Anti-PLA2R antibodies promote endothelial pyroptosis and a procoagulant phenotype through FcγRI signaling

BACKGROUND AND HYPOTHESIS: Thromboembolism is a serious complication of nephrotic syndrome and occurs disproportionately in membranous nephropathy (MN). Whether anti-phospholipase A2 receptor (PLA2R) antibodies and complement activation directly promote endothelial dysfunction and thrombosis is unclear. METHODS: In a retrospective cohort of biopsy-proven MN (n=45 with thromboembolism; 1:2 time-selected controls), we quantified anti-PLA2R antibodies, C3a, and C5a and analyzed their associations with thromboembolic events. Using human umbilical vein endothelial cells (HUVECs), we tested MN plasma, purified anti-PLA2R IgG (including IgG4), and IgG fragments, and interrogated Fc and complement receptor pathways. Readouts included pro/anti-coagulant factor expression, inflammasome/pyroptosis activation, and secreted mediators. RESULTS: Anti-PLA2R levels were higher in patients with thromboembolism than in those without and correlated with D-dimer and fibrin degradation products. A ROC-derived threshold of 92RU/mL was associated with greater thromboembolic risk. MN plasma and anti-PLA2R IgG induced a dose- and time-dependent procoagulant phenotype in HUVECs, upregulating tissue factor (TF), ICAM-1, and PAI-1 and increasing supernatant TF and sICAM-1. The Fc fragment reproduced these effects, whereas F(ab')2 did not. Anti-PLA2R colocalized with FcγRI; FcγRI silencing abrogated procoagulant responses and reduced NLRP3, caspase-1 p20, GSDMD-N, IL-1β, and IL-18. The NLRP3 inhibitor similarly suppressed pyroptosis and procoagulant readouts. Complement anaphylatoxins C3a/C5a further increased TF/ICAM-1 via C3aR/C5aR, and antagonists reversed MN-plasma-induced effects. CONCLUSIONS: Anti-PLA2R antibodies promote endothelial pyroptosis and a TF-high procoagulant phenotype through FcγRI signaling in vitro.Complement signaling amplifies this response. Targeting FcγRI-inflammasome pathways may mitigate thromboembolic risk in MN.