Effects Of Environmental Heavy Metal Co-exposure On Synapses AND SPAR And Snk Expression Of Rat

Objective:Heavy metal pollution has become one of the most main problem in today's environmental pollution.Arsenic(As),lead(Pb),mercury(Hg),cadmium(Cd)are the most dangerous kinds of poison.The epidemiological investigation and studies in vivo or in vitro,have found that they can destroy the major systems and organs in the body,such as blood and liver and kidney damage,especially for the nervous system.Pb,Hg,Cd,As will cause damage to the nervous system of different degrees,such as IQ reduced,the drop of learning and memory ability,and alzheimer's disease.The toxic exposure is becoming an important characteristic of environmental exposure,and it has been regarded as the most important way of study.With low dose exposure in the environment to rats,the four metal can through the blood-brain barrier into the brain,and cause subclinical brain dysfunction.So far,the current environment of a variety of heavy metal co-exposure can cause brain structure and/or function damage,but no study has explained its effect and possible mechanism.We established the rats mode of the actual environment four metal co-exposure simulation,discuss the influences of four metal exposure on rat growth,behavior and the impact of synapse structure,also we explained its possible mechanism.Methods:1?The animal model :Sexual maturity SPF SD rats(male and female 2:1)close cage,pregnant rats on the day of the pregnancies were randomly divided into the Control group(Control),1 MM x group(low dose group),5 MM x group(low dose group),10 MM x group(high dose group)and 20 MM x group(high dose group).The control group were feeded with distilled water,and the experimental groups were feeded with water containing lead acetate trihydrate(25 mg/L),cadmium chloride(7.5 mg/L),sodium arsenite(0.05 mg/L)and mercury chloride(0.15 mg/L)(1 MM x mixed dye venom)set of four metal mixed dye venom,and 5 times and 10 times and 20 times of 1 MM x mixed dye venom.2 ? Growth and neurobehavioral test : By observing the newborn rats' physiological development indicators(body length,tail length,anogenital distance),weight change,and anatomical examination to evaluate the effects of four metal joint exposure on rat growth.Rats of certain days after born,were used to functional test,such as Surface righting(PND4,7)and Negative geotaxis(PND7)and cliff avoidance(PND7)and Tail-flick test(PND10),testing environment four metal joint exposure to early neurobehavioral effects of rats.The Step-through test(PND17-18)and Morris water maze(PND17-PND22)were used to detect four metal effect on learning and memory ability of rats.3?Determination of heavy metal element content:When PND23,Inductively coupled plasma mass spectrometry(ICP-MS)and atomic fluorescence(AFS)were used to detect Pb,Cd,As and Hg content in the blood/brain.4?Synapse structure detection:Transmission electron microscopy techniques was used to observe rat hippocampal neurons synaptic structure change.5?Expression of gene and protein of SPAR and Snk :Real-time fluorescent quantitative PCR(RT-RCR)was used to detect the change of SPAR and Snk mRNA expression in hippocampal.Immunofluorescence was used to detect the change of SPAR and Snk protein expression in hippocampus.Results:1?The influence of growth and development and neural behavior of ratsThe effect of weight gain in rats of heavy environmental co-exposure(P<0.05).Organs such as brain,heart,kidney,cerebellum viscera coefficient with the increase of the dose in rising trend(P < 0.05).Femur with the increase of the dose in rising trend,but the 20 MM x group of viscera coefficient is less than 10 MM x group(P < 0.05).On the surface righting,the experimental groups were less than the control group(P < 0.05).On landing foot-splay test,in addition to 1 MM x group,with the increase of the dose in rising trend surface righting increased(P < 0.05).On cliff avoidance,with the decrease of the dose in rising trend(P < 0.05).On tail-flick test,only 10 x MM and 20 x MM is higher than the control group(P < 0.05).On step-through test,in addition to 1 MM x group,with the increase of the dose in rising trend of mistake(P < 0.05).On Morris water maze,only 10 x MM and 20 x MM is higher than the control group(P < 0.05).2?Heavy metal element content in the blood and brainHeavy metal content of the blood and brain with infected dose increase is on the rise,and 1 MM x group blood Pb,Cd,As and Hg levels of heavy metals(ug/L)were 10.60±3.95 and 0.41±0.11 and 1.98±0.15 and 0.82±0.04,is close to the actual environment of low measuring four metal joint exposure levels.3?The influence of synapse structureBy transmission electron microscopy can be observed that began to emerge from 10 MM x group reduced Numbers of organelles,mild swelling of mitochondria,part of the crest fracture,but still smooth nuclear membrane,chromatin evenly distributed.Density of the synapses and PSD thickness from 5 MM x than the control group decreased(P < 0.05),and neuron synaptic cleft is only 20 MM x group than the control group increased(P < 0.05).4?The influence of gene and protein expression of SPAR and SnkSPAR protein expression in 1 MM x group than the control group increased(P < 0.05),while other infected group is lower than the control group(P < 0.05),but the SPAR,Snk mRNA and Snk protein expression did not find the difference between groups(P > 0.05).Conclusion:1 ? Environmental heavy metal co-exposure can cause the growth and development of change in rats.2?Environmental heavy metal co-exposure can cause rat neural movement,feeling,and the damage of learning and memory.3?Environmental heavy metal co-exposure can cause rat hippocampal synapses of quantity,structure and function change.4?High dose environmental heavy metal co-exposure may cut SPAR protein expression caused by rat hippocampal synapses change.