Authors: Marples B., McGee M., Callan S., Bowen S., Thibodeau B., Michael D., Wilson G., Maddens M., Fontanesi J., Martinez A.
Journal: Radiotherapy and Oncology
https://doi.org/10.1016/j.radonc.2015.10.019
Abstract: Background and purpose To investigate if cranial X-irradiation reduces amyloid-β (Aβ) plaques and influences cognitive function in a transgenic mouse model of AD. Methods and materials B6.Cg-Tg (APPswePSEN1dE9)85Dbo/J AD-prone mice were given cranial X-irradiation. The number of Aβ plaques, along with expression of AD specific genes (84 genes: Mouse Alzheimer’s Disease RT2 Profiler™), radiation-associated cytokines (Milliplex® MAP Mouse Cytokine Chemokine Immunoassay) and immunohistoChemistry (IL10, IL-1β, Iba1 CD45) was assessed. Behavioral testing was performed to relate changes in Aβ burden to cognitive function using a Morris water-maze task. Results Single X-ray doses reduced the number (p = 0.002) and size (p = 0.01) of Aβ plaques. Low-dose fractionation produced greater 50.6% (1 Gy × 10), 72% (2 Gy × 5) and 78% (2 Gy × 10) reductions. Irradiation was associated with gene (Pkp4, 1.5-fold, p = 0.004) and proteomic (MIP-2, 8-fold, p = 0.0024) changes at 24-48 h. Microglia increased at 4 weeks post-irradiation (p = 0.001). The reduction in Aβ burden (2 Gy × 5) was associated with cognitive improvement (p = 0.012). Conclusion This is the first report that a clinically relevant course of external beam irradiation (2 Gy × 5) produces a significant reduction in AD-associated amyloid-β plaques with a subsequent improvement in cognitive function. However, longer-term studies are needed to define the precise underlying mechanism and longevity of this response.
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