Proton therapy induces a local microglial neuroimmune response

Daniëlle C Voshart, Myrthe Klaver, Yuting Jiang, Hilmar R J van Weering, Fleur van Buuren-Broek, Gideon P van der Linden, Davide Cinat, Harry H Kiewiet, Justin Malimban, Daniel A Vazquez-Matias, Luiza Reali Nazario, Ayla C Scholma, Jeffrey Sewdihal, Marc-Jan van Goethem, Peter van Luijk, Rob P Coppes, Lara Barazzuol*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

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Abstract

BACKGROUND AND PURPOSE: Although proton therapy is increasingly being used in the treatment of paediatric and adult brain tumours, there are still uncertainties surrounding the biological effect of protons on the normal brain. Microglia, the brain-resident macrophages, have been shown to play a role in the development of radiation-induced neurotoxicity. However, their molecular and hence functional response to proton irradiation remains unknown. This study investigates the effect of protons on microglia by comparing the effect of photons and protons as well as the influence of age and different irradiated volumes.

MATERIALS AND METHODS: Rats were irradiated with 14 Gy to the whole brain with photons (X-rays), plateau protons, spread-out Bragg peak (SOBP) protons or to 50 % anterior, or 50 % posterior brain sub-volumes with plateau protons. RNA sequencing, validation of microglial priming gene expression using qPCR and high-content imaging analysis of microglial morphology were performed in the cortex at 12 weeks post irradiation.

RESULTS: Photons and plateau protons induced a shared transcriptomic response associated with neuroinflammation. This response was associated with a similar microglial priming gene expression signature and distribution of microglial morphologies. Expression of the priming gene signature was less pronounced in juvenile rats compared to adults and slightly increased in rats irradiated with SOBP protons. High-precision partial brain irradiation with protons induced a local microglial priming response and morphological changes.

CONCLUSION: Overall, our data indicate that the brain responds in a similar manner to photons and plateau protons with a shared local upregulation of microglial priming-associated genes, potentially enhancing the immune response to subsequent inflammatory challenges.

Original languageEnglish
Article number110117
Number of pages8
JournalRadiotherapy and Oncology
Volume193
Early online date1-Mar-2024
DOIs
Publication statusPublished - Apr-2024

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