Constitutive expression of the anti-apoptotic Bcl-2 family member A1 in murine endothelial cells leads to transplant tolerance

Anti-apoptotic genes including those of the Bcl-2 family have been shown to have dual functionality in as much as they inhibit cell death but also regulate inflammation. Several anti-apoptotic molecules have been associated with endothelial cell (EC) survival following transplantation however their exact role has yet to be elucidated in respect to controlling inflammation. In this study we created mice expressing murine A1 (Bfl-1), a Bcl-2 family member, under the control of the human ICAM-2 promoter. Constitutive expression of A1 in murine vascular ECs conferred protection from cell death induced by the pro-inflammatory cytokine TNF-α. Importantly, in a mouse model of heart allograft transplantation, expression of A1 in vascular endothelium increased survival in the absence of CD8+ T cells. Better graft outcome in mice receiving an A1 transgenic heart correlated with a reduced immune infiltration, which maybe related to increased EC survival and reduced expression of adhesion molecules on ECs. In conclusion, constitutive expression of the anti-apoptotic molecule Bfl1 (A1) in murine vascular ECs leads to prolonged allograft survival due to modifying inflammation.