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Hypergravity-induced immunomodulation in a rodent model: hematological and lymphocyte function analyses
Michael J Pecaut1, Glen M Miller, Gregory A Nelson
1Department of Radiation Medicina, Loma Linda University School of Medicine, Loma Linda, CA 92354, USA. mpecaut@dominion.llumc.edu
Insights
Hypergravity exposure alters blood cell counts and immune cell function in mice. These changes, including reduced red blood cells and altered cytokine production, highlight potential health risks for astronauts during long space missions.
Area of Science:
- Space biology
- Physiology
- Immunology
Background:
- Altered gravity environments, such as those experienced during spaceflight or simulated hypergravity, can impact physiological systems.
- Understanding these effects is crucial for mitigating health risks in astronauts and for broader physiological research.
Purpose of the Study:
- To quantify the effects of chronic hypergravity (1, 2, and 3 G) on hematological parameters, immune cell proliferation, and cytokine secretion in mice.
- To investigate the time-dependent and gravity-level-dependent responses.
Main Methods:
- C57BL/6 mice were exposed to chronic centrifugation at 1, 2, or 3 G.
- Hematological parameters (erythrocyte counts, hematocrit, hemoglobin) were measured.
- Lymphoblastogenesis (spontaneous and mitogen-induced) and splenocyte cytokine production (IL-2, IL-4, TNF-α, IFN-γ) were assessed at various time points (1, 4, 7, 10, 21 days).
Main Results:
- Significant reductions in erythrocyte counts, hematocrit, and hemoglobin were observed by day 21.
- Thrombocyte counts showed a transient increase in the 3-G group.
- Immune cell blastogenesis varied with centrifugation duration, not gravity level.
- Splenocyte cytokine profiles changed, with increased IL-2, IL-4, and TNF-α, and decreased IFN-γ during the first week.
Conclusions:
- Chronic hypergravity exposure induces significant hematological alterations and modulates immune cell function in mice.
- These findings suggest potential health consequences of altered gravity for prolonged space missions.
- Further research is needed to fully understand the implications for human physiology in space.
Abstract:
The major purpose of this study was to quantify hypergravity-induced changes in erythrocyte and thrombocyte characteristics, spontaneous and mitogen-induced lymphoblastogenesis, and capacity of splenocytes to secrete immunoregulatory cytokines. C57BL/6 mice were subjected to chronic 1, 2, and 3 G; subsets were euthanized after 1, 4, 7, 10, and 21 days of centrifugation. Erythrocyte counts, hematocrit, and hemoglobin were significantly reduced by day 21 in both centrifuged groups. Hemoglobin concentration and volume per red blood cell were generally low, but an early, transient spike above normal was noted in thrombocyte counts in the 3-G group. Fluctuations above and below normal in blood and spleen cell spontaneous blastogenesis were dependent on the length of centrifugation time and not on the level of gravity. Depression in splenocyte responses to phytohemagglutinin and lipopolysaccharide due to gravity were noted when the data were expressed as stimulation indexes. Cytokine production by spleen cells was primarily affected during the first week of centrifugation: IL-2, IL-4, and tumor necrosis factor-alpha increased, whereas interferon-gamma decreased. These findings, although not identical to those reported for spaceflight, indicate that altered gravity can influence both hematological and functional variables that may translate into serious health consequences during extended missions.
