A Plasmin Inhibitor Prevents Lethal Acute Graft-Versus-Host Disease in Mice

Abstract 1897

Proinflammatory cytokines released upon cell damage can cause excessive tissue destruction in acute graft-versus-host disease (GVHD). Certain key cytokines for GVHD like TNF-α and Fas-ligand, are secreted by ectodomain shedding from matrix metalloproteinases (MMPs). Many MMP inhibitors have been developed and used over the last three or four decades, but its widespread use is hampered by severe side effects. We reported that the fibrinolytic system, above all plasmin formation promotes the activation of several MMPs. Therefore we hypothesized that plasmin inhibition might be a novel means to control acute GVHD in part by suppressing MMP and inflammatory cytokine secretion. We found that the fibrinolytic system is activated during the development of acute GVHD in mice and in humans. Here, we examined a novel plasmin inhibitor (YO-2) that inhibits MMP activation and inflammatory cytokines release for lethal acute GVHD model in mice. Administration of YO-2 into (BALB/c × C57BL/6) F1 that received C57BL/6 spleen cells showed markedly reduced mortality and weight loss in association with minimal signs of GVHD pathology in the liver, intestine, and hematopoietic tissues. Furthermore, our results suggest that administaration of YO-2 blocked the processing of inflammatory cytokines through MMP inhibition in vitro and in vivo. These data have major implications for transplantation medicine, as pharmacological inhibition of plasmin does not require the need for intensive immunosuppression. Our results suggest that YO-2 could be a novel molecular therapeutic agent for GVHD.