1
|
Jurtz VI, Skovbjerg G, Salinas CG, Roostalu U, Pedersen L, Hecksher-Sørensen J, Rolin B, Nyberg M, van de Bunt M, Ingvorsen C. Deep learning reveals 3D atherosclerotic plaque distribution and composition. Sci Rep 2020; 10:21523. [PMID: 33299076 PMCID: PMC7726562 DOI: 10.1038/s41598-020-78632-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2020] [Accepted: 11/26/2020] [Indexed: 12/14/2022] Open
Abstract
Complications of atherosclerosis are the leading cause of morbidity and mortality worldwide. Various genetically modified mouse models are used to investigate disease trajectory with classical histology, currently the preferred methodology to elucidate plaque composition. Here, we show the strength of light-sheet fluorescence microscopy combined with deep learning image analysis for characterising and quantifying plaque burden and composition in whole aorta specimens. 3D imaging is a non-destructive method that requires minimal ex vivo handling and can be up-scaled to large sample sizes. Combined with deep learning, atherosclerotic plaque in mice can be identified without any ex vivo staining due to the autofluorescent nature of the tissue. The aorta and its branches can subsequently be segmented to determine how anatomical position affects plaque composition and progression. Here, we find the highest plaque accumulation in the aortic arch and brachiocephalic artery. Simultaneously, aortas can be stained for markers of interest (for example the pan immune cell marker CD45) and quantified. In ApoE-/- mice we observe that levels of CD45 reach a plateau after which increases in plaque volume no longer correlate to immune cell infiltration. All underlying code is made publicly available to ease adaption of the method.
Collapse
MESH Headings
- Animals
- Aorta/pathology
- Aortic Diseases
- Apolipoproteins E/analysis
- Atherosclerosis/complications
- Atherosclerosis/pathology
- Deep Learning
- Disease Models, Animal
- Female
- Image Processing, Computer-Assisted/methods
- Imaging, Three-Dimensional/methods
- Male
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Microscopy, Fluorescence/methods
- Plaque, Atherosclerotic/diagnostic imaging
- Plaque, Atherosclerotic/metabolism
- Plaque, Atherosclerotic/pathology
- Receptors, LDL/analysis
Collapse
Affiliation(s)
| | - Grethe Skovbjerg
- Novo Nordisk A/S, Novo Nordisk Park, 2760, Maaloev, Denmark
- Gubra, 2970, Hoersholm, Denmark
| | | | | | - Louise Pedersen
- Novo Nordisk A/S, Novo Nordisk Park, 2760, Maaloev, Denmark
- University of Copenhagen, 1017, Copenhagen, Denmark
| | | | - Bidda Rolin
- Novo Nordisk A/S, Novo Nordisk Park, 2760, Maaloev, Denmark
- Gubra, 2970, Hoersholm, Denmark
| | - Michael Nyberg
- Novo Nordisk A/S, Novo Nordisk Park, 2760, Maaloev, Denmark
| | | | | |
Collapse
|
2
|
Salami A, El Shamieh S. Association between SNPs of Circulating Vascular Endothelial Growth Factor Levels, Hypercholesterolemia and Metabolic Syndrome. ACTA ACUST UNITED AC 2019; 55:medicina55080464. [PMID: 31405227 PMCID: PMC6723464 DOI: 10.3390/medicina55080464] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2019] [Revised: 07/26/2019] [Accepted: 08/08/2019] [Indexed: 01/24/2023]
Abstract
Background and Objectives: Four single nucleotide polymorphisms (SNPs); rs6921438 and rs4416670 in LOC100132354-C6orf223, rs6993770 in ZFPM2, and rs10738760 in VLDLR-KCNV2 were reported to explain up to 50% of the heritability of vascular endothelial growth factor circulating levels. These SNPs were also studied for possible associations with circulating lipid levels in supposedly healthy European individuals and in a limited number of Iranian individuals with metabolic syndrome. To go further, the association of those four SNPs with plasma lipid parameters, hypercholesterolemia and metabolic syndrome (MetS) was assessed. Materials and Methods: A cross-sectional study was conducted on 460 individuals chosen from the general population. Demographic and clinical data were collected and DNA was extracted and genotyped using Kompetitive allele specific PCR (KASP™). A meta-analysis followed, combining our participants with the Iranian individuals (n = 336). Results: Whereas rs10738760 was associated with total cholesterol (Tchol) (p = 0.01), rs6993770 showed significant associations with both Tchol and low-density lipoprotein cholesterol (LDL-C) levels (p = 0.007 and p = 0.01 respectively). Using a multivariate logistic regression model adjusted for different confounding factors, we found that rs6993770 was associated with hypercholesterolemia, specifically high Tchol (p = 0.01) and LDL-C levels (p = 0.01). Furthermore, rs10738760 was positively associated with the risk of MetS in these individuals (p = 0.02) and in the meta-analysis (OR = 1.67, p = 0.01). Conclusion: Our results suggest that whereas rs6993770 in ZFPM2 was positively associated with hypercholesterolemia, rs10738760 (VLDLR-KCNV2) has a possible implication in MetS in two Middle Eastern populations.
Collapse
Affiliation(s)
- Ali Salami
- Rammal Hassan Rammal Research Laboratory, Physio-toxicity (PhyTox) Research Group, Faculty of Sciences (V), Lebanese University, Nabatieh 1700, Lebanon
| | - Said El Shamieh
- Department of Medical Laboratory Technology, Faculty of Health Sciences, Beirut Arab University, Beirut 115020, Lebanon.
| |
Collapse
|
3
|
Yang F, Liu DY, Guo JT, Ge N, Zhu P, Liu X, Wang S, Wang GX, Sun SY. Circular RNA circ-LDLRAD3 as a biomarker in diagnosis of pancreatic cancer. World J Gastroenterol 2017; 23:8345-8354. [PMID: 29307994 PMCID: PMC5743505 DOI: 10.3748/wjg.v23.i47.8345] [Citation(s) in RCA: 142] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/03/2017] [Revised: 11/17/2017] [Accepted: 11/27/2017] [Indexed: 02/06/2023] Open
Abstract
AIM To analyze the diagnostic value of a circular RNA (circRNA), circ-LDLRAD3, in pancreatic cancer.
METHODS Expression levels of circ-LDLRAD3 were tested in both cells and clinical samples; the latter included 30 paired pancreatic cancer tissues and adjacent non-tumorous tissues, 31 plasma samples from patients with pancreatic cancer, and 31 plasma samples from healthy volunteers. Real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR) was performed to measure expression levels of circ-LDLRAD3 in cells and clinical samples; then, the relationship between clinicopathological factors of patient samples and expression of circ-LDLRAD3 in pancreatic cancer was analyzed. The diagnostic value of circ-LDLRAD3 was verified by receiver operating characteristic (ROC) curve analysis.
RESULTS Circ-LDLRAD3 was up-regulated in pancreatic cancer cell lines (P < 0.01), pancreatic cancer tissues (P < 0.01), and plasma samples from patients with pancreatic cancer (P < 0.01). High expression of circ-LDLRAD3 was significantly associated with venous invasion, lymphatic invasion, and metastasis. The area under the ROC curve of circ-LDLRAD3 alone or combination with CA19-9 was 0.67 and 0.87, respectively, with a sensitivity and specificity of 0.5738 (alone) and 0.7049 (alone), and 0.8033 (combination) and 0.9355 (combination), respectively.
CONCLUSION These data suggest that circ-LDLRAD3 may be a biomarker in the diagnosis of pancreatic cancer.
Collapse
Affiliation(s)
- Fan Yang
- Endoscopy Center, Shengjing Hospital of China Medical University, Shenyang 110004, Liaoning Province, China
| | - Dong-Yan Liu
- Medical Research Center, Shengjing Hospital of China Medical University, Benxi 117000, Liaoning Province, China
| | - Jin-Tao Guo
- Endoscopy Center, Shengjing Hospital of China Medical University, Shenyang 110004, Liaoning Province, China
| | - Nan Ge
- Endoscopy Center, Shengjing Hospital of China Medical University, Shenyang 110004, Liaoning Province, China
| | - Ping Zhu
- Endoscopy Center, Shengjing Hospital of China Medical University, Shenyang 110004, Liaoning Province, China
| | - Xiang Liu
- Endoscopy Center, Shengjing Hospital of China Medical University, Shenyang 110004, Liaoning Province, China
| | - Sheng Wang
- Endoscopy Center, Shengjing Hospital of China Medical University, Shenyang 110004, Liaoning Province, China
| | - Guo-Xin Wang
- Endoscopy Center, Shengjing Hospital of China Medical University, Shenyang 110004, Liaoning Province, China
| | - Si-Yu Sun
- Endoscopy Center, Shengjing Hospital of China Medical University, Shenyang 110004, Liaoning Province, China
| |
Collapse
|
4
|
Yao L, Gu X, Song Q, Wang X, Huang M, Hu M, Hou L, Kang T, Chen J, Chen H, Gao X. Nanoformulated alpha-mangostin ameliorates Alzheimer's disease neuropathology by elevating LDLR expression and accelerating amyloid-beta clearance. J Control Release 2016; 226:1-14. [PMID: 26836197 DOI: 10.1016/j.jconrel.2016.01.055] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2015] [Revised: 01/25/2016] [Accepted: 01/28/2016] [Indexed: 12/31/2022]
Abstract
Alzheimer's disease (AD), the most common form of dementia, is now representing one of the largest global healthcare challenges. However, an effective therapy is still lacking. Accumulation of amyloid-beta (Aβ) in the brain is supposed to trigger pathogenic cascades that eventually lead to AD. Therefore, Aβ clearance strategy is being actively pursued as a promising disease modifying therapy. Here, we found that α-mangostin (α-M), a polyphenolic xanthone derivative from mangosteen, up-regulated low density lipoprotein receptor (LDLR) expression in microglia and liver cells, and efficiently facilitated Aβ clearance. However, the in vivo application of α-M is limited due to its hydrophobic nature, poor aqueous solubility and stability, and thus low bioavailability and accumulation in the target organs. To overcome this limitation, α-M was encapsulated into the core of poly(ethylene glycol)-poly(l-lactide) (PEG-PLA) nanoparticles [NP(α-M)]. Such nanoencapsulation improved the biodistribution of α-M in both the brain and liver, enhanced the brain clearance of (125)I-radiolabeled Aβ1-42 in an LDLR-dependent manner, reduced Aβ deposition, attenuated neuroinflammatory responses, ameliorated neurologic changes and reversed behavioral deficits in AD model mice. These findings justified the concept that polyphenol-mediated modulation of LDLR expression might serve as a safe and efficient disease-modifying therapy for AD by accelerating Aβ clearance. It also demonstrated the powerful capacity of nanotechnology in modulating the biodistribution behavior of drug to improve its therapeutic efficacy in AD.
Collapse
Affiliation(s)
- Lei Yao
- Department of Pharmacology, Institute of Medical Sciences, Shanghai Jiaotong University School of Medicine, 280 South Chongqing Road, Shanghai, 200025, PR China
| | - Xiao Gu
- Department of Pharmacology, Institute of Medical Sciences, Shanghai Jiaotong University School of Medicine, 280 South Chongqing Road, Shanghai, 200025, PR China
| | - Qingxiang Song
- Department of Pharmacology, Institute of Medical Sciences, Shanghai Jiaotong University School of Medicine, 280 South Chongqing Road, Shanghai, 200025, PR China
| | - Xiaolin Wang
- Department of Pharmacology, Institute of Medical Sciences, Shanghai Jiaotong University School of Medicine, 280 South Chongqing Road, Shanghai, 200025, PR China
| | - Meng Huang
- Department of Pharmacology, Institute of Medical Sciences, Shanghai Jiaotong University School of Medicine, 280 South Chongqing Road, Shanghai, 200025, PR China
| | - Meng Hu
- Department of Pharmacology, Institute of Medical Sciences, Shanghai Jiaotong University School of Medicine, 280 South Chongqing Road, Shanghai, 200025, PR China
| | - Lina Hou
- Department of Pharmacology, Institute of Medical Sciences, Shanghai Jiaotong University School of Medicine, 280 South Chongqing Road, Shanghai, 200025, PR China
| | - Ting Kang
- Department of Pharmaceutics, Key Laboratory of Smart Drug Delivery, Ministry of Education & PLA, School of Pharmacy, Fudan University, 826 Zhangheng Road, Shanghai 201203, PR China
| | - Jun Chen
- Department of Pharmaceutics, Key Laboratory of Smart Drug Delivery, Ministry of Education & PLA, School of Pharmacy, Fudan University, 826 Zhangheng Road, Shanghai 201203, PR China
| | - Hongzhuan Chen
- Department of Pharmacology, Institute of Medical Sciences, Shanghai Jiaotong University School of Medicine, 280 South Chongqing Road, Shanghai, 200025, PR China.
| | - Xiaoling Gao
- Department of Pharmacology, Institute of Medical Sciences, Shanghai Jiaotong University School of Medicine, 280 South Chongqing Road, Shanghai, 200025, PR China.
| |
Collapse
|
5
|
Lammi C, Zanoni C, Arnoldi A. A simple and high-throughput in-cell Western assay using HepG2 cell line for investigating the potential hypocholesterolemic effects of food components and nutraceutics. Food Chem 2014; 169:59-64. [PMID: 25236198 DOI: 10.1016/j.foodchem.2014.07.133] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2013] [Revised: 07/25/2014] [Accepted: 07/28/2014] [Indexed: 01/28/2023]
Abstract
Since saving time and money are critical issues while developing innovative functional foods and nutraceutics, the use of specific and high-throughput assays for the fast screening of potentially bioactive ingredients is crucial. In this context, the aim of the present investigation was the development of an in-cell Western (ICW) assay, a quantitative colorimetric cell-based technique, at the HepG2 cell line for screening and evaluating the effects of potentially bioactive compounds on the low density lipoprotein (LDL) receptor (LDLR). It is known that LDLR plays a pivotal role in the binding and endocytosis of circulating LDL, increasing its plasma clearance. The ICW was optimised and validated using monacolin K, the main hypocholesterolemic component of red yeast rice. This provided a robust and reproducible assay useful for characterising the cholesterol-lowering properties of bioactive food components. To our knowledge, this is the first application of the ICW technique in the field of functional foods and nutraceutics.
Collapse
Affiliation(s)
- Carmen Lammi
- Dipartimento di Scienze Farmaceutiche, Università degli Studi di Milano, Milan, Italy
| | - Chiara Zanoni
- Dipartimento di Scienze Farmaceutiche, Università degli Studi di Milano, Milan, Italy
| | - Anna Arnoldi
- Dipartimento di Scienze Farmaceutiche, Università degli Studi di Milano, Milan, Italy.
| |
Collapse
|
6
|
Bujo H. [Novel biomarker for pathological immature cells--soluble form of LR11]. Rinsho Byori 2012; 60:469-476. [PMID: 22774576] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
LR11 (also called SorLA or SORL1), a member of the LDL receptor family, was originally discovered in 1996 from genes specifically expressed in the intimal smooth muscle cells of atherosclerotic plaques. The soluble form of LR11 (sLR11) as well as the membrane-bound form plays a key role in the phenotype conversion of medial smooth muscle cells into intimal smooth muscle cells through the activation of urokinase receptor/integrin-mediated intracellular pathways. The levels of sLR11 in serum or CSF are increased in patients with atherosclerotic diseases, Alzheimer's disease or malignant diseases including acute leukemias. The recently developed ELISA system using two specific antibodies against LR11 made it possible to measure sLR11 quantitatively and stably for many samples. Thus, a novel clinical examination is expected to detect the pathological immature cells important for the pathophysiology of the above diseases. The soluble receptor-based clinical approach, together with basic studies about the structure-function relationship, may shed light on the development of novel target therapy against pathological immature cells in the science fields of so far independently categorized diseases.
Collapse
Affiliation(s)
- Hideaki Bujo
- Department of Genome Research and Clinical Investigation, Chiba University Graduate School of Medicine, Chiba 260-8670, Japan.
| |
Collapse
|
7
|
Bhattacharya P, Chekmenev EY, Reynolds WF, Wagner S, Zacharias N, Chan HR, Bünger R, Ross BD. Parahydrogen-induced polarization (PHIP) hyperpolarized MR receptor imaging in vivo: a pilot study of 13C imaging of atheroma in mice. NMR Biomed 2011; 24:1023-8. [PMID: 21538638 PMCID: PMC3240663 DOI: 10.1002/nbm.1717] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2010] [Revised: 02/02/2011] [Accepted: 02/22/2011] [Indexed: 05/03/2023]
Abstract
MR techniques using hyperpolarized (13)C have successfully produced examples of angiography and intermediary metabolic imaging, but, to date, no receptor imaging has been attempted. The goal of this study was to synthesize and evaluate a novel hyperpolarizable molecule, 2,2,3,3-tetrafluoropropyl 1-(13)C-propionate-d(2,3,3) (TFPP), for the detection of atheromatous plaques in vivo. TFPP binds to lipid bilayers and its use in hyperpolarized MR could prove to be a major step towards receptor imaging. The precursor, 2,2,3,3-tetrafluoropropyl 1-(13)C-acrylate-d(2,3,3) (TFPA), binds to 1,2-dimyristoylphosphatidylcholine lipid bilayers with a 1.6-ppm chemical shift in the (19)F MR spectrum. This molecule was designed to be hyperpolarized through the addition of parahydrogen to the (13)C-acrylate moiety by parahydrogen-induced polarization. TFPA was hyperpolarized to TFPP to an extent similar to that of the hydroxyethylacrylate to hydroxyethylpropionate transition: 17 ± 4% for TFPP versus 20% for hydroxyethylpropionate; T(1) relaxation times (45 ± 2 s versus 55 ± 2 s) were comparable and the hyperpolarized properties of TFPP were characterized. Hydroxyethylacrylate, like TFPA, has a chemical structure with an acrylate moiety, but does not contain the lipid-binding tetrafluoropropyl functional group. Hyperpolarized TFPP binds to the lipid bilayer, appearing as a second, chemically shifted (13)C hyperpolarized MR signal with a further reduction in the longitudinal relaxation time (T(1) = 21 ± 1 s). In aortas harvested from low-density lipoprotein receptor knock-out mice fed with a high-fat diet for 9 months, and in which atheroma is deposited in the aorta and heart, TFPP showed greater binding to lipid on the intimal surface than in control mice fed a normal diet. When TFPP was hyperpolarized and administered in vivo to atheromatous mice in a pilot study, increased binding was observed on the endocardial surface of the intact heart compared with normally fed controls. Hyperpolarized TFPP has bio-sensing specificity for lipid, coupled with a 42,000-fold sensitivity gain in the MR signal at 4.7 T. Binding of TFPP with lipids results in the formation of a characteristic second peak in MRS. TFPP therefore has the potential to act as an in vivo molecular probe for atheromatous plaque imaging and may serve as a model of receptor-targeted bio-imaging with enhanced MR sensitivity.
Collapse
Affiliation(s)
- Pratip Bhattacharya
- Enhanced Magnetic Resonance Laboratory, Huntington Medical Research Institutes, Pasadena, CA 91105, USA.
| | | | | | | | | | | | | | | |
Collapse
|
8
|
Strøm TB, Holla ØL, Tveten K, Cameron J, Berge KE, Leren TP. Disrupted recycling of the low density lipoprotein receptor by PCSK9 is not mediated by residues of the cytoplasmic domain. Mol Genet Metab 2010; 101:76-80. [PMID: 20659812 DOI: 10.1016/j.ymgme.2010.05.003] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/20/2010] [Revised: 05/21/2010] [Accepted: 05/21/2010] [Indexed: 11/26/2022]
Abstract
Proprotein convertase subtilisin/kexin type 9 (PCSK9) post-translationally regulates the number of cell-surface low density lipoprotein receptors (LDLR). This is accomplished by the ability of PCSK9 to mediate degradation of the LDLR. The underlying mechanism involves binding of secreted PCSK9 to the epidermal growth factor-like repeat A of the extracellular domain of the LDLR at the cell surface, followed by lysosomal degradation of the internalized LDLR:PCSK9 complex. However, the mechanism by which the normal recycling of the LDLR is disrupted by PCSK9, remains to be determined. In this study we have investigated the role of the cytoplasmic domain of the LDLR for this process. This has been done by studying the ability of a mutant LDLR (K811X-LDLR) which lacks the cytoplasmic domain, to be degraded by PCSK9. We show that this mutant receptor is degraded by PCSK9. Thus, the machinery which directs the LDLR:PCSK9 complex to the lysosomes for degradation, does not interact with the cytoplasmic domain of the LDLR.
Collapse
Affiliation(s)
- Thea Bismo Strøm
- Medical Genetics Laboratory, Department of Medical Genetics, Oslo University Hospital Rikshospitalet, Oslo, Norway
| | | | | | | | | | | |
Collapse
|
9
|
Grundy SM, Vega GL, Kesäniemi YA. Abnormalities in metabolism of low density lipoproteins associated with coronary heart disease. Acta Med Scand Suppl 2009; 701:23-37. [PMID: 3907293 DOI: 10.1111/j.0954-6820.1985.tb08887.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Low density lipoprotein (LDL) is probably the most atherogenic of all the lipoproteins. Several abnormalities in LDL metabolism seem to be associated with coronary heart disease (CHD) one of them being an elevation of plasma LDL concentration. Recent findings suggest that disorders in the metabolism of LDL could be associated with accelerated atherosclerosis even without elevated LDL levels such as increased flux of LDL and changes in the LDL composition. Elevation of plasma LDL levels can be caused by two factors, first, a decrease in the clearance of LDL and second, an overproduction of this lipoprotein. Catabolism of LDL is largely determined by the LDL receptors as clearly shown in patients with familial hypercholesterolemia (FH). In this inherited disease the patients do not have normal LDL receptors and their LDL levels are remarkably elevated. LDL production is also increased in these subjects. In the rest of the population LDL levels are regulated by both the LDL clearance and production rate. The latter also seems to be related to the LDL receptor activity. The conversion of the LDL precursor, very low density lipoprotein (VLDL) to LDL is the most important factor regulating LDL synthesis. When the LDL receptor activity is low a large fraction of VLDL apolipoprotein B (apoB), the major structural protein in VLDL, is converted to LDL, and LDL production is high. On the other hand, only a small part of VLDL apoB is converted to LDL resulting in low LDL synthesis rate in conditions with high LDL receptor activity. The relationships between production and clearance of LDL are, however, more complex. There are individuals who produce a large number of VLDL and LDL particles but maintain LDL concentrations at a normal level by clearing their LDL very effectively. These subjects obviously have another abnormality in lipoprotein metabolism namely an overproduction of apoB. This disorder has been observed in several conditions like obesity, adult-onset diabetes mellitus, several patients with familial combined hyperlipidemia and some normolipidemic subjects with premature coronary heart disease. In all these conditions increased transport of LDL can be associated with coronary artery disease even in the absence of hypercholesterolemia. This raises the possibility that increased flux of LDL could itself be atherogenic possibly by overloading reverse cholesterol transport. Finally, there is some evidence that LDL particle composition may be important in the process of atherogenesis. High LDL apoB but normal LDL cholesterol levels, hyperapobetalipoproteinemia, has been associated with premature coronary heart disease.(ABSTRACT TRUNCATED AT 400 WORDS)
Collapse
|
10
|
Sohda T, Iwata K, Kitamura Y, Suzuki N, Takeyama Y, Irie M, Anan A, Nakane H, Yoshikane M, Watanabe H, Sakisaka S. Reduced expression of low-density lipoprotein receptor in hepatocellular carcinoma with paraneoplastic hypercholesterolemia. J Gastroenterol Hepatol 2008; 23:e153-6. [PMID: 17784865 DOI: 10.1111/j.1440-1746.2007.05115.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
BACKGROUND AND AIM Hepatocellular carcinoma (HCC) is frequently associated with paraneoplastic hypercholesterolemia. In familial hypercholesterolemia, genetic mutation of the low-density lipoprotein (LDL) receptor gene has been recognized as being a pathogenesis of the disease. We investigate the expression of a LDL receptor protein and gene abnormalities of a LDL receptor in HCC cells in cases with paraneoplastic hypercholesterolemia. METHODS Eleven patients with HCC associated with paraneoplastic hypercholesterolemia and seven patients with HCC who did not have hypercholesterolemia were studied. Paraffin-embedded tissues were obtained at operative resection, autopsy, or biopsy. Immunohistochemistry was performed using a monoclonal antibody against human LDL receptors. Confocal laser-scanning microscopy was used to observe the FITC-labeled LDL receptor. DNA samples were extracted from paraffin-embedded tissues. Since a LDL receptor gene is located on chromosome 19p13.2, a microsatellite marker, D19S413, was used to analyze the chromosomes. RESULTS Immunoreactive LDL receptors were observed all over the surface of non-tumorous hepatocytes. However, expression of the LDL receptor was significantly decreased in all HCC cells derived from the 11 patients with hypercholesterolemia. In contrast, the expression was retained in the HCC cells of all patients without hypercholesterolemia. In two patients with hypercholesterolemia, DNA analysis revealed a loss of heterozygosity on chromosome 19p13.2. CONCLUSION We demonstrated reduced expression of the LDL receptor in HCC cases with paraneoplastic hypercholesterolemia. LDL receptor genes with genomic disorders may cause decreased expression of the LDL receptor protein, leading to feed-back failure of the cholesterol regulation system, as seen in familial hypercholesterolemia. This is the first report considering the mechanism behind the development of paraneoplastic hypercholesterolemia in HCC.
Collapse
MESH Headings
- Adult
- Aged
- Carcinoma, Hepatocellular/chemistry
- Carcinoma, Hepatocellular/genetics
- Carcinoma, Hepatocellular/pathology
- Chromosomes, Human, Pair 19
- Chromosomes, Human, Pair 5
- Down-Regulation
- Female
- Gene Expression Regulation, Neoplastic
- Humans
- Hypercholesterolemia/genetics
- Hypercholesterolemia/metabolism
- Hypercholesterolemia/pathology
- Immunohistochemistry
- Liver Neoplasms/chemistry
- Liver Neoplasms/genetics
- Liver Neoplasms/pathology
- Loss of Heterozygosity
- Male
- Middle Aged
- Paraneoplastic Syndromes/genetics
- Paraneoplastic Syndromes/metabolism
- Paraneoplastic Syndromes/pathology
- Polymerase Chain Reaction
- Receptors, LDL/analysis
- Receptors, LDL/genetics
Collapse
Affiliation(s)
- Tetsuro Sohda
- Department of Gastroenterology and Medicine, Fukuoka University School of Medicine, Fukuoka, Japan.
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
11
|
Chen YX, Ruan XZ, Huang AL, Li Q, Moorhead JF, Varghese Z. Mechanisms of dysregulation of low-density lipoprotein receptor expression in HepG2 cells induced by inflammatory cytokines. Chin Med J (Engl) 2007; 120:2185-2190. [PMID: 18167199] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/25/2023] Open
Abstract
BACKGROUND Low-density lipoprotein (LDL) receptor is normally regulated via a feedback system that is dependent on intracellular cholesterol levels. We have demonstrated that cytokines disrupt cholesterol-mediated LDL receptor feedback regulation causing intracellular accumulation of unmodified LDL in peripheral cells. Liver is the central organ for lipid homeostasis. The aim of this study was to investigate the regulation of cholesterol exogenous uptake via LDL receptor and its underlying mechanisms in human hepatic cell line (HepG2) cells under physiological and inflammatory conditions. METHODS Intracellular total cholesterol (TC), free cholesterol (FC) and cholesterol ester (CE) were measured by an enzymic assay. Oil Red O staining was used to visualize lipid droplet accumulation in cells. Total cellular RNA was isolated from cells for detecting LDL receptor, sterol regulatory element binding protein (SREBP)-2 and SREBP cleavage-activating protein (SCAP) mRNA levels using real-time quantitative PCR. LDL receptor and SREBP-2 protein expression were examined by Western blotting. Confocal microscopy was used to investigate the translocation of SCAP-SREBP complex from the endoplasmic reticulum (ER) to the Golgi by dual staining with anti-human SCAP and anti-Golgin antibodies. RESULTS LDL loading increased intracellular cholesterol level, thereby reduced LDL receptor mRNA and protein expression in HepG2 cells under physiological conditions. However, interleukin 1 beta (IL-1 beta) further increased intracellular cholesterol level in the presence of LDL by increasing both LDL receptor mRNA and protein expression in HepG2. LDL also reduced the SREBP and SCAP mRNA level under physiological conditions. Exposure to IL-1 beta caused over-expression of SREBP-2 and also disrupted normal distribution of SCAP-SREBP complex in HepG2 by enhancing translocation of SCAP-SREBP from the ER to the Golgi despite a high concentration of LDL in the culture medium. CONCLUSIONS IL-1 beta disrupts cholesterol-mediated LDL receptor feedback regulation by enhancing SCAP-SREBP complex translocation from the ER to the Golgi, thereby increasing SREBP-2 mediated LDL receptor expression even in the presence of high concentration of LDL. This results in LDL cholesterol accumulation in hepatic cells via LDL receptor pathway under inflammatory stress.
Collapse
Affiliation(s)
- Ya-xi Chen
- Centre for Lipid Research, Key Laboratory of Molecular Biology on Infectious Diseases, Ministry of Education, Chongqing 400010, China
| | | | | | | | | | | |
Collapse
|
12
|
Wadsack C, Tabano S, Maier A, Hiden U, Alvino G, Cozzi V, Hüttinger M, Schneider WJ, Lang U, Cetin I, Desoye G. Intrauterine growth restriction is associated with alterations in placental lipoprotein receptors and maternal lipoprotein composition. Am J Physiol Endocrinol Metab 2007; 292:E476-84. [PMID: 17003234 DOI: 10.1152/ajpendo.00547.2005] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Among other factors, fetal growth requires maternal supply of cholesterol. Cellular cholesterol uptake is mainly mediated by the LDL receptor (LDL-R) and the scavenger receptor family. We hypothesized that expression levels of key receptors of these families were regulated differently in placentas from IUGR pregnancies with varying degrees of severity. Third-trimester placentas from IUGR pregnancies with (IUGR-S) and without (IUGR-M) fetal hemodynamic changes and from control (AGA) pregnancies were studied. LDL-R, LDL-R-related protein (LRP-1), and scavenger receptor class B type I (SR-BI) mRNA and protein levels were measured. Cholesterol concentration and composition of lipoproteins were analyzed enzymatically and by lipid electrophoresis, respectively, in maternal and umbilical cord blood. LDL-R mRNA levels in IUGR-M were similar to AGA but lower (P < 0.05) in IUGR-S. In contrast, LDL-R protein was twofold (IUGR-M) and 1.8-fold (IUGR-S) higher (P < 0.05) than in the AGA group. LRP-1 mRNA and protein levels were not altered in the IUGR cases. SR-BI mRNA was unchanged in IUGR, but protein levels were lower (P < 0.05) in IUGR-S than in the other groups. Maternal plasma concentrations of LDL cholesterol were higher (P < 0.05) in the AGA group (188.5 +/- 23.6 mg/dl) than in the IUGR-S group (154.2 +/- 26.1). Electrophoretic mobility of the LDL fraction in maternal plasma demonstrated significant changes in migration toward higher values (AGA 0.95 +/- 0.06, IUGR-M 1.12 +/- 0.11, P < 0.001; IUGR-S 1.28 +/- 0.20, P = 0.002). We conclude that LDL-R and SR-BI levels are altered in IUGR pregnancies. These differences were associated with changes in LDL, but not HDL, mobility and cholesterol concentration in maternal circulation.
Collapse
Affiliation(s)
- Christian Wadsack
- Clinic of Obstetrics and Gynecology, Medical University of Graz, Auenbruggerplatz 14, A-8036 Graz, Austria.
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
13
|
Bilek G, Kremser L, Wruss J, Blaas D, Kenndler E. Mimicking Early Events of Virus Infection: Capillary Electrophoretic Analysis of Virus Attachment to Receptor-Decorated Liposomes. Anal Chem 2007; 79:1620-5. [PMID: 17297964 DOI: 10.1021/ac061728m] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The attachment of human rhinovirus serotype 2 to an artificial cell membrane was followed by capillary electrophoresis. The cell membrane was mimicked by liposomes (average diameter of about 190 nm) containing a lipid with a nitrilotriacetic acid (NTA) group. This group, in the presence of Ni(2+) ions, served as anchor for the his(6)-tags of recombinant derivatives of the very-low-density lipoprotein (VLDL) receptor comprising either modules 1, 2, and 3 (V123) or five tandem copies of module 3 (V33333). We demonstrate by capillary electrophoresis with laser induced fluorescence detection of the liposomes that the minor receptor group rhinovirus HRV2 binds specifically to the receptor-decorated vesicles; the major receptor group rhinovirus HRV14, which uses a different receptor for cell binding, does not attach to the liposomes.
Collapse
Affiliation(s)
- Gerhard Bilek
- Institute for Analytical Chemistry, University of Vienna, A-1090 Vienna, Austria
| | | | | | | | | |
Collapse
|
14
|
Sobal G, Menzel EJ, Sinzinger H. Comparative binding of 125I-and 99mTc-d-labeled native and glycated low-density lipoprotein to human microvascular endothelial cells-potential for atherosclerosis imaging? J Recept Signal Transduct Res 2006; 26:693-707. [PMID: 17118806 DOI: 10.1080/10799890600939472] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Native (n), glycated (g), and glycoxidated (go) low-density lipoproteins (LDL) were labeled with 125I or 99mTc, and the labeling efficiency and binding were assessed for potential use of these LDL compounds in imaging analysis of atherosclerotic lesions (PPAR-gamma receptors) by determining the number of specific receptors for nLDL, gLDL or goLDL on human microvascular endothelial cells as well as the KDs using either 125I-or 99mTc-labeled LDLs. The specific activity of labeled gLDL and goLDL was much higher (for goLDL 20 times higher) than that of nLDL. Gel filtration of labeled LDLs revealed, however, that 99mTc-g/goLDL is significantly degraded by the labeling reaction. No fragmentation was observed for 99mTc-nLDL and all the 125I-labeled LDL forms. Binding studies using both 125I-and 99mTc-nLDL indicated a weak binding affinity (KD 10- 7mol/L) to human microvascular endothelial cells. The binding affinity of 125I-g/goLDL to these cells was significantly higher (KD 10- 9mol/L) and could be increased further by preactivation of the endothelial cells using TNFalpha. Incubation with 99mTc-goLDL, however, did not result in specific binding of the ligand, possibly as a consequence of the fragmentation of the lipoprotein during the labeling. Scatchard transformation of the binding data with 99mTc-gLDL revealed the presence of only a few binding sites. This was in contrast to the results obtained with 125I-labeled gLDL, which revealed a much higher membrane density of scavenger receptors for this ligand. We conclude that for in vitro binding studies as well as for potential in vivo imaging, only 125I-labeled goLDL should be used, whereas nLDL may be applied as 125I-or 99mTc-labeled ligand.
Collapse
Affiliation(s)
- Grazyna Sobal
- Department of Nuclear Medicine, Medical University of Vienna, Vienna, Austria.
| | | | | |
Collapse
|
15
|
Abstract
Interindividual variation exists in response to statin therapy. It has been hypothesized that subjects with higher baseline cholesterol synthesis rates are more sensitive to statins. To directly test this hypothesis, mice overexpressing the heterodimeric ATP-binding cassette (ABC) transporter G5/G8 (G5G8(Tg) mice) were treated with lovastatin because they have a compensatory increase in cholesterol biosynthesis as a result of increased cholesterol excretion into bile and feces. As expected, lovastatin treatment did not alter plasma and hepatic cholesterol levels in wild-type mice. Interestingly, this treatment significantly reduced plasma concentration and hepatic content of cholesterol by 42% and 17.3%, respectively, in the statin-treated versus untreated G5G8(Tg) mice despite a greater feedback upregulation of genes in the pathway of cholesterol biosynthesis in the lovastatin-treated G5G8(Tg) mice. The reduced plasma cholesterol concentration is unlikely to be attributed to LDL and HDL receptors because the protein levels of both receptors remained unchanged. Surprisingly, statin treatment resulted in an increase in biliary cholesterol concentration, which was associated with an upregulation in hepatic mRNA and protein levels of ABCG5 and ABCG8, and in hepatic mRNA levels of Niemann-Pick C1-Like 1 (NPC1L1), a gene that is required for intestinal cholesterol absorption. In conclusion, mice with higher endogenous cholesterol synthesis rates are more sensitive to statin. A synergistic hypocholesterolemic effect could be potentially achieved in humans by simultaneously inhibiting cholesterol biosynthesis and promoting ABCG5/ABCG8-mediated cholesterol excretion.
Collapse
Affiliation(s)
- Weiqing Tang
- Department of Pathology Section on Lipid Sciences, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA
| | | | | |
Collapse
|
16
|
Han SH, Chung MJ, Lee SJ, Rhee C. Digestion-resistant fraction from soybean [Glycine max (L.) Merrill] induces hepatic LDL receptor and CYP7A1 expression in apolipoprotein E-deficient mice. J Nutr Biochem 2006; 17:682-8. [PMID: 16517141 DOI: 10.1016/j.jnutbio.2005.11.004] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2005] [Revised: 10/31/2005] [Accepted: 11/08/2005] [Indexed: 10/25/2022]
Abstract
Soybean [Glycine max (L.) Merrill] is known to have hypocholesterolemic effects; however, the function and mechanism of its digestion-resistant fraction (RF) in cholesterol reduction is not clearly understood. In the present study, we investigated the hypocholesterolemic effects of the RF from soybean in C57BL/6J and apolipoprotein E (apoE)-deficient mice. RFs were prepared either from raw or preheated crops to measure compositional changes in RF during cooking. Preheating reduced the RF yields and the resistant starch (RS) fraction in RF. After 1 week of feeding, the raw soybean RF (5%, w/w) was the most effective in lowering plasma cholesterol concentrations by 27% (P<.05) in apoE-deficient (apoE-/-) mice. A smaller but significant reduction was found in C57BL/6J mice. The RF from preheated soybean tended to have lower hypocholesterolemic effects than did the RF from raw soybean in apoE-/- mice. This suggests the RS may be a key hypocholesterolemic component from soybean RF. RF consumption (5%, w/w) dramatically increased hepatic low-density lipoprotein receptor and cholesterol 7alpha-hydroxylase expression in both apoE-/- and C57BL/6J mice followed by increased bile acid excretion. 3-Hydroxy-3-methylglutaryl-coenzyme A reductase was only marginally altered. Our results show that the RF, especially from raw soybean containing high level of RS, significantly reduces plasma cholesterol concentrations under hyperlipidemic condition. The cholesterol was reduced by multiple mechanisms such as increased hepatic cholesterol uptake, cholesterol degradation into bile acids and bile acid excretion.
Collapse
Affiliation(s)
- Sung-Hee Han
- Department of Agricultural Chemistry, College of Life and Environmental Sciences, Korea University, Seoul 136-701, South Korea
| | | | | | | |
Collapse
|
17
|
Leon C, Wasan KM, Sachs-Barrable K, Johnston TP. Acute P-407 administration to mice causes hypercholesterolemia by inducing cholesterolgenesis and down-regulating low-density lipoprotein receptor expression. Pharm Res 2006; 23:1597-607. [PMID: 16783477 DOI: 10.1007/s11095-006-0276-8] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2006] [Accepted: 02/23/2006] [Indexed: 10/24/2022]
Abstract
PURPOSE Poloxamer 407 (P-407) is a chemical that induces a dose-controlled dyslipidemia in mice. Our aim was to determine the acute effects of P-407 treatment on the mechanisms that influence hepatic cholesterol homeostasis. METHODS We measured lipid levels in plasma and liver samples from control and P-407-treated mice (24 h post-i.p. injection of 0.5 g kg(-1) of P-407 or saline for the control mice). We measured acyl-coenzyme A:cholesterol acyltransferase (ACAT) and 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase activities in liver microsomes. The protein expression of ACAT2, scavenger receptor class B, type I (SR-BI), ATP-binding cassette transporter A1 (ABCA1), ATP-binding cassette transporter G8 (ABCG8), low-density lipoprotein receptor (LDLr), and actin was measured by immunoblot. RESULTS We found an increase in plasma cholesterol and triglyceride levels as well as increased hepatic cholesteryl esters (CE) in P-407-treated mice. The hepatic ACAT microsomal activity and ACAT2 protein expression were not altered by P-407. The protein expression of the LDLr was decreased in the livers of P-407-treated mice. This decrease was specific, because the expression of the SR-BI was unchanged. The P-407-induced hypercholesterolemia was accounted for by increased activity and protein expression of HMG-CoA reductase. ATP-binding cassette transporters A1 and G8 protein expression were not significantly different in P-407-treated mice compared to controls. CONCLUSIONS The increased hepatic CE levels, following P-407 treatment, was neither related to an up-regulation of ACAT2 nor enhanced SR-BI expression. Hypercholesterolemia was associated with an up-regulation of both the protein expression and activity of HMG-CoA reductase and decreased LDLr expression.
Collapse
Affiliation(s)
- Carlos Leon
- Division of Pharmaceutics and Biopharmaceutics, Faculty of Pharmaceutical Sciences, University of British Columbia, Vancouver, British Columbia, Canada
| | | | | | | |
Collapse
|
18
|
Offe K, Dodson SE, Shoemaker JT, Fritz JJ, Gearing M, Levey AI, Lah JJ. The lipoprotein receptor LR11 regulates amyloid beta production and amyloid precursor protein traffic in endosomal compartments. J Neurosci 2006; 26:1596-603. [PMID: 16452683 PMCID: PMC2638122 DOI: 10.1523/jneurosci.4946-05.2006] [Citation(s) in RCA: 223] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Alzheimer's disease (AD) is a neurodegenerative disorder characterized by progressive cognitive decline and neuropathological changes, including the deposition of amyloid beta (Abeta) in senile plaques. The mechanisms causing the disease and Abeta accumulation are not well understood, but important genetic associations with apolipoprotein E genotype and involvement of lipoprotein receptors have become apparent. LR11 (also known as SorLA), a member of the low-density lipoprotein receptor family, has been identified previously as an altered transcript in microarray analyses of samples from human AD cases. Here, we show neuronal expression of the lipoprotein receptor LR11 in control brain in regions vulnerable to AD neuropathology and marked reduction of LR11 expression in these regions in AD brains before cell death. Overexpression of LR11 drastically reduces levels of extracellular Abeta and also lowers levels of total cellular amyloid precursor protein (APP). LR11 colocalizes with APP and regulates its trafficking in endocytic compartments, which are important intracellular sites for APP processing and Abeta generation. Endogenous LR11 localizes to neuronal multivesicular bodies in both rat and human brain. The robust correlation between reduced LR11 expression and AD neuropathology and its potent effects on extracellular Abeta levels suggest that this neuronal lipoprotein receptor could play an important role in AD pathogenesis.
Collapse
|
19
|
Mayer H, Duit S, Hauser C, Schneider WJ, Nimpf J. Reconstitution of the Reelin signaling pathway in fibroblasts demonstrates that Dab1 phosphorylation is independent of receptor localization in lipid rafts. Mol Cell Biol 2006; 26:19-27. [PMID: 16354676 PMCID: PMC1317641 DOI: 10.1128/mcb.26.1.19-27.2006] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The Reelin signaling pathway operates in migrating neurons and is indispensable for their correct positioning during embryonic brain development. Many biochemical and cell biological studies to dissect the Reelin pathway at the molecular level are hampered by the lack of a cell line harboring a functional Reelin signaling pathway. Here we present fibroblast cell lines in which all required functional components of the pathway have been reconstituted. These cells react upon Reelin treatment in the same way as primary neurons. We have subsequently used these cell lines to study the subcellular localization of ApoER2 and the VLDL receptor and could demonstrate that receptor-mediated Dab1 phosphorylation does not depend on lipid rafts and that phosphorylated Dab1 remains bound to the receptor tail when the pathway is activated by Reelin.
Collapse
Affiliation(s)
- Harald Mayer
- Max F. Perutz Laboratories, Department of Medical Biochemistry, University Department at the Vienna Biocenter, Medical University of Vienna, Vienna, Austria
| | | | | | | | | |
Collapse
|
20
|
Han KH, Iijuka M, Shimada KI, Sekikawa M, Kuramochi K, Ohba K, Ruvini L, Chiji H, Fukushima M. Adzuki resistant starch lowered serum cholesterol and hepatic 3-hydroxy-3-methylglutaryl-CoA mRNA levels and increased hepatic LDL-receptor and cholesterol 7alpha-hydroxylase mRNA levels in rats fed a cholesterol diet. Br J Nutr 2006; 94:902-8. [PMID: 16351766 DOI: 10.1079/bjn20051598] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
We examined the effects of adzuki bean resistant starch on serum cholesterol and hepatic mRNA in rats fed a cholesterol diet. The mRNA coded for key regulatory proteins of cholesterol metabolism. The control rats were fed 15 % cornstarch (basal diet, BD). The experimental rats were fed BD plus a 0.5 % cholesterol diet (CD), or a 15 % adzuki resistant starch plus 0.5 % cholesterol diet (ACD) for 4 weeks. The serum total cholesterol and VLDL + intermediate density lipoprotein + LDL-cholesterol levels in the ACD group were significantly lower than those in the CD group throughout the feeding period. The total hepatic cholesterol concentrations in the CD and ACD groups were not significantly different. The faecal total bile acid concentration in the ACD group was significantly higher than that in the BD and CD groups. Total SCFA and acetic acid concentrations in the ACD group were significantly higher than those in the CD group but there were no significant differences in the concentrations between the ACD and BD groups. The hepatic LDL-receptor mRNA and cholesterol 7alpha-hydroxylase mRNA levels in the ACD group were significantly higher than those in the CD group and the hepatic 3-hydroxy-3-methylglutaryl (HMG)-CoA reductase mRNA level in the ACD group was significantly lower than in the CD group. The results suggest that adzuki resistant starch has a serum cholesterol-lowering function via enhancement of the hepatic LDL-receptor mRNA and cholesterol 7alpha-hydroxylase mRNA levels and faecal bile acid excretion, and a decrease in the hepatic HMG-CoA reductase mRNA level, when it is added to a cholesterol diet.
Collapse
Affiliation(s)
- Kyu-Ho Han
- Department of Animal Science, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Hokkaido 080-8555, Japan
| | | | | | | | | | | | | | | | | |
Collapse
|
21
|
Draeger A, Monastyrskaya K, Mohaupt M, Hoppeler H, Savolainen H, Allemann C, Babiychuk EB. Statin therapy induces ultrastructural damage in skeletal muscle in patients without myalgia. J Pathol 2006; 210:94-102. [PMID: 16799920 DOI: 10.1002/path.2018] [Citation(s) in RCA: 123] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Muscle pain and weakness are frequent complaints in patients receiving 3-hydroxymethylglutaryl coenzymeA (HMG CoA) reductase inhibitors (statins). Many patients with myalgia have creatine kinase levels that are either normal or only marginally elevated, and no obvious structural defects have been reported in patients with myalgia only. To investigate further the mechanism that mediates statin-induced skeletal muscle damage, skeletal muscle biopsies from statin-treated and non-statin-treated patients were examined using both electron microscopy and biochemical approaches. The present paper reports clear evidence of skeletal muscle damage in statin-treated patients, despite their being asymptomatic. Though the degree of overall damage is slight, it has a characteristic pattern that includes breakdown of the T-tubular system and subsarcolemmal rupture. These characteristic structural abnormalities observed in the statin-treated patients were reproduced by extraction of cholesterol from skeletal muscle fibres in vitro. These findings support the hypothesis that statin-induced cholesterol lowering per se contributes to myocyte damage and suggest further that it is the specific lipid/protein organization of the skeletal muscle cell itself that renders it particularly vulnerable.
Collapse
Affiliation(s)
- A Draeger
- Institute of Anatomy, Department of Cell Biology, University of Bern, Baltzerstrasse 2, 3012 Bern, Switzerland.
| | | | | | | | | | | | | |
Collapse
|
22
|
Shin Y, Vaziri ND, Willekes N, Kim CH, Joles JA. Effects of gender on hepatic HMG-CoA reductase, cholesterol 7alpha-hydroxylase, and LDL receptor in hereditary analbuminemia. Am J Physiol Endocrinol Metab 2005; 289:E993-8. [PMID: 16030068 DOI: 10.1152/ajpendo.00037.2005] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Hypoalbuminemia is accompanied by hypercholesterolemia in both nephrotic syndrome and hereditary analbuminemia. Hypercholesterolemia is more severe in the female than in the male Nagase analbuminemic rats (NAR). The sex difference in plasma cholesterol diminishes after ovariectomy (OVX) and reappears after estrogen replacement in the NAR. The molecular mechanism responsible for the sex difference in severity of hypercholesterolemia in NAR is not known and was investigated here. To this end, hepatic hydroxylmethylglutaryl (HMG)-CoA reductase, cholesterol 7alpha-hydroxylase, and LDL receptor were determined in male, female, and OVX female NAR and Sprague-Dawley (SD) rats. Plasma cholesterol, triglycerides, and hepatic HMG-CoA reductase activities were greater in both female and male NAR than in SD rats. This was coupled with upregulation of cholesterol 7alpha-hydroxylase in both male and female NAR compared with SD controls. LDL receptor in male NAR was similar to that in male SD rats but was significantly reduced in female NAR. OVX partially, but significantly, reduced plasma cholesterol and triglyceride levels in female NAR. This was coupled with a significant rise in hepatic cholesterol 7alpha-hydroxylase and a modest increase in hepatic LDL receptor. In contrast, OVX resulted in a mild elevation of plasma cholesterol and no significant changes in total hepatic HMG-CoA reductase, cholesterol 7alpha-hydroxylase, or LDL receptor in female SD rats. Thus the greater severity of hypercholesterolemia in the female NAR appears to be due, in part, to a combination of the constrained compensatory upregulation of cholesterol 7alpha-hydroxylase and LDL receptor deficiency.
Collapse
Affiliation(s)
- Youngshin Shin
- Division of Nephrology and Hypertension, UCI Medical Center, University of California-Irvine, 101 The City Drive, Rt. 81, Orange, CA 92868, USA
| | | | | | | | | |
Collapse
|
23
|
Misawa J, Moriwaki SI, Kohno E, Hirano T, Tokura Y, Takigawa M. The role of low-density lipoprotein receptors in sensitivity to killing by Photofrin-mediated photodynamic therapy in cultured human tumor cell lines. J Dermatol Sci 2005; 40:59-61. [PMID: 16039835 DOI: 10.1016/j.jdermsci.2005.01.009] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2004] [Revised: 01/24/2005] [Accepted: 01/25/2005] [Indexed: 11/25/2022]
|
24
|
Yu-Poth S, Yin D, Kris-Etherton PM, Zhao G, Etherton TD. Long-chain polyunsaturated fatty acids upregulate LDL receptor protein expression in fibroblasts and HepG2 cells. J Nutr 2005; 135:2541-5. [PMID: 16251608 DOI: 10.1093/jn/135.11.2541] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The objective of this study was to investigate the effect of individual PUFAs on LDL receptor (LDLr) expression in human fibroblasts and HepG2 cells, and to evaluate whether acyl CoA:cholesterol acyltransferase (ACAT) and sterol regulatory element-binding protein 1 (SREBP-1) were involved in the regulation of LDLr expression by fatty acids. When fibroblasts and HepG2 cells were cultured with serum-free defined medium for 48 h, there was a 3- to 5-fold (P < 0.05) increase in LDLr protein and mRNA levels. Incubation of fibroblasts and HepG2 cells in serum-free medium supplemented with 25-hydroxycholesterol (25OH-cholesterol, 5 mg/L) for 24 h decreased LDLr protein and mRNA levels by 50-90% (P < 0.05). Arachidonic acid [AA, 20:4(n-6)], EPA [20:5(n-3)], and DHA [22:6(n-3)] antagonized the depression of LDLr gene expression by 25OH-cholesterol and increased LDLr protein abundance 1- to 3-fold (P < 0.05), but had no significant effects on LDLr mRNA levels. Oleic (18:1), linoleic (18:2), and alpha-linolenic acids [18:3(n-3)] did not significantly affect LDLr expression. ACAT inhibitor (58-035, 1 mg/L) attenuated the regulatory effect of AA on LDLr protein abundance by approximately 40% (P < 0.05), but did not modify the regulatory effects of other unsaturated fatty acids in HepG2 cells. The present results suggest that AA, EPA, and DHA increase LDLr protein levels, and that ACAT plays a role in modulating the effects of AA on LDLr protein levels. Furthermore, the effects of the fatty acids appeared to be independent of any change in SREBP-1 protein.
Collapse
Affiliation(s)
- Shaomei Yu-Poth
- Graduate Program in Nutrition, The Pennsylvania State University, University Park, PA 16802, USA
| | | | | | | | | |
Collapse
|
25
|
Yu YH, Wang Y, Dong B, Sun SZ, Chen Y, Meng XH, Liu ZZ. Fluvastatin prevents renal injury and expression of lactin-like oxidized low-density lipoprotein receptor-1 in rabbits with hypercholesterolemia. Chin Med J (Engl) 2005; 118:621-6. [PMID: 15899115] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/02/2023] Open
Abstract
BACKGROUND Lipid abnormalities are often complicated by renal dysfunction. 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) are the first-line choice for lowering cholesterol levels. The present study was designed to investigate whether statins could prevent and invert the development of renal injury in cholesterol-fed rabbits and to find the possible mechanism of their effects by detecting gene and protein expression of lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) in the renal artery. METHODS Twenty-four male New Zealand white rabbits were divided into three groups: (1) control group, regular granules chow; (2) HC-diet group, granules chow with 1% cholesterol and 5% lard oil; and (3) fluvastatin group, 1% cholesterol and 5% lard oil diet plus fluvastatin [10 mg.kg(-1).d(-1)]. After 16 weeks, serum total cholesterol (TC), low-density lipoprotein (LDL) and creatinine (Cr) levels were measured. Renal hemodynamics and function, mainly including glomerular filtration rate (GFR) in vivo were quantified using (99m)Tc-DTPA single photon emission computed tomograph ((99m)Tc-DTPA SPECT). The thickness of the renal artery intima was quantitated in HE-stained segments by histomorphometry. Gene expression of LOX-1 in the renal artery was examined by semi-quantitative RT-PCR and its protein expression was evaluated by immunohistochemistry. RESULTS High cholesterol diet induced hypercholesterolemia (HC) complicated by renal dysfunction with increased levels of serum lipid and Cr, decreased GFR and delayed excretion and extensively thickened renal arterial intima in the HC-diet group. Rabbits in the control group showed a minimal LOX-1 expression (mRNA and protein) in the endothelium and neointima of the renal artery. Intimal proliferation of the renal artery in the HC-diet group was associated with a marked increase of LOX-1 expression (protein and mRNA). Treatment with fluvastatin improved renal function, attenuated intimal proliferation of the renal artery and markedly decreased the enhanced LOX-1 expression in the endothelium and neointima of the renal artery in rabbits. CONCLUSIONS Fluvastatin treatment could prevent the development of renal injury in patients with HC and early atherosclerosis (AS). This beneficial effect might be mediated by its pleiotropic effects including a decrease in total cholesterol exposure level and prevention of LOX-1 expression in atherosclerotic arteries.
Collapse
Affiliation(s)
- Yong-hui Yu
- Department of Pediatrics, Shandong Provincial Hospital, Shandong University, Jinan 250021, China
| | | | | | | | | | | | | |
Collapse
|
26
|
Ishibashi S. [LDL receptor activity]. Nihon Rinsho 2004; 62 Suppl 12:130-3. [PMID: 15658281] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/01/2023]
Affiliation(s)
- Shun Ishibashi
- Division of Endocrinology and Metabolism, Jichi Medical School
| |
Collapse
|
27
|
Kashiwakura Y, Watanabe M, Kusumi N, Sumiyoshi K, Nasu Y, Yamada H, Sawamura T, Kumon H, Takei K, Daida H. Dynamin-2 regulates oxidized low-density lipoprotein-induced apoptosis of vascular smooth muscle cell. Circulation 2004; 110:3329-34. [PMID: 15545517 DOI: 10.1161/01.cir.0000147828.86593.85] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND On exposure to oxidized low-density lipoprotein (oxLDL), vascular cells generally undergo apoptosis, which is one of the major pathogenic factors of atherosclerosis. In this study, we examined the role of dynamin (a crucial GTPase protein in endocytosis) in oxLDL-induced apoptosis of vascular smooth muscle cells (VSMC). METHODS AND RESULTS After oxLDL stimulation, dynamin-2 colocalized with LOX-1 around the cell surface, as well as oxLDL in the cytoplasm, suggesting that dynamin-2 was involved in scavenger receptor-mediated oxLDL endocytosis. Downregulation of dynamin-2 induced by dynamin-2 dominant negative plasmid (K44A) resulted in a decrease of oxLDL uptake and thereby in a reduction of apoptosis. These data demonstrated that dynamin-2 was involved in oxLDL-induced apoptosis via the oxLDL endocytotic pathway. On the other hand, dynamin-2 wild-type plasmid transfection promoted oxLDL-induced apoptosis without increasing oxLDL uptake. Interestingly, the p53 inhibitor pifithrin-alpha (PFT) significantly reduced apoptosis promoted by wild-type dynamin-2 (78% reduction compared with the PFT[-] condition). These results indicated that dynamin-2 enhanced oxLDL-induced apoptosis of VSMC by participating in the p53 pathway, probably as a signal transducer. Moreover, we demonstrated that, in advanced plaques of apolipoprotein E-/- mice, dynamin-2 expression was often enhanced in apoptotic VSMC, suggesting that dynamin-2 might participate in apoptosis of VSMC even in vivo. CONCLUSIONS Our data demonstrated that dynamin-2 at least partially regulated oxLDL-induced apoptosis of VSMC by participating in 2 independent pathways: the oxLDL endocytotic pathway and the p53 pathway. These findings suggest that dynamin-2 may serve as a new research or therapeutic target in vascular disease.
Collapse
MESH Headings
- Animals
- Apolipoproteins E/deficiency
- Apolipoproteins E/genetics
- Apoptosis/drug effects
- Benzothiazoles
- Coronary Vessels/cytology
- Dynamin II/analysis
- Dynamin II/genetics
- Dynamin II/physiology
- Endocytosis/physiology
- Humans
- Hyperlipoproteinemia Type II/metabolism
- Lipoproteins, LDL/pharmacology
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Muscle, Smooth, Vascular/cytology
- Muscle, Smooth, Vascular/drug effects
- Myocytes, Smooth Muscle/drug effects
- Myocytes, Smooth Muscle/enzymology
- Myocytes, Smooth Muscle/metabolism
- Receptors, LDL/analysis
- Receptors, Oxidized LDL
- Scavenger Receptors, Class E
- Signal Transduction/drug effects
- Thiazoles/pharmacology
- Toluene/analogs & derivatives
- Toluene/pharmacology
- Transfection
- Tumor Suppressor Protein p53/antagonists & inhibitors
- Tumor Suppressor Protein p53/physiology
Collapse
Affiliation(s)
- Yuji Kashiwakura
- Department of Cardiology, Juntendo University School of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo 113-8421, Japan.
| | | | | | | | | | | | | | | | | | | |
Collapse
|
28
|
Nishimura S, Akagi M, Yoshida K, Hayakawa S, Sawamura T, Munakata H, Hamanishi C. Oxidized low-density lipoprotein (ox-LDL) binding to lectin-like ox-LDL receptor-1 (LOX-1) in cultured bovine articular chondrocytes increases production of intracellular reactive oxygen species (ROS) resulting in the activation of NF-kappaB. Osteoarthritis Cartilage 2004; 12:568-76. [PMID: 15219572 DOI: 10.1016/j.joca.2004.04.005] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/03/2003] [Accepted: 04/05/2004] [Indexed: 02/02/2023]
Abstract
OBJECTIVE To examine the effect of oxidized low-density lipoprotein (ox-LDL) on the intracellular production of reactive oxygen species (ROS) in bovine articular chondrocytes (BACs) and to investigate whether this increase occurs through binding to the receptor lectin-like ox-LDL receptor-1 (LOX-1). Furthermore, to ascertain whether the binding of ox-LDL to LOX-1 results in NF-kappaB activation. DESIGN BACs were preincubated with 2',7'-dichlorofluorescin diacetate (DCFH-DA), a dye that allows the monitoring of intracellular ROS production for DCF by spectrofluorometry. BACs were incubated with native LDL and ox-LDL (10, 50, and 100 microg/ml) for 5 min at 37 degrees C and DCF formation was observed. BACs were also preincubated with anti-LOX-1 mAb (40 microg/ml) or ascorbic acid (10 microM). Nuclear extracts from BACs treated for the indicated periods with 50 microg/ml ox-LDL, and preincubated with anti-LOX-1 mAb or ascorbic acid, were prepared and analyzed by electrophoretic mobility shift assay (EMSA). RESULTS ox-LDL induced a significant dose-dependent increase in ROS production after 5-min incubation with BACs (P < 0.001). ROS formation was markedly reduced in BACs preincubated with anti-LOX-1 mAb and ascorbic acid (P < 0.001). Activation in BACs of the transcription factor NF-kappaB was evident after 5-min incubation with ox-LDL and was attenuated by anti-LOX-1 mAb and ascorbic acid. CONCLUSION ox-LDL binding to LOX-1 in BACs increased the production of intracellular ROS and activated NF-kappaB. Reduction of NF-kappaB activation by ascorbic acid indicates that the activation, at least in part, is ROS-dependent. These observations support the hypothesis that hypercholesterolemia is one of several risk factors for arthritis, and that lipid peroxidation products such as ox-LDL are involved in cartilage matrix degradation.
Collapse
Affiliation(s)
- Shunji Nishimura
- Department of Orthpaedic Surgery, Kinki University School of Medicine, 377-2 Ohno-Higashi, Osaka-Sayama City, Osaka 589-8511, Japan
| | | | | | | | | | | | | |
Collapse
|
29
|
Heo TH, Chang JH, Lee JW, Foung SKH, Dubuisson J, Kang CY. Incomplete Humoral Immunity against Hepatitis C Virus Is Linked with Distinct Recognition of Putative Multiple Receptors by E2 Envelope Glycoprotein. J Immunol 2004; 173:446-55. [PMID: 15210804 DOI: 10.4049/jimmunol.173.1.446] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Little is known about the role of the humoral immune response to hepatitis C virus (HCV). This study provides molecular evidence for the mechanism by which neutralizing Abs from the sera of chronic HCV patients have lower inhibitory activities against the binding of HCV E2 envelope protein to human hepatoma cell lines than to a lymphoma cell line. E2 binds to several putative receptors, specifically human CD81; human scavenger receptor, class B, type 1; and heparan sulfate. We have shown that E2 binds to target cells via these receptors in a noncompetitive manner. Thus, incomplete inhibition of one of the receptors leads to only a partial E2 blockade and, possibly, evasion of the host immune response. We demonstrated that the difference in and reduction of inhibition was closely related to impaired blockade of E2 binding to scavenger receptor, class B, type 1, and heparan sulfate. We have also shown that soluble E2 protein binds to multiple soluble receptors via separate binding domains on E2, providing further evidence for the distinct recognition of multiple cellular receptors by E2. This report suggests a novel finding that biased humoral immune responses to HCV E2 might provide an alternative mechanism for viral escape without the involvement of mutation. Additionally, our data give crucial consideration to the development of HCV vaccines that stimulate protective humoral immune responses.
Collapse
Affiliation(s)
- Tae-Hwe Heo
- Laboratory of Immunology, Institute of Pharmaceutical Sciences, College of Pharmacy, Seoul National University, Shillim-Dong, Kwanak-Gu, Seoul 151-742, Korea
| | | | | | | | | | | |
Collapse
|
30
|
Li H, Zhang Z, Blessington D, Nelson DS, Zhou R, Lund-Katz S, Chance B, Glickson JD, Zheng G. Carbocyanine labeled LDL for optical imaging of tumors. Acad Radiol 2004; 11:669-77. [PMID: 15172369 DOI: 10.1016/j.acra.2004.01.016] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2003] [Revised: 12/09/2003] [Accepted: 01/20/2004] [Indexed: 10/26/2022]
Abstract
RATIONALE AND OBJECTIVES The purpose of this study was to define and characterize carbocyanine labeled low-density lipoprotein (LDL) to be used in the optical imaging of LDL receptor (LDLr)-overexpressing tumor models. MATERIALS AND METHODS 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (DiI) was used to label LDL (DiI-LDL). Scatchard plots were generated to determine the maximum binding capacity B(max) and dissociation constants K(D) of DiI-LDL in B16 melanoma (B16) and hepatoblastoma G(2) (HepG(2)) cell lines. Selective uptake of DiI-LDL into both tumor cells and corresponding subcutaneous tumors in mice were demonstrated by confocal microscopy and three-dimensional Cryo-imaging, respectively. RESULTS The labeling efficiency of DiI-LDL was 61 ng DiI/microg LDL protein (34 mol DiI/mol LDL protein). B(max) and K(D) for B16 cells were 6.311 ng LDL/mg cell protein and 60.38 microg protein/mL (117 nM), respectively. B(max) and K(D) were 7.573 ng LDL/mg cell protein and 26.79 microg protein/mL (52 nM) for HepG(2) cells, respectively. Confocal microscopic images showed specific uptake of DiI-LDL throughout the cytoplasm in the B16/HepG(2) cells. Cryo-imaging demonstrated preferential accumulations of DiI-LDL in the viable tumor regions of both B16 and HepG(2) tumors compared with their adjacent normal tissues and corresponding necrotic tumor regions. In addition, uptake of DiI-LDL by the HepG(2) tumor was much higher than that of the B16 tumor, consistent with the fact that the probe binding affinity for LDLrs of HepG(2) cells is 2.3 times that of B16 cells. CONCLUSION This study suggested that carbocyanine labeled LDL could be used for optical imaging of tumors overexpressing LDLr.
Collapse
Affiliation(s)
- Hui Li
- Department of Radiology, University of Pennsylvania Medical School, Chemistry 1958 Wing, Room 284, Box 66, 250 South 33rd Street, Philadelphia, PA 19104 USA
| | | | | | | | | | | | | | | | | |
Collapse
|
31
|
Michaely P, Li WP, Anderson RGW, Cohen JC, Hobbs HH. The modular adaptor protein ARH is required for low density lipoprotein (LDL) binding and internalization but not for LDL receptor clustering in coated pits. J Biol Chem 2004; 279:34023-31. [PMID: 15166224 DOI: 10.1074/jbc.m405242200] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
ARH is an adaptor protein required for efficient endocytosis of low density lipoprotein (LDL) receptors (LDLRs) in selected tissues. Individuals lacking ARH (ARH-/-) have severe hypercholesterolemia due to impaired hepatic clearance of LDL. Immortalized lymphocytes, but not fibroblasts, from ARH-deficient subjects fail to internalize LDL. To further define the role of ARH in LDLR function, we compared the subcellular distribution of the LDLR in lymphocytes from normal and ARH-/- subjects. In normal lymphocytes LDLRs were predominantly located in intracellular compartments, whereas in ARH-/- cells the receptors were almost exclusively on the plasma membrane. Biochemical assays and quantification of LDLR by electron microscopy indicated that ARH-/- lymphocytes had >20-fold more LDLR on the cell surface and a approximately 27-fold excess of LDLR outside of coated pits. The accumulation of LDLR on the cell surface was not due to failure of receptors to localize in coated pits since the number of LDLRs in coated pits was similar in ARH-/- and normal cells. Despite the dramatic increase in cell surface receptors, LDL binding was only 2-fold higher in the ARH-/- lymphocytes. These findings indicate that ARH is required not only for internalization of the LDL.LDLR complex but also for efficient binding of LDL to the receptor and suggest that ARH stabilizes the associations of the receptor with LDL and with the invaginating portion of the budding pit, thereby increasing the efficiency of LDL internalization.
Collapse
MESH Headings
- Adaptor Proteins, Signal Transducing
- Adaptor Proteins, Vesicular Transport/deficiency
- Adaptor Proteins, Vesicular Transport/physiology
- Cell Line, Transformed
- Cell Membrane/chemistry
- Coated Pits, Cell-Membrane/chemistry
- Coated Pits, Cell-Membrane/metabolism
- Endocytosis
- Fluorescent Antibody Technique
- Humans
- Hypercholesterolemia/blood
- Immunohistochemistry
- Iodine Radioisotopes
- Lipoproteins, LDL/blood
- Lymphocytes/ultrastructure
- Microscopy, Electron
- Receptors, LDL/analysis
- Receptors, LDL/blood
Collapse
Affiliation(s)
- Peter Michaely
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
| | | | | | | | | |
Collapse
|
32
|
Wang L, Li ZY, Wang Y, He A, Xie MH, Zhan XM. [Study on low density lipoprotein receptor of adult Schistosoma japonicum]. Zhongguo Ji Sheng Chong Xue Yu Ji Sheng Chong Bing Za Zhi 2004; 20:90-3. [PMID: 12567567] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/28/2023]
Abstract
OBJECTIVE To provide a theoretical basis for the study of vaccines against Schistosoma japonicum, the receptor for human LDL in the tegument of adult Schistosoma japonicum was investigated. METHODS Proteins existed in adult Schistosoma japonicum membrane were extracted by Triton X-100 and purified through reverse-phase high performance liquid chromatography (HPLC), and the main protein peaks were then collected separately. 125I-LDL of human plasma as the ligand, through the radioautography and radioligand binding assay, the protein which can bind human serum 125I-LDL specifically was identified. The molecular weight and IEF were detected by SDS-PAGE. RESULTS According to the radioautography and radioligand binding assay, a protein with retention time of 10.5 min was proved to be able to bind human serum 125I-LDL specifically. SDS-PAGE revealed that the molecular weight of the purified protein is 60-65 kDa, and its IEF is 6.7. CONCLUSION LDL binding protein may exist on the surface of both male and female adult Schistosoma japonicum with the function of obtaining cholesterol from host circulating system.
Collapse
Affiliation(s)
- Liang Wang
- Department of Parasitology, Sun Yat-sen University of Medical Sciences, Guangzhou 510089
| | | | | | | | | | | |
Collapse
|
33
|
Duvillard L, Gambert P, Lizard G. [Flow cytometric study of low density lipoprotein receptors: biological and clinical interest]. Ann Biol Clin (Paris) 2004; 62:87-91. [PMID: 15047497] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/29/2023]
Abstract
Low density lipoprotein (LDL) carry 60 to 80% of plasma cholesterol. These particules are mainly catabolized by LDL receptor. Thus, LDL receptor plays an important role in the regulation of plasma LDL cholesterol concentration, which is correlated to the risk of developing cardiovascular disease. The intracellular concentration of free cholesterol exerts a negative feedback on LDL receptor expression at the cell surface. This expression is also modulated by a lot of hormones, drugs and cytokines. On the other hand, mutations of LDL receptor induce familial hypercholesterolaemia, a frequent genetic disorder (1 to 500 births for the heterozygous form). Flow cytometry is a simple and fast technic, allowing to quantify LDL receptor expression at the cell surface and to study its functionality. Two different ligands can be used with flow cytometry: either fluorochrome-labelled LDL or anti-LDL receptor monoclonal antibody detected by a fluorescent secondary antibody. In immunofluorescent assays, we can now precisely calculate the number of LDL receptor at the cell surface by using calibration kits. In this article, we summarize the different regulatory factors of LDL receptor expression and present the advantages and limits of the different flow cytometry assays for LDL receptor analysis.
Collapse
|
34
|
Sirtori CR, Lovati MR, Manzoni C, Castiglioni S, Duranti M, Magni C, Morandi S, D'Agostina A, Arnoldi A. Proteins of white lupin seed, a naturally isoflavone-poor legume, reduce cholesterolemia in rats and increase LDL receptor activity in HepG2 cells. J Nutr 2004; 134:18-23. [PMID: 14704287 DOI: 10.1093/jn/134.1.18] [Citation(s) in RCA: 141] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
White lupin (Lupinus albus, L.), a widely cultivated crop that has been consumed for many years in Western Europe, may provide a useful alternative for individuals wishing to substitute animal with plant proteins for cardiovascular disease prevention. Lupin seeds have a very low content of isoflavones, and lupin protein isolates are essentially isoflavone free. In rats fed a casein-based cholesterol + cholic acid diet, a relatively low daily intake (50 mg/d by gavage for 2 wk) of total lupin protein extract reduced plasma total and VLDL + LDL cholesterol concentrations by 21 and 30%, respectively (both P<0.001). In an attempt to elucidate the lipid-lowering mechanism, LDL receptor activity was evaluated in a human hepatoma cell line (HepG2). In this model, the lupin total protein extract was essentially inactive, whereas one purified minor protein component, conglutin gamma, had a remarkable upregulatory effect, with maximal increases of 53 and 21% (both P<0.05) for LDL uptake and degradation, respectively. This initial study indicates that lupin, although isoflavone free, has hypocholesterolemic activity similar to that of other leguminous proteins in an established animal model. Further, the cholesterol reduction appears to be associated with stimulation of LDL receptors by a well-defined protein component of the lupin seeds as demonstrated by in vitro studies.
Collapse
Affiliation(s)
- Cesare R Sirtori
- Department of Pharmacological Sciences, University of Milano, 20133 Milan, Italy.
| | | | | | | | | | | | | | | | | |
Collapse
|
35
|
Abstract
Conjugated linoleic acid (CLA) exerts anticarcinogenic and antiatherosclerotic effects in animals. The present study was conducted to examine the effects of CLA on LDL receptor (LDLr) expression in HepG2 cells, and to evaluate whether the sterol response element binding protein 1 (SREBP-1) and acyl CoA:cholesterol acyltransferase (ACAT) were involved in the regulation of LDLr expression by CLA. When HepG2 cells were cultured with serum-free DMEM for 48 h, there was a three- to fivefold (P<0.05) increase in LDLr protein and mRNA levels. Incubation of HepG2 cells in serum-free medium supplemented with 25-hydroxycholesterol (25OH, 5 mg/L) for 24 h decreased LDLr protein and mRNA by 50-70% (P<0.05) and mature SREBP-1 by 20-40% (P<0.05). CLA, but not linoleic acid, antagonized the depressive effects of 25OH and increased both LDLr protein and mRNA abundance twofold (P<0.05). LDLr protein and mRNA abundance were not different when HepG2 cells were cultured with CLA (0.4 mmol/L) plus 25OH in the presence or absence of an ACAT inhibitor (58-035, 1 mg/L). Furthermore, CLA had no effect on SREBP-1 abundance. These results suggest that CLA upregulates LDLr expression via a mechanism that is independent of ACAT and SREBP-1.
Collapse
Affiliation(s)
- Shaomei Yu-Poth
- Graduate Program in Nutrition, The Pennsylvania State University, University Park, PA 16802, USA
| | | | | | | | | |
Collapse
|
36
|
Lin Y, Meijer GW, Vermeer MA, Trautwein EA. Soy protein enhances the cholesterol-lowering effect of plant sterol esters in cholesterol-fed hamsters. J Nutr 2004; 134:143-8. [PMID: 14704307 DOI: 10.1093/jn/134.1.143] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
This study aimed to investigate whether the combination of plant sterol esters (PSE) with soy protein or soy isoflavones may have extra cholesterol-lowering effects. Male hamsters (n=20/group) were fed diets containing (g/100 g diet) (A) 20 casein (control), (B) 0.24 PSE, (C) 20 intact soy protein (replacing casein), (D) 0.02 soy isoflavones, (E) 0.24 PSE plus 20 soy protein (replacing casein), or (F) 0.24 PSE plus 0.02 soy isoflavones, for 5 wk. All diets contained 0.08 g cholesterol/100 g diet. Compared with the control diet, the PSE and soy protein diets significantly lowered the plasma total cholesterol concentration by 13% (P<0.05) and 9% (P<0.05), respectively, whereas the isoflavone diet (D) had no effect. The combination of PSE and soy protein (diet E) decreased plasma total cholesterol by 26% (P<0.05). The decrease in plasma cholesterol concentration was mainly in the non-HDL fraction. In addition, the combination of PSE and soy protein significantly decreased plasma triacylglycerol concentration (37%, P<0.05) and reduced cholesterol accumulation in the liver. The abundance of hepatic LDL-receptors was not influenced by any of the test diets. PSE selectively increased fecal excretion of neutral sterols by 190% (P<0.05), whereas soy protein increased fecal excretion of neutral sterols and bile acids by 66% (P<0.05) and 130% (P<0.05), respectively. The combination of PSE and soy protein increased the fecal excretion of neutral sterols and bile acids compared with PSE and soy protein alone. In conclusion, the combination of PSE and soy protein more dramatically lowers plasma lipids than the individual ingredients.
Collapse
Affiliation(s)
- Yuguang Lin
- Unilever Health Institute, Unilever R & D, Vlaardingen, The Netherlands.
| | | | | | | |
Collapse
|
37
|
Fellin R, Zuliani G, Arca M, Pintus P, Pacifico A, Montali A, Corsini A, Maioli M. Clinical and biochemical characterisation of patients with autosomal recessive hypercholesterolemia (ARH). Nutr Metab Cardiovasc Dis 2003; 13:278-286. [PMID: 14717060 DOI: 10.1016/s0939-4753(03)80032-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
BACKGROUND AND AIM Inherited hypercholesterolemias are common disorders characterised by elevated LDL-C levels and premature coronary heart disease. We have recently described a recessive form of hypercholesterolemia (autosomal recessive hypercholesterolemia, ARH) in which LDL catabolism is reduced because of a mutation in the gene coding for an adaptor protein that impairs LDL-receptor (LDL-R) activity in the liver. The aim of this study was to characterise in detail the phenotypes of subjects with homozygous and heterozygous ARH. METHODS AND RESULTS We have so far identified six Italian families with ARH and studied the clinical and biochemical characteristics of 11 homozygotes (age 13-47 years) and 12 obligate heterozygotes (age 42-83 years). The study protocol included an evaluation of the lipoprotein profile, LDL-R activity in fibroblasts, LDL binding activity, and apo E genotype; a structured questionnaire (CHD risk factors, medical history, current medications); a physical examination, resting and stress ECG, ultrasound examinations (heart, carotid arteries, Achilles tendons) and coronary angiography. The pedigrees were characterised by the absence of vertical transmission; consanguinity was documented in two families. Only the two previously described Sardinian mutations, ARH1 (c.432insA) and ARH2 (c.65G > A), were identified in the probands. All of the ARH homozygotes had large tendinous xanthomas, two had exertional angina, and four a positive stress ECG. None had experienced myocardial infarction or stroke. More than half had instrumental signs of atherosclerosis such as a positive stress ECG or positive carotid echo-doppler examination. The ARH heterozygotes were consistently normal and had a normal lipid profile. CONCLUSIONS The ARH phenotype resembles that of familial hypercholesterolemia (FH) homozygotes, but ARH may be a less serious illness. The absence of vertical transmission, and the presence of mild coronary heart disease and consanguinity, can suggest a possible diagnosis of ARH. ARH might be considered a phenocopy of FH but heterozygous subjects seem to have a consistently normal phenotype.
Collapse
Affiliation(s)
- R Fellin
- Second Department of Internal Medicine, University of Ferrara, Ferrara, Italy.
| | | | | | | | | | | | | | | |
Collapse
|
38
|
Miserez AR, Scharnagl H, Muller PY, Mirsaidi R, Stähelin HB, Monsch A, März W, Hoffmann MM. Apolipoprotein E3Basel: new insights into a highly conserved protein region. Eur J Clin Invest 2003; 33:677-85. [PMID: 12864777 DOI: 10.1046/j.1365-2362.2003.01180.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND Apolipoprotein E is important for the receptor-mediated uptake of triglyceride-rich lipoproteins. Mutations in the gene encoding apolipoprotein E may cause a reduced uptake of these lipoproteins. Particular apolipoprotein E mutations have been also found to be associated with nephrologic, neurologic, and even ophthalmologic diseases. Hence, a continuously expanding role in biology is being attributed to this protein. DESIGN Randomly selected volunteers from of a large Swiss cohort were genotyped for the common apolipoprotein E isoforms (apolipoprotein E2, apolipoprotein E3, apolipoprotein E4). RESULTS In one of the volunteers, a novel C-to-T mutation causing an alanine-to-valine substitution (A106V, designated apolipoprotein E3Basel) was discovered. Alanine at residue 106 is highly conserved between mammalian species and is located in the immediate vicinity of the 112C/R polymorphism (apolipoprotein E4). Recombinant apolipoprotein E3Basel, expressed in the baculovirus system, displayed no detectable reduction in its low density lipoprotein (LDL) receptor- and heparin-binding activities. Despite normal binding functions, apolipoprotein E3Basel might cause modifications in the lipoprotein pattern. In the index case, plasma triglycerides were elevated and in two further apolipoprotein E3Basel-carriers, cholesterol, phospholipid, apolipoprotein CIII levels, LDL-cholesterol/apoB-100- and VLDL-triglyceride/VLDL-cholesterol-ratios were higher compared with apolipoprotein E3Basel-noncarriers when pair-matched for age and gender. One of the four apolipoprotein E3Basel-carriers from the index family had a personal history of Alzheimer's disease. CONCLUSIONS Alanine at amino acid position 106 is highly conserved but not crucial in the receptor-mediated uptake of lipoprotein particles. Nevertheless, amino acid position 106 might be involved in the apolipoprotein E-dependent regulation of the lipoprotein lipase that hydrolyzes triglycerides and in the development of Alzheimer's disease.
Collapse
Affiliation(s)
- A R Miserez
- Department of Internal Medicine, University Hospital Bruderholz, Switzerland.
| | | | | | | | | | | | | | | |
Collapse
|
39
|
Jones C, Hammer RE, Li WP, Cohen JC, Hobbs HH, Herz J. Normal sorting but defective endocytosis of the low density lipoprotein receptor in mice with autosomal recessive hypercholesterolemia. J Biol Chem 2003; 278:29024-30. [PMID: 12746448 DOI: 10.1074/jbc.m304855200] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Autosomal recessive hypercholesterolemia (ARH) is a genetic form of hypercholesterolemia that clinically resembles familial hypercholesterolemia (FH). As in FH, the rate of clearance of circulating low density lipoprotein (LDL) by the LDL receptor (LDLR) in the liver is markedly reduced in ARH. Unlike FH, LDL uptake in cultured fibroblasts from ARH patients is normal or only slightly impaired. The gene defective in ARH encodes a putative adaptor protein that has been implicated in linking the LDLR to the endocytic machinery. To determine the role of ARH in the liver, ARH-deficient mice were developed. Plasma levels of LDL-cholesterol were elevated in the chow-fed Arh-/- mice (83 +/- 8 mg/dl versus 68 +/- 8 mg/dl) but were lower than those of mice expressing no LDLR (Ldlr-/-) (197 +/- 8 mg/dl). Cholesterol feeding elevated plasma cholesterol levels in both strains. The fractional clearance rate of radiolabeled LDL was reduced to similar levels in the Arh-/- and Ldlr-/- mice, whereas the rate of removal of alpha2-macroglobulin by the LDLR-related protein, which also interacts with ARH, was unchanged. Immunolocalization studies revealed that a much greater proportion of immunodetectable LDLR, but not LDLR-related protein, was present on the sinusoidal surface of hepatocytes in the Arh-/- mice. Taken together, these results are consistent with ARH playing a critical and specific role in LDLR endocytosis in the liver.
Collapse
MESH Headings
- Adaptor Proteins, Signal Transducing
- Adaptor Proteins, Vesicular Transport/genetics
- Adaptor Proteins, Vesicular Transport/physiology
- Animals
- Centrifugation, Density Gradient
- Cholesterol/blood
- Cholesterol, Dietary/administration & dosage
- Cholesterol, LDL/blood
- Endocytosis/genetics
- Hypercholesterolemia/genetics
- Hypercholesterolemia/metabolism
- Hyperlipoproteinemia Type II/genetics
- Iodine Radioisotopes
- Lipoproteins, LDL/blood
- Liver/chemistry
- Liver/metabolism
- Liver/ultrastructure
- Metabolic Clearance Rate
- Mice
- Mice, Knockout
- Receptors, LDL/analysis
- Receptors, LDL/genetics
- Receptors, LDL/physiology
Collapse
Affiliation(s)
- Christopher Jones
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9046, USA
| | | | | | | | | | | |
Collapse
|
40
|
Abstract
High-dose 17alpha-ethinyl estradiol treatment is associated with increased adrenal and decreased hepatic levels of scavenger receptor class B type 1 (SR-BI) in rats. In this paper we explored the mechanisms responsible for the differential regulation of SR-BI by estrogen in these two tIssues. Previously it was shown that estrogen-treated rats are profoundly hypolipidemic due to increased hepatic low density lipoprotein receptor (LDLR) activity, and that this effect is not maintained with hypophysectomy. To determine if the reduction in hepatic SR-BI was a direct or indirect effect of estrogen, we treated hypophysectomized rats with high-dose estrogen; the levels of SR-BI expression did not change in the livers or adrenals of these animals. To determine if the absence of response to estrogen in the adrenals of hypophysectomized animals was due to the absence of adrenocorticotropic hormone (ACTH), we examined the effect of estrogen treatment on SR-BI expression in animals treated with dexamethasone, which inhibits endogenous ACTH production. The administration of dexamethasone completely inhibited the increase in SR-BI expression in the adrenals of estrogen-treated rats. From these studies we conclude that estrogen does not have a direct effect on SR-BI expression in either the liver or the adrenals. In the liver, the decrease in SR-BI is dependent on the estrogen-induced increase in LDLR activity, and in the adrenal glands, ACTH is required for the estrogen-associated increase in expression of SR-BI.
Collapse
Affiliation(s)
- H Stangl
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas 75235, USA.
| | | | | | | | | |
Collapse
|
41
|
Morawietz H, Duerrschmidt N, Niemann B, Galle J, Sawamura T, Holtz J. Augmented endothelial uptake of oxidized low-density lipoprotein in response to endothelin-1. Clin Sci (Lond) 2002; 103 Suppl 48:9S-12S. [PMID: 12193044 DOI: 10.1042/cs103s009s] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Endothelin-1 (ET-1) may be involved in the development and progression of atherosclerosis. Furthermore, endothelin receptor blockade was shown to reduce the formation of atherosclerotic lesions in experimental studies. Another potent pro-atherosclerotic risk factor is oxidized low-density lipoprotein (oxLDL). Endothelial cells mediate the uptake of oxLDL by the recently identified lectin-like oxLDL receptor-1 (LOX-1), which accumulates in atherosclerotic lesions. In the present study, we analysed the effects of ET-1 on oxLDL uptake and LOX-1 expression in primary cultures of human umbilical vein endothelial cells (HUVEC). ET-1 stimulated uptake of oxLDL in HUVEC, which reached a maximum after 1 h. In further studies, we found a similar induction of LOX-1 mRNA and protein expression in response to ET-1. The augmented oxLDL uptake and the increased LOX-1 expression in response to ET-1 are mediated by the endothelin receptor B. Our data support a new pathophysiological mechanism by which locally and systemically increased ET-1 levels, e.g. in hypertensive patients, could promote LOX-1-mediated oxLDL uptake in human endothelial cells. This mechanism could promote the development and progression of endothelial dysfunction and atherosclerosis. In addition, endothelin receptor blockade could be considered as a new anti-atherosclerotic therapeutic principle.
Collapse
MESH Headings
- Arteriosclerosis/metabolism
- Cells, Cultured
- Endothelin-1/pharmacology
- Endothelium, Vascular/metabolism
- Humans
- Lipoproteins, LDL/metabolism
- RNA, Messenger/analysis
- Receptors, LDL/analysis
- Receptors, LDL/genetics
- Receptors, LDL/metabolism
- Receptors, Oxidized LDL
- Scavenger Receptors, Class E
- Stimulation, Chemical
- Umbilical Veins
Collapse
Affiliation(s)
- Henning Morawietz
- Institute of Pathophysiology, Faculty of Medicine, Martin Luther University Halle-Wittenberg, D-06097 Halle, Germany.
| | | | | | | | | | | |
Collapse
|
42
|
Li DY, Chen HJ, Staples ED, Ozaki K, Annex B, Singh BK, Vermani R, Mehta JL. Oxidized low-density lipoprotein receptor LOX-1 and apoptosis in human atherosclerotic lesions. J Cardiovasc Pharmacol Ther 2002; 7:147-53. [PMID: 12232563 DOI: 10.1177/107424840200700304] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
BACKGROUND Lectin-like oxidized LDL receptor-1 (LOX-1), a novel receptor for oxidized low-density lipoprotein, mediates oxidized low-density lipoprotein-induced apoptosis of endothelial cells, monocyte adhesion to endothelium, and phagocytosis of aged cells. The present study examined the role of LOX-1 and apoptosis in human atherosclerotic lesions. METHODS AND RESULTS Grafted vein (n = 8), human carotid artery endarterectomy (n = 11), and normal human internal mammary artery (n = 8) specimens were used to study the expression of LOX-1 and apoptosis. LOX-1 expression was determined by reverse transcriptase-polymerase chain reaction, Western analysis, and immunostaining. Presence of apoptosis was determined by fluorescent in situ nick end-labeling staining and by the presence of poly (ADP-ribose) polymerase protein (an apoptotic marker). Expression of LOX-1 was significantly increased in atherosclerotic grafted vein and carotid artery specimens compared with that in normal arteries. LOX-1 was expressed in endothelial cells, macrophages, and smooth muscle cells. LOX-1 was extensively expressed in the new blood vessels in the core of advanced atherosclerotic lesions. Double immunostaining showed LOX-1 expression to be colocalized with apoptotic cells. Fluorescent in situ nick end-labeling staining showed that the apoptotic cells were present mostly in the rupture-prone regions of the atherosclerotic plaque. CONCLUSION These observations indicate that LOX-1 is extensively expressed in the proliferated intima of grafted veins and in advanced atherosclerotic carotid arteries. Further, LOX-1 is colocalized with apoptotic cells. These observations may relate to the phenomenon of plaque rupture, and provide targets for developing new therapies.
Collapse
Affiliation(s)
- D Y Li
- Department of Surgery, University of Florida and the VA Medical Center, Gainesville, FL, USA
| | | | | | | | | | | | | | | |
Collapse
|
43
|
Gillian-Daniel DL, Bates PW, Tebon A, Attie AD. Endoplasmic reticulum localization of the low density lipoprotein receptor mediates presecretory degradation of apolipoprotein B. Proc Natl Acad Sci U S A 2002; 99:4337-42. [PMID: 11904390 PMCID: PMC123649 DOI: 10.1073/pnas.072557199] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Mutations in the low density lipoprotein (LDL) receptor (LDLR) cause hypercholesterolemia because of inefficient LDL clearance from the circulation. In addition, there is a paradoxical oversecretion of the metabolic precursor of LDL, very low density lipoprotein (VLDL). We recently demonstrated that the LDLR mediates pre-secretory degradation of the major VLDL protein, apolipoprotein B (apoB). Kinetic studies suggested that the degradation process is initiated in the secretory pathway. Here, we evaluated the ability of several LDLR variants that are stalled within the secretory pathway to regulate apoB secretion. Both a naturally occurring mutant LDLR and an LDLR consisting of only the ligand-binding domains and a C-terminal endoplasmic reticulum (ER) retention sequence were localized to the ER and not at the cell surface. In the presence of either of the ER-localized LDLRs, apoB secretion was essentially abolished. When the ligand-binding domain of the truncated receptor was mutated the receptor was unable to block apoB secretion, indicating that the inhibition of apoB secretion depends on the ability of the LDLR to bind to its ligand. These findings establish LDLR-mediated pre-secretory apoB degradation as a pathway distinct from reuptake of nascent lipoproteins at the cell surface. The LDLR provides an example of a receptor that modulates export of its ligand from the ER.
Collapse
|
44
|
Pal A, Hall BS, Nesbeth DN, Field HI, Field MC. Differential endocytic functions of Trypanosoma brucei Rab5 isoforms reveal a glycosylphosphatidylinositol-specific endosomal pathway. J Biol Chem 2002; 277:9529-39. [PMID: 11751913 DOI: 10.1074/jbc.m110055200] [Citation(s) in RCA: 82] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We demonstrate the presence of a glycosylphosphatidylinositol (GPI) anchor-specific endosomal pathway in the protozoan pathogen Trypanosoma brucei. In higher eukaryotes evidence indicates that GPI-anchored proteins are transported in both the endocytic and exocytic systems by mechanisms involving sequestration into specific membrane microdomains and consequently sorting into distinct compartments. This is potentially extremely important in trypanosomatids as the GPI anchor is the predominant mechanism for membrane attachment of surface macromolecules, including the variant surface glycoprotein (VSG). A highly complex developmentally regulated endocytic network, vital for nutrient uptake and evasion of the immune response, exists in T. brucei. In common with mammalian cells an early endosomal compartment is defined by Rab5 small GTPases, which control transport processes through the endosomal system. We investigate the function of two trypanosome Rab5 homologues. TbRAB5A and TbRAB5B, which colocalize in the procyclic stage, are distinct in the bloodstream form of the parasite. TbRAB5A endosomes contain VSG and transferrin, endocytosed by the T. brucei GPI-anchored transferrin receptor, whereas TbRAB5B endosomes contain the transmembrane protein ISG(100) but neither VSG nor transferrin. These findings indicate the presence of trypanosome endosomal pathways trafficking proteins through specific routes depending on the mode of membrane attachment. Ectopic expression of mutant TbRAB5A or -5B indicates that TbRAB5A plays a role in LDL endocytosis, whereas TbRAB5B does not, but both have a role in fluid phase endocytosis. Hence TbRAB5A and TbRAB5B have distinct functions in the endosomal system of T. brucei. A developmentally regulated GPI-specific endosomal pathway in the bloodstream form suggests that specialized transport of GPI-anchored proteins is required for survival in the mammalian host.
Collapse
Affiliation(s)
- Arun Pal
- Wellcome Trust Laboratories for Molecular Parasitology, Department of Biological Sciences, Imperial College of Science, London SW7 2AY, United Kingdom
| | | | | | | | | |
Collapse
|
45
|
Jaworska-Wilczynska M, Wilczynski GM, Engel WK, Strickland DK, Weisgraber KH, Askanas V. Three lipoprotein receptors and cholesterol in inclusion-body myositis muscle. Neurology 2002; 58:438-45. [PMID: 11839845 DOI: 10.1212/wnl.58.3.438] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
BACKGROUND An important aspect of inclusion-body myositis (IBM) vacuolated muscle fibers (VMF) is abnormal accumulation of amyloid-beta precursor protein (AbetaPP) epitopes and its product, amyloid-beta (Abeta), and of phosphorylated tau (p-tau) in the form of paired helical filaments. Lipoprotein receptors and cholesterol are known to play an important role in AbetaPP processing, Abeta production, and tau phosphorylation. METHODS In 10 IBM and 22 control muscle biopsies the authors immunolocalized low-density lipoprotein receptor (LDLR), very low-density lipoprotein receptor (VLDLR), and low-density lipoprotein receptor-related protein (LRP), and colocalized them with Abeta, p-tau, APOE, and free cholesterol. RESULTS In each biopsy, virtually all IBM VMF had strong LDLR-immunoreactive inclusions, which colocalized with Abeta, APOE, p-tau, and free cholesterol. VLDLR was increased mainly diffusely, but in approximately 50% of the VMF it was also accumulated in the form of inclusions colocalizing with Abeta, APOE, and free cholesterol, but not with p-tau. LRP inclusions were present in a few VMF. In all myopathies, a subset of regenerating and necrotizing muscle fibers had prominent diffuse accumulation of both LDLR and free cholesterol. At normal neuromuscular junctions (NMJ) postsynaptically, LDLR and VLDLR, but not LRP, were immunoreactive. CONCLUSIONS 1) Abnormal accumulation of LDLR, VLDLR, LRP, and cholesterol within IBM vacuolated muscle fibers suggests novel roles for them in the IBM pathogenesis. 2) Expression of LDLR and VLDLR at normal NMJ suggests physiologic roles for them in transsynaptic signaling pathways, increased internalization of lipoproteins there, or both. 3) Increased LDLR and free cholesterol in some regenerating and necrotizing muscle fibers suggest a role for them in human muscle fiber growth and repair and necrotic death.
Collapse
MESH Headings
- Amyloid beta-Peptides/analysis
- Apolipoproteins E/analysis
- Biopsy
- Cholesterol/analysis
- Humans
- Low Density Lipoprotein Receptor-Related Protein-1/analysis
- Microscopy, Immunoelectron
- Muscle Fibers, Skeletal/chemistry
- Muscle Fibers, Skeletal/pathology
- Muscle Fibers, Skeletal/ultrastructure
- Muscle, Skeletal/chemistry
- Muscle, Skeletal/pathology
- Myositis, Inclusion Body/metabolism
- Myositis, Inclusion Body/pathology
- Phosphorylation
- Receptors, LDL/analysis
- Receptors, Lipoprotein/analysis
- tau Proteins/analysis
- tau Proteins/metabolism
Collapse
Affiliation(s)
- M Jaworska-Wilczynska
- USC Neuromuscular Center, Department of Neurology, University of Southern California Keck School of Medicine, Good Samaritan Hospital, 637 S. Lucas Ave., Los Angeles, CA 90017-1912, USA
| | | | | | | | | | | |
Collapse
|
46
|
Fischer U, Birkenmeier G, Horn LC. Localization of alpha(2)-macroglobulin receptor/low-density lipoprotein receptor in third-trimester human placentas: a preliminary immunohistochemical study. Gynecol Obstet Invest 2002; 52:22-5. [PMID: 11549859 DOI: 10.1159/000052935] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The alpha(2)-macroglobulin receptor/low-density lipoprotein receptor-related protein (alpha(2)-M-R/LRP) is involved in a variety of transcellular transportations, e.g. of apolipoprotein E, and represents an inhibitor of proteinases. After creation of monoclonal antibodies of the alpha- and beta-subunits of the alpha(2)-M-R/LRP and its receptor-associated protein, we have tested their distribution in five 3rd-trimester placentas, using cryosections, immunohistochemically and by immunofluorescence. All three monoclonal antibodies showed positive staining in villous and extravillous cytotrophoblasts and intravillous vessels, but not in syncytiotrophoblasts. Thus, alpha(2)-M-R/LRP plays a possible role in the transplacental nutritional transportation process. It is necessary to search the distribution of alpha(2)-M-R/LRP under pathological conditions, like fetal growth retardation and preeclampsia.
Collapse
Affiliation(s)
- U Fischer
- Department of Obstetrics and Gynecology, University of Leipzig, Germany
| | | | | |
Collapse
|
47
|
Abstract
BACKGROUND Progression of diabetic nephropathy is closely associated with morphological changes in glomeruli, such as thickening of the glomerular basement membrane, mesangial expansion, and glomerulosclerosis. To elucidate early glomerular events, we compared the mitogenic activity and extracellular matrix production in mesangial cells (MC) isolated from diabetic rats prior to the manifestation of nephropathy and those showing overt nephropathy. This study may help to clarify the mechanisms underlying diabetic nephropathy and provide clues about early therapeutic interventions for preventing or slowing this process. METHODS Otsuka Long-Evans Tokushima Fatty (OLETF) rats, a chronic model for human type 2 diabetes mellitus, and age-matched control (LETO) rats were used. Glomerular cell numbers, expression of immediate early genes (c-Fos and c-Myc) and proliferating cell nuclear antigen (PCNA), and low-density lipoprotein (LDL) deposition were determined in renal tissue sections from rats aged 15 to 75 weeks. Mesangial cells (MCs) from OLETF rats at two different stages of the disease, that is, young (12- to 14-week-old) OLETF rats (y-OLETF) prior to the manifestation of nephropathy and old (48- to 50-week-old) OLETF rats (o-OLETF) showing nephropathy, were isolated and cultured. After stimulation with native (n-) or oxidized (ox-) LDL or angiotensin II (Ang II), DNA synthesis and extracellular matrix (ECM) production were examined. Cellular expression of LDL/scavenger receptors was analyzed using fluorescence-labeled LDL and binding to 125I-labeled-LDL. RESULTS The number of cells per glomerular cross section was significantly higher in OLETF rats than in LETO rats between 25 and 65 weeks of age. In OLETF glomeruli, c-Fos, c-Myc, and PCNA were transiently expressed in the early phase. Glomerular LDL deposition increased with the age of OLETF rats. Addition of a low dose of n-LDL (10 microg/mL) to the culture medium significantly stimulated DNA synthesis of y-OLETF MCs, as compared with o-OLETF MCs and LETO MCs (P < 0.05). A high dose of n-LDL (100 microg/mL) caused cytotoxic effects in all cells. Exposure to ox-LDL minimally affected DNA synthesis of OLETF or LETO MCs. LDL receptors and scavenger receptors were predominant in y-OLETF and o-OLETF, respectively. After stimulation with n-LDL and ox-LDL, expression of type I and type III collagen, along with transforming growth factor-beta (TGF-beta), was higher in o-OLETF MCs that in y-OLETF MCs or LETO MCs. Exposure to Ang II markedly induced DNA synthesis and ECM mRNA expression in y-OLETF MCs and o-OLETF MCs, respectively. CONCLUSIONS These findings indicate that the cell proliferation process precedes the evolution of diabetic glomerulopathy. The responses of OLETF MCs to n-LDL/ox-LDL and Ang II differed depending on the stage of diabetes. In the early phase, MCs were prone to proliferate, whereas in the late stage, MCs, which expressed higher levels of TGF-beta, tended to synthesize ECM. A functional switch in MCs may contribute to the development of glomerulosclerosis in diabetic nephropathy.
Collapse
Affiliation(s)
- Mitsuru Okada
- Department of Pediatrics, Kinki University School of Medicine, Osaka-Sayama, Japan
| | | | | | | |
Collapse
|
48
|
Lindén D, Alsterholm M, Wennbo H, Oscarsson J. PPARalpha deficiency increases secretion and serum levels of apolipoprotein B-containing lipoproteins. J Lipid Res 2001; 42:1831-40. [PMID: 11714852] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/22/2023] Open
Abstract
This study investigates the importance of peroxisome proliferator activated receptor alpha (PPARalpha) for serum apolipoprotein B (apoB) levels and hepatic secretion of apoB-containing lipoproteins. Total serum apoB and VLDL-apoB levels were higher in female PPARalpha-null mice compared with female wild-type mice, but no difference was seen in male mice. Furthermore, hepatic triglyceride secretion rate, determined in vivo after Triton WR1339 injection, was 2.4-fold higher in female PPARalpha-null mice compared with female wild-type mice, but no difference was observed in male mice. However, when fed a high fat diet, male PPARalpha-null mice displayed 2-fold higher serum levels of apoB and LDL cholesterol compared with male wild-type mice, but triglyceride levels were not affected. Hepatic LDL receptor protein levels were not influenced by PPARalpha deficiency, gender, or the fat diet. Hepatocyte cultures from female PPARalpha-null mice (cultured for 4 days in serum free medium) showed 2-fold higher total apoB secretion and increased secretion of apoB-48 VLDL, as well as 2.7-fold larger accumulation of VLDL-triglycerides in the medium compared with wild-type cultures. In conclusion, PPARalpha-deficient female mice, but not males, display high serum apoB associated with VLDL and increased hepatic triglyceride secretion. Moreover, male PPARalpha-null mice show increased susceptibility to high fat diet in terms of serum apoB levels.
Collapse
MESH Headings
- Animals
- Apolipoproteins B/blood
- Apolipoproteins B/genetics
- Apolipoproteins B/metabolism
- Blotting, Western
- Cells, Cultured
- Cholesterol/blood
- Cholesterol, LDL/blood
- Dietary Fats/administration & dosage
- Lipoproteins/blood
- Lipoproteins/metabolism
- Lipoproteins, VLDL/blood
- Lipoproteins, VLDL/metabolism
- Liver/metabolism
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- RNA, Messenger/analysis
- Receptors, Cytoplasmic and Nuclear/deficiency
- Receptors, Cytoplasmic and Nuclear/genetics
- Receptors, LDL/analysis
- Transcription Factors/deficiency
- Transcription Factors/genetics
- Triglycerides/blood
Collapse
Affiliation(s)
- D Lindén
- Department of Physiology, University of Göteborg, Box 434, S-405 30 Göteborg, Sweden.
| | | | | | | |
Collapse
|
49
|
Sonda S, Ting LM, Novak S, Kim K, Maher JJ, Farese RV, Ernst JD. Cholesterol esterification by host and parasite is essential for optimal proliferation of Toxoplasma gondii. J Biol Chem 2001; 276:34434-40. [PMID: 11457847 DOI: 10.1074/jbc.m105025200] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Upon host cell invasion the apicomplexan parasite Toxoplasma gondii resides in a specialized compartment termed the parasitophorous vacuole that is derived from the host cell membrane but modified by the parasite. Despite the segregation of the parasitophorous vacuole from the host endocytic network, the intravacuolar parasite has been shown to acquire cholesterol from the host cell. In order to characterize further the role of sterol metabolism in T. gondii biology, we focused our studies on the activity of acyl-CoA:cholesterol acyltransferase (ACAT), a key enzyme for maintaining the intracellular homeostasis of cholesterol through the formation of cholesterol esters. In this study, we demonstrate that ACAT and cholesterol esters play a crucial role in the optimal replication of T. gondii. Moreover, we identified ACAT activity in T. gondii that can be modulated by pharmacological ACAT inhibitors with a consequent detrimental effect on parasite replication.
Collapse
Affiliation(s)
- S Sonda
- Department of Medicine, Division of Infectious Diseases, University of California, San Francisco, California 94143-0868, USA
| | | | | | | | | | | | | |
Collapse
|
50
|
Morawietz H, Duerrschmidt N, Niemann B, Galle J, Sawamura T, Holtz J. Induction of the oxLDL receptor LOX-1 by endothelin-1 in human endothelial cells. Biochem Biophys Res Commun 2001; 284:961-5. [PMID: 11409887 DOI: 10.1006/bbrc.2001.5044] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In this study, we analyzed the effect of endothelin-1 (ET-1) on expression of the lectin-like oxidized low-density lipoprotein (oxLDL) receptor-1 LOX-1 and on oxLDL uptake in primary cultures of human umbilical vein endothelial cells (HUVEC). LOX-1 mRNA was quantified by standard-calibrated competitive RT-PCR, LOX-1 protein expression by Western analysis and endothelial oxLDL uptake using DiI-labeled oxLDL. ET-1 induces LOX-1 mRNA expression, reaching its maximum after 1 h (160 +/- 14% of control, 100 nM ET-1, P < 0.05). This increased ET-1-mediated LOX-1 mRNA expression could be inhibited by endothelin receptor B antagonist BQ-788. In addition, ET-1 stimulates LOX-1 protein expression and oxLDL uptake in HUVEC. The augmented oxLDL uptake by ET-1 is mediated by endothelin receptor B, but not by protein kinases. These data support a new pathophysiological mechanism how locally and systemically increased ET-1 levels could promote LOX-1-mediated oxLDL uptake in human endothelial cells and the development and progression of endothelial dysfunction and atherosclerosis.
Collapse
MESH Headings
- Biological Transport/drug effects
- Blotting, Western
- Cells, Cultured
- Endothelin Receptor Antagonists
- Endothelin-1/pharmacology
- Endothelium, Vascular/metabolism
- Gene Expression Regulation/drug effects
- Humans
- Kinetics
- Lipoproteins, LDL/metabolism
- Oligopeptides/pharmacology
- Piperidines/pharmacology
- Protein Kinases/metabolism
- RNA, Messenger/genetics
- Receptor, Endothelin B
- Receptors, LDL/analysis
- Receptors, LDL/biosynthesis
- Receptors, LDL/genetics
- Receptors, Oxidized LDL
- Reverse Transcriptase Polymerase Chain Reaction
- Scavenger Receptors, Class E
- Transcription, Genetic/drug effects
- Umbilical Veins
- Up-Regulation/drug effects
Collapse
Affiliation(s)
- H Morawietz
- Institute of Pathophysiology, Faculty of Medicine, Martin Luther University Halle-Wittenberg, Halle, Germany.
| | | | | | | | | | | |
Collapse
|