title: Diurnal variation of hepatic antioxidant gene expression in mice.
abstract: BACKGROUND
  This study was aimed to examine circadian variations of hepatic antioxidant components, including the Nrf2- pathway, the glutathione (GSH) system, antioxidant enzymes and metallothionein in mouse liver.
  
  
  RESULTS
  Adult mice were housed in light- and temperature-controlled facilities for 2 weeks, and livers were collected every 4 h during the 24 h period. Total RNA was isolated, purified, and subjected to real-time RT-PCR analysis. Hepatic mRNA levels of Nrf2, Keap1, Nqo1 and Gclc were higher in the light-phase than the dark-phase, and were female-predominant. Hepatic GSH presented marked circadian fluctuations, along with glutathione S-transferases (GST-α1, GST-µ, GST-π) and glutathione peroxidase (GPx1). The expressions of GPx1, GST-µ and GST-π mRNA were also higher in females. Antioxidant enzymes Cu/Zn superoxide dismutase (Sod1), catalase (CAT), cyclooxygenase-2 (Cox-2) and heme oxygenase-1 (Ho-1) showed circadian rhythms, with higher expressions of Cox-2 and CAT in females. Metallothionein, a small non-enzymatic antioxidant protein, showed dramatic circadian variation in males, but higher expression in females. The circadian variations of the clock gene Brain and Muscle Arnt-like Protein-1(Bmal1), albumin site D-binding protein (Dbp), nuclear receptor Rev-Erbα (Nr1d1), period protein (Per1 and Per2) and cryptochrome 1(Cry1) were in agreement with the literature. Furthermore, acetaminophen hepatotoxicity is more severe when administered in the afternoon when hepatic GSH was lowest.
  
  
  CONCLUSIONS
  Circadian variations and gender differences in transcript levels of antioxidant genes exist in mouse liver, which could affect body responses to oxidative stress at different times of the day.
authors.affiliation: Zunyi Medical College, Zunyi, China.
authors.forename: Yi-Qiao
authors.initials: YQ
authors.lastname: Xu
authors.forename: Dan
authors.initials: D
authors.lastname: Zhang
authors.forename: Tao
authors.initials: T
authors.lastname: Jin
authors.forename: Ding-Jun
authors.initials: DJ
authors.lastname: Cai
authors.forename: Qin
authors.initials: Q
authors.lastname: Wu
authors.forename: Yuanfu
authors.initials: Y
authors.lastname: Lu
authors.forename: Jie
authors.initials: J
authors.lastname: Liu
authors.forename: Curtis D
authors.initials: CD
authors.lastname: Klaassen
mesh_terms: D000082:Acetaminophen / Q000633:toxicity; D000375:Aging / Q000187:drug effects / Q000235:genetics; D000818:Animals; D000975:Antioxidants / Q000378:metabolism*; D056926:CLOCK Proteins / Q000235:genetics / Q000378:metabolism; D002940:Circadian Rhythm / Q000187:drug effects / Q000235:genetics*; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D005978:Glutathione / Q000378:metabolism; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D008107:Liver Diseases / Q000235:genetics / Q000473:pathology; D008297:Male; D008668:Metallothionein / Q000235:genetics / Q000378:metabolism; D051379:Mice; D051267:NF-E2-Related Factor 2 / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism
chemical_list: D000975:Antioxidants; D051267:NF-E2-Related Factor 2; C495636:Nfe2l2 protein, mouse; D012333:RNA, Messenger; D000082:Acetaminophen; D008668:Metallothionein; D056926:CLOCK Proteins; D005978:Glutathione