Glucose-regulated protein 78 autoantibody associates with blood-brain barrier disruption in neuromyelitis optica

Abstract

Neuromyelitis optica (NMO) is an inflammatory disorder mediated by antibodies to aquaporin-4 (AQP4) with prominent blood-brain barrier (BBB) breakdown in the acute phase of the disease. Anti-AQP4 antibodies are produced mainly in the periphery, yet they target the astrocyte perivascular end feet behind the BBB. We reasoned that an endothelial cell–targeted autoantibody might promote BBB transit of AQP4 antibodies and facilitate NMO attacks. Using monoclonal recombinant antibodies (rAbs) from patients with NMO, we identified two that strongly bound to the brain microvascular endothelial cells (BMECs). Exposure of BMECs to these rAbs resulted in nuclear translocation of nuclear factor κB p65, decreased claudin-5 protein expression, and enhanced transit of macromolecules. Unbiased membrane proteomics identified glucose-regulated protein 78 (GRP78) as the rAb target. Using immobilized GRP78 to deplete GRP78 antibodies from pooled total immunoglobulin G (IgG) of 50 NMO patients (NMO-IgG) reduced the biological effect of NMO-IgG on BMECs. GRP78 was expressed on the surface of murine BMECs in vivo, and repeated administration of a GRP78-specific rAb caused extravasation of serum albumin, IgG, and fibrinogen into mouse brains. Our results identify GRP78 antibodies as a potential component of NMO pathogenesis and GRP78 as a candidate target for promoting central nervous system transit of therapeutic antibodies.

Blood–brain barrier dysfunction in immuno-mediated neurological diseases

“…(2) the decrease in claudin-5 in the BBB after exposure to NMO sera was induced by the secretion of VEGF and MMP-2/9 from endothelial cells in an autocrine manner; (3) IgG from 50 AQP4 Ab-positive NMO sera samples was able to bind and activate BBB-endothelial cells via the NF-jB p65 pathway in vitro; (4) two AQP4-nonreactive monoclonal recombinant Abs (rAbs) prepared from CSF plasmablasts were present in NMO, and able to strongly activate BBB-endothelial cells; (5) glucoseregulated protein 78 (GRP78) as the target antigen of NMO-rAb was identified using proteome technology; (6) peripheral injection of a GRP78-specific NMO-rAb gave rise to increased BBB leakage in vivo; (7) the absorption of GRP78-specific Abs from NMO-IgG pooled from 50 patients resulted in a decreased effect on BBB-endothelial cell activation [59][60][61][62].…”

“…In contrast, cell surface of GRP78 is involved in NF-jB signal transduction [64]. As expression of GRP78 is abundant on cell surface of the BBB-endothelial cells, serum GRP78 autoantibodies can bind to and influence BBB-endothelial cells [62].…”

GRP78 antibodies are associated with blood–brain barrier breakdown in paraneoplastic cerebellar degeneration in Lambert‐Eaton myasthenic syndrome

“…We showed that IgG from PCD‐LEMS patients, not LEMS patients, could activate BBB‐endothelial cells: exposure of BBB‐endothelial cells to PCD‐LEMS IgG induced NF‐κB p65 nuclear translocation and ICAM‐1 up‐regulation, reduced claudin‐5 expression, increased permeability, and increased autocrine interleukin (IL)‐1β and IL‐8 secretion, although LEMS IgG did not have these effects. Because we previously reported that GRP78 autoantibodies bound to and activated BBB‐endothelial cells in neuromyelitis optica (NMO) patients, we next examined whether GRP78 autoantibodies were detectable with a pathogenic role in BBB dysfunction of not only NMO but also PCD‐LEMS patients through a new method based on the coimmunoprecipitation, known as a “living cell‐based‐antibody binding assay.” GRP78 autoantibodies were detected in the IgG of LEMS‐PCD (83.3%, n = 18), but showed lower levels in LEMS patients (6.6%, n = 15), and none were observed in the controls (n = 8). Removal of GRP78 autoantibodies reduced the biological effect of PCD‐LEMS IgG on BBB‐endothelial cells.…”

The 4th MS Summer College in Kobe (5–6 August 2017) Translational research and MS/NMOSD

“…Finally, Dr Fumitaka Shimizu of Yamaguchi University presented his recent high‐impact research showing that serum immunoglobulin G from NMOSD patients could activate blood–brain barrier endothelial cells. His research was recently published in Science Translational Medicine …”