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Tavori H, Giunzioni I, Predazzi IM, Plubell D, Shivinsky A, Miles J, Devay RM, Liang H, Rashid S, Linton MF, Fazio S. Human PCSK9 promotes hepatic lipogenesis and atherosclerosis development via apoE- and LDLR-mediated mechanisms. Cardiovasc Res 2016; 110:268-78. [PMID: 26980204 DOI: 10.1093/cvr/cvw053] [Citation(s) in RCA: 76] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/21/2015] [Accepted: 03/08/2016] [Indexed: 01/07/2023] Open
Abstract
AIMS Proprotein convertase subtilisin/kexin type 9 (PCSK9) promotes the degradation of hepatic low-density lipoprotein (LDL) receptors (LDLR), thereby, decreasing hepatocyte LDL-cholesterol (LDL-C) uptake. However, it is unknown whether PCSK9 has effects on atherogenesis that are independent of lipid changes. The present study investigated the effect of human (h) PCSK9 on plasma lipids, hepatic lipogenesis, and atherosclerotic lesion size and composition in transgenic mice expressing hPCSK9 (hPCSK9tg) on wild-type (WT), LDLR⁻/⁻, or apoE⁻/⁻ background. METHODS AND RESULTS hPCSK9 expression significantly increased plasma cholesterol (+91%), triglycerides (+18%), and apoB (+57%) levels only in WT mice. The increase in plasma lipids was a consequence of both decreased hepatic LDLR and increased hepatic lipid production, mediated transcriptionally and post-transcriptionally by PCSK9 and dependent on both LDLR and apoE. Despite the lack of changes in plasma lipids in mice expressing hPCSK9 and lacking LDLR (the main target for PCSK9) or apoE (a canonical ligand for the LDLR), hPCSK9 expression increased aortic lesion size in the absence of apoE (268 655 ± 97 972 µm² in hPCSK9tg/apoE⁻/⁻ vs. 189 423 ± 65 700 µm(2) in apoE⁻/⁻) but not in the absence of LDLR. Additionally, hPCSK9 accumulated in the atheroma and increased lesion Ly6C(hi) monocytes (by 21%) in apoE⁻/⁻ mice, but not in LDLR⁻/⁻ mice. CONCLUSIONS PCSK9 increases hepatic lipid and lipoprotein production via apoE- and LDLR-dependent mechanisms. However, hPCSK9 also accumulate in the artery wall and directly affects atherosclerosis lesion size and composition independently of such plasma lipid and lipoprotein changes. These effects of hPCSK9 are dependent on LDLR but are independent of apoE.
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Affiliation(s)
- Hagai Tavori
- Knight Cardiovascular Institute, Center for Preventive Cardiology, Oregon Health and Science University, Portland, OR, USA
| | - Ilaria Giunzioni
- Knight Cardiovascular Institute, Center for Preventive Cardiology, Oregon Health and Science University, Portland, OR, USA
| | - Irene M Predazzi
- Knight Cardiovascular Institute, Center for Preventive Cardiology, Oregon Health and Science University, Portland, OR, USA
| | - Deanna Plubell
- Knight Cardiovascular Institute, Center for Preventive Cardiology, Oregon Health and Science University, Portland, OR, USA
| | - Anna Shivinsky
- Knight Cardiovascular Institute, Center for Preventive Cardiology, Oregon Health and Science University, Portland, OR, USA
| | - Joshua Miles
- Knight Cardiovascular Institute, Center for Preventive Cardiology, Oregon Health and Science University, Portland, OR, USA
| | - Rachel M Devay
- Rinat Laboratory, Pfizer Inc., South San Francisco, CA, USA
| | - Hong Liang
- Rinat Laboratory, Pfizer Inc., South San Francisco, CA, USA
| | - Shirya Rashid
- Department of Pharmacology, Dalhousie University, Halifax, Nova Scotia, Canada Dalhousie Medicine New Brunswick University, Saint John, New Brunswick, Canada
| | - MacRae F Linton
- Division of Cardiovascular Medicine, Atherosclerosis Research Unit, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Sergio Fazio
- Knight Cardiovascular Institute, Center for Preventive Cardiology, Oregon Health and Science University, Portland, OR, USA
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Apolipoprotein e sets the stage: response to injury triggers neuropathology. Neuron 2013; 76:871-85. [PMID: 23217737 DOI: 10.1016/j.neuron.2012.11.020] [Citation(s) in RCA: 256] [Impact Index Per Article: 23.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/20/2012] [Indexed: 01/04/2023]
Abstract
Apolipoprotein (apo) E4 is the major genetic risk factor for Alzheimer's disease and is associated with poor clinical outcome following traumatic brain injury and other neuropathological disorders. Protein instability and an isoform-specific apoE property called domain interaction are responsible for these neuropathological effects. ApoE4 is the most neurotoxic isoform and can induce neuropathology through various cellular pathways. Neuronal damage or stress induces apoE synthesis as part of the repair response; however, when apoE4 is expressed in neurons, its unique conformation makes it susceptible to proteolysis, resulting in the generation of neurotoxic fragments. These fragments cause pathological mitochondrial dysfunction and cytoskeletal alterations. Here, we review data supporting the hypothesis that apoE4 (> apoE3 > apoE2) has direct neurotoxic effects and highlight studies showing that blocking domain interaction reverses these detrimental effects.
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Sabaretnam T, O’Reilly J, Kritharides L, Le Couteur DG. The effect of old age on apolipoprotein E and its receptors in rat liver. AGE (DORDRECHT, NETHERLANDS) 2010; 32:69-77. [PMID: 19809892 PMCID: PMC2829642 DOI: 10.1007/s11357-009-9115-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2009] [Accepted: 08/16/2009] [Indexed: 05/28/2023]
Abstract
Apolipoprotein E (apoE) is associated with aging and some age-related diseases. The majority of apoE is produced by hepatocytes for the receptor-mediated uptake of lipoproteins. Here, the effects of age on the hepatic expression and distribution of apoE and its receptors were determined using immunofluorescence, Western blots, and quantitative PCR in rat liver tissue and isolated hepatocytes. The expression of apoE mRNA and protein was not influenced significantly by aging. Immunofluorescence studies in isolated hepatocytes showed that apoE was more likely to be co-localized with early endosomes, golgi, and microtubules in isolated old hepatocytes. The mRNA expression of the receptor involved in sequestration of apoE, heparan sulfate proteoglycan was reduced in old age, without any significant effect on the expression of either the low-density lipoprotein receptor or low density-lipoprotein receptor-related protein. Old age is associated with changes in hepatic apoE intracellular trafficking and heparan sulfate proteoglycan expression that might contribute to age-related disease.
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Affiliation(s)
- Tharani Sabaretnam
- ANZAC Research Institute, University of Sydney, Sydney, Australia
- Department of Cardiology, Concord Hospital, Sydney, Australia
- Centre for Education and Research on Aging (CERA), University of Sydney, Sydney, Australia
| | - Jennifer O’Reilly
- ANZAC Research Institute, University of Sydney, Sydney, Australia
- Centre for Education and Research on Aging (CERA), University of Sydney, Sydney, Australia
| | - Leonard Kritharides
- ANZAC Research Institute, University of Sydney, Sydney, Australia
- Department of Cardiology, Concord Hospital, Sydney, Australia
- Centre for Vascular Research, School of Medical Sciences, University of New South Wales, Sydney, Australia
| | - David G. Le Couteur
- ANZAC Research Institute, University of Sydney, Sydney, Australia
- Centre for Education and Research on Aging (CERA), University of Sydney, Sydney, Australia
- Centre for Education and Research on Ageing, Concord RG Hospital, Hospital Road, Concord, Sydney, NSW 2139 Australia
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Elimination of GD3 synthase improves memory and reduces amyloid-β plaque load in transgenic mice. Neurobiol Aging 2009; 30:1777-91. [DOI: 10.1016/j.neurobiolaging.2007.12.022] [Citation(s) in RCA: 93] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2007] [Revised: 12/21/2007] [Accepted: 12/21/2007] [Indexed: 11/19/2022]
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Sabaretnam T, Harris MJ, Kockx M, Witting PK, Le Couteur DG, Kritharides L. Effects of hydrogen peroxide and apolipoprotein E isoforms on apolipoprotein E trafficking in HepG2 cells. Clin Exp Pharmacol Physiol 2009; 36:e96-102. [PMID: 19793104 DOI: 10.1111/j.1440-1681.2009.05306.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
1. The major source of apolipoprotein E (apoE) is the liver. In the present study, the effects of oxidative stress and apoE isoforms on apoE distribution and trafficking were established using the HepG2 liver tumour cell line. 2. Hydrogen peroxide (0, 25, 250 and 1000 micromol/L) was associated with rapid and concentration-dependent redistribution of apoE into the early endosomal compartment. This redistribution was achieved with a much lower concentration (25 micromol/L) than that needed to induce changes in intracellular apoE mRNA expression, apoE protein levels and markers of oxidative stress (250-1000 micromol/L). 3. Live cell imaging of apoE3-green fluorescent protein revealed a significant decrease in traffic velocity in response to oxidative stress. 4. The E4 isoform was associated with reduced trafficking velocity compared with the E3 isoform under basal conditions. 5. The results indicate that oxidative stress and apoE isoforms influence apoE trafficking and distribution within HepG2 cells. Altered apoE hepatocyte trafficking may provide a mechanistic link between oxidative stress, ageing and some diseases in older people.
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The effect of aging on the response of isolated hepatocytes to hydrogen peroxide and tert-butyl hydroperoxide. Toxicol In Vitro 2009; 24:123-8. [PMID: 19720132 DOI: 10.1016/j.tiv.2009.08.018] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2009] [Revised: 07/24/2009] [Accepted: 08/26/2009] [Indexed: 11/23/2022]
Abstract
Aging is associated with increased susceptibility to oxidative stress. To study this in the liver and to elucidate underlying mechanisms, hepatocytes from young (4-6 months) and old (24-26 months) rats were exposed to two oxidants, hydrogen peroxide and tert-butyl hydroperoxide. ATP content and mitochondrial activity were lower in old hepatocytes and decreased further with oxidative stress. Expression of Cu/Zn superoxide dismutase, Mn superoxide dismutase and catalase was not substantially influenced by oxidative stress in young and old hepatocytes, whereas glutathione peroxidase 1 expression was markedly increased only in young hepatocytes. Oxidative stress in young hepatocytes led to increased expression of apoE and movement of apoE to the early endosomes. In old hepatocytes, oxidative stress did not increase apoE expression and apoE was co-localized with early endosomes under control conditions. The results show that old age is associated with impaired hepatocyte responses of mitochondria, ATP, glutathione peroxidase 1 and apoE to oxidative stress.
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Knutson SK, Chyla BJ, Amann JM, Bhaskara S, Huppert SS, Hiebert SW. Liver-specific deletion of histone deacetylase 3 disrupts metabolic transcriptional networks. EMBO J 2008; 27:1017-28. [PMID: 18354499 PMCID: PMC2323257 DOI: 10.1038/emboj.2008.51] [Citation(s) in RCA: 209] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2008] [Accepted: 02/25/2008] [Indexed: 01/04/2023] Open
Abstract
Histone deacetylase 3 (Hdac3) is an enzymatic component of transcriptional repression complexes recruited by the nuclear hormone receptors. Inactivation of Hdac3 in cancer cell lines triggered apoptosis, and removal of Hdac3 in the germ line of mice caused embryonic lethality. Therefore, we deleted Hdac3 in the postnatal mouse liver. These mice developed hepatomegaly, which was the result of hepatocyte hypertrophy, and these morphological changes coincided with significant imbalances between carbohydrate and lipid metabolism. Loss of Hdac3 triggered changes in gene expression consistent with inactivation of repression mediated by nuclear hormone receptors. Loss of Hdac3 also increased the levels of Ppar gamma2, and treatment of these mice with a Ppar gamma antagonist partially reversed the lipid accumulation in the liver. In addition, gene expression analysis identified mammalian target of rapamycin signalling as being activated after deletion of Hdac3, and inhibition by rapamycin affected the accumulation of neutral lipids in Hdac3-null livers. Thus, Hdac3 regulates metabolism through multiple signalling pathways in the liver, and deletion of Hdac3 disrupts normal metabolic homeostasis.
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Affiliation(s)
- Sarah K Knutson
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Brenda J Chyla
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Joseph M Amann
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN, USA
- Department of Cancer Biology, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Srividya Bhaskara
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Stacey S Huppert
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Scott W Hiebert
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN, USA
- Vanderbilt-Ingram Cancer Center, Vanderbilt University School of Medicine, Nashville, TN, USA
- Department of Biochemistry, Vanderbilt University School of Medicine, 512 Preston Research Building, 23rd and Pierce Avenue, Nashville, TN 37232, USA. Tel.: +1 615 936 3582; Fax: +1 615 936 1790; E-mail:
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Kockx M, Jessup W, Kritharides L. Regulation of endogenous apolipoprotein E secretion by macrophages. Arterioscler Thromb Vasc Biol 2008; 28:1060-7. [PMID: 18388328 DOI: 10.1161/atvbaha.108.164350] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Apolipoprotein E has critical roles in the protection against atherosclerosis and is understood to follow the classical constitutive secretion pathway. Recent studies have indicated that the secretion of apoE from macrophages is a regulated process of unexpected complexity. Cholesterol acceptors such as apolipoprotein A-I, high density lipoprotein, and phospholipid vesicles can stimulate apoE secretion. The ATP binding cassette transporter ABCA1 is involved in basal apoE secretion and in lipidating apoE-containing particles secreted by macrophages. However, the stimulation of apoE secretion by apoA-I is ABCA1-independent, indicating the existence of both ABCA1-dependent and -independent pathways of apoE secretion. The release of apoE under basal conditions is also regulated, requiring intact protein kinase A activity, intracellular calcium, and an intact microtubular network. Mathematical modeling of apoE turnover indicates that whereas some pools of apoE are committed to either secretion or degradation, other pools can be diverted from degradation toward secretion. Targeted inhibition or stimulation of specific apoE trafficking pathways will provide unique opportunities to regulate the biology of this important molecule.
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Affiliation(s)
- Maaike Kockx
- Macrophage Biology Group, Centre for Vascular Research, Room 405C Wallace Wurth Building, University of New South Wales, High Street, Kensington, Sydney, NSW 2050, Australia
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Gusarova V, Seo J, Sullivan ML, Watkins SC, Brodsky JL, Fisher EA. Golgi-associated maturation of very low density lipoproteins involves conformational changes in apolipoprotein B, but is not dependent on apolipoprotein E. J Biol Chem 2007; 282:19453-62. [PMID: 17500069 DOI: 10.1074/jbc.m700475200] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The major protein component in secreted very low density lipoproteins (VLDL) is apoB, and it is established that these particles can reach sizes approaching 100 nm. We previously employed a cell-free system to investigate the nature of the vesicles in which this large cargo exits the endoplasmic reticulum (ER) (Gusarova, V., Brodsky, J. L., and Fisher, E. A. (2003) J. Biol. Chem. 278, 48051-48058). We found that apoB-containing lipoproteins exit the ER as dense lipid-protein complexes regardless of the final sizes of the particles and that further expansion occurs via post-ER lipidation. Here, we focused on maturation in the Golgi apparatus. In three separate approaches, we found that VLDL maturation (as assessed by changes in buoyant density) was associated with conformational changes in apoB. In addition, as the size of VLDL expanded, apoE concentrated in a subclass of Golgi microsomes or Golgi-derived vesicles that co-migrated with apoB-containing microsomes or vesicles, respectively. A relationship between apoB and apoE was further confirmed in co-localization studies by immunoelectron microscopy. These combined results are consistent with previous suggestions that apoE is required for VLDL maturation. To our surprise, however, we observed robust secretion of mature VLDL when apoE synthesis was inhibited in either rat hepatoma cells or apoE(-/-) mouse primary hepatocytes. We conclude that VLDL maturation in the Golgi involves apoB conformational changes and that the expansion of the lipoprotein does not require apoE; rather, the increase in VLDL surface area favors apoE binding.
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Affiliation(s)
- Viktoria Gusarova
- Department of Medicine, Leon Charney Division of Cardiology, New York University School of Medicine, New York, New York 10016, USA
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Rouzer CA, Ivanova PT, Byrne MO, Milne SB, Marnett LJ, Brown HA. Lipid profiling reveals arachidonate deficiency in RAW264.7 cells: Structural and functional implications. Biochemistry 2007; 45:14795-808. [PMID: 17144673 PMCID: PMC2443946 DOI: 10.1021/bi061723j] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Glycerophospholipids containing arachidonic acid (20:4) serve as the precursors for an array of biologically active lipid mediators, most of which are produced by macrophages. We have applied mass spectrometry-based lipid profiling technology to evaluate the glycerophospholipid structure and composition of two macrophage populations, resident peritoneal macrophages and RAW264.7 cells, with regard to their potential for 20:4-based lipid mediator biosynthesis. Fatty acid analysis indicated that RAW264.7 cells were deficient in 20:4 (10 +/- 1 mol %) compared to peritoneal macrophages (26 +/- 1 mol %). Mass spectrometry of total glycerophospholipids demonstrated a marked difference in the distribution of lipid species, including reduced levels of 20:4-containing lipids, in RAW264.7 cells compared to peritoneal macrophages. Enrichment of RAW264.7 cells with 20:4 increased the fatty acid to 20 +/- 1 mol %. However, the distribution of the incorporated 20:4 remained different from that of peritoneal macrophages. RAW264.7 cells pretreated with granulocyte-macrophage colony stimulating factor followed by lipopolysaccharide and interferon-gamma mobilized similar quantities of 20:4 and produced similar amounts of prostaglandins as peritoneal macrophages treated with LPS alone. LPS treatment resulted in detectable changes in specific 20:4-containing glycerophospholipids in peritoneal cells, but not in RAW264.7 cells. 20:4-enriched RAW264.7 cells lost 88% of the incorporated fatty acid during the LPS incubation without additional prostaglandin synthesis. These results illustrate that large differences in glycerophospholipid composition may exist, even in closely related cell populations, and demonstrate the importance of interpreting the potential for lipid-mediator biosynthesis in the context of overall glycerophospholipid composition.
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Affiliation(s)
- Carol A. Rouzer
- Department of Biochemistry, the Vanderbilt Institute of Chemical Biology, the Vanderbilt Ingram Cancer Center, Center in Molecular Toxicology, Center for Pharmacology and Drug Toxicology, Vanderbilt University School of Medicine, Nashville, TN 37232-0146 USA
| | - Pavlina T. Ivanova
- Department of Pharmacology, the Vanderbilt Institute of Chemical Biology, the Vanderbilt Ingram Cancer Center, Center in Molecular Toxicology, Center for Pharmacology and Drug Toxicology, Vanderbilt University School of Medicine, Nashville, TN 37232-0146 USA
| | - Mark O. Byrne
- Department of Pharmacology, the Vanderbilt Institute of Chemical Biology, the Vanderbilt Ingram Cancer Center, Center in Molecular Toxicology, Center for Pharmacology and Drug Toxicology, Vanderbilt University School of Medicine, Nashville, TN 37232-0146 USA
| | - Stephen B. Milne
- Department of Pharmacology, the Vanderbilt Institute of Chemical Biology, the Vanderbilt Ingram Cancer Center, Center in Molecular Toxicology, Center for Pharmacology and Drug Toxicology, Vanderbilt University School of Medicine, Nashville, TN 37232-0146 USA
| | - Lawrence J. Marnett
- Department of Biochemistry, the Vanderbilt Institute of Chemical Biology, the Vanderbilt Ingram Cancer Center, Center in Molecular Toxicology, Center for Pharmacology and Drug Toxicology, Vanderbilt University School of Medicine, Nashville, TN 37232-0146 USA
- Department of Chemistry, the Vanderbilt Institute of Chemical Biology, the Vanderbilt Ingram Cancer Center, Center in Molecular Toxicology, Center for Pharmacology and Drug Toxicology, Vanderbilt University School of Medicine, Nashville, TN 37232-0146 USA
| | - H. Alex Brown
- Department of Pharmacology, the Vanderbilt Institute of Chemical Biology, the Vanderbilt Ingram Cancer Center, Center in Molecular Toxicology, Center for Pharmacology and Drug Toxicology, Vanderbilt University School of Medicine, Nashville, TN 37232-0146 USA
- Department of Chemistry, the Vanderbilt Institute of Chemical Biology, the Vanderbilt Ingram Cancer Center, Center in Molecular Toxicology, Center for Pharmacology and Drug Toxicology, Vanderbilt University School of Medicine, Nashville, TN 37232-0146 USA
- To whom correspondence should be addressed. Tel: (615) 936-3888. Fax: (615) 936-6833.
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