Immunosuppressive effect of compound K on islet transplantation in an STZ-induced diabetic mouse model.

Islet transplantation is a therapeutic option for type 1 diabetes, but its long-term success is limited by islet allograft survival. Many factors imperil islet survival, especially the adverse effects and toxicity due to clinical immunosuppressants. Compound (Cpd) K is a synthesized analog of highly unsaturated fatty acids from Isatis tinctoria L. (Cruciferae). Here we investigated the therapeutic effect of Cpd K in diabetic mice and found that it significantly prolonged islet allograft survival with minimal adverse effects after 10 days. Furthermore, it reduced the proportion of CD4(+) and CD8(+) T cells in spleen and lymph nodes, inhibited inflammatory cell infiltration in allografts, suppressed serum interleukin-2 and interferon-γ secretion, and increased transforming growth factor-β and Foxp3 mRNA expression. Surprisingly, Cpd K and rapamycin had a synergistic effect. Cpd K suppressed proliferation of naïve T cells by inducing T-cell anergy and promoting the generation of regulatory T cells. In addition, nuclear factor-κB signaling was also blocked. Taken together, these findings indicate that Cpd K may have a potential immunosuppressant effect on islet transplantation.