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

Abstract

Erythrocytes, via release of ATP in areas of low oxygen (O(2)) tension, are components of a regulatory system for the distribution of perfusion in skeletal muscle ensuring optimal O(2) delivery to meet tissue needs. In type 2 diabetes (DM2), there are defects in O(2) supply to muscle as well as a failure of erythrocytes to release ATP. The goal of this study was to ascertain if a phosphodiesterase 3 (PDE3) inhibitor, cilostazol, would rescue low O(2)-induced ATP release from DM2 erythrocytes and, thereby, enable these cells to dilate isolated erythrocyte-perfused skeletal muscle arterioles exposed to decreased extraluminal O(2). Erythrocytes were obtained from healthy humans (HH; n = 12) and humans with DM2 (n = 17). We determined that 1) PDE3B is similarly expressed in both groups, 2) mastoparan 7 (G(i) activation) stimulates increases in cAMP in HH but not in DM2 erythrocytes, and 3) pretreatment of DM2 erythrocytes with cilostazol resulted in mastoparan 7-induced increases in cAMP not different from those in HH cells. Most importantly, cilostazol restored the ability of DM2 erythrocytes to release ATP in response to low O(2). In contrast with perfusion with HH erythrocytes, isolated hamster retractor muscle arterioles perfused with DM2 erythrocytes constricted in response to low extraluminal PO(2). However, in the presence of cilostazol (100 μM), DM2 erythrocytes induced vessel dilation not different from that seen with HH erythrocytes. Thus rescue of low O(2)-induced ATP release from DM2 erythrocytes by cilostazol restored the ability of erythrocytes to participate in the regulation of perfusion distribution in skeletal muscle.

The Age-Old Tale of Skeletal Muscle Vasodilation: New Ideas Regarding Erythrocyte Dysfunction and Intravascular ATP in Human Physiology

“…We openly acknowledge this limitation in our manuscript and are working to develop a selective antagonist. However, with respect to hypoxic vasodilation in resistance vessels, a number of important observations support our data: (1) perfusion of isolated resistance vessels with a buffer lacking erythrocytes fails to elicit vasodilation when extraluminal oxygen tension is reduced 11 ; (2) perfusion of isolated skeletal muscle resistance vessels with erythrocytes not capable of releasing ATP does not elicit vasodilation in response to this stimulus 12,13 ; (3) rescuing low O 2 -induced ATP release from diseased erythrocytes restores vasodilation when extraluminal oxygen tension is reduced. 12 These studies to date have not been performed within contracting muscle, and although this would be technically difficult, is certainly an area in need of future investigation.…”

“…However, with respect to hypoxic vasodilation in resistance vessels, a number of important observations support our data: (1) perfusion of isolated resistance vessels with a buffer lacking erythrocytes fails to elicit vasodilation when extraluminal oxygen tension is reduced 11 ; (2) perfusion of isolated skeletal muscle resistance vessels with erythrocytes not capable of releasing ATP does not elicit vasodilation in response to this stimulus 12,13 ; (3) rescuing low O 2 -induced ATP release from diseased erythrocytes restores vasodilation when extraluminal oxygen tension is reduced. 12 These studies to date have not been performed within contracting muscle, and although this would be technically difficult, is certainly an area in need of future investigation. In line with the authors' suggestion, we, too, would support in vivo animal experimentation aimed at deciphering the critical role of red cells to vasodilation through use of pannexin-1 knockout, but it must be acknowledged that ATP release is not universal to a single channel, and impaired ATP release appears to depend on the specific signaling pathway.…”

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

“…Importantly, it has been reported that low O 2 -induced ATP release from erythrocytes of humans with type 2 diabetes is severely impaired (38,42,44). Moreover, these cells do not stimulate dilation of isolated, perfused skeletal muscle arterioles exposed to reduced extraluminal O 2 , a model of increased tissue O 2 Fig.…”

“…In support of this hypothesis, it was reported that isolated skeletal muscle arterioles perfused with erythrocytes from healthy humans-cells that respond to low O 2 with ATP release-dilate when exposed to reduced, extraluminal O 2 , a model of increased tissue O 2 need (11,43). In contrast, low O 2 -induced ATP release from erythrocytes from humans with type 2 diabetes is severely impaired (38,42,44), and these cells do not stimulate dilation of isolated, perfused skeletal muscle arterioles under similar conditions (42).…”

“…This release of ATP stimulates local vasodilation, which is conducted upstream to feed arterioles, thereby directing perfusion to localized tissue areas lacking adequate oxygenation (11,13,43). However, erythrocytes from humans with type 2 diabetes exhibit an impairment in the ability to release ATP in response to reduced tissue O 2 tension, which limits their participation in this important mechanism for the control of perfusion distribution (38,42,44).…”