Abstract 9772: Antagonism of Rosuvastatin-induced Elevation of Circulating PCSK9 in Hamsters by Liver-specific Knockdown of HNF1α or HNF1β

Abstract

Proprotein convertase subtilisin/kexin type 9 (PCSK9) induces hepatic LDL receptor (LDLR) degradation and lowers the removal of LDL-cholesterol from circulation. Thus, PCSK9 has become an important therapeutic target for the treatment of hypercholesterolemia. The transcription of PCSK9 is prominently controlled by the HNF1 binding motif embedded in its proximal promoter region that binds to HNF1α or HNF1β as homodimers or heterodimers. Our previous in vivo studies showed that only HNF1α but not HNF1β regulates PCSK9 transcription in mouse liver. Statin has been shown to elevate circulating PCSK9 levels through stimulating PCSK9 gene transcription, which reduces the clinical efficacy of statin in LDL-cholesterol reduction. In this study, we utilized adenoviral shRNA expression vectors (Ad-shHNF1α and Ad-shHNF1β) to generate liver specific knockdown of HNF1α or HNF1β in hamsters to examine the impact of reduced expression of HNF1 transcription factors on statin-induced elevation of PCSK9. Administration of rosuvastatin (RSV) at a daily dose of 15 mg/kg to hamsters infected with a control adenovirus significantly increased liver PCSK9 mRNA levels by 94% and serum PCSK9 levels by 37%. However, injection of Ad-shHNF1α into hamsters largely abolished the RSV-induced elevation of PCSK9 serum levels and hepatic mRNA levels, which was accompanied by a significant increase in liver LDLR protein abundance by 64% as compared to hamsters injected with control virus. Surprisingly, injection of Ad-shHNF1β produced similar inhibitory effects on the RSV-induced PCSK9 expression as that of Ad-shHNF1α. This was different from the negative results of HNF1β knockdown conducted in mice. In addition to changes in PCSK9 levels, we observed a modest but significant reduction in serum non-HDL cholesterol level after knockdown of HNF1α (27%) or HNF1β (32%) in hamsters treated with RSV. Altogether, our study demonstrates that unlike mice, both HNF1α and HNF1β are positive regulators of hepatic PCSK9 transcription in hamster species and that transient, liver specific knockdown of either HNF1α or HNF1β could antagonize the RSV-induced elevation of serum PCSK9 and non-HDL cholesterol levels.