Narayanan S Anand
Department of Nutrition and Integrative Physiology, Florida State University, Tallahassee, FL, United States.
Front Physiol. 2023 Jul 3;14:1199175. doi: 10.3389/fphys.2023.1199175. eCollection 2023.
Gravity is a fundamental interaction that permeates throughout our Universe. On Earth, gravity gives weight to physical objects, and has been a constant presence throughout terrestrial biological evolution. Thus, gravity has shaped all biological functions, some examples include the growth of plants (e.g., gravitropism), the structure and morphology of biological parts in multicellular organisms, to its effects on our physiological function when humans travel into space. Moreover, from an evolutionary perspective, gravity has been a constant force on biology, and life, to our understanding, should have no reason to not experience the effects of gravity. Interestingly, there appear to be specific biological mechanisms that activate in the absence of gravity, with the space environment the only location to study the effects of a lack of gravity on biological systems. Thus, in this perspective piece, biological adaptations from the cellular to the whole organism levels to the presence and absence of gravity will be organized and described, as well as outlining future areas of research for gravitational biological investigations to address. Up to now, we have observed and shown how gravity effects biology at different levels, with a few examples including genetic (e.g., cell cycle, metabolism, signal transduction associated pathways, etc.), biochemically (e.g., cytoskeleton, NADPH oxidase, Yes-associated protein, etc.), and functionally (e.g., astronauts experiencing musculoskeletal and cardiovascular deconditioning, immune dysfunction, etc., when traveling into space). Based from these observations, there appear to be gravity-sensitive and specific pathways across biological organisms, though knowledge gaps of the effects of gravity on biology remain, such as similarities and differences across species, reproduction, development, and evolutionary adaptations, sex-differences, etc. Thus, here an overview of the literature is provided for context of gravitational biology research to-date and consideration for future studies, as we prepare for long-term occupation of low-Earth Orbit and cis-Lunar space, and missions to the Moon and Mars, experiencing the effects of Lunar and Martian gravity on biology, respectively, through our Artemis program.
引力是一种贯穿我们宇宙的基本相互作用。在地球上，引力赋予物理物体重量，并且在陆地生物进化过程中一直存在。因此，引力塑造了所有生物功能，一些例子包括植物的生长（例如，向地性）、多细胞生物中生物部分的结构和形态，以及人类进入太空时对我们生理功能的影响。此外，从进化的角度来看，引力一直是作用于生物的恒定力量，而且据我们所知，生命应该没有理由不受到引力的影响。有趣的是，似乎存在在没有引力的情况下激活的特定生物机制，而太空环境是研究缺乏引力对生物系统影响的唯一场所。因此，在这篇观点文章中，将整理和描述从细胞到整个生物体水平对引力存在和不存在的生物适应情况，并概述引力生物学研究未来需要解决的研究领域。到目前为止，我们已经观察并展示了引力如何在不同水平上影响生物学，一些例子包括基因层面（例如，细胞周期、代谢、信号转导相关途径等）、生物化学层面（例如，细胞骨架、NADPH氧化酶、Yes相关蛋白等）以及功能层面（例如，宇航员在进入太空时经历肌肉骨骼和心血管功能失调、免疫功能障碍等）。基于这些观察结果，似乎存在跨生物有机体的引力敏感和特定途径，尽管引力对生物学影响的知识空白仍然存在，例如不同物种之间的异同、繁殖、发育和进化适应、性别差异等。因此，本文提供了一份文献综述，作为迄今为止引力生物学研究的背景以及对未来研究的思考，因为我们正在为长期驻留近地轨道和地月空间做准备，并通过我们的阿尔忒弥斯计划执行前往月球和火星的任务，分别体验月球和火星引力对生物学的影响。
