Atherosclerosis and inflammation. Patterns of cytokine regulation in patients with peripheral arterial disease Original Research Article

Inflammatory phenomena at sites of atherosclerotic plaques are increasingly thought to be major determinants of the progression and clinical outcome of atherosclerotic disease. Therefore, attention is being paid to systemic markers/mediators which may reflect the inflammatory activity in the plaques. This study evaluates the pattern of the main proinflammatory cytokines tumor necrosis factor-α (TNFα), interleukin-1β (IL-1β), and interleukin-6 (IL-6), their soluble receptors/antagonist, and a variety of inflammatory markers, in patients with peripheral arterial disease (PAD). Eight patients with PAD suffering from claudicatio intermittens (CI), eight with critical limb ischemia (CLI) and eight controls (C) were studied. Blood samples were collected at baseline in all groups and, for C and CI, immediately after and 4 h after a 30-min treadmill test. Baseline: no differences in cytokine plasma levels were detected among the three groups. In contrast, soluble receptors of TNF (type I and II) and of IL-6, and IL-1β receptor antagonist (IL-1ra) were increased in CI and CLI patients, as compared to C. Of note, IL-1ra correlated with the occurrence and stage of the disease in a highly significant proportion of the patients, reaching a predictive value for the disease of P<0.0001. The opposite trend was observed for the soluble receptor of IL-1β. Notably, in the patients no alterations could be found in white blood cell counts, expression of CD11c adherence molecule by circulating monocytes or, in vitro, O2− release from zymosan-activated neutrophils. Moreover, plasma levels of platelet activating factor (PAF), of neutrophil elastase and of the acute phase reactants C-reactive protein (CRP) and α1-acid glycoprotein were not found to be significantly altered. In contrast, the acute-phase proteins α1-antitrypsin (α1AT) and haptoglobin (HG) were found to be increased. Effect of treadmill: IL-1β and TNFα remained at baseline levels following exercise, and IL-6 dropped to undetectable levels. Among cytokine antagonists, again the most relevant changes concerned the IL-1ra, which was significantly increased immediately after the treadmill test, both in CI and C, and returned to baseline levels after 4 h. In contrast, soluble TNFα, IL-1β and IL-6 receptors, PAF, and the other markers of leukocyte activation were not found to be altered. Soluble TNFα and IL-6 receptors were shown to inhibit the biological effects of their ligands. Similarly, IL-1ra and the acute phase proteins α1AT and HG have been reported to exert anti-inflammatory functions. The increased plasma levels of these agents, together with low levels of inflammatory cytokines and other pro-inflammatory mediators such as PAF and α1-acid glycoprotein, appear to draw an undescribed picture, so far, of upregulation of a composite systemic anti-inflammatory mechanism in atherosclerotic patients. IL-1ra appears to be a reliable marker of the state of activation of this mechanism. These results may provide a basis for developing new insights into the pathogenesis of the atherosclerotic disease.