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Updated: Feb 16, 2026

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UVA1 exposures change gene expression and circadian time-related protein CRY2 in human skin

Annina Haapasalo1, Olivia Liong2, Juha Jernman3

  • 1Department of Dermatology, Faculty of Medicine and Health Technology, Tampere University, Tampere, Finland; Department of Allergology and Dermatology, Tampere University Hospital, Tampere, Finland.

Journal of Photochemistry and Photobiology. B, Biology
|February 14, 2026
PubMed
Abstract

Insights

Low-dose ultraviolet A1 (UVA1) exposure alters skin gene expression and protein levels, including circadian clock genes, but does not affect deeper tissues. Continued skin protection from solar UVR is essential.

Area of Science:

  • Dermatology
  • Molecular Biology
  • Chronobiology

Background:

  • The molecular mechanisms of skin response to ultraviolet A1 (UVA1) are not fully understood.
  • Investigating the role of circadian clock genes in UVA1-induced skin changes is crucial.

Purpose of the Study:

  • To investigate the molecular mechanisms of low-dose UVA1 exposure on human skin.
  • To assess the contribution of diurnal preference and circadian clock genes to UVA1 effects.

Main Methods:

  • Healthy volunteers received UVA1 or violet light exposure.
  • Skin biopsies were analyzed using immunohistochemistry, transcriptomics, and RT-qPCR.
  • Gene enrichment and cellular deconvolution analyses were performed.

Main Results:

  • UVA1 exposure increased CRY2 and P53 protein levels.
  • 16 differentially expressed genes related to melanogenesis, cytotoxic protection, and circadian rhythm were identified.
  • UVA1 increased eosinophils and M0 macrophages, particularly in morning-type individuals.

Conclusions:

  • Low-dose UVA1 impacts skin gene expression, protein production, and cell fractions.
  • Effects of UVA1 exposure were limited to the skin and did not reach subcutaneous adipose tissue.
  • Protection against solar UVR remains vital regardless of diurnal preference.
Keywords:
ChronotypeCryptochromeProtein productionSkin biopsyTranscriptome

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