Smoking and Unstable Plaque in Acute Coronary Syndrome: A Systematic Review of The Role of Matrix Metalloproteinases

Smoking is a risk factor of acute coronary syndrome (ACS) that could increase matrix metalloproteinases (MMPs) levels, leading to unstable coronary artery plaque. The current review aimed to identify the relationship between smoking and MMPs in patients with ACS. Literature search was conducted from inception until March 2022 in three online databases. Risk of bias was assessed using the Newcastle-Ottawa Scale. A meta-analysis was performed, and the odds ratio (OR) together with its 95% confidence interval (CI) were determined. A total of 7,843 articles were identified, and only seven studies were included. Four studies investigated the MMP-3 and MMP-9 related genes and found that smokers with certain MMPs genotypes had high risk of ACS. Smoking also increased the MMPs level in patients with ACS compared with non-smokers. Additionally, a meta-analysis of two studies resulted in an increased odd of ACS in smokers with MMP-3 5A allele versus non-smokers with MMP-3 6A6A allele (OR: 15.94, 95% CI: 10.63-23.92; I(2)=55%). In conclusion, the current review highlights the role of MMPs in relation to smoking and ACS. The determination of these roles may help in identifying new ACS markers among smokers and the development of drug-targeted treatment.