Sulforaphane Attenuates Radiation-Induced Skin Damage By Regulating the Effects of Anti-Inflammation and Anti-Oxidation

Abstract

Radiotherapy (RT) is a major treatment for malignant tumors. Skin changes can be experienced by up to 95% of radiotherapy patients. Inflammation and oxidative stress (OS) have been shown to be generally associated to radiation-induced skin reactions (RISRs). The treatment of RISRs is particularly critical. This study is to observe the protective effect of sulforaphane (SFN) on RISRs. The mechanism of SFN in the prevention and treatment of RISRs will be discussed. We selected C57BL/6J male mice aged 8 weeks. After 1 week of adaptive feeding, we irradiated one thigh of mice at a time under intravenous anesthesia to establish a RISRs model. Mice were randomly allocated into four groups, including control group, SFN group, irradiation (IR) group and IR plus SFN group. SFN group and IR/SFN group were subcutaneously given SFN at 0.5 mg/kg daily in five days of each week for 4 weeks, while mice in the IR group received radiation plus equal amount of normal saline. After 8 weeks, all mice were euthanized for experiments. We used H&E staining to observe the morphological changes of mice skin tissue and TUNEL staining to observe the apoptosis of skin tissue cells. Then we used western-blot and immunohistochemical methods to detect the changes of apoptosis-related indicators including BAX, Bcl2 and caspase-3 in mice skin tissue, as well as the inflammatory response and oxidative stress indexes such as IL-6, TNF-α, 4HNE and 3NT. The results of H&E staining showed that in the mice skin of IR group, significant keratinization of epidermis, destruction of endothelial cells and infiltration of inflammatory cells could be observed. These pathological changes were not obvious in the control group and SFN group, but the skin structure in the IR/SFN group was significantly improved compared with the IR group. TUNEL staining results showed that TUNEL positive cells were significantly increased in the IR group (the TUNEL positive cells were quantitatively analyzed by full positive cells /1000 skin tissue cells). The number of skin apoptosis cells was significantly reduced in the SFN group and IR/SFN group (P<0.05). Western-blot results showed that the proteins expression of BAX, caspase3, TNF-α and IL-6 were significantly higher in the IR group, but not in the SFN group. After SFN treatment, the expression of BAX, caspase3, TNF-α and IL-6 was decreased compared with the IR group (P<0.05), while the expression of Bcl2 was decreased in the IR group and increased after SFN intervention (P<0.05). Immunohistochemical results showed that the expressions of 4HNE and 3NT in the IR group were significantly increased, while those in the SFN group and IR/SFN group were significantly decreased (P<0.05). SFN can inhibit the inflammatory response and oxidative stress to prevent or alleviate the RISRs.