Expression of Neutrophil Collagenase (Matrix Metalloproteinase-8) in Human Atheroma

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. Methods and 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-1␤, tumor necrosis factor-␣, 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.

Neutrophil Elastase in Human Atherosclerotic Plaques

“…5 Experiments used fresh monocytes or macrophages differentiated in culture in RPMI with 2% human serum (Sigma) for 3 to 10 days; 24 hours before and during stimulation, cells were incubated in serum-free media as previously described. 5,21 Venous blood was diluted 9:1 with 4% sodium citrate (Sigma) for neutrophil isolation. Cells were separated on neutrophil isolation medium gradients (Cardinal Associates Inc) and red cells were lysed with 155 mmol/L NH 4 Cl, 20 mmol/L NaHCO 3 , and 166 mol/L EDTA.…”

“…[2][3][4] We recently demonstrated that nonmyeloid cells found in atheroma express MMP-8, a collagenase previously associated with neutrophils. 5 This finding suggested to us that neutrophil elastase (NE) might also play a broader role than its name implies.…”

The balance of serum matrix metalloproteinase-8 and its tissue inhibitor in acute coronary syndrome and its recurrence

“…The amounts of both total and active MMP-8 are significantly higher in ruptured infarct tissue in patients with fatal myocardial infarction compared to the control infarct tissue [12]. Production of MMP-8 may reflect the disease state, since its activity is higher in asymptomatic patients with plaque progression or plaques prone to rupture compared to those with a stable disease [6,13]. The association of serum or plasma MMP-8 concentrations with cardiovascular diseases is, however, somewhat conflicting and rarely reported.…”

“…The fibrous cap of the atherosclerotic plaque is rich in collagen, which the MMPs secreted by the local macrophages can degrade. MMPs localize especially in the shoulder regions of the cap; this area is the most vulnerable to rupture resulting in thrombosis [5,6]. MMPs are endogenously inhibited by the specific tissue inhibitor of metalloproteinases (TIMP), which binds to the active MMP at a molar equivalence [7].…”

The role of matrix metalloproteinases and polymorphisms of their genes in the development of coronary heart disease

“…Впливаючи на біоактивні нематриксні молекули, вона може модифікувати імунну відповідь і брати участь у захисних протизапальних процесах [32 ˗ 37]. У дослідженнях in vitro [38] було пока-зано, що ендотеліальні клітини, макрофаги, ГМК у ділянці атеросклеротичних уражень експресують ММР-8 після стимулювання прозапальними цитокінами: IL-1β, ФНП-α, CD40, її експресія зростає в разі швидкого прогресування ушкодження. Сироватковий вміст ММР-8 асоційований із наявністю атеросклерозу [39,40], розвитком нес-табільності АСБ [41,42], ГКС [43] та із несприятливим серцево-судинним прогнозом [44].…”