Abstract
Inorganic nanoparticles are known to protect skin from ultraviolet rays (UVR) and delay photoaging. However, the photoprotective effects of these nanoparticles have not been broadly analyzed at a genetic level. The study objectives are as follows: (1) to investigate how UV-only and complete solar light can affect signaling pathways and genes related to photoaging in human dermal fibroblasts; (2) to investigate how TiO(2) and ZnO nanoparticles provide photoprotection at a genetic level. RNAseq identified pathways and genes that were significantly affected by both irradiation conditions. Extracellular matrix (ECM) remodeling, inflammation, and cell cycle-related genes were subsequently validated by qPCR. The photoprotective properties of < 100 nm TiO(2) and ZnO dispersions at a 25% active level were analyzed through quantitative differences in the irradiation-induced expression of these genes. There were < 15 signaling pathways affected by UV and complete solar light (p-value (-log10) > 1). Significant differences in gene expression following irradiation were found in MMP1, MMP3, PTGS1, PTGES, MDM2, CDKN1A, and CCNE2 (p ≤ 0.05) through qPCR. TiO(2) and ZnO minimized the irradiation-induced expression of genes involved in the inhibition of matrix metalloproteinases, prostanoid biosynthesis, and cell cycle pathways. Photoprotection was best observed in cell cycle-related genes, showing expression differences of up to 74% (p ≤ 0.0001). However, no distinct differences in photoprotection between TiO(2) and ZnO were found. The findings from this study serve as a framework for future optimization and development of inorganic sunscreen formulations to target genes that contribute to different aspects of skin aging.