Fig. 3.

Guanine deaminase (GDA) mediated ultraviolet (UV)-induced keratinocyte (KC) senescence via reactive oxygen species (ROS) production. (a, b) Dihydroethidium (DHE) staining in primary cultures of normal human skin keratinocytes with or without UVB irradiation (300 mJ/cm², 3 times) and (a) GDA knockdown or (b) GDA overexpression. (c-e) Immunofluorescence staining with senescence-associated (SA) β-Gal and western blot analysis of the relative ratios of p16 and p21 protein levels in KCs with or without UVB irradiation and (c) GDA knockdown, (d) GDA overexpression and N-acetyl-L-cysteine (NAC) pretreatment, or (e) H2O2 treatment and NAC pretreatment. Staining intensities were measured using Wright Cell Imaging Facility (WCIF) ImageJ software. β-Actin was used as an internal control for western blot analysis. Data represent means±standard deviation (SD) of 3 or 4 independent experiments. *p < 0.05 vs. control KCs, #p < 0.05 vs. UV-exposed or H₂O₂-treated KCs.