201
|
Hellemans K, Rombouts K, Quartier E, Dittié AS, Knorr A, Michalik L, Rogiers V, Schuit F, Wahli W, Geerts A. PPARbeta regulates vitamin A metabolism-related gene expression in hepatic stellate cells undergoing activation. J Lipid Res 2003; 44:280-95. [PMID: 12576510 DOI: 10.1194/jlr.m200376-jlr200] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Activation of cultured hepatic stellate cells correlated with an enhanced expression of proteins involved in uptake and storage of fatty acids (FA translocase CD36, Acyl-CoA synthetase 2) and retinol (cellular retinol binding protein type I, CRBP-I; lecithin:retinol acyltransferases, LRAT). The increased expression of CRBP-I and LRAT during hepatic stellate cells activation, both involved in retinol esterification, was in contrast with the simultaneous depletion of their typical lipid-vitamin A (vitA) reserves. Since hepatic stellate cells express high levels of peroxisome proliferator activated receptor beta (PPARbeta), which become further induced during transition into the activated phenotype, we investigated the potential role of PPARbeta in the regulation of these changes. Administration of L165041, a PPARbeta-specific agonist, further induced the expression of CD36, B-FABP, CRBP-I, and LRAT, whereas their expression was inhibited by antisense PPARbeta mRNA. PPARbeta-RXR dimers bound to CRBP-I promoter sequences. Our observations suggest that PPARbeta regulates the expression of these genes, and thus could play an important role in vitA storage. In vivo, we observed a striking association between the enhanced expression of PPARbeta and CRBP-I in activated myofibroblast-like hepatic stellate cells and the manifestation of vitA autofluorescent droplets in the fibrotic septa after injury with CCl4 or CCl4 in combination with retinol.
Collapse
Affiliation(s)
- Karine Hellemans
- Laboratory of Molecular Liver Cell Biology, Vrije Universiteit Brussel, 1090 Brussels, Belgium.
| | | | | | | | | | | | | | | | | | | |
Collapse
|
202
|
Yang C, Zeisberg M, Mosterman B, Sudhakar A, Yerramalla U, Holthaus K, Xu L, Eng F, Afdhal N, Kalluri R. Liver fibrosis: insights into migration of hepatic stellate cells in response to extracellular matrix and growth factors. Gastroenterology 2003; 124:147-59. [PMID: 12512039 DOI: 10.1053/gast.2003.50012] [Citation(s) in RCA: 215] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
BACKGROUND & AIMS In liver fibrosis, alterations within the space of Disse microenvironment occur and facilitate further progression of chronic liver disease. The normal basement membrane-like matrix present within the space of Disse converts to a matrix rich in fibril-forming collagens during fibrosis. METHODS To further understand the pathogenesis of liver fibrosis, we modified an in vitro Boyden chamber system to partially mimic in vivo conditions of hepatic stellate cells (HSCs) during health and disease. RESULTS Stimulation of HSCs with platelet-derived growth factor (PDGF)-BB, transforming growth factor (TGF)-beta1, and/or epithelial growth factor (EGF) resulted in an increase in their migratory capacity and up-regulated matrix metalloproteinase (MMP)-2 activity. Migration induced by PDGF-BB was associated with increased proliferation, whereas TGF-beta1/EGF-induced migration was proliferation independent. COL-3, an inhibitor of MMP-2 and MMP-9, inhibited migration of HSCs induced by direct activation of PDGF-BB or TGF-beta1 but had no effect on migration induced by chemotactic stimuli without direct contact, suggesting 2 distinct MMP-dependent and MMP-independent mechanisms of PDGF-BB- or TGF-beta1-induced migration. Additionally, we show that type I collagen by itself induced migration of HSCs. Migration induced by PDGF-BB, TGF-beta1, and collagen I could be inhibited by alpha(1)- and/or alpha(2)-integrin blocking antibodies, collectively suggesting an integrin-dependent, MMP-2-mediated migration of HSCs. CONCLUSIONS Basement membrane matrix integrity, composition, and cell-matrix interactions play an important role in anchoring HSCs and preventing them from spreading within the space of Disse and potentially elsewhere in the liver. Additionally, our data provide strong evidence for MMPs in regulation of HSCs migration.
Collapse
Affiliation(s)
- Changqing Yang
- Program in Matrix Biology, Gastroenterology and Renal Divisions, Department of Medicine, Beth Israel Deaconess Medical Center, 330 Brookline Avenue, Boston, MA 02215, USA
| | | | | | | | | | | | | | | | | | | |
Collapse
|
203
|
Cassiman D, Roskams T. Beauty is in the eye of the beholder: emerging concepts and pitfalls in hepatic stellate cell research. J Hepatol 2002; 37:527-35. [PMID: 12217608 DOI: 10.1016/s0168-8278(02)00263-5] [Citation(s) in RCA: 110] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- David Cassiman
- Department of Internal Medicine, University Hospital Gasthuisberg, KU Leuven, Herestraat 49, B-3000 Leuven, Belgium
| | | |
Collapse
|
204
|
Sauvant P, Sapin V, Abergel A, Schmidt CK, Blanchon L, Alexandre-Gouabau MC, Rosenbaum J, Bommelaer G, Rock E, Dastugue B, Nau H, Azaïs-Braesco V. PAV-1, a new rat hepatic stellate cell line converts retinol into retinoic acid, a process altered by ethanol. Int J Biochem Cell Biol 2002; 34:1017-29. [PMID: 12007639 DOI: 10.1016/s1357-2725(02)00023-7] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
During liver fibrogenesis or long term culture, hepatic stellate cells (HSCs) evolved from "quiescent" to activated phenotype called "myofibroblast-like", a transition prevented by retinoic acid (RA). Little is known about RA generation by HSCs. Our study aimed to check the ability of these cells to produce RA from retinol (Rol) and the alterations of this metabolic step by ethanol. To study this metabolic pathway, primary cultures of HSCs represent the most physiological model but technically suffer several drawbacks. To circumvent these problems, an immortalized rat HSC line (named PAV-1) has been established. We validated PAV-1 cell line as a convenient model to study retinoids metabolism by HSCs. Then, we showed that PAV-1 cells express Rol-binding proteins (RBPs), enzymes and nuclear receptors involved in RA signaling pathway. We also demonstrated in situ generation of functional all-trans-RA (ATRA), using transient transfections with a RA-sensitive reporter gene, in situ modulation of tissue transglutaminase (tTG) activity and HPLC experiments. This production was Rol dose-dependent; 4-methylpyrazole, citral, and ethanol-inhibited which argues in favor of an enzymatic process.In conclusion, we first demonstrate in situ RA generation from Rol in a newly immortalized rat HSC line, named PAV-1. Inhibition of RA production by ethanol in PAV-1 and recent data, suggesting fundamental role of RA to prevent fibrosis development in the liver, allow us to hypothesize that Rol metabolism could be a primary target for ethanol during development of hepatic fibrosis.
Collapse
Affiliation(s)
- Patrick Sauvant
- INRA-Unité des Maladies Métaboliques et Micronutriments; Equipe Vitamines, -Theix, 63122 Saint Genès Champanelle, Clermont-Ferrand, France.
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
205
|
During A, Hussain MM, Morel DW, Harrison EH. Carotenoid uptake and secretion by CaCo-2 cells: beta-carotene isomer selectivity and carotenoid interactions. J Lipid Res 2002; 43:1086-95. [PMID: 12091493 DOI: 10.1194/jlr.m200068-jlr200] [Citation(s) in RCA: 185] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In presence of oleate and taurocholate, differentiated CaCo-2 cell monolayers on membranes were able to assemble and secrete chylomicrons. Under these conditions, both cellular uptake and secretion into chylomicrons of beta-carotene (beta-C) were curvilinear, time-dependent (2-16 h), saturable, and concentration-dependent (apparent K(m) of 7-10 microM) processes. Under linear concentration conditions at 16 h incubation, the extent of absorption of all-trans beta-C was 11% (80% in chylomicrons), while those of 9-cis- and 13-cis-beta-C were significantly lower (2-3%). The preferential uptake of the all-trans isomer was also shown in hepatic stellate HSC-T6 cells and in a cell-free system from rat liver (microsomes), but not in endothelial EAHY cells or U937 monocyte-macrophages. Moreover, extents of absorption of alpha-carotene (alpha-C), lutein (LUT), and lycopene (LYC) in CaCo-2 cells were 10%, 7%, and 2.5%, respectively. Marked carotenoid interactions were observed between LYC/beta-C and beta-C/alpha-C. The present results indicate that beta-C conformation plays a major role in its intestinal absorption and that cis isomer discrimination is at the levels of cellular uptake and incorporation into chylomicrons. Moreover, the kinetics of cellular uptake and secretion of beta-C, the inhibition of the intestinal absorption of one carotenoid by another, and the cellular specificity of isomer discrimination all suggest that carotenoid uptake by intestinal cells is a facilitated process.
Collapse
Affiliation(s)
- Alexandrine During
- Human Nutrition Research Center, United States Department of Agriculture, Beltsville, Maryland 20705, USA.
| | | | | | | |
Collapse
|
206
|
Ikeda K, Wang LH, Torres R, Zhao H, Olaso E, Eng FJ, Labrador P, Klein R, Lovett D, Yancopoulos GD, Friedman SL, Lin HC. Discoidin domain receptor 2 interacts with Src and Shc following its activation by type I collagen. J Biol Chem 2002; 277:19206-12. [PMID: 11884411 DOI: 10.1074/jbc.m201078200] [Citation(s) in RCA: 96] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Discoidin domain receptor 2 (DDR2) is an unusual receptor tyrosine kinase in that its ligand is fibrillar collagen rather than a growth factor-like peptide. We examined signal transduction pathways of DDR2. Here we show that DDR2 is also unusual in that it requires Src activity to be maximally tyrosine-phosphorylated, and that Src activity also promotes association of DDR2 with Shc. The interaction with Shc involves a portion of Shc not previously implicated in interaction with receptor tyrosine kinases. These results identify Src kinase and the adaptor protein Shc as key signaling intermediates in DDR2 signal transduction. Furthermore, Src is required for DDR2-mediated transactivation of the matrix metalloproteinase-2 promoter. The data support a model in which Src and the DDR2 receptor cooperate in a regulated fashion to direct the phosphorylation of both the receptor and its targets.
Collapse
Affiliation(s)
- Kazuo Ikeda
- Department of Medicine, Division of Liver Diseases, Mount Sinai School of Medicine, New York, New York 10029, USA
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
207
|
Uchio K, Tuchweber B, Manabe N, Gabbiani G, Rosenbaum J, Desmoulière A. Cellular retinol-binding protein-1 expression and modulation during in vivo and in vitro myofibroblastic differentiation of rat hepatic stellate cells and portal fibroblasts. J Transl Med 2002; 82:619-28. [PMID: 12004002 DOI: 10.1038/labinvest.3780456] [Citation(s) in RCA: 82] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Cellular retinol-binding protein-1 (CRBP-1) is involved in vitamin A metabolism because it mediates both retinol esterification to retinyl esters and retinol oxidation to retinal and retinoic acid. CRBP-1 is highly expressed in the liver, particularly in hepatic stellate cells (HSC). In this study, we investigated the liver expression of CRBP-1 during experimental fibrogenesis. We also studied the regulation of CRBP-1 expression in cultured HSC and portal fibroblasts, two fibroblastic cell types involved in liver fibrogenesis. Fibrosis was induced in rats by carbon tetrachloride (CCl(4)) or bile duct ligation. Immunohistochemical staining was performed for CRBP-1 and alpha-smooth muscle (SM) actin, an activation marker of fibrogenic cells. CRBP-1 and alpha-SM actin expression was studied by Western blotting and/or Northern blot in primary cultures of HSC isolated by conventional methods and in portal fibroblasts that were obtained by outgrowth from the biliary tree after enzymatic digestion. In normal liver, contrary to HSC, portal fibroblasts did not express CRBP-1. After CCl(4) injury, CRBP-1 expression was maintained in myofibroblastic alpha-SM actin-positive HSC. After bile duct ligation, portal fibroblasts (which proliferated around ductular structures) acquired expression of both CRBP-1 and alpha-SM actin. During HSC activation in culture, CRBP-1 expression gradually increased until Day 5 when alpha-SM actin expression was obvious. Cultured portal fibroblasts developed both CRBP-1 and alpha-SM actin expression. In both cell populations, transforming growth factor-beta 1 treatment increased CRBP-1 expression. Thus, in normal liver, CRBP-1 expression was different among fibroblastic cells, a finding that adds to the concept of heterogeneity of liver fibrogenic cells. Furthermore, during myofibroblastic differentiation, HSC that lost their stores of retinol maintained a high level of CRBP-1 expression, whereas portal fibroblasts acquired CRBP1 expression. Together, these data suggest a correlation between CRBP-1 expression and myofibroblastic differentiation.
Collapse
Affiliation(s)
- Kozue Uchio
- Groupe de Recherches pour l'Etude du Foie, Université Victor Segalen Bordeaux 2, Bordeaux, France
| | | | | | | | | | | |
Collapse
|
208
|
Saxena NK, Ikeda K, Rockey DC, Friedman SL, Anania FA. Leptin in hepatic fibrosis: evidence for increased collagen production in stellate cells and lean littermates of ob/ob mice. Hepatology 2002; 35:762-71. [PMID: 11915021 PMCID: PMC2935193 DOI: 10.1053/jhep.2002.32029] [Citation(s) in RCA: 290] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Leptin is a 16-kd hormone that mediates a range of metabolic effects by using a transduction pathway from the long form of the leptin receptor, OB-R(L,) through Janus kinase-signal transducer and activator of transcription (Jak-Stat) signaling components. Leptin is produced by hepatic stellate cells (HSCs) but only following their "activation." Because activation of stellate cells is a central event in the fibrotic response to liver injury, we hypothesized that leptin may directly stimulate fibrogenesis in activated stellate cells via OB-R(L). We analyzed leptin receptors and their signaling partners in a stellate cell line (HSC-T6) as well as in primary stellate cell isolates. We also examined the effect of leptin on stellate cell expression of alpha(2)(I) collagen messenger RNA (mRNA) levels by ribonuclease protection analysis (RPA). Finally, we examined the role of leptin in in vivo fibrogenesis by inducing a wounding response in ob/ob mice, which lack functional leptin. HSC-T6 and culture-activated stellate cells expressed OB-R(L). Scatchard analysis verified specific binding of leptin to HSCs, with an association constant (K(d)) equal to 660 +/- 5.8 pmol/L. Exposure of HSCs to leptin resulted in significant increases in alpha(2)(I) collagen mRNA expression. Transient transfection with a promoter reporter construct showed a 3-fold increase in alpha(2)(I) collagen transgene activity. Leptin stimulated activation of Stat3 in activated HSCs. Finally, lean animals, but not ob/ob littermates, had significant fibrosis as assessed by picrosirius red staining and abundant alpha-smooth muscle actin staining. In conclusion, these results indicate that leptin is profibrogenic in activated HSCs and can signal via the Jak-Stat pathway. Up-regulation of leptin signaling in liver injury could contribute to enhanced fibrogenesis, particularly in states in which leptin levels are high.
Collapse
Affiliation(s)
- Neeraj K. Saxena
- Hepatology Section, University of Maryland School of Medicine, Baltimore, MD
| | - Kazuo Ikeda
- Division of Liver Diseases, Mount Sinai School of Medicine, New York, NY
| | - Don C. Rockey
- Duke Liver Center, Duke University Medical Center, Durham, NC
| | - Scott L. Friedman
- Division of Liver Diseases, Mount Sinai School of Medicine, New York, NY
| | - Frank A. Anania
- Hepatology Section, University of Maryland School of Medicine, Baltimore, MD
| |
Collapse
|
209
|
Nieto N, Friedman SL, Cederbaum AI. Cytochrome P450 2E1-derived reactive oxygen species mediate paracrine stimulation of collagen I protein synthesis by hepatic stellate cells. J Biol Chem 2002; 277:9853-64. [PMID: 11782477 DOI: 10.1074/jbc.m110506200] [Citation(s) in RCA: 136] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
To evaluate possible fibrogenic effects of CYP2E1-dependent generation of reactive oxygen species, a model was developed using co-cultures of HepG2 cells, which do (E47 cells) or do not (C34 cells) express cytochrome P450 2E1 (CYP2E1) with stellate cells. There was an increase in intra- and extracellular H(2)O(2), lipid peroxidation, and collagen type I protein in stellate cells co-cultured with E47 cells compared with stellate cells alone or co-cultured with C34 cells. The increase in collagen was prevented by antioxidants and a CYP2E1 inhibitor. CYP3A4 did not mimic the stimulatory effects found with CYP2E1. Collagen mRNA levels remained unchanged, and pulse-chase analysis indicated similar half-lives of collagen I protein between both co-cultures. However, collagen protein synthesis was increased in E47 co-culture. Hepatocytes from pyrazole-treated rats (with high levels of CYP2E1) induced collagen protein in primary stellate cells, and antioxidants and CYP2E1 inhibitors blocked this effect. These results suggest that increased translation of collagen mRNA by CYP2E1-derived reactive oxygen species is responsible for the increase in collagen protein produced by the E47 co-culture. These co-culture models may be useful for understanding the impact of CYP2E1-derived ROS on stellate cell function and activation.
Collapse
Affiliation(s)
- Natalia Nieto
- Department of Pharmacology and Biological Chemistry, Mount Sinai School of Medicine, New York, New York 10029, USA
| | | | | |
Collapse
|
210
|
Schnabl B, Choi YH, Olsen JC, Hagedorn CH, Brenner DA. Immortal activated human hepatic stellate cells generated by ectopic telomerase expression. J Transl Med 2002; 82:323-33. [PMID: 11896211 DOI: 10.1038/labinvest.3780426] [Citation(s) in RCA: 83] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Telomere shortening controls the entry of cells into senescence. Functional expression of the telomerase catalytic subunit (human telomerase reverse transcriptase or hTERT) stabilizes telomere length and extends the life span of various normal human cells. Our aim was to assess the role of telomerase activity and telomere maintenance in regulating the proliferation of activated human hepatic stellate cells (HSCs), to establish an immortal human HSC cell line. Human HSCs were isolated from surgical specimens of normal liver and infected with a retrovirus expressing hTERT. Ectopic expression of hTERT reconstituted telomerase activity and maintained telomere length in human HSCs. Control human HSCs, which were either not infected or infected with a retroviral vector containing only the neomycin resistance gene, showed no detectable telomerase activity and had slightly shortened telomeres. These telomerase-negative HSCs entered a nondividing state after about 9 to 15 passages and senesced. In contrast, telomerase-positive HSCs to date have undergone 69 passages. Telomerase-positive HSCs did not undergo oncogenic transformation and exhibit morphologic and functional characteristics of activated HSCs. Microarray and RT-PCR analysis showed that mRNA expression patterns in telomerase-positive HSCs are very similar to those in activated human HSCs. Plating telomerase-positive HSCs on a basement membrane-like matrix reverts them toward a more quiescent phenotype. In conclusion, introduction of hTERT into activated human HSCs immortalizes them and maintains their activated phenotype. This newly developed cell line will be a useful tool to study the cell biology of human HSCs in culture.
Collapse
Affiliation(s)
- Bernd Schnabl
- Departments of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
| | | | | | | | | |
Collapse
|
211
|
Olaso E, Ikeda K, Eng FJ, Xu L, Wang LH, Lin HC, Friedman SL. DDR2 receptor promotes MMP-2-mediated proliferation and invasion by hepatic stellate cells. J Clin Invest 2001. [PMID: 11696582 DOI: 10.1172/jci200112373] [Citation(s) in RCA: 195] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Type I collagen provokes activation of hepatic stellate cells during liver injury through mechanisms that have been unclear. Here, we tested the role of the discoidin domain tyrosine kinase receptor 2 (DDR2), which signals in response to type I collagen, in this pathway. DDR2 mRNA and protein are induced in stellate cells activated by primary culture or in vivo during liver injury. The receptor becomes tyrosine phosphorylated in response to either endogenous or exogenous type I collagen, whereas its expression is downregulated during cellular quiescence induced by growth on Matrigel. We developed stellate cell lines stably overexpressing either wild-type DDR2, a constitutively active chimeric DDR2 receptor (Fc-DDR2), a truncated receptor expressing the extracellular domain, or a kinase-dead DDR2 Cells overexpressing DDR2 showed enhanced proliferation and invasion through Matrigel, activities that were directly related to increased expression of active matrix metalloproteinase 2 (MMP-2). These data show that DDR2 is induced during stellate cell activation and implicate the phosphorylated receptor as a mediator of MMP-2 release and growth stimulation in response to type I collagen. Moreover, type I collagen-dependent upregulation of DDR2 expression establishes a positive feedback loop in activated stellate cells, leading to further proliferation and enhanced invasive activity.
Collapse
Affiliation(s)
- E Olaso
- Division of Liver Diseases and Department of Medicine, Mount Sinai School of Medicine, New York, New York 10029, USA
| | | | | | | | | | | | | |
Collapse
|
212
|
Soref CM, Di YP, Hayden L, Zhao YH, Satre MA, Wu R. Characterization of a novel airway epithelial cell-specific short chain alcohol dehydrogenase/reductase gene whose expression is up-regulated by retinoids and is involved in the metabolism of retinol. J Biol Chem 2001; 276:24194-202. [PMID: 11304534 DOI: 10.1074/jbc.m100332200] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Multiple retinoic acid responsive cDNAs were isolated from a high density cDNA microarray membrane, which was developed from a cDNA library of human tracheobronchial epithelial cells. Five selected cDNA clones encoded the sequence of the same novel gene. The predicted open reading frame of the novel gene encoded a protein of 319 amino acids. The deduced amino acid sequence contains four motifs that are conserved in the short-chain alcohol dehydrogenase/reductase (SDR) family of proteins. The novel gene shows the greatest homology to a group of dehydrogenases that can oxidize retinol (retinol dehydrogenases). The mRNA of the novel gene was found in trachea, colon, tongue, and esophagus. In situ hybridization of airway tissue sections demonstrated epithelial cell-specific gene expression, especially in the ciliated cell type. Both all-trans-retinoic acid and 9-cis-retinoic acid were able to elevate the expression of the novel gene in primary human tracheobronchial epithelial cells in vitro. This elevation coincided with an enhanced retinol metabolism in these cultures. COS cells transfected with an expression construct of the novel gene were also elevated in the metabolism of retinol. The results suggested that the novel gene represents a new member of the SDR family that may play a critical role in retinol metabolism in airway epithelia as well as in other epithelia of colon, tongue, and esophagus.
Collapse
Affiliation(s)
- C M Soref
- Center for Comparative Respiratory Biology and Medicine and the Department of Nutrition, University of California at Davis, 95616, USA
| | | | | | | | | | | |
Collapse
|
213
|
Ross AC, Zolfaghari R, Weisz J. Vitamin A: recent advances in the biotransformation, transport, and metabolism of retinoids. Curr Opin Gastroenterol 2001; 17:184-192. [PMID: 11224677 DOI: 10.1097/00001574-200103000-00015] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Advances in vitamin A research in 1999 and 2000 have improved the understanding the molecular processes through which beta-carotene and other provitamin A carotenoids are converted to vitamin A, the roles of cellular retinoid-binding proteins that serve as retinoid chaperones during metabolism, the regulation of retinoid transport, and the nature and regulation of several enzymes required for the absorption, storage, activation, and inactivation or degradation of retinoids. Not only has a clearer picture emerged of specific molecular processes, but it is also becoming evident that whole-body retinoid homeostasis is facilitated by close communication among organs due to the rapid interorgan recirculation of retinoids, and by the "autoregulation" by retinoic acid of several enzymes and retinoid-binding proteins that mediate retinoid homeostasis.
Collapse
Affiliation(s)
- A. Catharine Ross
- Department of Nutrition, The Pennsylvania State University, University Park, Pennsylvania; Department of Obstetrics and Gynecology, The Milton S. Hershey Medical Center, Hershey, Pennsylvania, USA
| | | | | |
Collapse
|
214
|
Paik J, Vogel S, Piantedosi R, Sykes A, Blaner WS, Swisshelm K. 9-cis-retinoids: biosynthesis of 9-cis-retinoic acid. Biochemistry 2000; 39:8073-84. [PMID: 10891090 DOI: 10.1021/bi992152g] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Retinoids function through conformational alterations of ligand-dependent nuclear transcription factors, the retinoic acid receptors, and retinoid X receptors. 9-cis-Retinoic acid is a known biological ligand for retinoid X receptors, but its synthesis pathway in vivo is largely unknown. Recently, we identified a cis-retinol dehydrogenase (cRDH) that oxidizes 9-cis-retinol to 9-cis-retinal. Since both the expression of cRDH mRNA and its substrate are found in liver, we studied 9-cis-retinol metabolism and 9-cis-retinoic acid biosynthesis in two hepatic-derived cell types, Hep G2 hepatoma cells and HSC-T6 stellate cells. Both cell lines accumulate similar amounts of 9-cis-retinol provided in the medium. However, Hep G2 cells preferentially incorporate all-trans-retinol when equimolar concentrations of all-trans- and 9-cis-retinol were provided. In contrast, HSC-T6 cells did not exhibit a preference between all-trans- and 9-cis-retinol under the same conditions. Esterification of 9-cis-retinol occurred in both cell types, likely by acyl-CoA:retinol acyltransferase and lecithin:retinol acyltransferase. In vitro enzyme assays demonstrated that both cell types can hydrolyze 9-cis-retinyl esters via retinyl ester hydrolase(s). In Hep G2 cells, 9-cis-retinoic acid synthesis was strongly inhibited by high concentrations of 9-cis-retinol, which may explain the low levels of 9-cis-retinol in liver of mice. Cell homogenates of Hep G2 can convert all-trans-retinol to 9-cis-retinal, suggesting that the free form of all-trans-retinol may be used as a source for 9-cis-retinol and, thus, 9-cis-retinoic acid synthesis. Our studies provide the basis for identification of additional pathways for the generation of 9-cis-retinoic acid in specialized tissues.
Collapse
Affiliation(s)
- J Paik
- Nutritional Sciences Program and Department of Pathology, University of Washington, Seattle, Washington 98195, USA
| | | | | | | | | | | |
Collapse
|
215
|
Moog F, Kotzerke J, Reske SN. FDG PET can replace bone scintigraphy in primary staging of malignant lymphoma. J Nucl Med 1999; 217:138-44. [PMID: 10492357 DOI: 10.1002/jcp.21481] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
UNLABELLED Recent studies indicated that 18F-fluorodeoxyglucose (FDG) PET may be more accurate than CT in staging nodal and extranodal malignant lymphoma. The objective of this study was to compare conventional bone scintigraphy as an established skeletal staging procedure with PET using FDG in the detection of osseous involvement in malignant lymphoma. METHODS Whole-body PET-based staging studies of 56 consecutive patients with proven Hodgkin's disease (n = 34) or non-Hodgkin's lymphoma (n = 22) were compared with the results of bone scintigraphy. Positive PET or bone scintigraphic findings were confirmed, if possible, by biopsy, MRI, CT or radiographic investigations. RESULTS Of the 56 patients studied, 12 were found to have skeletal involvement on both studies (PET, 30 regions; bone scintigraphy, 20 regions). Findings were confirmed in all 12 patients. FDG PET detected an additional 12 involved regions in 5 patients. This was subsequently verified in 3 patients, although the other 2 cases remained unresolved. Conversely, bone scintigraphy revealed five abnormalities compatible with lymphoma in 5 patients. Three of these lesions were found to be erroneous; final evaluation of the remaining two findings was not possible. CONCLUSION FDG PET is suitable for identifying osseous involvement in malignant lymphoma with a high positive predictive value and is thereby more sensitive and specific than bone scintigraphy.
Collapse
Affiliation(s)
- F Moog
- Department of Nuclear Medicine, University of Ulm, Germany
| | | | | |
Collapse
|