Efficacy and safety of rituximab in patients with PLA2R associated membranous nephropathy and resolved HCV infection.

Rituximab occasionally induces reactivation of hepatitis C virus (HCV) in patients with resolved HCV infection, sometimes with fatal consequences. As rituximab has become one of the first-line therapies for the treatment of phospholipase A2 receptor (PLA2R)-associated membranous nephropathy (MN) and is more widely used, there is a lack of studies reporting the effectiveness and safety of rituximab in patients with PLA2R-associated MN and resolved HCV infection. A single-center retrospective study was conducted on PLA2R-associated membranous nephropathy (MN) patients who were HCVAb positive but HCV-RNA negative and treated with rituximab. A total of 598 adult patients with PLA2R-associated MN who underwent rituximab therapy were screened. General clinical information, including gender, age, pathological data, and previous treatment plans, was collected from medical records. Routine blood tests, liver and kidney function assessments, blood lipid profiles, 24-h urine protein levels, anti-PLA2R antibody titers, circulating B-cell counts, and HCV viral loads were measured at the time of rituximab infusion and repeated at intervals of 1-3 months post-rituximab administration. A total of 8 patients were enrolled, with a median follow-up period of 19.00 (range: 16.00-25.25) months. Among the 8 patients, 5 were male, and the mean age was 50.13 ± 4.29 years. Histological findings indicated that tubuloreticular inclusions, mesangial deposits, intramembranous deposits, and subendothelial deposits were not observed in any of the 8 patients. The overall 1-year remission rate for these patients was 75%, accompanied by a significant reduction in proteinuria. Additionally, blood albumin levels increased significantly, and renal function remained stable. No increase in HCV viral load and stable liver function tests were observed throughout the entire follow-up period. This study suggested that on the basis of successful eradication of HCV virus with antiviral drugs, rituximab can effectively induce clinical remission of patients with PLA2R associated MN and resolved HCV infection, and does not lead to a significant increase in HCV virus load. However, this finding is based on a very small sample size and should be confirmed in larger clinical trials.

The fate of immune complexes in membranous nephropathy.

The most characteristic feature of membranous nephropathy (MN) is the presence of subepithelial electron dense deposits and the consequential thickening of the glomerular basement membrane. There have been great advances in the understanding of the destiny of immune complexes in MN by the benefit of experimental models represented by Heymann nephritis. Subepithelial immune complexes are formed in situ by autoantibodies targeting native autoantigens or exogenous planted antigens such as the phospholipase A2 receptor (PLA2R) and cationic BSA respectively. The nascent immune complexes would not be pathogenic until they develop into immune deposits. Podocytes are the major source of autoantigens in idiopathic membranous nephropathy. They also participate in the modulation and removal of the immune complexes to a large extent. The balance between deposition and clearance is regulated by a wide range of factors such as the composition and physicochemical properties of the immune complexes and the complement system. Complement components such as C3 and C1q have been reported to be precipitated with the deposits whereas a complement regulatory protein CR1 expressed by podocytes is involved in the phagocytosis of immune complexes by podocytes. Podocytes regulate the dynamic change of immune complexes which is disturbed in membranous nephropathy. To elucidate the precise fate of the immune complexes is essential for developing more rational and novel therapies for membranous nephropathy.

[Comparison of efficacy and safety of immunosuppressive therapy and rituximab targeting therapy in idiopathic membranous nephropathy].

Objective To assess the efficacy and safety of three treatment modalities (rituximab targeted B-cell therapy, calcium-phosphate inhibitor in conjunction with low-dose corticosteroids, and full-dose corticosteroids combined with cyclophosphamide) for patients at intermediate or high risk of idiopathic membranous nephropathy (IMN) and to analyze the factors impacting the remission rates of IMN. Methods A retrospective cohort study was conducted to analyze patients diagnosed with IMN in our nephrology department via renal biopsy, identifying a total of 148 patients at intermediate or high risk. These patients were categorized into three treatment groups: a RTX group with 60 patients receiving rituximab, a CNI group with 42 patients receiving calcineurin inhibitors, and a CTX group with 46 patients received cyclophosphamide. Baseline measurements of 24-hour urine protein, serum albumin, blood creatinine, uric acid, estimated glomerular filtration rate (eGFR), and serum anti-phospholipase A2 receptor antibody levels were recorded at the onset of the follow-up. Subsequently, changes in 24-hour urine protein, eGFR, remission rates, and occurrence of adverse events among the three patient groups were compared at 6, 12, and 18 months post-treatment. Moreover, COX regression analysis was employed to ascertain factors influencing the remission rate of IMN. Results At the outset of the follow-up period, no significant difference existed in baseline characteristics such as gender, age, 24-hour urine protein quantification, serum albumin, serum creatinine, uric acid, eGFR, serum anti-PLA2R antibody levels, body mass index (BMI), and systolic blood pressure among the patients, indicating the comparability of three groups. After 6 months, there were no notable changes in 24-hour urine protein quantification and eGFR among the three groups; however, remission rates in the RTX and CTX groups were lower than those in the CNI group. By the 12-month mark, 24-hour urine protein quantification in the RTX group significantly decreased compared to the CTX group, with overall remission rates showing no significant differences among the three groups. By the 18-month milestone, 24-hour urine protein quantification in the RTX group remained notably lower than that in the CTX group, with significantly higher eGFR levels. Additionally, the CTX group exhibited lower 24-hour urine protein quantification compared to the CNI group, with both RTX and CTX groups displaying higher remission rates than the CNI group. Predominant adverse reactions in the RTX group included infusion reactions and infections, whereas the CNI group were associated with metabolic syndrome and elevated serum creatinine, and the CTX group primarily experienced hepatic dysfunction. Multifactorial COX regression analysis revealed an association between baseline anti-PLA2R antibodies and remission rates of IMN (HR=1.162, 95% CI 1.078-1.249). Conclusion RTX therapy for IMN exhibits a gradual onset of action, boasting a superior disease remission rate at 18 months in comparison to CNI. It demonstrates a similarity to CTX in this aspect and offers prolonged maintenance of remission. Conversely, CNI demonstrates a rapid onset of action but poses a risk of exacerbating renal impairment in patients. Notably, elevated levels of serum anti-PLA2R antibodies emerge as an independent risk factor influencing remission in IMN.

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.

Membranous Nephropathy: Updates on Management.

Membranous nephropathy is a major etiology of nephrotic syndrome in adults and less frequently in children. Circulating antibodies to intrinsic podocyte antigens, such as M-type phospholipase A2 receptor, or to extrinsic proteins accumulate beneath the podocyte to cause damage via complement activation and/or other mechanisms. The availability of clinical testing for autoantibodies to M-type phospholipase A2 receptor has allowed noninvasive diagnosis of this form of membranous nephropathy and a means to monitor immunologic activity to guide immunosuppressive therapy. Treatment of membranous nephropathy includes optimal supportive care with renin-angiotensin-system blockers, lipid-lowering agents, diuretics, lifestyle changes, and additional immunosuppressive therapy in patients with an increased risk of progression to kidney failure. Rituximab has been recognized as a first-line immunosuppressive therapy for most membranous nephropathy patients with an increased risk of progressive disease, except those with life-threatening nephrotic syndrome or rapidly deteriorating kidney function from membranous nephropathy. This article discusses the major and minor antigens described in membranous nephropathy, the natural history of the disease, and guidelines for clinical management and immunosuppressive treatment.

A single-center, open label, randomized, controlled study of hydroxychloroquine sulfate in the treatment of low risk PLA2R-associated membranous nephropathy.

OBJECTIVE: To evaluate the efficacy and safety of hydroxychloroquine sulfate (HCQ) in the treatment of low risk phospholipase A2 receptor (PLA2R)-associated membranous nephropathy (MN). METHODS: A total of 110 patients with low risk PLA2R-associated MN were included in the study. Patients who met the inclusion and exclusion criteria were assigned randomly to two groups: the HCQ treatment group and the control group. The control group received standard supportive treatment according to the guidelines, while the HCQ treatment group received HCQ in addition to the supportive treatment. The clinical data of the patients were analyzed, with comparisons made at baseline and during the six-month follow-up period. Any adverse reactions were recorded. RESULTS: The baseline data were comparable between the HCQ treatment group and the control group. At the end of the six-month follow-up period, the reductions in urine protein excretion and serum PLA2R antibody titer were more notable in the HCQ treatment group than those in the control group, with these differences being statistically significant (p < 0.05). Compared to the control group, the HCQ treatment group had fewer patients who were converted from low risk to moderate-to-high risk (p = 0.084). There were also no severe adverse reactions in the HCQ treatment group. CONCLUSION: In patients with low risk PLA2R-associated MN, adequate supportive therapy combined with HCQ is superior to supportive therapy alone in controlling proteinuria and reducing serum PLA2R antibody titers. Additionally, our study demonstrated that the incidence of adverse reactions did not increase. TRIAL REGISTRATION: This study was registered in the Chinese Clinical Trial Registry (Registration No.: ChiCTR1900021757, Date of registration: 2019-03-08).

The correlation between anti-phospholipase A2 receptor antibodies and hypercoagulability in patients with idiopathic membranous nephropathy.

BACKGROUND: Patients with idiopathic membranous nephropathy (IMN) are more likely to be complicated by venous thromboembolism (VTE). The aim of the study was to investigate the potential association between anti-phospholipase A2 receptor (PLA2R) antibodies and hypercoagulability in patients with IMN. METHODS: A total of 168 patients with biopsy-proven IMN and 36 patients with biopsy-proven minimal change disease (MCD) were enrolled in this study. The clinical data, serum anti-PLA2R antibodies and coagulation-related indices of the patients were retrospectively analyzed. RESULTS: Patients with IMN were categorized into glomerular PLA2R staining-positive (GAg+) IMN group and glomerular PLA2R staining-negative (GAg-) IMN group in the study. Patients with IMN who were GAg + had lower PT, APTT and R time than patients with IMN who were GAg-, while the CI value was higher in patients with IMN who were GAg+. Patients with IMN who were GAg + were divided into the SAb+/GAg + group and the SAb-/GAg + group. Patients with IMN who were SAb+/GAg + had higher Fib and MA values than patients with IMN who were SAb-/GAg+. Correlation analysis showed that serum anti-PLA2R antibodies were positively correlated with fibrinogen, D-dimer, K time, CI value, α-angle, and MA value. Multiple linear regression analysis indicated that anti-PLA2R antibodies were independently correlated with fibrinogen and MA value. CONCLUSION: Our study provides a new perspective on the underlying mechanisms of hypercoagulability in patients with IMN. Anti-PLA2R antibodies are associated with hypercoagulability in patients with IMN and may affect coagulation in patients with IMN by affecting platelet aggregation function and fibrinogen counts.

Mannose-Binding Lectin Deposition in Membranous Nephropathy and Differentiation of Primary from Secondary Forms.

The differentiation between primary and secondary forms of membranous nephropathy (MN) is a cornerstone that is necessary for adequate decision making regarding the treatment options and behavior of each specific case. Kidney biopsy and antibody results can be controversial, and a unique biomarker has still not been found. BACKGROUND AND OBJECTIVES: We investigated the lack of mannose-binding lectin (MBL) deposition in patients with secondary MNs (sMNs) with the presence of IgG4 deposition in relation to the presence of MBL deposition in patients with primary MNs (pMNs). We also established a connection between the stage of MN and MBL deposition. MATERIALS AND METHODS: Materials from 72 renal biopsies with proven MN were used for immunohistochemistry staining (IHC) for the phospholipase A2 receptor (PLA2R), immunoglobulin subtype IgG4, and MBL. Patients were separated into one of the following three groups: primary MN (pMN), idiopathic MN (iMN), and secondary MN (sMN). Serum antibodies for PLA2R and thrombospondin type-I-domain-containing 7A (THSD7A) were also used for the precise evaluation of the type of MN, as well as for detecting positivity for PLA2R using IHC. Which stage of MN was present in relation to the deposition of MBL was evaluated. RESULTS: In total, 50 patients were positive for IgG4, 34 with pMN, 12 with iMN, and 4 with sMN. A total of 20 patients were positive for MBL, 14 with pMN and 6 with iMN; no MBL deposits were found in patients with sMN. MBL positivity was predominantly present in the first two stages of MN, with a gradual reduction in the later stages. CONCLUSIONS: The activation of the lectin-complement pathway occurs in the early stages of the disease and is associated with the deposition of IgG4; IgG4 deposition is present in sMN, but there is no MBL deposition. IgG4 cannot be used for the differentiation of primary from secondary MNs, but the lack of MBL can be used as a marker for sMN in the early stages of the disease.

The Prevalence, Characteristics, and Putative Mechanisms of Dual Antigen-Positive Membranous Nephropathy: The Underestimated Condition.

Following the discovery of podocyte phospholipase A2 receptor and thrombospondin type-1 domain-containing 7A, various potential target antigens for membranous nephropathy (MN) have been reported one after another. MN target antigens have now been identified in a significant proportion of patients, and a new classification framework classifies patients with MN based on the detected antigen and associated disease phenotype. A serology-based approach that does not require a histological diagnosis for patients suspected of having MN has also been proposed. However, there have been cases in which dual positivity for MN antigens and/or corresponding antibodies has been shown. Importantly, some of them showed a transition of the affected patient's immune responses to MN antigens, suggesting that serological diagnosis changes depending on the timing of the analysis. In this review, we provide detailed information on these cases and present an overview of our recent understanding of their putative mechanisms involved in these cases. Greater awareness is required to adequately recognize and develop appropriate therapeutic strategies for this condition.

Serum Phospholipase A2 Receptor Antibody Is Associated with Thrombogenesis in Patients with Idiopathic Membranous Nephropathy.

INTRODUCTION: Patients with idiopathic membranous nephropathy (IMN) are particularly susceptible to thromboembolism (TE). The phospholipase A2 receptor (PLA2R) antibody (Ab) has been indicated to work as an independent risk predictor for venous TE in IMN. This study aimed to further explore the predictive value of PLA2R Ab for both venous and arterial TE in IMN patients. METHODS: A total of 91 IMN patients were retrospectively selected and divided into anti-PLA2R-positive or anti-PLA2R-negative groups according to the anti-PLA2R Ab titer (cutoff: 20 RU/mL). Serum PLA2R Abs were estimated using ELISA. Anti-PLA2R-positive IMN patients were further assigned into two groups based on the presence or absence of TE. RESULTS: Twelve (18.18%) IMN patients with anti-PLA2R positivity had TE, including both venous and arterial TE. No TE occurred in the anti-PLA2R-negative group. IMN patients in the anti-PLA2R-positive group had significantly higher levels of total cholesterol and low-density lipoprotein than those in the anti-PLA2R-negative group. No significant difference was observed in the anti-PLA2R Ab titer between patients with and without TE. Patients with TE were significantly older than those without TE. CONCLUSION: This study demonstrates that the positive status of anti-PLA2R Abs contributes to thrombosis formation in IMN.

Ectodomain shedding of PLA2R1 is mediated by the metalloproteases ADAM10 and ADAM17.

Phospholipase A2 receptor 1 (PLA2R1) is a 180-kDa transmembrane protein that plays a role in inflammation and cancer and is the major autoantigen in membranous nephropathy, a rare but severe autoimmune kidney disease. A soluble form of PLA2R1 has been detected in mouse and human serum. It is likely produced by proteolytic shedding of membrane-bound PLA2R1 but the mechanism is unknown. Here, we show that human PLA2R1 is cleaved by A Disintegrin And Metalloprotease 10 (ADAM10) and ADAM17 in HEK293 cells, mouse embryonic fibroblasts, and human podocytes. By combining site-directed mutagenesis and sequencing, we determined the exact cleavage site within the extracellular juxtamembrane stalk of human PLA2R1. Orthologs and paralogs of PLA2R1 are also shed. By using pharmacological inhibitors and genetic approaches with RNA interference and knock-out cellular models, we identified a major role of ADAM10 in the constitutive shedding of PLA2R1 and a dual role of ADAM10 and ADAM17 in the stimulated shedding. We did not observe evidence for cleavage by ß- or γ-secretase, suggesting that PLA2R1 may not be a substrate for regulated intramembrane proteolysis. PLA2R1 shedding occurs constitutively and can be triggered by the calcium ionophore ionomycin, the protein kinase C activator PMA, cytokines, and lipopolysaccharides, in vitro and in vivo. Altogether, our results show that PLA2R1 is a novel substrate for ADAM10 and ADAM17, producing a soluble form that is increased in inflammatory conditions and likely exerts various functions in physiological and pathophysiological conditions including inflammation, cancer, and membranous nephropathy.

Phospholipid metabolism-related genotypes of PLA2R1 and CERS4 contribute to nonobese MASLD.

BACKGROUND: Abnormal phospholipid metabolism is linked to metabolic dysfunction-associated steatotic liver disease (MASLD) development and progression. We aimed to clarify whether genetic variants of phospholipid metabolism modify these relationships. METHODS: This case-control study consecutively recruited 600 patients who underwent MRI-based proton density fat fraction examination (240 participants with serum metabonomics analysis, 128 biopsy-proven cases) as 3 groups: healthy control, nonobese MASLD, and obese MASLD, (n = 200 cases each). Ten variants of phospholipid metabolism-related genes [phospholipase A2 Group VII rs1805018, rs76863441, rs1421378, and rs1051931; phospholipase A2 receptor 1 (PLA2R1) rs35771982, rs3828323, and rs3749117; paraoxonase-1 rs662 and rs854560; and ceramide synthase 4 (CERS4) rs17160348)] were genotyped using SNaPshot. RESULTS: The T-allele of CERS4 rs17160348 was associated with a higher risk of both obese and nonobese MASLD (OR: 1.95, 95% CI: 1.20-3.15; OR: 1.76, 95% CI: 1.08-2.86, respectively). PLA2R1 rs35771982-allele is a risk factor for nonobese MASLD (OR: 1.66, 95% CI: 1.11-1.24), moderate-to-severe steatosis (OR: 3.24, 95% CI: 1.96-6.22), and steatohepatitis (OR: 2.61, 95% CI: 1.15-3.87), while the paraoxonase-1 rs854560 T-allele (OR: 0.50, 95% CI: 0.26-0.97) and PLA2R1 rs3749117 C-allele (OR: 1.70, 95% CI: 1.14-2.52) are closely related to obese MASLD. After adjusting for sphingomyelin level, the effect of the PLA2R1 rs35771982CC allele on MASLD was attenuated. Furthermore, similar effects on the association between the CERS4 rs17160348 C allele and MASLD were observed for phosphatidylcholine, phosphatidic acid, sphingomyelin, and phosphatidylinositol. CONCLUSIONS: The mutations in PLA2R1 rs35771982 and CERS4 rs17160348 presented detrimental impact on the risk of occurrence and disease severity in nonobese MASLD through altered phospholipid metabolism.

Therapeutic plasmapheresis in idiopathic membranous nephropathy anti-PLA2R-related: A case series.

Membranous nephropathy is the most common cause of nephrotic syndrome (NS) in non-diabetic adults; in 80% of patients it is idiopathic (PMN). PMN has an autoimmune pathogenesis, 70%-85% of patients have increased titer of antibodies to the podocyte membrane antigen PLA2R. The etiological, prognostic and predictive role of the Ab anti-PLA2R is demonstrated. Standard therapy consists in anti-CD20 monoclonal antibody rituximab (RTX) combined with steroids or immunosuppressants according to the risk of progressive loss of kidney function. The immunosuppressive therapies are potentially associated to severe adverse events that lead to protocol suspension. Given their pivotal pathogenetic role, serum clearance of anti-PLA2R with plasmapheresis could have a beneficial impact on NS, particularly in patients not requiring or tolerating standard therapies. In this series, we present three cases of PMN anti-PLA2R related treated with a RTX plus plasmapheresis approach and demonstrate its overall effective role on anti-PLA2R titer and clinical outcomes.

Fibrinogen-albumin ratio predicts treatment response in phospholipase A2 receptor-associated membranous nephropathy with nephrotic syndrome.

BACKGROUND: The M-type phospholipase A2 receptor (PLA2R)-associated primary membranous nephropathy (PMN) is an immune-related disease in adults with increasing morbidity and variable treatment response, in which inflammation may contribute to the multifactorial immunopathogenesis. The relationship between fibrinogen-albumin ratio (FAR), serving as a novel inflammatory biomarker, and PMN is still unclear. Therefore, this study aims to clarify the association between FAR and disease activity and therapy response of PMN. METHODS: 110 biopsy-proven phospholipase A2 receptor (PLA2R) -associated PMN participants with nephrotic syndrome from January 2017 to December 2021 were recruited in the First Affiliated Hospital of Nanjing Medical University. The independent risk factors of non-remission (NR) and the predictive ability of FAR were explored by Cox regression and receiver-operating characteristic (ROC) curve analysis. According to the optimal cutoff value, study patients were categorized into the low-FAR group (≤the cutoff value) and the high-FAR group (>the cutoff value). Spearman's correlations were used to examine the associations between FAR and baseline clinicopathological characteristics. Kaplan-Meier method was used to assess the effects of FAR on remission. RESULTS: In the entire study cohort, 78 (70.9%) patients reached complete or partial remission (CR or PR). The optimal cutoff value of FAR for predicting the remission outcome (CR + PR) was 0.233. The Kaplan-Meier survival analysis demonstrated that the high-FAR group (>0.233) had a significantly lower probability to achieve CR or PR compared to the low-FAR group (≤0.233) (Log Rank test, p = 0.021). Higher levels of FAR were identified as an independent risk factor for NR, and the high-FAR group was associated with a 2.27 times higher likelihood of NR than the low-FAR group (HR 2.27, 95% CI 1.01, 5.13, p = 0.048). These relationships remained robust with further analysis among calcineurin inhibitors (CNIs)-receivers. In the multivariate Cox regression model, the incidence of NR was 4.00 times higher in the high-FAR group than in the low-FAR group (HR 4.00, 95% CI 1.41, 11.31, p = 0.009). Moreover, ROC analysis revealed the predictive value of FAR for CR or PR with a 0.738 area under curve (AUC), and the AUC of anti-PLA2R Ab was 0.675. When combining FAR and anti-PLA2R Ab, the AUC was boosted to 0.766. CONCLUSIONS: FAR was significantly correlated with proteinuria and anti-PLA2R Ab in PMN. As an independent risk factor for NR, FAR might serve as a potential inflammation-based prognostic tool for identifying cases with poor treatment response, and the best predictive cutoff value for outcomes was 0.233.

Quantification of urinary podocyte-derived migrasomes for the diagnosis of kidney disease.

Migrasomes represent a recently uncovered category of extracellular microvesicles, spanning a diameter range of 500 to 3000 nm. They are emitted by migrating cells and harbour a diverse array of RNAs and proteins. Migrasomes can be readily identified in bodily fluids like serum and urine, rendering them a valuable non-invasive source for disease diagnosis through liquid biopsy. In this investigation, we introduce a streamlined and effective approach for the capture and quantitative assessment of migrasomes, employing wheat germ agglutinin (WGA)-coated magnetic beads and flow cytometry (referred to as WBFC). Subsequently, we examined the levels of migrasomes in the urine of kidney disease (KD) patients with podocyte injury and healthy volunteers using WBFC. The outcomes unveiled a substantial increase in urinary podocyte-derived migrasome concentrations among individuals with KD with podocyte injury compared to the healthy counterparts. Notably, the urinary podocyte-derived migrasomes were found to express an abundant quantity of phospholipase A2 receptor (PLA2R) proteins. The presence of PLA2R proteins in these migrasomes holds promise for serving as a natural antigen for the quantification of autoantibodies against PLA2R in the serum of patients afflicted by membranous nephropathy. Consequently, our study not only pioneers a novel technique for the isolation and quantification of migrasomes but also underscores the potential of urinary migrasomes as a promising biomarker for the early diagnosis of KD with podocyte injury.

Deep analysis of total serum N-glycome suggests glyco-signatures for phospholipase A2 receptor 1-related idiopathic membranous nephropathy diagnosis.

Idiopathic membranous nephropathy (IMN) is an antibody-mediated and kidney-specific autoimmune disease, with the antigen phospholipase A2 receptor 1 (PLA2R1) accounting for approximately 70% of IMN cases. Although a variety of new podocyte target antigens and their autoantibodies have been identified, they are still of limited diagnostic and therapeutic value due to lack of high specificity and sensitivity. N-glycans play vital roles in renal system and their pathobiological relevance has become increasingly recognized in many kidney diseases, but not fully explored in IMN. To find possible glyco-signatures for PLA2R1-related IMN diagnosis, we herein established a comprehensive workflow for total serum N-glycome analysis based on our recently developed mass spectrometry (MS)-based N-glycan purification method, named Ultrafast Glycoprotein Immobilization for Glycan extraction (UltraGIG). A total of 191 N-glycans were identified from IMN patients, representing the largest N-glycome dataset in IMN. Compared to healthy controls, up-regulation of sialylation and core-fucosylation as well as down-regulation of galactosylation were observed in PLA2R1-positive IMN patients, and up-regulation of hyper-galactosylation was specific for PLA2R1-negative IMN patients. A six-glycan marker panel consisting of H4N3S1, H4N3F1, H6N4S2, H6H5F1S2, H6N5 and H6N6F1S1, was proposed to aid in the accurate diagnosis of PLA2R1-related IMN, which provided new insights into IMN biomarker study. SIGNIFICANCE: PLA2R1-related IMN is a kidney-specific autoimmune disease with a high risk of developing end-stage renal disease (ESRD) and even kidney failure. Current biomarkers are still of limited diagnostic and therapeutic value due to lack of high specificity and sensitivity. An in-depth MS analysis of total serum N-glycome of PLA2R1-related IMN patients was conducted for the first time. We generated the largest dataset of serum N-glycome for IMN to date, and proposed a novel six-glycan marker panel that may help the accurate diagnosis of PLA2R1-related IMN.

Diagnosis of membranous nephropathy with Anti-GBM glomerulonephritis: a case series report.

BACKGROUND: The concomitant occurrence of membranous nephropathy and anti-glomerular basement (anti-GBM) disease has been previously described but is extremely rare. However, delayed recognition or misdiagnosis leads to delayed treatment, resulting in worse renal and patient outcomes. CASE PRESENTATION: We present 3 patients with rapidly progressive glomerulonephritis (RPGN), anti-GBM and serum-positive M-type phospholipase A2 receptor (anti-PLA2R) antibody. Renal biopsies revealed PLA2R-associated membranous nephropathy with anti-GBM glomerulonephritis. We analyzed the clinical and pathological characteristics and discussed that the correct diagnosis of membranous nephropathy with anti-GBM should rely on a combination of renal biopsy findings and serological testing. Despite aggressive treatment, one patient received maintenance hemodialysis, one patient progressed to CKD 3 stage, and the other patient died of cerebral infarction. CONCLUSION: The simultaneous occurrence of membranous nephropathy and anti-GBM disease is extremely rare. The correct diagnosis of membranous nephropathy with anti-GBM relies on a combination of renal biopsy findings and serological testing. Early diagnosis is needed to improve the renal dysfunction.

Macrocarpal B blocks the binding between the phospholipase A2 receptor and its antibodies.

The pathogenic role of anti-phospholipase A2 receptor (PLA2R) antibodies in primary membranous nephropathy (MN) has been well-established. This study aimed to identify potential small-molecule inhibitors against the PLA2R-antibody interaction, offering potential therapeutic benefits. A comprehensive screening of over 4000 small-molecule compounds was conducted by ELISA to assess their inhibitory effects on the binding between the immobilized full-length extracellular PLA2R and its antibodies. The affinity of anti-PLA2R IgG from MN patients and the inhibitory efficacy of each compound were evaluated via surface plasmon resonance (SPR). Human podocyte injuries were analyzed using CCK-8 assay, wound healing assay, western blot analysis, and immunofluorescence, after exposure to MN plasma +/- blocking compound. Fifteen compounds were identified as potential inhibitors, demonstrating inhibition rates >20 % for the PLA2R-antibody interaction. Anti-PLA2R IgG exhibited a consistent affinity among patients (KD = 10-8 M). Macrocarpal B emerged as the most potent inhibitor, reducing the antigen-antibody interaction by nearly 30 % in a dose-dependent manner, comparable to the performance of the 31-mer peptide from the CysR domain. Macrocarpal B bound to the immobilized PLA2R with an affinity of 1.47 × 10-6 M, while showing no binding to anti-PLA2R IgG. Human podocytes exposed to MN plasma showed decreased podocin expression, impaired migration function, and reduced cell viability. Macrocarpal B inhibited the binding of anti-PLA2R IgG to podocytes and reduced the cellular injuries.

The co-occurrence of sarcoidosis and anti-PLA2R-associated membranous nephropathy in a patient with underlying genetic susceptibility.

BACKGROUND: Sarcoidosis is a multisystemic inflammatory disease, characterized by the presence of non-caseating, epithelioid granulomas. Glomerular disease in patients with sarcoidosis is rare and membranous nephropathy (MN) is cited as the most common. The association between the two diseases remained unclear. This article reported a case of co-occurrence of sarcoidosis and anti-PLA2R-associated MN, to provide a possible relationship between these two entities. CASE PRESENTATION: A 61-year-old Chinese Han woman with a history of sarcoidosis was admitted to our hospital for nephrotic syndrome. Her sarcoidosis was diagnosed according to the adenopathy observed on the computed tomography scan and the biopsy of lymph nodes. The MN presented with nephrotic syndrome with a PLA2R antibody titer of 357RU/ml, and the final diagnosis was based on a renal biopsy. The patient's sarcoidosis was remitted after treatment with prednisone. One year later MN was diagnosed, and she was treated with prednisone combined with calcineurin inhibitors, based on a full dose of renin-angiotensin system (RAS) inhibitor. The patient's sarcoidosis had been in remission while the MN was recurrent, and her renal function deteriorated to end-stage renal disease 6 years later due to discontinuation of immunosuppression. A genetic test led to the identification of the HLA-DRB1*0301 and HLA-DRB1*150 genes associated with both sarcoidosis and MN, which provides a new possible explanation of the co-occurrence of these two diseases. CONCLUSION: This case suggested for the first time a potential genetic connection between idiopathic MN and sarcoidosis which needs further studies in the future.

Predictive value of the domain specific PLA2R antibodies for clinical remission in patients with primary membranous nephropathy: A retrospective study.

BACKGROUND: M-type phospholipase A2 receptor (PLA2R) is a major auto-antigen of primary membranous nephropathy(PMN). Anti-PLA2R antibody levels are closely associated with disease severity and therapeutic effectiveness. Analysis of PLA2R antigen epitope reactivity may have a greater predictive value for remission compared with total PLA2R-antibody level. This study aims to elucidate the relationship between domain-specific antibody levels and clinical outcomes of PMN. METHODS: This retrospective analysis included 87 patients with PLA2R-associated PMN. Among them, 40 and 47 were treated with rituximab (RTX) and cyclophosphamide (CTX) regimen, respectively. The quantitative detection of -immunoglobulin G (IgG)/-IgG4 targeting PLA2R and its epitope levels in the serum of patients with PMN were obtained through time-resolved fluorescence immunoassays and served as biomarkers in evaluating the treatment effectiveness. A predictive PMN remission possibility nomogram was developed using multivariate logistic regression analysis. Discrimination in the prediction model was assessed using the area under the receiver operating characteristic curve (AUC-ROC).Bootstrap ROC was used to evaluate the performance of the prediction model. RESULTS: After a 6-month treatment period, the remission rates of proteinuria, including complete remission and partial remission in the RTX and CTX groups, were 70% and 70.21% (P = 0.983), respectively. However, there was a significant difference in immunological remission in the PLA2R-IgG4 between the RTX and CTX groups (21.43% vs. 61.90%, P = 0.019). Furthermore, we found differences in PLA2R-CysR-IgG4(P = 0.030), PLA2R-CTLD1-IgG4(P = 0.005), PLA2R-CTLD678-IgG4(P = 0.003), and epitope spreading (P = 0.023) between responders and non-responders in the CTX group. Multivariate logistic analysis showed that higher levels of urinary protein (odds ratio [OR], 0.49; 95% confidence interval [CI], 0.26-0.95; P = 0.035) and higher levels of PLA2R-CTLD1-IgG4 (OR, 0.79; 95%CI,0.62-0.99; P = 0.041) were independent risk factors for early remission. A multivariate model for estimating the possibility of early remission in patients with PMN is presented as a nomogram. The AUC-ROC of our model was 0.721 (95%CI, 0.601-0.840), in consistency with the results obtained with internal validation, for which the AUC-ROC was 0.711 (95%CI, 0.587-0.824), thus, demonstrating robustness. CONCLUSIONS: Cyclophosphamide can induce immunological remission earlier than rituximab at the span of 6 months. The PLA2R-CTLD1-IgG4 has a better predict value than total PLA2R-IgG for remission of proteinuria at the 6th month.