Diamide decreases deformability of rabbit erythrocytes and attenuates low oxygen tension-induced ATP release

Abstract

Exposure of erythrocytes to reduced oxygen (O2) tension activates the heterotrimeric G protein Gi, resulting in accumulation of cAMP and release of ATP. The mechanism by which exposure of erythrocytes to reduced O2 tension activates Gi is not known. Here we investigate the hypothesis that, in rabbit erythrocytes, ATP release in response to exposure to reduced O2 tension requires membrane deformation. If this hypothesis is correct, then decreasing the deformability of the erythrocyte membrane should decrease the release of ATP in response to reduced O2 tension. We report that treating erythrocytes with diamide, a compound that decreases erythrocyte deformability, inhibits low O2 tension induced ATP release. Treating erythrocytes with diamide does not, however, interfere with cAMP accumulation or ATP release in response to a direct activator of Gi (mastoparan 7) or in response to receptor mediated activation of Gs (the prostacyclin analog, iloprost). These results demonstrate that diamide (100 μM) does not directly inhibit the signaling pathways for ATP release from rabbit erythrocytes and support the hypothesis that deformability of the erythrocyte membrane is required for low O2 tension-induced ATP release from these cells.

Low O2-induced ATP release from erythrocytes of humans with type 2 diabetes is restored by physiological ratios of C-peptide and insulin

“…However, studies of the deformability of erythrocytes from humans with type 2 diabetes have yielded conflicting results (4,8,37,49). This is important, because we and others have demonstrated that reduced erythrocyte deformability can inhibit low O 2 -induced ATP release (45). Here, we examined the deformability of erythrocytes of healthy humans and humans with type 2 diabetes in the absence and presence of insulin and C-peptide.…”

A selective phosphodiesterase 3 inhibitor rescues low Po2-induced ATP release from erythrocytes of humans with type 2 diabetes: implication for vascular control

“…5) (13, 23, 26 -28). Under this construct, exposure of erythrocytes to reduced O 2 results in hemoglobin desaturation and an associated conformational change in the hemoglobin molecule (17,34). Although the mechanism is not fully understood, this change in hemoglobin saturation/conformation results in activation of the heterotrimeric G protein G i and increases in cAMP (34).…”

Simvastatin and GGTI-2133, a geranylgeranyl transferase inhibitor, increase erythrocyte deformability but reduce low O2tension-induced ATP release

“…The finding that simvastatin treatment inhibited low O 2 tension-induced ATP release was unexpected. Previous reports (42,46) using healthy human erythrocytes have shown that there is a link between low O 2 tensioninduced ATP release and erythrocyte deformability. Thus, while Y-27632 increased both erythrocyte deformability and low O 2 tension-induced ATP release, erythrocytes stiffened with the cytoskeletal crosslinker diamide were less deformable and had impaired low O 2 tension-induced ATP release (42,46).…”

“…Such a mechanism is consistent with studies (16,37) in which shear stress was shown to activate G i in other cell types and suggests that reduced membrane deformability would decrease low O 2 tension-induced activation of G i . Importantly, previous studies have shown that reduced membrane deformability inhibits low O 2 tension-induced ATP release from erythrocytes (42,46), whereas increased deformability of these cells augments ATP release in response to this stimulus (46).…”