Serum levels of interleukin-18 in patients with stable and unstable angina pectoris.

Recent evidence suggests that atherosclerosis is an inflammatory disorder in which cytokines appear to play an important role. Special attention centered over the possible contribution of cytokines to the destabilization of the plaque. IL-18 is a proinflammatory cytokine of the IL-1 family, recognized for its ability to promote IFN-gamma secretion. It has recently been detected in human plaques and its administration was associated with increased atherosclerosis in apolipoprotein E (apoE) mice concomitant with an increase in plaque infiltrating inflammatory cells. In our study, we investigated whether patients with established atherosclerosis, with either stable or unstable angina, possessed high levels of IL-18. Patients with stable angina (n=48) were from the outpatient clinic whereas patients with unstable angina (n=73) were recruited upon admission and prior to performance of coronary angiography. Control patients (n=19) were healthy subjects with no evidence of coronary artery disease. Serum levels of IL-18 were assayed by ELISA. Patients with stable and unstable angina exhibited higher serum levels of IL-18 (77.1+/-7.2 and 61.5+/-5.1 pg/ml, respectively) in comparison to control subjects (p=0.002 and p=0.02, respectively). However, levels of IL-18 did not differ significantly between patients with stable and unstable angina. No differences were evident in the serum concentrations of IL-18 in patients with unstable angina (n=17) upon admission and 1-3 months later when the angina was already controlled. Although IL-18 serum levels appear elevated in the presence of coronary atherosclerosis, there is no evidence to associate this progression towards plaque instability.