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Induction of inducible Nitric Oxide Synthase (iNOS) expression by oxLDL inhibits macrophage derived foam cell migration.

Atherosclerosis 235, 213-222 (2014)
DOI
Open Access Green as soon as Postprint is submitted to ZB.
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 1400W (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 1400W 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.
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Publication type Article: Journal article
Document type Scientific Article
Keywords Migration ; Inos ; Oxldl; Focal Adhesion; Tyrosine Phosphorylation; Atherosclerotic Lesions; Lipid Peroxides; Knockout Mice; Peroxynitrite; Superoxide; Mouse; No; Arteriosclerosis
Reviewing status