Expression profile of BAFF in peripheral blood from patients of IgA nephropathy: Correlation with clinical features and Streptococcus pyogenes infection

Serum BAFF levels are associated with the prognosis of idiopathic membranous nephropathy

OBJECTIVE

High serum levels of B-cell activation factor (BAFF) and a proliferation-inducing ligand (APRIL) have been observed in patients with idiopathic membranous nephropathy (iMN); however, their relationships with disease severity and progression remain unclear.

METHODS

Patients with iMN diagnosed via renal biopsy were enrolled in this study. The concentrations of BAFF and APRIL were determined using ELISA kits. Proteinuria remission, including complete remission (CR) and partial remission (PR), and renal function deterioration were defined as clinical events. The Cox proportional hazards method was used to analyze the relationship between cytokine levels and disease progression.

RESULTS

Seventy iMN patients were enrolled in this study, with a median follow-up time of 24 months (range 6-72 months). The serum levels of BAFF and APRIL were higher in iMN patients than in healthy controls but lower than those in minimal change disease (MCD) patients. The serum BAFF level was positively correlated with the serum APRIL level, serum anti-phospholipase A2 receptor (anti-PLA2R) antibody level, and 24-h proteinuria and negatively correlated with the serum albumin (ALB) level. However, no significant correlation was observed between the serum APRIL level and clinical parameters. According to the multivariate Cox proportional hazards regression model adjusted for sex, age, systolic blood pressure (SBP), estimated glomerular filtration rate (eGFR), immunosuppressive agent use, 24-h proteinuria, APRIL level, and anti-PLA2R antibody, only the serum BAFF level was identified as an independent predictor of PR (HR, 0.613; 95% CI, 0.405-0.927; p = 0.021) and CR of proteinuria (HR, 0.362; 95% CI, 0.202-0.648; p < 0.001).

CONCLUSIONS

A high serum BAFF level is associated with severe clinical manifestations and poor disease progression in patients with iMN.

Transcriptome Analysis of BAFF/BAFF-R System in Murine Nephrotoxic Serum Nephritis

Chronic kidney disease (CKD) is an emerging cause for morbidity and mortality worldwide. Acute kidney injury (AKI) can transition to CKD and finally to end-stage renal disease (ESRD). Targeted treatment is still unavailable. NF-κB signaling is associated with CKD and activated by B cell activating factor (BAFF) via BAFF-R binding. In turn, renal tubular epithelial cells (TECs) are critical for the progression of fibrosis and producing BAFF. Therefore, the direct involvement of the BAFF/BAFF-R system to the pathogenesis of CKD is conceivable. We performed non-accelerated nephrotoxic serum nephritis (NTN) as the CKD model in BAFF KO (B6.129S2-Tnfsf13btm1Msc/J), BAFF-R KO (B6(Cg)-Tnfrsf13ctm1Mass/J) and wildtype (C57BL/6J) mice to analyze the BAFF/BAFF-R system in anti-glomerular basement membrane (GBM) disease using high throughput RNA sequencing. We found that BAFF signaling is directly involved in the upregulation of collagen III as BAFF ko mice showed a reduced expression. However, these effects were not mediated via BAFF-R. We identified several upregulated genes that could explain the effects of BAFF in chronic kidney injury such as Txnip, Gpx3, Igfbp7, Ccn2, Kap, Umod and Ren1. Thus, we conclude that targeted treatment with anti-BAFF drugs such as belimumab may reduce chronic kidney damage. Furthermore, upregulated genes may be useful prognostic CKD biomarkers.

Decrypting the Pathological Pathways in IgA Nephropathy

IgAN is the most common form of glomerulonephritis affecting 2000000 people annually. The disease ultimately progresses to chronic renal failure and ESRD. In this article, we focused on a comprehensive understanding of the pathogenesis of the disease and thus identifying different target proteins that could be essential in therapeutic approaches in the management of the disease. Aberrantly glycosylated IgA1 produced by the suppression of the enzyme β-1, 3 galactosyltransferase ultimately triggered the formation of IgG autoantibodies which form complexes with Gd-IgA1. The complex gets circulated through the blood vessels through monocytes and ultimately gets deposited in the glomerular mesangial cells via CD71 receptors present locally. This complex triggers the inflammatory pathways activating the alternate complement system, various types of T Cells, toll-like receptors, cytokines, and chemokines ultimately recruiting the phagocytic cells to eliminate the Gd-IgA complex. The inflammatory proteins cause severe mesangial and podocyte damage in the kidney which ultimately initiates the repair process following chronic inflammation by an important protein named TGFβ1. TGF β1 is an important protein produced during chronic inflammation mediating the repair process via various downstream transduction proteins and ultimately producing fibrotic proteins which help in the repair process but permanently damage the glomerular cells.

New-onset IgA nephropathy following COVID-19 vaccination

Coronavirus disease 2019 (COVID-19) pandemic, caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has caused significant economic and health damage worldwide. Rapid vaccination is one of the key strategies to curb severe illness and death due to SARS-CoV-2 infection. Hundreds of millions of people worldwide have received various COVID-19 vaccines, including mRNA vaccines, inactivated vaccines and adenovirus-vectored vaccines, but the side effects and efficacy of most vaccines have not been extensively studied. Recently, there have been increasing reports of immunoglobulin A nephropathy (IgAN) after COVID-19 vaccination, however, whether their relationship is causal or coincidental remains to be verified. Here, we summarize the latest clinical evidence of IgAN diagnosed by renal biopsy associated with the COVID-19 vaccine published by 10 July 2022 with the largest sample size, and propose a hypothesis for the pathogenesis between them. At the same time, the new opportunity presented by COVID-19 vaccine allows us to explore the mechanism of IgAN recurrence for the first time. Indeed, we recognize that large-scale COVID-19 vaccination has enormous benefits in preventing COVID-19 morbidity and mortality. The purpose of this review is to help guide the clinical assessment and management of IgA nephropathy post-COVID-19 vaccination and to enrich the 'multi-hit' theory of IgA nephropathy.

The Gut and Kidney Crosstalk in Immunoglobulin A Nephropathy

Immunoglobulin A nephropathy(IgAN) is the most common primary glomerulonephritis worldwide. The working model for the pathogenesis of IgAN involves a multistep process starting from the production of galactose-deficient and polymeric immunoglobulin A-1 (gd-IgA1) that enters systemic circulation from gut-associated lymphoid tissue (GALT). Galactose-deficient IgA are targeted by endogenous IgG, leading to the formation of circulating immune complexes that deposit in the mesangium and resulting in glomerular inflammation. Disease onset and relapses are often associated with gut infections, supporting the hypothesis that the gut plays an important pathogenic role. In the presence of microbial pathogens or food antigens, activated dendritic cells in the gut mucosa induce T cell dependent and independent B cell differentiation into IgA secreting plasma cells. In IgAN patients, this promotes the systemic release of mucosal gd-IgA1. Not all bacterial strains have the same capacity to elicit IgA production, and little is known about the antigen specificity of the pathogenic gd-IgA1. However, efficacy of treatments targeting gut inflammation support a pathogenic link between the bowel immune system and IgAN. Herein, we review the evidence supporting the role of gut inflammation in IgAN pathogenesis.

Interleukin-33 Exacerbates IgA Glomerulonephritis in Transgenic Mice Overexpressing B Cell Activating Factor

BACKGROUND

The cytokine IL-33 is an activator of innate lymphoid cells 2 (ILC2s) in innate immunity and allergic inflammation. B cell activating factor (BAFF) plays a central role in B cell proliferation and differentiation, and high levels of this protein cause excess antibody production, including IgA. BAFF-transgenic mice overexpress BAFF and spontaneously develop glomerulonephritis that resembles human IgA nephropathy.

METHODS

We administered IL-33 or PBS to wild-type and BAFF-transgenic mice. After treating Rag1-deficient mice with IL-33, with or without anti-CD90.2 to preferentially deplete ILC2s, we isolated splenocytes, which were adoptively transferred into BAFF-transgenic mice.

RESULTS

BAFF-transgenic mice treated with IL-33 developed more severe kidney dysfunction and proteinuria, glomerular sclerosis, tubulointerstitial damage, and glomerular deposition of IgA and C3. Compared with wild-type mice, BAFF-transgenic mice exhibited increases of CD19⁺ B cells in spleen and kidney and ILC2s in kidney and intestine, which were further increased by administration of IL-33. Administering IL-33 to wild-type mice had no effect on kidney function or histology, nor did it alter the number of ILC2s in spleen, kidney, or intestine. To understand the role of ILC2s, splenocytes were transferred from IL-33-treated Rag1-deficient mice into BAFF-transgenic mice. Glomerulonephritis and IgA deposition were exacerbated by transfer of IL-33-stimulated Rag1-deficient splenocytes, but not by ILC2 (anti-CD90.2)-depleted splenocytes. Wild-type mice infused with IL-33-treated Rag1-deficient splenocytes showed no change in kidney function or ILC2 numbers or distribution.

CONCLUSIONS

IL-33-expanded ILC2s exacerbated IgA glomerulonephritis in a mouse model. These findings indicate that IL-33 and ILC2s warrant evaluation as possible mediators of human IgA nephropathy.

Single-cell RNA-sequencing reveals distinct immune cell subsets and signaling pathways in IgA nephropathy

BACKGROUND

IgA nephropathy (IgAN) is the most common primary glomerulonephritis globally. Increasing evidence suggests the importance of host immunity in the development of IgAN, but its dynamics during the early stage of IgAN are still largely unclear.

RESULTS

Here we successfully resolved the early transcriptomic changes in immune cells of IgAN by conducting single-cell RNA-sequencing (scRNA-seq) with peripheral blood mononuclear cells. The differentially expressed genes (DEGs) between control and IgAN were predominantly enriched in NK cell-mediated cytotoxicity and cell killing pathways. Interestingly, we discovered that the number and cytotoxicity of NK cells are significantly reduced in IgAN patients, where both the number and marker genes of NK cells were negatively associated with the clinical parameters, including the levels of urine protein creatinine ratio (UPCR), serum galactose-deficient IgA1 and IgA. A distinctive B cell subset, which had suppressed NFκB signaling was predominantly in IgAN and positively associated with disease progression. Moreover, the DEGs of B cells were enriched in different viral infection pathways. Classical monocytes also significantly changed in IgAN and a monocyte subset expressing interferon-induced genes was positively associated with the clinical severity of IgAN. Finally, we identified vast dynamics in intercellular communications in IgAN.

CONCLUSIONS

We dissected the immune landscape of IgAN at the single-cell resolution, which provides new insights in developing novel biomarkers and immunotherapy against glomerulonephritis.

Fecal Microbiota Transplantation Modulates Renal Phenotype in the Humanized Mouse Model of IgA Nephropathy

Immunoglobulin A nephropathy (IgAN) is the most common primary glomerulonephritis. Several observations suggest that gut microbiota could be implicated in IgAN pathophysiology. Aiming at exploring whether microbiota modulation is able to influence disease outcome, we performed fecal microbiota transplantation (FMT) from healthy controls (HC-sbjs), non-progressor (NP-pts) and progressor (P-pts) IgAN patients to antibiotic-treated humanized IgAN mice (α1KI-CD89Tg), by oral gavage. FMT was able to modulate renal phenotype and inflammation. On one hand, the microbiota from P-pts was able to induce an increase of serum BAFF and galactose deficient-IgA1 levels and a decrease of CD89 cell surface expression on blood CD11b⁺ cells which was associated with soluble CD89 and IgA1 mesangial deposits. On the other hand, the microbiota from HC-sbjs was able to induce a reduction of albuminuria immediately after gavage, an increased cell surface expression of CD89 on blood CD11b⁺ cells and a decreased expression of KC chemokine in kidney. Higher serum BAFF levels were found in mice subjected to FMT from IgAN patients. The main bacterial phyla composition and volatile organic compounds profile significantly differed in mouse gut microbiota. Microbiota modulation by FMT influences IgAN phenotype opening new avenues for therapeutic approaches in IgAN.

Is complement the main accomplice in IgA nephropathy? From initial observations to potential complement-targeted therapies

IgA Nephropathy (IgAN) is the main cause of primary glomerulonephritis, globally. This disease is associated with a wide range of clinical presentations, variable prognosis and a spectrum of histological findings. More than fifty years after its first description, this heterogeneity continues to complicate efforts to understand the pathogenesis. Nevertheless, involvement of the complement system in IgAN was identified early on. Dysfunction of the immunoglobulin A (IgA) system, the principal offender in this disease, including modification of isoforms and glycoforms of IgA1, the nature of immune complexes and autoantibodies to galactose deficient IgA1 might all be responsible for complement activation in IgAN. However, the specific mechanisms engaging complement are still under examination. Research in this domain should allow for identification of patients that may benefit from complement-targeted therapy, in the foreseeable future.

Role of the intestinal MALT in pathogenesis of the IgA-nephropathy

Modern view on pathogenesis of immunoglobulin (Ig)A-nephropathy and possible relation to intestinal MALT-system activity is presented in the article. Aberrant glycosylation of IgA and increased association of IgA-nephropathy with intestinal diseases or abnormal intestinal permeability are discussed in details. Based on supposed entero-renal pathogenesis of the disease future treatment modalities are considered. Relevant worlds literature is cited.

BAFF signaling drives interstitial transformation of mouse renal tubular epithelial cells in a Pin1-dependent manner

Aberrant expression of B cell–activating factor belonging to TNF superfamily (BAFF) and its receptors results in abnormal biological activities in hematopoietic and non-hematopoietic cells and is closely associated with the occurrence and development of various diseases. However, the biological significance and potential mechanisms underlying BAFF signaling in renal tubular epithelial cells (RTECs) remain unknown. This study aimed to investigate the biological role of BAFF signaling in RTECs. Mice primary RTECs were applied. The proliferation status and apoptotic rates were examined by MTS assay and flow cytometry, respectively. The expression of BAFF and its receptors was analyzed via flow cytometry and sodium ion transport function, and cytokeratin-18 expression was detected through immunofluorescence staining. In addition, Pin1 was knocked down via siRNA and its expression was assessed through reverse transcription PCR. Lastly, western blotting was performed to analyze E-cadherin, ɑ-SMA, and Pin1 expression. Results suggested that BAFF-R was significantly upregulated upon IFN-γ stimulation, and enhancement of BAFF signaling promoted cell survival and reduced their apoptotic rate, while simultaneously reducing the epithelial phenotype and promoting the interstitial transformation of cells. Furthermore, Pin1 was significantly increased, along with the upregulation of BAFF signaling in the RTECs, and participated in interstitial transformation induced by BAFF signaling. Collectively, the present results elucidate the potential mechanism of loss of normal function of RTECs under long-term high dose of BAFF stimulation provides a potential therapeutic target for renal interstitial fibrosis, and underlining mechanisms of shortening of long-term outcomes of kidney allografts via augmenting of BAFF signaling.

Comprehensive analysis of IgA nephropathy expression profiles: identification of potential biomarkers and therapeutic agents

Background

IgA nephropathy (IgAN) is a kidney disease recognized by the presence of IgA antibody depositions in kidneys. The underlying mechanisms of this complicated disease are remained to be explored and still, there is an urgent need for the discovery of noninvasive biomarkers for its diagnosis. In this investigation, an integrative approach was applied to mRNA and miRNA expression profiles in PBMCs to discover a gene signature and novel potential targets/biomarkers in IgAN.

Methods

Datasets were selected from gene expression omnibus database. After quality control checking, two datasets were analyzed by Limma to identify differentially expressed genes/miRNAs (DEGs and DEmiRs). Following identification of DEmiR-target genes and data integration, intersecting mRNAs were subjected to different bioinformatic analyses. The intersecting mRNAs, DEmiRs, related transcription factors (from TRRUST database), and long-non coding RNAs (from LncTarD database) were used for the construction of a multilayer regulatory network via Cytoscape.

Result

“GSE25590” (miRNA) and “GSE73953” (mRNA) datasets were analyzed and after integration, 628 intersecting mRNAs were identified. The mRNAs were mainly associated with “Innate immune system”, “Apoptosis”, as well as “NGF signaling” pathways. A multilayer regulatory network was constructed and several hub-DEGs (Tp53, STAT3, Jun, etc.), DEmiRs (miR-124, let-7b, etc.), TFs (NF-kB, etc.), and lncRNAs (HOTAIR, etc.) were introduced as potential factors in the pathogenesis of IgAN.

Conclusion

Integration of two different expression datasets and construction of a multilayer regulatory network not only provided a deeper insight into the pathogenesis of IgAN, but also introduced several key molecules as potential therapeutic target/non-invasive biomarkers.

B cell and monocyte phenotyping: A quick asset to investigate the immune status in patients with IgA nephropathy

Background

IgA nephropathy (IgAN) advances from multiple pathogenic “hits” resulting in poorly O-galactosylated IgA1 glycoforms (Gd-IgA1), production of antibodies and glomerular deposition of immune complexes. A sequence of immune responses arising from plasma cells, T cells and antigen presenting cells (APCs), causes glomerular injury. This study was designed to phenotype subsets of B cells, monocytes and T cells in the peripheral circulation and their association with inflammatory cytokines and kidney function in patients with IgAN, healthy controls (HC) and disease controls with autosomal dominant polycystic kidney disease (ADPKD).

Methods

Patients with IgAN (n = 13), median estimated glomerular filtration rate (eGFR) of 57 ml/min/1.73m² (IQR 42–84), patients with ADPKD (n = 13) matched for kidney function, gender and age and gender and age-matched HC (n = 13) were recruited. CD3+ and CD3- peripheral blood mononuclear cells were isolated and profiled based on their specific surface markers for different subsets of monocytes, B and T cells and analyzed by flow cytometry. Cytokines were analyzed by ELISA.

Results

We observed a significant decrease in the proportion of pre-switched B cells and plasmablasts, but an increase in long-lived plasma cells in the peripheral circulation of IgAN patients compared to HC. The proportion of non-classical monocytes was significantly higher in IgAN patients compared to both HC and ADPKD. We also report an association between sCD40L levels and the proportion of pre-switched B cells, as well as sCD40L and MCP-1 levels and albuminuria in IgAN patients.

Conclusions

We applied an easy-access method to analyze subsets of immune cells as well as relevant inflammatory mediators in IgAN patients. Our data demonstrate an altered B cell profile that indicates a pathophysiological role of the B cell lineage and an increased proportion of non-classical monocytes that suggests their role in the disease process.

microRNA-630 Regulates Underglycosylated IgA1 Production in the Tonsils by Targeting TLR4 in IgA Nephropathy

IgA nephropathy (IgAN) is the most common primary glomerular disease. The characteristic pathology involves immune complexes formed by the deposition of IgA1 and underglycosylated IgA1 aggregates in the mesangial area, which may be accompanied by the deposition of IgG and/or IgM and complement components. However, the molecular mechanisms of IgAN remain unclear. In the present study, microarray analysis showed that the expression of microRNA-630 (miR-630) was significantly reduced in palatal tonsils from IgAN patients compared with chronic tonsillitis. Additionally, bioinformatic analysis showed that Toll-like receptor 4 (TLR4) was the predicted target gene of miR-630 and was regulated by miR-630. When miR-630 was overexpressed in palatal tonsil mononuclear cells from IgAN patients, the expression of TLR4 was reduced and the content of IgA1 in the cell culture supernatant was decreased, and the level of galactosylation in the IgA1 hinge region was increased. Moreover, immunohistochemical analysis showed that the expression of TLR4 in IgAN patients was significantly increased. After knocking down the expression of TLR4, both the concentration of IgA1 and the binding force of IgA1 with broad bean lectin were significantly reduced in IgAN. Furthermore, the mechanism study demonstrated that TLR4 might regulate the expression of IL-1β and IL-8 through NF-κB signaling pathway to modulate the concentration of IgA1 and the glycosylation level of IgA1. This interesting finding may offer new insight into the molecular mechanism of IgAN.

TLR7 in B cells promotes renal inflammation and Gd-IgA1 synthesis in IgA nephropathy

TLR7 has been linked to the pathogenesis of glomerulonephritis, but its precise roles are not clear. In this study, we evaluated the roles of TLR7 in IgA nephropathy (IgAN). TLR7 proteins were abundant in CD19+ B cells infiltrated in the kidneys of patients with IgAN. The intensities of both intrarenal TLR7 and CD19 proteins were closely associated with kidney function (estimated glomerular filtration rate [eGFR] and serum creatinine concentration) and renal histopathology (tubular atrophy, leukocyte infiltration, tubulointerstitial fibrosis, and global glomerulosclerosis) in patients with IgAN. Meanwhile, TLR7 mRNA levels were significantly increased in peripheral blood B cells of patients with IgAN. TLR7+CD19+ B cells expressed inflammatory cytokines (IL-6 and IL-12) in kidneys and produced high levels of IgA1 and galactose deficient-IgA1 (Gd-IgA1) in peripheral blood of patients with IgAN. Mechanistically, TLR7 activated B cells to produce high levels of Gd-IgA1 via the TLR7-GALNT2 axis in IgAN. Protein levels of GALNT2 were increased by overexpression of TLR7, while they were reduced by TLR7 knockdown in B cells. GALNT2 overexpression augmented Gd-IgA1 production in B cells derived from patients with IgAN. Taken together, high TLR7 expression in B cells has dual roles in the development and progression of IgAN, by facilitating renal inflammation and Gd-IgA1 antibody synthesis.

The Role of Immune Modulation in Pathogenesis of IgA Nephropathy

IgA nephropathy (IgAN) is the most prevalent primary glomerulonephritis worldwide, with diverse clinical manifestations characterized by recurrent gross hematuria or microscopic hematuria, and pathological changes featuring poorly O-galactosylated IgA1 deposition in the glomerular mesangium. Pathogenesis has always been the focus of IgAN studies. After 50 years of research, most scholars agree that IgAN is a group of clinicopathological syndromes with certain common immunopathological characteristics, and multiple mechanisms are involved in its pathogenesis, including immunology, genetics, and environmental or nutritional factors. However, the precise pathogenetic mechanisms have not been fully determined. One hypothesis about the pathogenesis of IgAN suggests that immunological factors are engaged in all aspects of IgAN development and play a critical role. A variety of immune cells (e.g., dendritic cells, NK cells, macrophages, T-lymphocyte subsets, and B-lymphocytes, etc.) and molecules (e.g., IgA receptors, Toll-like receptors, complements, etc.) in innate and adaptive immunity are involved in the pathogenesis of IgAN. Moreover, the abnormality of mucosal immune regulation is the core of IgAN immunopathogenesis. The roles of tonsil immunity or intestinal mucosal immunity, which have received more attention in recent years, are supported by mounting evidence. In this review, we will explore the latest research insights on the role of immune modulation in the pathogenesis of IgAN. With a better understanding of immunopathogenesis of IgAN, emerging therapies will soon become realized.

BAFF is involved in the pathogenesis of IgA nephropathy by activating the TRAF6/NF‑κB signaling pathway in glomerular mesangial cells

The aim of the present study was to investigate the involvement of B cell-activating factor (BAFF) in the pathogenesis of IgA nephropathy by activating the tumor necrosis factor receptor-associated factor 6 (TRAF6)/NF-κB signaling pathway in glomerular mesangial cells. For the clinical analysis, blood, urine and kidney tissue samples were collected from 58 patients diagnosed with primary IgA nephropathy by renal biopsy. For the in vitro study, glomerular mesangial cells were divided into five groups: Control (con)-short hairpin RNA (shRNA) (control group); con-shRNA + BAFF (20 ng/ml); con-shRNA + BAFF + BAFF-RFc chimera protein (500 µg/ml); TRAF6-shRNA; and TRAF6-shRNA + BAFF (20 ng/ml). For the in vivo experiments, 60 Sprague-Dawley rats were randomly divided into four groups: Con-small interfering RNA (siRNA) (control group); con-siRNA + IgA (IgA nephropathy group), BAFF-RFc chimera protein (2 µg/ml) + IgA, and TRAF6-siRNA (0.2 µM) + IgA. Reverse transcription-quantitative PCR was performed to evaluate the mRNA expression levels of TRAF6, connective tissue growth factor (CTGF), fibronectin (FN) and NF-κBP65. Western blot analysis was used to detect the protein expression levels of TRAF6, FN, CTGF and phosphorylated-NF-κBP65 in glomerular mesangial cells and kidney tissues. The results revealed that plasma BAFF levels were positively correlated with the severity of pathological damage in patients with IgA nephropathy. In vitro, BAFF induced the mRNA and protein expression of TRAF6, CTGF, FN and NF-κBP65 in glomerular mesangial cells. After the BAFF-RFc chimera protein was added to inhibit the binding of BAFF and BAFF-receptor (-R), this effect was reduced. In vivo, inhibition of the effects of BAFF via injection with the BAFF-R Fc chimera protein reduced kidney damage in rats suffering from IgA nephropathy. The effect on the expression of signaling pathway-associated proteins was also alleviated. In conclusion, BAFF enhanced the expression of fibroblast factors in the kidneys by activating the TRAF6/NF-κB signaling pathway.

Serum Levels of BAFF and APRIL Predict Clinical Response in Anti-PLA2R-Positive Primary Membranous Nephropathy

Primary membranous nephropathy (PMN) is a renal-specific autoimmune disease caused by circulating autoantibodies that target glomerular podocyte antigens (PLA2R/THSD7A). However, very little is known on the molecular mechanisms controlling B cell response in this nephropathy. The present study was aimed at correlating the serum levels of B cell activators BAFF/BLyS and APRIL with the presence of anti-PLA2R antibodies in PMN patients and with long-term clinical outcome. To this aim, 51 patients with anti-PLA2R-positive biopsy-proven PMN and nephrotic range proteinuria (>3.5 g/24 hours) were enrolled between January 2009 and December 2015 and treated with conventional 6-month immunosuppressive therapy. After 6 months, 29 patients (56.9%) cleared circulating anti-PLA2R, while in remaining 22 (43.1%), they persisted. Intriguingly, in the first group, baseline serum levels of BAFF/BLyS and APRIL were significantly lower than those in the second one. Moreover, after 6 months of immunosuppressive therapy, an overall reduction in both cytokine serum levels was observed. However, in PMN patients with anti-PLA2R clearance, this reduction was more prominent, as compared with those with anti-PLA2R persistence. When related to clinical outcome, lower baseline BAFF/BLyS (<6.05 ng/mL) and APRIL (<4.20 ng/mL) serum levels were associated with significantly higher probability to achieve complete or partial remission after 24-month follow-up. After dividing the entire study cohort into three groups depending on both cytokine baseline serum levels, patients with both BAFF/BLyS and APRIL below the cut-off showed a significantly higher rate of complete or partial remission as compared with patients with only one cytokine above the cut-off, while the composite endpoint was achieved in a very low rate of patients with both cytokines above the cut-off. Taken together, these results provide new insights into the role of BAFF/BLyS and APRIL in both the pathogenesis of anti-PLA2R-positive PMN and the response to immunosuppressive therapy.

Elevated hsa-miR-590-3p expression down-regulates HMGB2 expression and contributes to the severity of IgA nephropathy

Peripheral blood mononuclear cells (PBMCs) play important roles in the pathogenesis of IgA nephropathy (IgAN). Our study aimed to provide a deep understanding of IgAN and focused on the dysregulation of hsa‐miR‐590‐3p and its target gene HMGB2 in PBMCs. Three gene expression profile datasets (GSE14795, GSE73953 and GSE25590) were downloaded from the GEO database. The DEGs (differentially expressed genes)‐miRNA network that was associated with IgAN was constructed by Cytoscape, and HMGB2 and hsa‐miR‐590‐3p were selected for further exploration. The dual‐luciferase reporter system was utilized to verify their interaction. Then, the expression levels of HMGB2 and hsa‐miR‐590‐3p in PBMCs were detected by qPCR in another cohort, and the correlation of their expression levels with the clinical pathological manifestations and serum Gd‐IgA1(galactose‐deficient IgA1) levels was also investigated. HMGB2 was identified as the target gene of hsa‐miR‐590‐3p. Furtherly, the elderly patients had higher HMGB2 expression levels than the expression levels of the younger patients. As the serum creatinine, serum BUN levels increased, the expression of HMGB2 decreased; Besides, the HMGB2 expression was positively correlated with serum complement 3(C3) levels, and it also had a negative correlation with the diastolic blood pressure, but not reach statistical significance. What is more, both hsa‐miR‐590‐3p and HMGB2 expression had a slight correlation tendency with serum Gd‐IgA1 levels in the whole population. In conclusion, HMGB2, the target gene of hsa‐miR‐590‐3p, was identified to correlate with the severity of IgAN, and this provides more clues for the pathogenesis of IgAN.

Treatment of IgA nephropathy: Recent advances and prospects

IgA nephropathy, identified 50 years ago in France, is the most frequent glomerular disease worldwide. The course is variable, but in most of the cases there is a relentless decline in renal function, reaching end-stage renal failure in 10-60% of the cases after 10 years and in 40% after 20 years. These data justify the interest for finding a suitable therapeutic approach particularly in progressive cases. A supportive care, including renin-angiotensin system inhibitors is the priority in cases with slowly declining renal function, particularly when developing proteinuria. The recent supportive versus immunosuppressive therapy for the treatment of progressive IgA nephropathy (STOP-IgAN) randomized and controlled trial has further stressed the benefit of a strict supportive care including also life-style changes, protein and salt restriction. However, there is clear evidence from observational studies (including the European Validation Study of the Oxford Classification of IgA nephropathy [VALIGA]) and a new randomized and controlled trial (Therapeutic Evaluation of Steroids in IgA Nephropathy Global [TESTING]) of additional benefits of corticosteroid treatment in patients with proteinuric IgA nephropathy. However, the present treatment schedules carry severe side effects, mostly infectious complications, which indicate the need for less toxic interventions. The recent focus on the role of gut-kidney axis in IgA nephropathy has led to the search of corticosteroid formulations targeting the intestinal mucosal immune system (gut-associated lymphoid tissue). The NEFIGAN trial obtained interesting results in terms of reduction of proteinuria and stabilization of renal function using a budesonide formulation allowing a selective drug delivery at intestinal gut-associated lymphoid tissue sites. The adverse events, particularly infections, were found to be not clinically relevant. The possibility of a personalized approach to the treatment according to the renal biopsy lesions (Oxford MEST score) is supported by several uncontrolled studies and deserves great attention in the next future. New treatments options for IgA nephropathy include drugs targeting BAFF, a B-cell factor crucial for IgA synthesis or targeting the complement system, and also the possibility of acting directly on the deposited IgA by selective protease digestion.

BAFF and APRIL expression as an autoimmune signature of membranous nephropathy

Background

Based on the fact that B-cell activating factor (BAFF) and a proliferation-inducing ligand (APRIL) have a regulatory role in B cell biology, excessive levels of these cytokines can promote autoimmune pathogenesis. However, the expression and implication remain unresolved in cases of membranous nephropathy (MN).

Results

The plasma BAFF levels of the primary MN patients were higher than those of healthy controls but lower than those of secondary MN patients, whereas the APRIL levels were similar between the MN patients and healthy controls. The BAFF levels were higher in relapse cases, whereas the APRIL levels were higher in the patients who did not experience remission compared with the counterpart patients. The ectopic expression of BAFF and APRIL was observed in the glomeruli or circulating B cells of MN patients, and this high expression trend was similar to that of lupus patients.

Conclusions

Expression profile of BAFF and APRIL in MN is similar to that of other autoimmune disease, which affects the kidney outcomes.

Methods

Plasma BAFF and APRIL levels were measured upon kidney biopsy in patients with primary (n = 89) and secondary MN (n = 13), and the results were compared with the levels in healthy controls (n = 111). The kidney outcomes (e.g., remission and relapse) were traced for the median of 3 years. Aberrant expression of the cytokines was evaluated in the kidney and circulating B cells using immunohistochemistry and flow cytometry analyses, respectively.