Eicosanoid-mediated contractility of hepatic stellate cells.
Ontology highlight
ABSTRACT:
SUBMITTER: Kawada N
PROVIDER: S-EPMC1132795 | biostudies-other | 1992 Jul
REPOSITORIES: biostudies-other
Similar Datasets
Project description:The inflammasome is a cytoplasmic multiprotein complex that has recently been identified in immune cells as an important sensor of signals released by cellular injury and death. Analogous to immune cells, hepatic stellate cells (HSC) also respond to cellular injury and death. Our aim was to establish whether inflammasome components were present in HSC and could regulate HSC functionality. Monosodium urate (MSU) crystals (100 microg/ml) were used to experimentally induce inflammasome activation in LX-2 and primary mouse HSC. Twenty-four hours later primary mouse HSC were stained with alpha-smooth muscle actin and visualized by confocal microscopy, and TGF-beta and collagen1 mRNA expression was quantified. LX-2 cells were further cultured with or without MSU crystals for 24 h in a transwell chemotaxis assay with PDGF as the chemoattractant. We also examined inhibition of calcium (Ca(2+)) signaling in LX-2 cells treated with or without MSU crystals using caged inositol 1,4,5-triphosphate (IP(3)). Finally, we confirmed an important role of the inflammasome in experimental liver fibrosis by the injection of carbon tetrachloride (CCl(4)) or thioacetamide (TAA) in wild-type mice and mice lacking components of the inflammasome. Components of the inflammasome are expressed in LX-2 cells and primary HSC. MSU crystals induced upregulation of TGF-beta and collagen1 mRNA and actin reorganization in HSCs from wild-type mice but not mice lacking inflammasome components. MSU crystals inhibited the release of Ca(2+) via IP(3) in LX-2 cells and also inhibited PDGF-induced chemotaxis. Mice lacking the inflammasome-sensing and adaptor molecules, NLRP3 and apoptosis-associated speck-like protein containing CARD, had reduced CCl(4) and TAA-induced liver fibrosis. We concluded that inflammasome components are present in HSC, can regulate a variety of HSC functions, and are required for the development of liver fibrosis.
| S-EPMC2697939 | biostudies-literature
Project description:Hepatic stellate cells (HSCs) are a significant component of the hepatocellular carcinoma (HCC) tumor microenvironment (TME). Activated HSCs transform into myofibroblast-like cells to promote fibrosis in response to liver injury or chronic inflammation, leading to cirrhosis and HCC. The hepatic TME is comprised of cellular components, including activated HSCs, tumor-associated macrophages, endothelial cells, immune cells, and non-cellular components, such as growth factors, proteolytic enzymes and their inhibitors, and other extracellular matrix (ECM) proteins. Interactions between HCC cells and their microenvironment have become topics under active investigation. These interactions within the hepatic TME have the potential to drive carcinogenesis and create challenges in generating effective therapies. Current studies reveal potential mechanisms through which activated HSCs drive hepatocarcinogenesis utilizing matricellular proteins and paracrine crosstalk within the TME. Since activated HSCs are primary secretors of ECM proteins during liver injury and inflammation, they help promote fibrogenesis, infiltrate the HCC stroma, and contribute to HCC development. In this review, we examine several recent studies revealing the roles of HSCs and their clinical implications in the development of fibrosis and cirrhosis within the hepatic TME.
| S-EPMC7419619 | biostudies-literature
Project description:Liver fibrosis is a complex fibrotic process that develops early in the course of cirrhosis and is caused by chronic liver damage. The activation of hepatic stellate cells is primarily responsible for the fibrosis process. Studies show that NRP1 influences HSC motility and migration. However, whether NRP1 regulates HSC activation remains unknown. C57BL/6 male mice (6–8 weeks old) were intraperitoneally injected with 10% CCl4 in olive oil (5 μl/g body weight) every three days for four weeks to create an animal model of liver fibrosis. Control mice received olive oil (5 μl/g body weight). Different assays such as immunohistochemistry, immunostaining, Western blotting, qRT-PCR, immunoprecipitation, immunoprecipitation, and GST pull-down assays, and in vivo and in vitro ubiquitination assays were conducted. We found that NRP1 expression was significantly elevated both in mouse and human fibrotic livers, mainly in activated HSCs at the fibrotic foci. NRP1 promoted HSC activation via the cytokine TGF-β1, VEGFA, and PDGF-BB. Moreover, USP9X was found to be a critical deubiquitinating enzyme for the stability and high activity of NRP1 and NRP1 deubiquitination mediated by USP9X enhanced HSC activation and liver fibrosis. NRP1 deubiquitination mediated by USP9X enhances HSC activation, implying that targeting NRP1 or USP9X potentiates novel options in the treatment of liver fibrosis.
| S-EPMC9849111 | biostudies-literature
Project description:AMP-activated protein kinase (AMPK) regulates lipid, cholesterol, and glucose metabolism in specialized metabolic tissues, such as muscle, liver, and adipose tissue. Agents that activate AMPK, such as metformin and 5-aminoimidazole-4-carboxamide-1-beta-4-ribofuranoside (AICAR), have beneficial effects on liver glucose and lipid metabolism. In addition, AMPK activation in proliferating hepatic stellate cells (HSC) induces growth arrest and inhibits hepatic fibrosis. As metformin and AICAR act in different ways to achieve their effects, our aim was to examine the effects of AMPK activation in quiescent HSCs with these two agents on HSC function. We found that phospho-AMPK levels were markedly upregulated by both AICAR and metformin in quiescent HSCs. However, although AICAR treatment induced cell death, cells treated with metformin did not differ from untreated controls. AICAR-mediated HSC cell death was paralleled by loss of expression of the TGF-? decoy receptor Bambi, whereas metformin increased Bambi expression. Transfection of siRNA-Bambi into HSCs also induced cell death, mimicking the effects of AICAR, whereas overexpression of Bambi partially rescued AICAR-treated cells. As Bambi has previously been shown to promote cell survival through Wnt/?-catenin signaling, a reporter incorporating binding sites for a downstream target of this pathway was transfected into HSCs and was induced. We conclude that although AICAR and metformin both activate AMPK in quiescent HSCs, AICAR rapidly induced cell death, whereas metformin-treated cells remained viable. The finding that metformin increases Bambi expression and activates Wnt/?-catenin signaling provides a possible mechanistic explanation for this observation. These results suggest that AICAR and metformin may confer disease-specific therapeutic benefits.
| S-EPMC3324648 | biostudies-literature
Project description:ADAMTS13 is a circulating zinc metalloprotease that cleaves the hemostatic glycoprotein von Willebrand factor (VWF) in a shear-dependent manner. Deficiency in ADAMTS13, owing to genetic mutations or autoimmune inhibitors, causes thrombotic thrombocytopenic purpura (TPP). Northern blot analysis has shown that ADAMTS13 is expressed primarily in the liver. By using real-time RT-PCR, we confirmed that in mice the liver had the highest level of the ADAMTS13 transcript. To identify the liver cell-type-specific origin of ADAMTS13, we used in situ hybridization techniques to investigate the pattern of ADAMTS13 expression in the liver; analyzed the ADAMTS13 proteolytic activity in the culture media of fractionated liver cells; and confirmed ADAMTS13 expression with RT-PCR analysis and cloning of the mouse ADAMTS13 gene. The results revealed that ADAMTS13 was expressed primarily in cell fractions enriched in hepatic stellate cells. The mouse ADAMTS13 cloned from primary hepatic stellate cells was similar to its human counterpart in digesting VWF and was susceptible to suppression by EDTA or the IgG inhibitors of patients with TTP. Since hepatic stellate cells are believed to play a major role in the development of hepatic fibrosis and cirrhosis, the identification of the liver cell-type expressing ADAMTS13 will have important implications for understanding pathophysiological mechanisms regulating ADAMTS13 expression.
| S-EPMC2573995 | biostudies-literature
Project description:Hepatic stellate cells (HSC) are the major cellular drivers of liver fibrosis. Upon liver inflammation caused by a broad range of insults including non-alcoholic fatty liver, HSC transform from a quiescent into a proliferating, fibrotic phenotype. Although much is known about the pathophysiology of this process, exact cellular processes which occur in HSC and enable this transformation remain yet to be elucidated. In order to investigate this HSC transformation, we employed a simple, yet reliable model of HSC activation via an increase in growth medium serum concentration (serum activation). For that purpose, immortalized human LX-2 HSC were exposed to either 1% or 10% fetal bovine serum (FBS). Resulting quiescent (1% FBS) and activated (10% FBS) LX-2 cells were then subjected to in-depth mass spectrometry-based proteomics analysis as well as comprehensive phenotyping. Protein network analysis of activated LX-2 cells revealed an increase in the production of ribosomal proteins and proteins related to cell cycle control and migration, resulting in higher proliferation and faster migration phenotypes. Interestingly, we also observed a decrease in the expression of cholesterol and fatty acid biosynthesis proteins in accordance with a concomitant loss of cytosolic lipid droplets during activation. Overall, this work provides an update on HSC activation characteristics using contemporary proteomic and bioinformatic analyses and presents an accessible model for HSC activation. Data are available via ProteomeXchange with identifier PXD029121.
| S-EPMC8657869 | biostudies-literature
Project description:Hepatic stellate cells (HSCs) comprise a minor cell population in the liver but serve numerous critical functions in the normal liver and in response to injury. HSCs are primarily known for their activation upon liver injury and for producing the collagen-rich extracellular matrix in liver fibrosis. In the absence of liver injury, HSCs reside in a quiescent state, in which their main function appears to be the storage of retinoids or vitamin A-containing metabolites. Less appreciated functions of HSCs include amplifying the hepatic inflammatory response and expressing growth factors that are critical for liver development and both the initiation and termination of liver regeneration. Recent single-cell RNA sequencing studies have corroborated earlier studies indictaing that HSC activation involves a diverse array of phenotypic alterations and identified unique HSC populations. This review serves to highlight these many functions of HSCs, and to briefly describe the recent genetic tools that will help to thoroughly investigate the role of HSCs in hepatic physiology and pathology.
| S-EPMC9012702 | biostudies-literature
Project description:EZH2, a histone H3 lysine-27-specific methyltransferase, is involved in diverse physiological and pathological processes including cell proliferation and differentiation. However, the role of EZH2 in liver fibrosis is largely unknown. In this study, it was identified that EZH2 promoted Wnt pathway-stimulated fibroblasts in vitro and in vivo by repressing Dkk-1, which is a Wnt pathway antagonist. The expression of EZH2 was increased in CCl4 -induced rat liver and primary HSCs as well as TGF-?1-treated HSC-T6, whereas the expression of Dkk1 was reduced. Silencing of EZH2 prevented TGF-?1-induced proliferation of HSC-T6 cells and the expression of ?-SMA. In addition, knockdown of Dkk1 promoted TGF-?1-induced activation of HSCs. Moreover, silencing of EZH2 could restore the repression of Dkk-1 through trimethylation of H3K27me3 in TGF-?1-treated HSC-T6 cells. Interestingly, inhibition of EZH2 had almost no effect on the activation of HSC when Dkk1 was silenced. Collectively, EZH2-mediated repression of Dkk1 promotes the activation of Wnt/?-catenin pathway, which is an essential event for HSC activation.
| S-EPMC5618695 | biostudies-literature
Project description:Hepatic stellate cell (HSC) activation on liver injury facilitates fibrosis. Hepatokines affecting HSCs are largely unknown. Here we show that hepcidin inhibits HSC activation and ameliorates liver fibrosis. We observe that hepcidin levels are inversely correlated with exacerbation of fibrosis in patients, and also confirm the relationship in animal models. Adenoviral delivery of hepcidin to mice attenuates liver fibrosis induced by CCl4 treatment or bile duct ligation. In cell-based assays, either hepcidin from hepatocytes or exogenous hepcidin suppresses HSC activation by inhibiting TGF?1-mediated Smad3 phosphorylation via Akt. In activated HSCs, ferroportin is upregulated, which can be prevented by hepcidin treatment. Similarly, ferroportin knockdown in HSCs prohibits TGF?1-inducible Smad3 phosphorylation and increases Akt phosphorylation, whereas ferroportin over-expression has the opposite effect. HSC-specific ferroportin deletion also ameliorates liver fibrosis. In summary, hepcidin suppresses liver fibrosis by impeding TGF?1-induced Smad3 phosphorylation in HSCs, which depends on Akt activated by a deficiency of ferroportin.
| S-EPMC5192182 | biostudies-literature
Project description:Liver fibrosis is a progressive and debilitating condition characterized by the excessive deposition of extracellular matrix proteins. Stellate cell activation, a major contributor to fibrogenesis, is influenced by Transforming growth factor (TGF-β)/SMAD signaling. Although Krüppel-like-factor (KLF) 10 is an early TGF-β-inducible gene, its specific role in hepatic stellate cell activation remains unclear. Our previous study demonstrated that KLF10 knockout mice develop severe liver fibrosis when fed a high-sucrose diet. Based on these findings, we aimed to identify potential target molecules involved in liver fibrosis and investigate the mechanisms underlying the KLF10 modulation of hepatic stellate cell activation. By RNA sequencing analysis of liver tissues from KLF10 knockout mice with severe liver fibrosis induced by a high-sucrose diet, we identified ATF3 as a potential target gene regulated by KLF10. In LX-2 cells, an immortalized human hepatic stellate cell line, KLF10 expression was induced early after TGF-β treatment, whereas ATF3 expression showed delayed induction. KLF10 knockdown in LX-2 cells enhanced TGF-β-mediated activation, as evidenced by elevated fibrogenic protein levels. Further mechanistic studies revealed that KLF10 knockdown promoted TGF-β signaling and upregulated ATF3 expression. Conversely, KLF10 overexpression suppressed TGF-β-mediated activation and downregulated ATF3 expression. Furthermore, treatment with the chemical chaperone 4-PBA attenuated siKLF10-mediated upregulation of ATF3 and fibrogenic responses in TGF-β-treated LX-2 cells. Collectively, our findings suggest that KLF10 acts as a negative regulator of the TGF-β signaling pathway, exerting suppressive effects on hepatic stellate cell activation and fibrogenesis through modulation of ATF3 expression. These results highlight the potential therapeutic implications of targeting the KLF10-ATF3 axis in liver fibrosis treatment.
| S-EPMC10454374 | biostudies-literature