Objective To investigate the protective effect and mechanism of taurine on the cytotoxicity of iohexol on HK-2 cells. Methods HK-2 cells were exposed to iohexol at different dosage (25, 50, 100, 125 gI/L) for 6 h and at the dose of 100 gl/L for different time(2 h, 4 h, 6 h). Then taurine (3,12,24 mmol/L) was coincubated with iohexol (100 gI/L) for 6 h.Cell viability was assessed by CCK-8 assay. Cell apoptosis was determined by Hoechest 33342 flurescence stains,flow cytometry with Annexin V-FITC/PI double stains and caspase-3 activity by colorimetric assay. Bcl-2 and Bax expression were examined by Western blot. Intracellular ROS was detected by flow cytometry with fluorescent probe DCFH-DA. Results Iohexol decreased HK-2 cell viability and induced apoptosis in concentration-dependant and time-dependant manner (all P＜0.05). ROS was increased following iohexol (100 gI/L for 6 h) treatment (P＜0.05). Taurine increased cell viability and attenuated apoptosis in dose-dependant manner. The cell viability levels in taurine intervention (3,12,24 mmol/L) group were significantly increased compared with that in iohexol treated group respectively [(88.00±1.00)%, (91.33±0.58)%, (95.67±1.52) % vs (76.67±1.53)%, all P＜0.05]. Apoptosis rate by flow cytometry were decreased respectively [(8.84±1.75)%,(7.86±1.82)%, (6.30±1.50)% vs (11.98±0.39)%, all P＜0.05]. Caspase-3 activities were decreased respectively [(1.33±0.10), (1.27±0.06), (1.10±0.04) vs (1.42±0.13), all P＜0.05].Taurine up-regulated the expression of Bcl-2, and decreased the intracellular ROS (all P＜0.05).Conclusions Iohexol induces cell apoptosis and oxidative stress. Taurine attenuates direct cytotoxic effect induced by iohexol. The anti-oxidative stress effect and up-regulated Bcl-2 expression may partly account for the protection of taurine.

Objective To explore the protective effect and mechanism of antioxidant N-acetyl-L-cysteine (NAC)on the cytotoxicity induced by iohexol in HK-2 cells. Methods The incubated HK-2 cells were divided into four groups:control group,iohexol group,NAC group,and NAC+iohexol group(pre-incubated with NAC and then co-incubated with iohexol).The cell viability was tested by CCK-8 assay;cell apoptosis was determined by Hoechst 33342 fluorescence staining and flow cytometry with Annexin V-FITC/PI double staining.Intracelluar ROS waft detected by flow cytometry with DCFH-DA fluorescence staining.The signaling transduction pathways were investigated by Western blotting and immunofluorescence staining. Results Iohexol decreased cell viability,and increased apoptosis in a dose-and time-dependent manner.In iohexol(100 gl/L,6 h)group,ROS was increased by 1.30-fold of control(P＜0.05).In NAC(5,10,15 mmol/L)+iohexol groups,the cell viability was increased by 104%,118%,130%respectively,and iohexol group was 63% (P＜0.05, respectively); apoptosis rate was decreased by 13.51%, 13.46%, 12.23% respectively, and iohexol group was 24.41% (P＜0.05, respectively); ROS was decreased by 1.05-fold, 0.93-fold, 0.86-fold respectively, and iohexol group was 1.3-fold (P＜0.05, respectively).Iohexol induced the increase of p53 phosphorylatian and activity, then up-regulation of Bax and down-regulation of Bcl-2 protein expression. Iohexol induced the release of cytochrome C from mitochondria to cytoplasm, all of which caused final activation of caspase-3. The expression levels of p53, Bax and caspase-3 were decreased, while Bcl-2 protein expression level was increased by NAC. Conclusions Iohexol induces the increase of apeptosis rate and ROS generation in HK-2 cells. NAC attenuates this iohexol-induced cytotoxicity by decreasing intracelluar ROS, which is mairdy through the intrinsic pathway.