Background: Bcl-2 has been shown to have antioxidant properties. Early oxidative stress is an important antigen-independent factor that contributes to the development of graft coronary artery disease (GCAD). We hypothesized that adenoviral up-regulation of bcl-2 would decrease early oxidative stress and inhibit GCAD after heart transplantation.
Methods: PVG rat hearts were treated with adenovirus carrying the human bcl-2 gene (AdvBcl-2) or null adenovirus (AdvNull) then transplanted into the abdomens of PVG recipients. After 4 days of reperfusion to allow adenoviral gene expression, grafts were retransplanted into ACI rat recipients and reperfused for 4 or 8 hours or 90 days (cyclosporine A 7.5 mg/kg on postoperative day [POD] 0-9). Production of tumor necrosis factor (TNF)-alpha after 4 hours and oxidized glutathione (GSSG) after 8 hours indicated development of oxidative stress. 90-day allografts were assessed for GCAD by way of computerized morphometry.
Results: Over-expression of bcl-2 at the time of allograft reperfusion was confirmed by Western blotting. Whereas AdvNull-treated hearts demonstrated elevated TNF-alpha levels after 4 hours and increased GSSG after 8 hours of reperfusion, AdvBcl-2-treated hearts were no different from nontransplanted hearts. AdvBcl-2 treatment also resulted in decreased luminal narrowing and intima-to-media ratio at POD 90.
Conclusions: Bcl-2 over-expression interrupts the development of oxidative stress in reperfused rat-heart allografts. Early up-regulation of bcl-2 also decreases GCAD, indicating the importance of early oxidative stress and the role that bcl-2 may play in the long-term function of heart transplants.