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Cunningham RP, Porat-Shliom N. Liver Zonation - Revisiting Old Questions With New Technologies. Front Physiol 2021; 12:732929. [PMID: 34566696 PMCID: PMC8458816 DOI: 10.3389/fphys.2021.732929] [Citation(s) in RCA: 60] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Accepted: 08/10/2021] [Indexed: 12/12/2022] Open
Abstract
Despite the ever-increasing prevalence of non-alcoholic fatty liver disease (NAFLD), the etiology and pathogenesis remain poorly understood. This is due, in part, to the liver's complex physiology and architecture. The liver maintains glucose and lipid homeostasis by coordinating numerous metabolic processes with great efficiency. This is made possible by the spatial compartmentalization of metabolic pathways a phenomenon known as liver zonation. Despite the importance of zonation to normal liver function, it is unresolved if and how perturbations to liver zonation can drive hepatic pathophysiology and NAFLD development. While hepatocyte heterogeneity has been identified over a century ago, its examination had been severely hindered due to technological limitations. Recent advances in single cell analysis and imaging technologies now permit further characterization of cells across the liver lobule. This review summarizes the advances in examining liver zonation and elucidating its regulatory role in liver physiology and pathology. Understanding the spatial organization of metabolism is vital to further our knowledge of liver disease and to provide targeted therapeutic avenues.
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Affiliation(s)
- Rory P Cunningham
- Thoracic and GI Malignancies Branch, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, MD, United States
| | - Natalie Porat-Shliom
- Thoracic and GI Malignancies Branch, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, MD, United States
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2
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Mitani S, Takayama K, Nagamoto Y, Imagawa K, Sakurai F, Tachibana M, Sumazaki R, Mizuguchi H. Human ESC/iPSC-Derived Hepatocyte-like Cells Achieve Zone-Specific Hepatic Properties by Modulation of WNT Signaling. Mol Ther 2017; 25:1420-1433. [PMID: 28462819 DOI: 10.1016/j.ymthe.2017.04.006] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2016] [Revised: 04/02/2017] [Accepted: 04/05/2017] [Indexed: 01/05/2023] Open
Abstract
The function of hepatocytes largely depends on their position in the liver lobule. Although the method of differentiating hepatocytes from human pluripotent stem cells has been largely improved over the past decade, there remains no technique for generating hepatocyte-like cells (HLCs) with zone-specific hepatic properties. In this study, we searched for the factors that promote acquisition of zone-specific properties of HLCs. Here, we identified that WNT7B and WNT8B secreted from hepatocytes and cholangiocytes play important roles in achieving perivenous zone-specific characteristics, such as the enhancement of glutamine secretion, citric acid cycle, cytochrome P450 (CYP) 1A2 metabolism, and CYP1A2 induction capacities. We also found that WNT inhibitory factor (WIF-1) secreted from cholangiocytes was necessary for achieving periportal zone-specific characteristics, such as the enhancement of urea secretion and gluconeogenesis capacities. Therefore, WNT signal modulators secreted from hepatocytes or cholangiocytes conferred zone-specific hepatic properties onto HLCs.
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Affiliation(s)
- Seiji Mitani
- Laboratory of Biochemistry and Molecular Biology, Graduate School of Pharmaceutical Sciences, Osaka University, Osaka 565-0871, Japan
| | - Kazuo Takayama
- Laboratory of Biochemistry and Molecular Biology, Graduate School of Pharmaceutical Sciences, Osaka University, Osaka 565-0871, Japan; PRESTO, Japan Science and Technology Agency, Saitama 332-0012, Japan; K-CONNEX, Kyoto University, Kyoto 606-8302, Japan; Laboratory of Hepatocyte Regulation, National Institute of Biomedical Innovation, Health and Nutrition, Osaka 567-0085, Japan
| | - Yasuhito Nagamoto
- Laboratory of Biochemistry and Molecular Biology, Graduate School of Pharmaceutical Sciences, Osaka University, Osaka 565-0871, Japan; Laboratory of Hepatocyte Regulation, National Institute of Biomedical Innovation, Health and Nutrition, Osaka 567-0085, Japan
| | - Kazuo Imagawa
- Department of Child Health, Faculty of Medicine, University of Tsukuba, Ibaragi 305-8575, Japan
| | - Fuminori Sakurai
- Laboratory of Biochemistry and Molecular Biology, Graduate School of Pharmaceutical Sciences, Osaka University, Osaka 565-0871, Japan; Laboratory of Regulatory Sciences for Oligonucleotide Therapeutics, Clinical Drug Development Project, Graduate School of Pharmaceutical Sciences, Osaka University Osaka 565-0871, Japan
| | - Masashi Tachibana
- Laboratory of Biochemistry and Molecular Biology, Graduate School of Pharmaceutical Sciences, Osaka University, Osaka 565-0871, Japan
| | - Ryo Sumazaki
- Department of Child Health, Faculty of Medicine, University of Tsukuba, Ibaragi 305-8575, Japan
| | - Hiroyuki Mizuguchi
- Laboratory of Biochemistry and Molecular Biology, Graduate School of Pharmaceutical Sciences, Osaka University, Osaka 565-0871, Japan; Laboratory of Hepatocyte Regulation, National Institute of Biomedical Innovation, Health and Nutrition, Osaka 567-0085, Japan; Global Center for Medical Engineering and Informatics, Osaka University, Osaka 565-0871, Japan.
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Preference of Conjugated Bile Acids over Unconjugated Bile Acids as Substrates for OATP1B1 and OATP1B3. PLoS One 2017; 12:e0169719. [PMID: 28060902 PMCID: PMC5218478 DOI: 10.1371/journal.pone.0169719] [Citation(s) in RCA: 76] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2016] [Accepted: 12/20/2016] [Indexed: 12/12/2022] Open
Abstract
Bile acids, the metabolites of cholesterol, are signaling molecules that play critical role in many physiological functions. They undergo enterohepatic circulation through various transporters expressed in intestine and liver. Human organic anion-transporting polypeptides (OATP) 1B1 and OATP1B3 contribute to hepatic uptake of bile acids such as taurocholic acid. However, the transport properties of individual bile acids are not well understood. Therefore, we selected HEK293 cells overexpressing OATP1B1 and OATP1B3 to evaluate the transport of five major human bile acids (cholic acid, chenodeoxycholic acid, deoxycholic acid, ursodeoxycholic acid, lithocholic acid) together withtheir glycine and taurine conjugates via OATP1B1 and OATP1B3. The bile acids were quantified by liquid chromatography-tandem mass spectrometry. The present study revealed that cholic acid, chenodeoxyxcholic acid, and deoxycholic acid were transported by OATP1B1 and OATP1B3, while ursodeoxycholic acid and lithocholic acid were not significantly transported by OATPs. However, all the conjugated bile acids were taken up rapidly by OATP1B1 and OATP1B3. Kinetic analyses revealed the involvement of saturable OATP1B1- and OATP1B3-mediated transport of bile acids. The apparent Km values for OATP1B1 and OATP1B3 of the conjugated bile acids were similar (0.74-14.7 μM for OATP1B1 and 0.47-15.3 μM for OATP1B3). They exhibited higher affinity than cholic acid (47.1 μM for OATP1B1 and 42.2 μM for OATP1B3). Our results suggest that conjugated bile acids (glycine and taurine) are preferred to unconjugated bile acids as substrates for OATP1B1 and OATP1B3.
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Murray JW, Han D, Wolkoff AW. Hepatocytes maintain greater fluorescent bile acid accumulation and greater sensitivity to drug-induced cell death in three-dimensional matrix culture. Physiol Rep 2014; 2:2/12/e12198. [PMID: 25524275 PMCID: PMC4332201 DOI: 10.14814/phy2.12198] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2022] Open
Abstract
Primary hepatocytes undergo phenotypic dedifferentiation upon isolation from liver that typically includes down regulation of uptake transporters and up regulation of efflux transporters. Culturing cells between layers of collagen in a three‐dimensional (3D) “sandwich” is reported to restore hepatic phenotype. This report examines how 3D culturing affects accumulation of fluorophores, the cytotoxic response to bile acids and drugs, and whether cell to cell differences in fluorescent anion accumulation correlate with differences in cytotoxicity. Hepatocytes were found to accumulate fluorescent bile acid (FBA) at significantly higher levels than the related fluorophores, carboxyfluorescein diacetate, (4.4‐fold), carboxyfluorescein succinimidyl ester (4.8‐fold), and fluorescein (30‐fold). In 2D culture, FBA accumulation decreased to background levels by 32 h, Hoechst nuclear accumulation strongly decreased, and nuclear diameter increased, indicative of an efflux phenotype. In 3D culture, FBA accumulation was maintained through 168 h but at 1/3 the original intensity. Cell to cell differences in accumulated FBA did not correlate with levels of liver zonal markers L‐FBAP (zone 1) or glutamine synthetase (zone 3). Cytotoxic response to hydrophobic bile acids, acetaminophen, and phalloidin was maintained in 3D culture, and cells with higher FBA accumulation showed 12–18% higher toxicity than the total population toward hydrophobic bile acids (P < 0.05). Long‐term imaging showed oscillations in the accumulation of FBA over periods of hours. Overall, the studies suggest that high accumulation of FBA can indicate the sensitivity of cultured hepatocytes to hydrophobic bile acids and other toxins. These studies use automated image analysis and fluorescent dye accumulation to demonstrate that 3D culturing enhances organic anion accumulation and cytotoxic response in long‐term hepatocyte cultures. The level of anion accumulation was found to vary through days in culture and also between single cells, and higher fluorescent bile acid accumulation correlated with higher toxic response to hydrophobic bile acids.
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Affiliation(s)
- John W Murray
- Department of Anatomy and Structural Biology, Division of Gastroenterology and Liver Diseases, Marion Bessin Liver Research Center, Albert Einstein College of Medicine, Montefiore Medical Center, Bronx, New York
| | - Dennis Han
- Department of Anatomy and Structural Biology, Division of Gastroenterology and Liver Diseases, Marion Bessin Liver Research Center, Albert Einstein College of Medicine, Montefiore Medical Center, Bronx, New York
| | - Allan W Wolkoff
- Department of Anatomy and Structural Biology, Division of Gastroenterology and Liver Diseases, Marion Bessin Liver Research Center, Albert Einstein College of Medicine, Montefiore Medical Center, Bronx, New York
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5
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Csanaky IL, Aleksunes LM, Tanaka Y, Klaassen CD. Role of hepatic transporters in prevention of bile acid toxicity after partial hepatectomy in mice. Am J Physiol Gastrointest Liver Physiol 2009; 297:G419-33. [PMID: 19497955 PMCID: PMC2739828 DOI: 10.1152/ajpgi.90728.2008] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The enterohepatic recirculation of bile acids (BAs) is important in several physiological processes. Although there has been considerable research on liver regeneration after two-thirds partial hepatectomy (PHx), little is known about how the liver protects itself against BA toxicity during regeneration. In this study, various BAs in plasma and liver, the composition of micelle-forming bile constituents, as well as gene expression of the main hepatobiliary transporters were quantified in sham-operated and PHx mice 24 and 48 h after surgery. PHx did not influence the hepatic concentrations of taurine-conjugated BAs (T-BA) but increased the concentration of glycine-conjugated (G-BA) and unconjugated BAs. Total BA excretion (microg x min(-1) x g liver wt(-1)) increased 2.4-fold and was accompanied by a 55% increase in bile flow after PHx. The plasma concentrations of T-BAs (402-fold), G-BAs (17-fold), and unconjugated BAs (500-fold) increased. The mRNA and protein levels of the BA uptake transporter Ntcp were unchanged after PHx, whereas the canalicular Bsep protein increased twofold at 48 h. The basolateral efflux transporter Mrp3 was induced at the mRNA (2.6-fold) and protein (3.1-fold) levels after PHx, which may contribute to elevated plasma BA and bilirubin levels. Biliary phospholipid excretion was nearly doubled in PHx mice, most likely owing to increased mRNA expression of the phospholipid transporter, Mdr2. In conclusion, the remnant liver after PHx excretes 2.5-fold more BAs and three times more phospholipids per gram liver than the sham-operated mouse liver. Upregulation of phospholipid transport may be important in protecting the biliary tract from BA toxicity during PHx.
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Affiliation(s)
- Iván L. Csanaky
- Department of Pharmacology, Toxicology, and Therapeutics, University of Kansas Medical Center, Kansas City, Kansas
| | - Lauren M. Aleksunes
- Department of Pharmacology, Toxicology, and Therapeutics, University of Kansas Medical Center, Kansas City, Kansas
| | - Yuji Tanaka
- Department of Pharmacology, Toxicology, and Therapeutics, University of Kansas Medical Center, Kansas City, Kansas
| | - Curtis D. Klaassen
- Department of Pharmacology, Toxicology, and Therapeutics, University of Kansas Medical Center, Kansas City, Kansas
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6
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Conolly RB. Commentary on "Toxicity testing in the 21st century: implications for human health risk assessment" by Krewski et al. RISK ANALYSIS : AN OFFICIAL PUBLICATION OF THE SOCIETY FOR RISK ANALYSIS 2009; 29:480-497. [PMID: 19076324 DOI: 10.1111/j.1539-6924.2008.01165.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Affiliation(s)
- Rory B Conolly
- National Center for Computational Toxicology, Office of Research and Development, U.S. Environmental Protection Agency, MD B205-01, Research Triangle Park, NC 27711, USA.
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Fouassier L, Beaussier M, Schiffer E, Rey C, Barbu V, Mergey M, Wendum D, Callard P, Scoazec JY, Lasnier E, Stieger B, Lienhart A, Housset C. Hypoxia-induced changes in the expression of rat hepatobiliary transporter genes. Am J Physiol Gastrointest Liver Physiol 2007; 293:G25-35. [PMID: 17615179 DOI: 10.1152/ajpgi.00175.2006] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Cholestatic disorders may arise from liver ischemia (e.g., in liver transplantation) through various mechanisms. We have examined the potential of hypoxia to induce changes in the expression of hepatobiliary transporter genes. In a model of arterial liver ischemia subsequent to complete arterial deprivation of the rat liver, the mRNA levels of VEGF, a hypoxia-inducible gene, were increased fivefold after 24 h. The pattern of VEGF-induced expression and ultrastructural changes, including swelling of the endoplasmic reticulum, indicated that hypoxia affected primarily cholangiocytes, but also hepatocytes, predominantly in the periportal area. Serum and bile analyses demonstrated liver dysfunction of cholestatic type with reduced bile acid biliary excretion. Fluorescence-labeled ursodeoxycholic acid used as a tracer displayed no regurgitation, eliminating bile leakage as a significant mechanism of cholestasis in this model. In liver tissue, a marked reduction in the mRNA levels of Na(+)-taurocholate-cotransporting polypeptide (Ntcp), bile salt export protein (Bsep), and multidrug resistance-associated protein 2 (Mrp2) and an increase in those of Cftr were detected before bile duct proliferation occurred. In cultured hepatocytes, a nontoxic hypoxic treatment caused a decrease in the mRNA and protein expression of Ntcp, Bsep, and Mrp2 and in the mRNA levels of nuclear factors involved in the transactivation of these genes, i.e., HNF4alpha, RXRalpha, and FXR. In bile duct preparations, hypoxic treatment elicited an increase in Cftr transcripts, along with a rise in cAMP, a major regulator of Cftr expression and function. In conclusion, hypoxia triggers a downregulation of hepatocellular transporters, which may contribute to cholestasis, whereas Cftr, which drives secretion in cholangiocytes, is upregulated.
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Affiliation(s)
- Laura Fouassier
- INSERM U680, Faculté de Médecine Pierre et Marie Curie, Site Saint-Antoine, 27 rue Chaligny, 75571 Paris Cedex 12, France
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8
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Alrefai WA, Gill RK. Bile acid transporters: structure, function, regulation and pathophysiological implications. Pharm Res 2007; 24:1803-23. [PMID: 17404808 DOI: 10.1007/s11095-007-9289-1] [Citation(s) in RCA: 323] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2007] [Accepted: 02/28/2007] [Indexed: 12/11/2022]
Abstract
Specific transporters expressed in the liver and the intestine, play a critical role in driving the enterohepatic circulation of bile acids. By preserving a circulating pool of bile acids, an important factor influencing bile flow, these transporters are involved in maintaining bile acid and cholesterol homeostasis. Enterohepatic circulation of bile acids is fundamentally composed of two major processes: secretion from the liver and absorption from the intestine. In the hepatocytes, the vectorial transport of bile acids from blood to bile is ensured by Na+ taurocholate co-transporting peptide (NTCP) and organic anion transport polypeptides (OATPs). After binding to a cytosolic bile acid binding protein, bile acids are secreted into the canaliculus via ATP-dependent bile salt excretory pump (BSEP) and multi drug resistant proteins (MRPs). Bile acids are then delivered to the intestinal lumen through bile ducts where they emulsify dietary lipids and cholesterol to facilitate their absorption. Intestinal epithelial cells reabsorb the majority of the secreted bile acids through the apical sodium dependent bile acid transporter (ASBT) and sodium independent organic anion transporting peptide (OATPs). Cytosolic ileal bile acid binding protein (IBABP) mediates the transcellular movement of bile acids to the basolateral membrane across which they exit the cells via organic solute transporters (OST). An essential role of bile acid transporters is evident from the pathology associated with their genetic disruption or dysregulation of their function. Malfunctioning of hepatic and intestinal bile acid transporters is implicated in the pathophysiology of cholestatic liver disease and the depletion of circulating pool of bile acids, respectively. Extensive efforts have been recently made to enhance our understanding of the structure, function and regulation of the bile acid transporters and exploring new potential therapeutics to treat bile acid or cholesterol related diseases. This review will highlight current knowledge about structure, function and molecular characterization of bile acid transporters and discuss the implications of their defects in various hepatic and intestinal disorders.
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Affiliation(s)
- Waddah A Alrefai
- Section of Digestive Diseases and Nutrition, Department of Medicine, University of Illinois at Chicago, Chicago, Illinois 60612, USA.
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Trauner M, Boyer JL. Bile salt transporters: molecular characterization, function, and regulation. Physiol Rev 2003; 83:633-71. [PMID: 12663868 DOI: 10.1152/physrev.00027.2002] [Citation(s) in RCA: 668] [Impact Index Per Article: 31.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Molecular medicine has led to rapid advances in the characterization of hepatobiliary transport systems that determine the uptake and excretion of bile salts and other biliary constituents in the liver and extrahepatic tissues. The bile salt pool undergoes an enterohepatic circulation that is regulated by distinct bile salt transport proteins, including the canalicular bile salt export pump BSEP (ABCB11), the ileal Na(+)-dependent bile salt transporter ISBT (SLC10A2), and the hepatic sinusoidal Na(+)- taurocholate cotransporting polypeptide NTCP (SLC10A1). Other bile salt transporters include the organic anion transporting polypeptides OATPs (SLC21A) and the multidrug resistance-associated proteins 2 and 3 MRP2,3 (ABCC2,3). Bile salt transporters are also present in cholangiocytes, the renal proximal tubule, and the placenta. Expression of these transport proteins is regulated by both transcriptional and posttranscriptional events, with the former involving nuclear hormone receptors where bile salts function as specific ligands. During bile secretory failure (cholestasis), bile salt transport proteins undergo adaptive responses that serve to protect the liver from bile salt retention and which facilitate extrahepatic routes of bile salt excretion. This review is a comprehensive summary of current knowledge of the molecular characterization, function, and regulation of bile salt transporters in normal physiology and in cholestatic liver disease and liver regeneration.
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Affiliation(s)
- Michael Trauner
- Division of Gastroenterology and Hepatology, Department of Internal Medicine, Karl-Franzens University, School of Medicine, Graz, Austria
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Twisk J, Hoekman MF, Mager WH, Moorman AF, de Boer PA, Scheja L, Princen HM, Gebhardt R. Heterogeneous expression of cholesterol 7 alpha-hydroxylase and sterol 27-hydroxylase genes in the rat liver lobulus. J Clin Invest 1995; 95:1235-43. [PMID: 7883972 PMCID: PMC441462 DOI: 10.1172/jci117773] [Citation(s) in RCA: 52] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
We investigated the lobular localization and molecular level of expression of cholesterol 7 alpha-hydroxylase and sterol 27-hydroxylase, two key enzymes in bile acid synthesis, in isolated periportal and pericentral hepatocytes and by in situ hybridization of rat liver. Enzyme activity, mRNA, and gene transcription of cholesterol 7 alpha-hydroxylase were predominant in pericentral hepatocytes of control rats, being 7.9-, 9.9-, and 4.4-fold higher than in periportal hepatocytes, respectively. Similar localization was found for sterol 27-hydroxylase: 2.9-, 2.5-, and 1.7-fold higher enzyme activity, mRNA, and gene transcription, respectively, was found in pericentral hepatocytes. Interruption of the enterohepatic circulation with colestid resulted in upregulation of these parameters for both enzymes, as a consequence of stimulated gene expression mainly in the periportal zone. In contrast, mRNA levels and gene transcription of 3-hydroxy-3-methylglutaryl CoA reductase showed opposite lobular distribution. Selective periportal expression for the latter was enhanced, but remained local, after colestid treatment. In situ hybridization showed unambiguously that cholesterol 7 alpha-hydroxylase mRNA is localized exclusively in the pericentral zone and that sterol 27-hydroxylase mRNA is expressed preferentially in the pericentral region, though less pronounced. Administration of colestid led to expression of both genes within a larger area of the liver lobulus. In conclusion, we suggest that cholesterol 7 alpha-hydroxylase and sterol 27-hydroxylase are coordinately regulated by the bile acid gradient over the lobulus, resulting in predominant expression in the pericentral zone. Opposite lobular localization of cholesterol and bile acid synthesis provides an alternative view to interregulation of these metabolic pathways.
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Affiliation(s)
- J Twisk
- Gaubius Laboratory, TNO-PG, Leiden, The Netherlands
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Twisk J, de Wit EC, Princen HM. Suppression of sterol 27-hydroxylase mRNA and transcriptional activity by bile acids in cultured rat hepatocytes. Biochem J 1995; 305 ( Pt 2):505-11. [PMID: 7832767 PMCID: PMC1136391 DOI: 10.1042/bj3050505] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
In previous work we have demonstrated suppression of cholesterol 7 alpha-hydroxylase by bile acids at the level of mRNA and transcription, resulting in a similar decline in bile acid synthesis in cultured rat hepatocytes [Twisk, Lehmann and Princen (1993) Biochem. J. 290, 685-691]. In view of the substantial contribution of the 'alternative' or '27-hydroxylase' route to total bile acid synthesis, as demonstrated in cultured rat hepatocytes and in vivo in humans, we here evaluate the effects of various bile acids commonly found in bile of rats on the regulation of sterol 27-hydroxylase in cultured rat hepatocytes. Addition of taurocholic acid, the predominant bile acid in rat bile, to the culture medium of rat hepatocytes resulted in a 72% inhibition of sterol 27-hydroxylase activity. The effect was exerted at the level of sterol 27-hydroxylase mRNA, showing a time- and dose-dependent decline with a maximal suppression (-75%) at 50 microM taurocholic acid after 24 h of culture. The decline in mRNA followed first-order kinetics with an apparent half-life of 13 h. Under these conditions cholesterol 7 alpha-hydroxylase mRNA (-91%) and bile acid synthesis (i.e. chenodeoxycholic and beta-muricholic acid, -81%) were also maximally suppressed. In contrast, no change was found in the level of lithocholic acid 6 beta-hydroxylase mRNA. Assessment of the transcriptional activity of a number of genes involved in routing of cholesterol towards bile acids showed similar suppressive effects of taurocholate on expression of the sterol 27-hydroxylase and cholesterol 7 alpha-hydroxylase genes (-43% and -42% respectively), whereas expression of the lithocholic 6 beta-hydroxylase gene was not affected. Taurocholic acid and unconjugated cholic acid were equally as effective in suppressing sterol 27-hydroxylase mRNA. The more hydrophobic bile acids, chenodeoxycholic acid and deoxycholic acid, also produced a strong inhibition of 57% and 76% respectively, whereas the hydrophilic beta-muricholic acid was not active. We conclude that (1) a number of bile acids, at physiological concentrations, suppress sterol 27-hydroxylase by down-regulation of sterol 27-hydroxylase mRNA and transcriptional activity and (2) co-ordinated suppression of both sterol 27-hydroxylase and cholesterol 7 alpha-hydroxylase results in inhibition of bile acid synthesis in cultured rat hepatocytes.
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Affiliation(s)
- J Twisk
- Gaubius Laboratory TNO-PG, Leiden, The Netherlands
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12
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Ugele B, Kempen HJ, Kempen JM, Gebhardt R, Meijer P, Burger HJ, Princen HM. Heterogeneity of rat liver parenchyma in cholesterol 7 alpha-hydroxylase and bile acid synthesis. Biochem J 1991; 276 ( Pt 1):73-7. [PMID: 2039484 PMCID: PMC1151145 DOI: 10.1042/bj2760073] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Periportal and perivenous hepatocytes were isolated from rat liver by digitonin/collagenase perfusion for investigating the acinar distribution of bile acid synthesis. The specific activity of cholesterol 7 alpha-hydroxylase (EC 1.14.13.17) was 7.9-fold higher in perivenous cells than in periportal hepatocytes. Mass production of bile acids differed 4.4-fold between cultured perivenous and periportal hepatocytes. In contrast, the levels of free cholesterol in homogenates and microsomes derived from both subfractions were similar. Feeding of rats with the bile-acid-sequestering anion-exchange resin colestid resulted in a pronounced stimulation of cholesterol 7 alpha-hydroxylase activity and bile acid mass production, but decreased the perivenous/periportal ratio of both parameters. These results demonstrate that bile acid mass production, but decreased the perivenous hepatocytes, possibly owing to feedback suppression by bile acids from the enterohepatic circulation. Furthermore, the opposite acinar localization of cholesterol and bile acid biosynthesis provides an interesting alternative to current views of the regulation of their metabolic pathways.
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Affiliation(s)
- B Ugele
- Physiologisch-Chemisches Institut, Universität Tübingen, Federal Republic of Germany
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13
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Smit MJ, Temmerman AM, Havinga R, Kuipers F, Vonk RJ. Short- and long-term effects of biliary drainage on hepatic cholesterol metabolism in the rat. Biochem J 1990; 269:781-8. [PMID: 2390068 PMCID: PMC1131655 DOI: 10.1042/bj2690781] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The present study concerns short- and long-term effects of interruption of the enterohepatic circulation (EHC) on hepatic cholesterol metabolism and biliary secretion in rats. For this purpose, we employed a technique that allows reversible interruption of the EHC, during normal feeding conditions, and excludes effects of anaesthesia and surgical trauma. [3H]Cholesteryl oleate-labelled human low-density lipoprotein (LDL) was injected intravenously in rats with (1) chronically (8 days) interrupted EHC, (2) interrupted EHC at the time of LDL injection and (3) intact EHC. During the first 3 h after interruption of the EHC, bile flow decreased to 50% and biliary bile acid, phospholipid and cholesterol secretion to 5%, 11% and 19% of their initial values respectively. After 8 days of bile diversion, biliary cholesterol output and bile flow were at that same level, but bile acid output was increased 2-3-fold and phospholipid output was about 2 times lower. The total amount of cholesterol in the liver decreased after interruption of the EHC, which was mainly due to a decrease in the amount of cholesteryl ester. Plasma disappearance of LDL was not affected by interruption of the EHC. Biliary secretion of LDL-derived radioactivity occurred 2-4 times faster in chronically interrupted rats as compared with the excretion immediately after interruption of the EHC. Radioactivity was mainly in the form of bile acids under both conditions. This study demonstrates the very rapid changes that occur in cholesterol metabolism and biliary lipid composition after interruption of the EHC. These changes must be taken into account in studies concerning hepatic metabolism of lipoprotein cholesterol and subsequent secretion into bile.
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Affiliation(s)
- M J Smit
- Department of Pediatrics, University of Groningen, The Netherlands
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Abstract
A large number of histological, histochemical and biochemical techniques are available for studying liver cell heterogeneity. Structural differences are recognized by morphometric analyses of electron micrographs. The zonal heterogeneity of enzyme activities can be demonstrated by histochemistry and more precisely by ultramicrobiochemical assays in microdissected periportal and perivenous tissue. Immunohistochemistry is useful for quantifying and localizing proteins, especially isoenzymes, without depending on their biological activity. The zonal quantification of specific mRNA can be achieved by in situ hybridization. The different structural and enzymic equipment of periportal and perivenous tissue found by these techniques has led to the concept of metabolic zonation. This hypothesis can be confirmed by determination of metabolic rates in perfused liver after selective zonal damage, in separated periportal and perivenous hepatocytes as well as in periportal and perivenous tissue of perfused liver by non-invasive techniques.
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Affiliation(s)
- N R Katz
- Institut für Klinische Chemie und Pathobiochemie, Universitätsklinikum Giessen, Germany
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Lamri Y, Roda A, Dumont M, Feldmann G, Erlinger S. Immunoperoxidase localization of bile salts in rat liver cells. Evidence for a role of the Golgi apparatus in bile salt transport. J Clin Invest 1988; 82:1173-82. [PMID: 2459158 PMCID: PMC442667 DOI: 10.1172/jci113714] [Citation(s) in RCA: 71] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The mechanisms of intracellular transport of bile acids from the sinusoidal pole to the canalicular pole of the hepatocyte are poorly understood. There is physiological and autoradiographic evidence for a vesicular pathway. The purpose of this study was to determine the localization of natural bile acids in the liver using antibodies against cholic acid conjugates and ursodeoxycholic acid. An indirect immunoperoxidase technique was used on rat liver sections fixed either with paraformaldehyde (PF) and saponin, a membrane-permeabilizing agent that allows penetration of antibodies into the cell, or with PF alone. Retention of taurocholate in the liver after tissue processing was 26 +/- SD 15% of the bile acid initially present. When sections fixed with PF and saponin were incubated with the antibody against cholic acid conjugates, a granular cytoplasmic staining was observed by light microscopy in all hepatocytes. By electron microscopy, strong electron-dense deposits were observed mostly on vesicles of the Golgi apparatus (GA) and, sometimes, in the smooth endoplasmic reticulum (SER). After taurocholate infusion, the intensity of the reaction increased. When the liver was fixed with PF alone, almost no reaction was visible on light microscopy, but on electron microscopy the label was localized on the hepatocyte plasma membrane, mainly on the bile canalicular domain and to a lesser extent on the sinusoidal domain. With the antibody against ursodeoxycholic acid, no staining was observed in three of four livers, and a slight staining was observed in one. However, after infusion of ursodeoxycholic acid, staining of GA and SER vesicles was observed when the liver was fixed with PF and saponin. With PF alone, the reaction was intense on the canalicular membrane. These results support the view that, within the limits of the method, vesicles from the GA and possibly vesicles of the SER are involved in the intracellular transport of bile acids before canalicular secretion.
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Affiliation(s)
- Y Lamri
- Institut National de la Santé et de la Recherche Médicale U-24, Clichy, France
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Affiliation(s)
- R Coleman
- Department of Biochemistry, University of Birmingham, U.K
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Singer II, Kawka DW, Kazazis DM, Alberts AW, Chen JS, Huff JW, Ness GC. Hydroxymethylglutaryl-coenzyme A reductase-containing hepatocytes are distributed periportally in normal and mevinolin-treated rat livers. Proc Natl Acad Sci U S A 1984; 81:5556-60. [PMID: 6382266 PMCID: PMC391745 DOI: 10.1073/pnas.81.17.5556] [Citation(s) in RCA: 80] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Mevinolin is a potent inhibitor of 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMG-CoA reductase; EC 1.1.1.34), an enzyme that catalyzes the rate-limiting step in cholesterol biosynthesis. We have been studying the hepatic distribution of reductase with immunofluorescence microscopy and liver ultrastructure with electron microscopy in normal and drug-treated rats. In control animals, only about 20% of the hepatocytes were reductase positive. These cells were localized in the periportal lobular zones. The numbers of positive hepatocytes in animals given mevinolin or cholestyramine (or both) were directly proportional to the activities of the HMG-CoA reductase determined biochemically. This induction of HMG-CoA reductase immunofluorescence was centered periportally. Rats given 0.075% mevinolin alone had a homogeneous distribution of reductase staining in their hepatocyte cytoplasm, whereas a combination of 0.25% mevinolin and 3% cholestyramine caused a 150-fold increase in enzyme activity and induced prominent juxtanuclear immunofluorescent globules of HMG-CoA reductase in all hepatocytes. With electron microscopy, these bodies were composed of tightly packed stacks of smooth endoplasmic reticulum cysternae and aggregates of branched smooth endoplasmic reticulum tubules. Our data suggest that a subpopulation of periportal rat hepatocytes may be uniquely specialized for cholesterol synthesis.
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St Hilaire RJ, Hradek GT, Jones AL. Hepatic sequestration and biliary secretion of epidermal growth factor: evidence for a high-capacity uptake system. Proc Natl Acad Sci U S A 1983; 80:3797-801. [PMID: 6304738 PMCID: PMC394139 DOI: 10.1073/pnas.80.12.3797] [Citation(s) in RCA: 89] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Epidermal growth factor (EGF) promotes hepatocyte growth and is bound in the liver by specific receptors. We have determined hepatic uptake of EGF in intact rats after an intravenous or intraportal injection of a bolus of 125I-labeled EGF. Ninety-nine percent of the intraportal dose was taken up by the liver in 3 min, whereas only 58% of the intravenous dose appeared in the liver in 10 min. Uptake was inhibited by simultaneous treatment with an excess of unlabeled EGF. At time zero, uptake appeared to be complete. Disappearance from the liver followed first-order kinetics. Within 90 min of an intraportal injection, an average of 19% of the injected radioisotope appeared in bile, of which approximately one-fifth was shown to be immunoprecipitable with a specific anti-EGF antiserum. Light microscopic autoradiography demonstrated a very steep portal-to-central lobular concentration gradient consistent with a high-capacity uptake system. After intraportal injection or after incubation with cultured hepatocytes, labeled EGF was shown to be bound to its hepatic receptors. The main receptor-ligand complex had a Mr of approximately equal to 160,000-170,000, determined by NaDodSO4/polyacrylamide gel electrophoresis.
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Simon FR, Sutherland EM, Gonzalez M. Regulation of bile salt transport in rat liver. Evidence that increased maximum bile salt secretory capacity is due to increased cholic acid receptors. J Clin Invest 1982; 70:401-11. [PMID: 7096571 PMCID: PMC371249 DOI: 10.1172/jci110630] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Expansion of the bile salt pool size in rats increases maximum excretory capacity for taurocholate. We examined whether increased bile salt transport is due to recruitment of centrolobular transport units or rather to adaptive changes in the hepatocyte. Daily sodium cholate (100 mg/100 g body wt) was administered orally to rats. This treatment was well tolerated for at least 4 d and produced an 8.2-fold expansion of the bile salt pool. This expanded pool consisted predominently (99%) of cholic and deoxycholic acids. Significantly increased bile salt transport was not observed until 16 h after bile acid loading, and maximum elevations of transport capacity to 2.3-fold of control required approximately 2 d. In contrast, maximum sulfobromophthalein excretion rates increased 2.2-fold as early as 4 h and actually fell to 1.5-fold increase at 4 d. We studied the possibility that this adaptive increase in bile salt secretory transport was due to changes in canalicular surface membrane area, lipid composition, or increased number of putative carriers. Canalicular membrane protein recovery and the specific activities of leucine aminopeptidase, Mg(++)-ATPase and 5'-nucleotidase activities were unaltered by bile salt pool expansion. The content of free and esterified cholesterol and total phospholipids was unchanged in liver surface membrane fractions compared with control values. In contrast, sodium cholate administration selectively increased specific [(14)C]cholic acid binding sites twofold in liver surface membrane fractions. Increased numbers of [(14)C]cholic acid receptors (a) was associated with the time-dependent increase in bile salt transport, and (b) was selective for the taurine conjugate of cholate and (c) was reduced by chenodeoxycholate. Changes in bile acid binding sites 16 h following taurocholate and chenodeoxycholate and the lack of change with glycocholate was associated with comparable changes in bile salt transport. In conclusion, selective bile salts increase bile salt transport in the liver through an adaptive increase in the density of putative bile acid carriers in liver surface membrane.
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