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

Mechanism of Action of Dihydroquercetin in the Prevention and Therapy of Experimental Liver Injury

Liver disease is a global health problem that affects the well-being of tens of thousands of people. Dihydroquercetin (DHQ) is a flavonoid compound derived from various plants. Furthermore, DHQ has shown excellent activity in the prevention and treatment of liver injury, such as the inhibition of hepatocellular carcinoma cell proliferation after administration, the normalization of oxidative indices (like SOD, GSH) in this tissue, and the down-regulation of pro-inflammatory molecules (such as IL-6 and TNF-α). DHQ also exerts its therapeutic effects by affecting molecular pathways such as NF-κB and Nrf2. This paper discusses the latest research progress of DHQ in the treatment of various liver diseases (including viral liver injury, drug liver injury, alcoholic liver injury, non-alcoholic liver injury, fatty liver injury, and immune liver injury). It explores how to optimize the application of DHQ to improve its effectiveness in treating liver diseases, which is valuable for preparing potential therapeutic drugs for human liver diseases in conjunction with DHQ.

Deciphering Acetaminophen-Induced Hepatotoxicity: The Crucial Role of Transcription Factors like Nuclear Factor Erythroid 2-Related Factor 2 as Genetic Determinants of Susceptibility to Drug-Induced Liver Injury

Acetaminophen (APAP) is the most commonly used over-the-counter medication throughout the world. At therapeutic doses, APAP has potent analgesic and antipyretic effects. The efficacy and safety of APAP are influenced by multifactorial processes dependent upon dosing, namely frequency and total dose. APAP poisoning by repeated ingestion of supratherapeutic doses, depletes glutathione stores in the liver and other organs capable of metabolic bioactivation, leading to hepatocellular death due to exhausted antioxidant defenses. Numerous genes, encompassing transcription factors and signaling pathways, have been identified as playing pivotal roles in APAP toxicity, with the liver being the primary organ studied due to its central role in APAP metabolism and injury. Nuclear factor erythroid 2-related factor 2 (NRF2) and its array of downstream responsive genes are crucial in counteracting APAP toxicity. NRF2, along with its negative regulator Kelch-like ECH-associated protein 1, plays a vital role in regulating intracellular redox homeostasis. This regulation is significant in modulating the oxidative stress, inflammation, and hepatocellular death induced by APAP. In this review, we provide an updated overview of the mechanisms through which NRF2 activation and signaling critically influence the threshold for developing APAP toxicity. We also describe how genetically modified rodent models for NRF2 and related genes have been pivotal in underscoring the significance of this antioxidant response pathway. While NRF2 is a primary focus, the article comprehensively explores other genetic factors involved in phase I and phase II metabolism of APAP, inflammation, oxidative stress, and related pathways that contribute to APAP toxicity, thereby providing a holistic understanding of the genetic landscape influencing susceptibility to this condition. SIGNIFICANCE STATEMENT: This review summarizes the genetic elements and signaling pathways underlying APAP-induced liver toxicity, focusing on the crucial protective role of the transcription factor NRF2. This review also delves into the genetic intricacies influencing APAP safety and potential liver harm. It also emphasizes the need for deeper insight into the molecular mechanisms of hepatotoxicity, especially the interplay of NRF2 with other pathways.

Celastrol-loaded biomimetic nanodrug ameliorates APAP-induced liver injury through modulating macrophage polarization

Drug-induced liver injury (DILI) is a major concern in clinical treatment as well as postmarketing surveillance, showing an urgent requirement for the development of protective medications. Celastrol (Cel), a highly active natural product extracted from the roots of Tripterygium wilfordii, has a potential liver protective activity due to its antioxidant and anti-inflammatory effects. However, the further application of Cel to DILI remains a challenge because of its short half-life, low solubility, and toxic side effects. Herein, we developed a Cel-loaded biomimetic nanodrug based on erythrocyte membrane vesicles (EMV) for protecting the liver from acetaminophen (APAP)-induced liver injury. The Cel-loaded EMV (C-EMV) with lower cytotoxicity had a well-sustained release effect and exhibited excellent ability for liver accumulation under physiological and pathological conditions. By suppressing the inflammatory response of pro-inflammatory macrophage M1 polarization while stimulating anti-inflammatory macrophage M2 polarization, C-EMV could significantly alleviate the primary pathological manifestations related to liver injury, including aberrant elevation of biochemical indicators, histopathological alterations, neutrophil infiltration as well as hepatocyte DNA fragmentation. The macrophage depletion experiment further demonstrated that the protective effect of C-EMV on APAP-induced liver injury appeared to be dependent on hepatic macrophages. Therefore, C-EMV as a biomimetic nanodrug exhibits great potential for attenuating the progress of DILI, providing a new approach to protecting the liver from DILI as well as other liver inflammatory diseases through a targeted nanodelivery system. KEY MESSAGES: EMV biomimetic nanocarrier has good monodispersity and sustained-release property. EMV biomimetic nanocarrier displays excellent liver-targeting capability under physiological and pathological conditions. C-EMV biomimetic nanodrug with lower cytotoxicity regulates macrophage polarization in vitro and in vivo. C-EMV biomimetic nanodrug can significantly alleviate APAP-induced liver injury. The protective effect of C-EMV on APAP-induced liver injury is dependent on hepatic macrophages.

Gut inflammation and adaptive immunity amplify acetaminophen toxicity in bowel and liver

BACKGROUND AND AIM

Prevention of liver failure arising from accidental or deliberate paracetamol (acetaminophen [APAP]) overdose remains a vexed health problem despite well-publicized guidelines for its early detection and treatment. It is recognized that the gut may aggravate liver pathology, via the gut-liver axis. The main aim of this study was to assess the role of the colon in APAP-induced liver toxicity.

METHODS

Liver necrosis and colitis were studied following sublethal doses of APAP administered intraperitoneally to C57Bl/6 wild-type (WT) mice, as well as to C57Bl/6 Winnie mice, which develop a spontaneous colitis caused by a SNP in Muc2, and WT mice with acute DSS-induced colitis. Repeated APAP exposure was studied in WT and Rag1 ko mice that lack mature T and B lymphocytes.

RESULTS

APAP overdose resulted in significant colonic injury in WT mice (P < 0.05), which resolved by 24 h. Underlying colitis was not associated with liver necrosis, but colitis exacerbated APAP-induced liver injury and extended APAP-colonic injury. Prior APAP exposure exacerbated both APAP-liver and APAP-colonic injury more so in WT than Rag1 ko mice. APAP impaired barrier function with increased intestinal permeability and associated bacterial translocation to the liver and spleen in mice with the Winnie phenotype.

CONCLUSIONS

This study identifies novel roles for APAP in causing colitis, the amplification of APAP-liver toxicity where there is underlying colitis, and involvement of immune memory in APAP-toxicity. The latter could be key for decoding the poorly understood but important clinical entity of chronic APAP liver failure.

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.

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.

Targeting innate immune responses to attenuate acetaminophen-induced hepatotoxicity

Acetaminophen (APAP) hepatotoxicity is an important cause of acute liver failure, resulting in massive deaths in many developed countries. Currently, the metabolic process of APAP in the body has been well studied. However, the underlying mechanism of APAP-induced liver injury remains elusive. Increasing clinical and experimental evidences indicate that the innate immune responses are involved in the pathogenesis of APAP-induced acute liver injury (AILI), in which immune cells have dual roles of inducing inflammation to exacerbate hepatotoxicity and removing dead cells and debris to help liver regeneration. In this review, we summarize the latest findings of innate immune cells involved in AILI, particularly emphasizing the activation of innate immune cells and their different roles during the injury and repair phases. Moreover, current available treatments are discussed according to the different roles of innate immune cells in the development of AILI. This review aims to update the knowledge about innate immune responses in the pathogenesis of AILI, and provide potential therapeutic interventions for AILI.

Naringin alleviates acetaminophen-induced acute liver injury by activating Nrf2 via CHAC2 upregulation

Severe acetaminophen (APAP)-induced hepatic damage is the second most common cause for hepatic transplantation. Clinically, hepatic damage caused by APAP is treated using N-acetyl-L-cysteine, which can induce numerous side effects. Naringin, a bioflavonoid abundant in grapefruit and other citrus fruits, displays marked antiinflammatory and antioxidant activities. Herein, we aimed to investigate the potential mechanism underlying naringin-mediated protection against APAP-induced acute hepatotoxicity. We observed that naringin afforded protection against APAP-induced acute liver failure in mice. Importantly, pretreatment with naringin before APAP administration further increased antioxidant enzyme expression, inhibited the production of proinflammatory cytokines, and activated apoptotic pathways. Furthermore, we observed that the protective effect was associated with the upregulation of cation transport regulator-like protein 2 (CHAC2) and nuclear factor erythroid derived-2-related factor 2 (Nrf2). Notably, CHAC2 knockdown inhibited Nrf2 activation and naringin-mediated antioxidant, antiinflammatory, and antiapoptotic effects in APAP-induced liver injury. Likewise, si-Nrf2 blocked the protective effect of naringin against APAP-induced liver injury. Collectively, our results indicate that naringin may be a potent CHAC2 activator, alleviating APAP-induced hepatitis via CHAC2-mediated activation of the Nrf2 pathway. These data provide new insights into mechanisms through which CHAC2 regulates APAP-induced liver injury by targeting Nrf2, which should be considered a novel therapeutic target.

Targeting the sterile inflammatory response during acetaminophen hepatotoxicity with natural products

The sterile inflammatory response observed after hepatic necrosis caused by an acetaminophen (APAP) overdose has been a controversial topic for years. In a recent review, Gong et al. (2021) provided a list of studies investigating the mechanisms of inflammation during APAP-induced injury and recovery as well as those using natural products as anti-inflammatory intervention strategies in this context. However, the review lacks a critical assessment of the cited literature, which leads to the amplification of questionable mechanistic conclusions. We feel it is necessary to express our concerns regarding such superficial reviews of a scientific field, which hamper progress and are not helpful in advancing the field.