Levonorgestrel-ethinyl estradiol impairs hepatic lipid clearance to induce hypercholesterolemia via PCSK9-mediated LDLR and CD36 dysregulation.

Levonorgestrel-ethinyl estradiol (LNG/EE), a widely used oral contraceptive, is associated with metabolic toxicity including dyslipidemia and increased atherosclerotic cardiovascular disease (ASCVD) risk, but the underlying mechanisms remain unclear. Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a key regulator of lipid metabolism, and its role in LNG/EE-induced hypercholesterolemia is undefined. To clarify whether PCSK9 mediates LNG/EE-induced dyslipidemia, we conducted in vivo experiments using female wild-type (WT) and PCSK9 knockout (PCSK9-/-) mice, as well as in vitro assays with AML12 and HepG2 hepatocytes. WT mice received LNG/EE (0.0005 mg/d levonorgestrel +0.0001 mg/d ethinyl estradiol per mouse) or distilled water intragastrically for 12 weeks; hepatocytes were treated with LNG/EE (100 nM LNG + 10 nM EE) with/without PCSK9 knockdown. In WT mice, LNG/EE significantly increased circulating and hepatic PCSK9 (P < 0.05), reduced hepatic LDL receptor (LDLR) (P < 0.05), elevated low-density lipoprotein cholesterol (LDL-C), total cholesterol (TC), triglycerides (TG) (all P < 0.05), and decreased high-density lipoprotein cholesterol (HDLC) (P < 0.05). These changes were absent in PCSK9-/- mice. In vitro, PCSK9 knockdown attenuated LNG/EE-induced Cluster of Differentiation 36 (CD36) suppression (P < 0.05) and enhanced low-density lipoprotein (Dil-LDL) uptake. This study demonstrates LNG/EE induces hypercholesterolemia via PCSK9 upregulation, promoting LDLR degradation and CD36 downregulation. PCSK9 inhibitors may be a promising therapy for OC-associated hypercholesterolemia.