Biochanin A alleviates cognitive impairment and hippocampal mitochondrial damage in ovariectomized APP/PS1 mice.

BACKGROUND

Estrogen deficiency leads to mitochondrial defects that precede Alzheimer's disease (AD)-associated pathological changes in a postmenopausal mouse model. Biochanin A (BCA) is a phytoestrogen isolated from Trifolium pratense L. used to relieve postmenopausal problems in women. In previous work, we observed that oral BCA treatment led to neuroprotection in an ovariectomized rat model. The objective of this study was to investigate whether and how BCA protects against hippocampal mitochondrial damage in a postmenopausal model of AD.

METHOD

APP/PS1 mice underwent bilateral ovariectomy and then, seven days later, received oral BCA at 20 or 40 mg/kg, or oral estradiol at 0.5 mg/kg, daily for 90 days. Sham animals were not ovariectomized and received no additional treatments. Cognitive function was examined using the passive avoidance task, novel object recognition test, and Morris water maze test. The level of circulating estrogen in vivo was assessed indirectly by measuring the wet weight of the uterus. We detected Aβ deposition and PGC-1α in brain by immunohistochemistry; p62, by immunofluorescence; and ERα, ERβ, PGC-1α, NRF1, mtTFA, Drp1, OPA1, Mfn2, Beclin1, LC3B, Pink1, and Parkin by immunoblotting.

RESULTS

BCA treatment rescued cognitive decline and reduced Aβ deposition and BACE1 expression in the hippocampus of ovariectomized APP/PS1 mice. BCA reversed the imbalance of mitochondrial dynamics caused by ovariectomy by increasing the expression of phospho-Drp1 (ser637), OPA1, and Mfn2. BCA reversed abnormal mitophagy induced by ovariectomy by increasing the expression of Beclin1, LC3B, Pink1, and Parkin, as well as by reducing the expression of p62.

CONCLUSIONS

BCA treatment enhances learning and memory abilities and alleviates AD symptoms in a postmenopausal model of AD. A possible mechanism is that BCA rescues the reduction of mitochondrial biogenesis, imbalance of mitochondrial dynamics, and abnormal mitophagy caused by ovariectomy. This study supports further research on BCA to develop treatments for postmenopausal women with AD.