Abstract
Purpose:
Age related macular degeneration (AMD) is a major cause of blindness in the industrial world. Human retinal pigment epithelial (hRPE) cells have been implicated in the pathogenesis of AMD. Since oxidative stress plays an important role in cell death and stimulates VEGF, an angiogenic factor, in hRPE cells, we investigated the effect of querectin, a flavonoid that protects against oxidative injury, on VEGF synthesis.
Methods:
Human retinal pigment epithelial (hRPE) cells were cultured from non-pathologic human eyes obtained from the Michigan Eye Bank. Cell proliferation was quantitated by 3H-thymidine incorporation, while cell viability was quantitated with trypan blue exclusion. The effect of hydrogen peroxide and quercetin on VEGF synthesis was quantitated using 14C-methionine immunochemistry. Qualitative VEGF expression was documented using immunohistochemistry. Statistical analysis was performed using Microsoft Excel.
Results:
Fetal bovine serum (FBS) stimulated hRPE cell proliferation and viability in a dose dependent manner. Hydrogen peroxide reduced cell viability, also in a dose-dependent manner (0 to 0.5 mM). However, the combination of quercetin and hydrogen peroxide lead to less cell damage when compared to the effects of hydrogen peroxide alone. Increasing concentrations of hydrogen peroxide stimulated a statistically significant dose dependent increase in the production of VEGF as indicated by 14C-methionine incorporation. Quercetin reduced the 0.5 mM hydrogen peroxide inhibition of VEGF synthesis when compared to 0.5 mM hydrogen peroxide alone (360.11 ± 74.88 vs. 793.68 ± 125, CPM ± SEM, p< 0.05, n=8). Phase contrast microscopy confirms there is greater morphological cell damage with hydrogen peroxide than control and that quercetin can at least partially prevent the damage seen in hydrogen peroxide exposed cells.
Conclusions:
Oxidative stress caused by hydrogen peroxide results in reduced hRPE cell viability and proliferation. Quercetin, a flavonoid that protects against oxidative cellular injury, can prevent this damage. Quercetin can also inhibit hydrogen peroxide induced increases in VEGF synthesis, a known angiogenic factor involved in proliferative ocular diseases. Therefore, quercetin may be of therapeutic value in preventing or treating AMD.
Keywords: 424 antioxidants •
694 retinal culture •
412 age-related macular degeneration