Nicotine Induces Nme2-mediated Apoptosis In Mouse Testis

Background and purpose: Smoking is one of the world’s largest public health problems,multiple studies have shown that smoking has a negative effect to male reproductive health.Our laboratory has found that cigarette smoke treatment would induce DNA damage,apoptosis and other effects in mouse spermatozoa,then cause negative effects on the semen quality,offspring’s birth rate and survival rate in male mice.Prior research found that male mice’s RNA expression profile in spermatozoa can be influenced by nicotine,which is the main harmful matter in cigarette smoke,and Nme2 is one of the changed genes.NME2 protein is associate with telomerase activity,which could be connected to spermatogenic cells apoptosis.In order to study the effects of smoking on spermatogenic cells apoptosis,this paper mainly investigated the molecular mechanism of nicotine effect testicular cells apoptosis via telomerase activity changing.Methods: The nicotine treated experimental mouse model was built to simulate heavy smokers.TUNEL method was used to detect the apoptosis rate in mouse testis,and then the Realtime PCR and TRAPRealtime PCR methods were used to define the relative telomere length and telomerase activity in mouse testis and spermatozoa.Nme2 was screened out from changed RNA expression profile of nicotine treated and control group mouse spermatozoa.Then the expression quantity of Nme2 in mouse testis were detected through RTPCR and Western blot.The BSP method were used to find out the methylation level change of Nme2 promoter in nicotine treated mouse testis.NME2 over-expressed and nicotine treated Hela cell model were built and the relative telomerase activity,telomere length and apoptosis rate of the model cells were detected using above methods.Results: In nicotine treated mouse,increased apoptosis rate and decreased telomerase activity in testis,and shortened telomere length in spermatozoa were detected.Further results shows nicotine up-regulated NME2 expression in testis by Nme2 promoter hypomethylation.Compare with control group,we detected lower telomerase activity,shorter telomere length and higher apoptotic rate in NME2 over-expressed and nicotine treated Hela cell model.Which suggested us NME2 inhibits telomerase activity and reduces telomere length in vitro,and then promotes apoptosis.Conclusion:Our study suggests that nicotine may induce apoptosis in mouse spermatogenic cells via down-regulated telomerase activity caused telomere length reduction by Nme2 promoter hypomethylation.