title: eNOS protects from atherosclerosis despite relevant superoxide production by the enzyme in apoE mice.
abstract: BACKGROUND
  All three nitric oxide synthase (NOS) isoforms are expressed in atherosclerotic plaques. NOS enzymes in general catalyse NO production. However, under conditions of substrate and cofactor deficiency, the enzyme directly catalyse superoxide formation. Considering this alternative chemistry, the effects of NOS on key events in spontaneous hyperlipidemia driven atherosclerosis have not been investigated yet. Here, we evaluate how endothelial nitric oxide synthase (eNOS) modulates leukocyte/endothelial- (L/E) and platelet/endothelial- (P/E) interactions in atherosclerosis and the production of nitric oxide (NO) and superoxide by the enzyme.
  
  
  RESULTS
  Intravital microscopy (IVM) of carotid arteries revealed significantly increased L/E-interactions in apolipoproteinE/eNOS double knockout mice (apoE(-/-)/eNOS(-/-)), while P/E-interactions did not differ, compared to apoE(-/-). eNOS deficiency increased macrophage infiltration in carotid arteries and vascular cell adhesion molecule-1 (VCAM-1) expression, both in endothelial and smooth muscle cells. Despite the expression of other NOS isoforms (inducible NOS, iNOS and neuronal NOS, nNOS) in plaques, Electron Spin Resonance (ESR) measurements of NO showed significant contribution of eNOS to total circulating and vascular wall NO production. Pharmacological inhibition and genetic deletion of eNOS reduced vascular superoxide production, indicating uncoupling of the enzyme in apoE(-/-) vessels.
  
  
  CONCLUSIONS
  Overt plaque formation, increased vascular inflammation and L/E- interactions are associated with significant reduction of superoxide production in apoE(-/-)/eNOS(-/-) vessels. Therefore, lack of eNOS does not cause an automatic increase in oxidative stress. Uncoupling of eNOS occurs in apoE(-/-) atherosclerosis but does not negate the enzyme's strong protective effects.
authors.affiliation: Medizinische Klinik I/Herz-Kreislaufzentrum, University of Würzburg, Würzburg, Germany.
authors.forename: Padmapriya
authors.initials: P
authors.lastname: Ponnuswamy
authors.forename: Angelika
authors.initials: A
authors.lastname: Schröttle
authors.forename: Eva
authors.initials: E
authors.lastname: Ostermeier
authors.forename: Sabine
authors.initials: S
authors.lastname: Grüner
authors.forename: Paul L
authors.initials: PL
authors.lastname: Huang
authors.forename: Georg
authors.initials: G
authors.lastname: Ertl
authors.forename: Ulrich
authors.initials: U
authors.lastname: Hoffmann
authors.forename: Bernhard
authors.initials: B
authors.lastname: Nieswandt
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Kuhlencordt
mesh_terms: D000818:Animals; D001057:Apolipoproteins E / Q000235:genetics*; D050197:Atherosclerosis / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism; D001808:Blood Vessels / Q000378:metabolism / Q000473:pathology; D019610:Cytoprotection / Q000235:genetics; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009569:Nitric Oxide / Q000378:metabolism / Q000494:pharmacology; D052250:Nitric Oxide Synthase Type III / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*; D017382:Reactive Oxygen Species / Q000378:metabolism; D013481:Superoxides / Q000378:metabolism*
chemical_list: D001057:Apolipoproteins E; D017382:Reactive Oxygen Species; D013481:Superoxides; D009569:Nitric Oxide; D052250:Nitric Oxide Synthase Type III; C496315:Nos3 protein, mouse