Objective To develop an apoptosis model of nucleus pulposus cells in cell culture.Methods To mimic the nutrient-deficient microenvironment of degenerative intervertebral disc,nucleus pulposus cells derived from infant SD rat disc were cultured under serum limiting conditions.Nucleus pulposus cells were cultured in culture medium contai-ning 1%, 3%, 5%, 8%and 10%fetal bovine serum( FBS) respectively to select the optimum FBA concentration.Apoptosis was assessed by flow cytometry, Western blot,cell counting kit, and immunofluorescence technique.Results The flow cy-tometry revealed that apoptosis rate of the nucleus pulposus cells increased with decreasing concentration of FBS, and 3%FBS used in the experimental group was the most effective concentration to induce apoptosis(P<0.05).Western blot dem-onstrated significantly higher expression of Bax and caspase-3 enzyme in the 3%FBS group than in the 10%FBS group, while bcl-2 activity decreased.The results of CCK-8 test indicated that the nucleus pulposus cells got slower proliferation in the medium containing 3%FBS.Immunofluoresence analysis showed that FAS expression was significantly higher in the 3%FBS group than in the 10%FBS group.Conclusions 3%FBS condition may induce apoptosis in the nucleus pulposus cells and compromise the cell function to induce intervertebral disc degeneration.The caspase family should be involved in the process.

Objective To evaluate the potential feasibility of γ-H2AX foci as a biodosimetry after exposure to ionizing radiation by comparing DNA double-strand break repair kinetics in rat blood lymphocytes with that in human lymphocytes.Methods Peripheral blood lymphocytes separated from Sprague-Dawley(SD) male rats and healthy adults were exposed to γ-rays,and some rats were also subjected to total body irradiation.The inductions of DNA repair-related foci of γ-H2AX,pATM (S1981) and pDNA-PKcs (T2609) were detected with immunofluorescence staining technique at different time points post-irradiation,and the status of their co-localization was analyzed.Results The induction kinetics of γ-H2AX foci in rat lymphocytes was similar to that observed in human lymphocytes.The frequencies of γ-H2AX foci peaked at 30 min after γ-ray irradiation (trst =62.64,th =28.52,P ＜ 0.05),then decreased rapidly after 6 h post-irradiation (trat =45.96,th =14.80,P ＜0.05),and the residual foci number remained only about 3％-8％ of its maximal value at 24 h post-irradiation.At 30 min after γ-ray irradiation,the frequencies of pATM (S1981) and pDNA-PKcs (T2609) foci in rat and human lymphocytes significantly higher than those of nonirradiated control (trat =21.05,25.80,th =11.07,29.52,P ＜ 0.05),and the frequencies of co-localization of pATM (S1981) or pDNA-PKcs (T2609) foci with γ-H2AX foci also markedly increased by 26％-32％ in irradiated lymphocytes of rat and human (trat =5.34,9.14,thuman =18.32,51.28,P ＜0.05).Moreover,γ-H2AX foci incidence in rat lymphocytes in vitro was consistent with that induced by total body irradiation of rat.The number of γ-H2AX foci in irradiated rat lymphocytes increased with irradiation dose in a linear dose-dependent manner,its slope was similar to that of irradiated human lymphocytes reported by other laboratory.Conclusions Rat is a useful animal model to evaluate radiation biodosimetry with γ-H2AX foci in lymphocytes.The co-activation of ATM and DNA-PK plays an important role in DSB repair in the irradiated lymphocytes of rat and human.

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.