Clinical value of renal phospholipase A2 receptor deposit in the prognosis evaluation and treatment options of idiopathic membranous nephropathy: A retrospective cohort study.

AIM: Phospholipase A2 receptor (PLA2R) is a target antigen for idiopathic membranous nephropathy (IMN). However, the association between renal PLA2R antigen and disease prognosis had not been fully investigated. In addition, there was a paucity of studies investigating the difference of therapeutic effects between cyclophosphamide and cyclosporine A in PLA2R-associated IMN. METHODS: This retrospective cohort study recruited 300 eligible patients diagnosed with biopsy-proven IMN between September 2015 and July 2018 in Guangdong Provincial People's Hospital. The remission of proteinuria was compared between PLA2R-associated and non-PLA2R-associated IMN. The difference of therapeutic effects between cyclophosphamide and cyclosporine A were also investigated in PLA2R-associated IMN. RESULTS: The positive rate of renal PLA2R antigen in recruited IMN patients was 82.3%. Non-PLA2R-associated IMN patients had a higher probability to achieve remission than PLA2R-associated IMN patients (Log-rank test, P = .013). Multivariate COX analysis showed that renal PLA2R antigen was an independent risk factor for not achieving remission in IMN patients (Hazard Ratio: 1.619; 95% confidence interval: 1.133 to 2.313; P = .008). In PLA2R-associated IMN, patients receiving cyclophosphamide had a higher probability to achieve remission compared with those receiving cyclosporine A (Log-rank test, P = .018) while there was no difference in renal survival. Multivariate COX regression analysis showed that compared with cyclosporine A, patients receiving cyclophosphamide had a higher probability to achieve remission. CONCLUSION: Phospholipase A2 receptor -associated IMN patients had a lower probability to achieve remission compared with non-PLA2R-associated IMN. Compared with cyclosporine A, cyclophosphamide exerted better therapeutic effects in remission of proteinuria and may be the preferred immunosuppressant for PLA2R-associated IMN. SUMMARY AT A GLANCE This article highlighted the prognostic value of intra-renal phospholipase A2 receptor deposition in idiopathic membranous nephropathy (IMN). Renal phospholipase A2 receptor (PLA2R)-associated IMN patients had a lower probability to achieve remission compared with non-PLA2R-associated IMN.

Immunological Pathogenesis of Membranous Nephropathy: Focus on PLA2R1 and Its Role.

Membranous nephropathy (MN) is the major cause of nephrotic syndrome with special pathological features, caused by the formation of immune complexes in the space between podocytes and the glomerular basement membrane. In idiopathic membranous nephropathy (IMN) the immune complexes are formed by circulating antibodies binding mainly to one of two naturally-expressed podocyte antigens: the M-type receptor for secretory phospholipase A2 (PLA2R1) and the Thrombospondin type-1 domain-containing 7A (THSD7A). Formation of antibodies against PLA2R1 is much more common, accounting for 70-80% of IMN. However, the mechanism of anti-podocyte antibody production in IMN is still unclear. In this review, we emphasize that the exposure of PLA2R1 is critical for triggering the pathogenesis of PLA2R1-associated MN, and propose the potential association between inflammation, pollution and PLA2R1. Our review aims to clarify the current research of these precipitating factors in a way that may suggest future directions for discovering the pathogenesis of MN, leading to additional therapeutic targets and strategies for the prevention and early treatment of MN.

High-Dose Rituximab and Early Remission in PLA2R1-Related Membranous Nephropathy.

BACKGROUND AND OBJECTIVES: Different rituximab protocols are used to treat membranous nephropathy. We compared two rituximab protocols in patients with membranous nephropathy. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: Twenty-eight participants from the NICE cohort received two infusions of 1-g rituximab at 2-week intervals, whereas 27 participants from the Prospective Randomized Multicentric Open Label Study to Evaluate Rituximab Treatment for Membranous Nephropathy (GEMRITUX) cohort received two infusions of 375 mg/m2 at 1-week interval. We measured serum rituximab levels and compared remission at month 6 and before any treatment modification and analyzed factors associated with remission and relapses. RESULTS: Remissions occurred in 18 (64%) versus eight (30%) from the NICE and GEMRITUX cohort (P=0.02) at month 6, respectively, and in 24 (86%) versus 18 (67%) participants (P=0.12) before treatment modification, respectively. Median time to remission was 3 [interquartile range (IQR), 3-9] and 9 [IQR, 6-12] months for NICE and GEMRITUX cohorts respectively (P=0.01). Participants from the NICE cohort had higher circulating level of rituximab and lower CD19 counts (3.3 µg/L [IQR, 0.0-10.8] versus 0.0 [IQR, 0.0-0.0] P<0.001 and 0.0 [IQR, 0.0-2.0] versus 16.5 [IQR, 2.5-31.0] P<0.001) at month 3, lower level of anti-PLA2R1 antibodies at month 6 (0.0 [IQR, 0.0-8.0] versus 8.3 [IQR, 0.0-73.5] P=0.03). In the combined study population, lower epitope spreading at diagnosis and higher rituximab levels at month 3 were associated with remissions at month 6 (13/26 (50%) versus 22/29 (76%) P=0.05 and 2.2 µg/ml [IQR, 0.0-10.9] versus 0.0 µg/ml [IQR, 0.0-0.0] P<0.001 respectively). All non-spreaders entered into remission whatever the protocol. Eight of the 41 participants who reached remission had relapses. Epitope spreading at diagnosis (8/8 (100%) versus 16/33 (48%) P=0.01) and incomplete depletion of anti-PLA2R1 antibodies at month 6 (4/8 (50%) versus 5/33 (9%) P=0.05) were associated with relapses. CONCLUSIONS: Our work suggests that higher dose rituximab protocol is more effective on depletion of B-cells and lack of epitope spreading is associated with remission of membranous nephropathy.

HLA-DRB1*15:01 and HLA-DRB3*02:02 in PLA2R-Related Membranous Nephropathy.

Idiopathic membranous nephropathy (MN) is associated with HLA; however, the HLA allele involved remains unknown. To identify the HLA risk alleles associated with phospholipase A2 receptor (PLA2R)-related MN in the Chinese population, we sequenced the entire MHC region in DNA samples from 99 patients with PLA2R-related MN, 50 patients with PLA2R-unrelated MN, and 100 healthy subjects. Two HLA risk alleles, HLA-DRB1*15:01 and HLA-DRB3*02:02, independently and strongly associated with an increased risk of PLA2R-related MN. After adjusting for HLA-DRB1*15:01 and HLA-DRB3*02:02, no other alleles showed significant association with PLA2R-related MN. A replication study in an independent cohort of 293 participants with PLA2R-related MN and 285 healthy controls validated these findings. In a joint analysis, a multivariate logistic regression model confirmed that HLA-DRB1*15:01 (odds ratio [OR], 24.9; 95% confidence interval [95% CI], 15.3 to 42.6; P=2.3×10-35) and HLA-DRB3*02:02 (OR, 17.7; 95% CI, 11.0 to 30.3; P=8.0×10-29) independently and strongly associated with PLA2R-related MN. As many as 98.7% of patients with PLA2R-related MN, compared with 43.9% of control subjects, carried at least one HLA risk allele. Subjects with either risk allele had higher odds of developing PLA2R-related MN than those without a risk allele (OR, 98.9; 95% CI, 44.4 to 281.7; P=2.5×10-23). These HLA risk alleles also associated with the age at disease onset in patients with PLA2R-related MN. In conclusion, our findings provide clear evidence that the HLA-DRB1*15:01 and HLA-DRB3*02:02 alleles independently and strongly associate with PLA2R-related MN in the Chinese population.

MHC Class II Risk Alleles and Amino Acid Residues in Idiopathic Membranous Nephropathy.

Epitopes of phospholipase A2 receptor (PLA2R), the target antigen in idiopathic membranous nephropathy (iMN), must be presented by the HLA-encoded MHC class II molecules to stimulate autoantibody production. A genome-wide association study identified risk alleles at HLA and PLA2R loci, with the top variant rs2187668 within HLA-DQA1 showing a risk effect greater than that of the top variant rs4664308 within PLA2R1. How the HLA risk alleles affect epitope presentation by MHC class II molecules in iMN is unknown. Here, we genotyped 261 patients with iMN and 599 healthy controls at the HLA-DRB1, HLA-DQA1, HLA-DQB1, and HLA-DPB1 loci with four-digit resolution and extracted the encoded amino acid sequences from the IMGT/HLA database. We predicted T cell epitopes of PLA2R and constructed MHC-DR molecule-PLA2R peptide-T cell receptor structures using Modeler. We identified DRB1*1501 (odds ratio, 4.65; 95% confidence interval [95% CI], 3.39 to 6.41; P<0.001) and DRB1*0301 (odds ratio, 3.96; 95% CI, 2.61 to 6.05; P<0.001) as independent risk alleles for iMN and associated with circulating anti-PLA2R antibodies. Strong gene-gene interaction was noted between rs4664308(AA) and HLA-DRB1*1501/DRB1*0301. Amino acid positions 13 (P<0.001) and 71 (P<0.001) in the MHC-DRß1 chain independently associated with iMN. Structural models showed that arginine13 and alanine71, encoded by DRB1*1501, and lysine71, encoded by DRB1*0301, facilitate interactions with T cell epitopes of PLA2R. In conclusion, we identified two risk alleles of HLA class II genes and three amino acid residues on positions 13 and 71 of the MHC-DRß1 chain that may confer susceptibility to iMN by presenting T cell epitopes on PLA2R.

[Role of M-type phospholipase A2 receptor and its antibody in hepatitis B virus-associated membranous nephropathy].

OBJECTIVE: To examine levels of M-type phospholipase A2 receptor (PLA2R) and its antibody in the patients with hepatitis B virus-associated membranous nephropathy (HBV-MN), and to explore the correlation of PLA2R with laboratory parameters and pathological characteristics.
 Methods: A total of 49 adult patients with biopsy-proved HBV-MN were enrolled in this study. Levels of anti-PLA2R antibody in serum and PLA2R in renal tissue were detected. Patients were assigned into two groups: a positive PLA2R group and a negative PLA2R group. Differences in laboratory parameters and pathological characteristics were compared between the two groups.
 Results: Of 49 patients with HBV-MN, 17 had positive PLA2R expression in renal tissues. In the positive PLA2R group, 10 patients were positive for serum anti-PLA2R antibody. Patients with positive PLA2R expression in renal tissues showed higher levels of 24 hour urinary protein [(4.6±3.9) g/d], serum HbsAg (70.5%) and renal HbsAg expression (71%), while lower level of serum albumin [(24.1±7.5) g/L] than those of the negative group.
 Conclusion: PLA2R is expressed in the renal tissues and serum anti-PLA2R antibody can be detected in some HBV-MN patients. Positive PLA2R expression in renal tissue might be related to HbsAg deposition in serum and renal tissues. Patients with positive PLA2R expression in renal tissue have more severe glomerular sclerosis.

Phospholipase A2 Receptor-Related Membranous Nephropathy and Mannan-Binding Lectin Deficiency.

Most patients with idiopathic membranous nephropathy (IMN) have IgG4 autoantibodies against phospholipase A2 receptor (PLA2R). C3 and C5b-9 are found in immune deposits of IMN kidney biopsy specimens, but the pathway of complement activation in IMN remains elusive. We report the case of a patient who developed IMN with intense staining for PLA2R, IgG4, C3, C5b-9, factor B, and properdin and very weak staining for C1q, C4d, and IgG1. Measurement of mannan binding lectin (MBL) antigenic level and activity revealed MBL deficiency. Genotyping revealed a heterozygous (A/C) polymorphism in codon 57 of MBL2 exon 1 associated with homozygous and heterozygous variations in the promoter region at -550 (L/L) and -221 (X/Y), respectively, suggesting that the patient harbored the LXA/LYC haplotypes linked to MBL deficiency. Genetic sequencing in 77 consecutive patients with IMN identified four patients with MBL2 promoter and coding region variations associated with MBL deficiency and the same complement pattern in immune deposits as the index patient. In contrast, patients with wild-type MBL2 had immune deposits with intense Cd4 staining. Thus, IMN can develop in patients with complete MBL deficiency, with complement activated mainly by the alternative pathway, whereas the lectin pathway is also activated in those with wild-type MBL2.

[New physiopathological roles for the PLA2R1 receptor in cancer and membranous nephropathy]. / Nouveaux rôles physiopathologiques pour le récepteur PLA2R1 dans le cancer et la glomérulonéphrite extramembraneuse.

PLA2R1 is a large transmembrane receptor of 180-kDa that belongs to the superfamily of C-type lectins. It was discovered because of its high affinity for secreted phospholipases A2 (sPLA2), enzymes that play a key role in lipid mediator synthesis. Early PLA2R1 physiological roles include the clearance of sPLA2 from the extracellular medium and/or promotion of their actions. Over the last four years, two independent studies suggested that PLA2R1 plays a role in cancer as a tumor gene suppressor and is the major target antigen of auto-immune antibodies involved in idiopathic membranous nephropathy, a severe human kidney disease. These novel findings shed light on PLA2R1 and pave the way for its use as a reliable biomarker and an attractive therapeutic target in these diseases.

PLA2R1: expression and function in cancer.

The phospholipase A2 receptor 1 (PLA2R1 or PLA2R) was isolated twenty years ago for its ability to bind several secretory phospholipase A2 proteins (sPLA2). Since its identification, it has attracted only a limited interest, mainly in the sPLA2 biology field, as it is viewed uniquely as a regulator of sPLA2 activities. Recent discoveries outline novel important functions of this gene in cancer biology. Indeed, PLA2R1 gain or loss of function experiments in vitro and in vivo shows that this receptor promotes several tumor suppressive responses including senescence, apoptosis and inhibition of transformation. Supporting a tumor suppressive role of PLA2R1, its expression decreases in numerous cancers, and known oncogenes such as HIF2α and c-MYC repress its expression. PLA2R1 promoter methylation, a classical way to repress tumor suppressive gene expression in cancer cells, is observed in leukemia, in kidney and in breast cancer cells. Mechanistically, PLA2R1 activates the kinase JAK2 and orients its activity towards a tumor suppressive one. PLA2R1 also promotes accumulation of reactive oxygen species which induce cell death and senescence. This review compiles recent data demonstrating an unexpected tumor suppressive role of PLA2R1 and outlines the future work needed to improve our knowledge of the functions of this gene in cancer.

PLA2R1 kills cancer cells by inducing mitochondrial stress.

Little is known about the biological functions of the phospholipase A2 receptor (PLA2R1) except that it has the ability to bind a few secreted phospholipases A2 (sPLA2's). We have previously shown that PLA2R1 regulates senescence in normal human cells. In this study, we investigated the ability of PLA2R1 to control cancer cell growth. Analysis of expression in cancer cells indicates a marked PLA2R1 decrease in breast cancer cell lines compared to normal or nontransformed human mammary epithelial cells. Accordingly, PLA2R1 ectopic expression in PLA2R1-negative breast cancer cell lines led to apoptosis, whereas a prosenescence response was predominantly triggered in normal cells. PLA2R1 structure-function studies and the use of chemical inhibitors of sPLA2-related signaling pathways suggest that the effect of PLA2R1 is sPLA2-independent. Functional experiments demonstrate that PLA2R1 regulation of cell death is driven by a reactive oxygen species (ROS)-dependent mechanism. While screening for ROS-producing complexes involved in PLA2R1 biological responses, we identified a critical role for the mitochondrial electron transport chain in PLA2R1-induced ROS production and cell death. Taken together, this set of data provides evidence for an important role of PLA2R1 in controlling cancer cell death by influencing mitochondrial biology.

Age-related changes in the response of intestinal cells to 1α,25(OH)2-vitamin D3.

The hormonally active form of vitamin D(3), 1α,25(OH)(2)-vitamin D(3), acts in intestine, its major target tissue, where its actions are of regulatory and developmental importance: regulation of intracellular calcium through modulation of second messengers and activation of mitogenic cascades leading to cell proliferation. Several causes have been postulated to modify the hormone response in intestinal cells with ageing, among them, alterations of vitamin D receptor (VDR) levels and binding sites, reduced expression of G-proteins and hormone signal transduction changes. The current review summarizes the actual knowledge regarding the molecular and biochemical basis of age-impaired 1α,25(OH)(2)-vitamin D(3) receptor-mediated signaling in intestinal cells. A fundamental understanding why the hormone functions are impaired with age will enhance our knowledge of its importance in intestinal cell physiology.

Thermal tolerance of contractile function in oxidative skeletal muscle: no protection by antioxidants and reduced tolerance with eicosanoid enzyme inhibition.

Mechanisms for the loss of muscle contractile function in hyperthermia are poorly understood. This study identified the critical temperature, resulting in a loss of contractile function in isolated diaphragm (thermal tolerance), and then tested the hypotheses 1) that increased reactive oxygen species (ROS) production contributes to the loss of contractile function at this temperature, and 2) eicosanoid metabolism plays an important role in preservation of contractile function in hyperthermia. Contractile function and passive force were measured in rat diaphragm bundles during and after 30 min of exposure to 40, 41, 42 or 43 degrees C. Between 40 and 42 degrees C, there were no effects of hyperthermia, but at 43 degrees C, a significant loss of active force and an increase in passive force were observed. Inhibition of ROS with the antioxidants, Tiron or Trolox, did not inhibit the loss of contractile force at 43 degrees C. Furthermore, treatment with dithiothreitol, a thiol (-SH) reducing agent, did not reverse the effects of hyperthermia. A variety of global lipoxygenase (LOX) inhibitors further depressed force during 43 degrees C and caused a significant loss of thermal tolerance at 42 degrees C. Cyclooxygenase (COX) inhibitors also caused a loss of thermal tolerance at 42 degrees C. Blockage of phospholipase with phospholipase A(2) inhibitors, bromoenol lactone or arachidonyltrifluoromethyl ketone failed to significantly prevent the loss of force at 43 degrees C. Overall, these data suggest that ROS do not play an apparent role in the loss of contractile function during severe hyperthermia in diaphragm. However, functional LOX and COX enzyme activities appear to be necessary for maintaining normal force production in hyperthermia.