| 1. |
- Abletshauser, C, et al.
(author)
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Biosensing of arteriosclerotic nanoplaque formation and interaction with an HMG-CoA reductase inhibitor
- 2002
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In: Acta Physiologica Scandinavica. - 0001-6772 .- 1365-201X. ; 176, s. 131-146
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Journal article (peer-reviewed)abstract
- Proteoheparan sulphate can be adsorbed to a methylated silica surface in a monomolecular layer via its transmembrane hydrophobic protein core domain. As a result of electrostatic repulsion, its anionic glycosaminoglycan side chains are stretched out into the blood substitute solution, thereby representing one receptor site for specific lipoprotein binding through basic amino acid-rich residues within their apolipoproteins. The binding process was studied by ellipsometric techniques suggesting that high-density lipoprotein (HDL) has a high binding affinity and a protective effect on interfacial heparan sulphate proteoglycan layers with respect to low-density lipoprotein (LDL) and Ca2+ complexation. Low-density lipoprotein was found to deposit strongly at the proteoheparan sulphate-coated surface, particularly in the presence of Ca2+, apparently through complex formation 'proteoglycan-LDL-calcium'. This ternary complex build-up may be interpreted as arteriosclerotic nanoplaque formation on the molecular level responsible for the arteriosclerotic primary lesion. On the other hand, HDL bound to heparan sulphate proteoglycan protected against LDL deposition and completely suppressed calcification of the proteoglycan-lipoprotein complex. In addition, HDL was able to decelerate the ternary complex deposition. Therefore, HDL attached to its proteoglycan receptor sites is thought to raise a multidomain barrier, selection and control motif for transmembrane and paracellular lipoprotein uptake into the arterial wall. Although much remains unclear regarding the mechanism of lipoprotein depositions at proteoglycan-coated surfaces, it seems clear that the use of such systems offers possibilities for investigating lipoprotein deposition at a 'nanoscopic' level under close to physiological conditions. In particular, Ca2+-promoted LDL deposition and the protective effect of HDL even at high Ca2+ and LDL concentrations agree well with previous clinical observations regarding risk and beneficial factors for early stages of atherosclerosis. Considering this, the system was tested on its reliability in a biosensor application in order to unveil possible acute pleiotropic effects of the lipid lowering drug fluvastatin. The very low-density lipoprotein (VLDL)/intermediate-density lipoprotein (IDL)/LDL plasma fraction from a high risk patient with dyslipoproteinaemia and type 2 diabetes mellitus showed beginning arteriosclerotic nanoplaque formation already at a normal blood Ca2+ concentration, with a strong increase at higher Ca2+ concentrations. Fluvastatin, whether applied to the patient (one single 80 mg slow release matrix tablet) or acutely in the experiment (2.2 μmol L-1), markedly slowed down this process of ternary aggregational nanoplaque complexation at all Ca2+ concentrations used. This action resulted without any significant change in lipid concentrations of the patient. Furthermore, after ternary complex build-up, fluvastatin, similar to HDL, was able to reduce nanoplaque adsorption and size. These immediate effects of fluvastatin have to be taken into consideration while interpreting the clinical outcome of long-term studies.
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| 2. |
- Siegel, G, et al.
(author)
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A receptor-based biosensor for lipoprotein docking at the endothelial surface and vascular matrix
- 2001
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In: Biosensors & bioelectronics. - 0956-5663 .- 1873-4235. ; 16, s. 895-904
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Journal article (peer-reviewed)abstract
- Proteoheparan sulfate can be adsorbed to a methylated silica surface in a monomolecular layer via its transmembrane hydrophobic protein core domain. Due to electrostatic repulsion, its anionic glycosaminoglycan side chains are stretched out into the blood substitute solution, representing a receptor site for specific lipoprotein binding through basic amino acid-rich residues within their apolipoproteins. The binding process was studied by ellipsometric techniques showing that HDL has a high binding affinity to the receptor and a protective effect on interfacial heparan sulfate proteoglycan layers, with respect to LDL and Ca2+ complexation. LDL was found to deposit strongly at the proteoheparan sulfate, particularly in the presence of Ca2+, thus creating the complex formation `proteoglycan¯low density lipoprotein¯calcium'. This ternary complex build-up may be interpreted as arteriosclerotic nanoplaque formation on the molecular level responsible for the arteriosclerotic primary lesion. On the other hand, HDL bound to heparan sulfate proteoglycan protected against LDL docking and completely suppressed calcification of the proteoglycan¯lipoprotein complex. In addition, HDL and aqueous garlic extract were able to reduce the ternary complex deposition and to disintegrate HS-PG/LDL/Ca2+ aggregates. Although much remains unclear regarding the mechanism of lipoprotein depositions at proteoglycan-coated surfaces, it seems clear that the use of such systems offers possibilities for investigating lipoprotein deposition at a `nanoscopic' level under close to physiological conditions. In particular, Ca2+-promoted LDL deposition and the protective effect of HDL, even at high Ca2+ and LDL concentrations, agree well with previous clinical observations regarding risk and beneficial factors for early stages of atherosclerosis. Therefore, we believe that the system can be of some use in investigations, e.g. of the interplay between different lipoproteins in arteriosclerotic plaque formation, as well as in high throughput screening of candidate drugs to atherosclerosis in a biosensor application
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| 3. |
- Siegel, Günter, et al.
(author)
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Atherogenesis and plaque rupture, surface/interface-related phenomena
- 2018
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In: Colloids and Surfaces A. - : ELSEVIER SCIENCE BV. - 0927-7757 .- 1873-4359. ; 557, s. 28-35
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Journal article (peer-reviewed)abstract
- In atherogenesis, free oxygen radicals cause a lipid peroxidation of apoB100-containing lipoproteins in the blood, at the blood-endothelium-interface and in the subendothelial space. These lipoproteins easily aggregate, bind to their receptor heparan sulfate proteoglycan and calcify to arteriosclerotic nanoplaques (ternary complexes). Nanoplaque formation was measured by ellipsometry, both in vitro on an HS-PG coated hydrophobic silica surface and also in vivo on living human coronary endothelial cells, which had overgrown the silica surface. Reversely, we show with the same techniques that, in dependence on the degree of peroxidation and epitope in concern, oxLDL attacks its molecular receptor and thus can induce degradation of arteriosclerotic plaques and, in a combined action with inflammatory processes, even a plaque rupture. In a previous work, we had found PML-NB, fibrous cap (collagens, proteoglycans) and HSBGF binding sites (e.g., TGF beta 1) up-regulated and NF kappa B down-regulated. With this background knowledge we created a molecular feedback control circuit model where PML-NB functions as regulation centre, fibrous cap as controlled variable, HSBGF binding sites as receptor and NF kappa B as effector. Since NF kappa B is inhibited by one reaction strand in this model and inhibits itself collagen and proteoglycan synthesis in the fibrous cap of the plaque, this double check (disinhibition) causes a stabilization of the fibrous cap through a specially strong collagen and proteoglycan production, which in addition is supported by circulating TGF beta. TGF beta furthers also calcification, so that fibrous cap tensile strength and resistance to shear stress are imparted. This way, a plaque rupture may possibly be averted.
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| 4. |
- Siegel, G, et al.
(author)
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Physicochemical binding properties of the proteoglycan receptor for serum lipoproteins
- 1999
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In: Atherosclerosis. - 0021-9150 .- 1879-1484. ; 144, s. 59-67
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Journal article (peer-reviewed)abstract
- Proteoheparan sulfate can be adsorbed to a methylated silica surface in a monomolecular layer via its transmembrane hydrophobic protein core domain. Due to electrostatic repulsion, its anionic polysugar side chains are stretched out into the blood substitute solution representing a co-receptor for specific lipoprotein binding through basic amino acid-rich residues within their apolipoproteins. The binding process was studied by ellipsometric techniques showing that oxLDL had a deleterious effect on heparan sulfate proteoglycan binding and conformation. Ca2+ binding to and storage on the proteoheparan sulfate/LDL compound formed a 'heterotrimeric' HS-PG/LDL/Ca2+ complex of high stability, aggregability and deposit coating. On the other hand, HDL bound to heparan sulfate proteoglycan protected against LDL docking and completely suppressed calcification of the proteoglycan/lipoprotein complex.
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| 5. |
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| 6. |
- Siegel, G, et al.
(author)
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Tumor cell locomotion and metastatic spread
- 1998
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In: Microscopy research and technique (Print). - 1059-910X .- 1097-0029. ; 43, s. 276-282
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Journal article (peer-reviewed)abstract
- The cytoskeletal filament proteins cu-actinin, filamin, desmin, and filamin-desmin aggregates were adsorbed to a hydrophobic silica surface. The adsorbed amount as measured by ellipsometric methods after rinsing and equilibration was 2.7 mg/m(2) for alpha-actinin and 0.4 mg/m(2) for filamin plus desmin, respectively. Adsorbed layer thicknesses in physiological salt solution were about 107 nm, 89 nm, 108 nm and 93 nm for alpha-actinin, filamin, desmin, and cross-linked filamin-desmin, respectively. Ca2+ ions in a concentration of 10(-4), 10(-3), and 2.52 mmol/l had no effect on the adsorbed amount, refractive index, and adsorbed layer thickness of the individual intermediate filament proteins. Cross-linked filamin-desmin, however, reacted markedly upon the addition of these Ca2+ concentrations with a change in refractive index and adsorbed layer thickness. The layer formed by the filamin- desmin complex contracted by 2-3, 6-7, and 6-7 nm, respectively. The maximum shortening occurred at 1 mu mol/l Ca2+. The Ca2+-dependent adsorbed layer changes of cross-linked filamin-desmin supports the contractile mechanisms in muscular tissues and forms the basis for migration and motility in nonmuscular cells. These motional events are crucially involved in peripheral organ perfusion, inflammation, and tumor invasion and metastasis.
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| 7. |
- Siegel, G, et al.
(author)
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Vascular smooth muscle, a multiply feedback-coupled system of high versatility, modulation and cell-signaling variability
- 1997
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In: Int J Microcirc. - 0167-6865. ; 17, s. 360-373
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Journal article (peer-reviewed)abstract
- Under normal conditions, the various vascular regulatory effector influences are interwoven in a dynamic, and not a static, circulatory system. The reaction of a smooth muscle cell is thus reflected only incompletely by the stationary activation curve `developed tension versus membrane potential'. The missing time domain in this relationship is a reflection of our as yet limited understanding of the system´s behavior in space and time. It should be emphasized that rythmogenic properties of vascular smooth muscle are closely coupled to a functioning circulation.The electrical and mechanical oscillations, which can be traced back to rhythmic activity of the active electrogenic Na+K+ pump, could originate in the allosteric qualities of the enzyme phosphofructokinase (PFK).Thus, PFK represents a rhythmogenic enzyme which may serve as an example of the connection between the biological properties on a molecular level and the spatiotemporal system`s behavior.The cardiovascular system and its rhythmicity may be dominated by only a few control points, one of which is distinguished by the viscoelastic properties of a blood flow sensor macromolecule.Therefore, the three prominent control points PFK, (Na++K+)-ATPase and flow sensor conformation -acting as negatively feedback-couple nonlinear synergetic order papameter are sufficient to initiate the periodic events in the cardiovascular system and to provide a plausible explanation for their causal origin.
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