Increasing evidence shows that OX40 ligand (OX40L, also known as tumor necrosis factor superfamily member 4, TNFSF4) system plays an important role in the pathogenesis of atherosclerosis. We investigate whether OX40L system (serum and monocytes OX40L levels) expression is disordered and the relationship with matrix metalloproteinases (MMPs) level and stability of coronary atherosclerotic plaque in patients with an acute coronary syndrome (ACS).

Thirty normal controls and 150 patients including 40 with stable angina (SA), 70 with unstable angina (UA), and 40 with acute myocardial infarction (AMI) were investigated. The expression of OX40L on monocytes was analyzed by flow cytometry, serum soluble OX40L and MMP-9, MMP-3 level was determined by ELISA. All coronary stenosis with ≥30% diameter reduction was assessed by angiographic coronary stenosis morphology.

Patients with ACS showed a significant increase of OX40L (61.5±11.5 MFI) expression on monocytes compared with control (28.9±7.4 MFI) and SA group (31.2±8.1 MFI) (p<0.001). sOX40L also showed higher level in patients with ACS (34.6±9.3pg/ml) than in control (10.2±4.7pg/ml, p<0.001) and SA group (11.4±5.8pg/ml, p<0.001). Serum MMP-3 and MMP-9 in patients with ACS were 2 times greater than those in control. A positive correlation was found between MMP-9, MMP-3 and OX40L expression on monocytes as well as on sOX40L levels. A positive correlation was also observed between OX40L expression with sOX40L level and complex coronary stenosis (r₁=0.61, r₂=0.57, p<0.001).

Patients with ACS show increased OX40L system expression which may create a proinflammatory and prothrombotic milieu for aggravating the development of atherosclerosis and instability of atherosclerotic plaques, and may be a valuable marker for predicting the severity of ACS.