Inhibiting Effect And Mechanism Of Folic Acid On β-amyloid Deposition In The Brain Of APP/PS1 Transgenic Mouse

Objective To observe the effect of folic acid on the APP / PS1 mice brain amyloid in APP cleavage pathway and explore the mechanism of inhibition of Aβ deposition, and To provide science basis for studying the therapeutic and preventive effects of folic acid on neurodegenerative diseases.Methods The 6-month-old male APP/PS1 mice were randomly assigned to four groups.The groups were: folate-deficient diet plus daily gavage with water(AD+FA-D), control diet plus daily gavage with water(AD+FA-N), control diet plus daily gavage with 120μg/kg folic acid(AD+FA-L), control diet plus daily gavage with 600 μg/kg folic acid(AD+FA-H).Wild type mice were fed the control and gavaged daily with water(WT+FA-N), the same old with APP/PS1 mice. The AD+FA-D groups with the folate-deficient diet and the other groups with control diet, AD+FA-L groups give 120μg/kg bw·d folic acid solution, the AD+FA-H groups give 600μg/kg bw·d folic acid solution,other groups give double distilled water. Weighed mouse body once a week.During 60 days intervention, we adjusted intragastic volume according to the body weight. Serum folate concentration was measured by IMMULITE folic acid chemiluminescent immunoassay kit. The m RNA expression levels of APP, BACE1,ADAM9,ADAM10 and PS1 in brains were quantified by real-time PCR. The protein expression levels of APP, BACE1, ADAM9, ADAM10, PS1, NCT in brains were detected by Western blot. The expressions of β-amytoid protein in the brain tissue were measured by immunohistochemistry. The expression levels of Aβ1–40 and Aβ1–42 in the brain tissue were measured by enzyme linked immunosorbent assay.Results Folic acid intervention in 60 days, IMMULITE method to detect serum folate concentration results as follows: before the intervention, 5 groups of serum folate concentration at the same level, as the change of intervention1 week after intervention, serum folate concentration were changed in 5 groups. AD+FA-D group serum folate concentration was lower than other groups, serum folate levels in AD+FA-L group and AD+FA-H group were higher than that in AD+FA-N group(P<0.05). Immunohistochemistry detection of brain Aβ protein results revealed that a highly significant decreased of Aβ protein expressions in AD+FA-H group(P<0.05) in brains compared with AD+FA-N group, and a significant increased in AD+FA-D group(P<0.05), the Aβ protein expressions in brains increase was not significant differences in AD+FA-L group(P>0.05). ELISA detection of brain tissue in Aβ1–40 and Aβ1–42 result showed that compared with AD+FA-N group,the expression levels of Aβ1–40 in the brain were not significant differences, in addition to WT+FA-N group Aβ1–40 levels have fallen.Compared with AD+FA-N group, the expression levels of Aβ1–42 in the brain were significant decreased in AD+FA-H group(P<0.05), a significant increased in AD+FA-D group(P<0.05), but there were not significant differences in AD+FA-L group(P>0.05). RT-PCR detection of brain tissue APP, BACE1, ADAM9, ADAM10, PS1 m RNA levels shows:compared with AD+FA-N group,m RNA expressions of APP,BACE1 and PS1 in brains were significantly increased in AD+FA-D group(P<0.05), however,m RNA expressions of ADAM9, ADAM10 in brains were significantly reduced in AD+FA-D group(P<0.05). Compared with AD+FA-N group, m RNA expressions of APP, BACE1 and PS1 in brains were significantly reduced in AD+FA-L group and AD+FA-H group(P<0.05), but m RNA expressions of ADAM9, ADAM10 in brains were significantly increased in AD+FA-L group and AD+FA-H group(P<0.05). Western blot detection of brain tissue APP, BACE1, ADAM9, ADAM10, PS1 protein expression results show that compared with AD+FA-N group, protein expressions of APP, BACE1 and PS1 in brains were significantly increased in AD+FA-D group(P<0.05), however, protein expressions of ADAM9, ADAM10 in brains were significantly reduced in AD+FA-D group(P<0.05). Compared with AD+FA-N group, protein expressions of APP, BACE1 and PS1 in brains were significantly reduced in AD+FA-L group and AD+FA-H group(P<0.05), but protein expressions of ADAM9, ADAM10 in brains were significantly increased in AD+FA-L group and AD+FA-H group(P<0.05).Protein expression of NCT in brains were not significant differences in each group(P>0.05).Conclusion The experimental results show that folic acid supplementation can reduce brain Aβ deposition and the levels of Aβ1–42, Folic acid deficiency can promote the brain tissue Aβ deposition and the levels of Aβ1–42. Folic acid by inhibiting amyloid in brain tissue of mice generated secretion pathway enzymes BACE1, PS1 NCT of m RNA and protein expression, and reduce the generation of Aβ, while increasing m RNA and protein expression levels of non-amyloid secretion pathway enzymes ADAM9, ADAM10 in the brain tissue of mice to reduce Aβ generation,reduce the production of Aβ.