Acute exposure to hypobaric hypoxia upregulates the expression of hypoxia-inducible factor-1α and vascular endothelial growth factor

Abstract

Hypoxia is a stress factor frequently encountered during flight and a common cause of tissue and cell injury experienced by in-flight crew. Effects of hypoxia on the body can vary depending on the duration and severity of hypoxic exposure. As symptoms can differ among individuals, the measures taken to address hypoxia can be greatly improved by understanding its effects. It is critically important for pilots, cabin crew, and in-flight medical professionals to familiarize themselves with hypoxia and the factors that affect its presentation. In this study, we investigated the effect of hypoxia on the expression of vascular endothelial growth factor (VEGF) in mice using a hypoxic-exposure model. Experimental animals were placed in a hypobaric chamber at 8,000 ft for 1 h (n=5), 3 h (n=5), or 6 h (n=5). Immediately after hypoxic exposure, protein concentration of VEGF and mRNA levels of hypoxiainducible factor-1α (HIF-1α) and VEGF were analyzed in serum and liver tissue homogenates. Exposure to hypobaric hypoxia significantly upregulated the expression of both HIF-1α and VEGF mRNA, but not hepatic VEGF mRNA. Our data indicate that acute exposure to hypobaric hypoxia upregulates serum mRNA levels of HIF-1α and VEGF in mice, and that the liver is less likely to be the source of elevated serum VEGF mRNA. In contrast, serum VEGF protein level may be regulated by other factors. Further investigations to confirm or disprove our preliminary results are required.