AUTHOR=Kröpfl Julia M. , Kammerer Tobias , Faihs Valentina , Gruber Hans-Jürgen , Stutz Jan , Rehm Markus , Stelzer Ingeborg , Schäfer Simon T. , Spengler Christina M. 

TITLE=Acute Exercise in Hypobaric Hypoxia Attenuates Endothelial Shedding in Subjects Unacclimatized to High Altitudes

JOURNAL=Frontiers in Physiology

VOLUME=Volume 10 - 2019

YEAR=2020

URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2019.01632

DOI=10.3389/fphys.2019.01632

ISSN=1664-042X

ABSTRACT=Travel of unacclimatized subjects to high altitude has been growing in popularity. Changes of endothelial shedding (circulating endothelial cells, ECs) and hematopoietic stem and progenitor cells (CPCs) during physical exercise in hypobaric hypoxia, however, are not well understood. We investigated the change of ECs and CPCs when exposed to high altitude, after acute exercise therein, and after an overnight stay in hypobaric hypoxia in eleven healthy unacclimatized subjects. Blood withdrawal was done at baseline (520m a.s.l.; baseline), after passive ascent to 3883m a.s.l. (arrival), after acute physical exercise (±400m, post-exercise) and after an overnight stay at 3883m a.s.l. (24h). Mature blood cells, ECs and CPCs were assessed by a hematology analyzer and flow cytometry, respectively. Presence of matrix metalloproteinases (MMPs), their activity and hematopoietic cytokines were assessed in serum and plasma. EC and CPC concentrations significantly decreased after exercise (p=0.019, p=0.007, respectively). CPCs remained low until the next morning (24h, p=0.002), while EC concentrations returned back to baseline. MMP-9 decreased at arrival (p=0.021), stayed low post-exercise (p=0.033) and returned to baseline at 24h (p=0.035 to post-exercise). MMP-activity did not change throughout the study. Circulating MMP-9 concentrations, but not MMP-activity, were associated with EC concentrations (rrm=0.48, p=0.010). CPC concentrations were not linked to hematopoietic cytokines. Acute exercise at high altitude attenuated endothelial shedding, but did not enhance regenerative CPCs. Results were not linked to endothelial matrix remodeling or CPC mobilization. These results provide information to better understand the endothelium and immature immune system during an active, short-term sojourn at high altitude.