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Editors Selection IGR 7-3

Basic research: Annexin

Comment by Leonard A. Levin on:

11780 Retinal ganglion cell apoptosis in glaucoma is related to intraocular pressure and IOP-induced effects on extracellular matrix, Guo L; Moss SE; Alexander RA et al., Investigative Ophthalmology and Visual Science, 2005; 46: 175-182

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Guo and colleagues (12) studied annexin V binding in whole-mounts of rat retinas from eyes with elevated intraocular pressure. They also correlated these changes with levels of extracellular matrix materials, such as collagen and laminin, as well as matrix metalloproteinase-9 (MMP-9) and tissue inhibitor of matrix metalloproteinase-1 (TIMP-1). One finding was dramatically high rates of annexin V binding in retinal ganglion cells of eyes with ocular hypertension. Annexin V is typically used as a marker of apoptosis, but the observed rates of annexin V binding were greater than the amount of retinal ganglion cell apoptosis typically seen in an ocular hypertension model of glaucoma in the rat. It is therefore more likely that the positive cells are not simply undergoing apoptosis but are in a 'distressed' state that eventually may result in apoptosis (and also may be reversible).

Dramatically high rates of annexin V binding in retinal ganglion cells of eyes with ocular hypertension were found

Second, Guo and colleagues found a correlation between MMP-9 activity, annexin V binding, and a decrease in laminin immunostaining. However, some of the correlations were based on masked observer ratings of immunostained retinas, instead of more quantitative western blotting. They suggest that the increased intraocular pressure causes changes in the extracellular matrix in the inner retina which contributes to retinal ganglion cell death. However, they acknowledge that the extracellular matrix changes in the retina could also result from axonal damage to retinal ganglion cells. Overall, these are thought-provoking findings, and should stimulate further work in the field.

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