Abstract

A reconstructed human epidermal model (RHE) colonized with human microbiota and sebum was developed to reproduce the complexity of the skin ecosystem in vitro. The RHE model was exposed to simulated solar radiation (SSR) with or without SPF50+ sunscreen (with UVB, UVA, long UVA and visible light protection). Structural identification of discriminating metabolites was acquired by nuclear magnetic resonance, and metabolomic fingerprints were identified using reverse-phase ultra-high-performance liquid chromatography and high-resolution mass spectrometry, followed by pathway enrichment analysis.

Over 50 metabolites were significantly altered by SSR (p < 0.05, log2 values), showing elevated skin oxidative stress (glutathione and purine pathways, urea cycle) and altered skin microbiota (branched-chain amino acid cycle and tryptophan pathway). RNA sequencing showed the relative abundance of various SSR-modified bacteria and fungal species. This study identified highly precise metabolomic fingerprints and metagenomic modifications of sun-exposed skin to help elucidate the interactions between the skin and its microbiota. 
 
The application of SPF50+ sunscreen protected the skin ecosystem from the deleterious effects of SSR and preserved physiological interactions. These innovative technologies could thus be used to assess the efficacy of photoprotectants.