Protective Effects and Molecular Mechanism of Total Flavonoids from Lycium Barbarum Leaves on Photoaged Human Dermal Fibroblasts

OBJECTIVE: To investigate the effects and corresponding mechanisms of total flavonoids (TFL) from Lycium barbarum leaves on photoaged human dermal fibroblasts (HDFs). METHODS: Crude TFL was extracted with 70% ethanol, and a Rutin standard curve was drawn using the sodium nitrite-aluminum nitrate-sodium hydroxide colorimetry method to calculate its yield and mass concentration. After that, the photoaging HDFs model was established by UVA combined with 8-MOP. CCK-8 was performed to assess the influence of TFL on the proliferation of HDFs and photoaging HDFs. β-galactosidase (SA-β-gal) staining and activity assays were performed to evaluate the activity of SA-β-gal and the rate of SA-β-gal-positive cells in HDFs cells. The level of skin ECM proteins and oxidative stress-related substances in HDFs cells of each group was determined by ELISA and biochemical detection, respectively. Apoptosis of HDFs in each group was assessed by flow cytometry. The expressions of MAPK signaling pathway-related proteins in HDFs were detected by western blot. RESULTS: The yield rate of TFL extracted by 70% ethanol was 41.9%, and its purity rate was 34.6%. TFL at 25, 50, and 100 μg/mL was able to greatly promote the proliferation of HDFs. A photoaged HDFs model was successfully constructed by combining UVA irradiation at 9 J/cm(2) and 8-MOP at 50 mg/L. TFL treatment could significantly inhibit apoptosis, SA-β-gal-positive cell staining rate, SA-β-gal activity, lactate dehydrogenase (LDH) leakage, and malondialdehyde (MDA) content in photoaged HDFs. Further, TFL increased the proliferative activity, superoxide dismutase (SOD) activity, catalase (CAT) activity, type I collagen (Col I), hydroxyproline (HYP), and hyaluronic acid (HA) level of photoaged HDFs in a dose-dependent manner. Additional experiments suggested that TFL played a protective role by downregulating MAPK signaling pathway activity in photoaged HDFs cells. CONCLUSION: TFL could inhibit oxidative stress and apoptosis, promote cell proliferation and the level of ECM-related component proteins, and participate in antiphotoaging in a concentration-dependent manner. The protective role of TFL in photoaged HDFs might be related to its inhibition of MAPK signaling pathways.