Effects Of Lithium Carbonate On White Matter Demyelination Model Caused By Cuprizone In Mice

BackgroundThe etiology and pathogenesis of many psychiatric disorders,such as schizophrenia,depression,and bipolar disorder,are not yet clear.Some studies suggest that changes in the structure and function of white matter may be one of the pathogenesis of many mental diseases including schizophrenia.Lithium carbonate is a kind of commonly used emotional stabilizers in the psychiatry.In addition to stabilizing mood,the neurotrophic and neuroprotective effects of lithium carbonate have also been widely confirmed in recent years.However,whether lithium carbonate can repair damaged white matter by repairing damaged myelin sheath is still unclear,which may provide new therapeutic ideas for promoting the recovery of mental diseases and disorders of the nervous system.This is worthy of further study.ObjectivesThrough establishing a mouse model of demyelination in white matter,we study how lithium carbonate affect that the mouse weight,behaviors,recovery of myelination in prefrontal lobe and hippocampus,and analysis the relationship of between change of behaviors and alteration of white matter.In this study,we could find the role that lithium carbonate plays in the white matter demyelination model caused by cuprizone.Methods1.The C57BL/6 mice were fed one week to adapt new environment and then for behavioral evaluation;the mice with lighter weight and poorer behavioral performance were eliminated.60 mice with uniform behavioral phenotypes were screened out and randomly divided into two groups,that is the cuprizone?CPZ?group?n=30?and the control?CON?group?n=30?.For the next 6 weeks,the CPZ group was given a diet containing 0.2%CPZ daily,while the CON group was fed the normal diet the same volume as the CPZ group.And all of the mice were evaluated for weight every week.2.When the model was established after six weeks,behavioral assessment was performed on the CON group and the CPZ group.Then 10 samples were taken from each group in order to analyse the overall modeling situation by Western blot and immunofluorescence histochemical.After the analysis,the CON components were further divided into CON+Sham group and CON+LiCO3 group,10 mice in each group,and the two groups were respectively given normal artificial feed and artificial feed containing 0.2%LiCO₃.Similarly,the CPZ group was also divided into CPZ+Sham group and CPZ+LiCO₃group,10 mice in each group,and the two groups were respectively given artificial normal feed and artificial feed containing 0.2%LiCO₃,which lasted two weeks.3.We performed sucrose water preference test,open field test and rotarod test to evaluate the effects of CPZ modelling and lithium carbonate intervention on mice behavioral performance.4.By immunofluorescence histochemical method,we detected the expression of MBP in corpus callosum.Western blot was used to test the levels of MBP and CNPase protein in the prefrontal lobe and hippocampus of these mice.We tested integral optical density?IOD?values by Image Pro plus software and then they were compared between those groups.5.SPSS21.0 was used to analyse those mass of data.We selected corresponds statistical methods according to the characteristics of data.Those data which obeys the normal distribution was presented by mean±SD.Independent samples t test was adopted to compare mean values of two different groups.And we used One-way ANOVA to analyse the measurement data in multiple groups.Besides,the repeated measurement data were analyzed by repetitive measurement deviation analysis and least significant test?LST test?was for multiple comparison.When P<0.05,the results have significant difference.Results1.Effect of CPZ on miceBefore establishing the CPZ model,there was no significant difference in body weight and behavioral indexes between mice in the CON group and the CPZ group?P>0.05?.From the end of the first week to the sixth week of establishing the CPZ model,weight of mice in the CPZ group was significantly smaller than that in the CON group?P<0.05?.In the field experiment,the total distance of the open field in the CPZ group was significantly shorter than that in the CON group?P<0.05?,but there was no significant difference in the distance of the boundary area between the two groups?P>0.05?.In sucrose water experiment,the results was of no significant difference between the two groups?P>0.05?.In the rotarod experiment,the residence time of the rod in the CPZ group was less than that in the CON group;and the difference was statistically significant?P<0.05?.The results of Western blot showed that the expression of MBP and CNPase protein in the prefrontal cortex of the CPZ group was lower than that in the CON group?P<0.05?.When it came to hippocampus,it was the same as the prefrontal cortex?P<0.05?.The data from immunofluorescence indicated that the mean fluorescence intensity of MBP in the CPZ group was significantly lower than that in the CON group?P<0.05?.2.Interventional effect of LiCO₃ on miceAfter 2 weeks of administration with lithium carbonate,there was significant difference in the body reconstitution among the four groups:CON+Sham,CON+LiCO₃,CPZ+Sham,and CPZ+LiCO3?P<0.05?.Pairwise comparison showed that the weight of CON+Sham group was higher than the other three groups,and the difference was statistically significant?P<0.05?.The weight of CPZ+Sham was higher than that of CPZ+LiCO₃ group,and the difference was statistically significant?P<0.05?.There was no statistical difference between the other groups?P>0.05?.There was also significant difference in sucrose water preference index among the four groups?P<0.05?.Pairwise comparison showed that the sucrose water preference index in CON+LiCO3 group and CPZ+LiCO3 group were higher than those in CON+Sham group?P<0.05?.The sucrose water preference index in CPZ+LiCO3 group was higher than that in CPZ+Sham group?P<0.05?.There was no statistical difference between the other groups?P>0.05?.There was no significant difference in the total distance of movement and the boundary distance among the four groups in the open field test?F=0.034,P=0.991??F=0.132,P=0.940?.There was a statistically significant difference in the retention time among the four groups of mice in the rotarod experiment?F=10.751,P=0.000?.Pairwise comparison showed that the retention time of the mice in the CON+Sham group,the CON+LiCO₃group and the CPZ+Sham group was higher than that in the CPZ+Sham group,and the difference was statistically significant?P<0.05?.There was no statistical difference between the other groups?P>0.05?.The results of Western blot after 2 weeks of lithium carbonate intervention suggested that there was a statistically significant difference in the relative expression levels of MBP and CNPase in the prefrontal cortex among CON+Sham,CON+LiCO₃,CPZ+Sham,and CPZ+LiCO₃ groups?P<0.05?.Pairwise comparison showed that the relative expressions of MBP and CNPase in the prefrontal cortex of CON+Sham group and CON+LiCO₃ group were higher than those in CPZ+Sham group and CPZ+LiCO₃ group?P<0.05?.The relative expression of MBP and CNPase in the prefrontal cortex of CPZ+LiCO₃ group was higher than that in CPZ+Sham group,and the difference was statistically significant?P<0.05?.There was no statistical difference between the other groups?P>0.05?.At the same time,the relative expression of MBP and CNPase in the hippocampus was also statistically significant?P<0.05?.The relative expression levels of MBP and CNPase in the hippocampus of CPZ+Sham group were significantly lower than those in the other three groups?P<0.05?.The relative expression of CNPase in hippocampus of mice in CON+LiCO₃ group was higher than that in CON+Sham group?P<0.05?.There was no statistical difference between the other groups?P>0.05?.Establishing the CPZ model two weeks later,the results of immunofluorescence found that the average optical density of MBP in the four groups was significantly different from each other?F=27.996,P=0.000?.The comparison between the two groups showed that the mean fluorescence intensity?AOD?of MBP in the CON+Sham group and the CON+LiCO3 group was higher than that in the CPZ+Sham group and the CPZ+LiCO3group?P<0.05?.The average fluorescence intensity?AOD?of MBP in CPZ+LiCO₃ group was higher than that in CPZ+Sham group,and the difference was statistically significant?P<0.05?.There was no statistical difference between the other groups?P>0.05?.Conclusions1.Lithium carbonate can improve the ability of balance and pleasure experience in demyelinated mice,but at the same time it may inhibit the increase of body weight.2.Lithium carbonate can promote demyelinayion repair in CPZ mice,while it has no significant influence on the myelin sheath in CON mice.