Purified IgG from aquaporin-4 neuromyelitis optica spectrum disorder patients alters blood-brain barrier permeability.

Alvaro Cobo-Calvo,Sandrine Blondel,Nathalie Strazielle,Anne Ruiz,Jean-François Ghersi-Egea,Chloé Richard,Sylvie Cavagna,Romain Marignier,Pascale Giraudon,Mária A Deli

doi:10.1371/journal.pone.0238301

Abstract

BackgroundNeuromyelitis optica spectrum disorders (NMOSD) is a primary astrocytopathy driven by antibodies directed against the aquaporin-4 water channel located at the end-feet of the astrocyte. Although blood-brain barrier (BBB) breakdown is considered one of the key steps for the development and lesion formation, little is known about the molecular mechanisms involved. The aim of the study was to evaluate the effect of human immunoglobulins from NMOSD patients (NMO-IgG) on BBB properties.MethodsFreshly isolated brain microvessels (IBMs) from rat brains were used as a study model. At first, analysis of the secretome profile from IBMs exposed to purified NMO-IgG, to healthy donor IgG (Control-IgG), or non-treated, was performed. Second, tight junction (TJ) proteins expression in fresh IBMs and primary cultures of brain microvascular endothelial cells (BMEC) was analysed by Western blotting (Wb) after exposition to NMO-IgG and Control-IgG. Finally, functional BBB properties were investigated evaluating the presence of rat-IgG in tissue lysate from brain using Wb in the rat-model, and the passage of NMO-IgG and sucrose in a bicameral model.ResultsWe found that NMO-IgG induces functional and morphological BBB changes, including: 1) increase of pro-inflammatory cytokines production (CXCL-10 [IP-10], IL-6, IL-1RA, IL-1β and CXCL-3) in IBMs when exposed to NMO-IgG; 2) decrease of Claudin-5 levels by 25.6% after treatment of fresh IBMs by NMO-IgG compared to Control-IgG (p = 0.002), and similarly, decrease of Claudin-5 by at least 20% when BMEC were cultured with NMO-IgG from five different patients; 3) a higher level of rat-IgG accumulated in periventricular regions of NMO-rats compared to Control-rats and an increase in the permeability of BBB after NMO-IgG treatment in the bicameral model.ConclusionHuman NMO-IgG induces both structural and functional alterations of BBB properties, suggesting a direct role of NMO-IgG on modulation of BBB permeability in NMOSD.

Highlights

Neuromyelitis optica spectrum disorders (NMOSD) is a severe autoimmune disease of the central nervous system (CNS) that mainly affects the optic nerve and the spinal cord
Neuromyelitis optica spectrum disorders (NMOSD) is a primary astrocytopathy driven by antibodies directed against the aquaporin-4 water channel located at the end-feet of the astrocyte
The discovery of a serum antibody, termed aquaporin-4 antibody, directed against the aquaporin4 (AQP4) channel expressed at the CNS interfaces, has enhanced the understanding of NMOSD which is considered an autonomous entity with distinctive pathophysiology, different from multiple sclerosis [1]

Summary

Introduction

Neuromyelitis optica spectrum disorders (NMOSD) is a severe autoimmune disease of the central nervous system (CNS) that mainly affects the optic nerve and the spinal cord. Contrary to the extended evidence concerning AQP4-IgG involvement in NMOSD tissue lesion formation, the mechanisms for antibody penetration into the CNS, still awaits elucidation. NMO-IgG has been observed to access the brain from the blood (blood-CNS barrier) through fenestrated endothelial cells in circumventricular organs such as the area postrema where AQP4 protein is highly expressed [2,3]. In vitro models have shown that either the NMO-IgG itself [5,6], or other components from the serum of NMOSD patients (such as matrix-metalloproteinase 2/9 protein, antibodies against brain endothelial cells, or glucose-regulated protein-78) may alter the blood brain barrier (BBB) at the glio-vascular unit (blood-CNS barrier) [7,8,9]. The aim of the study was to evaluate the effect of human immunoglobulins from NMOSD patients (NMO-IgG) on BBB properties

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Conclusion