SHORT COMMUNICATION BLUE-LIGHT PHASE SHIFTS PER3 GENE EXPRESSION IN HUMAN LEUKOCYTES Katrin Ackermann, Tracey L. Sletten, Victoria L. Revell, Simon N. Archer, and Debra J. Skene Centre for Chronobiology, Faculty of Health and Medical Sciences, University of Surrey, Guildford, Surrey, UK The timing of clock gene expression in human leukocytes was investigated following a phase-advancing light stimulus to determine whether the response is wavelength- and/or age-dependent. PERIOD3 (PER3) clock gene expression in leukocytes and plasma melatonin were analyzed before and after monochromatic blue and green light exposure. Significant phase advances were observed in the peak timing of both PER3 expression and melatonin following blue but not green light. The amplitude of the PER3 rhythm at baseline was significantly reduced with age. However, age did not affect the response of the PER3 rhythm to light. (Author correspondence: d.skene@surrey.ac.uk) Keywords PERIOD3, Phase shift, Melatonin, Leukocytes, Blue light INTRODUCTION In humans, as in other mammals, most physiological and behavioral functions exhibit circadian (daily) oscillations that are driven by an endogenous clock located in the suprachiasmatic nuclei (SCN) of the anterior hypothalamus (see, e.g., Dardente & Cermakian, 2007; Reppert & Weaver, 2002). Besides its critical role in vision, environmental light also has important non-image-forming effects and is considered to be the main zeitgeber, or time cue, responsible for the entrainment of the cir- cadian clock to the external 24 h light-dark cycle. Photic input to the clock Chronobiology International, 26(4): 769–779, (2009) Copyright # Informa Healthcare USA, Inc. ISSN 0742-0528 print/1525-6073 online DOI: 10.1080/07420520902929045 Submitted December 11, 2008, Returned for revision January 16, 2009, Accepted January 26, 2009 The first two authors contributed equally to this study. Tracey L. Sletten is currently at the Sleep and Chronobiology Group, School of Psychology, Psychiatry and Psychological Medicine, Monash University, Victoria, Australia. Address correspondence to Prof. Debra J. Skene, Centre for Chronobiology, Faculty of Health and Medical Sciences, University of Surrey, Guildford, Surrey, GU2 7XH, UK Tel.: þ44 (0)1483 689706; Fax: þ44 (0)1483 686401; E-mail: d.skene@surrey.ac.uk Chronobiology International, 26(4): 769–779, (2009) Copyright # Informa Healthcare USA, Inc. 769 Chronobiol Int Downloaded from informahealthcare.com by University of Surrey on 01/04/13 For personal use only.