MATRIX METALLOPROTEINASE INHIBITOR (ONO-4817) ATTENUATES ISCHEMIA-REPERFUSION INJURY IN AN ISOLATED RAT LUNG

Abstract

P69 Aims: Ischemia-reperfusion injury is a major factor affecting early phase of lung transplantation. Matrix metalloproteinases (MMPs) is known to play a role in degradation of basement membrane to promote neutrophil extravasation. However, the role of MMPs in lung reperfusion injury has not been fully illustrated. Therefore, by using MMP inhibitor (ONO-4817, Ono LTD, Osaka, Japan) that is mainly effective to MMP-2 and MMP-9, we investigated the role of MMPs in ischemia-reperfusion of lung, especially in the regard of promoting migration of leukocytes in bronchoalveolar lavage (BAL). Methods: We used an isolated rat lung model. After flushed with low-potassium dextran (LPD) solution and stored for 18 hours at 4 degrees C, the lungs were reperfused with diluted blood (20% of hematocrit) for 120 minutes in perfusion circuit, with (MMPI group, n=7) and without (IR group, n=7) MMP inhibitor (5ug/ml, ONO-4817). The lungs immediately reperfused without ischemia, served as control (Control group, n=7). During reperfusion, outflow blood gas tension, pulmonary artery pressure and airway pressure was measured. The reperfused lungs were examined for pathology and for tissue malondialdehyde (MDA) level. In another series of lungs, BAL sample were taken after reperfusion and the expression of adhesion molecules (CD11c and CD31) in alveolar macrophages was analyzed by flow cytometry. Results: Oxygenation capacity was significantly impaired during 120 minutes of reperfusion in IR group, whereas it was preserved in MMPI group (p<0.01) as well as in Control group. Pulmonary artery pressure was similar between IR and MMPI groups during reperfusion. Peak airway pressure was higher in IR group during reperfusion compared with the other 2 groups (p<0.01). Microscopic examination of the lung showed the extravasations and migrations of neutrophils into the interstitial tissues and alveolus in IR group, damaging the lung tissue, whereas their infiltration was modest in the MMPI group. After reperfusion, the cell number in BAL increased in IR group (1,128,000±53,000) compared with Control group (802,000±69,000, p<0.01), whereas it remained low in MMPI group (670,000±52,000, p<0.01). The expressions of CD11c and CD31 in alveolar macrophages similarly increased in IR (17.16±2.67% and 6.52±0.36%) and in MMPI groups (15.88±2.52% and 8.85±2.27%) after reperfusion, and both of them were significantly higher than in Control group (3.22±0.14% and 1.68±0.09%). Tissue MDA level in lung after reperfusion increased higher in IR group (24.4±1.21nmol/WETg) compared with those in Control group (18.0±0.94nmol/WETg, p<0.05), whereas it remained lower in MMPI group (16.6±2.16nmol/WETg, p<0.01). Conclusions: Our data show that the MMP inhibitor (ONO-4817) effectively attenuates ischemia-reperfusion lung injury by preventing migration of neutrophils into the interstitial space and alveolus in lung, thereby reducing the production of oxygen free radicals. Moreover, our data suggests that MMP inhibitor might not be effective in preventing the activation of alveolar macrophages.