The Effect Of Alpha-Synuclein In Manganese-Induced Endoplasmic Reticulum Stress In Neurocyte Of Mouse

Objective:Manganese（Mn）is one of the essential trace elements for humanbeings and Mn plays an important role in brain phusiological function and homeostasis.Mn reaches the brain by transport across the blood-brain barrier via various,thusmechanisms.Chronic overexposure to Mn can have a detrimental effect on the brain resulting in a disease state referred to as manganism.The primary source of Mn toxicity is occupational exposure.As the exposures in smelting and ferromanganese industries,it also could be use of methylcyclopentadienyl Mn tricarbonyl（MMT）,increasing the levels of Mn in air leads to wider non-occupational exposure.The over expression ofαlpha-synuclein（α-Syn）plays a very important role in the neurotoxicity of Mn.Mn can induce endoplasmic reticulum stress（ERS）,which induce brain damage,but the mechanism is unclear.Then what’s the relationship betweenα-Syn and Mn-induced ERS We used the wild-type andα-Syn gene knockout mice,to observe the behavior change and detect the Mn level,the neuronal apoptosis rate,and the expressions of molecules related to endoplasmic reticulum stress three signaling pathways:PERK、IRE1 and ATF6 signal pathways.To explore the role ofα-Syn in Mn-induced ERS and understand the mechanism of ERS.Methods:We choose 40 wile-type C57 mice(α-Syn^+/+)and 40α-Syn gene knockout mice(α-Syn^-/-)and randomly divided into four groups respectively:α-Syn^+/+control group、α-Syn^-/-control group:the mice were given 0.9%NaCl solution intraperitoneally i.p.,α-Syn^+/+Mn（50）andα-Syn^-/-Mn（50）group:the mice were given 50μmol/kg MnCl₂i.p.,α-Syn^+/+Mn（100）andα-Syn^-/-Mn（100）group:the mice were given 100μmol/kg MnCl₂ i.p.,α-Syn^+/+Mn（200）andα-Syn^-/-Mn（200）group:the mice were given200μmol/kg MnCl₂ i.p..The injectioncapacity continued for 4 weeks,measured the mice weight every week and observed the behavioral changes.After the last injection,the mice were sacrificesd,The striatum were isolated and detected of Mn level,the neuronal apoptosis rate,and the expressions of molecules related to endoplasmic reticulum stress three signaling pathways.Results:1.With the increase of Mn concentration,Mn level was constantly increasing in the wild-type andα-Syn^-/-mice.The difference was statistically significant.2.With the increase of Mn concentration,apoptosis rate was constantly increasing in the wild-type andα-Syn^-/-mice.The difference was statistically significant.3.With the increase of Mn concentration,the expresstion level of bothα-Syn protein and mRNA inα-Syn^+/+Mn（200）group.The difference was statistically significant.4.With the increase of Mn concentration,compared with the control group,in Mn（200）group,the expresstion of PERK、ATF4 and eIF2αprotein were increased in wild-type andα-Syn^-/-mice.In wild-type mice the expresstion of phospho-PERK、eIF2αand ATF4mRNA significantly increased,however,α-Syn^-/-mice were markedly lower than that in the wild-type mice.The difference was statistically significant.5.With the increase of Mn concentration,compared with the control group,in the each group of wild-type andα-Syn^-/-mice,the expresstion of IRE1 protein an phospho-IRE1 were significantly increased.as well as the total and spliced XBP-1.However,α-Syn^-/-mice were markedly higher than that in the wild-type mice.The difference was statistically significant.6.With the increase of Mn concentration,compared with the control group,in Mn（200）group,the expresstion of CHOP and Cleaved Caspase12 protein were significantly increased in wild-type andα-Syn^-/-mice,andα-Syn^-/-mice were markedly higher than that in the wild-type mice.The difference was statistically significant.Conclusion:1.Mn can induce ER stress three signaling pathways:PERK-eIF2a、IRE1and ATF6 signaling pathway;2.α-Syn is associated with Mn-induced activation of PERK-eIF2αsignaling pathway in ER stress;3.α-Syn has a protective effect in the excessive activation of ER stress.