Role of Oxidative Stress in the Colonic Complications of Murine Syngeneic Graft-versus-host Disease

Syngeneic graft-versus-host disease (SGVHD) develops in mice following lethal irradiation, reconstitution with syngeneic bone marrow (BM) and treatment with a short course of the immunosuppressive agent cyclosporine A (CsA). The development of SGVHD is a complex process resulting from the cooperative interaction of multiple effector cell populations and inflammatory mediators contributing to the pathogenesis of this inducible disease. Using gene expression analysis, flow cytometric analysis and immunohistochemistry, time course studies revealed increased reactive oxygen and nitrogen species in the tissues of CsA-treated animals compared to bone marrow transplantation (BMT) controls during the induction of SGVHD (d0-21 post-BMT). Studies were undertaken to determine the effect of CsA-induced oxidative stress on the induction of SGVHD. In vivo treatment with the superoxide dismutase mimetic, manganese (III) meso-tetrakis (4-benzoic acid) porphyrin (MnTBAP), during (d0-21 post BMT), or after CsA therapy (>d21 post-BMT), caused a reduction in the development of clinical symptoms of SGVHD (weight loss, diarrhea). Interestingly, treatment with MnTBAP resulted in a significant reduction in the deposition of peroxynitrite in the colons of CsA-MnTBAP-treated versus control CsA-treated SGVHD animals. These studies suggest a role for oxidative stress in the development of mur-