The Protective Effects of Unripe Apple (Malus pumila) Extract on Ultraviolet B-Induced Skin Photoaging Mouse Model

An unripe apple (immature fruit of Malus pumila Mill) contains more polyphenols than mature fruit. To explore the anti-photoaging effects of unripe apple extract (UAE), we investigated the effects of UAE on wrinkle improvement, skin moisturizing, skin inflammation, and antioxidant activities using the ultraviolet B (UVB)-irradiated SKH1-hr hairless mouse model. The mice were irradiated with UVB (0.18 J/cm(2)) three times per week and orally administrated UAE (100, 200, or 400 mg/kg) once a day for 15 weeks. The administration of UAE significantly prevented UVB-induced wrinkle formation and skin water loss, potentially by increasing the effects of UAE on type I collagen (COL1) and hyaluronic acid through the transcriptional regulation of COL1 alpha (COL1A1 and COL1A2), hyaluronan synthesis (HAS1, HAS2, and HAS3) and the matrix metalloproteinase (MMP1, MMP9, and MMP13) gene. Moreover, UAE significantly reduced UVB-induced skin edema, infiltrated neutrophils, and pro-inflammatory cytokine interleukin-1 beta (IL-1 beta), while increasing the anti-inflammatory cytokine IL-10. UAE also exerted anti-oxidative stress properties by increasing the glutathione content and inhibiting lipid peroxidation and superoxide anion production. The histopathological analysis demonstrated that UAE-induced anti-inflammation, anti-oxidative stress, and anti-apoptotic properties on the UVB-irradiated skin tissues. Therefore, UAE may be an effective natural resource to mitigate UVB-induced skin photoaging.