Role and mechanisms of autophagy in acetaminophen-induced liver injury

The regulation of GSH/GPX4-mediated lipid accumulation confirms that schisandra polysaccharides should be valued equally as lignans

ETHNOPHARMACOLOGICAL RELEVANCE

Acetaminophen (APAP) induced liver injury (AILI) is a common cause of clinical hepatic damage and even acute liver failure. Our previous research has shown that Schisandra chinensis lignan extract (SLE) can exert a hepatoprotective effect by regulating lipid metabolism. Although polysaccharides from Schisandra chinensis (S. chinensis), like lignans, are important components of S. chinensis, their pharmacological activity and target effects on AILI have not yet been explored.

AIM OF THE STUDY

This study aims to quantitatively reveal the role of SCP in the pharmacological activity of S. chinensis, and further explore the pharmacological components, potential action targets and mechanisms of S. chinensis in treating AILI.

MATERIALS AND METHODS

The therapeutic effect of SCP on AILI was systematically determined via comparing the efficacy of SCP and SLE on in vitro and in vivo models. Network pharmacology, molecular docking and multi-omics techniques were then used to screen and verify the action targets of S. chinensis against AILI.

RESULTS

SCP intervention could significantly improve AILI, and the therapeutic effect was comparable to that of SLE. Notably, the combination of SCP and SLE did not produce mutual antagonistic effects. Subsequently, we found that both SCP and SLE could significantly reverse the down-regulation of GPX4 caused by the APAP modeling, and then further improving lipid metabolism abnormalities.

CONCLUSIONS

Hepatoprotective effects of SCP and SLE is most correlated with their regulation of GSH/GPX4-mediated lipid accumulation. This is the first exploration of the hepatoprotective effect and potential mechanism of SCP in treating AILI, which is crucial for fully utilizing S. chinensis and developing promising AILI therapeutic agents.

Central Mechanisms of Acetaminophen Hepatotoxicity: Mitochondrial Dysfunction by Protein Adducts and Oxidant Stress

Acetaminophen (APAP) is an analgesic and antipyretic drug used worldwide, which is safe at therapeutic doses. However, an overdose can induce liver injury and even liver failure. Mechanistic studies in mice beginning with the seminal papers published by B.B. Brodie's group in the 1970s have resulted in important insight into the pathophysiology. Although the metabolic activation of APAP with generation of a reactive metabolite, glutathione depletion, and protein adduct formation are critical initiating events, more recently, mitochondria have come into focus as an important target and decision point of cell death. This review provides a comprehensive overview of the induction of mitochondrial superoxide and peroxynitrite formation and its propagation through a mitogen-activated protein kinase cascade, the mitochondrial permeability transition pore opening caused by iron-catalyzed protein nitration, and the mitochondria-dependent nuclear DNA fragmentation. In addition, the role of adaptive mechanisms that can modulate the pathophysiology, including autophagy, mitophagy, nuclear erythroid 2 p45-related factor 2 activation, and mitochondrial biogenesis, are discussed. Importantly, it is outlined how the mechanisms elucidated in mice translate to human hepatocytes and APAP overdose patients, and how this mechanistic insight explains the mechanism of action of the clinically approved antidote N-acetylcysteine and led to the recent discovery of a novel compound, fomepizole, which is currently under clinical development. SIGNIFICANCE STATEMENT: Acetaminophen (APAP)-induced liver injury is the most frequent cause of acute liver failure in western countries. Extensive mechanistic research over the last several decades has revealed a central role of mitochondria in the pathophysiology of APAP hepatotoxicity. This review article provides a comprehensive discussion of a) mitochondrial protein adducts and oxidative/nitrosative stress, b) mitochondria-regulated nuclear DNA fragmentation, c) adaptive mechanisms to APAP-induced cellular stress, d) translation of cell death mechanisms to overdose patients, and e) mechanism-based antidotes against APAP-induced liver injury.

The SIRT2-AMPK axis regulates autophagy induced by acute liver failure

This study explores the role of SIRT2 in regulating autophagy and its interaction with AMPK in the context of acute liver failure (ALF). This study investigated the effects of SIRT2 and AMPK on autophagy in ALF mice and TAA-induced AML12 cells. The results revealed that the liver tissue in ALF model group had a lot of inflammatory cell infiltration and hepatocytes necrosis, which were reduced by SIRT2 inhibitor AGK2. In comparison to normal group, the level of SIRT2, P62, MDA, TOS in TAA group were significantly increased, which were decreased in AGK2 treatment. Compared with normal group, the expression of P-PRKAA1, Becilin1 and LC3B-II was decreased in TAA group. However, AGK2 enhanced the expression of P-PRKAA1, Becilin1 and LC3B-II in model group. Overexpression of SIRT2 in AML12 cell resulted in decreased P-PRKAA1, Becilin1 and LC3B-II level, enhanced the level of SIRT2, P62, MDA, TOS. Overexpression of PRKAA1 in AML12 cell resulted in decreased SIRT2, TOS and MDA level and triggered more autophagy. In conclusion, the data suggested the link between AMPK and SIRT2, and reveals the important role of AMPK and SIRT2 in autophagy on acute liver failure.

Identification of autophagy-related signatures in nonalcoholic fatty liver disease and correlation with non-parenchymal cells of the liver

Non-alcoholic fatty liver disease (NAFLD) is a chronic hepatic disease. The incidence and prevalence of NAFLD have increased greatly in recent years, and there is still a lack of effective drugs. Autophagy plays an important role in promoting liver metabolism and maintaining liver homeostasis, and defects in autophagy levels are considered to be related to the development of NAFLD. However, the molecular mechanisms of autophagy in NAFLD still remain unknown. In this study, we identified 6 autophagy-associated hub genes using gene expression profiles obtained from the GSE48452 and GSE89632 datasets. Biomarkers were screened according to gene significance (GS) and module membership (MM) using weighted gene co-expression network analysis (WGCNA), and the immune infiltration landscape of the liver in NAFLD patients was explored using the CIBERSORT algorithm. Subsequently, we analyzed the relationship between liver non-parenchymal cells and autophagy-related hub genes using scRNA-seq data (GSE129516). Finally, we separated the NAFLD patients into two groups based on 6 hub genes by consensus clustering and screened 10 potential autophagy-related small molecules based on the cMAP database.

tBHQ mitigates fatty liver ischemia-reperfusion injury by activating Nrf2 to attenuate hepatocyte mitochondrial damage and macrophage STING activation

BACKGROUND

Liver ischemia-reperfusion (IR) injury is an inevitable pathophysiological process in various liver surgeries. Previous studies have found that IR injury is exacerbated in fatty liver due to significant hepatocellular damage and macrophage inflammatory activation, though the underlying mechanisms are not fully understood. In this study, we aim to explore the role and mechanism of Nrf2 (Nuclear factor erythroid 2-related factor 2) signaling in regulating hepatocellular damage and macrophage immune response in fatty liver IR injury.

METHODS

The study used high-fat diet-induced fatty liver mice to establish an IR model, alongside an in vitro co-culture system of primary hepatocytes and macrophages. This approach was used to examine mitochondrial dysfunction, oxidative stress, mitochondrial DNA (mtDNA) release, and activation of macrophage STING (Stimulator of interferon genes) signaling. We also conducted recovery verification using H-151 (a STING inhibitor) and tBHQ (an Nrf2 activator).

RESULTS

Compared to the control group, mice on a high-fat diet demonstrated more severe liver IR injury, as evidenced by increased histological damage, elevated liver enzyme levels, and heightened inflammatory markers. The HFD group showed significant oxidative stress and mitochondrial dysfunction and damage post-IR, as indicated by elevated levels of ROS and lipid peroxidation markers, and decreased antioxidant enzyme activity. Elevated mtDNA release from hepatocytes post-IR activated macrophage STING signaling, worsening inflammation and liver damage. However, STING signaling inhibition with H-151 in vivo or employing STING knockout macrophages significantly reduced these injuries. In-depth mechanism studies have found that the transfer of Nrf2 protein into the nucleus of liver cells after IR in fatty liver is reduced. Pre-treatment with tBHQ ameliorated liver oxidative stress, mitochondrial damage and suppressed the macrophage STING signaling activation.

CONCLUSIONS

Our study reveals a novel mechanism where the interaction between hepatocellular damage and macrophage inflammation intensifies liver IR injury in fatty liver. Enhancing Nrf2 activation to protect mitochondrial from oxidative stress damage and inhibiting macrophage STING signaling activation emerge as promising strategies for clinical intervention in fatty liver IR injury.

Deletion of Glyoxalase 1 Exacerbates Acetaminophen-Induced Hepatotoxicity in Mice

Acetaminophen (APAP) overdose triggers a cascade of intracellular oxidative stress events, culminating in acute liver injury. The clinically used antidote, N-acetylcysteine (NAC), has a narrow therapeutic window, and early treatment is essential for a satisfactory therapeutic outcome. For more versatile therapies that can be effective even at late presentation, the intricacies of APAP-induced hepatotoxicity must be better understood. Accumulation of advanced glycation end products (AGEs) and the consequent activation of the receptor for AGEs (RAGE) are considered one of the key mechanistic features of APAP toxicity. Glyoxalase 1 (Glo-1) regulates AGE formation by limiting the levels of methylglyoxal (MEG). In this study, we studied the relevance of Glo-1 in the APAP-mediated activation of RAGE and downstream cell death cascades. Constitutive Glo-1-knockout mice (GKO) and a cofactor of Glo-1, ψ-GSH, were used as tools. Our findings showed elevated oxidative stress resulting from the activation of RAGE and hepatocyte necrosis through steatosis in GKO mice treated with high-dose APAP compared to wild-type controls. A unique feature of the hepatic necrosis in GKO mice was the appearance of microvesicular steatosis as a result of centrilobular necrosis, rather than the inflammation seen in the wild type. The GSH surrogate and general antioxidant ψ-GSH alleviated APAP toxicity irrespective of the Glo-1 status, suggesting that oxidative stress is the primary driver of APAP toxicity. Overall, the exacerbation of APAP hepatotoxicity in GKO mice suggests the importance of this enzyme system in antioxidant defense against the initial stages of APAP overdose.

A Review of the Role of Caveolin-1 in Acetaminophen-Induced Liver Injury

BACKGROUND

Acetaminophen (APAP) is commonly used as an antipyretic and analgesic agent. Excessive APAP can induce liver toxicity, known as APAP-induced liver injury (ALI). The metabolism and pathogenesis of APAP have been extensively studied in recent years, and many cellular processes such as autophagy, mitochondrial oxidative stress, mitochondrial dysfunction, and liver regeneration have been identified to be involved in the pathogenesis of ALI. Caveolin-1 (CAV-1) as a scaffold protein has also been shown to be involved in the development of various diseases, especially liver disease and tumorigenesis. The role of CAV-1 in the development of liver disease and the association between them remains a challenging and uncharted territory.

SUMMARY

In this review, we briefly explore the potential therapeutic effects of CAV-1 on ALI through autophagy, oxidative stress, and lipid metabolism. Further research to better understand the mechanisms by which CAV-1 regulates liver injury will not only enhance our understanding of this important cellular process, but also help develop new therapies for human disease by targeting CAV-1 targets.

KEY MESSAGES

This review briefly summarizes the potential protective mechanisms of CAV-1 against liver injury caused by APAP.

AIM2 regulates autophagy to mitigate oxidative stress in aged mice with acute liver injury

The cytoplasmic pattern recognition receptor, absent in melanoma 2 (AIM2), detects cytosolic DNA, activating the inflammasome and resulting in pro-inflammatory cytokine production and pyroptotic cell death. Recent research has illuminated AIM2's contributions to PANoptosis and host defense. However, the role of AIM2 in acetaminophen (APAP)-induced hepatoxicity remains enigmatic. In this study, we unveil AIM2's novel function as a negative regulator in the pathogenesis of APAP-induced liver damage in aged mice, independently of inflammasome activation. AIM2-deficient aged mice exhibited heightened lipid accumulation and hepatic triglycerides in comparison to their wild-type counterparts. Strikingly, AIM2 knockout mice subjected to APAP overdose demonstrated intensified liver injury, compromised mitochondrial stability, exacerbated glutathione depletion, diminished autophagy, and elevated levels of phosphorylated c-Jun N-terminal kinase (JNK) and extracellular signal-regulated kinase (ERK). Furthermore, our investigation revealed AIM2's mitochondrial localization; its overexpression in mouse hepatocytes amplified autophagy while dampening JNK phosphorylation. Notably, induction of autophagy through rapamycin administration mitigated serum alanine aminotransferase levels and reduced the necrotic liver area in AIM2-deficient aged mice following APAP overdose. Mechanistically, AIM2 deficiency exacerbated APAP-induced acute liver damage and inflammation in aged mice by intensifying oxidative stress and augmenting the phosphorylation of JNK and ERK. Given its regulatory role in autophagy and lipid peroxidation, AIM2 emerges as a promising therapeutic target for age-related acute liver damage treatment.

Dysfunction of autophagy in high-fat diet-induced non-alcoholic fatty liver disease

ABBREVIATIONS

ACOX1: acyl-CoA oxidase 1; ADH5: alcohol dehydrogenase 5 (class III), chi polypeptide; ADIPOQ: adiponectin, C1Q and collagen domain containing; ATG: autophagy related; BECN1: beclin 1; CRTC2: CREB regulated transcription coactivator 2; ER: endoplasmic reticulum; F2RL1: F2R like trypsin receptor 1; FA: fatty acid; FOXO1: forkhead box O1; GLP1R: glucagon like peptide 1 receptor; GRK2: G protein-coupled receptor kinase 2; GTPase: guanosine triphosphatase; HFD: high-fat diet; HSCs: hepatic stellate cells; HTRA2: HtrA serine peptidase 2; IRGM: immunity related GTPase M; KD: knockdown; KDM6B: lysine demethylase 6B; KO: knockout; LAMP2: lysosomal associated membrane protein 2; LAP: LC3-associated phagocytosis; LDs: lipid droplets; Li KO: liver-specific knockout; LSECs: liver sinusoidal endothelial cells; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MAP3K5: mitogen-activated protein kinase kinase kinase 5; MED1: mediator complex subunit 1; MTOR: mechanistic target of rapamycin kinase; MTORC1: mechanistic target of rapamycin complex 1; NAFLD: non-alcoholic fatty liver disease; NASH: non-alcoholic steatohepatitis; NFE2L2: NFE2 like bZIP transcription factor 2; NOS3: nitric oxide synthase 3; NR1H3: nuclear receptor subfamily 1 group H member 3; OA: oleic acid; OE: overexpression; OSBPL8: oxysterol binding protein like 8; PA: palmitic acid; RUBCNL: rubicon like autophagy enhancer; PLIN2: perilipin 2; PLIN3: perilipin 3; PPARA: peroxisome proliferator activated receptor alpha; PRKAA2/AMPK: protein kinase AMP-activated catalytic subunit alpha 2; RAB: member RAS oncogene family; RPTOR: regulatory associated protein of MTOR complex 1; SCD: stearoyl-CoA desaturase; SIRT1: sirtuin 1; SIRT3: sirtuin 3; SNARE: soluble N-ethylmaleimide-sensitive factor attachment protein receptor; SQSTM1/p62: sequestosome 1; SREBF1: sterol regulatory element binding transcription factor 1;SREBF2: sterol regulatory element binding transcription factor 2; STING1: stimulator of interferon response cGAMP interactor 1; STX17: syntaxin 17; TAGs: triacylglycerols; TFEB: transcription factor EB; TP53/p53: tumor protein p53; ULK1: unc-51 like autophagy activating kinase 1; VMP1: vacuole membrane protein 1.

High-throughput screening of novel TFEB agonists in protecting against acetaminophen-induced liver injury in mice

Macroautophagy (referred to as autophagy hereafter) is a major intracellular lysosomal degradation pathway that is responsible for the degradation of misfolded/damaged proteins and organelles. Previous studies showed that autophagy protects against acetaminophen (APAP)-induced injury (AILI) via selective removal of damaged mitochondria and APAP protein adducts. The lysosome is a critical organelle sitting at the end stage of autophagy for autophagic degradation via fusion with autophagosomes. In the present study, we showed that transcription factor EB (TFEB), a master transcription factor for lysosomal biogenesis, was impaired by APAP resulting in decreased lysosomal biogenesis in mouse livers. Genetic loss-of and gain-of function of hepatic TFEB exacerbated or protected against AILI, respectively. Mechanistically, overexpression of TFEB increased clearance of APAP protein adducts and mitochondria biogenesis as well as SQSTM1/p62-dependent non-canonical nuclear factor erythroid 2-related factor 2 (NRF2) activation to protect against AILI. We also performed an unbiased cell-based imaging high-throughput chemical screening on TFEB and identified a group of TFEB agonists. Among these agonists, salinomycin, an anticoccidial and antibacterial agent, activated TFEB and protected against AILI in mice. In conclusion, genetic and pharmacological activating TFEB may be a promising approach for protecting against AILI.

Modulation of the HIF-1α-NCOA4-FTH1 Signaling Axis Regulating Ferroptosis-induced Hepatic Stellate Cell Senescence to Explore the Anti-hepatic Fibrosis Mechanism of Curcumol

INTRODUCTION

Senescence of activated hepatic stellate cells (HSC) reduces extracellular matrix expression to reverse liver fibrosis. Ferroptosis is closely related to cellular senescence, but its regulatory mechanisms need to be further investigated. The iron ions weakly bound to ferritin in the cell are called labile iron pool (LIP), and together with ferritin, they maintain cellular iron homeostasis and regulate the cell's sensitivity to ferroptosis.

METHODS

We used lipopolysaccharide (LPS) to construct a pathological model group and divided the hepatic stellate cells into a blank group, a model group, and a curcumol 12.5 mg/L group, a curcumol 25 mg/L group, and a curcumol 50 mg/L group. HIF-1α-NCOA4- FTH1 signalling axis, ferroptosis and cellular senescence were detected by various cellular molecular biology experiments.

RESULT

We found that curcumol could induce hepatic stellate cell senescence by promoting iron death in hepatic stellate cells. Curcumol induced massive deposition of iron ions in hepatic stellate cells by activating the HIF-1α-NCOA4-FTH1 signalling axis, which further led to iron overload and lipid peroxidation-induced ferroptosis. Interestingly, our knockdown of HIF-1α rescued curcumol-induced LIP and iron deposition in hepatic stellate cells, suggesting that HIF-1α is a key target of curcumol in regulating iron metabolism and ferroptosis. We were able to rescue curcumol-induced hepatic stellate cell senescence when we reduced LIP and iron ion deposition using iron chelators.

CONCLUSION

Overall, curcumol induces ferroptosis and cellular senescence by increasing HIF-1α expression and increasing NCOA4 interaction with FTH1, leading to massive deposition of LIP and iron ions, which may be the molecular biological mechanism of its anti-liver fibrosis.

Deletion of Glyoxalase 1 exacerbates acetaminophen-induced hepatotoxicity in mice

Acetaminophen (APAP) overdose triggers a cascade of intracellular oxidative stress events culminating in acute liver injury. The clinically used antidote, N-acetylcysteine (NAC) has a narrow therapeutic window and early treatment is essential for satisfactory therapeutic outcome. For more versatile therapies that can be effective even at late-presentation, the intricacies of APAP-induced hepatotoxicity must be better understood. Accumulation of advanced glycation end-products (AGEs) and consequent activation of the receptor for AGEs (RAGE) are considered one of the key mechanistic features of APAP toxicity. Glyoxalase-1 (Glo-1) regulates AGE formation by limiting the levels of methylglyoxal (MEG). In this study, we studied the relevance of Glo-1 in APAP mediated activation of RAGE and downstream cell-death cascades. Constitutive Glo-1 knockout mice (GKO) and a cofactor of Glo-1, ψ-GSH, were employed as tools. Our findings show elevated oxidative stress, activation of RAGE and hepatocyte necrosis through steatosis in GKO mice treated with high-dose APAP compared to wild type controls. A unique feature of the hepatic necrosis in GKO mice is the appearance of microvesicular steatosis as a result of centrilobular necrosis, rather than inflammation seen in wild type. The GSH surrogate and general antioxidant, ψ-GSH alleviated APAP toxicity irrespective of Glo-1 status, suggesting that oxidative stress being the primary driver of APAP toxicity. Overall, exacerbation of APAP hepatotoxicity in GKO mice suggests the importance of this enzyme system in antioxidant defense against initial stages of APAP overdose.

Unveiling the power of microenvironment in liver regeneration: an in-depth overview

The liver serves as a vital regulatory hub for various physiological processes, including sugar, protein, and fat metabolism, coagulation regulation, immune system maintenance, hormone inactivation, urea metabolism, and water-electrolyte acid-base balance control. These functions rely on coordinated communication among different liver cell types, particularly within the liver's fundamental hepatic lobular structure. In the early stages of liver development, diverse liver cells differentiate from stem cells in a carefully orchestrated manner. Despite its susceptibility to damage, the liver possesses a remarkable regenerative capacity, with the hepatic lobule serving as a secure environment for cell division and proliferation during liver regeneration. This regenerative process depends on a complex microenvironment, involving liver resident cells, circulating cells, secreted cytokines, extracellular matrix, and biological forces. While hepatocytes proliferate under varying injury conditions, their sources may vary. It is well-established that hepatocytes with regenerative potential are distributed throughout the hepatic lobules. However, a comprehensive spatiotemporal model of liver regeneration remains elusive, despite recent advancements in genomics, lineage tracing, and microscopic imaging. This review summarizes the spatial distribution of cell gene expression within the regenerative microenvironment and its impact on liver regeneration patterns. It offers valuable insights into understanding the complex process of liver regeneration.

Natural Products for Acetaminophen-Induced Acute Liver Injury: A Review

The liver plays a vital role in metabolism, synthesis, and detoxification, but it is susceptible to damage from various factors such as viral infections, drug reactions, excessive alcohol consumption, and autoimmune diseases. This susceptibility is particularly problematic for patients requiring medication, as drug-induced liver injury often leads to underestimation, misdiagnosis, and difficulties in treatment. Acetaminophen (APAP) is a widely used and safe drug in therapeutic doses but can cause liver toxicity when taken in excessive amounts. This study aimed to investigate the hepatotoxicity of APAP and explore potential treatment strategies using a mouse model of APAP-induced liver injury. The study involved the evaluation of various natural products for their therapeutic potential. The findings revealed that natural products demonstrated promising hepatoprotective effects, potentially alleviating liver damage and improving liver function through various mechanisms such as oxidative stress and inflammation, which cause changes in signaling pathways. These results underscore the importance of exploring novel treatment options for drug-induced liver injury, suggesting that further research in this area could lead to the development of effective preventive and therapeutic interventions, ultimately benefiting patients with liver injury caused by medicine.

Caveolin-1 protects against liver damage exacerbated by acetaminophen in non-alcoholic fatty liver disease by inhibiting the ERK/HIF-1α pathway

Acetaminophen (APAP) is a common antipyretic and analgesic drug that can cause long-term liver damage after an overdose. Non-alcoholic fatty liver disease (NAFLD) increases susceptibility to APAP. In NAFLD, excessive accumulation of lipids leads to an abnormal increase in hypoxia-inducible factor-1α (HIF-1α). Caveolin-1 (CAV1) may protect against NAFLD by inhibiting HIF-1α. This research aimed to determine whether CAV1 could attenuate APAP-exacerbated liver injury in NAFLD by inhibiting oxidative stress involving HIF-1α. In this study, 7-week-old C57BL/6 mice were fed a high-fat diet (HFD) for eight weeks, followed by the instillation of APAP. Levels of oxidative stress and liver lipid deposition were determined, and p-ERK1/2 and HIF-1α protein expression were measured by the Western blot (WB) method. In the APAP-treated group, the level of CAV1 was decreased, while the levels of HIF-1α and reactive oxygen species (ROS) were significantly increased. AML12 cells were treated with a mixture of palmitic acid (PA) and oleic acid (OA) (1:2 mix) for 48 h, and APAP was added for the last 24 h. Overexpression of CAV1 in AML12 cells significantly inhibited the expression of ROS and HIF-1α. And the results of immunofluorescence after treatment with CAV1-SiRNA showed that the HIF-1α levels were significantly increased in mitochondria. In conclusion, our experimental results suggest that CAV1 has a protective function in the fatty liver based on preventing oxidative stress, which involves HIF-1α. Thus, upregulation of CAV1 may attenuate APAP-exacerbated liver injury in NAFLD.

Epidemiology and Management of Drug-induced Liver Injury: Importance of the Updated RUCAM

Drug-induced liver injury (DILI) is a major cause of acute liver injury, liver failure, and liver transplantation worldwide. In recent years, immune checkpoint inhibitors have become widely used. This has led to an increase in DILI, for which pathophysiology and management methods differ significantly from the past. As the number of cases of acute liver injury and liver transplantation due to DILI is expected to increase, information about a DILI is becoming more valuable. DILI is classified into two types according to its etiology: intrinsic DILI, in which the drug or its metabolites cause liver damage that is dose-dependent and predictable; and idiosyncratic DILI, in which liver damage is also dose-independent but unpredictable. In addition, depending on the course of the disease, chronic DILI or drug-induced autoimmune hepatitis may be present. The number of DILI cases caused by antimicrobial agents is decreasing, whereas that caused by drugs for malignant tumors and health foods is increasing. The Roussel Uclaf Causality Assessment Method is widely used to assess causality in DILI. Liver injury is a type of immune-related adverse event. The pattern of hepatic injury in immune-related adverse events is mostly hepatocellular, but mixed type and bile stasis have also been reported. Sclerosing cholangitis caused by immune checkpoint inhibitors has also been reported as a unique type of injury. Treatment mainly comprises withdrawal of immune checkpoint inhibitors and steroid administration; however, mycophenolate mofetil may be considered if the disease is refractory to steroids.

Goji Ferment Ameliorated Acetaminophen-Induced Liver Injury in vitro and in vivo

This study aimed to investigate the hepatoprotective effects of lyophilized powder of goji ferment (LPGF) against acetaminophen (APAP)-induced hepatic damage in Hep3B cells and in mice. Eleven strains of lactic acid bacteria (LAB) were selected and their hepatoprotection against APAP-induced cellular damage in Hep3B cell line was evaluated. Four strains of LAB, including BCRC11652 (Leuconostoc mesenteroides subsp. mesenteroides), BCRC14619 (Lactobacillus gasseri), KODA-1 (Pediococcus acidilactici), and KODA-2 (Limosilactobacillus fermentum), have hepatoprotective potential against APAP in vitro. Goji significantly stimulated the growth of individual and combined strains of LAB and the optimal fermented condition was the treatment of goji at 10% (w/w) for 24 h. The prepared lyophilized powder of goji ferment (LPGF) containing fifteen combinations of LAB strains was used to explore their hepatoprotection in vitro. LPGF containing all combinations of LAB strains, except for KODA-2, significantly restored APAP-reduced cell viability and improved APAP-increased cellular levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST). In mice model, LPGF containing BCRC11652, BCRC14619, and KODA-2 was chosen to evaluate its hepatoprotection against APAP-induced liver injury. LPGF at diverse doses have a tendency but no significant improvement on APAP-reduced body weight gain and liver weight. LPGF significantly decreased APAP-increased serum ALT and AST levels in a dose-dependent manner. At the end of experiment, LPGF significantly and dose-dependently reversed APAP-reduced activities of GSH and antioxidant enzymes, including glutathione peroxidase, superoxide dismutase, and catalase in hepatic tissue. Overall, LPGF was demonstrated to exhibit hepatoprotection against APAP-induced liver injury in vitro and in vivo.

Pien Tze Huang attenuated acetaminophen-induced liver injury by autophagy mediated-NLRP3 inflammasome inhibition

ETHNOPHARMACOLOGICAL RELEVANCE

Pien Tze Huang is a classic traditional Chinese medicinal product, used for inflammatory diseases as stated in Chinese Pharmacopoeia. In particular, it is effective in treating liver diseases and pro-inflammatory conditions. Acetaminophen (APAP) is a widely used analgesic drug, but its over-dose is associated with acute liver failure where the clinical approved antidote treatment is limited. Inflammation has been considered as one of the therapeutic targets against APAP-induced liver injury.

AIM OF THE STUDY

We aimed to explore the therapeutic potential of Pien Tze Huang tablet (PTH) on protecting liver against APAP-induced liver injury through its strong anti-inflammatory pharmacological action.

MATERIALS AND METHODS

Wild-type C57BL/6 mice were given PTH (75, 150 and 300 mg/kg) by oral gavage 3 days before the APAP injection (400 mg/kg). The protective effect of PTH was assessed by aspartate aminotransferase (AST) and alanine transaminase (ALT) levels and pathological staining. The mechanisms underlying PTH's hepatoprotective effects were investigated in nucleotide-binding domain (NOD)-like receptor protein 3 (NLRP3) knock-out (NLRP3^-/-), over expression NLRP3 (oe-NLRP3) mice, and wild-type mice with the injection of autophagy inhibitor (3-methyladenine, 3-MA).

RESULTS

APAP-exposed mice resulted in evident liver injury which was evidenced by hepatic necrosis and elevated levels of AST and ALT in the wild-type C57BL/6 mice. PTH dose-dependently reduced ALT, AST and upregulated autophagy activity. In addition, PTH significantly reduced elevated levels of proinflammatory cytokines and NLRP3 inflammasome. The liver protective effect of PTH (300 mg/kg) was still obvious in the oe-NLRP3 mice, however, it became insignificant in the NLRP3^-/- mice. When PTH (300 mg/kg) was co-treated with 3-MA to the wild-type C57BL/6 mice, the NLRP3 inhibition were reversed when autophagy was blocked.

CONCLUSION

PTH exerted a beneficial effect in protecting liver against APAP-induced liver injury. The underlying molecular mechanism was associated with the NLRP3 inflammasome inhibition which was likely driven by the upregulated autophagy activity. Our study underpins the traditional use of PTH in protecting liver through its anti-inflammatory action.

Ratiometric and discriminative visualization of autophagic processes with a novel dual-responded lysosome-specific fluorescent probe

BACKGROUND

Autophagy is a critical self-eating pathway involved in numerous physiological and pathological processes. Lysosomal degradation of dysfunctional organelles and invading microorganisms is central to the autophagy mechanism and essential for combating disease-related conditions. Therefore, monitoring fluctuations in the lysosomal microenvironment is vital for tracking the dynamic process of autophagy. Although much effort has been put into designing probes for measuring lysosomal viscosity or pH separately, there is a need to validate the concurrent imaging of the two elements to enhance the understanding of the dynamic progression of autophagy.

METHODS

Probe HFI was synthesized in three steps and was developed to visualize changes in viscosity and pH within lysosomes for real-time autophagy tracking. Then, the spectrometric determination was carried out. Next, the probe was applied to image autophagy in cells under nutrient-deprivation or external stress. Additionally, the performance of HFI to monitor autophagy was employed to evaluate acetaminophen-induced liver injury.

RESULTS

We constructed a ratiometric dual-responsive probe, HFI, with a large Stokes shift over 200 nm, dual-wavelength emission, and small background interference. The ratiometric fluorescent signal (R = I ₆₁₀/I ₄₆₀) of HFI had an excellent correlation with both viscosity and pH. More importantly, high viscosity and low pH had a synergistic promotion effect on the emission intensity of HFI, which enabled it to specially lit lysosomes without disturbing the inherent microenvironment. We then successfully used HFI to monitor intracellular autophagy induced by starvation or drugs in real-time. Interestingly, HFI also enabled us to visualize the occurrence of autophagy in the liver tissue of a DILI model, as well as the reversible effect of hepatoprotective drugs on this event.

CONCLUSIONS

In this study, we developed the first ratiometric dual-responsive fluorescent probe, HFI, for real-time revealing autophagic details. It could image lysosomes with minimal perturbation to their inherent pH, allowing us to track changes in lysosomal viscosity and pH in living cells. Ultimately, HFI has great potential to serve as a useful indicator for autophagic changes in viscosity and pH in complex biological samples and can also be used to assess drug safety.

Loss of microRNA-21 protects against acetaminophen-induced hepatotoxicity in mice

Acetaminophen (APAP)-induced Acute Liver Failure (ALF) is recognized as the most common cause of ALF in Western societies. APAP-induced ALF is characterized by coagulopathy, hepatic encephalopathy, multi-organ failure, and death. MicroRNAs are small, non-coding RNAs that regulate gene expression at the post-transcriptional level. MicroRNA-21 (miR-21) is dynamically expressed in the liver and is involved in the pathophysiology of both acute and chronic liver injury models. We hypothesize that miR-21genetic ablation attenuates hepatotoxicity following acetaminophen intoxication. Eight-week old miR-21knockout (miR21KO) or wild-type (WT) C57BL/6N male mice were injected with acetaminophen (APAP, 300 mg/kg BW) or saline. Mice were sacrificed 6 or 24 h post-injection. MiR21KO mice presented attenuation of liver enzymes ALT, AST, LDH compared with WT mice 24 h post-APAP treatment. Moreover, miR21KO mice had decreased hepatic DNA fragmentation and necrosis than WT mice after 24 h of APAP treatment. APAP-treated miR21KO mice showed increased levels of cell cycle regulators CYCLIN D1 and PCNA, increased autophagy markers expression (Map1LC3a, Sqstm1) and protein (LC3AB II/I, p62), and an attenuation of the APAP-induced hypofibrinolytic state via (PAI-1) compared with WT mice 24 post-APAP treatment. MiR-21 inhibition could be a novel therapeutic approach to mitigate APAP-induced hepatotoxicity and enhance survival during the regenerative phase, particularly to alter regeneration, autophagy, and fibrinolysis. Specifically, miR-21 inhibition could be particularly useful when APAP intoxication is detected at its late stages and the only available therapy is minimally effective.

Integrated Imaging and Proteomic Sensors Resolve Proteome Aggregation in Liver Caused by Non-steroidal Anti-inflammatory Drug Overdose

Given the extreme heterogeneity and the loss of defined protein structures, misfolded and aggregated proteins are technically challenging to visualize and analyze. Herein, we assembled an integrated sensor system to resolve aggregated proteome in live cells and animal liver tissues that are overdosed by non-steroidal anti-inflammatory drugs (NSAIDs). A fluorogenic protein aggregation sensor (AggStain) first discovered the presence of aggregated proteome upon overdosing liver cells with NSAIDs. A solvatochromic protein aggregation sensor (AggRetina) further quantified the compactness (polarity) inside these cellular aggregates. Importantly, we exploited a proteomic sensor (AggLink) to selectively capture aggregated proteins upon NSAID overdose and profile their composition, revealing global collapse of cellular protein homeostasis. Finally, we detected subtle proteome aggregation in mouse liver tissue without obvious acute injury at a low NSAID dosage. Overall, we demonstrated an integrated sensor toolset for proteome aggregation studies and unveiled for the first time that NSAID overdose can cause proteome aggregation in liver cells and tissues.

Mitochondria in Acetaminophen-Induced Liver Injury and Recovery: A Concise Review

Mitochondria are critical organelles responsible for the maintenance of cellular energy homeostasis. Thus, their dysfunction can have severe consequences in cells responsible for energy-intensive metabolic function, such as hepatocytes. Extensive research over the last decades have identified compromised mitochondrial function as a central feature in the pathophysiology of liver injury induced by an acetaminophen (APAP) overdose, the most common cause of acute liver failure in the United States. While hepatocyte mitochondrial oxidative and nitrosative stress coupled with induction of the mitochondrial permeability transition are well recognized after an APAP overdose, recent studies have revealed additional details about the organelle's role in APAP pathophysiology. This concise review highlights these new advances, which establish the central role of the mitochondria in APAP pathophysiology, and places them in the context of earlier information in the literature. Adaptive alterations in mitochondrial morphology as well as the role of cellular iron in mitochondrial dysfunction and the organelle's importance in liver recovery after APAP-induced injury will be discussed.

Molecular mechanism and research progress on pharmacology of ferulic acid in liver diseases

Ferulic acid (FA) is a natural polyphenol, a derivative of cinnamic acid, widely found in Angelica, Chuanxiong and other fruits, vegetables and traditional Chinese medicine. FA contains methoxy, 4-hydroxy and carboxylic acid functional groups that bind covalently to neighbouring adjacent unsaturated Cationic C and play a key role in many diseases related to oxidative stress. Numerous studies have shown that ferulic acid protects liver cells and inhibits liver injury, liver fibrosis, hepatotoxicity and hepatocyte apoptosis caused by various factors. FA has protective effects on liver injury induced by acetaminophen, methotrexate, antituberculosis drugs, diosbulbin B and tripterygium wilfordii, mainly through the signal pathways related to TLR4/NF-κB and Keap1/Nrf2. FA also has protective effects on carbon tetrachloride, concanavalin A and septic liver injury. FA pretreatment can protect hepatocytes from radiation damage, protects the liver from damage caused by fluoride, cadmium and aflatoxin b1. At the same time, FA can inhibit liver fibrosis, inhibit liver steatosis and reduce lipid toxicity, improve insulin resistance in the liver and exert the effect of anti-liver cancer. In addition, signalling pathways such as Akt/FoxO1, AMPK, PPAR γ, Smad2/3 and Caspase-3 have been shown to be vital molecular targets for FA involvement in improving various liver diseases. Recent advances in the pharmacological effects of ferulic acid and its derivatives on liver diseases were reviewed. The results will provide guidance for the clinical application of ferulic acid and its derivatives in the treatment of liver diseases.

Research progress on the mitochondrial mechanism of age-related non-alcoholic fatty liver

Non-alcoholic fatty liver disease (NAFLD) has become the most common chronic liver disease worldwide. Reduced activity and slower metabolism in the elderly affect the balance of lipid metabolism in the liver leading to the accumulation of lipids. This affects the mitochondrial respiratory chain and the efficiency of β-oxidation and induces the overproduction of reactive oxygen species. In addition, the dynamic balance of the mitochondria is disrupted during the ageing process, which inhibits its phagocytic function and further aggravates liver injury, leading to a higher incidence of NAFLD in the elderly population. The present study reviewed the manifestations, role and mechanism of mitochondrial dysfunction in the progression of NAFLD in the elderly. Based on the understanding of mitochondrial dysfunction and abnormal lipid metabolism, this study discusses the treatment strategies and the potential therapeutic targets for NAFLD, including lipid accumulation, antioxidation, mitophagy and liver-protecting drugs. The purpose is to provide new ideas for the development of innovative drugs for the prevention and treatment of NAFLD.

Endoplasmic Reticulum Stress and Mitochondrial Stress in Drug-Induced Liver Injury

Drug-induced liver injury (DILI) is a widespread and harmful disease closely linked to mitochondrial and endoplasmic reticulum stress (ERS). Globally, severe drug-induced hepatitis, cirrhosis, and liver cancer are the primary causes of liver-related morbidity and mortality. A hallmark of DILI is ERS and changes in mitochondrial morphology and function, which increase the production of reactive oxygen species (ROS) in a vicious cycle of mutually reinforcing stress responses. Several pathways are maladapted to maintain homeostasis during DILI. Here, we discuss the processes of liver injury caused by several types of drugs that induce hepatocyte stress, focusing primarily on DILI by ERS and mitochondrial stress. Importantly, both ERS and mitochondrial stress are mediated by the overproduction of ROS, destruction of Ca2+ homeostasis, and unfolded protein response (UPR). Additionally, we review new pathways and potential pharmacological targets for DILI to highlight new possibilities for DILI treatment and mitigation.

Cross-talk between the RAS-ERK and mTOR signalings-associated autophagy contributes to tripterygium glycosides tablet-induced liver injury

BACKGROUND AND AIMS

Drug-induced liver injury (DILI) remains a critical issue and a hindrance to clinical application of Tripterygium Glycosides Tablet (TGT) despite its favorable therapeutic efficacy in rheumatoid arthritis. Herein, we aimed to elucidate the molecular mechanisms underlying TGT-induced hepatotoxicity.

METHODS

Chemical profiling of TGT was identified by UPLC-Q/TOF-MS/MS and its putative targets were predicted based on chemical structure similarity calculation. Following "DILI-related gene-TGT putative target" interaction network construction, a list of key network targets was screened according to nodes' topological importance and functional relevance. Both in vivo and in vitro experiments were performed to determine drug hepatotoxicity and the underlying mechanisms.

RESULT

A total of 49 chemical components and 914 putative targets of TGTs were identified. Network calculation and functional modularization screened RAS-ERK and mTOR signalings-associated autophagy to be one of the candidate targets of TGT-induced hepatotoxicity. Experimentally, TGT significantly activated RAS-ERK axis, elevated the number of autophagosomes and the expression of LC3II protein, but reduced the expression of p62 protein and suppressed mTOR phosphorylation in the liver tissues of TGT-induced acute liver injury mice and chronic liver injury mice in vivo and AML12 cells in vitro. Moreover, TGT and mL-098 (an activator of RAS) co-treatment reduced AML12 cell viability via regulating autophagy and TGT-induced liver injury-related indicators more dramatically than TGT treatment alone, whereas Salirasib (an inhibitor of RAS) had an opposite effect.

CONCLUSION

RAS-ERK-mTOR cross-talk may play a crucial role in TGT-induced hepatocyte autophagy, offering a promising target for developing novel therapeutics to combat TGT-induced hepatotoxicity.

Antioxidant-Based Preventive Effect of Phytochemicals on Anticancer Drug-Induced Hepatotoxicity

Significance: Drug-induced liver injury (DILI) or hepatotoxicity has been a hot issue to overcome on the safety and physiological function of the liver, since it is known to have biochemical, cellular, immunological, and molecular alterations in the liver mainly induced by alcohol, chemicals, drugs, heavy metals, and genetic factors. Recently efficient therapeutic and preventive strategies by some phytochemicals are of interest, targeting oxidative stress-mediated hepatotoxicity alone or in combination with anticancer drugs. Recent Advances: To assess DILI, the variety of in vitro and in vivo animal models has been developed mainly by using carbon tetrachloride, d-galactosamine, acetaminophen, and lipopolysaccharide. Also, the mechanisms on hepatotoxicity by several drugs and herbs have been explored in detail. Recent studies reveal that antioxidants including vitamins and some phytochemicals were reported to prevent against DILI. Critical Issues: Antioxidant therapy with some phytochemicals is noteworthy, since oxidative stress is critically involved in DILI via production of chemically reactive oxygen species or metabolites, impairment of mitochondrial respiratory chain, and induction of redox cycling. Future Directions: For efficient antioxidant therapy, DILI susceptibility, Human Leukocyte Antigen genetic factors, biomarkers, and pathogenesis implicated in hepatotoxicity should be further explored in association with oxidative stress-mediated signaling, while more randomized preclinical and clinical trials are required with optimal safe doses of drugs and/or phytochemicals alone or in combination for efficient clinical practice along with the development of advanced DILI diagnostic tools.

Thymoquinone attenuates hepatic lipid accumulation by inducing autophagy via AMPK/mTOR/ULK1-dependent pathway in nonalcoholic fatty liver disease

Thymoquinone (TQ) has been proved to exert wide-ranging pharmacological activities, with anti-inflammatory, antioxidant, anticonvulsant, antimicrobial, anti-tumor, and antidiabetic properties. In this study, we investigated the beneficial effects of TQ on a high-fat diet (HFD)-induced nonalcoholic fatty liver disease (NAFLD) in C57BL/6 N mice in vivo and free fatty acid (FFA)-induced human hepatocellular carcinoma HepG2 cells in vitro. Further, the underlying mechanisms of TQ to promote hepatic autophagy were also discovered. Data showed that TQ caused (p < 0.01) body weight reduction, improved glucose homeostasis, alleviated hepatosteatosis, and decreased hepatic lipid accumulation related to the induction of autophagy in HFD-fed mice. In vitro, TQ obviously increased (p < 0.01) autophagic flux in FFA-induced HepG2 cells and consequently reduced the lipid accumulation in combination with activation of AMPK/mTOR/ULK1 signaling pathways. Moreover, pharmacological inhibition of the AMPK pathway by addition with AMPK inhibitor Compound C (CC) or silence of ULK1 by transfection with siRNA(ULK1) into HepG2 cells reversed these beneficial effects of TQ on triggering hepatic autophagy and reducing lipid accumulation (p < 0.01). Taken together, these results suggested that TQ alleviated hepatic lipid accumulation by triggering autophagy through the AMPK/mTOR/ULK1-dependent signaling pathway. Our study supports a potential role for TQ in ameliorating NAFLD.

Deficiency of NLR family member NLRC5 alleviates alcohol induced hepatic injury and steatosis by enhancing autophagy of hepatocytes

Steatosis is regarded as an early response of the liver to excessive alcohol consumption, which ultimately results in alcoholic liver disease (ALD). Hepatocytes are the primary drivers of the pathological process known as hepatic damage and steatosis, which is characterized by significant fat accumulation and an abundance of fat vacuoles. NLRs, a family member of pattern recognition receptors, have recently been found to be crucial in liver disorders. In this study, we examined the possible impact of NLRC5, the largest NLR family member, on alcohol-induced fatty liver development using a gene knock-out mouse model. The mouse liver was severely damaged and developed steatosis as a result of chronic and excessive ethanol use, and this damage was prevented by the lack of NLRC5. Additionally, NLRC5 deletion reversed ethanol's ability to increase the serum concentrations of TG, T-CHO, ALT, and AST. Absence of NLRC5 reduced ethanol-stimulated aberrant expression of the vital regulators of lipid synthesis and metabolism, SREBP-1c, FAS and PPAR-α. Furthermore, loss- and gain-of-function research indicated that NLRC5 might affect the autophagy pathway in alcohol-induced hepatic steatosis progression. The functional role of NLRC5 in ALD is obviously impacted by the autophagy inducer rapamycin as well as the autophagy inhibitor 3-MA. Our research showed that NLRC5 was involved in ethanol-induced injury and steatosis of the liver, and may be considered a suitable therapeutic target for treating ALD.

Self-assembled FGF21 nanoparticles alleviate drug-induced acute liver injury

Acetaminophen (N-acetyl-p-aminophenol, APAP) is a common antipyretic agent and analgesic. An overdose of APAP can result in acute liver injury (ALI). Oxidative stress and inflammation are central to liver injury. N-acetylcysteine (NAC), a precursor of glutathione, is used commonly in clinical settings. However, the window of NAC treatment is limited, and more efficacious alternatives must be found. Endogenous cytokines such as fibroblast growth factor (FGF) 21 can improve mitochondrial function while decreasing intracellular oxidative stress and inflammatory responses, thereby exhibiting antioxidant-like effects. In this study, self-assembled nanoparticles comprising chitosan and heparin (CH) were developed to deliver FGF21 (CH-FGF21) to achieve the sustained release of FGF21 and optimize the in vivo distribution of FGF21. CH-FGF21 attenuated the oxidative damage and intracellular inflammation caused by APAP to hepatocytes effectively. In a murine model of APAP-induced hepatotoxicity, CH-FGF21 could alleviate ALI progression and promote the recovery of liver function. These findings demonstrated that a simple assembly of CH nanoparticles carrying FGF21 could be applied for the treatment of liver diseases.

Schisandra chinensis essential oil attenuates acetaminophen-induced liver injury through alleviating oxidative stress and activating autophagy

CONTEXT

Schisandra chinensis (Turcz.) Baill. (Magnoliaceae) essential oil (SCEO) composition is rich in lignans that are believed to perform protective effects in the liver.

OBJECTIVE

This study investigates the effects of SCEO in the treatment of acetaminophen (APAP)-induced liver injury in mice.

MATERIALS AND METHODS

C57BL/6 mice (n = 56) were randomly divided into seven groups: normal; APAP (300 mg/kg); APAP plus bicyclol (200 mg/kg); APAP plus SCEO (0.25, 0.5, 1, 2 g/kg). Serum biochemical parameters for liver function, inflammatory factors, and antioxidant activities were determined. The protein expression levels of Nrf2, GCLC, GCLM, HO-1, p62, and LC3 were assessed by western blotting. Nrf2, GCLC, HO-1, p62, and LC3 mRNA were detected by real-time PCR.

RESULTS

Compared to APAP overdose, SCEO (2 g/kg) pre-treatment reduced the serum levels of AST (79.4%), ALT (84.6%), TNF-α (57.3%), and IL-6 (53.0%). In addition, SCEO (2 g/kg) markedly suppressed cytochrome P450 2E1 (CYP2E1) (15.4%) and attenuated the exhaustion of GSH (43.6%) and SOD (16.8%), and the accumulation of MDA (22.6%) in the liver, to inhibit the occurrence of oxidative stress. Moreover, hepatic tissues from our experiment revealed that SCEO pre-treatment mitigated liver injury caused by oxidative stress by increasing Nrf2, HO-1, and GCL. Additionally, SCEO activated autophagy, which upregulated hepatic LC3-II and decreased p62 in APAP overdose mice (p < 0.05).

DISCUSSION AND CONCLUSIONS

Our evidence demonstrated that SCEO protects hepatocytes from APAP-induced liver injury in vivo and the findings will provide a reliable theoretical basis for developing novel therapeutics.

Hepatoprotective Effects of Radish (Raphanus sativus L.) on Acetaminophen-Induced Liver Damage via Inhibiting Oxidative Stress and Apoptosis

Alcohol and drug overdoses cause liver diseases such as cirrhosis, hepatitis, and liver cancer globally. In particular, an overdose of acetaminophen (APAP), which is generally used as an analgesic and antipyretic agent, is a major cause of acute hepatitis, and cases of APAP-induced liver damage are steadily increasing. Potential antioxidants may inhibit the generation of free radicals and prevent drug-induced liver damage. Among plant-derived natural materials, radishes (RJ) and turnips (RG) have anti-inflammatory, anticancer, and antioxidant properties due to the presence of functional ingredients, such as glucosinolate and isothiocyanate. Although various functions have been reported, in vivo studies on the antioxidant activity of radishes are insufficient. Therefore, we aim to evaluate the hepatoprotective effects of RG and RJ in APAP-induced liver-damaged mice. RG and RJ extracts markedly improved the histological status, such as inflammation and infiltration, of mice liver tissue, significantly decreased the levels of alanine transaminase, aspartate aminotransferase, and malondialdehyde, and significantly increased the levels of glutathione, superoxide dismutase and catalase in the APAP-induced liver-damaged mice. In addition, RG and RJ extracts significantly increased the expression of Nrf-2 and HO-1, which are antioxidative-related factors, and regulated the BAX and BCL-2, thereby showing anti-apoptosis activity. These results indicated that RG and RJ extracts protected mice against acute liver injury, attributed to a reduction in both oxidative stress and apoptosis. These findings have clinical implications for the use of RG and RJ extracts as potential natural candidates for developing hepatoprotective agents.

Long-Term Consumption of Food-Derived Chlorogenic Acid Protects Mice against Acetaminophen-Induced Hepatotoxicity via Promoting PINK1-Dependent Mitophagy and Inhibiting Apoptosis

Hepatotoxicity brought on by acetaminophen (APAP) is significantly impacted by mitochondrial dysfunction. Mitophagy, particularly PINK1-mediated mitophagy, maintains the stability of cell function by eliminating damaged mitochondria. One of the most prevalent dietary polyphenols, chlorogenic acid (CGA), has been shown to have hepatoprotective properties. It is yet unknown, nevertheless, whether its defense against hepatocyte apoptosis involves triggering PINK1-mediated mitophagy. In vitro and in vivo models of APAP-induced hepatotoxicity were established to observe CGA's effect and mechanism in preventing hepatotoxicity in the present study. Serum aminotransferase levels, mouse liver histology, and the survival rate of HepG2 cells and mice were also assessed. The outcomes showed that CGA could reduce the activities of serum enzymes such as alanine transaminase (ALT), aspartate transaminase (AST), and lactate dehydrogenase (LDH), and alleviate liver injury in mice. It could also significantly increase the cell viability of HepG2 cells and the 24-h survival rate of mice. TUNEL labeling and Western blotting were used to identify the hepatocyte apoptosis level. According to data, CGA could significantly reduce liver cell apoptosis in vivo. Additionally, Tom20 and LC3II colocalization in mitochondria may be facilitated by CGA. CGA considerably increased the levels of genes and proteins associated with mitophagy (PINK1, Parkin, LC3II/LC3I), while considerably decreasing the levels of p62 and Tom20, suggesting that it might activate PINK1/Parkin-mediated mitophagy in APAP-induced liver damage. Additionally, the protection of CGA was reduced when PINK1 was knocked down by siPINK1 in HepG2 cells, and it did not upregulate mitophagy-related proteins (PINK1, Parkin, LC3II/LC3I). In conclusion, our findings revealed that long-term consumption of food-derived CGA could prevent APAP hepatotoxicity via increasing PINK1-dependent mitophagy and inhibiting hepatocyte apoptosis.

Cold exposure-induced endoplasmic reticulum stress regulates autophagy through the SIRT2/FoxO1 signaling pathway

Cold is a factor affecting health in humans and animals. The liver, a major metabolic center, is highly susceptible to ambient air temperature. Recent studies have shown that endoplasmic reticulum (ER) stress is associated with the liver, and regulates the occurrence and development of liver injury and autophagy. However, the mechanism underlying the relationship between cold exposure and ER stress in the liver is not well understood. In this study, we investigated the effect of ER stress on liver autophagy and its mechanism under cold exposure. AML12 cells were treated with Tg to construct an ER stress model, and the level of autophagy increased. To further explore the mechanism through which ER stress regulates autophagy, we knocked down SIRT2 with shRNA in Tg-treated AML12 cells. Knockdown of SIRT2 significantly increased ER stress and autophagy, increased FoxO1 acetylation, and promoted its entry into the nucleus. To further verify the results of in vitro experiments, we exposed mice to 4°C for 3 h per day for 3 weeks to exacerbate the burden on the liver after cold exposure. Cold exposure damaged the structure and function of the liver and promoted the inflammatory response. It also activated ER stress and promoted autophagy. In addition, cold exposure inhibited the expression of SIRT2, promoted FoxO1 acetylation, and enhanced the interaction with autophagy. Our findings indicated that cold exposure induces liver damage, ER stress, and autophagy through the SIRT2/FoxO1 pathway. These findings suggest that SIRT2 may be a potential target for regulating health under cold exposure.

Astaxanthin Activated the Nrf2/HO-1 Pathway to Enhance Autophagy and Inhibit Ferroptosis, Ameliorating Acetaminophen-Induced Liver Injury

Acetaminophen (APAP)-induced liver injury (AILI) is a common liver disease in clinical practice. Only one clinically approved drug, N-acetylcysteine (NAC), for the treatment of AILI is available in clinics, but novel treatment strategies are still needed due to the complicated pathological changes of AILI and the side effects of NAC. Here, we found that astaxanthin (ASX) can prevent AILI through the Nrf2/HO-1 pathway. After treatment with ASX, there was a positive activation of the Nrf2/HO-1 pathway in AILI models both in vivo and in vitro accompanied by enhanced autophagy and reduced ferroptosis. In APAP-challenged L02 liver cells, ASX reduced autophagy and enhanced apoptosis of the cells. Furthermore, we developed ASX-loaded hollow mesoporous silica nanoparticles (HMSN@ASX) to improve the aqueous solubility of ASX and targeted delivery of ASX to the liver and then significantly improve the therapeutic effects. Taken together, we found that ASX can protect against AILI by activating the Nrf2/HO-1 pathway, which mainly affects oxidative stress, autophagy, and ferroptosis processes, and the HMSN@ASX nanosystem can target the liver to enhance the treatment efficiency of AILI.

Exploration of the Protective Mechanism of Naringin in the Acetaminophen-Induced Hepatic Injury by Metabolomics

Naringin is a dihydroflavone which was found in citrus fruits. Previous studies have indicated the antiapoptotic, antioxidative stress, and anti-inflammatory effects of naringin. It can improve many common diseases, including fibrosis or hepatotoxicity, cardiovascular disease, and diabetes. Acetaminophen (APAP) is a frequently used painkiller, and hepatotoxic side effects limit its use. The purpose of the current examination is to find the impact of naringin on APAP-induced hepatic injury. Firstly, we pretreated mice model groups with naringin. Then, the liver injury model was established by injecting intraperitoneally into mice with APAP. After the mice were euthanized, we obtained serum and liver tissue samples from the mice. Finally, these samples were analyzed using a metabolomics approach to find the underlying mechanism of the effects of naringin on APAP-induced liver injury and provide a new treatment strategy for APAP-induced liver injury. Our data indicate that naringin significantly improves APAP-induced liver injury in mice and reduces the expression levels of liver injury markers in a dose-dependent manner. Furthermore, analysis of differential metabolites in mice with liver injury showed that naringin reduced APAP-induced hepatotoxicity due to reversing multiple metabolite expression levels and the rescue of energy, amino acid, and purine metabolism.

Palmatine attenuates hepatocyte injury by promoting autophagy via the AMPK/mTOR pathway after alcoholic liver disease

Alcoholic liver disease is one of the diseases with the highest fatality rate worldwide. The cellular process of autophagy which recycles damaged organelles to maintain protein and organelle homeostasis is found to positively influence survival during hepatic insufficiency, although the mechanism is poorly understood. Palmatine (PLT) has a variety of biological functions, such as broad-spectrum antibacterial action, neuroprotective, antioxidant stress, and antiviral and anti-inflammatory activities. However, it is not known whether PLT has a protective effect against alcoholic liver injury. Here, we investigated the protective effect of PLT in a cellular model of alcohol-induced acute liver injury and further explored its mechanism of action. In this study, we show for the first time that PLT attenuates alcohol-induced hepatocyte injury by promoting autophagy to play an essential protective role. As PLT treatment induced a brief increase in LC3-II conversion and p62 degradation, it also upregulated the expression of ATG5 and ATG7. The expression levels of the proapoptotic proteins Bax, Caspase 3, and Caspase 9 significantly decreased, while the antiapoptotic protein levels of Bcl-2 upregulated after treatment with PLT. However, in presence of the autophagy inhibitor, 3-methyladenine, the effect of PLT in inhibiting ethanol-induced hepatocyte injury reversed significantly. Mechanistically, the protective effects of PLT may be mediated by promoting the activation of the AMP-activated protein kinase/mammalian target of rapamycin signaling pathway. Therefore, we believe that the development of alcoholic liver injuries may be controlled by PLT by inhibiting hepatocyte apoptosis through the autophagy pathway. The study lays a solid theoretical and practical basis for future animal models and clinical studies of PLT.

The secretome obtained under hypoxic preconditioning from human adipose-derived stem cells exerts promoted anti-apoptotic potentials through upregulated autophagic process

BACKGROUND

Hypoxic preconditioning (HP) is a stem cell preconditioning modality designed to augment the therapeutic effects of mesenchymal stem cells (MSCs). Although autophagy is expected to play a role in HP, very little is known regarding the relationship between HP and autophagy.

METHODS AND RESULTS

The adipose-derived stem cell (ASC)-secretome obtained under normoxia (NCM) and ASC-secretome obtained under HP (HCM) were obtained by culturing ASCs for 24 h under normoxic (21% partial pressure of O₂) and hypoxic (1% partial pressure of O₂) conditions, respectively. Subsequently, to determine the in vivo effects of HCM, each secretome was injected into 70% partially hepatectomized mice, and liver specimens were obtained. HCM significantly reduced the apoptosis of thioacetamide-treated AML12 hepatocytes and promoted the autophagic processes of the cells (P < 0.05). Autophagy blockage by either bafilomycin A1 or ATG5 siRNA significantly abrogated the anti-apoptotic effect of HCM (P < 0.05), demonstrating that HCM exerts its anti-apoptotic effect by promoting autophagy. The effect of HCM - reduction of cell apoptosis and promotion of autophagic process - was also demonstrated in a mouse model.

CONCLUSIONS

HP appears to induce ASCs to release a secretome with enhanced anti-apoptotic effects by promoting the autophagic process of ASCs.

Autophagy: A Key Regulator of Homeostasis and Disease: An Overview of Molecular Mechanisms and Modulators

Autophagy is a highly conserved lysosomal degradation pathway active at basal levels in all cells. However, under stress conditions, such as a lack of nutrients or trophic factors, it works as a survival mechanism that allows the generation of metabolic precursors for the proper functioning of the cells until the nutrients are available. Neurons, as post-mitotic cells, depend largely on autophagy to maintain cell homeostasis to get rid of damaged and/or old organelles and misfolded or aggregated proteins. Therefore, the dysfunction of this process contributes to the pathologies of many human diseases. Furthermore, autophagy is highly active during differentiation and development. In this review, we describe the current knowledge of the different pathways, molecular mechanisms, factors that induce it, and the regulation of mammalian autophagy. We also discuss its relevant role in development and disease. Finally, here we summarize several investigations demonstrating that autophagic abnormalities have been considered the underlying reasons for many human diseases, including liver disease, cardiovascular, cerebrovascular diseases, neurodegenerative diseases, neoplastic diseases, cancers, and, more recently, infectious diseases, such as SARS-CoV-2 caused COVID-19 disease.

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.

An Experimental Study Reveals the Protective Effect of Autophagy against Realgar-Induced Liver Injury via Suppressing ROS-Mediated NLRP3 Inflammasome Pathway

Realgar, a poisonous traditional Chinese medicine, has been shown to cause liver injury when used for long periods or overdoses. However, the underlying molecular mechanisms and therapeutic targets have not been fully elucidated. The aim of this study is to explore the role of autophagy in sub-chronic realgar exposure-induced liver injury. Here, the liver injury model was established by continuously administrating mice with 1.35 g/kg realgar for 8 weeks. 3-methyladenine (3-MA) and rapamycin (RAPA) were used to regulate autophagy. The results showed that realgar induced abnormal changes in liver function, pathological morphology, expression of inflammatory cytokines, and upregulated NLRP3 inflammasome pathway in mouse livers. RAPA treatment (an inducer of autophagy) significantly improved realgar-induced liver injury and NLRP3 inflammasome activation, while 3-MA (an inhibitor of autophagy) aggravated the realgar-induced liver injury and NLRP3 inflammasome activation. Furthermore, we found that realgar-induced NLRP3 inflammasome activation in mouse livers is mediated by ROS. RAPA eliminates excessive ROS, inhibits NF-κB nuclear translocation and down-regulates the TXNIP/NLRP3 axis, consequently suppressing ROS-mediated NLRP3 inflammasome activation, which may be the underlying mechanism of the protective effect of autophagy on realgar-induced liver injury. In conclusion, the results of this study suggest that autophagy alleviates realgar-induced liver injury by inhibiting ROS-mediated NLRP3 inflammasome activation. Autophagy may represent a therapeutic target in modulating realgar-induced liver injury.

Hepatic SIRT6 Modulates Transcriptional Activities of FXR to Alleviate Acetaminophen-induced Hepatotoxicity

BACKGROUND & AIMS

Excessive acetaminophen (APAP) intake causes oxidative stress and inflammation, leading to fatal hepatotoxicity; however, the mechanism remains unclear. This study aims to explore the protective effects and detailed mechanisms of sirtuin 6 (SIRT6) in the defense against APAP-induced hepatotoxicity.

METHODS

Hepatocyte-specific SIRT6 knockout mice, farnesoid X receptor (FXR) knockout mice, and mice with genetic or pharmacological activation of SIRT6 were subjected to APAP to evaluate the critical role of SIRT6 in the pathogenesis of acute liver injury. RNA sequences were used to investigate molecular mechanisms underlying this process.

RESULTS

Hepatic SIRT6 expression was substantially reduced in the patients and mice with acute liver injury. The deletion of SIRT6 in mice and mice primary hepatocytes led to high N-acetyl-p-benzo-quinoneimine and low glutathione levels in the liver, thereby enhancing APAP overdose-induced liver injury, manifested as increased hepatic centrilobular necrosis, oxidative stress, and inflammation. Conversely, overexpression or pharmacological activation of SIRT6 enhanced glutathione and decreased N-acetyl-p-benzo-quinoneimine, thus alleviating APAP-induced hepatotoxicity via normalization of liver damage, inflammatory infiltration, and oxidative stress. Our molecular analysis revealed that FXR is regulated by SIRT6, which is associated with the pathological progression of ALI. Mechanistically, SIRT6 deacetylates FXR and elevates FXR transcriptional activity. FXR ablation in mice and mice primary hepatocytes prominently blunted SIRT6 overexpression and activation-mediated ameliorative effects. Conversely, pharmacological activation of FXR mitigated APAP-induced hepatotoxicity in SIRT6 knockout mice.

CONCLUSIONS

Our current study suggests that SIRT6 plays a crucial role in APAP-induced hepatotoxicity, and pharmacological activation of SIRT6 may represent a novel therapeutic strategy for APAP overdose-induced liver injury.

Potential deleterious effects of paracetamol dose regime used in Nigeria versus that of the United States of America

Paracetamol, also known as acetaminophen (N-acetyl-para-aminophenol, APAP) is the world's most used over-the-counter analgesic-antipyretic drug. Despite its good safety profile, acetaminophen can cause severe hepatotoxicity in overdose, and poisoning from paracetamol has become a major public health concern. Paracetamol is now the major cause of acute liver failure in the United States and Europe. This systematic review aims at examining the likelihood of paracetamol use in Nigeria causing more liver toxicity vis-à-vis the reduced maximum recommended daily adult dose of 3 g for the 500 mg tablet. Online searches were conducted in the databases of PubMed, Google Scholar and MEDLINE for publications using terms like "paracetamol toxicity," "acetaminophen and liver toxicity," "paracetamol and liver diseases in Nigeria," and other variants. Further search of related references in PubMed was carried out, and synthesis of all studies included in this review finalized. There were 94 studies that met the inclusion criteria. Evaluation of hepatic disorder was predicated mostly on a constellation of clinical features and limited clinical laboratory investigations. Determination of blood paracetamol concentration was rarely reported, thus excluding paracetamol poisoning as one of the likely causes of liver disorders in Nigeria. In Nigeria and elsewhere, several factors are known to increase paracetamol's predisposition to liver injury. They include: the over-the-counter status of paracetamol, use of fixed-dose combinations of paracetamol with other drugs, malnutrition, dose miscalculations, and chronic alcohol consumption. The tendency to exceed the new paracetamol maximum daily dose of 3 g in Nigeria may increase its risk for hepatotoxicity than observed in the United States of America known for emphasizing lower dose of the drug. In addition to recommending the new maximal daily paracetamol dose allowance, the historical maximum daily adult dose of 4 g should be de-emphasized in Nigeria.

Construction of PIK3C3 Transgenic Pig and Its Pathogenesis of Liver Damage

As a member of the PIKs family, PIK3C3 participates in autophagy and plays a central role in liver function. Several studies demonstrated that the complete suppression of PIK3C3 in mammals can cause hepatomegaly and hepatosteatosis. However, the function of PIK3C3 overexpression on the liver and other organs is still unknown. In this study, we successfully generated PIK3C3 transgenic pigs through somatic cell nuclear transfer (SCNT) by designing a specific vector for the overexpression of PIK3C3. Plasmid identification was performed through enzyme digestion and transfected into the fetal fibroblasts derived from Diannan miniature pigs. After 2 weeks of culturing, six positive colonies obtained from a total of 14 cell colonies were identified through PCR. One positive cell line was selected as the donor cell line for SCNT for the construction of PIK3C3transgenic pigs. Thirty single blastocysts were collected and identified as PIK3C3 transgenic-positive blastocysts. Two surrogates became pregnant after transferring the reconstructed embryos into four surrogates. Fetal fibroblasts of PIK3C3-positive fetuses identified through PCR were used as donor cells for SCNT to generate PIK3C3 transgenic pigs. To further explore the function of PIK3C3 overexpression, genotyping and phenotyping of the fetuses and piglets obtained were performed by PCR, immunohistochemical, HE, and apoptosis staining. The results showed that inflammatory infiltration and vacuolar formation in hepatocytes and apoptotic cells, and the mRNA expression of NF-κB, TGF-β1, TLR4, TNF-α, and IL-6 significantly increased in the livers of PIK3C3 transgenic pigs when compared with wild-type (WT) pigs. Immunofluorescence staining showed that LC3B and LAMP-1-positive cells increased in the livers of PIK3C3 transgenic pigs. In the EBSS-induced autophagy of the porcine fibroblast cells (PFCs), the accumulated LC3II protein was cleared faster in PIK3C3 transgenic (PFCs) thanWT (PFCs). In conclusion, PIK3C3 overexpression promoted autophagy in the liver and associated molecular mechanisms related to the activation of ULK1, AMBR1, DRAM1, and MTOR, causing liver damage in pigs. Therefore, the construction of PIK3C3 transgenic pigs may provide a new experimental animal resource for liver diseases.

Recent insights into the pathogeneses and therapeutic targets of liver diseases: Summary of the 4th Chinese American Liver Society/Society of Chinese Bioscientists in America Hepatology Division Symposium in 2021

The 4th Chinese American Liver Society (CALS)/Society of Chinese Bioscientists in America (SCBA) Hepatology Division Annual Symposium was held virtually on October 29-30, 2021. The goal of the CALS Symposium was to present and discuss the recent research data on the pathogeneses and therapeutic targets of liver diseases among the CALS members, trainees and invited speakers. Here we briefly introduce the history of the CALS/SCBA Hepatology Division and highlight the presentations that focus on the current progresses on basic and translational research in liver metabolism, bile acid biology, alcohol-related liver disease, drug-induced liver injury, cholestatic liver injury, non-alcoholic fatty liver disease/non-alcoholic steatohepatitis and liver cancer.

Recommendations for the use of the acetaminophen hepatotoxicity model for mechanistic studies and how to avoid common pitfalls

Acetaminophen (APAP) is a widely used analgesic and antipyretic drug, which is safe at therapeutic doses but can cause severe liver injury and even liver failure after overdoses. The mouse model of APAP hepatotoxicity recapitulates closely the human pathophysiology. As a result, this clinically relevant model is frequently used to study mechanisms of drug-induced liver injury and even more so to test potential therapeutic interventions. However, the complexity of the model requires a thorough understanding of the pathophysiology to obtain valid results and mechanistic information that is translatable to the clinic. However, many studies using this model are flawed, which jeopardizes the scientific and clinical relevance. The purpose of this review is to provide a framework of the model where mechanistically sound and clinically relevant data can be obtained. The discussion provides insight into the injury mechanisms and how to study it including the critical roles of drug metabolism, mitochondrial dysfunction, necrotic cell death, autophagy and the sterile inflammatory response. In addition, the most frequently made mistakes when using this model are discussed. Thus, considering these recommendations when studying APAP hepatotoxicity will facilitate the discovery of more clinically relevant interventions.

Protective effect and mechanism of chitooligosaccharides on acetaminophen-induced liver injury

Currently, drug-induced liver injury caused by acetaminophen (APAP) is the second leading cause of human liver transplantation. The only clinical antidote treatment for APAP-induced liver injury is N-acetyl-L-cysteine (NAC), which has many side effects. Chitooligosaccharides (COS) are processed from naturally occurring chitin through chemical desalting and deproteinization, biological enzymatic hydrolysis and other processes. In this study, we constructed in vitro and in vivo models of APAP-induced liver injury to study COS of two molecular weights (MWs), which are COST (MW ≤ 1000 Da) and COSM (MW ≤ 3000 Da). The results showed that COST and COSM can significantly reduce the levels of serum ALT and AST and liver MDA, TNF-α, IL-1β and IL-6, and increase the levels and activity of GSH, SOD, GSH-Px and CAT. A mechanistic study found that COST and COSM can significantly reduce the expression of liver CYP2E1, Keap1, p-ASK1/ASK1, p-MKK4/MKK4, p-JNK/JNK, Caspase-3 and Bax and increase the expression of Nrf2, HO-1, eNOS, SOD and Bcl-XL. COST and COSM can inhibit toxic APAP metabolism, inhibit oxidative damage and the apoptosis pathway, increase activation of the liver antioxidant pathway, and ultimately ameliorate APAP-induced liver oxidative damage.