Hyperglycemia exacerbates acetaminophen-induced acute liver injury by promoting liver-resident macrophage proinflammatory response via AMPK/PI3K/AKT-mediated oxidative stress

Formononetin attenuates hepatic injury in diabetic mice by regulating macrophage polarization through the PTP1B/STAT6 axis

BACKGROUND

Formononetin (FNT) is an isoflavone known for its anti-inflammatory properties and has been shown to reduce insulin resistance in Type 2 Diabetes Mellitus (T2DM). However, its effects and the underlying mechanisms in diabetic liver injury remain largely unexplored.

METHODS

We established a T2DM-induced liver injury mouse model by feeding high-fat diet, followed by injecting streptozotocin. The mice were then treated with FNT and the liver function in these mice was assessed. Macrophage markers in FNT-treated T2DM mice or human THP-1 cells were evaluated using flow cytometry, RT-qPCR, and Western blotting. The expression of PTP1B and STAT6 in mouse liver tissues and THP-1 cells was analyzed. Molecular docking predicted the interaction between PTP1B and STAT6, which was validated via co-immunoprecipitation (Co-IP) and phos-tag analysis. Microscale thermophoresis (MST) assessed the binding affinity of FNT to PTP1B.

RESULTS

FNT treatment significantly ameliorated blood glucose levels, hepatocyte apoptosis, inflammatory response, and liver dysfunction in T2DM mice. Moreover, FNT facilitated M2 macrophage polarization in both T2DM mice and high glucose (HG)-induced THP-1-derived macrophages. The PTP1B/STAT6 axis, deregulated in T2DM mice, was normalized by FNT treatment, which counteracted the T2DM-induced upregulation of PTP1B and downregulation of phosphorylated STAT6. Molecular docking and subsequent analyses revealed that PTP1B binds to and dephosphorylates STAT6 at the S325A site. In contrast, FNT strongly binds to PTP1B and influences its expression at the K116A site, promoting M2 polarization of THP-1 cells via downregulation of PTP1B.

CONCLUSION

Formononetin mitigates diabetic hepatic injury by fostering M2 macrophage polarization via the PTP1B/STAT6 axis.

Triptolide-induced acute liver injury and its mechanism with estradiol in regulating macrophage-mediated inflammation and hepatocyte function

Triptolide (TP), a diterpene from Tripterygium wilfordii, exhibits potent anti-inflammatory, immunomodulatory, and antitumor properties but is limited by severe hepatotoxicity. This study investigates sex differences in TP-induced liver injury and the protective role of estradiol (E2) in modulating macrophage-mediated inflammation and hepatocyte function. An acute liver injury model was established in male and female Balb/c mice using intraperitoneal TP injection. Liver function tests, histological analyses, and immunohistochemical staining were performed. THP-1 macrophage and various liver cell lines were used to study the effects of TP and E2 in vitro. Virtual screening, molecular docking, luciferase assays, and qPCR were employed to identify potential targets and elucidate underlying mechanisms. TP caused more severe liver injury in female mice, evidenced by increased liver indices, aspartate aminotransferase (AST) levels, and extensive hepatocyte damage. TP promoted M1 macrophage polarization, enhancing inflammation, particularly in female mice. E2 mitigated TP-induced inflammatory responses by downregulating pro-inflammatory cytokines and macrophage activation markers. Molecular docking and functional assays identified Nuclear receptor subfamily 1 group I member 2 (NR1I2) as a key target mediating the protective effects of E2. The study highlights significant sex differences in TP-induced hepatotoxicity, with females being more susceptible. E2 exerts protective effects against TP-induced liver injury by modulating immune responses, presenting a potential therapeutic approach to mitigate drug-induced liver injury (DILI). Further research on NR1I2 could lead to targeted therapies for reducing drug-induced liver damage.

TBC1D1 is an energy-responsive polarization regulator of macrophages via governing ROS production in obesity

Energy status is linked to the production of reactive oxygen species (ROS) in macrophages, which is elevated in obesity. However, it is unclear how ROS production is upregulated in macrophages in response to energy overload for mediating the development of obesity. Here, we show that the Rab-GTPase activating protein (RabGAP) TBC1D1, a substrate of the energy sensor AMP-activated protein kinase (AMPK), is a critical regulator of macrophage ROS production and consequent adipose inflammation for obesity development. TBC1D1 deletion decreases, whereas an energy overload-mimetic non-phosphorylatable TBC1D1S231A mutation increases, ROS production and M1-like polarization in macrophages. Mechanistically, TBC1D1 and its downstream target Rab8a form an energy-responsive complex with NOX2 for ROS generation. Transplantation of TBC1D1S231A bone marrow aggravates diet-induced obesity whereas treatment with an ultra-stable TtSOD for removal of ROS selectively in macrophages alleviates both TBC1D1S231A mutation- and diet-induced obesity. Our findings therefore have implications for drug discovery to combat obesity.

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.

Diabetes Accelerates Steatohepatitis in Mice: Liver Pathology and Single-Cell Gene Expression Signatures

Glucose lowering independently reduces liver fibrosis in human nonalcoholic fatty liver disease. This study investigated the impact of diabetes on steatohepatitis and established a novel mouse model for diabetic steatohepatitis. Male C57BL/6J mice were fed a 60% high-fat diet (HFD) and injected with carbon tetrachloride (CCl4) and streptozotocin (STZ) to induce diabetes. The HFD+CCl4+STZ group showed more severe liver steatosis, hepatocyte ballooning, and regenerative nodules compared with other groups. Diabetes up-regulated inflammatory cytokine-associated genes and increased the M1/M2 macrophage ratios in the liver. Single-cell RNA sequencing analysis of nonparenchymal cells in the liver showed that diabetes reduced Kupffer cells and increased bone marrow-derived recruited inflammatory macrophages, such as Ly6Chi-RM. Diabetes globally reduced liver sinusoidal endothelial cells (LSECs). Furthermore, genes related to the receptor for advanced glycation end products (RAGE)/Toll-like receptor 4 (TLR4) were up-regulated in Ly6Chi-RM and LSECs in mice with diabetes, suggesting a possible role of RAGE/TLR4 signaling in the interaction between inflammatory macrophages and LSECs. This study established a novel diabetic steatohepatitis model using a combination of HFD, CCl4, and STZ. Diabetes exacerbated steatosis, hepatocyte ballooning, fibrosis, regenerative nodule formation, and the macrophage M1/M2 ratios triggered by HFD and CCl4. Single-cell RNA sequencing analysis indicated that diabetes activated inflammatory macrophages and impairs LSECs through the RAGE/TLR4 signaling pathway. These findings open avenues for discovering novel therapeutic targets for diabetic steatohepatitis.

Obesity phenotype induced by high-fat diet promotes diethylnitrosamine (DEN)-induced precancerous lesions by M1 macrophage polarization in mice liver

Liver precancerous lesions are the key to improving the efficacy of cancer treatment because of the extremely poor prognosis of HCC patients in moderate and late stages. Obesity-related HCC progression is closely related to the inflammatory microenvironment, in which macrophages are one of the major constituents. In the present study, we ask whether obesity promotes diethylnitrosamine (DEN)-induced precancerous lesions by M1 macrophage polarization. First, an association between obesity and liver precancerous lesions was determined by histopathological observations, immunochemistry and immunoblotting. The characteristics of early precancerous lesions (trabecular thickening) appeared earlier eight weeks in obese mice than in normal diet mice after DEN induction. The glutathione S-transferase placental-1 (Gstp 1) and alpha-fetoprotein (AFP) expression in obese mice after DEN induction was higher than that in the same period after DEN injection in normal diet mice. Furthermore, there was a significant increase in the total macrophage number (F4/80+) of DEN and M1 macrophage number (CD86+F4/80+) in obese mice compared with that in normal diet mice. Besides, the expressions of four pro-inflammatory factors in DEN-induced obese mice were significantly higher compared with that in normal diet mice. Additionally, angiogenesis was revealed by immunostaining assay to be associated with the inflammatory response. All the results demonstrate that obesity promotes DEN-induced precancerous lesions by inducing M1 macrophage polarization and angiogenesis.

[Total saponins of Panax japonicus alleviates CCl4-induced acute liver injury in rats by regulating the PI3K/AktNF-κB signaling pathway]

OBJECTIVE

To investigate the protective effect of total saponins of Panax japonicus (TSPJ) against CCl4-induced acute liver injury (ALI) in rats and explore the underlying pharmacological mechanisms.

METHODS

Male SD rat models of CCl4-induced ALI were given intraperitoneal injections of distilled water, 100 mg/kg biphenyl bisabololol, or 50, 100, and 200 mg/kg TSPJ during modeling (n=8). Liver functions (AST, ALT, TBil and ALP) of the rats were assessed and liver pathologies were observed with HE staining. Immunohistochemistry was used to detect the expressions of PI3K/Akt/NF-κB signaling pathway molecules in liver tissue; ELISA was used to determine the levels of T-SOD, GSH-Px, and MDA. Western blotting was performed to detect the expression levels of PI3K-Akt and SIRT6-NF-κB pathways in the liver tissue.

RESULTS

Network pharmacological analysis indicated that the key pathways including PI3K/Akt mediated the therapeutic effect of TSPJ on ALI. In the rat models of ALI, treatments with biphenyl bisabololol and TSPJ significantly ameliorated CCl4-induced increase of serum levels AST, ALT, ALP, TBil and MDA and decrease of T-SOD and GSH-Px levels (all P < 0.01). The rat models of ALI showed significantly increased expression of p-NF-κB (P < 0.01), decreased expressions of PI3K, p-Akt and SIRT6 proteins, and elevated expression levels of p-NF-κB, TNF-α and IL-6 proteins in the liver, which were all significantly improved in the treatment groups (P < 0.05 or 0.01).

CONCLUSION

TSPJ can effectively alleviate CCl4-induced ALI in rats by suppressing inflammatory responses and oxidative stress in the liver via regulating the PI3K/Akt and SIRT6/NF-κB pathways.

Effects of hyperglycemia on the TGF-β pathway in trabecular meshwork cells

BACKGROUND

Hyperglycemia, which can lead to apoptosis, hypertrophy, fibrosis, and induces hyperinflammation in diabetic vascular complications due to oxidative stress. In order to elucidate the potential dual roles and regulatory signal transduction of TGF-β1 and TGF-β2 in human trabecular meshwork cells (HTMCs), we established an oxidative cell model in HTMCs using 5.5, 25, 50, and 100 mM d-glucose-supplemented media and characterized the TGF-β-related oxidative stress pathway.

METHODS

Further analysis was conducted to investigate oxidative damage and protein alterations in the HTMC caused by the signal transduction. This was done through a series of qualitative cell function studies, such as cell viability/apoptosis analysis, intracellular reactive oxygen species (ROS) detection, analysis of calcium release concentration, immunoblot analysis to detect the related protein expression alteration, and analysis of cell fibrosis to study the effect of different severities of hyperglycemia. Also, we illustrated the role of TGF-β1/2 in oxidative stress-induced injury by shRNA-mediated knockdown or stimulation with recombinant human TGF-β1 protein (rhTGF-β1).

RESULTS

Results from the protein expression analysis showed that p-JNK, p-p38, p-AKT, and related SMAD family members were upregulated in HTMCs under hyperglycemia. In the cell functional assays, HTMCs treated with rhTGFβ-1 (1 ng/mL) under hyperglycemic conditions showed higher proliferation rates and lower ROS and calcium levels.

CONCLUSIONS

To summarize, mechanistic analyses in HTMCs showed that hyperglycemia-induced oxidative stress activated TGF-β1 along with its associated pathway.

GENERAL SIGNIFICANCE

While at low concentrations, TGF-β1 protects cells from antioxidation, whereas at high concentrations, it accumulates in the extracellular matrix, causing further HTMC dysfunction.

A study integrated metabolomics and network pharmacology to investigate the effects of Shicao in alleviating acute liver injury

ETHNOPHARMACOLOGICAL RELEVANCE

Shicao is the aerial part of Achillea alpina L., a common herb found mainly in Europe, Asia, and North America. Traditional Chinese medicine has a history of thousands of years and is widely used to treat various diseases.

AIM OF STUDY

To explore the hepatoprotective effects of Shicao on CCl4-induced acute liver injury.

METHODS

A rat model of acute liver injury was established and liver function indices were assessed to evaluate the protective effect of Shicao on the liver. Untargeted metabolomics of the serum and liver tissues was conducted using UPLC-Q-TOF/MS to identify differential metabolites related to acute liver injury. A network of metabolite-reaction-enzyme-gene constituents was constructed using network pharmacology. Hub targets and key components of the effect of Shicao on acute liver injury were screened from the network.

RESULTS

Compared to the model group, Shicao improved the degree of liver damage through the assessment of the liver index, ALT and AST levels, and hepatic pathology slices, demonstrating its hepatoprotective effect against acute liver injury in rats. 10 and 38 differential metabolites involved in acute liver injury were identified in serum and liver tissues, respectively. Most of these were regulated or restored following treatment with Shicao, which mainly consisted of bile acids, lipids, and nucleotides such as taurocholic acid, LysoPC (17:0), and adenosine diphosphate ribose. Through the network of metabolite-reaction-enzyme-gene-constituents, 10 key components and 5 hub genes, along with 7 crucial differential metabolites, were mainly involved in glycerophospholipid metabolism, purine metabolism, biosynthesis of unsaturated fatty acids, and primary bile acid biosynthesis, which may play important roles in the prevention of acute liver injury by Shicao.

CONCLUSION

This study revealed that Shicao had protective effects against CCl4-induced liver injury in rats. It was speculated that the ingredients of Shicao might be closely related to the hub targets, thereby regulating the levels of key metabolites, affecting inflammatory response and oxidative stress and attenuate the liver injury consequently. This study provides a basis for further investigation of its therapeutic potential and the mechanism of action.

The Modulation of Phospho-Extracellular Signal-Regulated Kinase and Phospho-Protein Kinase B Signaling Pathways plus Activity of Macrophage-Stimulating Protein Contribute to the Protective Effect of Stachydrine on Acetaminophen-Induced Liver Injury

Stachydrine, a prominent bioactive alkaloid derived from Leonurus heterophyllus, is a significant herb in traditional medicine. It has been noted for its anti-inflammatory and antioxidant characteristics. Consequently, we conducted a study of its hepatoprotective effect and the fundamental mechanisms involved in acetaminophen (APAP)-induced liver injury, utilizing a mouse model. Mice were intraperitoneally administered a hepatotoxic dose of APAP (300 mg/kg). Thirty minutes after APAP administration, mice were treated with different concentrations of stachydrine (0, 2.5, 5, and 10 mg/kg). Animals were sacrificed 16 h after APAP injection for serum and liver tissue assays. APAP overdose significantly elevated the serum alanine transferase levels, hepatic pro-inflammatory cytokines, malondialdehyde activity, phospho-extracellular signal-regulated kinase (ERK), phospho-protein kinase B (AKT), and macrophage-stimulating protein expression. Stachydrine treatment significantly decreased these parameters in mice with APAP-induced liver damage. Our results suggest that stachydrine may be a promising beneficial target in the prevention of APAP-induced liver damage through attenuation of the inflammatory response, inhibition of the ERK and AKT pathways, and expression of macrophage-stimulating proteins.

Non-canonical BIM-regulated energy metabolism determines drug-induced liver necrosis

Paracetamol (acetaminophen, APAP) overdose severely damages mitochondria and triggers several apoptotic processes in hepatocytes, but the final outcome is fulminant necrotic cell death, resulting in acute liver failure and mortality. Here, we studied this switch of cell death modes and demonstrate a non-canonical role of the apoptosis-regulating BCL-2 homolog BIM/Bcl2l11 in promoting necrosis by regulating cellular bioenergetics. BIM deficiency enhanced total ATP production and shifted the bioenergetic profile towards glycolysis, resulting in persistent protection from APAP-induced liver injury. Modulation of glucose levels and deletion of Mitofusins confirmed that severe APAP toxicity occurs only in cells dependent on oxidative phosphorylation. Glycolytic hepatocytes maintained elevated ATP levels and reduced ROS, which enabled lysosomal recycling of damaged mitochondria by mitophagy. The present study highlights how metabolism and bioenergetics affect drug-induced liver toxicity, and identifies BIM as important regulator of glycolysis, mitochondrial respiration, and oxidative stress signaling.

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.

Hepatocyte-specific deletion of small heterodimer partner protects mice against acetaminophen-induced hepatotoxicity via activation of Nrf2

Acetaminophen (APAP) overdose stands as the primary cause of acute liver failure in the United States. APAP hepatotoxicity involves hepatic glutathione (GSH) depletion and mitochondrial damage. To counteract the toxicity of APAP, the nuclear factor erythroid 2 like 2 (Nrf2) activates the expression of genes responsible for drug detoxification and GSH synthesis. In this study, we present evidence that the elimination of hepatocyte small heterodimer partner, a critical transcriptional repressor for liver metabolism, results in Nrf2 activation and protects mice from APAP-induced acute liver injury. Initial investigations conducted on wildtype (WT) mice revealed a swift downregulation of Shp mRNA within the first 24 h after APAP administration. Subsequent treatment of hepatocyte-specific Shp knockout (ShpHep-/-) mice with 300 mg/kg APAP for 2 h exhibited comparable bioactivation of APAP with that observed in the WT controls. However, a significant reduction in liver injury was observed in ShpHep-/- after APAP treatment for 6 and 24 h. The decreased liver injury correlated with a faster recovery of GSH, attributable to heightened expression of Nrf2 target genes involved in APAP detoxification and GSH synthesis. Moreover, in vitro studies revealed that SHP protein interacted with NRF2 protein, inhibiting the transcription of Nrf2 target genes. These findings hold relevance for humans, as overexpression of SHP hindered APAP-induced NRF2 activation in primary human hepatocytes. In conclusion, our studies have unveiled a novel regulatory axis involving SHP and NRF2 in APAP-induced acute liver injury, emphasizing SHP as a promising therapeutic target in APAP overdose-induced hepatotoxicity.

Melatonin: a promising neuroprotective agent for cerebral ischemia-reperfusion injury

Cerebral ischemia-reperfusion (CIR) injury is initiated by the generation of reactive oxygen species (ROS), which leads to the oxidation of cellular proteins, DNA, and lipids as an initial event. The reperfusion process impairs critical cascades that support cell survival, including mitochondrial biogenesis and antioxidant enzyme activity. Failure to activate prosurvival signals may result in increased neuronal cell death and exacerbation of CIR damage. Melatonin, a hormone produced naturally in the body, has high concentrations in both the cerebrospinal fluid and the brain. However, melatonin production declines significantly with age, which may contribute to the development of age-related neurological disorders due to reduced levels. By activating various signaling pathways, melatonin can affect multiple aspects of human health due to its diverse range of activities. Therefore, understanding the underlying intracellular and molecular mechanisms is crucial before investigating the neuroprotective effects of melatonin in cerebral ischemia-reperfusion injury.

Exploring the potential of treating chronic liver disease targeting the PI3K/Akt pathway and polarization mechanism of macrophages

Chronic liver disease is a significant public health issue that can lead to considerable morbidity and mortality, imposing an enormous burden on healthcare resources. Understanding the mechanisms underlying chronic liver disease pathogenesis and developing effective treatment strategies are urgently needed. In this regard, the activation of liver resident macrophages, namely Kupffer cells, plays a vital role in liver inflammation and fibrosis. Macrophages display remarkable plasticity and can polarize into different phenotypes according to diverse microenvironmental stimuli. The polarization of macrophages into M1 pro-inflammatory or M2 anti-inflammatory phenotypes is regulated by complex signaling pathways such as the PI3K/Akt pathway. This review focuses on investigating the potential of using plant chemicals targeting the PI3K/Akt pathway for treating chronic liver disease while elucidating the polarization mechanism of macrophages under different microenvironments. Studies have demonstrated that inhibiting M1-type macrophage polarization or promoting M2-type polarization can effectively combat chronic liver diseases such as alcoholic liver disease, non-alcoholic fatty liver disease, and liver fibrosis. The PI3K/Akt pathway acts as a pivotal modulator of macrophage survival, migration, proliferation, and their responses to metabolism and inflammatory signals. Activating the PI3K/Akt pathway induces anti-inflammatory cytokine expression, resulting in the promotion of M2-like phenotype to facilitate tissue repair and resolution of inflammation. Conversely, inhibiting PI3K/Akt signaling could enhance the M1-like phenotype, which exacerbates liver damage. Targeting the PI3K/Akt pathway has tremendous potential as a therapeutic strategy for regulating macrophage polarization and activity to treat chronic liver diseases with plant chemicals, providing new avenues for liver disease treatment.

IL-33/ST2 antagonizes STING signal transduction via autophagy in response to acetaminophen-mediated toxicological immunity

BACKGROUND

Interleukin-33 (IL-33), defined as "alarming", exert diverse functions through signaling via the suppression of tumorigenicity 2 (ST2). However, the physiological roles of IL-33/ST2 signaling during acetaminophen (APAP)-induced liver injury are still poorly understood by modern medicine (AILI). This research aims to explore the relationship between IL-33/ST2 and stimulator of interferon (IFN) response cGAMP interactor 1 (STING)-mediated signal transduction.

METHODS

C57BL/6N mice (WT) and IL-33-deficient mice (KO) were intraperitoneally injected with APAP (250 mg/kg). Recombinant IL-33 (500 ng/mouse) and the cGAS/STING inhibitor RU.521 (200 g/kg) were combined to treat AILI. For mechanistic research in vitro, CRISPR-mediated KD technology, immunoprecipitation, mass spectrometry, and immunofluorescence were utilized.

RESULTS

We discovered that IL-33 deficient mice had increased APAP-induced hepatotoxicity, DNA accumulation, and type 1 IFN production. Mechanistic analysis revealed that IL-33/ST2 enhanced the interaction between Beclin-1 and STING, disrupting STING dimerization, IRF3 phosphorylation, nuclear transport, and IFN-1 gene transcription in HepaRG and Huh7 cells. Beclin-1 interacted with the C-terminus of STING, causing Lys338 acetylation and autophagy degradation of STING. ST2 depletion increased STING signal transduction and IFN-1 promoter activity. Surprisingly, the cGAS/STING inhibitor RU.521 and recombinant IL-33 together improved AILI in vivo.

CONCLUSIONS

These results shed insight on the potential of inhibiting cGAS/STING as a therapy for AILI and emphasize the crucial role of IL-33/ST2 signaling in the regulation of APAP-induced STING signaling. Video Abstract.

Acetaminophen-Induced Hepatotoxicity in Obesity and Nonalcoholic Fatty Liver Disease: A Critical Review

The epidemic of obesity, type 2 diabetes and nonalcoholic liver disease (NAFLD) favors drug consumption, which augments the risk of adverse events including liver injury. For more than 30 years, a series of experimental and clinical investigations reported or suggested that the common pain reliever acetaminophen (APAP) could be more hepatotoxic in obesity and related metabolic diseases, at least after an overdose. Nonetheless, several investigations did not reproduce these data. This discrepancy might come from the extent of obesity and steatosis, accumulation of specific lipid species, mitochondrial dysfunction and diabetes-related parameters such as ketonemia and hyperglycemia. Among these factors, some of them seem pivotal for the induction of cytochrome P450 2E1 (CYP2E1), which favors the conversion of APAP to the toxic metabolite N-acetyl-p-benzoquinone imine (NAPQI). In contrast, other factors might explain why obesity and NAFLD are not always associated with more frequent or more severe APAP-induced acute hepatotoxicity, such as increased volume of distribution in the body, higher hepatic glucuronidation and reduced CYP3A4 activity. Accordingly, the occurrence and outcome of APAP-induced liver injury in an obese individual with NAFLD would depend on a delicate balance between metabolic factors that augment the generation of NAPQI and others that can mitigate hepatotoxicity.

Macrophage Polarization and Reprogramming in Acute Inflammation: A Redox Perspective

Macrophage polarization refers to the process by which macrophages can produce two distinct functional phenotypes: M1 or M2. The balance between both strongly affects the progression of inflammatory disorders. Here, we review how redox signals regulate macrophage polarization and reprogramming during acute inflammation. In M1, macrophages augment NADPH oxidase isoform 2 (NOX2), inducible nitric oxide synthase (iNOS), synaptotagmin-binding cytoplasmic RNA interacting protein (SYNCRIP), and tumor necrosis factor receptor-associated factor 6 increase oxygen and nitrogen reactive species, which triggers inflammatory response, phagocytosis, and cytotoxicity. In M2, macrophages down-regulate NOX2, iNOS, SYNCRIP, and/or up-regulate arginase and superoxide dismutase type 1, counteract oxidative and nitrosative stress, and favor anti-inflammatory and tissue repair responses. M1 and M2 macrophages exhibit different metabolic profiles, which are tightly regulated by redox mechanisms. Oxidative and nitrosative stress sustain the M1 phenotype by activating glycolysis and lipid biosynthesis, but by inhibiting tricarboxylic acid cycle and oxidative phosphorylation. This metabolic profile is reversed in M2 macrophages because of changes in the redox state. Therefore, new therapies based on redox mechanisms have emerged to treat acute inflammation with positive results, which highlights the relevance of redox signaling as a master regulator of macrophage reprogramming.

Cajaninstilbene Acid Ameliorates Acetaminophen-Induced Liver Injury Through Enhancing Sestrin2/AMPK-Mediated Mitochondrial Quality Control

Acetaminophen (APAP)-induced liver injury (AILI) is the main cause of acute liver failure in the developed countries. The present study aimed to evaluate the therapeutic efficacy of cajaninstilbene acid (CSA), a major stilbene compound derived from the leaves of pigeon pea [Cajanus cajan (L.) Millsp.], against AILI. CSA (50, 75 mg/kg, p. o.) was administered to male C57BL/6 N mice 0.5 h after a toxic dose of APAP (300 mg/kg, i. p.). The direct effect of CSA on hepatocytes was tested on primary mouse hepatocytes. Serum transaminases, hematoxylin and eosin staining, TUNEL and propidium iodide staining were used to assess hepatic damage and cell death. The results demonstrated that APAP-induced liver injury was ameliorated by CSA, as evidenced by decreased alanine aminotransferase and aspartate aminotransferase levels in the serum, and fewer necrotic and apoptotic hepatocytes in vitro and in vivo. Consequently, the inflammation in response to APAP overdose was inhibited by CSA. Without affecting APAP metabolic activation, CSA interrupted the sustained JNK-Sab-ROS activation loop and alleviated oxidative stress. Additionally, CSA promoted mitochondrial quality control, including mitochondrial biogenesis and mitophagy, as revealed by increased PGC-1α, TFAM, LC3-Ⅱ, PINK1 and mitochondrial Parkin expression and decreased p62 expression. Further mechanistic investigations showed that independent of CAMKK2, LKB1-mediated AMPK activation, which was promoted by Sestrin2, might be responsible for the protective effect of CSA. Our study demonstrates that CSA alleviates APAP-induced oxidative stress and enhanced mitochondrial quality control through Sestrin2/AMPK activation, thereby protecting against AILI,.

Macrophage Polarization and Its Role in Liver Disease

Macrophages are important immune cells in innate immunity, and have remarkable heterogeneity and polarization. Under pathological conditions, in addition to the resident macrophages, other macrophages are also recruited to the diseased tissues, and polarize to various phenotypes (mainly M1 and M2) under the stimulation of various factors in the microenvironment, thus playing different roles and functions. Liver diseases are hepatic pathological changes caused by a variety of pathogenic factors (viruses, alcohol, drugs, etc.), including acute liver injury, viral hepatitis, alcoholic liver disease, metabolic-associated fatty liver disease, liver fibrosis, and hepatocellular carcinoma. Recent studies have shown that macrophage polarization plays an important role in the initiation and development of liver diseases. However, because both macrophage polarization and the pathogenesis of liver diseases are complex, the role and mechanism of macrophage polarization in liver diseases need to be further clarified. Therefore, the origin of hepatic macrophages, and the phenotypes and mechanisms of macrophage polarization are reviewed first in this paper. It is found that macrophage polarization involves several molecular mechanisms, mainly including TLR4/NF-κB, JAK/STATs, TGF-β/Smads, PPARγ, Notch, and miRNA signaling pathways. In addition, this paper also expounds the role and mechanism of macrophage polarization in various liver diseases, which aims to provide references for further research of macrophage polarization in liver diseases, contributing to the therapeutic strategy of ameliorating liver diseases by modulating macrophage polarization.

Review on oxidative stress relation on COVID-19: Biomolecular and bioanalytical approach

COVID-19 disease has put life of people in stress worldwide from many aspects. Since the virus has mutated in absolutely short period of time the challenge to find a suitable vaccine has become harder. Infection to COVID-19, especially at severe life threatening states is highly dependent on the strength of the host immune system. This system is partially dependent on the balance between oxidative stress and antioxidant. Besides, this virus still has unknown mechanism of action companied by a probable commune period. From another hand, some reactive oxygen species (ROS) levels can be helpful on the state determination of the disease. Thus it could be possible to use modern bioanalytical techniques for their detection and determination, which could indicate the disease state at the golden time window since they have the potential to show whether specific DNA, RNA, enzymes and proteins are affected. This also could be used as a preclude study or a reliable pathway to define the best optimized time of cure beside effective medical actions. Herein, some ROS and their relation with SARS-CoV-2 virus have been considered. In addition, modern bioelectroanalytical techniques on this approach from quantitative and qualitative points of view have been reviewed.

The Notch signaling pathway regulates macrophage polarization in liver diseases

The liver is not only the main metabolic site of exogenous compounds and drugs, but also an important immune organ in the human body. When a large number of nonself substances (such as drugs, alcohol, pathogens, microorganisms and their metabolites) enter the liver, they will cause serious liver diseases, including liver fibrosis, liver cirrhosis, liver failure, and hepatocellular carcinoma (HCC). Macrophages are the first line of defense against the invasion of exogenous pathogens and significant cellular components of the innate immune system. Macrophages have strong heterogeneity and plasticity. When different pathogens invade the body, they cause different types of polarization of macrophages through different molecular mechanisms. Notch signaling is considered to be the key regulator of the biological function of macrophages. Activating Notch signaling can regulate the differentiation of macrophages into M1 and play a role in promoting inflammation and antitumor activity, while blocking Notch signaling can polarize macrophages to M2, suppressing inflammation and promoting tumor growth. However, there are few studies on regulation of macrophage polarization by the Notch signaling pathway in liver diseases. Therefore, in this review, we will introduce the role of the Notch signaling pathway in regulating macrophage polarization in liver diseases.

Catalpol Weakens Depressive-like Behavior in Mice with Streptozotocin-induced Hyperglycemia via PI3K/AKT/Nrf2/HO-1 Signaling Pathway

Depression has huge social risks of high incidence, disability, and suicide. Its prevalence and harm in people with hyperglycemia are 2-3 times higher than in normal people. However, antidepressants with precise curative effects and clear mechanisms for patients with hyperglycemia are currently lacking. Prescriptions containing Rehmannia glutinosa, a traditional medicinal herb with a wide range of nutritional and medicinal values, are often used as antidepressants in Chinese clinical medicine. Catalpol is one of the main effective compounds of R. glutinosa, with multiple biological activities such as hypoglycemia. Here, the antidepressant effect of catalpol on the pathological state of streptozotocin (STZ)-induced hyperglycemia and the underlying molecular mechanisms were analyzed. Results showed that administering catalpol orally to hyperglycemic mice for 21 consecutive days significantly reversed the abnormalities in tail suspension, forced swimming, and open field tests. Catalpol also reversed the abnormal phosphorylation of phosphoinositide 3-kinase (PI3K) and protein kinase B (AKT) and the abnormal levels of nuclear factor erythroid 2-related factor 2 (Nrf2) protein, heme oxygenase-1 (HO-1), and antioxidants, including superoxide dismutase, glutathione peroxidase, glutathione-s transferase, reduced glutathione, and malondialdehyde in the hippocampus and frontal cortex of STZ-induced hyperglycemic mice. Thus, catalpol attenuates depressive-like behavior in pathological hyperglycemic state, and the antidepressant mechanism could at least be partly attributed to the upregulation of the PI3K/AKT/Nrf2/HO-1 signaling pathway in both brain regions, thus restoring the balance between oxidative and antioxidant damage. These data expanded the scientific understanding of catalpol and provided preclinical experimental evidence for its application.

Sanghuangporus sanghuang Mycelium Prevents Paracetamol-Induced Hepatotoxicity through Regulating the MAPK/NF-κB, Keap1/Nrf2/HO-1, TLR4/PI3K/Akt, and CaMKKβ/LKB1/AMPK Pathways and Suppressing Oxidative Stress and Inflammation

Liver damage induced by paracetamol overdose is the main cause of acute liver failure worldwide. In order to study the hepatoprotective effect of Sanghuangporus sanghuang mycelium (SS) on paracetamol-induced liver injury, SS was administered orally every day for 6 days in mice before paracetamol treatment. SS decreased serum aminotransferase activities and the lipid profiles, protecting against paracetamol hepatotoxicity in mice. Furthermore, SS inhibited the lipid peroxidation marker malondialdehyde (MDA), hepatic cytochrome P450 2E1 (CYP2E1), and the histopathological changes in the liver and decreased inflammatory activity by inhibiting the production of proinflammatory cytokines in paracetamol-induced acute liver failure. Moreover, SS improved the levels of glutathione (GSH), superoxide dismutase (SOD), glutathione peroxidase (GPx), and catalase in the liver. Significantly, SS diminished mitogen-activated protein kinase (MAPK), Toll-like receptor 4 (TLR4), phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt), and the nuclear factor-kappa B (NF-κB) axis, as well as upregulated the Kelch-like ECH-associated protein 1 (Keap1)/erythroid 2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1) pathway, in paracetamol-induced mice. SS mainly inhibited the phosphorylation of the liver kinase B1 (LKB1), Ca²⁺/calmodulin-dependent kinase kinase β (CaMKKβ), and AMP-activated protein kinase (AMPK) protein expression. Furthermore, the protective effects of SS on paracetamol-induced hepatotoxicity were abolished by compound C, an AMPK inhibitor. In summary, we provide novel molecular evidence that SS protects liver cells from paracetamol-induced hepatotoxicity by inhibiting oxidative stress and inflammation.

Interleukin 33 mediates hepatocyte autophagy and innate immune response in the early phase of acetaminophen-induced acute liver injury

Despite interleukin 33 (IL-33) functions as an "alarmin" released from hepatic dead cells in response to tissue damages, the interrelationship between IL-33-mediated hepatocyte autophagy and innate immune response in the acetaminophen (APAP)-induced liver injury (AILI) process remains obscure. This study aimed to explore the regulation of IL-33 on hepatocyte autophagy and macrophage polarization after APAP challenge in vivo and vitro. We found IL-33 released from hepatic necrosis was elevated in the AILI mouse model. Blockage of IL-33 exacerbated liver injury by consuming liver-resident macrophages cells (Kupffer cells, KCs) and promoting hepatic inflammatory factors secretion, such as TNF-α, IL-6 and IL-1β in the early phase of liver injury. Interestingly, IL-33 deficiency further activated hepatocyte autophagy and disrupted M2 macrophage polarization post-APAP challenge in vivo and vitro, which can be reversed by recombinant IL-33 treatment. Mechanistically, administration of IL-33 can directly enhance M2 polarization via PI3K/Akt signaling pathway and activate protective hepatocyte autophagy via AMPKα/mTOR signaling pathway in the AILI process. In conclusion, our data firstly demonstrates that IL-33 exerts protective effects on hepatocytes through the activation of autophagy and functions as an innate immunity regulator mediating macrophage polarization in the early phase of AILI.

TGR5 Regulates Macrophage Inflammation in Nonalcoholic Steatohepatitis by Modulating NLRP3 Inflammasome Activation

Nonalcoholic steatohepatitis (NASH) is a chronic liver disease associated with dysregulation of liver metabolism and inflammation. G-protein coupled bile acid receptor 1 (TGR5) is a cell surface receptor that is involved in multiple metabolic pathways. However, the functions of TGR5 in regulating macrophage innate immune activation in NASH remain unclear. Here, we found that TGR5 expression was decreased in liver tissues from humans and mice with NASH. Compared to wild type (WT) mice, TGR5-knockout (TGR5^−/−) mice exhibited exacerbated liver damage, increased levels of proinflammatory factors, and enhanced M1 macrophage polarization. Moreover, TGR5 deficiency facilitated M1 macrophage polarization by promoting NLRP3 inflammasome activation and caspase-1 cleavage. Taken together, our findings revealed that TGR5 signaling attenuated liver steatosis and inflammation and inhibited NLRP3-mediated M1 macrophage polarization in NASH.

Mycobacterium tuberculosis Heat-Shock Protein 16.3 Induces Macrophage M2 Polarization Through CCRL2/CX3CR1

Mycobacterium tuberculosis, the pathogen of tuberculosis (TB), can survive in host macrophages and induce macrophages to M2 phenotype might result in latent MTB infection. During the latent phase, the expression of MTB heat-shock protein 16.3 (Hsp16.3) is markedly increased among most of bacterial proteins, but the role of Hsp16.3 in macrophage M2 polarization is not clear. In this work, we found that macrophages incubated with 100 ng/ml MTB Hsp16.3 increased the production of Arg-1, IL-10, TGF-beta, and CD206. These results showed that MTB Hsp16.3 may induce macrophage M2 phenotype. And the interaction of Hsp16.3 with macrophages was found to depend on chemokine receptors CCRL2 and CX3CR1. Additionally, we used overexpression and silencing techniques to further verify the effect of CCRL2 and CX3CR1 on MTB Hsp16.3-induced M2 polarization macrophages. Furthermore, we explored the downstream signaling molecules of CCRL2 and CX3CR1 and we found MTB Hsp16.3 altered the signal transduction of the AKT/ERK/p38-MAPK. Taken together, this study provides evidence that MTB Hsp16.3 promotes macrophages to M2 phenotype and explores its underlying mechanism.

Acidic fibroblast growth factor attenuates type 2 diabetes-induced demyelination via suppressing oxidative stress damage

Prolonged type 2 diabetes mellitus (T2DM) produces a common complication, peripheral neuropathy, which is accompanied by nerve fiber disorder, axon atrophy, and demyelination. Growing evidence has characterized the beneficial effects of acidic fibroblast growth factor (aFGF) and shown that it relieves hyperglycemia, increases insulin sensitivity, and ameliorates neuropathic impairment. However, there is scarce evidence on the role of aFGF on remodeling of aberrant myelin under hyperglycemia condition. Presently, we observed that the expression of aFGF was rapidly decreased in a db/db T2DM mouse model. Administration of exogenous aFGF was sufficient to block acute demyelination and nerve fiber disorganization. Furthermore, this strong anti-demyelinating effect was most likely dominated by an aFGF-mediated increase of Schwann cell (SC) proliferation and migration as well as suppression of its apoptosis. Mechanistically, the beneficial biological effects of aFGF on SC behavior and abnormal myelin morphology were likely due to the inhibition of hyperglycemia-induced oxidative stress activation, which was most likely activated by kelch-like ECH-associated protein 1 (Keap1)/nuclear factor erythroid-derived-like 2 (Nrf2) signaling. Thus, this evidence indicates that aFGF is a promising protective agent for relieving myelin pathology through countering oxidative stress signaling cascades under diabetic conditions.

Cytochrome P450 2E1 should not be neglected for acetaminophen-induced liver injury in metabolic diseases with altered insulin levels or glucose homeostasis

Acetaminophen (APAP) hepatotoxicity is mediated by N-acetyl-p-benzoquinone imine (NAPQI), a highly toxic metabolite generated by cytochrome P450 2E1 (CYP2E1). Thus, pathological conditions increasing CYP2E1 activity can favour APAP-induced liver injury, which is characterized by massive hepatocellular necrosis and secondary sterile inflammation. In a recent work, Wang et al. showed that APAP-induced hepatotoxicity was exacerbated in a murine model of type 1 diabetes induced by the administration of streptozotocin (STZ). Higher hepatotoxicity was in particular associated with a stronger proinflammatory response of the resident macrophages. Although the authors carried out numerous investigations, they did not study hepatic CYP2E1, nor discussed the possible role of this enzyme in the exacerbation of APAP hepatotoxicity. However, numerous investigations reported hepatic CYP2E1 induction in STZ-treated rodents, which could be secondary to insulinopenia and ketosis. This commentary also discusses the role of insulin resistance in CYP2E1 induction observed in obesity and nonalcoholic fatty liver disease. Investigators studying APAP-induced liver injury in the context of insulinopenia or hyperinsulinemia are thus encouraged to consider CYP2E1 as a significant player in the observed phenotypic changes.

LncRNA SNHG4 Attenuates Inflammatory Responses by Sponging miR-449c-5p and Up-Regulating STAT6 in Microglial During Cerebral Ischemia-Reperfusion Injury

Background

Inflammatory response mediated by microglia plays a key role in cerebral ischemia-reperfusion injury. This study intends to probe the role of lncRNA SNHG4 in regulating the inflammatory response of the microglia during cerebral ischemia reperfusion.

Materials and Methods

Blood samples and cerebrospinal fluid samples were collected from acute cerebral infarction (ACI) patients and healthy controls. The middle cerebral artery occlusion (MCAO) models were constructed with rats. LPS induction and oxygen-glucose deprivation methods were respectively applied to simulate the activation of microglia in vitro. qRT-PCR was employed to determine the expressions of SNHG4, miR-449c-5p and related inflammatory factors in vivo and in vitro. The inflammatory responses of the microglia subject to the varied expressions of SNHG4 and miR-449c-5p were detected. Luciferase assays were conducted to verify the crosstalk involving SNHG4, miR-449c-5p and STAT6.

Results

Compared with the control group, the expression of SNHG4 derived from the samples of ACI patients and the microglia of MCAO group were remarkably down-regulated, but the expression of miR-449c-5p was dramatically up-regulated. Overexpression of SNHG4 and knock-down of miR-449c-5p could inhibit the expression of pro-inflammatory cytokine in the microglia and promote the expression of anti-inflammatory factors. Meanwhile, the phospho-STAT6 was up-regulated, whereas the knock-down of SNHG4 and over-expression of miR-449c-5p in microglia had the opposite effects. Luciferase assay confirmed that SNHG4 could target miR-449c-5p, while miR-449c-5p could target STAT6.

Conclusion

SNHG4 can regulate STAT6 and repress inflammation by adsorbing miR-449c-5p in microglia during cerebral ischemia-reperfusion injury.

Salidroside protects mice against CCl4-induced acute liver injury via down-regulating CYP2E1 expression and inhibiting NLRP3 inflammasome activation

Salidroside (Sal), a natural phenolic compound isolated from Rhodiola sachalinensis, has been utilized as anti-inflammatory and antioxidant for centuries, however, its effects against liver injury and the underlying mechanisms are unclear. This study was designed to evaluate the protective effects and underlying mechanisms of Sal on carbon tetrachloride (CCl4)-induced acute liver injury (ALI) in mice. C57BL/6 mice were pretreated with Sal before CCl4 injection, the serum and liver tissue were collected to evaluate liver damage and molecular indices. The results showed that Sal pretreatment dose-dependently attenuated CCl4-induced acute liver injury, as indicated by lowering the activities of serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT), and inhibiting hepatic pathological damage and apoptosis. In addition, Sal alleviated CCl4-primed oxidative stress and inflammatory response by restoring hepatic glutathione (GSH), superoxide dismutase (SOD), catalase (CAT), malondialdehyde (MDA), and inhibiting cytokines. Finally, Sal also down-regulated the expression of cytochrome P4502E1 (CYP2E1), and Nod-like receptor protein 3 (NLRP3) inflammasome activation in the liver of mice by CCl4. Our study demonstrates that Sal exerts its hepatoprotective effects on ALI through its antioxidant and anti-inflammatory effects, which might be mediated by down-regulating CYP2E1 expression and inhibiting NLRP3 inflammasome activation.

Diabetes induces hepatocyte pyroptosis by promoting oxidative stress-mediated NLRP3 inflammasome activation during liver ischaemia and reperfusion injury

Background

Although diabetes mellitus has been reported to aggravate liver ischaemia and reperfusion (IR) injury, the basic mechanism remains largely unknown. The object of the present study was to determine the role of oxidative stress and hepatocellular pyroptosis in liver IR injury in diabetic mice.

Methods

Db/db and C57BL/6 mice at 8 weeks of age were subjected to liver IR injury. Liver injury and hepatocyte cell death were analyzed. A NOD-like receptor family pyrin domain-containing 3 protein (NLRP3) inflammasome antagonist (CY09) and a reactive oxygen species (ROS) antagonist (N-Acetyl-L-cysteine, NAC) were used to determine the role of ROS-mediated hepatocellular pyroptosis in diabetic mice post-IR.

Results

Aggravated liver IR injury was found in db/db mice compared to C57BL/6 control mice, as demonstrated by increased serum alanine aminotransaminase (ALT) and aspartate aminotransaminase (AST) levels, liver architecture damage and Suzuki scores. Interestingly, IR induces the pyroptosis of hepatocytes in db/db mice, as evidenced by enhanced NLRP3 inflammasome activation, increased numbers of terminal deoxynucleotidyl transferase dUTP nick end labelling (TUNEL)-positive hepatocytes and increased gene expression of interleukin-1β (IL-1β) and IL-18 in livers post-IR. The inhibitory effect of CY09, an NLRP3 antagonist, efficiently abrogated the exacerbation effects of diabetes on liver IR injury in db/db mice. Furthermore, increased ROS expression was detected in db/db mice compared to control mice after IR. ROS scavenging by NAC pretreatment markedly inhibited hepatocellular NLRP3 inflammasome activation and pyroptosis in the db/db mice post-IR, indicating that ROS play an essential role in mediating hepatocyte pyroptosis in the setting of diabetes mellitus.

Conclusions

Our results demonstrate that diabetes induces hepatocyte pyroptosis by promoting oxidative stress-mediated NLRP3 inflammasome activation during liver IR injury. Strategies targeting ROS and NLRP3 inflammasome activation would be beneficial for preventing liver IR injury in diabetic patients.

Contribution of Macrophage Efferocytosis to Liver Homeostasis and Disease

The clearance of apoptotic cells is pivotal for both maintaining tissue homeostasis and returning to homeostasis after tissue injury as part of the regenerative resolution response. The liver is known for its capacity to remove aged and damaged cells from the circulation and can serve as a graveyard for effector T cells. In particular Kupffer cells are active phagocytic cells, but during hepatic inflammatory responses incoming neutrophils and monocytes may contribute to pro-inflammatory damage. To stimulate resolution of such inflammation, myeloid cell function can change, via sensing of environmental changes in the inflammatory milieu. Also, the removal of apoptotic cells via efferocytosis and the signaling pathways that are activated in macrophages/phagocytes upon their engulfment of apoptotic cells are important for a return to tissue homeostasis. Here, we will discuss, how efferocytosis mechanisms in hepatic macrophages/phagocytes may regulate tissue homeostasis and be involved in tissue regeneration in liver disease.

Methane Alleviates Acetaminophen-Induced Liver Injury by Inhibiting Inflammation, Oxidative Stress, Endoplasmic Reticulum Stress, and Apoptosis through the Nrf2/HO-1/NQO1 Signaling Pathway

Acetaminophen- (APAP-) induced hepatic injury is an important clinical challenge. Oxidative stress, inflammation, apoptosis, and endoplasmic reticulum stress (ERS) contribute to the pathogenesis. Methane has potential anti-inflammatory, antioxidant, and antiapoptotic properties. This project was aimed at studying the protective effects and relative mechanisms of methane in APAP-induced liver injury. In the in vivo experiment, C57BL/6 mice were treated with APAP (400 mg/kg) to induce hepatic injury followed by methane-rich saline (MRS) 10 ml/kg i.p. after 12 and 24 h. We observed that MRS alleviated the histopathological lesions in the liver, decreased serum aminotransferase levels, reduced the levels of inflammatory cytokines, suppressed the nuclear factor-κB expression. Further, we found that MRS relieved oxidative stress by regulating the Nrf2/HO-1/NQO1 signaling pathway and their downstream products after APAP challenge. MRS also regulated proteins associated with ERS-induced apoptosis. In the in vitro experiment, the L-02 cell line was treated with APAP (10 mM) to induce hepatic injury. We found that a methane-rich medium decreased the levels of reactive oxygen species (DHE fluorescent staining), inhibited apoptosis (cell flow test), and regulated the Nrf2/HO-1/NQO1 signaling pathway. Our data indicated that MRS prevented APAP-induced hepatic injury via anti-inflammatory, antioxidant, anti-ERS, and antiapoptotic properties involving the Nrf2/HO-1/NQO1 signaling pathway.