The effect of the platelet-activating factor inhibitor TCV-309 on reperfusion injury in a canine model of ischemic lung

Cytosolic phospholipase A2 inhibition attenuates ischemia-reperfusion injury in an isolated rat lung model

BACKGROUND

Arachidonic acid metabolites and platelet-activating factor (PAF) are potentially involved in ischemia-reperfusion (IR) lung injury. A key enzyme regulating their metabolism is cytosolic phospholipase A2 (cPLA2). Arachidonyl trifluoromethyl ketone (AACOCF3) is reported to be a potent cPLA2 inhibitor. In the present study, we hypothesized that pharmacological inhibition of cPLA2 might ameliorate IR lung injury.

METHODS

To test the hypothesis, we examined the effects of AACOCF3 in an isolated rat lung model. Three groups were defined (n=6, each): in the vehicle group, lungs were perfused for 2 hours without an ischemic period. In the ischemic groups, 20 mg/kg of AACOCF3 (AACOCF3 group) or saline (control group) was i.v. administered 15 min before lung harvest. Lungs were flushed with LPD solution, cold-stored 18 hours, and reperfused for 2 hours.

RESULTS

IR increased cPLA2 activity mainly via alveolar macrophages, sPLA2 activity, thromboxane and leukotriene formation, and the expression of PAF receptor, whereas AACOCF3 treatment significantly reduced all of these. Compared to the vehicle group, the wet-to-dry ratio, proteins in BAL, and MPO activity increased significantly by twofold, fourfold, and threefold, respectively. Furthermore, the PO2 dropped from 615.7+/-31.2 to 452.1+/-30.9 mmHg at the end of reperfusion (P<0.001). AACOCF3 treatment maintained the PO2 at a level similar to the vehicle group throughout reperfusion and reduced significantly the alveolar-capillary leakage, edema formation, and neutrophil extravasation.

CONCLUSION

Pharmacological inhibition of the cPLA2 cascade decreases bioactive lipid formation and attenuates IR-induced lung injury.

Lung transplantation. Lung preservation

Over the past decade, improvements in the technique of lung preservation have led to significant reduction in the incidence of ischemia-reperfusion-induced lung injury after lung transplantation. The challenge remains to improve the number of donor lungs available for transplantation. While the number of patients on the waiting list is constantly increasing, only 10% to 30% of donor lungs are currently being used for transplantation. Hence, the development of new strategies to assess, repair, and improve the quality of the lungs could have a tremendous impact on the number of transplants performed. In addition, an improved understanding of the mechanisms involved in lung preservation might help elucidate the potential link between acute lung injury and chronic graft dysfunction. In the future, genetic analysis using novel technologies such as microarray analysis will help researchers determine which genes control the injury seen in the transplantation process. Hopefully, this information will provide new insights into the mechanisms of injury and reveal potential new strategies and targets for therapies to improve lung preservation.

Ischemia-reperfusion-induced lung injury

Ischemia-reperfusion-induced lung injury is characterized by nonspecific alveolar damage, lung edema, and hypoxemia occurring within 72 hours after lung transplantation. The most severe form may lead to primary graft failure and remains a significant cause of morbidity and mortality after lung transplantation. Over the past decade, better understanding of the mechanisms of ischemia-reperfusion injury, improvements in the technique of lung preservation, and the development of a new preservation solution specifically for the lung have been associated with a reduction in the incidence of primary graft failure from approximately 30 to 15% or less. Several strategies have also been introduced into clinical practice for the prevention and treatment of ischemia-reperfusion-induced lung injury with various degrees of success. However, only three randomized, double-blinded, placebo-controlled trials on ischemia-reperfusion-induced lung injury have been reported in the literature. In the future, the development of new agents and their application in prospective clinical trials are to be expected to prevent the occurrence of this potentially devastating complication and to further improve the success of lung transplantation.

Low-dose endobronchial gene transfer to ameliorate lung graft ischemia-reperfusion injury

OBJECTIVE

This study was undertaken to determine whether low-dose endobronchial transfer to the donor of the gene for human interleukin 10 would decrease ischemia-reperfusion injury in lung transplantation.

METHODS

Experiments used male Fischer rats. Donor animals underwent right thoracotomy. A catheter was introduced into the left main bronchus, and vector was instilled. Group I (n = 6) received 2 x 10(7) plaque-forming units of adenovirus encoding human interleukin 10, group II (n = 6) received an adenovirus control encoding beta-galactosidase, and group III (n = 6) received saline solution. After instillation the left main bronchus was clamped for 60 minutes. Lungs were removed 24 hours later and stored in low-potassium dextran glucose solution for 18 hours before left lung transplantation. Graft function was assessed at 24 hours immediately before the animals were killed. Ratio of wet to dry weight and tissue myeloperoxidase activity were measured. Transgenic expression of human interleukin 10 was evaluated by means of enzyme-linked immunosorbent assay and immunohistochemical assay.

RESULTS

Arterial oxygenation was significantly improved in group I relative to groups II and III (257.6 +/- 59.7 mm Hg vs 114.6 +/- 66.9 mm Hg and 118.6 +/- 91.1 mm Hg, P =.008 and P =.007, respectively). Neutrophil sequestration, as measured by myeloperoxidase activity, was also significantly reduced in group I relative to groups II and III (0.141 +/- 0.025 vs 0.304 +/- 0.130 and 0.367 +/- 0.153 Delta optical density units/[min. mg protein], P =.029 and P =.004, respectively). Enzyme-linked immunosorbent assay and immunohistochemical assay demonstrated the expression of human interleukin 10 in transfected lungs only.

CONCLUSIONS

Low-dose endobronchial transfer to the donor of the gene for human interleukin 10 ameliorated ischemia-reperfusion injury in rodent lung transplantation by improving graft oxygenation and reducing neutrophil sequestration. Only 2 x 10(7) plaque-forming units of adenoviral vector were required for functional transgenic expression. Endobronchial gene transfer to lung grafts may be a useful delivery route even at low doses.