Abstract

BACKGROUND Postmenopausal women exhibit elevated proprotein convertase subtilisin/kexin type 9 (PCSK9) levels, increasing atherosclerosis risk. Xiaoyao San (XYS), a classic herbal formula renowned for its ability to soothe the liver and relieve depression, is widely used in China to manage perimenopausal syndrome. Previous studies have found that it alleviates hepatic lipid accumulation through the Estrogen receptor α (ERα) signaling pathway, but its role in postmenopausal atherosclerosis via the PCSK9 regulatory mechanism remains unclear. PURPOSE This study investigated XYS effects on delaying postmenopausal atherosclerosis by modulating hepatic PCSK9 transcription. METHODS AND RESULTS ApoE⁻/⁻ mice underwent bilateral ovariectomy and were fed a high-fat and high-fructose diet for 14 weeks to establish a postmenopausal atherosclerosis model. Using H&E staining, Oil Red O staining, Western blotting, and immunofluorescence, XYS reduced hepatic/serum PCSK9 and upregulated LDLR, attenuating dyslipidemia and atherosclerosis. Mechanistically, RNA-seq identified estrogen receptor signaling and the LXRα/SREBP-1c axis of fatty acid synthesis as the key molecular pathways. XYS upregulated ERα, suppressing LXRα/SREBP-1c-mediated hepatic steatosis and PCSK9 transcription. Consistent results were observed in insulin-treated cell models. Luciferase reporter assays demonstrated that XYS reduced sterol regulatory element (SRE)-dependent PCSK9 promoter activity. Notably, both in vivo targeted knockdown of hepatic ERα and in vitro treatment with the ERα antagonist ICI 182,780 reversed XYS-induced suppression of LXRα/SREBP-1c-mediated PCSK9 transcription, highlighting the critical role of hepatic ERα activation in XYS's inhibition of postmenopausal atherosclerosis progression. CONCLUSIONS