Evidence that the effect of physical exercise on NK cell activity is mediated by epinephrine

Abstract

The present study was designed to test the hypothesis that the changes in natural killer (NK) cell activity in response to physical exercise were mediated by increased epinephrine concentrations. Eight healthy volunteers 1) exercised on a bicycle ergometer (60 min, 75% of maximal O2 uptake) and 2) on a later day were given epinephrine as an intravenous infusion to obtain plasma epinephrine concentrations comparable with those seen during exercise. Blood samples were collected in the basal state, during the last minutes of exercise or epinephrine infusion, and 2 h later. The NK cell activity (lysis/fixed number of mononuclear cells) increased during exercise and epinephrine infusion and dropped below basal levels 2 h afterward. The increased NK cell activity during exercise and the epinephrine infusion resulted from an increased concentration of NK (CD16+) cells in the peripheral blood. On the other hand, the decreased NK cell activity demonstrated 2 h after exercise and epinephrine infusion did not simply reflect preferential removal of NK cells from the blood, because the proportion of CD16+ cells was normalized. On the basis of the finding that indomethacin abolished the suppressed NK cell activity in vitro and the demonstration of a twofold increase in the proportion of monocytes (CD14+ cells) 2 h after exercise and epinephrine infusion, we suggest that, after stress, prostaglandins released by monocytes are responsible for downregulation of NK cell function. Our findings support the hypothesis that increased plasma epinephrine during physical stress causes a redistribution of mononuclear subpopulations that results in altered function of NK cells.

Attenuation of natural killer cell activity during 2-h exercise in individuals with spinal cord injuries

“…Thus, increased concentrations of adrenaline during exercise resulted in significant increase of NKCA. 2,3,15,16 In the present study, plasma adrenaline concentrations increased significantly (Po0.05) immediately after exercise in both SCI and able-bodied subjects. However, NKCA increased after 2-h exercise in able-bodied subjects while it decreased in SCI subjects.…”

“…16 In the present study, NKCA in SCI subjects decreased immediately after 2 h exercise; however, the number of NK cell at that period was stable and similar to that before exercise. Thus, the cytotoxic function of NK cells might be suppressed only during the exercise.…”

“…2,3,15,16 Kappel et al 16 reported that adrenaline administration in eight healthy individuals increased NKCA and such rise correlated with plasma adrenaline concentrations. Thus, increased concentrations of adrenaline during exercise resulted in significant increase of NKCA.…”

“…However, several studies have examined exercise immunology in able-bodied subjects, and the subject numbers in some of these well-controlled studies were less than 10 persons. 4,6,15 Furthermore, it was difficult to recruit individuals with SCIs who met the strict inclusion criteria of the present study including completion of the 2-h arm crank ergometer exercise.…”

“…It is widely known that persons with SCI easily develop infections of the urinary tract, respiratory tract and skin, because they seem to have weak host defense mechanisms. 5,6 In two separate studies, 7,8 we reported that a high-intensity exercise (wheelchair full marathon race) induced a transient suppression of NKCA in competitive wheelchair racers with SCI between T5 and L1, while wheelchair half marathon race induced activation of NK cell function in recreational athletes with SCI between T7 and L1. To our knowledge, there are no studies that examined NKCA during exercise of well-controlled duration and intensity in SCI subjects.…”