Exercise and epinephrine affect equine leukocytes distribution and gene expression in a distinct but closely related pattern

Background: In horses-athletes, exercise has been shown to be an important regulator of immune cells and their functions, and catecholamines to be essential components of the physiological response to exercise.
Objectives: The purpose of the present study was to compare immunological reactions and molecular events during exercise and epinephrine infusion.
Methods: Horses were submitted to exercise or epinephrine infusion for 10 min. Blood samples were collected at T0, T5, Tl0, T20 and T40 min for biochemistry and haematology at T0 and T20 min for RNA extraction and microarray analysis.
Results: In both protocols, packed-cell-volume and neutrophils peaked at T5 and T10, and returned to baseline at T40. Lymphocytes increased at T5 with exercise and at T20 with epinephrine and then remained high until the end of the protocols. Between T0 and T20, 55 probes, coding for 25 genes, and 19 probes, coding for 11 genes, were differentially regulated with epinephrine and exercise respectively (P<0.001). Ten of the genes over-expressed with epinephrine were related to inflammatory response and leukocytes trafficking and activation. Among the genes with the highest significant fold changes following exercise were FOS, DUSP-1 and CXCL1. FOS was over-expressed in both conditions. Among genes differentially regulated, Ingenuity software identified 3 overlapping functional networks with epinephrine and 1 functional network with exercise that overlapped the 3 epinephrine networks.
Conclusions: Circulating leukocytes distribution and gene expression are rapidly affected following exercise and epinephrine infusion. Distinct but closely-related sets of gene activities were shown to be altered with exercise and epinephrine, with lesser changes in the immunological pattern with physical stress than epinephrine alone, arguing for compensatory mechanisms in exercise.