PCSK9 inhibitors suppress oxidative stress and inflammation in atherosclerotic development by promoting macrophage autophagy

Objectives: Proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors, a novel class of cholesterol-lowering drugs, can reduce atherosclerosis independent of systemic lipid changes. However, the mechanism by which PCSK9 inhibition protects against arteriosclerosis has not been fully elucidated. Recent evidence has demonstrated a correlation between PCSK9 inhibitors and oxidative stress, which accelerates atherosclerotic development. Moreover, an increasing number of studies have shown that Autophagy protects the vasculature against atherosclerosis. Therefore, the aims of this study were to investigate the effect of PCSK9 inhibition on oxidative stress and Autophagy in atherosclerosis and determine whether Autophagy regulates PCSK9 inhibition-mediated oxidative stress and inflammation in macrophages.

Methods: Male apolipoprotein E (ApoE)^-/- mice were fed a high-fat diet (HFD) for 8 weeks and then received the PCSK9 inhibitor (evolocumab), vehicle, or evolocumab plus chloroquine (CQ) for another 8 weeks. ApoE^-/- mice in the control group were fed a regular (i.e., non-high-fat) diet for 16 weeks. Additional in vitro experiments were performed in oxidized low-density lipoprotein (ox-LDL)-treated human acute monocytic leukemia cell line THP-1-derived macrophages to mimic the pathophysiologic process of atherosclerosis.

Results: PCSK9 inhibitor treatment reduced oxidative stress, lipid deposition, and plaque lesion area and induced Autophagy in HFD-fed ApoE^-/- mice. Most importantly, the administration of chloroquine (CQ), an Autophagy Inhibitor, significantly reduced the beneficial effects of PCSK9-inhibitor treatment on oxidative stress, lipid accumulation, inflammation, and atherosclerotic lesions in HFD-fed ApoE^-/- mice. The in vitro experiments further showed that the PCSK9 inhibitor enhanced autophagic flux in ox-LDL-treated THP-1-derived macrophages, as indicated by increases in the numbers of autophagosomes and autolysosomes. Moreover, the Autophagy Inhibitor CQ also reduced PCSK9 inhibition-mediated protection against oxidative stress, generation of Reactive Oxygen Species (ROS) and inflammation in ox-LDL-treated THP-1-derived macrophages.

Conclusions: This study reveals a novel protective mechanism by which PCSK9 inhibition enhances Autophagy and thereby reduces oxidative stress and inflammation in atherosclerosis.

Atherosclerosis; autophagy; inflammation; oxidative stress; proprotein convertase subtilisin/kexin type 9.