Melatonin : a promising drug to ameliorate main human space exploration risks

Abstract

Abstract: Melatonin is a small indole molecule synthesized by most cells in the mammalian body. Circulating melatonin secreted by the pineal gland is a circadian signal that regulates main rhythmic physiological processes, including sleep-wake cycle and biological rhythms in cardiovascular function, metabolism, and immune response. Both intracellular and extracellular melatonin have been shown to act as an effective protector for free radicals molecular and tissue injury. During human space exploration crewmembers will be exposed to several risks, including exposure to radiation in the form of high-energy galactic cosmic rays and solar particle events, bone loss and neurological disorders induced by microgravity, and sleep disruption. Due to its important chronobiotic and cytoprotective effect, melatonin treatment could be a potential effective strategy to protect against most space radiation hazards. It has an anti-osteoclastogenic activity and a pro-osteoblastic activity that may reduce bone-loss induced by microgravity. Also, melatonin is potentially effective to prevent neurodegeneration that may result from long term space exploration. Finally, its chronobiotic and hypnotic properties may help to improve sleep and circadian synchronization, decreasing in turn, the risk of fatigue, performance decrements and adverse health outcomes. Melatonin was presumably present from the very beginning of life in Earth and evidence suggests that it could be a helpful partner for our first steps outside the planet.