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Conformation and Physical Structure of Tropoelastin from Human Vascular Cells: Influence of Cells Lipid Loading

DOI: 10.1155/2014/391242

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Aggregated low density lipoproteins (agLDL) contribute to massive intracellular cholesteryl ester (CE) accumulation in human vascular smooth muscle cells (VSMC). Our aim was to determine the conformational and physical structure of agLDL and elastic material produced either by control human VSMC or by agLDL-loaded human VSMC (agLDL-VSMC). At the conformational level scanned by FTIR spectroscopy, a new undefined, probably non-H-bonded, structure for tropoelastin produced by agLDL-VSMC is revealed. By differential scanning calorimetry, a decrease of water affinity and a drop of the glass transition associated with aggregated tropoelastin (from 200°C to 159°C) in the supernatant from agLDL VSMC are evidenced. This second phenomenon is due to an interaction between agLDL and tropoelastin as detected by the weak specific FTIR absorption band of agLDL in supernatant from agLDL-loaded VSMC. 1. Introduction VSMC in atherosclerotic lesion are unable to produce normal elastic fibers due to atherosclerotic risk factors such as diabetes and associated hyperglycemia, endothelial dysfunction, and inflammation [1, 2]. If experimental hypercholesterolemia decreases the wall elastin content in vivo [3] and in vitro systems [4], the role of hypercholesterolemia in the altered VSMC elastogenic capacity and the possible mechanisms involved are not yet elucidated. VSMC become foam cells through the uptake of diversely modified LDLs [5, 6], whereas the aggregation of LDLs (agLDL) seems to be a key condition for lipid accumulation in VSMCs [7, 8]. Intracellular cholesterol accumulation alters proteoglycan composition [9] and collagen assembly [10] in VSMC, but it is unknown whether intracellular lipid may change the physical characteristics of the tropoelastin synthesized by human VSMC. The aim of this work was to characterize agLDL as well as tropoelastin produced by agLDL-lipid-loaded human VSMC versus that produced by control VSMC using polymer characterization techniques that were previously shown to be efficient in checking the molecular architecture and chain dynamics of proteins [11, 12]. 2. Materials and Methods 2.1. Human VSMC Primary cultures of human VSMC were obtained from nonatherosclerotic areas of human coronary arteries from hearts explanted during heart transplantation at Hospital of Santa Creu i Sant Pau as previously described [5, 6]. Donors of the explanted hearts were men between 40 and 60 years old. Explants were incubated at 37°C in a humidified atmosphere of 5% CO2. Cells grown out of explants were suspended in a solution of trypsin/EDTA and

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