摘要:
目的 探索糖原合成激酶-3β(GSK-3β)/β-连环蛋白信号通路对贫铀(depleted uranium,DU)致人肾近曲小管上皮HK-2细胞损伤的作用.方法 不同浓度DU染毒HK-2细胞3 ~24 h,采用免疫荧光法检测肾损伤分子-1(KIM-1)和中性粒细胞明胶酶相关脂质运载蛋白(NGAL)表达水平以观察DU诱导HK-2细胞的损伤,免疫荧光法检测β-连环蛋白核转位,Western blot法检测p-GSK-3β(S9)、GSK-3β、β-连环蛋白及c-myc蛋白表达变化,观察GSK-3β/β-连环蛋白信号通路的时相变化;采用GSK-3β(KD)质粒瞬时转染和GSK-3β特异性抑制剂TDZD-8处理抑制HK-2细胞的GSK-3β活性,采用β-连环蛋白质粒瞬时转染HK-2细胞使其过表达,观察GSK-3β活性和β-连环蛋白表达变化对DU染毒致HK-2细胞损伤的影响.结果 300和600μmol/L DU染毒致HK-2细胞KIM-1和NGAL阳性细胞率随染毒时间的延长和染毒剂量的增加而增加,染毒后6、9和24 h明显高于空白对照组(KIM-1阳性细胞率:t=11.06、18.97、30.49,P<0.05;t=6.79、16.02、85.45,P<0.05;NGAL阳性细胞率:t=11.78、11.37、34.29,P<0.05;=7.34、21.63、36.84,P<0.05);p-GSK-3β(S9)/GSK-3β比值和核β-连环蛋白阳性细胞率于染毒后3、6、9和24 h明显高于空白对照组[p-GSK-3β(S9)/GSK-3β比值:t=3.95、4.69、5.40、3.34,P<0.05];核β-连环蛋白阳性细胞率:t=4.61、6.52、36.64、14.93,P<0.05),于染毒后9h达峰值,还激活了β-连环蛋白下游靶基因c-myc的蛋白表达.瞬时转染GSK-3β(KD)质粒明显抑制了HK-2细胞的GSK-3β活性(t=8.07,P<0.05),降低了DU致染毒HK-2细胞的KIM-1阳性细胞率(t=24.77,P<0.05).TDZD-8抑制GSK-3β活性的同时提高了β-连环蛋白核转位,亦能显著降低DU染毒诱导HK-2细胞的KIM-1阳性细胞率(=6.25、6.73,P<0.05).而且,β-连环蛋白过表达显著减轻了DU诱导的HK-2细胞损伤(t=7.48,P<0.05).结论 GSK-3β/β-连环蛋白信号通路是调控DU致HK-2细胞毒性的关键通路,抑制GSK-3β活性及β-连环蛋白表达能有效拮抗DU诱导的HK-2细胞损伤.%Objective To investigate the effects of glycogen synthase kinase-3β (GSK-3β) and β-catenin signaling on the human renal proximal tubular epithelial HK-2 cell injury induced by depleted uranium(DU),and provide a new enlightenment for the development of DU antidotes.Methods H K-2 cells were exposed to different concentrations of DU for 3-24 h,then the protein expressions of kidney injury molecule 1 (KIM-1),neutrophil gelatinase-associated lipocalin (NGAL) and nuclear β-catenin were detected by immunofluorescence staining.The protein expressions of p-GSK-3 β(S9),GSK-3β and cmyc were detected by Western blot assay.HK-2 cells were transiently transfected by GSK-3β (KD) plasmid or treated by TDZD-8 to inhibit the activity of GSK-3β specifically.Other HK-2 cells were transiently transfected by β-catenin plasmid to overexpress the β-catenin protein.Results The percentages of KIM-1 and NGAL-positive cells increased with DU exposure time and concentrations from 300 and 600 μmol/L,and they were significantly higher than those of the blank control at 6-24 h of DU exposure (KIM-1-positive cells:t =11.06,18.97,30.49,P <0.05;t =6.79,16.02,85.45,P < 0.05;NGAL-positive cells:t =11.78,11.37,34.29,P <0.05;t =7.34,21.63,36.84,P <0.05).In contrast,the ratio of p-GSK-3β (S9) to GSK-3β and percentage of nuclear β-catenin-positive cells were significantly higher than that of the blank control at 3-24 h of DU exposure (p-GSK-3β(S9)/GSK-3β:t =3.95,4.69,5.40,3.34,P < 0.05;nuclear β-catenin-positive cells:t =4.61,6.52,36.64,14.93,P < 0.05) with a maximum response at 9 h of DU exposure accompanied with corresponding increase of protein level of c-myc,a downstream target gene of β-catenin.Transient transfection of HK-2 cells with GSK-3β (KD) plasmid significantly inhibited the activity of GSK-3β (t =8.07,P < 0.05) and reduced the DU-increased percentage of KIM-1-positive cells (t =24.77,P < 0.05).Treatment cells with TDZD-8 inhibited the activity of GSK-3β and enhanced the percentage of nuclear β-catenin-positive cells,and it also significantly reduced the percentage of KIM-1-positive cells in HK-2 cells exposed to DU (t =6.25,6.73,P < 0.05).Moreover,overexpression of β-catenin significantly reduced DU-induced cell injury (t =7.48,P < 0.05).Conclusions GSK-3β/β-catenin signaling plays a key role in regulating the DU-induced cytotoxicity of HK-2 cells.Inhibition of GSK-3β activity and overexpression of β-catenin can protect the HK-2 cells from DU-induced damage.