Enhancement of NAD⁺-dependent SIRT1 deacetylase activity by methylselenocysteine resets the circadian clock in carcinogen-treated mammary epithelial cells.

Mingzhu Fang,Wei-Ren Guo,Helmut Zarbl,Hwan-Goo Kang,Youngil Park

doi:10.18632/oncotarget.6002

Mingzhu Fang, Wei-Ren Guo + Show 3 more

Open Access

https://doi.org/10.18632/oncotarget.6002

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Journal: Oncotarget	Publication Date: Oct 26, 2015
Citations: 67	License type: cc-by

Affiliation: Rutgers, The State University of New Jersey

Abstract

We previously reported that dietary methylselenocysteine (MSC) inhibits N-methyl-N-nitrosourea (NMU)-induced mammary tumorigenesis by resetting circadian gene expression disrupted by the carcinogen at the early stage of tumorigenesis. To investigate the underlying mechanism, we developed a circadian reporter system comprised of human mammary epithelial cells with a luciferase reporter driven by the promoter of human PERIOD 2 (PER2), a core circadian gene. In this in vitro model, NMU disrupted cellular circadian rhythm in a pattern similar to that observed with SIRT1-specific inhibitors; in contrast, MSC restored the circadian rhythms disrupted by NMU and protected against SIRT1 inhibitors. Moreover, NMU inhibited intracellular NAD+/NADH ratio and reduced NAD+-dependent SIRT1 activity in a dose-dependent manner, while MSC restored NAD+/NADH and SIRT1 activity in the NMU-treated cells, indicating that the NAD+-SIRT1 pathway was targeted by NMU and MSC. In rat mammary tissue, a carcinogenic dose of NMU also disrupted NAD+/NADH oscillations and decreased SIRT1 activity; dietary MSC restored NAD+/NADH oscillations and increased SIRT1 activity in the mammary glands of NMU-treated rats. MSC-induced SIRT1 activity was correlated with decreased acetylation of BMAL1 and increased acetylation of histone 3 lysine 9 at the Per2 promoter E-Box in mammary tissue. Changes in SIRT1 activity were temporally correlated with loss or restoration of rhythmic Per2 mRNA expression in NMU-treated or MSC-rescued rat mammary glands, respectively. Together with our previous findings, these results suggest that enhancement of NAD+-dependent SIRT1 activity contributes to the chemopreventive efficacy of MSC by restoring epigenetic regulation of circadian gene expression at early stages of mammary tumorigenesis.

Highlights

The circadian clock regulates a wide range of cellular and physiological processes in a precise and sustained rhythm with a periodicity of ~24 hrs
Given that the Sirtuin 1 (SIRT1) activity is regulated by intracellular NAD+/NADH, we investigated the effects of NMU and MSC on the NAD+-SIRT1 pathway and their impact on mammary circadian clock using both in vitro and in vivo models
We previously reported that dietary MSC inhibits NMU-induced mammary tumorigenesis by resetting circadian gene expression disrupted by the carcinogen at early stages of tumorigenesis

Summary

Introduction

The circadian clock regulates a wide range of cellular and physiological processes in a precise and sustained rhythm with a periodicity of ~24 hrs. As circadian proteins accumulate in the cell, they are post-translationally modified and transported to the nucleus to repress or activate Clock:Bmal transcriptional activity. In this way, core circadian genes limit their own transcription and set up the rhythmic expression of CGs and CCGs [2]. Core circadian genes limit their own transcription and set up the rhythmic expression of CGs and CCGs [2] These intrinsic molecular oscillators can be reset by external signals including light, genotoxic stress, nutrients, hormones, and environmental signals [1,2,3,4]. Circadian clocks integrate a wide variety of environmental and cellular inputs to maintain normal cellular and physiological homeostasis under changing conditions

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