Combination of N, N′‐dicyclohexyl‐N‐arachidonic acylurea and tacrolimus prolongs cardiac allograft survival in mice

Current immunosuppressive agents for organ transplantation are not ideal due to their strong toxicity and adverse effects. Hence, there is an urgent need to develop novel immunosuppressive agents. The compound N, N'-dicyclohexyl-N-arachidonic acylurea (DCAAA) is a novel highly unsaturated fatty acid from the traditional Chinese medicinal plant, Radix Isatidis. In this study, we systematically investigated the toxicity, immunosuppressive effect, and mechanisms underlying this activity of DCAAA. The toxicity tests showed that DCAAA treatment did not lead to red blood cell hemolysis and did not affect the liver and kidney functions in mice. Lymphocyte transformation test showed that DCAAA treatment inhibited lymphocyte proliferation in a dose-dependent manner. In vivo cardiac allotransplantation experiment showed that DCAAA treatment could suppress the immune rejection and significantly prolong the survival of cardiac allografts in recipient mice by reducing the proportion of CD4(+) T cells in the spleen and grafts, concentration of interferon-gamma in the supernatant and serum, and infiltration of inflammatory cells in the grafts. Moreover, combination treatment with DCAAA and tacrolimus had a synergistic effect in preventing acute rejection of heart transplants. In vitro molecular biology experiments showed that DCAAA treatment inhibited activation of the T cell receptor-mediated phosphoinostide 3-kinase (PI3K)-protein kinase B (Akt) pathway, thereby arresting cell cycle transition from G1 to the S phase, and inhibiting lymphocyte proliferation. Overall, our study reveals a novel, low-toxicity immunosuppressive agent that has the potential to reduce the toxic side effects of existing immunosuppressive agents when used in combination with them.