Mechanisms of hepatic fibrogenesis induced by hepatitis C virus (HCV), one of the leading causes of liver fibrosis, are not fully understood. We studied transcriptional up‐regulation of transforming growth factor β (TGF‐β), especially TGF‐β2, which is mediated by activation of liver‐enriched transcription factor cAMP‐responsive element‐binding protein, hepatocyte specific (CREBH) triggered by HCV infection and its functional significance for induction of profibrogenic phenotypes by interaction of HCV‐infected cells with hepatic stellate cells (HSCs). Compared to TGF‐β1, expression of TGF‐β2 mRNA was induced faster and to a higher level upon HCV infection. Serum TGF‐β2 levels in hepatitis C patients were higher compared to those in healthy individuals and were positively correlated with hepatic fibrosis stages F0‐F2. TGF‐β2 promoter activity was decreased and increased, respectively, by silencing and overexpression of CREBH. CREBH recognition sites were identified in the TGF‐β2 promoter. CREBH binding to the promoter and its increase in cells expressing HCV Core‐NS2 were shown by gel mobility shift and chromatin immunoprecipitation, respectively. The active form of CREBH was detectable in HCV‐infected chimeric mice with human livers and cells expressing HCV proteins. Involvement of CREBH in HCV‐induced fibrogenic response was further demonstrated in the CREBH null‐mutant mouse model. Fibrogenic phenotypes were assessed using co‐cultures of HCV‐infected cells and HSCs. Expressions of fibrogenic factors and TGF‐β1 increasing in the co‐cultures was prevented by TGF‐β2‐ or CREBH silencing. Conclusion: CREBH was identified as a key positive regulator of TGF‐β2 transcription in HCV‐infected cells. TGF‐β2 released from infected cells potentially contributes to cross‐induction of TGF‐β in an autocrine manner through its own signaling pathway, leading to an increase in fibrogenic responses in adjacent HSCs. (Hepatology 2017;66:1430–1443).

Hepatitis C virus (HCV) has been recognized as a major cause of chronic liver diseases worldwide. It has been suggested that HCV infects not only hepatocytes but also mononuclear lymphocytes including B cells that express the CD81 molecule, a putative HCV receptor. HCV infection of B cells is the likely cause of B-cell dysregulation disorders such as mixed cryoglobulinemia, rheumatoid factor production, and B-cell lymphoproliferative disorders that may evolve into non-Hodgkin's lymphoma (NHL). Epidemiological data indicate an association between HCV chronic infection and the occurrence of B-cell NHL, suggesting that chronic HCV infection is associated at least in part with B-cell lymphomagenesis. In this paper, we aim to provide an overview of recent literature, including our own, to elucidate a possible role of HCV chronic infection in B-cell lymphomagenesis.

Hepatic steatosis, characterized by lipid accumulation in hepatocytes, is a key diagnostic feature in patients with chronic hepatitis C virus (HCV) infection. This study aimed to clarify the involvement of phospholipid metabolic pathways in the pathogenesis of HCV-induced steatosis. The expression and distribution of lipid species in the livers of human liver chimeric mice were analyzed using imaging mass spectrometry. Triglyceride accumulation and lipid droplet formation were studied in phospholipase A2 group 4C (PLA2G4C) knockout or overexpressing cells. Imaging mass spectrometry of the infected mouse model revealed increased lysophosphatidylcholine levels and decreased phosphatidylcholine levels in HCV-positive regions of the liver. Among the transcripts associated with phosphatidylcholine biosynthesis, upregulation of PLA2G4C mRNA was most pronounced following HCV infection. Activation of the transcription factor NF-κB and upregulation of c-Myc were important for activation of PLA2G4C transcription by HCV infection and expression of the viral proteins Core-NS2. The amount and size of lipid droplets were reduced in PLA2G4C-knockout cells. Inhibition of NF-κB or c-Myc activity suppressed lipid droplet formation in HCV-infected cells. HCV infection promoted the stabilization of lipid droplets, but this stability was reduced in PLA2G4C-knockout cells. Overexpression of PLA2G4C decreased the levels of phosphatidylcholine species in the lipid droplet fraction and led to lower levels of key factors involved in lipolysis (breakdown of triglycerides into glycerol and free fatty acids), such as ATGL, PLIN1 and ABHD5 on the lipid droplets. HCV infection markedly increases PLA2G4C expression. This may alter the phospholipid composition of the lipid droplet membrane, leading to stabilization and enlargement of the droplets. The involvement of phospholipid metabolism pathways in the pathogenesis of hepatitis C virus (HCV)-related liver diseases remains unclear. We found that PLA2G4C expression is upregulated through NF-κB and c-Myc activation upon HCV infection, and this upregulation is associated with a decrease in phosphatidylcholine species. The increased expression of PLA2G4C resulted in changes in the phospholipid composition of lipid droplets, led to the dissociation of lipolysis-related factors from the lipid droplet surface and the accumulation of lipid content within the droplets. These findings suggest that the disruption of the phospholipid metabolism pathway caused by HCV infection may contribute to the development of HCV-associated fatty liver. It would be interesting to determine whether alcohol- and/or metabolic dysfunction-associated steatohepatitis are also associated with increased PLA2 activity, altered phospholipid composition and decreased levels of ATGL and its cofactors in lipid droplet membranes.

New antiviral agents are needed for the treatment of hepatitis B virus (HBV) infection because currently available drugs do not completely eradicate chronic HBV in patients. Phosphorylation dynamics of the HBV core protein (HBc) regulate several processes in the HBV life cycle, including nucleocapsid formation, cell trafficking, and virus uncoating after entry. In this study, the SRPK inhibitors SPHINX31, SRPIN340, and SRPKIN-1 showed concentration-dependent anti-HBV activity. Detailed analysis of the effects of SRPKIN-1, which exhibited the strongest inhibitory activity, on the HBV replication process showed that it inhibits the formation of infectious particles by inhibiting pregenomic RNA packaging into capsids and nucleocapsid envelopment. Mass spectrometry analysis combined with cell-free translation system experiments revealed that hyperphosphorylation of the C-terminal domain of HBc is inhibited by SRPKIN-1. Further, SRPKIN-1 exhibited concentration-dependent inhibition of HBV infection not only in HepG2-hNTCP-C4 cells but also in fresh human hepatocytes (PXB cells) and in the single-round infection system. Treatment with SRPKIN-1 at the time of infection reduced the nuclease sensitivity of HBV DNA in the nuclear fraction. These results suggest that SRPKIN-1 has the potential to not only inhibit the HBV particle formation process but also impair the early stages of viral infection.