Transient decrease of neutrophil chemotaxis following aerobic exercise

PURPOSE: Intense exercise affects the immune system, increasing the susceptibility of athletes to viral and bacterial infections. We have previously shown a significant decrease of fMLP-neutrophil migration 24 h after aerobic exercise. In this study we aimed to look at the differential effect of different chemoattractants on neutrophil migration following aerobic exercise, to determine the recovery time, and to better understand the role of the cell skeleton behind the impaired chemotaxis. METHODS: Sixteen female volunteers aged 22-30 yr were tested before, 24, and 48 h after aerobic exercise (30 min running at 70% (.)VO(2max). The submaximal exercise test was conducted a week after the (.)VO(2max) test.We studied the membrane cell receptor response to fMLP, IL-8, and C5a, which have specific ligand-receptor pathways. Further, we studied the cytoskeletal response by investigating the cell polarization and the F-actin polymerization. RESULTS: Significant decrease of the neutrophil net chemotaxis was detected with fMLP, IL-8 and C5a, 24 h after exercise (50 +/- 5%, P = 0.0001; 48 +/- 12%, P = 0.0015; and 32 +/- 11%, P = 0.011, respectively). Complete recovery was observed within 48 h with all chemoattractants. Normal neutrophil random migration and F-actin polymerization were found. Decreased neutrophil polarization was detected (46 +/- 6% vs 22 +/- 8% of polarized cells, before and after effort, respectively; P = 0.004). Correlation between polarization and chemotactic migration was found (r = 0.945; P = 0.001). CONCLUSIONS: The impaired chemotactic response, observed 24 h after exercise, was similar using different chemoattractants. This finding indicates a possible exercise-induced effect on a common factor at the ligand-receptor level. The abnormal cell polarization indicates skeletal dysfunction that should be further investigated and elucidated. The normal fMLP-stimulated-F-actin polymerization reflects an adequate pathway of signal transduction for the formyl peptide.