DNA-PKcs Inhibition Extends Allogeneic Skin Graft Survival

Abstract Background Organ transplantation is life-saving and continued investigations into immunological mechanisms that drive organ rejection are needed to improve immunosuppression therapies and prevent graft failure. DNA-dependent protein kinase catalytic subunit, DNA-PKcs, is a critical component of both the cellular and humoral immune responses. In this study, we investigate the contribution of DNA-PKcs to allogeneic skin graft rejection to potentially highlight a novel strategy for inhibiting transplant rejection. Methods Fully MHC mismatched murine allogeneic skin graft studies were performed by transplanting skin from BalbC mice to C57bl6 mice and treating with either vehicle or the DNA-PKcs inhibitor NU7441. Graft rejection, cytokine production, immune cell infiltration, and donor-specific antibody (DSA) formation were analyzed. Results DNA-PKcs inhibition significantly reduced necrosis and extended graft survival compared to controls (mean survival 14 days vs 9 days respectively). Inhibition reduced the production of the cytokines Interleukin (IL)2, IL4, IL6, IL10, TNFα, and IFNγ and the infiltration of CD3+ lymphocytes into grafts. Furthermore, DNA-PKcs inhibition reduced the number of CD19+ B cells and CD19+ CD138+ plasma cells coinciding with a significant reduction in DSAs. At a molecular level, we determined that the immunosuppressive effects of DNA-PKcs inhibition were mediated, in part, via inhibition of NFκB signaling through reduced expression of the p65 subunit. Conclusion Our data confirm that DNA-PKcs contributes to allogeneic graft rejection and highlight a novel immunological function for DNA-PKcs in the regulation of NFκB and concomitant cytokine production.