title: Biological Rhythms in the Skin.
abstract: Circadian rhythms, ≈24 h oscillations in behavior and physiology, are reflected in all cells of the body and function to optimize cellular functions and meet environmental challenges associated with the solar day. This multi-oscillatory network is entrained by the master pacemaker located in the suprachiasmatic nucleus (SCN) of the hypothalamus, which directs an organism's rhythmic expression of physiological functions and behavior via a hierarchical system. This system has been highly conserved throughout evolution and uses transcriptional-translational autoregulatory loops. This master clock, following environmental cues, regulates an organism's sleep pattern, body temperature, cardiac activity and blood pressure, hormone secretion, oxygen consumption and metabolic rate. Mammalian peripheral clocks and clock gene expression have recently been discovered and are present in all nucleated cells in our body. Like other essential organ of the body, the skin also has cycles that are informed by this master regulator. In addition, skin cells have peripheral clocks that can function autonomously. First described in 2000 for skin, this review summarizes some important aspects of a rapidly growing body of research in circadian and ultradian (an oscillation that repeats multiple times during a 24 h period) cutaneous rhythms, including clock mechanisms, functional manifestations, and stimuli that entrain or disrupt normal cycling. Some specific relationships between disrupted clock signaling and consequences to skin health are discussed in more depth in the other invited articles in this IJMS issue on Sleep, Circadian Rhythm and Skin.
authors.affiliation: The Estee Lauder Companies; 125 Pinelawn Rd., Melville, NY 11747, USA. mmatsui@estee.com.|Institute of Human Nutrition, College of Physicians &amp; Surgeons, Columbia University, New York, NY 10032, USA. mmatsui@estee.com.
authors.forename: Mary S
authors.initials: MS
authors.lastname: Matsui
authors.affiliation: The Estee Lauder Companies; 125 Pinelawn Rd., Melville, NY 11747, USA. epelle@estee.com.|Environmental Medicine, New York University School of Medicine, New York, NY 10016, USA. epelle@estee.com.
authors.forename: Edward
authors.initials: E
authors.lastname: Pelle
authors.affiliation: The Estee Lauder Companies; 125 Pinelawn Rd., Melville, NY 11747, USA. kdong@estee.com.
authors.forename: Kelly
authors.initials: K
authors.lastname: Dong
authors.affiliation: The Estee Lauder Companies; 125 Pinelawn Rd., Melville, NY 11747, USA. npernode@estee.com.|Materials Science and Engineering, Stony Brook University, Stony Brook, NY 11794, USA. npernode@estee.com.
authors.forename: Nadine
authors.initials: N
authors.lastname: Pernodet
mesh_terms: D000818:Animals; D057906:Circadian Clocks; D002940:Circadian Rhythm; D015870:Gene Expression; D005786:Gene Expression Regulation; D006801:Humans; D012879:Skin Physiological Phenomena; D013493:Suprachiasmatic Nucleus / Q000378:metabolism*
keywords: Krüppel-like factor 9; circadian rhythm; clock genes and skin; glucocorticoids; keratinocyte differentiation; oxidative stress; sebum; skin aging; skin barrier; trans-epidermal water loss