AbstractPolyunsaturated fatty acids (PUFA) in membrane lipids are prone to attack by reactive oxygen species (ROS), and the resulting lipid peroxidation can cause injury and death of cells. Glutathione peroxidase 4 (Gpx4) is an antioxidant defense enzyme that can directly detoxify lipid hydroperoxides generated by ROS. Overexpression of Gpx4 has been shown to be protective against oxidative damage in several cell lines. We examined in this study the stress response of neurons with increased expression of Gpx4, because neurons are especially vulnerable to oxidative injury as a result of their high content of PUFA. Our results show that primary culture cortical neurons derived from Gpx4 transgenic mice, which had increased expression of Gpx4, had increased cell survival and reduced level of apoptosis after exposure to t‐butyl hydroperoxide and hydrogen peroxide. We also studied the protective role of Gpx4 against β‐amyloid toxicity, because β‐amyloid‐induced neural toxicity is believed to be mediated through lipid peroxidation. Primary culture cortical neurons from Gpx4 transgenic mice had significantly less cell toxicity than their wild‐type counterparts after exposure to Aβ25–35 and Aβ1–40 peptides, and apoptosis induced by Aβ25–35 was attenuated in neurons from Gpx4 transgenic mice. Our data demonstrate that overexpression of Gpx4 protects neurons against oxidative injury and β‐amyloid‐induced cytotoxicity. © 2006 Wiley‐Liss, Inc.