Viral, T Cell, and Cytokine Determinants of Hepatic Stellate Cell Activation

在美国和欧洲，慢性丙型肝炎病毒（HCV）感染已成为肝脏相关发病率和死亡率的主要原因。慢性丙型肝炎进展为晚期肝纤维化和最终肝硬化是肝衰竭和原发性肝癌发展的关键预测因素。然而，只有20-30%的患者在平均20年的感染后才会发展成肝硬化，而其他人则进展缓慢或根本没有进展。肝星状细胞和肌成纤维细胞是肝纤维化的效应细胞，在进展过程中负责细胞外基质成分的过度沉积，它们似乎对纤维化反应一致。 刺激。相反，HCV感染的肝细胞和宿主对HCV的免疫应答似乎是决定肝星状细胞和肌成纤维细胞（统称为肝星状细胞）活化状态的主要因素，最有可能是通过释放促纤维化因子。此外，病毒基因型和变体（准种）可能间接（通过与免疫系统的相互作用）或直接（通过感染肝细胞内的改变）刺激肝星状细胞活化，从而导致纤维化和进展。此外，在HCV肝病中，如肝脂肪变性和氧化应激增强等已确立的进展辅助因子的机制作用在很大程度上尚未探索。为了模拟肝星状细胞的细胞外环境，我们将使用来自一系列HCV复制肝细胞系和来自来自缓慢和快速进展患者的CD 4+、CD 8+和NK T细胞亚群的条件培养基来检验以下假设：具有复制型HCV的肝细胞系释放驱动肝星状细胞活化的促纤维化因子，和 一个主要的促纤维化因子是TGF β 1。2.不同的HCV基因型（1b型对2b型）和某些准种（定义为重要序列区域，即核心、NS 4 B和NS 5A中的突变）在复制子细胞或核心、NS 4 B/NS 5A转染的肝细胞中引发不同水平的促纤维化因子。3. HCV诱导的肝细胞脂质代谢和氧化应激的改变导致TGF-β 1和其他促纤维化因子的释放增强。4.慢性HCV感染中关键炎性细胞（CD 4+、CD 8+和NK T细胞）释放的细胞因子谱在快速与缓慢进展的患者中更具纤维化性，并鉴定这些T细胞亚群释放的关键纤维化因子。 预计更好地了解HCV诱导的肝脏纤维化反应及其与其他外在和内在促纤维化触发因素和途径的合作或相互作用将有助于更好地了解HCV肝病进展和针对慢性丙型肝炎的新型抗纤维化治疗。

Chronic hepatitis C virus (HCV) infection has become a major cause of liver related morbidity and mortality in the USA and Europe. Progression of chronic hepatitis C to advanced liver fibrosis and finally cirrhosis is the key predictor of liver failure and the development of primary liver cancer. However, cirrhosis develops in only 20-30% of patients after a mean of 20 years of infection, while others progress more slowly or not at all. Hepatic stellate cells and myofibroblasts, the effector cells of liver fibrosis that are responsible for excess deposition of extracellular matrix components during progression, seem to respond uniformly to fibrogenic stimuli. On the contrary, HCV infected hepatocytes and the host's immune response to HCV appear to be major factors that determine the activation state of hepatic stellate cells and myofibroblasts (collectively termed hepatic stellate cells), most likely via release of profibrogenic factors. In addition, viral genotype and variants (quasispecies) may indirectly (via interaction with the immune system) or directly (via alterations within the infected hepatocytes) stimulate hepatic stellate cell activation and thus fibrogenesis and progression. Furthermore, the mechanistic role of well established cofactors of progression in HCV liver disease, such as hepatic steatosis and enhanced oxidative stress is largely unexplored. To mimic the extracellular environment of hepatic stellate cells, we will use conditioned media from a spectrum of HCV replicating hepatocytic cell lines and from CD4+, CD8+ and NK T cell subsets derived from slow and rapid progressor patients to test the hypothesis that 1. hepatocytic cell lines with replicating HCV release profibrogenic factors that drive activation of hepatic stellate cells, and that a major profibrogenic factor thus released is TGFbeta1. 2. different HCV genotypes (type 1b vs. 2b) and certain quasispecies, defined as mutations in sequence regions of importance, namely in Core, NS4B and NS5A, elicit different levels of profibrogenic factors in the replicon cells or in Core, NS4B/NS5A transfected hepatocytic cells. 3. HCV induced hepatocyte alterations in lipid metabolism and oxidative stress lead to enhanced release of TGF-beta1 and other profibrogenic factors. 4. the cytokine profile released by key inflammatory cells in chronic HCV infection (CD4+, CD8+ and NK T cells) is more fibrogenic in patients with rapid vs. slow progression, and identify the key fibrogenic factors released by these T cell subsets. It is expected that a better understanding of the HCV-induced fibrogenic response in the liver and its cooperation or interaction with other extrinsic and intrinsic profibrogenic triggers and pathways will lead to a better understanding of HCV liver disease progression and to novel antifibrotic treatments tailored to chronic hepatitis C.