A novel HDAC6 inhibitor attenuate APAP-induced liver injury by regulating MDH1-mediated oxidative stress.

Glutathione (GSH) depletion, mitochondrial damage, and oxidative stress have been implicated in the pathogenesis of acetaminophen (APAP) hepatotoxicity. Here, we demonstrated that the expression of histone deacetylase 6 (HDAC6) is highly elevated, whereas malate dehydrogenase 1 (MDH1) is downregulated in liver tissues and AML-12 cells induced by APAP. The therapeutic benefits of LT-630, a novel HDAC6 inhibitor on APAP-induced liver injury, were also substantiated. On this basis, we demonstrated that LT-630 improved the protein expression and acetylation level of MDH1. Furthermore, after overexpression of MDH1, an upregulated NADPH/NADP+ ratio and GSH level and decreased cell apoptosis were observed in APAP-stimulated AML-12 cells. Importantly, MDH1 siRNA clearly reversed the protection of LT-630 on APAP-stimulated AML-12 cells. In conclusion, LT-630 could ameliorate liver injury by modulating MDH1-mediated oxidative stress induced by APAP.

Blocking ATP-P1Rs axis attenuate alcohol-related liver fibrosis.

AIMS: The aim of this study was to explore the fibrogenic effects of ATP-P1Rs axis and ATP-P2Rs axis on alcohol-related liver fibrosis (ALF). MATERIALS AND METHODS: C57BL/6J CD73 knock out (KO) mice were used in our study. 8-12 weeks male mice were used as an ALF model in vivo. In conclusion, after one week of adaptive feeding, 5 % alcohol liquid diet was given for 8 weeks. High-concentration alcohol (31.5 %, 5 g/kg) was administered by gavage twice weekly, and 10 % CCl4 intraperitoneal injections (1 ml/kg) were administered twice weekly for the last two weeks. The mice in the control group were injected intraperitoneally with an equivalent volume of normal saline. Fasting for 9 h after the last injection, blood samples were collected, and related indicators were tested. In vitro, rat hepatic stellate cells (HSCs) were treated with 200 µM acetaldehyde to establish an alcoholic liver fibrosis for 48 h, then tested related indicators. KEY FINDINGS: We found that both adenosine receptors including adenosine A1, A2A, A2B, A3 receptors (A1R, A2AR, A2BR, A3R) and ATP receptors including P2X7, P2Y2 receptors (P2X7R, P2Y2R) were expressed increased in ALF. After CD73 was knocked out, we found that adenosine receptors expression decreased, ATP expression increased, and fibrosis degree decreased. SIGNIFICANCE: Based on the research, we discovered that adenosine plays a more important role in ALF. Therefore, blocking the ATP-P1Rs axis represented a potential treatment for ALF, and CD73 will become a potential therapeutic target.

CD73 aggravates alcohol-related liver fibrosis by promoting autophagy mediated activation of hepatic stellate cells through AMPK/AKT/mTOR signaling pathway.

CD73 is a membrane-bound glycoprotein that can dephosphorylate AMP to adenosine. Increasing evidence has shown that CD73 is involved in the occurrence and development of liver fibrosis. However, the potential mechanism by which CD73 affects the progression of alcohol-related liver fibrosis (ALF) remains unknown. This study aimed to examine the role and mechanism of CD73 in autophagy in HSC-T6 cells and its role in ALF in mice that treated with alcohol plus CCl4. We found that CD73 knockout reduced serum alanine aminotransferase and aspartate aminotransferase levels and decreased liver injury and collagen deposition. Furthermore, autophagy-related indicators were downregulated in the liver fibrosis tissues of CD73-/- (EtOH + CCl4) mice. In vitro, the expression of CD73 and autophagy increased in activated HSC-T6 cells. Autophagy inhibitor, 3-methyladenine, reduced autophagy and activation of acetaldehyde-induced HSC-T6 cells. When using CD73-siRNA, autophagy in HSC-T6 cells was found to be downregulated. However, the CD73 plasmid increased the activation and autophagy of hepatic stellate cells (HSCs). In addition, CD73 induced autophagy through the AMPK/AKT/mTOR pathway, which is characterized by an increase in the ratio of P-AMPKα/AMPKα and a decrease in the ratio of P-AKT/AKT and P-mTOR/mTOR. Our study found that CD73 promotes HSCs activation by regulating autophagy through the AMPK/AKT/mTOR signaling pathway.

Upregulation of acid sensing ion channel 1a (ASIC1a) by hydrogen peroxide through the JNK pathway.

Oxidative stress is intimately tied to neurodegenerative diseases, including Parkinson's disease and amyotrophic lateral sclerosis, and acute injuries, such as ischemic stroke and traumatic brain injury. Acid sensing ion channel 1a (ASIC1a), a proton-gated ion channel, has been shown to be involved in the pathogenesis of these diseases. However, whether oxidative stress affects the expression of ASIC1a remains elusive. In the current study, we examined the effect of hydrogen peroxide (H2O2), a major reactive oxygen species (ROS), on ASIC1a protein expression and channel function in NS20Y cells and primary cultured mouse cortical neurons. We found that treatment of the cells with H2O2 (20 µM) for 6 h or longer increased ASIC1a protein expression and ASIC currents without causing significant cell injury. H2O2 incubation activated mitogen-activated protein kinases (MAPKs) pathways, including the extracellular signal-regulated kinase1/2 (ERK1/2), c-Jun N-terminal kinase (JNK), and p38 pathways. We found that neither inhibition of the MEK/ERK pathway by U0126 nor inhibition of the p38 pathway by SB203580 affected H2O2-induced ASIC1a expression, whereas inhibition of the JNK pathway by SP600125 potently decreased ASIC1a expression and abolished the H2O2-mediated increase in ASIC1a expression and ASIC currents. Furthermore, we found that H2O2 pretreatment increased the sensitivity of ASIC currents to the ASIC1a inhibitor PcTx1, providing additional evidence that H2O2 increases the expression of functional ASIC1a channels. Together, our data demonstrate that H2O2 increases ASIC1a expression/activation through the JNK signaling pathway, which may provide insight into the pathogenesis of neurological disorders that involve both ROS and activation of ASIC1a.

Margatoxin mitigates CCl4­induced hepatic fibrosis in mice via macrophage polarization, cytokine secretion and STAT signaling.

A number of macrophage phenotypes have been previously identified as crucial regulators in the progression of hepatic fibrosis (HF). Cytokines from macrophages or Kupffer cells (KCs) have also been identified to be important regulators in HF. Blocking Kv1.3 in models of HF, regulating macrophage polarization and cytokine secretion have not yet been assessed as potential treatments options for this condition. In the current study, a model of carbon tetrachloride (CCl4)­induced HF was established and examined the effects of margatoxin (MgTX; an inhibitor of Kv1.3) on HF. Hematoxylin and eosin, Masson's trichrome and immunohistochemistry staining were performed to determine whether MgTX can alleviate liver fibrosis. To elucidate the mechanisms through which MgTX attenuates liver injury, reverse transcription­quantitative PCR and western blot analysis were used to detect polarized macrophage markers in RAW264.7 cells and cytokines were examined using ELISA. Furthermore, macrophage polarization signal transducer and activator of transcription (STAT) signaling, which is associated with macrophage polarization, was identified in RAW264.7 cells. The results revealed that MgTX protected the mice from CCl4­induced liver fibrosis. Furthermore, MgTX decreased the expression of M1 phenotype biomarkers, and increased the expression of M2 phenotype biomarkers in CCl4­induced HF. Additionally, the production of pro­inflammatory cytokines was decreased and interleukin­10 production was increased in the serum of mice with HF injected with MgTX. Furthermore, MgTX was found to regulate the expression of M1 markers by suppressing p­STAT1 activity and increasing the expression of M2 markers by promoting p­STAT6 activity. On the whole, the findings of this study demonstrate that MgTX is able to alleviate CCl4­induced HF in mice, possibly via macrophage polarization, cytokine secretion and STAT signaling.

Hotair facilitates hepatic stellate cells activation and fibrogenesis in the liver.

Long non-coding RNAs (lncRNAs) are increasingly recognized as major players in regulating various biological processes. LncRNA HOX transcript antisense RNA (Hotair) has been extensively studied in cancer. However, the role of Hotair in liver fibrosis remains unknown. Here we observed that Hotair expression was significantly increased in CCl4-induced mouse liver fibrosis models, human fibrotic livers and activated hepatic stellate cells (HSCs) by TGF-ß1 stimulation. Enforced expression of Hotair in LX-2 cells promoted cell proliferation and activation while inhibition of its expression had an opposite effect. Furthermore, we found that Hotair may act as an endogenous 'sponge' of miR-148b, which regulates expression of the DNMT1/MEG3/p53 pathways in HSCs. Intriguingly, Hotair enhanced polycomb repressive complex 2 (PRC2) occupancy and histone H3K27me3 repressive marks, specifically at the MEG3 promoter region. Finally, we found that Hotair forms an RNA/DNA hybrid and recruits PRC2 to MEG3 promoter. These data suggest that Hotair inhibition may represent a promising therapeutic option for suppressing liver fibrosis.

Effect of Redox-Modifying Agents on the Activity of Channelrhodopsin-2.

BACKGROUND: The algal protein Channelrhodopsin-2 (ChR2) has been widely used in recent years in optogenetic technique to investigate the functions of complex neuronal networks through minimally invasive and temporally precise photostimulation of genetically defined neurons. However, as with any other new technique, current optogentic approaches have various limitations. In addition, how ChR2 may behave in response to complex biochemical changes associated with various physiological/pathological conditions is largely unknown. AIM: In this study, we investigated whether a change in redox state of the cell affects the activity of ChR2 channels. METHODS: Whole-cell patch-clamp recordings were used to examine the effect of reducing and oxidizing agents on ChR2 currents activated by blue light. RESULTS: We show that the reducing agent dithiothreitol (DTT) dramatically potentiates the ChR2 currents in a reversible and concentration-dependent manner. Glutathione, an endogenous reducing agent, shows a similar effect on ChR2 currents. The oxidizing agent 5,5'-dithio-bis-(2-nitrobenzoic acid) (DTNB) has no effect on ChR2 currents by itself; however, it completely reverses the potentiating effect of DTT. DTT also causes a shift in the current-voltage relationship by 23 ± 4.31 mV, suggesting a change in ion selectivity. CONCLUSION: Taken together, these data suggest that redox modification of ChR2 plays an important role in its sensitivity to the light stimulation. Our findings not only help for a better understanding of how ChR2 may behave in physiological/pathological conditions where changes in redox state are common, but also provide a new direction for further optimization of this important opsin.

Protocatechuic Aldehyde Attenuates Cisplatin-Induced Acute Kidney Injury by Suppressing Nox-Mediated Oxidative Stress and Renal Inflammation.

Cisplatin is a classic chemotherapeutic agent widely used to treat different types of cancers including ovarian, head and neck, testicular and uterine cervical carcinomas. However, cisplatin induces acute kidney injury by directly triggering an excessive inflammatory response, oxidative stress, and programmed cell death of renal tubular epithelial cells, all of which lead to high mortality rates in patients. In this study, we examined the protective effect of protocatechuic aldehyde (PA) in vitro in cisplatin-treated tubular epithelial cells and in vivo in cisplatin nephropathy. PA is a monomer of Traditional Chinese Medicine isolated from the root of S. miltiorrhiza (Lamiaceae). Results show that PA prevented cisplatin-induced decline of renal function and histological damage, which was confirmed by attenuation of KIM1 in both mRNA and protein levels. Moreover, PA reduced renal inflammation by suppressing oxidative stress and programmed cell death in response to cisplatin, which was further evidenced by in vitro data. Of note, PA suppressed NAPDH oxidases, including Nox2 and Nox4, in a dosage-dependent manner. Moreover, silencing Nox4, but not Nox2, removed the inhibitory effect of PA on cisplatin-induced renal injury, indicating that Nox4 may play a pivotal role in mediating the protective effect of PA in cisplatin-induced acute kidney injury. Collectively, our data indicate that PA blocks cisplatin-induced acute kidney injury by suppressing Nox-mediated oxidative stress and renal inflammation without compromising anti-tumor activity of cisplatin. These findings suggest that PA and its derivatives may serve as potential protective agents for cancer patients receiving cisplatin treatment.

Emerging role of microRNAs in regulating macrophage activation and polarization in immune response and inflammation.

Diversity and plasticity are hallmarks of macrophages. Classically activated macrophages are considered to promote T helper type 1 responses and have strong microbicidal, pro-inflammatory activity, whereas alternatively activated macrophages are supposed to be associated with promotion of tissue remodelling and responses to anti-inflammatory reactions. Transformation of different macrophage phenotypes is reflected in their different, sometimes even opposite, roles in various diseases or inflammatory conditions. MicroRNAs (miRNAs) have emerged as critical regulators of macrophage polarization (MP). Several miRNAs are induced by Toll-like receptors signalling in macrophages and target the 3'-untranslated regions of mRNAs encoding key molecules involved in MP. Therefore, identification of miRNAs related to the dynamic changes of MP and understanding their functions in regulating this process are important for discussing the molecular basis of disease progression and developing novel miRNA-targeted therapeutic strategies. Here, we review the current knowledge of the role of miRNAs in MP with relevance to immune response and inflammation.

Inhibitory effects of long noncoding RNA MEG3 on hepatic stellate cells activation and liver fibrogenesis.

Long noncoding RNAs (lncRNAs) are being increasingly recognized as major players in governing fundamental biological processes through diverse mechanisms. Maternally expressed gene 3 (MEG3) is an imprinted gene located at 14q32 that encodes a lncRNA correlated with several human cancers. Recently, the methylation-dependent downregulation of MEG3 has been described in liver cancers. However, its biological functional role in liver fibrosis remains unknown. In our study, MEG3 levels were remarkably decreased in CCl4-induced mouse liver fibrosis models and human fibrotic livers as demonstrated by real-time quantitative PCR. Moreover, the expression of MEG3 was downregulated in human hepatic stellate cell lines LX-2 cells in response to transforming growth factor-ß1 (TGF-ß1) stimulation in dose and time-dependent manner. Enforced expression of MEG3 in LX-2 cells inhibited TGF-ß1-induced cell proliferation, while promoting cell apoptosis. In addition, hypermethylation of MEG3 promoter was identified by methylation-specific PCR and MEG3 expression was robustly increased by the inhibition of methylation with either 5-aza-2-deoxycytidine (5-azadC), or siRNA to DNA methyltransferase 1 (DNMT1) in TGF-ß1-induced LX-2 cells. More importantly, overexpression of MEG3 could activate p53 and mediate cytochrome c release, subsequently leading to caspase-3-dependent apoptosis in TGF-ß1-treated LX-2 cells. These findings suggested that MEG3 may play an important role in stellate cell activation and liver fibrosis progression and act as a novel potential therapeutic target for liver fibrosis.

Long noncoding RNAs: Novel insights into hepatocelluar carcinoma.

Recent advances in non-protein coding part of human genome analysis have discovered extensive transcription of large RNA transcripts that lack of coding protein function, termed long noncoding RNAs (lncRNAs). It is becoming evident that lncRNAs may be an important class of pervasive genes involved in carcinogenesis and metastasis. However, the biological and molecular mechanisms of lncRNAs in diverse diseases are not yet fully understood. Thus, it is anticipated that more efforts should be made to clarify the lncRNAs world. Moreover, accumulating studies have demonstrated that a class of lncRNAs are dysregulated in hepatocellular carcinoma(HCC) and closely related with tumorigenesis, metastasis, prognosis or diagnosis. In this review, we will briefly discuss the regulation and functional role of lncRNAs in HCC, therefore evaluating the potential of lncRNAs as prospective novel therapeutic targets in HCC.

New advances of DNA methylation in liver fibrosis, with special emphasis on the crosstalk between microRNAs and DNA methylation machinery.

Epigenetics refers to the study of heritable changes in the pattern of gene expression that is controlled by a mechanism specifically not due to changes the primary DNA sequence. Well-known epigenetic mechanisms include DNA methylation, post-translational histone modifications and RNA-based mechanisms including those controlled by small non-coding RNAs (miRNAs). Recent studies have shown that epigenetic modifications orchestrate the hepatic stellate cell (HSC) activation and liver fibrosis. In this review we focus on the aberrant methylation of CpG island promoters of select genes is the prominent epigenetic mechanism to effectively silence gene transcription facilitating HSC activation and liver fibrosis. Furthermore, we also discuss epigenetic dysregulation of tumor-suppressor miRNA genes by promoter DNA methylation and the interaction of DNA methylation with miRNAs involved in the regulation of HSC activation and liver fibrosis. Recent advances in epigenetics alterations in the pathogenesis of liver fibrosis and their possible use as new therapeutic targets and biomarkers.