Endothelial activation following prolonged hypobaric hypoxia.

Prolonged exposure to low oxygen may induce adaptive changes which can be either beneficial or deleterious to cell survival. We examined the effect of prolonged moderate hypobaric hypoxia on CNS endothelial cell (EC) function. Exposure to hypoxia resulted in expression of EC activation markers, the cell surface adhesion proteins intracellular adhesion molecule-1 and E-selectin. Induction of the major histocompatibility complex (MHC) class II molecule as well as increased constitutive expression of the transferrin receptor and the glucose transporter-1 protein was also detected within 24 h of exposure to hypobaric hypoxia. Constitutive expression of the MHC class I molecule increased by 48 h. Expression of most EC activation markers increased with time from 0 to 2 weeks. By 3 weeks of exposure to hypobaric hypoxia, ECs returned to their quiescent state with the exception of sustained expression of E-selectin and elevated glut-1. Little to no significant increase in expression of vascular cell adhesion molecule-1 was seen at any time period.