(18)F-Labeling of Mannan for Inflammation Research with Positron Emission Tomography

Area of Science:

• Immunology
• Radiochemistry
• Medical Imaging

Background:

• Mannan from Saccharomyces cerevisiae is implicated in inducing psoriasis and psoriatic arthritis in mouse models.
• These induced phenotypes closely mimic human inflammatory diseases, suggesting mannan's role in pathogenesis.

Purpose of the Study:

• To develop a fluorine-18 ((18)F) labeled mannan for in vitro and in vivo imaging using positron emission tomography (PET).
• To investigate the distribution and binding characteristics of (18)F-fluoromannan in biological systems.

Main Methods:

• Synthesis of (18)F-fluoromannan via click chemistry using (18)F-bicyclo[6.1.0]nonyne.
• In vivo imaging of (18)F-fluoromannan in mouse aorta with atherosclerotic lesions.
• Assessment of (18)F-fluoromannan distribution in healthy rats, focusing on macrophage-rich organs.
• Confirmation of biological activity using (19)F-labeled mannan to induce disease models.

Main Results:

• [(18)F]fluoromannan successfully visualized atherosclerotic lesions in mouse aorta with significantly higher binding compared to controls (P < 0.001).
• In healthy rats, radioactivity accumulated in macrophage-rich organs (liver, spleen, bone marrow) and was excreted via urine.
• The (19)F-labeled mannan retained its ability to induce psoriasis and psoriatic arthritis, confirming preserved biological function.

Conclusions:

• Fluorine-18 labeled mannan is a viable radiotracer for imaging atherosclerotic lesions using PET.
• (18)F-fluoromannan distribution highlights its uptake in macrophage-rich tissues, relevant for inflammatory disease research.
• Chemical modification for radiolabeling preserves mannan's pathogenic role in psoriasis and psoriatic arthritis models.