Comparative Binding of125I-and99mTc-Labeled Native and Glycated Low-Density Lipoprotein to Human Microvascular Endothelial Cells-Potential for Atherosclerosis Imaging?
| Autor: | Grazyna Sobal, Ernst Johannes Menzel, Helmut Sinzinger |
|---|---|
| Rok vydání: | 2006 |
| Předmět: |
Adult
Diagnostic Imaging Male Glycosylation Plasma protein binding Biochemistry Iodine Radioisotopes chemistry.chemical_compound Humans Fragmentation (cell biology) Binding site Scavenger receptor Receptor Molecular Biology Microcirculation Endothelial Cells Technetium Cell Biology Middle Aged Atherosclerosis Ligand (biochemistry) Lipoproteins LDL Receptors LDL chemistry Isotope Labeling Low-density lipoprotein Female Protein Binding Lipoprotein |
| Zdroj: | Journal of Receptors and Signal Transduction. 26:693-707 |
| ISSN: | 1532-4281 1079-9893 |
| Popis: | 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. |
| Databáze: | OpenAIRE |
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