Fluorofenidone inhibits UV-A induced senescence in human dermal fibroblasts via the mammalian target of rapamycin-dependent SIRT1 pathway

The aim of this study was to investigate the protective effect of fluorofenidone (5-methyl-1-[3-fluorophenyl]-2-[1H]-pyridone, AKF-PD) on ultraviolet (UV)-A-induced senescence in human dermal fibroblasts (HDF) and examine the mechanisms involved. HDF were treated with AKF-PD. Senescence-associated (SA)--galactosidase level, cell viability and expression of p16 were evaluated. In addition, UV-A-irradiated HDF were treated with AKF-PD, rapamycin and MHY1485; SA--galactosidase staining, 3-(4 5-dimethylthiazol-2-yl)-2 5-diphenyltetrazolium bromide assay and western blot for SIRT1 were performed; and phosphorylated mammalian target of rapamycin (p-mTOR) expression and reactive oxygen species (ROS) levels were measured. Intracellular ROS was detected by the 2,7-dichlorofluroescein diacetate probe. Our results showed that AKF-PD substantially attenuated the changes of p16 expression, SA--galactosidase staining and cellular proliferation induced by UV-A irradiation in HDF. AKF-PD rescued the increased mTOR phosphorylation and reduced SIRT1 expression induced by UV-A irradiation in HDF. AKF-PD and rapamycin together had a synergistic effect on p-mTOR reduction and SIRT1 increase. mTOR activator MHY1485 partly blocked the above effects. Moreover, intracellular ROS level induced by UV-A irradiation could partly decrease by AKF-PD, and MHY1485 could reduce this effect. Our results indicated that AKF-PD could alleviate HDF senescence induced by UV-A-irradiation by inhibiting the p-mTOR and increasing SIRT1. Moreover, AKF-PD may be a potential treatment material for skin.