Signal transduction in cells of the immune system in microgravity

Life on Earth developed in the presence and under the constant influence of gravity. Gravity has been present during the entire evolution, from the first organic molecule to mammals and humans. Modern research revealed clearly that gravity is important, probably indispensable for the function of living systems, from unicellular organisms to men. Thus, gravity research is no more or less a fundamental question about the conditions of life on Earth. Since the first space missions and supported thereafter by a multitude of space and ground-based experiments, it is well known that immune cell function is severely suppressed in microgravity, which renders the cells of the immune system an ideal model organism to investigate the influence of gravity on the cellular and molecular level. Here we review the current knowledge about the question, if and how cellular signal transduction depends on the existence of gravity, with special focus on cells of the immune system. Since immune cell function is fundamental to keep the organism under imnological surveillance during the defence against pathogens, to investigate the effects and possible molecular mechanisms of altered gravity is indispensable for long-term space flights to Earth Moon or Mars. Thus, understanding the impact of gravity on cellular functions on Earth will provide not only important informations about the development of life on Earth, but also for therapeutic and preventive strategies to cope successfully with medical problems during space exploration

Voluntary Blame-Taking Behavior: Kinship before Friendship and no Effect of Incentives

Inspired by theories of prosocial behavior, we tested the effect of relationship status and incentives on intended voluntary blame-taking in two experiments (Experiment 2 was pre-registered). Participants (NE1 = 211, NE2 = 232) imagined a close family member, a close friend, or an acquaintance and read a scenario that described this person committing a minor traffic offence. The person offered either a monetary, social or no incentive for taking the blame. Participants indicated their willingness to take the blame and reasons for and against blame-taking. Overall, a sizable proportion of participants indicated to be willing to take the blame (E1: 57.8%; E2: 34.9%). Blame-taking rates were higher for family members than close friends or acquaintances in both experiments, as expected. Unexpectedly, there was no difference between a close friend and an acquaintance in Experiment 2. Social incentives did not have an effect on voluntary blame-taking in either experiment. Neither did we find an interaction between relationship status and incentives. The results highlight the importance of kin relationships in the context of voluntary blame-taking

Pharmacological countermeasures to spaceflight-induced alterations of the immune system

Human bioastronautic programs have grown during the last 50 years. Medical and physiological findings from these missions have demonstrated that spaceflight impacts almost all physiological systems, including bone demineralization and reduced immunological competence. These adaptive responses can affect crew health and performance. Indeed, about half of the astronauts encountered immune dysregulations during space travels. Developing efficient countermeasures to preserve the astronaut’s immune system is therefore a prerequisite before undertaking future long-duration space missions. In this chapter, we present promising pharmacological countermeasures to mitigate that risk

Effects of Spaceflight on the Immune System

The immune system belongs to the most affected systems during spaceflight, and sensitivity of cells of the human immune system to reduced gravity has been confirmed in numerous studies in real and simulated microgravity. Immune system dysfunction during spaceflight represents a substantial risk for exploration class mission knowledge about the clinical, cellular, and genetic basis of immune system response, and adaptation to altered gravity will provide key information for appropriate risk management, efficient monitoring, and countermeasures against existing limiting factors for human health and performance during manned exploration of the solar system. In spite of the immune system dysregulation, studies indicate an adaptation reaction of the immune system to the new microgravity environment, at least for the T-cell system, starting after 2 weeks and continuing until 6 months or longer, reflected by cytokine concentrations in blood plasma or in stimulation assays. At the cellular level, rapid adaptation responses could be detected as early as after seconds until minutes in T cells and macrophages. Therefore, adaptive responses of cells and the whole organism could be expected under microgravity and altered gravity in general. Preventive countermeasures should therefore consider support and stabilization of the endogenous adaptation programs. Potential countermeasures for risk mitigation are summarized in this chapter. We assume that the immune systems not only have a significant adaptation potential when challenged with low gravitational environments but also provide interesting preventive and therapeutic options for long-term space missions

Cellular and Molecular Responses to Gravitational Force-Triggered Stress in Cells of the Immune System

Sensitivity of the human immune system to microgravity has been supposed since the first Apollo missions and was demonstrated during several space missions in the past. In vitro experiments demonstrated that cells of the immune system are exceptionally sensitive to microgravity. Therefore, serious concerns arose whether spaceflight-associated immune system weakening ultimately precludes the expansion of human presence beyond Earth’s orbit. In human cells, gravitational forces may be sensed by an individual cell in the context of altered extracellular matrix mechanics, cell shape, cytoskeletal organization, or internal prestress in the cell–tissue matrix. The development of cellular mechanosensitivity and signal transduction was probably an evolutionary requirement to enable our cells to sense their individual microenvironment. Therefore it is possible that the same mechanisms, which enable human cells to sense and to cope with mechanical stress, are potentially dangerous in microgravity. This chapter reviews the most recent developments in investigation to elucidate the influence of microgravity on immune cell signaling and functions and hereby bridges the phenotypic changes to transcriptome and epigenetic regulators