The Role of Nitric Oxide in the Cataract Development: A Possible Mechanism of Lens Opacity

ABSTRACT

PURPOSE: To assess the role of nitric oxide in the development of cataract by detection of nitrotyrosine, which is a reaction product of peroxynitrite with tyrosine. METHODS: We have collected aqueous humor and anterior capsule of lens after cataract surgery from 14 eyes. We classified lens opacities into three types such as nuclear sclerosis, cortical and posterior subcapsular opacity. Nitrite, stable oxidative product of nitric oxide, was measured in the aqueous humor and immunohistochemical staining for nitrotyrosine was performed to examine anterior capsules. RESULTS: The concentrations of nitric oxide in aqueous humor were 0.0698+/-0.0036, 0.0652+/-0.0116, and 0.0700+/-0.0022 mM in nuclear sclerosis, cortical and posterior subcapsular opacity, respectively and no significant differences existed among lens opacity types. In lenses with cortical and posterior subcapsular opacity, the expression of nitrotyrosine was observed around epithelial cell and intercellular space. There was no expression of nitrotyrosine in lenses with nuclear sclerosis. CONCLUSIONS: This results suggest that nitration of tyrosine by peroxynitrite is possibly related to the cataractogenesis of lenses with cortical and posterior subcapsular opacity.