title: Macrophage expression of active MMP-9 induces acute plaque disruption in apoE-deficient mice.
abstract: The majority of acute clinical manifestations of atherosclerosis are due to the physical rupture of advanced atherosclerotic plaques. It has been hypothesized that macrophages play a key role in inducing plaque rupture by secreting proteases that destroy the extracellular matrix that provides physical strength to the fibrous cap. Despite reports detailing the expression of multiple proteases by macrophages in rupture-prone regions, there is no direct proof that macrophage-mediated matrix degradation can induce plaque rupture. We aimed to test this hypothesis by retrovirally overexpressing the candidate enzyme MMP-9 in macrophages of advanced atherosclerotic lesions of apoE-/- mice. Despite a greater than 10-fold increase in the expression of MMP-9 by macrophages, there was only a minor increase in the incidence of plaque fissuring. Subsequent analysis revealed that macrophages secrete MMP-9 predominantly as a proform, and this form is unable to degrade the matrix component elastin. Expression of an autoactivating form of MMP-9 in macrophages in vitro greatly enhances elastin degradation and induces significant plaque disruption when overexpressed by macrophages in advanced atherosclerotic lesions of apoE-/- mice in vivo. These data show that enhanced macrophage proteolytic activity can induce acute plaque disruption and highlight MMP-9 as a potential therapeutic target for stabilizing rupture-prone plaques.
authors.affiliation: Department of Pathology, University of Washington, Harborview Medical Center, Seattle, Washington 98104-2499, USA. peter.j.gough@gsk.com
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Gough
authors.forename: Ivan G
authors.initials: IG
authors.lastname: Gomez
authors.forename: Paul T
authors.initials: PT
authors.lastname: Wille
authors.forename: Elaine W
authors.initials: EW
authors.lastname: Raines
mesh_terms: D000818:Animals; D001057:Apolipoproteins E / Q000172:deficiency* / Q000235:genetics; D050197:Atherosclerosis / Q000201:enzymology / Q000235:genetics* / Q000473:pathology; D016026:Bone Marrow Transplantation; D017364:Collagenases / Q000378:metabolism; D003433:Crosses, Genetic; D005260:Female; D008264:Macrophages / Q000201:enzymology*; D053508:Matrix Metalloproteinase 12; D053509:Matrix Metalloproteinase 13; D020780:Matrix Metalloproteinase 9 / Q000235:genetics* / Q000378:metabolism; D008666:Metalloendopeptidases / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout
chemical_list: D001057:Apolipoproteins E; D017364:Collagenases; D053509:Matrix Metalloproteinase 13; D008666:Metalloendopeptidases; C507081:Mmp13 protein, mouse; D020780:Matrix Metalloproteinase 9; D053508:Matrix Metalloproteinase 12