title: Expression of neutrophil collagenase (matrix metalloproteinase-8) in human atheroma: a novel collagenolytic pathway suggested by transcriptional profiling.
abstract: BACKGROUND
  Loss of interstitial collagen, particularly type I collagen, the major load-bearing molecule of atherosclerotic plaques, renders atheroma prone to rupture. Initiation of collagen breakdown requires interstitial collagenases, a matrix metalloproteinase (MMP) subfamily consisting of MMP-1, MMP-8, and MMP-13. Previous work demonstrated the overexpression of MMP-1 and MMP-13 in human atheroma. However, no study has yet evaluated the expression of MMP-8, known as "neutrophil collagenase," the enzyme that preferentially degrades type I collagen, because granulocytes do not localize in plaques.
  
  
  RESULTS
  Transcriptional profiling and reverse transcription-polymerase chain reaction analysis revealed inducible expression of MMP-8 transcripts in CD40 ligand-stimulated mononuclear phagocytes. Western blot analysis demonstrated that 3 atheroma-associated cell types, namely, endothelial cells, smooth muscle cells, and mononuclear phagocytes, expressed MMP-8 in vitro upon stimulation with proinflammatory cytokines such as interleukin-1beta, tumor necrosis factor-alpha, or CD40 ligand. MMP-8 protein elaborated from these atheroma-associated cell types migrated as 2 immunoreactive bands, corresponding to the molecular weights of the zymogen and the active molecule. Extracts from atherosclerotic, but not nondiseased arterial tissue, contained similar immunoreactive bands. Moreover, all 3 cell types expressed MMP-8 mRNA and protein in human atheroma in situ. Notably, MMP-8 colocalized with cleaved but not intact type I collagen within the shoulder region of the plaque, a frequent site of rupture.
  
  
  CONCLUSIONS
  These data point to MMP-8 as a previously unsuspected participant in collagen breakdown, an important determinant of the vulnerability of human atheroma.
authors.affiliation: Leducq Center for Cardiovascular Research, Cardiovascular Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA.
authors.forename: M P
authors.initials: MP
authors.lastname: Herman
authors.forename: G K
authors.initials: GK
authors.lastname: Sukhova
authors.forename: P
authors.initials: P
authors.lastname: Libby
authors.forename: N
authors.initials: N
authors.lastname: Gerdes
authors.forename: N
authors.initials: N
authors.lastname: Tang
authors.forename: D B
authors.initials: DB
authors.lastname: Horton
authors.forename: M
authors.initials: M
authors.lastname: Kilbride
authors.forename: R E
authors.initials: RE
authors.lastname: Breitbart
authors.forename: M
authors.initials: M
authors.lastname: Chun
authors.forename: U
authors.initials: U
authors.lastname: Schönbeck
mesh_terms: D001011:Aorta / Q000201:enzymology / Q000473:pathology; D001161:Arteriosclerosis / Q000201:enzymology* / Q000473:pathology; D023201:CD40 Ligand; D002339:Carotid Arteries / Q000201:enzymology / Q000473:pathology; D002478:Cells, Cultured; D003094:Collagen / Q000378:metabolism*; D016207:Cytokines / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000201:enzymology / Q000473:pathology; D020869:Gene Expression Profiling; D006801:Humans; D007963:Leukocytes, Mononuclear / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D020784:Matrix Metalloproteinase 8 / Q000096:biosynthesis* / Q000235:genetics*; D009131:Muscle, Smooth, Vascular / Q000201:enzymology / Q000473:pathology; D010586:Phagocytes / Q000201:enzymology / Q000473:pathology; D012333:RNA, Messenger / Q000096:biosynthesis; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D016207:Cytokines; D012333:RNA, Messenger; D023201:CD40 Ligand; D003094:Collagen; D020784:Matrix Metalloproteinase 8