Expression of Clock Genes in Human Peripheral Blood Mononuclear Cells throughout the Sleep/Wake and Circadian Cycles

Abstract

The rhythmic expression of circadian clock genes in the neurons of the suprachiasmatic nucleus (SCN) underlies the manifestation of endogenous circadian rhythmicity in behavior and physiology. Recent evidence demonstrating rhythmic clock gene expression in non-SCN tissues suggests that functional clocks exist outside the central circadian pacemaker of the brain. In this investigation, the nature of an oscillator in peripheral blood mononuclear cells (PBMCs) is evaluated by assessing clock gene expression throughout both a typical sleep/wake cycle (LD) and during a constant routine (CR). Six healthy men and women aged (mean+/-SEM) 23.7+/-1.6 yrs participated in this five-day investigation in temporal isolation. Core body temperature and plasma melatonin concentration were measured as markers of the central circadian pacemaker. The expression of HPER1, HPER2, and HBMAL1 was quantified in PBMCs sampled throughout an uninterrupted 72 h period. The core body temperature minimum and the midpoint of melatonin concentration measured during the CR occurred 2:17+/-0:20 and 3:24 +/-0:09 h before habitual awakening, respectively, and were well aligned to the sleep/wake cycle. HPER1 and HPER2 expression in PBMCs demonstrated significant circadian rhythmicity that peaked early after wake-time and was comparable under LD and CR conditions. HBMAL1 expression was more variable, and peaked in the middle of the wake period under LD conditions and during the habitual sleep period under CR conditions. For the first time, bi-hourly sampling over three consecutive days is used to compare clock gene expression in a human peripheral oscillator under different sleep/wake conditions.

Krüppel-like factor 9 is a circadian transcription factor in human epidermis that controls proliferation of keratinocytes

“…This phase relation was as expected from the molecular makeup of the circadian clockwork. In general, substantial interindividual variances were detected in "amplitudes" (defined as maximum minus minimum expression in the analyzed time frame) of daytime-dependent genes similar to other studies using human blood mononuclear cells or oral mucosa as human tissue source (16)(17)(18). This is likely primarily attributable to interindividual differences in the epidermal oscillator, because we find a strong correlation of Per1 and Rev-Erbα amplitudes between individual subjects ( Fig.…”

Simulated Night Shift Disrupts Circadian Rhythms of Immune Functions in Humans

“…They were studied individually in time isolation for 6 d at the Centre for Study and Treatment of Circadian Rhythms of the Douglas Mental Health University Institute in May to August in 2013 and 2014. Participants were recruited as previously reported (34), and they gave their written informed consent, as approved by the Douglas Institute Ethic Board and within the ethical standard of the Declaration of Helsinki. For $7 d prior to laboratory admission, subjects maintained a stable sleep/wake schedule, with an average sleep duration of 07h59 6 00h02, to stabilize circadian rhythmicity (34).…”

“…Participants were recruited as previously reported (34), and they gave their written informed consent, as approved by the Douglas Institute Ethic Board and within the ethical standard of the Declaration of Helsinki. For $7 d prior to laboratory admission, subjects maintained a stable sleep/wake schedule, with an average sleep duration of 07h59 6 00h02, to stabilize circadian rhythmicity (34). Subjects were admitted to a time-free laboratory environment for 6 d ( Fig.…”

“…In central and peripheral clocks, rhythms with a period of ∼ 24 h are generated by autoregulatory feedback loops involving clock genes (e.g., CLOCK, BMAL1, Period or PER1-3, Cryptochrome or CRY1-2) (32). Hence, immune cells (e.g., monocytes/macrophages, lymphocytes) have the molecular clock machinery and display circadian gene expression (19,20,25,(33)(34)(35).…”

Circadian rhythms of angiogenic factors in skin and wound tissue in per2-mutant mice

“…Circadian gene Period 2 (per2) and another circadian gene, Cryptochrome1, whose expression in the implanted tumor cells exhibits a circadian oscillation, inhibit the hypoxia-induced Vegf promoter activity [4]. Other studies demonstrated that Period 1 (per1), another member of the Period family, and per2 exhibit circadian oscillations in mRNA expression in human peripheral leucocytes [5][6][7][8].…”