Neutrophil Death Induced By A Triathlon Competition In Elite Athletes

Abstract

PURPOSE: The effect of a triathlon competition on death of neutrophils from elite athletes was investigated. METHODS: Blood was collected from eleven sedentary volunteers and twelve triathletes under rest and after a Half Ironman triathlon competition (2 Km swimming, 80 Km, cycling and 20 Km running). RESULTS: The triathlon competition increased DNA fragmentation by 3-fold, phosphatidylserine externalization by 2-fold and ROS production by 3.3-fold in neutrophils when compared to the results at rest. The plasma level of products of lipid peroxidation (TBARS) from triathletes after competition increased, suggesting occurrence of oxidative stress. Expression of bcl-xL was decreased by 69% and of bax was increased by 61%, whereas intracellular neutral lipid accumulation was lowered by 65% after the competition. A positive correlation was found between the proportion of neutrophils with DNA fragmentation and the increase in plasma free fatty acid concentration (r=0.688, p<0.05), which was elevated by 3-fold after competition. The plasma levels of oleic, linoleic and stearic acids were increased by 1.6, 1.6 and 2.4-fold, respectively, in triathletes when compared with sedentary volunteers. The plasma concentration of these three fatty acids found after a triathlon competition was toxic for 3 h cultured neutrophils obtained from sedentary volunteers. The maximal tolerable (non-toxic) concentration for neutrophils was of 100 μM for oleic and linoleic acids and 200 μM for stearic acid. CONCLUSIONS: Triathlon competition induced neutrophil death possibly by apoptosis as indicated by DNA fragmentation and phosphatidylserine externalization. Increase in plasma levels of oleic, linoleic and stearic acids induced by the competition might be involved in the neutrophil death possibly by increasing ROS production and decreasing intracellular neutral lipid accumulation. This research has been supported by FAPESP, CNPq and CAPES.