Space radiation health risks to hematopoietic, neural, and gastrointestinal systems in astronauts

The rapid progress in global deep space exploration presents astronauts with a complex space radiation environment that substantially exceeds that of near-Earth orbit. Space radiation primarily consists of galactic cosmic rays (GCRs) and solar particle events (SPEs), which exhibit strong penetrative capability and considerable biological damaging potential. These factors may induce persistent oxidative stress, mitochondrial dysfunction, DNA double-strand breaks, and repair pathway challenges. This review examines the impacts of space radiation on the hematopoietic, neural, and gastrointestinal systems. Human spaceflight observations indicate that exposure to space radiation may be associated with bone marrow suppression, reduced lymphocyte counts, diminished thymic output, and immune dysfunction, which may heighten susceptibility to infection and inflammation. Preclinical animal model research indicates that even low doses of space-relevant radiation may induce cognitive decline, memory deficits, anxiety-like behaviors, and neurodegenerative alterations, though these findings remain to be validated in human astronauts. Proposed mechanisms include impaired hippocampal synaptic plasticity, neuroinflammatory activation, and mitochondrial energy metabolism imbalance. Radiation has been shown to compromise the intestinal epithelial barrier, induce intestinal stem cell senescence, and disturb gut microbiome equilibrium in preclinical models. These gastrointestinal alterations may potentially exacerbate neurocognitive dysfunction and promote chronic inflammation via the gut-brain axis, based on mechanistic evidence from animal studies. Currently, there remains an insufficient systematic understanding of the cumulative effects, sex differences, and individual susceptibility associated with long-term low-dose composite radiation exposure. Integrating aerospace medicine is imperative to address these knowledge gaps and safeguard astronaut health during future deep-space missions.