Synergistic Effects of Weightlessness, Isoproterenol, and Radiation on DNA Damage Response and Cytokine Production in Immune Cells

Abstract

The implementation of rotating-wall vessels (RWVs) for studying the effect of lack of gravity has attracted attention, especially in the fields of stem cells, tissue regeneration, and cancer research. Immune cells incubated in RWVs exhibit several features of immunosuppression including impaired leukocyte proliferation, cytokine responses, and antibody production. Interestingly, stress hormones influence cellular immune pathways affected by microgravity, such as cell proliferation, apoptosis, DNA repair, and T cell activation. These pathways are crucial defense mechanisms that protect the cell from toxins, pathogens, and radiation. Despite the importance of the adrenergic receptor in regulating the immune system, the effect of microgravity on the adrenergic system has been poorly studied. Thus, we elected to investigate the synergistic effects of isoproterenol (a sympathomimetic drug), radiation, and microgravity in nonstimulated immune cells. Peripheral blood mononuclear cells were treated with the sympathomimetic drug isoproterenol, exposed to 0.8 or 2 Gy γ-radiation, and incubated in RWVs. Mixed model regression analyses showed significant synergistic effects on the expression of the β2-adrenergic receptor gene (ADRB2). Radiation alone increased ADRB2 expression, and cells incubated in microgravity had more DNA strand breaks than cells incubated in normal gravity. We observed radiation-induced cytokine production only in microgravity. Prior treatment with isoproterenol clearly prevents most of the microgravity-mediated effects. RWVs may be a useful tool to provide insight into novel regulatory pathways, providing benefit not only to astronauts but also to patients suffering from immune disorders or undergoing radiotherapy.

Immunological Changes During Space Travel: A Ground-Based Evaluation of the Impact of Neutron Dose Rate on Plasma Cytokine Levels in Human Whole Blood Cultures

“…Currently, NASA's most advanced GCR simulators provides some insight into the effect of GCR on biological systems [70]. A recent study by Moreno-Villanueva and colleagues examined the combined and individual effects of γ-radiation (radiation source undefined), simulated microgravity and physiological stress on isolated, unstimulated, peripheral blood mononuclear cells [29]. They concluded that radiation significantly influenced cytokine secretion but only under simulated microgravity conditions.…”

“…An important objective for future experiments is to take the additional layers of spaceflight complexity into consideration by mimicking the synergistic effect of multiple space stressors in a ground-based experiment, as outlined by Moreno-Villanueva et al [29]. In addition, the future goal should also include in vivo experiments with neutrons and other high-LET radiation qualities relevant to the space radiation environment, with special emphasis for spaceflight-relevant low dose rates.…”

“…For this pilot study, four key cell-mediated immunity cytokines, IFN-γ, IL-10, IL-2, and TNF-α were quantified down to their respective assay limits of 0.4, 1.6, 1.8, and 1.2 pg/ml. The R&D systems (Minnesota, USA) Luminex assay was conducted exactly to the manufacturer's instructions as described elsewhere [29] with two exceptions: only four cytokines were analysed here and the Luminex assays were performed on a MAGPIX R system (Luminex Corp., Texas, USA). A further 1 to 1 dilution of the plasma in assay diluent was performed to render analyte concentrations within the assay's linear range.…”

“…For example, several ground-based studies could clearly demonstrate the dramatic impact of microgravity on the immune system [21][22][23][24][25][26][27][28]. However, during space travel, radiation and psychological stress factors (e.g., isolation, sleep deprivation, and heavy workload) may have a significant synergistic or antagonistic effect on human immunity [29,30]. Here, terrestrial analogues offer not only financial and repeatability advantages but also the opportunity to determine the relative contribution of the individual space stressors to the observed health effect by simulating them both individually and in combination.…”

“…Here, the lymphocytes were intentionally stimulated ex vivo to mimic a challenged immune scenario, to monitor the disruptive effect of neutron dose and dose rate on the cytokine release profile. This method has been extensively used to study immune system dysregulation in several ex vivo studies related to short and long duration spaceflights and in terrestrial analogues [13,29,50,51].…”