to repress mRNA expression of cytochrome P-450 (CYP) 1A2, CYP3A4, CYP2B6 and CYP2C9 and of the sinusoidal sodium-taurocholate co-transporting polypeptide (NTCP); such IL-22 effects were concentration-dependent for CYP3A4 (IC50 = 1.7 ng/mL), CYP2B6 (IC50 = 0.9 ng/mL) and NTCP (IC50 = 1.8 ng/mL). Activity of CYP1A2 (phenacetin O-deethylation), CYP3A4 (midazolam hydroxylation) and CYP2B6 (bupropion hydroxylation), as well as that of NTCP (taurocholate uptake) were concomitantly decreased in IL-22-treated HepaRG cells; by contrast, activity of organic anion transporter polypeptides (OATPs) (estrone-3-sulfate uptake) and of organic cation transporter (OCT) 1 (tetra-ethylammonium uptake) remained unchanged. IL-22 was next found to activate the Janus kinase (JAK)/signal transducer and activator of transcription (STAT) 3 pathway, whose inhibition by the JAK inhibitor ruxolitinib fully prevented the IL-22-mediated CYP3A4, CYP2B6 and NTCP repression in HepaRG cells. This JAK-dependent down-regulation of hepatic drug detoxifying proteins, notably of CYPs, by IL-22 may contribute to alteration of pharmacokinetics in patients suffering from acute and chronic inflammatory diseases and may be the source of drug-drug interactions.

Mechanisms and pathophysiological significance of sterile inflammation during acetaminophen hepatotoxicity

Acetaminophen (APAP) is a widely used analgesic drug, which can cause severe liver injury after an overdose. The intracellular signaling mechanisms of APAP-induced cell death such as reactive metabolite formation, mitochondrial dysfunction and nuclear DNA fragmentation have been extensively studied. Hepatocyte necrosis releases damage-associated molecular patterns (DAMPs) which activate cytokine and chemokine formation in macrophages. These signals activate and recruit neutrophils, monocytes and other leukocytes into the liver. While this sterile inflammatory response removes necrotic cell debris and promotes tissue repair, the capability of leukocytes to also cause tissue injury makes this a controversial topic. This review summarizes the literature on the role of various DAMPs, cytokines and chemokines, and the pathophysiological function of Kupffer cells, neutrophils, monocytes and monocyte-derived macrophages, and NK and NKT cells during APAP hepatotoxicity. Careful evaluation of results and experimental designs of studies dealing with the inflammatory response after APAP toxicity provide very limited evidence for aggravation of liver injury but support of the hypothesis that these leukocytes promote tissue repair. In addition, many cytokines and chemokines modulate tissue injury by affecting the intracellular signaling events of cell death rather than toxicity of leukocytes. Reasons for the controversial results in this area are also discussed.

IL-18/IL-18BP and IL-22/IL-22BP: Two interrelated couples with therapeutic potential

Interleukin (IL)-18 and IL-22 are key components of cytokine networks that play a decisive role in (pathological) inflammation, host defense, and tissue regeneration. Tight regulation of cytokine-driven signaling, inflammation, and immunoactivation is supposed to enable nullification of a given deleterious trigger without mediating overwhelming collateral tissue damage or even activating a cancerous face of regeneration. In fact, feedback regulation by specific cytokine opponents is regarded as a major means by which the immune system is kept in balance. Herein, we shine a light on the interplay between IL-18 and IL-22 and their opponents IL-18 binding protein (IL-18BP) and IL-22BP in order to provide integrated information on their biology, pathophysiological significance, and prospect as targets and/or instruments of therapeutic intervention.

Vitamin D protects against oxidative stress, inflammation and hepatorenal damage induced by acute paracetamol toxicity in rat

Acute paracetamol (APAP) toxicity is a leading cause of liver, and less commonly renal, injuries through oxidative stress and inflammation. Albeit vitamin D (VD) is a well-known anti-oxidant and anti-inflammatory hormone, there is no report on its potential protective/therapeutic actions against APAP acute toxicity. This study, therefore, measured the interplay between APAP toxicity and the hepatorenal expressions of the VD-metabolising enzymes (Cyp2R1, Cyp27b1 & cyp24a1), receptor (VDR) and binding protein (VDBP) alongside the effects of VD treatment on APAP-induced hepatorenal injuries. Thirty-two male rats were distributed equally into negative (NC) and positive (PC) controls besides VD prophylactic (P-VD) and therapeutic (T-VD) groups. All groups, except the NC, received a single oral dose of APAP (1200 mg/kg). The P-VD also received by intraperitoneal injection two cycles of VD₃ (1000 IU/Kg/day; 5 days/week) prior to, and a third round after, APAP administration. Similarly, the T-VD group received VD₃ (3000 IU/Kg/day) for five successive days post-APAP intoxication. Euthanasia was on the sixth day post-APAP toxicity. The PC group had marked alterations in the hepatorenal biochemical parameters, upregulation in cellular cleaved caspase-3 as well as pronounced increase in the numbers of apoptotic/necrotic cells by TUNEL technique. The PC group plasma levels of 25-hydroxyvitamin D (25-OH VD) also declined markedly and coincided with significant inhibitions in the expression of Cyp2R1 and Cyp27b1 enzymes and VDR, whereas the VDBP and Cyp24a1 increased substantially, in the hepatorenal tissues at the gene and protein levels compared with the NC group. Coherently, the lipid peroxidation marker (MDA) and pro-inflammatory cytokines (IL1β, IL6, IL17A, IFN-γ & TNF-α) augmented significantly, while the anti-oxidative markers (GSH, GPx & CAT) and anti-inflammatory cytokines (IL10 & IL22) diminished substantially, in the PC hepatorenal tissues. Both VD regimens alleviated the APAP-induced hepatorenal damages and restored the 25-OH VD levels together with the hepatorenal expression of Cyp2R1, Cyp27b1, Cyp24a1, VDR and VDBP. Additionally, MDA and all the targeted pro-inflammatory cytokines declined, whereas all the anti-oxidative and anti-inflammatory markers increased, in both VD groups hepatorenal tissues and the results were significantly different than the PC group. Although the P-VD anti-inflammatory and anti-oxidative stress actions were more pronounced than the T-VD group, the results remained markedly abnormal than the NC group. In conclusion, this report is the first to reveal that the circulatory VD levels alongside the hepatorenal VD-metabolising enzymes and VDR are pathologically altered following acute APAP toxicity. Moreover, the prophylactic protocol showed better anti-oxidative and anti-inflammatory effects than the therapeutic regimen against APAP-induced hepatorenal injuries.

Integrative proteomics and immunochemistry analysis of the factors in the necrosis and repair in acetaminophen-induced acute liver injury in mice

Acetaminophen (APAP) overdose-induced acute liver injury (AILI) is a significant clinical problem worldwide, the hepatotoxicity mechanisms are well elucidated, but the factors involved in the necrosis and repair still remain to be investigated. APAP was injected intraperitoneally in male Institute of Cancer Research (ICR) mice. Quantitative proteome analysis of liver tissues was performed by 2-nitrobenzenesulfenyl tagging, two-dimensional-nano high-performance liquid chromatography separation, and matrix-assisted laser desorption/ionization-time of flight mass spectrometry analysis. Diffrenetial proteins were verified by the immunochemistry method. 36 and 44 differentially expressed proteins were identified, respectively, at 24 hr after APAP (200 or 300 mg·kg ^-1 ) administration. The decrease in the mitochondrial protective proteins Prdx6, Prdx3, and Aldh2 accounted for the accumulation of excessive reactive oxygen species (ROS) and aldehydes, impairing mitochondria structure and function. The Gzmf combined with Bax and Apaf-1 jointly contributed to the necrosis. The blockage of Stat3 activation led to the overexpression of unphosphorylated Stat3 and the overproduction of Bax. The overexpression of unphosphorylated Stat3 represented necrosis; the alternation from Stat3 to p-Stat3 in necrotic regions represented hepatocytes from death to renewal. The high expressions of P4hα1, Ncam, α-SMA, and Cygb were involved in the liver repair, they were not only the markers of activated HSC but also represented an intermediate stage of hepatocytes from damage or necrosis to renewal. Our data provided a comprehensive report on the profile and dynamic changes of the liver proteins in AILI; the involvement of Gzmf and the role of Stat3 in necrosis were revealed; and the role of hepatocyte in liver self-repair was well clarified.

Enhanced Regeneration and Hepatoprotective Effects of Interleukin 22 Fusion Protein on a Predamaged Liver Undergoing Partial Hepatectomy

Liver ischemia-reperfusion injury (IRI) and regeneration deficiency are two major challenges for surgery patients with chronic liver disease. As a survival factor for hepatocytes, interleukin 22 (IL-22) plays an important role in hepatoprotection and the promotion of regeneration after hepatectomy. In this study, we aim to investigate the roles of an interleukin 22 fusion protein (IL-22-FP) in mice with a predamaged liver after a two-third partial hepatectomy (PHx). Predamaged livers in mice were induced by concanavalin A (ConA)/carbon tetrachloride (CCl4) following PHx with or without IL-22-FP treatment. A hepatic IRI mouse model was also used to determine the hepatoprotective effects of IL-22-FP. In the ConA/CCl4 model, IL-22-FP treatment alleviated liver injury and accelerated hepatocyte proliferation. Administration of IL-22-FP activated the hepatic signal transducer and activator of transcription 3 (STAT3) and upregulated the expression of many mitogenic proteins. IL-22-FP treatment prior to IRI effectively reduced liver damage through decreased aminotransferase and improved liver histology. In conclusion, IL-22-FP promotes liver regeneration in mice with predamaged livers following PHx and alleviates IRI-induced liver injury. Our study suggests that IL-22-FP may represent a promising therapeutic drug against regeneration deficiency and liver IRI in patients who have undergone PHx.

Enhanced autophagy contributes to protective effects of IL-22 against acetaminophen-induced liver injury

Acute or acute-on-chronic liver failure is a leading cause of death in liver diseases without effective treatment. Interleukin-22 (IL-22) is currently in clinical trials for the treatment of severe alcoholic hepatitis, but the underlying mechanisms remain to be explored. Autophagy plays a critical role in alleviating liver injury. The aim of the current study is to explore the role of autophagy in IL-22-mediated hepato-protective effect against acetaminophen (APAP)-induced liver injury. Methods: A model of acute liver injury induced by APAP was used in vivo. IL-22 was administrated to the APAP-treated mice. Hepatocytes were pre-incubated with IL-22, followed by exposure to APAP for in vitro analyses. Results: IL-22 administration significantly reduced serum ALT and AST, hepatic reactive oxygen species, and liver necrosis in APAP-challenged mice. APAP treatment increased hepatic autophagosomes, which was further intensified by IL-22 co-treatment. Hepatic LC3-II was moderately upregulated after APAP administration without obvious alteration of phosphorylation of AMP-activated kinase (p-AMPK). IL-22 pretreatment significantly upregulated hepatic LC3-II and p-AMPK in APAP-treated mice. IL-22 also alleviated APAP-induced cytotoxicity and upregulated LC3-II and p-AMPK expression in cultured hepatocytes treated with APAP in vitro. When p-AMPK was blocked with compound C (an AMPK inhibitor), IL-22-mediated LC3-II conversion and protection against APAP-induced cytotoxicity was weakened. Conclusions: Enhanced AMPK-dependent autophagy contributes to protective effects of IL-22 against APAP-induced liver injury.

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.

A Prominent Role of Interleukin-18 in Acetaminophen-Induced Liver Injury Advocates Its Blockage for Therapy of Hepatic Necroinflammation

Acetaminophen [paracetamol, N-acetyl-p-aminophenol (APAP)]-induced acute liver injury (ALI) not only remains a persistent clinical challenge but likewise stands out as well-characterized paradigmatic model of drug-induced liver damage. APAP intoxication associates with robust hepatic necroinflammation the role of which remains elusive with pathogenic but also pro-regenerative/-resolving functions being ascribed to leukocyte activation. Here, we shine a light on and put forward a unique role of the interleukin (IL)-1 family member IL-18 in experimental APAP-induced ALI. Indeed, amelioration of disease as previously observed in IL-18-deficient mice was further substantiated herein by application of the IL-18 opponent IL-18-binding protein (IL-18BPd:Fc) to wild-type mice. Data altogether emphasize crucial pathological action of this cytokine in APAP toxicity. Adding recombinant IL-22 to IL-18BPd:Fc further enhanced protection from liver injury. In contrast to IL-18, the role of prototypic pro-inflammatory IL-1 and tumor necrosis factor-α is controversially discussed with lack of effects or even protective action being repeatedly reported. A prominent detrimental function for IL-18 in APAP-induced ALI as proposed herein should relate to its pivotal role for hepatic expression of interferon-γ and Fas ligand, both of which aggravate APAP toxicity. As IL-18 serum levels increase in patients after APAP overdosing, targeting IL-18 may evolve as novel therapeutic option in those hard-to-treat patients where standard therapy with N-acetylcysteine is unsuccessful. Being a paradigmatic experimental model of ALI, current knowledge on ill-fated properties of IL-18 in APAP intoxication likewise emphasizes the potential of this cytokine to serve as therapeutic target in other entities of inflammatory liver diseases.

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.

Biochemical targets of drugs mitigating oxidative stress via redox-independent mechanisms

Acute or chronic oxidative stress plays an important role in many pathologies. Two opposite approaches are typically used to prevent the damage induced by reactive oxygen and nitrogen species (RONS), namely treatment either with antioxidants or with weak oxidants that up-regulate endogenous antioxidant mechanisms. This review discusses options for the third pharmacological approach, namely amelioration of oxidative stress by 'redox-inert' compounds, which do not inactivate RONS but either inhibit the basic mechanisms leading to their formation (i.e. inflammation) or help cells to cope with their toxic action. The present study describes biochemical targets of many drugs mitigating acute oxidative stress in animal models of ischemia-reperfusion injury or N-acetyl-p-aminophenol overdose. In addition to the pro-inflammatory molecules, the targets of mitigating drugs include protein kinases and transcription factors involved in regulation of energy metabolism and cell life/death balance, proteins regulating mitochondrial permeability transition, proteins involved in the endoplasmic reticulum stress and unfolded protein response, nuclear receptors such as peroxisome proliferator-activated receptors, and isoprenoid synthesis. The data may help in identification of oxidative stress mitigators that will be effective in human disease on top of the current standard of care.

Engineered fibroblast growth factor 19 protects from acetaminophen-induced liver injury and stimulates aged liver regeneration in mice

The liver displays a remarkable regenerative capacity triggered upon tissue injury or resection. However, liver regeneration can be overwhelmed by excessive parenchymal destruction or diminished by pre-existing conditions hampering repair. Fibroblast growth factor 19 (FGF19, rodent FGF15) is an enterokine that regulates liver bile acid and lipid metabolism, and stimulates hepatocellular protein synthesis and proliferation. FGF19/15 is also important for liver regeneration after partial hepatectomy (PH). Therefore recombinant FGF19 would be an ideal molecule to stimulate liver regeneration, but its applicability may be curtailed by its short half-life. We developed a chimaeric molecule termed Fibapo in which FGF19 is covalently coupled to apolipoprotein A-I. Fibapo retains FGF19 biological activities but has significantly increased half-life and hepatotropism. Here we evaluated the pro-regenerative activity of Fibapo in two clinically relevant models where liver regeneration may be impaired: acetaminophen (APAP) poisoning, and PH in aged mice. The only approved therapy for APAP intoxication is N-acetylcysteine (NAC) and no drugs are available to stimulate liver regeneration. We demonstrate that Fibapo reduced liver injury and boosted regeneration in APAP-intoxicated mice. Fibapo improved survival of APAP-poisoned mice when given at later time points, when NAC is ineffective. Mechanistically, Fibapo accelerated recovery of hepatic glutathione levels, potentiated cell growth-related pathways and increased functional liver mass. When Fibapo was administered to old mice prior to PH, liver regeneration was markedly increased. The exacerbated injury developing in these mice upon PH was attenuated, and the hepatic biosynthetic capacity was enhanced. Fibapo reversed metabolic and molecular alterations that impede regeneration in aged livers. It reduced liver steatosis and downregulated p21 and hepatocyte nuclear factor 4 α (Hnf4α) levels, whereas it stimulated Foxm1b gene expression. Together our findings indicate that FGF19 variants retaining the metabolic and growth-promoting effects of this enterokine may be valuable for the stimulation of liver regeneration.

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.

Type I Interferon Supports Inducible Nitric Oxide Synthase in Murine Hepatoma Cells and Hepatocytes and during Experimental Acetaminophen-Induced Liver Damage

Cytokine regulation of high-output nitric oxide (NO) derived from inducible NO synthase (iNOS) is critically involved in inflammation biology and host defense. Herein, we set out to characterize the role of type I interferon (IFN) as potential regulator of hepatic iNOS in vitro and in vivo. In this regard, we identified in murine Hepa1-6 hepatoma cells a potent synergism between pro-inflammatory interleukin-β/tumor necrosis factor-α and immunoregulatory IFNβ as detected by analysis of iNOS expression and nitrite release. Upregulation of iNOS by IFNβ coincided with enhanced binding of signal transducer and activator of transcription-1 to a regulatory region at the murine iNOS promoter known to support target gene expression in response to this signaling pathway. Synergistic iNOS induction under the influence of IFNβ was confirmed in alternate murine Hepa56.1D hepatoma cells and primary hepatocytes. To assess iNOS regulation by type I IFN in vivo, murine acetaminophen (APAP)-induced sterile liver inflammation was investigated. In this model of acute liver injury, excessive necroinflammation drives iNOS expression in diverse liver cell types, among others hepatocytes. Herein, we demonstrate impaired iNOS expression in type I IFN receptor-deficient mice which associated with diminished APAP-induced liver damage. Data presented indicate a vital role of type I IFN within the inflamed liver for fine-tuning pathological processes such as overt iNOS expression.

Hypothermia Promotes Interleukin-22 Expression and Fine-Tunes Its Biological Activity

Disturbed homeostasis as a result of tissue stress can provoke leukocyte responses enabling recovery. Since mild hypothermia displays specific clinically relevant tissue-protective properties and interleukin (IL)-22 promotes healing at host/environment interfaces, effects of lowered ambient temperature on IL-22 were studied. We demonstrate that a 5-h exposure of endotoxemic mice to 4°C reduces body temperature by 5.0° and enhances splenic and colonic il22 gene expression. In contrast, tumor necrosis factor-α and IL-17A were not increased. In vivo data on IL-22 were corroborated using murine splenocytes and human peripheral blood mononuclear cells (PBMC) cultured upon 33°C and polyclonal T cell activation. Upregulation by mild hypothermia of largely T-cell-derived IL-22 in PBMC required monocytes and associated with enhanced nuclear T-cell nuclear factor of activated T cells (NFAT)-c2. Notably, NFAT antagonism by cyclosporin A or FK506 impaired IL-22 upregulation at normothermia and entirely prevented its enhanced expression upon hypothermic culture conditions. Data suggest that intact NFAT signaling is required for efficient IL-22 induction upon normothermic and hypothermic conditions. Hypothermia furthermore boosted early signal transducer and activator of transcription 3 activation by IL-22 and shaped downstream gene expression in epithelial-like cells. Altogether, data indicate that hypothermia supports and fine-tunes IL-22 production/action, which may contribute to regulatory properties of low ambient temperature.

Hypoxic modulation of hepatocyte responses to the cytokine interleukin-22

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

Cooperation between the bacterial-derived short-chain fatty acid butyrate and interleukin-22 detected in human Caco2 colon epithelial/carcinoma cells

By generating biologically active factors luminal microbiota shape the intestinal micro-milieu thereby regulating pathological processes such as inflammation and carcinogenesis. Preclinical data suggest that bacterial-derived butyrate and the signal transducer and activator of transcription (STAT)-3 activating cytokine interleukin (IL)-22 display concordant protective properties at the inflamed colonic epithelium. Herein, biochemical cooperation between the short-chain fatty acid butyrate and IL-22 was investigated by focusing on human Caco2 colon epithelial/carcinoma cells. We report that physiological levels of butyrate enhance IL-22 signaling thereby enforcing expression of the prototypic STAT3-downstrean target genes α1-antichymotrypsin and suppressor of cytokine signaling (SOCS)-3. A dual mode of butyrate action on the IL-22/STAT3 axis was identified. Butyrate acted by upregulating IL-22R1, the decisive chain of the heterodimeric IL-22 receptor, and, independent from that, has the potential to directly amplify STAT3-mediated gene activation as detected by chromatin immunoprecipitation analysis of STAT3 binding to the SOCS3 promoter. Since trichostatin A acted similarly, inhibition of histone deacetylases is likely at the root of these butyrate biological properties. The mutual benefit gained from interactions between the host and commensal intestinal bacteria-derived factors is an expanding field of research beginning to affect clinical practice. Data presented herein propose a supportive and fine-tuning role for butyrate in IL-22 signaling that might be therapeutically exploited by local butyrate administration or by increasing its bacterial production in the context of a fiber-rich diet. © 2016 BioFactors, 43(2):283-292, 2017.

Chlorogenic acid inhibits cholestatic liver injury induced by α-naphthylisothiocyanate: involvement of STAT3 and NFκB signalling regulation

OBJECTIVES

Chlorogenic acid (CGA) is one of the most widely consumed polyphenols in diets and is recognized to be a natural hepatoprotective agent. Here, we evaluated the protective effect and the potential mechanism of CGA against ɑ-naphthylisothiocyanate (ANIT)-induced cholestasis and liver injury.

METHODS

Twenty-five male 129/Sv mice were administered with CGA, and ANIT challenge was performed at 75 mg/kg on the 4th day. Blood was collected and subjected to biochemical analysis; the liver tissues were examined using histopathological analysis and signalling pathways.

KEY FINDINGS

Chlorogenic acid almost totally attenuated the ANIT-induced liver damage and cholestasis, compared with the ANIT group. Dose of 50 mg/kg of CGA significantly prevented ANIT-induced changes in serum levels of alanine aminotransferase, alkaline phosphatases, total bile acid, direct bilirubin, indirect bilirubin (5.3-, 6.3-, 18.8-, 158-, 41.4-fold, P<0.001) and aspartate aminotransferase (4.6-fold, P<0.01). Expressions of the altered bile acid metabolism and transport-related genes were normalized by cotreatment with CGA. The expressions of interleukin 6, tumour necrosis factor-α and suppressor of cytokine signalling 3 were found to be significantly decreased (1.2-fold, ns; 11.0-fold, P<0.01; 4.4-fold, P<0.05) in the CGA/ANIT group. Western blot revealed that CGA inhibited the activation and expression of signal transducer and activator of transcription 3 and NFκB.

CONCLUSIONS

These data suggest that CGA inhibits both ANIT-induced intrahepatic cholestasis and the liver injury. This protective effect involves down-regulation of STAT3 and NFκB signalling.

Interleukin-22 ameliorates acute severe pancreatitis-associated lung injury in mice

AIM

To investigate the potential protective effect of exogenous recombinant interleukin-22 (rIL-22) on L-arginine-induced acute severe pancreatitis (SAP)-associated lung injury and the possible signaling pathway involved.

METHODS

Balb/c mice were injected intraperitoneally with L-arginine to induce SAP. Recombinant mouse IL-22 was then administered subcutaneously to mice. Serum amylase levels and myeloperoxidase (MPO) activity in the lung tissue were measured after the L-arginine administration. Histopathology of the pancreas and lung was evaluated by hematoxylin and eosin (HE) staining. Expression of B cell lymphoma/leukemia-2 (Bcl-2), Bcl-xL and IL-22RA1 mRNAs in the lung tissue was detected by real-time PCR. Expression and phosphorylation of STAT3 were analyzed by Western blot.

RESULTS

Serum amylase levels and MPO activity in the lung tissue in the SAP group were significantly higher than those in the normal control group (P < 0.05). In addition, the animals in the SAP group showed significant pancreatic and lung injuries. The expression of Bcl-2 and Bcl-xL mRNAs in the SAP group was decreased markedly, while the IL-22RA1 mRNA expression was increased significantly relative to the normal control group (P < 0.05). Pretreatment with PBS did not significantly affect the serum amylase levels, MPO activity or expression of Bcl-2, Bcl-xL or IL-22RA1 mRNA (P > 0.05). Moreover, no significant differences in the degrees of pancreatic and lung injuries were observed between the PBS and SAP groups. However, the serum amylase levels and lung tissue MPO activity in the rIL-22 group were significantly lower than those in the SAP group (P < 0.05), and the injuries in the pancreas and lung were also improved. Compared with the PBS group, rIL-22 stimulated the expression of Bcl-2, Bcl-xL and IL-22RA1 mRNAs in the lung (P < 0.05). In addition, the ratio of p-STAT3 to STAT3 protein in the rIL-22 group was significantly higher than that in the PBS group (P < 0.05).

CONCLUSION

Exogenous recombinant IL-22 protects mice against L-arginine-induced SAP-associated lung injury by enhancing the expression of anti-apoptosis genes through the STAT3 signaling pathway.

The Effects of IL-22 on the Inflammatory Mediator Production, Proliferation, and Barrier Function of HUVECs

The aim of this study was to investigate the effects of interleukin (IL)-22 on proliferation function and inflammatory mediator production and barrier function of human umbilical vein endothelial cells (HUVECs). The expression of mRNA was detected by RT-PCR. The proliferation ability of cells was evaluated using a cell counting kit assay. Real-time quantitative PCR and Western blot were used to detect the expression of inflammatory mediators. The endothelial barrier permeability was assessed by measuring permeability to FITC-labeled dextran. The distribution of occludin was detected by immunofluorescence. IL-22R1 mRNA expression was noted in HUVECs. IL-22 could enhance the proliferation ability of HUVECs and suppress lipopolysaccharide (LPS)-induced proliferation inhibition in these cells. IL-22 also enhanced the production of CCL2 and CCL20 by HUVECs. Besides, IL-22 could improve barrier function and decrease LPS-induced increased cellular permeability and inhibit the LPS-induced destruction of occludin in HUVECs. IL-22 may play a protective role in the development of vasculitis.

STAT3, a Key Parameter of Cytokine-Driven Tissue Protection during Sterile Inflammation - the Case of Experimental Acetaminophen (Paracetamol)-Induced Liver Damage

Acetaminophen (APAP, N-acetyl-p-aminophenol, or paracetamol) overdosing is a prevalent cause of acute liver injury. While clinical disease is initiated by overt parenchymal hepatocyte necrosis in response to the analgetic, course of intoxication is substantially influenced by associated activation of innate immunity. This process is supposed to be set in motion by release of danger-associated molecular patterns (DAMPs) from dying hepatocytes and is accompanied by an inflammatory cytokine response. Murine models of APAP-induced liver injury emphasize the complex role that DAMPs and cytokines play in promoting either hepatic pathogenesis or resolution and recovery from intoxication. Whereas the function of key inflammatory cytokines is controversially discussed, a subclass of specific cytokines capable of efficiently activating the hepatocyte signal transducer and activator of transcription (STAT)-3 pathway stands out as being consistently protective in murine models of APAP intoxication. Those include foremost interleukin (IL)-6, IL-11, IL-13, and IL-22. Above all, activation of STAT3 under the influence of these cytokines has the capability to drive hepatocyte compensatory proliferation, a key principle of the regenerating liver. Herein, the role of these specific cytokines during experimental APAP-induced liver injury is highlighted and discussed in a broader perspective. In hard-to-treat or at-risk patients, standard therapy may fail and APAP intoxication can proceed toward a fatal condition. Focused administration of recombinant STAT3-activating cytokines may evolve as novel therapeutic approach under those ill-fated conditions.

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

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

Mitigation of paracetamol-induced reproductive damage by chrysin in male rats via reducing oxidative stress

Paracetamol (PRC) is a nonsteroidal anti-inflammatory drug used widely as a painkiller for various diseases and as the symptomatic flu cure in several countries worldwide. PRC toxicity may occur under conditions of the overdose usage. Chrysin (CR) is a flavonoid that is naturally present in several plants, honey and propolis. The aim of this study was to investigate the effects of CR (at the doses of 25 mg kg^-1 and 50 mg kg^-1 ) pre-treatment over seven consecutive days against PRC-induced reproductive toxicity in male rats. Our results showed that PRC toxicity decreased the sperm motility, and increased dead sperm rate, abnormal sperm cell rate, apoptosis and MDA levels in testicular tissues. Pre-treatment with CR at the dose of 25 and 50 mg kg^-1 for 7 days mitigated side effects of acute PRC toxicity in male reproductive system proportionally in a dose-dependent manner. This possible protection mechanism might be dependent on the antioxidant activity of CR. In conclusion, pre-treatment with CR at the dose of 25 and 50 mg kg^-1 for 7 days can be the beneficial against PRC-induced reproductive toxicity proportionally in a dose-dependent manner.

Mechanisms of interleukin-22’s beneficial effects in acute pancreatitis

Acute pancreatitis (AP) is a disorder characterized by parenchymal injury of the pancreas controlled by immune cell-mediated inflammation. AP remains a significant challenge in the clinic due to a lack of specific and effective treatment. Knowledge of the complex mechanisms that regulate the inflammatory response in AP is needed for the development of new approaches to treatment, since immune cell-derived inflammatory cytokines have been recognized to play critical roles in the pathogenesis of the disease. Recent studies have shown that interleukin (IL)-22, a cytokine secreted by leukocytes, when applied in the severe animal models of AP, protects against the inflammation-mediated acinar injury. In contrast, in a mild AP model, endogenous IL-22 has been found to be a predominantly anti-inflammatory mediator that inhibits inflammatory cell infiltration via the induction of Reg3 proteins in acinar cells, but does not protect against acinar injury in the early stage of AP. However, constitutively over-expressed IL-22 can prevent the initial acinar injury caused by excessive autophagy through the induction of the anti-autophagic proteins Bcl-2 and Bcl-X_L. Thus IL-22 plays different roles in AP depending on the severity of the AP model. This review focuses on these recently reported findings for the purpose of better understanding IL-22’s regulatory roles in AP which could help to develop a novel therapeutic strategy.

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.

Tristetraprolin regulation of interleukin-22 production

Interleukin (IL)-22 is a STAT3-activating cytokine displaying characteristic AU-rich elements (ARE) in the 3'-untranslated region (3'-UTR) of its mRNA. This architecture suggests gene regulation by modulation of mRNA stability. Since related cytokines undergo post-transcriptional regulation by ARE-binding tristetraprolin (TTP), the role of this destabilizing protein in IL-22 production was investigated. Herein, we demonstrate that TTP-deficient mice display augmented serum IL-22. Likewise, IL-22 mRNA was enhanced in TTP-deficient splenocytes and isolated primary T cells. A pivotal role for TTP is underscored by an extended IL-22 mRNA half-life detectable in TTP-deficient T cells. Luciferase-reporter assays performed in human Jurkat T cells proved the destabilizing potential of the human IL-22-3'-UTR. Furthermore, overexpression of TTP in HEK293 cells substantially decreased luciferase activity directed by the IL-22-3'-UTR. Transcript destabilization by TTP was nullified upon cellular activation by TPA/A23187, an effect dependent on MEK1/2 activity. Accordingly, IL-22 mRNA half-life as determined in TPA/A23187-stimulated Jurkat T cells decreased under the influence of the MEK1/2 inhibitor U0126. Altogether, data indicate that TTP directly controls IL-22 production, a process counteracted by MEK1/2. The TTP-dependent regulatory pathway described herein likely contributes to the role of IL-22 in inflammation and cancer and may evolve as novel target for pharmacological IL-22 modulation.

Prenatal acetaminophen affects maternal immune and endocrine adaptation to pregnancy, induces placental damage, and impairs fetal development in mice

Acetaminophen (APAP; ie, Paracetamol or Tylenol) is generally self-medicated to treat fever or pain and recommended to pregnant women by their physicians. Recent epidemiological studies reveal an association between prenatal APAP use and an increased risk for asthma. Our aim was to identify the effects of APAP in pregnancy using a mouse model. Allogeneically mated C57Bl/6J females were injected i.p. with 50 or 250 mg/kg APAP or phosphate-buffered saline on gestation day 12.5; nonpregnant females served as controls. Tissue samples were obtained 1 or 4 days after injection. APAP-induced liver toxicity was mirrored by significantly increased plasma alanine aminotransferase levels. In uterus-draining lymph nodes of pregnant dams, the frequencies of mature dendritic cells and regulatory T cells significantly increased on 250 mg/kg APAP. Plasma progesterone levels significantly decreased in dams injected with APAP, accompanied by a morphologically altered placenta. Although overall litter sizes and number of fetal loss remained unaltered, a reduced fetal weight and a lower frequency of hematopoietic stem cells in the fetal liver were observed on APAP treatment. Our data provide strong evidence that prenatal APAP interferes with maternal immune and endocrine adaptation to pregnancy, affects placental function, and impairs fetal maturation and immune development. The latter may have long-lasting consequences on children's immunity and account for the increased risk for asthma observed in humans.

Disruptive chemicals, senescence and immortality

Carcinogenesis is thought to be a multistep process, with clonal evolution playing a central role in the process. Clonal evolution involves the repeated 'selection and succession' of rare variant cells that acquire a growth advantage over the remaining cell population through the acquisition of 'driver mutations' enabling a selective advantage in a particular micro-environment. Clonal selection is the driving force behind tumorigenesis and possesses three basic requirements: (i) effective competitive proliferation of the variant clone when compared with its neighboring cells, (ii) acquisition of an indefinite capacity for self-renewal, and (iii) establishment of sufficiently high levels of genetic and epigenetic variability to permit the emergence of rare variants. However, several questions regarding the process of clonal evolution remain. Which cellular processes initiate carcinogenesis in the first place? To what extent are environmental carcinogens responsible for the initiation of clonal evolution? What are the roles of genotoxic and non-genotoxic carcinogens in carcinogenesis? What are the underlying mechanisms responsible for chemical carcinogen-induced cellular immortality? Here, we explore the possible mechanisms of cellular immortalization, the contribution of immortalization to tumorigenesis and the mechanisms by which chemical carcinogens may contribute to these processes.