The Effect Of Tea Polyphenols On The Production Of Ros By NIT-1 Cells In Different Concentrations Of Glucose Culture Media

Objective To investigate the effect of different glucose concentrations on the production of reactive oxygen species (ROS) in NIT-1 cells, and the interventional effect of tea polyphenols (TPs) on that.Methods 1. NIT-1 cells were cultured in complete DMEM medium with 5.6 mmol/L glucose, and the proliferation of NIT-1 cells treated with various concentrations of TPs was determined by CCK-8. 2. Being cultured in L-DMEM, H-DMEM with or without two different concentrations of TPs, NIT-1 cells were divided into four groups: NG group (glucose 5.6mmol/L, incubated 48 hours); HG group (glucose 25 mmol/L, incubated 48 hours); HG1 group (glucose 25 mmol/L, with 1μg/ml TPs, incubated 48 hours); HG5 group (glucose 25 mmol/L, with 5μg/ml TPs, incubated 48 hours). After the treatment, the level of ROS in NIT-1 cells was quantitated by flow cytometry. 3. According to the concentration of glucose in medium and with or without TPs, NIT-1 cells were divided into six groups: NG group (glucose 5.6mmol/L, without TPs, incubated 48 hours), NG+T group (glucose 5.6mmol/L, with 5μg/ml TPs, incubated 48 hours); MG group (glucose 16.7mmol/L, without TPs, incubated 48 hours), MG+T group (glucose 16.7mmol/L, with 5μg/ml TPs, incubated 48 hours); HG group (glucose 25 mmol/L, without TPs, incubated 48 hours), HG+T group (glucose 25 mmol/L, with 5μg/ml TPs, incubated 48 hours). 4. After the treatment, the level of ROS in NIT-1 cells was quantitated; and the insulin concentrations in culture medium were detected by radio-immunity after glucose-stimulated insulin secretion test.Results 1. When the concentration is 1 or 5μg/ml, the proliferation of NIT-1 cells was not affected significantly by TPs. 2. The level of ROS in NG group and HG5 group was lower than HG group (P<0.05), there is no differences between HG group and HG1 group (P>0.05). 3. The expression of ROS in MG group and HG group was markly higher than NG group (P<0.05), the expression of ROS in MG group was markly lower than HG group (P<0.05); compare with NG+T group, ROS expression was higher in MG+T group and HG+T group (P<0.05), the expression of ROS in MG+T group was markly lower than HG+T group (P<0.05); the level of ROS between NG group and NG+T group was the same (P>0.05); the expression of ROS in MG+T group was lower than MG group (P<0.05); the expression of ROS in HG group was higher than HG+T group (P<0.05). 4. Compare with NG group, Insulin secretion decrease when NIT-1 cells were incubated in HG group and MG group (P<0.05), Insulin secretion in MG group was markly higher than HG group (P<0.05); both in NG+T group and MG+T group, Insulin secretion increase compare with HG+T group (P<0.05), Insulin secretion in MG+T group was markly lower than NG+T group (P<0.05); between the same concentration of glucose, there were no differences in Insulin secretion (P>0.05).Conclusion 1. TPs with the concentrations of 1μg/ml and 5μg/ml has no toxic effect on NIT-1 cells. 2. High glucose contributes to the increase of ROS expression in NIT-1 cells, the more expression of ROS when the oncentration of glucose is higher. 3. TPs with the concentration of 5μg/ml can reduce high glucose-induced expression of ROS in NIT-1 cells, proving that TPs with this concentration could reduce the oxidative damage from high glucose to NIT-1 cells. 4. The Insulin secretion of NIT-1 cells is not effected significantly by TPs with the concentration of 5μg/ml in high glucose, indicating that TPs with this concentration could not repair or improve the function of secreting Insulin in NIT-1 cells which were injured by high glucose.