title: Inhibitory effect of PCSK9 on Abca1 protein expression and cholesterol efflux in macrophages.
abstract: Proprotein convertase subtilisin/kexin type 9 (PCSK9) may have extra-hepatic effects on cholesterol homeostasis of vascular macrophages. In this study, we aimed to investigate PCSK9 role on the anti-atherogenic process of ATP binding cassette transporter A1 (Abca1)-mediated cholesterol efflux.
  
  
  
  Abca1-mediated cholesterol efflux was evaluated by a radioisotopic technique in mouse peritoneal macrophages (MPM) from wild-type (WT) or LDL receptor knock-out (Ldlr-/-) mice exposed to human recombinant PCSK9, in the presence of liver X receptor/retinoid X receptor (LXR/RXR) ligands or acetylated LDL (AcLDL) to stimulate Abca1 expression. Protein and gene expression was evaluated by Western blot and quantitative real time PCR, respectively.
  
  
  
  PCSK9 inhibited Abca1-mediated cholesterol efflux induced by LXR/RXR agonists in WT MPM (-55%, p < 0.05) but not in Ldlr-/-MPM. This effect was fully abrogated by the co-incubation with an anti-PCSK9 antibody. The inhibition of Abca1-dependent efflux induced by PCSK9 was associated with a reduction of Abca1 protein expression only in WT cells. Abca1 gene expression was significantly downregulated by PCSK9 in WT macrophages (-64%, p < 0.001) and, to a lesser extent, in MPM lacking Ldlr (-35%, p < 0.001). The inhibitory effect on Abca1-mediated efflux was also confirmed in AcLDL-treated macrophages. PCSK9 had a marginal or no effect on the expression of the lipid transporters Sr-b1 and Abcg1.
  
  
  
  PCSK9 plays a direct role on Abca1-mediated cholesterol efflux through a downregulation of Abca1 gene and Abca1 protein expression. This extrahepatic effect may influence relevant steps in the pathogenesis of atherosclerosis, such as foam cell formation.
authors.affiliation: Dipartimento di Farmacia, Università degli Studi di Parma, Parco Area delle Scienze 27/A, Parma, Italy.
authors.forename: Maria Pia
authors.initials: MP
authors.lastname: Adorni
authors.affiliation: Dipartimento di Farmacia, Università degli Studi di Parma, Parco Area delle Scienze 27/A, Parma, Italy.
authors.forename: Eleonora
authors.initials: E
authors.lastname: Cipollari
authors.affiliation: Dipartimento di Farmacia, Università degli Studi di Parma, Parco Area delle Scienze 27/A, Parma, Italy.
authors.forename: Elda
authors.initials: E
authors.lastname: Favari
authors.affiliation: Dipartimento di Farmacia, Università degli Studi di Parma, Parco Area delle Scienze 27/A, Parma, Italy. Electronic address: ilaria.zanotti@unipr.it.
authors.forename: Ilaria
authors.initials: I
authors.lastname: Zanotti
authors.affiliation: Dipartimento di Farmacia, Università degli Studi di Parma, Parco Area delle Scienze 27/A, Parma, Italy.
authors.forename: Francesca
authors.initials: F
authors.lastname: Zimetti
authors.affiliation: Dipartimento di Scienze Farmacologiche e Biomolecolari, Università degli Studi di Milano, Milano, Italy.
authors.forename: Alberto
authors.initials: A
authors.lastname: Corsini
authors.affiliation: Dipartimento di Scienze Farmacologiche e Biomolecolari, Università degli Studi di Milano, Milano, Italy.
authors.forename: Chiara
authors.initials: C
authors.lastname: Ricci
authors.affiliation: Dipartimento di Farmacia, Università degli Studi di Parma, Parco Area delle Scienze 27/A, Parma, Italy.
authors.forename: Franco
authors.initials: F
authors.lastname: Bernini
authors.affiliation: Dipartimento di Scienze del Farmaco, Università degli Studi di Padova, Padova, Italy.
authors.forename: Nicola
authors.initials: N
authors.lastname: Ferri
mesh_terms: D064286:ATP Binding Cassette Transporter 1 / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D001692:Biological Transport; D002478:Cells, Cultured; D002784:Cholesterol / Q000378:metabolism*; D015536:Down-Regulation; D005838:Genotype; D008024:Ligands; D008077:Lipoproteins, LDL / Q000494:pharmacology; D000071518:Liver X Receptors / Q000819:agonists / Q000378:metabolism; D017737:Macrophages, Peritoneal / Q000187:drug effects* / Q000201:enzymology; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D010641:Phenotype; D000071449:Proprotein Convertase 9 / Q000494:pharmacology*; D011973:Receptors, LDL / Q000172:deficiency / Q000235:genetics; D047488:Retinoid X Receptors / Q000819:agonists / Q000378:metabolism
chemical_list: D064286:ATP Binding Cassette Transporter 1; D002784:Cholesterol; D008024:Ligands; D008077:Lipoproteins, LDL; D000071518:Liver X Receptors; D000071449:Proprotein Convertase 9; D011973:Receptors, LDL; D047488:Retinoid X Receptors; C577833:Abca1 protein, mouse; C032629:acetyl-LDL; C472125:PCSK9 protein, human
keywords: ABCA1; Cholesterol efflux; Macrophage; PCSK9