Small-molecule inhibitors of NMO-IgG binding to aquaporin-4 reduce astrocyte cytotoxicity in neuromyelitis optica.
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.
Department of Medicine, University of California, San Francisco, CA 94143-0521, USA.
Lukmanee
L
Tradtrantip
Hua
H
Zhang
Marc O
MO
Anderson
Samira
S
Saadoun
Puay-Wah
PW
Phuan
Marios C
MC
Papadopoulos
Jeffrey L
JL
Bennett
A S
AS
Verkman
D000818:Animals; D051401:Aquaporin 4 / Q000378:metabolism*; D001253:Astrocytes / Q000378:metabolism*; D007074:Immunoglobulin G / Q000378:metabolism*; D051379:Mice; D009471:Neuromyelitis Optica / Q000473:pathology*; D051381:Rats; D011916:Rats, Inbred F344; D054852:Small Molecule Libraries
D051401:Aquaporin 4; D007074:Immunoglobulin G; D054852:Small Molecule Libraries