Low-dose ionizing radiation promotes motor recovery and brain rewiring by resolving inflammatory response after brain injury and stroke

• Published in: Brain, behavior, and immunity behavior, and immunity, 2024-01, Vol.115, p.43-63
• Main Authors: Au, Ngan Pan Bennett, Wu, Tan, Kumar, Gajendra, Jin, Yuting, Li, Yolanda Yuen Tung, Chan, Shun Lam, Lai, Joseph Ho Chi, Chan, Kannie Wai Yan, Yu, Kwan Ngok, Wang, Xin, Ma, Chi Him Eddie
• Format: Article
• Language: English
• Subjects: Low-dose ionizing radiation; Microglia polarization; Photothrombotic stroke; Traumatic brain injury
• ISSN: 0889-1591; 1090-2139
• DOI: 10.1016/j.bbi.2023.09.015

•LDIR reduces lesion size in TBI and ischemic stroke.•LDIR accelerates motor function recovery after TBI and ischemic stroke.•LDIR resolves inflammatory response after brain injury.•LDIR increases microglial clustering and facilitates effective glial scar clearance at injury site.•LDIR promotes brain rewiring and restores brain activity after ischemic stroke. Traumatic brain injury (TBI) and stroke share a common pathophysiology that worsens over time due to secondary tissue injury caused by sustained inflammatory response. However, studies on pharmacological interventions targeting the complex secondary injury cascade have failed to show efficacy. Here, we demonstrated that low-dose ionizing radiation (LDIR) reduced lesion size and reversed motor deficits after TBI and photothrombotic stroke. Magnetic resonance imaging demonstrated significant reduction of infarct volume in LDIR-treated mice after stroke. Systems-level transcriptomic analysis showed that genes upregulated in LDIR-treated stoke mice were enriched in pathways associated with inflammatory and immune response involving microglia. LDIR induced upregulation of anti-inflammatory- and phagocytosis-related genes, and downregulation of key pro-inflammatory cytokine production. These findings were validated by live-cell assays, in which microglia exhibited higher chemotactic and phagocytic capacities after LDIR. We observed substantial microglial clustering at the injury site, glial scar clearance and reversal of motor deficits after stroke. Cortical microglia/macrophages depletion completely abolished the beneficial effect of LDIR on motor function recovery in stroke mice. LDIR promoted axonal projections (brain rewiring) in motor cortex and recovery of brain activity detected by electroencephalography recordings months after stroke. LDIR treatment delayed by 8 h post-injury still maintained full therapeutic effects on motor recovery, indicating that LDIR is a promising therapeutic strategy for TBI and stroke.