DYNAMIC EXERCISE LEADS TO AN INCREASE IN CIRCULATING ICAM-1 - FURTHEREVIDENCE FOR ADRENERGIC MODULATION OF CELL-ADHESION

Acute mental and physical stress lead to a marked lymphocytosis, with circulating natural killer cell numbers showing the most prominent inc rease. Many studies have linked these acute stress effects on lymphocy tes with an increase in catecholamine levels. However, the molecular m echanisms which mediate this redistribution of lymphocytes from lympho cyte reservoirs into the circulation remain unknown. We hypothesized t hat this form of lymphocytosis was in part due to shedding of cell adh esion molecules from the cell surface and a subsequent detachment of l ymphocytes adhering to the vascular endothelium in lymphocyte reservoi rs. In this study, healthy human volunteers (n = 12) were exercised on a treadmill until exhaustion. The circulating levels of the soluble c ell adhesion molecules ICAM-1 and E-Selectin were determined by ELISA. The subjects were then randomly assigned to treatment with either pro pranolol or metoprolol and repeated the exercise protocol after 1 week of treatment. Prior to drug treatment, soluble ICAM-1 levels rose fro m 258 +/- 19 to 321 +/- 28 ng/ml following exercise and returned to ap proximate baseline levels of 263 +/- 22 ng/ml after 1 h of rest. This highly significant effect of exercise on circulating ICAM-1 levels (p < .005) was mitigated after treatment with the beta-adrenergic antagon ists. Soluble E-Selectin levels were not significantly affected by exe rcise. These results suggest that dynamic exercise leads to shedding o f the cell adhesion molecule ICAM-1 via adrenergic mechanisms. We beli eve that these findings will contribute to the understanding of how ph ysical and mental stress modulate lymphocyte migration and adhesion. ( C) 1997 Academic Press.