Hepatitis B virus X protein induces apoptosis and cell cycle deregulation through interfering with DNA repair and checkpoint responses

Chronic Hepatitis B Virus Persistence: Mechanisms and Insights

Chronic hepatitis B (CHB) virus infection can lead to severe liver diseases, including cirrhosis and hepatocellular carcinoma. The chronicity of the hepatitis B virus (HBV) occurs because of the persistence of viral covalently closed circular DNA (cccDNA) within hepatocytes. The cccDNA serves as the template for viral replication and is central to HBV, maintaining a viral reservoir within the host. Despite therapeutic advancements, eliminating cccDNA remains elusive due to its evasion of immune surveillance. This review explores the formation and maintenance of cccDNA, highlighting host factors influencing cccDNA stability and viral replication. It also discusses current treatment strategies, including interferon-based therapies and nucleoside/nucleotide analogs, which aim to suppress viral replication. Emerging therapies such as gene editing and molecular interventions hold promise for targeting cccDNA directly. Currently, research is focused on making medications that target host factors of interest to disrupt or clear the viral reservoir. However, future research should focus on innovative approaches that directly target the cccDNA minichromosome, aiming for sustained viral suppression and potentially a cure for the HBV infection.

The Predictive Role of miRNAs in Hepatitis B Vaccine Response of Metabolic Dysfunction-Associated Steatotic Liver Disease Patients

(1) Background: Metabolic dysfunction-associated steatotic liver disease (MASLD) is the most common chronic liver disease. Although the changes in the expression levels of microRNAs (miRNAs) in hepatitis B virus-related diseases have been evaluated, no study has evaluated the role of miRNAs in HBV vaccine response in MASLD patients. We aimed to determine the miRNA expression profile in MASLD patients according to HBV vaccine response. (2) Methods: Overall, 100 MASLD patients and 100 controls were included, and anti-HBs levels were measured after three doses of HBV vaccine administration. After collecting blood samples, 22 different miRNA expression profiles were analyzed by RT-PCR analysis, and changes in the expression levels of potential miRNAs were further verified in all study groups. (3) Results: The miR-146a expression level considerably increased in MASLD patients compared to the control group. Furthermore, miR-99a and miR-640 expression levels significantly increased in AntiHBs (-) healthy individuals. (4): Conclusions: miR-146a could be used as the diagnostic marker in MASLD patients. Furthermore, the miR-99a and miR-640 expression levels could predict hepatitis B vaccine response. However, validation studies are required to verify the biomarker potential of miRNAs within a more significant number of patients.

New bitongling (NBTL) ameliorates rheumatoid arthritis in rats through inhibiting JAK2/STAT3 signaling pathway

Rheumatoid arthritis (RA) is featured by a variety of physical symptoms and fibroblast-like synoviocytes (FLSs) abnormal proliferation. Increasing evidence has demonstrated that traditional Chinese medicine exerts an important role in RA treatment. New bitongling (NBTL) as one of the traditional Chinese medicine has been reported to be involved in the progression of RA, but the exact mechanism is unclear. In our study, we intended to investigate the effect of NBTL on RA to identify the mechanisms related to JAK2/STAT3 signaling pathway. Extracts of Tripterygium wilfordii (TW), a traditional Chinese herbal medicine, have been widely used for treating RA in China for several decades, so, TW was used as a positive control drug for TBNL. RA rats were constructed by immunization with collagen type II to evaluate the action of NBTL in vivo. Body weight and arthritic index were evaluated. Hematoxylin and Eosin staining was performed to analysis the morphological changes of ankle joints tissue. TUNEL and flow cytometry were performed to examine cell apoptosis, while CCK8 and Ethynyl-2'-deoxyuridine (EdU) were performed to examine cell proliferation. In addition, the markers of inflammation were detected by Western blot, ELISA, and RT-qPCR. Firstly, we find that rats treated with NBTL or TW not only reduced swelling degree and bone destruction, but also repressed IL-1 β and IL-6 levels. In addition, NBTL and TW could increase the weight of rats, and promote the level of IL-10 and IL-4 in vivo. Furthermore, NBTL inhibited inflammation of FLS, induced cell apoptosis and hindered cell proliferation, which was reversed by dipeptidyl peptidase (DPP), a JAK2/STAT3 pathway activator. Taken together, NBTL potentially retarded RA via JAK2/STAT3 pathway, highlighting novel mechanisms associated with RA.

Hepatitis B virus infection is not associated with fatty liver disease: Evidence from a cohort study and functional analysis

Chronic hepatitis B virus (HBV) infection has been reported to be associated with the prevalence of non-alcoholic fatty liver disease (NAFLD). However, the present study demonstrated that the incidence of fatty liver disease in HBV-infected subjects (16/152, 10.5%) was not significantly different from in non-HBV-infected subjects (292/1,714, 17%), following adjustment for age (odds ratio=0.656; 95% confidence interval=0.379–1.134; P=0.131). Hepatitis B protein X (HBx) is considered a key regulator in HBV infection and several studies have confirmed that HBx serves a pivotal role in the process of fatty liver disease. In the present study, it was demonstrated that HBx-expressing cells exhibited increased mitochondrial membrane potential, ATP generation, and endogenous mitochondrial respiration. In addition, higher levels of mitochondrial reactive oxygen species (ROS) were detected in HBx-expressing cells compared with in control cells. Increased ROS production may contribute to increased lipid droplet formation in HBx-expressing cells, whereas the removal of ROS with N-acetylcysteine may decrease the accumulation of lipid droplets in a time-dependent manner. In conclusion, the present findings indicated that HBV, and perhaps more specifically HBx, was not a protective factor against NAFLD. HBx may function as a risk factor for fatty liver disease, based on the findings of the present functional study; however, further studies are required to clarify the effects of HBx on hepatic steatosis.

HBx gene transfection affects the cycle of primary renal tubular epithelial cells through regulating cyclin expression

Hepatitis B virus X protein (HBx) has been previously demonstrated to be associated with the regulation of cell proliferation; however, the exact mechanisms underlying this effect remain unclear. The present study aimed to investigate the regulatory mechanism of HBx on the cycle progression of primary renal tubular epithelial cells. Primary renal tubular epithelial cells of Sprague Dawley (SD) rats were separated and cultured. The morphology of cultured cells was characterized by immunohistochemical analysis and the results demonstrated that primary renal tubular epithelial cells with the expected morphology and distribution were successfully separated and cultured from SD rats. HBx gene pcDNA3.1/myc vector and empty vector were constructed and transfected into cells as HBx and empty groups, respectively. Following transfection, the mRNA and protein levels of HBx, cyclin A, cyclin D1 and cyclin E in cells were determined by reverse transcription‑quantitative polymerase chain reaction and western blot analysis, respectively. The results demonstrated that following HBx gene transfection, the mRNA and protein levels of HBx, cyclin A, cyclin D1 and cyclin E in cells were significantly upregulated, compared with the empty control group (P<0.05). Furthermore, cell apoptosis and the cell cycle were evaluated by Annexin V‑fluorescein isothiocyanate/propidium iodide staining and flow cytometry. HBx gene transfection significantly inhibited the cell apoptosis (P<0.05), promoted cell cycle progression from the G1 to S phase and arrested the cell cycle in the S phase. Therefore, the results of the present study indicated that HBx gene transfection may regulate the apoptosis and cell cycle of primary renal tubular epithelial cells by affecting the expression of cyclins. The results of the present study may improve the understanding of pathogenesis associated with HBV‑associated glomerulonephritis, and may also provide insight and theoretical support for the future design and development of drugs for the treatment of hepatitis B virus.

Downregulation of mPGES-1 Expression via EGR1 Plays an Important Role in Inhibition of Caffeine on PGE2 Synthesis of HBx(+) Hepatocytes

We investigated the mechanism of caffeine in influencing HBx(+) hepatocytes to synthesize PGE₂. The inhibitory effect of caffeine on hepatocyte proliferation increased with increasing caffeine concentrations (200–800 μM) and treatment times (1–7 days), which was first observed at the second test time point (caffeine treatment for 4 days). The inhibition of caffeine on the growth of HL7702-HBx and HepG2-HBx cells was most obvious at 800 μM caffeine and at caffeine treatment for 7 days. The PGE₂ secretion and the expression of mPGES-1 and EGR1 were downregulated, whereas PPARγ expression was upregulated. The mPGES-1 promoter activity of HBx(+) hepatocytes decreased more significantly than that of HBx(−) hepatocytes. Moreover, the expression of EGR1 and PPARγ changed more significantly in HBx(+) hepatocytes cultured for 12 to 24 hours in the presence of 5 mM caffeine. This limited success may be attributed to caffeine releasing the binding of HBx and PPARγ and furthermore affecting the mPGES-1 expression by EGR1 in HBx(+) hepatocytes. The results indicate that caffeine could effectively reduce PGE₂ synthesis in HBx(+) hepatocytes by specifically blocking the PPARγ-EGR1-mPGES-1 pathway, thereby providing a new evidence of molecular biology for the hypothesis that drinking coffee is beneficial to HBV-infected patients.

Increased frequency of micronuclei in the lymphocytes of patients chronically infected with hepatitis B or hepatitis C virus

In this study, we analysed the frequency of micronuclei (MN), nucleoplasmic bridges (NPBs) and nuclear buds (NBUDs) and evaluated mutagen-induced sensitivity in the lymphocytes of patients chronically infected with hepatitis B virus (HBV) or hepatitis C virus (HCV). In total, 49 patients with chronic viral hepatitis (28 HBV-infected and 21 HCV-infected patients) and 33 healthy, non-infected blood donor controls were investigated. The frequencies (‰) of MN, NPBs and NBUDs in the controls were 4.41 ± 2.15, 1.15 ± 0.97 and 2.98 ± 1.31, respectively. The frequencies of MN and NPBs were significantly increased (p < 0.0001) in the patient group (7.01 ± 3.23 and 2.76 ± 2.08, respectively) compared with the control group. When considered separately, the HBV-infected patients (7.18 ± 3.57) and HCV-infected patients (3.27 ± 2.40) each had greater numbers of MN than did the controls (p < 0.0001). The HCV-infected patients displayed high numbers of NPBs (2.09 ± 1.33) and NBUDs (4.38 ± 3.28), but only the HBV-infected patients exhibited a significant difference (NPBs = 3.27 ± 2.40, p < 0.0001 and NBUDs = 4.71 ± 2.79, p = 0.03) in comparison with the controls. Similar results were obtained for males, but not for females, when all patients or the HBV-infected group was compared with the controls. The lymphocytes of the infected patients did not exhibit sensitivity to mutagen in comparison with the lymphocytes of the controls (p = 0.06). These results showed that the lymphocytes of patients who were chronically infected with HBV or HCV presented greater chromosomal instability.

Proteomic profiling of the human cytomegalovirus UL35 gene products reveals a role for UL35 in the DNA repair response

Human cytomegalovirus infections involve the extensive modification of host cell pathways, including cell cycle control, the regulation of the DNA damage response, and averting promyelocytic leukemia (PML)-mediated antiviral responses. The UL35 gene from human cytomegalovirus is important for viral gene expression and efficient replication and encodes two proteins, UL35 and UL35a, whose mechanism of action is not well understood. Here, affinity purification coupled with mass spectrometry was used to identify previously unknown human cellular targets of UL35 and UL35a. We demonstrate that both viral proteins interact with the ubiquitin-specific protease USP7, and that UL35 expression can alter USP7 subcellular localization. In addition, UL35 (but not UL35a) was found to associate with three components of the Cul4(DCAF1) E3 ubiquitin ligase complex (DCAF1, DDB1, and DDA1) previously shown to be targeted by the HIV-1 Vpr protein. The coimmunoprecipitation and immunofluorescence microscopy of DCAF1 mutants revealed that the C-terminal region of DCAF1 is required for association with UL35 and mediates the dramatic relocalization of DCAF1 to UL35 nuclear bodies, which also contain conjugated ubiquitin. As previously reported for the Vpr-DCAF1 interaction, UL35 (but not UL35a) expression resulted in the accumulation of cells in the G(2) phase of the cell cycle, which is typical of a DNA damage response, and activated the G(2) checkpoint in a DCAF1-dependent manner. In addition, UL35 (but not UL35a) induced γ-H2AX and 53BP1 foci, indicating the activation of DNA damage and repair responses. Therefore, the identified interactions suggest that UL35 can contribute to viral replication through the manipulation of host responses.

The hepatitis B virus X protein modulates hepatocyte proliferation pathways to stimulate viral replication

Worldwide, there are over 350 million people who are chronically infected with the human hepatitis B virus (HBV); chronic HBV infections are associated with the development of hepatocellular carcinoma (HCC). The results of various studies suggest that the HBV X protein (HBx) has a role in the development of HBV-associated HCC. HBx can regulate numerous cellular signal transduction pathways, including those that modulate cell proliferation. Many previous studies that analyzed the impact of HBx on cell proliferation pathways were conducted using established or immortalized cell lines, and when HBx was expressed in the absence of HBV replication, and the precise effect of HBx on these pathways has often differed depending on experimental conditions. We have studied the effect of HBx on cell proliferation in cultured primary rat hepatocytes, a biologically relevant system. We demonstrate that HBx, both by itself and in the context of HBV replication, affected the levels and activities of various cell cycle-regulatory proteins to induce normally quiescent hepatocytes to enter the G(1) phase of the cell cycle but not to proceed to S phase. We linked HBx regulation of cell proliferation to cytosolic calcium signaling and HBx stimulation of HBV replication. Cumulatively, our studies suggest that HBx induces normally quiescent hepatocytes to enter the G(1) phase of the cell cycle and that this calcium-dependent HBx activity is required for HBV replication. These studies identify an essential function of HBx during HBV replication and a mechanism that may connect HBV infections to the development of HCC.