Molecular signatures of trauma-hemorrhagic shock-induced lung injury: Hemorrhage- and injury-associated genes

The etiology of trauma-hemorrhagic shock (T/HS)-induced acute lung injury has been difficult to elucidate because of, at least in part, the inability of in vivo studies to separate the noninjurious pulmonary effects of trauma-hemorrhage from the tissue-injurious ones. To circumvent this in vivo limitation, we used a model of T/HS in which T/HS lung injury was abrogated by dividing the mesenteric lymph duct. In this way, it was possible to separate the pulmonary injurious response from the noninjurious systemic response to T/HS by comparing the pulmonary molecular responses of rats subjected to T/HS, which did and did not develop lung injury, with those of nonshocked rats. Using high-density oligonucleotide arrays and treatment group comparisons of whole lung tissue collected at 3 h after the end of the shock or sham-shock period, 139 of 8,799 assessed genes were identified by significant analysis of microarrays. Hemorrhage without the secondary effects of lung injury modulated the expression of 21 genes such as interleukin 1 beta, metallothionein-2, and myeloctomatosis oncogene (c-myc). In response to injury, 42 genes were identified to be differentially expressed. Upregulated genes included the L1 retroposon and guanine deaminase, whereas downregulated genes included catalase and superoxide dismutase 1. Real-time polymerase chain reaction confirmed the differential expression for selected genes. PathwayAssist analysis identified interleukin 1 beta as a central regulator of two subpathways of stress response-related genes (c-myc and superoxide dismutase 1/catalase) as well as several unrelated genes such as lipoprotein lipase. Our model system provided a unique opportunity to distinguish the molecular changes associated with T/HS-induced acute lung injury from the systemic molecular response to T/HS.