Alpha-Fodrin is Cleaved by Caspase-3 in a Chronic Ocular Hypertensive (COH) Rat Model of Glaucoma

Purpose alpha-Fodrin is a neuronal cytoskeletal protein and a known caspase-3 target. We sought to determine whether caspase-3 cleaves alpha-fodrin in COH rat retinas and whether this process is reduced by adeno-associated virus (AAV)-induced retinal ganglion cell expression of baculovirus inhibitory repeat-containing 4 (BIRC4), a potent caspase-3 inhibitor. Methods Ocular hypertension was induced unilaterally in five rat eyes by limbal injection of hypertonic saline. In a similar experiment, ocular hypertension was induced in four eyes pre-treated with an intravitreal injection of AAV-BIRC4 to assess alpha-fodrin cleavage. Western immunoblotting was performed on all retinas. Results Caspase-3 cleavage of alpha-fodrin yields a specific 120kDa protein fragment. COH retina immunoblots indicated significantly more caspase-3 cleavage of alpha-fodrin than controls (P Conclusions This confirms our previous finding of caspase-3 cleavage of alpha-fodrin in COH retinas and parallels pathology seen in Alzheimer's disease, in which neurons undergo chronic caspase activation, slow build-up of cleavage products, and delayed apoptosis. If caspase activation in glaucoma leads to protracted rather than rapid retinal ganglion cell apoptosis, a much longer therapeutic window exists for apoptosis inhibition with caspase inhibitors such as BIRC4.