The goal of this application is to characterize epigenetic and non-epigenetic functions of SIRT1 in adaptive responses during dental fluorosis. Fluoride is an effective caries prophylactic, however chronic over-exposure can result in dental fluorosis. More than 30% of children in the U.S. suffer from dental fluorosis. Our ultimate goal is to develop novel strategies that prevent or reduce dental fluorosis while keeping the benefit of prophylactic public water fluoridation to prevent caries. Recently we reported that fluoride activates SIRT1 and autophagy as an adaptive response to protect cells from cell stress. It is known that SIRT1 deacetylates histones to repress gene expression (epigenetic deacetylation). SIRT1 also deacetylates a number of non-histone proteins (non-epigenetic deacetylation) functioning in the regulation of autophagy, mitochondria metabolism, cell survival and organismal lifespan. However, the exact functions of SIRT1 and its downstream targets in dental fluorosis are unknown. Our goal in this proposal is to identify how SIRT1 functions in fluoride-induced stress responses and to find appropriate targets that could be modulated pharmacologically for the treatment of dental fluorosis. Our central hypothesis is that SIRT1 can play protective roles by intiating autophagy and regulating epigenetics in dental fluorosis. To test our hypothesis we propose three specific AIMs. AIM 1. Identify SIRT1 non-histone targets in ameloblast-derived cells treated with fluoride in vitro. AIM 2. Identify SIRT1 histone targets in ameloblast-derived cells treated with fluoride in vitro. AIM 3. Determine if SIRT1 over expression or conditional knockout effects enamel development and dental fluorosis in vivo. To attain these AIMs, we will use SIRT1 overexpressor and knockout ameloblast-like cells LS8 (LS8 Sirt1/over and LS8Sirt1/KO cells) established by the CRISPR/Cas9 technology in vitro. We will analyze the role of SIRT1 using SIRT1 over expressing mice (SIRT1super) and conditional knockout mice (SIRT1cKO) in vivo. Once epigenetic and non-epigenetic SIRT1 function in enamel pathophysiology is revealed, it may be possible to develop novel strategies to pharmacologically manipulate SIRT1 function to prevent dental fluorosis.

Project Narrative The prevalence of dental fluorosis among the population is increasing, however the mechanisms of the adaptive response that protects us from fluorosis remain unknown. Here we show that SIRT1 is part of a fluoride-induced adaptive response pathway and our focus is to identify how it protects us from the toxic effects of high-level fluoride exposure. Our preliminary studies strongly suggest that enhancing SIRT1 function will alleviate dental fluorosis.