About this Research Topic
Cardio-vascular Dysfunction and Physiological Manifestations Induced by Environmental Conditions
Nature and its associated environmental conditions, known as environmental architecture, have both shaped and influenced the evolution of our bodies and the systemic functioning of our organs over the aeons. Natural phenomenon, and our physiological adaptations to these, such as gravity, altitude, food sources and physical activity/inactivity play an important role in regulating tissue and organ homeostasis. So pivotal and robust are these changes that they can be seen at the epigenetic level, and impact various organ systems including that of the skeletal, muscle, neuro-vestibular, and importantly, cardiovascular system. Moreover, it plays a crucial role in the regulation of metabolism.
Our cardiovascular system is particularly well adapted to the gravity factor set at 1G, allowing efficient blood flow throughout the body under various conditions such as rest, physical exertion, standing, sitting and lying. Astonishingly, a reduction in gravitational stimuli will induce, very rapidly, a physiological and systemic de-conditioning. Space flight and ground-based models of microgravity such as Bed Rest and Dry Immersion have shown the possibilities and limitations of human adaptation to a reduction in gravitational stimulation. Over the course of the past 50 years, studies have demonstrated that the space environment and microgravity in particular, will cause changes that may affect the performance of astronauts. These physiological changes are now better understood: prolonged exposure to a weightlessness environment can lead to significant loss of bone, muscle mass, strength, cardiovascular and sensory-motor de-conditioning, immune, hormonal and metabolism changes. These changes in turn are associated with an orthostatic intolerance and a decrease of global exercise capacity. These effects can be observed under conditions of weightlessness and in ground-based models of microgravity (bed rest, dry immersion, hindlimb unloading of rodents, cells in culture, …) but also in situations of physical inactivity. Indeed, recent missions have revealed a new suite of physiological adaptations and consequences of space flight. Astronauts exposed to prolonged weightlessness experience ocular changes and physiological structural alterations. Direct physiological factors associated with gravity act on the heart and vessels (changes in hydrostatic pressure and transmural pressure, changes in shear stress) and which lead to both morphological and functional remodelling (eutrophic or hypertrophic remodelling, endothelial dysfunction, inflammation, epigenetic changes etc). Circulating factors within the cardiovascular compartment (hormones, microparticles, platelets, white blood cells, extracellular/circulating miRNAs (ECmiRNA) and long non-coding RNAs (lncRNA) are influenced by gravitational stimuli and may contribute to the adaptive changes observed in the cardiovascular system.
The same rationale can be applied in other physiological situations such as physical inactivity, confinement, hyperbaric and hypoxic conditions, high altitude as well as thermal changes. Importantly, novel studies and evolving new paradigms suggest that the physiological and pathophysiological responses to extreme environmental challenges (e.g. hypobaric hypoxia, hyperbaria, microgravity, cold, heat) may be similar to responses seen in critical illness. Therefore, understanding the (patho)-physiological mechanisms and adaptations to such challenges may provide scientists and clinicians with a window of opportunity to investigate the aetiology of many chronic conditions, and thus develop novel, more effective preventative and management strategies.
The aim of this Research Topic is to collectively gather research, studies, opinions, reviews and novel thinking and findings from the cornucopia of work being undertaken in this field of medicine and human physiology. This Research Topic will focus on different environmental conditions in humans and both animal and cell models, with particular attention to integrative physiology and consequences on the cardiovascular compartment. We will emphasise environmental conditions involving gravity changes, altitude, physical activity and inactivity, as well as comparing the observed changes induced by other environmental conditions. Through this understanding, better counter measures and preventive strategies will be proposed.
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