Fibroblasts derived from Gpx1 knockout mice display senescent-like features and are susceptible to H 2O 2-mediated cell death

Abstract

The Free Radical Theory of Aging proposes that reactive oxygen species (ROS) contribute to the pathophysiology of aging. Our previous data highlight the importance of antioxidant enzymes, superoxide dismutase 1 (Sod1) and glutathione peroxidase 1 (Gpx1), in regulating this process. Previously, we demonstrated that a perturbation in the Sod1-to-Gpx1 ratio, as a consequence of Sod1 overexpression, leads to senescence-like changes. We proposed that this was mediated via the Sod1 dismutation product H 2O 2, because H 2O 2 induced similar changes in control cells. However, it has been suggested that H 2O 2 production, via Sod1 dismutation, is rate-limited by the availability of the substrate O 2 − , and therefore age-related changes may occur as a result of other functions of Sod1. In this study, we test this notion in fibroblasts derived from Gpx1 null mutant mice (Gpx1−/−) that have elevated H 2O 2 as a consequence of the lack of its removal by Gpx1. We demonstrate senescence-like changes in Gpx1−/− fibroblasts that include (1) reduced proliferative capacity, DNA synthesis, and responsiveness to EGF and serum; (2) elevated levels of Cip1; (3) increased NF-κB activation; and (4) morphological features of senescent cells. Gpx1−/− fibroblasts also demonstrate a dose-dependent susceptibility to H 2O 2-induced apoptosis. Our findings suggest that Gpx1 is protective against both ROS-mediated senescence-like changes and oxidant-mediated cell death.