The most recent American Association of Blood Banks survey found that 40,000 units of blood are required daily for general medicine, hematology/oncology, surgery, and for accident and trauma victims. While blood transfusions are an extremely important component of critical healthcare, complications associated with transfusion of blood components still exist. It is well-established that the red blood cell (RBC) undergoes many physical and chemical changes during storage. Increased oxidative stress, formation of advanced glycation endproducts, and microparticle formation are all known to occur during RBC storage. Furthermore, it is also known that patients who receive a transfusion have reduced levels of available nitric oxide (NO), a major determinant in blood flow. However, the origin of this reduced NO bioavailability is not completely understood. Here, we show that a simple modification to the glucose concentration in the solutions used to process whole blood for subsequent RBC storage results in a remarkable change in the ability of these cells to stimulate NO. In a controlled in vitro microflow system, we discovered that storage of RBCs in normoglycemic versions of standard storage solutions resulted in RBC-derived ATP release values 4 weeks into storage that were significantly greater than day 1 release values for those RBCs stored in conventional solutions. During the same storage duration, microfluidic technologies enabled measurements of endothelium-derived NO that were stimulated by the ATP release from the stored RBCs. In comparison to currently accepted processing solutions, the NO production increased by more than 25% in the presence of the RBCs stored in the normoglycemic storage solutions. Control experiments using inhibitors of ATP release from the RBCs, or ATP binding to the endothelium, strongly suggest that the increased NO production by the endothelium is directly related to the ability of the stored RBCs to release ATP. We anticipate these findings to represent a starting point in controlling glucose levels in solutions used for blood component storage, especially considering that current solutions contain glucose at levels that are nearly 20-fold greater than blood glucose levels of a healthy human, and even 10-fold greater than levels found in diabetic bloodstreams.

C-peptide does not affect NO production in bPAECs directly but can impact NO production through an erythrocyte-mediated mechanism. Furthermore, in the absence of Zn(2+), C-peptide does not stimulate this NO production directly or indirectly. These results suggest that C-peptide, in the presence of Zn(2+), may be a determinant in purinergic receptor signalling via its ability to stimulate the release of ATP from erythrocytes.

■ AbstractInspired by previous reports, our group has recently demonstrated that C-peptide exerts beneficial effects upon interactions with red blood cells (RBCs). These effects can be measured in RBCs obtained from animal models of both type 1 diabetes and type 2 diabetes, though to different extents. To date, the key metrics that have been measured involving C-peptide and RBCs include an increase in glucose uptake by these cells and a subsequent increase in adenosine triphosphate (ATP) release. Importantly, to date, our group has only been able to elicit these beneficial effects when the C-peptide is prepared in the presence of Zn 2+ . The C-peptide-induced release of ATP is of interest when considering that ATP is a purinergic signaling molecule known to stimulate the production of nitric oxide (NO) in the endothelium and in platelets. This NO production has been shown to participate in smooth muscle relaxation and subsequent vessel dilation. Furthermore, NO is a well-established platelet inhibitor. The objective of this review is to provide information pertaining to C-peptide activity on RBCs. Special attention is paid to the necessity of Zn 2+ activation, and the origin of that activation in vivo. Finally, a mechanism is proposed that explains how C-peptide is exerting its effects on other cells in the bloodstream, particularly on endothelial cells and platelets, via its ability to stimulate the release of ATP from RBCs.