Overexpression of human Bcl-2 in syngeneic rat donor lungs preserves posttransplant function and reduces intragraft caspase activity and interleukin-1β production

Background. A significant cause of primary graft failure in lung transplantation is ischemia-reperfusion (I/R). I/R injury generates proinflammatory cytokines, such as interleukin (IL)-1β, and activates the caspase-mediated pathways of alveolar epithelial apoptosis. The authors investigated whether gene transfer of the human antiapoptotic protein Bcl-2 by means of intratracheal adenoviral administration would preserve posttransplant lung function and reduce intragraft activated caspase activity and IL-1β production in syngeneic rat donor lung grafts. Methods. First, 1.0 × 10⁹ plaque-forming units of AdvBcl-2 in phosphate-buffered saline (PBS), AdvNull empty vector in PBS, or PBS alone was administered intratracheally to ACI (RT1^a) rats. Then, the left lungs were procured after 24 hr of in vivo incubation and orthotopically transplanted after 1 hr of cold ischemia into syngeneic recipients. After 2 hr of reperfusion, peak inspiratory pressures (PIP) and donor pulmonary vein PaO₂ was measured in all grafts; grafts were then excised and protein extracts were analyzed by enzyme-linked immunosorbent assay (ELISA) and activated caspase-3 and caspase-9 assays. Results. Human Bcl-2 transgene overexpression in donor lung grafts was demonstrated by ELISA of tissue homogenates. Pretreatment of donor lungs with AdvBcl-2 resulted in reduced PIP and increased lung isograft pulmonary vein PaO₂ compared with AdvNull or PBS-alone treated controls. In addition, AdvBcl-2 pretreatment led to diminished cytochrome c release into cytosolic extracts and reduced intragraft IL-1β production and inhibited intragraft caspase-3 and caspase-9 activity. Conclusions. Adenoviral overexpression of human Bcl-2 protein limits I/R injury in rat lung isografts. These data suggest that the use of Bcl-2 gene transfer to human lung donors may reduce the oxidative stress of pulmonary grafts after transplantation in clinical lung transplantation.