L-Carnitine Protects Human Retinal Pigment Epithelial Cells from Oxidative Damage

Abstract

Purpose: To determine the efficacy of L-carnitine (LC) against oxidative changes in human retinal pigment epithelium (RPE) cells. Methods: The RPE cells from human donor eyes were cultured in Hams F-10 medium. The effect of LC on H₂O₂-induced morphologic changes in the RPE cells was analyzed by light microscopy. Reduction in cell death after the impact of LC treatment on H₂O₂-treated cells was analyzed by MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assays. In addition, the effect of H₂O₂ on the activity of RPE-antioxidant enzymes, glutathione (GSH) and superoxide dismutase (SOD), and LC-induced protection was also determined. Results: LC protected the RPE cells by inhibiting the peroxide-induced cytopathic effect from 50% to 10%. Nuclear condensation observed in 40% of the H₂O₂-treated cells decreased to 20% after LC treatment. The MTT assays demonstrated that 100 μM oxidant caused appreciable cell death, which was reduced by LC treatment; however, 100% protection was not achieved. Significant peroxide-induced cell death was seen within 5 hr of H₂O₂ treatment, and a quantifiable reduction was observed after LC treatment for a similar time period. The change in the antioxidant potential of the RPE induced by oxidative stress was restored by LC treatment, as demonstrated by an increase in GSH and SOD activities. Conclusions: LC is capable of protecting the RPE cells from H₂O₂-induced oxidative damage, implying that micronutrients can have a positive effect and can play an important role in the treatment of oxidation-induced ocular disorders. Further studies are needed to understand the mechanism of LC-induced protection to the RPE cells.

KEYWORDS:

• aging
• enzymes
• L-carnitine
• morphology
• oxidation
• RPE