Abstract: Objective To investigate the protective effects of crocin on photoaged skin fibroblasts, and elucidate the mechanism of crocin on anti-photoaging, which could provide new evidence for clinical application of crocin. Methods 1. Human skin fibroblasts were isolated and treated with different concentration of crocin (0, 50, 100, 100μM) for 72 hours. CCK-8 assay was performed to detect cell proliferation. 2. Fibroblasts were irradiated with different doses of ultraviolet light (25, 50, 100 mJ/cm2), cell proliferation was measured by CCK-8 kit after 72 hours. 3. Fibroblasts were treated with different concentration of crocin (0, 50, 100, 100μM) for 24 hours and irradiated by ultraviolet light (100 mJ/cm2). Intracellular reactive oxygen species (ROS) were analyzed immediately by flow cytometry. Cell cycles were analyzed 48 hours after irradiation by flow cytometry. Seventy-two hours after treatment, cell proliferation was measured by CCK-8 kit, total RNA was extracted, and the expression of type Ⅰ collagen were detected by RT-PCR. Results 1. Low concentration of crocin (50, 100 μM) had no significant effect on the proliferation of skin fibroblasts while high concentration of crocin (200μM) promoted cell proliferation. 2. Ultraviolet irradiation inhibited the proliferation of skin fibroblast in a dose dependent manner. 3. Ultraviolet irradiation enhanced cellular level of ROS, and inhibited cell proliferation and the expression of typeⅠcollagen. Crocin (12.5, 25, 50, 100μM) treatment reduced the production of ROS caused by ultraviolet irradiation, and restored the cell cycle, cell proliferation, and type I collagen expression. Conclusion Crocin prevent the photoaging of dermal fibroblasts against ultraviolet irradiation by reducing the cellular level of ROS and restoring the cell cycle and type I collagen expression.

Key words: Skin photoaging, Crocin, Antioxidation