The impact of high and low dose ionising radiation on the central nervous system

Abstract

Responses of the central nervous system (CNS) to stressors and injuries, such as ionising radiation, are modulated by the concomitant responses of the brains innate immune effector cells, microglia. Exposure to high doses of ionising radiation in brain tissue leads to the expression and release of biochemical mediators of ‘neuroinflammation’, such as pro-inflammatory cytokines and reactive oxygen species (ROS), leading to tissue destruction. Contrastingly, low dose ionising radiation may reduce vulnerability to subsequent exposure of ionising radiation, largely through the stimulation of adaptive responses, such as antioxidant defences. These disparate responses may be reflective of non-linear differential microglial activation at low and high doses, manifesting as an anti-inflammatory or pro-inflammatory functional state. Biomarkers of pathology in the brain, such as the mitochondrial Translocator Protein 18 kDa (TSPO), have facilitated in vivo characterisation of microglial activation and ‘neuroinflammation’ in many pathological states of the CNS, though the exact function of TSPO in these responses remains elusive. Based on the known responsiveness of TSPO expression to a wide range of noxious stimuli, we discuss TSPO as a potential biomarker of radiation-induced effects.

Upregulated epithelial junction expression represents a novel parameter of the epithelial radiation response to fractionated irradiation in oral mucosa

“…In contrast to large single doses, conventional fractionation doses, as used in this study, seem to trigger responses other than cell death, i. e. changes in cell function. Similar findings have been reported for the central nervous system and skin [42–44]. We hypothesize that the upregulation of epithelial junctions potentially represents a twofold mechanism.…”

Mortality from Circulatory Diseases and other Non-Cancer Outcomes among Nuclear Workers in France, the United Kingdom and the United States (INWORKS)

“…This association has not been reported previously; therefore, it may well be spurious. That said, 53% of the deaths in this disease grouping are attributed to dementia, and there have been some equivocal suggestions in recent studies of a possible link between Alzheimer’s disease and ionizing radiation (28–31). Dementia is an increasingly common cause of death among the elderly, and with extended follow-up these cohorts may provide useful empirical information on any potential effect at low dose.…”

Mortality from Circulatory System Diseases among French Uranium Miners: A Nested Case-Control Study

“…This association has not been reported previously; therefore, it may well be spurious. That said, 53% of the deaths in this disease grouping are attributed to dementia, and there have been some equivocal suggestions in recent studies of a possible link between Alzheimer's disease and ionizing radiation (28)(29)(30)(31). Dementia is an increasingly common cause of death among the elderly, and with extended followup these cohorts may provide useful empirical information on any potential effect at low dose.…”