Xenon Treatment Protects against Remote Lung Injury after Kidney Transplantation in Rats

Background: Ischemia-reperfusion injury (IRI) of renal grafts may cause remote organ injury including lungs. The authors aimed to evaluate the protective effect of xenon exposure against remote lung injury due to renal graft IRI in a rat renal transplantation model. Methods: For in vitro studies, human lung epithelial cell A549 was challenged with H2O2, tumor necrosis factor-, or conditioned medium from human kidney proximal tubular cells (HK-2) after hypothermia-hypoxia insults. For in vivo studies, the Lewis renal graft was stored in 4 degrees C Soltran preserving solution for 24 h and transplanted into the Lewis recipient, and the lungs were harvested 24 h after grafting. Cultured lung cells or the recipient after engraftment was exposed to 70% Xe or N-2. Phospho (p)-mammalian target of rapamycin (mTOR), hypoxia-inducible factor-1 (HIF-1), Bcl-2, high-mobility group protein-1 (HMGB-1), TLR-4, and nuclear factor B (NF-B) expression, lung inflammation, and cell injuries were assessed. Results: Recipients receiving ischemic renal grafts developed pulmonary injury. Xenon treatment enhanced HIF-1, which attenuated HMGB-1 translocation and NF-B activation in A549 cells with oxidative and inflammatory stress. Xenon treatment enhanced p-mTOR, HIF-1, and Bcl-2 expression and, in turn, promoted cell proliferation in the lung. Upon grafting, HMGB-1 translocation from lung epithelial nuclei was reduced; the TLR-4/NF-B pathway was suppressed by xenon treatment; and subsequent tissue injury score (nitrogen vs. xenon: 26 1.8 vs. 10.7 +/- 2.6; n = 6) was significantly reduced. Conclusion: Xenon treatment confers protection against distant lung injury triggered by renal graft IRI, which is likely through the activation of mTOR-HIF-1 pathway and suppression of the HMGB-1 translocation from nuclei to cytoplasm.