Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

2 Publications
Radiolabeling of human apolipoproteins using SH-reactive 18F-labeling agents: a potential approach for characterization and differentiation of metabolism of native and modified lipoproteins by small animal positron emission tomography (PET) in vivo
Pietzsch, J.; Berndt, M.; Wüst, F.; van den Hoff, J.;
Oxidative modification of LDL is regarded as a crucial event in atherogenesis. Data concerning the role of circulating oxidized LDL (oxLDL) in the development of atherosclerosis are scarce. One reason for this is the shortage of methods for direct assessment of metabolism of oxLDL in vivo. We report a new methodology for labeling of both native LDL (nLDL) and oxLDL with the positron emitter fluorine-18 (18F; t½=109.7 min) by conjugation with SH-reactive N-[6-(4-[18F]fluorobenzylidene)-aminooxyhexyl]maleimide ([18F]MHAA) and the use of 18F-labeled LDL particles in dynamic PET studies in male Kyoto-Wistar rats. For labeling experiments, pools of chemically and biochemically well characterized human nLDL and oxLDL (modified by hemin/H2O2) particles, respectively, were used. Radiosynthesis of [18F]MHAA started with the preparation of [18F]fluorobenzaldehyde. In a one-pot procedure N-(6-aminooxyhexyl)maleimide was added to the generated aldehyde and after-wards [18F]MHAA was isolated by HPLC. Preparation of [18F]MHAA was achieved within 70 min with radiochemical yields of 34±5% (corrected for decay) and purity of >96%. [18F]MHAA was shown to react efficiently and selectively with SH-groups of various peptides and proteins under mild conditions. LDL labeling with [18F]MHAA resulted in radiochemical yields of 20±10% (corrected for decay) and specific radioactivity of 150-300 GBq/µmol. Radiolabeling of nLDL and oxLDL using [18F]MHAA caused neither additional oxidative structural modifications of LDL lipids and proteins nor alteration of their biological activity and functionality in vitro, respectively. The method was evaluated with respect to uptake of 18F-labeled LDL in human hepatoma cells (HepG2) and monocytes/macrophages (THP-1), respectively. Biodistribution studies in rats revealed high in vivo stability for the 18F-labeled LDL. The metabolic fate of the 18F-labeled LDL in vivo was delineated by dynamic PET studies using a dedicated small animal tomograph (spatial resolution of <2 mm). Data were compared to former studies using the NH2-reactive 18F-labeling agent N-succinimidyl-4-[18F]fluorobenzoate. In conclusion, 18F-labeling of LDL and the use of small animal PET provide a valuable tool for mapping sites of both nLDL and oxLDL metabolism in animal models in vivo.
  • Abstract in refereed journal
    Amino Acids 29(2005)1, 18-19
    DOI: 10.1007/s00726-005-0220-y
  • Invited lecture (Conferences)
    9th International Congress on Proteins and Amino Acids, 08.-12.08.2005, Wien, Österreich

Publ.-Id: 8025 - Permalink