Hepatitis B virus X protein modulates apoptosis in human renal proximal tubular epithelial cells by activating the JAK2/STAT3 signaling pathway

HBx promotes glomerular podocyte-induced immune cell responses

BACKGROUND

Podocytes, as intrinsic renal cells, can also express MHC-II and costimulatory molecules under inflammatory conditions, suggesting that they may act as antigen-presenting cells (APCs) to activate immune cell responses and then lead to immune-mediated renal injury. They are already recognized as main targets in the pathogenic mechanism of hepatitis B virus (HBV)-associated glomerulonephritis (HBV-GN). Previous studies also have indicated that inflammatory cells infiltration and immune-mediated tissue injury are evident in the kidney samples of patients with HBV-GN. However, the role of podocytes immune disorder in the pathogenic mechanism of HBV-GN remains unclear.

METHODS

Renal function and inflammatory cells infiltration were measured in HBV transgenic (HBV-Tg) mice. In vitro, podocytes/CD4+ T cells or macrophages co-culture system was established. Then, the expression of HBx, CD4, and CD68 was determined by immunohistochemistry, while the expression of MHC-II, CD40, and CD40L was determined by immunofluorescence. Co-stimulatory molecules expression was examined by flow cytometry. The levels of inflammatory factors were detected by ELISA.

RESULTS

In vivo, renal function was obviously impaired in HBV-Tg mice. HBx was significantly upregulated and immune cells infiltrated in the glomerulus of HBV-Tg mice. Expression of MHC-II and costimulatory molecule CD40 increased in the podocytes of HBV-Tg mice; CD4+ T cells exhibited increased CD40L expression in glomerulus. In vitro, CD40 expression was markedly elevated in HBx-podocytes. In co-culture systems, HBx-podocytes stimulated CD4+ T cells activation and caused the imbalance between IFN-γ and IL-4. HBx-podocytes also enhanced the adhesion ability of macrophages and induced the release of proinflammatory mediators.

CONCLUSION

Taken together, these podocyte-related immune disorder may be involved in the pathogenic mechanism of HBV-GN.

Hepatitis B virus-targeting sodium taurocholate cotransporting polypeptide mediates HBV infection and damage in human renal podocytes

Hepatitis B virus (HBV) may directly infect human podocytes (HPCs). However, the mechanism of direct infection is unclear. We found that HPCs express sodium taurocholate cotransporting polypeptide (NTCP), a specific receptor for HBV entry into hepatocytes. Thus, we investigated whether NTCP mediates HBV infection and damage in HPCs and further clarified the specific mechanism. We constructed shRNA-NTCP1,2, shRNA-NC, WT-NTCP, and MUT-NTCP and transfected them into HPCs. HPCs were infected with HBV, and HBV infection markers were detected by enzyme-linked immunosorbent assay (ELISA) and real-time quantitative PCR (RT-qPCR). The functional changes in HPCs were detected by Transwell migration and scratch assays, apoptosis was evaluated by flow cytometry (FCM), and podocytoskeletal proteins (nephrin, CD2AP, and synaptopodin) were determined by western blotting (WB). Compared with the control HPCs, HPCs infected with HBV showed increased levels of HBV infection markers and apoptosis along with decreased podocytoskeletal protein expressions, cell vitality, proliferation, and migration. Compared with the HPCs infected with HBV, the HPCs transfected with HBV + shRNA-NTCP, and HBV + MUT-NTCP showed decreased levels of HBV infection markers and apoptosis along with increased podocytoskeletal protein expressions, cell vitality, proliferation, and migration; the opposite effects were observed in the HPCs transfected with HBV + WT-NTCP. Overall, the changes to NTCP affected the susceptibility of HPCs to HBV and modulated HPC damage and repair. NTCP can mediate direct HBV infection and damage human podocytes, and the NTCP 157-165 locus is the main site of HBV entry. The findings provide a new target and theoretical basis for HBV-associated glomerulonephritis.

IMPORTANCE

This study identified for the first time that sodium taurocholate cotransporting polypeptide (NTCP) can mediate HBV direct infection and damage to human podocytes, and the NTCP157-165 locus is the main HBV entry site. The findings provide theoretical support for the pathogenesis of direct infection of HBV with kidney tissue. The findings provide a new target and theoretical basis for the treatment of HBV-related glomerulonephritis (HBV-GN). Blocking NTCP is a new target for the treatment of HBV-GN. We found that tacrolimus, a calcineurin inhibitor that blocks NTCP, can effectively treat HBV-GN. This study also provides a theoretical basis for the effective and safe treatment of immunosuppressant tacrolimus for HBV-GN.

Exosomal miR-223-3p from bone marrow mesenchymal stem cells targets HDAC2 to downregulate STAT3 phosphorylation to alleviate HBx-induced ferroptosis in podocytes

Background: Hepatitis B virus associated-glomerulonephritis (HBV-GN) is one of the major secondary renal diseases in China, and microRNAs (miRNAs) in bone marrow mesenchymal stem cell-derived exosomes (BMSC-Exo) can attenuate HBV-X protein (HBx)-induced ferroptosis in renal podocytes, but the exact mechanism remains unclear. This study aimed to investigate the protective mechanism of miR-223-3p in BMSC-Exo in HBx-induced ferroptosis in podocytes. Methods: The study employed human renal podocyte cells (HPCs), bone marrow-derived mesenchymal stem cells (BMSCs), as well as kidney tissue from C57BL/6 mice and HBx transgenic mice. Initially, the correlation between STAT3 phosphorylation and ferroptosis was authenticated through the administration of signal transducer and activator of transcription 3 (STAT3) phosphorylation inhibitors in both in vivo and in vitro settings. Furthermore, the effect of HDAC2 overexpression on STAT3 phosphorylation was examined. Subsequently, the association between BMSC-Exo carrying miR-223-3p, HDAC2, and the phosphorylation of STAT3 in HPCs ferroptosis and injury induced by HBx was assessed. The interaction between miR-223-3p and HDAC2 was confirmed via RNA immunoprecipitation assay. Various techniques such as cell counting kit-8 assay, western blot, RT-qPCR, immunofluorescence, flow cytometry, lipid peroxidation assay kit, iron assay kit, transmission electron microscopy, and hematoxylin-eosin staining were employed to visualize the extent of HBx-induced podocyte injury and ferroptosis in both in vivo and in vitro. Results: The attenuation of podocyte ferroptosis can be achieved by inhibiting the phosphorylation of STAT3 in podocytes induced by HBx. Conversely, the upregulation of HDAC2 can enhance STAT3 phosphorylation, thereby promoting podocyte ferroptosis. MiR-223-3p was capable of directly exerting negative regulation on HDAC2 expression. BMSC-Exo carrying miR-223-3p can effectively suppress the expression of HDAC2, ultimately leading to reduce HBx-induced ferroptosis in podocytes by targeting HDAC2 with miR-223-3p and downregulating STAT3 phosphorylation. Conclusion: This study evidences the potential of BMSC-Exo mediated delivery of miR-223-3p in mitigating HBx-induced ferroptosis in podocytes, thereby offering a novel therapeutic target and approach for treating HBV-GN and alleviating renal injury.

The Role of HBx Protein in Diseases Beyond the Liver

HBX gene is essential for HBV replication, evading the surveillance of the immune system by integrating its sequence into the human genome. It also exists stably in human cells by inhibiting the expression and activity of mismatch repair-related pathway genes. Previous reviews have comprehensively summarized the role of HBx in liver-related diseases. Our article complements the summary of research on HBx in diseases other than liver disease. Through a comprehensive literature search and reading, we found that HBx is expressed in the kidney, placenta, lung and other organs of HBV-infected patients, and is closely related to the occurrence and development of diseases such as nephritis, diffuse large B-cell lymphoma, and gastric cancer. However, in the clinical treatment of these diseases, HBV infection and the role of HBx have not attracted sufficient attention, and there is no corresponding treatment strategy. Therefore, more research on HBx in diseases other than the liver is particularly necessary, and we hope that our article can provide some insight into the treatment of related diseases.

Role of ROS/JAK2/STAT3 signaling pathway in di-n-butyl phthalate-induced testosterone synthesis inhibition and antagonism of lycopene

Di-n-butyl phthalate (DBP) causes adverse effects on male reproduction, especially testosterone synthesis inhibition. However, the specific mechanism of DBP-induced testosterone synthesis inhibition and its effective intervention measures of prevention and treatment are scarce presently. Lycopene (LYC) plays beneficial roles in male infertility because of its antioxidant activity. Nevertheless, it is unclear whether LYC could prevent DBP-induced male reproductive toxicity. By in vitro and in vivo investigations, this study demonstrated that DBP activated ROS/JAK2/STAT3 signaling pathway, promoted mitophagy and apoptosis, which in turn inhibited testosterone synthesis. Additionally, another major finding was that LYC supplement could reverse the above change, presenting as the restraint of ROS/JAK2/STAT3 signaling pathway, reduction of mitophagy and apoptosis, and improvement of testosterone synthesis. Our study facilitates deeper understandings of the mechanism in DBP-induced testosterone synthesis inhibition, and identifies LYC as the effective prevention and control strategies for DBP poisoning.

Regulation of Pattern-Recognition Receptor Signaling by HBX During Hepatitis B Virus Infection

As a small DNA virus, hepatitis B virus (HBV) plays a pivotal role in the development of various liver diseases, including hepatitis, cirrhosis, and liver cancer. Among the molecules encoded by this virus, the HBV X protein (HBX) is a viral transactivator that plays a vital role in HBV replication and virus-associated diseases. Accumulating evidence so far indicates that pattern recognition receptors (PRRs) are at the front-line of the host defense responses to restrict the virus by inducing the expression of interferons and various inflammatory factors. However, depending on HBX, the virus can control PRR signaling by modulating the expression and activity of essential molecules involved in the toll-like receptor (TLR), retinoic acid inducible gene I (RIG-I)-like receptor (RLR), and NOD-like receptor (NLR) signaling pathways, to not only facilitate HBV replication, but also promote the development of viral diseases. In this review, we provide an overview of the mechanisms that are linked to the regulation of PRR signaling mediated by HBX to inhibit innate immunity, regulation of viral propagation, virus-induced inflammation, and hepatocarcinogenesis. Given the importance of PRRs in the control of HBV replication, we propose that a comprehensive understanding of the modulation of cellular factors involved in PRR signaling induced by the viral protein may open new avenues for the treatment of HBV infection.

Adiponectin alleviated renal cell apoptosis and inflammation via inactivation of JAK2/STAT3 signal pathway in an acute pyelonephritis mouse model

Background

Acute pyelonephritis (APN), an acute and severe kidney infection, is usually treated with antibiotics. However, APN treatment has become increasingly challenging because of bacterial resistance. Adiponectin, an adipokine, has recently been reported to exhibit profound anti-inflammatory and anti-apoptotic effects. However, the effect of adiponectin on the outcomes of APN treatment remains unclear. In this study, we aimed to investigate the effects of adiponectin on APN and the mechanisms underlying these effects.

Methods

Wild-type C57 mice and adiponectin-knockout (KO) mice were divided into 6 groups: the wild-type control group, the wild-type model group, the wild-type adiponectin intervention group, the KO control group, the KO model group, and the adiponectin-KO intervention group. We measured white blood cell (WBC) and neutrophil counts (NC) using a multispecies hematology analyzer; tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) using enzyme-linked immunosorbent assay (ELISA); blood urea nitrogen (BUN) and serum creatinine (SCr) levels using colorimetry; and the protein levels of JAK2, STAT3, p-JAK2, p-STAT3, Bcl-2, and Bax in renal tissues using western blot analysis. Apoptotic cells were detected using the transferase-mediated dUTP nick end labelling (TUNEL) assay.

Results

Compared to the wild-type mice, the KO mice showed a more severe inflammatory response and kidney damage after Escherichia coli infection. After treatment with exogenous adiponectin injection, the inflammatory response, oxidative stress, and kidney damage were partly alleviated. Adiponectin KO led to JAK2/STAT3 signaling activation, and exogenous adiponectin administration inactivated JAK2/STAT3 signaling in the APN model. APN can lead to an increase in the level of the protein Bax and a decrease in the level of the bcl-2 protein, thereby increasing apoptosis; this effect was inhibited by adiponectin.

Conclusions

Through use of a pyelonephritis mouse model, we demonstrated that adiponectin might alleviate renal cell apoptosis and inflammatory response by inactivating the JAK2/STAT3 signaling pathway.

Induced Mitochondrial Alteration and DNA Damage via IFNGR-JAK2-STAT1-PARP1 Pathway Facilitates Viral Hepatitis Associated Hepatocellular Carcinoma Aggressiveness and Stemness

Simple Summary

Hepatitis virus is a major risk factor for liver cancer. We analyzed possible synergism between momelotinib and sorafenib in hepatitis virus-associated liver cancer. The combined effect of momelotinib and sorafenib both at in vitro and in vivo synergistically sup-presses the proliferation of vHCC cells and effectively reduces the tumor burden. Our results showed that momelotinib effectively suppressed the expression of the IFNGR-JAK-STAT-PARP1 pathway, which results in the downregulation of cancer stem cell genes and enhances the antitumor efficacy of sorafenib by initiating the expression of apoptosis-related genes and inhibiting the DNA repair gene in vHCC cells, thus maximizing its therapeutic potential for patients with HCC.

Abstract

Background: Hepatitis virus is a major risk factor for liver cancer. The mitochondrial dysfunction IFN gamma-related pathways are activated after virus infection. Jak family-related protein is involved in the downstream of IFN gamma-related pathways. However, the effect of the IFNGR-JAK-STAT pathway acting as functional regulators of their related protein expression on virus infection and hepatocellular carcinoma (HCC) remains unclear. Interestingly, the role of the DNA repair gene (PARP1) in therapy resistant cancers also has not been studied and explored well. In this study, we hypothesized that momelotinib could suppress the progression of HCC by targeting Jak family related and PARP1 DNA repair protein. Based on this observation, we link the relevant targets of the JAK family and the potential applications of targeted therapy inhibitors. Methods: We analyzed possible synergism between momelotinib and sorafenib in hepatitis virus-associated liver cancer. Immunostaining, colony formation assay, cell invasion, migration, and tumorsphere-formation assay were used for drug cytotoxicity, cell viability, and possible molecular mechanism. Result: We first demonstrated that the expression of Jak1 and 2 is significantly upregulated in vHCC than in nvHCC/normal liver tissues. In addition, the gene expression of IFN gamma-related pathways is activated after virus infection. Additionally, we found that momelotinib significantly inhibited the growth of HCC cells and reduces the expression of Jak2, which showed the importance of momelotinib in targeting Jak2 and reducing tumorigenesis in HCC. Meanwhile, momelotinib effectively inhibited the IFNGR-JAK-STAT pathway and reduced the migratory/invasive ability of vHCC cells through down-regulating EMT biomarkers (E-cadherin and vimentin), transcription factor (Slug), and significantly inhibits the DNA damage repair enzyme PARP1. It also induced cell apoptosis of vHCC cells. Furthermore, the combined effect of momelotinib and sorafenib both at in vitro and in vivo synergistically suppresses the proliferation of vHCC cells and effectively reduces the tumor burden. Conclusions: Our results showed that momelotinib effectively suppressed the expression of the IFNGR-JAK-STAT-PARP1 pathway, which results in the downregulation of cancer stem cell genes and enhances the antitumor efficacy of sorafenib by initiating the expression of apoptosis-related genes and inhibiting the DNA repair gene in vHCC cells, thus maximizing its therapeutic potential for patients with HCC.

The Dynamic Interface of Viruses with STATs

Viruses commonly antagonize the antiviral type I interferon response by targeting signal transducer and activator of transcription 1 (STAT1) and STAT2, key mediators of interferon signaling. Other STAT family members mediate signaling by diverse cytokines important to infection, but their relationship with viruses is more complex. Importantly, virus-STAT interaction can be antagonistic or stimulatory depending on diverse viral and cellular factors. While STAT antagonism can suppress immune pathways, many viruses promote activation of specific STATs to support viral gene expression and/or produce cellular conditions conducive to infection. It is also becoming increasingly clear that viruses can hijack noncanonical STAT functions to benefit infection. For a number of viruses, STAT function is dynamically modulated through infection as requirements for replication change. Given the critical role of STATs in infection by diverse viruses, the virus-STAT interface is an attractive target for the development of antivirals and live-attenuated viral vaccines. Here, we review current understanding of the complex and dynamic virus-STAT interface and discuss how this relationship might be harnessed for medical applications.

Echinacoside promotes the proliferation of human renal tubular epithelial cells by blocking the HBX/TREM2‑mediated NF‑κB signalling pathway

Hepatitis B virus X (HBX) protein is required for the replication of HBV and plays a role in the progression of hepatitis in humans. However, the underlying function of HBX during HBV‑induced chronic glomerulonephritis (HBV‑GN) is unknown. Echinacoside (ECH) is a phenylethanoid glycoside from the Cistanche genus, which possesses strong antiapoptosis and neuroprotective activities. In the present study, the function of HBX and the relationship between HBX and ECH in human renal tubular epithelial cells (RTECs; HK‑2 cell line) were explored. Reverse transcription‑quantitative PCR and western blot analyses were used to quantify the mRNA and protein expression levels of HBX in HK‑2 cells, respectively. The Cell Counting Kit‑8 assay was performed to analyse cell proliferation. Flow cytometry analysis was used to determine the rate of apoptosis. HBX showed antiproliferative and proapoptotic effects in HK‑2 cells and was positively associated with triggering receptor expressed on myeloid cells 2 (TREM2) expression. Furthermore, ECH disrupted the function of HBX in HK‑2 cells, functioning as an HBX suppressor. Moreover, a specific NF‑κB inhibitor, PDTC, was used to further examine the relationship between HBX and NF‑κB. The results suggested that NF‑κB was involved in the HBX/TREM2 signaling pathway and negatively regulated TREM2 expression in RTECs. The present study provided novel insights into the function of HBX, and also indicated the potential value of ECH as a therapeutic agent for HBV‑GN.

Cordyceps sinensis attenuates HBx‑induced cell apoptosis in HK‑2 cells through suppressing the PI3K/Akt pathway

The authors' previous studies demonstrated that the major renal damage from hepatitis B virus infection is HBx‑induced apoptosis of renal tubular epithelial cells. Cordyceps sinensis is one of the most valuable of traditional Chinese medicines and is extensively used to treat chronic renal diseases. However, there is no research on the potential renal protective effect of C. sinensis on HBx‑induced apoptosis of renal tubular cells. The protective effect and underlying mechanism of C. sinensis were examined using a renal tubular epithelial cell line stably overexpressing HBx. HK‑2 cells were stably transfected with pCMV‑HBx to establish HBx‑overexpression in an in vitro cell model and HK‑2 cells transfected with an empty vector were generated as a control. The effect of C. sinensis on cell proliferation and apoptosis, the phosphatidylinositol‑3‑kinase (PI3K)/protein kinase B (Akt) signaling pathway, and the enzyme activity of caspase‑3 and caspase‑9 was measured. The present study demonstrated that HBx transfection inhibited cell proliferation; increased apoptosis, caspase‑3 and caspase‑9 activity; and increased the activity of the PI3K/Akt pathway. Treatment with C. sinensis attenuated all of these HBx‑induced responses. HBx triggered apoptosis and activated the PI3K/Akt signaling pathway in HK‑2 cells. C. sinensis treatment significantly attenuated the effect of HBx, at least in part by suppressing the PI3K/Akt signaling pathway.

Impact of the Interaction of Hepatitis B Virus with Mitochondria and Associated Proteins

Around 350 million people are living with hepatitis B virus (HBV), which can lead to death due to liver cirrhosis and hepatocellular carcinoma (HCC). Various antiviral drugs/nucleot(s)ide analogues are currently used to reduce or arrest the replication of this virus. However, many studies have reported that nucleot(s)ide analogue-resistant HBV is circulating. Cellular signaling pathways could be one of the targets against the viral replication. Several studies reported that viral proteins interacted with mitochondrial proteins and localized in the mitochondria, the powerhouse of the cell. And a recent study showed that mitochondrial turnover induced by thyroid hormones protected hepatocytes from hepatocarcinogenesis mediated by HBV. Strong downregulation of numerous cellular signaling pathways has also been reported to be accompanied by profound mitochondrial alteration, as confirmed by transcriptome profiling of HBV-specific CD8 T cells from chronic and acute HBV patients. In this review, we summarize the ongoing research into mitochondrial proteins and/or signaling involved with HBV proteins, which will continue to provide insight into the relationship between mitochondria and HBV and ultimately lead to advances in viral pathobiology and mitochondria-targeted antiviral therapy.

Betulinic Acid Attenuates T-2-Toxin-Induced Testis Oxidative Damage Through Regulation of the JAK2/STAT3 Signaling Pathway in Mice

T-2 toxin is one of the most toxic type A trichothecene mycotoxins in nature, and it exhibits reproductive toxicity. Betulinic acid (BA) is a natural pentacyclic triterpene compound found in species of Betula, and it has been reported to have antioxidant activity. The aim of the present study was to investigate the protective effect of BA on T-2-toxin-induced testicular injury in mice and explore its molecular mechanism. Sixty adult male mice were randomly divided into groups. The mice were pretreated orally with BA (0.25, 0.5, and 1.0 mg/kg) daily for 14 days, and the T-2 toxin (4 mg/kg body weight) was administered via intraperitoneal injection to induce oxidative stress after the last administration of BA. BA pretreatment significantly increased the secreted levels of testosterone and sperm motility. Moreover, BA pretreatment significantly increased the total antioxidant capacity (T-AOC), the activity of SOD and CAT, and the content of GSH, and it reduced the content of MDA. Furthermore, BA relieved testicular injury and reduced the number of apoptotic cells, and it significantly decreased the protein expression of Janus kinase 2 (JAK2), signal transducers and activators of transcription 3 (STAT3), caspsae-3, and Bcl-2-associated X protein (Bax). BA also increased the expression of B-cell lymphoma-2 (Bcl-2). We suggest that BA reduced the oxidative damage induced by T-2 toxin, and that these protective effects may be partially mediated by the JAK2/STAT3 signaling pathway.

Hepatitis B virus infection as a risk factor for chronic kidney disease

Introduction: Hepatitis B virus is an important cause of liver disease and has numerous extra-hepatic manifestations. HBV leads to important morbidity and mortality in the general population and recent evidence suggests a role of HBV in the incidence and progression of chronic kidney disease. Areas covered: The mechanisms underlying the link between HBV and CKD remain unclear. Nucleos(t)ide analogues for the antiviral treatment of HBV are currently available; these drugs are provided with high efficacy even in patients with CKD. Expert opinion: A recent meta-analysis of clinical studies showed that HBV results in a greater risk of CKD in the general population. According to an updated review (studies were identified from PubMed, EMBASE, and the Cochrane database), we retrieved six clinical studies (n = 1,034,773 unique patients), adjusted RR, 1.41 (95% CI, 1.09; 1.82, P < 0.001). The significant heterogeneity observed precluded more definitive conclusions. Various mechanisms have been cited to explain the greater risk of CKD among HBsAg positive carriers. Novel evidence shows that untreated HBV and therapy with nucleos(t)ide analogues are associated with increased and decreased risk of end-stage renal disease in CKD population, respectively. We recommend that patients with HBV are assessed for kidney function and urinary changes at baseline and over the follow-up.

High expression of ubiquitin carboxyl-terminal hydrolase 22 is associated with poor prognosis in hepatitis B virus-associated liver cancer

Deubiquitinating enzymes regulate protein activity and cell homeostasis by removing ubiquitin moieties from various substrates. Ubiquitin carboxyl-terminal hydrolase 22 (USP22) is a member of the deubiquitinating protease family and is associated with the development of several tumor types. A previous study demonstrated that USP22 is highly expressed in liver cancer, and its high expression is associated with resistance to chemotherapy. However, the role of USP22 in hepatitis B virus (HBV)-associated liver cancer has not yet been elucidated. The current study demonstrated that USP22 was highly expressed in the tissues of patients with HBV-associated liver cancer, and its high expression was associated with clinicopathological characteristics, including tumor size, clinical stage and prognosis. Further results indicated that USP22 may regulate the proliferative and apoptotic abilities of HepG2.2.15 cells. Additionally, investigation into the underlying mechanism, using small interfering RNA, revealed that the downregulation of USP22 inhibited proliferation and promoted apoptosis though the phosphoinositide 3-kinase/protein kinase B signaling pathway. Therefore, USP22 has the potential to be used as an independent predictor of patient prognosis, as well as a therapeutic target for the treatment of HBV-associated liver cancer.

Hepatitis B virus X protein decreases nephrin expression and induces podocyte apoptosis via activating STAT3

The gene for hepatitis B virus X protein (HBx) comprises the smallest open reading frame in the HBV genome, and the protein product can activate various cell signaling pathways and regulate apoptosis, among other effects. However, in different cell types and under different external conditions, its mechanism of action differs. In the present study, the effect of HBx on the viability and apoptosis of mouse podocyte clone 5 (MPC5) cells was investigated. The cells were transfected with the HBx gene using pEX plasmid, and real-time quantitative PCR and western blot analysis were used to test the transfection efficiency and assess related protein expression. The highest expression of HBx occurred at 48 h after MPC5 cells were transfected with HBx. The expression of nephrin protein in the HBx transfection group was lower than that in blank and negative control groups. Following transfection of the HBx gene, podocyte viability was suppressed, while the rate of cell apoptosis was increased; moreover, the expression of signal transducer and activator of transcription 3 (STAT3) and phospho-STAT3 was increased compared with in the control groups. The present study suggests that STAT3 activation may be involved in the pathogenic mechanism of renal injuries caused by HBV injection. Thus STAT3 is a potential molecular target in the treatment of HBV-GN.

STAT3 roles in viral infection: antiviral or proviral?

Signal transducer and activator of transcription 3 (STAT3) is a transcription factor which can be activated by cytokines, growth factor receptors, and nonreceptor-like tyrosine kinase. An activated STAT3 translocates into the nucleus and combines with DNA to regulate the expression of target genes involved in cell proliferation, differentiation, apoptosis and metastasis. Recent studies have shown that STAT3 plays important roles in viral infection and pathogenesis. STAT3 exhibits a proviral function in several viral infections, including those of HBV, HCV, HSV-1, varicella zoster virus, human CMV and measles virus. However, in some circumstances, STAT3 has an antiviral function in other viral infections, such as enterovirus 71, severe acute respiratory syndrome coronavirus and human metapneumovirus. This review summarizes the roles of STAT3 in viral infection and pathogenesis, and briefly discusses the molecular mechanisms involved in these processes.

Hepatitis B virus X protein and proinflammatory cytokines synergize to enhance TRAIL-induced apoptosis of renal tubular cells by upregulation of DR4

Persistent infection with hepatitis B virus (HBV) may lead to HBV-associated glomerulonephritis (HBV-GN). Presence of HBV-DNA and -RNA in renal tubular epithelial cells (RTECs) suggests direct virus-induced injury. Increase in proinflammatory cytokines is also observed under these conditions. Apoptosis by tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) plays a significant role in the pathogenesis of HBV-infections. However, the effects of HBV X protein (HBx) on TRAIL-induced apoptosis of RTECs especially under certain inflammatory conditions remain obscure. Here, we show that HBx synergizes with proinflammatory cytokines to significantly increase TRAIL-induced apoptosis of RTECs. HBx markedly up-regulates death receptor-4 (DR4) expression by enhancing the activation of nuclear factor-kappa B (NF-κB) in the presence of proinflammatory cytokines. Dramatic increase in DR4 expression leads to the sensitization of RTECs to TRAIL-induced apoptosis. Furthermore, in patients with HBV-GN, DR4 expression in the kidneys is significantly elevated and is positively correlated with the HBx and proinflammatory cytokines expression. These findings provide a novel insight into the underlying mechanisms of renal tubule lesions induced by HBx in HBV-GN.

AG490, a JAK2-specific inhibitor, downregulates the expression and activity of organic anion transporter-3

Human organic anion transporter-3 (hOAT3) is richly expressed in the kidney, where it plays critical roles in the secretion of clinically important drugs, including anti-viral therapeutics, anti-cancer drugs, antibiotics, antihypertensives, and anti-inflammatories. In the current study, we examined the role of AG490, a specific inhibitor of the Janus tyrosine kinase 2 (JAK2), in hOAT3 transport activity in the kidney COS-7 cells. AG490 induced a time- and concentration-dependent inhibition of hOAT3-mediated uptake of estrone sulfate, a prototypical substrate for the transporter. The inhibitory effect of AG490 correlated with a reduced expression of hOAT3 at the cell surface. Our lab previously demonstrated that Nedd4-2, a ubiquitin ligase, down regulates OAT expression and transport activity by enhancing OAT ubiquitination, which leads to an internalization of OAT from cell surface to intracellular compartments and subsequent degradation. In the current study, we showed that treatment of hOAT3-expressing cells with AG490 resulted in an enhanced hOAT3 ubiquitination and degradation, which was accompanied by a strengthened association of Nedd4-2 with hOAT3 and a reduction in Nedd4-2 phosphorylation. SiRNA knockdown of endogenous Nedd4-2 abrogated the effects of AG490 on hOAT3. In summary, our study demonstrated that AG490 regulates hOAT3 expression and transport activity through the modulation of Nedd4-2.

Interference of Apoptosis by Hepatitis B Virus

Hepatitis B virus (HBV) causes liver diseases that have been a consistent problem for human health, leading to more than one million deaths every year worldwide. A large proportion of hepatocellular carcinoma (HCC) cases across the world are closely associated with chronic HBV infection. Apoptosis is a programmed cell death and is frequently altered in cancer development. HBV infection interferes with the apoptosis signaling to promote HCC progression and viral proliferation. The HBV-mediated alteration of apoptosis is achieved via interference with cellular signaling pathways and regulation of epigenetics. HBV X protein (HBX) plays a major role in the interference of apoptosis. There are conflicting reports on the HBV interference of apoptosis with the majority showing inhibition of and the rest reporting induction of apoptosis. In this review, we described recent studies on the mechanisms of the HBV interference with the apoptosis signaling during the virus infection and provided perspective.

STAT3 activation in infection and infection-associated cancer

The Janus kinase/signal transducers and activators for transcription (JAK/STAT) pathway plays crucial roles in regulating apoptosis, proliferation, differentiation, and the inflammatory response. The JAK/STAT families are composed of four JAK family members and seven STAT family members. STAT3 plays a key role in inducing and maintaining a pro-carcinogenic inflammatory microenvironment. Recent evidence suggests that STAT3 regulates diverse biological functions in pathogenesis of diseases, such as infection and cancer. In the current review, we will summarize the research progress of STAT3 activation in infection and cancers. We highlight our recent study on the novel role of STAT3 in Salmonella infection-associated colon cancer. Infection with bacterial AvrA-expressing Salmonella activates the STAT3 pathway, which induces the β-catenin signals and enhances colonic tumorigenesis. STAT3 may be a promising target in developing prevention and treatment for infectious diseases and infection-associated cancers.

Hepatitis B Virus Activates Signal Transducer and Activator of Transcription 3 Supporting Hepatocyte Survival and Virus Replication

BACKGROUND & AIMS

The human hepatitis B virus (HBV) is a major cause of chronic hepatitis and hepatocellular carcinoma, but molecular mechanisms driving liver disease and carcinogenesis are largely unknown. We therefore studied cellular pathways altered by HBV infection.

METHODS

We performed gene expression profiling of primary human hepatocytes infected with HBV and proved the results in HBV-replicating cell lines and human liver tissue using real-time polymerase chain reaction and Western blotting. Activation of signal transducer and activator of transcription (STAT3) was examined in HBV-replicating human hepatocytes, HBV-replicating mice, and liver tissue from HBV-infected individuals using Western blotting, STAT3-luciferase reporter assay, and immunohistochemistry. The consequences of STAT3 activation on HBV infection and cell survival were studied by chemical inhibition of STAT3 phosphorylation and small interfering RNA-mediated knockdown of STAT3.

RESULTS

Gene expression profiling of HBV-infected primary human hepatocytes detected no interferon response, while genes encoding for acute phase and antiapoptotic proteins were up-regulated. This gene regulation was confirmed in liver tissue samples of patients with chronic HBV infection and in HBV-related hepatocellular carcinoma. Pathway analysis revealed activation of STAT3 to be the major regulator. Interleukin-6-dependent and -independent activation of STAT3 was detected in HBV-replicating hepatocytes in cell culture and in vivo. Prevention of STAT3 activation by inhibition of Janus tyrosine kinases as well as small interfering RNA-mediated knockdown of STAT3-induced apoptosis and reduced HBV replication and gene expression.

CONCLUSIONS

HBV activates STAT3 signaling in hepatocytes to foster its own replication but also to prevent apoptosis of infected cells. This very likely supports HBV-related carcinogenesis.

Expression of cleaved caspase-3 in renal tubular cells in Plasmodium falciparum malaria patients

AIM

In Plasmodium falciparum malaria, the clinical manifestation of acute kidney injury (AKI) is commonly associated with acute tubular necrosis (ATN) in the kidney tissues. Renal tubular cells often exhibit various degrees of cloudy swelling, cell degeneration, and frank necrosis. To study individual cell death, this study evaluates the degree of renal tubular necrosis in association with apoptosis in malarial kidneys.

METHODS

Kidney tissues from P. falciparum malaria with AKI (10 cases), and without AKI (10 cases) were evaluated for tubular pathology. Normal kidney tissues from 10 cases served as controls. Tubular necrosis was assessed quantitatively in kidney tissues infected with P. falciparum malaria, based on histopathological evaluation. In addition, the occurrence of apoptosis was investigated using cleaved caspase-3 marker. Correlation between tubular necrosis and apoptosis was analyzed.

RESULTS

Tubular necrosis was found to be highest in P. falciparum malaria patients with AKI (36.44% ± 3.21), compared to non-AKI (15.88% ± 1.63) and control groups (2.58% ± 0.39) (all p < 0.001). In the AKI group, the distal tubules showed a significantly higher degree of tubular necrosis than the proximal tubules (p = 0.021) and collecting tubules (p = 0.033). Tubular necrosis was significantly correlated with the level of serum creatinine (r = 0.596, p = 0.006), and the occurrence of apoptosis (r = 0.681, p = 0.001).

CONCLUSION

In malarial AKI, the process of apoptosis occurs in ATN.

Hepatitis B Virus X Protein Reduces Podocyte Adhesion via Downregulation of α3β1 Integrin

BACKGROUND/AIMS

Hepatitis B virus (HBV)-associated glomerulonephritis (HBV-GN) is characterized by a reduced number of podocytes due to apoptosis and shedding from the basement membrane. However, the pathological mechanism of HBV-GN is unclear. We previously showed that hepatitis B virus X protein (HBx) promotes apoptosis in tubular epithelial cells. In this study, we transfected podocytes with HBx and examined the effects on adhesion and apoptosis of these cells.

METHODS

Podocytes were transfected with pc-DNA3.1 (+)-HBx. One control group was not transfected and another control group was transfected with empty plasmids. Podocyte adhesion was assessed by a fluorescence assay, apoptosis was measured by flow cytometry and fluorescence microscopy, and expression of α3β1 integrin was determined by western blotting and the reverse transcription polymerase chain reaction (RT-PCR). Activity of caspase-8 was measured by a spectrophotometric assay.

RESULTS

Relative to controls, podocytes with pc-DNA3.1(+)-HBx had reduced cell adhesion, increased apoptosis, reduced expression of α3β1 integrin, and increased caspase-8 activity. β1 integrin blockage reduced podocyte adhesion, but increased apoptosis and caspase-8 activity. Treatment of transfected podocytes with a caspase-8 inhibitor (Z-IETD-FMK) had no effect on the HBx-mediated integrin downregulation and reduced podocyte adhesion, suggesting that α3β1 integrin downregulaton is sufficient to alter cell adhesion.

CONCLUSIONS

Our in vitro results indicate that HBx reduced podocyte adhesion and expression of α3β1 integrin, and increased apoptosis. Moreover, HBx-mediated downregulation of α3β1 integrin expression is sufficient to reduce podocyte adhesion. HBx-induced apoptosis of podocytes may contribute to HBV-GN.

Hepatitis B virus X protein promotes renal epithelial-mesenchymal transition in human renal proximal tubule epithelial cells through the activation of NF-κB

Hepatitis B virus (HBV)-associated glomerulo-nephritis is the most common extra-hepatic disorder occurring with hepatitis B virus infection. In the present study, we hypothesized that HBV X protein (HBx) may play a critical role in renal interstitial fibrosis, as HBx has been shown to induce epithelial-mesenchymal transition (EMT) in renal cells. For this purpose, we successfully transfected HBx plasmid into human renal proximal tubule epithelial cells (HK-2 cells). We found that transfection with HBx plasmid significantly downregulated E-cadherin expression and upregulated α-smooth muscle actin, collagen I and fibronectin expression in a time- and concentration-dependent manner (at the lower concentrations and earlier time points). HBx also increased nuclear factor-κB (NF-κB) phosphorylation in a time- and concentration-dependent manner (again at the lower concentrations and earlier time points); however, it did not alter the phosphorylation of Smad2, Smad3, p38, phosphoinositide 3-kinase (PI3K) or extracellular signal-regulated kinase (ERK). Thus, the findings of this study demonstrate that HBx promotes EMT in renal HK-2 cells, and the potential underlying mechanisms may involve the activation of the NF-κB signaling pathway.

HBxAg suppresses apoptosis of human placental trophoblastic cell lines via activation of the PI3K/Akt pathway

The aim of this study is to investigate the effect of hepatitis B virus X (HBx) protein on the apoptosis of placental trophoblastic cells and its potential mechanism. A pcDNA3.1 expression vector of HBx gene was built and transfected into JEG-3 and HTR-8 human placental trophoblastic cell lines, respectively. After transfection for 48 h, RT-PCR and immunofluorescence analyses showed that HBx mRNA and protein expression was detected in JEG-3 and HTR-8 cells. Flow cytometry revealed that early apoptosis of JEG-3 and HTR-8 cells was reduced by pcDNA-HBx transfection. Immunofluorescence and Western blotting showed that PI3K and p-Akt were significantly upregulated in HTR-8 cells. HBx ectopic expression did not change the viability of JEG-3 and HTR-8 cells when the PI3K/Akt pathway was blocked by its specific inhibitor LY294002. Moreover, the pcDNA-PI3K expression vector and pcDNA-HBx were transfected individually or co-transfected into the cells. The results showed that pcDNA-PI3K/pcDNA-HBx co-transfection promoted the expression of PI3K protein compared with the pcDNA-PI3K transfection group but did not increase the expression of HBx protein compared with pcDNA-HBx transfection group. In conclusion, HBx gene can be transferred into JEG-3 and HTR-8 human placental trophoblastic cell lines and cause inhibition of cell apoptosis. Its effect of apoptosis inhibition is related to the activation of the PI3K/Akt signaling pathway.

Hepatitis B virus X protein modulates renal tubular epithelial cell-induced T-cell and macrophage responses

Renal tubular epithelial cells (RTECs) have an active role in renal inflammation, functioning as antigen-presenting cells as they constitutively express major histocompatibility complex-II and co-stimulatory molecules that can activate T cells and macrophages. Previous studies indicate that inflammatory cell infiltration and tubulointerstitial fibrosis are present in renal biopsies from Hepatitis B virus (HBV)-associated glomerulonephritis (HBV-GN) patients. We hypothesized that disorder RTECs may be involved in the progression of HBV-GN. Here, we measured renal function and inflammatory cells infiltration in C57BL/6J-TgN mice, and data showed that in C57BL/6J-TgN mice HBV x protein (HBx) mainly deposited in RTECs, and CD4(+) T cells and macrophages infiltrated into the interstitium. In vitro HBx upregulated CD40 expression in RTECs. In HK-2/CD4(+) T cells co-culture system, we found that HBx-stimulated HK-2 cells could activate CD4(+) T cells, promote their proliferation, and lead to an imbalance of interleukin (IL)-4 and interferon-γ. In HK-2/macrophages co-culture system, we found that HBx-stimulated HK-2 cells also increased macrophage adherent capacity and promoted MCP-1 and tumor necrosis factor-α and IL-1β secretion. These immune dysfunction may contribute to the pathogenesis of HBV-GN.

HBV serum and renal biopsy markers are associated with the clinicopathological characteristics of HBV-associated nephropathy

BACKGROUND

Accumulated evidence has shown that hepatitis B virus infection is associated with numerous types of nephropathy but it remains to clarify the different role of HBV markers, either in serum or deposit in kidney, in the pathogenesis of HBV-associated nephropathy. In this study, we investigated the relationship between HBV markers and HBV-associated nephropathy by using multi-linear regression in Chinese patients with HBV-associated membranous nephropathy (MN).

METHODS

A total of 196 cases of HBV-associated MN, which were diagnosed based on renal biopsy, were collected during the period of January 2000 to December 2009 from our hospital. Serum and renal biopsy HBV markers included HBsAg, anti-HBs, HBeAg, anti-HBe, and anti-HBC. HBV-associated nephropathy was characterized by a panel of clinical manifestations and pathological parameters, which included proteinuria, hematuria, serum creatinine, hypertension, and renal damage in glomeruli, tubules, interstitium, and blood vessels. Multilinear regression was used to analyze the relationship between the HBV markers in serum and renal biopsy and the clinicopathological characteristics of HBV-associated nephropathy.

RESULTS

After analysis of the clinical and pathological data in 196 cases of HBV-associated membranous nephropathy, this study revealed that glomerular lesion was marginally associated with serum HBsAg (P = 0.0528), Anti-HBs (P = 0.0978), but significantly associated with the presence of IgA (P = 0.0242), IgG (P < 0.0001) and C3 (P = 0.0064) in renal biopsy. There was no significant association between glomerular lesion and HBV markers in kidney. The presence of crescent and renal tube impairment was not related to HBV markers. The renal fibrosis was significantly related to gender (P = 0.023), age (P = 0.0211), HBsAg (P = 0.0001) and HBcAg (P = 0.0083) and C3 (P = 0.0299) in renal biopsy. Notably, the renal blood vessel impairment was significantly related to systolic Blood Pressure (SBP) (P < 0.0001), diastolic blood pressure (DBP) (P = 0.0002), serum HBsAg (P = 0.0428), serum HBeAg (P = 0.0766), FRA (P = 0.0002), and HBsAg (P = 0.0241) and HBcAg (P = 0.0599) in renal tissues. Also, the renal interstitial infiltration was related to patient age (P = 0.015, SBP (P < 0.0001), DBP (P = 0.0001), C3 (P = 0.0028), FRA (P = 0.0165), HBsAg (P = 0.0016) and HBcAg (P = 0.0203) in kidney biopsy. These results suggest that the major pathological changes in kidneys in HBV patients are related to one or more HBV markers, such as HBsAg, HBeAg, or anti-HBs antibody. Besides, most of the pathological changes in kidneys are related to C3 and FRA in kidney tissues. The clinical markers of nephropathy, such as proteinuria, hematuria and creatine serum levels, were also evaluated for their relationship with HBV markers in serum and kidney tissues. We found proteinuria was marginally related to HBV DNA (P = 0.0537), significantly related to IgA (0.0223). Hematouria was significantly related to IgA (P = 0.0434), IgG (P < 0.0001), and C1q (P = 0.0282). The serum creatine level was related to patient gender (P = 0.0077), SBP (P < 0.0001), DBP (0.0049), IgG (P-0.0006), and C3 (P = 0.0113). These clinical manifestations were not related to HBV markers in either serum or kidney. These results indicate that some of clinical manifestations of nephropathy are related to HBV markers, but the relationship is limited.

The deposition of Notch1 in hepatitis B virus-associated nephropathy and its role in hepatitis B virus X protein-induced epithelial-mesenchymal transdifferentiation and immunity disorder in renal tubular epithelial cells

Notch1 plays an important role in the regulation of immune responses and epithelial-mesenchymal transdifferentiation (EMT). Previous studies have observed inflammatory cell infiltration and tubulointerstitial fibrosis in the renal biopsies from patients with HBV-associated glomerulonephritis (HBV-GN). We hypothesized that Notch1 may be involved in the progression of HBV-GN. In this study, we evaluated the distribution of Notch1 in patients with HBV-GN. Our results showed that Notch1 was mainly distributed in renal tubules and the interstitial area, and the expression levels of Notch1 had a positive correlation with the renal tubular pathology. In this respect, we used human proximal tubular epithelial cells (HK-2) as target cells, which were transiently transfected with the hepatitis B virus X (HBx) gene using a eukaryotic vector. HBx expression resulted in significantly increased detection of Notch1, alpha-smooth muscle actin (α-SMA), major histocompatibility complex-II (MHC-II), CD40 and interleukin-4 (IL-4). At the same time, E-cadherin and interferon-γ (IFN-γ) expression levels were significantly inhibited. These HBx-induced phenotypes were exacerbated by upregulation of Notch1. Knock-down of Notch1 by specific shRNA caused decreases of α-SMA, MHC-II, CD40 and IL-4, and increases of E-cadherin and IFN-γ. These findings suggest that Notch1 is significantly associated with renal tubular and interstitial lesions. Notch1 can mediate HBx-induced EMT of HK-2 cells, promote HBx-induced increases in immune molecule expression and exacerbation of cytokine disorders, which may contribute to the progression of HBV-GN. Inhibitors of Notch1 signalling may be useful as new therapeutics for the treatment of HBV-GN.

Hepatitis B virus x protein induces autophagy via activating death-associated protein kinase

Hepatitis B virus x protein (HBX), a product of hepatitis B virus (HBV), is a multifunctional protein that regulates viral replication and various cellular functions. Recently, HBX has been shown to induce autophagy; however, the responsible mechanism is not fully known. In this study, we established stable HBX-expressing epithelial Chang cells as the platform to study how HBX induced autophagy. The results showed that the overexpression of HBX resulted in starvation-induced autophagy. HBX-induced autophagy was related to its ability to dephosphorylate/activate death-associated protein kinase (DAPK). The block of DAPK by its siRNA significantly counteracted HBX-mediated autophagy, confirming the positive role of DAPK in this process. HBX also induced Beclin 1, which functions at the downstream of the DAPK-mediated autophagy pathway. Although HBX could activate JNK, a kinase known to participate in autophagy in certain conditions, the change in JNK failed to influence HBX-induced autophagy. In conclusion, HBX induces autophagy via activating DAPK in a pathway related to Beclin 1, but not JNK. This new finding should help us to understand the role of autophagy in HBX-mediated pathogenesis and thus may provide targets for intervening HBX-related disorders.

Genome-wide effects of DNA methyltransferase inhibitor on gene expression in double-stranded RNA transfected porcine PK15 cells

Double-stranded RNA (dsRNA) is produced in host cells during viral replication. The effects of DNA demethylation on gene expression in dsRNA transfected swine cells are unclear. The study aims to profile the transcriptome changes which are induced by DNA methyltransferase inhibitor (Aza-CdR) in porcine PK15 cells transfected with viral-like dsRNA (Poly(I:C)). A total of 44, 76 and 952 differentially expressed genes (DEGs) were detected in the cells treated by Poly(I:C) plus Aza-CdR (P+A), Poly(I:C) (P) or Aza-CdR (A) alone compared to the controls (C). Immune response-related pathways are observed in the comparison of A vs. C and P vs. C, and the genes in the pathways were recovered in the comparison of (P+A) vs. C. GO analysis indicated that Aza-CdR has negative regulatory effects on viral reproduction. The results suggest that the stimulant of Poly(I:C) could be regressed by Aza-CdR. These observations provide new insights into the epigenetic regulatory effects on viral replication.

Role of hepatitis B virus X protein in hepatocarcinogenesis

Hepatocellular carcinoma (HCC) is the fifth most common cancer in the world and the third most common cause of cancer-related death. Chronic hepatitis B virus (HBV) infection has been identified as a major risk factor for HCC. Evidence suggests that the HBV X protein (HBx) plays a crucial role in the carcinogenesis of HCC. HBx is a multifunctional regulator that plays a key role in the occurrence, development, invasion and metastasis of cancers. Due to its important roles in the development of HCC, the research on the HBx protein has become a hot topic in recent years. This review describes the latest advances in understanding the role of the HBx protein in hepatocarcinogenesis.

Construction and identification of a green fluorescent protein expression vector carrying the HBx gene (pHBx-EGFP) and its expression in hepatocellular carcinoma cell line Bel 7402

AIM: To construct an eukaryotic expression vector carrying hepatitis B virus X (HBx) gene and enhanced green fluorescent protein gene (pHBx-EGFP), and to express it transiently in hepatocellular carcinoma (HCC) Bel 7402 cells for observing the expression and cellular localization of HBx-EGFP fusion protein and providing an experimental tool for investigating the function of HBx gene.

METHODS: pcDNA3.1-HBx was used to amplify the HBx gene fragment by polymerase chain reaction (PCR). Recombinant DNA technology was used to insert the HBx gene into the eukaryotic expression vector pEGFP to obtain a recombinant vector pHBx-EGFP. After the recombinant vector or pEGFP was transfected into Bel 7402 cells for 24 h, the expression and subcellular location of HBx-EGFP was detected under an inverted fluorescence microscope, and the expression of HBx protein in total cellular proteins was detected by Western blot.

RESULTS: Restriction digestion and DNA sequence analyses verified that the recombinant plasmid was constructed successfully. After the HBx-EGFP recombinant plasmid was transfected into Bel 7402 cells, it was found that HBx-EGFP was present in the perinuclear region, while EGFP was distributed throughout the cells. Western blot analysis demonstrated that EGFP and HBx were expressed efficiently.

CONCLUSION: A recombinant eukaryotic fluorescent expression vector carrying the HBx gene (pHBx-EGFP) has been constructed successfully, which could express EGFP and HBx in Bel 7402 cells.