The metabolism of big endothelin-1 axis and lipids affects carotid atherosclerotic plaque stability - the possible opposite effects of treatment with statins and aspirin.

Background: The understanding of endothelin's role in carotid plaque instability is limited. We have studied the big endothelin-1 (ET-1) axis and its role in carotid plaque stability in patients undergoing carotid endarterectomy (CEA). The interactions of endothelins with known CVD risk factors were also evaluated.

Methods: We studied 77 patients, who were divided into subgroups based on the optimal cut-off for grey-scale median (GSM), a marker of plaque instability. GSM values < 46.87 were designated as unstable carotid plaque, while GSM ≥ 46.87 were assigned to stable plaque. Twelve people without carotid atherosclerosis served as controls. Big ET-1, ET-1 and ET-1 (1-31) were measured and the endothelin-converting enzyme-1 (ECE-1) and chymase activity were calculated. Clinical and laboratory parameters were also evaluated.

Results: ET-1 levels and ECE-1 activity were increased in all patient groups compared to controls (all P < 0.001) - and were higher in patients with unstable plaque than in those with stable plaque (P < 0.01). ET-1 (1-31) did not differ between the groups. ET-1 levels and ECE-1 activity inversely correlated with total cholesterol, LDL-cholesterol, and GSM values, whereas GSM was positively associated with total cholesterol and LDL fractions. Detailed analysis of patients according to the pharmacotherapy used revealed that statins favored ET-1 formation independently of cholesterol-lowering properties, whereas aspirin reduced this effect.

Conclusions: ET-1 formation is the main pathway of big ET-1 metabolism in patients with carotid atherosclerosis, especially in those with plaque instability. Statins and aspirin appear to have opposing effects on ET-1 formation, suggesting the greater benefit related to plaque stability in patients taking both drugs concomitantly.