17Beta-Estradiol Suppresses Hydrogen Peroxide-Induced Nuclear Factor Kappa B Activation in HT22 Cells

Kim, Pil J., 17beta-estradiol suppresses hydrogen peroxide-induced nuclear factor κappa B activation in HT22 cells. Master of Science (Biomedical Sciences), May, 2008, 78pp., 20 illustrations, 66 titles. Reactive oxygen species (ROS) are natural byproducts of normal cellular reactions. They are oxygen ions, free (non)radicals, and peroxides that are highly reactive with normal macromolecules, such as lipids, DNA, and proteins. Cells are normally able to defend against the damages of ROS via enzymes that neutralize them into water. However, when cells are not able to cope with the accumulation of ROS, distributions in signaling pathways and gene transcription will occur, which will ultimately lead to cell death. It is now widely accepted that increased oxidative stress-induced damage in the brain is a major cause of neurodegenerative diseases, such as Alzheimer’s disease (AD). Nuclear factor κappa-B (NFκB) is not only a ubiquitously expressed transcription factor but also a signaling protein that is activated by ROS-induced oxidative stress. Our laboratory has demonstrated the neuroprotective effects of 17β-estradiol (E2) are elicited via an anti-oxidant effect. The purpose of this project was to determine the role of NFκB activation in E2-mediated neuroprotection against hydrogen peroxide (H2O2)-induced oxidative stress. HT-22, a murine immortalized hippocampal neuronal cell line, was utilized to determine whether NFκB is activated by hydrogen peroxide-induced oxidative stress and whether E2 suppresses H2O2-induced NFκB activation. We observed that H2O2 activated NFκB by phosphorylation of IκBα (pIκBα), one of the NFκB inhibitor proteins, reduction of total IκBα, and induction of NFκB (p65) nuclear translocation. In contrast, E2 suppressed H2O2-induced NFκB activation by dramatic reducing pIκBα, increasing total IκBα, and inhibiting p65 nuclear translocation. Our results show that one of the mechanisms by which estrogens are neuroprotective against oxidative stress is through the attenuation of H2O2-induced NFκB activation.