Uncoupling protein-2 is an antioxidant that is up-regulated in the enamel organ of fluoride-treated rats

Abstract

Dental fluorosis is characterized by subsurface hypomineralization and retention of enamel matrix proteins. Fluoride (F−) exposure generates reactive oxygen species (ROS) that can cause ER-stress. We therefore screened oxidative stress arrays to identify genes regulated by F− exposure. Vitamin E is an antioxidant so we asked if a diet high in vitamin E would attenuate dental fluorosis. Maturation stage incisor enamel organs (EO) were harvested from F− treated rats and mice were assessed to determine if vitamin E ameliorates dental fluorosis. Uncoupling protein-2 (Ucp2) was significantly up-regulated by F− (~1.5 & 2.0 fold for the 50 or 100 ppm F− treatment groups respectively). Immunohistochemical results on maturation stage rat incisors demonstrated that UCP2 protein levels increased with F− treatment. UCP2 down-regulates mitochondrial production of ROS, which decreases ATP production. Thus, in addition to reduced protein translation caused by ER-stress, a reduction in ATP production by UCP2 may contribute to the inability of ameloblasts to remove protein from the hardening enamel. Fluoride treated mouse enamel had significantly higher quantitative fluorescence (QF) than the untreated controls. No significant QF difference was observed between control and vitamin E enriched diets within a given F− treatment group. Therefore, a diet rich in vitamin E did not attenuate dental fluorosis. We have identified a novel oxidative stress response gene that is up-regulated in vivo by F− and activation of this gene may adversely affect ameloblast function

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