No abstract

Ischemia-reperfusion lung injury limits lung transplantation. Neutrophil activation and/or xanthine oxidase-mediated purine degradation may cause toxic oxygen metabolite production and lung injury. We investigated whether circulating blood elements are involved in the pathogenesis of ischemia-reperfusion lung injury. Isolated rat lungs were perfused with physiological salt solution (PSS) stabilized with Ficoll until circulating blood elements were not detected in the lung effluent. Lungs were then rendered ischemic by stopping ventilation and perfusion for 45 min at room temperature. Lung injury occurred and was quantitated by the accumulation of 125I-bovine serum albumin into lung parenchyma and alveolar lavage fluid during reperfusion. Lung injury occurred, in the absence of circulating blood elements, when ischemic lungs were reperfused with PSS-Ficoll solution alone. Reperfusion with whole blood or PSS-Ficoll supplemented with human or rat neutrophils did not increase lung injury. Furthermore, during lung ischemia, the presence of neutrophils did not enhance injury. Experiments using PSS-albumin perfusate and quantitating lung injury by permeability-surface area product yielded similar results. Microvascular pressures were not different and could not account for the results. Toxic O2 metabolites were involved in the injury because addition of erythrocytes or catalase to the perfusate attenuated the injury. Thus reperfusion after lung ischemia causes injury that is dependent on a nonneutrophil source of toxic O2 metabolites.

We tested the hypothesis that monocrotaline would activate arachidonic acid metabolism in rats. If activation occurred before the pulmonary hypertension developed, arachidonate metabolites could play a role in the hypertensive monocrotaline injury. We found that 1 wk after monocrotaline administration 6-ketoprostaglandin F1 alpha and leukotriene C4 were increased in lung lavages. At 3 wk when pulmonary hypertension was well developed, lung lavage contained increased 6-ketoprostaglandin F1 alpha and thromboxane B2. In addition, the number and activity of white blood cells in the lavages was increased, and abnormal alveolar macrophages were present. The lung extract contained slow-reacting substances including leukotriene D4. Indomethacin administration inhibited the formation of cyclooxygenase metabolites but did not prevent pulmonary hypertension. Diethylcarbamazine administration reduced the numbers and activity of inflammatory cells, increased pulmonary hypertension, prevented right ventricular hypertrophy, and inhibited the formation of slow-reacting substances. We concluded that arachidonate metabolism was activated before pulmonary hypertension developed, that the inflammatory cells in the alveolus accompanied the hypertensive process, and that diethylcarbamazine attenuated both the monocrotaline-induced inflammatory response and the pulmonary hypertension.

Cerulein-induced acute pancreatitis in rats is associated with acute lung injury characterized by increased pulmonary microvascular permeability, increased wet lung weights, and histologic features of alveolar capillary endothelial cell and pulmonary parenchymal injury. The alveolar capillary permeability index is increased 1.8-fold after a 3-hour injury (0.30 to 0.54, p less than 0.05). Gravimetric analysis shows a similar 1.5-fold increase in wet lung weights at 3 hours (0.35% vs. 0.51% of total body weight, p less than 0.05). Histologic features assessed by quantitative morphometric analysis include significant intra-alveolar hemorrhage (0.57 +/- 0.08 vs. 0.12 +/- 0.02 RBC/alveolus at 6 hours, p less than 0.001); endothelial cell disruption (28.11% vs. 4.3%, p less than 0.001); and marked, early neutrophil infiltration (7.45 +/- 0.53 vs. 0.83 +/- 0.18 PMN/hpf at 3 hours, p less than 0.001). The cerulein peptide itself, a cholecystokinin (CCK) analog, is naturally occurring and is not toxic and in several in vitro settings including exposure to pulmonary artery endothelial cells, Type II epithelial cells, and an ex vivo perfused lung preparation. The occurrence of this ARDS-like acute lung injury with acute pancreatitis provides an excellent experimental model to investigate mechanisms and mediators involved in the pathogenesis of ARDS.

We hypothesized that Iloprost, a long-acting prostacyclin analog, would inhibit neutrophil (PMN)-induced lung injury and decrease PMN adherence to vascular endothelium. Human PMNs infused into isolated buffer-perfused rat lungs subsequently stimulated with phorbol myristate acetate (PMA) resulted in lung injury as assessed by the accumulation of [125I]bovine serum albumin (125I-BSA) in lung parenchyma and alveolar lavage fluid. Addition of Iloprost to the lung perfusate, prior to activation of the PMNs, reduced lung injury as assessed by a decrease in the accumulation of 125I-BSA in the lung. This protective effect was not due to the vasodilatory effect of Iloprost. Protection by Iloprost was not linked to a reduction in PMA-induced PMN superoxide production since Iloprost did not reduce the amount of superoxide released into lung perfusate. In vitro, Iloprost caused a dose-dependent inhibition of PMA-stimulated PMN adherence to endothelial cells. Iloprost did not affect the number of Mo1 adhesion molecules constitutively expressed or the number of receptors expressed on the PMNs following PMA. Addition of cAMP or dibutyryl cAMP to the endothelial cells mimicked the effects of Iloprost, diminishing PMA-stimulated PMN adhesion. In separate experiments, addition of the phosphodiesterase inhibitor IBMX to Iloprost resulted in a greater inhibition of PMA-stimulated PMN adherence, while addition of an adenylate cyclase inhibitor, SQ 22,536, or cAMP antibodies with the Iloprost abolished Iloprost's inhibitory effect on PMN adhesion. Thus, Iloprost inhibits PMA-activated PMN-induced lung injury despite continued superoxide production. Iloprost inhibition of PMN adhesion is dependent on cAMP.