Local effects of human PCSK9 on the atherosclerotic lesion.
Proprotein convertase subtilisin/kexin type 9 (PCSK9) promotes atherosclerosis by increasing low-density lipoprotein (LDL) cholesterol levels through degradation of hepatic LDL receptor (LDLR). Studies have described the systemic effects of PCSK9 on atherosclerosis, but whether PCSK9 has local and direct effects on the plaque is unknown. To study the local effect of human PCSK9 (hPCSK9) on atherosclerotic lesion composition, independently of changes in serum cholesterol levels, we generated chimeric mice expressing hPCSK9 exclusively from macrophages, using marrow from hPCSK9 transgenic (hPCSK9tg) mice transplanted into apoE(-/-) and LDLR(-/-) mice, which were then placed on a high-fat diet (HFD) for 8 weeks. We further characterized the effect of hPCSK9 expression on the inflammatory responses in the spleen and by mouse peritoneal macrophages (MPM) in vitro. We found that MPMs from transgenic mice express both murine (m) Pcsk9 and hPCSK9 and that the latter reduces macrophage LDLR and LRP1 surface levels. We detected hPCSK9 in the serum of mice transplanted with hPCSK9tg marrow, but did not influence lipid levels or atherosclerotic lesion size. However, marrow-derived PCSK9 progressively accumulated in lesions of apoE(-/-) recipient mice, while increasing the infiltration of Ly6C(hi) inflammatory monocytes by 32% compared with controls. Expression of hPCSK9 also increased CD11b- and Ly6C(hi) -positive cell numbers in spleens of apoE(-/-) mice. In vitro, expression of hPCSK9 in LPS-stimulated macrophages increased mRNA levels of the pro-inflammatory markers Tnf and Il1b (40% and 45%, respectively) and suppressed those of the anti-inflammatory markers Il10 and Arg1 (30% and 44%, respectively). All PCSK9 effects were LDLR-dependent, as PCSK9 protein was not detected in lesions of LDLR(-/-) recipient mice and did not affect macrophage or splenocyte inflammation. In conclusion, PCSK9 directly increases atherosclerotic lesion inflammation in an LDLR-dependent but cholesterol-independent mechanism, suggesting that therapeutic PCSK9 inhibition may have vascular benefits secondary to LDL reduction.
Knight Cardiovascular Institute, Center for Preventive Cardiology, Oregon Health and Science University, Portland, OR, USA.
Ilaria
I
Giunzioni
Knight Cardiovascular Institute, Center for Preventive Cardiology, Oregon Health and Science University, Portland, OR, USA.
Hagai
H
Tavori
Department of Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, Nashville, TN, USA.
Roman
R
Covarrubias
Department of Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, Nashville, TN, USA.
Amy S
AS
Major
Division of Cardiovascular Medicine, Atherosclerosis Research Unit, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, USA.
Lei
L
Ding
Division of Cardiovascular Medicine, Atherosclerosis Research Unit, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, USA.
Youmin
Y
Zhang
Rinat-Pfizer Inc., South San Francisco, CA, USA.
Rachel M
RM
DeVay
Rinat-Pfizer Inc., South San Francisco, CA, USA.
Liang
L
Hong
University of South Carolina School of Medicine, Columbia, SC, USA.
Daping
D
Fan
Knight Cardiovascular Institute, Center for Preventive Cardiology, Oregon Health and Science University, Portland, OR, USA.
Irene M
IM
Predazzi
Department of Pharmacology, Dalhousie University, Halifax, Nova Scotia, and Saint John, New Brunswick, Canada.
Shirya
S
Rashid
Division of Cardiovascular Medicine, Atherosclerosis Research Unit, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, USA.|Department of Pharmacology, Vanderbilt University Medical Center, Nashville, TN, USA.
MacRae F
MF
Linton
Knight Cardiovascular Institute, Center for Preventive Cardiology, Oregon Health and Science University, Portland, OR, USA.
Sergio
S
Fazio
D000818:Animals; D050197:Atherosclerosis / Q000378:metabolism* / Q000473:pathology; D004195:Disease Models, Animal; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D006801:Humans; D007150:Immunohistochemistry; D047468:Immunoprecipitation; D017737:Macrophages, Peritoneal / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008822:Mice, Transgenic; D000071449:Proprotein Convertase 9; D043484:Proprotein Convertases / Q000378:metabolism*; D011973:Receptors, LDL / Q000378:metabolism; D012697:Serine Endopeptidases / Q000378:metabolism*; D018183:Transplantation Chimera
D011973:Receptors, LDL; C472125:PCSK9 protein, human; D000071449:Proprotein Convertase 9; D043484:Proprotein Convertases; D012697:Serine Endopeptidases
LDLR; PCSK9; atherosclerotic lesion; inflammation; macrophages; mouse models