Expression of neutrophil collagenase (matrix metalloproteinase-8) in human atheroma: a novel collagenolytic pathway suggested by transcriptional profiling.
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.
Herman
M P
MP
Leducq Center for Cardiovascular Research, Cardiovascular Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA.
Sukhova
G K
GK
Libby
P
P
Gerdes
N
N
Tang
N
N
Horton
D B
DB
Kilbride
M
M
Breitbart
R E
RE
Chun
M
M
Schönbeck
U
U
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
D016207:Cytokines; D012333:RNA, Messenger; D023201:CD40 Ligand; D003094:Collagen; D020784:Matrix Metalloproteinase 8