Hepatic protein-tyrosine phosphatase 1B disruption and pharmacological inhibition attenuate ethanol-induced oxidative stress and ameliorate alcoholic liver disease in mice

NUP85 alleviates lipid metabolism and inflammation by regulating PI3K/AKT signaling pathway in nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is one of the common causes of chronic liver disease in the world. The problem of NAFLD had become increasingly prominent. However, its pathogenesis is still indistinct. As we all know, NAFLD begins with the accumulation of triglyceride (TG), leading to fatty degeneration, inflammation and other liver tissues damage. Notably, structure of nucleoporin 85 (NUP85) is related to lipid metabolism and inflammation of liver diseases. In this study, the results of researches indicated that NUP85 played a critical role in NAFLD. Firstly, the expression level of NUP85 in methionine-choline-deficient (MCD)-induced mice increased distinctly, as well as the levels of fat disorder and inflammation. On the contrary, knockdown of NUP85 had the opposite effects. In vitro, AML-12 cells were stimulated with 2 mm free fatty acids (FFA) for 24 h. Results also proved that NUP85 significantly increased in model group, and increased lipid accumulation and inflammation level. Besides, NUP85 protein could interact with C-C motif chemokine receptor 2 (CCR2). Furthermore, when NUP85 protein expressed at an extremely low level, the expression level of CCR2 protein also decreased, accompanied with an inhibition of phosphorylation of phosphoinositol-3 kinase (PI3K)-protein kinase B (AKT) signaling pathway. What is more, trans isomer (ISRIB), a targeted inhibitor of NUP85, could alleviate NAFLD. In summary, our findings suggested that NUP85 functions as an important regulator in NAFLD through modulation of CCR2.

Hepatic protein tyrosine phosphatase Shp2 disruption mitigates the adverse effects of ethanol in the liver by modulating oxidative stress and ERK signaling

AIMS

Chronic excessive alcohol intake is a significant cause of alcohol-associated liver disease (ALD), a leading contributor to liver-related morbidity and mortality. The Src homology phosphatase 2 (Shp2; encoded by Ptpn11) is a widely expressed protein tyrosine phosphatase that modulates hepatic functions, but its role in ALD is mostly uncharted.

MAIN METHODS

Herein, we explore the effects of liver-specific Shp2 genetic disruption using the established chronic-plus-binge mouse model of ALD.

KEY FINDINGS

We report that the hepatic Shp2 disruption had beneficial effects and partially ameliorated ethanol-induced injury, inflammation, and steatosis in the liver. Consistently, Shp2 deficiency was associated with decreased ethanol-evoked activation of extracellular signal-regulated kinase (ERK) and oxidative stress in the liver. Moreover, primary hepatocytes with Shp2 deficiency exhibited similar outcomes to those observed upon Shp2 disruption in vivo, including diminished ethanol-induced ERK activation, inflammation, and oxidative stress. Furthermore, pharmacological inhibition of ERK in primary hepatocytes mimicked the effects of Shp2 deficiency and attenuated oxidative stress caused by ethanol.

SIGNIFICANCE

Collectively, these findings highlight Shp2 as a modulator of hepatic oxidative stress upon ethanol challenge and suggest the evaluation of this phosphatase as a potential therapeutic target for ALD.

Targeting Protein Phosphatases for the Treatment of Chronic Liver Disease

There exists a huge number of patients suffering from chronic liver disease worldwide. As a disease with high incidence and mortality worldwide, strengthening the research on the pathogenesis of chronic liver disease and the development of novel drugs is an important issue related to the health of all human beings. Phosphorylation modification of proteins plays a crucial role in cellular signal transduction, and phosphatases are involved in the development of liver diseases. Therefore, this article summarized the important role of protein phosphatases in chronic liver disease with the aim of facilitating the development of drugs targeting protein phosphatases for the treatment of chronic liver disease.

The PTP1B inhibitor MSI-1436 ameliorates liver insulin sensitivity by modulating autophagy, ER stress and systemic inflammation in Equine metabolic syndrome affected horses

BACKGROUND

Equine metabolic syndrome (EMS) is a multifactorial pathology gathering insulin resistance, low-grade inflammation and past or chronic laminitis. Among the several molecular mechanisms underlying EMS pathogenesis, increased negative insulin signalling regulation mediated by protein tyrosine phosphatase 1 B (PTP1B) has emerged as a critical axis in the development of liver insulin resistance and general metabolic distress associated to increased ER stress, inflammation and disrupted autophagy. Thus, the use of PTP1B selective inhibitors such as MSI-1436 might be considered as a golden therapeutic tool for the proper management of EMS and associated conditions. Therefore, the present investigation aimed at verifying the clinical efficacy of MSI-1436 systemic administration on liver metabolic balance, insulin sensitivity and inflammatory status in EMS affected horses. Moreover, the impact of MSI-1436 treatment on liver autophagy machinery and associated ER stress in liver tissue has been analysed.

METHODS

Liver explants isolated from healthy and EMS horses have been treated with MSI-1436 prior to gene and protein expression analysis of main markers mediating ER stress, mitophagy and autophagy. Furthermore, EMS horses have been intravenously treated with a single dose of MSI-1436, and evaluated for their metabolic and inflammatory status.

RESULTS

Clinical application of MSI-1436 to EMS horses restored proper adiponectin levels and attenuated the typical hyperinsulinemia and hyperglycemia. Moreover, administration of MSI-1436 further reduced the circulating levels of key pro-inflammatory mediators including IL-1β, TNF-α and TGF-β and triggered the Tregs cells activation. At the molecular level, PTP1B inhibition resulted in a noticeable mitigation of liver ER stress, improvement of mitochondrial dynamics and consequently, a regulation of autophagic response. Similarly, short-term ex vivo treatment of EMS liver explants with trodusquemine (MSI-1436) substantially enhanced autophagy by upregulating the levels of HSC70 and Beclin-1 at both mRNA and protein level. Moreover, the PTP1B inhibitor potentiated mitophagy and associated expression of MFN2 and PINK1. Interestingly, inhibition of PTP1B resulted in potent attenuation of ER stress key mediators' expression namely, CHOP, ATF6, HSPA5 and XBP1.

CONCLUSION

Presented findings shed for the first time promising new insights in the development of an MSI-1436-based therapy for proper equine metabolic syndrome intervention and may additionally find potential translational application to human metabolic syndrome treatment.

The PTP1B selective inhibitor MSI-1436 mitigates Tunicamycin-induced ER stress in human hepatocarcinoma cell line through XBP1 splicing modulation

Protein tyrosine phosphatase PTP1B is considered as a key metabolic enzyme that has been reported to be associated with insulin resistance onset, and underlying cellular metabolic malfunctions, including ER stress and mitochondrial failure. In this study, effects of selective PTP1B inhibition using MSI-1436 on cellular apoptosis, oxidative stress, mitochondrial dysfunction and ER stress have been assessed using an in vitro model of Tunicamycin induced ER stress in HepG2 cell line. Inhibition of PTP1B using MSI-1436 significantly increased cell viability and reduced the number of apoptotic cells as well as the expression of key apoptosis initiators and effectors. MSI-1436 further mitigated ER stress, by downregulating the expression of IRE1, ATF6 and PERK transcripts, all being key ER stress sensors. Interestingly, MSI-1436 inhibited the XBP1 splicing, and thus its UPR-associated transcriptional activity. PTP1B inhibition further enabled to restore proper mitochondrial biogenesis, by improving transmembrane potential, and diminishing intracellular ROS while restoring of endogenous antioxidant enzymes genes expression. PTP1B inhibition using MSI-1436 could improve cellular apoptosis and metabolic integrity through the mitigation of ER and mitochondrial stress signalling pathways, and excessive ROS accumulation. This strategy may be useful for the treatment of metabolic disorders including IR, NAFLD and diabetes.

Ptpn1 deletion protects oval cells against lipoapoptosis by favoring lipid droplet formation and dynamics

Activation of oval cells (OCs) has been related to hepatocyte injury during chronic liver diseases including non-alcoholic fatty liver disease (NAFLD). However, OCs plasticity can be affected under pathological environments. We previously found protection against hepatocyte cell death by inhibiting protein tyrosine phosphatase 1B (PTP1B). Herein, we investigated the molecular and cellular processes involved in the lipotoxic susceptibility in OCs expressing or not PTP1B. Palmitic acid (PA) induced apoptotic cell death in wild-type (Ptpn1+/+) OCs in parallel to oxidative stress and impaired autophagy. This lipotoxic effect was attenuated in OCs lacking Ptpn1 that showed upregulated antioxidant defences, increased unfolded protein response (UPR) signaling, higher endoplasmic reticulum (ER) content and elevated stearoyl CoA desaturase (Scd1) expression and activity. These effects in Ptpn1-/- OCs concurred with an active autophagy, higher mitochondrial efficiency and a molecular signature of starvation, favoring lipid droplet (LD) formation and dynamics. Autophagy blockade in Ptpn1-/- OCs reduced Scd1 expression, mitochondrial fitness, LD formation and restored lipoapoptosis, an effect also recapitulated by Scd1 silencing. PTP1B immunostaining was detected in OCs from mouse liver and, importantly, LDs were found in OCs from Ptpn1-/- mice with NAFLD. In conclusion, we demonstrated that Ptpn1 deficiency restrains lipoapoptosis in OCs through a metabolic rewiring towards a "starvation-like" fate, favoring autophagy, mitochondrial fitness and LD formation. Dynamic LD-lysosomal interations likely ensure lipid recycling and, overall, these adaptations protect against lipotoxicity. The identification of LDs in OCs from Ptpn1-/- mice with NAFLD opens therapeutic perspectives to ensure OC viability and plasticity under lipotoxic liver damage.

Deletion of p38γ attenuates ethanol consumption- and acetaminophen-induced liver injury in mice through promoting Dlg1

Acetaminophen (APAP) is one of the major causes of drug-induced acute liver injury, and ethanol may aggravate APAP-induced liver injury. The problem of ethanol- and APAP-induced liver injury becomes increasingly prominent, but the mechanism of ethanol- and APAP-induced liver injury remains ambiguous. p38γ is one of the four isoforms of P38 mitogen activated protein kinases, that contributes to inflammation in different diseases. In this study we investigated the role of p38γ in ethanol- and APAP-induced liver injury. Liver injury was induced in male C57BL/6 J mice by giving liquid diet containing 5% ethanol (v/v) for 10 days, followed by gavage of ethanol (25% (v/v), 6 g/kg) once or injecting APAP (200 mg/kg, ip), or combined the both treatments. We showed that ethanol significantly aggravated APAP-induced liver injury in C57BL/6 J mice. Moreover, the expression level of p38γ was up-regulated in the liver of ethanol-, APAP- and ethanol+APAP-treated mice. Knockdown of p38γ markedly attenuated liver injury, inflammation, and steatosis in ethanol+APAP-treated mice. Liver sections of p38γ-knockdown mice displayed lower levels of Oil Red O stained dots and small leaky shapes. AML-12 cells were exposed to APAP (5 mM), ethanol (100 mM) or combined treatments. We showed that P38γ was markedly increased in ethanol+APAP-treated AML-12 cells, whereas knockdown of p38γ significantly inhibited inflammation, lipid accumulation and oxidative stress in ethanol+APAP-treated AML-12 cells. Furthermore, we revealed that p38γ could combine with Dlg1, a member of membrane-associated guanylate kinase family. Deletion of p38γ up-regulated the expression level of Dlg1 in ethanol+APAP-treated AML-12 cells. In summary, our results suggest that p38γ functions as an important regulator in ethanol- and APAP-induced liver injury through modulation of Dlg1.

Melatonin Alleviates PM2.5-Induced Hepatic Steatosis and Metabolic-Associated Fatty Liver Disease in ApoE-/- Mice

Background

Exposure to fine particulate matter (PM_2.5) is associated with the risk of developing metabolic-associated fatty liver disease (MAFLD). Melatonin is the main secreted product of the pineal gland and has been reported to prevent hepatic lipid metabolism disorders. However, it remains uncertain whether melatonin could protect against PM_2.5-induced MAFLD.

Methods and Results

The purpose of our study was to investigate the mitigating effects of melatonin on hepatic fatty degeneration accelerated by PM_2.5 in vivo and in vitro. Histopathological analysis and ultrastructural images showed that PM_2.5 induced hepatic steatosis and lipid vacuolation in ApoE^−/− mice, which could be effectively alleviated by melatonin administration. Increased ROS production and decreased expression of antioxidant enzymes were detected in the PM_2.5-treated group, whereas melatonin showed recovery effects after PM_2.5-induced oxidative damage in both the liver and L02 cells. Further investigation revealed that PM_2.5 induced oxidative stress to activate PTP1B, which in turn had a positive feedback regulation effect on ROS release. When a PTP1B inhibitor or melatonin was administered, SP1/SREBP-1 signalling was effectively suppressed, while Nrf2/Keap1 signalling was activated in the PM_2.5-treated groups.

Conclusion

Our study is the first to show that melatonin alleviates the disturbance of PM_2.5-triggered hepatic steatosis and liver damage by regulating the ROS-mediated PTP1B and Nrf2 signalling pathways in ApoE^−/− mice. These results suggest that melatonin administration might be a prospective therapy for the prevention and treatment of MAFLD associated with air pollution.

1-O-Actylbritannilactone Ameliorates Alcohol-Induced Hepatotoxicity through Regulation of ROS/Akt/NF-κB-Mediated Apoptosis and Inflammation

1-O-Acetylbritannilactone (ABL) is a marker component of Inula britannica L. and is reported to exhibit multiple pharmacological activities, including antiaging, anti-inflammatory, and antidiabetic properties. Although the protective effect of Inula britannica L. on animal models of liver injury has been widely reported, the effect of ABL on alcohol-induced liver damage has not been confirmed. The present study was designed to investigate the protective effect of ABL against alcohol-induced LO2 human normal liver cell injury and to further clarify the underlying mechanism. Our results revealed that ABL at concentrations of 0.5, 1, and 2 μM could remarkably suppress the decreased viability of LO2 cells stimulated by alcohol. In addition, ABL pretreatment improved alcohol-induced oxidative damage by decreasing the level of reactive oxygen species (ROS) and the excessive consumption of glutathione peroxidase (GSH-Px), while increasing the level of catalase (CAT) in LO2 cells. Moreover, Western blotting analysis showed that ABL pretreatment activated protein kinase B (Akt) phosphorylation, increased downstream antiapoptotic protein Bcl-2 expression, and decreased the phosphorylation level of the caspase family including caspase 9 and caspase 3 proteins, thereby attenuating LO2 cell apoptosis. Importantly, we also found that ABL significantly inhibits the activation of the nuclear factor-kappa B (NF-κB) signaling pathway by reducing the secretion of proinflammatory factors including tumor necrosis factor-α (TNF-α) and interleukin (IL-1β). In conclusion, the current research clearly suggests that the protective effect of ABL on alcohol-induced hepatotoxicity may be achieved in part through regulation of the ROS/Akt/NF-κB signaling pathway to inhibit inflammation and apoptosis in LO2 cells. (The article path map has not been seen.).

Glucopyranose from Pleurotus geesteranus prevent alcoholic liver diseases by regulating Nrf2/HO-1-TLR4/NF-κB signalling pathways and gut microbiota

This study investigated the effects of PGPs (Pleurotus geesteranus polysaccharides), a glucopyranose isolated from the mycelium of Pleurotus geesteranus and characterized with the main chain of →4)-α-D-Glcp-(1→, on the prevention against alcohol liver diseases (ALD), with the aim of providing a theoretical basis for the application of P. geesteranus as prebiotic agents in preventing and treating gut dysbiosis and alcohol-related metabolic disorders in individuals with ALD. The results showed that PGP treatment reduced oxidative stress by up-regulating the Nrf2/HO-1 signalling pathways, and decreased the pro-inflammatory factors by down-regulating TLR4/NF-κB signalling pathways. Furthermore, we validated effects of PGPs on balancing the gut-liver axis by maintaining the integrity of the intestinal epithelial barrier of decreasing intestinal permeability, increasing intestinal tight-junction protein and mucin expression and elevating the abundance of short-chain fatty acids (SCFAs) producers in the intestine by regulating the microbiota composition.

Isoliquiritigenin-mediated miR-23a-3p inhibition activates PGC-1α to alleviate alcoholic liver injury

BACKGROUND

Alcoholic liver disease (ALD), one of the most prevalent forms of liver disease, has received wide attention worldwide. However, limited efficient and appropriate therapeutic agents were responded to ALD. Isoliquiritigenin (ISL), a flavonoid isolated from liquorice, possesses multiple pharmacological activities.

PURPOSE

The current study investigated the hepatoprotective effect of ISL against ALD and further elucidate the involvement of miR-23a-3p/peroxisome proliferative activated receptor-γ coactivator 1 alpha (PGC-1α) in vivo and in vitro experiments.

STUDY DESIGN AND METHODS

In the study, H&E and Oil Red O staining were employed to detect liver histopathological changes and the accumulation of lipid droplets. Quantitative real-time PCR, bioinformatics, luciferase assay, immunofluorescence staining, reactive oxygen species (ROS), Western blot, and siRNA were used to further explore the mechanism of ISL protection.

RESULTS

ISL significantly reduced the liver-to-body weight ratios and biochemical index. The staining results showed that ISL remarkedly ameliorated the histopathological changes in the liver. Furthermore, ISL promoted fatty acid metabolism via induction in the expression of PGC-1α-target genes PPARα, CPT1α, and ACADs, and inhibited the ROS, TNF-α, IL-1β, and IL-6 expression. Bioinformatics and Luciferase assay analysis confirmed that miR-23a-3p might bind to PGC-1α mRNA in ALD. Significantly, the expression of miR-23a-3p was increased in the ALD, which was significantly decreased by ISL. In addition, the miR-23a-3p inhibitor also promoted lipid metabolism in ALD via PGC-1α activation.

CONCLUSIONS

We first demonstrated that ISL could alleviate ALD, and further verified that ISL exerted protective effects through modulating miR-23a-3p/PGC-1α-mediated lipid metabolism in vivo and in vitro.

Ferulic Acid Ameliorates Hepatic Inflammation and Fibrotic Liver Injury by Inhibiting PTP1B Activity and Subsequent Promoting AMPK Phosphorylation

Chronic inflammation in response to persistent exogenous stimuli or damage results in liver fibrosis, which subsequently progresses into malignant liver diseases with high morbidity and mortality. Ferulic acid (FA) is a phenolic acid widely isolated from abundant plants and exhibits multiple biological activities including anti-oxidant, anti-inflammation and enhancement of immune responses. Adenosine monophosphate-activated protein kinase (AMPK) functions as a critical energy sensor and is regulated through the phosphorylation of liver kinases like LKB1 or dephosphorylation by protein tyrosine phosphatases (PTPs). However, the role of FA in carbon tetrachloride (CCl₄)-induced chronic inflammation and liver fibrosis and AMPK activation has not been elucidated. Here we reported that FA ameliorated CCl₄-induced inflammation and fibrotic liver damage in mice as indicated by reduced levels of serum liver function enzyme activities and decreased expression of genes and proteins associated with fibrogenesis. Additionally, FA inhibited hepatic oxidative stress, macrophage activation and HSC activation via AMPK phosphorylation in different liver cells. Mechanically, without the participation of LKB1, FA-induced anti-inflammatory and anti-fibrotic effects were abrogated by a specific AMPK inhibitor, compound C. Combining with the results of molecular docking, surface plasmon resonance and co-immunoprecipitation assays, we further demonstrated that FA directly bound to and inhibited PTP1B, an enzyme responsible for dephosphorylating key protein kinases, and eventually leading to the phosphorylation of AMPK. In summary, our results indicated that FA alleviated oxidative stress, hepatic inflammation and fibrotic response in livers through PTP1B-AMPK signaling pathways. Taken together, we provide novel insights into the potential of FA as a natural product-derived therapeutic agent for the treatment of fibrotic liver injury.

Oxidative stress in obesity-associated hepatocellular carcinoma: sources, signaling and therapeutic challenges

Obesity affects more than 650 million individuals worldwide and is a well-established risk factor for the development of hepatocellular carcinoma (HCC). Oxidative stress can be considered as a bona fide tumor promoter, contributing to the initiation and progression of liver cancer. Indeed, one of the key events involved in HCC progression is excessive levels of reactive oxygen species (ROS) resulting from the fatty acid influx and chronic inflammation. This review provides insights into the different intracellular sources of obesity-induced ROS and molecular mechanisms responsible for hepatic tumorigenesis. In addition, we highlight recent findings pointing to the role of the dysregulated activity of BCL-2 proteins and protein tyrosine phosphatases (PTPs) in the generation of hepatic oxidative stress and ROS-mediated dysfunctional signaling, respectively. Finally, we discuss the potential and challenges of novel nanotechnology strategies to prevent ROS formation in obesity-associated HCC.

Sinapic Acid Reduces Oxidative Stress and Pyroptosis via Inhibition of BRD4 in Alcoholic Liver Disease

Alcoholic liver disease (ALD) is one of the main causes of death in chronic liver disease. Oxidative stress and pyroptosis are important factors leading to ALD. Bromodomain-containing protein 4 (BRD4) is a factor that we have confirmed to regulate ALD. As a phenolic acid compound, sinapic acid (SA) has significant effects in antioxidant, anti-inflammatory and liver protection. In this study, we explored whether SA regulates oxidative stress and pyroptosis through BRD4 to play a protective effect in ALD. Male C57BL/6 mice and AML-12 cells were used for experiments. We found that SA treatment largely abolished the up-regulation of BRD4 and key proteins of the canonical pyroptosis signalling in the liver of mice fed with alcohol, while conversely enhanced the antioxidant response. Consistantly, both SA pretreatment and BRD4 knockdown inhibited oxidative stress, pyroptosis, and liver cell damage in vitro. More importantly, the expression levels of BRD4 and pyroptosis indicators increased significantly in ALD patients. Molecule docking analysis revealed a potent binding of SA with BRD4. In conclusion, this study demonstrates that SA reduces ALD through BRD4, which is a valuable lead compound that prevents the ALD process.

Soluble Epoxide Hydrolase Hepatic Deficiency Ameliorates Alcohol-Associated Liver Disease

BACKGROUND & AIMS

Alcohol-associated liver disease (ALD) is a significant cause of liver-related morbidity and mortality worldwide and with limited therapies. Soluble epoxide hydrolase (sEH; Ephx2) is a largely cytosolic enzyme that is highly expressed in the liver and is implicated in hepatic function, but its role in ALD is mostly unexplored.

METHODS

To decipher the role of hepatic sEH in ALD, we generated mice with liver-specific sEH disruption (Alb-Cre; Ephx2^fl/fl). Alb-Cre; Ephx2^fl/fl and control (Ephx2^fl/fl) mice were subjected to an ethanol challenge using the chronic plus binge model of ALD and hepatic injury, inflammation, and steatosis were evaluated under pair-fed and ethanol-fed states. In addition, we investigated the capacity of pharmacologic inhibition of sEH in the chronic plus binge mouse model.

RESULTS

We observed an increase of hepatic sEH in mice upon ethanol consumption, suggesting that dysregulated hepatic sEH expression might be involved in ALD. Alb-Cre; Ephx2^fl/fl mice presented efficient deletion of hepatic sEH with corresponding attenuation in sEH activity and alteration in the lipid epoxide/diol ratio. Consistently, hepatic sEH deficiency ameliorated ethanol-induced hepatic injury, inflammation, and steatosis. In addition, targeted metabolomics identified lipid mediators that were impacted significantly by hepatic sEH deficiency. Moreover, hepatic sEH deficiency was associated with a significant attenuation of ethanol-induced hepatic endoplasmic reticulum and oxidative stress. Notably, pharmacologic inhibition of sEH recapitulated the effects of hepatic sEH deficiency and abrogated injury, inflammation, and steatosis caused by ethanol feeding.

CONCLUSIONS

These findings elucidated a role for sEH in ALD and validated a pharmacologic inhibitor of this enzyme in a preclinical mouse model as a potential therapeutic approach.