Fluorine-18 radiolabeling of S100/calgranulins: a potential approach for characterization of receptors for advanced glycation endproducts in vivo


Fluorine-18 radiolabeling of S100/calgranulins: a potential approach for characterization of receptors for advanced glycation endproducts in vivo

Hoppmann, S.; Haase, C.; Schwietzke, U.; Wüst, F.; Steinbach, J.; Pietzsch, J.

Introduction:

The interaction of S100/calgranulins, a multigenic family of Ca2+-modulated proteins, with receptors for advanced glycation endproducts, e.g., RAGE and AGERs, is hypothesized to be of high relevance in the pathogenesis of various diseases including cardiovascular diseases, inflammatory processes, and cancerogenesis. However, data concerning the role of circulating S100/calgranulins in these pathologies are scarce. Furthermore, it is currently not known whether RAGE or AGERs are universal S100/calgranulin receptors in vivo. One reason for this is the shortage of suitable radiolabeling methods for direct assessment of metabolic pathways of S100/calgranulins in vivo. We report a novel radiotracer approach using radiolabeling of recombinant human S100A1 with fluorine-18 (18F) and the application of 18F-labeled S100A1 (18F-S100A1) in dynamic small animal positron emission tomography (PET) studies in rats.

Experimental:

Human S100A1 was cloned in the bacterial expression vector pGEX-6P-1 and expressed in E. coli strain BL21. Radiolabeling of purified S100A1 was performed by conjugation with N-succinimidyl-4-(18F)fluorobenzoate ([18F]SFB). 18F-S100A1 was used for investigations of stability in vitro and in vivo. The metabolic fate of 18F-S100A1 in rats in vivo was delineated by dynamic PET studies using a dedicated small animal PET system.

Results and Discussion:

Radiolabeling of S100A1 with [18F]SFB at pH 7.4 resulted in 18F-S100A1 specifically labeled at the N-terminal glycine residue with radiochemical yields of 2-6% (decay-corrected) and effective specific activities of 0.5-1 GBq/µmol, respectively. In vitro experiments, and biodistribution and metabolite studies in rats in vivo revealed high stability for the 18F-S100A1. The organ-specific in vivo distribution and kinetics of 18F-S100A1 correlated well with the anatomical localization of receptors for advanced glycation endproducts, e.g., in blood vessels and lungs. In the presence of glycated human low density lipoprotein (glycLDL), a well characterized RAGE ligand, mean plasma residence time of 18F-S100A1 increased by 40% from 29.6±1.5 min to 41.3±2.1 min and lung associated retention of 18F-S100A1 decreased by 57% first indicating circulating S100A1 to be a specific ligand for receptors for advanced glycation endproducts in rats in vivo. Data were compared to former small animal PET studies using the 18F-labeled glycLDL.

Conclusion:

Radiolabeling of S100/calgranulins with 18F and the use of small animal PET provides novel probes to delineate functional expression of RAGE and AGERs under normal and pathophysiological conditions in rodent models of disease in vivo.

Acknowledgement: This study was supported in part by the DFG (grant no. Pi 304/1-1).

Keywords: S100 Proteins; Small Animal PET; Inflammation; Cancerogenesis; Receptors for Advanced Glycation End Products

  • Lecture (Conference)
    17th International Symposium on Radiopharmaceutical Sciences, 30.04.-04.05.2007, Aachen, Deutschland
  • Abstract in refereed journal
    Journal of Labelled Compounds and Radiopharmaceuticals 50(2007)Suppl. 1, S28
    ISSN: 0362-4803

Permalink: https://www.hzdr.de/publications/Publ-9810
Publ.-Id: 9810