Time course of housekeeping gene expression changes in diffuse alveolar damage induced by hyperoxia exposure in mice.

We have found diffuse alveolar damage (DAD) has taken place in some patients under mechanical ventilation with high-inspired oxygen concentrations. To clarify the molecular pathophysiology of this, the time course of gene expression changes induced by hyperoxia exposure in mouse lungs was examined using real-time quantitative polymerase chain reaction (real-time qPCR). Our raw data and those normalized with glyceraldehyde 3-phosphate dehydrogenase (GAPDH) showed that: (1) there is a decrease in levels of mRNAs for surfactant-associated protein C (SFTPC), cytochrome P450, 2F2 (CYP2F2), Claudin 1 (CLDN1), membrane-associated zonula occludens protein-1 (ZO-1), lysozyme (LYZS), and this suggests alveolar dysfunction and a disruption of the immune system, (2) we confirmed apoptotic conditions, such as significant up-regulations of mRNA levels in Myc and Galectin-3, and (3) hyperoxic conditions probably yielded reactive oxygen species (ROS), which resulted in a malignant cycle of ROS production by Myc overexpression [Shimada I, Matsui K, Brinkmann B, Hohoff C, Hiraga K, Tabuchi Y, et al. Novel transcript profiling of diffuse alveolar damage induced by hyperoxia exposure in mice: normalization by glyceraldehyde 3-phosphate dehydrogenase. Int J Legal Med 2008;122:373-83]. In this experiment, GAPDH was up-regulated when hyperoxia exposure was continued. Therefore, we reexamined our data and found that: (1) mRNA levels of other housekeeping genes, including beta(2)-microglobulin (beta2M), ribosomal protein: large P2 (RPLP2), and importin 8 (IPO8) altered to a lesser extent, (2) mRNA levels of beta2M and IPO8 were down-regulated when hyperoxia exposure was continued, and (3) our previous work was validated by normalization with these three housekeeping genes.