Modulations of Neuroendocrine Stress Responses During Confinement in Antarctica and the Role of Hypobaric Hypoxia

Abstract

The Antarctic continent is an environment of extreme conditions. Only few research stations exist that are occupied throughout the year. The German station Neumayer III and the French-Italian Concordia station are such research platforms and human outposts. The seasonal shifts of complete daylight (summer) to complete darkness (winter) as well as massive changes in outside temperatures (down to -80°C at Concordia) during winter result in complete confinement of the crews from the outside world. In addition, the crew at Concordia is subjected to hypobaric hypoxia of ∼650 hPa as the station is situated at high altitude (3,233 m). We studied three expedition crews at Neumayer III (sea level) (n = 16) and two at Concordia (high altitude) (n = 15) to determine the effects of hypobaric hypoxia on hormonal/metabolic stress parameters [endocannabinoids (ECs), catecholamines, and glucocorticoids] and evaluated the psychological stress over a period of 11 months including winter confinement. In the Neumayer III (sea level) crew, EC and n-acylethanolamide (NAE) concentrations increased significantly already at the beginning of the deployment (p < 0.001) whereas catecholamines and cortisol remained unaffected. Over the year, ECs and NAEs stayed elevated and fluctuated before slowly decreasing till the end of the deployment. The classical stress hormones showed small increases in the last third of deployment. By contrast, at Concordia (high altitude), norepinephrine concentrations increased significantly at the beginning (p < 0.001) which was paralleled by low EC levels. Prior to the second half of deployment, norepinephrine declined constantly to end on a low plateau level, whereas then the EC concentrations increased significantly in this second period during the overwintering (p < 0.001). Psychometric data showed no significant changes in the crews at either station. These findings demonstrate that exposition of healthy humans to the physically challenging extreme environment of Antarctica (i) has a distinct modulating effect on stress responses. Additionally, (ii) acute high altitude/hypobaric hypoxia at the beginning seem to trigger catecholamine release that downregulates the EC response. These results (iii) are not associated with psychological stress.

Sex differences in stress and immune responses during confinement in Antarctica

“…Additionally, the cytokine release after various stimulations was defined as secondary outcome parameter to evaluate the immune response. Parts of the data have been used for a comparison with data from another Antarctic research station in a recent publication [22].…”

“…Quantification of the EC concentrations of anandamide (AEA), 2-arachidonoylglycerol (2-AG), and the NAEs oleoylethanolamide (OEA), palmitoylethanolamide (PEA), and stearoylethanolamide (SEA) was executed at the Institute of Doping Analysis und Sports Biochemistry, Kreischa, Germany. The exact method has been described previously [22].…”

“…Activated by physical or emotional stress, it supports the organism in its adaptation to new environmental and physiological challenges [44][45][46]. In a recently published study of our group [22], we examined the course of EC and NAE concentrations in exclusively male participants of overwintering campaigns at either Neumayer III at sea level or Concordia Station at high altitude of 3200 m to discern the effects of hypobaric hypoxia. As we detected significantly elevated EC and NAE concentrations during the confinement in the participants at Neumayer III but not at Concordia, we assumed an activation of the EC system by exposure to the physically challenging environment of Antarctica that is altered and diminished by hypobaric hypoxia at Concordia.…”

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“…16 October when compared to baseline data but fluctuated in the normal range. 17 In view of the above, it could be ascertained that both the factors i.e. non-availability of fresh rations, as well as absence of sunlight during the winter months contributed towards the progressive reduction of Haemoglobin concentration and there by resulting in anaemic status of the expedition members during this period.…”

‘White Mars’ – nearly two decades of biomedical research at the Antarctic Concordia station

“…Concordia (Crucian et al, 2011;Feuerecker et al, 2012Feuerecker et al, , 2014. Oxygen In another study from the same team it was investigated how chronic hypobaric hypoxia affects the stress-related endocannabinoid system (ECS) (Strewe et al, 2018b), which plays an important role in coping with stress reactions. Results revealed a significant increase (up to 10-fold) of stress-related metabolites under normoxic conditions at Neumayer, a German Antarctic station at sea-level.…”