Published online Dec 21, 2015. doi: 10.3748/wjg.v21.i47.13225
Peer-review started: August 30, 2015
First decision: September 29, 2015
Revised: October 14, 2015
Accepted: November 13, 2015
Article in press: November 13, 2015
Published online: December 21, 2015
AIM: To investigate the co-incidence of apoptosis, autophagy, and unfolded protein response (UPR) in hepatitis B (HBV) and C (HCV) infected hepatocytes.
METHODS: We performed immunofluorescence confocal microscopy on 10 liver biopsies from HBV and HCV patients and tissue microarrays of HBV positive liver samples. We used specific antibodies for LC3β, cleaved caspase-3, BIP (GRP78), and XBP1 to detect autophagy, apoptosis and UPR, respectively. Anti-HCV NS3 and anti-HBs antibodies were also used to confirm infection. We performed triple blind counting of events to determine the co-incidence of autophagy (LC3β punctuate), apoptosis (cleaved caspase-3), and unfolded protein response (GRP78) with HBV and HCV infection in hepatocytes. All statistical analyses were performed using SPSS software for Windows (Version 16 SPSS Inc, Chicago, IL, United States). P-values < 0.05 were considered statistically significant. Statistical analyses were performed with Mann-Whitney test to compare incidence rates for autophagy, apoptosis, and UPR in HBV- and HCV-infected cells and adjacent non-infected cells.
RESULTS: Our results showed that infection of hepatocytes with either HBV and HCV induces significant increase (P < 0.001) in apoptosis (cleavage of caspase-3), autophagy (LC3β punctate), and UPR (increase in GRP78 expression) in the HCV- and HBV-infected cells, as compared to non-infected cells of the same biopsy sections. Our tissue microarray immunohistochemical expression analysis of LC3β in HBVNeg and HBVPos revealed that majority of HBV-infected hepatocytes display strong positive staining for LC3β. Interestingly, although XBP splicing in HBV-infected cells was significantly higher (P < 0.05), our analyses show a slight increase of XBP splicing was in HCV-infected cells (P > 0.05). Furthermore, our evaluation of patients with HBV and HCV infection based on stage and grade of the liver diseases revealed no correlation between these pathological findings and induction of apoptosis, autophagy, and UPR.
CONCLUSION: The results of this study indicate that HCV and HBV infection activates apoptosis, autophagy and UPR, but slightly differently by each virus. Further studies are warranted to elucidate the interconnections between these pathways in relation to pathology of HCV and HBV in the liver tissue.
Core tip: For the first time, the current study has addressed the co-incidence of apoptosis, autophagy, and unfolded protein response in the liver tissue of hepatitis B and hepatitis C (HBV, and HCV) infected patients. The results showed that all of these events are activated at the same time by HBV and HCV infection in the liver. All of these pathways probably are involved in replication and pathogenesis of HBV and HCV infection; therefore their modulation would probably be beneficial for new therapeutic approaches in these diseases.