title: Varenicline enhances oxidized LDL uptake by increasing expression of LOX-1 and CD36 scavenger receptors through α7nAChR in macrophages.
abstract: Varenicline is a widely used and effective drug for smoking cessation. It is a partial agonist of the α4β2nicotinic acetylcholine receptor (nAChR) and full agonist of α7nAChR. We have reported that varenicline aggravates formation of atherosclerotic plaques through α7nAChR in apolipoprotein E knockout mice. However, little is known about its effects on macrophages in atherosclerotic plaques. Here, we ascertained whether varenicline promotes oxidized low-density lipoprotein (oxLDL) uptake in mouse peritoneal macrophages in vitro and clarified its mechanism. We investigated the effects of varenicline (1-10μM) on expression of scavenger receptors (lectin-like oxidized LDL receptor-1 (LOX-1), cluster of differentiation (CD) 36 and scavenger receptor class A (SR-A)) in RAW264.7 cells. Expression of protein and mRNA was determined by western blotting and real-time quantitative reverse transcription-polymerase chain reaction, respectively. Effects of varenicline (10μM) on oxLDL uptake were examined by counting the number of macrophages stained with oil red O and hematoxylin. Varenicline significantly increased expression of the protein and mRNA of LOX-1 and CD36, but not SR-A, in RAW264.7 cells, and increased oxLDL uptake in macrophages. These effects of varenicline were blocked significantly by an α7nAChR antagonist, methyllycaconitine (MLA) (50nM), but not by an α4β2nAChR antagonist, dihydro-β-erythroidine hydrobromide (DHβE) (1μM). These data suggest that varenicline promotes oxLDL uptake by upregulating expression of LOX-1 and CD36 through α7nAChR in macrophages. We found that varenicline significantly activated extracellular signal-regulated kinase 1/2 (ERK1/2) and nuclear factor-kappa B (NF-κB) signaling pathways in RAW264.7 cells. This activation was blocked by MLA but not DHβE. Therefore, ERK1/2-NF-κB signaling pathway is highly likely to be responsible for varenicline-induced upregulation of LOX-1 and CD36 expression through α7nAChR in macrophages. These processes probably contribute to varenicline-aggravated atherosclerotic plaque formation. Hence, an increased risk of cardiovascular events upon varenicline treatment could occur, and must be considered in patients (especially those suffering from cardiovascular diseases).
authors.affiliation: Department of Pharmaceutical Care and Health Sciences, Faculty of Pharmaceutical Sciences, Fukuoka University, Fukuoka 814-0180, Japan.
authors.forename: Yuki
authors.initials: Y
authors.lastname: Kanaoka
authors.affiliation: Department of Pharmaceutical Care and Health Sciences, Faculty of Pharmaceutical Sciences, Fukuoka University, Fukuoka 814-0180, Japan.
authors.forename: Mitsuhisa
authors.initials: M
authors.lastname: Koga
authors.affiliation: Department of Pharmaceutical Care and Health Sciences, Faculty of Pharmaceutical Sciences, Fukuoka University, Fukuoka 814-0180, Japan.
authors.forename: Keita
authors.initials: K
authors.lastname: Sugiyama
authors.affiliation: Department of Pharmaceutical Care and Health Sciences, Faculty of Pharmaceutical Sciences, Fukuoka University, Fukuoka 814-0180, Japan.
authors.forename: Kaoru
authors.initials: K
authors.lastname: Ohishi
authors.affiliation: Department of Pharmaceutical Care and Health Sciences, Faculty of Pharmaceutical Sciences, Fukuoka University, Fukuoka 814-0180, Japan.
authors.forename: Yasufumi
authors.initials: Y
authors.lastname: Kataoka
authors.affiliation: Department of Pharmaceutical Care and Health Sciences, Faculty of Pharmaceutical Sciences, Fukuoka University, Fukuoka 814-0180, Japan. Electronic address: atyama@fukuoka-u.ac.jp.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Yamauchi
mesh_terms: D000818:Animals; D018955:CD36 Antigens / Q000235:genetics / Q000378:metabolism*; D002454:Cell Differentiation / Q000187:drug effects; D008077:Lipoproteins, LDL / Q000378:metabolism*; D008264:Macrophages / Q000187:drug effects* / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D048052:Mitogen-Activated Protein Kinase 3 / Q000235:genetics / Q000378:metabolism; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism; D000067996:RAW 264.7 Cells; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051117:Scavenger Receptors, Class A / Q000235:genetics / Q000378:metabolism; D051127:Scavenger Receptors, Class E / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D015854:Up-Regulation; D000068580:Varenicline / Q000009:adverse effects*; D064569:alpha7 Nicotinic Acetylcholine Receptor / Q000819:agonists / Q000235:genetics* / Q000378:metabolism
chemical_list: D018955:CD36 Antigens; D008077:Lipoproteins, LDL; D016328:NF-kappa B; C495138:Olr1 protein, mouse; D012333:RNA, Messenger; D051117:Scavenger Receptors, Class A; D051127:Scavenger Receptors, Class E; D064569:alpha7 Nicotinic Acetylcholine Receptor; C099252:oxidized low density lipoprotein; D048052:Mitogen-Activated Protein Kinase 3; D000068580:Varenicline
keywords: Atherosclerosis; Scavenger receptor; Varenicline; oxLDL uptake; α(7) nAChR