title: The circadian clock and glucocorticoids--interactions across many time scales.
abstract: Glucocorticoids are steroid hormones of the adrenal gland that are an integral component of the stress response and regulate many physiological processes, including metabolism and immune response. Their release into the blood is highly dynamic and occurs in about hourly pulses, the amplitude of which is modulated in a daytime dependent fashion. In addition, in many species seasonal changes in basal glucocorticoid levels have been reported. In their target tissues, glucocorticoids bind to cytoplasmic receptors of the nuclear receptor superfamily. Upon binding, these receptors regulate transcription in a highly dynamic fashion, which involves stochastic binding to regulatory DNA elements on a time scale of seconds and heat shock protein mediated receptor-ligand complex recycling within minutes. The glucocorticoid hormone system interacts with another highly dynamic system, the circadian clock. The circadian clock is an endogenous biological timing mechanism that allows organisms to anticipate regular daily changes in their environment. It regulates daily rhythms of glucocorticoid release by a variety of mechanisms, modulates glucocorticoid signaling and is itself influenced by glucocorticoids. Here, we discuss mechanisms, functions and interactions of the circadian and glucocorticoid systems across time scales ranging from seconds (DNA binding by transcriptional regulators) to years (seasonal rhythms).
authors.affiliation: Institute of Toxicology and Genetics, Karlsruhe Institute of Technology (KIT), Campus Nord, Postfach 3640, D-76021 Karlsruhe, Germany. Electronic address: thomas.dickmeis@kit.edu.
authors.forename: Thomas
authors.initials: T
authors.lastname: Dickmeis
authors.forename: Benjamin D
authors.initials: BD
authors.lastname: Weger
authors.forename: Meltem
authors.initials: M
authors.lastname: Weger
mesh_terms: D000311:Adrenal Glands / Q000378:metabolism; D000818:Animals; D057906:Circadian Clocks; D025461:Feedback, Physiological; D005786:Gene Expression Regulation; D005938:Glucocorticoids / Q000502:physiology*; D006801:Humans; D012621:Seasons; D015398:Signal Transduction; D014158:Transcription, Genetic
chemical_list: D005938:Glucocorticoids
keywords: Circadian clock; Glucocorticoid; Pulsatile release; Seasonal rhythms; Signaling; Transcription