Effects of JNK/c-Jun pathway and its target gene on oxidative stress-induced apoptosis of human lensepithelial ceil / 中华实验眼科杂志

ABSTRACT

Background The pathogenesis and development of cataract is associated with oxidative stress-induced apoptosis of human lens epithelial cells(LECs).BH3-only protein is a factor that can initiate apoptosis,and thus the apoptotic process is probably related to the activation of the c-Jun N-terminal kinase(JNK).However,the relationship between oxidative stress-induced apoptosis of human LECs and the JNK pathway remains to be illuminated.Objective This study was to investigate the effects of the JNK/c-Jun pathway and its target gene,Bim (Bcl-2 interacting mediator of cell death)and PU M A(p53 up-regulated modulator of apoptosis),on oxidative stressinduced apoptosis of human LECs.Methods The human LECs cell line(HLEC-B3)was cultured and passaged in DMEM with 10％ fetal bovine serum in vitro.Confluent cells were incubated in 24 well plates and divided into 4 groups.Hydrogen peroxide(H2O2)(50 μmol/L)was used to treat the cells for 4,8 or 12 hours,and cells without H2O2 treatment served as the control group.Apoptosis was detected using Hoechst 33258 staining and quantified by counting the number of cells with pyknotic nuclei.In addition,confluent cells were seeded in 6 well plates,and Western blot and RT-PCR were used to detect the expression of the caspase-3,c-Jun,Bim and PUMA proteins and their mRNA in HLEC-B3,respectively.The JNK/c-Jun pathway inhibitors,CEP11004 or SP600125,were added into cultured media with H2O2,and cells treated with DMSO or H2O2 only served as negative and positive control groups.The expression of the p-JNK,JNK,p-c-Jun,c-Jun,Bim,PUMA proteins was detected by Western blot and apoptosis was assayed using Hoechst 33258 staining.200 pmoL/L of Bim or PUMA small interference RNA(siBim or siPUMA)fragments were transfected into the cells for 24 hours,respectively,and H2O2 was then used to treat the cells for 8 hours.The expression of the Bim and PUMA protein and their mRNA in the cells was detected by Western blot and RT-PCR,respectively.Results After H2O2 treatment in HLEC-B3 cells for 4,8,or 12 hours,the rates of apoptosis were 4.30％±1.15％,27.08％±0.74％ and 46.59％±0.91％,showing a significant difference among them (F=1909.433,P=0.000),and those of the 4,8,12 hour groups were significantly increased in comparison to the control group(P =0.049,0.000,0.000).Compared to untreated cells,the levels of expression of the JNK,Bim,PUMA proteins and their mRNA in HLEC-B3 cells were significantly elevated.After the addition of CEP11004 or SP600125,the expression of these protein and mRNA in HLEC-B3 cells in the presence of H2O2 was significantly weaker than that in the DMSO control group(P =0.000,0.000).After the tranfection of siBim or siPUMA,the apoptosis rates of the H2O2 treated groups were significantly higher than those in the Bim-/-or PIMA-/-group (P＜0.05).Conclusions H2O2 can activate the JNK/c-Jun pathway and up-regulate the expression of its target genes Bim and PUMA in human LECs in a time-dependent manner.Inhibiting the JNK/c-Jun pathway and interfering with the expression of Bim and PUMA can protect human LECs against oxidative stress-induced apoptosis.