Kaempferol Protects against D-Galactose-Induced Premature Ovarian Failure and Endoplasmic Reticulum Stress in Ovarian Granulosa Cells by Promoting Estrogen Receptor 1 Expression

Abstract

Background: The efficacy of Chinese herbal medicine on premature ovarian failure (POF) and possible targets of kaempferol (KAE) for treating POF are revealed. This study is designed to determine the efficacy of KAE, a major bioactive component of Tu Si Zi (Semen Cuscutae), on POF. Methods: Female C57BL/6 mice were divided into four groups and treated for 42 days as follows: control group (normal saline injection), KAE group (5 mg/kg/day KAE, tail vein injection), D-galactose (D-gal) group (200 mg/kg/day D-gal, subcutaneous injection for POF model), and D-gal + KAE group (both KAE and D-gal treatments). The number of ovarian follicles and the apoptosis of ovarian cells were assessed using Hematoxylin-Eosin (HE) staining and terminal deoxynucleotidyl transferase dUTP Nick-End labeling (TUNEL) assay. Serum hormone levels were quantified using enzyme-linked immunosorbent assay (ELISA). The viability and apoptosis of D-gal-treated ovarian granulosa cells (OGCs) were detected using Cell Counting Kit-8 and flow cytometry assays. Quantitative reverse transcription polymerase chain reaction (qRT-PCR) and Western blot were used for gene expression quantification. Results: Tu Si Zi most probably regulated the genes related to the gamma-aminobutyric acid signaling pathway. D-gal treatment reduced body weight, the number of primordial, primary, secondary, and antral follicles, as well as the serum level of estradiol. It increased the levels of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) and promoted the apoptosis of ovarian cells (p < 0.001). These effects were reversed via KAE (p < 0.001). D-gal repressed the mRNA and protein levels of estrogen receptor 1 (ESR1) in mice and OGCs, which could be reversed by KAE treatment (p < 0.001). Additionally, the effects of KAE on the viability and apoptosis and the protein levels of apoptosis-and endoplasmic reticulum stress-regulated factors in D-gal-treated OGCs were reversed via silencing ESR1 (p < 0.001). Conclusions: KAE has been found to protect against ovarian injury and endoplasmic reticulum (ER) stress by promoting ESR1, suggesting that KAE holds great promise for the treatment of POF.