F-18-FEAnGA for PET of beta-Glucuronidase Activity in Neuroinflammation

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Abstract

Activation of microglia is a hallmark of inflammatory, infectious, and degenerative diseases of the central nervous system. Several studies have indicated that there is an increase in release of beta-glucuronidase by activated microglia into the extracellular space at the site of neuroinflammation. beta-glucuronidase is involved in the hydrolysis of glycosaminoglycans on the cell surface and the degradation of the extracellular matrix. Therefore, beta-glucuronidase might be a biomarker for ongoing neurodegeneration induced by neuroinflammation. In this study, we investigated whether the PET tracer F-18-FEAnGA was able to detect beta-glucuronidase release during neuroinflammation in a rat model of herpes encephalitis. Methods: Male Wistar rats were intranasally inoculated with herpes simplex virus 1 (HSV-1) or phosphate-buffered saline as a control. C-11-(R)-PK11195 and F-18-FEAnGA small-animal PET scans were acquired for 60 min. Logan graphical analysis was used to calculate F-18-FEAnGA distribution volumes (DVLogan) in various brain areas. Results: After administration of F-18-FEAnGA, the area under the activity concentration-versus-time curve of the whole brain was 2 times higher in HSV-1-infected rats than in control rats. In addition, the DVLogan of F-18-FEAnGA was most increased in the frontopolar cortex, frontal cortex, bulbus olfactorius, cerebral cortex, cerebellum, and brainstem of HSV-1-infected rats, when compared with control rats. The conversion of F-18-FEAnGA to 4-hydroxy-3-nitrobenzyl alcohol was found to be 1.6 times higher in HSV-1-infected rats than in control rats and correlated with the DVLogan of F-18-FEAnGA in the same areas of the brain. Furthermore, the DVLogan of F-18-FEAnGA also correlated with beta-glucuronidase activity in the same brain regions. In addition, DVLogan of F-18-FEAnGA showed a tendency to correlate with C-11-(R)-PK11195 uptake (marker for activated microglia) in the same brain regions. Conclusion: Despite relatively low brain uptake, F-18-FEAnGA was able to detect an increased release of beta-glucuronidase during neuroinflammation.

Original languageEnglish
Pages (from-to)451-458
Number of pages8
JournalJournal of Nuclear Medicine
Volume53
Issue number3
DOIs
Publication statusPublished - 1-Mar-2012

Keywords

  • HSV-1
  • beta-glucuronidase
  • [F-18]FEAnGA
  • PET
  • neuroinflammation
  • ALZHEIMERS-DISEASE
  • ENZYME-ACTIVITIES
  • BRAIN
  • ENCEPHALITIS
  • INFLAMMATION
  • DISORDERS
  • MICROGLIA
  • BINDING
  • RELEASE

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