Folic acid and S-adenosylmethionine reverse Homocysteine-induced Alzheimer's disease-like pathological changes in rat hippocampus by modulating PS1 and PP2A methylation levels.

Background: Abnormally elevated homocysteine (Hcy) is recognized as a biomarker and risk factor for Alzheimer's disease (AD). However, the underlying mechanisms by which Hcy affects AD are still unclear.
Objectives: This study aimed to elucidate the effects and mechanisms by which Hcy affects AD-like pathological changes in the hippocampus through in vivo and in vitro experiments, and to investigate whether folic acid (FA) and S-adenosylmethionine (SAM) supplementation could improve neurodegenerative injuries.
Methods: In vitro experiments hippocampal neurons of rat were treated with Hcy, FA or SAM for 24 h; while the hyperhomocysteinemia (HHcy) in Wistar rats was established by intraperitoneal injection of Hcy, and FA was added to feed. The expression of β-amyloid (Aβ), phosphorylated tau protein, presenilin 1 (PS1) at the protein level and the activity of protein phosphatase 2A (PP2A) were detected, the immunopositive cells for Aβ and phosphorylated tau protein in the rat hippocampus were also evaluated by immunohistochemical staining.
Results: FA and SAM significantly repressed Hcy-induced AD-like pathological changes in the hippocampus, including the increased tau protein phosphorylation at Ser214, Ser396 and the expression of Aβ _42. In addition, Hcy-induced PS1 expression increased at the protein level and PP2A activity decreased, while FA and SAM were able to retard that.
Conclusions: The increase in PS1 expression and decrease in PP2A activity may be the mechanisms underlying the Hcy-induced AD-like pathology. FA and SAM significantly repressed the Hcy-induced neurodegenerative injury by modulating PS1 and PP2A methylation levels.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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