Abstract
Whereby several types of cultured cells are sensitive to gravity, the immune system belongs to the most affected systems during spaceflight. Since reactive oxygen species/reactive nitrogen species (ROS/RNS) are serving as signals of cellular homeostasis, particularly in the cells of the immune system, we investigated the immediate effect of altered gravity on the transcription of 86 genes involved in reactive oxygen species metabolism, antioxidative systems, and cellular response to oxidative stress, using parabolic flight and suborbital ballistic rocket experiments and microarray analysis. In human myelomonocytic U937 cells, we detected a rapid response of 19.8% of all of the investigated oxidative stress-related transcripts to 1.8 g of hypergravity and 1.1% to microgravity as early as after 20 s. Nearly all (97.2%) of the initially altered transcripts adapted after 75 s of hypergravity (max. 13.5 g), and 100% adapted after 5 min of microgravity. After the almost complete adaptation of initially altered transcripts, a significant second pool of differentially expressed transcripts appeared. In contrast, we detected nearly no response of oxidative stress-related transcripts in human Jurkat T cells to altered gravity. In conclusion, we assume a very well-regulated homeostasis and transcriptional stability of oxidative stress-related pathways in altered gravity in cells of the human immune system.
Highlights
Gravitational force and “oxidative stress” are constant determinants of Earth’s evolutionary history [1,2] and probably played a crucial role in the evolution of life [2,3,4] and its homeostasis [2,5]
In human myelomonocytic U937 cells, we detected a rapid response of 19.8% of all of the investigated oxidative stress-related transcripts to 1.8 g of hypergravity and 1.1% to microgravity as early as after 20 s
As already described by Thiel [35,36], human U937 myelomonocytic cells and human Jurkat T cells were subjected to 20 s of hypergravity (1.8 g) and subsequently to 20 s of microgravity during the first parabola of parabolic flight campaigns (19th and 23rd German Aerospace Center (DLR) PFC), and samples were obtained at the end of each flight phase
Summary
Gravitational force and “oxidative stress” are constant determinants of Earth’s evolutionary history [1,2] and probably played a crucial role in the evolution of life [2,3,4] and its homeostasis [2,5]. Cellular and molecular processes induced and regulated by reactive oxygen and nitrogen species (ROS and RNS), and referred to as “oxidative stress” [6], were first perceived as largely negative and pathological, but are understood as “physiological states” that elicit a decisive shift in patterns of gene expression [2]. Oxidative stress is considered not as a simple by-product of respiration [7], but rather as an intrinsically driving force of the evolution of life on Earth [2], including chemiosmotic coupling, mitonuclear coadaptation [2], and the evolution of symbiotic associations [4]. Normalizing the redox homeostasis could mitigate a portion of the adverse phenomena seen in spaceflight, increasing the level of health and safety during exploration class missions [16]
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