Mechanism of protective effect of sulforaphane against radiation-induced lung injury in mice

Abstract

Objective To investigate the radioprotective function and its mechanism of Sulforaphane (SF) in mice acute radiation-induced lung injury. Methods Totally 40 female C57BL/6J mice were equally divided into 5 groups randomly. Group A, treated by SF 3 mg/kg plus radiation; group B, treated by SF 5 mg/kg plus radiation; group C, treated by SF 10 mg/kg plus radiation; radiation group with a single dose of 12 Gy in 6 MV X-ray by a linear accelerator, and control group with sham radiation. The mice in drug group were administered intraperitoneally with different concentration of SF every other day from 7 d before irradiation to 7 d after irradiation, while the same volume of DMSO plus physiological saline solvent was given in the control and radiation groups. After being sacrificed at 14 d of SF administration, the pathomorphological changes of mice were observed in trauma lung tissue, the positioning and expression of NLRP3 was observed by immunohistochemical staining, the levels of IL-6, TNF-α and TGF-β1 in bronchoalveolar lavage fluid (BALF) were measured by ELISA, the expressions of NLRP3 and IL-1β mRNA in lung tissue were assayed by qRT-PCR, the expressions of NF-κB p65, NLRP3 and IL-1β proteins in lung tissue were assayed by Western blot, the activity of NF-κB was detected by EMSA. Results In comparison with radiation group, there was an obvious amelioration in pathological injury of lung tissue in the treatment groups: the expression of NLRP3 in lung tissue decreased; the concentration of NLRP3 in the drug intervention group (SF 10 mg / kg) markedly decreased (F= 42.750, P<0.05). the IL-6, TNF-a and TGF-β1 levels in BALF decreased(tIL-6=-62.65-21.00; tTNF-α=-32.18-16.57; tTGF-β1=-58.22-46.11, P<0.05); the expressions of NLRP3 and IL-1β mRNA markedly decreased (tNLRP3=-6.56-5.68; tIL-1β=-29.75--21.20, P<0.05), and the expressions of NF-κB p65, NLRP3 and IL-1β proteins decreased (tNF-κB p65=-34.00--1.71, tNLRP3=-25.01--16.91, tIL-1β=-73.70--55.14, P<0.05); the relative expressions of NF-κB p65 and NLRP3 were reduced in a dose-dependent manner (r=0.945, 0.926); and the activity of NF-κB were obviously reduced (tNF-κB=-38.68, -614.82, -2 831.40, P<0.05). Conclusions Sulforaphane effectively alleviates the RILI in lung of mice by downregulating the expressions of inflammatory factor NLRP3. Key words: Sulforaphane; Radiation-induced lung injury; NLR Family, Pyrin Domain-Containing 3 Protein; Nuclear factor-κB; Interleukin-1β