Abstract
Sunlight is an important factor in regulating the central circadian rhythm, including the modulation of our sleep/wake cycles. Sunlight had also been discovered to have a prominent influence on our skin’s circadian rhythm. Overexposure or prolonged exposure to the sun can cause skin photodamage, such as the formation of irregular pigmentation, collagen degradation, DNA damage, and even skin cancer. Hence, this review will be looking into the detrimental effects of sunlight on our skin, not only at the aspect of photoaging but also at its impact on the skin’s circadian rhythm. The growing market trend of natural-product-based cosmeceuticals as also caused us to question their potential to modulate the skin’s circadian rhythm. Questions about how the skin’s circadian rhythm could counteract photodamage and how best to maximize its biopotential will be discussed in this article. These discoveries regarding the skin’s circadian rhythm have opened up a completely new level of understanding of our skin’s molecular mechanism and may very well aid cosmeceutical companies, in the near future, to develop better products that not only suppress photoaging but remain effective and relevant throughout the day.
Highlights
The circadian rhythm is a 24 h periodic cycle that modulates the behavior and physiology of almost every living organism on Earth
When HaCaT cells were irradiated by 12.5 mJ/cm2 BB-ultraviolet B (UVB), miR-142-3p microRNA was increased, which in turn suppressed the expression of brain and muscle ARNT-like protein 1 (BMAL1) mRNA and protein, leading to an increase in DNA damage [28]
Another hallmark of photoaging is the formation of wrinkles and sagging skin [66]. This is known as ‘solar elastosis’, whereby it describes the histopathologic changes occurring as elastic tissue in the dermal layer degenerates due to prolonged exposure to the sun [67]. The occurrence of this is due to the cumulative exposure of our skin to ultraviolet rays (UVR) which increases the production of matrix metalloproteinases (MMPs) that degrade the extracellular matrix (ECM) proteins in our skin
Summary
The circadian rhythm is a 24 h periodic cycle that modulates the behavior and physiology of almost every living organism on Earth. It had been discovered that Rev-erbα and Rorα but all members of Rev-erb (α and β) and Ror (α, β and γ) can regulate the expression of BMAL1 [5] The discovery of these genes and proteins enables further understanding of how biological processes in humans are influenced by the circadian rhythm, through the light–dark cycle and through sunlight. The research question had slowly begun shifting to focus solely on UVR-induced skin photodamage but the scope had widened to include the effect UVR has on the skin’s circadian rhythm This is because the skin was discovered to possess a multi-oscillatory system whereby different types of skin cells at different levels had autonomous oscillation that is fine-tuned to adapt to environmental changes which surpassed the common notion about the damage and regeneration concept in human skin that it predominantly servs as the first line of barrier against UVR assaults [20]. By tapping into mother nature, a rich source of chemical leads, and the structural diversity of natural active ingredients, researchers may discover some useful compounds that could modulate the skin’s circadian rhythm
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