The central clock controls the daily rhythm of Aqp5 expression in salivary glands
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Salivary secretion displays day–night variations that are controlled by the circadian clock. The central clock in the suprachiasmatic nucleus (SCN) regulates daily physiological rhythms by prompting peripheral oscillators to adjust to changing environments. Aquaporin 5 (Aqp5) is known to play a key role in salivary secretion, but the association between Aqp5 and the circadian rhythm is poorly understood. The aim of our study was to evaluate whether Aqp5 expression in submandibular glands (SMGs) is driven by the central clock in the SCN or by autonomous oscillations. We observed circadian oscillations in the activity of period circadian protein homolog 2 and luciferase fusion protein (PER2::LUC) in cultured SMGs with periodicity depending on core clock genes. A daily rhythm was detected in the expression profiles of Aqp5 in SMGs in vivo. In cultured SMGs ex vivo, clock genes showed distinct circadian rhythms, whereas Aqp5 expression did not. These data indicate that daily Aqp5 expression in the mouse SMG is driven by the central clock in the SCN.
KeywordsCircadian rhythm Salivary gland Suprachiasmatic nucleus Aquaporin 5 Period 2
H.U. and W.N. designed the research; H.U., T.J.N., N.N.T., and W.N. performed the research; A.O.K., H.O., T.T., and T.S. contributed new reagents/analytic tools; H.U., T.J.N., N.N.T., and W.N. analyzed the data; H.U., T.J.N., N.N.T., and W.N. wrote the paper.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
This work was supported by JSPS KAKENHI grant numbers 26462809, 26860160, 26861780. N.N.T. is a research fellow of the Japan Society for the Promotion of Science.
All applicable international, national, and/or institutional guidelines for the care and use of animals were followed. The Protocol was approved by the Animal Care and Use Committee at Osaka University.
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