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Scott L Friedman - One of the best experts on this subject based on the ideXlab platform.
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mechanisms of hepatic Stellate Cell activation
Nature Reviews Gastroenterology & Hepatology, 2017Co-Authors: Takuma Tsuchida, Scott L FriedmanAbstract:Activation of hepatic Stellate Cells (HSCs) in liver injury is the primary driver of hepatic fibrosis. In this Review, Tsuchida and Friedman detail the varied intraCellular and extraCellular signalling pathways leading to HSC activation, as well as the role of HSCs in liver fibrosis resolution and as therapeutic targets.
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emerging and disease specific mechanisms of hepatic Stellate Cell activation
Seminars in Liver Disease, 2015Co-Authors: Scott L Friedman, Michael C Wallace, Derek A MannAbstract:The last decade has seen a rapid expansion in our understanding of the mechanisms leading to hepatic Stellate Cell activation. The classic activation pathway of initiation, perpetuation and regression remains as a useful model; however, the emergence of several new pathways and mediators has revealed a deeper complexity than previously appreciated. Although core fibrogenic pathways exist across organs and disease types, there is accumulating evidence for disease- and context-specific mechanisms that may modulate or drive hepatic fibrogenesis. Hence, a “one size fits all” approach to antifibrotic therapy may not be appropriate for all disease settings. The authors present a focused and concise update of the most recent advances in our understanding of hepatic Stellate Cell activation pathways, while highlighting several challenges that may be constraining progress. This summary provides a foundation to further expand our knowledge of this unique Cell type and its contributions to human liver disease.
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Stellate Cells and Hepatic Fibrosis
Stellate Cells in Health and Disease, 2015Co-Authors: Daisuke Hasegawa, Michael C Wallace, Scott L FriedmanAbstract:Hepatic fibrosis is a programmed response to parenchymal injury orchestrated primarily by the hepatic Stellate Cell (HSC), a pleiotropic non-parenchymal Cell that resides in the perisinusoidal space of Disse. When the liver is injured, several signaling pathways converge upon the Stellate Cell, which promote transdifferentiation to an activated myofibroblast, and acquisition of phenotypic changes that culminate in extraCellular matrix deposition. If the injury persists, hepatic fibrosis develops and may progress to cirrhosis, liver failure, hepatoCellular cancer, and death. With HSCs positioned at the nexus of hepatic fibrosis, a greater appreciation of its complex biology may hasten our progress toward developing effective anti-fibrotic therapies.
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reduced hepatic Stellate Cell expression of kruppel like factor 6 tumor suppressor isoforms amplifies fibrosis during acute and chronic rodent liver injury
Hepatology, 2013Co-Authors: Zahra Ghiassinejad, Virginia Hernandezgea, Christopher Woodrell, Ursula E Lang, Katja Dumic, Allison J Kwong, Scott L FriedmanAbstract:Kruppel-like factor 6 (KLF6), a zinc finger transcription factor and tumor suppressor, is induced as an immediate-early gene during hepatic Stellate Cell (HSC) activation. The paradoxical induction of a tumor suppressor in HSCs during proliferation led us to explore the biology of wildtype KLF6 (KLF6WT) and its antagonistic, alternatively spliced isoform KLF6SV1 in cultured HSCs and animal models. The animal models generated include a global heterozygous KLF6 mouse (Klf6+/−), and transgenic mice expressing either hKLF6WT or hKLF6SV1 under the control of the Collagen α2 (I) promoter to drive HSC-specific gene expression following injury. The rat Klf6 transcript has multiple splice forms that are homologous to those of the human KLF6 gene. Following a transient increase, all rat Klf6 isoforms decreased in response to acute carbon tetrachloride (CCl4) liver injury and culture-induced activation. After acute CCl4, Klf6+/− mice developed significantly increased fibrosis and enhanced fibrogenic messenger RNA (mRNA) and protein expression. In contrast, HSC-specific transgenic mice overexpressing KLF6WT or KLF6SV1 developed significantly diminished fibrosis with reduced expression of fibrogenic genes. Chromatin IP and quantitative reverse-transcription polymerase chain reaction in mouse HSCs overexpressing KLF6WT demonstrated KLF6WT binding to GC boxes in promoters of Colα1 (I), Colα2 (I), and beta-platelet-derived growth factor receptor (β-Pdgfr) with reduced gene expression, consistent with transcriptional repression by KLF6. Stellate Cells overexpressing either KLF6WT or KLF6SV1 were more susceptible to apoptotic stress based on poly (ADP-ribose) polymerase (PARP) cleavage. Conclusion: KLF6 reduces fibrogenic activity of HSCs by way of two distinct mechanisms, direct transcriptional repression of target fibrogenic genes and increased apoptosis of activated HSCs. These results suggest that following its initial induction, sustained down-regulation of KLF6 in liver injury may allow de-repression of fibrogenic genes and decreased Stellate Cell clearance by inhibiting apoptosis. (HEPATOLOGY 2013)
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pathogenesis of liver fibrosis
Annual Review of Pathology-mechanisms of Disease, 2011Co-Authors: Virginia Hernandezgea, Scott L FriedmanAbstract:Liver fibrosis is a major cause of morbidity and mortality worldwide due to chronic viral hepatitis and, more recently, from fatty liver disease associated with obesity. Hepatic Stellate Cell activation represents a critical event in fibrosis because these Cells become the primary source of extraCellular matrix in liver upon injury. Use of Cell-culture and animal models has expanded our understanding of the mechanisms underlying Stellate Cell activation and has shed new light on genetic regulation, the contribution of immune signaling, and the potential reversibility of the disease. As pathways of fibrogenesis are increasingly clarified, the key challenge will be translating new advances into the development of antifibrotic therapies for patients with chronic liver disease.
William S. Blaner - One of the best experts on this subject based on the ideXlab platform.
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an immortalized rat liver Stellate Cell line hsc t6 a new Cell model for the study of retinoid metabolism in vitro
Journal of Lipid Research, 2000Co-Authors: Silke Vogel, Scott L Friedman, Roseann Piantedosi, Jorge Frank, Avraham Lalazar, Don C Rockey, William S. BlanerAbstract:Hepatocytes and hepatic Stellate Cells play impor- tant roles in retinoid storage and metabolism. Hepatocytes process postprandial retinyl esters and are responsible for secretion of retinol bound to retinol-binding protein (RBP) to maintain plasma retinol levels. Stellate Cells are the body's major Cellular storage sites for retinoid. We have character- ized and utilized an immortalized rat Stellate Cell line, HSC- T6 Cells, to facilitate study of the Cellular aspects of hepatic retinoid processing. For comparison, we also carried out parallel studies in Hepa-1 hepatocytes. Like activated pri- mary Stellate Cells, HSC-T6 express myogenic and neural crest cytoskeletal filaments. HSC-T6 Cells take up and ester- ify retinol in a time- and concentration-dependent manner. Supplementation of HSC-T6 culture medium with free fatty acids (up to 300 m M ) does not affect retinol uptake but does enhance retinol esterification up to 10-fold. RT-PCR analy- sis indicates that HSC-T6 Cells express all 6 retinoid nuclear receptors (RAR a , - b , - g , and RXR a , - b , - g ) and like primary Stellate Cells, HSC-T6 Stellate Cells express Cellular retinol- binding protein, type I (CRBP) but fail to express either retinol-binding protein (RBP) or transthyretin (TTR). Addi- tion of retinol (10 2 8 -10 2 5 M ) or all- trans -retinoic acid (10 2 10 - 10 2 6 M ) rapidly up-regulates CRBP expression. Using RAR- specific agonists and antagonists and an RXR-specific ago- nist, we show that members of the RAR-receptor family modulate HSC-T6 CRBP expression. Thus, HSC-T6 Cells display the same retinoid-related phenotype as primary stel- late Cells in culture and will be a useful tool for study of he- patic retinoid storage and metabolism. —Vogel, S., R. Pian- tedosi, J. Frank, A. Lalazar, D. C. Rockey, S. L. Friedman, and W. S. Blaner. An immortalized rat liver Stellate Cell line (HSC-T6): a new Cell model for the study of retinoid metab- olism in vitro. J. Lipid Res. 2000. 41: 882-893.
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an immortalized rat liver Stellate Cell line hsc t6 a new Cell model for the study of retinoid metabolism in vitro
Journal of Lipid Research, 2000Co-Authors: Silke Vogel, Scott L Friedman, Roseann Piantedosi, Jorge Frank, Avraham Lalazar, Don C Rockey, William S. BlanerAbstract:Hepatocytes and hepatic Stellate Cells play important roles in retinoid storage and metabolism. Hepatocytes process postprandial retinyl esters and are responsible for secretion of retinol bound to retinol-binding protein (RBP) to maintain plasma retinol levels. Stellate Cells are the body's major Cellular storage sites for retinoid. We have characterized and utilized an immortalized rat Stellate Cell line, HSC-T6 Cells, to facilitate study of the Cellular aspects of hepatic retinoid processing. For comparison, we also carried out parallel studies in Hepa-1 hepatocytes. Like activated primary Stellate Cells, HSC-T6 express myogenic and neural crest cytoskeletal filaments. HSC-T6 Cells take up and esterify retinol in a time- and concentration-dependent manner. Supplementation of HSC-T6 culture medium with free fatty acids (up to 300 micrometer) does not affect retinol uptake but does enhance retinol esterification up to 10-fold. RT-PCR analysis indicates that HSC-T6 Cells express all 6 retinoid nuclear receptors (RARalpha, -beta, -gamma, and RXRalpha, -beta, -gamma) and like primary Stellate Cells, HSC-T6 Stellate Cells express Cellular retinol-binding protein, type I (CRBP) but fail to express either retinol-binding protein (RBP) or transthyretin (TTR). Addition of retinol (10(-8)-10(-5) m) or all-trans-retinoic acid (10(-10)-10(-6) m) rapidly up-regulates CRBP expression. Using RAR-specific agonists and antagonists and an RXR-specific agonist, we show that members of the RAR-receptor family modulate HSC-T6 CRBP expression.Thus, HSC-T6 Cells display the same retinoid-related phenotype as primary Stellate Cells in culture and will be a useful tool for study of hepatic retinoid storage and metabolism.
Don C Rockey - One of the best experts on this subject based on the ideXlab platform.
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preproendothelin 1 expression is negatively regulated by ifnγ during hepatic Stellate Cell activation
American Journal of Physiology-gastrointestinal and Liver Physiology, 2012Co-Authors: Tianxia Li, Don C RockeyAbstract:Endothelin-1 (ET-1), a powerful vasoconstrictor peptide, is produced by activated hepatic Stellate Cells (HSC) and promotes Cell proliferation, fibrogenesis, and contraction, the latter of which has been thought to be mechanistically linked to portal hypertension in cirrhosis. Interferon-γ (IFNγ), a Th1 cytokine produced by T Cells, inhibits Stellate Cell proliferation, fibrogenesis, and muscle-specific gene expression. Whether IFNγ-induced inhibitory effects are linked to regulation of ET-1 expression in activated Stellate Cells remains unknown. Here we examined IFNγ's effects on preproET-1 mRNA expression and the signaling pathways underlying this process. We demonstrated that preproET-1 mRNA expression in HSCs was prominently increased during Cell culture-induced activation; IFNγ significantly inhibited both preproET-1 mRNA expression and ET-1 peptide production. Similar results were found in an in vivo model of liver injury and intraperitoneal administration of IFNγ. PreproET-1 promoter analysis revealed that IFNγ-induced inhibition of preproET-1 mRNA expression was closely linked to the AP-1 and Smad3 signaling pathways. Furthermore, IFNγ reduced JNK phosphorylation, which tightly was associated with decreased phosphorylation of downstream factors c-Jun and Smad3 and decreased binding activity of c-Jun and Smad3 in the preprpET-1 promoter. Importantly, IFNγ reduced both c-Jun mRNA and protein levels. Given the important role of ET-1 in wound healing, our results suggest a novel negative signaling network by which IFNγ inhibits preproET-1 expression, highlighting one potential molecular mechanism for IFNγ-induced host immunomodulation of liver fibrogenesis.
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Hepatic fibrosis, Stellate Cells, and portal hypertension.
Clinics in Liver Disease, 2006Co-Authors: Don C RockeyAbstract:Hepatic fibrogenesis is the common result of injury to the liver. It is believed to be a critical factor that leads to hepatic dysfunction and may be important in portal hypertension. The fibrogenic response is a complex process in which accumulation of extraCellular matrix proteins, tissue contraction, and alteration in blood flow are prominent. A critical event in fibrogenesis is activation of resident perisinusoidal Cells that are termed "hepatic Stellate Cells". Stellate Cell activation is characterized by many important phenotypes, including enhanced extraCellular matrix synthesis and prominent contractility. Given the central role of Stellate Cell activation in hepatic fibrogenesis (and portal hypertension), effective therapy for hepatic fibrogenesis is most likely will be directed at this event.
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Hepatic blood flow regulation by Stellate Cells in normal and injured liver.
Seminars in Liver Disease, 2001Co-Authors: Don C RockeyAbstract:Hepatic Stellate Cells have received considerable attention as key components of the fibrogenic response to injury. Beyond this feature, they also have been implicated as regulators of sinusoidal vascular tone, and in disease states, in the pathogenesis of intrahepatic portal hypertension. The basis for this latter concept is derived from the following: (a) Stellate Cells are situated in a perisinusoidal orientation within the sinusoid, optimized for sinusoidal constriction; (b) a series of studies performed over the past decade have demonstrated that perisinusoidal Stellate Cells exhibit a remarkable capacity for Cellular contraction, a characteristic that is most prominent after liver injury and Stellate Cell activation; and (c) in vivo microscopy studies have revealed that Stellate Cells can mediate sinusoidal constriction. Available evidence indicates that liver injury leads to a vascular disorder in which endothelin-1 is overproduced by Stellate Cells and endothelial Cell-derived nitric oxide production is reduced. These abnormalities, in the context of exaggerated Stellate Cell contractility after liver injury, set up a paradigm in which Stellate Cells contribute to the increased intrahepatic resistance typical of portal hypertension. Furthermore, because Stellate Cell contractility and the mediators that control this function are dynamic processes, strategies that target exaggerated contractility provide an opportunity for novel therapeutics in intrahepatic portal hypertension.
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an immortalized rat liver Stellate Cell line hsc t6 a new Cell model for the study of retinoid metabolism in vitro
Journal of Lipid Research, 2000Co-Authors: Silke Vogel, Scott L Friedman, Roseann Piantedosi, Jorge Frank, Avraham Lalazar, Don C Rockey, William S. BlanerAbstract:Hepatocytes and hepatic Stellate Cells play impor- tant roles in retinoid storage and metabolism. Hepatocytes process postprandial retinyl esters and are responsible for secretion of retinol bound to retinol-binding protein (RBP) to maintain plasma retinol levels. Stellate Cells are the body's major Cellular storage sites for retinoid. We have character- ized and utilized an immortalized rat Stellate Cell line, HSC- T6 Cells, to facilitate study of the Cellular aspects of hepatic retinoid processing. For comparison, we also carried out parallel studies in Hepa-1 hepatocytes. Like activated pri- mary Stellate Cells, HSC-T6 express myogenic and neural crest cytoskeletal filaments. HSC-T6 Cells take up and ester- ify retinol in a time- and concentration-dependent manner. Supplementation of HSC-T6 culture medium with free fatty acids (up to 300 m M ) does not affect retinol uptake but does enhance retinol esterification up to 10-fold. RT-PCR analy- sis indicates that HSC-T6 Cells express all 6 retinoid nuclear receptors (RAR a , - b , - g , and RXR a , - b , - g ) and like primary Stellate Cells, HSC-T6 Stellate Cells express Cellular retinol- binding protein, type I (CRBP) but fail to express either retinol-binding protein (RBP) or transthyretin (TTR). Addi- tion of retinol (10 2 8 -10 2 5 M ) or all- trans -retinoic acid (10 2 10 - 10 2 6 M ) rapidly up-regulates CRBP expression. Using RAR- specific agonists and antagonists and an RXR-specific ago- nist, we show that members of the RAR-receptor family modulate HSC-T6 CRBP expression. Thus, HSC-T6 Cells display the same retinoid-related phenotype as primary stel- late Cells in culture and will be a useful tool for study of he- patic retinoid storage and metabolism. —Vogel, S., R. Pian- tedosi, J. Frank, A. Lalazar, D. C. Rockey, S. L. Friedman, and W. S. Blaner. An immortalized rat liver Stellate Cell line (HSC-T6): a new Cell model for the study of retinoid metab- olism in vitro. J. Lipid Res. 2000. 41: 882-893.
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an immortalized rat liver Stellate Cell line hsc t6 a new Cell model for the study of retinoid metabolism in vitro
Journal of Lipid Research, 2000Co-Authors: Silke Vogel, Scott L Friedman, Roseann Piantedosi, Jorge Frank, Avraham Lalazar, Don C Rockey, William S. BlanerAbstract:Hepatocytes and hepatic Stellate Cells play important roles in retinoid storage and metabolism. Hepatocytes process postprandial retinyl esters and are responsible for secretion of retinol bound to retinol-binding protein (RBP) to maintain plasma retinol levels. Stellate Cells are the body's major Cellular storage sites for retinoid. We have characterized and utilized an immortalized rat Stellate Cell line, HSC-T6 Cells, to facilitate study of the Cellular aspects of hepatic retinoid processing. For comparison, we also carried out parallel studies in Hepa-1 hepatocytes. Like activated primary Stellate Cells, HSC-T6 express myogenic and neural crest cytoskeletal filaments. HSC-T6 Cells take up and esterify retinol in a time- and concentration-dependent manner. Supplementation of HSC-T6 culture medium with free fatty acids (up to 300 micrometer) does not affect retinol uptake but does enhance retinol esterification up to 10-fold. RT-PCR analysis indicates that HSC-T6 Cells express all 6 retinoid nuclear receptors (RARalpha, -beta, -gamma, and RXRalpha, -beta, -gamma) and like primary Stellate Cells, HSC-T6 Stellate Cells express Cellular retinol-binding protein, type I (CRBP) but fail to express either retinol-binding protein (RBP) or transthyretin (TTR). Addition of retinol (10(-8)-10(-5) m) or all-trans-retinoic acid (10(-10)-10(-6) m) rapidly up-regulates CRBP expression. Using RAR-specific agonists and antagonists and an RXR-specific agonist, we show that members of the RAR-receptor family modulate HSC-T6 CRBP expression.Thus, HSC-T6 Cells display the same retinoid-related phenotype as primary Stellate Cells in culture and will be a useful tool for study of hepatic retinoid storage and metabolism.
Elmar R Burchardt - One of the best experts on this subject based on the ideXlab platform.
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the role of tgfβ1 in initiating hepatic Stellate Cell activation in vivo
Journal of Hepatology, 1999Co-Authors: C Hellerbrand, Branko Stefanovic, Frank Giordano, Elmar R BurchardtAbstract:Abstract Background/Aims: The activation of hepatic Stellate Cells is a key initiating event in hepatic fibrogenesis. Although TGFβ1 is a potent inducer of collagen α1(I) expression in vitro and elevated levels of TGFβ1 are found in patients and experimental animals with hepatic fibrosis and cirrhosis, the role of increased TGFβ1 in the initiation of hepatic Stellate Cell activation in vivo is unknown. We used two experimental approaches to study this relationship: 1) Induction of an acute liver injury with carbon tetrachloride (CCl 4 ) in normal and TGFβ1-knockout (ko) mice, and 2) overexpression of TGFβ1 in the liver of wild-type mice using a recombinant replication-deficient adenovirus encoding human TGFβ1 (Ad-TGFβ1). Methods: TGFβ1-ko mice ( n =6) and normal mice ( n =6) were injected once intraperitoneally (ip) with CCl 4 (1 μl/g BW) or mineral oil. Wild-type mice ( n =3) were injected intravenously with Ad-TGFβ1 (10 10 pfu) or a control virus expressing β-galactosidase (Ad-LacZ, 10 10 pfu). Animals were sacrificed after 3 days and total liver RNA was prepared. The expression of collagen α1(I) mRNA normalized to GAPDH mRNA was measured by RNase protection assay, α-smooth muscle actin (α-sma) protein expression was analyzed by Western blotting. The expression of TGFβ1, TGFβ2, and TGFβ3 mRNAs were determined semi-quantitatively with RT-PCR. Results: The collagen α1(I) mRNA was increased 10-fold in CCl 4 -treated wild-type mice compared to the controls. This increase was reduced about 80% in the TGFβ1-ko mice. The TGFβ1 mRNA levels in the wild-type mice were proportional to the collagen α1(I) mRNA levels. α-sma, a marker of hepatic Stellate Cell activation, was expressed earlier and at a higher level in wild-type mice than TGFβ-ko mice after CCl 4 treatment. The Ad-TGFβ1 infected mice had 14-fold higher hepatic TGFβ protein levels and 15-fold higher collagen α1(I) mRNA levels than the Ad-LacZ-infected control mice. Collagen α1(I) mRNA levels were proportional to the transgenic TGFβ1 mRNA levels, while the endogenous TGFβ1 was only slightly higher than in the controls. TGFβ2 and TGFβ3 mRNA levels were elevated in CCl 4 -treated wild-type and TGFβ1-ko mice and in Ad-TGFβ1-infected mice compared to the controls. Conclusions: Absence of TGFβ1 inhibits hepatic collagen α1(I) mRNA and α-sma protein expression by the toxic stimulus CCl 4 , and targeted TGFβ1 overexpression increases collagen α1(I) mRNA and α-sma protein levels in the liver in vivo. Other TGFβ family members do not compensate for the TGFβ1 deficiency. This indicates that TGFβ1 accelerates, but is not absolutely required, for the activation of hepatic Stellate Cells.
Silke Vogel - One of the best experts on this subject based on the ideXlab platform.
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an immortalized rat liver Stellate Cell line hsc t6 a new Cell model for the study of retinoid metabolism in vitro
Journal of Lipid Research, 2000Co-Authors: Silke Vogel, Scott L Friedman, Roseann Piantedosi, Jorge Frank, Avraham Lalazar, Don C Rockey, William S. BlanerAbstract:Hepatocytes and hepatic Stellate Cells play impor- tant roles in retinoid storage and metabolism. Hepatocytes process postprandial retinyl esters and are responsible for secretion of retinol bound to retinol-binding protein (RBP) to maintain plasma retinol levels. Stellate Cells are the body's major Cellular storage sites for retinoid. We have character- ized and utilized an immortalized rat Stellate Cell line, HSC- T6 Cells, to facilitate study of the Cellular aspects of hepatic retinoid processing. For comparison, we also carried out parallel studies in Hepa-1 hepatocytes. Like activated pri- mary Stellate Cells, HSC-T6 express myogenic and neural crest cytoskeletal filaments. HSC-T6 Cells take up and ester- ify retinol in a time- and concentration-dependent manner. Supplementation of HSC-T6 culture medium with free fatty acids (up to 300 m M ) does not affect retinol uptake but does enhance retinol esterification up to 10-fold. RT-PCR analy- sis indicates that HSC-T6 Cells express all 6 retinoid nuclear receptors (RAR a , - b , - g , and RXR a , - b , - g ) and like primary Stellate Cells, HSC-T6 Stellate Cells express Cellular retinol- binding protein, type I (CRBP) but fail to express either retinol-binding protein (RBP) or transthyretin (TTR). Addi- tion of retinol (10 2 8 -10 2 5 M ) or all- trans -retinoic acid (10 2 10 - 10 2 6 M ) rapidly up-regulates CRBP expression. Using RAR- specific agonists and antagonists and an RXR-specific ago- nist, we show that members of the RAR-receptor family modulate HSC-T6 CRBP expression. Thus, HSC-T6 Cells display the same retinoid-related phenotype as primary stel- late Cells in culture and will be a useful tool for study of he- patic retinoid storage and metabolism. —Vogel, S., R. Pian- tedosi, J. Frank, A. Lalazar, D. C. Rockey, S. L. Friedman, and W. S. Blaner. An immortalized rat liver Stellate Cell line (HSC-T6): a new Cell model for the study of retinoid metab- olism in vitro. J. Lipid Res. 2000. 41: 882-893.
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an immortalized rat liver Stellate Cell line hsc t6 a new Cell model for the study of retinoid metabolism in vitro
Journal of Lipid Research, 2000Co-Authors: Silke Vogel, Scott L Friedman, Roseann Piantedosi, Jorge Frank, Avraham Lalazar, Don C Rockey, William S. BlanerAbstract:Hepatocytes and hepatic Stellate Cells play important roles in retinoid storage and metabolism. Hepatocytes process postprandial retinyl esters and are responsible for secretion of retinol bound to retinol-binding protein (RBP) to maintain plasma retinol levels. Stellate Cells are the body's major Cellular storage sites for retinoid. We have characterized and utilized an immortalized rat Stellate Cell line, HSC-T6 Cells, to facilitate study of the Cellular aspects of hepatic retinoid processing. For comparison, we also carried out parallel studies in Hepa-1 hepatocytes. Like activated primary Stellate Cells, HSC-T6 express myogenic and neural crest cytoskeletal filaments. HSC-T6 Cells take up and esterify retinol in a time- and concentration-dependent manner. Supplementation of HSC-T6 culture medium with free fatty acids (up to 300 micrometer) does not affect retinol uptake but does enhance retinol esterification up to 10-fold. RT-PCR analysis indicates that HSC-T6 Cells express all 6 retinoid nuclear receptors (RARalpha, -beta, -gamma, and RXRalpha, -beta, -gamma) and like primary Stellate Cells, HSC-T6 Stellate Cells express Cellular retinol-binding protein, type I (CRBP) but fail to express either retinol-binding protein (RBP) or transthyretin (TTR). Addition of retinol (10(-8)-10(-5) m) or all-trans-retinoic acid (10(-10)-10(-6) m) rapidly up-regulates CRBP expression. Using RAR-specific agonists and antagonists and an RXR-specific agonist, we show that members of the RAR-receptor family modulate HSC-T6 CRBP expression.Thus, HSC-T6 Cells display the same retinoid-related phenotype as primary Stellate Cells in culture and will be a useful tool for study of hepatic retinoid storage and metabolism.
