Kaempferol-induced GPER upregulation attenuates atherosclerosis via the PI3K/AKT/Nrf2 pathway

CONTEXT: The effect of kaempferol, a regulator of oestrogen receptors, on atherosclerosis (AS) and the underlying mechanism is elusive. OBJECTIVE: To explore the effect and mechanism of kaempferol on AS. METHODS AND MATERIALS: In vivo, C57BL/6 and apolipoprotein E (APOE)(–/–) mice were randomly categorized into six groups (C57BL/6: control, ovariectomy (OVX), high-fat diet (HFD); APOE(–/–): OVX-HFD, OVX-HFD + kaempferol (50 mg/kg) and OVX-HFD + kaempferol (100 mg/kg) and administered with kaempferol for 16 weeks, intragastrically. Oil-Red and haematoxylin–eosin (HE) staining were employed to examine the effect of kaempferol. In vitro, human aortic endothelial cells (HAECs) were pre-treated with or without kaempferol (5, 10 or 20 μM), followed by administration with kaempferol and oxidized low-density lipoprotein (ox-LDL) (200 μg/mL). The effect of kaempferol was evaluated using flow cytometry, and TdT-mediated dUTP Nick-End Labelling (TUNEL). RESULTS: In vivo, kaempferol (50 and 100 mg/kg) normalized the morphology of blood vessels and lipid levels and suppressed inflammation and apoptosis. It also activated the G protein-coupled oestrogen receptor (GPER) and PI3K/AKT/nuclear factor-erythroid 2-related factor 2 (Nrf2) pathways. In vitro, ox-LDL (200 μg/mL) reduced the cell viability to 50% (IC(50)). Kaempferol (5, 10 or 20 μM) induced-GPER activation increased cell viability to nearly 10%, 19.8%, 30%, and the decreased cellular reactive oxygen species (ROS) generation (16.7%, 25.6%, 31.1%), respectively, consequently attenuating postmenopausal AS. However, the protective effects of kaempferol were blocked through co-treatment with si-GPER. CONCLUSIONS: The beneficial effects of kaempferol against postmenopausal AS are associated with the PI3K/AKT/Nrf2 pathways, mediated by the activation of GPER.