Reduced deformability contributes to impaired deoxygenation‐induced ATP release from red blood cells of older adult humans

Key points Red blood cells (RBCs) release ATP in response to deoxygenation, which can increase blood flow to help match oxygen supply with tissue metabolic demand. This release of ATP is impaired in RBCs from older adults, but the underlying mechanisms are unknown. In this study, improving RBC deformability in older adults restored deoxygenation‐induced ATP release, whereas decreasing RBC deformability in young adults reduced ATP release to the level of that of older adults. In contrast, treating RBCs with a phosphodiesterase 3 inhibitor did not affect ATP release in either age group, possibly due to intact intracellular signalling downstream of deoxygenation as indicated by preserved cAMP and ATP release responses to pharmacological Gi protein activation in RBCs from older adults. These findings are the first to demonstrate that the age‐related decrease in RBC deformability is a primary mechanism of impaired deoxygenation‐induced ATP release, which may have implications for treating impaired vascular control with advancing age. In response to haemoglobin deoxygenation, red blood cells (RBCs) release ATP, which binds to endothelial purinergic receptors and stimulates vasodilatation. This ATP release is impaired in RBCs from older vs. young adults, but the underlying mechanisms are unknown. Using isolated RBCs from young (24 ± 1 years) and older (65 ± 2 years) adults, we tested the hypothesis that age‐related changes in RBC deformability (Study 1) and cAMP signalling (Study 2) contribute to the impairment. RBC ATP release during normoxia (PO2 ∼112 mmHg) and hypoxia (PO2 ∼20 mmHg) was quantified with the luciferin–luciferase technique following RBC incubation with Y‐27632 (Rho‐kinase inhibitor to increase deformability), diamide (cell‐stiffening agent), cilostazol (phosphodiesterase 3 inhibitor), or vehicle control. The mean change in RBC ATP release from normoxia to hypoxia in control conditions was significantly impaired in older vs. young (∼50% vs. ∼120%; P