title: Effects of caffeine on circadian phase, amplitude and period evaluated in cells in vitro and peripheral organs in vivo in PER2::LUCIFERASE mice.
abstract: OBJECTIVE
  Caffeine is one of the most commonly used psychoactive substances. Circadian rhythms consist of the main suprachiasmatic nucleus (SCN) clocks and peripheral clocks. Although caffeine lengthens circadian rhythms and modifies phase changes in SCN-operated rhythms, the effects on caffeine on the phase, period and amplitude of peripheral organ clocks are not known. In addition, the role of cAMP/Ca(2+) signalling in effects of caffeine on rhythm has not been fully elucidated.
  
  
  METHODS
  We examined whether chronic or transient application of caffeine affects circadian period/amplitude and phase by evaluating bioluminescence rhythm in PER2::LUCIFERASE knock-in mice. Circadian rhythms were monitored in vitro using fibroblasts and ex vivo and in vivo for monitoring of peripheral clocks.
  
  
  RESULTS
  Chronic application of caffeine (0.1-10 mM) increased period and amplitude in vitro. Transient application of caffeine (10 mM) near the bottom of the decreasing phase of bioluminescence rhythm caused phase advance in vitro. Caffeine (0.1%) intake caused a phase delay under light-dark or constant dark conditions, suggesting a period-lengthening effect in vivo. Caffeine (20 mg·kg(-1) ) at daytime or at late night-time caused phase advance or delay in bioluminescence rhythm in the liver and kidney respectively. The complicated roles of cAMP/Ca(2+) signalling may be involved in the caffeine-induced increase of period and amplitude in vitro.
  
  
  CONCLUSIONS
  Caffeine affects circadian rhythm in mice by lengthening the period and causing a phase shift of peripheral clocks. These results suggest that caffeine intake with food/drink may help with food-induced resetting of peripheral circadian clocks.
authors.affiliation: Laboratory of Physiology and Pharmacology, School of Advanced Science and Engineering, Waseda University, Shinjuku-ku, Tokyo, Japan.
authors.forename: Seira
authors.initials: S
authors.lastname: Narishige
authors.forename: Mari
authors.initials: M
authors.lastname: Kuwahara
authors.forename: Ayako
authors.initials: A
authors.lastname: Shinozaki
authors.forename: Satoshi
authors.initials: S
authors.lastname: Okada
authors.forename: Yuko
authors.initials: Y
authors.lastname: Ikeda
authors.forename: Mayo
authors.initials: M
authors.lastname: Kamagata
authors.forename: Yu
authors.initials: Y
authors.lastname: Tahara
authors.forename: Shigenobu
authors.initials: S
authors.lastname: Shibata
mesh_terms: D000818:Animals; D002110:Caffeine / Q000494:pharmacology*; D000697:Central Nervous System Stimulants / Q000494:pharmacology*; D002940:Circadian Rhythm / Q000187:drug effects*; D005347:Fibroblasts / Q000187:drug effects*; D055879:Gene Knock-In Techniques; D066298:In Vitro Techniques; D007668:Kidney / Q000187:drug effects*; D008099:Liver / Q000187:drug effects*; D008156:Luciferases / Q000235:genetics; D051379:Mice; D056950:Period Circadian Proteins / Q000187:drug effects* / Q000235:genetics
chemical_list: D000697:Central Nervous System Stimulants; C513312:Per2 protein, mouse; D056950:Period Circadian Proteins; D002110:Caffeine; D008156:Luciferases