Simulated Flight, Muscle Genetics, and Inflammatory Indicators in Mice

St. Pierre Schneider B, Moonie S, Fulkerson ND, Nicholas J, Bammler T, Voss JG. Simulated flight, muscle genetics, and inflammatory indicators in mice. Aviat Space Environ Med 2013; 84:840–4.

Introduction: Skeletal muscle discomfort commonly occurs during long-distance air travel. Although the effects of high altitude on muscle have been well-studied, the effects of short-term exposure to the altitude at which aircraft cabins are pressurized, 2438 m, have not. The primary aim of this study was to examine global gene expression in the gastrocnemius muscle after simulated flight. Inflammatory indicators were also assessed in the muscle. Methods: Thirty-five mice were evenly exposed to normobaria or hypobaria (2438 m) for ∼8-9 h. Microarray and ribonucleic acid (RNA) analyses were performed. Additionally, macrophage and neutrophil presence was examined. Results: Fourteen genes were downregulated in females after hypobaria. These genes included those related to epithelial homeostasis, such as the keratins, and genes activated by cellular insult. In contrast, four noncoding, regulatory RNAs were upregulated in males. No difference in proinflammatory cytokine gene and messenger RNA (mRNA) expression was detected between normobaria and hypobaria. The mean number of CD68-positive leukocytes per mm² and mean area percentage of the CD68 antigen in muscle of normobaric (NB) and hypobaric (HB) mice were 53-54 and ∼0.2%, respectively. Discussion: Simulated flight does not activate a proinflammatory response in healthy muscle. However, epithelial and cellular defense genes may be downregulated in females, whereas regulatory RNAs may be upregulated in males.