Cranial irradiation significantly reduces beta amyloid plaques in the brain and improves cognition in a murine model of Alzheimer's Disease (AD)

Background and purpose: To investigate if cranial X-irradiation reduces amyloid-beta (A beta) 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 A beta plaques, along with expression of AD specific genes (84 genes: Mouse Alzheimer's Disease RT2 Profiler (TM)), radiation-associated cytokines (Milliplex (R) MAP Mouse Cytokine Chemokine Immunoassay) and immunohistochemistry (IL10, IL-1 beta, Iba1 CD45) was assessed. Behavioral testing was performed to relate changes in All 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 A beta plaques. Low-dose fractionation produced greater 50.6% (1 Gy x 10), 72% (2 Gy x 5) and 78% (2 Gy x 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 A beta burden (2 Gy x 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 x 5) produces a significant reduction in AD-associated amyloid-beta 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. (C) 2015 Elsevier Ireland Ltd. All rights reserved.