Ultraviolet irradiation alters transforming growth factor β/Smad pathway in human skin in vivo

Tai Hao Quan, Tian Yuan He, Sewon Kang, John J. Voorhees, Gary J. Fisher

Research output: Contribution to journalArticlepeer-review

Abstract

Solar ultraviolet irradiation damages human skin and causes premature skin aging and skin cancer. As transforming growth factor β plays an important role in regulating cell growth and extracellular matrix synthesis, we investigated expression of transforming growth factor β isoforms, transforming growth factor β receptors, and transforming growth factor β regulated Smad transcription factors following irradiation with an ultraviolet B source and solar-simulated ultraviolet irradiation of human skin in vivo. Full-thickness, sun-protected adult human skin expressed transforming growth factor β1, β2, and β3 transcripts in a ratio of 1:5:3, as determined by quantitative real-time reverse transcription polymerase chain reaction. Northern analysis demonstrated that the ultraviolet irradiation (2 minimal erythema dose) caused moderate (2-3-fold) gradual increases of transforming growth factor β1 and β3 mRNA expression during 3 d post exposure. In contrast, expression of transforming growth factor β2 mRNA, the predominant form of transforming growth factor β in human skin, decreased within 4 h after ultraviolet irradiation. In situ hybridization revealed transforming growth factor β1, β2, and β3 mRNA expression in cells throughout the epidermis and the dermis in nonirradiated skin. Following ultraviolet or solar-simulated ultraviolet irradiation, transforming growth factor β1 and β3 mRNA were increased and transforming growth factor β2 mRNA was reduced throughout the epidermis and dermis. No significant changes were observed in transforming growth factor β type I receptor mRNA expression after ultraviolet irradiation. In contrast, transforming growth factor β type II receptor mRNA expression was reduced 60% within 4 h following ultraviolet exposure in human skin in vivo. Transforming growth factor β type II receptor mRNA levels remained reduced for 8 h and recovered by 24 h post ultraviolet. In situ hybridization revealed that ultraviolet or solar-simulated ultraviolet irradiation caused loss of transforming growth factor β type II receptor mRNA in basal and suprabasal cells in the epidermis and dermal cells. In addition, no significant changes were observed in Smad2, Smad3, and Smad4 expression after ultraviolet irradiation. In contrast, ultraviolet and solar-simulated ultraviolet irradiation rapidly induced gene expression of Smad7, which antagonizes the actions of the transforming growth factor β/Smad pathway. Smad7 mRNA induction occurred throughout the epidermis and dermal cells as determined by in situ hybridization. Ultraviolet irradiation also caused reduced DNA binding of Smad3/4 in human skin in vivo. Reduced Smad3/4 DNA binding was observed within 4 h following irradiation. Taken together, these results demonstrate that ultraviolet and solar-simulated ultraviolet irradiation alter the transforming growth factor β/Smad pathway in human skin in vivo. Ultraviolet induction of Smad7 and reduction of transforming growth factor β2 and transforming growth factor β type II receptor should diminish transforming growth factor β signaling, and probably contribute to the decrease of transforming growth factor β regulated type I and type III procollagen gene expression observed in ultraviolet and solar-simulated ultraviolet irradiated human skin in vivo.

Original languageEnglish (US)
Pages (from-to)499-506
Number of pages8
JournalJournal of Investigative Dermatology
Volume119
Issue number2
DOIs
StatePublished - 2002
Externally publishedYes

Keywords

  • Human skin
  • Smad pathway
  • TGF-β
  • Ultraviolet

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Dermatology
  • Cell Biology

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