Suppression of hepatitis C virus replication by cyclosporine A

在临床可达到的浓度下，环孢素A在体外特异性抑制丙型肝炎病毒复制。在这项研究中，我们研究了环孢菌素A对HCV复制的作用机制。使用表达嵌合荧光素酶报告蛋白的HCV复制子系统分析环孢菌素A对HCV复制的体外作用。环孢菌素A对HCV复制子表达的显著影响，以及与环孢菌素A具有相同作用机制的FK 506没有这种影响，表明涉及环孢菌素A的细胞内配体亲环素。瞬时和稳定敲低细胞质亲环素A，B和C的表达的shRNA表达载体抑制HCV复制显着。环孢菌素类似物，环孢菌素D，缺乏免疫抑制活性，但表现出亲环素结合，诱导了类似的抑制HCV复制。此外，环孢菌素A处理Huh 7细胞诱导未折叠的蛋白质反应，例如细胞BiP/GRP 78的表达。用毒胡萝卜素和巯基乙醇处理细胞，诱导未折叠蛋白反应，抑制HCV复制，表明环孢素诱导的未折叠蛋白反应可能有助于抑制HCV蛋白加工和复制。环孢菌素A的抗HCV活性是通过亲环素的特异性阻断介导的，并且这些分子可能构成抗HCV治疗剂的新靶点。

Cyclosporin A specifically suppresses hepatitis C virus replication in vitro at clinically achievable concentrations. In this study, we investigated the mechanisms of action of cyclosporin A against HCV replication. The in-vitro effects of cyclosporin A on HCV replication were analyzed using HCV replicon system that expresses chimeric luciferase reporter protein. The significant effects of cyclosporin A on expression of an HCV replicon, and the absence of such effects of FK506 which shares mechanisms of action with cyclosporin A, suggested the involvement of intracellular ligands of cyclosporin A, the cyclophilins. Transient and stable knock-down of the expression of cytoplasmic cyclophilins A, B and C by shRNA-expressing vectors suppressed HCV replication significantly. A cyclosporin analogue, cyclosporin D, which lacks immunosuppressive activity but exhibits cyclophilin binding, induced a similar suppression of HCV replication. Furthermore, cyclosporin A treatment of Huh7 cells induced an unfolded protein response exemplified by expression of cellular BiP/GRP78. Treatment of cells with thapsigargin and mercaptoethanol, which induce the unfolded protein responses, suppressed HCV replication, suggesting that the cyclosporin-induced unfolded protein responses mignt contribute to the suppression of HCV protein processing and replication. The anti-HCV activity of cyclosporin A is mediated through a specific blockade of cyclophilins and these molecules may constitute novel targets for anti-HCV therapeutics.