Inhibitors of Inducible Nitric Oxide Synthase Prevent Damage to Human Lens Epithelial Cells Induced by Interferon-Gamma and Lipopolysaccharide

Abstract

We previously found that Ca²⁺ concentrations, inducible nitric oxide synthase (iNOS) mRNA, and protein expression in lenses of the Shumiya cataract rat (SCR) increase with the development of cataracts. In this study, we investigated the change in Ca²⁺-ATPase activities and ATP levels in the human lens epithelial cell line SRA 01/04 (HLE cells) with the stimulation of interferon-gamma (IFN-γ) and lipopolysaccharide (LPS). Expression levels of iNOS mRNA in HLE cells, which were determined using semiquantitative reverse transcription-polymerase chain reaction (RT-PCR) and quantitative real-time RT-PCR methods, increased during stimulation with IFN-γ (1000 IU) and LPS (100 ng/ml). NO release from HLE cells, expressed as the sum of NO₂⁻ and NO₃⁻ levels, increased with the increase in iNOS expression levels. Ca²⁺-ATPase activities increased and ATP levels decreased in HLE cells stimulated with the combination of IFN-γ and LPS. Furthermore, both diethyldithiocarbamate and aminoguanidine attenuated the increase in Ca²⁺-ATPase activities and the decrease in ATP levels. These results suggest that excessive production of NO may cause mitochondrial damage, resulting in an increased Ca²⁺ concentration in the lens. The increase in Ca²⁺ concentration in the lens may increase Ca²⁺-ATPase activities.