Formation of p62-positive inclusion body is associated with macrophage polarization in non-alcoholic fatty liver disease

Autophagy alterations in obesity, type 2 diabetes, and metabolic dysfunction-associated steatotic liver disease: the evidence from human studies

Autophagy is an evolutionarily conserved process that plays a pivotal role in the maintenance of cellular homeostasis and its impairment has been implicated in the pathogenesis of various metabolic diseases including obesity, type 2 diabetes (T2D), and metabolic dysfunction-associated steatotic liver disease (MASLD). This review synthesizes the current evidence from human studies on autophagy alterations under these metabolic conditions. In obesity, most data point to autophagy upregulation during the initiation phase of autophagosome formation, potentially in response to proinflammatory conditions in the adipose tissue. Autophagosome formation appears to be enhanced under hyperglycemic or insulin-resistant conditions in patients with T2D, possibly acting as a compensatory mechanism to eliminate damaged organelles and proteins. Other studies have proposed that prolonged hyperglycemia and disrupted insulin signaling hinder autophagic flux, resulting in the accumulation of dysfunctional cellular components that can contribute to β-cell dysfunction. Evidence from patients with MASLD supports autophagy inhibition in disease progression. Nevertheless, given the available data, it is difficult to ascertain whether autophagy is enhanced or suppressed in these conditions because the levels of autophagy markers depend on the overall metabolism of specific organs, tissues, experimental conditions, or disease duration. Owing to these constraints, determining whether the observed shifts in autophagic activity precede or result from metabolic diseases remains challenging. Additionally, autophagy-modulating strategies are shortly discussed. To conclude, more studies investigating autophagy impairment are required to gain a more comprehensive understanding of its role in the pathogenesis of obesity, T2D, and MASLD and to unveil novel therapeutic strategies for these conditions.

Macrophage Perspectives in Liver Diseases: Programmed Death, Related Biomarkers, and Targeted Therapy

Macrophages, as important immune cells of the organism, are involved in maintaining intrahepatic microenvironmental homeostasis and can undergo rapid phenotypic changes in the injured or recovering liver. In recent years, the crucial role of macrophage-programmed cell death in the development and regression of liver diseases has become a research hotspot. Moreover, macrophage-targeted therapeutic strategies are emerging in both preclinical and clinical studies. Given the macrophages' vital role in complex organismal environments, there is tremendous academic interest in developing novel therapeutic strategies that target these cells. This review provides an overview of the characteristics and interactions between macrophage polarization, programmed cell death, related biomarkers, and macrophage-targeted therapies. It aims to deepen the understanding of macrophage immunomodulation and molecular mechanisms and to provide a basis for the treatment of macrophage-associated liver diseases.

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.

Emerging role of lipophagy in liver disorders

Lipophagy is a selective degradation of lipids by a lysosomal-mediated pathway, and dysregulation of lipophagy is linked with the pathological hallmark of many liver diseases. Downregulation of lipophagy in liver cells results in abnormal accumulation of LDs (Lipid droplets) in hepatocytes which is a characteristic feature of several liver pathologies such as nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH). Contrarily, upregulation of lipophagy in activated hepatic stellate cells (HSCs) is associated with hepatic fibrosis and cirrhosis. Lipid metabolism reprogramming in violent cancer cells contributes to the progression of liver cancer. In this review, we have summarized the recent studies focusing on various components of the lipophagic machinery that can be modulated for their potential role as therapeutic agents against a wide range of liver diseases.

MMP10 alleviates non-alcoholic steatohepatitis by regulating macrophage M2 polarization

BACKGROUND

Non-alcoholic steatohepatitis (NASH), the most severe form of non-alcoholic fatty liver disease (NAFLD), is currently untreatable with a clinically validated treatment. Matrix Metallopeptidase 10 (MMP10) is a common host-response-gene involved in the immune response. However, it remains unknown whether and how MMP10 influences NASH development by modulating macrophage function.

METHODS

In vitro, MMP10 overexpression (MMP10-OE), MMP10 knockout (MMP10-KO), proliferator-activated receptor γ (PPARγ)-OE, and control plasmids were transfected into primary Kupffer cells, which were then cultured with or without Interleukin (IL)-4 stimulation. MMP10-OE mice and MMP10-KO mice were fed a normal chow diet (NCD) or a high-fat diet (HFD) for 30 weeks to study the role of MMP10 in NASH model. Hepa1-6 cells were cultured with or without free fatty acid (FFA) treatment for 24 h.

RESULTS

MMP10 is downregulated in NASH, and M1/M2 indicators are significantly imbalanced. MMP10 is triggered in response to M2 macrophages polarization. MMP10 overexpression diminishes hepatic steatosis and inflammation in HFD-induced NASH. Mechanistically, PPARγ can bind to the MMP10 promoter and then up-regulates MMP10 expression, which is engaged when IL-4 stimulates M2 macrophage polarization. The downstream STAT3 signaling pathway is further activated to induce M2 polarization, which results in a decreased expression of the pro-inflammatory IL-1β and tumor necrosis factor (TNF)-a and an increased expression of the anti-inflammatory IL-10, ultimately alleviating NASH progression.

CONCLUSIONS

We demonstrate that IL-4 effectively promotes MMP10 expression via PPARγ, and MMP10 overexpression modulates macrophage polarization, hepatic steatosis, and fibrosis, offering prospective targets for NASH treatment.

Enhancement of biochemical and genomic pathways through lycopene-loaded nano-liposomes: Alleviating insulin resistance, hepatic steatosis, and autophagy in obese rats with non-alcoholic fatty liver disease: Involvement of SMO, GLI-1, and PTCH-1 genes

Non-alcoholic fatty liver (NAFL) is a prevalent hepatic disorder of global significance that can give rise to severe complications. This research endeavor delves into the potential of nano-liposomal formulated Lycopene (Lip-Lyco) in averting the development of obesity and insulin resistance, both of which are major underlying factors contributing to NAFL. The investigation further scrutinizes the impact of Lip-Lyco on intricate cellular pathways within the liver tissue of rats induced with NAFL, specifically focusing on the progression of steatosis and fibrosis. To establish an obesity-NAFL model, twenty rats were subjected to a high-fat diet (HFD) for a duration of twelve weeks, after which they received an oral treatment of Lip-Lyco (10mg/kg) for an additional eight weeks. Another group of sixteen non-obese rats were subjected to treatment with or without Lip-Lyco, serving as a control for comparison. Results: The rats on a hypercaloric diet had high body mass index (BMI) and insulin resistance, reflected in disturbed serum adipokines and lipid profiles. Oxidative stress, inflammation, and apoptosis were evident in hepatic tissue, and the autophagic process in hepatocytes was inhibited. Additionally, the hedgehog pathway was activated in the liver tissue of NAFL group. Lip-Lyco was found to counteract all these aspects of NAFL pathogenesis. Lip-Lyco exhibited antioxidant, anti-inflammatory, hypoglycemic, antiapoptotic, autophagy-inducing, and Hedgehog signaling inhibitory effects. This study concludes that Lip-Lyco, a natural compound, has promising therapeutic potential in combating NAFLdisease. However, more experimental and clinical studies are required to confirm the effectiveness of lycopene in treating NAFLdisease.

Intravascular hemolysis triggers NAFLD characterized by a deregulation of lipid metabolism and lipophagy blockade

Intravascular hemolysis is a common feature of different clinical entities, including sickle cell disease and malaria. Chronic hemolytic disorders are associated with hepatic damage; however, it is unknown whether heme disturbs lipid metabolism and promotes liver steatosis, thereby favoring the progression to nonalcoholic fatty liver disease (NAFLD). Using an experimental model of acute intravascular hemolysis, we report here the presence of liver injury in association with microvesicular lipid droplet deposition. Hemolysis promoted serum hyperlipidemia and altered intrahepatic triglyceride fatty acid composition, with increments in oleic, palmitoleic, and palmitic acids. These findings were related to augmented expression of transporters involved in fatty acid uptake (CD36 and MSR1) and deregulation of LDL transport, as demonstrated by decreased levels of LDL receptor and increased PCSK9 expression. Hemolysis also upregulated hepatic enzymes associated with cholesterol biosynthesis (SREBP2, HMGC1, LCAT, SOAT1) and transcription factors regulating lipid metabolism (SREBP1). Increased LC3II/LC3I ratio and p62/SQSTM1 protein levels were reported in mice with intravascular hemolysis and hepatocytes stimulated with heme, indicating a blockade of lipophagy. In cultured hepatocytes, cell pretreatment with the autophagy inductor rapamycin diminished heme-mediated toxicity and accumulation of lipid droplets. In conclusion, intravascular hemolysis enhances liver damage by exacerbating lipid accumulation and blocking the lipophagy pathway, thereby promoting NAFLD. These new findings have a high translational potential as a novel NAFLD-promoting mechanism in individuals suffering from severe hemolysis episodes. © 2023 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Therapeutic implications of targeting autophagy and TGF-β crosstalk for the treatment of liver fibrosis

Liver fibrosis is characterized by the excessive deposition and accumulation of extracellular matrix components, mainly collagens, and occurs in response to a broad spectrum of triggers with different etiologies. Under stress conditions, autophagy serves as a highly conserved homeostatic system for cell survival and is importantly involved in various biological processes. Transforming growth factor-β1 (TGF-β1) has emerged as a central cytokine in hepatic stellate cell (HSC) activation and is the main mediator of liver fibrosis. A growing body of evidence from preclinical and clinical studies suggests that TGF-β1 regulates autophagy, a process that affects various essential (patho)physiological aspects related to liver fibrosis. This review comprehensively highlights recent advances in our understanding of cellular and molecular mechanisms of autophagy, its regulation by TGF-β, and the implication of autophagy in the pathogenesis of progressive liver disorders. Moreover, we evaluated crosstalk between autophagy and TGF-β1 signalling and discussed whether simultaneous inhibition of these pathways could represent a novel approach to improve the efficacy of anti-fibrotic therapy in the treatment of liver fibrosis.

Exercise against nonalcoholic fatty liver disease: Possible role and mechanism of lipophagy

Nonalcoholic fatty liver disease (NAFLD) is one of the most common causes of chronic liver disease worldwide. NAFLD is prevalent in about 30% of people worldwide. The lack of physical activity is considered as one of the risks for NAFLD, and approximately one-third of NAFLD patients hardly engage in physical activity. It is acknowledged that exercise is one of the optimal non-pharmacological methods for preventing and treating NAFLD. Different forms of exercise such as aerobic exercise, resistance exercise and even simply physical activity in a higher level can be beneficial in reducing liver lipid accumulation and disease progression for NAFLD patients. In NAFLD patients, exercise is helpful in lowering steatosis and enhancing liver function. The mechanisms underlying the prevention and treatment of NAFLD by exercise are various and complex. Current studies on the mechanisms have focused on the pro-lipolytic, anti-inflammatory, and antioxidant and lipophagy. Promotion of lipophagy is regarded as an important mechanism for prevention and improvement of NAFLD by exercise. Recent studies have investigated the above mechanism, yet the potential mechanism has not been completely elucidated. Thus, in this review, we cover the recent advances of exercise-promoted lipophagy in NAFLD treatment and prevention. Furthermore, given the fact that exercise activates SIRT1, we discuss the possible regulatory mechanisms of lipophagy by SIRT1 during exercise. These mechanisms need to be verified by further experimental studies.

Cassiae Semen improves non-alcoholic fatty liver disease through autophagy-related pathway

Objective

Cassiae Semen (CS, Juemingzi in Chinese) has been used for thousands of years in ancient Chinese history for relieving constipation, improving liver function as well as preventing myopia. Here we aimed to elucidate the anti-steatosis effect and underlying mechanism of CS against non-alcoholic fatty liver disease (NAFLD).

Methods

High-performance liquid chromatography (HPLC) was used to identify the major components of CS water extract. Mice were fed with a high-fat and sugar-water (HFSW) diet to induce hepatic steatosis and then treated with CS. The anti-NAFLD effect was determined by measuring serum biomarkers and histopathology staining. Additionally, the effects of CS on cell viability and lipid metabolism in oleic acid and palmitic acid (OAPA)-treated HepG2 cells were measured. The expression of essential genes and proteins involved in lipid metabolism and autophagy signalings were measured to uncover the underlying mechanism.

Results

Five compounds, including aurantio-obtusin, rubrofusarin gentiobioside, cassiaside C, emodin and rhein were simultaneously identified in CS extract. CS not only improved the diet-induced hepatic steatosis in vivo, as indicated by decreased number and size of lipid droplets, hepatic and serum triglycerides (TG) levels, but also markedly attenuated the OAPA-induced lipid accumulation in hepatocytes. These lipid-lowering effects induced by CS were largely dependent on the inhibition of fatty acid synthase (FASN) and the activation of autophagy-related signaling, including AMP-activated protein kinase (AMPK), light chain 3-II (LC3-II)/ LC3-1 and autophagy-related gene5 (ATG5).

Conclusion

Our study suggested that CS effectively protected liver steatosis via decreasing FASN-related fatty acid synthesis and activating AMPK-mediated autophagy, which might become a promising therapeutic strategy for relieving NAFLD.

p62/SQSTM1 in liver diseases: the usual suspect with multifarious identities

p62/Sequestosome-1 (SQSTM1) is a selective autophagy receptor that recruits and delivers intracellular substrates for bulk clearance through the autophagy lysosomal pathway. Interestingly, p62 also serves as a signaling scaffold to participate in the regulation of multiple physiological processes, including oxidative stress response, metabolism, inflammation, and programmed cell death. Perturbation of p62 activity has been frequently found to be associated with the pathogenesis of many liver diseases. p62 has been identified as a critical component of protein aggregates in the forms of Mallory-Denk bodies (MDBs) or intracellular hyaline bodies (IHBs), which are known to be frequently detected in biopsy samples from alcoholic steatohepatitis (ASH), non-alcoholic steatohepatitis (NASH), and hepatocellular carcinoma (HCC) patients. Importantly, abundance of these p62 inclusion bodies is increasingly recognized as a biomarker for NASH and HCC. Although the level of p62 bodies seems to predict the progression and prognosis of these liver diseases, understanding of the underlying mechanisms by which p62 regulates and contributes to the development and progression of these diseases remains incomplete. In this review, we will focus on the function and regulation of p62, and its pathophysiological roles in the liver, by critically reviewing the findings from preclinical models that recapitulate the pathogenesis and manifestation of these liver diseases in humans. In addition, we will also explore the suitability of p62 as a predictive biomarker and a potential therapeutic target for the treatment of liver diseases, including NASH and HCC, as well as recent development of small-molecule compounds for targeting the p62 signaling axis.

Programmed cell death and lipid metabolism of macrophages in NAFLD

Non-alcoholic fatty liver disease (NAFLD) has now become the leading chronic liver disease worldwide with lifestyle changes. This may lead to NAFLD becoming the leading cause of end-stage liver disease in the future. To date, there are still no effective therapeutic drugs for NAFLD. An in-depth exploration of the pathogenesis of NAFLD can help to provide a basis for new therapeutic agents or strategies. As the most important immune cells of the liver, macrophages play an important role in the occurrence and development of liver inflammation and are expected to become effective targets for NAFLD treatment. Programmed cell death (PCD) of macrophages plays a regulatory role in phenotypic transformation, and there is also a certain connection between different types of PCD. However, how PCD regulates macrophage polarization has still not been systematically elucidated. Based on the role of lipid metabolic reprogramming in macrophage polarization, PCD may alter the phenotype by regulating lipid metabolism. We reviewed the effects of macrophages on inflammation in NAFLD and changes in their lipid metabolism, as well as the relationship between different types of PCD and lipid metabolism in macrophages. Furthermore, interactions between different types of PCD and potential therapeutic agents targeting of macrophages PCD are also explored.

Fagopyrum dibotrys extract alleviates hepatic steatosis and insulin resistance, and alters autophagy and gut microbiota diversity in mouse models of high-fat diet-induced non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is a major global health concern with increasing prevalence, with a lack of currently available effective treatment options; thus, the investigation of novel therapeutic approaches is necessary. The study aimed to investigate the outcomes and mechanisms of action of Fagopyrum dibotrys extract (FDE) in a high-fat diet (HFD)-induced mouse model of obesity. The findings showed that FDE supplementation attenuated glucose tolerance, insulin resistance (IR), hepatic steatosis, and abnormal lipid metabolism. In addition, FDE also promoted autophagic activity and inhibited the phosphorylation of transcription factor EB in HFD-fed mice. Furthermore, gut microbiota characterization via 16S rRNA sequencing revealed that the supplementation of FDE increased Bacteroidetes and Verrucomicrobia populations while decreased Firmicutes, thus modifying the gut microbiome. FDE also increased the relative abundance of Akkermansia. Our findings suggest that FDE may protect against HFD-induced NAFLD by activating autophagy and alleviating dysbiosis in the gut microbiome. FDE may be beneficial as a nutraceutical treatment for NAFLD.

Single-cell transcriptomes identifies characteristic features of mouse macrophages in liver Mallory-Denk bodies formation

Mallory-Denk bodies (MDBs) consist of intracellular aggregates of misfolded proteins in ballooned hepatocytes and serve as important markers of progression in certain liver diseases. Resident hepatic macrophage-mediated inflammation influences the development of chronic liver diseases and cancer. Here, the first systematic study of macrophages heterogeneity in mice was conducted to illustrate the pathogenesis of MDB formation using single-nucleus RNA sequencing (snRNA-seq). Furthermore, we provided transcriptional profiles of macrophages obtained from the fractionation of mouse liver tissues following chronic injury. We equally identified seven discrete macrophage subpopulations, each involved in specific cellular activated pathways such as basal metabolism, immune regulation, angiogenesis, and cell cycle regulation. Among these, a specific macrophage cluster (Cluster4), a subpopulation specifically expressing genes that regulate cell division and the cell cycle, was identified. Interestingly, we found that CCR2 was significantly induced in Cluster2, thereby inducing monocytes to migrate to macrophages to promote MDB pathogenesis. Thus, our study is the first to demonstrate the heterogeneity of macrophages associated with liver MDB formation in mice through single-cell resolution. This serves as the basis for further insights into the pathogenesis of liver MDB formation and molecular mechanisms of chronic liver disease progression.

Endurance exercise-mediated metabolic reshuffle attenuates high-caloric diet-induced non-alcoholic fatty liver disease

INTRODUCTION AND AIM

Non-alcoholic fatty liver disease (NAFLD) is one of the most common diseases in the United States. Metabolic distress (obese diabetes) is the main causative element of NAFLD. While there is no cure for NAFLD, endurance exercise (EEx) has emerged as a therapeutic strategy against NAFLD. However, mechanisms of EXE-induced hepatic protection especially in female subjects remain unidentified. Thus, the aim of the study is to examine molecular mechanisms of EXE-induced hepatic protection against diet-induced NAFLD in female mice.

MATERIAL AND METHODS

Nine-week-old female C57BL/6J mice were randomly divided into three groups: normal-diet control group (CON, n=11); high-fat diet/high-fructose group (HFD/HF, n=11); and HFD/HF+EEx group (HFD/HF+EEx, n=11). The mice assigned to HFD/HF and HFD/HF+EEx groups were fed with HFD/HF for 12 weeks, after which the mice assigned to the EEx group began treadmill exercise for 12 weeks, with HFD/HF continued.

RESULTS

EEx attenuated hepatic steatosis, reduced de novo lipogenesis (reduction in ATP-Citrate- Lyase and diacylglycerol-O-acyltransferase 1), and enhanced mitochondrial biogenesis and fatty-acid activation (oxidative phosphorylation enzymes and Acyl-CoA synthetase1). Also, EEx prevented upregulation of gluconeogenic proteins (glyceraldehyde-3-phosphate dehydrogenase, glucose-6-phosphatase, and phosphoenolpyruvate-carboxykinase1), premature senescence (suppression of p53, p22, and p16, tumor-necrosis-factor-α, and interleukin-1β, and oxidative stress), and autophagy deficiency. Furthermore, EXE reversed apoptosis arrest (cleaved cysteine-dependent-aspartate-directed protease3 and Poly-(ADP-ribose)-polymerase1).

CONCLUSION

EEx-mediated reparations of metabolic and redox imbalance (utilization of pentose phosphate pathway), and autophagy deficiency caused by metabolic distress critically contribute to preventing/delaying severe progression of NAFLD. Also, EEx-induced anti-senescence and cell turnover are crucial protective mechanisms against NAFLD.

High expression of H2A histone family member Y promotes the proliferation and autophagy of hepatocellular carcinoma cells

Hepatocellular carcinoma is a common malignant tumor and the third most common cause of cancer-related deaths. In this study, we selected H2AFY as a potential oncogene from three online databases, and verified differential expression between normal and liver cancer tissues. Moreover, H2AFY expression was significantly correlated with the clinical characteristics and the survival of liver cancer patients. H2AFY expression was correlated with poor prognosis of liver cancer patients. H2AFY expression was also significantly higher in liver cancer cells. Knockdown and overexpression of H2AFY in liver cancer cells showed that H2AFY promoted the proliferation and clone formation of liver cancer cells but had no significant effects on the migration and invasion ability of liver cancer cells. Western blot analysis, immunohistochemistry, and immunofluorescence double staining confirmed that H2AFY upregulated LC3 and p62 expression in liver cancer tissues and cells. In conclusion, H2AFY is highly expressed in liver cancer cells and tissues, and promotes the proliferation and autophagy of liver cancer cells. H2AFY is a potential target for liver cancer therapy.Abbreviations: APLF: aprataxin pnk-like factor; HCC: Hepatocellular carcinoma; H2AFY: H2A histone family member Y.

Autophagic dysfunction in the liver enhances the expression of insoluble nuclear proteins 14-3-3ζ and importin α4

AIMS

Autophagic dysfunction is associated with the progression of various liver diseases, including nonalcoholic fatty liver disease (NAFLD). However, serum markers for evaluating autophagic function have not been reported. Highly insoluble nuclear proteins participate in many cellular functions and are potential diagnostic markers for cancer. We performed a proteomic analysis of the hepatic nuclear insoluble fraction to identify novel autophagy-related diagnostic biomarkers.

MAIN METHODS

The insoluble nuclear protein fraction was extracted from the livers of Atg7^F/F, Atg7^F/F:alb-Cre (hepatocyte-specific autophagy-deficient mice), C57BL/6 J, and KKA^y (NAFLD model) mice. Proteins were separated by two-dimensional electrophoresis and visualized by silver staining. Protein spots were identified using mass spectrometry. The localization of proteins in hepatocytes was verified by immunofluorescence using a confocal microscope.

KEY FINDINGS

The levels of insoluble nuclear proteins 14-3-3ζ and importin α4 were upregulated following hepatic autophagy dysfunction and were detectable in serum. Under normal conditions, these proteins are mainly distributed in the cytoplasm, whereas autophagic dysfunction induces their translocation to the nucleus. Incubation with an autophagy inhibitor up-regulated these proteins expression in the insoluble nuclear fraction of primary hepatocytes. Treatment with EGF or insulin enhanced 14-3-3ζ expression in the nuclear insoluble fraction; in contrast, the addition of rapamycin downregulated 14-3-3ζ expression. Importin α4 expression was increased in the nuclear insoluble fraction after incubation with tunicamycin or hydrogen peroxide.

SIGNIFICANCE

Accumulation of 14-3-3ζ and importin α4 as nuclear-insoluble proteins may be associated with autophagic dysfunction. Our findings indicate that these proteins might be useful diagnostic biomarkers for liver diseases with autophagic disorders.

PERK prevents hepatic lipotoxicity by activating the p62-ULK1 axis-mediated noncanonical KEAP1-Nrf2 pathway

Hepatic lipotoxicity is a crucial factor in nonalcoholic steatohepatitis resulting from excessive saturated fatty acid-induced reactive oxygen species (ROS)-mediated cell death, which is associated with the accumulation of endoplasmic reticulum (ER) stress in the liver. The unfolded protein response (UPR) alleviates ER stress by restoring ER protein folding homeostasis. However, whether UPR contributes ROS elimination under lipotoxicity remains unclear. The Kelch like ECH-associated protein 1 (KEAP1)-nuclear factor, erythroid 2 like 2 (Nrf2) pathway provides antioxidant defense against lipotoxic stress by eliminating ROS and can be activated by the p62-Unc-51 like autophagy activating kinase 1 (ULK1) axis. However, the upstream molecular regulator of the p62-ULK1 axis-induced KEAP1-Nrf2 pathway in the same context remains unidentified. Here, we demonstrated that PKR-like ER kinase (PERK), a UPR sensor, directly phosphorylates p62 and ULK1, thereby activating the noncanonical KEAP1-Nrf2 pathway. We also elucidated the molecular mechanism underlying the PERK-mediated p62-ULK1 axis-dependent noncanonical KEAP1-Nrf2 pathway, which could represent a promising therapeutic strategy against hepatic lipotoxicity.

•

Hepatic lipotoxicity is a crucial factor in the progression of NASH, associated with the increased ER stress.

•

PERK, one of UPR sensors, activates noncanonical KEAP1-Nrf2 pathway by phosphorylating p62 at S351.

•

PERK also phosphorylates ULK1 at S317, which mediates autophagic KEAP1 degradation and Nrf2 activation.

•

PERK protects mouse liver against lipotoxicity via Nrf2 activation.

p62 works as a hub modulation in the ageing process

p62 (also known as SQSTM1) is widely used as a predictor of autophagic flux, a process that allows the degradation of harmful and unnecessary components through lysosomes to maintain protein homeostasis in cells. p62 is also a stress-induced scaffold protein that resists oxidative stress. The multiple domains in its structure allow it to be connected with a variety of vital signalling pathways, autophagy and the ubiquitin proteasome system (UPS), allowing p62 to play important roles in cell proliferation, apoptosis and survival. Recent studies have shown that p62 is also directly or indirectly involved in the ageing process. In this review, we summarize in detail the process by which p62 regulates ageing from multiple ageing-related signs with the aim of providing new insight for the study of p62 in ageing.

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.

Endoplasmic Reticulum Stress and Autophagy in the Pathogenesis of Non-alcoholic Fatty Liver Disease (NAFLD): Current Evidence and Perspectives

PURPOSE OF REVIEW

Non-alcoholic fatty liver disease (NAFLD) is one of the most common causes of chronic liver disease with rising prevalence worldwide. Herein, we provide a comprehensive overview of the current knowledge supporting the role of ER stress and autophagy processes in NAFLD pathogenesis and progression. We also highlight the interrelation between these two pathways and the impact of ER stress and autophagy modulators on NAFLD treatment.

RECENT FINDINGS

The pathophysiological mechanisms involved in NAFLD progression are currently under investigation. The endoplasmic reticulum (ER) stress and the concomitant unfolded protein response (UPR) seem to contribute to its pathogenesis mainly due to high ER content in the liver which exerts significant metabolic functions and can be dysregulated. Furthermore, disruption of autophagy processes has also been identified in NAFLD. The crucial role of these two pathways in NAFLD is underlined by the fact that they have recently emerged as promising targets of therapeutic interventions. There is a greater need for finding the natural/chemical compounds and drugs which can modulate the ER stress pathway and autophagy for the treatment of NAFLD. Clarifying the inter-relation between these two pathways and their interaction with inflammatory and apoptotic mechanisms will allow the development of additional therapeutic options which can better target and reprogram the underlying pathophysiological pathways, aiming to attenuate NAFLD progression.

Autophagy in Hepatic Steatosis: A Structured Review

Steatosis is the accumulation of neutral lipids in the cytoplasm. In the liver, it is associated with overeating and a sedentary lifestyle, but may also be a result of xenobiotic toxicity and genetics. Non-alcoholic fatty liver disease (NAFLD) defines an array of liver conditions varying from simple steatosis to inflammation and fibrosis. Over the last years, autophagic processes have been shown to be directly associated with the development and progression of these conditions. However, the precise role of autophagy in steatosis development is still unclear. Specifically, autophagy is necessary for the regulation of basic metabolism in hepatocytes, such as glycogenolysis and gluconeogenesis, response to insulin and glucagon signaling, and cellular responses to free amino acid contents. Also, genetic knockout models for autophagy-related proteins suggest a critical relationship between autophagy and hepatic lipid metabolism, but some results are still ambiguous. While autophagy may seem necessary to support lipid oxidation in some contexts, other evidence suggests that autophagic activity can lead to lipid accumulation instead. This structured literature review aims to critically discuss, compare, and organize results over the last 10 years regarding rodent steatosis models that measured several autophagy markers, with genetic and pharmacological interventions that may help elucidate the molecular mechanisms involved.

The ménage à trois of autophagy, lipid droplets and liver disease

Autophagic pathways cross with lipid homeostasis and thus provide energy and essential building blocks that are indispensable for liver functions. Energy deficiencies are compensated by breaking down lipid droplets (LDs), intracellular organelles that store neutral lipids, in part by a selective type of autophagy, referred to as lipophagy. The process of lipophagy does not appear to be properly regulated in fatty liver diseases (FLDs), an important risk factor for the development of hepatocellular carcinomas (HCC). Here we provide an overview on our current knowledge of the biogenesis and functions of LDs, and the mechanisms underlying their lysosomal turnover by autophagic processes. This review also focuses on nonalcoholic steatohepatitis (NASH), a specific type of FLD characterized by steatosis, chronic inflammation and cell death. Particular attention is paid to the role of macroautophagy and macrolipophagy in relation to the parenchymal and non-parenchymal cells of the liver in NASH, as this disease has been associated with inappropriate lipophagy in various cell types of the liver.Abbreviations: ACAT: acetyl-CoA acetyltransferase; ACAC/ACC: acetyl-CoA carboxylase; AKT: AKT serine/threonine kinase; ATG: autophagy related; AUP1: AUP1 lipid droplet regulating VLDL assembly factor; BECN1/Vps30/Atg6: beclin 1; BSCL2/seipin: BSCL2 lipid droplet biogenesis associated, seipin; CMA: chaperone-mediated autophagy; CREB1/CREB: cAMP responsive element binding protein 1; CXCR3: C-X-C motif chemokine receptor 3; DAGs: diacylglycerols; DAMPs: danger/damage-associated molecular patterns; DEN: diethylnitrosamine; DGAT: diacylglycerol O-acyltransferase; DNL: de novo lipogenesis; EHBP1/NACSIN (EH domain binding protein 1); EHD2/PAST2: EH domain containing 2; CoA: coenzyme A; CCL/chemokines: chemokine ligands; CCl_4: carbon tetrachloride; ER: endoplasmic reticulum; ESCRT: endosomal sorting complexes required for transport; FA: fatty acid; FFAs: free fatty acids; FFC: high saturated fats, fructose and cholesterol; FGF21: fibroblast growth factor 21; FITM/FIT: fat storage inducing transmembrane protein; FLD: fatty liver diseases; FOXO: forkhead box O; GABARAP: GABA type A receptor-associated protein; GPAT: glycerol-3-phosphate acyltransferase; HCC: hepatocellular carcinoma; HDAC6: histone deacetylase 6; HECT: homologous to E6-AP C-terminus; HFCD: high fat, choline deficient; HFD: high-fat diet; HSCs: hepatic stellate cells; HSPA8/HSC70: heat shock protein family A (Hsp70) member 8; ITCH/AIP4: itchy E3 ubiquitin protein ligase; KCs: Kupffer cells; LAMP2A: lysosomal associated membrane protein 2A; LDs: lipid droplets; LDL: low density lipoprotein; LEP/OB: leptin; LEPR/OBR: leptin receptor; LIPA/LAL: lipase A, lysosomal acid type; LIPE/HSL: lipase E, hormone sensitive type; LIR: LC3-interacting region; LPS: lipopolysaccharide; LSECs: liver sinusoidal endothelial cells; MAGs: monoacylglycerols; MAPK: mitogen-activated protein kinase; MAP3K5/ASK1: mitogen-activated protein kinase kinase kinase 5; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MCD: methionine-choline deficient; MGLL/MGL: monoglyceride lipase; MLXIPL/ChREBP: MLX interacting protein like; MTORC1: mechanistic target of rapamycin kinase complex 1; NAFLD: nonalcoholic fatty liver disease; NAS: NAFLD activity score; NASH: nonalcoholic steatohepatitis; NPC: NPC intracellular cholesterol transporter; NR1H3/LXRα: nuclear receptor subfamily 1 group H member 3; NR1H4/FXR: nuclear receptor subfamily 1 group H member 4; PDGF: platelet derived growth factor; PIK3C3/VPS34: phosphatidylinositol 3-kinase catalytic subunit type 3; PLIN: perilipin; PNPLA: patatin like phospholipase domain containing; PNPLA2/ATGL: patatin like phospholipase domain containing 2; PNPLA3/adiponutrin: patatin like phospholipase domain containing 3; PPAR: peroxisome proliferator activated receptor; PPARA/PPARα: peroxisome proliferator activated receptor alpha; PPARD/PPARδ: peroxisome proliferator activated receptor delta; PPARG/PPARγ: peroxisome proliferator activated receptor gamma; PPARGC1A/PGC1α: PPARG coactivator 1 alpha; PRKAA/AMPK: protein kinase AMP-activated catalytic subunit; PtdIns3K: class III phosphatidylinositol 3-kinase; PtdIns3P: phosphatidylinositol-3-phosphate; PTEN: phosphatase and tensin homolog; ROS: reactive oxygen species; SE: sterol esters; SIRT1: sirtuin 1; SPART/SPG20: spartin; SQSTM1/p62: sequestosome 1; SREBF1/SREBP1c: sterol regulatory element binding transcription factor 1; TAGs: triacylglycerols; TFE3: transcription factor binding to IGHM enhancer 3; TFEB: transcription factor EB; TGFB1/TGFβ: transforming growth factor beta 1; Ub: ubiquitin; UBE2G2/UBC7: ubiquitin conjugating enzyme E2 G2; ULK1/Atg1: unc-51 like autophagy activating kinase 1; USF1: upstream transcription factor 1; VLDL: very-low density lipoprotein; VPS: vacuolar protein sorting; WIPI: WD-repeat domain, phosphoinositide interacting; WDR: WD repeat domain.

Exploring the mechanism of PingTang No.5 capsule on nonalcoholic fatty liver disease through network pharmacology and experimental validation

PingTang No.5 capsule (PT5), a modified Traditional Chinese Medicine (TCM) formula of Zexie Decoction, is used to treat patients with lipid metabolism disorders in our hospital. The present study was designed to investigate the mechanisms of PT5 in treating non-alcoholic fatty liver disease (NAFLD). PT5 information including ingredients, pharmacological properties, and potential targets was obtained from TCM databases. The candidate targets of PT5 were predicted by network pharmacological analysis, and the possible pathway and mechanism were obtained from DAVID database, followed by experimental validation in NAFLD mice model treated with PT5. Total 328 compounds were selected using the threshold oral bioactivity (OB) > 30% or drug-likeness (DL) > 0.1 of pharmacology characteristic, and 1033 candidate targets obtained to construct the network analysis. The 113 targets were selected from the intersection between candidate targets of PT5 and NAFLD relative gene. These targets were evaluated in diabetic complications, cancer, Hepatitis B, Fluid shear stress and atherosclerosis, and TNF signaling pathway. TNF-α was the important factor in protein interaction analysis of STRING and involved in the lipid regulation and oxidative stress in NAFLD. When administrated to the NAFLD mice, PT5 reduced weight, blood fatty acids, decreased the adipocyte size, and improved the metabolism. Besides, the molecular verification of lipid metabolism increased and oxidative stress reduced that interpreted the mechanism of PT5 preventing liver cell from lipid accumulation and injury of NAFLD. These results presented PT5 have the potential therapy as an alternative treatment for NAFLD.

Phenotypic Changes in Macrophage Activation in a Model of Nonalcoholic Fatty Liver Disease using Microminipigs

Aim: Non-alcoholic fatty liver disease (NAFLD) is one of the most common chronic liver disorders associated with metabolic syndrome, and its prevalence has been on the rise. The pathogenesis of NAFLD has not yet been sufficiently elucidated due to the multifactorial nature of the disease, although the activation of macrophages/Kupffer cells is considered to be involved. We previously reported an animal model of NAFLD using Microminipigs ^TM (µMPs) fed high-fat diets containing cholesterol with or without cholic acid. The aim of this study was to investigate the phenotypic changes of macrophages that occur during the development of NAFLD.

Methods: Immunohistochemistry of macrophages, lymphocytes, and stellate cells was performed using liver samples, and the density of positive cells was analyzed.

Results: The number of Iba-1-positive macrophages increased with increasing cholesterol content in the diet. The numbers of CD163-positive macrophages and CD204-positive macrophages also increased with increasing cholesterol content in the diet; however, the proportion of CD204-positive macrophages among Iba-1-positive macrophages was significantly reduced by cholic acid supplementation.

Conclusion: The results suggest that lipid accumulation induced macrophage recruitment in swine livers, and that the number of M2-like macrophages increased at the early stage of NAFLD, while the number of M1-like macrophages increased at the late stage of NAFLD, resulting in a liver condition like non-alcoholic steatohepatitis. We provide evidence of the phenotypic changes that occur in macrophages during the development of NAFLD that has never been reported before using µMPs.

Autophagy and liver cancer

Autophagy is a highly conserved catabolic process that degrades cytosolic proteins and organelles via formation of autophagosomes that fuse with lysosomes to form autolysosomes, whereby autophagic cargos are degraded. Numerous studies have demonstrated that autophagy plays a critical role in the regulation of liver physiology and homeostasis, and impaired autophagy leads to the pathogenesis of various liver diseases such as viral hepatitis, alcohol associated liver diseases (AALD), non-alcoholic fatty liver diseases (NAFLD), and liver cancer. Recent evidence indicates that autophagy may play a dual role in liver cancer: inhibiting early tumor initiation while promoting progression and malignancy of already formed liver tumors. In this review, we summarized the progress of current understanding of how hepatic viral infection, alcohol consumption and diet-induced fatty liver diseases impair hepatic autophagy. We also discussed how impaired autophagy promotes liver tumorigenesis, and paradoxically how autophagy is required to promote the malignancy and progression of liver cancer. Understanding the molecular mechanisms underlying how autophagy differentially affects liver cancer development and progression may help to design better therapeutic strategies for prevention and treatment of liver cancer.

Lipophagy Impairment Is Associated With Disease Progression in NAFLD

Non-alcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease in Western countries and is associated with aging and features of metabolic syndrome. Lipotoxicity and oxidative stress are consequent to dysregulation of lipid metabolism and lipid accumulation, leading to hepatocyte injury and inflammation. Lipophagy consists in selective degradation of intracellular lipid droplets by lysosome and mounting evidence suggests that lipophagy is dysregulated in NAFLD. Here we demonstrate lipophagy impairment in experimental models of NAFLD and in a NAFLD patient cohort by histomorphological and molecular analysis. High fat diet-fed C57BL/6J male mice and high-fat/high-glucose cultured Huh7 cells showed accumulation of both p62/SQSTM1 and LC3-II protein. In 59 NAFLD patients, lipid droplet-loaded lysosomes/lipolysosomes and p62/SQSTM1 clusters correlated with NAFLD activity score (NAS) and with NAS and fibrosis stage, respectively, and levels of expression of lysosomal genes, as well as autophagy-related genes, correlated with NAS and fibrosis stage. An increased amount of lipid droplets, lipolysosomes and autophagosomes was found in subjects with NAFLD compared to healthy subjects at ultrastructural level. In conclusion, here we observed that NAFLD is characterized by histological, ultrastructural and molecular features of altered autophagy that is associated with an impaired lipid degradation. Impaired autophagy is associated with features of advanced disease. Lipopolysosomes, as individuated with light microscopy, should be further assessed as markers of disease severity in NAFLD patients.

Self-eating: friend or foe? The emerging role of autophagy in fibrotic diseases

Fibrosis occurs in most human organs including the liver, lung, heart and kidney, and is crucial for the progression of most chronic diseases. As an indispensable catabolic process for intracellular quality control and homeostasis, autophagy occurs in most mammalian cells and is implicated in many biological processes including fibrogenesis. Although advances have been made in understanding autophagy process, the potential role of autophagy in fibrotic diseases remains controversial and has recently attracted a great deal of attention. In the current review, we summarize the commonalities of autophagy affecting different types of fibrosis in different organs, including the liver, lung, heart, and kidney as well as in cystic fibrosis, systematically outline the contradictory results and highlight the distinct role of autophagy during the various stages of fibrosis. In summary, the exact role autophagy plays in fibrogenesis depends on specific cell types and different stimuli, and identifying and evaluating the pathogenic contribution of autophagy in fibrogenesis will promote the discovery of novel therapeutic strategies for the clinical management of these fibrotic diseases.

Scoparone improves hepatic inflammation and autophagy in mice with nonalcoholic steatohepatitis by regulating the ROS/P38/Nrf2 axis and PI3K/AKT/mTOR pathway in macrophages

BACKGROUND AND AIMS

Scoparone has been shown to ameliorate many forms of liver disease, and several underlying molecular mechanisms involved have been previously revealed. However, the potential role of scoparone in autophagy, which is dysregulated in nonalcoholic fatty liver disease-nonalcoholic steatohepatitis (NAFLD-NASH), has not been evaluated. In the current study, we investigated the effect and potential mechanisms of scoparone in hepatic autophagy in mice with NASH.

METHODS

In vivo, mice were fed a methionine-choline deficient (MCD) diet to establish a NASH model and then subjected to treatment with or without scoparone for 4 weeks. In vitro, scoparone was applied in a hepatocellular lipid overload model in AML12 cells challenged with palmitic acid (PA) and in lipopolysaccharide (LPS)-induced RAW264.7 cells.

RESULTS

Scoparone improved impaired autophagy and several key features of NASH in mice fed an MCD diet. In vitro, scoparone had an effect on the autophagy of macrophages but not hepatocytes. In RAW264.7 cells, scoparone reduced the LPS-induced accumulation of autophagosomes and autophagy substrates, the production of reactive oxygen species (ROS) and the inflammatory response. Scoparone inhibited the upregulation of p62 transcription, which is mediated by the ROS/P38/Nrf2 axis. Chloroquine (CQ), an inhibitor of autophagic flux, significantly inhibited scoparone-mediated protection against inflammation. In addition, scoparone suppressed activation of the PI3K/AKT/mTOR pathway, and MHY1485 (an mTOR activator that inhibits autophagy) inhibited the anti-inflammatory effect of scoparone.

CONCLUSIONS

In LPS-induced macrophages, scoparone regulates autophagy and further suppresses inflammation by inhibiting the ROS/P38/Nrf2 axis and PI3K/AKT/mTOR pathway and enhancing autophagic flux. Scoparone may improve hepatic autophagy and NASH partly through enhancing autophagy in macrophages but not hepatocytes. Scoparone is expected to become a novel therapeutic drug for NASH or diseases associated with dysregulated autophagy in macrophages.

The Role of Lipophagy in the Development and Treatment of Non-Alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) or metabolic (dysfunction) associated liver disease (MAFLD), is, with a global prevalence of 25%, the most common liver disorder worldwide. NAFLD comprises a spectrum of liver disorders ranging from simple steatosis to steatohepatitis, fibrosis, cirrhosis and eventually end-stage liver disease. The cause of NAFLD is multifactorial with genetic susceptibility and an unhealthy lifestyle playing a crucial role in its development. Disrupted hepatic lipid homeostasis resulting in hepatic triglyceride accumulation is an hallmark of NAFLD. This disruption is commonly described based on four pathways concerning 1) increased fatty acid influx, 2) increased de novo lipogenesis, 3) reduced triglyceride secretion, and 4) reduced fatty acid oxidation. More recently, lipophagy has also emerged as pathway affecting NAFLD development and progression. Lipophagy is a form of autophagy (i.e. controlled autolysosomal degradation and recycling of cellular components), that controls the breakdown of lipid droplets in the liver. Here we address the role of hepatic lipid homeostasis in NAFLD and specifically review the current literature on lipophagy, describing its underlying mechanism, its role in pathophysiology and its potential as a therapeutic target.

Interleukin-4 affects microglial autophagic flux

Interleukin-4 plays an important protective role in Alzheimer's disease by regulating microglial phenotype, phagocytosis of amyloid-β, and secretion of anti-inflammatory and neurotrophic cytokines. Recently, increasing evidence has suggested that autophagy regulates innate immunity by affecting M1/M2 polarization of microglia/macrophages. However, the role of interleukin-4 in microglial autophagy is unknown. In view of this, BV2 microglia were treated with 0, 10, 20 or 50 ng/mL interleukin-4 for 24, 48, or 72 hours. Subsequently, light chain 3-II and p62 protein expression levels were detected by western blot assay. BV2 microglia were incubated with interleukin-4 (20 ng/mL, experimental group), 3-methyladenine (500 μM, autophagy inhibitor, negative control group), rapamycin (100 nM, autophagy inductor, positive control group), 3-methyladenine + interleukin-4 (rescue group), or without treatment for 24 hours, and then exposed to amyloid-β (1 μM, model group) or vehicle control (control) for 24 hours. LC3-II and p62 protein expression levels were again detected by western blot assay. In addition, expression levels of multiple markers of M1 and M2 phenotype were assessed by real-time fluorescence quantitative polymerase chain reaction, while intracellular and supernatant amyloid-β protein levels were measured by enzyme-linked immunosorbent assay. Our results showed that interleukin-4 induced microglial autophagic flux, most significantly at 20 ng/mL for 48 hours. Interleukin-4 pretreated microglia inhibited blockade of amyloid-β-induced autophagic flux, and promoted amyloid-β uptake and degradation partly through autophagic flux, but inhibited switching of amyloid-β-induced M1 phenotype independent on autophagic flux. These results indicate that interleukin-4 pretreated microglia increases uptake and degradation of amyloid-β in a process partly mediated by autophagy, which may play a protective role against Alzheimer's disease.

Splenectomy Promotes Macrophage Polarization in a Mouse Model of Concanavalin A- (ConA-) Induced Liver Fibrosis

Background

Splenectomy can improve liver function and survival in patients with autoimmune hepatitis (AIH) and liver cirrhosis. We investigated the underlying mechanism in a mouse model of concanavalin A- (ConA-) induced liver fibrosis.

Methods

We used ConA to induce immune liver fibrosis in BALB/c mice. Splenectomy was performed alone or with the administration of dexamethasone (DEX). Changes in blood and liver tissues were evaluated.

Results

Mice treated with ConA for 7 weeks developed advanced liver fibrosis, while splenectomy suppressed liver fibrosis. Although the populations of macrophages/monocytes and M1 macrophages decreased after splenectomy, the inflammatory factors associated with M2 macrophages increased after splenectomy. Furthermore, the population of circulating CD11b⁺Ly6C^high myeloid-derived suppressor cells (MDSCs) increased after splenectomy. After ConA treatment, elevated levels of activated and total NF-kBp65/p50 combined with DNA were observed in hepatic tissues. In contrast, the levels of NF-κB p65/p50 decreased after splenectomy.

Conclusions

Splenectomy may promote the polarization of CD11b⁺Ly6C^high MDSCs and the differentiation of M2 macrophages while restricting the level of NF-κB p65-p50 heterodimers. These factors may suppress the progression of liver fibrosis.

Molecular pathways of nonalcoholic fatty liver disease development and progression

Nonalcoholic fatty liver disease (NAFLD) is a main hepatic manifestation of metabolic syndrome. It represents a wide spectrum of histopathological abnormalities ranging from simple steatosis to nonalcoholic steatohepatitis (NASH) with or without fibrosis and, eventually, cirrhosis and hepatocellular carcinoma. While hepatic simple steatosis seems to be a rather benign manifestation of hepatic triglyceride accumulation, the buildup of highly toxic free fatty acids associated with insulin resistance-induced massive free fatty acid mobilization from adipose tissue and the increased de novo hepatic fatty acid synthesis from glucose acts as the "first hit" for NAFLD development. NAFLD progression seems to involve the occurrence of "parallel, multiple-hit" injuries, such as oxidative stress-induced mitochondrial dysfunction, endoplasmic reticulum stress, endotoxin-induced, TLR4-dependent release of inflammatory cytokines, and iron overload, among many others. These deleterious factors are responsible for the triggering of a number of signaling cascades leading to inflammation, cell death, and fibrosis, the hallmarks of NASH. This review is aimed at integrating the overwhelming progress made in the characterization of the physiopathological mechanisms of NAFLD at a molecular level, to better understand the factor influencing the initiation and progression of the disease.

Review article: drug-induced liver injury in the context of nonalcoholic fatty liver disease - a physiopathological and clinical integrated view

BACKGROUND

Nonalcoholic fatty disease (NAFLD) is the most common liver disease, since it is strongly associated with obesity and metabolic syndrome pandemics. NAFLD may affect drug disposal and has common pathophysiological mechanisms with drug-induced liver injury (DILI); this may predispose to hepatoxicity induced by certain drugs that share these pathophysiological mechanisms. In addition, drugs may trigger fatty liver and inflammation per se by mimicking NAFLD pathophysiological mechanisms.

AIMS

To provide a comprehensive update on (a) potential mechanisms whereby certain drugs can be more hepatotoxic in NAFLD patients, (b) the steatogenic effects of drugs, and (c) the mechanism involved in drug-induced steatohepatitis (DISH).

METHODS

A language- and date-unrestricted Medline literature search was conducted to identify pertinent basic and clinical studies on the topic.

RESULTS

Drugs can induce macrovesicular steatosis by mimicking NAFLD pathogenic factors, including insulin resistance and imbalance between fat gain and loss. Other forms of hepatic fat accumulation exist, such as microvesicular steatosis and phospholipidosis, and are mostly associated with acute mitochondrial dysfunction and defective lipophagy, respectively. Drug-induced mitochondrial dysfunction is also commonly involved in DISH. Patients with pre-existing NAFLD may be at higher risk of DILI induced by certain drugs, and polypharmacy in obese individuals to treat their comorbidities may be a contributing factor.

CONCLUSIONS

The relationship between DILI and NAFLD may be reciprocal: drugs can cause NAFLD by acting as steatogenic factors, and pre-existing NAFLD could be a predisposing condition for certain drugs to cause DILI. Polypharmacy associated with obesity might potentiate the association between this condition and DILI.

Magnesium isoglycyrrhizinate alleviates liver injury in obese rats with acute necrotizing pancreatitis

OBJECTIVE

For patients with acute necrotizing pancreatitis (ANP), a high body mass index (BMI) increases the likelihood of acute hepatic injury (AHI). In the current study, we explored whether magnesium isoglycyrrhizinate (MgIg) could alleviate ANP-induced liver injury in obese rats.

METHODS

Sprague-Dawley (SD) rats were selected for the present study, and the ANP model was established by retrograde injection of 5% sodium taurocholate into the biliary-pancreatic duct. Thirty-six SD rats were randomly assigned to six groups: the normal (N), standard rat chow (SRC) normal (SN), SRC ANP (S-ANP), high-fat diet (HFD) normal (H-N), HFD ANP (H-ANP), and MgIg pretreatment HFD ANP (H-ANPT) groups. The rats in the H-ANPT group were treated with MgIg (30 mg/kg) intragastrically for 7 days before the ANP model was established. The rats were sacrificed 12 h after ANP was established, and the blood and pancreatic and liver tissues were collected. Differences in the physiology, pathology and cellular and molecular responses of the rats in each group were examined.

RESULT

Analyses of serum amylase lipase, alanine aminotransferase and aspartate aminotransferase indicated that obesity aggravated ANP-induced hepatic injury and that MgIg improved liver function. The superoxide dismutase, malondialdehyde, M1 macrophage, M2 macrophage, neutrophil, NF-κB, IL-1β and caspase-3 levels in liver tissue showed that MgIg attenuated H-ANP-induced hepatic injury by inhibiting oxidative stress and inflammation.

CONCLUSION

Obesity aggravated ANP-induced liver injury via oxidative stress and inflammatory reactions. MgIg alleviated oxidative stress and decreased the inflammatory reaction, protecting the liver against the AHI induced by ANP in obese rats.

Nrf2 in alcoholic liver disease

Alcoholic liver disease (ALD) is a leading cause of morbidity and mortality of liver disorders and a major health issue globally. ALD refers to a spectrum of liver pathologies ranging from steatosis, steatohepatitis, fibrosis, cirrhosis and even hepatocellular carcinoma. Various mechanisms, including oxidative stress, protein and DNA modification, inflammation and impaired lipid metabolism, have been implicated in the pathogenesis of ALD. Further, reactive oxygen species (ROS) in particular, have been identified as a key component in the initiation and progression of ALD. Nuclear factor erythroid 2 like 2 (Nrf2) is a master regulator of the intracellular adaptive antioxidant response to oxidative stress, and aids in the detoxification of a variety of toxicants. Given its cytoprotective role, Nrf2 has been extensively studied as a therapeutic target for ALD. Paradoxically, however, emerging evidence have revealed that Nrf2 may be implicated in the progression of ALD. In this review, we summarize the role of Nrf2 in the development of ALD and discuss the underlying mechanisms. Clearly, more comprehensive studies with proper animal and cell models and in human are needed to verify the potential therapeutic role of Nrf2 in ALD.

Targeting autophagy in liver cancer

Autophagy is a catabolic cellular process conserved in animals. It is characterized by the main role of recycling all the non-functional products of the cells. Once, autophagy players detect non-functioning sub-cellular organelles and proteins, they start the so-called nucleation process. The organelles will be surrounded by a double membrane vesicle mainly constituted by endoplasmic reticulum (ER) membrane and autophagy proteins, e.g., MAP1LC3B, Beclin-1, VPS34, Unc-51 like autophagy activating kinase (ULK1) and ubiquitination-related proteins. Then the autophagic membrane will go through an elongation phase involving additional autophagy players. Once the autophagic vesicle is complete, the sub-cellular organelles will be isolated from the rest of the cytosol and driven to the final fusion with lysosomes. Here, the digestion process will end. Alteration and or impairment of autophagy have been shown to be correlated with development of diseases affecting the central nervous system, e.g., Alzheimer and other neurodegenerative diseases. Nonetheless, autophagy defect is responsible for tumorigenesis in blood and solid malignancies, in particular liver cancer. Malignancies of the liver are determined by several genetics and epigenetics mechanisms triggering the up-regulation of survival mechanisms and resistance to cell death. Furthermore, liver cancer could result from pathologic conditions like cirrhosis and fibrosis related to virus infection, aflatoxin, alcohol consumption and high fat diet together with insulin resistance. The role exerted by autophagy in the pathogenesis of the liver and tumor development has been evidenced in recent years. The alteration of autophagy assumes a fundamental role for liver tumorigenesis determining an accumulation of non-functional proteins and organelles that trigger oxidative stress leading to genotoxic stress and gene alterations. Furthermore, the absence of this degradation mechanism could prompt the cells to alter their metabolic status and turn into malignant cells. Interestingly, the heterozygous loss of function of Beclin-1 is able to trigger liver tumorigenesis or even the simple accumulation of proteins caused by the block of the final autolysosome fusion and degradation process is responsible for liver cancer development. This review highlights the importance of targeting the autophagy process in liver cancer in order to restore its function and to promote autophagy-mediated cell demise.