Lanthanum Induced Oxidative Stress Increases The Expression Of Autophagy Related Genes By Activating The ROS/JNK Signaling Pathway

Objective:Rare Earth Elements?REEs?include 15 lanthanides and scandium and yttrium in the periodic table of elements,which eutical industry and so on.However,more and more attentions was paid on the environment,ecology and human health damage induced by REEs recently.REEs are easily enrich in the natural environment,which could enter the body through the way of gastrointestinal or respiratory,then accumulate in the tissues and organs,and finally cause damage on liver,kidney,heart,immune system,nerve system,endocrine system and genetic system.In recent years the nervous system damage by REEs has been paid more attention.Epidemiological investigation showed that REEs are likely to be the cause of children's intelligence decrease.These results confirmed that REEs can lead to the central nervous system?CNS?dysfunction,but its mechanism is not exact.Lanthanum?La?is one widely used of REEs,and is not easy to degrade in environmental media.Lanthanum has strong biological activity and accumulation effect in the brain,and can stabilized in the environmental medium,so it is often used as a typical rare earth element s to explore the REEs effects on the nervous system.Studies showed that La can induce neurotoxicity and impair cognitive function by influencing the distribution of trace elements,inducing oxidative stress,interfering with the Ca2⁺,enzymes and neurotransmitters dynamic balance.More research evidence displayed that lanthanum can result in developmental defect of the CNS,neurobehavioral changes,decline in learning and memory ability,and neuronal morphology and structural abnormalities,nervous behavior changes,learning and memory impairment.Therefore,further research in this area is of great significance for finding effective molecular targets and protecting people's health.Autophagy is a lysosomal dependent degradation pathway prevalent in eukaryotic cells,which can transport damaged proteins and senescent organelles into lysosomes.It can not only maintain cellular homeostasis through the mechanism of removing intracellular excessive and abnormal protein or organelles,even pathogenic microorganisms,but also promote the recycle of amino acids.It can provide much material for a variety biochemical process.At the same time autophagy also participate in the pathophysiological process in immunity,differentiation and development,aging,microorganisms removal,cancer and so on.Autophagy has duality for cells:moderate level of autophagy can protect cells from harmful factors damage,promote cell survival;but the high or low level of autophagy induced autophagic cell death?autophagy-mediated cell death,ACD?,which is the II type cell programmed death occurrence of.Multiple exogenous chemicals can induce oxidative stress?oxidative stress,OS?.OS is an abnormal condition resulting from the imbalance of body oxidation system and antioxidant system,resulting in a large number of reactive oxygen species?ROS?prodution.It can cause physiological and biochemical processes,resulting in tissue cell damage and death.Studies have shown that ROS can induce autophagy through multiple signal pathways.ROS,which activates the c-Jun NH2-terminal Kinase?JNK?signaling pathway and leads to the continuous enhancement of autophagy,is thought to be an important mechanism to induce cell death in c-Jun.Through the animal experiment,this paper was performed to observe the effects of La on cell autophagy related-ROS/JNK signaling pathway,and different levels of autophagy,which could elucidate the mechanism of neurotoxicity of La,and provide theoretical and experimental basis for the prevention and treatment of the neurotoxicity induced by La.Methods:A total of 80 healthy adult SPF Wistar rats?male and female half respectively?,weighed 240±10g,were provided by the experimental animal center of China Medical University?license number:SYXK?Liao?2013-0001?.The laboratory animal feeding environment:the indoor temperature was 22±1?,the relative humidity was 45⁵5%,the day and night period was 12 h,and all the animals were free to feed the drinking water and food.Female animals were adapted to the surrounding environment for 1 w,and then randomly divided into control group?distilled water?,low dose of LaCl₃ group?distilled water contained 0.25%LaCl₃?,middle dose of LaCl₃ group?distilled water contained 0.5%LaCl₃?and high dose of LaCl₃ group?distilled water contained 1.0%LaCl₃?.10 female rats in each group were mated with male animals?1:1?,and the sperm were found in the checked out in the vaginal of female animals on the next morning,which were regarded as pregnancy and marked the zero day of pregnancy,and exposured to LaCl3 in distilled drinking water.Rats in each group before weaning by sucking milk exposure to La,After weaning,rats were permitted free to access to food and drinking water for 1 month.Morris water maze test was used to determine the changes of rats spatial learning and memory abilities,shuttle box test was used to test rats avoidance response ability;using probe to determine ROS content in brain tissue of rats;real-time PCR was used to determine the mRNA transcription level of JNK1/2/3,c-Jun,foxO1,foxO3a,BECN1,LC3b,and Atg4b;western blot was used to measure the protein expression level of p-JNK and determination of JNK1/2/3,c-Jun,p-c-Jun,foxO1,p-foxO1,foxO3a,p-foxO3a Western blot protein.Results:1.The effects of La on the learning and memory ability of the offspring.?1?Morris water maze navigation experiment,the time and swimming distance in LaCl₃ exposed rats were higher than those of the control group,compared with the control group,rats in LaCl₃ exposed rats found the platform performed disorderly,without purpose.In the space exploration test,0.25%,0.50%,1.0%LaCl₃ exposed rats showed that higher time in the target quadrant and the number of crossing the platform than the control group,the search platform strategy performed rarely enter the target quadrant and badly ability of learning and memory;?2?In the shuttle box test,the frequency of electric shock,the time of electric shock and the active escape latency of LaCl3 were significantly higher than those of the control group.2.The effect of La on the content of ROS in rats hippocampus.Compared with the control group,the level of ROS in the hippocampus increased gradually with the increasing of LaCl₃ exposure,and the difference between the two groups was statistically significant?P<0.05?;3?Lanthanum exposure during pregnancy and lactation can activate nerve cells in hippocampal ROS/JNK/c-Jun and ROS/JNK/FoxOs signal pathways,with the increasing of LaCl₃ exposure,upregulate hippocampal nerve cell transcription of FoxO1 and p-JNK,p-c-Jun?ser63?,p-c-Jun?ser73?,FoxO1,p-FoxO1?Ser256?,p-FoxO1?Thr24?,p-FoxO3a?Ser253?protein expression,statistical significance of autophagy related gene BECN1,LC3b and Atg4b btranscription level increased gradually.Conclusion:1?LaCl₃ exposure during pregnancy and lactation can make rats the learning and memory ability and avoidance response ability dysfunction;2?LaCl₃exposure during pregnancy and lactation can increase the level of ROS in hippocampus nerve cells of rats;3?LaCl₃ exposure during pregnancy and lactation can activate the ROS/JNK signaling pathway in hippocampus nerve cells,up-regulate d expression of LC3-b,Becn1,Atg4,enhance the level of autophagy,and then cause nerve cells impaired,lead to rats learning and memory ability disorder ultimately.