The role of bradykinin in lung ischemia-reperfusion injury in a rat lung transplantation model.

PURPOSE: To investigate the role of bradykinin in a rat lung transplantation (LTx) model and preliminarily discuss the relationship between bradykinin and CD26/DPP-4. METHODS: Rats were randomly divided into four groups: Control (CON), Sham, low potassium dextranglucose (LPD), and AB192 (n=15/group). Orthotopic single LTx was performed in the LPD and AB192 groups. The donor lungs were flush-perfused and preserved with low potassium dextranglucose (LPD) or LPD+CD26/DPP-4 catalytic inhibitor (AB192). LTx was performed after 18 h cold ischemia time and harvested two days post-LTx. Blood gas analysis (PO2), wet/dry weight ratio (W/D), myeloperoxidase activity (MPO), and lipid peroxidation (MDA) were analyzed at 48 hr after transplantation. Immunohistochemical (IHC) analysis was performed in the same sample and validated by Western-Blot. RESULTS: Compared to the LPD group, the AB192 group showed higher PO2, lower W/D ratio, and decreased MPO and MDA. IHC studies showed strong bradykinin β2 receptor (B2R) staining in the LPD group, especially in inflammatory cells, alveolar macrophages, and respiratory epithelial cells. Expression of B2R by Western-Blot was significantly different between the AB192 and LPD groups. CONCLUSION: Bradykinin may be a competitive substrate of DPP-4, and decreased bradykinin levels may enhance protective effects against ischemia/reperfusion injury during LTx.