The role of N-acetylcysteine amide in defending primary human retinal pigment epithelial cells against tert-butyl hydroperoxide- induced oxidative stress

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Abstract
Free Radicals and Antioxidants,2017,7,2,172-177.
Published:March 2017
Type:Original Article
Authors:
Author(s) affiliations:

Hsiu-Jen Wang1, Yue-Wern Huang2, Shakila Tobwala1, Annalise Pfaff1, Robert Aronstam3, Nuran Ercal4

1Department of Chemistry, Missouri University of Science and Technology, Rolla, Missouri, USA.

2Department of Biological Sciences, Missouri University of Science and Technology, Rolla, Missouri, USA.

3College of Science and Technology at Bloomsburg University, Bloomsburg, Pennsylvania, USA.

4Department of Chemistry, Richard K. Vitek/FCR Endowed Chair in Biochemistry, Missouri University of Science and Technology, Rolla, Missouri, USA.

Abstract:

Background: Age-related macular degeneration (AMD) is a leading cause of blindness in the United States among adults age 60 and older. While oxidative stress is implicated in the pathogenesis of AMD, dietary antioxidants have been shown to delay AMD progression in clinical studies. We hypothesized that N-acetylcysteine amide (NACA), a thiol antioxidant, would protect retinal pigment epithelium and impede progression of retinal degeneration. Methods: tert-Butyl hydroperoxide (TBHP) was used to induce oxidative stress in cell cultures. The goal was to evaluate the efficacy of NACA in an in vitro model of AMD in primary human retinal pigment epithelial cells (HRPEpiC). Results: Our data indicates that TBHP generated reactive oxygen species (ROS), which reduced cell viability, depleted glutathione (GSH) levels, and compromised glutathione reductase (GR) activity. Pretreatment with NACA significantly reduced ROS generation, restored GSH levels and GR activity, and recovered transepithelial electrical resistance. Pretreatment with NACA did not decrease the number of dying cells as determined by flow cytometry analysis. However, survival was significantly improved when cells were co-exposed to NACA and TBHP after a shortened pretreatment period. Conclusion: Our data suggest that pretreatment with NACA reduces sublethal but not lethal effects of TBHP in HRPEpiC. NACA significantly improves cell survival when administered prior to and during oxidative damage similar to that observed in the development of dry AMD. These results indicate that continuation of a thiol antioxidant regimen for treatment of AMD is beneficial throughout the course of the disease, and NACA is a potent antioxidant that should be further evaluated for this purpose.