Expression Of Phospholipase A2 Receptor Research Articles

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

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.

Anti-Phospholipase A2 Receptor (PLA2R) Antibody and Glomerular PLA2R Expression in Japanese Patients with Membranous Nephropathy.

The phospholipase A2 receptor (PLA2R) is the major target antigen (Ag) in idiopathic membranous nephropathy (IMN). Recently, several types of immunoassay systems for anti-PLA2R antibody (Ab) have been developed. However, the correlation of serum anti-PLA2R Abs and glomerular expression of PLA2R Ag, and their association with clinicopathological characteristics have yet to be proven in Japanese patients. We examined serum anti-PLA2R Abs by both ELISA and cell-based indirect immunofluorescence assay (CIIFA), and glomerular PLA2R expression by immunofluorescence (IF) in 59 biopsy-proven MN patients including IMN (n = 38) and secondary MN (SMN) (n = 21). In this study, anti-PLA2R Abs were present in 50% of IMN patients, but was absent in SMN patients. The concordance rate between ELISA and CIIFA was 100%. Serum IgG levels were significantly lower in anti-PLA2R Ab-positive patients. Serum albumin levels correlated inversely with serum anti-PLA2R Ab titers. The prevalence and intensity of glomerular staining for IgG4 by IF were significantly higher in anti-PLA2R Ab-positive patients than in -negative patients. Glomerular PLA2 Ag expression evaluated by IF was positive in 52.6% of IMN patients, but was absent in SMN patients. The concordance rate between the prevalence of glomerular PLA2R Ag expression and anti-PLA2R Ab was 84.2%. The prevalence of anti-PLA2R Abs measured by ELISA/CIIFA was equivalent to previous Japanese studies evaluated using Western blotting. These analyses showed an excellent specificity for the diagnosis of IMN, and anti-PLA2R positivity was associated with some clinicopathological features, especially glomerular IgG4-dominant deposition.

Expression of renal PLA2R in patients with idiopathic membranous nephropathy and its relationship with the curative effect of immunotherapy

To detect the expression of renal M-type phospholipase A2 receptor (PLA2R) in patients with idiopathic membranous nephropathy (IMN), and to explore the relationship between renal PLA2R and the curative effect of immunotherapy. A total of 56 patients who were diagnosed as IMN from January 2012 to June 2014 in the department of nephrology in First People's Hospital, Shanghai Jiaotong University, were included in this study. The expression of renal PLA2R was detected by immumofluorescence assay. The IMN patients were treated with corticosteroids and cyclophosphamide, and the relationship between renal PLA2R and the curative effect of immunotherapy was observed. The ratio of PLA2R related IMN (renal PLA2R-positive) patients was 71.4%(40/56). The recovery conditions in proteinuria and serum albumin were better in the non-PLA2R related IMN group since 6 months after the treatment (P<0.05). The overall response rate in PLA2R related IMN group was 58.3%, 62.5% and 62.5% after 6, 9, 12 months, respectively. However, the overall response rate in non-PLA2R related IMN group almost reached 100% after treatment for 6 months. Compared with PLA2R related IMN group, the time which patients reached complete remission was significantly shorter in the non-PLA2R related IMN group [(5.4±3.5) vs (10.5±1.6) months, P<0.05]. Detection of renal PLA2R can be helpful to diagnose IMN. Non-PLA2R related IMN patients usually have a better curative effect of immunotherapy and a shorter time to onset of efficacy.

Expression of phospholipase A2 receptor in primary cultured podocytes derived from dog kidneys.

Phospholipase A2 receptor (PLA2R) expressed in human podocytes has been highlighted as a causative autoantigen of human idiopathic membranous nephropathy. However, its expression was found to be minimal or absent in murine and rat podocytes. In this study, immunofluorescence revealed the expression of PLA2R in the glomerular podocytes in the kidney tissue sections of dogs. We then attempted to culture canine podocytes and investigate the expression of PLA2R in these cells. Glomeruli were isolated from dog kidneys and cultured to obtain podocytes using nylon mesh-based isolation method as followed for isolating rat podocytes. The cultured cells expressed PLA2R mRNA and protein in addition to other podocyte markers (synaptopodin, podocin and nephrin). These results indicate that the canine podocytes express PLA2R.

Prevalence of Enhanced Granular Expression of Thrombospondin Type-1 Domain-Containing 7A in the Glomeruli of Japanese Patients with Idiopathic Membranous Nephropathy.

Membranous nephropathy (MN) is a leading cause of nephrotic syndrome in adults. Autoantibodies against M-type phospholipase A2 receptor (PLA2R) and thrombospondin type-1 domain-containing 7A (THSD7A), which mainly belong to the IgG4 subclass, were reported as associated antibodies for the development of MN. Although PLA2R is a major target antigen for idiopathic MN, the prevalence of MN patients seropositive for PLA2R in Japan is lower than that in other countries. In this study, we conducted immunohistochemical analysis of the presence of THSD7A and PLA2R in renal specimens of MN patients to estimate the prevalence of THSD7A/PLA2R-related idiopathic MN in Japan. Enhanced granular expression of THSD7A and PLA2R was detected in 9.1% and 52.7%, respectively, of the patients with idiopathic MN. Although none of patients with secondary MN displayed enhanced granular expression of THSD7A, 5.4% of them had enhanced granular expression of PLA2R. In conclusion, the prevalence of enhanced granular expression of THSD7A in the glomeruli of Japanese patients with idiopathic MN was higher than the prevalence of MN patients seropositive for THSD7A in USA and Europe.

Membranous Nephropathy Associated With Immunological Disorder-Related Liver Disease: A Retrospective Study of 10 Cases.

The association between membranous nephropathy (MN) and immunological disorder-related liver disease has not been extensively investigated, and the specific features of this uncommon association, if any, remain to be determined.We retrospectively identified 10 patients with this association. We aimed to describe the clinical, biological, and pathological characteristics of these patients and their therapeutic management. The possible involvement of the phospholipase A2 receptor (PLA2R) in these apparent secondary forms of MN was assessed by immunohistochemistry with renal and liver biopsy specimens.The mean delay between MN and liver disease diagnoses was 3.9 years and the interval between the diagnosis of the glomerular and liver diseases was <1.5 years in 5 patients. MN was associated with a broad spectrum of liver diseases including primary biliary cirrhosis (PBC), autoimmune hepatitis (AIH), and primary sclerosing cholangitis (PSC). AIH whether isolated (n = 3) or associated with PBC (n = 2) or PSC (n = 2) was the most frequent autoimmune liver disease. Circulating PLA2R antibodies were detected in 4 out of 9 patients but the test was performed under specific immunosuppressive treatment in 3 out of 9 patients. Seven of the 9 patients with available renal tissue specimens displayed enhanced expression of PLA2R in glomeruli whereas PLA2R was not expressed in liver parenchyma from these patients or in normal liver tissue. The study of immunoglobulin (Ig) subclasses of deposits in glomeruli revealed that the most frequent pattern was the coexistence of IgG1 and IgG4 immune deposits with IgG4 predominating.Detection of PLA2R antibodies in glomeruli but not in liver parenchyma is a common finding in patients with MN associated with autoimmune liver disease, suggesting that these autoantibodies are not exclusively detected in idiopathic MN.

Phospholipase A2 Receptor Antibodies in Membranous Nephropathy

The discovery of the M-type phospholipase A2 receptor (PLA2R) as a major antigen in idiopathic membranous nephropathy (iMN) was a breakthrough and established iMN as an autoimmune disease.1 Subsequent studies confirmed that antibodies against PLA2R were present in approximately 70% of incident iMN patients (reviewed by Hofstra and Wetzels2). The potential role of measuring PLA2R antibodies for clinical practice was suggested by studies showing that the presence of PLA2R antibodies supported a diagnosis of iMN,2–4 changes in antibody levels paralleled clinical disease activity,5 disappearance of antibodies preceded and predicted subsequent decrease of proteinuria,6 and high titers of antibodies were associated with a low likelihood of spontaneous remission.7 In this issue of JASN, Hoxha et al. report their findings in a large cohort of 163 patients with MN.8 PLA2R antibodies (both IgG and IgG4) were measured in serum obtained within 6 months from kidney biopsy. The authors used an ELISA assay and immunofluorescence testing (IFT) (both commercially available in Europe).9 PLA2R antibodies were detected in 133 patients (82%). The median follow-up was 12 months, and the majority of patients (101 of 133) started immunosuppressive therapy within 3 months after presentation. Hoxha et al. show that PLA2R antibodies decreased during follow-up. The decrease in PLA2R antibodies preceded the decrease in proteinuria. The authors concluded that “there was a remarkable time lag between the rather rapid fall in antibody levels at 3 months and the protracted reduction in proteinuria.”8 These data confirm earlier findings and indicate that an immunologic remission precedes clinical remission in patients with iMN.6,10 Although no PLA2R antibodies were found in patients with complete remission, PLA2R antibodies were still present in a low titer in 50% of patients with a partial remission. These data indicate that a partial remission may not always reflect the absence of disease activity. The authors next analyzed the association between antibody levels at baseline and remission at 12 months after presentation. PLA2R antibody levels were significantly higher in 28 patients without remission than in 39 patients with remission. The median time to remission was significantly longer in patients with antibody levels above versus below the median (15 versus 9 months). The authors concluded that the PLA2R antibody level was “an independent risk factor for not achieving remission.”8 Such a conclusion, if valid and applicable to untreated patients, could improve individualized patient care. However, the data from the study by Hoxha et al. do not allow to conclude that antibody levels can help to accurately identify patients who will develop a spontaneous remission because most of Hoxha's patients were treated. Moreover, because treated patients nearly all developed a remission, the antibody levels merely predicted the time to remission. Although their patient cohort is large, the study by Hoxha et al. is limited because of the relatively short follow-up period, the use of various immunosuppressive treatment regimens, and the unnecessary early start of immunosuppressive therapy in many patients. The reported findings cannot change current guidelines for diagnosis and treatment of patients with iMN. Evidently, more rigid study protocols are needed to reliably answer the most relevant questions. Certainly, Hoxha et al. could perform additional analyses to answer some of the following unresolved questions.

Can Genetics Risk-Stratify Patients with Membranous Nephropathy?

Can Genetics Risk-Stratify Patients with Membranous Nephropathy?

Enhanced expression of the M-type phospholipase A2 receptor in glomeruli correlates with serum receptor antibodies in primary membranous nephropathy

The M-type phospholipase A2 receptor (PLA2R) is the major target antigen in idiopathic membranous nephropathy with detectable autoantibodies in the serum of up to 70% of patients. In retrospective studies, the PLA2R-autoantibody titer in the serum was sometimes negative indicating their measurement alone may be inconclusive. In order to better differentiate between primary and secondary membranous nephropathy, we conducted a prospective study that included 88 patients with a histologic diagnosis of membranous nephropathy. Immunohistochemical analysis for PLA2R was faintly positive in kidneys from normal individuals and patients with various other glomerular injuries. In 61 of the 88 patients, PLA2R expression was strongly positive in glomeruli, and in 60 of these patients PLA2R autoantibodies were also detected in the serum. The 27 patients negative for serum PLA2R autoantibodies were faintly positive for PLA2R staining in glomeruli and in 15 of these patients a secondary cause was found. The remaining 12 patients have a yet undetected secondary cause of membranous nephropathy or have different glomerular antigens other than PLA2R. Thus, increased staining for PLA2R in glomeruli of renal biopsies tightly correlates with the presence of PLA2R autoantibodies in the serum and this may help discriminate between primary and secondary membranous nephropathy.

Abstract A159: Epigenetic silencing of the M-type phospholipase A2 receptor gene in leukemic cells.

Abstract Background: The M-type phospholipase A2 receptor (PLA2R) plays a crucial role in a number of different signaling pathways and may act as tumor-suppressor. In the current study the expression and methylation of the PLA2R gene in the myeloid U937 cell line and blood leukocytes of patients with leukemia were analyzed. Methods. Expression of PLA2R in U937 cells was studied using RT-quantitative PCR. To determine methylation levels of the PLA2R locus, bisulfite-modified DNA fragments were sequenced. Identification of different 5′-CpG methylation sites in normal and leukemic patients was followed by methylation specific-high resolution melting (MS-HRM) analysis to quantify PLA2R methylations. Results: Our data establish that expression of PLA2R is completely down-regulated in U937 cells. Simultaneously, a 100% methylation of PLA2R promoter and down-stream regions was found in this cell line; after exposure of the cells to 5-aza-2 -deoxycytidine, PLA2R was re-expressed. MS-HRM analyzes in 34 patients with different types of leukemia indicated an average PLA2R methylation of 30%±18%, whereas in 52 normal subjects methylation levels were below 10%. In a preliminary study of high-risk myelodysplastic syndrome patients (MDS), three patients had increased PLA2R methylations. In the course of treatment with azacitidine (Vidaza) as methyltransferase inhibitor, two of these patients were responders in contrast to one patient who was a non-responder with increased methylation levels in blood leukocytes during treatment. Another patient with minimal residual disease after treatment of AML underwent preemptive treatment with azacitidine to avoid hematological relapse (HR). After two azacitidine cycles a minor cell fraction with 100% methylated PLA2R was completely diminished. However, three weeks later methylation of the PLA2R promoter increased to 50%, with 9% blasts detectable in blood samples. After further azacitidine treatment cycle, blasts diminished in blood samples but the methylation of PLA2R in blood leukocytes remained at 35%. During the following seven weeks with no further azacitidine treatment blasts increased up to 44% suggesting that the treatment with azacitidine was effective but not efficient enough to prevent a HR in this patient. Conclusions: The study shows for the first time that the PLA2R promoter and down-stream regions in leukemic cells are hypermethylated and that the determination of PLA2R methylation by MS-HRM may be useful as a biomarker in the diagnosis and therapeutic treatment of high-risk MDS and AML patients. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr A159.

The M‐type receptor PLA2R regulates senescence through the p53 pathway

Senescence is a stable proliferative arrest induced by various stresses such as telomere erosion, oncogenic or oxidative stress. Compelling evidence suggests that it acts as a barrier against tumour development. Describing new mechanisms that favour an escape from senescence can thus reveal new insights into tumorigenesis. To identify new genes controlling the senescence programme, we performed a loss-of-function genetic screen in primary human fibroblasts. We report that knockdown of the M-type receptor PLA2R (phospholipase A2 receptor) prevents the onset of replicative senescence and diminishes stress-induced senescence. Interestingly, expression of PLA2R increases during replicative senescence, and its ectopic expression results in premature senescence. We show that PLA2R regulates senescence in a reactive oxygen species-DNA damage-p53-dependent manner. Taken together, our study identifies PLA2R as a potential new tumour suppressor gene crucial in the induction of cellular senescence through the activation of the p53 pathway.

Enhanced Tissue Expression and Elevated Circulating Level of Phospholipase A2 Receptor during Murine Endotoxic Shock

Phospholipase A2 receptor (PLA2R) mediates a variety of biological responses elicited by mammalian secretory phospholipase A2 (sPLA2). In mice, group IB sPLA2 (sPLA2-IB) acts as an endogenous ligand of PLA2R, and analysis of PLA2R-deficient mice has demonstrated a critical role of the sPLA2-IB/PLA2R system in the production of proinflammatory cytokines such as tumor necrosis factor α (TNF-α) in the development of endotoxic shock. Here, we generated specific antibodies against a recombinant soluble form of PLA2R and examined its expression in the lung and spleen where a remarkable elevation of TNF-α expression has been observed during endotoxemia. Immunohistochemical analysis revealed the expression of PLA2R in type II alveolar epithelial cells and a subset of splenic lymphocytes, and its expression levels were markedly enhanced at 1 h after endotoxin challenge. Analysis with a newly developed sandwich enzyme-linked immunosorbent assay system revealed the presence of a soluble form of PLA2R in plasma of wild-type mice compared with its absence in plasma of PLA2R-deficient mice. After exposure to endotoxin, its circulating level was significantly elevated to the maximum level at 2–3 h after the treatment. These results suggest that tissue expression and the circulating level of PLA2R are elevated during murine endotoxemia, which might be relevant to its potential roles in the production of proinflammatory mediators during the development of inflammatory conditions.