PCSK9 attenuates efferocytosis in endothelial cells and promotes vascular aging

Abstract

Aims: Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a serine protease that binds to low-density lipoprotein receptors. Efferocytosis is the process by which phagocytes remove apoptotic cells. Both PCSK9 and efferocytosis play important roles in regulating redox biology and inflammation, the key factors contributing to vascular aging. This study was designed to investigate the impact of PCSK9 on efferocytosis in endothelial cells (ECs) and its implications in vascular aging. Methods and Results: Studies were performed in primary human aortic ECs (HAECs) and primary mouse aortic ECs (MAECs) isolated from male wild-type (WT) and PCSK9 -/- mice, and in young and aged mice treated with saline or the PCSK9 inhibitor Pep2-8. Our findings include that recombinant PCSK9 protein induces defective efferocytosis and aging marker senescence-associated-β-galactosidase (SA-β-gal) expression in ECs, while PCSK9 -/- restores efferocytosis and inhibits SA-β-gal activity. Further studies in aged mice showed that endothelial deficiency of MerTK, a critical receptor for efferocytosis that allows phagocytes to detect the presence of apoptotic cells, may be an indicator of vascular dysfunction in the aortic arch. Pep2-8 treatment markedly restored efferocytosis in endothelium from the aged mice. A proteomics study in the aortic arch from aged mice revealed that Pep2-8 administration significantly downregulates expression of NOX4, MAPK subunits, NF-κB, and secretion of pro-inflammatory cytokines, all known to promote vascular aging. Immunofluorescent staining showed that Pep2-8 administration upregulates expression of eNOS and downregulates expression of pro-IL-1β, NF-κB and p22 phox compared to saline treated group. Conclusions: These findings provide initial evidence for the ability of aortic ECs to accomplish efferocytosis and argue for a role of PCSK9 in attenuating EC efferocytosis, thereby leading to vascular dysfunction and acceleration in vascular aging.

Loss of Endothelial Annexin A1 Aggravates Inflammation‐Induched Vascular Aging

“…[ 4 ] ANXA1 expression was consistently reduced in both the replicative senescence model and under chronic TNF‐α treatment to simulate the inflammaging state in vitro. However, in recent years, except for HUVECs, more kinds of endothelial cells need to be performed since several kinds of endothelial cells, like cultured endothelial cells from rat aorta, human aorta, [ 37 ] and bovine pulmonary artery, [ 38 ] can simulate endothelial cells status. In recent years, various studies focused on vascular calcification and vascular aging used these cells for investigation.…”

Disturbed flow impairs MerTK-mediated efferocytosis in aortic endothelial cells during atherosclerosis

“…However, there are some limitations in our current study. First, it has been shown that MerTK is expressed in macrophages 39 , vascular ECs 8 , 27 , and vascular smooth muscle cells (SMCs) 40 .…”

“…We recently reported that primary aortic ECs have high ability to perform efferocytosis and EC efferocytosis plays important roles in vascular aging 8 . However, the previous studies did not show the direct link between blood flow patterns and EC efferocytosis as well as the interaction between blood flow patterns and MerTK expression.…”