Key result
Simulated galactic cosmic rays drive a ~2-fold increase in cardiac fibrosis and elevate SBP in rats.
Why the study?
The potential impact of galactic cosmic rays on the risk of developing degenerative cardiovascular disease during long-duration space exploratory missions was a major unknown.
Does exposure to multiple ion beams representative of galactic cosmic rays cause cardiovascular disease in mature male rats?
Does exposure to multiple ion beams representative of galactic cosmic rays cause cardiovascular disease in mature male rats?
Effect estimate: 2-fold increase
p-value: p=<0.001
Exposure to a combination of three high-energy ion beams representative of galactic cosmic rays induces perivascular cardiac fibrosis and increases systolic blood pressure in a rat model.
May signal cardiovascular risks for spaceflight; leaves open human translation.
Long-duration space exploratory missions to the Earth's moon and the planet Mars are actively being planned. Such missions will require humans to live for prolonged periods beyond low earth orbit where astronauts will be continuously exposed to high energy galactic cosmic rays (GCRs). A major unknown is the potential impact of GCRs on the risks of developing degenerative cardiovascular disease, which is a concern to NASA. A ground-based rat model has been used to provide a detailed characterization of the risk of long-term cardiovascular disease from components of GCRs at radiation doses relevant to future human missions beyond low earth orbit. Six month old male WAG/RijCmcr rats were irradiated at a ground-based charged particle accelerator facility with high energy ion beams broadly representative of GCRs: protons, silicon and iron. Irradiation was given either as a single ion beam or as a combination of three ion beams. For the doses used, the single ion beam studies did not show any significant changes in the known cardiac risk factors and no evidence of cardiovascular disease could be demonstrated. In the three ion beam study, the total cholesterol levels in the circulation increased modestly over the 270 day follow up period, and inflammatory cytokines were also increased, transiently, 30 days after irradiation. Perivascular cardiac collagen content, systolic blood pressure and the number of macrophages found in the kidney and in the heart were each increased 270 days after irradiation with 1.5 Gy of the three ion beam grouping. These findings provide evidence for a cardiac vascular pathology and indicate a possible threshold dose for perivascular cardiac fibrosis and increased systemic systolic blood pressure for complex radiation fields during the 9 month follow up period. The development of perivascular cardiac fibrosis and increased systemic systolic blood pressure occurred at a physical dose of the three ion beam grouping (1.5 Gy) that was much lower than that required to show similar outcomes in earlier studies with the same rat strain exposed to photons. Further studies with longer follow up periods may help determine whether humans exposed to lower, mission-relevant doses of GCRs will develop radiation-induced heart disease.
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Lenarczyk et al. (2023) studied Radiation-induced cardiovascular disease. Three sequentially delivered, rapidly switched beams of high energy ions (protons, 28Si, 56Fe) vs. Sham irradiation was evaluated on Perivascular cardiac collagen content (2-fold increase, p=<0.001). Exposure to 1.5 Gy of multiple ion beams representative of galactic cosmic rays caused a two-fold increase in perivascular cardiac fibrosis and elevated systolic blood pressure in mature male rats.
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