Matrix Metalloproteinase Genetic Polymorphisms and Outcome of Non-ST Elevated Acute Coronary Syndromes

Non-ST elevation acute coronary syndrome (NSTEACS) is a syndrome encompassing a spectrum of clinical manifestations between ischemic heart disease and acute myocardial infarction. It represents an important cause of morbidity and hospitalization in western countries: its incidence is estimated around 2/1000 subjects/year and about 10% of patients with acute coronary syndrome develop an acute myocardial infarction within 6 months. Another reason of concern is that patients require an invasive treatment, usually PTCA or CABG. ACS encompasses features of both an inflammatory and thrombotic disease; their abnormalities could be critical for evolution and complication of acute coronary syndrome.

Many inflammatory and coagulation indicators have been investigated, although the critical factors responsible for complications in NSTEACS remain elusive.

Matrix remodeling and consequent erosion or fissuration of the unstable plaque is supposed to be a key step of the development of acute coronary syndromes.

Neutral matrix metalloproteinases 1, 3 and 9 have been demonstrated to be actively produced in atherosclerotic tissue, compared to unaffected arteries. Mechanisms responsible for such increased expression might be related to inflammation, but also genetic regulation could account for an increased expression leading to a different clinical outcome of the syndrome.

Genetic polymorphisms are described for all three MMPs involved in ACS. MMP-1 insertion of a G in position creates an ets binding site that induces an eight times increase of the synthesis rate. For MMP-3 (stromelysin) polymorphism, a deletion of an A (adenosine) in position -1171 doubles the transcription activity and has been recently associated with acute myocardial infarction and progression of coronary stenosis. In MMP-9 a more complex polymorphism involves a microsatellite (AC) repeat in position -90 to -131. The mechanism leading to increased MMP-9 expression is probably related to the transition to Z-DNA within the microsatellite, which eases transcription. In vitro studies show that the longer the tandem repeats sequence, the higher the transcription.