Prominent role of exopeptidase DPP III in estrogen-mediated protection against hyperoxia in vivo

A number of age-related diseases have a low incidence in females, which is attributed to a protective effect of sex hormones. For instance, the female sex hormone estrogen (E2) has a well established cytoprotective effect against oxidative stress, which strongly contributes to ageing. However, the mechanism by which E2 exerts its protective activity remains elusive. In this study we address the question whether the E2-induced protective effect against hyperoxia is mediated by the Nrf-2/Keap-1 signaling pathway. In particular, we investigate the E2-induced expression and cellular distribution of DPP III monozinc exopeptidase, a member of the Nrf-2/Keap-1 pathway, upon hyperoxia treatment. We find that DPP III accumulates in the nucleus in response to hyperoxia. Further, we show that combined induction of hyperoxia and E2 administration have an additive effect on the nuclear accumulation of DPP III. The level of nuclear accumulation of DPP III is comparable to nuclear accumulation of Nrf-2 in healthy female mice exposed to hyperoxia. In ovariectomized females exposed to hyperoxia, supplementation of E2 induced upregulation of DPP III, Ho-1, Sirt-1 and downregulation of Ppar-γ. While other cytoprotective mechanisms cannot be excluded, these findings demonstrate a prominent role of DPP III, along with Sirt-1, in the E2-mediated protection against hyperoxia.