The Correlation Of MCT1 Expression And Vulnerability Of Oligodendrocyte Lineage Cells

BACKGROUND:After brain injury,the white matter is severely damaged accompanying clear demyelination phenomenon.The myelin sheath of white matter fibers is formed by the OPCs(OPCs,oligodendrocyte precursor cells)which wrapped gradually around axons and in this course the OPCs matured into OLs(OLs,Oligodendrocytes).But OLs is prone to death in the ischemic and anoxia,causing the abscission of the myelin sheath and the bare axons of neurons,which is not conducive to the rapid transmission of nerve signal.The mechanisms of more vulnerability of OPCs than OLs in ischemic and anoxia environment have not yet been elucidated.Checking what the mechanisms are and improving the rate of differentiation and maturation of OPCs are urgent issues required to be settled in brain injury.Monocarboxylate transporters 1(MCT1)are primarily responsible for the transport of lactic acid(monocarboxylic acid)in myelin to axons.The previous study found that absence of lactate transporters related MCT1 caused the degradation of neurons.But in the case of cerebral ischemia or hypoglycemia,how does MCT1 expression change in cortex and striatum?How does MCT1 express during the development of oligodendrocyte?How to adjust MCT1 expression in position and amount under the circumstances of oxygen-glucose deprivation(OGD)or low-glucose?Whether the expression of MCT1 is related to the vulnerability of cells?These questions have not been fully elucidated.So we designed this project to check those problems.PURPOSE:1.To analyze of cerebral cortex and striatum MCT1 expression after cerebral ischemia;2.To analyze the MCT1 expression following the differentiation of OPCs in vitro;3.To analyze the relationship between cell survival and MCT1 expression after oxygen and glucose deprivation in OPCs and OLs;4.To analyze how the two cells regulate the expression of the monocarboxylate transporter MCT1 in the condition of normal oxygen and low-glucose.METHODS:1.After one hour of middle cerebral artery occlusion(MCAO)and then reperfusion for 72 hours,the cortex and striatum of mice were stripped off.MCT1 and apoptotic proteins were detected by Western blot.The expression of inflammatory factors was detected by Elisa method.One-way ANOVA and Turkey test were used for statistical analysis to calculate the expression of MCT1 in cortex and striatum after cerebral ischemia.2.The OPCs were cultured and differentiated,collected cells every 24h after the beginning of differentiation and for 7 days.Immunofluorescence and Western blot was used to detect the expression of MCT1.3.Cells included OPCs?OLs?and OPCs with high level of MCT1 expression were cultured in oxygen-glucose deprivation circumstance for 1 or 1.5 hours respectively the normal incubated for 72 hours.Immunofluorescence and Western blot were used to detect the expression of MCT1.The cell viability was detected by MTT assay and the apoptosis was detected by Tunel assay.4.Cells were cultured in low-glucose(LG)medium(5.5mM)or low-glucose medium with ImM sodium pyruvate for 6 hours.Immunofluorescence and Western blot were used to analyze the expression and location of MCT1.RESULTS:1.After MCAO,MCT1 expression was increased in striatum rather than in cortex.2.The expression of MCT1 was gradually decreased in the course of cell differentiation as well as those of expressed in membrane.3.In oxygen-glucose deprivation(OGD)test,the expression of MCT1 in OPCs group increased after 1 hour OGD and 72 hours recover and some cells die;while after 1.5 hours OGD and 72 hours recover,expression of MCT1 was sharply decreased accompanied by a large number of cells death.In OLs group,it is found that cells death only occur after 1.5 hours OGD while MCT1 expression did not alter.Increasing the expression of MCT1 in OPCs treated with lactate significantly improved the survival of OPCs in 1 hour OGD.4.In low-glucose test,expressions of MCT1 in body and processes were reduced.Sodium pyruvate has not effect on MCT1 expression.Total expression of MCT1 in OLs did not alter while MCT1 in body was increased(P<0.05)and sodium pyruvate reverse this change.Conclusions:The MCT1 is involved in the mechanism of ischemia-hypoxia in striatum.MCT1 expression was gradually decreased following OPCs differentiation.Under OGD and low-glucose stimulation,MCT1 expression in OPCs was reduced and moved to cytoplasm leading to functional loss and cell death,while MCT1 expression and location in oligodendrocyte has no changes and more oligodendrocyte survive after stimulations.The expression of MCT1 to some extent determines the vulnerability of oligodendrocyte lineage cell.