The existence of oxygen is a necessary condition for aerobic metabolism and energy production, as is essential for most living things. Too much or too little oxygen can be life-threatening, so it is important to study the mechanism of how organisms respond quickly to the changing oxygen levels. When the oxygen demand exceeds the oxygen supply, the cells become hypoxic. This paper discusses the characteristics of the oxygen and the mechanism of the hypoxia adaptation under physiological and pathological conditions. Hypoxia can be considered in a positive aspect, the role in the hypoxic preconditioning, and the related history and research progress are reviewed, including preconditioning in extreme environments such as high altitude, and related clinical diseases, as well as the prospect of treatment of stroke diseases.

oxygen  /  oxygen sensor  /  hypoxic preconditioning  /  neuroprotection