Higher levels of plasma matrix metalloproteinase-2 are associated with a significantly increased risk of arterial thrombosis in patients with the antiphospholipid syndrome

Abstract

Alterations in the structure of extracellular matrix (ECM) play akey role in atherothrombosis. Matrix metalloproteinases (MMPs), afamily of zinc-dependent proteases produced and released by endo-thelial and smooth muscle cells, monocytes and platelets, degradeECM. There is evidence that MMPs are involved in cardiovascular dis-ease [1,2], but also in inflammatory disorders of the respiratory, gas-trointestinal, osteoarticular and central nervous systems [3].Plasma levels of some MMPs, and in particular of MMP-2, havebeen established as biomarkers of cardiovascular risk [1,2], but theyhave also been found to be increased in connective tissue disorders,likerheumatoidarthritis,systemiclupuserythematosusandSjogren'ssyndrome [3].No data are available instead on plasma MMPs in the anti-phospholipid syndrome (APS), an autoimmune condition characterizedby the occurrence of thrombotic events or pregnancy complications as-sociated with antiphospholipid antibodies (aPL). Among thromboticmanifestations of APS, both arterial and venous thrombosis may occur.However, so far no features have been identi fied distinguishing APS pa-tients undergoing arterial thrombotic events versus those developingvenous thromboembolism (VTE).AimofthepresentstudywastoexplorewhetherplasmaMMP-2isincreased in APS patients and to test if this marker can identifypatients undergoing arterial versus venous thrombosis.77 patients with APS (both primary and secondary), definedaccording to the international consensus criteria [4], (48 females,mean age 47±8 years), and 69 age- and sex-matched healthy con-trols (40 females, mean age 45±7 years) without concomitant riskfactors for cardiovascular disease, enrolled in two previously pub-lishedstudies[5,6], wereincluded inthepresentstudy.OftheAPSpa-tients,30 (22primaryand 8 secondary)(39%)had ahistoryof arterialthrombosis (mean time from event: 3.7±3 years), 41 (53%) (29 pri-mary and 12 secondary) a history of VTE (mean time from event:5±3 years) and six (8%) had obstetric manifestations. A group of pa-tients with history of arterial thrombosis (n=30, 16 females, 7 MI,5 stroke, 18 PAD) but no APS was alsostudied to distinguishthe role ofMMP-2 as a marker of vascular disease per se from a specific increaselinked to APS. Informed consent was obtained from each patient andthe study protocol, conformed to the ethical guidelines of the Declara-tion of Helsinki, was approved by the Local Ethic Committees (deliber-ation number 433/03). The authors of this manuscript have certifiedthattheycomplywiththePrinciplesofEthicalPublishingintheInterna-tional Journal of Cardiology.Plasma, obtained by centrifugation of 3.8% citrated venous bloodat 3000 g for 20 min, was immediately frozen and stored at −80 °Cfor later assay of MMP-2 by zymography, as described [7]. Intra-and inter-assay coefficients of variation of MMP-2 measurementswere 2.3% and 3.9%, respectively (n=8). All measurements were car-ried out by investigators blinded as to the patients' characteristics.The association of MMP-2 levels with history of arterial or venousthrombosis was evaluated by binary logistic regression analysis.Odds ratio (OR) and 95% confidence intervals (CIs) were calculatedconsidering the thrombotic event (arterial vs venous) as dependentvariable. Independent variables were: MMP-2 levels and age as con-tinuous variables, and sex (male vs female), oral anticoagulation(yes/no) and triple positivity for aPL (LAC, ACA, anti-β2GPI) (yes/no), as dichotomous variables. A two-sidedp-valueb0.05 was consid-ered as statistically significant. All analyses were performed with thestatistical package SPSS for Windows.PlasmaMMP-2wassignificantly higher in APSpatientsthanin con-trol subjects (Fig. 1A). When further subdivided in relation to clinicalmanifestations, MMP-2 levels were significantly higher in patientswith a previous arterial event than in patients with a previous VTE orin healthy controls (Fig. 1B). APS patients with obstetric manifesta-tions had MMP-2 levels similar to those of patients with VTE(740.9±94.2 ng/ml). MMP-2 levels in patients without APS but withprevious arterial thrombosis were higher than controls (682.6±84.3