Circulating interleukin-6 and interleukin-6 receptors in patients with acute and recent myocardial infarction

Interleukin-6 (IL-6), a proinflammatory cytokine, plays a key role in the pathogenesis of coronary artery disease (CAD). We investigated circulating IL-6 and its receptors in patients with CAD. We evaluated 39 Japanese patients with CAD (30 males and 9 females aged 36-79 years), measuring their plasma levels of IL-6 and IL-6 receptors alpha and beta (IL-6R alpha, IL-6R beta). Circulating levels of IL-6, IL-6R alpha and IL-6R beta were measured by an enzyme-linked immunosorbent assay. Blood was sampled immediately after admission and again after 1, 2, 3, 6 and 9 h, then every 12 h for 5 days. Atrial natriuretic peptide (ANP) and B-type natriuretic peptide (BNP) were measured on day 3 after symptom onset. Plasma levels of IL-6 and IL-6Rs were significantly increased in 28 patients with acute myocardial infarction (AMI) compared with 15 normal controls. However, neither IL-6 nor IL-6Rs showed an increase in 6 patients with angina pectoris. We observed two peaks for circulating IL-6 in AMI, the first of which showed a significant correlation with ANP as well as BNP. These results may help to explain why the amount of IL-6 produced is closely related to the severity of myocardial dysfunction in patients with CAD.