UVA and to UV-oxidized lipids proteomic regulation of the human keratinocytes

Ultraviolet light is the dominant environmental oxidative skin stressor and a major skin aging factor. We studied which oxidized phospholipid (OxPL) mediators Ultraviolet A (UVA) would generate in primary human keratinocytes (KC). Mass spectrometric analysis of the oxidized phospholipidome of KC immediately or 24h post stress revealed dynamic changes in abundance of 174 oxidized phosphocholine species. Exposure to UVA and to in vitro UVA - oxidized phospholipids both activated, on transcriptome and proteome level, NRF2/antioxidant response signaling and lipid metabolizing enzyme expression, whereas UVA additionally initiated the unfolded protein response (UPR). We identified Nupr1 as an upstream transcriptional regulator of UVA/OxPL mediated gene expression that is itself transcriptionally regulated by reactive lipids, which also aggregate and crosslink recombinant Nupr1 protein. Nupr1 governs the basal and stress regulated expression of cell cycle, redox reactive, autophagy- and lipid metabolizing genes in epidermal keratinocytes, making it a potential key factor in skin ROS responses, -aging and -pathology.