Ministry of Education (MOE) Key Laboratory of Gene Function and Regulation, School of Life Sciences, State Key Laboratory of Biocontrol, Sun Yat-sen University, Guangzhou, China.
State Key Laboratory of Space Medicine Fundamentals and Application, China Astronaut Research and Training Center, Beijing, China.
Life Sci Space Res (Amst). 2024 Feb;40:115-125. doi: 10.1016/j.lssr.2023.09.006. Epub 2023 Sep 22.
The circadian clock extensively regulates physiology and behavior. In space, astronauts encounter many environmental factors that are dramatically different from those on Earth; however, the effects of these factors on circadian rhythms and the mechanisms remain largely unknown. The present study aimed to investigate the changes in the mouse diurnal rhythm and gut microbiome under simulated space capsule conditions, including microgravity, noise and low atmospheric pressure (LAP). Noise and LAP were loaded in the capsule while the conditions in the animal room remained constant. The mice in the capsule showed disturbed locomotor rhythms and faster adaptation to a 6-h phase advance. RNA sequencing of hypothalamus samples containing the suprachiasmatic nucleus (SCN) revealed that microgravity simulated by hind limb unloading (HU) and exposure to noise and LAP led to decreases in the quantities of differentially expressed genes (DEGs), including circadian clock genes. Changes in the rhythmicity of genes implicated in pathways of cardiovascular deconditioning and more concentrated phases were found under HU or noise and LAP. Furthermore, 16S rRNA sequencing revealed dysbiosis in the gut microbiome, and noise and LAP may repress the temporal discrepancy in the microbiome community structure induced by microgravity. Changes in diurnal oscillations were observed in a number of gut bacteria with critical physiological consequences on metabolism and immunodefense. We also found that the superimposition of noise and LAP may repress normal changes in global gene expression and adaptation in the gut microbiome. Our data demonstrate that in addition to microgravity, exposure to noise and LAP affect the robustness of circadian rhythms and the community structure of the gut microbiome, and these factors may interfere with each other in their adaptation to respective conditions. These findings are important for furthering our understanding of the alterations in circadian rhythms in the complex environment of space.
昼夜节律广泛调节生理和行为。在太空中，宇航员会遇到许多与地球环境截然不同的环境因素；然而，这些因素对昼夜节律和机制的影响在很大程度上仍然未知。本研究旨在调查模拟太空舱条件下，包括微重力、噪声和低气压（LAP）对小鼠昼夜节律和肠道微生物组的影响。在太空舱中加载噪声和 LAP，而动物室的条件保持不变。太空舱中的小鼠表现出运动节律紊乱，并且更快地适应 6 小时的相位提前。含有视交叉上核（SCN）的下丘脑样本的 RNA 测序显示，后肢悬吊（HU）模拟的微重力以及暴露于噪声和 LAP 导致差异表达基因（DEGs）的数量减少，包括昼夜节律基因。在 HU 或噪声和 LAP 下，发现与心血管适应不良和更集中相位相关的途径中的基因节律性发生变化。16S rRNA 测序显示肠道微生物组失调，噪声和 LAP 可能抑制微重力引起的微生物组群落结构时间差异。在一些具有代谢和免疫防御关键生理后果的肠道细菌中观察到昼夜波动变化。我们还发现，噪声和 LAP 的叠加可能会抑制肠道微生物组中正常的昼夜变化和全球基因表达的适应。我们的数据表明，除了微重力之外，暴露于噪声和 LAP 会影响昼夜节律的稳健性和肠道微生物组的群落结构，并且这些因素可能在适应各自条件时相互干扰。这些发现对于进一步了解太空复杂环境中昼夜节律的变化很重要。
