Inhibition of macrophage proliferation dominates plaque regression in response to cholesterol lowering

Josef Madl,T.-S Dederichs ,Jan Kornemann,Peter Kohl,Dennis Wolf,Bianca Dufner,Florian Willecke,H.m.g Princen ,Carmen Härdtner,Diana Sharipova,C Ehlert ,Andreas Zirlik,Christoph Bode,Rafael Kaeser,Filip K Świrski ,Tobias Böettler ,Timo Heidt,Ingo Hilgendorf,Peter Stachon,Simon Rauterberg,Katja Krebs,Christopher Starz,Benoît Ho‐Tin‐Noé ,Clinton S Robbins,Jiadai Zou,Elsbeth Pieterman ,Alina Jander,Natalie Hoppe,Constantin Von Zur Mühlen

doi:10.1007/s00395-020-00838-4

Abstract

Statins induce plaque regression characterized by reduced macrophage content in humans, but the underlying mechanisms remain speculative. Studying the translational APOE*3-Leiden.CETP mouse model with a humanized lipoprotein metabolism, we find that systemic cholesterol lowering by oral atorvastatin or dietary restriction inhibits monocyte infiltration, and reverses macrophage accumulation in atherosclerotic plaques. Contrary to current believes, none of (1) reduced monocyte influx (studied by cell fate mapping in thorax-shielded irradiation bone marrow chimeras), (2) enhanced macrophage egress (studied by fluorescent bead labeling and transfer), or (3) atorvastatin accumulation in murine or human plaque (assessed by mass spectrometry) could adequately account for the observed loss in macrophage content in plaques that undergo phenotypic regression. Instead, suppression of local proliferation of macrophages dominates phenotypic plaque regression in response to cholesterol lowering: the lower the levels of serum LDL-cholesterol and lipid contents in murine aortic and human carotid artery plaques, the lower the rates of in situ macrophage proliferation. Our study identifies macrophage proliferation as the predominant turnover determinant and an attractive target for inducing plaque regression.

Highlights

International guidelines recommend treating patients with atherosclerotic disease with high-dose statins [20, 41]
We examined the relative contribution of monocyte infiltration, macrophage proliferation, death and egress in APOE*3Leiden.Cholesteryl ester transfer protein (CETP) mice, which model human-like lipid changes in response to oral statin treatment
To study mechanisms of statin-mediated plaque regression, we induced atherosclerosis in APOE*3-Leiden.CETP mice by feeding a 1.25% cholesterol diet over 12 weeks, accelerating plaque formation, followed by 4 weeks of 0.05% cholesterol diet to lower plasma cholesterol levels to about 10 mmol/L, that would allow for lipid normalization by subsequent therapeutic intervention

Summary

Introduction

International guidelines recommend treating patients with atherosclerotic disease with high-dose statins [20, 41]. These and other findings have fueled the debate as to whether the beneficial effects of statins are primarily attributed to lipid lowering or to pleiotropic, i.e. anti-inflammatory and directly vasoprotective, effects [23, 40]. Multiple in vitro studies documented lipid-independent effects of statins on macrophages and endothelial cells, and statin treatment of Apolipoprotein E (Apoe)-deficient mice limited atherogenesis and monocyte recruitment without affecting cholesterol levels [3, 21, 51, 69]. APOE*3Leiden.Cholesteryl ester transfer protein (CETP) mice, a translational mouse model with a humanized lipoprotein metabolism [70], respond to oral statin treatment with (V)LDL-cholesterol lowering, and showed attenuated plaque formation when fed a Western diet [25]. The authors proposed impaired monocyte recruitment into atherosclerotic lesions and suppressed inflammation as underlying mechanisms [26, 64]

Methods

Results

Conclusion