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

Targeting cathepsin C ameliorates murine acetaminophen-induced liver injury

Acetaminophen (APAP) overdosing is a major cause of acute liver failure worldwide and an established model for drug-induced acute liver injury (ALI). While studying gene expression during murine APAP-induced ALI by 3'mRNA sequencing (massive analysis of cDNA ends, MACE), we observed splenic mRNA accumulation encoding for the neutrophil serine proteases cathepsin G, neutrophil elastase, and proteinase-3 - all are hierarchically activated by cathepsin C (CtsC). This, along with increased serum levels of these proteases in diseased mice, concurs with the established phenomenon of myeloid cell mobilization during APAP intoxication. Objective: In order to functionally characterize CtsC in murine APAP-induced ALI, effects of its genetic or pharmacological inhibition were investigated. Methods and Results: We report on substantially reduced APAP toxicity in CtsC deficient mice. Alleviation of disease was likewise observed by treating mice with the CtsC inhibitor AZD7986, both in short-term prophylactic and therapeutic protocols. This latter observation indicates a mode of action beyond inhibition of granule-associated serine proteases. Protection in CtsC knockout or AZD7986-treated wildtype mice was unrelated to APAP metabolization but, as revealed by MACE, realtime PCR, or ELISA, associated with impaired expression of inflammatory genes with proven pathogenic roles in ALI. Genes consistently downregulated in protocols tested herein included cxcl2, mmp9, and angpt2. Moreover, ptpn22, a positive regulator of the toll-like receptor/interferon-axis, was reduced by targeting CtsC. Conclusions: This work suggests CtsC as promising therapeutic target for the treatment of ALI, among others paradigmatic APAP-induced ALI. Being also currently evaluated in phase III clinical trials for bronchiectasis, successful application of AZD7986 in experimental APAP intoxication emphasizes the translational potential of this latter therapeutic approach.

Unveiling the flames: macrophage pyroptosis and its crucial role in liver diseases

Macrophages play a critical role in innate immunity, with approximately 90% of the total macrophage population in the human body residing in the liver. This population encompasses both resident and infiltrating macrophages. Recent studies highlight the pivotal role of liver macrophages in various aspects such as liver inflammation, regeneration, and immune regulation. A novel pro-inflammatory programmed cell death, pyroptosis, initially identified in macrophages, has garnered substantial attention since its discovery. Studies investigating pyroptosis and inflammation progression have particularly centered around macrophages. In liver diseases, pyroptosis plays an important role in driving the inflammatory response, facilitating the fibrotic process, and promoting tumor progression. Notably, the role of macrophage pyroptosis cannot be understated. This review primarily focuses on the role of macrophage pyroptosis in liver diseases. Additionally, it underscores the therapeutic potential inherent in targeting macrophage pyroptosis.

Research progress on rodent models and its mechanisms of liver injury

The liver is the most important organ for biological transformation in the body and is crucial for maintaining the body's vital activities. Liver injury is a serious pathological condition that is commonly found in many liver diseases. It has a high incidence rate, is difficult to cure, and is prone to recurrence. Liver injury can cause serious harm to the body, ranging from mild to severe fatty liver disease. If the condition continues to worsen, it can lead to liver fibrosis and cirrhosis, ultimately resulting in liver failure or liver cancer, which can seriously endanger human life and health. Therefore, establishing an rodent model that mimics the pathogenesis and severity of clinical liver injury is of great significance for better understanding the pathogenesis of liver injury patients and developing more effective clinical treatment methods. The author of this article summarizes common chemical liver injury models, immune liver injury models, alcoholic liver injury models, drug-induced liver injury models, and systematically elaborates on the modeling methods, mechanisms of action, pathways of action, and advantages or disadvantages of each type of model. The aim of this study is to establish reliable rodent models for researchers to use in exploring anti-liver injury and hepatoprotective drugs. By creating more accurate theoretical frameworks, we hope to provide new insights into the treatment of clinical liver injury diseases.

Sterile liver injury induces a protective tissue-resident cDC1-ILC1 circuit through cDC1-intrinsic cGAS-STING-dependent IL-12 production

Tissue-resident immune cells are critical to the initiation and potentiation of inflammation. However, the tissue-protective cellular communication networks initiated by resident immunity during sterile inflammation are not well understood. Using single-cell transcriptomic analysis, we show the liver-resident cell connectome and signalome during acute liver injury. These analyses identify Il12b as a central regulator of liver injury-associated changes in gene expression. Interleukin (IL)-12 produced by conventional type 1 dendritic cells (cDC1s) is required for protection during acute injury through activation of interferon (IFN)-γ production by liver-resident type 1 innate lymphoid cells (ILC1s). Using a targeted in vivo CRISPR-Cas9 screen of innate immune sensing pathways, we find that cDC1-intrinsic cGAS-STING signaling acts upstream of IL-12 production to initiate early protective immune responses. Our study identifies the core communication hubs initiated by tissue-resident innate immune cells during sterile inflammation in vivo and implicates cDC1-derived IL-12 as an important regulator of this process.

Therapeutic Perspectives of IL1 Family Members in Liver Diseases: An Update

Interleukin (IL) 1 superfamily members are a cornerstone of a variety of inflammatory processes occurring in various organs including the liver. Progression of acute and chronic liver diseases regardless of etiology depends on the stage of hepatocyte damage, the release of inflammatory cytokines and disturbances in gut microbiota. IL1 cytokines and receptors can have pro- or anti-inflammatory roles, even dual functionalities conditioned by the microenvironment. Developing novel therapeutic strategies to block the IL1/IL1R signaling pathways seems like a reasonable option. This mode of action is now exploited by anakinra and canakinumab, which are used to treat different inflammatory illnesses, and studies in liver diseases are on the way. In this mini review, we have focused on the IL1 superfamily members, given their crucial role in liver inflammation diseases, specifically discussing their potential role in developing new treatment strategies.

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.

Liver alterations are not improved by inulin supplementation in alcohol use disorder patients during alcohol withdrawal: A pilot randomized, double-blind, placebo-controlled study

Background

Emerging evidence highlights that targeting the gut microbiota could be an interesting approach to improve alcohol liver disease due to its important plasticity. This study aimed to evaluate the effects of inulin supplementation on liver parameters in alcohol use disorder (AUD) patients (whole sample) and in a subpopulation with early alcohol-associated liver disease (eALD).

Methods

Fifty AUD patients, hospitalized for a 3-week detoxification program, were enrolled in a randomized, double-blind, placebo-controlled study and assigned to prebiotic (inulin) versus placebo for 17 days. Liver damage, microbial translocation, inflammatory markers and 16S rDNA sequencing were measured at the beginning (T1) and at the end of the study (T2).

Findings

Compared to placebo, AST (β = 8.55, 95% CI [2.33:14.77]), ALT (β = 6.01, 95% CI [2.02:10.00]) and IL-18 (β = 113.86, 95% CI [23.02:204.71]) were statistically significantly higher in the inulin group in the whole sample at T2. In the eALD subgroup, inulin supplementation leads to specific changes in the gut microbiota, including an increase in Bifidobacterium and a decrease of Bacteroides. Despite those changes, AST (β = 14.63, 95% CI [0.91:28.35]) and ALT (β = 10.40, 95% CI [1.93:18.88]) at T2 were higher in the inulin group compared to placebo. Treatment was well tolerated without important adverse events or side effects.

Interpretation

This pilot study shows that 17 days of inulin supplementation versus placebo, even though it induces specific changes in the gut microbiota, did not alleviate liver damage in AUD patients. Further studies with a larger sample size and duration of supplementation with adequate monitoring of liver parameters are needed to confirm these results. Gut2Brain study: https://clinicaltrials.gov/ct2/show/NCT03803709

Funding

Fédération Wallonie-Bruxelles, FRS-FNRS, Fondation Saint-Luc.

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.

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.

Drug-induced liver injury and prospect of cytokine based therapy; A focus on IL-2 based therapies

Drug-induced liver injury (DILI) is one of the most frequent sources of liver failure and the leading cause of liver transplant. Common non-prescription medications such as non-steroidal anti-inflammatory drugs (NSAIDs), acetaminophen, and other prescription drugs when taken at more than the recommended doses may lead to DILI. The severity of DILI is affected by factors such as age, ethnicity, race, gender, nutritional status, on-going liver diseases, renal function, pregnancy, alcohol consumption, and drug-drug interactions. Characteristics of DILI-associated inflammation include apoptosis and necrosis of hepatocytes and hepatic infiltration of pro-inflammatory immune cells. If untreated or if the inflammation continues, DILI and associated hepatic inflammation may lead to development of hepatocarcinoma. The therapeutic approach for DILI-associated hepatic inflammation depends on whether the inflammation is acute or chronic. Discontinuing the causative medication, vaccination, and special dietary supplementation are some of the conventional approaches to treat DILI. In this review, we discuss a concise overview of DILI-associated liver complications, and current therapeutic options with special emphasis on biologics including the scope of cytokine therapy in hepatic repair and resolution of inflammation caused by over- the-counter (OTC) or prescription drugs.

Immune-Mediated Drug-Induced Liver Injury: Immunogenetics and Experimental Models

Drug-induced liver injury (DILI) is a challenging clinical event in medicine, particularly because of its ability to present with a variety of phenotypes including that of autoimmune hepatitis or other immune mediated liver injuries. Limited diagnostic and therapeutic tools are available, mostly because its pathogenesis has remained poorly understood for decades. The recent scientific and technological advancements in genomics and immunology are paving the way for a better understanding of the molecular aspects of DILI. This review provides an updated overview of the genetic predisposition and immunological mechanisms behind the pathogenesis of DILI and presents the state-of-the-art experimental models to study DILI at the pre-clinical level.

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.

Study on the protective effect and mechanism of Dicliptera chinensis (L.) Juss (Acanthaceae) polysaccharide on immune liver injury induced by LPS

The purpose of this study is to use Dicliptera chinensis (L.) Juss (Acanthaceae) polysaccharide (DCP) to act on the NF-κB inflammatory pathway and Fas/FasL ligand system, in order to find a new method to improve immune liver injury. Lipopolysaccharide (LPS) was used to establish an injury model in vivo (Kunming mice) and in vitro (LO2 cells). In this experiment, hematoxylin-eosin (H&E) staining and related biochemical indicators were used to observe the pathological changes of liver tissues, oxidative stress and inflammatory reactions. Immunohistochemistry, ELISA, RT-PCR and Western blot were used to detect protein or mRNA expressions associated with inflammation response and apoptosis. The experimental results show that the model group has obvious liver cell damage and inflammatory infiltration. After DCP intervention, it could significantly reduce the levels of ALT, AST, ALP, TBIL and MDA in serum, and increase the content of SOD and GSH-Px. In addition, DCP can reduce the expression level of NF-κB in the liver and reduce the release of downstream inflammatory factors TNF-α, IL-6 and IL-1β, thereby reducing the inflammation. At the same time, DCP can significantly inhibit the expression of Fas/FasL ligand system and apoptosis related-proteins and mRNA, which in turn can reduce cell apoptosis. In conclusion, DCP can alleviate liver injury by inhibiting liver inflammation and apoptosis, which provides a new strategy for clinical treatment of immune liver injury.

Distinct Effects of Inflammation on Cytochrome P450 Regulation and Drug Metabolism: Lessons from Experimental Models and a Potential Role for Pharmacogenetics

Personalized medicine strives to optimize drug treatment for the individual patient by taking into account both genetic and non-genetic factors for drug response. Inflammation is one of the non-genetic factors that has been shown to greatly affect the metabolism of drugs—primarily through inhibition of cytochrome P450 (CYP450) drug-metabolizing enzymes—and hence contribute to the mismatch between the genotype predicted drug response and the actual phenotype, a phenomenon called phenoconversion. This review focuses on inflammation-induced drug metabolism alterations. In particular, we discuss the evidence assembled through human in-vitro models on the effect of inflammatory mediators on clinically relevant CYP450 isoform levels and their metabolizing capacity. We also present an overview of the current understanding of the mechanistic pathways via which inflammation in hepatocytes may modulate hepatic functions that are critical for drug metabolism. Furthermore, since large inter-individual variability in response to inflammation is observed in human in-vitro models and clinical studies, we evaluate the potential role of pharmacogenetic variability in the inflammatory signaling cascade and how this can modulate the outcome of inflammation on drug metabolism and response.

Intestinal IL-17R Signaling Constrains IL-18-Driven Liver Inflammation by the Regulation of Microbiome-Derived Products

Interleukin (IL)-17 signaling to the intestinal epithelium regulates the intestinal microbiome. Given the reported links between intestinal dysbiosis, bacterial translocation, and liver disease, we hypothesize that intestinal IL-17R signaling plays a critical role in mitigating hepatic inflammation. To test this, we study intestinal epithelium-specific IL-17RA-deficient mice in an immune-driven hepatitis model. At the naive state, these mice exhibit microbiome dysbiosis and increased translocation of bacterial products (CpG DNA), which drives liver IL-18 production. Upon disease induction, absence of enteric IL-17RA signaling exacerbates hepatitis and hepatocyte cell death. IL-18 is necessary for disease exacerbation and is associated with increased activated hepatic lymphocytes based on Ifng and Fasl expression. Thus, intestinal IL-17R regulates translocation of TLR9 ligands and constrains susceptibility to hepatitis. These data connect enteric Th17 signaling and the microbiome in hepatitis, with broader implications on the effects of impaired intestinal immunity and subsequent release of microbial products observed in other extra-intestinal pathologies.

Castillo-dela Cruz et al. describe a unique protective role of intestinal IL-17RA in hepatitis. Disruption of intestinal IL-17RA signaling results in microbiome dysbiosis and translocation of bacterial products, specifically unmethylated CpG DNA, to the liver. This promotes IL-18 production and subsequent lymphocyte activation and cell death to exacerbate liver inflammation.

Paracetamol-induced metabolic and cardiovascular changes are prevented by exercise training

Paracetamol (PAR) is the most frequently consumed non-prescription drug, yet it is well known to induce toxicity. Here, we have evaluated the effects of exercise training on vascular dysfunction induced by PAR. Rats were distributed among four groups: (a) Sedentary; (b) Exercise; (c) Sedentary+PAR; and (d) Exercise+PAR. The exercise comprised swimming 50 min/d, 5 d/wk for 6 weeks (+PAR in the last 2 weeks, at 400 mg/kg/d/p.o.). After killing, the rats' blood and aortas were collected for biochemical analysis of hepatic transaminases, TBARs reaction, glutathione, glutathione reductase, SOD, and catalase. In vitro vascular relaxation was measured using acetylcholine and sodium nitroprusside in the presence or absence of tiron (an antioxidant). Vascular protein expression (eNOS and sGC) also were analysed. Increased transaminases after PAR treatment were found to be reduced by exercise. Vasodilation was impaired by PAR only in the sedentary group. Exercise prevented alterations in lipoperoxidation and glutathione levels after PAR exposure. Glutaathione reductase and SOD also were increased by PAR but were normalized in the exercised group. Catalase activity and protein expressions did not change in any group. PAR treatment caused impairment in both vasodilation and redox balance; however, exercise training prevented the vascular and redox system dysfunction induced by PAR treatment.

Sinomenine Attenuates Acetaminophen-Induced Acute Liver Injury by Decreasing Oxidative Stress and Inflammatory Response via Regulating TGF-β/Smad Pathway in vitro and in vivo

Introduction

Liver disease is common and often life-threatening. Sinomenine (SIN) is an active ingredient extracted from  Sinomenium acutum. This study investigated the protective effect and mechanism of sinomenine (SIN) on acetaminophen (APAP)-induced liver injury from in vitro and in vivo.

Methods

In vivo experiments, mice were randomly divided into six groups (n=10): control group, model group, SIN (25 mg/kg) group, SIN (50 mg/kg) group, SIN (100 mg/kg) group and SIN (100 mg/kg) + SRI-011381 group. Alanine transaminases (ALT), aspartate transaminases (AST) and alkaline phosphatase (ALP) were detected. The pathological lesion was measured by HE staining. Apoptosis was measured by TUNEL staining. In vitro experiments, BRL-3A cells were treated with APAP (7.5 mM) and then subjected to various doses of SIN (10, 50 and 100 μg/mL) at 37°C for 24 h. Inflammatory factors and oxidative stress index were measured by ELISA. The expression of proteins was detected by Western blot.

Results

The results showed that compared with the control group, the levels of ALT, AST and ALP in the serum of APAP-induced mice were significantly increased, followed by liver histological damage and hepatocyte apoptosis. Besides, APAP reduced the activity of SOD and GSH-Px, while increasing the content of MDA and LDH. Notably, APAP also promoted the expression of NLRP3, ASC, caspase-1 and IL-1β. Interestingly, SIN treatment dose-dependently reduced APAP-induced liver injury and oxidative stress, inhibited the activation of NLRP3 inflammasomes, and reduced the levels of inflammatory cytokines. In vitro studies have shown that SIN treatment significantly reduced the viability of BRL-3A cells and oxidative stress and inflammation. In addition, the Western blotting analysis showed that SIN inhibited the activation of TGF-β/Smad pathway in a dose-dependent manner in vitro and in vivo. These effects were significantly reversed by TGF-β/Smad activator SRI-011381 or TGF-β overexpression.

Discussion

The study indicates that SIN attenuates APAP-induced acute liver injury by decreasing oxidative stress and inflammatory response via TGF-β/Smad pathway in vitro and in vivo.

Human genetic basis of fulminant viral hepatitis

In rare cases, hepatitis A virus (HAV) and hepatitis B virus (HBV) can cause fulminant viral hepatitis (FVH), characterized by massive hepatocyte necrosis and an inflammatory infiltrate. Other viral etiologies of FVH are rarer. FVH is life-threatening, but the patients are typically otherwise healthy, and normally resistant to other microbes. Only a small minority of infected individuals develop FVH, and this is the key issue to be addressed for this disease. In mice, mouse hepatitis virus 3 (MHV3) infection is the main model for dissecting FVH pathogenesis. Susceptibility to MHV3 differs between genetic backgrounds, with high and low mortality in C57BL6 and A/J mice, respectively. FVH pathogenesis in mice is related to uncontrolled inflammation and fibrinogen deposition. In humans, FVH is typically sporadic, but rare familial forms also exist, suggesting that there may be causal monogenic inborn errors. A recent study reported a single-gene inborn error of human immunity underlying FVH. A patient with autosomal recessive complete IL-18BP deficiency was shown to have FVH following HAV infection. The mechanism probably involves enhanced IL-18- and IFN-γ-dependent killing of hepatocytes by NK and CD8 T cytotoxic cells. Proof-of-principle that FVH can be genetic is important clinically, for the affected patients and their families, and immunologically, for the study of immunity to viruses in the liver. Moreover, the FVH-causing IL18BP genotype suggests that excessive IL-18 immunity may be a general mechanism underlying FVH, perhaps through the enhancement of IFN-γ immunity.

Are Liver Pericytes Just Precursors of Myofibroblasts in Hepatic Diseases? Insights from the Crosstalk between Perivascular and Inflammatory Cells in Liver Injury and Repair

Cirrhosis, a late form of liver disease, is characterized by extensive scarring due to exacerbated secretion of extracellular matrix proteins by myofibroblasts that develop during this process. These myofibroblasts arise mainly from hepatic stellate cells (HSCs), liver-specific pericytes that become activated at the onset of liver injury. Consequently, HSCs tend to be viewed mainly as myofibroblast precursors in a fibrotic process driven by inflammation. Here, the molecular interactions between liver pericytes and inflammatory cells such as macrophages and neutrophils at the first moments after injury and during the healing process are brought into focus. Data on HSCs and pericytes from other tissues indicate that these cells are able to sense pathogen- and damage-associated molecular patterns and have an important proinflammatory role in the initial stages of liver injury. On the other hand, further data suggest that as the healing process evolves, activated HSCs play a role in skewing the initial proinflammatory (M1) macrophage polarization by contributing to the emergence of alternatively activated, pro-regenerative (M2-like) macrophages. Finally, data suggesting that some HSCs activated during liver injury could behave as hepatic progenitor or stem cells will be 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.

Interleukin-1 Family Cytokines: Keystones in Liver Inflammatory Diseases

The pyrogenic property being the first activity described, members of the interleukin-1 superfamily (IL-1α, IL-1β, IL-18, and the newest members: IL-33, IL-36, IL-37, and IL-38) are now known to be involved in several inflammatory diseases such as obesity, atherosclerosis, cancer, viral and parasite infections, and auto-inflammatory syndromes as well as liver diseases. Inflammation processes are keystones of chronic liver diseases, of which the etiology may be viral or toxic, as in alcoholic or non-alcoholic liver diseases. Inflammation is also at stake in acute liver failure involving massive necrosis, and in ischemia-reperfusion injury in the setting of liver transplantation. The role of the IL-1 superfamily of cytokines and receptors in liver diseases can be either protective or pro-inflammatory, depending on timing and the environment. Our review provides an overview of current understanding of the IL-1 family members in liver inflammation, highlighting recent key investigations, and therapeutic perspectives. We have tried to apply the concept of trained immunity to liver diseases, based on the role of the members of the IL-1 superfamily, first of all IL-1β but also IL-18 and IL-33, in modulating innate lymphoid immunity carried by natural killer cells, innate lymphoid cells or innate T-αβ lymphocytes.

No IL-18BP? Avoid HAV

Fulminant viral hepatitis occurs in a very small number of infected individuals. Until now, the basis for this phenotype has remained unknown. In this issue of JEM, Belkaya et al. (https://doi.org/10.1084/jem.20190669) identify a deletion in the IL18BP gene in a severely affected child that results in excessive natural killer cell activation and uncontrolled killing of hepatocytes.

Inherited IL-18BP deficiency in human fulminant viral hepatitis

Fulminant viral hepatitis (FVH) is a devastating and unexplained condition that strikes otherwise healthy individuals during primary infection with common liver-tropic viruses. We report a child who died of FVH upon infection with hepatitis A virus (HAV) at age 11 yr and who was homozygous for a private 40-nucleotide deletion in IL18BP, which encodes the IL-18 binding protein (IL-18BP). This mutation is loss-of-function, unlike the variants found in a homozygous state in public databases. We show that human IL-18 and IL-18BP are both secreted mostly by hepatocytes and macrophages in the liver. Moreover, in the absence of IL-18BP, excessive NK cell activation by IL-18 results in uncontrolled killing of human hepatocytes in vitro. Inherited human IL-18BP deficiency thus underlies fulminant HAV hepatitis by unleashing IL-18. These findings provide proof-of-principle that FVH can be caused by single-gene inborn errors that selectively disrupt liver-specific immunity. They also show that human IL-18 is toxic to the liver and that IL-18BP is its antidote.

Exposure to acetaminophen impairs vasodilation, increases oxidative stress and changes arterial morphology of rats

Acetaminophen (APAP) is one of the most widely consumed drugs in the world. Studies have shown renal and hepatic damage as the direct result of high oxidative stress induced by APAP. Since the cardiovascular system is sensitive to oxidative stress and literature describes increased cardiovascular dysfunction in APAP consumers, this work aimed to evaluate harmful effects of APAP on the vascular system. Rats were exposed to APAP (400 mg/kg/day in drinking water) for 14 days. Plasma and aortas were collected and stored in - 80 °C and a selection of arteries was prepared for isometric tension recordings, morphological, immunohistochemical and protein expression analysis. The APAP-treated group presented increased transaminases (ALT/AST) and malondialdehyde levels in the plasma compared to controls. Lipid peroxidation, glutathione reductase and superoxide dismutase levels were increased in the plasma and arteries of the APAP group. Nevertheless, glutathione level was reduced as compared to control group. The vasodilation response to acetylcholine and sodium nitroprusside (0.1 nM to 10 µM) was also impaired after APAP treatment; however, the vascular relaxation was restored after treatment with vitamin C (100 µM). Arteries from the APAP group presented reduced wall thickness, collagen deposition, elastic fibers and increased immunoreactivity to nitrotyrosine. eNOS and sGC protein expression remained unchanged and were at similar levels as controls. These findings showed higher oxidative stress and impaired vasodilation in rats exposed to APAP. Furthermore, arteries presented reduced cell layers, collagen, elastin deposition and significantly increased immunoreactivity to nitrotyrosine after APAP treatment.

Cytokine profiles in acute liver injury-Results from the US Drug-Induced Liver Injury Network (DILIN) and the Acute Liver Failure Study Group

Changes in levels of cytokines and chemokines have been proposed as possible biomarkers of tissue injury, including liver injury due to drugs. Recently, in acute drug-induced liver injury (DILI), we showed that 19 of 27 immune analytes were differentially expressed and that disparate patterns of immune responses were evident. Lower values of serum albumin (< 2.8 g/dL) and lower levels of only four analytes, namely, IL-9, IL-17, PDGF-bb, and RANTES, were highly predictive of early death [accuracy = 96%]. The goals of this study were to assess levels of the same 27 immune analytes in larger numbers of subjects to learn whether the earlier findings would be confirmed in new and larger cohorts of subjects, compared with a new cohort of healthy controls. We studied 127 subjects with acute DILI enrolled into the US DILIN. We also studied 118 subjects with severe acute liver injury of diverse etiologies, enrolled into the ALF SG registry of subjects. Controls comprised 63 de-identified subjects with no history of liver disease and normal liver tests. Analytes associated with poor outcomes [death before 6 months, n = 32 of the total of 232 non-acetaminophen (Apap) subjects], were lower serum albumin [2.6 vs 3.0 g/dL] and RANTES [6,458 vs 8,999 pg/mL] but higher levels of IL-6 [41 vs 18], IL-8 [78 vs 48], and MELD scores [30 vs 24]. Similar patterns were observed for outcome of death/liver transplant within 6 months. A model that included only serum albumin < 2.8 g/dL and RANTES below its median value of 11,349 had 83% (or 81%) accuracy for predicting early death (or early death/liver transplant) in 127 subjects from DILIN. No patterns of serum immune analytes were reflective of the etiologies of acute liver failure, but there were cytokine patterns that predicted prognosis in both acute DILI and ALF.