tert-Butylhydroquinone (tBHQ) protects hepatocytes against lipotoxicity via inducing autophagy independently of Nrf2 activation

Salvianolic acid A attenuates non-alcoholic fatty liver disease by regulating the AMPK-IGFBP1 pathway

Non-alcoholic fatty liver disease (NAFLD) affects approximately a quarter of the population and, to date, there is no approved drug therapy for this condition. Individuals with type 2 diabetes mellitus (T2DM) are at a significantly elevated risk of developing NAFLD, underscoring the urgency of identifying effective NAFLD treatments for T2DM patients. Salvianolic acid A (SAA) is a naturally occurring phenolic acid that is an important component of the water-soluble constituents isolated from the roots of Salvia miltiorrhiza Bunge. SAA has been demonstrated to possess anti-inflammatory and antioxidant stress properties. Nevertheless, its potential in ameliorating diabetes-associated NAFLD has not yet been fully elucidated. In this study, diabetic ApoE-/- mice were employed to establish a NAFLD model via a Western diet. Following this, they were treated with different doses of SAA (10 mg/kg, 20 mg/kg) via gavage. The study demonstrated a marked improvement in liver injury, lipid accumulation, inflammation, and the pro-fibrotic phenotype after the administration of SAA. Additionally, RNA-seq analysis indicated that the primary pathway by which SAA alleviates diabetes-induced NAFLD involves the cascade pathways of lipid metabolism. Furthermore, SAA was found to be effective in the inhibition of lipid accumulation, mitochondrial dysfunction and ferroptosis. A functional enrichment analysis of RNA-seq data revealed that SAA treatment modulates the AMPK pathway and IGFBP-1. Further experimental results demonstrated that SAA is capable of inhibiting lipid accumulation through the activation of the AMPK pathway and IGFBP-1.

Protective Effect of Tertiary Butylhydroquinone against Obesity-induced Skeletal Muscle Pathology in Post-weaning High Fat Diet Fed Rats

BACKGROUND

Obesity deleteriously affects skeletal muscle functionality starting from infancy to adulthood, leading to dysfunctional skeletal muscle.

OBJECTIVES

This study, therefore, evaluated the protective action of tert-butylhydroquinone (tBHQ) against obesity-induced skeletal muscle pathology in high-fat diet (HFD) fed rats.

METHODS

Twenty post-weaning male albino rats were randomized into four groups of five rats each as: Group 1 (control), Group 2 (HFD), Group 3 (orlistat) and Group 4 (tBHQ). Group one received rat pellets for 12 weeks, while groups 2 to 4 received HFD for 12 weeks. At the end of week 8, obesity was confirmed with Lee Obesity Index and body mass index values of ≥ 303 and ≥ 0.68 gcm2, respectively. Group 3 was given oral administration of orlistat (10 mg/kg, once daily), while group 4 was given oral administration of tBHQ (25 mg/kg, once daily). Administration of orlistat and tBHQ commenced from week 9 to the end of the experiment.

RESULTS

Chronic exposure of post-weaning rats to HFD led to their development of the metabolic syndrome phenotypes in adulthood, characterized by obesity, hyperglycemia, dyslipidaemia, hyperinsulinaemia, insulin resistance as well as induction of oxidative stress and alteration of skeletal muscle markers, which were mitigated following supplementation with orlistat and tBHQ.

CONCLUSION

The study showed the anti-obesity potentials of tBHQ and its protective action against HFD obesity-induced skeletal muscular pathology.

Design and Synthesis of Novel Indole Ethylamine Derivatives as a Lipid Metabolism Regulator Targeting PPARα/CPT1 in AML12 Cells

Peroxisome proliferator-activated receptor alpha (PPARα) and carnitine palmitoyltransferase 1 (CPT1) are important targets of lipid metabolism regulation for nonalcoholic fatty liver disease (NAFLD) therapy. In the present study, a set of novel indole ethylamine derivatives (4, 5, 8, 9) were designed and synthesized. The target product (compound 9) can effectively activate PPARα and CPT1a. Consistently, in vitro assays demonstrated its impact on the lipid accumulation of oleic acid (OA)-induced AML12 cells. Compared with AML12 cells treated only with OA, supplementation with 5, 10, and 20 μM of compound 9 reduced the levels of intracellular triglyceride (by 28.07%, 37.55%, and 51.33%) with greater inhibitory activity relative to the commercial PPARα agonist fenofibrate. Moreover, the compound 9 supplementations upregulated the expression of hormone-sensitive triglyceride lipase (HSL) and adipose triglyceride lipase (ATGL) and upregulated the phosphorylation of acetyl-CoA carboxylase (ACC) related to fatty acid oxidation and lipogenesis. This dual-target compound with lipid metabolism regulatory efficacy may represent a promising type of drug lead for NAFLD therapy.

DMF-Activated Nrf2 Ameliorates Palmitic Acid Toxicity While Potentiates Ferroptosis Mediated Cell Death: Protective Role of the NO-Donor S-Nitroso-N-Acetylcysteine

Nonalcoholic fatty liver disease (NAFLD) is the most prevalent chronic liver disease that can develop into an aggressive form called nonalcoholic steatohepatitis (NASH), which ultimately progresses to cirrhosis, hepatocellular carcinoma (HCC), and end-stage liver failure. Currently, the deterioration of NAFLD is attributed to specific lipid toxicity which could be due to lipotoxicity and/or ferroptosis. In the current study, we evaluated the involvement of the nuclear factor erythroid 2 (NFE2)-related factor 2 (Nrf-2), which is a main activator of phase II metabolism in the two types of lipid-induced toxicity in hepatocytes, lipotoxicity by saturated fatty acids, and in ferroptosis, and the effect of NO donor treatment. AML12 cells were exposed to 600 μM palmitic acid to induce lipotoxicity or treated with 20 μM erastin or 5 μM RSL3 for ferroptosis. In SFA-lipotoxicity, pretreatment with the Nrf2 activator dimethyl fumarate (DMF) managed to ameliorate the cells and the oxidative stress level while aggravating ferroptosis due to emptying the thiol pool. On the other hand, the nitric oxide (NO)-donor, S-nitroso-N-acetylcysteine (NAC-SNO) proved to be effective in the prevention of hepatocytes ferroptosis.

Tert-butylhydroquinone protects the retina from oxidative stress in STZ-induced diabetic rats via the PI3K/Akt/eNOS pathway

This study aims to investigate whether tert-butylhydroquinone protects the retina from oxidative stress in STZ-induced experimental diabetic rats through the activation of phosphinositide 3-kinase (PI3K)/Akt/endothelial nitric oxide synthase (eNOS) pathway.In vitro, NO, reactive oxygen species(ROS), eNOS, p-eNOS Ser1179, Akt, p-Akt Ser473 and L-NAME protein expression was analyzed within rMC-1 cells cultivated within normal control(NC), high glucose (HG) and HG-containing tert-butyl hydroquinone (tBHQ) (5 μM) medium. We confirmed tBHQ's protection through administering inhibitors of PI3K and Akt. In vivo, tBHQ was administered at a ratio of 1% (w/w) to diabetic rats was induced through an STZ injection (65 mg/kg) for a 3-month period, and the retinal expression of eNOS, p-eNOS Ser1179, Akt, and p-Akt Ser473 proteins was measured using Western blotting (WB) assay. We also utilized the TUNEL kit for detecting retinal cell apoptosis. The changes of retinal morphology and visual function were measured by performing hematoxylin-eosin staining (HE staining) and electroretinograms. In vitro, ROS levels were increased in the high glucose group, NO levels were decreased, and the relative expression of Akt/p-Akt Ser473 and eNOs/p-eNOS Ser1179 was reduced. tBHQ abolished these changes, and these effects were suppressed by specific inhibitors. In vivo, tBHQ upregulated retinal protein expression in STZ-induced diabetic rats, reduced retinal apoptotic cell numbers, and partially prevented abnormalities in retinal function and structure caused by diabetes. tBHQ alleviates oxidative stress during diabetic retinopathy by upregulating the PI3K/Akt/eNOS pathway and partially restoring the structure and function of the retina. It may play a role in delaying vision loss caused by diabetic retinopathy.

Advances in Immunosuppressive Agents Based on Signal Pathway

Immune abnormality involves in various diseases, such as infection, allergic diseases, autoimmune diseases, as well as transplantation. Several signal pathways have been demonstrated to play a central role in the immune response, including JAK/STAT, NF-κB, PI3K/AKT-mTOR, MAPK, and Keap1/Nrf2/ARE pathway, in which multiple targets have been used to develop immunosuppressive agents. In recent years, varieties of immunosuppressive agents have been approved for clinical use, such as the JAK inhibitor tofacitinib and the mTOR inhibitor everolimus, which have shown good therapeutic effects. Additionally, many immunosuppressive agents are still in clinical trials or preclinical studies. In this review, we classified the immunosuppressive agents according to the immunopharmacological mechanisms, and summarized the phase of immunosuppressive agents.

Cimifugin Ameliorates Lipotoxicity-Induced Hepatocyte Damage and Steatosis through TLR4/p38 MAPK- and SIRT1-Involved Pathways

Objective. Hepatic metabolic disorder induced by lipotoxicity plays a detrimental role in metabolic fatty liver disease pathogenesis. Cimifugin (Cim), a coumarin derivative extracted from the root of Saposhnikovia divaricata, possesses multiple biological properties against inflammation, allergy, and oxidative stress. However, limited study has addressed the hepatoprotective role of Cim. Here, we investigate the protective effect of Cim against lipotoxicity-induced cytotoxicity and steatosis in hepatocytes and clarify its potential mechanisms. Methods. AML-12, a nontransformed mouse hepatocyte cell line, was employed in this study. The cells were incubated with palmitate or oleate to imitate hepatotoxicity or steatosis model, respectively. Results. Cim significantly reversed palmitate-induced hepatocellular injury in a dose-dependent manner, accompanied by improvements in oxidative stress and mitochondrial damage. Cim pretreatment reversed palmitate-stimulated TLR4/p38 MAPK activation and SIRT1 reduction without affecting JNK, ERK1/2, and AMPK pathways. The hepatoprotective effects of Cim were abolished either through activating TLR4/p38 by their pharmacological agonists or genetical silencing SIRT1 via special siRNA, indicating a mechanistic involvement. Moreover, Cim treatment improved oleate-induced hepatocellular lipid accumulation, which could be blocked by either TLR4 stimulation or SIRT1 knockdown. We observed that SIRT1 was a potential target of TLR4 in palmitate-treated hepatocytes, since TLR4 agonist LPS aggravated, whereas TLR4 antagonist CLI-095 alleviated palmitate-decreased SIRT1 expression. SIRT1 knockdown did not affect palmitate-induced TLR4. In addition, TLR4 activation by LPS significantly abolished Cim-protected SIRT1 reduction induced by palmitate. These results collaboratively indicated that TLR4-regulated SIRT1 pathways was mechanistically involved in the protective effects of Cim against lipotoxicity. Conclusion. In brief, we demonstrate the protective effects of Cim against lipotoxicity-induced cell death and steatosis in hepatocytes. TLR4-regulated p38 MAPK and SIRT1 pathways are involved in Cim-protected hepatic lipotoxicity. Cim is a potential candidate for improving hepatic metabolic disorders mediated by lipotoxicity.

Tert-Butylhydroquinone alleviates insulin resistance and liver steatosis in diabetes

OBJECTIVES:

This work aimed to determine tert-Butylhydroquinone (TBHQ)'s effects on insulin resistance (IR) and liver steatosis in diabetic animals and to explore the underpinning mechanisms.

MATERIALS AND METHODS:

Male ApoE^-/-mice underwent streptozocin (STZ) administration while receiving a sucrose/fat-rich diet for type 2 diabetes mellitus (T2DM) establishment. This was followed by a 6-week TBHQ administration. Body weight, fasting (FBG) and postprandial (PBG) blood glucose amounts, and insulin concentrations were measured, and the oral glucose tolerance test (OGTT) was carried out. Hematoxylin and eosin (H and E) staining and immunoblot were carried out for assessing histology and protein amounts in the liver tissue samples. In addition, cultured HepG2 cells were administered HClO and insulin for IR induction, and immunoblot was carried out for protein evaluation. Finally, the cells were stained with the Hoechst dye for apoptosis evaluation.

RESULTS:

The model animals showed T2DM signs, and TBHQ decreased FBG, ameliorated glucose tolerance and reduced liver steatosis in these animals. In addition, TBHQ markedly upregulated AMPKα2, GLUT4 and GSK3 β, as well as phosphorylated PI3K and AKT in the liver of mice with T2DM. In agreement, TBHQ decreased HClO-and insulin-related IR in cells and suppressed apoptosis through AMPKα2/PI3K/AKT signaling.

CONCLUSIONS:

TBHQ alleviates IR and liver steatosis in a mouse model of T2DM likely through AMPKα2/PI3K/AKT signaling.

Atractylenolide I Ameliorates Acetaminophen-Induced Acute Liver Injury via the TLR4/MAPKs/NF-κB Signaling Pathways

Background: Acetaminophen (APAP) overdose results in the production of reactive oxygen species (ROS), induces hepatocyte necrosis, and leads to acute liver failure. Atractylenolide I (AO-I), a phytochemical found in Atractylodes macrocephala Koidz, is known to exhibit antioxidant activity. However, its clinical benefits against drug-induced liver injury remain largely unclear.

Purpose: This study aimed at evaluating the protective effects of AO-I against APAP-induced acute liver injury.

Methods: C57BL/6 mice were administered 500 mg/kg APAP to induce hepatotoxicity. AO-Ⅰ (60 and 120 mg/kg) was intragastrically administered 2 h before APAP dosing. Liver histopathological changes, oxidative stress and hepatic inflammation markers from each group were observed.

Results: We observed that AO-I treatment significantly reversed APAP-induced liver injury, as evidenced by improved plasma alanine transaminase (ALT) level, aspartate aminotransferase (AST) and liver H&E stain. APAP treatment increased liver malondialdehyde (MDA) content and reduced catalase (CAT) and glutathione (GSH) level; however, these effects were alleviated by AO-I intervention. Moreover, AO-I treatment significantly inhibited APAP-induced activation of pro-inflammatory factors, such as IL-1β, IL-6, and TNF-α, at both the mRNA and protein levels. Mechanistic studies revealed that AO-I attenuated APAP-induced activation of TLR4, NF-κB and MAPKs (including JNK and p38).

Conclusion: AO-I mediates protective effects against APAP-induced hepatotoxicity via the TLR4/MAPKs/NF-κB pathways. Thus, AO-I is a candidate therapeutic compound for APAP-induced hepatotoxicity.

Tert-butylhydroquinone attenuates osteoarthritis by protecting chondrocytes and inhibiting macrophage polarization

Aims

Tert-butylhydroquinone (tBHQ) has been identified as an inhibitor of oxidative stress-induced injury and apoptosis in human neural stem cells. However, the role of tBHQ in osteoarthritis (OA) is unclear. This study was carried out to investigate the role of tBHQ in OA.

Methods

OA animal model was induced by destabilization of the medial meniscus (DMM). Different concentrations of tBHQ (25 and 50 mg/kg) were intraperitoneally injected in ten-week-old female mice. Chondrocytes were isolated from articular cartilage of mice and treated with 5 ng/ml lipopolysaccharide (LPS) or 10 ng/ml interleukin 1 beta (IL-1β) for 24 hours, and then treated with different concentrations of tBHQ (10, 20, and 40 μM) for 12 hours. The expression levels of malondialdehyde (MDA) and superoxide dismutase (SOD) in blood were measured. The expression levels of interleukin 6 (IL-6), IL-1β, and tumour necrosis factor alpha (TNF-α) leptin in plasma were measured using enzyme-linked immunoabsorbent assay (ELISA) kits. The expression of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) and mitogen-activated protein kinase (MAPK) signalling pathway proteins, and macrophage repolarization-related markers, were detected by western blot.

Results

Tert-butylhydroquinone significantly attenuated cartilage destruction in DMM-induced mice in vivo. It demonstrated clear evidence of inhibiting IL-1β-induced chondrocyte apoptosis, inflammation, and differentiation defect in vitro. Meanwhile, tBHQ inhibited LPS-induced activation of NF-κB and MAPK signalling pathways, and also inhibited LPS-induced reactive oxygen species production and macrophages repolarization in vitro.

Conclusion

Taken together, tBHQ might be a potential therapeutic strategy for protecting against OA development.

Cite this article: Bone Joint Res 2021;10(11):704–713.

Tertiary butylhydroquinone alleviated liver steatosis and increased cell survival via β-arrestin-2/PI3K/AKT pathway

OBJECTIVES

This study aimed to evaluate the effects and the underlying mechanisms of tertiary butylhydroquinone (TBHQ) on diabetic liver steatosis and cell survival.

MATERIALS AND METHODS

We performed streptozocin injection and used a high-sugar-high-fat diet for mice to develop an animal model of type 2 diabetes mellitus (T2DM). Bodyweight, blood glucose levels, and content of insulin were measured on all of the mice. The liver tissues were observed by hematoxylin-eosin staining. Protein levels of the liver were measured by Western blot analysis in mice. Primary hepatocytes were induced by hypochlorous acid (HClO) and insulin to form insulin resistance (IR). Primary hepatocyte apoptosis was observed by Hoechst staining. The PI3K/AKT signaling pathway and β-arrestin-2 factor were evaluated by Western blot assay.

RESULTS

TBHQ reduced the blood glucose level and content of insulin in serum, increased body weight, and effectively alleviated liver steatosis in diabetic mice. TBHQ significantly up-regulated the expression of p-PI3K, p-AKT, GLUT4, GSK3β, and β-arrestin-2 in the liver of diabetic mice. Cell experiments confirmed that TBHQ increased the survival ability of primary hepatocytes, and TBHQ improved the expression of p-PI3K, p-AKT, GLUT4, and GSK3β by activating β-arrestin-2 in primary hepatocytes.

CONCLUSION

TBHQ could alleviate liver steatosis and increase cell survival, and the mechanism is due in part to β-arrestin-2 activation.

Metformin and tBHQ Treatment Combined with an Exercise Regime Prevents Osteosarcopenic Obesity in Middle-Aged Wistar Female Rats

Osteosarcopenic obesity (OSO) is characterized by bone density, mass, and muscle strength loss, in conjunction with adipose tissue increase. OSO impairs physical activity and mobility, provoking autonomy loss; also, it is known that augmenting body fat in the elderly decreases life expectancy. The main factors influencing this health deterioration are the inflammatory environment induced by adipose tissue and its infiltration into muscle tissue, which leads to oxidative stress generation. Currently, there are several treatments to delay OSO, among which exercise training stands out because it improves muscle fiber quality and quantity and decreases adipose tissue. We have recently demonstrated that the combined treatment between moderate exercise and metformin slows sarcopenia's onset by a mechanism that includes adipose reduction and REDOX regulation. On the other hand, tert-butylhydroquinone (tBHQ) is a well-known antioxidant that counteracts oxidative stress. Therefore, to slow down obesity's harmful effects on muscle mass and bone mineral density, we performed different interventions, including combining a Fartlek-type exercise routine with metformin and tBHQ administration, in a model of middle-aged female Wistar rats with obesity induced with a hypercaloric diet. Our results showed that the combined exercise-metformin-tBHQ treatment increased muscle mass and strength, decreased body weight, body mass index, and fat percentage, and improved redox status, thus increasing animal survival.

Comprehensive Analysis of the Expression Profiles of Hepatic lncRNAs in the Mouse Model of Alcoholic Liver Disease

Background and Aim: The worldwide prevalence of alcoholic liver disease (ALD) due to escalating alcohol consumption has presented an unprecedented pressure on human health. A few studies have determined long non-coding RNAs (lncRNAs) involved in the pathogenesis of liver diseases. However, the roles of lncRNAs in ALD development is still poorly understood.

Methods: An ALD mouse model was established and confirmed. Expression profiles of lncRNAs were obtained by whole transcriptome sequencing. The altered lncRNAs in ALD mice were further verified by qRT-PCR. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses were used to enrich the functions of these lncRNAs. In combination with miRNA and mRNA profiles, we constructed concise endogenous RNA (ceRNA) networks. The function of the most up/downregulated lnRNA was further verified and investigated in both ALD model and AML-12 cells.

Results: Totally, five downregulated lncRNAs were obtained and verified in ALD mice. The GO term and KEGG pathway analyses revealed that the identified lncRNAs were associated with alcohol-induced hepatic oxidative damage, cellular inflammation, and lipid metabolism. Combination the differentially modulated miRNAs and mRNAs with ceRNA network analysis, we constructed five ceRNA networks and obtained 30 miRNAs and 25 mRNAs that may participate in ALD. Further, we verified and investigate the function of the most downregulated lnc_1700023H06Rik. Depletion lnc_1700023H06Rik reduced genes encoding for lipid metabolism, especially mRNA Acat2 (ENSMUST00000159697) and Pgrmc2 (ENSMUST00000058578) both in vivo and in vitro. Knocking down lnc_1700023H06Rik induced triglyceride accumulation and lactate dehydrogenase leakage in AML12 cells, consisting with that in alcohol-treated cells.

Conclusion: The five remarkably downregulated lncRNAs in ALD mouse model were identified as novel biomarkers, highlighting the key role of lncRNAs in the development of ALD. The effect of lnc_1700023H06Rik plays a pivotal role in lipid deposition and its pathological pathway in ALD needs further investigation.

Facing Cell Autophagy in Gastric Cancer - What Do We Know so Far?

Autophagy is a process by which misfolded proteins and damaged organelles in the lysosomes of tumor cells were degraded reusing decomposed substances and avoiding accumulation of large amounts of harmful substances. Here, the role of autophagy in the development of malignant transformation of gastric tumors, and the underlying mechanisms involved in autophagy formation, and the application of targeted autophagy in the treatment of gastric cancer were summarized.

Upregulation of antioxidant and autophagy pathways via NRF2 activation protects spinal cord neurons from ozone damage

Ozone therapy can relieve multiple types of pain but exhibits potential neurotoxicity, the mechanism of which is unclear. The present study aimed to identify the role of nuclear factor (erythroid-derived-2)-related 2 (NRF2) in preventing spinal cord injury caused by ozone overdose. Primary neuronal cells were extracted from newborn Wistar rats and authenticated by immunofluorescence using anti-microtubule-associated protein 2 as a cell type-specific marker. Cell viability assay with different ozone concentrations (0, 10, 20, 30 and 40 µg/ml) was used to determine the concentration that caused primary neuron injury; 30 min of 40 µg/ml ozone therapy notably decreased cell viability to 71%. In order to test the effects of ozone, the cells were divided into five treatment groups [0-, 30- and 40 µg/ml ozone, tert-butylhydroquinone (tBHQ) + 40 µg/ml ozone (T40) and tBHQ (T0)]. Cells in the T40 and T0 groups received 40 µmol/l tBHQ on the fifth day of SCN cultivation. Reverse transcription-quantitative PCR and western blotting showed that protein expression levels of heme oxygenase-1 (HO-1) and mRNA expression levels of HO-1 and NRF2 were decreased. NRF2, ubiquitin-binding protein p62 and microtubule-associated proteins 1A/1B light chain 3B expression levels were decreased following treatment with 40 µg/ml ozone. Immunofluorescence showed that NRF2 nuclear expression levels also decreased following 40 µg/ml ozone treatment. However, cells in the T40 group did not display decreased NRF2 nuclear expression levels. Normal/Apoptotic/Necrotic Cell Detection kit revealed that necrosis rate increased following treatment with 40 µg/ml ozone; however, the T40 group did not exhibit this increased necrosis. At 40 µg/ml, ozone increased spinal cord neuron (SCN) death in vitro. Moreover, treatment with 40 µg/ml ozone damaged SCNs. The p62/NRF2/antioxidant response element pathway prevented such injury. tBHQ activated this pathway, upregulated autophagy and increased local nuclear NRF2 concentration, thus enhancing the antioxidant system to protect SCNs from injury caused by high concentrations of ozone.

Tert-butylhydroquinone attenuates doxorubicin-induced dysregulation of testicular cytoprotective and steroidogenic genes, and improves spermatogenesis in rats

Doxorubicin (DOX) is a broad-spectrum chemotherapeutic drug used in the treatment of cancers. It acts by generating reactive oxygen species in target cells. The actions are, however, not limited to cancerous cells as it attacks healthy cells, killing them. This study investigated the benefits of the antioxidant, tert-butylhydroquinone (tBHQ), on testicular toxicity following DOX therapy. Twenty-four adult male albino rats were assigned randomly into four groups (n = 6), namely: normal control (NC), tBHQ, DOX and tBHQ + DOX groups. tBHQ (50 mg/kg body weight in 1% DMSO) was administered orally for 14 consecutive days, while a single DOX dose (7 mg/kg body weight) was administered intraperitoneally on Day 8. DOX decreased sperm count, motility and viability, and decreased the levels of steroidogenesis-related proteins, and reproductive hormones. Furthermore, DOX decreased the expression of antioxidant cytoprotective genes, and decreased the protein level of proliferating cell nuclear antigen in the testis. Conversely, DOX increased the expression of pro-inflammatory and pro-apoptotic genes in the testis. These negative effects were ameliorated following the intervention with tBHQ. Our results suggest that tBHQ protects the testis and preserves both steroidogenesis and spermatogenesis in DOX-treated rats through the suppression of oxidative stress, inflammation and apoptosis.

Inhibition of TLR4/MAPKs Pathway Contributes to the Protection of Salvianolic Acid A Against Lipotoxicity-Induced Myocardial Damage in Cardiomyocytes and Obese Mice

The occurrence of lipotoxicity during obesity-associated cardiomyopathy is detrimental to health. Salvianolic acid A (SAA), a natural polyphenol extract of Salvia miltiorrhiza Bunge (Danshen in China), is known to be cardioprotective. However, its clinical benefits against obesity-associated cardiomyocyte injuries are unclear. This study aimed at evaluating the protective effects of SAA against lipotoxicity-induced myocardial injury and its underlying mechanisms in high fat diet (HFD)-fed mice and in palmitate-treated cardiomyocyte cells (H9c2). Our analysis of aspartate aminotransferase and creatine kinase isoenzyme-MB (CM-KB) levels revealed that SAA significantly reversed HFD-induced myocardium morphological changes and improved myocardial damage. Salvianolic acid A pretreatment ameliorated palmitic acid-induced myocardial cell death and was accompanied by mitochondrial membrane potential and intracellular reactive oxygen species improvement. Analysis of the underlying mechanisms showed that SAA reversed myocardial TLR4 induction in HFD-fed mice and H9c2 cells. Palmitic acid-induced cell death was significantly reversed by CLI-95, a specific TLR4 inhibitor. TLR4 activation by LPS significantly suppressed SAA-mediated lipotoxicity protection. Additionally, SAA inhibited lipotoxicity-mediated expression of TLR4 target genes, including MyD88 and p-JNK/MAPK in HFD-fed mice and H9c2 cells. However, SAA did not exert any effect on palmitic acid-induced SIRT1 suppression and p-AMPK induction. In conclusion, our data shows that SAA protects against lipotoxicity-induced myocardial damage through a TLR4/MAPKs mediated mechanism.

Ferulic acid alleviates lipotoxicity-induced hepatocellular death through the SIRT1-regulated autophagy pathway and independently of AMPK and Akt in AML-12 hepatocytes

Background

Lipotoxicity-induced cell death plays a detrimental role in the pathogenesis of metabolic diseases. Ferulic acid, widespread in plant-based food, is a radical scavenger with multiple bioactivities. However, the benefits of ferulic acid against hepatic lipotoxicity are largely unclear. Here, we investigated the protective effect of ferulic acid against palmitate-induced lipotoxicity and clarified its potential mechanisms in AML-12 hepatocytes.

Methods

AML-12 mouse hepatocytes were exposed to palmitate to mimic lipotoxicity. Different doses (25, 50, and 100 μM) of ferulic acid were added 2 h before palmitate treatment. Cell viability was detected by measuring lactate dehydrogenase release, nuclear staining, and the expression of cleaved-caspase-3. Intracellular reactive oxygen species content and mitochondrial membrane potential were analysed by fluorescent probes. The potential mechanisms were explored by molecular biological methods, including Western blotting and quantitative real-time PCR, and were further verified by siRNA interference.

Results

Our data showed that ferulic acid significantly inhibited palmitate-induced cell death, rescued mitochondrial membrane potential, reduced reactive oxygen species accumulation, and decreased inflammatory factor activation, including IL-6 and IL-1beta. Ferulic acid significantly stimulated autophagy in hepatocytes, whereas autophagy suppression blocked the protective effect of ferulic acid against lipotoxicity. Ferulic acid-activated autophagy, which was triggered by SIRT1 upregulation, was mechanistically involved in its anti-lipotoxicity effects. SIRT1 silencing blocked most beneficial changes induced by ferulic acid.

Conclusions

We demonstrated that the phytochemical ferulic acid, which is found in plant-based food, protected against hepatic lipotoxicity, through the SIRT1/autophagy pathway. Increased intake of ferulic acid-enriched food is a potential strategy to prevent and/or improve metabolic diseases with lipotoxicity as a typical pathological feature.

Activation of the AMPK-SIRT1 pathway contributes to protective effects of Salvianolic acid A against lipotoxicity in hepatocytes and NAFLD in mice

Background: Salvianolic acid A (Sal A), a natural polyphenol compound extracted from Radix Salvia miltiorrhiza (known as Danshen in China), possesses a variety of potential pharmacological activities. The aim of this study is to determine mechanisms of hepatoprotective effects of Sal A against lipotoxicity both in cultured hepatocytes and in a mouse model of fatty liver disease. Methods: High-fat and high-carbohydrate diet (HFCD)-fed C57BL/6J mice were employed to establish hepatic lipotoxicity in a mouse model. Two doses of Sal A were administered every other day via intraperitoneal injection (20 and 40 mg/kg BW, respectively). After a 10-week intervention, liver injury was detected by immunohistochemical and biochemical analyses. For in vitro studies, we used HepG2, a human hepatoma cell line, and exposed them to palmitic acid to induce lipotoxicity. The protective effects of Sal A on palmitic acid-induced lipotoxicity were examined in Sal A-pretreated HepG2 cells. Results: Sal A treatments attenuated body weight gain, liver injury, and hepatic steatosis in mice exposed to HFCD. Sal A pretreatments ameliorated palmitic acid-induced cell death but did not reverse effects of HFCD- or palmitate-induced activations of JNK, ERK1/2, and PKA. Induction of p38 phosphorylation was significantly reversed by Sal A in HFCD-fed mice but not in palmitate-treated HepG2 cells. However, Sal A rescued hepatic AMP-activated protein kinase (AMPK) suppression and sirtuin 1 (SIRT1) downregulation by both HFCD feeding in mice and exposure to palmitate in HepG2 cells. Sal A dose-dependently up-regulated p-AMPK and SIRT1 protein levels. Importantly, siRNA silencing of either AMPK or SIRT1 gene expression abolished the protective effects of Sal A on lipotoxicity. Moreover, while AMPK silencing blocked Sal A-induced SIRT1, silencing of SIRT1 had no effect on Sal A-triggered AMPK activation, suggesting SIRT1 upregulation by Sal A is mediated by AMPK activation. Conclusion: Our data uncover a novel mechanism for hepatoprotective effects of Sal A against lipotoxicity both in livers from HFCD-fed mice and palmitic acid-treated hepatocytes.

A Novel STAT3-Mediated GATA6 Pathway Contributes to tert-Butylhydroquinone- (tBHQ-) Protected TNFα-Activated Vascular Cell Adhesion Molecule 1 (VCAM-1) in Vascular Endothelium

The activation of vascular cell adhesion molecule 1 (VCAM-1) in vascular endothelial cells has been well considered implicating in the initiation and processing of atherosclerosis. Oxidative stress is mechanistically involved in proatherosclerotic cytokine-induced VCAM-1 activation. tert-Butylhydroquinone (tBHQ), a synthetic phenolic antioxidant used for preventing lipid peroxidation of food, possesses strongly antioxidant capacity against oxidative stress-induced dysfunction in various pathological process. Here, we investigated the protective role of tBHQ on tumor necrosis factor alpha- (TNFα-) induced VCAM-1 activation in both aortic endothelium of mice and cultured human vascular endothelial cells and uncovered its potential mechanisms. Our data showed that tBHQ treatment significantly reversed TNFα-induced activation of VCAM-1 at both transcriptional and protein levels. The mechanistic study revealed that inhibiting neither nuclear factor (erythroid-derived 2)-like 2 (Nrf2) nor autophagy blocked the beneficial role of tBHQ. Alternatively, tBHQ intervention markedly alleviated TNFα-increased GATA-binding protein 6 (GATA6) mRNA and protein expressions and its translocation into nucleus. Further investigation indicated that tBHQ-inhibited signal transducer and activator of transcription 3 (STAT3) but not mitogen-activated protein kinase (MAPK) pathway contributed to its protective role against VCAM-1 activation via regulating GATA6. Collectively, our data demonstrated that tBHQ prevented TNFα-activated VCAM-1 via a novel STAT3/GATA6-involved pathway. tBHQ could be a potential candidate for the prevention of proatherosclerotic cytokine-caused inflammatory response and further dysfunctions in vascular endothelium.

Cannabinoid-Induced Autophagy and Heme Oxygenase-1 Determine the Fate of Adipose Tissue-Derived Mesenchymal Stem Cells under Stressful Conditions

The administration of adipose tissue-derived mesenchymal stem cells (ADMSCs) represents a promising therapeutic option after myocardial ischemia or myocardial infarction. However, their potential is reduced due to the high post-transplant cell mortality probably caused by oxidative stress and mitogen-deficient microenvironments. To identify protection strategies for ADMSCs, this study investigated the influence of the non-psychoactive phytocannabinoid cannabidiol (CBD) and the endocannabinoid analogue R(+)-methanandamide (MA) on the induction of heme oxygenase-1 (HO-1) and autophagy under serum-free conditions. At a concentration of 3 µM, CBD induced an upregulation of HO-1 mRNA and protein within 6 h, whereas for MA only a late and comparatively lower increase in the HO-1 protein could be detected after 48 h. In addition, both cannabinoids induced time- and concentration-dependent increases in LC3A/B-II protein, a marker of autophagy, and in metabolic activity. A participation of several cannabinoid-binding receptors in the effect on metabolic activity and HO-1 was excluded. Similarly, knockdown of HO-1 by siRNA or inhibition of HO-1 activity by tin protoporphyrin IX (SnPPIX) had no effect on CBD-induced autophagy and metabolic activity. On the other hand, the inhibition of autophagy by bafilomycin A₁ led to a significant decrease in cannabinoid-induced metabolic activity and to an increase in apoptosis. Under these circumstances, a significant induction of HO-1 expression after 24 h could also be demonstrated for MA. Remarkably, inhibition of HO-1 by SnPPIX under conditions of autophagy deficit led to a significant reversal of apoptosis in cannabinoid-treated cells. In conclusion, the investigated cannabinoids increase metabolic viability of ADMSCs under serum-free conditions by inducing HO-1-independent autophagy but contribute to apoptosis under conditions of additional autophagy deficit via an HO-1-dependent pathway.

Autophagy and Liver Diseases

Autophagy plays an important role in the physiology and pathology of the liver. It is involved in the development of many liver diseases such as α-1-antitrypsin deficiency, chronic hepatitis virus infection, alcoholic liver disease, nonalcoholic fatty liver disease, and liver cancer. Autophagy has thus become a new target for the treatment of liver diseases. How to treat liver diseases by regulating autophagy has been a hot topic.

Tert-butylhydroquinone mitigates Carbon Tetrachloride induced Hepatic Injury in mice

Tert-butylhydroquinone (tBHQ) is an antioxidant compound that exhibits cytoprotective effect in many tissues under pathological condition. However, its role in carbon tetrachloride (CCL4) induced liver injury is still unclear. Here we established a carbon tetrachloride induced hepatic injury model in mice to determine whether tBHQ can mitigate CCL4 induced liver damage. In our study, we found tBHQ exhibited protective effects in CCL4 treated mice model. TBHQ markedly improved hepatic function and decreased hepatic histopathological damage in vivo. In addition, tBHQ reduced levels of pro-inflammatory cytokines in mice model. Moreover, tBHQ mitigated apoptosis of hepatocytes, oxidative stress and lipid peroxidation in vivo and in vitro. We also found the possible mechanism of protective effects of tBHQ was associated with activation of Nrf2/ heme oxygenase-1 (HO-1) pathway. In conclusion, our study revealed tBHQ can be a potential therapeutic drug in treatment of acute hepatic injury.

An Evaluation of the In Vitro Roles and Mechanisms of Silibinin in Reducing Pyrazinamide- and Isoniazid-Induced Hepatocellular Damage

Tuberculosis remains a significant infectious lung disease that affects millions of patients worldwide. Despite numerous existing drug regimens for tuberculosis, drug-induced liver injury is a major challenge that limits the effectiveness of these therapeutics. Two drugs that form the backbone of the commonly administered quadruple antitubercular regimen, that is, pyrazinamide (PZA) and isoniazid (INH), are associated with such hepatotoxicity. Yet, we lack safe and effective alternatives to the antitubercular regimen. Consequently, current research largely focuses on exploiting the hepatoprotective effect of nutraceutical compounds as complementary therapy. Silibinin, a herbal product widely believed to protect against various liver diseases, potentially provides a useful solution given its hepatoprotective mechanisms. In our study, we identified silibinin’s role in mitigating PZA- and INH-induced hepatotoxicity and elucidated a deeper mechanistic understanding of silibinin’s hepatoprotective ability. Silibinin preserved the viability of human foetal hepatocyte line LO2 when co-administered with 80 mM INH and decreased apoptosis induced by a combination of 40 mM INH and 10 mM PZA by reducing oxidative damage to mitochondria, proteins, and lipids. Taken together, this proof-of-concept forms the rational basis for the further investigation of silibinin’s hepatoprotective effect in subsequent preclinical studies and clinical trials.

NF-κB and Keap1 Interaction Represses Nrf2-Mediated Antioxidant Response in Rabbit Hemorrhagic Disease Virus Infection

The rabbit hemorrhagic disease virus (RHDV), which belongs to the family Caliciviridae and the genus Lagovirus, causes lethal fulminant hepatitis in rabbits. RHDV decreases the activity of antioxidant enzymes regulated by Nrf2 in the liver. Antioxidants are important for the maintenance of cellular integrity and cytoprotection. However, the mechanism underlying the regulation of the Nrf2-antioxidant response element (ARE) signaling pathway by RHDV remains unclear. Using isobaric tags for relative and absolute quantification (iTRAQ) technology, the current study demonstrated that RHDV inhibits the induction of ARE-regulated genes and increases the expression of the p50 subunit of the NF-κB transcription factor. We showed that RHDV replication causes a remarkable increase in reactive oxygen species (ROS), which is simultaneously accompanied by a significant decrease in Nrf2. It was found that nuclear translocation of Keap1 plays a key role in the nuclear export of Nrf2, leading to the inhibition of Nrf2 transcriptional activity. The p50 protein partners with Keap1 to form the Keap1-p50/p65 complex, which is involved in the nuclear translocation of Keap1. Moreover, upregulation of Nrf2 protein levels in liver cell nuclei by tert-butylhydroquinone (tBHQ) delayed rabbit deaths due to RHDV infection. Considered together, our findings suggest that RHDV inhibits the Nrf2-dependent antioxidant response via nuclear translocation of Keap1-NF-κB complex and nuclear export of Nrf2 and provide new insight into the importance of oxidative stress during RHDV infection.IMPORTANCE Recent studies have reported that rabbit hemorrhagic disease virus (RHDV) infection reduced Nrf2-related antioxidant function. However, the regulatory mechanisms underlying this process remain unclear. The current study showed that the NF-κB p50 subunit partners with Keap1 to form the Keap1-NF-κB complex, which plays a key role in the inhibition of Nrf2 transcriptional activity. More importantly, upregulated Nrf2 activity delayed the death of RHDV-infected rabbits, strongly indicating the importance of oxidative damage during RHDV infection. These findings may provide novel insights into the pathogenesis of RHDV.

Hepatitis C virus core or NS3/4A protein expression preconditions hepatocytes against oxidative stress and endoplasmic reticulum stress

Objectives: The occurrence of oxidative stress and endoplasmic reticulum (ER) stress in hepatitis C virus (HCV) infection has been demonstrated and play an important role in liver injury. During viral infection, hepatocytes must handle not only the replication of the virus, but also inflammatory signals generating oxidative stress and damage. Although several mechanisms exist to overcome cellular stress, little attention has been given to the adaptive response of hepatocytes during exposure to multiple noxious triggers.

Methods: In the present study, Huh-7 cells and hepatocytes expressing HCV Core or NS3/4A proteins, both inducers of oxidative and ER stress, were additionally challenged with the superoxide anion generator menadione to mimic external oxidative stress. The production of reactive oxygen species (ROS) as well as the response to oxidative stress and ER stress were investigated.

Results: We demonstrate that hepatocytes diminish oxidative stress through a reduction in ROS production, ER-stress markers (HSPA5 [GRP78], sXBP1) and apoptosis (caspase-3 activity) despite external oxidative stress. Interestingly, the level of the autophagy substrate protein p62 was downregulated together with HCV Core degradation, suggesting that hepatocytes can overcome excess oxidative stress through autophagic degradation of one of the stressors, thereby increasing cell survival.

Duscussion: In conclusion, hepatocytes exposed to direct and indirect oxidative stress inducers are able to cope with cellular stress associated with viral hepatitis and thus promote cell survival.

Nrf-2 signaling inhibits intracranial aneurysm formation and progression by modulating vascular smooth muscle cell phenotype and function

BACKGROUND

Oxidative stress and vascular smooth muscle cell (VSMC) phenotypic modulation influence intracranial aneurysm (IA) formation and progression. Oxidative stress plays an important role in phenotype switching, and nuclear factor erythroid 2-related factor 2 (Nrf-2) is one of the main antioxidant systems. Unfortunately, little is known about how Nrf-2 signaling influences VSMC phenotype switches during IA pathogenesis.

METHODS

We examined the effect of Nrf-2 activation IA on formation and progression in an elastase-induced rat IA model. We also developed a hydrogen peroxide (H₂O₂)-induced VSMC oxidative damage model. Then, we analyzed VSMC phenotype changes in the setting of Nrf-2 activation or inhibition in vitro. The proliferation, migration ability, and apoptosis rate of VSMCs were tested. Lastly, we measured the expression levels of antioxidant enzymes and inflammatory cytokines downstream of Nrf-2.

RESULTS

Nrf-2 activation suppressed IA formation and progression in vivo. We confirmed Nrf-2 nuclear translocation and a VSMC switch from the contractile to synthetic phenotype. Nrf-2 activation inhibited the proliferation, migratory ability, and apoptosis rate enhanced by H₂O₂. Quantitative real-time polymerase chain reaction (PCR) and western blot analysis revealed that Nrf-2 activation promoted antioxidant enzymes and VSMC-specific marker gene expressions but decreased pro-inflammatory cytokine levels.

CONCLUSION

These results suggest that Nrf-2 exerts protective effects against IA development by preventing VSMCs from changing to a synthetic phenotype.

Nrf2-regulated miR-380-3p Blocks the Translation of Sp3 Protein and Its Mediation of Paraquat-Induced Toxicity in Mouse Neuroblastoma N2a Cells

Laboratorial and epidemiological research has established a relationship between paraquat (PQ) exposure and a risk for Parkinson's disease. Previously, we have investigated the effects of nuclear factor erythroid 2 related factor 2 (Nrf2) and microRNAs in PQ-induced neurotoxicity, addressing the function of miR-380-3p, a microRNA dysregulated by PQ, as well as Nrf2 deficiency. Nrf2 is known to mediate the expression of a variety of genes, including noncoding genes. By chromatin immunoprecipitation, we identified the relationship between Nrf2 and miR-380-3p in transcriptional regulation. qRT-PCR, Western blots, and dual-luciferase reporter gene assay showed that miR-380-3p blocked the translation of the transcription factor specificity protein-3 (Sp3) in the absence of degradation of Sp3 mRNA. Results based on cell counting analysis, annexin v-fluorescein isothiocyanate/propidium iodide double-staining assay, and propidium iodide staining showed that overexpression of miR-380-3p inhibited cell proliferation, increased the apoptotic rate, induced cell cycle arrest, and intensified the toxicity of PQ in mouse neuroblastoma (N2a [Neuro2a]) cells. Knockdown of Sp3 inhibited cell proliferation and eclipsed the alterations induced by miR-380-3p in cell proliferation. Two mediators of apoptosis and cell cycle identified in previous studies as Sp3-regulated, namely cyclin-dependent kinase inhibitor 1 (p21) and calmodulin (CaM), were dysregulated by PQ, but not Sp3 deficiency. In conclusion, Nrf2-regulated miR-380-3p inhibited cell proliferation and enhanced the PQ-induced toxicity in N2a cells potentially by blocking the translation Sp3 mRNA. We conclude that CaM and p21 were involved in PQ-induced toxicity.

Hepatic SIRT3 Upregulation in Response to Chronic Alcohol Consumption Contributes to Alcoholic Liver Disease in Mice

Background

Alcoholic liver disease (ALD) is a type of chronic liver disease caused by chronic ethanol overconsumption. The pathogenesis of ALD is complex and there is no effective clinical treatment thus far. SIRT3 is an NAD⁺-dependent deacetylase primarily located inside mitochondria, and reports on the effect of chronic alcohol exposure on liver SIRT3 expression are scarce. This study aims to investigate the effect of chronic alcohol consumption on hepatic SIRT3 expression and its role in alcoholic-induced liver injury.

Methods

Using the Lieber-DeCarli mouse model of ALD, we analyzed the regulation of SIRT3 and the effect of liver-specific knocking-down of SIRT3 on alcohol-induced liver injury. HepG2 and AML12 hepatocytes were employed to detect the biological function of SIRT3 on alcohol-induced hepatic cytotoxicity and its potential mechanism.

Results

Chronic alcohol exposure led to hepatic SIRT3 upregulation and liver-specific SIRT3 knockdown alleviated alcoholic feeding-induced liver injury and lipid accumulation, which is associated with improved autophagy induction. In addition, autophagy induction contributed to the cytoprotective effect of SIRT3 knockdown on ethanol-induced hepatocyte cell death.

Conclusion

In summary, our data suggest that hepatic SIRT3 upregulation in response to chronic alcohol exposure and liver-specific SIRT3 knockdown, induced autophagy activation further alleviating alcoholic-induced liver injury, which represents a novel mechanism in this process.

Activation of KEAP1/NRF2/P62 signaling alleviates high phosphate-induced calcification of vascular smooth muscle cells by suppressing reactive oxygen species production

Vascular calcification is a complication of diseases and conditions such as chronic kidney disease, diabetes, and aging. Previous studies have demonstrated that high concentrations of inorganic phosphate (Pi) can induce oxidative stress and vascular smooth muscle cell calcification. KEAP1 (Kelch-like ECH-associated protein 1)/NF-E2-related factor 2 (NRF2) signaling has been shown to play important roles in protecting cells from oxidative stress. The current study aims to investigate the possible involvement of the KEAP1/NRF2/P62 -mediated antioxidant pathway in vascular calcification induced by high Pi levels. Exposure of vascular smooth muscle cells (VSMCs) to high Pi concentrations promoted the accumulation of reactive oxygen species (ROS) and the nuclear translocation of NRF2, along with an increase in P62 levels and a decrease in KEAP1 levels. A classic NRF2 activator, tert-butylhydroquinone (tBHQ), significantly decreased ROS levels and calcium deposition in VSMCs by promoting the nuclear translocation of NRF2 and upregulating P62 and KEAP1 expression. In contrast, silencing NRF2 and P62 with siRNAs increased the levels of ROS and calcium deposition in VSMCs. In conclusion, VSMC calcification can be alleviated by the activation of the KEAP1/NRF2/P62 antioxidative pathway, which could have a protective role when it is exogenously activated by tBHQ.

Attenuation of Palmitic Acid-Induced Lipotoxicity by Chlorogenic Acid through Activation of SIRT1 in Hepatocytes

SCOPE

Saturated free fatty acids (FFAs) induce hepatocyte lipotoxicity, wherein oxidative stress-associated mitochondrial dysfunction is mechanistically involved. Chlorogenic acid (CGA), a potent antioxidant and anti-inflammatory compound, protects against high-fat-diet-induced oxidative stress and mitochondrial dysfunction in liver. This study investigates whether CGA protects against FFA-induced hepatocyte lipotoxicity via the regulation of mitochondrial fission/fusion and elucidates its underlying mechanisms.

METHODS AND RESULTS

AML12 cell, a non-transformed hepatocyte cell line, is treated with palmitate. Here, it is shown that CGA prevents palmitate-induced lipotoxicity by activation of SIRT1 regulated mitochondrial morphology. CGA treatment mitigates oxidative stress and mitochondrial dysfunction, as evidenced by a decrease in reactive oxygen species (ROS) production, and an increase in mitochondrial mass and mitochondrial membrane potential. CGA also significantly decreases Bax expression and thereby reduces mitochondria-mediated caspase-dependent apoptosis. Mechanistically, CGA attenuates ROS-induced mitochondrial fragmentation by inhibiting dynamin-related protein 1 (Drp1) and enhancing Mfn2 expression. In contrast, the inhibitory effects of CGA on the generation of mitochondrial ROS and Drp1 are blocked by siRNA knockdown of SIRT1.

CONCLUSION

Collectively, these findings show that supplementation with CGA protects hepatocytes from FFA-induced lipotoxicity through activation of SIRT1, which reverses the oxidative stress and dysfunction of mitochondrial biogenesis directly.

SVIP alleviates CCl4-induced liver fibrosis via activating autophagy and protecting hepatocytes

Prolonged parenchymal cell death leads to activation of fibrogenic cells and extracellular matrix accumulation and eventually liver fibrosis. Autophagy, a major catabolic process of intracellular degradation and recycling, participates in hepatic fibrosis. However, the precise role of autophagy in the pathogenesis of hepatic fibrosis is controversial. The present study aims to investigate the key role of small VCP/p97 interacting protein (SVIP) against CCl₄-induced hepatic fibrosis via activating autophagy. Autophagy could be activated by SVIP in HepG2 cells, but starvation cannot increase SVIP expression in vitro and in vivo. Moreover, SVIP expression, in agreement with autophagic activity and the volume of lipid droplets, first increases and then decreases during the progression of liver fibrosis with CCl₄ treatment in vivo and in vivo. Further, overexpression of SVIP can protect HepG2 cells from the toxicity of CCl₄, which could be enhanced by starvation. Finally, starvation keeps SVIP and autophagy at such high levels in the rat livers that markedly delays the progress of hepatic fibrosis. Probably, the protective effect of SVIP is associated with stabilizing nuclear factor (erythroid-derived 2)-related factor 2 (Nrf2) and transcription factor EB (TFEB). The current study provides insight into the biological role of SVIP and autophagy in regulating hepatic fibrosis, targeting SVIP might be a novel therapeutic strategy in the future.

Palmitic acid induces human osteoblast-like Saos-2 cell apoptosis via endoplasmic reticulum stress and autophagy

Palmitic acid (PA) is the most common saturated long-chain fatty acid in food that causes cell apoptosis. However, little is known about the molecular mechanisms of PA toxicity. In this study, we explore the effects of PA on proliferation and apoptosis in human osteoblast-like Saos-2 cells and uncover the signaling pathways involved in the process. Our study showed that endoplasmic reticulum (ER) stress and autophagy are involved in PA-induced Saos-2 cell apoptosis. We found that PA inhibited the viability of Saos-2 cells in a dose- and time-dependent manner. At the same time, PA induced the expression of ER stress marker genes (glucose-regulated protein 78 (GRP78) and CCAAT/enhancer binding protein homologous protein (CHOP)), altered autophagy-related gene expression (microtubule-associated protein 1 light chain 3 (LC3), ATG5, p62, and Beclin), promoted apoptosis-related gene expression (Caspase 3 and BAX), and affected autophagic flux. Inhibiting ER stress with 4-PBA diminished the PA-induced cell apoptosis, activated autophagy, and increased the expression of Caspase 3 and BAX. Inhibiting autophagy with 3-MA attenuated the PA and ER stress-induced cell apoptosis and the apoptosis-related gene expression (Caspase 3 and BAX), but seemed to have no obvious effects on ER stress, although the CHOP expression was downregulated. Taken together, our results suggest that PA-induced Saos-2 cell apoptosis is activated via ER stress and autophagy, and the activation of autophagy depends on the ER stress during this process.

Fecal Microbiota Transplantation Beneficially Regulates Intestinal Mucosal Autophagy and Alleviates Gut Barrier Injury

The gut microbiota plays a crucial role in human and animal health, and its disorder causes multiple diseases. Over the past decade, FMT has gained increasing attention due to the success in treating Clostridium difficile infection (CDI) and inflammatory bowel disease (IBD). Although FMT appears to be effective, how FMT functions in the recipient remains unknown. Whether FMT exerts this beneficial effect through a series of changes in the host organism caused by alteration of gut microbial structure is also not known. In the present study, newborn piglets and E. coli K88-infected piglets were selected as models to explore the interplay between host and gut microbiota following FMT. Our results showed that FMT triggered intestinal mucosal autophagy and alleviated gut barrier injury caused by E. coli K88. This report provides a theoretical basis for the use of FMT as a viable therapeutic method for gut microbial regulation.

Fecal microbiota transplantation (FMT) is one of the most effective ways to regulate the gut microbiota. Here, we investigated the effect of exogenous fecal microbiota on gut function from the perspective of analysis of the mucosal proteomes in a piglet model. A total of 289 differentially expressed proteins were annotated with 4,068 gene ontology (GO) function entries in the intestinal mucosa, and the levels of autophagy-related proteins in the forkhead box O (FoxO) signaling pathway were increased whereas the levels of proteins related to inflammation response were decreased in the recipient. Then, to assess the alleviation of epithelial injury in the Escherichia coli K88-infected piglets following FMT, intestinal microbiome-metabolome responses were determined. 16S rRNA gene sequencing showed that the abundances of beneficial bacteria, such as Lactobacillus and Succinivibrio, were increased whereas those of Enterobacteriaceae and Proteobacteria bacteria were decreased in the infected piglets following FMT. Metabolomic analysis revealed that levels of 58 metabolites, such as lactic acid and succinic acid, were enhanced in the intestinal lumen and that seven metabolic pathways, such as branched-chain amino acid metabolism pathways, were upregulated in the infected piglets following FMT. In concordance with the metabolome data, results of metagenomics prediction analysis also demonstrated that FMT modulated the metabolic functions of gut microbiota associated with linoleic acid metabolism. In addition, intestinal morphology was improved, a result that coincided with the decrease of intestinal permeability and the enhancement of mucins and mucosal expression of tight junction proteins in the recipient. Taken together, the results showed that FMT triggered intestinal mucosal protective autophagy and alleviated gut barrier injury through alteration of the gut microbial structure.

IMPORTANCE The gut microbiota plays a crucial role in human and animal health, and its disorder causes multiple diseases. Over the past decade, FMT has gained increasing attention due to the success in treating Clostridium difficile infection (CDI) and inflammatory bowel disease (IBD). Although FMT appears to be effective, how FMT functions in the recipient remains unknown. Whether FMT exerts this beneficial effect through a series of changes in the host organism caused by alteration of gut microbial structure is also not known. In the present study, newborn piglets and E. coli K88-infected piglets were selected as models to explore the interplay between host and gut microbiota following FMT. Our results showed that FMT triggered intestinal mucosal autophagy and alleviated gut barrier injury caused by E. coli K88. This report provides a theoretical basis for the use of FMT as a viable therapeutic method for gut microbial regulation.

The TLR4-IRE1α pathway activation contributes to palmitate-elicited lipotoxicity in hepatocytes

Lipotoxicity induced by saturated fatty acids (SFAs) plays a pathological role in the development of non‐alcoholic fatty liver disease (NAFLD); however, the exact mechanism(s) remain to be clearly elucidated. Toll‐like receptor (TLR) 4 plays a fundamental role in activating the innate immune system. Intriguingly, hepatocytes express TLR4 and machinery for TLR4 signalling pathway. That liver‐specific TLR4 knockout mice are protective against diet‐induced NAFLD suggests that hepatocyte TLR4 signalling pathway plays an important role in NAFLD pathogenesis. Herein, using cultured hepatocytes, we sought to directly examine the role of TLR4 signalling pathway in palmitate‐elicited hepatotoxicity and to elucidate underlying mechanism(s). Our data reveal that palmitate exposure up‐regulates TLR4 expression at both mRNA and protein levels in hepatocytes, which are associated with NF‐κB activation. The inhibition of TLR4 signalling pathway through both pharmacological and genetic approaches abolished palmitate‐induced cell death, suggesting that TLR4 signalling pathway activation contributes to palmitate‐induced hepatotoxicity. Mechanistic investigations demonstrate that inositol‐requiring enzyme 1α (IRE1α), one of three major signal transduction pathways activated during endoplasmic reticulum (ER) stress, is the downstream target of palmitate‐elicited TLR4 activation and mechanistically implicated in TLR4 activation‐triggered cell death in response to palmitate exposure. Collectively, our data identify that the TLR4‐IRE1α pathway activation contributes to palmitate‐elicited lipotoxicity in hepatocytes. Our findings suggest that targeting TLR4‐IRE1α pathway can be a potential therapeutic choice for the treatment of NAFLD as well as other metabolic disorders, with lipotoxicity being the principal pathomechanism.

Identification of long non-coding RNAs biomarkers for early diagnosis of myocardial infarction from the dysregulated coding-non-coding co-expression network

Long non-coding RNAs (lncRNAs) have recently been shown as novel promising diagnostic or prognostic biomarkers for various cancers. However, lncRNA expression patterns and their predictive value in early diagnosis of myocardial infarction (MI) have not been systematically investigated. In our study, we performed a comprehensive analysis of lncRNA expression profiles in MI and found altered lncRNA expression pattern in MI compared to healthy samples. We then constructed a lncRNA-mRNA dysregulation network (DLMCEN) by integrating aberrant lncRNAs, mRNAs and their co-dysregulation relationships, and found that some of mRNAs were previously reported to be involved in cardiovascular disease, suggesting the functional roles of dysregulated lncRNAs in the pathogenesis of MI. Therefore, using support vector machine (SVM) and leave one out cross-validation (LOOCV), we developed a 9-lncRNA signature (termed 9LncSigAMI) from the discovery cohort which could distinguish MI patients from healthy samples with accuracy of 95.96%, sensitivity of 93.88% and specificity of 98%, and validated its predictive power in early diagnosis of MI in another completely independent cohort. Functional analysis demonstrated that these nine lncRNA biomarkers in the 9LncSigAMI may be involved in myocardial innate immune and inflammatory response, and their deregulation may lead to the dysfunction of the inflammatory and immune system contributing to MI recurrence. With prospective validation, the 9LncSigAMI identified by our work will provide additional diagnostic information beyond other known clinical parameters, and increase the understanding of the molecular mechanism underlying the pathogenesis of MI.

Increased expression of sterol regulatory element binding protein‑2 alleviates autophagic dysfunction in NAFLD

Sterol regulatory element binding protein-2 (SREBP-2) is an important transcription factor in lipid homeostasis. A previous study showed that SREBP-2 also activated autophagic genes during cell-sterol depletion. Alterations in autophagy are reported to be involved in the pathogenesis of nonalcoholic fatty liver disease (NAFLD). However, whether the regulation of SREBP-2 restores dysfunctional autophagy in hepatocytes during NAFLD remains to be elucidated. In the present study, a steatosis model was established with palmitic acid (PA) treatment at the indicated times and concentrations. Autophagosomes in hepatocytes were visualized by confocal microscopy after transfection with a tandem GFP-mCherry-LC3 construct. Autophagy-associated protein levels were analyzed by western blot analysis. Loss- and gain-of-function studies were performed to examine the role of SREBP-2 in the regulation of hepatocyte autophagy. It was demonstrated that PA induced autophagy and enhanced autophagic flux at the early stage, whereas prolonged treatment with PA resulted in dysfunction of autophagy in the PA-induced steatotic hepatocytes. In addition, different cellular models presented with differing dysfunctional autophagy in response to fatty acid overload. It was also confirmed that SREBP-2 regulated autophagy-related gene expression in hepatocytes, and it was shown that the overexpression of SREBP-2 increased the expression of autophagy-related genes, but did not affect the inhibition of the autophagic flux in lipid-overloaded HL-7702 cells. By contrast, increased SREBP-2 partly restored the inhibited autophagic activity in lipid-overloaded hepatoma HepG2 cells. Taken together, the present study demonstrated that autophagic function was impaired in lipid-overloaded human hepatocytes, and the differential effect of PA on autophagy was associated with the duration of PA and the cell type. Under these conditions, the overexpression of SREBP-2 alleviated the inhibited autophagic activity rather than the inhibition of autophagic flux. Consequently, the results indicated that restoration of autophagy dysfunction via the regulation of SREBP-2 may be a potential therapeutic target for the treatment of NAFLD.

Effects of probiotic Bacillus as a substitute for antibiotics on antioxidant capacity and intestinal autophagy of piglets

The objective of this study was to evaluate effects of probiotic Bacillus amyloliquefaciens (Ba) as a substitute for antibiotics on growth performance, antioxidant ability and intestinal autophagy of piglets. Ninety piglets were divided into three groups: G1 (containing 150 mg/Kg aureomycin in the diet); G2 (containing 75 mg/Kg aureomycin and 1 × 10⁸ cfu/Kg Ba in the diet); G3 (containing 2 × 10⁸ cfu/Kg Ba in the diet without any antibiotics). Each treatment had three replications of ten pigs per pen. Results showed that Ba replacement significantly increased the daily weight gain of piglets. Moreover, improved antioxidant status in serum and jejunum was noted in Ba-fed groups as compared with aureomycin group. Increased gene expression of antioxidant enzymes and elevated nuclear factor erythroid 2 related factor 2 (Nrf2) in jejunum was also observed in Ba-fed groups. Besides, Ba replacement significantly decreased jejunal c-Jun N-terminal kinase (JNK) phosphorylation compared with antibiotic group. Western blotting results also revealed that replacing all antibiotics with Ba initiated autophagy in the jejunum as evidenced by increased microtubule-associated protein 1 light chain 3 II (LC3-II) abundance. Taken together, these results indicate that replacing aureomycin with Ba can improve growth performance and antioxidant status of piglets via increasing antioxidant capacity and intestinal autophagy, suggesting a good potential for Ba as an alternative to antibiotics in feed.

Autophagic compound database: A resource connecting autophagy-modulating compounds, their potential targets and relevant diseases

OBJECTIVES

Autophagy, a highly conserved lysosomal degradation process in eukaryotic cells, can digest long-lived proteins and damaged organelles through vesicular trafficking pathways. Nowadays, mechanisms of autophagy have been gradually elucidated and thus the discovery of small-molecule drugs targeting autophagy has always been drawing much attention. So far, some autophagy-related web servers have been available online to facilitate scientists to obtain the information relevant to autophagy conveniently, such as HADb, CTLPScanner, iLIR server and ncRDeathDB. However, to the best of our knowledge, there is not any web server available about the autophagy-modulating compounds.

METHODS

According to published articles, all the compounds and their relations with autophagy were anatomized. Subsequently, an online Autophagic Compound Database (ACDB) (http://www.acdbliulab.com/) was constructed, which contained information of 357 compounds with 164 corresponding signalling pathways and potential targets in different diseases.

RESULTS

We achieved a great deal of information of autophagy-modulating compounds, including compounds, targets/pathways and diseases. ACDB is a valuable resource for users to access to more than 300 curated small-molecule compounds correlated with autophagy.

CONCLUSIONS

Autophagic compound database will facilitate to the discovery of more novel therapeutic drugs in the near future.

Reversible Keap1 inhibitors are preferential pharmacological tools to modulate cellular mitophagy

Mitophagy orchestrates the autophagic degradation of dysfunctional mitochondria preventing their pathological accumulation and contributing to cellular homeostasis. We previously identified a novel chemical tool (hereafter referred to as PMI), which drives mitochondria into autophagy without collapsing their membrane potential (ΔΨ_m). PMI is an inhibitor of the protein-protein interaction (PPI) between the transcription factor Nrf2 and its negative regulator, Keap1 and is able to up-regulate the expression of autophagy-associated proteins, including p62/SQSTM1. Here we show that PMI promotes mitochondrial respiration, leading to a superoxide-dependent activation of mitophagy. Structurally distinct Keap1-Nrf2 PPI inhibitors promote mitochondrial turnover, while covalent Keap1 modifiers, including sulforaphane (SFN) and dimethyl fumarate (DMF), are unable to induce a similar response. Additionally, we demonstrate that SFN reverses the effects of PMI in co-treated cells by reducing the accumulation of p62 in mitochondria and subsequently limiting their autophagic degradation. This study highlights the unique features of Keap1-Nrf2 PPI inhibitors as inducers of mitophagy and their potential as pharmacological agents for the treatment of pathological conditions characterized by impaired mitochondrial quality control.

Age-related cataracts: Role of unfolded protein response, Ca2+ mobilization, epigenetic DNA modifications, and loss of Nrf2/Keap1 dependent cytoprotection

Age-related cataracts are closely associated with lens chronological aging, oxidation, calcium imbalance, hydration and crystallin modifications. Accumulating evidence indicates that misfolded proteins are generated in the endoplasmic reticulum (ER) by most cataractogenic stresses. To eliminate misfolded proteins from cells before they can induce senescence, the cells activate a clean-up machinery called the ER stress/unfolded protein response (UPR). The UPR also activates the nuclear factor-erythroid-2-related factor 2 (Nrf2), a central transcriptional factor for cytoprotection against stress. Nrf2 activates nearly 600 cytoprotective target genes. However, if ER stress reaches critically high levels, the UPR activates destructive outputs to trigger programmed cell death. The UPR activates mobilization of ER-Ca2+ to the cytoplasm and results in activation of Ca2+-dependent proteases to cleave various enzymes and proteins which cause the loss of normal lens function. The UPR also enhances the overproduction of reactive oxygen species (ROS), which damage lens constituents and induce failure of the Nrf2 dependent cytoprotection. Kelch-like ECH-associated protein 1 (Keap1) is an oxygen sensor protein and regulates the levels of Nrf2 by the proteasomal degradation. A significant loss of DNA methylation in diabetic cataracts was found in the Keap1 promoter, which overexpresses the Keap1 protein. Overexpressed Keap1 significantly decreases the levels of Nrf2. Lower levels of Nrf2 induces loss of the redox balance toward to oxidative stress thereby leading to failure of lens cytoprotection. Here, this review summarizes the overall view of ER stress, increases in Ca2+ levels, protein cleavage, and loss of the well-established stress protection in somatic lens cells.

Sirtuin 3 acts as a negative regulator of autophagy dictating hepatocyte susceptibility to lipotoxicity

Lipotoxicity induced by saturated fatty acids (SFAs) plays a central role in the pathogenesis of nonalcoholic fatty liver disease (NAFLD); however, the exact mechanisms remain to be fully elucidated. Sirtuin 3 (SIRT3) is a nicotinamide adenine dinucleotide-dependent deacetylase located primarily inside mitochondria. In this study, we demonstrated that an SFA-rich high-fat diet (HFD) was more detrimental to the liver than an isocaloric unsaturated HFD rich in fatty acids. Unexpectedly, SIRT3 expression and activity were significantly elevated in the livers of mice exposed to the SFA-rich HFD. Using cultured HepG2 and AML-12 hepatocytes, we demonstrated that unlike monounsaturated fatty acids, SFAs up-regulate SIRT3 expression and activity. SIRT3 overexpression renders both the liver and hepatocytes susceptible to palmitate-induced cell death, which can be alleviated by SIRT3 small interfering RNA (siRNA) transfection. In contrast, SIRT3 suppression protects hepatocytes from palmitate cytotoxicity. Further studies revealed that SIRT3 acts as a negative regulator of autophagy, thereby enhancing the susceptibility of hepatocytes to SFA-induced cytotoxicity. Mechanistic investigations revealed that SIRT3 overexpression causes manganese superoxide dismutase deacetylation and activation, which depleted intracellular superoxide contents, leading to adenosine monophosphate-activated protein kinase (AMPK) inhibition and mammalian target of rapamycin C1 activation, resulting in autophagy suppression. In contrast, SIRT3 siRNA gene silencing enhanced autophagy flux. A similar result was observed in the liver tissue of SIRT3 knockout mice.

CONCLUSION

Our data indicate that SIRT3 is a negative regulator of autophagy whose activation by SFAs contributes to lipotoxicity in hepatocytes and suggest that restraining SIRT3 overactivation can be a potential therapeutic choice for the treatment of NAFLD as well as other metabolic disorders, with lipotoxicity being the principal pathomechanism. (Hepatology 2017;66:936-952).

Tert-butylhydroquinone promotes angiogenesis and improves heart functions in rats after myocardial infarction

BACKGROUND

Hypertension is an increased risk of heart failure and acute myocardial infarction (MI). Tert-butylhydroquinone (tBHQ), as an antioxidant, shows multiple cardioprotective actions including the reduction in blood pressure. The aim of this study was to investigate whether and how tBHQ improves heart functions in rats.

METHODS

The MI model was established in WKY and spontaneously hypertensive rats (SHRs) by ligation of left anterior descending coronary artery. Akt phosphorylation was examined by western blot in human umbilical vein endothelial cells (HUVECs) or in rats. Angiogenesis was assessed by immunohistochemistry and immunofluorescence. Heart function was determined by echocardiography.

RESULTS

tBHQ increased Akt phosphorylation, promoted cell proliferations and migrations in HUVECs, which were abolished by Akt inhibitor wortmannin. In SHRs following MI, administration of tBHQ significantly increased Akt phosphorylation, promoted angiogenesis, reduced infarct size, and improved heart functions after 14 postoperative days. Importantly, these in vivo effects of tBHQ were ablated by wortmannin in SHRs.

CONCLUSION

tBHQ via Akt activation promotes ischemia-induced angiogenesis and improves heart functions in hypertensive rats. In perspectives, the application of tBHQ should be considered in patients with ischemic diseases such as MI and stroke.

The gene expression profile of a drug metabolism system and signal transduction pathways in the liver of mice treated with tert-butylhydroquinone or 3-(3'-tert-butyl-4'-hydroxyphenyl)propylthiosulfonate of sodium

Tert-butylhydroquinone (tBHQ) is a highly effective phenolic antioxidant used in edible oils and fats in foods as well as in medicines and cosmetics. TBHQ has been shown to have both chemoprotective and carcinogenic effects. Furthermore, it has potential anti-inflammatory, antiatherogenic, and neuroprotective activities. TBHQ induces phase II detoxification enzymes via the Keap1/Nrf2/ARE mechanism, which contributes to its chemopreventive functions. Nonetheless, there is growing evidence that biological effects of tBHQ may be mediated by Nrf2-independent mechanisms related to various signaling cascades. Here, we studied changes in gene expression of phase I, II, and III drug metabolizing enzymes/transporters as well as protein levels and activities of cytochromes P450 (CYPs) elicited by tBHQ and its structural homolog TS-13 in the mouse liver. Next, we carried out gene expression analysis to identify signal transduction pathways modulated by the antioxidants. Mice received 100 mg/kg tBHQ or TS-13 per day or only vehicle. The liver was collected at 12 hours and after 7 days of the treatment. Protein and total RNA were extracted. Gene expression was analyzed using Mouse Drug Metabolism and Signal Transduction PathwayFinder RT2Profiler™PCR Arrays. A western blot analysis was used to measure protein levels and a fluorometric assay was employed to study activities of CYPs. Genes that were affected more than 1.5-fold by tBHQ or TS-13 treatment compared with vehicle were identified. Analysis of the gene expression data revealed changes in various genes that are important for drug metabolism, cellular defense mechanisms, inflammation, apoptosis, and cell cycle regulation. Novel target genes were identified, including xenobiotic metabolism genes encoding CYPs, phase II/III drug metabolizing enzymes/transporters. For Cyp1a2 and Cyp2b, we observed an increase in protein levels and activities during tBHQ or TS-13 treatment. Changes were found in the gene expression regulated by NFκB, androgen, retinoic acid, PI3K/AKT, Wnt, Hedgehog and other pathways.

Tert-buthylhydroquinone pre-conditioning exerts dual effects in old female rats exposed to 3-nitropropionic acid

The brain is a very susceptible organ to structural and functional alterations caused by oxidative stress and its vulnerability increases with age. Understanding the antioxidant response activated by the transcription factor Nrf2 has become very important in the aging field in order to activate cellular protection. However, the role of Nrf2 inducers during old age has not been completely understood. Our aim was to activate the Nrf2 pathway by pre-treating old rats with a widely used Nrf2-inducer, tert-buthylhydroquinone (tBHQ), prior to 3-nitropropionic acid (3-NP) insult, in order to evaluate its effects at a behavioral, morphological and biochemical levels. 3-NP has been used to reproduce the biochemical and pathophysiological characteristics of Huntington's disease due to an oxidative effect. Our results suggest that tBHQ confers an important protective effect against 3-NP toxicity; nevertheless, Nrf2 seems not to be the main protective pathway associated to neuroprotection. Hormetic responses include the activation of more than one transcription factor. Nrf2 and NFκB are known to simultaneously initiate different cellular responses against stress by triggering parallel mechanisms, therefore NFκB nuclear accumulation was also evaluated.

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Old rats are able to activate an hormetic response against 3NP toxicity.

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tBHQ pre-conditioning exerts an antioxidant-prooxidant, dual role in old rats.

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tBHQ activates a crosstalk mechanism between NFκB and Nrf2.