目的 以钙调蛋白磷酸酶(CN)为靶酶,从中草药中寻找高效、低毒的免疫抑制剂.方法 以CN为靶点,筛选并分离能够抑制其活性的天然化合物.在细胞和动物水平评价该化合物的免疫抑制效果及毒副作用,并通过荧光猝灭、分子对接、免疫印迹、双荧光素酶报告基因、实时定量PCR等实验探究天然化合物与CN的作用机理及可能的免疫抑制作用机制.结果 槲皮苷在体外和细胞内均能抑制CN的活性,并且能够有效抑制小鼠脾细胞的增殖,缓解小鼠迟发超敏反应.毒理研究结果显示,槲皮苷对实验小鼠无急性毒性,且毒副作用很小.荧光猝灭实验和分子对接分析表明,槲皮苷可能与CN上的两个位点相结合,并通过CN-NFAT通路参与调节免疫反应.结论 通过筛选获得了新型CN抑制剂槲皮苷.槲皮苷具有成为新型低毒免疫抑制剂的潜在可能.“,”Objective This study aimed to search for immunosuppressants with high-efficiency and low-toxicity from Chinese herbal medicine using calcineurin (CN) as the target enzyme.Methods Natural compound which could inhibit the activity of the target enzyme,CN,was screened and one effective compound was identified and isolated.The immunosuppressive effect and toxic side effects of the compound were evaluated at the cellular and animal levels.The underlying immunosuppressive mechanism was explored using fluorescence spectroscopy,molecular docking,Westem blot,dual-luciferase reporter gene,real-time PCR,etc.Results Quercitrin inhibited CN activity both in vitro and in vivo.In addtion,it reduced the proliferation of splenocyte and ameliorated DTH symptoms in mice.Toxicological study showed that quercitfin had no or minimal toxic side effects on experimental animals.Fluorescence spectroscopy and molecular docking analysis showed that quercitrin may bind to two sites on the CN and regulate immune responses through the CN-NFAT pathway.Conclusion We identified a new CN inhibitor,quercitrin,which could be a useful novel immunosuppressant with low toxicity.