Stat3 pathway correlates with the roles of leptin in mouse liver fibrosis and sterol regulatory element binding protein-1c expression of rat hepatic stellate cells

JTCD attenuates HF by inhibiting activation of HSCs through PPARα-TFEB axis-mediated lipophagy

BACKGROUND

Hepatic fibrosis (HF) is an intermediate stage in the progression of chronic liver disease to cirrhosis and has been shown to be a reversible pathological process. Known evidence suggests that activation of hepatic stellate cells (HSCs) and degradation of their lipid droplets (LDs) play an indispensable role in the process of HF. Jiawei Taohe Chengqi Decoction (JTCD) can inhibit the activation of HSCs in the process of HF, but the exact mechanism remains to be elucidated.

PURPOSE

The aim of this study is to determine whether JTCD inhibits lipophagy and to explore the possible mechanisms of its HF effect in HSCs by regulating the PPARα/TFEB axis.

METHODS

Network pharmacology and molecular docking were firstly applied to predict the potential mechanism of JTCD for the treatment of HF. In vivo, a mouse model of HF was constructed using carbon tetrachloride (CCl4) solution, and the efficacy of JTCD was assessed by staining of pathological sections, oil red O staining, immunofluorescence (IF), immunohistochemistry (IHC) staining, Western blotting and qRT-PCR. The intervention of JTCD was verified in vitro by induction of activated LX-2 cells with TGF-β solution and intervention using agonists and antagonists of PPARα. Finally, transient transfection of cells using TFEB siRNA was performed for validation studies.

RESULTS

JTCD effectively alleviated CCl4-induced HF in mice and reduced the levels of HF markers α-smooth muscle actin (α-SMA) and collagen I (COL1A1), and inhibited PPARα expression and lipophagy process. In vitro, JTCD delayed the degradation of LDs and reduced lipophagy in LX-2 cells, suggesting a mechanism involving PPARα/TFEB axis signaling regulation.

Bromodomain protein 4 mediates the roles of TGFβ1-induced Stat3 signaling in mouse liver fibrogenesis

Epigenetic reader Bromodomain protein 4 (BrD4) functions as a global genomic regulator to direct hepatic stellate cell (HSC) activation (a key step in liver fibrogenesis) and liver fibrosis. The pivotal pro-fibrotic cytokine transforming growth factor-β1 (TGFβ1) signals through both Smad and Stat3 to elicit a wide array of biological effects. Stat3 is widely acknowledged as a regulator of gene transcription and is involved in fibrosis of multiple tissues. The present study focused on BrD4 function implication in the roles of TGFβ1-induced Stat3 signaling in HSC activation and liver fibrosis by using heterozygous TGFβ1 knockout mice and HSC culture. Results showed that Stat3 was required for TGFβ1-induced BrD4 expression in HSCs. BrD4 expression paralleled Stat3 activation in activated HSCs in human cirrhotic livers. BrD4 was involved in the roles of TGFβ1-induced Stat3 in HSC activation and liver fibrogenesis. Smad3 bound to phosphorylated-Stat3 and contributed to TGFβ1-induced Stat3 signaling. BrD4 expression induced by Stat3 signaling required the early-immediate gene Egr1. Egr1 had a positive feedback on Stat3 activation. In conclusion, a network consisting of Stat3 signaling, Smad3 signaling, Egr1, and BrD4 was involved in the effects of TGFβ1 on liver fibrosis, providing new toxicological mechanisms for TGFβ1 in liver fibrogenesis.

New Perspectives on Chinese Medicine in Treating Hepatic Fibrosis: Lipid Droplets in Hepatic Stellate Cells

Hepatic fibrosis (HF) is a wound healing response featuring excessive deposition of the extracellular matrix (ECM) and activation of hepatic stellate cells (HSCs) that occurs during chronic liver injury. As an initial stage of various liver diseases, HF is a reversible pathological process that, if left unchecked, can escalate into cirrhosis, liver failure, and liver cancer. HF is a life-threatening disease presenting morbidity and mortality challenges to healthcare systems worldwide. There is no specific and effective anti-HF therapy, and the toxic side effects of the available drugs also impose a heavy financial burden on patients. Therefore, it is significant to study the pathogenesis of HF and explore effective prevention and treatment measures. Formerly called adipocytes, or fat storage cells, HSCs regulate liver growth, immunity, and inflammation, as well as energy and nutrient homeostasis. HSCs in a quiescent state do not proliferate and store abundant lipid droplets (LDs). Catabolism of LDs is characteristic of the activation of HSCs and morphological transdifferentiation of cells into contractile and proliferative myofibroblasts, resulting in the deposition of ECM and the development of HF. Recent studies have revealed that various Chinese medicines (e.g., Artemisia annua, turmeric, Scutellaria baicalensis Georgi, etc.) are able to effectively reduce the degradation of LDs in HSCs. Therefore, this study takes the modification of LDs in HSCs as an entry point to elaborate on the process of Chinese medicine intervening in the loss of LDs in HSCs and the mechanism of action for the treatment of HF.

Mangiferin prevents hepatocyte epithelial-mesenchymal transition in liver fibrosis via targeting HSP27-mediated JAK2/STAT3 and TGF-β1/Smad pathway

Hepatocytes has been confirmed to undergo EMT and can be converted into myofibroblasts during hepatic fibrogenesis. However, the mechanism of hepatocyte EMT regulation in hepatic fibrosis, particularly through HSP27 (human homologue of rodent HSP25), remains unclear. Mangiferin (MAN), a compound extracted from Mangifera indica L, has been reported to attenuate liver injury. This study aimed to investigate the mechanisms underlying HSP27 inhibition and the anti-fibrotic effect of MAN in liver fibrosis. Our results revealed that the expression of HSP27 was remarkably increased in the liver tissues of patients with liver cirrhosis and CCl₄ -induced fibrotic rats. However, HSP27 shRNA treatment significantly alleviated fibrosis. Furthermore, MAN was found to inhibit CCl₄ - and TGF-β1-induced liver fibrosis and reduced hepatocyte EMT. More importantly, MAN decreased HSP27 expression to suppress the JAK2/STAT3 pathway, and subsequently blocked TGF-β1/Smad signaling, which were consistent with its protection against CCl₄ -induced EMT and liver fibrosis. Together, these results suggest that HSP27 may play a crucial role in hepatocyte EMT and liver fibrosis by activating JAK2/STAT3 signaling and TGF-β1/Smad pathway. The suppression of HSP27 expression by MAN may be a novel strategy for attenuating the hepatocyte EMT in liver fibrosis.

Leptin: an entry point for the treatment of peripheral tissue fibrosis and related diseases

Leptin is a small peptide mainly secreted by adipocyte, which acts on the central nervous system of the hypothalamus to regulate the body's energy balance by inhibiting food intake, it also can directly act on specific cells through leptin receptors (for example, ObRa, which exists in the blood-brain barrier or kidneys), thereby affect cell metabolism. Excessive deposition of extracellular matrix (ECM) causes damage to normal tissues or destruction of organ structure, which will eventually lead to tissue or organ fibrosis. The sustainable development of fibrosis can lead to structural damage and functional decline of organs, and even exhaustion, which seriously threatens human health and life. In recent years, studies have found that leptin directly alleviates the fibrosis process of various tissues and organs in mammals. Therefore, we speculate that leptin may become a significant treatment for fibrosis of various tissues and organs in the future. So, the main purpose of this review is to explore the specific mechanism of leptin in the process of fibrosis in multiple tissues and organs, and to provide a theoretical basis for the treatment of various tissues and organs fibrosis and related diseases caused by it, which is of great significance in the future.

Prothymosin α promotes colorectal carcinoma chemoresistance through inducing lipid droplet accumulation

Colorectal cancer (CRC) affects millions of people worldwide. Chemoresistance seriously impairs the therapeutic effects. Lipid droplets (LDs) abnormally accumulate in CRC supported chemoresistance. Exploring the mechanism of LD-induced chemoresistance is extremely important for improving prognosis of CRC patients. The expression of PTMA was increased in both CRC tissues and cells, which was positively correlated with LD production. PTMA facilitated chemoresistance to gemcitabine by inducing LD production in CRC cells. PTMA enhanced LD biogenesis and chemoresistance to gemcitabine by promoting SREBP-1-mediated lipogenesis and STAT3 activation in CRC.

ASIC1a inhibits cell pyroptosis induced by acid-induced activation of rat hepatic stellate cells

The activation of hepatic stellate cells (HSCs) is associated with liver fibrosis, the pathological feature of most forms of chronic hepatic damage, and is accompanied by abnormal deposition of the extracellular matrix (ECM). During the pathological process, acid-sensing ion channel 1a (ASIC1a), which is responsible for Ca2+ transportation, is involved in the activation of HSCs. It has previously been identified that ASIC1a is related to pyroptosis in articular chondrocytes. However, it remains unclear whether ASIC1a restrains pyroptosis during liver fibrosis. Here, we determined that the levels of pyroptosis-associated speck-like protein, gasdermin D, caspase-1, nucleotide-binding oligomerization domain (NOD)-like receptor 3, and apoptosis-associated speck-like protein (ASC) decreased, while the level of α-smooth muscle actin and collagen-I increased upon introduction of ASIC1a into an acid-induced model. Inhibition or silencing of ASIC1a and the use of Ca2+ -free medium were able to promote the pyroptosis of activated HSCs, which reduced their deposition. In summary, our study indicates that ASIC1a inhibits pyroptosis of HSCs and that inhibition of ASIC1a may be able to promote pyroptosis to relieve liver fibrosis.

Leptin promotes methionine adenosyltransferase 2A expression in hepatic stellate cells by the downregulation of E2F-4 via the β-catenin pathway

Most obese patients develop hyperleptinaemia. Leptin, mainly produced by adipocytes, demonstrates a promotional role in liver fibrosis. Hepatic stellate cell (HSC) activation, a key step in liver fibrogenesis, requires global reprogramming of gene expression. The remodeling of DNA methylation is a mechanism of the epigenetic regulation of gene expression. The biosynthesis of S-adenosylmethionine, a principle biological methyl donor, is catalyzed by methionine adenosyltransferase (MAT) such as MATⅡ which has been shown to promote HSC activation in vitro. This study was mainly aimed to determine the effect of leptin on MAT2A expression (the catalytic subunit of MATⅡ) in HSCs. Results showed that MAT2A knockdown reduced leptin-induced HSC activation and liver fibrosis in the leptin-deficient mouse model. Leptin promoted MAT2A expression in HSCs and increased MAT2A promoter activity. The axis of the β-catenin pathway/E2F-4 mediated the effect of leptin on MAT2A expression. Leptin-induced β-catenin signaling reduced E2F-4 expression and thus abated E2F-4 binding to MAT2A promoter at a site around -2779 bp, leading to an increase in the MAT2A promoter activity. These data might shed more light on the mechanisms responsible for liver fibrogenesis in obese patients with hyperleptinaemia.

Transforming growth factor beta 1 induces methylation changes in lung fibroblasts

Idiopathic pulmonary fibrosis is a complex disease of unknown etiology. Environmental factors can affect disease susceptibility via epigenetic effects. Few studies explore global DNA methylation in lung fibroblasts, but none have focused on transforming growth factor beta-1 (TGF-β1) as a potential modifier of the DNA methylome. Here we analyzed changes in methylation and gene transcription in normal and IPF fibroblasts following TGF-β1 treatment. We analyzed the effects of TGF-β1 on primary fibroblasts derived from normal or IPF lungs treated for 24 hours and 5 days using the Illumina 450k Human Methylation array and the Prime View Human Gene Expression Array. TGF-β1 induced an increased number of gene expression changes after short term treatment in normal fibroblasts, whereas greater methylation changes were observed following long term stimulation mainly in IPF fibroblasts. DNA methyltransferase 3 alpha (DMNT3a) and tet methylcytosine dioxygenase 3 (TET3) were upregulated after 5-days TGF-β1 treatment in both cell types, whereas DNMT3a was upregulated after 24h only in IPF fibroblasts. Our findings demonstrate that TGF-β1 induced the upregulation of DNMT3a and TET3 expression and profound changes in the DNA methylation pattern of fibroblasts, mainly in those derived from IPF lungs.

Dihydroartemisinin attenuates alcoholic fatty liver through regulation of lipin-1 signaling

Alcoholic liver disease (ALD) is generated from excessive alcohol consumption, characterized by hepatic steatosis. Mechanistically, excessive hepatic lipid accumulation was attributed to the aberrant lipin-1 signaling during the development of alcoholic steatosis in rodent species and human. Dihydroartemisinin (DHA) has been recently identified to relieve hepatocytes necrosis and prevent from hepatic steatosis in alcohol-induced liver diseases; however, the role of DHA in ALD has not been elucidated completely. Therefore, this study was aimed to further identify the potential mechanisms of pharmacological effects of DHA on ALD. Results demonstrated that DHA regulated the expression and nucleocytoplasmic shuttling of lipin-1 in mice with chronic ethanol exposure. Results confirmed that the disruption of lipin-1 signaling abolished the suppression of DHA on alcohol-induced hepatic steatosis. Interestingly, DHA also significantly improved liver injury, and inflammation mediated by lipin-1 signaling in chronic alcohol-fed mice. in vivo experiments further consolidated the concept that DHA protected against hepatocyte lipoapoptosis dependent on the regulation of nucleocytoplasmic shuttling of lipin-1 signaling, resulting in attenuated ratio of Lpin1 β/α. Obvious increases in cell apoptosis were observed in alcohol-treated lipin1β-overexpressed mice. Although DHA attenuated cell apoptosis, overexpression of lipin-1β neutralized DHA action. DHA ameliorated activation of endoplasmic reticulum stress through inhibiting activation of JNK and CHOP, which was abrogated by overexpression of lipin-1β. In summary, DHA significantly improved liver injury, steatosis and hepatocyte lipoapoptosis in chronic alcohol-fed mice via regulation of lipin-1 signaling.

Maternal cinnamon intake during lactation led to visceral obesity and hepatic metabolic dysfunction in the adult male offspring

PURPOSE

Studies with foods, known to promote health benefits in addition to the nutritive value, show that their consumption by pregnant and/or lactating females could induce negative outcomes to the offspring. It is well characterized that cinnamon intake promotes benefits to energy homeostasis. The present study aimed to analyze the effects of the consumption of an aqueous extract of cinnamon by lactating female rats on the endocrine-metabolic outcomes in the adult offspring.

METHODS

Lactating dams (Wistar rats) were supplemented with cinnamon aqueous extract (400 mg/kg body weight/day) for the entire lactating period. The male adult offspring were evaluated at 180 days old (CinLac).

RESULTS

The offspring presented visceral obesity (P = 0.001), hyperleptinemia (P = 0.002), and hyperinsulinemia (P = 0.016). In the liver, CinLac exhibited reduced p-IRβ (P = 0.018) suggesting insulin resistance. However, phosphorylation of IRS1 (P = 0.041) and AKT (P = 0.050) were increased. JAK2 (P = 0.030) and p-STAT3 (P = 0.015) expressions were higher, suggesting that the activation of IRS1/AKT in the CinLac group could have resulted from the increased activation of leptin signaling. Although we observed no changes in the gluconeogenic pathway, the CinLac group exhibited lower hepatic glycogen content (P = 0.005) accompanied by increased p-GSK3β (P = 0.011). In addition, the CinLac group showed increased hepatic triacylglycerol content (P = 0.049) and a mild steatosis (P = 0.001), accompanied by reduced PPARα mRNA expression (P = 0.005).

CONCLUSION

We conclude that maternal intake of aqueous extract of cinnamon induces long-term molecular, metabolic, and hormonal changes in the adult progeny, including visceral obesity, higher lipid accumulation, and lower glycogen content in the liver.

Advances in therapeutic options for portal hypertension

Portal hypertension represents one of the major clinical consequences of chronic liver disease, having a deep impact on patients' prognosis and survival. Its pathophysiology defines a pathological increase in the intrahepatic vascular resistance as the primary factor in its development, being subsequently aggravated by a paradoxical increase in portal blood inflow. Although extensive preclinical and clinical research in the field has been developed in recent decades, no effective treatment targeting its primary mechanism has been defined. The present review critically summarizes the current knowledge in portal hypertension therapeutics, focusing on those strategies driven by the disease pathophysiology and underlying cellular mechanisms.

Bone marrow derived-mesenchymal stem cells downregulate IL17A dependent IL6/STAT3 signaling pathway in CCl4-induced rat liver fibrosis

Therapeutic potential of bone marrow–derived mesenchymal stem cells (BM-MSCs) has been reported in several animal models of liver fibrosis. Interleukin (IL) 17A, IL6 and Stat3 have been described to play crucial roles in chronic liver injury. However, the modulatory effect of MSCs on these markers was controversial in different diseases. BM-MSCs might activate the IL6/STAT3 signaling pathway and promote cell invasion in hepatocellular carcinoma, but the immunomodulatory role of BM-MSCs on IL17A/IL6/STAT3 was not fully elucidated in liver fibrosis. In the present study, we evaluated the capacity of the BM-MSCs in the modulation of cytokines milieu and signal transducers, based on unique inflammatory genes Il17a and Il17f and their receptors Il17rc and their effect on the IL6/STAT3 pathway in CCl₄-induced liver fibrosis in rats. A single dose of BM-MSCs was administered to the group with induced liver fibrosis, and the genes and proteins of interest were evaluated along six weeks after treatment. Our results showed a significant downregulation of Il17a, Il17ra, il17f and Il17rc genes. In accordance, BM-MSCs administration declined IL17, IL2 and IL6 serum proteins and downregulated IL17A and IL17RA proteins in liver tissue. Interestingly, BM-MSCs downregulated both Stat3 mRNA expression and p-STAT3, while Stat5a gene was downregulated and p-STAT5 protein was elevated. Also P-SMAD3 and TGFβR2 proteins were downregulated in response to BM-MSCs treatment. Collectively, we suggest that BM-MSCs might play an immunomodulatory role in the treatment of liver fibrosis through downregulation of IL17A affecting IL6/STAT3 signaling pathway.

Expression patterns of STAT3, ERK and estrogen-receptor α are associated with development and histologic severity of hepatic steatosis: a retrospective study

BACKGROUND

Hepatic steatosis renders hepatocytes vulnerable to injury, resulting in the progression of preexisting liver disease. Previous animal and cell culture studies implicated mammalian target of rapamycin (mTOR), signal transducer and activator of transcription-3 (STAT3), extracellular signal-regulated kinase (ERK) and estrogen-receptor α in the pathogenesis of hepatic steatosis and disease progression. However, to date there have been few studies performed using human liver tissue to study hepatic steatosis. We examined the expression patterns of mTOR, STAT3, ERK and estrogen-receptor α in liver tissues from patients diagnosed with hepatic steatosis.

METHODS

We reviewed the clinical and histomorphological features of 29 patients diagnosed with hepatic steatosis: 18 with non-alcoholic fatty liver disease (NAFLD), 11 with alcoholic fatty acid disease (AFLD), and a control group (16 biliary cysts and 22 hepatolithiasis). Immunohistochemistry was performed on liver tissue using an automated immunostainer. The histologic severity of hepatic steatosis was evaluated by assessing four key histomorphologic parameters common to NAFLD and AFLD: steatosis, lobular inflammation, ballooning degeneration and fibrosis.

RESULTS

mTOR, phosphorylated STAT3, phosphorylated pERK, estrogen-receptor α were found to be more frequently expressed in the hepatic steatosis group than in the control group. Specifically, mTOR was expressed in 78% of hepatocytes, and ERK in 100% of hepatic stellate cells, respectively, in patients with NAFLD. Interestingly, estrogen-receptor α was diffusely expressed in hepatocytes in all NALFD cases. Phosphorylated (active) STAT3 was expressed in 73% of hepatocytes and 45% of hepatic stellate cells in patients with AFLD, and phosphorylated (active) ERK was expressed in hepatic stellate cells in all AFLD cases. Estrogen-receptor α was expressed in all AFLD cases (focally in 64% of AFLD cases, and diffusely in 36%). Phosphorylated STAT3 expression in hepatocytes and hepatic stellate cells correlated with severe lobular inflammation, severe ballooning degeneration and advanced fibrosis, whereas diffusely expressed estrogen-receptor α correlated with a mild stage of fibrosis.

CONCLUSIONS

Our data indicate ERK activation and estrogen-receptor α may be relevant in the development of hepatic steatosis. However, diffuse expression of estrogen-receptor α would appear to impede disease progression, including hepatic fibrosis. Finally, phosphorylated STAT3 may also contribute to disease progression.

SREBP-regulated lipid metabolism: convergent physiology - divergent pathophysiology

Cellular lipid metabolism and homeostasis are controlled by sterol regulatory-element binding proteins (SREBPs). In addition to performing canonical functions in the transcriptional regulation of genes involved in the biosynthesis and uptake of lipids, genome-wide system analyses have revealed that these versatile transcription factors act as important nodes of convergence and divergence within biological signalling networks. Thus, they are involved in myriad physiological and pathophysiological processes, highlighting the importance of lipid metabolism in biology. Changes in cell metabolism and growth are reciprocally linked through SREBPs. Anabolic and growth signalling pathways branch off and connect to multiple steps of SREBP activation and form complex regulatory networks. In addition, SREBPs are implicated in numerous pathogenic processes such as endoplasmic reticulum stress, inflammation, autophagy and apoptosis, and in this way, they contribute to obesity, dyslipidaemia, diabetes mellitus, nonalcoholic fatty liver disease, nonalcoholic steatohepatitis, chronic kidney disease, neurodegenerative diseases and cancers. This Review aims to provide a comprehensive understanding of the role of SREBPs in physiology and pathophysiology at the cell, organ and organism levels.

Effects of telmisartan on improving leptin resistance and inhibiting hepatic fibrosis in rats with non-alcoholic fatty liver disease

The present study aimed to investigate the impacts of telmisartan (TEL) on hepatic fibrosis, serum leptin, leptin protein in liver tissue and its mRNA expression level in rats with non-alcoholic fatty liver disease (NAFLD). Male Sprague Dawley rats were randomly divided into the control (N), model (M), polyene phosphatidylcholine (P) and TEL (T) groups. Group M and the intervention groups were given a high-fat diet for 12 weeks to induce NAFLD, followed by 4 weeks of intragastric administration of normal saline (1.0 ml/kg/day), polyene phosphatidylcholine (PPC; 123.1 mg/kg/day) and TEL (8 mg/kg/day). The liver tissue was then assessed for the NAFLD activity score and fibrosis score (FS), and serum biochemistry and leptin levels were determined. Additionally, leptin protein expression levels were examined by western blotting and the expression of leptin mRNA was investigated by reverse transcription-polymerase chain reaction. TEL significantly improved FS in rats (P<0.01) and was more effective than PPC. TEL significantly reduced the expression of serum leptin, as well as the expression levels of leptin protein and its mRNA in liver tissue (P<0.01); however, the effects of PPC were not significant (P>0.05). TEL reduced serum leptin, leptin protein and its mRNA in the liver tissue of NAFLD rats, and improved the pathological indicators of liver fibrosis.

GRIM-19 Restricts HCV Replication by Attenuating Intracellular Lipid Accumulation

Gene-associated with retinoid-interferon-induced mortality 19 (GRIM-19) targets multiple signaling pathways involved in cell death and growth. However, the role of GRIM-19 in the pathogenesis of hepatitis virus infections remains unexplored. Here, we investigated the restrictive effects of GRIM-19 on the replication of hepatitis C virus (HCV). We found that GRIM-19 protein levels were reduced in HCV-infected Huh7 cells and Huh7 cells harboring HCV replicons. Moreover, ectopically expressed GRIM-19 caused a reduction in both intracellular viral RNA levels and secreted viruses in HCVcc-infected cell cultures. The restrictive effect on HCV replication was restored by treatment with siRNA against GRIM-19. Interestingly, GRIM-19 overexpression did not alter the level of phosphorylated STAT3 or its subcellular distribution. Strikingly, forced expression of GRIM-19 attenuated an increase in intracellular lipid droplets after oleic acid (OA) treatment or HCVcc infection. GRIM-19 overexpression abrogated fatty acid-induced upregulation of sterol regulatory element-binding transcription factor-1 (SREBP-1c), resulting in attenuated expression of its target genes such as fatty acid synthase (FAS) and acetyl CoA carboxylase (ACC). Treatment with OA or overexpression of SREBP-1c in GRIM-19-expressing, HCVcc-infected cells restored HCV replication. Our results suggest that GRIM-19 interferes with HCV replication by attenuating intracellular lipid accumulation and therefore is an anti-viral host factor that could be a promising target for HCV treatment.

Nrf2 Knockdown Disrupts the Protective Effect of Curcumin on Alcohol-Induced Hepatocyte Necroptosis

It has emerged that hepatocyte necroptosis plays a critical role in chronic alcoholic liver disease (ALD). Our previous study has identified that the beneficial therapeutic effect of curcumin on alcohol-caused liver injury might be attributed to activation of nuclear factor (erythroid-derived 2)-like 2 (Nrf2), whereas the role of curcumin in regulating necroptosis and the underlying mechanism remain to be determined. We first found that chronic alcohol consumption triggered obvious hepatocyte necroptosis, leading to increased expression of receptor-interacting protein 1, receptor-interacting protein 3, high-mobility group box 1, and phosphorylated mixed lineage kinase domain-like in murine livers. Curcumin dose-dependently ameliorated hepatocyte necroptosis and alleviated alcohol-caused decrease in hepatic Nrf2 expression in alcoholic mice. Then Nrf2 shRNA lentivirus was introduced to generate Nrf2-knockdown mice. Our results indicated that Nrf2 knockdown aggravated the effects of alcohol on liver injury and necroptosis and even abrogated the inhibitory effect of curcumin on necroptosis. Further, activated Nrf2 by curcumin inhibited p53 expression in both livers and cultured hepatocytes under alcohol stimulation. The next in vitro experiments, similar to in vivo ones, revealed that although Nrf2 knockdown abolished the suppression of curcumin on necroptosis of hepatocytes exposed to ethanol, p53 siRNA could clearly rescued the relative effect of curcumin. In summary, for the first time, we concluded that curcumin attenuated alcohol-induced hepatocyte necroptosis in a Nrf2/p53-dependent mechanism. These findings make curcumin an excellent candidate for ALD treatment and advance the understanding of ALD mechanisms associated with hepatocyte necroptosis.

STAT3 Inhibition Suppresses Hepatic Stellate Cell Fibrogenesis: HJC0123, a Potential Therapeutic Agent for Liver Fibrosis

Hepatic Stellate Cells (HSCs) are the major source of the excessive extracellular matrix (ECM) production that replaces liver parenchyma with fibrous tissue during liver fibrosis. The signal transducer and activator of transcription 3 (STAT3) promotes HCSs survival, proliferation, and activation contributing to fibrogenesis. We have previously used a fragment-based drug design approach and have discovered a novel STAT3 inhibitor, HJC0123. Here, we explored the biological effects of HJC0123 on the fibrogenic properties of HSCs. HJC0123 treatment resulted in the inhibition of HSCs proliferation at submicromolar concentrations. HJC0123 reduced the phosphorylation, nuclear translocation, and transcriptional activity of STAT3. It decreased the expression of STAT3-regulated proteins, induced cell cycle arrest, promoted apoptosis and downregulated SOCS3. HJC0123 treatment inhibited HSCs activation and downregulated ECM protein fibronectin and type I collagen expression. In addition, HJC0123 increased IL-6 production and decreased TGF-β induced Smad2/3 phosphorylation. These results demonstrate that HJC0123 represents a novel STAT3 inhibitor that suppresses the fibrogenic properties of HSCs, suggesting its therapeutic potential in liver fibrosis.

Potentials of the elevated circulating miR-185 level as a biomarker for early diagnosis of HBV-related liver fibrosis

Early diagnosis of liver fibrosis is critical for early intervention and prognosis of various chronic liver diseases. Conventional repeated histological assessment is impractical due to the associated invasiveness. In the current study, we evaluated circulating miR-185 as a potential biomarker to predict initiation and progression of liver fibrosis. We found that miR-185 was significantly up-regulated in blood specimens from patients with HBV-liver fibrosis and rats with liver fibrosis, the miR-185 levels were correlated with liver fibrosis progression, but not with the different viral loads in HBV-infected patients. miR-185 was observed in collagen deposition regions during advanced liver fibrosis. We found that differences in miR-185 levels facilitated the discrimination between early-staged or advanced-staged liver fibrosis and the healthy controls with high specificity, sensitivity, and likelihood ratio using receiver-operator characteristic analysis. miR-185 targeted SREBF1, and increased expression of COL1A1 and a-SMA genes that are hallmarks of liver fibrosis. Our data supported that circulating miR-185 levels could be used as potential biomarkers for the early diagnosis of liver fibrosis.

Panax notoginseng saponins ameliorates experimental hepatic fibrosis and hepatic stellate cell proliferation by inhibiting the Jak2/ Stat3 pathways

OBJECTIVE

To investigate the inhibitory effect of Panax notoginseng saponins (PNS) on liver fibrosis and explore the underlying mechanisms.

METHODS

Carbon tetrachloride (CCl4)-treated rats and hepatic stellate cells (HSCs) were used. The effect of PNS on CCl4-induced liver fibrosis was studied with histochemical and biochemical analysis. Transforming growth factor (TGF)-β1, α-smooth muscle actin (α-SMA), and collagen I mRNA expression were determined by reverse transcripwhile, the protein expression levels of α-SMA, collagen I, phosphorylation-Janus activated kinase signal transducer (p-Jak2)/Jak2, and phosphorylation-activator of transcription (p-Stat)3/Stat3 were determined by immunohistochemistry and/or immunoblotting.

RESULTS

PNS treatment significantly improved the liver function of rats as indicated by decreased serum enzymatic activities of alanine aminotransferase and aspartate aminotransferase. Histopathological results indicated that PNS alleviated liver damage and reduced the formation of fibrous septa. Moreover, PNS significantly decreased liver hydroxyproline and significantly attenuated expressions of collagen I, α-SMA, TGF-β1, p-Jak2 / Jak2, and p-Stat3/Stat3 in the rat liver fibrosis model and HSCs.

CONCLUSION

PNS can relieve liver fibrosis by modulating Jak2/Stat3 signaling transduction pathway, which may be one of its mechanisms to suppress hepatic fibrosis.

Targeted blockade of JAK/STAT3 signaling inhibits proliferation, migration and collagen production as well as inducing the apoptosis of hepatic stellate cells

Protein tyrosine kinases belonging to the Janus kinase (JAK) family are associated with many cytokine receptors, which, on ligand binding, regulate important cellular functions such as proliferation, apoptosis and differentiation. The protective effects of JAK inhibitors on fibrotic diseases such as myelofibrosis and bone marrow fibrosis have been demonstrated in previous studies. The JAK inhibitor SHR0302 is a synthetic molecule that potently inhibits all members of the JAK family, particularly JAK1. However, its effect on hepatic fibrosis has not been investigated to date, to the best of our knowledge. In the present study, the effects of SHR0302 on the activation, proliferation, migration and apoptosis of hepatic stellate cells (HSCs) as well as HSC collagen production were investigated. Our data demonstrated that treatment with SHR0302 (10-9-10-5 mol/l) exerted an inhibitory effect on the activation, proliferation and migration of HSCs. In addition, the expression of collagen I and collagen III were significantly decreased following treatment with SHR0302. Furthermore, SHR0302 induced the apoptosis of HSCs, which was demonstrated by Annexin V/PI staining. SHR0302 significantly increased the activation of caspase-3 and Bax in HSCs whereas it decreased the expression of Bcl-2. SHR0302 also inhibited the activation of Akt signaling pathway. The pharmacological inhibition of the JAK1/signal transducer and activator of transcription (STAT)3 pathway led to the disruption of functions essential for HSC growth. Taken together, these findings provide evidence that SHR0302 may have the potential to alleviate hepatic fibrosis by targeting HSC functions.

Liganded Vitamin D Receptor Through Its Interacting Repressor Inhibits the Expression of Type I Collagen α1

Hepatic fibrosis is a reversible process involving plenty of transcription factors and pathways. Vitamin D receptor (VDR) as a member of ligand-induced transcription factors can interact with 9-cis retinoid X receptor (RXR) and VDR-interacting repressor (VDIR) to mediate transactivation or transrepression in the absence or in the presence of VDR ligand to regulate the expression of VDR target genes. The active form of vitamin D [1α,25(OH)2D3] can downregulate the expression of type I collagen both α1 and α2 (COLIα1 and COLIα2) in hepatic stellate cells (HSC-T6) in a time-dependent fashion, which provides a new direction for hepatic fibrosis therapy. As one of VDR target genes, rat COLIα1 gene contains 1αnVDRE (E-box1 and E-box2) in its promoter, and unliganded VDR/RXR may bind to 1αnVDRE through VDIR to mediate transactivation, whereas liganded VDR/RXR may bind to 1αnVDRE through VDIR for transrepression. The results suggested a sort of relying on each other relationship between VDR/RXR and VDIR in regulating the expression of COLIα1 gene in HSC-T6 cells, which established VDR as a potential target for blocking and even reversing hepatic fibrosis.

Vitamin A and insulin are required for the maintenance of hepatic stellate cell quiescence

Transdifferentiation of vitamin A-storing hepatic stellate cells (HSCs) to vitamin A-depleted myofibroblastic cells leads to liver fibrosis. Vitamin A regulates lipid accumulation and gene transcription, suggesting that vitamin A is involved in the maintenance of HSC quiescence under a physiological condition. However, the precise mechanism remains elusive because there is no appropriate in vitro culture system for quiescent HSCs. Here, we show that treatment of quiescent HSCs with vitamin A partially maintained the accumulation of lipid droplets and expression of quiescent HSC markers (glial fibrillary acidic protein, peroxisome proliferator-activator receptor-γ and CCAAT/enhancer-binding protein-α) and also the expression of myofibroblastic markers (α-smooth muscle actin, heat shock protein 47 and collagen type I). On the other hand, combined treatment with vitamin A and insulin sustained the characteristic of HSC quiescence and completely suppressed the expression of myofibroblastic markers through activation of the JAK2/STAT5 signaling pathway and increased expression of sterol regulatory element binding protein-1. These treated HSCs transdifferentiated to myofibroblastic cells under a culture condition with fetal bovine serum. The results suggest an important role of vitamin A and insulin in the maintenance of HSC quiescence under a physiological condition.

Adipocytokine expression associated with miRNA regulation and diagnosis of NASH in obese patients with NAFLD

BACKGROUND & AIMS

Non-alcoholic fatty liver disease (NAFLD) is strongly associated with visceral adiposity. The secretion of adipocytokines from white adipose tissue (WAT) promoting necroinflammation, and/or fibrosis may play important roles in the pathogenesis of non-alcoholic steatohepatits (NASH). In a previous study, reduced expression of a number of miRNA species in WAT concomitant with histological diagnosis of NASH was successfully demonstrated. In this study, we measure the expression of several predicted miRNA regulatory targets relevant to NAFLD and NASH including mTOR, FAS, IL20, SEMA4C, ADAMTS6 and IL13RA. We then examine hepatic receptor expression by immunohistochemical staining and qPCR.

METHODS

White adipose tissue was collected from 24 obese patients undergoing bariatric surgery with biopsy-proven NAFLD. Extracted total RNAs from the adipose tissue were reverse transcribed and profiled for gene expression by qPCR for specific individual mRNA targets defined after identification by any two of three of the major prediction services: miRanda, TarBase or PicTar. All liver biopsies were read by a singly hepatopathologist. The same liver tissue was used to stain for hepatic receptor expression for FASLG and IL20. Additionally, the same tissue was used for qPCR for FASLG and IL20.

RESULTS

Increases in the expression of IL13RA, mTOR, IL20, SEMA4C and FAS were detected and negatively correlated with putative regulatory miRNA. Hepatic receptor expression for FAS and IL20 was noted to correlate with markers of inflammation and severity of NAFLD.

CONCLUSION

These data are consistent with the hypothesis that specific adipocytokines secreted by WAT will impact hepatic tissue and participate in the pathogenesis of NASH.

Inhibition of Janus kinase-2 signalling pathway ameliorates portal hypertensive syndrome in partial portal hypertensive and liver cirrhosis rats

BACKGROUND AND AIMS

JAK2/STAT3 signalling promotes fibrosis, angiogenesis and inflammation in many diseases; however, the role of this pathway in portal hypertension remains obscure. This study aimed to explore the function of JAK2/STAT3 signalling in portal hypertension and estimate the potential therapeutic effect of treatment with the specific inhibitor AG490.

METHODS

Rats induced by partial portal vein ligation and common bile duct ligation were treated with AG490 for two weeks. Haemodynamic parameters were assessed. The levels of phospho-STAT3 protein and related cytokines were detected by western blotting of splanchnic organs. Liver, spleen and intestine characterization was performed using histological analyses. Peripheral blood cell counts were also detected.

RESULTS

High levels of phospho-STAT3 protein were detected in portal hypertensive rats. AG490 effectively inhibited JAK2/STAT3 signalling and its downstream cytokines and provided protective effects by decreasing splanchnic neovascularization and inflammation and by attenuating portal pressure and hyperdynamic splanchnic circulation. In cirrhosis rats, AG490 inhibited intrahepatic fibrosis, angiogenesis and inflammation. AG490 improved the peripheral blood cell counts and the splenomegaly observed in these rats.

CONCLUSIONS

JAK2/STAT3 signalling is essential in portal hypertension, and targeting JAK2/STAT3 may be a promising therapy to treat this condition.

Adipokines levels are associated with the severity of liver disease in patients with alcoholic cirrhosis

AIM

To investigate the adipokine levels of leptin, adiponectin, resistin, visfatin, retinol-binding protein 4 (RBP4), apelin in alcoholic liver cirrhosis (ALC).

METHODS

Forty non-diabetic ALC patients [median age: 59 years, males: 35 (87.5%), Child-Pugh (CP) score: median 7 (5-12), CP A/B/C: 18/10/12, Model for End-stage Liver Disease (MELD): median 10 (6-25), follow-up: median 32.5 mo (10-43)] were prospectively included. The serum adipokine levels were estimated in duplicate by ELISA. Somatometric characteristics were assessed with tetrapolar bioelectrical impedance analysis. Pearson's rank correlation coefficient was used to assess possible associations with adipokine levels. Univariate and multivariate Cox regression analysis was used to determine independent predictors for overall survival.

RESULTS

Body mass index: median 25.9 (range: 20.1-39.3), fat: 23.4% (7.6-42.1), fat mass: 17.8 (5.49-45.4), free fat mass: 56.1 (39.6-74.4), total body water (TBW): 40.6 (29.8-58.8). Leptin and visfatin levels were positively associated with fat mass (P < 0.001/P = 0.027, respectively) and RBP4 with TBW (P = 0.025). Median adiponectin levels were significantly higher in CPC compared to CPA (CPA: 7.99 ± 14.07, CPB: 7.66 ± 3.48, CPC: 25.73 ± 26.8, P = 0.04), whereas median RBP4 and apelin levels decreased across the spectrum of disease severity (P = 0.006/P = 0.034, respectively). Following adjustment for fat mass, visfatin and adiponectin levels were significantly increased from CPA to CPC (both P < 0.001), whereas an inverse correlation was observed for both RBP4 and apelin (both P < 0.001). In the multivariate Cox regression analysis, only MELD had an independent association with overall survival (HR = 1.53, 95%CI: 1.05-2.32; P = 0.029).

CONCLUSION

Adipokines are associated with deteriorating liver function in a complex manner in patients with alcoholic liver cirrhosis.

Stat3 signaling activation crosslinking of TGF-β1 in hepatic stellate cell exacerbates liver injury and fibrosis

BACKGROUND/AIMS

The role of signal transducer and activator of transcription 3 (Stat3) in liver fibrosis is still controversial. Since hepatic stellate cells (HSCs) and transforming growth factor-β1 (TGF-β1) are central to the fibrogenesis, our goal was to clarify the mechanism of Stat3 crosslinking of TGF-β1 signaling.

METHODS

Stat3, TGF-β1 mRNA and protein expressions were examined in liver tissues of chronic hepatitis B (CHB) patients and diethylinitrosamine (DEN)-induced rat fibrosis model. The effect of Stat3 activation or suppression on TGF-β1 signaling in HSCs was tested in vitro and in vivo.

RESULTS

Stat3 expression as well as TGF-β1 was increased in CHB patients and DEN-induced fibrosis rat model. This was strongly correlated with increase in fibrosis staging. TGF-β1, a mediator of fibrosis, was enhanced by Stat3, but suppressed by siRNA-mediated RNA knockdown of Stat3 (siStat3) or Janus kinase 2 inhibitor (AG490) both in vivo and in vitro. Stat3 crosslinking TGF-β1 signaling plays an important role in HSC activation and increasing fibrosis related products. TGF-β1 could not achieve profibrogenic cytokine and anti-apoptosis characteristics without Stat3 activation in HSCs.

CONCLUSION

We provide a novel role of Stat3 cooperating TGF-β1 in activation and anti-apoptotic effect of HSCs. Stat3 worsens liver fibrosis through the up-regulation of TGF-β1 and fibrotic product expression.

Inhibition of ASICs reduces rat hepatic stellate cells activity and liver fibrosis: an in vitro and in vivo study

Hepatic fibrosis is a chronic inflammation-associated disease, which is involved in the infiltration of inflammatory cells and releasing of proinflammatory cytokines. In the pathological process, protons are released by damaged cells and acidosis is considered to play a critical role in cell injury. Although the underlying mechanism (s) remain ill-defined, ASICs (acid-sensing ion channels) are assumed to be involved in this process. The diuretic, amiloride, is neuroprotective in models of cerebral ischemia, a property attributable to the inhibition of central ASICs by the drug. However, the effect of inhibition of ASICs by amiloride in the liver fibrotic process remains unclear. We found that amiloride (25, 50, or 100 μM) could restrain acid-induced HSCs at pH6 in vitro. In vivo experiments showed that amiloride could significantly alleviate liver injury, decreasing levels of profibrogenic cytokines, collagen deposition, and reducing pathological tissue damage. In summary, amiloride inhibits hepatic fibrosis in vivo and in vitro, which is probably associated with the downregulation of ASICs.

Exogenous hydrogen sulfide alleviates high glucose-induced cardiotoxicity via inhibition of leptin signaling in H9c2 cells

Hydrogen sulfide (H₂S) protects cardiomyoblasts against high glucose (HG)-induced injury by inhibiting the activation of p38 mitogen-activated protein kinase (MAPK). This study aims to determine whether the leptin-p38 MAPK pathway is involved in HG-induced injury and whether exogenous H2S prevents the HG-induced insult through inhibition of the leptin-p38 MAPK pathway in H9c2 cells. H9c2 cells were treated with 35 mM glucose (HG) for 24 h to establish a HG-induced cardiomyocyte injury model. Cell viability; mitochondrial membrane potential (ΔΨ m); apoptosis; reactive oxygen species (ROS) level; and leptin, leptin receptor, and p38 MAPK expression level were measured by the methods indicated. The results showed pretreatment of H9c2 cells with NaHS before exposure to HG led to an increase in cell viability, decrease in apoptotic cells, ROS generation, and a loss of ΔΨ m. Exposure of H9c2 cells to 35 mM glucose for 24 h significantly upregulated the expression levels of leptin and leptin receptors. The increased expression levels of leptin and leptin receptors were markedly attenuated by pretreatment with 400 μM NaHS. In addition, the HG-induced increase in phosphorylated (p) p38 MAPK expression was ameliorated by pretreatment with 50 ng/ml leptin antagonist. In conclusion, the present study has demonstrated for the first time that the leptin-p38 MAPK pathway contributes to the HG-induced injury in H9c2 cells and that exogenous H₂S protects H9c2 cells against HG-induced injury at least in part by inhibiting the activation of leptin-p38 MAPK pathway.

Interactions among bone, liver, and adipose tissue predisposing to diabesity and fatty liver

Growing epidemiological evidence connects obesity and its complications, including metabolic syndrome, diabetes, and nonalcoholic fatty liver disease (NAFLD) to reduced bone health and osteoporosis. Parallel to human studies, experimental data disclosed a complex network of interaction among adipose tissue, the liver, and the bone, which reciprocally modulate the function of each other. The main mediators of such crosstalk include hormonal/cytokine signals from the bone (osteopontin, osteocalcin, and osteoprotegerin), the liver (fetuin-A), and adipose tissue [leptin, tumor necrosis factor-α (TNF-α), and adiponectin]. Dysregulation of this network promotes the development of diabesity, NAFLD, and osteoporosis. We will review recent advances in understanding the mechanisms of bone-liver-adipose tissue interaction predisposing to obesity, diabetes, NAFLD, and osteoporosis and their potential clinical implications.