Effect Of Methylene Blue On Aβ And Related Protein Expression In Hippocampal Formation Of APP/PS1 Mouse

ObjectiveAlzheimer disease is a degenerative disease of the brain that causes dementia. UCH-L1 is down-regulated in idiopathic AD and APP/PS1 mouse. Rember. the main component of which is MB, the PhaseⅡdata seem to have been impressive. MB delays senescence at nM levels in normal human lung fibroblasts (IMR90) by enhancing mitochondrial function. There is few study on the effect of MB on UCH-L1 and spine density in APP/PS1 mouse.In the present study, we examined the effect of oral MB treatment on the neurodegenerative pathology and memory deficitsβ-amyoid precursor protein (APP) and presenilin 1 (PS1) double-transgenic mice, a well established AD mouse model. When systemically administered to 4-month-old APP/PS1 mice for 3 months, MB effectively improves cognition of APP/PS1 transgenic (Tg) mice not by altering AB burden but by up-regulating the level of UCH-L1 and increasing the density of dendritic spine.Materials and Methods1. Experimental animal grouping:Animal studies followed protocols approved by the Laboratory Animal Centre of China Medical University. We utilized either C57/BL6 mice (wild type) or APP/PS1 mice. APP/PS1 transgenic mice and wild-type littermates were assigned into three groups:MB-treated APP/PS1 mice, untreated APP/PS 1 mice, wild-type mice. Treated groups received MB (25 mg/kg per day) Untreated groups received normal drinking water. Treatment was started when the mice were 4 months old and was continued for 3 months.2. Step-down Avoidance Test for testing learning and remembrance ability of mice was used. Stepdown latency and the number of error were recorded.3. Thiazine red stainning was performed to observe the SPs of APP/PS1 mouse.4. Aβ1-40 and Aβ1-42 Elisas and Aβstainning was performed.5. Immunohistochemistry and Western blotting for UCH-L1 were performed.6. Golgi stainning of spine density was performed.7. Image collection analysis system was applied. The data were expressed as Mean±SD and were analyzed by SPSS 11.0 statistical package. The differences among group were compared with one-way analysis of variance. P＜0.05 was regarded as the significant difference and P＜0.01 was regarded as the extremely significant difference.Results1. Results of step down avoidence test:APP/PS1 mice presented lower step-down latency than mice WT groups. APP/PS1 mice treated with MB showed higher values of step-down latency than APP/PS1 mice treated with vehicle (P＜0.01). MB treated transgenic mice showed no statistical difference with WT mice (P＞0.05).2. SPs was observed in the hippocampus of APP/PS1 mouse aged 7 years.3. Aβ1-40 and Aβ1-42 Elisas:MB had no effect on the hippocampal soluble or insoluble Aβ1-40 or Aβ1-42 levels as analyzed by Elisa.4. immunofluorescence and western blotting of UCH-L1:4 months of treatment with MB reestablished normal levels of UCH-L1 in 7-month-old transgenic animals. (P＜0.01, WT versus APP/PS1; P＜0.01, APP/PS1 versus APP/PS1 plus MB; P=0.05, WT versus APP/PS1 plus MB; n=10). Consistent with these results, immunohistological analysis of UCH-Ll revealed a decrease in the transgenic mice, which was returned to control levels by MB5. Results of Golgi stainning:Compared with model group, the spine density of MB treated group was increased (P＜0.01). There is no statistical difference between treated transgenic mice and WT mice.Conclusions1. MB can delay the natural progression of cognitive abnormalities of APP/PS1 mouse.2. MB had no effect on Aβ1-40 or Aβ1-42 levels.3. MB up regulats the expression of UCH-L1 and increases the spine density of APP/PS 1 mouse.4. MB increases the spine density of APP/PS1 mouse.