Nitric Oxide Inhibits ATP Release from Erythrocytes

Abstract

Erythrocytes have been reported to release ATP from intracellular stores into the surrounding environment in response to decreased oxygen tension and mechanical deformation. This erythrocyte-derived ATP can then act on purinergic receptors present on vascular endothelial cells, resulting in the synthesis and bidirectional release of nitric oxide (NO). NO released abluminally produces relaxation of vascular smooth muscle, thereby increasing vascular caliber, leading to a decrease in deformation-induced ATP release from erythrocytes. In contrast, NO released into the vascular lumen could interact directly with formed elements in the blood, including the erythrocyte. Here, we investigate the hypothesis that NO functions in a negative-feedback manner to inhibit ATP release from the erythrocyte. The NO donor N-(2-aminoethyl)-N-(2-hydroxy-2-nitrosohydrazino)-1,2-ethylenediamine (spermine NONOate) decreased total pulmonary resistance in a dose-dependent manner when administered to isolated perfused rabbit lungs. ATP release from rabbit erythrocytes in response to decreased oxygen tension or mechanical deformation was inhibited by preincubation with spermine NONOate (100 nM, 20 min). Importantly, incubating rabbit erythrocytes with spermine (100 nM, 20 min), the polyamine remaining after the liberation of NO from spermine NONOate, did not affect decreased oxygen tension-induced ATP release. Mechanical deformation-induced ATP release was also inhibited when erythrocytes were preincubated with spermine NONOate. However, NO-depleted spermine NONOate had no effect on mechanical deformation-induced ATP release from rabbit erythrocytes. These data provide support for the hypothesis that NO inhibits ATP release from erythrocytes, thereby identifying an additional role of NO in the regulation of vascular resistance.The erythrocyte, via its ability to release ATP, has been identified as a potential regulator of vascular resistance (Ellsworth et al., 1995;Sprague et al., 1996). The release of ATP from intracellular stores into the surrounding environment is reported to occur in response to distinct physiological stimuli. One such stimulus, mechanical deformation, can occur as the erythrocyte passes through small resistance vessels and capillaries of the microcirculation or in response to increases in linear flow velocity. Sprague et al. (1996) reported that both rabbit and human erythrocytes release ATP in response to mechanical deformation produced by passage of erythrocytes through filters with an average pore size of 5 m. Human and hamster erythrocytes have also been reported to release ATP in response to decreased oxygen tension and/or reduced pH (Bergfeld and Forrester, 1992;Ellsworth et al., 1995), environments the erythrocyte would encounter as it traverses skeletal muscle and other oxygenconsuming organs.Once released from the erythrocyte into the circulation, ATP can activate purinergic receptors, specifically those of the P 2y subfamily, present on the vascular endothelium, resulting in the synthesis and release...

Purinergic signaling in the lumen of a normal nephron and in remodeled PKD encapsulated cysts

“…Schwiebert et al also documented the appearance of P2X 7 to a significant degree at the mRNA level in primary cultures of human polycystic kidney disease (PKD) cells versus non-PKD human renal epithelial cell primary cultures as controls [101]. In a collaborative study with McCoy and Stanton, they showed expression of P2Y 1 and P2Y 2 as well as P2X 3 and P2X 4 in mIMCD-K2 cells [94]. In studies in mouse DCT cells by Quamme and coworkers and by Wingo and coworkers in mIMCD-3 cells, expression and function of both P2Y and P2X purinoceptors was concluded [92,93].…”

“…Within the glomerular capillaries, red and white blood cells alike are squeezed through these small capillaries and deformed in the process. Sprague and coworkers studied deformationinduced adenosine 5′ triphosphate (ATP) release in erythrocytes for many years, as have others [1][2][3]. With regard to mechanically released ATP, ATP and their metabolites are present in plasma at finite amounts, and the amount of nucleotides and nucleosides freely filtered at the glomerulus is likely to be low to negligible.…”

Homeostasis of Extracellular ATP in Human Erythrocytes

“…Several reports published over recent years have shown that an increase in intracellular cyclic AMP (cAMP) concentration triggered ATP release from human erythrocytes (6,7). Receptor-mediated ATP release in human erythrocytes involves activation of heterotrimeric G proteins G s or G i/o (3,8,9). Regarding the G s pathway, activation of ␤-adrenergic receptors by various agonists was reported to stimulate adenylyl cyclase, with concomitant increases in cAMP levels and protein kinase A activity (6,10).…”

“…All of these represent physiological conditions to which erythrocytes are exposed in the vasculature, e.g. when passing through constricted vessels or in the contracting striated muscle (3). Once in the extracellular medium, extracellular ATP (ATPe) 5 can trigger different cellular responses by interacting with P receptors on the cell surface while at the same time its concentration is controlled by the activities of one or more ectonucleotidases (4,5).…”

“…2 CONICET postdoctoral fellowship holder. 3 Career researchers from CONICET. 4 To whom correspondence should be addressed: carrying ions and signaling molecules between the cytoplasm and extracellular space (14).…”