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Induction of endoplasmic reticulum-derived oxidative stress by an occult infection related S surface antigen variant

In-Kyung Lee¹, Seoung-Ae Lee¹, Hong Kim¹

¹In-Kyung Lee, Seoung-Ae Lee, Hong Kim, You-Sub Won, Bum-Joon Kim, Department of Microbiology and Immunology, Liver Research Institute, Cancer Research Institute and SNUMRC, College of Medicine, Seoul National University, Seoul 110-799, South Korea.

World Journal of Gastroenterology

|June 17, 2015

Abstract

Aim:

To investigate the mechanism of endoplasmic reticulum (ER) stress induction by an occult infection related hepatitis B virus S surface antigen (HBsAg) variant.

Methods:

We used an HBsAg variant with lower secretion capacity, which was a KD variant from a Korean subject who was occultly infected with the genotype C. We compared the expression profiles of ER stress-related proteins between HuH-7 cells transfected with HBsAg plasmids of a wild-type and a KD variant using Western blot.

Results:

Confocal microscopy indicated that the KD variant had higher levels of co-localization with ER than the wild-type HBsAg. The KD variant up-regulated ER stress-related proteins and induced reactive oxygen species (ROS) compared to the wild-type via an increase in calcium. The KD variant also down-regulated anti-oxidant proteins (HO-1, catalase and SOD) compared to the wild-type, which indicates positive amplification loops of the ER-ROS axis. The KD variant also induced apoptotic cell death via the up-regulation of caspase proteins (caspase 6, 9 and 12). Furthermore, the KD variant induced a higher level of nitric oxide than wild-type HBsAg via the up-regulation of the iNOS protein.

Conclusion:

Our data indicate that occult infection related HBsAg variants can lead to ER-derived oxidative stress and liver cell death in HuH-7 cells.

Keywords:

Apoptotic cell death Colocalization Endoplasmic reticulum oxidative stress Hepatitis B virus KD variant Reactive oxidative species

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