Altered expression of S100 fused-type proteins in human skin due to ultraviolet B irradiation.

Ultraviolet B (UVB) radiation profoundly affects epidermal homeostasis by inducing DNA damage, reactive oxygen species generation, and stress signalling. This review summarizes recent findings on the dynamic regulation of S100 fused-type proteins, including filaggrin (FLG), filaggrin 2 (FLG2), cornulin (CRNN), repetin (RPTN), hornerin (HRNR), trichohyalin (TCHH), and trichohyalin like protein 1 (TCHHL1) in human skin after UVB irradiation. In experiments using human skin xenografts, UVB (500 mJ/cm²) irradiation transiently upregulates proliferation-related proteins (TCHHL1, RPTN, and HRNR) and barrier-related proteins (CRNN, FLG2, and FLG) within two days, with normalization by day 7. These temporal changes correlate with activation of the ERK/p38 MAPK and STAT3 pathways, suggesting the existence of a coordinated regulatory network linking proliferation and differentiation during barrier repair. Altered expression in S100 fused-type proteins may serve as biomarkers of acute UVB responses and as targets for promoting epidermal recovery after photodamage.