Light-Dark Variations in Neopterin Serum Levels in Patients with ST-Segment Elevation Acute Coronary Syndrome Undergoing Primary Angioplasty

Introduction and objectives. Activation of the cell-mediated immune system plays an important role in atherogenesis and in triggering the development of acute coronary syndrome. Neopterin, a biomarker of cell-mediated immune system activity, is also a well-known biomarker of coronary artery disease. It is known that the occurrence of coronary heart disease events is not distributed evenly throughout the day but instead undergoes cyclical variation. In addition, both the number and activity level of immune system cells also vary throughout the 24-h circadian period. We studied how the serum concentration of neopterin varies during the light and dark phases of the day in patients with ST-segment elevation acute coronary syndrome who had undergone primary angioplasty and in a group of control subjects without evidence of atherosclerotic disease. Methods. The serum concentration of neopterin was determined at 10:00 in the morning (i.e., in light) and at 03:00 at night (i.e., in darkness) in 96 patients and 84 control subjects under strictly controlled conditions of light and darkness. Results. Significant light-dark variations were observed in the serum concentration of neopterin in both patients with ST-segment elevation acute coronary syndrome (i.e., 10.2 +/- 3.8 nmol/L in light vs. 8.84 +/- 2.22 nmol/L in darkness; P<.001) and control subjects (i.e., 6.98 +/- 1.96 nmol/L in light vs. 5.87 +/- 2 nmol/L in darkness; P<.001). Moreover, levels were significantly higher in patients (P<.001). Conclusions. Diurnal variations in cell-mediated immune system activity were observed in both patients with ST-segment elevation acute coronary syndrome who underwent primary angioplasty and in a control group. Moreover, activity was significantly higher in patients.