18F‑Labeling of Mannan for Inflammation Research with Positron Emission Tomography

• Published in: ACS medicinal chemistry letters 2016-09, Vol.7 (9), p.826-830
• Main Authors: Li, Xiang-Guo, Hagert, Cecilia, Siitonen, Riikka, Virtanen, Helena, Sareila, Outi, Liljenbäck, Heidi, Tuisku, Jouni, Knuuti, Juhani, Bergman, Jörgen, Holmdahl, Rikard, Roivainen, Anne
• Format: Article
• Language: English
• Subjects: Letter
• ISSN: 1948-5875; 1948-5875
• DOI: 10.1021/acsmedchemlett.6b00160

Recently mannan from Saccharomyces cerevisiae has been shown to be able to induce psoriasis and psoriatic arthritis in mice, and the phenotypes resemble the corresponding human diseases. To investigate the pathological processes, we set out to label mannan with fluorine-18 (18F) and study the 18F-labeled mannan in vitro and in vivo with positron emission tomography (PET). Accordingly, mannan has been transformed into 18F-fluoromannan with 18F-bicyclo­[6.1.0]­nonyne. In mouse aorta, the binding of [18F]­fluoromannan to the atherosclerotic lesions was clearly visualized and was significantly higher compared to blocking assays (P < 0.001) or healthy mouse aorta (P < 0.001). In healthy rats the [18F]­fluoromannan radioactivity accumulated largely in the macrophage-rich organs such as liver, spleen, and bone marrow and the excess excreted in urine. Furthermore, the corresponding 19F-labeled mannan has been used to induce psoriasis and psoriatic arthritis in mice, which indicates that the biological function of mannan is preserved after the chemical modifications.