Modulatory effects of α- and γ-tocopherols on 4-hydroxyestradiol induced oxidative stresses in MCF-10A breast epithelial cells

The elevated level of circulating estradiol increases the risk of breast tumor development. To gain further insight into mechanisms involved in their actions, we investigated the molecular mechanisms of 4-hydroxyestradiol (4-OHE(2)) to initiate and/or promote abnormal cell growth, and of alpha- or gamma-tocopherol to inhibit this process. MCF-10A, human breast epithelial cells were incubated with 0.1 microM 4-OHE(2), either with or without 30 microM tocopherols for 96 h. 4-OHE(2) caused the accumulation of intracellular ROS, while cellular GSH/GSSG ratio and MnSOD protein levels were decreased, indicating that there was an oxidative burden. 4-OHE(2) treatment also changed the levels of DNA repair proteins, BRCA1 and PARP-1. gamma-Tocopherol suppressed the 4-OHE(2)-induced increases in ROS, GSH/GSSG ratio, and MnSOD protein expression, while alpha-tocopherol up-regulated BRCA1 and PARP-1 protein expression. In conclusion, 4-OHE(2) increases oxidative stress reducing the level of proteins related to DNA repair. Tocopherols suppressed oxidative stress by scavenging ROS or up-regulating DNA repair elements.