Relationship between Lectin-like oxidized low-density lipoprotein receptor 1 expression and preoperative echogenic findings of vulnerable carotid plaque

Purpose Lectin-like oxidized low-density lipoprotein 1 (LOX1) is an important cell surface receptor for the progression of atherosclerosis. Our purpose is to clarify the relationships of LOX1 and atherosclerotic factors for the vulnerability of carotid plaque and preoperative echogenic findings. Methods We examined LOX1 expression, matrix metalloproteinase (MMP)-2, 9, and tissue inhibitor of MMP (TIMP)-2 by immunohistochemical analysis using carotid endarterectomy specimens obtained from 14 patients. Groups were divided into stable plaque group A and vulnerable plaque group B by preoperative echogenic findings of carotid plaques. Endothelial immunoreactivity was calculated, and the immunohistochemical findings were compared. Results LOX1 was remarkably expressed, especially in smooth muscle cells in vulnerable plaque and colocalized in MMP-9 positive cells and apoptotic cells. All LOX1, MMP-2, 9, and TIMP2 were remarkably expressed in the subendothelial layer in group B compared with group A. The endothelial LOX1 index was 63.75±4.92 in group A and 83.0±5.02 in group B (p=0.02). The endothelial MMP-2 index was 24.38±5.50 in group A and 32.83± 6.79 in group B (p=0.01). The endothelial MMP-9 index was 46.13±6.31 in group A and 59.17±2.14 in group B (p=0.002). The endothelial TIMP-2 index had no significant difference between two groups (p=0.14). Conclusion LOX-1 may play an important role in the progression of vulnerable carotid plaque and might regulate vulnerable plaque formation in cooperation with MMPs and TIMP-2. Endothelial MMP-2 might suppress TIMP-2 activation in vulnerable plaques.