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Foxo1 Attenuates NaF-Induced Apoptosis of LS8 Cells through the JNK and Mitochondrial Pathways

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Abstract

Fluoride-induced ameloblast apoptosis is a key event in dental fluorosis development. Forkhead box o1 (Foxo1) is a transcription factor involved in cell apoptosis. The present study aims to investigate the effect of Foxo1 on ameloblast apoptosis induced by fluoride in vitro and to explore its possible mechanism. Ameloblast-like cells (LS8 cells) were exposed to various concentrations of NaF for up to 48 h. Foxo1 activation was modulated using lentiviral vectors, and cell apoptosis was measured by flow cytometry. The expression levels of Foxo1, c-Jun N-terminal kinase (JNK), and some well-known regulators of the mitochondrial pathway of apoptosis (cytoplasmic cytochrome c, cleaved caspase-9, cleaved caspase-3, Bcl-2, and Bax) were detected by quantitative real-time PCR, western blot, and immunofluorescence assay. The results showed significantly decreased expression and increased phosphorylation of Foxo1 in NaF-treated LS8 cells. Further investigation revealed that forced Foxo1 activation with lentiviral vectors attenuated NaF-induced apoptosis of LS8 cells, markedly decreasing protein levels of cytoplasmic cytochrome c, cleaved caspase-9, and cleaved caspase-3 while increasing the Bcl-2/Bax ratio and JNK expression level. These findings suggest that Foxo1 attenuated NaF-induced apoptosis of LS8 cells via inhibiting the mitochondrial pathway and activating JNK.

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Acknowledgments

This study was funded by the National Natural Science Foundation of China (Grant No. 81470034). We thank Professor Malcolm L. Snead (Department of Biomedical Sciences, University of Southern California) for donation of LS8 cells.

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Authors and Affiliations

  1. Clinical Research Center of Shaanxi Province for Dental and Maxillofacial Diseases, Department of Preventive Dentistry, College of Stomatology, Xi’an Jiaotong University, 98 XiWu Road, Xi’an, Shaanxi, 710004, People’s Republic of China

    Juedan Li, Lin Zhao, Xiaomeng Zhao, Peng Wang, Yan Liu & Jianping Ruan

  2. Department of Oral Pathology, College of Stomatology, Ningxia Medical University, 1160 Shengli Street, Yinchuan, 750021, People’s Republic of China

    Lin Zhao

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  1. Juedan Li
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Correspondence to Jianping Ruan.

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Li, J., Zhao, L., Zhao, X. et al. Foxo1 Attenuates NaF-Induced Apoptosis of LS8 Cells through the JNK and Mitochondrial Pathways. Biol Trace Elem Res 181, 104–111 (2018). https://doi.org/10.1007/s12011-017-1015-1

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