Hepatitis B virus X protein modulates renal tubular epithelial cell-induced T-cell and macrophage responses. Immunol Cell Biol. 2016;94:266-273. [PMID: 26365016 DOI: 10.1038/icb.2015.85]

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.

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.

HBx-induced PLA2R overexpression mediates podocyte pyroptosis through the ROS-NLRP3 signaling pathway

INTRODUCTION

Hepatitis B virus-associated glomerulonephritis (HBV-GN) is one of the main types of secondary glomerular diseases, and podocyte injury is an important pathogenic mechanism of HBV-GN, participating in the occurrence and development of HBV-GN. However, the specific mechanism of podocyte injury remains to be studied.

METHODS

Human renal podocytes cultured in vitro were divided into six groups. The podocyte morphology was observed under a transmission electron microscope, and the expression of M-type phospholipase A₂ receptor (M-PLA₂R) on the podocyte membrane was observed by indirect immunofluorescence staining under a fluorescence microscope. The pyroptosis rate and reactive oxygen species (ROS) of podocytes were assessed by FLICA/PI double staining and flow cytometry. Western blot (WB) and quantitative real-time PCR (qPCR) were used to determine the expression of PLA₂R, nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3), apoptosis-associated speck-like protein containing card (ASC), caspase-1, IL-1β, and IL-18.

RESULTS

Hepatitis B virus X (HBx) transfected into human renal podocytes in vitro induced the overexpression of PLA₂R. Moreover, the overexpressed PLA₂R combined with secretory phospholipase A₂ group IB (sPLA₂-IB) aggravated podocyte injury and increased the pyroptosis rate. In addition, the expression of ROS, the NLRP3 inflammasome and downstream inflammatory factors was increased. In contrast, after inhibiting the expression of PLA₂R and ROS, podocyte damage was alleviated, and the pyroptosis rate and the expression of genes related to the ROS-NLRP3 signaling pathway were decreased.

CONCLUSION

HBx-induced PLA₂R overexpression on the podocyte membrane can significantly upregulate the ROS-NLRP3 signaling pathway, thereby mediating podocyte pyroptosis.

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.

Hepatitis B Virus-Related Glomerulonephritis with Positive and Negative Serum HBsAg: Different Clinicopathologic Characteristics of Two Clinical Subtypes

INTRODUCTION

The clinicopathologic characteristics of Hepatitis B virus-associated glomerulonephritis (HBV-GN) patients with different serum HBsAg are not well known. This study aims to investigate the characteristics and treatments between HBV-GN patients with positive and negative serum HBsAg.

METHODS

A retrospective review of patients with renal biopsies in Guangdong Provincial People's Hospital from 2005 to 2018 was performed. Clinicopathological data, treatments and remission of proteinuria were collected and compared between HBsAg+ and HBsAg- group.

RESULTS

A total of 101 HBV-GN were recruited. Serum HBsAg+ and HBsAg- patients accounted for 62.4% and 37.6%, respectively. HBsAg+ group had poor kidney and liver functions. Pathological data showed the percentage of membranous nephropathy in HBsAg- group is significantly higher than that of HBsAg+ group (60.3% HBsAg+ vs 89.5% HBsAg-, P<0.05). Chronic renal tubular/interstitial injury was more prevalent in HBsAg+ group (16.9% HBsAg+ vs 2.6% HBsAg-, P<0.05). The deposition sites of immune complexes were significant different between the two groups. In addition, more HBsAg+ patients were given anti-HBV and less were given corticosteroid or immunosuppressants for treatment than that of HBsAg- patients. Percentages of clinical remission were increasing in both HBsAg+ and HBsAg- patients from 1, 3, 6 months to 1 year (18.75%, 45.2%, 67.8%, 82.4% vs 24.4%, 41.2%, 62.8%, 59.3%). The differences of remission betwen two groups were not significant (P>0.05).

CONCLUSION

The clinicopathological characteristics and treatments of HBV-GN with serum HBsAg+ and HBsAg- were distinct, which indicated that the pathogenesis might be different and specific treatments were needed for HBV-GN patients with different serum HBsAg.

Mechanisms of kidney dysfunction in the cirrhotic patient: Non-hepatorenal acute-on-chronic kidney damage considerations

Renal dysfunction is a common finding in cirrhotic patients and has a great physiologic, and therefore, prognostic relevance. The combination of liver disease and renal dysfunction can occur as a result of systemic conditions that affect both the liver and the kidney, although primary disorders of the liver complicated by renal dysfunction are much more common. As most of the renal dysfunction scenarios in cirrhotic patients correspond to either prerenal azotemia or hepatorenal syndrome (HRS), physicians tend to conceive renal dysfunction in cirrhotic patients as mainly HRS. However, there are many systemic conditions that may cause both a "baseline" chronic kidney damage and a superimposed kidney dysfunction when this systemic condition worsens. The main aim of this article is to review some of the most important non prerenal non-HRS considerations regarding acute on chronic kidney dysfunction in cirrhotic patients, including renal manifestation of related to non-alcoholic steatohepatitis (NASH) viral hepatitis, the effect of cardiorenal syndrome in cirrhotics and corticosteroid-deficiency associated renal dysfunction.

Subclinical proximal tubulopathy in hepatitis B: The roles of nucleot(s)ide analogue treatment and the hepatitis B virus

BACKGROUND

The recommended monitoring tools for evaluating nucleot(s)ide analogue renal toxicity, such as estimated glomerular filtration rate (eGFR) and phosphatemia, are late markers of proximal tubulopathy. Multiple early markers are available, but no consensus exists on their use.

AIM

To determine the 24 mo prevalence of subclinical proximal tubulopathy (SPT), as defined with early biomarkers, in treated vs untreated hepatitis B virus (HBV)-monoinfected patients.

METHODS

A prospective, non-randomized, multicenter study of HBV-monoinfected patients with a low number of renal comorbidities was conducted. The patients were separated into three groups: Naïve, starting entecavir (ETV) treatment, or starting tenofovir disoproxil (TDF) treatment. Data on the early markers of SPT, the eGFR and phosphatemia, were collected quarterly. SPT was defined as a maximal tubular reabsorption of phosphate/eGFR below 0.8 mmoL/L and/or uric acid fractional excretion above 10%. The prevalence and cumulative incidence of SPT at month 24 (M24) were calculated. Quantitative data were analyzed using analyses of variance or Kruskal-Wallis tests, whereas chi-squared or Fisher’s exact tests were used to analyze qualitative data. Multivariate analyses were used to adjust for any potential confounding factors.

RESULTS

Of the 196 patients analyzed, 138 (84 naïve, 28 starting ETV, and 26 starting TDF) had no SPT at inclusion. At M24, the prevalence of SPT was not statistically different between naïve and either treated group (21.1% vs 30.7%, P < 0.42 and 50.0% vs 30.7%, P = 0.32 for ETV and TDF, respectively); no patient had an eGFR lower than 50 mL/min/1.73 m² or phosphatemia less than 0.48 mmoL/L. In the multivariate analysis, no explanatory variables were identified after adjustment. The cumulative incidence of SPT over 24 mo (25.5%, 13.3%, and 52.9% in the naïve, ETV, and TDF groups, respectively) tended to be higher in the TDF group vs the naïve group (hazard ratio: 2.283, P = 0.05). SPT-free survival at M24 was 57.6%, 68.8%, and 23.5% for the naïve, ETV, and TDF groups, respectively. The median survival time without SPT, evaluated only in the TDF group, was 5.9 mo.

CONCLUSION

The prevalence and incidence of SPT was higher in TDF-treated patients compared to naïve patients. SPT in the naïve population suggests that HBV can induce renal tubular toxicity.

CD40/CD40L Signaling as a Promising Therapeutic Target for the Treatment of Renal Disease

The cluster of differentiation 40 (CD40) is activated by the CD40 ligand (CD40L) in a variety of diverse cells types and regulates important processes associated with kidney disease. The CD40/CD40L signaling cascade has been comprehensively studied for its roles in immune functions, whereas the signaling axis involved in local kidney injury has only drawn attention in recent years. Clinical studies have revealed that circulating levels of soluble CD40L (sCD40L) are associated with renal function in the setting of kidney disease. Levels of the circulating CD40 receptor (sCD40), sCD40L, and local CD40 expression are tightly related to renal injury in different types of kidney disease. Additionally, various kidney cell types have been identified as non-professional antigen-presenting cells (APCs) that express CD40 on the cell membrane, which contributes to the interactions between immune cells and local kidney cells during the development of kidney injury. Although the potential for adverse CD40 signaling in kidney cells has been reported in several studies, a summary of those studies focusing on the role of CD40 signaling in the development of kidney disease is lacking. In this review, we describe the outcomes of recent studies and summarize the potential therapeutic methods for kidney disease which target CD40.

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.

The histone demethylase LSD1 promotes renal inflammation by mediating TLR4 signaling in hepatitis B virus-associated glomerulonephritis

Renal inflammation significantly contributes to the progression of hepatitis B virus (HBV)-associated glomerulonephritis (HBV-GN), but the mechanisms that control its precise regulation remain largely unknown. In this study, we showed that the lysine-specific demethylase 1 (LSD1) was significantly upregulated in renal tissue of HBV-GN patients, and its expression was positively correlated with inflammation. Functionally, LSD1 could promote HBV-induced release of proinflammatory mediators in HK-2 cells, a human renal tubular epithelial (RTE) cell line. Mechanistic investigations suggested that LSD1 directly promoted the transcription of the inflammatory-related gene Tlr4 by eliminating the mono- or di-methylation of H3K9 near its promoter. Knockdown of Lsd1 further inhibited TLR4-NF-κB/JNK signaling cascades, and subsequently decreased HBV-induced production of proinflammatory mediators in HK-2 cells. Co-transfection with Tlr4-expressing plasmids counteracted these effects. Meanwhile, downregulation of abovementioned TLR4-related pathways using small-molecule inhibitors attenuated inflammation. Importantly, LSD1 inhibitor tranylcypromine (TCP) could inhibit TLR4-NF-κB/JNK signaling axis and alleviate renal inflammation in HBV transgenic mice. Taken together, our data identify LSD1 as a novel regulator of renal inflammation and as a potential therapeutic target in HBV-GN.

14-3-3ζ binds to hepatitis B virus protein X and maintains its protein stability in hepatocellular carcinoma cells

14‐3‐3ζ, a phosphopeptide‐binding molecule, is reportedly overexpressed in the cancerous tissues of patients with hepatocellular carcinoma (HCC). Hepatitis B virus (HBV) protein X (HBx) draws intensive attention in HBV‐related HCC because it not only regulates HBV replication, but also promotes carcinogenesis by interacting with various tumor or antitumor molecules. This study is performed to investigate whether and how 14‐3‐3ζ interacts with HBx. The coimmunoprecipitation (Co‐IP) results showed that 14‐3‐3ζ bond to HBx in HBV‐infected Hep3B HCC cells and CSQT‐2 portal vein tumor thrombosis (PVTT) cells. By performing Co‐IP assay in HBV‐free Huh7 cells expressing wild‐type HBx, mutant HBx‐S31A, or HBx‐S31D (serine³¹ was mutated into alanine³¹ or aspartic acid³¹), we found that the phosphorylated serine³¹ with its near amino acid residues constituted a RPLphosphoS³¹GP (R, arginine; P, proline; L, leucine; S, serine; G, glycine) motif in HBx for 14‐3‐3ζ docking. This 14‐3‐3ζ‐HBx interaction was partly impaired when Akt signaling transduction was blocked by LY294002. Furthermore, 14‐3‐3ζ silencing augmented HBx ubiquitination and decreased its expression in cancer cells and xenograft tumor. The migratory and invasive abilities of CSQT‐2 cells were inhibited upon 14‐3‐3ζ silencing, whereas partly restored by HBx overexpression. Additionally, 14‐3‐3ζ positively correlated with HBx to be overexpressed in the primary HCC tissues (r = 0.344) and metastatic PVTT (r = 0.348). In summary, findings of this study reveal a novel 14‐3‐3ζ‐HBx interaction in HCC cells and suggest 14‐3‐3ζ as a candidate target for treating HBV‐related HCC.

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.