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Review
. 2019 Mar;40(3):351-357.
doi: 10.1038/s41401-018-0035-5. Epub 2018 Jun 19.

Positron emission tomography of type 2 cannabinoid receptors for detecting inflammation in the central nervous system

Ruiqing Ni  1 , Linjing Mu  2   3 , Simon Ametamey  2
Affiliations
Review

Positron emission tomography of type 2 cannabinoid receptors for detecting inflammation in the central nervous system

Ruiqing Ni et al. Acta Pharmacol Sin. 2019 Mar.

Abstract

Cannabinoid receptor CB2 (CB2R) is upregulated on activated microglia and astrocytes in the brain under inflammatory conditions and plays important roles in many neurological diseases, such as Alzheimer's disease, amyotrophic lateral sclerosis, and ischemic stroke. The advent of positron emission tomography (PET) using CB2R radiotracers has enabled the visualization of CB2R distribution in vivo in animal models of central nervous system inflammation, however translation to humans has been less successful. Several novel CB2R radiotracers have been developed and evaluated to quantify microglial activation. In this review, we summarize the recent preclinical and clinical imaging results of CB2R PET tracers and discuss the prospects of CB2R imaging using PET.

Keywords: cannabinoid receptor CB2; inflammation; microglia; neurological diseases; positron emission tomography.

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Conflict of interest statement

The authors declare no conflicts of interest.

Figures

Fig. 1
Fig. 1
Chemical structures of CB2R tracers of oxoquinoline, thiazole, oxadiazole, and thiophene-based derivatives
Fig. 2
Fig. 2
Representative in vitro autoradiograms of CB2R tracers. a [11C]RSR-056 on spleen slices from a wild-type CD1 mouse. b [11C]RSR-056 on cervical spinal cord from a healthy control and a patient with amyotrophic lateral sclerosis (ALS). c [18F]RS-126 on spleen slices from a Wistar rat. Left: baseline binding; right: blockade with CB2R antagonist GW405833
Fig. 3
Fig. 3
Representative in vivo microPET images of coronal CD1 mouse brain sections (Bregma −1.5 mm ± 0.3 mm) by averaging dynamic data at 20–60 min after the intravenous injection of [11C]RSR-056. a Vehicle-treated mouse. b LPS-treated mouse. c LPS-treated mouse with antagonist GW405833. Scale 0–0.5. SUV standard uptake value
See this image and copyright information in PMC

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