Neuroprotection against superoxide anion radical by metallocorroles in cellular and murine models of optic neuropathy.

Corroles are tetrapyrrolic macrocycles that have come under increased attention because of their unique capabilities for oxidation catalysis, reduction catalysis, and biomedical applications. Corrole-metal complexes (metallocorroles) can decompose certain reactive oxygen species (ROS), similar to metalloporphyrins. We investigated whether Fe-, Mn-, and Ga-corroles have neuroprotective effects on neurons and correlated this with superoxide scavenging activity in vitro and in vivo. Apoptosis was induced in retinal ganglion cell-5 neuronal precursor cells by serum deprivation. Cell death was measured with sodium 3'-[1-[(phenylamino)-carbonyl]-3,4-tetrazolium]-bis (4-methoxy-6-nitro) benzene-sulfonic acid hydrate and calcein-AM/propidium iodide assays. Fe- and Mn-corroles, but not the non-redox-active Ga-corrole used as control, reduced RGC-5 cell death after serum deprivation. Serum deprivation caused increased levels of intracellular superoxide, detected by an increase in the fluorescence intensity of 2-hydroxyethidium, and this was blocked by Fe- and Mn-corroles, but not Ga-corrole. In vivo real-time confocal imaging of retinas after optic nerve transection assessed the superoxide production within individual rat retinal ganglion cells. Fe- and Mn-corroles, but not Ga-corrole, scavenged neuronal superoxide in vivo. Given that the neuroprotective activity of metallocorroles correlated with superoxide scavenging activity, Fe- and Mn-corroles could be candidate drugs for delaying neuronal death after axonal injury in optic neuropathies, such as glaucoma.