Abstract
ObjectiveHepatitis B virus X protein (HBx) is a pivotal factor for HBV-induced hepatitis. Herein, we sought to investigate HBx-mediated NLR pyrin domain containing 3 (NLRP3) inflammasome activation and pyroptosis under oxidative stress.MethodsThe effect of HBx on the NLRP3 inflammasome was analyzed by enzyme-linked immunosorbent assays, quantitative reverse transcription-polymerase chain reaction, western blotting, and immunofluorescence in hepatic HL7702 cells. Pyroptosis was evaluated by western blotting, lactate dehydrogenase release, propidium iodide staining, and transmission electron microscopy. NLRP3 expression in the inflammasome from liver tissues was assessed by immunohistochemistry.ResultsIn hydrogen peroxide (H2O2)-stimulated HL7702 cells, HBx triggered the release of pro-inflammatory mediators apoptosis-associated speck-like protein containing a CARD (ASC), interleukin (IL)-1β, IL-18, and high-mobility group box 1 (HMGB1); activated NLRP3; and initiated pro-inflammatory cell death (pyroptosis). HBx localized to the mitochondria, where it induced mitochondrial damage and production of mitochondrial reactive oxygen species (mitoROS). Treatment of HL7702 cells with a mitoROS scavenger attenuated HBx-induced NLRP3 activation and pyroptosis. Expression levels of NLRP3, ASC, and IL-1β in liver tissues from patients were positively correlated with HBV DNA concentration.ConclusionsThe NLRP3 inflammasome was activated by elevated mitoROS levels and mediated HBx-induced liver inflammation and hepatocellular pyroptosis under H2O2-stress conditions.
Highlights
Hepatitis B virus (HBV) is an oncogenic virus presently responsible for approximately 350 million cases of chronic infections worldwide [1]
The results showed that pHBx, pHBx-Hepatitis B virus X protein (HBx), and pHBV successfully expressed their corresponding proteins; while, no expression was detected from the control plasmids (Fig. 1b, c)
Considering that early HBV infection is primarily characterized by chronic liver inflammation, rather than employ a model of liver cancer development, we instead chose to use the standard liver cell line HL7702 to explore activation of intrahepatic cytokine networks induced by HBx
Summary
Hepatitis B virus (HBV) is an oncogenic virus presently responsible for approximately 350 million cases of chronic infections worldwide [1]. HBV’s persistence is reportedly associated with an increased risk of cirrhosis and hepatocellular carcinoma (HCC) [2]. The hepatitis viral X protein (HBx), encoded by the HBV X gene, is implicated in HBV-related hepatitis, cirrhosis, and the initiation of HCC [3, 4]. HBx localizes in the cytoplasm, nucleus, and mitochondria, where it affects signal transduction, transcription, and mitochondrial function [5, 6]. NLR pyrin domain containing 3 (NLRP3) is a cytoplasmic pattern recognition receptor that is widely distributed in hepatic parenchymal cells and non-substantial cells [7,8,9]. The NLRP3 inflammasome, which consists of NLRP3, inflammasome adaptor protein apoptosis-associated specklike protein containing CARD (ASC), and pro-caspase-1,
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