Hyperoxia-induced alterations in the pulmonary proteome of juvenile rats

High inspired concentrations of oxygen (hyperoxia) are often necessary to counteract tissue hypoxia during the treatment of ARDS. Reactive oxygen species generated by hyperoxic therapy may influence the expression of the pulmonary proteome and the application of discovery proteomics to the hyperoxic lung has the potential to divulge mechanisms regulating the expression of specific proteins integral to lung injury and repair. The present study examined the proteome derived from 30-day-old Sprague-Dawley rats exposed to room air (RA) and 95% O2 (Ox) for 24-72 hours using 2-dimensional difference in-gel electrophoresis (2D-DIGE) coupled with MALDI-ToF/ToF mass spectrometry. A total of 870 protein spots were visualized by 2D-DIGE across all gels. Mass spectral analysis identified 51 proteins representing 187 of the 214 significantly altered spots. Molecular and cellular function analysis grouped the identified proteins into free radical scavenging, cell death, cell-to-cell signaling, and cellular movement categories. The majority of the differences in the protein spots between RA and Ox occurred at 72 hours, with albumin, annexin A6 (AnxA6), and transferrin being increased, and mitochondrial Lon peptidase 1 being decreased by at least 20%. In Ox animals, AnxA6 protein expression increased three-fold without an increase in mRNA expression. Bioinformatic analysis of the AnxA6 transcript revealed the presence of a putative internal ribosome entry site within the 5'-untranslated region. These findings indicate that hyperoxia induces significant alterations in the pulmonary proteome which are temporally related. In addition, hyperoxia selectively enhances the expression of some proteins whose transcripts contain sequence motifs, which impart translational regulation.