Tissue-specific downregulation of type VII collagen gene (COL7A1) transcription in cultured epidermal keratinocytes by ultraviolet A radiation (UVA) and UVA-inducible cytokines, with special reference to cutaneous photoaging

UVA, TNF-α and IL-1β inhibit COL7A1 expression at the transcriptional level by acting on nucleotides −524 to −22 of the promoter region. These results suggest that UVA-induced downregulation of COL7A1 transcription in epidermal keratinocytes diminishes anchoring fibrils formation, resulting in skin fragility. Additional external factors including physical forces and UVB radiation in the sun-exposed areas may further promote deep wrinkle formation.