Paeonia delavayi seed oil alleviates UVB-induced inflammation, oxidative stress and photoaging in keratinocytes through inhibition of PI3K/Akt/mTOR and NF-κB signaling pathways

UVB is one of the external stimuli posing a significant threat to the skin. Excessive exposure to UVB may trigger intracellular effects including inflammatory responses and oxidative stress, leading to severe skin issues. Peony seed oil is a nut oil unique to China, rich in unsaturated fatty acids, and reported to possess anti-inflammatory and antioxidant properties. Paeonia delavayi is a distinctive subspecies within the peony family, primarily distributed in southwestern China and high-altitude regions. This study aims to investigate the roles and underlying mechanisms of P. delavayi seed oil (PDSO) in protecting skin from UVB-induced damage. We found that treatment with PDSO effectively mitigated the adverse effects of UVB exposure on NHEK cells, including reduced viability and impaired migratory capacity. Additionally, PDSO significantly suppressed the upregulation of pro-inflammatory genes such as TNF, IL6, CXCL8 and PTGS2 in keratinocytes induced by UVB. Subsequent studies indicated that PDSO also alleviated UVB-induced oxidative stress and photoaging in NHEK cells, manifested by reducing ROS and MDA levels, upregulating antioxidant-related genes expression, and suppressing the expression of genes associated with cellular senescence. RNA-sequencing analysis and western blot assay revealed that PDSO exerts an inhibitory effect on the PI3K/Akt/mTOR pathway. We also found that PDSO suppressed the activation of the NF-κB pathway in UVB-irradiated NHEK cells. Thus, this study demonstrates that PDSO holds significant potential in protecting skin from UVB-induced damage and reveals that its mechanism of action involves the PI3K/Akt/mTOR and NF-κB signaling pathways.