In a previous blog I explained how the biorhythm works. In this blog we will discuss this further, in particular the relationship of the biorhythm at the cellular level and the skin will be highlighted.
The result of the biorhythm is a flexible clock system, with a period of about a day that continuously adapts to the timing of ambient light, sunlight, but also the light from electronic devices that reach a part of your brain (SCN) through your eyes. But what effect does this have on your skin?
Biorhythm and the skin
The circadian clock, the ancient system that regulates human physiology based on diurnal variation. The clock has a natural influence on the functioning of our skin. Day and night create very different environments for the skin. At night, the risk of physical injury decreases and UV exposure decreases. However, during the day the skin is exposed to warmer temperatures and, for example, the water loss of the skin increases. Research in recent years has focused on variations of the circadian rhythm in human skin and its influence on the processes from within.
Like every organ, the skin has its own biorhythm. The skin consists of three different layers, the epidermis, the dermis (dermis) and the subcutaneous connective tissue (subcutaneous fat). These layers in turn consist of different skin cells. These skin cells form different tissues of the skin and protect the skin against dehydration, hypothermia, infections and other external influences. Basal cells, pigment cells, keratinocytes, Langerhans cells and Merkel’s touch corpuscles are such cells. These cells are constantly moving and each has an active circadian clock that is likely to regulate different functions in different cell types.
Since the epidermis has a constant cell renewal, the correct timing of events is crucial. For example, research has shown that this cycle of cell renewal and the number of cell divisions is highest around 1 a.m. and lowest around 1 p.m. In mice, this came to light when they were exposed to UVB at night. The recovery of DNA is then at its lowest.
In addition, UVB rays caused more DNA damage and a higher incidence of skin cancer than during the day. But functions such as trans epidermal water loss (moisture loss from the deeper skin layers), hydration of the stratum corneum (outer skin layer) and the immune system are also regulated by the circadian clock. Once again it has been proven in mice that the severity of a skin reaction caused by an infection can depend on the time of day.
Biorhythms and aging (of the skin)
In addition to cell cycle regulation, circadian rhythms are also related to stem cell aging. A stem cell is a cell that is located in the bone marrow in the bones, but also in the hypothalamus. This cell is capable of changing into another cell type, known as differentiating.
Stem cells have no identity and can still develop into a specialized cell type. This process is triggered when one cell is damaged, at which point signaling compounds are secreted into the blood and end up with the stem cells. The stem cells are then lured to the relevant area via the blood. This ensures that the damaged cell is replaced by a new cell. So you can imagine that this process is part of the aging process. For example, recent research has shown that the hypothalamus plays a particularly important role in this. As you could read in my previous blog about the biorhythm, the hypothalamus (an important part of the brain) is also involved in the biorhythm process.
American researchers investigated whether stem cells in the hypothalamus were responsible for aging. This was then tested on mice. They removed the stem cells from some mice and added new stem cells from other mice. The mice with significantly fewer stem cells showed remarkable signs of aging and a shortened lifespan. The researchers then concluded that loss of stem cells in the hypothalamus causes aging. However, studies must now determine whether this process also occurs in humans and/or whether loss of subcutaneous fat and delayed tissue healing occur with the loss of stem cells.
The Role of Ultraviolet Light
Most people are well aware that ultraviolet light (UV light) causes DNA damage at the cellular level. UV-B radiation therefore has the greatest daily impact on our skin and is most closely associated with disrupting circadian clock gene expression. Too much damage can manifest itself in skin cancer. Fortunately, there is a machine in every cell of your body to repair DNA damage as quickly as possible. However, a disturbed biorhythm throws a spanner in the works and makes it more difficult for cells to recover.
You are now reading this blog from your iPad, iPhone or laptop and you probably spend more hours a day on these devices.
Can the use of these devices be harmful to your skin is the big question.
YAAAEEEEEE, it’s a yes and nee. On the one hand, you are exposed to another form of light pollution, namely HEV (high-energy visible light), “blue light”. In addition to the natural form of blue light that comes from the sun, it also comes from your mobile devices. But how much of this light is harmful to your skin.
On the other hand, most studies indicate that from 40j/cm2 (the amount of energy on one cm2) is harmful to your skin and can affect your skin barrier. To provide insight into how you achieve that 40j/cm2, the following example:
When you play Angry Birds on your iPhone 5s (4 inch screen, distance 22.5 cm ): it emits 16.4 µW/cm² of visible light, so it takes you 28.2 days to reach 40 J/cm². So it will take a while before you reach the limit. However, the amount of radiation does increase with the size of your screen.
In addition, the use of electric lighting in modern times makes people more susceptible to prolonged exposure to light throughout the year. Due to this disruption of the biorhythm, a wide variety of stresses on different cells such as stem cells, pigment cells and keratinocytes can arise.
Today’s modern lifestyle prevents the correct setting of the central circadian clock, as we can get up before sunrise and go to bed much later than sunset. The amount of artificial blue light is of great importance here and brings the circadian clock out of its natural rhythm. Blue light is the quality of light that makes us more alert and awake because the light inhibits the release of melatonin. These can be either artificial light sources, but especially the use of electronic devices that emit predominantly blue light. Since the central clock sets the peripheral clocks, the skin is an organ that suffers from this situation.
The central clock is found in the brain, also called the suprachiasmatic nucleus (SCN), and the peripheral clocks are present in almost all organs and tissues, including the skin. The peripheral clocks are controlled by the central clock and this clock is controlled by the light. So it is all connected. When this is disrupted and no longer in balance, we can speak of an epidermal jet lag, which of course also occurs when time is shifted as a result of long-haul flights. The epidermal jet lag causes cell division and regeneration (recovery) to be disrupted, which leads to skin disorders and syndromes that differ from muscle diseases to eczema.
Skin protection from epidermal jet lag?
Living a life with the sun, but avoiding direct sunlight on the skin sounds simple, but we see that the implementation is still difficult.
The role of the circadian clock in the skin needs further investigation, simply considering a ‘skin clock’ may help explain the physiological role of circadian variations on the continuously dividing skin cells. Elucidation of the biorhythms can lead to the optimization of wound healing therapy and a better understanding of the aging cell.
Desotelle, J. A., Wilking, M. J., Ahmad, N. (2012) The circadian control of skin and cutaneous photodamage. Department of dermatology, photochemistry and photobiology.
Gringras, P., Middleton, B., Skene, D. J., Revell, V. L. (2015) Bigger, brighter, bluer-better? Current light-emitting devices- adverse sleep properties and preventative strategies. Fronties in public health. 3:233.
Hettwer, S., Gyenge, E. B., Obermayer, B. (N.D.) Influence of cosmetic formualtations on the skin’s circadian clok.
Masri, S., Kinouchi, K., Sassone-Corsi, P. (2015) Circadian clocks, epigenetics and cancer. Current Opinion, 27-1.
Vaughn AR, Clark AK, Sivamani RK, Shi VY. Circadian rhythm in atopic dermatitis-Pathophysiology and implications for chronotherapy. Pediatr Dermatol. 2018;35(1):152‐157
Aoyama S, Shibata S. The Role of Circadian Rhythms in Muscular and Osseous Physiology and Their Regulation by Nutrition and Exercise. Front Neurosci. 2017;11:63.
Wang, H., van Spyk. E., Liu, Q., Geyfman, M., Salmans, M. L., Kumar, V., Ihler, A., Li, N., Takahashi, S., Andersen, B. (2017) Time restricted feeding uncouples the cicadian clock and the cell cycle of epidermal stem cells, and alters the sensitivity to UVB-induced DNA damage. Cell reports.
Now that you are here
The light spectrum is vastly wider than what we can perceive. The visible spectrum of light has a wavelength between 380 nm and 750 nm. The differences in wavelengths are seen by the eye as different colors
Until recently, visible light was thought to be relatively inert compared to its spectral neighbors, ultraviolet and infrared radiation. However, it has recently been reported in the literature that visible light can cause redness in fair skin, and pigment changes in darker skinned individuals. More on the dark side of light