Gravitational stress during parabolic flights reduces the number of circulating innate and adaptive leukocyte subsets in human blood.

Gravitational stress occurs during space flights or certain physical activities including extreme sports, where the change in experienced gravitational acceleration can reach large magnitudes. These changes include reduction and increase in the physical forces experienced by the body and may potentially induce pathogenic alterations of physiological processes. The immune system is known to regulate most functions in the human organism and previous studies suggest an impairment of the immune function under gravitational stress. However, systematic studies aiming to investigate the effect of gravitational stress on cellular immune response in humans are lacking. Since parabolic flights are considered as feasible model to investigate a short-term impact of gravitational changes, we evaluated the influence of gravitational stress on the immune system by analyzing leukocyte numbers before and after parabolic flight maneuvers in human blood. To correct for circadian effects, samples were taken at the corresponding time points on ground the day before the flight. The parabolic flight maneuvers led to changes in numbers of different leukocyte subsets. Naïve and memory T and B cell subsets decreased under gravitational stress and lower numbers of basophils and eosinophils were observed. Only circulating neutrophils increased during the parabolic flight. The observed changes could not be attributed to stress-induced cortisol effects, since cortisol levels were not affected. Our data demonstrate that the gravitational stress by parabolic flights can affect all parts of the human immune system. Consequently, it is possible that gravitational stress can have clinically relevant impacts on the control of immune responses.

Small platelet microparticle levels are increased in pulmonary arterial hypertension.

BACKGROUND: The various aetiologies and risk factors for pulmonary arterial hypertension (PAH) lead to close phenotypes with small differences. Plasma microparticles have been shown to be increased in vascular pathologies including PAH. The aim of this study was to determine whether the levels of endothelial and platelet-derived microparticles could vary between different forms of PAH: idiopathic PAH (iPAH), heritable PAH associated with BMPR2 (Bone morphogenetic protein receptor, type II) mutation (hPAH) and PAH associated with connective tissue diseases (aPAH). MATERIALS AND METHODS: Microparticles were analysed using flow cytometry in plasma from controls and iPAH, hPAH and aPAH patients. Platelet-derived MP (PMP) were defined as CD31(+)/CD41(+) and endothelial-derived MP (EMP) as CD31(+)/CD41(-). Two populations of PMP were isolated according to their size, defining small PMP (0·3-0·5 µm) and large PMP (0·5-0·9 µm). BMPR2 genotype, clinical and biologic parameters were recorded. RESULTS: EMP and small PMP levels in iPAH, hPAH and aPAH were similar and were significantly increased as compared with controls. No differences in large PMP levels were observed. After adjusting for age, sex, proBNP and CRP, EMP and small PMP levels did not correlate with clinical parameters. CONCLUSIONS: iPAH, hPAH and aPAH were characterized by increased levels of EMP and of small PMP, a new class of PMP which seems to be differentially produced than large PMP.