MicroRNAs (miRNAs) play a central role in the regulation of many cellular processes including physiological and psychological stress reaction pathways. Psychological stress is an important factor for the genesis and maintenance of many diseases. Several miRNAs have already been described to be involved in its regulation. The presence of miRNAs in all body fluids implies a widespread role in communication throughout the whole organism and together with their stability makes them formidable candidates as biomarkers. Alterations of stress-associated miRNA expression levels have been found in the brain and whole blood of humans and animals. In this paper, we review the participation of miRNAs in stress-reactive processes as well as their usability as salivary biomarkers of such processes. In conclusion, we suggest that salivary miRNAs may be useful as noninvasive biomarkers to assess epigenetic regulation processes of chronic or acute psychological stress reactions.
Stress is an important co-factor for the genesis and maintenance of many diseases and is known to have an effect on gene expression via epigenetic regulation. MicroRNAs (miRNAs) appear to function as one of the key factors of this regulation. This is the first study to investigate the response of 11 stress-associated miRNAs in human saliva - as a non-invasive source - in an experimental condition of acute psychological stress, and also their correlation with established psychological (subjective stress perception), physiological (heart rate and heart rate variability) and biochemical stress parameters (salivary cortisol and alpha-amylase). 24 healthy participants between 20 and 35 years of age were investigated, using the Trier Social Stress Test (TSST) to induce acute psychological stress. Stress-associated changes were significant for miR-20b, -21 and 26b, and changes in miR-16 and -134 were close to significance, recommending further research on these miRNAs in the context of stress reactions. Significant correlations with alpha-amylase suggest their integration in sympathetic stress regulation processes. Additionally, our results demonstrate the TSST as a reliable tool for studying salivary miRNAs as non-invasive indicators of epigenetic processes in acute psychological stress reactions.
Colored light is applied in medicine in the treatment of various diseases. The aim of this study was to investigate potential effects of exposure to blue and red light on brain and muscle blood volume ([tHb]) and tissue oxygenation (StO2) measured by noninvasive near-infrared spectrophotometry (NIRS). Ten healthy volunteers were included in a randomized crossover study. Blue light exposure leads to decreased oxygen consumption in the brain and the skeletal muscle. I ntr oductionLight of different colors (CL) is applied for various medical conditions to improve the physical, emotional or mental state of patients. Examples are the use of blue light in the treatment of the neonatal jaundice [1], a phenomenon due to the immature liver function of newborns, the application of red [2] and UV light in dermatology (physical level), and the use of bright white light to treat seasonal affective disorders [3] (emotional or mental level). It is known that blue light is strongly absorbed by the skin, suppresses melatonin production and is generally associated with coldness. In contrast, red light penetrates tissue relatively deeply and is associated with warmth. However, little is known about the effects of CL on hemodynamics and tissue oxygenation.We therefore investigated potential effects of blue and red light, being the two main colors used in medical treatments, on blood volume and tissue oxygenation in the brain and skeletal leg muscle using near-infrared spectrophotometry (NIRS). M ater ials and methodsTen healthy volunteers (5 male, 5 female; mean age 27, range 23-44 years) were measured during blue and red light exposure. Light was generated using thermal white light sources (60W, OSRAM Inc., Germany) and color filters (Lee Inc., Germany). During exposure phases the CL was projected onto a white wall. The subjects were seated in a comfortable chair facing the wall. Subjects were asked to keep their eyes open throughout the entire measurement. Otherwise the room was completely dark and instruments were shielded in order to avoid ambient light.All subjects were measured twice on different days, exposed to blue or red light in a randomized crossover protocol. The protocol consisted of 8 min baseline (darkness), 10 min CL (blue or red) exposure, followed by 16 min recovery (darkness). Blood volume, i.e. total hemoglobin concentration ([tHb] in µM) and tissue oxygen saturation (StO 2 in %) were measured with a Hamamatsu NIRO 300 instrument. One sensor was attached to the forehead and the other to the lateral calf muscle. Using a paired t-test the last 5 min of the baseline were compared to the first and last 5 min of the CL exposure, and to 3 periods of 5 min of the recovery. Blue and red exposures were compared by a linear mixed effects (LME) model (R statistical software).
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