Effects of nocturnal light on (clock) gene expression in peripheral organs: a role for the autonomic innervation of the liver

• Published in: PloS one 2009-05, Vol.4 (5), p.e5650
• Main Authors: Cailotto, Cathy, Lei, Jun, van der Vliet, Jan, van Heijningen, Caroline, van Eden, Corbert G, Kalsbeek, Andries, Pévet, Paul, Buijs, Ruud M
• Format: Article
• Language: English
• Subjects: Adrenal Glands - metabolism; Adrenal Glands - radiation effects; Analysis; Animals; Autonomic Denervation; Autonomic nervous system; Autonomic Nervous System - radiation effects; Biological clocks; Biological Clocks - genetics; Biological Clocks - radiation effects; Biosynthesis; Circadian rhythm; Circadian Rhythm - genetics; Circadian Rhythm - radiation effects; Circadian rhythms; Clock gene; CLOCK protein; Darkness; Diabetes; Diabetes and Endocrinology; Endocrine system; Endocrinology; Exposure; Fatty acids; Fibroblasts; Gene expression; Gene Expression Regulation - radiation effects; Genes; Genetic research; Glucose; Homeostasis; Hormones - metabolism; Hypothalamus; Innervation; Kinases; Light; Light effects; Liver; Liver - innervation; Liver - metabolism; Liver - radiation effects; Male; Mammals; Melatonin; Metabolism; Nervous system; Neuroscience; Neurosciences; Nocturnal; Organ Specificity - genetics; Organ Specificity - radiation effects; Organs; Oscillators; Physiological aspects; Physiology; Physiology/Endocrinology; Physiology/Integrative Physiology; Pineal gland; Pineal Gland - metabolism; Pineal Gland - radiation effects; Proteins; Rats; Rats, Wistar; Rodents; Studies; Suprachiasmatic nucleus; Time of use
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0005650

The biological clock, located in the hypothalamic suprachiasmatic nucleus (SCN), controls the daily rhythms in physiology and behavior. Early studies demonstrated that light exposure not only affects the phase of the SCN but also the functional activity of peripheral organs. More recently it was shown that the same light stimulus induces immediate changes in clock gene expression in the pineal and adrenal, suggesting a role of peripheral clocks in the organ-specific output. In the present study, we further investigated the immediate effect of nocturnal light exposure on clock genes and metabolism-related genes in different organs of the rat. In addition, we investigated the role of the autonomic nervous system as a possible output pathway of the SCN to modify the activity of the liver after light exposure. First, we demonstrated that light, applied at different circadian times, affects clock gene expression in a different manner, depending on the time of day and the organ. However, the changes in clock gene expression did not correlate in a consistent manner with those of the output genes (i.e., genes involved in the functional output of an organ). Then, by selectively removing the autonomic innervation to the liver, we demonstrated that light affects liver gene expression not only via the hormonal pathway but also via the autonomic input. Nocturnal light immediately affects peripheral clock gene expression but without a clear correlation with organ-specific output genes, raising the question whether the peripheral clock plays a "decisive" role in the immediate (functional) response of an organ to nocturnal light exposure. Interestingly, the autonomic innervation of the liver is essential to transmit the light information from the SCN, indicating that the autonomic nervous system is an important gateway for the SCN to cause an immediate resetting of peripheral physiology after phase-shift inducing light exposures.