دانلود رایگان مقاله نقش هیپوکسی و سازگاری عروق به شرایط شدید

Abstract

The study of vascular adaptation to extreme conditions, and in particular to hypoxia, represents a unique opportunity in cardiovascular physiology, with relevant translational implications. First, it has crucial clinical consequences for about 140 million people worldwide living at high altitude and chronically exposed to hypobaric hypoxia. Second, an increasing number of lowlanders are exposed to high altitude for recreational or working purposes, including aged, diseased individuals: in these cases, hypoxia could be a trigger for acute cardiovascular events. Finally, hypoxia plays a major role in the pathogenesis of many diseases and chronic conditions, as respiratory (i.e. chronic obstructive pulmonary disease and obstructive sleep apnea syndrome) and cardiovascular disorders (i.e. heart failure, ischemic heart disease and cerebrovascular disease). Thus, results from field studies at high altitude might be important for a deeper understanding of their pathophysiology. This review is aimed at summarizing the main findings in the field of chronic and acute vascular adaptation to hypoxia, focusing on the role of nitric oxide (NO) and endothelial function, as well as large artery behavior.

Perspectives and future directions for research

Vascular physiology at high altitude is a complex research field, influenced by several regulatory pathways with different impact over time: thus, future studies should include serial multi-parametric evaluations in order to achieve a better comprehension of the timing of the phenomena. Furthermore, an accurate standardization of techniques used and of ascent protocols is mandatory. The role of confounding factors such as blood viscosity, hydration, nutrition patterns, socio-economic status should be ascertained, especially for studies regarding native Andean, Himalayan or Ethiopian populations. Genotypephenotype correlation studies, for different patterns of acute and chronic systemic vascular adaptation to hypoxia, are still lacking and they could help identify mechanisms beyond different routes of adaptation. In particular, no information are available on vascular function and structure of the inhabitants of the Ethiopian plateau, which are likely to exhibit a totally different pattern of genetic variants.38 The metabolic aspects, such the role of insulin resistance,39 are still to be explored among mechanisms underlying vascular dysfunction at high altitude. The clinical consequences of individual vascular response to hypoxia in high-altitude dwellers and in lowlanders exposed to high altitude for working or recreational reasons are an exciting and promising field of research. Finally, exposure to hypoxia might constitute a sort of “stress test” for the cardiovascular system, possibly unmasking predisposition to cardiovascular disease at an early stage, in parallel to the results obtained for pulmonary vascular function.40