The Effect Of Lead On The Neural Activity Of Dugesia Japonica

Lead is a widely distributed heavy metal.Although we have taken various measures to reduce the use of lead,it still seriously jeopardizes human health.Studies have shown that the nervous system is an important target for lead.Lead can cause irreversible damage to neural function.It also can affect the plasticity of hippocampal synapses and disturb neurotransmission.In addition,mitochondrial swelling,fragmentating,and matrix content decleasing can be caused in the cell after lead stress.However,in the study of neural cells and nervous system,the link between mitochondrial division,fragmentation and neural activity changes caused by lead is rarely reported.In this study,Dugesia japonica was used as experimental material to study the relationship between mitochondrial division and neural activity under lead stress.This study adopted the Dugesia japonica as the experimental animal and treated with lead(P group):80 mg/L lead acetate solution was used for acute toxicity,and various periods were selected(6 h,12 h,24 h,36 h,48 h),variations of behavior,the level of movement,mitochondrial structure and number,ROS content,mitochondrial membrane potential,the level of Drp-1,synapsin and CaM were analyzed.Secondly,in order to study the effects of mitochondrial division and intracellular[Ca2+]on the neural activity of planaria after lead stress,we set up two group,the mitochondrial division inhibitor Mdivi-1 was treated for 24 h and continued to be treated with lead(M group),and lead and BAPTA-AM was treated together(group B),the stress time was the same as above,and the above-mentioned experimental indicators were tested to study the effect of lead on the neuronal activity of D.japonica and to explore the relationship between mitochondrial fragmentation and neurotransmitter delivery.The study mainly obtained the following results:1.Plane shape of the planaria worms showed obvious morphological changes,and the exercise ability was significantly reduced after 12 hours.In groups M and B,Mdivi-1 and BAPTA-AM treatment reversed the effects of lead on the behavior and motor ability of planaria.And Mdivi-1 works better.2.The length of mitochondria began to shorten after exposure to lead solution for 12 hours.However,mitochondria became shorter and the number of mitochondria decreased with the prolongation of the time.The level of ROS in cells increased significantly and mitochondrial membrane potential increased after exposure to lead solution for 24 hours.Simultaneously,the number of active mitochondria also decreased significantly.The results showed that the damage of lead to mitochondrial structure and function of planaria was mainly observed after exposure to lead for 24 hours.Whereas,treatment with Mdivi-1 and BAPTA-AM delayed the mitochondrial morphological changes and reduced mitochondrial damage.3.The transcription level of mitochondrial division marker protein Drp-1 was significantly increased in early lead stress(6 h),and the expression of Drp-1 protein was also significantly increased after 24 h.Synapsin I(6 h)mRNA expression was significantly down-regulated.The results showed that the effect of lead on nuclear gene transcription preceded the change of mitochondria.Whereas,the activity of Drp-1 and synapsinI can be suppressed significantly when treated with Mdivi-1 or BAPTA-AM,and the mechanism remains to be studied.4.5-HT showed a significant decrease at lead stress 12 h,and reached a minimum at 24 h.The level of 5-HT rebounded and returned to the control level at 48 h.In the M group,the 5-HT content was not significantly different from the C group.In addition,the contents of 5-HT in group M and group B increased significantly at 12 h and 24 h compared with group P,and reached the normal level.Compared with group P,the content of 5-HT in group M increased significantly at 36h.At the same time,compared with the C group,the MAO activity in the M group also did not change.Compared with the P group,the MAO activity was significantly Lower than P group.Shows that inhibition of excessive mitochondrial division can effectively reduce the 5-HT decomposition under lead stress.5.The change of expression level of CaM mRNA and p-CaM expression occurred at 48 h and 36 h respectively,indicating that its function was not upstream of mitochondrial division and neurotransmitter changes.Both Mdivi-1 and BAPTA-AM treatment delayed CaM activation,presumably,it related to the subsequent activation of Synapsin I.In summary,we think that morphological and motor performance change caused by lead stress are mainly related to mitochondrial division and changes of neuronal activity caused by mitochondrial dysfunction.Mdivi-1 can inhibit mitochondrial division by curbing the expression of Drpl,and thus antagonize the mitochondrial fragmentation.At the same time,on the basis of mitochondrial morphological stability,Mdivi-1 can reduce the production of ROS,elevate mitochondrial membrane potential,and stabilize the activity of MAO,that making the main neurotransmitter 5-HT in the synapse of the planaria is kept stable,which allows the planaria to recover from both morphological and motor ability,and reduces the toxicological effects of lead from the mitochondrial pathway.This pathway is earlier than[Ca2+]and should not be related to[Ca2+]regulation.In addition,Mdivi-1 can also increase the expression of synapsin I,but the upregulation of Synapsin I occurs after it activating.It is speculated that the activation of CaM may be related to the phosphorylation of Synapsin I.In addition,the intracellular Ca2+abnormal changes also have a certain influence on neural activity,but its secondary to mitochondrial division.In view of the experimental results of neural activity of planaria under lead stress after Mdivi-1 inhibiting mitochondrial division,it is speculated that mitochondrial division-related genes may serve as targets for lead injury repairing,and the development of safer mitochondrial division inhibitors may curb Pb2+ stress-induced nervous system injury and has an important therapeutic value.