Vitamin E succinate inhibits proliferation and migration of retinal pigment epithelial cells in vitro: therapeutic implication for proliferative vitreoretinopathy.

Abstract

Retinal pigment epithelial (RPE) cells play an important role in proliferative vitreoretinopathy (PVR). Vitamin E succinate is an ester form of a potent biological antioxidant, vitamin E, and has unique effects on various cells. We examined the effect of vitamin E succinate on proliferation and migration of cultured bovine RPE cells, since these are critical steps in the development of PVR. Bovine RPE cells were cultured in minimal essential medium (MEM) containing 10% fetal calf serum (MEM-10). Cells were incubated with MEM-10 containing 25 microM vitamin E, vitamin E succinate, butylated hydroxytoluene (BHT) or d-mannitol. Cell proliferation was assessed by counting cell numbers on days 2, 4 and 6. 3H-Thymidine uptake was also examined in RPE cells incubated with various forms of vitamin E-- vitamin E, vitamin E succinate, Trolox, gamma-tocopherol, vitamin E acetate, vitamin E phosphate, vitamin E nicotinate--or antioxidants-- BHT or d-mannitol (25 microM each). RPE cell migration was studied as follows: A small area (5 x 15 mm) of confluent cultured RPE cells was denuded using a straight razor blade and incubation was continued for 20 h with MEM-10 containing vitamin E, vitamin E succinate, gamma-tocopherol or BHT. The number of cells that migrated into the denuded area from the wound edge in each microscopic field (x20) was counted and expressed as a percentage of control (MEM-10 alone). The antioxidants, vitamin E and BHT, stimulated RPE cell proliferation and 3H-thymidine incorporation compared with the control, while vitamin E succinate significantly inhibited both proliferation and 3H-thymidine uptake (IC50, 23 microM). Other forms of vitamin E or d-mannitol had no effect. Neither vitamin E nor BHT had a significant effect on RPE cell migration (108.2% and 112.6% of control, respectively), but vitamin E succinate inhibited migration (58.3%). Cell viability, assessed by the trypan blue dye exclusion test, was not impaired by a 3-day incubation with 50 microM of vitamin E succinate. An ester form of a physiological antioxidant, vitamin E succinate, inhibits RPE cell proliferation and migration without causing cellular toxicity. These findings suggest its therapeutic potential for the pharmacological treatment of PVR.