Increased endothelial cell uptake of erythrocyte-derived extracellular vesicles carrying arginase-1 induces endothelial dysfunction in type 2 diabetes

Background Recently, we have demonstrated that red blood cells (RBCs) from individuals with type 2 diabetes (T2D-RBCs) induce endothelial dysfunction. However, the mechanism by which RBCs communicate with the vessel is unknown. Extracellular vesicles (EVs) are actively secreted by practically all cell types, including RBCs, and represent a novel mechanism of intercellular communication. However, the involvement of EVs from RBC in the development of endothelial dysfunction remains to be elucidated. Purpose This study was designed to test the hypothesis that EVs are key players in the communication and the transfer of signalling between RBCs and the vascular endothelium to induce endothelial dysfunction in T2D. Methods RBCs from T2D patients and age-matched healthy controls (H-RBCs) were incubated for 18h with Krebs-Henseleit buffer (20% haematocrit) for EV release. RBC-derived EVs in the conditioned medium were isolated using a membrane affinity column. The EVs were co-incubated with mouse aortae to evaluate endothelium-dependent relaxation and with endothelial cells for expression analysis. The uptake of the EVs by endothelial cells and their content of arginase-1 were determined. The functional involvement of arginase was investigated using pharmacological interventions and expression analyses. All animal experiments were performed according to the principles of laboratory animal care (NIH Publication no. 85-23 revised 1985) and human procedures according to the declaration of Helsinki with approval by the Swedish Ethical Review Authority. Results The uptake of EVs derived from T2D-RBCs by endothelial cells was 2-fold greater than that of EVs from H-RBCs (Fig. 1A-B). Inhibiting the uptake of EVs derived from T2D-RBCs by the addition of heparin during the co-incubation rescued the endothelial function (Fig. 1C). Arginase-1 was detected in RBC-derived EVs (Fig. 2A). Arginase-1 mRNA and protein levels were increased in endothelial cells following co-incubation with EVs derived from T2D-RBCs (Fig. 2B-D). Additionally, the increase in arginase-1 protein induced by EVs derived from T2D-RBCs in endothelial cells was observed also following mRNA silencing for arginase-1 (Fig. 2E-F). Finally, mouse aortae co-incubated with EVs derived from T2D-RBCs in the presence or absence of the arginase inhibitor 2(S)-amino-6-boronohexanoic acid significantly attenuated the impairment in endothelial function induced by EVs derived from T2D-RBCs (Fig. 2G). Conclusion Increased uptake of RBC-derived EVs by the endothelial cells is an important feature of the endothelial dysfunction induced by these EVs in T2D. In addition, these EVs carry arginase-1 protein to induce endothelial dysfunction. The mechanism underlying the increased uptake of EVs in target cells is of importance to identify in future studies, as it could lead to new treatment strategies.