Spaceflight‐induced alterations in cerebral artery vasoconstrictor, mechanical, and structural properties: implications for elevated cerebral perfusion and intracranial pressure

Abstract

Evidence indicates that cerebral blood flow is both increased and diminished in astronauts on return to Earth. Data from ground-based animal models simulating the effects of microgravity have shown that decrements in cerebral perfusion are associated with enhanced vasoconstriction and structural remodeling of cerebral arteries. Based on these results, the purpose of this study was to test the hypothesis that 13 d of spaceflight [Space Transportation System (STS)-135 shuttle mission] enhances myogenic vasoconstriction, increases medial wall thickness, and elicits no change in the mechanical properties of mouse cerebral arteries. Basilar and posterior communicating arteries (PCAs) were isolated from 9-wk-old female C57BL/6 mice for in vitro vascular and mechanical testing. Contrary to that hypothesized, myogenic vasoconstrictor responses were lower and vascular distensibility greater in arteries from spaceflight group (SF) mice (n=7) relative to ground-based control group (GC) mice (n=12). Basilar artery maximal diameter was greater in SF mice (SF: 236±9 μm and GC: 215±5 μm) with no difference in medial wall thickness (SF: 12.4±1.6 μm; GC: 12.2±1.2 μm). Stiffness of the PCA, as characterized via nanoindentation, was lower in SF mice (SF: 3.4±0.3 N/m; GC: 5.4±0.8 N/m). Collectively, spaceflight-induced reductions in myogenic vasoconstriction and stiffness and increases in maximal diameter of cerebral arteries signify that elevations in brain blood flow may occur during spaceflight. Such changes in cerebral vascular control of perfusion could contribute to increases in intracranial pressure and an associated impairment of visual acuity in astronauts during spaceflight.

Up-regulation of ryanodine receptor expression increases the calcium-induced calcium release and spontaneous calcium signals in cerebral arteries from hindlimb unloaded rats

“…In MCA, we have observed the opposite effect: an increase of RyR1 expression correlated with the suspected increase of blood loading. Very recently, it has been demonstrated that vasoconstriction was decreased in basilar arteries from mice exposed to μG during spaceflight [41]. However, in HU animals our results are all clearly in favor of an increase in vascular reactivity.…”

28-Day hindlimb unweighting reduces expression of Rho kinase and inhibits its effects in femoral artery of rat

“…Animal studies applying mice experiencing real spaceflight [28] and tailsuspended hindlimb unweighting (HU) rats [10,18,24,34,35] also give support to the involvement of microgravity-induced vascular responsiveness adaptations in postflight orthostatic intolerance. However, mechanisms underlying the aforementioned abnormal vascular responsiveness have not been fully elucidated.…”

Increased intracranial pressure in mini-pigs exposed to simulated solar particle event radiation

“…During a long duration space mission, astronauts are expected to have greater exposure to cosmic radiation at a steady, but low, dose rate, compared to SPE radiation that delivers a high dose in shorter time periods [32]. Other space flight conditions/stressors, such as elevated cabin carbon dioxide concentrations, may also be a confounding contributor to changes in cerebral blood flow and ICP [33, 34]. …”