Cellular activation in response to physical exercise: the effect of platelets and granulocytes on monocyte reactivity

After physical exercise monocytes have been shown to express more lipopolysaccharide (LPS)-induced tissue factor activity compared with monocytes at rest. This is in contrast to LPS-induced tumor necrosis factor (TNF)-alpha production, which is reduced after physical exercise. Furthermore, LPS-induced tissue factor activity in monocytes at rest has been shown to be dependent on platelets and granulocytes, whereas LPS-induced TNF-alpha is not affected by these cells. The aim of the present study was to test how platelets and granulocytes affect LPS-induced tissue factor activity in monocytes observed after exercise. This was done by separating the different blood cells before and after exercise, followed by recombination of the cells in plasma and quantification of LPS-induced tissue factor activity in vitro. Two groups of subjects with different aerobic endurance levels were tested to reveal possible differences as a result of physical conditioning. The results of the present study showed that the major effect of exercise was associated with a change in the reactivity of monocytes themselves, since monocytes from blood samples taken after running recombined with platelets, and granulocytes showed the greatest increase in tissue factor activity. Platelets and granulocytes stressed by physical exercise had no further enhancing effect on LPS-induced tissue factor activity other than that observed at rest. The lowest LPS-induced tissue factor activity in all combinations of blood cells was found in athletes, compared with less trained subjects, both at rest and in response to exercise.