title: Induction of inducible nitric oxide synthase (iNOS) expression by oxLDL inhibits macrophage derived foam cell migration.
abstract: OBJECTIVE
  Deletion of inducible nitric oxide synthase (iNOS) in apolipoprotein E knockout mice was shown to mitigate the extent of arteriosclerosis. Oxidized low density lipoprotein (oxLDL) inhibits macrophage migration and traps foam cells, possibly through a mechanism involving oxidative stress. Here, we addressed whether a reduction of iNOS-mediated oxidative stress remobilizes macrophage-derived foam cells and may reverse plaque formation.
  
  
  METHODS
  Migration of RAW264.7 cells and bone marrow cells was quantified using a modified Boyden chamber. iNOS expression, phalloidin staining, focal adhesion kinase phosphorylation, lipid peroxides, nitric oxide (NO) and reactive oxygen species (ROS) production were assessed.
  
  
  RESULTS
  oxLDL treatment significantly reduced cell migration compared to unstimulated cells (p < 0.05). This migratory arrest was reversed by co-incubation with a pharmacologic iNOS inhibitor 1400 W (p < 0.05) and iNOS-siRNA (p > 0.05). Furthermore, apoE/iNOS double knockout macrophages do not show migratory arrest in response to oxLDL uptake, compared to apoE knockout controls (p > 0.05). We documented significantly increased iNOS expression following oxLDL treatment and downregulation using 1400 W and small inhibitory RNA (siRNA). iNOS inhibition was associated with a reduction in NO and peroxynitrite (ONOO-)- and increased superoxide generation. Trolox treatment of RAW264.7 cells restored migration indicating that peroxynitrite mediated lipid peroxide formation is involved in the signaling pathway mediating cell arrest..
  
  
  CONCLUSIONS
  Here, we provide pharmacologic and genetic evidence that oxLDL induced iNOS expression inhibits macrophage-derived foam cell migration. Therefore, reduction of peroxynitrite and possibly lipid hydroperoxide levels in plaques represents a valuable therapeutic approach to reverse migratory arrest of macrophage-derived foam cells and to impair plaque formation.
authors.affiliation: Division of Vascular Medicine, Medical Clinic and Policlinic IV, University Hospital Munich, Munich, Germany.
authors.forename: H
authors.initials: H
authors.lastname: Huang
authors.affiliation: Division of Vascular Medicine, Medical Clinic and Policlinic IV, University Hospital Munich, Munich, Germany.
authors.forename: P
authors.initials: P
authors.lastname: Koelle
authors.affiliation: Division of Vascular Medicine, Medical Clinic and Policlinic IV, University Hospital Munich, Munich, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Fendler
authors.affiliation: Division of Vascular Medicine, Medical Clinic and Policlinic IV, University Hospital Munich, Munich, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Schröttle
authors.affiliation: Division of Vascular Medicine, Medical Clinic and Policlinic IV, University Hospital Munich, Munich, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Czihal
authors.affiliation: Division of Vascular Medicine, Medical Clinic and Policlinic IV, University Hospital Munich, Munich, Germany.
authors.forename: U
authors.initials: U
authors.lastname: Hoffmann
authors.affiliation: Helmholtz Center Munich, Institute of Developmental Genetics, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Conrad
authors.affiliation: Division of Vascular Medicine, Medical Clinic and Policlinic IV, University Hospital Munich, Munich, Germany. Electronic address: peter.kuhlencordt@med.uni-muenchen.de.
authors.forename: P J
authors.initials: PJ
authors.lastname: Kuhlencordt
mesh_terms: D000818:Animals; D050197:Atherosclerosis / Q000097:blood / Q000235:genetics; D001854:Bone Marrow Cells / Q000166:cytology; D002465:Cell Movement; D003599:Cytoskeleton / Q000378:metabolism; D005487:Foam Cells / Q000166:cytology*; D051416:Focal Adhesion Protein-Tyrosine Kinases / Q000378:metabolism; D020868:Gene Silencing; D015227:Lipid Peroxidation; D008077:Lipoproteins, LDL / Q000737:chemistry*; D008264:Macrophages / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009569:Nitric Oxide / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II / Q000235:genetics / Q000378:metabolism*; D018384:Oxidative Stress; D010766:Phosphorylation; D058226:Plaque, Atherosclerotic / Q000097:blood / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction
chemical_list: D008077:Lipoproteins, LDL; D017382:Reactive Oxygen Species; C099252:oxidized low density lipoprotein; D009569:Nitric Oxide; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse; D051416:Focal Adhesion Protein-Tyrosine Kinases
keywords: Migration; iNOS; oxLDL