We report here evidence in support of the role of 17-β-estradiol (E2)-induced mitochondrial (mt) reactive oxygen species (ROS) as signal-transducing messengers. Based on monitoring the oxidation of 2’,7’-dichlorodihydrofluorescein by spectrofluorometry and flow cytometry we have identified that exposure of E2 triggers the immediate rapid production of intracellular ROS ranging from a one- to several-fold increase in a variety of cells. E2 stimulated ROS production does not correlate with the activity of the estrogen receptor (ER) because ROS generation was also induced in the ER negative cell line MDA-MB-468. The ROS is most likely hydrogen peroxide based on its inhibition by antioxidants and catalase and lack of any effects of E2 on O2-or NO• formation. The functional consequences of E2-induced ROS formation included enhanced cell adhesion as shown by elevated expression of CDC42, a marker of cell adhesion. E2-induced ROS activated the binding of AP-1 and CREB as measured by ELISA. In addition to ERs as signaling molecules, our findings further revealed that E2-induced mtROS also act as signal transducing messengers and suggests new targets for the development of antioxidant-based drugs or antioxidant gene therapy for the prevention and treatment of estrogen-dependent cancer.

[Proc Amer Assoc Cancer Res, Volume 46, 2005]