a-Ionone protects against UVB-induced photoaging in epidermal keratinocytes

Objective: To evaluate whether a-ionone, an aromatic compound mainly found in raspberries, carrots, roasted almonds, fruits, and herbs, inhibits UVB-mediated photoaging and barrier dysfunction in a human epidermal keratinocyte cell line (HaCaT cells). Methods: The anti-photoaging effect of a-ionone was evaluated by detecting the expression of barrierrelated genes and matrix metalloproteinases (MMPs) in HaCaT cells. The levels of reactive oxygen species, oxidation product, antioxidant enzyme, and inflammatory factors were further analysed to underline the protective effect of a-ionone on epidermal photoaging. Results: It was found that a-ionone attenuated UVB-induced barrier dysfunction by reversing keratin 1 and filaggrin in HaCaT cells. a-Ionone also reduced the protein amount of MMP-1 and mRNA expression of MMP-1 and MMP-3 in UVB-irradiated HaCaT cells, implying protective effects on extracellular matrix. Furthermore, HaCaT cells exposed to a-ionone showed significant decreases in interleukin (IL)-1b, IL-6, IL-8, and tumor necrosis factor-a as compared to UVB-irradiated HaCaT cells. a-Ionone treatment significantly inhibited the UVB-induced intracellular reactive oxygen species increase and malondialdehyde accumulation. Therefore, the beneficial effects of a-ionone on inhibiting MMPs secretion and barrier damage may be related to attenuated inflammation and oxidative stress. Conclusion: Our results highlight the protective effects of a-ionone on epidermal photoaging and promote its clinic application as a potential natural anti-photodamage agent in future. (c) 2022 Tianjin Press of Chinese Herbal Medicines. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).