Abstract
Despite the observed severe effects of microgravity on mammalian cells, many astronauts have completed long term stays in space without suffering from severe health problems. This raises questions about the cellular capacity for adaptation to a new gravitational environment. The International Space Station (ISS) experiment TRIPLE LUX A, performed in the BIOLAB laboratory of the ISS COLUMBUS module, allowed for the first time the direct measurement of a cellular function in real time and on orbit. We measured the oxidative burst reaction in mammalian macrophages (NR8383 rat alveolar macrophages) exposed to a centrifuge regime of internal 0 g and 1 g controls and step-wise increase or decrease of the gravitational force in four independent experiments. Surprisingly, we found that these macrophages adapted to microgravity in an ultra-fast manner within seconds, after an immediate inhibitory effect on the oxidative burst reaction. For the first time, we provided direct evidence of cellular sensitivity to gravity, through real-time on orbit measurements and by using an experimental system, in which all factors except gravity were constant. The surprisingly ultra-fast adaptation to microgravity indicates that mammalian macrophages are equipped with a highly efficient adaptation potential to a low gravity environment. This opens new avenues for the exploration of adaptation of mammalian cells to gravitational changes.
Highlights
The gravitational force has been constant throughout the 4 billion years of Earth’s evolutionary history[1] and probably played a crucial role in the evolutionary explosion of organisms[2]
We demonstrated for the first time and through real-time measurements on board of the International Space Station (ISS) that mammalian cells have the capacity to adapt to microgravity within seconds
We developed the TRIPLE LUX A experiment system, which enables real-time on orbit measurement of oxidative burst reaction in mammalian NR8383 macrophage cells and the following real-time data downlink to Earth (Figs 1 and 2)
Summary
The gravitational force has been constant throughout the 4 billion years of Earth’s evolutionary history[1] and probably played a crucial role in the evolutionary explosion of organisms[2]. Not great or the pattern of change across various functions is not consistent[6] This leads to the hypothesis that the cells of the body must have an enormous capacity to adapt to microgravity, be capable of reacting to altered environmental conditions and of restoring cellular functions to a considerable degree. Some studies reported that key cellular mechanisms are altered in microgravity, followed by an adaptation of the system to the new circumstances by executing countermeasure actions Such countermeasures include the modification of the cytoskeleton and nuclear morphology, which occurs after 32 hours[7]. The oxidative burst reaction represents one of the key elements in the innate immune response, and it is the most important barrier against microbes invading the body[8]. This fast inhibition facilitates the determination of threshold levels of gravity sensitivity and the investigation of adaptation and re-adaptation effects
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