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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 (K D  = 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., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: The author is an Editorial Board Member/Editor-in-Chief/Associate Editor/Guest Editor for [Bioorganic & Medicinal Chemistry] and was not involved in the editorial review or the decision to publish this article., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

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., Competing Interests: The authors have nothing to disclose., (Copyright © 2019 Giuseppe Stefano Netti et al.)

Rationale: Crescent formation is rare in primary membranous nephropathy (MN). Anti-phospholipase A2 receptor (PLA2R) antibodies are detectable in these patients. The mechanism and treatments are unknown., Patient Concerns: A 72-year-old female patient who presented with nephrotic syndrome, hematuria, and rapidly progressive kidney dysfunction., Diagnoses: Kidney biopsy was performed and the diagnosis was MN in combination with crescentic glomerulonephritis. Circulating anti-PLA2R IgG3 and IgG4 were detected of high level., Interventions: The patient received plasma exchange and rituximab besides corticosteroids., Outcomes: The patient achieved complete remission of proteinuria and recovery of kidney function after the clearance of anti-PLA2R antibodies., Lesson: This case suggests a pathogenic role of anti-PLA2R antibodies in the mechanism of crescent formation in MN, which may need intensive therapy to eliminate the antibodies quickly.

Since the identification of PLA2R (M-type phospholipase A2 receptor) as the first human antigenic target in primary membranous nephropathy (MN), perpetual progress has been made in understanding the pathogenesis of this disease. Accumulating clinical data support a pathogenic role for the anti-PLA2R antibodies (PLA2R ABs), but confirmation in an animal model is still lacking. However, PLA2R ABs were related to disease activity and outcome, as well as to response therapy. Accordingly, PLA2R ABs assay seems to be promising tool not only to diagnose MN but also to predict the course of the disease and could open the way to personalize therapy. Nevertheless, validation of a universal assay with high precision and definition of cut-off levels, followed by larger studies with a prolonged follow-up period, are needed to confirm these prospects.

Membranous nephropathy (MN) is a rare manifestation of IgG4-related disease. Interestingly, the significance of IgG4 has also been documented in idiopathic MN (IMN). Previous studies reported that urine IgG4/IgG ratios were significantly higher in IMN compared with other kinds of nephropathy, indicating that impairment of charge selectivity barrier seemed to be an obvious characteristic of IMN. Although high blood concentration of IgG4 is very common in IgG4-related MN, no study about the urine IgG4 has been described before. Here, we present a 55-year-old male with IgG4-related MN. Complete remission of proteinuria was promptly achieved by glucocorticoid treatment without immunosuppressant. Consistent with previous reports, the serum antibody against M-type phospholipase A2 receptor was negative. Surprisingly, although the blood concentration of IgG4/IgG reached as high as 36 %, the urine concentration of IgG4/IgG was only 5 %. The calculated ratio of the renal clearance of IgG4 to IgG of this patient (0.15) was obviously lower than that of five patients with IMN (0.53∼0.81). We speculated that this phenomenon might be a clue of the different pathogenesis between IgG4-related MN and IMN.

Introduction: Phospholipases A(2) have been implicated in various pathological conditions, such as rheumatoid arthritis, cardiovascular diseases, neurological disorders and cancer. The scientific community focuses on the search of potent and selective PLA(2) inhibitors of each PLA(2) class in order to identify novel medicinal agents. At present, only one lipoprotein-associated PLA(2) (LpPLA(2)) inhibitor has reached Phase III clinical trials for the treatment of atherosclerosis., Areas Covered: This review article focuses on the role of the most important PLA(2)s in inflammatory diseases and other severe pathological conditions presented in patent literature from June 2009 to September 2012., Expert Opinion: Even though the role of each PLA(2) in different diseases or pathological conditions is not yet definitively identified, the progress in the quest for potent and selective PLA(2) inhibitors is exciting and the use of such inhibitors as medicinal agent looks now more promising than ever.

Oxidative stress and mitochondrial permeability transition (MPT) are important mechanisms in acetaminophen (APAP) toxicity. The MPT inhibitor trifluoperazine (TFP) reduced MPT, oxidative stress, and toxicity in freshly isolated hepatocytes treated with APAP. Since hypoxia inducible factor-one alpha (HIF-1α) is induced very early in APAP toxicity, a role for oxidative stress in the induction has been postulated. In the present study, the effect of TFP on toxicity and HIF-1α induction in B6C3F1 male mice treated with APAP was examined. Mice received TFP (10mg/kg, oral gavage) prior to APAP (200mg/kg IP) and at 7 and 36h after APAP. Measures of metabolism (hepatic glutathione and APAP protein adducts) were comparable in the two groups of mice. Toxicity was decreased in the APAP/TFP mice at 2, 4, and 8h, compared to the APAP mice. At 24 and 48h, there were no significant differences in toxicity between the two groups. TFP lowered HIF-1α induction but also reduced the expression of proliferating cell nuclear antigen, a marker of hepatocyte regeneration. TFP can also inhibit phospholipase A(2), and cytosolic and secretory PLA(2) activity levels were reduced in the APAP/TFP mice compared to the APAP mice. TFP also lowered prostaglandin E(2) expression, a known mechanism of cytoprotection. In summary, the MPT inhibitor TFP delayed the onset of toxicity and lowered HIF-1α induction in APAP treated mice. TFP also reduced PGE(2) expression and hepatocyte regeneration, likely through a mechanism involving PLA(2)., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Background: The recent finding that phospholipase-A(2)-receptor antibodies (PLA(2)R-AB) may play a role in the development of primary membranous glomerulonephritis (MGN) offers the opportunity to measure a marker to help diagnose, classify and eventually monitor the course of patients with MGN., Methods: We developed an immunofluorescence test, which allows the easy and specific analysis of the presence of PLA(2)R-AB in serum. The usefulness of this test was studied in 153 healthy blood donors, 90 patients with non-membranous glomerular injuries, 17 patients with a secondary form of MGN and 100 patients with biopsy-proven primary MGN. In addition, in five patients with biopsy-proven MGN, PLA(2)R-AB levels were monitored prospectively for up to 18 months following a single dose of rituximab (RTX) (375 mg/m(2) body surface)., Results: PLA(2)R-AB were not found in healthy controls or patients with glomerular lesions other than biopsy-proven primary MGN. Fifty-two patients with primary MGN (52%) were positive for PLA(2)R-AB. The levels ranged from 1:10 to 1:3200. In patients who had MGN and were treated with RTX the fall in PLA(2)R-AB levels was followed by a decrease in proteinuria, whereas an increase in PLA(2)R-AB levels was associated with an increase in proteinuria., Conclusions: These studies show that the new test allows the monitoring of PLA(2)R-AB levels in patients with MGN and may help in making therapeutic decisions for these patients.

Endothelins (ETs) are a family of three peptides (ET-1, ET-2, ET-3) that are implicated in the physiological control of vascular smooth muscle cell (VSMC) and myocardial contractility and growth. ET-1 is vasoactive peptide that acts via ET-A receptors coupling inducing vascular smooth muscle cell contraction. ET-1 is involved in the development and maintenance of hypertension. Aim of this study was to investigate whether ET-1 can induce vascular smooth muscle cell proliferation through arachidonic acid (AA) metabolites formed via cytochrome P¬450 (CYP-450). VSMC proliferation was measured by [3H]thymidine incorporation in cultured cells treated by ET-1 (10 to l00 nmol/L) in presence of different inhibitors of CYP-450 (17-ODYA 5 μmol/L), lipoxygenase (LO) (baicalein 20 μmol/L) and cyclooxygenase (COX) (indomethacin 5 μmol/L). ET-1 (10 to 100 nmol/L) induced VSMC proliferation and this effect was attenuated by CYP-450 inhibitor (17-ODYA) and lipoxygenase (LO) inhibitor (baicalein) but not by cyclooxygenase (COX) inhibitor (indomethacin). CYP-450 and LO metabolites of AA, 20-hydroxyeicosatetraenoic acid (HETE) and 12-HETE increased [3H]thymidine incorporation in VSMC. Inhibitors of MAP kinase (PD-98059 50 μmol/L) and cPLA2 (MAFP 50 μmol/L) attenuated ET-1 as well as 20-HETE induced VSMC proliferation. These results suggest AA metabolites via CYP-450 mediates ET-1 induce VSMC proliferation.

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.