Methyl Quercetin Inhibits Radiation-induced Senescence and TGF-β1-induced Myofibroblast Differentiation Through...

Previously, we demonstrated that continuous oral delivery of quercetin attenuated radiation-induced dermal fibrosis in C3H/HeN mice exposed to 35 Gy of ionizing radiation. Quercetin was rapidly metabolized and primarily detected in plasma, liver, and urine as methylated metabolites. The current study aimed to investigate the biological effects of methylated quercetin on radiation-induced cellular senescence and macrophage polarization, and to evaluate its therapeutic potential for ameliorating radiation-induced skin fibrosis. Skin tissue was collected from C3H/HeN mice fed quercetin-formulated or control chow and exposed to 0 Gy or 35 Gy at 150 days postirradiation. In mice irradiated with 35 Gy, quercetin chow administration reduced epidermis thickness, the number of cells that were positive for senescent markers (p21, p16) positive cells and vimentin-positive cells in the skin, compared with control chow administration. Also, the number of cells positive for macrophage markers (F4/80, CD206) were decreased. These in vivo results were consistent with findings in NIH/3T3 fibroblasts irradiated with either 0 Gy or 17.5 Gy in the presence of 3-O-methylquercetin (MQ) or vehicle. X-gal staining and p21 expression detected by Western blotting indicated that radiation-induced cellular senescence, but it was decreased by pretreatment of MQ. Senescence-associated secretory phenotype (SASP) factors including TGF-β1 and Pai-1 were significantly higher in the irradiated fibroblasts but decreased in the presence of MQ. In addition, MQ pretreatment reduced cell proliferation and vimentin expression via canonical TGF-β1 signaling. Furthermore, conditioned media (CM) from irradiated fibroblasts induced M2 polarization of Raw264.7 macrophages, whereas CM from MQ-treated irradiated fibroblasts decreased M2 macrophage expression. Taken together, these results indicate that MQ is a potential senomorphic agent, reducing SASP expression to mitigate radiation-induced skin senescence and macrophage polarization, and exerting protective effects against radiation-induced skin fibrosis.