Sustained Cytokine Secretion in Cultured Peripheral Blood Mononuclear Cells After A Brief Bout Of Exercise

Abstract

1571 Background: Several groups including our own have demonstrated that cytokines and growth factors are induced by brief bouts of exercise. Few studies have compared the intracellular and secreted levels of cytokines and their implications in health and disease. Purpose: To examine the effects of a brief bout of strenuous exercise on cytokine secretion in peripheral blood mononuclear cells (PBMCs) in vitro. Methods: Six healthy untrained men (age 20 ± 4 years) performed 30 min of continuous cycling exercise at 70% of maximal VO2. Blood samples were drawn at pre-exercise (t = 0 min), peak exercise (t = 30 min), and 1 hour post-exercise (t = 90 min). PBMCs were isolated using Ficoll-Paque-Plus, washed with HBSS and resuspended in AIM V serum free media. Cells were cultured in AIM V serum free media without an exogenous stimulus at a density of 1 × 106 cells/ml under 5% CO2 and harvested at 1, 6, 12 and 24 hours post-culture. Cytokine levels (IL-1β, TNFα, IL-6, IL-1ra and IL-8) obtained from serum and tissue culture media samples were measured using ultra-sensitive ELISAs. Results: Maximal levels of IL-8, TNFα and IL-1ra in the serum were attained at peak exercise (30 min). In contrast, serum levels of IL-6 and IL-1β continued to increase at post-exercise (90 min). Significant cytokine secretion patterns are evident among cultured PBMCs harvested at 1,6,12 and 24 hours from blood collect during pre, peak and post-exercise (Tabel 1: IL-6 secretion patterns). Conclusions: Exercise is a major stimulus for induced and sustained cytokine production in PBMCs. Our results represent a novel way of assessing cytokine induction and secretion patterns in PBMCs that is not readily apparent from measurements of circulating serum cytokine concentrations alone. There are a number of experiments in which mediator production of cells in vitro is used to understand stress/inflammatory mechanisms that occur with acute changes in physiological conditions in vivo. Further studies are needed to elucidate the contribution of these cytokine inductions in vivo. Supported by NIH grants HD-26939 and GCRC MO1 RR00827Table