The role of the toll-like receptor TLR4 in hepatitis B virus-associated glomerulonephritis

DNA methyltransferase 1 knockdown reverses PTEN and VDR by mediating demethylation of promoter and protects against renal injuries in hepatitis B virus-associated glomerulonephritis

Background

Aberrant DNA methylation patterns, including hypermethylation of key genes that inhibit fibrosis and inflammation, have been described in human kidney diseases. However, the role of DNA methyltransferase 1 (DNMT1) in hepatitis B virus-associated glomerulonephritis (HBV-GN) remains unclear.

Methods

We explored the underlying mechanism by establishing HBV X protein (HBx) overexpressing renal tubular epithelial (HK-2) cells and human podocytes with DNMT1 knockdown. Using RNA-sequencing to determine the downstream targets of DNMT1 and evaluate its levels of promoter methylation. HBV transgenic mice were used to examine the effects of DNMT1 inhibitor on renal in vivo.

Results

DNMT1 was significantly upregulated in the renal tissue of HBV-GN patients, accompanied by injuries of HK-2 cells and podocytes. HBx markedly upregulated DNMT1 and induced epithelial-mesenchymal transition (EMT) and inflammation in HK-2 cells and human podocytes. This increased DNMT1 expression was attenuated after DNMT1 knockdown, accompanied by restored HK-2 cells and podocyte injuries resulting from the activation of PI3K/Akt/mTOR and nuclear factor-kappa B (NF-κB) pathways. Hypermethylation of the phosphatase and tensin homolog (PTEN) promoter and vitamin D receptor (VDR) was induced in HBx-overexpressing HK-2 cells and podocytes, respectively, whereas DNMT1 knockdown effectively corrected these alterations. Furthermore, PTEN and VDR ablation resulted in marked EMT and inflammation induction in HBx-overexpressing HK-2 cells and human podocytes even with DNMT1 knockdown. Downregulation of the PI3K/Akt/mTOR-related pathway attenuated HBx-induced EMT and inflammation in HK-2 cells. Luciferase reporter assay revealed VDR as a direct target of the Snail family transcriptional repressor 1 (SNAI1) in HBx-overexpressing podocytes. DNA methylation inhibitor 5-azacytidine alleviated urinary protein and renal inflammation in HBV transgenic mice via PTEN-PI3K/Akt signaling and VDR signaling axis.

Conclusions

Our study clarifies the potential epigenetic mechanisms underlying HBx-induced renal injuries in HBV-GN and the renoprotective effects of inhibiting DNMT1, which can provide important insights into the development of treatments for HBV-GN.

Valsartan in Combination with Tripterygium Glycosides Protects against Chronic Nephritis via the Toll-Like Receptor 4 Pathway

Objective. Valsartan has been studied to exert effects on kidney disease. However, the concrete function of valsartan in combination with tripterygium glycosides in chronic nephritis remained largely unknown. The study was designed to unravel the impacts of valsartan and tripterygium glycosides in chronic nephritis through the Toll-like Receptor 4 (TLR4) pathway. Methods. The renal function indicators such as serum creatinine (Scr), blood urea nitrogen (BUN) and β2 microglobulin (β2-MG), 24 h urine protein (Upro) levels, and blood lipid indicators such as total cholesterol (TC), low-density lipoprotein (LDL-C), triacylglycerol (TG) and high-density lipoprotein (HDL-C), inflammatory factors (e.g., IL-1β and IL-8), and the proportion of T lymphocyte subpopulations (CD4+ and CD8+) were detected in chronic nephritis patients before and after treatment with valsartan alone or valsartan combined with tripterygium glycosides. Symptoms of adverse reactions were recorded. TLR4 expression in the patients’ serum was examined. Results. Compared to patients before treatment, after treatment with valsartan alone or valsartan combined with tripterygium glycosides, the renal function indicators Scr, BUN, and 24 h levels were reduced, and TC, TG, and LDL-C levels were reduced, while HDL-C levels were elevated; inflammatory responses (IL-1β and IL-8) were mitigated; CD4+ ratio and CD4+/CD8+ ratio increased yet CD8+ ratio decreased; TLR4 expression was silenced after treatment. All of the changes were more obvious in patients after being treated with valsartan combined with tripterygium glycosides. Conclusion. Valsartan in combination with tripterygium glycosides protects against chronic nephritis via suppressing the Toll-like Receptor 4 pathway.

Adjuvanted recombinant HBV vaccine (HBV-AS04) is effective over extended follow-up in dialysis population. An open-label non randomized trial

BACKGROUND

Patients on regular dialysis show a poor response to hepatitis B vaccine due to uremia. A recombinant HB vaccine (containing an improved adjuvant system AS04, HBV-AS04) has been licensed but the evidence on its efficacy and safety in dialysis population over the long term is extremely limited.

AIM

We have measured antibody (anti-HBs) persistence for up to 72 months in a large cohort of patients on long-term dialysis (with susceptibility to HBV infection) who underwent vaccination with HBV-AS04 vaccine.

METHODS

Patients were prospectively recruited to receive four 20-mcg doses of HBV-AS04 by intramuscular route (deltoid muscle). Two vaccine schedules were adopted: 0,1,2, and 3 month (n=217 patients) and 0,1,2, and 6 month (n=31 patients). Anti-HBs antibody concentrations were tested at 1,2,3, 4, 7 and 12 months and then every year up to 72 months. Multivariate analysis was made to find the baseline parameters that were associated with the immune response to HBV-AS04 vaccine.

RESULTS

Two hundred and seventy-two patients were included and 248 completed the study. At completion of vaccine schedule, the frequency of responders (anti-HBs titers≥10mIU/mL) was 81.5% (202/248) (mean anti-HBs antibody titers, 384.9±391.9mIU/mL), according to per-protocol analysis. On the grounds of univariate analysis, age was lower in responder than non- responder patients to HBV AS04 even if no statistical significance was achieved (P=0.09). The sero-protection rate at month 72 was 77% (7/9) (anti-HBs antibody titers, 184.9±360.1mIU/mL, P=0.001). Multivariate analysis found a relationship between sero-response rate and age (P=0.04). No major side effects and no de novo HBV episodes were observed.

CONCLUSIONS

Our open-label nonrandomized trial performed in a 'real-world' practice showed the persistence of anti-HBs antibody among responder patients over a very long follow-up. Studies with longer observation periods are under way.

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.

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.

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.

Telbivudine attenuates UUO-induced renal fibrosis via TGF-β/Smad and NF-κB signaling

Renal fibrosis yields decreased renal function and is a potent contributor to chronic kidney disease (CKD). Telbivudine (LdT) is an anti-hepatitis B virus (HBV) drug that has been found to steadily improve renal function, but the mechanism of drug action is unclear. One explanation is that LdT impacts inflammatory or fibrotic pathways. In this study, we investigated renal protection by LdT in a rat model of unilateral ureteral obstruction (UUO). UUO rats received oral gavage of LdT (1, 1.5, or 2g/kg/day) for 5weeks. Kidney tissues were examined histopathologically with hematoxylin and eosin and Masson's trichrome stain. To assess proliferation of myofibroblasts and matrix accumulation, α-smooth muscle actin (α-sma) and collagen type I and III were detected. Interleukin-1 (IL-1) and tumor necrosis factor (TNF)-α were evaluated as a measure of proinflammatory cytokines. Transforming growth factor (TGF)-β and nuclear factor-κB (NF-κB) were considered the canonical signaling components in our investigation of the underlying mechanism of LdT action. Histopathology results indicated that LdT ameliorates renal injury and matrix accumulation. Expression of α-sma and collagen I/III as well as key fibrotic signaling factors in the TGF-β/Smad pathway were downregulated. In addition, LdT suppressed the release of IL-1 and TNF-α and decreased the expression of NF-κB by inhibiting toll-like receptor 4. Taken together, these findings indicate that LdT can attenuate renal fibrosis and inflammation via TGF-β/Smad and NF-κB pathways in UUO.

Relationship between genotypes and clinical manifestation, pathology, and cccDNA in Chinese children with hepatitis B virus-associated glomerulonephritis

BACKGROUND

Hepatitis B virus-associated glomerulonephritis (HBV-GN) is one of the extrahepatic manifestations after HBV infection, which would cause great clinical harm to people. The present study was undertaken to investigate the HBV-GN genotypes and its clinical relevance in Chinese children.

METHODS

A total of 41 HBV-infected children diagnosed with HBV-GN were enrolled in the study. All patients underwent liver and kidney biopsy. The genotypes and cccDNA were detected in their serum samples to analyze the relationship between HBV genotypes and clinical characteristics, cccDNA, and pathology.

RESULTS

Among the 41 children with HBV-GN, 29 (70.7%) had genotype C, 10 (24.4%) had genotype B, 2 (4.9%) had genotype B/C, and none of them had genotype non-B/C. Most children had genotypes B or C; moreover, the genotype C was the most frequent one. The incidence of hematuria and albuminuria, reduction in complement C3, increase in serum alanine aminotransferase levels and renal insufficiency in the children with genotype C were significantly higher than those in the children with genotype B (P<0.05); however, there was no statistically significant difference in hypertension and hepatomegaly (P>0.05). The frequency of HBV cccDNA positive in the genotype C group was significantly higher than that in the genotype B group (72.4% vs. 30.0%, P<0.05). No difference was observed in hepatic inflammation grades and stages of fibrosis between the two groups (P>0.05).

CONCLUSIONS

Genotype C was the most frequent genotype in the described group of patients with HBV-GN, and the liver and kidney damage indicators were more likely to occur in patients with genotype C.

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.

Upregulation of toll-like receptor 4 on T cells in PBMCs is associated with disease aggravation of HBV-related acute-on-chronic liver failure

Immune-mediated inflammatory injury is an important feature of the disease aggravation of hepatitis B virus-related acute-on-chronic liver failure (ACLF). Toll-like receptors (TLRs) have been shown previously to play a pivotal role in the activation of innate immunity. The purpose of this study was to characterize the TLR4 expression in peripheral blood mononuclear cells (PBMCs) of ACLF patients and its possible role in the disease aggravation. Twelve healthy subjects, 15 chronic HBV-infected (CHB) patients and 15 ACLF patients were enrolled in this study. The TLR4 expression in PBMCs and T cells of all subjects was examined by real-time PCR and flow cytometry. The correlation of TLR4 expression on T cells with the markers of disease aggravation was evaluated in ACLF patients. The ability of TLR4 ligands stimulation to induce inflammatory cytokine production in ACLF patients was analyzed by flow cytometry. The results showed that TLR4 mRNA level was upregulated in PBMCs of ACLF patients compared to that in the healthy subjects and the CHB patients. Specifically, the expression of TLR4 on CD4(+) and CD8(+) T cells of PBMCs was significantly increased in ACLF patients. The TLR4 levels on CD4(+) and CD8(+) T cells were positively correlated with serum total bilirubin (TBIL), direct bilirubin (DBIL), international normalized ratio (INR) levels and white blood cells (WBCs), and negatively correlated with serum albumin (ALB) levels in the HBV-infected patients, indicating TLR4 pathway may play a role in the disease aggravation of ACLF. In vitro TLR4 ligand stimulation on PBMCs of ACLF patients induced a strong TNF-α production by CD4(+) T cells, which was also positively correlated with the serum markers for liver injury severity. It was concluded that TLR4 expression is upregulated on T cells in PBMCs, which is associated with the aggravation of ACLF.

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.

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.

Toll-like receptor 4 and hepatitis B infection: molecular mechanisms and pathogenesis

Hepatitis B virus (HBV) infection mainly causes liver disease, including inflammation, cirrhosis, and hepatocellular carcinoma (HCC). It has been documented that prolonged hepatitis B-infected patients are unable to clear HBV from hepatocytes completely. Previous investigations have suggested that various genetic and immunologic parameters may be responsible for the induction of prolonged infection forms. Toll-like receptors (TLRs), as members of pathogen recognition receptors (PRRs), play critical roles in the recognition of viruses and the induction of appropriate immune responses. Thus, TLRs may be considered as essential sensors for the recognition of HBV and the induction of immune responses against this virus. It has been documented that TLR4 plays key roles in the detection of several microbial pathogen-associated molecular pattern molecules, including bacterial lipopolysaccharide (LPS), as well as endogenous ligands (damage-associated molecular pattern molecules) and subsequently activates pro-inflammatory transcription factors in either MYD88 or TRIF dependent pathways. Previous investigations have proposed that TLR4 might be involved in appropriate immune responses against HBV. Therefore, the aim of this review is to present the recent data regarding the important roles of TLR4 in HBV recognition and regulation of immune responses against this virus, and also its roles in the pathogenesis of cirrhosis and HCC as complications of prolonged hepatitis B infections.