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Published in: Journal of Neuroinflammation 1/2017

Open Access 01-12-2017 | Research

Purinergic receptors P2Y12R and P2X7R: potential targets for PET imaging of microglia phenotypes in multiple sclerosis

Authors: Wissam Beaino, Bieneke Janssen, Gijs Kooij, Susanne M. A. van der Pol, B. van Het Hof, Jack van Horssen, Albert D. Windhorst, Helga E. de Vries

Published in: Journal of Neuroinflammation | Issue 1/2017

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Abstract

Background

Microglia are major players in the pathogenesis of multiple sclerosis (MS) and may play a dual role in disease progression. The activation status of microglia in vivo is highly dynamic and occurs as a continuum, with the pro-inflammatory and anti-inflammatory phenotypes on either end of this spectrum. Little is known about in vivo dynamics of microglia phenotypes in MS due to the lack of diagnostic tools. Positron emission tomography (PET) imaging is a powerful non-invasive technique that allows real-time imaging of microglia activation phenotypes in the central nervous system, depending on the availability of selective PET tracers. Our objective is to investigate and characterize the expression of the purinergic receptors P2Y12R and P2X7R as potential targets for PET tracer development and subsequent PET imaging in order to evaluate the dynamics of microglia status in vivo.

Methods

We used immunohistochemical analysis to explore the expression of P2Y12R and P2X7R in experimental autoimmune encephalomyelitis (EAE) post-mortem tissues and different stages of well-characterized MS lesions. We evaluated by quantitative real-time polymerase chain reaction the expression of P2Y12R and P2X7R in human polarized microglia, and we performed autoradiography binding assay with radiolabeled P2Y12R and P2X7R antagonists using MS and rat EAE tissues.

Results

Here, we demonstrate that P2X7R is associated with a pro-inflammatory phenotype of human microglia in vitro, and is highly expressed in microglia in MS lesions as well as during the peak of EAE. In contrast, P2Y12R was associated with an anti-inflammatory phenotype in human microglia in vitro and was expressed at lower levels in active inflammatory MS lesions compared to normal-appearing white matter (NAWM) and similarly in EAE, while its expression increased in the remission phase of EAE. Binding of radiolabeled tracers specific for P2Y12R and P2X7R on ex vivo tissues validated the value of these receptors as PET imaging targets for microglia phenotypes in vivo.

Conclusion

Our results suggest that P2Y12R and P2X7R are excellent targets for PET imaging to discriminate distinct microglia phenotypes in MS. Ultimately, this may provide insight into the role of microglia in disease progression and monitor novel treatment strategies to alter microglia phenotype.
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Literature
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go back to reference Garcia-Vallejo JJ, van Dijk W, van Het Hof B, van Die I, Engelse MA, Hinsbergh V, Victor WM, Gringhuis SI. Activation of human endothelial cells by tumor necrosis factor-alpha results in profound changes in the expression of glycosylation-related genes. J Cell Physiol. 2006;206:203–10. https://doi.org/10.1002/jcp.20458 .CrossRefPubMed Garcia-Vallejo JJ, van Dijk W, van Het Hof B, van Die I, Engelse MA, Hinsbergh V, Victor WM, Gringhuis SI. Activation of human endothelial cells by tumor necrosis factor-alpha results in profound changes in the expression of glycosylation-related genes. J Cell Physiol. 2006;206:203–10. https://​doi.​org/​10.​1002/​jcp.​20458 .CrossRefPubMed
Metadata
Title
Purinergic receptors P2Y12R and P2X7R: potential targets for PET imaging of microglia phenotypes in multiple sclerosis
Authors
Wissam Beaino
Bieneke Janssen
Gijs Kooij
Susanne M. A. van der Pol
B. van Het Hof
Jack van Horssen
Albert D. Windhorst
Helga E. de Vries
Publication date
01-12-2017
Publisher
BioMed Central
Published in
Journal of Neuroinflammation / Issue 1/2017
Electronic ISSN: 1742-2094
DOI
https://doi.org/10.1186/s12974-017-1034-z

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