Effects of long-term space flight on erythrocytes and oxidative stress of rodents

Abstract

Erythrocyte and hemoglobin losses have been frequently observed in humans during space missions; these observations have been designated as "space anemia". Erythrocytes exposed to microgravity have a modified rheology and undergo hemolysis to a greater extent. Cell membrane composition plays an important role in determining erythrocyte resistance to mechanical stress and it is well known that membrane composition might be influenced by external events, such as hypothermia, hypoxia or gravitational strength variations. Moreover, an altered cell membrane composition, in particular in fatty acids, can cause a greater sensitivity to peroxidative stress, with increase in membrane fragility. Solar radiation or low wavelength electromagnetic radiations (such as gamma rays) from the Earth or the space environment can split water to generate the hydroxyl radical, very reactive at the site of its formation, which can initiate chain reactions leading to lipid peroxidation. These reactive free radicals can react with the non-radical molecules, leading to oxidative damage of lipids, proteins and DNA, etiologically associated with various diseases and morbidities such as cancer, cell degeneration, and inflammation. Indeed, radiation constitutes on of the most important hazard for humans during long-term space flights. With this background, we participated to the MDS tissue-sharing program performing analyses on mice erythrocytes flown on the ISS from August to November 2009. Our results indicate that space flight induced modifications in cell membrane composition and increase of lipid peroxidation products, in mouse erythrocytes. Moreover, antioxidant defenses in the flight erythrocytes were induced, with a significant increase of glutathione content as compared to both vivarium and ground control erythrocytes. Nonetheless, this induction was not sufficient to prevent damages caused by oxidative stress. Future experiments should provide information helpful to reduce the effects of oxidative stress exposure and space anemia, possibly by integrating appropriate dietary elements and natural compounds that could act as antioxidants.

Figure 1. Thiobarbituric acid reactive substances (TBARS) content (pmol/mg Hb, mean± SD) in PTN and wild type mice erythrocytes after space flight. MDS-ISS (black bars), Ground MDS controls (line bars) and vivarium (white bars).

* p<0.05 MDS-ISS vs Ground MDS control. Statistical analysis performed only on PTN mice.

Figure 2. Antioxidant enzymes and glutathione content in PTN and wild type mice erythrocytes after space flight.

A: Total glutathione (GSH) content (nmol/g Hb, mean+sd) B: glutathione peroxidase (GPx) (U/g Hb, mean+ SD) C: Glutathione reductase (GR) (U/g Hb, mean+ SD). MDS-ISS, (black bars), Ground MDS controls (line bars) and vivarium (white bars). * p<0.05 MDS-ISS vs Ground MDS control. Statistical analysis performed only on PTN mice.

Figure 3. Catalase (Panel A, U/mg Hb+SD) and Superoxide dismutase (Panel B U/g HB+SD) activities in PTN and wild type mice erythrocytes after space flight.

MDS-ISS (black bars), Ground MDS controls (line bars) and vivarium (white bars). * p<0.05 MDS-ISS vs Ground MDS control. Statistical analysis performed only on PTN mice.

Figure 4. Total omega-3 fatty acid content (black bars) and phosphatidylcholine DHA content (white bars) in PTN mice erythrocytes after space flight (MDS-ISS, Ground MDS controls).

* p<0.05 MDS-ISS vs Ground MDS control.