Alterations in Nitric Oxide‐Mediated Signals in Coronary Arteries Following Spaceflight

Abstract

Proportional cardiovascular disease mortality rates are not different between US astronauts that have flown in low Earth orbit (LEO) and those that have never flown orbital missions in space. While these data suggest that spaceflight (SF) in LEO holds nominal long‐term cardiovascular health consequences, to date the acute effect of SF on coronary artery function has not been explored. The purpose of this study was to examine murine coronary artery contractile, dilatory, and mechanical properties following SF in LEO aboard the International Space Station (ISS). Twenty C57BL/6J mice were housed in a specially designed rodent habitat and were launched to the ISS aboard a Falcon 9 rocket (Space‐X CRS‐12). Following ~33 days of SF in LEO, the Dragon capsule containing the mice splashed down in the Pacific Ocean. Within 33–41 hours of returning to Earth, the left anterior descending (LAD) coronary arteries were cleared of surrounding cardiac tissue and mounted in a Danish Myotech wire myograph. LADs were then exposed to agonists that allowed for the examination of endothelial (EC) and smooth muscle cell (SMC) function. Vivarium controls (VC), consisting of mice housed in conventional vivarium cages, and habitat controls (HC), which were housed in the same type cages as those flown on orbit and maintained under similar pCO2, temperature, humidity, and light conditions, were used for comparison. The passive pressure‐diameter relationship was not different between SF and either control. SMC‐dependent vasoconstriction to U46619, a thromboxane receptor agonist, was significantly greater in HC versus SF at only a single dose, while vasoconstriction to isosmotic KCl was unaltered. LADs from SF mice preconstricted with U46619 exhibited similar EC‐dependent vasodilation to the muscarinic receptor agonist acetylcholine when compared to VC and HC. Acetylcholine and ADPβS (a P2Y1 receptor agonist)‐mediated vasodilation were completely absent in all LADs preconstricted with KCl in the presence of the nitric oxide synthase inhibitor, L‐NAME. In vessels preconstricted with U46619 vasodilation to the EC‐dependent vasodilator ADPβS was similar between SF and both controls, with SF LADs exhibiting less dependence on nitric oxide (NO)‐mediated mechanisms as observed in the presence of L‐NAME. LADs from SF mice exhibited a right‐ward shift to the NO donor and SMC‐dependent vasodilator, DEA NONOate. Collectively, these data suggest that subtle changes in LAD function occur following spaceflight in LEO. In particular, NO‐mediated signals were the most affected, as indicated by decreased SMC sensitivity to exogenous NO. In addition, while the magnitude of vasodilation to ADPβS was unchanged, SF animals exhibited less dependence on NO‐mediated signals. These ADPβS responses suggest a shift away from the canonical NO‐mediated pathway of vasodilation. These data represent the first examination of coronary artery function following SF and suggest that function is well maintained due to subtle mechanistic adaptations.Support or Funding InformationThis work was supported by NASA Space Biology grant NNX16AC28G.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.