Effect of inflammation induced by prolonged exercise on circulating erythroid progenitors and markers of erythropoiesis.

Background: Exercise in humans augments the mobilization of circulating hematopoietic progenitor cells (CD34(+)) from the bone marrow. We investigated the effect of inflammation on erythroid marrow activity by mobilization of erythroid progenitor cells (EPs) along with soluble markers of erythropoiesis.

Methods: Ten healthy athletes who participated in an ultradistance foot race participated in the study. Peripheral blood mononuclear cells were isolated, before (phase I), at the end (phase II), and at 48 h post-race (phase III). EPs were detected as burst colony forming units (BFU-e) and colonies were scored at day 14. Markers of inflammation (C-reactive protein, serum amyloid-A, interleukin-6, ferritin and S100B) and bone marrow activity (erythropoietin, soluble transferrin receptor and lipocalin-2) were assessed.

Results: An approximately three-fold decrease in BFU-e number was observed at phase II. sTfR concentrations were also decreased at phase II and remained decreased at phase III. However, EPO and lipocalin-2 concentrations reached a maximum value at phase II, with a tendency to decrease at phase III.

Conclusions: These findings indicate that exercise-induced inflammation modulates bone marrow homeostasis leading to an increase in leukocyte turnover and a decrease in erythroid compartment. It appears that lipocalin-2 is the main factor that regulates the production and mobilization of EPs.