Toxicity of Cholesterol Oxides on Cultured Neuroretinal Cells

Purpose: By using nerve growth factor-differentiated PC12 cells as a model for sympathetic neurons, we have recently shown that cholesterol oxides are toxic to cells of neural origin. Since lipid metabolism is known to be involved in some pathological conditions associated with the visual system, we sought to extend this line of research by studying the potential cytotoxicity of cholesterol oxides on primary cultures derived from neuroretinas.

Methods: Dissociated cultures derived from neuroretinas of 1-day-old Sprague-Dawley rats were used in this series of studies. Immunohistochemical staining was used to identify neuronal and glial cell types in these cultures. MTT assay was used to determine the cytotoxicity of cholesterol oxides, including 7-beta-OH-, 7-keto-, 19-OH-, 22(R)-OH-, 22(S)-OH- and 25-OH-cholesterol.

Results: Among the cholesterol oxides tested, 7-beta-OH- and 7-keto-cholesterol were the most effective in causing cell death, such that 20 micrograms/ml (50 microM) of these agents killed approximately 80% of cells in 3 days. A time-dependent experiment indicated that 10 micrograms/ml of 7-beta-cholesterol was able to kill 50% of cells in approximately 5 h. A number of pharmacological agents were tested for their ability to prevent cell death induced by cholesterol oxides. Among them, vitamin E and methyl-beta-cyclodextrin were able to prevent cholesterol oxide-induced cell death in a dose-dependent manner.

Conclusions: These results suggest that, in addition to causing pathological changes in cells directly involved in atherosclerosis, cholesterol oxides may be toxic to cells derived from neuroretinas.