Enhanced levels of soluble and membrane-bound CD137 levels in patients with acute coronary syndromes

Background: Increasing evidence shows that costimulatory molecules of the tumor necrosis factor superfamily such as CD40/CD40 ligand and OX40/OX40 ligand have been implicated in atherosclerosis. We investigated whether the expression levels of the tumor necrosis factor superfamily members CD137 in serum and membrane-bound were related to acute coronary syndromes (ACS). Methods: Thirty normal controls and 210 patients, including 70 with stable angina (SA), 80 with unstable angina (UA), and 60 with acute myocardial infarction (AMI), were enrolled in our study. The expression of CD137 in peripheral monocytes was analyzed by flow cytometry. Serum soluble CD137 (sCD137) and C-reactive protein levels were measured by commercially available ELISA. Results: The expression of CD137 in peripheral monocytes in patients with UA [14.2 +/- 3.5 mean fluorescence intensity (MFI)] and AMI (15.1 +/- 4.4 MFI) was significantly higher than those inpatients with SA (6.5 +/- 2.4 MFI) and controls (7.1 +/- 3.5 MFI). sCD137 in patients with UA (16.7 +/- 4.9 ng/ml) and AMI (19.1 +/- 43 ng/ml) were significantly higher than those in patients with SA (3.4 +/- 1.4 ng/ml) and controls (3.9 +/- 1.3 ng/ml) (p<0.001). C-reactive protein level in serum in patients with UA (13.8 +/- 3.3 ng/ml) and AMI (15.5 +/- 4.7 ng/ml) were also higher than those in patients with SA (1.4 +/- 0.4 ng/ml) and controls (1.3 +/- 03 ng/ml). It was interesting that percutaneous transluminal coronary angioplasty (PTCA) induced a marked rise in sCD137 levels in SA patients, while CD137 expression in peripheral monocytes showed no difference between SA patients with PTCA before and after. A positive correlation was found between sCD137 and serum C-reactive protein levels (r=0.681; p<0.0001). Conclusion: Patients with ACS showed increased soluble and membrane-bound CD137 expression. sCD137 level showed a significantly positive correlation with CRP level in patients with ACS. The relation between sCD137 and ACS needs further researches, (C) 2009 Elsevier B.V. All rights reserved.