Cytokine signatures in atherosclerotic claudicants.

BACKGROUND

Iron accumulation and inflammation may affect atherosclerosis. This study intended to define a cytokine signature in atherosclerotic claudicants and to determine whether reduction in serum ferritin by phlebotomy influenced this pattern.

METHODS

Ninety-one subjects with peripheral vascular disease (PVD; mean age, 67 years) were recruited from the VA Cooperative Iron and Atherosclerosis Study (FeAST) testing the hypothesis that ferritin reduction to 25 ng/ml may ameliorate atherosclerosis. Cytokines TNF-a, IL-2, IL-6, and IL-10 were analyzed by enzyme amplified sensitivity assay (EASIA). Fasting iron and cholesterol panels, complete blood count, C-reactive protein (CRP), uric acid, fibrinogen, glucose, and hemoglobin A1c levels were also quantified. Values were compared with "healthy" controls (n = 21; mean age, 56 years). After randomization of PVD to phlebotomy (intervention group [IG], n = 44) or control (nonintervention group [NG], n = 47), analyses were compared at 6 and 12 months using t test, Wilcoxon rank sum test, chi-square, and robust MM regression.

FINDINGS

Age, glucose, and hemoglobin A1c were higher in PVD compared with healthy controls (P < 0.01), whereas serum iron (P < 0.01) and percentage of transferrin saturation (P < 0.05) were lower. Tumor necrosis factor-alpha (TNF-alpha; P < 0.05), IL-6 (P < 0.01), and CRP (P < 0.05) levels were higher in the PVD group, whereas IL-10 was lower (P < 0.01). At 6 months post phlebotomy, ferritin levels were reduced (P < 0.01), although ferritin levels were reduced less in smokers. IL-6 and fibrinogen, CRP and ferritin levels correlated positively. At 6 and 12 months, subjects with TNF-alpha (n= 15) and IL-6 (n = 10) levels in the upper 25th percentile were reduced by phlebotomy.

INTERPRETATION

An inflammatory cytokine signature exists in atherosclerosis. Elevated levels of TNF-alpha and IL-6, reportedly associated with recurrent and future myocardial infarction, were reduced by phlebotomy. The utility of the iron/inflammatory hypotheses will ultimately relate to clinical outcomes obtained prospectively by the FeAST trial.