Mechanism of nicotine in inducing apoptosis of umbilical cord mesenchymal stem cells

Aim: To explore the effects of nicotine on intracellular nitric oxide,Calcium ion and expression of α7nAchR in umbilical cord mesenchymal stem cells. Methods: MSCs were treated with different concentrations of nicotine.The level of NO was detected by nitrate reductase method at 24、36、48h;after cultured with nicotine for 24h,cells were stained using by fluo-3/AM and the change of Ca2+ was determined by flow cytometer.The expression of α7nAchR was detected by Real-time Quantitative PCR. Results: After treated with nicotine,the nitric oxide level in each experimental group were significantly higher than that of the control group at 24h and 36h(P0.05),in a dose and time dependent manners,however at 48 h the levels of NO in 0.8 mg/mL group and1.0 mg/mL group were lower than the control group,which may be related with the increased cells apoptosis.After treated with nicotine,the Ca2+ fluorescence intensity in each experimental group(0.6,0.8,1.0 mg/mL) were(141.26±16.01),(164.90±18.39),(198.76±17.63),respectively,which were higher than the control group(119.30±14.14).The expression of α7nAchR was detected in MSCs,and was found to be up-regulated after treated with nicotine in a dose-dependent manner and a time-dependent manner. Conclusion:Nicotine can promote MSCs apoptosis by up-regulating the expression of α7nAchR,stimulating MSCs to release NO and elevating the intracellular Ca2+.