Dysregulation of
iron metabolism, and resultant cytotoxicity, has been implicated in the pathogenesis of
multiple sclerosis (MS) and other neurodegenerative processes.
Iron accumulation promotes cytotoxicity through various mechanisms including oxidative stress and
glutamate toxicity, and occurs in both MS patients and in the
experimental autoimmune encephalomyelitis (EAE) model of MS. Divalent
Metal Transporter1, a major
iron importer in cells, is stimulated by signaling of Dexras1, a
small G protein member of the Ras family. Dexras1 is activated by S-nitrosylation by
nitric oxide (NO) produced by either
inducible nitric oxide synthase in activated microglia/macrophages or
neuronal nitric oxide synthase in neurons. Here we show Dexras1 exacerbates oxidative stress-induced neurodegeneration in experimental
optic neuritis, an inflammatory demyelinating optic nerve condition that occurs in MS and EAE. Dexras1 deletion, as well as treatment with the
iron chelator deferiprone, preserves vision and attenuates retinal ganglion cell (RGC) and axonal loss during EAE
optic neuritis. These results suggest that
iron entry triggered by NO-activated Dexras1 signaling is a potential mechanism of neuronal death in experimental
optic neuritis. The current data suggest modulation of Dexras1 signaling and
iron chelation are potential novel treatment strategies for
optic neuritis and MS, and possibly other
optic neuropathies as well.