Prominent Steatosis with Hypermetabolism of the Cell Line Permissive for Years of Infection with Hepatitis C Virus

Abstract

Most of experiments for HCV infection have been done using lytic infection systems, in which HCV-infected cells inevitably die. Here, to elucidate metabolic alteration in HCV-infected cells in a more stable condition, we established an HCV-persistently-infected cell line, designated as HPI cells. This cell line has displayed prominent steatosis and supported HCV infection for more than 2 years, which is the longest ever reported. It enabled us to analyze metabolism in the HCV-infected cells integrally combining metabolomics and expression arrays. It revealed that rate-limiting enzymes for biosynthesis of cholesterol and fatty acids were up-regulated with actual increase in cholesterol, desmosterol (cholesterol precursor) and pool of fatty acids. Notably, the pentose phosphate pathway was facilitated with marked up-regulation of glucose-6-phosphate dehydrogenase, a rete-limiting enzyme, with actual increase in NADPH. In its downstream, enzymes for purine synthesis were also up-regulated resulting in increase of purine. Contrary to common cancers, the TCA cycle was preferentially facilitated comparing to glycolysis pathway with a marked increase of most of amino acids. Interestingly, some genes controlled by nuclear factor (erythroid-derived 2)-like 2 (Nrf2), a master regulator of antioxidation and metabolism, were constitutively up-regulated in HPI cells. Knockdown of Nrf2 markedly reduced steatosis and HCV infection, indicating that Nrf2 and its target genes play important roles in metabolic alteration and HCV infection. In conclusion, HPI cell is a bona fide HCV-persistently-infected cell line supporting HCV infection for years. This cell line sustained prominent steatosis in a hypermetabolic status producing various metabolites. Therefore, HPI cell is a potent research tool not only for persistent HCV infection but also for liver metabolism, overcoming drawbacks of the lytic infection systems.

HCV 3a Core Protein Increases Lipid Droplet Cholesteryl Ester Content via a Mechanism Dependent on Sphingolipid Biosynthesis

“…The fact that HCV may interact with the cholesterol synthesis pathway has been suggested previously. HMGCoA reductase, a key enzyme of the cholesterol biosynthesis pathway, was shown to be elevated in HCV patients [39] and cholesterol levels are increased in Huh-7 cells infected with HCV [40,41]. In addition, our observation that statins, well known inhibitors of HMGCoA reductase, impede the increase of LD size caused by HCV 3a core protein, points out the crucial role that CE could play in HCV-induced steatosis as well as in HCV life cycle.…”

Counteraction of HCV-Induced Oxidative Stress Concurs to Establish Chronic Infection in Liver Cell Cultures

“…It is known that GSH de novo synthesis is driven by Nrf2 (nuclear factor erythroid 2-related factor), one of the major cellular defense mechanisms against oxidative stress and a master regulator of different cytoprotective genes including those involved in the antioxidant GSH pathway [61]. It has been recently demonstrated that higher expression of nuclear Nrf2 contributes to persistent HCV infection and that knockdown of Nrf2 suppresses its persistent infection [62]. The authors suggest that the nuclear translocation of p-Nrf2 might play an important role in the expression of the genes which contribute to regulate apoptosis and HCV persistence [25,26,30,62].…”

“…It has been recently demonstrated that higher expression of nuclear Nrf2 contributes to persistent HCV infection and that knockdown of Nrf2 suppresses its persistent infection [62]. The authors suggest that the nuclear translocation of p-Nrf2 might play an important role in the expression of the genes which contribute to regulate apoptosis and HCV persistence [25,26,30,62]. Accordingly, we found higher mRNA levels of GCL and GS enzymes during the recovery period; at the same time, Nrf2 protein content was highly expressed during the chronic phase.…”

Identification of disordered metabolic networks in postpartum dairy cows with left displacement of the abomasum through integrated metabolomics and pathway analyses

“…During gluconeogenesis and ketogenesis, NH 3 obtained from the deamination of amino acids is used to generate carbamoyl phosphate, and this product can be decomposed into citrulline and pyrimidine. Certain amino acids involved in the urea cycle, such as proline, ornithine arginine and citrulline, have been confirmed to participate in the TCA cycle by affecting the formation of fumarate [29,41]. Pyrimidine is used to synthesize uridine, which can be phosphorylated to produce uridine triphosphate.…”