ISO-1, a macrophage migration inhibitory factor antagonist, prevents N-methyl-d-aspartate-induced retinal damage

Macrophage migration inhibitory factor (MIF) has been shown to play an important role in a variety of inflammatory and immune-mediated diseases. The inflammatory responses contribute to retinal neuronal degeneration. However, the role of MIF in the progression of retinal degeneration has not yet been elucidated. In this study, we determined whether pharmacological inhibition of MIF protects against the retinal damage induced by N-methyl-d-aspartate (NMDA) in rats. Intravitreal injection of NMDA (200 nmol) resulted in (1) cell loss in the ganglion cell layer and reduction in the thickness of the inner plexiform layer, (2) an increase in apoptotic cells, (3) a decrease in parvalbumin-positive amacrine cells, (4) accumulation of leukocytes, and (5) microglia activation. Injection of (S,R)-3-(4-hydroxyphenyl)-4,5-dihydro-5- isoxazole acetic acid methyl ester (ISO-1, 100 nmol), a MIF antagonist, significantly attenuated these NMDA-induced responses. These findings suggest that ISO-1 exerts protective effects against retinal injuries and that MIF may be a target for neuroprotective intervention in retinal diseases associated with glutamate-induced excitotoxicity.