Scientists may have discovered what causes a mysterious space phenomenon

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(Original Article) FROM: https://www.nature.com/articles/s41591-021-01637-7 Hemolysis contributes to anemia during long-duration space flight Guy Trudel, Nibras Shahin, Timothy Ramsay, Odette Laneuville & Hakim Louati (2022-01-14) Abstract Anemia in astronauts has been noted since the first space missions, but the mechanisms contributing to anemia in space flight have remained unclear. Here, we show that space flight is associated with persistently increased levels of products of hemoglobin degradation, carbon monoxide in alveolar air and iron in serum, in 14 astronauts throughout their 6-month missions onboard the International Space Station. One year after landing, erythrocytic effects persisted, including increased levels of hemolysis, reticulocytosis and hemoglobin. These findings suggest that the destruction of red blood cells, termed hemolysis, is a primary effect of microgravity in space flight and support the hypothesis that the anemia associated with space flight is a hemolytic condition that should be considered in the screening and monitoring of both astronauts and space tourists. Main As humankind plans extraterrestrial travel, understanding the health implications of living in space will be critical to planning safe journeys. Space anemia was previously documented and characterized by a 10–12% decrease in red blood cell (RBC) mass happening in the first 10 days in space1. Current understanding of space anemia is that the decrease in RBCs constitutes an acute adaptation to major hemodynamic events of cephalad fluid shifts, hemoconcentration and low erythropoietin (EPO) levels upon entering microgravity1,2. Thereafter, beyond 10 days in space, when the hemoglobin concentration returns to near-earthly values, erythrocytic regulation would proceed normally, but this has not been measured precisely2. Recently, astronauts were found to remain mildly hemoconcentrated throughout long-duration mission3, and epidemiological data showed that the severity, time to recovery and longitudinal effects of postflight anemia were proportional to the time spent in space4. These reports challenged the current understanding of space anemia. Longer missions to the moon and Mars, as well as space tourism and commercialization, require a better understanding of space-induced anemia. Because astronaut orthostatism, exercise tolerance and fatigue are key functions affected by anemia, RBC management will be vital for human missions landing on extraterrestrial worlds without medical supervision. While a variety of hypothetical causes (e.g., RBC dysfunction, decreased production, sequestration or increased destruction) have been proposed for space anemia, the physiologic mechanisms are not fully established5, and studying these mechanisms in space is challenging. Hemolysis releases hemoglobin, and heme rings are broken down by heme oxygenases6. Each heme molecule produces one ferrous iron, one carbon monoxide (CO) and one biliverdin molecule. In basal conditions, approximately 85% of endogenously produced CO arises from hemoglobin6. The quantification of CO molecules eliminated is therefore a direct measure of hemolysis. Recently developed methods to precisely quantify endogenous CO now permit the measurement of hemolysis in space7. Using these methods, 20 participants showed increased hemolysis (by an average of 23%) throughout 60 days of the antiorthostatic bed-rest microgravity analogue8. These findings suggested that increased hemolysis may be an important primary effect of the microgravity analogue, a hypothesis never tested in space. We therefore measured hemolysis markers in breath and blood samples from astronauts preflight, four times inflight and up to 1 year after their 6-month missions to the International Space Station (ISS)... (SNIP)

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