Effect of space flight factors on health of cosmonauts in the near and late term after space flights

Cytogenetical studies of cosmonauts' peripheral blood lymphocytes after space flights on MIR orbital station showed a statistically significant increase in the yields of radiation-induced chromosomal aberrations. However, similar studies with in vitro irradiation of biological objects with accelerated charged particles are of great importance for elucidation of the nature of cytogenetical damage induced in vivo. It is also important to investigate the structure of cosmonatus' diseases over their life, in particular, lens opacities and oncological diseases. Thus, the purpose of the investigations planned is to study cytogenetical damage in blood lymphocytes from cosmonauts after space flights on the ISS in vivo, as well as in donor blood lymphocytes after in vitro exposure to accelerated charged particles. The tasks of the project are as follows: determination of the yields and types of chromosomal aberrations in cosmonauts' blood lymphocytes before and after space flights, comparative studies of biological effects induced in vitro by different types of ionizing radiation in human blood lymphocytes in ground experiments, assessment of cytogenetical risks, analysis of the structure of cosmonatus' diseases comparing with that of whole population, study of the mortality and frequency of cataracts and oncological diseases in cosmonauts. The results to be obtained will be used for setting of health norms applied to the influence of radiations of different types, and for elaboration of measures to reduce health risks from space flight factors.     

Chromosome aberrations in the blood lymphocytes of astronauts after space flight.

Cytogenetic analysis of the lymphocytes of astronauts provides a direct measurement of space radiation damage in vivo, which takes into account individual radiosensitivity and considers the influence of microgravity and other stress conditions. Chromosome exchanges were measured in the blood lymphocytes of eight crew members after their respective space missions, using fluorescence in situ hybridization (FISH) with chromosome painting probes. Significant increases in aberrations were observed after the long-duration missions. The in vivo dose was derived from the frequencies of translocations and total exchanges using calibration curves determined before flight, and the RBE was estimated by comparison with individually measured physical absorbed doses. The values for average RBE were compared to the average quality factor (Q) from direct measurements of the lineal energy spectra using a tissue-equivalent proportional counter (TEPC) and radiation transport codes. The ratio of aberrations identified as complex was slightly higher after flight, which is thought to be an indication of exposure to high-LET radiation. To determine whether the frequency of complex aberrations measured in metaphase spreads after exposure to high-LET radiation was influenced by a cell cycle delay, chromosome damage was analyzed in prematurely condensed chromosome samples collected from two crew members before and after a short-duration mission. The frequency of complex exchanges after flight was higher in prematurely condensed chromosomes than in metaphase cells for one crew member.     

Chromosome aberrations of clonal origin are present in astronauts' blood lymphocytes

Radiation-induced chromosome translocations remain in peripheral blood cells over many years, and can potentially be used to measure retrospective doses or prolonged low-dose rate exposures. However, several recent studies have indicated that some individuals possess clones of cells with balanced chromosome abnormalities, which can result in an overestimation of damage and, therefore, influence the accuracy of dose calculations. We carefully examined the patterns of chromosome damage found in the blood lymphocytes of twelve astronauts, and also applied statistical methods to screen for the presence of potential clones. Cells with clonal aberrations were identified in three of the twelve individuals. These clonal cells were present in samples collected both before and after space flight, and yields are higher than previously reported for healthy individuals in this age range (40-52 years of age). The frequency of clonal damage appears to be even greater in chromosomes prematurely condensed in interphase, when compared with equivalent analysis in metaphase cells. The individuals with clonal aberrations were followed-up over several months and the yields of all clones decreased during this period. Since clonal aberrations may be associated with increased risk of tumorigenesis, it is important to accurately identify cells containing clonal rearrangements for risk assessment as well as biodosimetry.     

The volume of extracellular fluid under conditions of long-term space flights

The volume of extracellular fluid (the bromine space) was determined in 18 cosmonauts 30 days before the start of a space flight and on the first day after landing. The duration of space flights on the Mir orbital station was from 126 to 438 days. Moreover, the volume of extracellular fluid was determined in seven cosmonauts directly during long-term space flights approximately two weeks before landing. After long-term space flights, the volume of extracellular fluid was decreased in all cosmonauts studied. The bromine space volume was significantly decreased compared to its initial preflight value. A decrease in the volume of extracellular fluid was caused not only by the reduction in the dense mass of the body but also by its dehydration. These processes developed independently of the duration of weightlessness but are mainly determined by the individual features of human beings.     

Calcium metabolism and its regulation in man during adaptation to microgravitation

This work generalizes the results of studies of calcium metabolism in the participants of long-term space flights of 30 to 438 days on the Salyut and Mir orbital stations during 1978–1998. The results of pre- and postflight examination of 44 cosmonauts (18 subjects participated twice in long-term space flights) were analyzed. After space flights of medium (of 3 to 6 months) and long (of 6 to 14 months) duration, the total blood calcium content was increased, mainly due to its ionized fraction; the blood level of parathyroid hormone was significantly increased and the level of calcitonin was decreased. The content of osteocalcin was increased after space flights. Calcium kinetics was studied using stable isotopes in three cosmonauts before, during, and after the 115-day flight. During the flight, intestinal absorption of calcium and its gastrointestinal excretion were decreased, whereas its renal excretion was increased. Early postflight intestinal absorption was, on average, lower than during the flight, whereas intestinal excretion increased. Both renal and intestinal excretion of calcium were not normalized 3.5 to 4.5 months after the glight. The mathematical models used for evaluating the rates of main calcium flows revealed increased bone tissue resorption that resulted in the negative bone balance during the flight. The conclusion about the decreased rate of bone tissue remodeling and its increased resorption was confirmed by biochemical data, including endocrine markers.     

Antibodies to muscle fiber antigens in the cosmonauts after a space flight]

The study of serum samples, obtained from 15 cosmonauts before and after space flights, with the use of the indirect fluorescent method showed that in 7 cosmonauts antibodies to different elements of the human heart muscle appeared after flights. Strong and very strong luminescence of the elements of heart muscle tissue was detected in the cosmonauts after the third space flight. When studying the sera on sections of bovine heart muscle tissue, the reactions of the sera taken before and after flights were found to have no essential differences.     

Changes in hemodynamic and post-flights orthostatic tolerance of cosmonauts under application of the preventive device--thigh cuffs bracelets in short-term flights

Specific aims: to evaluate the influence of the use thigh cuffs "Bracelet" on the hemodynamic adaptation to microgravity during short-term (up to a month) space flights, in-flight tolerance to LBNP-tests and post-flight orthostatic tolerance. 6 cosmonauts applied and 7 others did not apply the occlusive cuffs when on flight. The "Bracelet" device notably relieved the cosmonauts from the subjective discomfort following by the blood redistribution at initial period of exposure to microgravity. It was established that "Bracelet" lessened shifts in central and peripheral hemodynamics typical for exposure to microgravity, venous stasis in the cervical-cephalic region in particular. There were no differences between the hemodynamic reaction on LBNP-test in cosmonauts who applied and not applied "Bracelet" during short-term flights. The objective data are received, that the application of the device during short-term space flight does not make negative effects on post-flight orthostatic tolerance.     

Bone Mineral Density and Molecular Genetic Markers of Bone Remodeling in Blood of Cosmonauts after Long-term Missions on Board the International Space Station

The results of the investigation of the bone system of 24 Russian cosmonauts after long-term (124–199 days) missions on board the International space station (ISS) are presented. Functional adaptation of the bone system involves some complex changes in the metabolic activity of osteoblasts and osteoclasts, such as alterations of the serum concentrations of osteocalcin, tartrate-resistant acid phosphatase (TRAP), osteoprotegerin, and the activator ligand of the receptor of nuclear factor kappa-B (RANKL); in addition, in peripheral blood leucocytes, there are changes in the expression of genes regulating the development of skeletal system and bone mineral metabolism. Significant variability in the mineral density of femoral neck and molecular genetic markers studied after long-term space flights indicates individual variability of the balance of the processes of bone remodeling, bone formation and resorption. Significant bone mass losses in the femoral bone of cosmonauts are associated with more pronounced changes in the markers of metabolic activity of osteoclasts.     

Metabolic features of cosmonauts after ballistic descent from the Earth orbit

The features of metabolic reactions in five cosmonauts after long-term flights on the International Space Station (ISS) and landing along a ballistic trajectory and in the cosmonauts returning to Earth in the mode of automatic controlled descent were studied. Venous blood samples were collected, and 50 biochemical parameter values that reflect the functional state of organs and tissues and characterize the main metabolic pathways were determined. On the first day of the recovery period after ballistic descent, the activity of the myocardial, liver, and gastrointestinal enzymes in the blood serum of cosmonauts was increased 1.3- to 2.1-fold; a number of the parameter values exceeded the upper normal limit. The level of C-reactive protein increased fivefold as compared with the preflight values. Marked signs of glycolysis, glycogenolysis and lipolysis activation as well as disorders of acid–base balance were observed. Changes in the biochemical parameter values in cosmonauts after landing along a ballistic trajectory differed significantly from those revealed in the same cosmonauts after long-term missions followed by automatic controlled descent to Earth. Negative metabolic changes tendency after landing along a ballistic trajectory remained for at least 14 days of the recovery period. It was concluded that changes in the metabolic reactions of cosmonauts after long-term missions to the ISS depend on the flights final stage conditions. After landing on Soyuz spaceships in the ballistic descent mode, the cosmonauts had adverse prognosis changes in the biochemical values characterizing the state of the cardiovascular system and marked shifts in the activity of the liver and gastrointestinal constellation enzymes. The dynamics of carbohydrate, lipid, and protein metabolism as well as acid–base balance indicates a significant tension of all body systems and exhaustion of its functional reserves.     

Reference values of the hemostasis system indices in cosmonauts

The values of 11 diagnostically significant hemostasis system indices were determined during the preflight (30–45 days before start) clinical and physiological examination of 39 cosmonauts aged 35 to 54 years, who were the members of the main and backup crews of missions to the International Space Station (ISS) during the period from 2007 to 2014. Since most of the cosmonauts performed several flights over this period and were repeatedly included in backup crews, each of them underwent examinations one to five times. The reference values were calculated for each of the studied indices. It was found that the reference ranges for the parameters indicative of the integral pro- and anticoagulant and fibrinolytic blood plasma potential were somewhat narrowed and close to the boundaries of general population ranges, which indicates that the cosmonauts had a relatively decreased procoagulant potential and increased regulative potential of the hemostasis system. This was probably due to the criteria of selection, physical training status, and emotional status of crew members during the preflight professional activity, when adaptive changes against stressinducing effects occur in the body. The cosmonauts who underwent strict medical examination may also have some genetic features in which they differ from the general population and which provide higher body resistance and more rapid adaptation processes.     

Space radiation does not induce a significant increase of intrachromosomal exchanges in astronauts’ lymphocytes

Chromosome aberration analysis in astronauts has been used to provide direct, biologically motivated estimates of equivalent doses and risk associated to cosmic radiation exposure during space flight. However, the past studies concentrated on measurements of dicentrics and translocations, while chromosome intrachanges (inversions) have never been measured in astronauts’ samples. Recent data reported in the literature suggest that densely ionizing radiation can induce a large fraction of intrachanges, thus leading to the suspicion that interchanges grossly underestimate the cosmic radiation-induced cytogenetic damage in astronauts. We have analyzed peripheral blood lymphocytes from 11 astronauts involved in short- or long-term space flights in low-Earth orbit using high-resolution multicolor banding to assess the frequency of intrachromosomal exchanges in both pre- and post-flight samples. We did not detect any inversions in chromosome 5 from a total of 2800 cells in astronauts’ blood. In addition, no complex type exchanges were found in a total of 3590 astronauts’ lymphocytes analyzed by multifluor fluorescence in situ hybridisation. We conclude that, within the statistical power of this study, the analysis of interchanges for biological dosimetry in astronauts does not significantly underestimate the space radiation-induced cytogenetic damage, and complex-type exchanges or intrachanges have limited practical use for biodosimetry at very low doses.     

Reference values of blood biochemical indices in Russian cosmonauts

In the period from 2000 to 2012, the values of 40 diagnostically significant biochemical indices in venous blood were determined during the preflight clinical and physiological examination of 28 Russian cosmonauts aged 35 to 54, members of the main and backup crews of missions on board the International Space Station. The examination was conducted 45-30 days prior to the launch. Since most cosmonauts performed several flights during this period and they were repeatedly included in backup crews, each of the cosmonauts participated in preflight examinations one to five times. The reference values were calculated for each of the studied indices. It was found that reference interval boundaries for 15 indices were narrower as compared to the generally accepted ranges. The upper boundaries of the reference ranges of the activities of a number of enzymes, as well as of the concentrations of some metabolites of energy and plasticity metabolism, were higher than the population’s mean values. Thus, it was found that Russian cosmonauts, being a specific professional team, had reference values of a number of blood biochemical indices that were different from the population’s mean values. This was due to the characteristics of selection, physical training, and psychic and emotional states of crew members during the preflight period.     

The Effect of Long-term Space Flights on Human Urine Proteins Functionally Related to Endothelium

It is known that long-term space flights lead to dysregulation of the cardiovascular system, and the endothelium is the most important functional element of such dysregulation. In order to find the signs of endothelial dysfunction in cosmonauts who have been in long-term space flights, we collected urine samples from 21 cosmonauts before the flight and on the first and seventh days after landing. The urine samples were investigated by chromatography–mass spectrometry analysis. Proteins were identified using the MaxQuant software and the SwissProt database. The software package Perseus was used for semi-quantitative analysis. The reconstruction of associative molecular networks was performed using the ANDSystem software. We identified 200 different proteins in urine samples of 21 Russian cosmonauts. The ANDSystem software made it possible to determine seven processes related to endothelium functioning. These processes had direct relations to 17 urine proteins, which were functionally associated with the endothelium. At the same time, eight proteins (such as serotransferrin, prostate-specific antigen, fibrinogen gamma chain, UFO tyrosine kinase receptor, aminopeptidase N, vascular cell adhesion molecule 1, osteopontin, and syndecan-4) were significantly changed (p < 0.01) at different points of the recovery period (the first and seventh days). Thus, we performed the first study of the urine protein composition in cosmonauts for the evaluation of signs of endothelial dysfunction after space flight using proteomics methods.     

Complex chromosomal rearrangements induced in vivo by heavy ions

It has been suggested that the ratio complex/simple exchanges can be used as a biomarker of exposure to high-LET radiation. We tested this hypothesis in vivo, by considering data from several studies that measured complex exchanges in peripheral blood from humans exposed to mixed fields of low- and high-LET radiation. In particular, we studied data from astronauts involved in long-term missions in low-Earth-orbit, and uterus cancer patients treated with accelerated carbon ions. Data from two studies of chromosomal aberrations in astronauts used blood samples obtained before and after space flight, and a third study used blood samples from patients before and after radiotherapy course. Similar methods were used in each study, where lymphocytes were stimulated to grow in vitro, and collected after incubation in either colcemid or calyculin A. Slides were painted with whole-chromosome DNA fluorescent probes (FISH), and complex and simple chromosome exchanges in the painted genome were classified separately. Complex-type exchanges were observed at low frequencies in control subjects, and in our test subjects before the treatment. No statistically significant increase in the yield of complex-type exchanges was induced by the space flight. Radiation therapy induced a high fraction of complex exchanges, but no significant differences could be detected between patients treated with accelerated carbon ions or X-rays. Complex chromosomal rearrangements do not represent a practical biomarker of radiation quality in our test subjects.     

The State of the System of Signaling Pattern Recognition Receptors of Monocytes and Granulocytes in the Cosmonauts’ Peripheral Blood before and after Long-Term Flights on Board the International Space Station

The system of signaling pattern recognition receptors was studied in eight cosmonauts at the ages from 35 to 56 years before and after long-term space flights (SFs) on board the International Space Station (ISS). The peripheral blood samples were analyzed for the content of monocytes and granulocytes that express the signaling pattern recognition Toll-like receptors (TLRs) with surface (TLR1, TLR2, TLR4, TLR5, and TLR6) and intracellular (TLR3, TLR8, and TLR9) localization. The serum concentration of basic ligands of TLR2 (HSP60) and TLR4 (HSP70 and HMGB1) were also measured. The results of the studies showed a growth of the HSP60, HSP70, and HMGB1 concentrations on the first day after long-term flight. The increase in the concentration of endogenous ligands was followed by a growth of the number of both monocytes and granulocytes that express the respective pattern recognition receptors, TLR2 and TLR4, in the overwhelming majority of the examined cosmonauts. Thesse relationships suggest that changes in the system of signaling pattern recognition receptors may be due to the prevailing influence of endogenous ligands in response to the effect of long-term spaceflight factors on the human body.     

Persistence of chromosome aberrations in mice acutely exposed to 56Fe+26 ions

Space exploration has the potential to yield exciting and significant discoveries, but it also brings with it many risks for flight crews. Among the less well studied of these are health effects from space radiation, which includes the highly charged, energetic particles of elements with high atomic numbers that constitute the galactic cosmic rays. In this study, we demonstrated that 1 Gy iron ions acutely administered to mice in vivo resulted in highly complex chromosome damage. We found that all types of aberrations, including dicentrics as well as translocations, insertions and acentric fragments, disappear rapidly with time after exposure, probably as a result of the death of heavily damaged cells, i.e. cells with multiple and/or complex aberrations. In addition, numerous cells have apparently simple exchanges as their only aberrations, and these cells appear to survive longer than heavily damaged cells. Eight weeks after exposure, the frequency of cells showing cytogenetic damage was reduced to less than 20% of the levels evident at 1 week, with little further decline apparent over an additional 8 weeks. These results indicate that exposure to 1 Gy iron ions produces heavily damaged cells, a small fraction of which appear to be capable of surviving for relatively long periods. The health effects of exposure to high-LET radiation in humans on prolonged space flights should remain a matter of concern.     

Individual cytogenetic and molecular-biological characteristics of lymphocytes in blood of pilots and cosmonauts

The purpose of this paper was the investigation of the pilots and of cosmonauts individual sensitivity to the fly conditions, to the additional irradiation (in the dose of 1 Gy), the adaptive response manifestation (in the doses 0.05 and 0.5 Gy). The DNA comet assay (the double strand DNA breaks was determined) and the method of unstable chromosome aberrations in metaphase was used. The human blood lymphocytes was the object of investigation. The significant individual differences were discovered in pilots and in cosmonauts in the initial DNA damage; in the sensitivity to the additional irradiation. The frequency of the adaptive response induction was decreased in the pilots in the comparison with the control group. The adaptive response was registered in cosmonauts (3 men). It is supposed that DNA damage, chromosome aberrations, sensitivity to the additional irradiation, the adaptive response manifestations can be used as biological markers of individual risk disease.     

Calcium metabolism characteristics in microgravity]

The results of research of calcium exchange parameters at cosmonauts taken part in long space flights (SF) onboard of orbital stations "SALUT" and "MIR" within 1978-1998 were generalized. The analysis of data received during observation of 44 cosmonauts (18 of them have taken part in long SF twice) was done. The observation was carried out before and after SF by duration 30-438 days. The content of a total calcium in blood serum was increased basically by the increase of its ionized fraction after flights of moderate (3-6 months) and large duration (6-14 months) along with the significant increase of PTH and decrease of calcitonin levels. The content of osteocalcin after SF was increased. Three cosmonauts participated in research of calcium kinetics using stable isotopes before, in time and after a 115-day SF. Reduction of intestinal absorption, excretion through a gastrointestinal tract, and increase of calcium excretion with urine were marked in time of SF. In early postflight period a level of intestinal absorption, on the average, was much lower than in SF, and the calcium removal through intestine was increased. Both renal and intestinal excretion of calcium were not normalized in 3.5-4.5 months after end of SF. Increase of resorbtive processes in bone tissues which induced negative bone balance during flight was observed in all test subjects, proceeding from estimations of speed of the basic calcium flows made on the basis of mathematical modeling. The conclusion about decrease in speed of bone tissue remodeling and strengthening of its resorption proves to be true by data of research of biochemical and endocrine markers.     

Medical care for Russian cosmonauts on board the ISS

Established with the personal participation of O.G. Gazenko, the Russian system of medical care for cosmonauts has been largely preserved to this day. The system was fully functional on board the orbital complex Mir and, with appropriate modifications, has been adopted as the core of the medical care for Russian members of ISS crews. In 2000–2008, 22 cosmonauts were members of 17 ISS missions lasting from 140 to 216 days. The main functions of the medical care system were to control health, physical, and mental performance, and to support space research. Readaptation to normal gravity was, in most cases, similar to what has been typical on the return from Russian orbital stations; some deviations are accounted for by the use of in-flight countermeasures. The paper presents some aspects of the theoretical work of Academician Gazenko in the field of medical care in space flights. It outlines the principles of ISS medical management. The integrated medical support system combines medical equipment and items available in the Russian and U.S. segments; the integrated medical group consists of flight surgeons, medical experts, and biomedical engineers of international partners and coordinates the planning and implementation of medical operations. In addition, challenges of health care in the phase of ISS operation are defined.