Expression of estrogen receptor α in human breast cancer cells regulates mitochondrial oxidative stress under simulated microgravity

This study investigated intracellular oxidative stress and its underlying mechanisms in a rotary cell culture system used to achieve a simulated microgravity (SMG) environment. Experiments were conducted with human breast cancer cell lines MCF-7 (an estrogen receptor (ER) alpha positive cell line) and MDA-MB-231 (an ER alpha negative cell line) encapsulated in alginate/collagen carriers. After 48 h, SMG led to oxidative stress and DNA damage in the MDA-MB-231 cells but a significant increase in mitochondrial activity and minimal DNA damage in the MCF-7 cells. The activity of superoxide dismutase (SOD) significantly increased in the MCF-7 cells and decreased in MDA-MB-231 cells in the SMG environment compared with a standard gravity control. Moreover, SMG promoted expression of ER alpha and protein kinase C (PKC) epsilon in MCF-7 cells treated with PKC inhibitor Go6983. Overall, exposure to SMG increased mitochondrial activity in ER alpha positive cells but induced cellular oxidative damage in ER alpha negative cells. Thus, ER alpha may play an important role in protecting cells from oxidative stress damage under simulated microgravity. (C) 2012 COSPAR. Published by Elsevier Ltd. All rights reserved.