title: Enhancement of NAD⁺-dependent SIRT1 deacetylase activity by methylselenocysteine resets the circadian clock in carcinogen-treated mammary epithelial cells.
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.
authors.affiliation: Robert Wood Johnson Medical School, Rutgers, The State University of New Jersey, Piscataway, NJ, USA.|School of Public Health, Rutgers, The State University of New Jersey, Piscataway, NJ, USA.|Environmental and Occupational Health Sciences Institute, Rutgers, The State University of New Jersey, Piscataway, NJ, USA.|NIEHS Center for Environmental Exposures and Disease, Rutgers, The State University of New Jersey, Piscataway, NJ, USA.|Cancer Institute of New Jersey, Rutgers, The State University of New Jersey, Piscataway, NJ, USA.
authors.forename: Mingzhu
authors.initials: M
authors.lastname: Fang
authors.affiliation: Robert Wood Johnson Medical School, Rutgers, The State University of New Jersey, Piscataway, NJ, USA.
authors.forename: Wei-Ren
authors.initials: WR
authors.lastname: Guo
authors.affiliation: Veterinary Drugs & Biologics Division, Animal and Plant Quarantine Agency, Anyang 430-757, Republic of Korea.
authors.forename: Youngil
authors.initials: Y
authors.lastname: Park
authors.affiliation: Veterinary Drugs & Biologics Division, Animal and Plant Quarantine Agency, Anyang 430-757, Republic of Korea.
authors.forename: Hwan-Goo
authors.initials: HG
authors.lastname: Kang
authors.affiliation: Robert Wood Johnson Medical School, Rutgers, The State University of New Jersey, Piscataway, NJ, USA.|School of Public Health, Rutgers, The State University of New Jersey, Piscataway, NJ, USA.|Environmental and Occupational Health Sciences Institute, Rutgers, The State University of New Jersey, Piscataway, NJ, USA.|NIEHS Center for Environmental Exposures and Disease, Rutgers, The State University of New Jersey, Piscataway, NJ, USA.|Cancer Institute of New Jersey, Rutgers, The State University of New Jersey, Piscataway, NJ, USA.
authors.forename: Helmut
authors.initials: H
authors.lastname: Zarbl
mesh_terms: D000818:Animals; D016588:Anticarcinogenic Agents / Q000494:pharmacology*; D002273:Carcinogens / Q000633:toxicity; D047369:Chromatin Immunoprecipitation; D057906:Circadian Clocks / Q000187:drug effects*; D044127:Epigenesis, Genetic; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism; D005260:Female; D006801:Humans; D008321:Mammary Glands, Animal / Q000187:drug effects / Q000378:metabolism; D042361:Mammary Glands, Human / Q000187:drug effects* / Q000378:metabolism; D008770:Methylnitrosourea / Q000633:toxicity; D009243:NAD / Q000378:metabolism; D051381:Rats; D011916:Rats, Inbred F344; D060888:Real-Time Polymerase Chain Reaction; D017279:Selenocysteine / Q000031:analogs & derivatives* / Q000494:pharmacology; D056564:Sirtuin 1 / Q000378:metabolism*; D014162:Transfection
chemical_list: D016588:Anticarcinogenic Agents; D002273:Carcinogens; D017279:Selenocysteine; D009243:NAD; D008770:Methylnitrosourea; C447939:SIRT1 protein, human; D056564:Sirtuin 1; C002979:selenomethylselenocysteine
keywords: N-methyl-N-nitrosourea; SIRT1; circadian clock; methylselenocysteine; period 2