Small-molecule inhibitors of NMO-IgG binding to aquaporin-4 reduce astrocyte cytotoxicity in neuromyelitis optica

• Published in: The FASEB journal Vol. 26; no. 5; p. 2197
• Main Authors: Tradtrantip, Lukmanee, Zhang, Hua, Anderson, Marc O, Saadoun, Samira, Phuan, Puay-Wah, Papadopoulos, Marios C, Bennett, Jeffrey L, Verkman, A S
• Format: Journal Article
• Language: English
• Published: United States 01.05.2012
• Subjects: Animals; Aquaporin 4 - metabolism; Astrocytes - metabolism; Immunoglobulin G - metabolism; Mice; Neuromyelitis Optica - pathology; Rats; Rats, Inbred F344; Small Molecule Libraries
• ISSN: 1530-6860
• DOI: 10.1096/fj.11-201608

Neuromyelitis optica (NMO) is an inflammatory demyelinating disease of spinal cord and optic nerve caused by pathogenic autoantibodies (NMO-IgG) against astrocyte aquaporin-4 (AQP4). We developed a high-throughput screen to identify blockers of NMO-IgG binding to human AQP4 using a human recombinant monoclonal NMO-IgG and transfected Fisher rat thyroid cells stably expressing human M23-AQP4. Screening of ∼60,000 compounds yielded the antiviral arbidol, the flavonoid tamarixetin, and several plant-derived berbamine alkaloids, each of which blocked NMO-IgG binding to AQP4 without affecting AQP4 expression, array assembly, or water permeability. The compounds inhibited NMO-IgG binding to AQP4 in NMO patient sera and blocked NMO-IgG-dependent complement- and cell-mediated cytotoxicity with IC(50) down to ∼5 μM. Docking computations identified putative sites of blocker binding at the extracellular surface of AQP4. The blockers did not affect complement-dependent cytotoxicity caused by anti-GD3 antibody binding to ganglioside GD3. The blockers reduced by >80% the severity of NMO lesions in an ex vivo spinal cord slice culture model of NMO and in mice in vivo. Our results provide proof of concept for a small-molecule blocker strategy to reduce NMO pathology. Small-molecule blockers may also be useful for other autoimmune diseases caused by binding of pathogenic autoantibodies to defined targets.