Interleukin-4 deficiency protects mice from acetaminophen-induced liver injury and inflammation by prevention of glutathione depletion

Good Cells Go Bad: Immune Dysregulation in the Transition from Acute Liver Injury to Liver Failure After Acetaminophen Overdose

The role of inflammatory cells and other components of the immune system in acetaminophen (APAP)-induced liver injury and repair has been extensively investigated. Although this has resulted in a wealth of information regarding the function and regulation of immune cells in the liver after injury, apparent contradictions have fueled controversy around the central question of whether the immune system is beneficial or detrimental after APAP overdose. Ultimately, this may not be a simple assignment of "good" or "bad." Clinical studies have clearly demonstrated an association between immune dysregulation and a poor outcome in patients with severe liver damage/liver failure induced by APAP overdose. To date, studies in mice have not uniformly replicated this connection. The apparent disconnect between clinical and experimental studies has perhaps stymied progress and further complicated investigation of the immune system in APAP-induced liver injury. Mouse models are often dismissed as not recapitulating the clinical scenario. Moreover, clinical investigation is most often focused on the most severe APAP overdose patients, those with liver failure. Notably, recent studies have made it apparent that the functional role of the immune system in the pathogenesis of APAP-induced liver injury is highly context dependent and greatly influenced by the experimental conditions. In this review, we highlight some of these recent findings and suggest strategies seeking to resolve and build on existing disconnects in the literature. SIGNIFICANCE STATEMENT: Acetaminophen overdose is the most frequent cause of acute liver failure in the United States. Studies indicate that dysregulated innate immunity contributes to the transition from acute liver injury to acute liver failure. In this review, we discuss the evidence for this and the potential underlying causes.

Antifibrotic activity of carbon quantum dots in a human in vitro model of non-alcoholic steatohepatitis using hepatic stellate cells

Around 33% of the global population suffers from non-alcoholic fatty liver disease (NAFLD). From these patients, 30% of them progress into non-alcoholic steatohepatitis (NASH), the critical point where lack of treatment leads to cirrhosis and hepatic failure. Moreover, to date, there are no approved therapeutic options available for NASH. It is known that hepatic stellate cell (HSC) activation contributes the most to hepatic disfunction, leading to reactive oxygen species (ROS) accumulation and chronic inflammation, and that the use of nanomaterials to deliver antioxidants may have potential to reduce the activity of activated HSCs. Therefore, we implemented a human in vitro co-culture model in which we take into consideration two factors related to NASH and fibrosis: human hepatic stellate cells from a NASH diagnosed donor (HHSC-N) and peripheral blood mononuclear cells (PBMCs), particularly lymphocytes. The co-cultures were treated with: (1) carbon quantum dots (CD) or (2) lactoferrin conjugated CD (CD-LF) for 24 h or 72 h. CD and CD-LF treatments significantly downregulated profibrotic genes' expression levels of ACTA2, COL1A1, and TIMP1 in co-cultured HHSC-N at 72 h. Also, we assayed the inflammatory response by quantifying the concentrations of cytokines IL-22, IL-10, IFN-γ and IL-4 present in the co-culture's conditioned media whose concentrations may suggest a resolution-associated response in progress. Our findings may serve as a starting point for the development of a NASH treatment using bio-nanotechnology.

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.

Inhibition of BTK improved APAP-induced liver injury via suppressing proinflammatory macrophages activation by restoring mitochondrion function

BACKGROUND

Acetaminophen (APAP) overdose can cause severe liver injury and APAP-induced liver injury (AILI) is one of the leading causes of acute liver failure (ALF). Bruton's tyrosine kinase (BTK) is a key tyrosine kinase in immune responses, which plays an important role in many inflammatory diseases. However, its effect on AILI is still not clear. Here, we aimed to assess the effect of BTK on AILI and explore its underlying mechanism.

METHODS

In our study, western blot and immunohistochemistry were used to detect the expression of BTK in AILI. The C57BL/6 mice were used to check the protective effect of BTK inhibition on AILI and the activation of BTK was confirmed in mice macrophages treated with APAP. Immunofluorescence, immunohistochemistry, oxygen consumption rate (OCR) detection, polymerase chain reaction (PCR), flow cytometry and western blot were used to determine the role of BTK in mitochondrial dynamics and function of macrophages and the underlying mechanisms in AILI.

RESULTS

Our results showed that BTK upregulated in AILI. BTK inhibition protected mice from AILI and BTK was activated in mice macrophages in response to APAP. Mechanically, BTK inhibition promoted mitochondrial fusion and restored mitochondrial function through phospholipase C gamma 2 (PLCγ2)-reactive oxygen species (ROS)-Optic Atrophy 1(OPA1) pathway in macrophages and finally suppressed the release of proinflammatory cytokines.

CONCLUSIONS

In conclusion, we found that BTK inhibition protected mice from AILI by restoring the mitochondrial function of macrophages through the improvement of the mitochondrial dynamic imbalance via PLCγ2-ROS-OPA1 signaling pathway, which indicated that BTK might be a potential therapeutic target of AILI.

The Dual Role of Innate Immune Response in Acetaminophen-Induced Liver Injury

Acetyl-para-aminophenol (APAP), a commonly used antipyretic analgesic, is becoming increasingly toxic to the liver, resulting in a high rate of acute hepatic failure in Europe and the United States. Excessive APAP metabolism in the liver develops an APAP-protein adduct, which causes oxidative stress, MPTP opening, and hepatic necrosis. HMGB-1, HSP, nDNA, mtDNA, uric acid, and ATP are DMAPs released during hepatic necrosis. DMAPs attach to TLR4-expressing immune cells such KCs, macrophages, and NK cells, activating them and causing them to secrete cytokines. Immune cells and their secreted cytokines have been demonstrated to have a dual function in acetaminophen-induced liver injury (AILI), with a role in either proinflammation or pro-regeneration, resulting in contradicting findings and some research confusion. Neutrophils, KCs, MoMFs, NK/NKT cells, γδT cells, DCs, and inflammasomes have pivotal roles in AILI. In this review, we summarize the dual role of innate immune cells involved in AILI and illustrate how these cells initiate innate immune responses that lead to persistent inflammation and liver damage. We also discuss the contradictory findings in the literature and possible protocols for better understanding the molecular regulatory mechanisms of AILI.

The dual role of immune response in acetaminophen hepatotoxicity: Implication for immune pharmacological targets

Acetaminophen (APAP), one of the most widely used antipyretic and analgesic drugs, principally contributes to drug-induced liver injury when taken at a high dose. APAP-induced liver injury (AILI) results in extensive necrosis of hepatocytes along with the occurrence of multiple intracellular events such as metabolic activation, cell injury, and signaling pathway activation. However, the specific role of the immune response in AILI remains controversial for its complicated regulatory mechanisms. A variety of inflammasomes, immune cells, inflammatory mediators, and signaling transduction pathways are activated in AILI. These immune components play antagonistic roles in aggravating the liver injury or promoting regeneration. Recent experimental studies indicated that natural products showed remarkable therapeutic effects against APAP hepatotoxicity due to their favorable efficacy. Therefore, this study aimed to review the present understanding of the immune response in AILI and attempted to establish ties among a series of inflammatory cascade reactions. Also, the immune molecular mechanisms of natural products in the treatment of AILI were extensively reviewed, thus providing a fundamental basis for exploring the potential pharmacological targets associated with immune interventions.

Protective effect of ISO-1 with inhibition of RIPK3 up-regulation and neutrophilic accumulation on acetaminophen-induced liver injury in mice

Overdose use of acetaminophen (APAP) often occurs a severe liver injury, and its liver injury is lethal in some cases. Macrophage migration inhibitory factor (MIF) is expressed in a variety of cells and has multifunctional roles. However, the role of MIF in APAP-induced liver injury has not been fully investigated. In this study, we investigated whether treatment with (S,R)-3-(4-hydroxyphenil)-4,5-dihydro-5-isoxazole acetic acid methyl ester (ISO-1), a MIF inhibitor, protected mice from acute APAP-induced liver injury. Acute liver injury was induced by injection of APAP (300 mg/kg body weight). Mice were treated with a single injection of ISO-1(15 mg/kg body weight) 1 h (h) before APAP administration. Histological, biochemical and molecular analyses were performed in liver of mice 12 h after APAP administration. ISO-1 remarkably improved the histological findings of APAP-induced liver injury in mice. The increases in serum levels of alanine aminotransferase (ALT), and macrophage inflammatory protein-2 (MIP-2) by APAP were inhibited by ISO-1. In addition, ISO-1 reduced the increased number of the myeloperoxidase-staining cells and that of TUNEL-positive staining cells in the liver of mice with APAP-induced liver injury. Up-regulation of hepatic receptor interacting protein kinase (RIPK)3 and heat shock protein70 by APAP was suppressed in the liver of mice given ISO-1. These results provide the additional evidence that inhibition of MIF activity may be clinically effective for treatment of acute APAP-induced liver injury.

Mitochondrial depolarization and repolarization in the early stages of acetaminophen hepatotoxicity in mice

Mitochondrial injury and depolarization are primary events in acetaminophen hepatotoxicity. Previous studies have shown that restoration of mitochondrial function in surviving hepatocytes, which is critical to recovery, is at least partially accomplished via biogenesis of new mitochondria. However, other studies indicate that mitochondria also have the potential to spontaneously repolarize. Although repolarization was previously observed only at a sub-hepatotoxic dose of acetaminophen, we postulated that mitochondrial repolarization in hepatocytes outside the centrilobular regions of necrosis might contribute to recovery of mitochondrial function following acetaminophen-induced injury. Our studies utilized longitudinal intravital microscopy of millimeter-scale regions of the mouse liver to characterize the spatio-temporal relationship between mitochondrial polarization and necrosis early in acetaminophen-induced liver injury. Treatment of male C57BL/6J mice with a single intraperitoneal 250 mg/kg dose of acetaminophen resulted in hepatotoxicity that was apparent histologically within 2 h of treatment, leading to 20 and 60-fold increases in serum aspartate aminotransferase and alanine aminotransferase, respectively, within 6 h. Intravital microscopy of the livers of mice injected with rhodamine123, TexasRed-dextran, propidium iodide and Hoechst 33342 detected centrilobular foci of necrosis within extended regions of mitochondrial depolarization within 2 h of acetaminophen treatment. Although regions of necrosis were more apparent 6 h after acetaminophen treatment, the vast majority of hepatocytes with depolarized mitochondria did not progress to necrosis, but rather recovered mitochondrial polarization within 6 h. Recovery of mitochondrial function following acetaminophen hepatotoxicity thus involves not only biogenesis of new mitochondria, but also repolarization of existing mitochondria. These studies also revealed a spatial distribution of necrosis and mitochondrial depolarization whose single-cell granularity is inconsistent with the hypothesis that communication between neighboring cells plays an important role in the propagation of necrosis during the early stages of APAP hepatotoxicity. Small islands of healthy, intact cells were frequently found surrounded by necrotic cells, and small islands of necrotic cells were frequently found surrounded by healthy, intact cells. Time-series studies demonstrated that these "islands", consisting in some cases of single cells, are persistent; over a period of hours, injury does not spread from individual necrotic cells to their neighbors.

IL-33 signalling in liver immune cells enhances drug-induced liver injury and inflammation

OBJECTIVE AND DESIGN

The aim of this study was to investigate the contribution of IL-33/ST2 axis in the onset and progression of acute liver injury using a mice model of drug-induced liver injury (DILI).

MATERIAL AND TREATMENTS

DILI was induced by overdose administration of acetaminophen (APAP) by oral gavage in wild-type BALB/c, ST2-deficient mice and in different bone marrow chimeras. Neutrophils were depleted by anti-Ly6G and macrophages with clodronate liposomes (CLL).

METHODS

Blood and liver were collected for biochemical, immunologic and genetic analyses. Mice were imaged by confocal intravital microscopy and liver non-parenchymal cells and hepatocytes were isolated for flow cytometry, genetic and immunofluorescence studies.

RESULTS

Acetaminophen overdose caused a massive necrosis and accumulation of immune cells within the liver, concomitantly with IL-33 and chemokine release. Liver non-parenchymal cells were the major sensors for IL-33, and amongst them, neutrophils were the major players in amplification of the inflammatory response triggered by IL-33/ST2 signalling pathway.

CONCLUSION

Blockage of IL-33/ST2 axis reduces APAP-mediated organ injury by dampening liver chemokine release and activation of resident and infiltrating liver non-parenchymal cells.

The impact of sterile inflammation in acute liver injury

BACKGROUND

The liver has a number of functions in innate immunity. These functions predispose the liver to innate immune-mediated liver injury when inflammation goes unchecked. Significant progress has been made in the last 25 years on sterile inflammatory liver injury in a number of models; however, a great deal of controversy and many questions about the nature of sterile inflammation still exist.

AIM

The goal of this article is to review sterile inflammatory liver injury using both a basic approach to what constitutes the inflammatory injury, and through examination of current models of liver injury and inflammation. This information will be tied to human patient conditions when appropriate.

RELEVANCE FOR PATIENTS

Inflammation is one of the most critical factors for managing in-patient liver disease in a number of scenarios. More information is needed for both scientists and clinicians to develop rational treatments.

Tributyltin chloride induces renal dysfunction by inflammation and oxidative stress in female rats

Tributyltin chloride (TBT) is an organometallic pollutant that is used as a biocide in antifouling paints. TBT induces several toxic and endocrine-disrupting effects. However, studies evaluating the effects of TBT on renal function are rare. This study demonstrates that TBT exposure is responsible for improper renal function as well as the development of abnormal morphophysiology in mammalian kidneys. Female rats were treated with TBT, and their renal morphophysiology was assessed. Morphophysiological abnormalities such as decreased glomerular filtration rate and increased proteinuria levels were observed in TBT rats. In addition, increases in inflammation, collagen deposition and α-smooth muscle actin (α-SMA) protein expression were observed in TBT kidneys. A disrupted cellular redox balance and apoptosis in kidney tissue were also observed in TBT rats. TBT rats demonstrated reduced serum estrogen levels and estrogen receptor-α (ERα) protein expression in renal cortex. Together, these data provide in vivo evidence that TBT is toxic to normal renal function and that these effects may be associated with renal histopathology complications, such as inflammation and fibrosis.

Assessing the Effect of Leptin on Liver Damage in Case of Hepatic Injury Associated with Paracetamol Poisoning

Background Aim. In case of high-dose acetaminophen intake, the active metabolite can not bind to the glutathione, thereby inducing cellular necrosis through binding to the cytosol proteins. This trial was performed to histologically and biochemically investigate whether leptin was protective against liver damage induced by paracetamol at toxic doses. Material and Method. In our trial, 30 female rats, divided into 5 groups, were used. IP leptin administration was performed after an hour in the group of rats, in which paracetamol poisoning was induced. The groups were as follows: Group 1: the control group, Group 2: 20 µg/kg leptin, Group 3: 2 g/kg paracetamol, Group 4: 2 g/kg paracetamol + 10 µg/kg leptin, and Group 5: 2 g/kg paracetamol + 20 µg/kg leptin. Results. The most significant increase was observed in the PARA 2 g/kg group, while the best improvement among the treatment groups occurred in the PARA 2 g/kg + LEP 10 µg/kg group (p < 0.05). While the most significant glutathione (GSH) reduction was observed in the PARA 2 g/kg group, the best improvement was in the PARA 2 g/kg + LEP 10 µg/kg group (p < 0.05). Conclusion. Liver damage occurring upon paracetamol poisoning manifests with hepatocyte breakdown occurring as a result of inflammation and oxidative stress. Leptin can prevent this damage thanks to its antioxidant and anti-inflammatory efficacy.

Understanding liver immunology using intravital microscopy

The liver has come a long way since it was considered only a metabolic organ attached to the gastrointestinal tract. The simultaneous ascension of immunology and intravital microscopy evidenced the liver as a central axis in the immune system, controlling immune responses to local and systemic agents as well as disease tolerance. The multiple hepatic cell populations are organized in a vascular environment that promotes intimate cellular interactions, including initiation of innate and adaptive immune responses, rapid leukocyte recruitment, pathogen clearance and production of a variety of immune mediators. In this review, we focus on the advances in liver immunology supported by intravital microscopy in diseases such as isquemia/reperfusion, acute liver injury and infections.

Cannabidiol rescues acute hepatic toxicity and seizure induced by cocaine

Cocaine is a commonly abused illicit drug that causes significant morbidity and mortality. The most severe and common complications are seizures, ischemic strokes, myocardial infarction, and acute liver injury. Here, we demonstrated that acute cocaine intoxication promoted seizure along with acute liver damage in mice, with intense inflammatory infiltrate. Considering the protective role of the endocannabinoid system against cell toxicity, we hypothesized that treatment with an anandamide hydrolysis inhibitor, URB597, or with a phytocannabinoid, cannabidiol (CBD), protects against cocaine toxicity. URB597 (1.0 mg/kg) abolished cocaine-induced seizure, yet it did not protect against acute liver injury. Using confocal liver intravital microscopy, we observed that CBD (30 mg/kg) reduced acute liver inflammation and damage induced by cocaine and prevented associated seizure. Additionally, we showed that previous liver damage induced by another hepatotoxic drug (acetaminophen) increased seizure and lethality induced by cocaine intoxication, linking hepatotoxicity to seizure dynamics. These findings suggest that activation of cannabinoid system may have protective actions on both liver and brain induced by cocaine, minimizing inflammatory injury promoted by cocaine, supporting its further clinical application in the treatment of cocaine abuse.

Drug-induced hepatotoxicity: metabolic, genetic and immunological basis

Drug-induced hepatotoxicity is a significant cause of acute liver failure and is usually the primary reason that therapeutic drugs are removed from the commercial market. Multiple mechanisms can culminate in drug hepatotoxicity. Metabolism, genetics and immunology separately and in concert play distinct and overlapping roles in this process. This review will cover papers we feel have addressed these mechanisms of drug-induced hepatotoxicity in adults following the consumption of commonly used medications. The aim is to generate discussion around "trigger point" papers where the investigators generated new science or provided additional contribution to existing science. Hopefully these discussions will assist in uncovering key areas that need further attention.