Ultraviolet B radiation modifies circadian time in epidermal skin and in subcutaneous adipose tissue

Abstract

Ultraviolet radiation (UVR) reaching the skin is a carcinogen, inducing immunosuppression and DNA mutations, 1 and the wavelengths of ultraviolet light B (UVB) represent a biologically very active part of it. 2 The chromophores transduct the electromagnetic energy of UVB into neural, chemical, and hormonal signals to produce rapid (neural) or slow (humoral or immune) responses at the local and systemic levels. 3,4 Skin irradiated by UVB can activate both the central and local hypothalamic-pituitary-adrenal (HPA) axis to turn on homeostatic responses and deactivate local and systemic damage. 4,5 Locally UVB irradiation of the skin leads to activation of pro-opiomelanocortin (POMC) and corticotropin-releasing hormone (CRH) in epidermal and dermal skin, produces cutaneous POMC peptides and activates the corresponding receptors that are important regulators on the pigmentary and the inflammatory reactions. 6-8 In addition, keratinocytes stimulated by UVB can, as a rapid effect, secrete, for example, Summary Background: Recent findings suggest that circadian time regulates cellular functions in the skin and may affect protection against ultraviolet radiation (UVR). It is not known, however, whether UVR through skin directly affects the expression of circadian genes. We investigated the effect of ultraviolet B (UVB) exposure on cryptochrome circadian clock 1 (CRY1), cryptochrome circadian clock 2 (CRY2), and circadian associated repressor of transcription (CIART) genes.Methods: Healthy volunteers (n = 12) were exposed to narrow-band UVB radiation of four standard erythemal dose (SED). Epidermal/dermal and subcutaneous adipose tissue samples were obtained by punch biopsies from irradiated and non-irradiated skin 10 cm away from the irradiated site 24 hours after UVB exposure. Gene expression of CRY1, CRY2, and CIART was measured using RT-PCR (TaqMan). Results: Ultraviolet B radiation affected mRNA expression in the epidermal/dermal skin and in the subcutaneous adipose tissue. It down-regulated expression of CRY2 gene in the epidermal/dermal skin, whereas it up-regulated expression of CRY1 and CIART genes in the subcutaneous adipose tissue. Conclusion:We showed for the first time that UVB radiation affects expression of circadian genes in the subcutaneous adipose tissue. Further studies are warranted to understand the mechanisms in detail.

Differential Regulation of Circadian Clock Genes by UV-B Radiation and 1,25-Dihydroxyvitamin D: A Pilot Study during Different Stages of Skin Photocarcinogenesis

“…Knowledge regarding the direct effects of UVB radiation on CCG expression, on the other hand, is limited. In fact, since the study by Kawara et al in 2002 [ 40 ], only one in vitro [ 41 ] and one in vivo [ 42 ] study have specifically investigated the effects of UVB on CCGs in keratinocytes and not vice versa. None of those studies in fact elaborated on the time-specific effects of UVB radiation.…”

“…Future studies are planned to explicitly investigate these connections, particularly focusing on the mechanistic links between CCG dysregulation and key cancer pathways such as p53. UVB has been shown to directly influence CCG expression in epidermal skin and subcutaneous adipose tissue in vivo [ 42 ], although the exact rhythmicity effects over time and the consequences of those effects need further research.…”

Enhancing Skin Anti-Aging through Healthy Lifestyle Factors

“…also affect "clocks" in peripheral tissues, including the skin [166][167][168]. The communications between the central SCN clock and the skin clock(s) coordinate various functions (i.e., homeostasis, proliferation/repair, immune and stress responses) [166][167][168], Notably, the circadian skin clock(s) in the epidermis, dermis and hypodermis can be altered/disrupted by sunburn (UV-induced erythema), aging, infections, hydration, inflammatory dermal disorders, food intake, sleep, and injury/wound healing [166][167][168][169][170][171][172]. The biological rhythms in the skin and skin clock genes have been reviewed in detail elsewhere [166,[168][169][170].…”

Cosmeceutical Therapy: Engaging the Repercussions of UVR Photoaging on the Skin’s Circadian Rhythm

“…Later experimentations on the epidermis and dermis layers of adult skin type II and III biopsies then demonstrated significant downregulation of CRY2 after exposure to NB-UVB. In comparison to CRY2 , CRY1 only experienced a slight increase in expression 24 h after irradiation, giving rise to a significant CRY1/2 ratio [ 25 ]. The mention of this ratio is important as a significant CRY1/2 ratio is an indicator of the occurrence of DNA damage given that CRY2 −/− cells have a higher propensity to elevate DNA damage accumulation [ 35 ].…”