Physical exercise increases urinary excretion of lipoxin A4 and related compounds

Abstract

Lipoxins (LX) are lipoxygenase-derived eicosanoids with potent anti-inflammatory activities and vascular bed-dependent vasodilatory actions. LX can be formed in vitro and in vivo in a number of conditions, and we have reported that immunoreactive LXA4 (iLXA4) is physiologically excreted with human urine. Using a recently developed LX extraction method coupled to an ELISA, we examined whether iLXA4 excretion was modified by strenuous exercise, which is known to trigger potential LX-forming events. Maximal exertion significantly increased iLXA4 urinary excretion in nine healthy volunteers (0.061 ± 0.023 vs. 0.113 ± 0.057 ng/mg creatinine; P = 0.028). iLXA4 levels returned to baseline after 6 h and increased, although at a smaller extent, after 24 h. A significant correlation ( r = 0.988) was denoted between iLXA4 ELISA measurements and reversed-phase high-performance liquid chromatography quantitation of a previously described urinary tetraene, confirming its LXA4-related nature. These findings show for the first time that an increase in excretion of LXA4-related compounds can be observed in response to strenuous exercise. This may be the reflection of an enhanced LX biosynthesis, which may represent a safeguard mechanism that keeps the inflammatory reaction triggered by physical stress under control.