The Toxic Effect On Neurons By Lanthanum And The Possible Mechanism Research

ForewordOur nation is the country with the most rare earths storage and output in the world. The rare earths have been widely applied in all kinds of fields, thus invade the animal and human body through variety of approaches inevitably, therefore, make search on the rare earths elements' influence and the mechanism to the psychological function of animal and human body, and explore the rare earths' safe intake has become the subject focused by the researcher.The research indicated there was neurotoxicity in the rare earths, the high grade nervous center was much sensitive to its toxicity compared with other organs. The epidemiology investigation in the rare earths diggings in the south of Jiangxi province showed that the cognitive behaviour ability, perceiving behaviour ability and learning ability decreased in this area, which pointed out that the long-term low dosage rare eatths intake affected the brain function. The animal experimental material declared that the rare earths could get through the blood-brain obstacle and accumulate in the brain organization, and affect the learning memory through the approaches of affecting the metabolic vigor of neuron cell, affecting the neuron transmitter release and intake, and damaging the hippocampus area structure to promote the cell apoptosis, etc.The lanthanum is the representatives of the light rare earths with active chemical quality. Its ionic radius is similar as Ca2+. The research discovered, the lanthanum with low concentration would not affect the metabolic vigor of cortical cells of mouse, but the 3.0mmol/L lanthanum could increase the calcium phosphate ratio directly, and intensified the glutamic acid's excitability neurotoxicity damage. It not only made research but also approved that if the calcium iron in the nerve cells of the rats, mice and hippocampus in the group of 1.0%lanthanum chloride drinking increased, the apoptosis rate of the hippocampus neurons obviously increased, and the learning and memory ability decreased. The research dealt with the chemical contamination of the lanthanum chloride to the cortical neurons in vitro culture, observed the affection of the lanthanum exposure in different doses to the free calcium concentration, endochylema, the mitochondrial cytochrome c content, caspase-3 expression level and apoptosis, and discussed the lanthanum chloxide's toxic action mechanism to the central nervous system.Experimental GroupingThe LaCl3 is confected with the DMEM without blood serum, the final concentration is 0.01,0.1,1.0,2.0mmol/L separately, the DMEM without blood serum is applied in the comparative group.Research Methods1.Nerve cell identification, NSE immunocyte chemical method2. Cells morphological observation, Inverted microscope3.Cell viability test, MTT method4. Apoptosis test, Flow Cytometry5.Cells free calcium ion concentration test, Fura-2/AM fluorescence probe method6.Endochylema and the mitochondrial cytochrome c content test, chemistry colorimetry7. Caspase-3 activation test, Western-Blot methodResults1. Nerve cell identificationIt could see that most of the plasma was dyed into palm yellow under the microscope. Selected 10 visual fields in every glass piece and calculated the positive cells proportion, the immune positive cells could reach over 90%, therefore, the cells in culture could be made as the neuronal vitro mode.2. Cell viabilityThere was a certain toxicity to the neurons for the lanthanum chloride. There was statistic difference among the dose group and comparative group (p<0.01). With the increase of the exposure dose, the cell viability gradually decreased. A certain dose and reflection relationship existed, and half quantity of cells were depressed in 1.0mmol/L.3. Apoptosis testWith the increase of the lanthanum chloride dosage, the apoptosis rate trended to increase. Besides the 0.01 mmol/L dose group, the lanthanum chloride exposured the apoptosis rate increased compared with the comparative group (p<0.01)4. [Ca2+]i changeThe cells [Ca2+] of the neurons in the lanthanum exposure group increased obviously, the difference from the comparative group was obviously(p<0.05or 0.01), and increased with the increase of the lanthanum's exposure dose. The difference among all the dose groups was also obvious(p<0.05or 0.01).5. Change of the content of mitochondrial and plasma cytochrome cThe content of mitochondrial cytochrome of neurons in all lanthanum exposure groups decreased, the c content of plasma cytochrome increased, the difference was obvious compared with the comparative group (p<0.05), and showed the dose-reflection relationship with the increase of chemical contaminated dose.6. Protein expression change of caspase-3With the increase of the dose LaCl3, the procaspase-3 (32kD) expression decreased gradually, which indicated the activated caspase-3 protein increased gradually, and the difference among the 0.1,1.0m M dose group and comparative group was obvious (p<0.05)Conclusion1. The lanthanum chloride can make the cortical neurons Ca2+in vitro culture increase and cause the cells calcium dyshomeostasis.2. The lanthanum chloride can make the content of the cortical neurons mitochondrial cytochrome c in vitro culture decrease, conent of the plasma cytochrome c increase, the protein expression of procaspase-3 decrease, point out the cytochrome c being released into the plasma by the mitochondria, and activate the capase-3.3. The lanthanum chloride can decrease the cortical neurons viability in vitro culture and elicit the apoptosis.