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Saunders RA, Fujii K, Alabanza L, Ravatn R, Kita T, Kudoh K, Oka M, Chin KV. Altered phospholipid transfer protein gene expression and serum lipid profile by topotecan. Biochem Pharmacol 2010; 80:362-9. [PMID: 20416282 PMCID: PMC2883626 DOI: 10.1016/j.bcp.2010.04.015] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2010] [Revised: 04/11/2010] [Accepted: 04/13/2010] [Indexed: 01/19/2023]
Abstract
Camptothecin (CPT) and its structural analogues including topotecan and irinotecan, are inhibitors of topoisomerase I. These drugs are clinically active against a broad spectrum of cancers. To understand the genesis of chemotherapeutic resistance to the CPT family of anticancer drugs, we examined by gene expression profiling the pharmacological response to topotecan in the human hepatoma HepG2 cells and found a striking induction of the phospholipid transfer protein (PLTP) gene expression by topotecan. We showed that activation of PLTP gene expression is specific to CPT and its analogues including specific enantiomers that inhibit topoisomerase I. PLTP-mediated lipid transfer to high-density lipoprotein (HDL) is thought to be important for shuttling and redistribution of lipids between lipoproteins, which are normally returned to the liver for metabolism via the reverse cholesterol transport pathway. Hence, we asked whether elevated PLTP levels might increase the transfer of drugs into HDL. We observed that CPT was not accumulated in HDL and other lipoproteins. In addition, topotecan treatment in mice caused a marked reduction in serum HDL that was accompanied by an increase in triglyceride and cholesterol levels. These results showed that PLTP does not mediate the transfer of topoisomerase I inhibitors to serum lipoproteins. However, elevated serum PLTP levels following treatment with topoisomerase I inhibitors in cancer patients may serve as a biomarker for monitoring the development of hypertriglyceridemia and acute pancreatitis.
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Affiliation(s)
- Rudel A. Saunders
- Department of Medicine, The University of Toledo, College of Medicine, Toledo, OH, United States
- Center for Diabetes and Endocrine Research, The University of Toledo, College of Medicine, Toledo, OH United States
| | - Kazuyuki Fujii
- Department of Medicine, The University of Toledo, College of Medicine, Toledo, OH, United States
- Department of Obstetrics and Gynecology, National Defense Medical College, 3-2 Namiki, Tokorozawa, Saitama, Japan
| | - Leah Alabanza
- Department of Medicine, The University of Toledo, College of Medicine, Toledo, OH, United States
- Baker Institute for Animal Health, Cornell Veterinary College, Ithaca, NY, United States
| | - Roald Ravatn
- Department of Medicine, The University of Toledo, College of Medicine, Toledo, OH, United States
| | - Tsunekazu Kita
- Department of Gynecology, Saitama Cancer Center, Adachi-Gun, Japan
| | - Kazuya Kudoh
- Department of Obstetrics and Gynecology, National Defense Medical College, 3-2 Namiki, Tokorozawa, Saitama, Japan
| | - Masahiro Oka
- Division of Dermatology, Department of Clinical Molecular Medicine, Kobe University, Graduate School of Medicine, Kobe, Japan
| | - Khew-Voon Chin
- Department of Medicine, The University of Toledo, College of Medicine, Toledo, OH, United States
- Center for Diabetes and Endocrine Research, The University of Toledo, College of Medicine, Toledo, OH United States
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Abstract
Plasma levels of high-density lipoprotein (HDL) cholesterol and its major protein, apolipoprotein A-I, are inversely correlated with the incidence of atherosclerotic cardiovascular disease. Low HDL cholesterol and apolipoprotein A-I levels often are found in association with other cardiovascular risk factors, including the metabolic syndrome, insulin resistance, and type 2 diabetes mellitus. However, overexpression of apolipoprotein A-I in animals has been shown to reduce progression and even induce regression of atherosclerosis, indicating that apolipoprotein A-I is directly protective against atherosclerosis. A major mechanism by which apolipoprotein A-I inhibits atherosclerosis may be by promoting cholesterol efflux from macrophages and returning it to the liver for excretion, a process termed reverse cholesterol transport. This article focuses on new developments in the regulation of reverse cholesterol transport and the clinical implications of those developments.
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Affiliation(s)
- Daniel J Rader
- Preventive Cardiology/Lipid Research Center, University of Pennsylvania Health System, Philadelphia, Pennsylvania 19104, USA.
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Tan KCB, Shiu SWM, Wong Y. Plasma phospholipid transfer protein activity and small, dense LDL in type 2 diabetes mellitus. Eur J Clin Invest 2003; 33:301-6. [PMID: 12662160 DOI: 10.1046/j.1365-2362.2003.01132.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND Phospholipid transfer protein (PLTP) and cholesteryl ester transfer protein (CETP) remodel circulating lipoproteins and play a role in the antiatherogenic reverse cholesterol transport pathway. The present study determined whether abnormalities in the LDL subfraction pattern in type 2 diabetic patients were related to changes in lipid transfer proteins. METHODS Low-density lipoprotein (LDL) subfractions were measured by density gradient ultracentrifugation and plasma PLTP and CETP activities by radiometric assays in 240 diabetic patients and 136 controls. RESULTS The diabetic patients had lower LDL-I (P < 0.001) and higher LDL-III concentrations than the controls (P < 0.001). Plasma PLTP activity was increased (P < 0.001) whereas no significant differences were seen in CETP activity. In the diabetic patients, small, dense LDL-III correlated with plasma triglyceride (r = 0.18, P < 0.01), HDL (r = -0.14, P < 0.05), PLTP (r = 0.29, P < 0.001) and CETP activity (r = 0.15, P < 0.05). Linear regression analysis showed that plasma PLTP activity, triglyceride and age were the major determinants of LDL-III concentration (r2 = 28%, P < 0.001). The univariate relationship between CETP and LDL-III was no longer significant after adjusting for PLTP activity. CONCLUSIONS The increase in plasma PLTP activity was independently associated with small, dense LDL concentrations in type 2 diabetes. Hence, elevated PLTP activity might have both antiatherogenic and pro-atherogenic potential in these patients.
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Affiliation(s)
- K C B Tan
- Department of Medicine, University of Hong Kong.
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Tu AY, Albers JJ. Functional analysis of the transcriptional activity of the mouse phospholipid transfer protein gene. Biochem Biophys Res Commun 2001; 287:921-6. [PMID: 11573953 DOI: 10.1006/bbrc.2001.5687] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Phospholipid transfer protein (PLTP) plays an important role in the metabolism of plasma high density lipoprotein. The mouse gene encoding PLTP and its promoter region has been cloned in our laboratory. The present study was conducted to functionally analyze the transcriptional regulation of the mouse PLTP gene. The results indicated that DNA sequences between -245 and -69 were responsible for the full promoter activity and binding motifs for transcription factor Sp1 and AP-2 within this functional promoter region were synergistically essential for the basal transcription. The transcriptional activity of this gene was significantly increased by chenodeoxycholic acid and fenofibrate, suggesting that transcription factor farnesoid X-activated receptor (FXR) and peroxisome proliferator-activated receptor (PPAR) are likely involved in the transcriptional regulation. DNA sequence analysis suggests that DNA sequences from -407 to -395 and from -393 to -381 are homologous to the recognition motifs of FXR, and those from -859 to -847 and from -309 to -297 are similar to the potential binding motif for PPAR. These findings provide a molecular basis for further investigation of the physiological function and regulation of the PLTP gene in mice.
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Affiliation(s)
- A Y Tu
- Department of Medicine, Northwest Lipid Research Laboratories, University of Washington, 2121 N. 35th Street, Seattle, WA 98103, USA.
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Cheung MC, Wolfbauer G, Kennedy H, Brown BG, Albers JJ. Plasma phospholipid transfer protein activity in patients with low HDL and cardiovascular disease treated with simvastatin and niacin. BIOCHIMICA ET BIOPHYSICA ACTA 2001; 1537:117-24. [PMID: 11566255 DOI: 10.1016/s0925-4439(01)00064-3] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Plasma phospholipid transfer protein (PLTP) is an important modulator of high-density lipoprotein (HDL) metabolism, regulating its particle size, composition, and mass. In patients with low HDL and cardiovascular disease (CVD), plasma PLTP activity is positively correlated with the concentration of HDL particles containing apo A-I but not apo A-II (Lp(A-1)). We recently completed a study to determine the effect of simvastatin and niacin (S-N) therapy on disease progression/regression in these patients, and found that this therapy selectively increased Lp(A-I). To determine if PLTP was also increased with this drug therapy, we measured the PLTP activity in the plasma of 30 of these patients obtained at baseline and after 12 months of therapy, and compared the changes to a similar group of 31 patients who received placebo for the drugs. No significant increase in PLTP activity was observed in either group of patients. However, changes in apo A-I and A-II between these two time points were correlated with the corresponding change in PLTP activity. The correlation coefficients were r=0.57 (P=0.001) and r=0.43 (P=0.02) for apo A-I, and r=0.54 (P=0.002) and r=0.41 (P=0.02) for apo A-II in the placebo and S-N group, respectively. At baseline, PLTP activity correlated positively with the percent of plasma apo A-I associated with Lp(A-I) (r=0.38, P=0.04) and the amounts of apo A-I in these particles (r=0.43, P=0.02). These relationships persisted in patients who took placebo for 12 months (r=0.46, P=0.009 and r=0.37, P=0.04, respectively), but was attenuated in those treated with S-N. These data indicate that S-N-induced increase in Lp(A-I) was PLTP-independent. It also confirms our previous observation that an interrelationship exists between PLTP and apo-specific HDL particle subclasses in CVD patients with low HDL, and that this relationship is altered by drug intervention.
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Affiliation(s)
- M C Cheung
- Division of Metabolism, Endocrinology, and Nutrition, University of Washington, School of Medicine, Seattle 98103, USA.
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Tu AY, Albers JJ. Glucose regulates the transcription of human genes relevant to HDL metabolism: responsive elements for peroxisome proliferator-activated receptor are involved in the regulation of phospholipid transfer protein. Diabetes 2001; 50:1851-6. [PMID: 11473048 DOI: 10.2337/diabetes.50.8.1851] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Phospholipid transfer protein (PLTP) plays an important role in human plasma HDL metabolism. Clinical data have recently indicated that plasma PLTP activity and mass were both higher in diabetic patients concomitant with hyperglycemia. The present study shows that high glucose increases both PLTP mRNA and functional activity in HepG2 cells, due to a significant increase in the promoter activity of human PLTP gene. The glucose-responsive elements are located between -759 and -230 of the PLTP 5'-flanking region, within which two binding motifs (-537 to -524 and -339 to -327) for either peroxisome proliferator-activated receptor or farnesoid X-activated receptor are involved in this glucose-mediated transcriptional regulation. This finding suggests that high glucose upregulates the transcription of human PLTP gene via nuclear hormone receptors. In addition, high glucose increases mRNA levels for several genes that are functionally important in HDL metabolism, including human ATP-binding cassette transporter A1, apolipoprotein A-I, scavenger receptor BI, and hepatic lipase. The functional promoter activities of these genes are enhanced by high glucose in three cell lines tested, indicating that glucose may also regulate these genes at the transcriptional level. Our findings provide a molecular basis for a role of hyperglycemia in altered HDL metabolism.
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MESH Headings
- ATP-Binding Cassette Transporters/genetics
- Apolipoprotein A-I/genetics
- Apolipoprotein A-II/genetics
- Carcinoma, Hepatocellular
- Carrier Proteins/genetics
- DNA-Binding Proteins/metabolism
- Gene Expression Regulation/drug effects
- Gene Expression Regulation/physiology
- Glucose/pharmacology
- Humans
- Lipase/genetics
- Lipoproteins, HDL/metabolism
- Liver Neoplasms
- Membrane Proteins/genetics
- Phospholipid Transfer Proteins
- Promoter Regions, Genetic
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Receptors, Cytoplasmic and Nuclear/metabolism
- Receptors, Immunologic/genetics
- Receptors, Lipoprotein
- Receptors, Scavenger
- Reverse Transcriptase Polymerase Chain Reaction
- Scavenger Receptors, Class B
- Transcription Factors/metabolism
- Transcription, Genetic/drug effects
- Transcription, Genetic/physiology
- Tumor Cells, Cultured
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Affiliation(s)
- A Y Tu
- Department of Medicine, Northwest Lipid Research Laboratories, University of Washington, Seattle, Washington 98103, USA.
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Kawashiri MA, Maugeais C, Rader DJ. High-density lipoprotein metabolism: molecular targets for new therapies for atherosclerosis. Curr Atheroscler Rep 2000; 2:363-72. [PMID: 11122767 DOI: 10.1007/s11883-000-0074-4] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
New therapeutic approaches to the prevention and treatment of atherosclerotic cardiovascular disease (ASCVD) are needed. Plasma levels of high-density lipoprotein (HDL) cholesterol are inversely associated with risk of ASCVD. Genes involved in the metabolism of HDL represent potential targets for the development of such therapies. Because HDL metabolism is a dynamic process, the effect of a specific HDL-oriented intervention on atherosclerosis cannot necessarily be predicted by its effect on the plasma HDL cholesterol level. Based on available data in animal models, some gene products are candidates for pharmacologic upregulation, infusion, or overexpression, including apolipoprotein (apo)A-I, apoE, apoA-IV, lipoprotein lipase (LPL), ATP-binding cassette protein 1 (ABC1), lecithin cholesterol acyltransferase (LCAT), and scavenger receptor B-I (SR-BI). In contrast, some gene products are potential candidates for inhibition, including apoA-II, cholesteryl ester transfer protein (CETP), and hepatic lipase. The next decade will witness the transition from preclinical studies to clinical trials of a variety of new therapies targeted toward HDL metabolism and atherosclerosis.
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Affiliation(s)
- M A Kawashiri
- University of Pennsylvania Medical Center, 614 BRBII/III, 421 Curie Blvd, Philadelphia, PA 19104, USA
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Rader DJ, Maugeais C. Genes influencing HDL metabolism: new perspectives and implications for atherosclerosis prevention. MOLECULAR MEDICINE TODAY 2000; 6:170-5. [PMID: 10740256 DOI: 10.1016/s1357-4310(00)01673-7] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Atherosclerotic cardiovascular disease (ASCVD) is the most common cause of morbidity and mortality in Western societies. Current therapies, such as reduction of plasma cholesterol, significantly reduce, but do not come close to eliminating, the complications of ASCVD. Therefore, novel therapeutic approaches to the prevention of acute coronary events and progression of atherosclerosis are still needed. The complex metabolism of high density lipoproteins represents an attractive potential target for therapeutic intervention. Here, we will discuss those components of the high density lipoprotein metabolism and lipid transport pathways that are potential preventative or therapeutic targets for ASCVD.
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Affiliation(s)
- D J Rader
- University of Pennsylvania Medical Center, 614 BRBII/III 421 Curie Blvd., Philadelphia, PA 19104, USA.
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Murdoch SJ, Carr MC, Hokanson JE, Brunzell JD, Albers JJ. PLTP activity in premenopausal women: relationship with lipoprotein lipase, HDL, LDL, body fat, and insulin resistance. J Lipid Res 2000. [DOI: 10.1016/s0022-2275(20)32057-5] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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Tu AY, Albers JJ. DNA sequences responsible for reduced promoter activity of human phospholipid transfer protein by fibrate. Biochem Biophys Res Commun 1999; 264:802-7. [PMID: 10544012 DOI: 10.1006/bbrc.1999.1597] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Phospholipid transfer protein (PLTP) plays an important role in plasma lipid and lipoprotein metabolism. We have previously cloned and characterized the promoter region of the human PLTP gene. The present study was conducted to determine if the promoter activity of the human PLTP gene is affected by fibrate, a hypolipidemic drug, and to identify DNA sequences that are responsible for the effect. The results indicated that the promoter activity of the PLTP gene was significantly reduced by fenofibrate, and the area that was mainly responsive to the reducing effect by fibrate was located between -377 and -230 of the 5'-flanking region. The DNA sequence analysis suggested that each area of the DNA sequences from -342 to -323 and from -322 to -299 has two repeated sequences, which are inverted and homologous to the recognition motif of peroxisome proliferator-activated receptor (PPAR), namely the PPAR-responsive element (PPRE). Mutagenesis of these PPRE-like sequences, especially that at -322 to -299, abolished most of the reducing effects of fibrate on the PLTP promoter activity. These findings strongly suggest that the PPRE-like elements are responsible for the reduced promoter activity of the human PLTP gene by fibrate.
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Affiliation(s)
- A Y Tu
- Department of Medicine, Northwest Lipid Research Laboratories, University of Washington, Seattle, Washington, 98103, USA
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Wolfbauer G, Albers JJ, Oram JF. Phospholipid transfer protein enhances removal of cellular cholesterol and phospholipids by high-density lipoprotein apolipoproteins. BIOCHIMICA ET BIOPHYSICA ACTA 1999; 1439:65-76. [PMID: 10395966 DOI: 10.1016/s1388-1981(99)00077-3] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
High-density lipoprotein (HDL) apolipoproteins remove excess cholesterol from cells by an active transport pathway that may protect against atherosclerosis. Here we show that treatment of cholesterol-loaded human skin fibroblasts with phospholipid transfer protein (PLTP) increased HDL binding to cells and enhanced cholesterol and phospholipid efflux by this pathway. PLTP did not stimulate lipid efflux in the presence of albumin, purified apolipoprotein A-I, and phospholipid vesicles, suggesting specificity for HDL particles. PLTP restored the lipid efflux activity of mildly trypsinized HDL, presumably by regenerating active apolipoproteins. PLTP-stimulated lipid efflux was absent in Tangier disease fibroblasts, induced by cholesterol loading, and inhibited by brefeldin A treatment, indicating selectivity for the apolipoprotein-mediated lipid removal pathway. The lipid efflux-stimulating effect of PLTP was not attributable to generation of prebeta HDL particles in solution but instead required cellular interactions. These interactions increased cholesterol efflux to minor HDL particles with electrophoretic mobility between alpha and prebeta. These findings suggest that PLTP promotes cell-surface binding and remodeling of HDL so as to improve its ability to remove cholesterol and phospholipids by the apolipoprotein-mediated pathway, a process that may play an important role in enhancing flux of excess cholesterol from tissues and retarding atherogenesis.
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Affiliation(s)
- G Wolfbauer
- Department of Medicine, Box 356426, University of Washington, Seattle, WA 98195-6426, USA
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Albers JJ, Pitman W, Wolfbauer G, Cheung MC, Kennedy H, Tu AY, Marcovina SM, Paigen B. Relationship between phospholipid transfer protein activity and HDL level and size among inbred mouse strains. J Lipid Res 1999. [DOI: 10.1016/s0022-2275(20)33369-1] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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