| Objective: Cultured rat renal tubular epithelial cells NRK52E were used to explore whether curcumin could induce the expression of heme oxygenase-1(HO-1) to attenuate cytotoxicity caused by diatrizoate.Methods: Cultured NRK52E cells were used in our research which was divided into four parts:1. NRK52E cells were incubated with diatrizoate in different dose(0,50,100,200μL/mL) for 4h.The cell viability and lactate dehydrogenase(LDH) activity in the supernatants were detected to analysise the quantity - effect relations of cytotoxicity caused by diatrizoate. 2. NRK52E cells were incubated with diatrizoate at a concentration of 100μL/mL for 0h,2h,4h,6h respectively. Meanwhile, NRK52E cells incubated with mannitol which osmotic pressure was equated to 100μL/mL diatrizoate for 6h were used as osmotic pressure control. The cell viability and LDH activity in the supernatants were measured to analysise the time - effect relations of cytotoxicity caused by diatrizoate and to explore the effect of osmotic pressure on cells. 3. NRK52E cells were incubated with curcumin (CMN) at a series of concentrations (0,5,10,20μmol/L) for 8h. The cell viability and LDH activity in the supernatants were detected to confirm if curcumin is cytotoxic to NRK52E cells.At the same time, the quantity and activity of HO-1 protein were measured to investigate the expression of HO-1 induced by CMN . 4. To understand whether CMN could play a protective effects against cell injury by diatrizoate and its possible mechanism. NRK52E cells were randomLy divided into group A, group B, group C ,group D, NRK52E cells in each group were incubated with only culture medium,100μL/mL diatrizoate,100μL/mL diatrizoate+ 10μmol/L CMN,100μL/mL diatrizoate+10μmol/L CMN+10μmol/L zinc protoporphyrinⅨ(ZnppⅨ) for 4h respectively. The cell viability, LDH activity and malonaldehyde(MDA) content in the supernatants were detected. Cell apoptosis was determined by flow cytometry with AnnexinV-FITC/PI double stains.The expression of HO-1,bcl-2,bax were examined by western blot. Results:1.Diatrizoate could decrease cell viability and increase LDH activity in the supernatant in time-dependant and dose-dependant manner(P<0.05 respectively). Osmotic pressure created from 100μL/mL diatrizoate had no effect on cell injury.2.At the range of 0-20μmol/L, CMN had no marked cytotoxicity(P>0.05),in addition, CMN could increase the expression of HO-1 in dose-dependant manner (P<0.05).3. Compared with group A, the other groups include group B, group C,group D exhibited significant decreased cell viability (P<0.05 respectively), elevated LDH activity and MDA content in supernatant (P<0.05 respectively)and increased cell apoptosis (P<0.05) as well as the expression of bcl-2,bax (P<0.05 respectively),but the ratio of bcl-2/bax was increased markedly only in group C(P<0.05). Additionally,the expression of HO-1 were increased in B,C,D groups(P<0.05 respectively) ,especially in group C(P<0.05). However, the HO-1 activity was increased in group C(P<0.05) but decreased in group D(P<0.05). Compared with group B and D, cell viability was increased in group C, LDH activity and MDA content in supernatant (P<0.05 respectively) as well as cell apoptosis decreased significantly (P<0.05 respectively),while the expression of HO-1,bcl-2,bax and ratio of bcl-2/bax were elevated markedly (P<0.05 respectively).Conclusions:Diatrizoate had direct cytotoxicity to NRK52E cells in dose and time-dependent manner. At the range of 0-20μmol/L, CMN was not cytotoxic to NRK52E cells, on the contrary,it could attenuate cytotoxicity induced by diatrizoate.Its protective mechanism was probabaly related to up-regulation the expression of HO-1,which decreased oxidative stress and inhibited cell apoptosis.
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