DataSheet_1_The Impact of Mevastatin on HCV Replication and Autophagy of Non-Transformed HCV Replicon Hepatocytes Is Influenced by the Extracellular Lipid Uptake.pdf

Statins efficiently inhibit cholesterol synthesis by blocking 3-hydroxy-3-methylglutaryl (HMG)-CoA reductase in the mevalonate pathway. However, the effect of statins on intracellular cholesterol is partially counterbalanced by a consequent increased uptake of extracellular lipid sources. Hepatitis C virus (HCV) infection induces intracellular accumulation of cholesterol by promoting both new synthesis and uptake of circulating lipoproteins, which is required for HCV replication and release. Hepatocytes respond to the increase in intracellular cholesterol levels by inducing lipophagy, a selective type of autophagy mediating the degradation of lipid deposits within lysosomes. In a cellular system of HCV replication based on HuH7 hepatoma cells, statin treatment was shown to be sufficient to decrease intracellular cholesterol, which is accompanied by reduced HCV replication and decreased lipophagy, and has no apparent impact on endocytosis-mediated cholesterol uptake. To understand whether these results were influenced by an altered response of cholesterol influx in hepatoma cells, we analyzed the effect of statins in non-transformed murine hepatocytes (MMHD3) harboring subgenomic HCV replicons. Notably, we found that total amount of cholesterol is increased in MMHD3 cells upon mevastatin treatment, which is associated with increased HCV replication and lipophagy. Conversely, mevastatin is able to reduce cholesterol amounts only when cells are grown in the presence of delipidated serum to prevent extracellular lipid uptake. Under this condition, HCV replication is reduced and autophagy flux is severely impaired. Altogether, these results indicate that both de novo synthesis and extracellular uptake have to be targeted in non-transformed hepatocytes in order to decrease intracellular cholesterol levels and consequently limit HCV replication.

他汀类药物（Statins）通过阻断甲羟戊酸途径中的3-羟基-3-甲基戊二酰辅酶A（HMG-CoA）还原酶，高效抑制胆固醇合成。然而，他汀类药物对细胞内胆固醇的作用会被随之增强的胞外脂质摄取部分抵消。丙型肝炎病毒（HCV）感染可通过促进胆固醇的从头合成与循环脂蛋白摄取，诱导细胞内胆固醇蓄积，这一过程是HCV复制与释放所必需的。肝细胞可通过激活脂噬（lipophagy）——一种介导溶酶体内脂质沉积物降解的选择性自噬——来应对细胞内胆固醇水平的升高。在基于HuH7肝癌细胞的HCV复制细胞模型中，已有研究证实他汀类药物处理可有效降低细胞内胆固醇水平，同时伴随HCV复制水平降低与脂噬水平下降，且对胞吞介导的胆固醇摄取无明显影响。为探明上述结果是否受肝癌细胞胆固醇内流应答改变的影响，我们在携带亚基因组HCV复制子的非转化型小鼠肝细胞（MMHD3）中分析了他汀类药物的作用。值得注意的是，我们发现经美伐他汀处理后的MMHD3细胞内总胆固醇含量升高，这与HCV复制水平及脂噬水平增强相关。与之相反，仅当细胞在去脂血清中培养以阻断胞外脂质摄取时，美伐他汀才能降低细胞内胆固醇含量。在此条件下，HCV复制水平被抑制，且自噬流严重受损。综上，上述结果表明，若要降低非转化型肝细胞的细胞内胆固醇水平并进而限制HCV复制，需同时靶向胆固醇的从头合成与胞外摄取途径。