Microgravity and Cosmic Radiations during Space Exploration as a Window into Neurodegeneration on Earth

Astronauts involved in long-duration spaceflight missions are exposed to specific risk factors known to induce profound changes of brain structure and function whose potential long-lasting effects are still under investigation.1 These changes range from sleep alterations, modifications of brain morphometry, vision impairment, mood shifts, and loss of appetite as well as cognitive deficits, including decrements in attention and executive functions.2 Among the substantial list of stressors, the effects of microgravity and galactic cosmic radiations constitute the most relevant ones and are at the core of current and future NASA efforts to identify effective countermeasures. Interestingly, while reduced gravity force seems responsible for cephalad fluid shift that potentially affects protein clearance mechanisms, cosmic radiations seem to promote the accumulation of amyloid-β in mouse models, induce neuroinflammation, and further alter hippocampal-related cognition.2 Considering available evidence, a pattern of spaceflight-induced accelerated brain aging seems to emerge in addition to established aging-like effects on cardiovascular and musculoskeletal systems (ie, carotid intima-media thickness increments, inflammatory response, bone loss, muscle atrophy, and DNA telomere modifications, as documented in the recent 1-year long NASA Twin Study1). While this raises important issues about astronauts’ health, it can also constitute a window into the neurophysiopathology of neurodegenerative processes in humans, which could potentially benefit life on Earth.