Suppression of hepatitis C virus replication by cyclosporine A

环孢素A在体外以临床可达到的浓度特异性地抑制丙型肝炎病毒的复制。在本研究中，我们研究了环孢菌素A抗丙型肝炎病毒复制的作用机制。利用表达嵌合荧光素酶报告蛋白的丙型肝炎病毒复制子系统，分析环孢菌素A对丙型肝炎病毒复制的影响。环孢菌素A对丙型肝炎病毒复制子的表达有显著影响，而与环孢菌素A有共同作用机制的FK506没有这种作用，提示环孢菌素A的细胞内配体参与了亲环素的作用。短发夹状RNA表达载体瞬时而稳定地下调胞浆亲环素A、B和C的表达，显著抑制了丙型肝炎病毒的复制。环孢素类似物，环孢素D，缺乏免疫抑制活性，但显示亲环素结合，诱导类似的抑制丙型肝炎病毒复制。此外，环孢菌素A处理Huh7细胞诱导了未折叠的蛋白反应，例如细胞Bip/GRP78的表达。用诱导未折叠蛋白反应的thapsigargin和巯基乙醇处理细胞，可抑制丙型肝炎病毒的复制，提示环孢素诱导的未折叠蛋白反应可能有助于抑制丙型肝炎病毒的蛋白加工和复制。环孢菌素A的抗丙型肝炎病毒活性是通过特异性阻断环孢菌素介导的，这些分子可能成为抗丙型肝炎病毒治疗的新靶点。

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.