Enhanced Expression of the S100A8/A9 Complex in Acute Myocardial Infarction Patients

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Background: S100A8/A9 complex (S100A8/A9) is expressed in activated human neutrophils and macrophages. Enhanced expression of S100A8/A9 in atherosclerotic plaque of patients with unstable angina pectoris (UAP) has been demonstrated, but its profile in acute myocardial infarction (AMI) has not been clarified. Methods and Results: Serum S100A8/A9 levels were serially measured in patients with AMI (n=55) and UAP (n=16) during the acute period. The expression of S100A8/A9 was examined immunohistochemically in the infarcted myocardium of 7 autopsied patients with AMI. Serum S100A8/A9 levels on the 1st day were 1,118±115 (SE) ng/ml in AMI patients as compared with 787±147 ng/ml in UAP patients. On days 3-5, serum S100A8/A9 levels in AMI patients reached a peak value and were significantly higher than the values in UAP patients (1,690±144 ng/ml vs 844±100 ng/ml; P<0.0001). In AMI patients, peak S100A8/A9 levels positively correlated with peak white blood cell and neutrophil counts, and peak creatine kinase-MB and peak C-reactive protein levels. Double immunostaining revealed that S100A8/A9 was specifically expressed in neutrophils and macrophages infiltrating the infarcted myocardium. Conclusions: S100A8/A9 is implicated in the pathophysiology of AMI and may be an additional biomarker of the local inflammatory response following AMI.