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Exosomes, abundant in blood, deliver various molecules to recipient cells. Endothelial cells are directly exposed to circulating substances. The purpose of this study is to explore the response of endothelial cells to serum exosomes (SExos) and the implications of SExos in diabetes-associated vasculopathy.
The exosomes from the db/m+mouse serum were purified and characterized by ultracentrifugation, transmission electronic microscopy as well as Nano C particle analyzer. Confocal microscopy was used to observe the uptake of SExos as well as NO generation by endothelium. Comparative proteomics was performed to analyze the different protein profiles in db/db or db/m+ mouse SExos. The qPCR and Western blotting were carried out to detected miRNA and protein expression. Adeno-associated viruses were constructed to mediate arginase 1or arginase1 shRNA ectopic over-expression or knockdown in primary endothelial cells and/or mouse aortas. Wire myograph system and pressure myograph system were utilized to analysis the endothelium-dependent relaxation in mouse conduit arteries and resistant arteries.
In the present study, SExos from diabetic db/db mouse were taken up by aortic endothelial cells, which severely impaired endothelial function in non-diabetic db/m+ mice. The exosomal proteins but not RNAs account for db/db SExos-induced endothelial dysfunction. Comparative proteomics analysis showed significant increase of arginase 1 in db/db SExos. Silence or overexpression of arginase 1 confirmed its essential role in db/dbSExos-induced endothelial dysfunction.
This study is probably the first demonstration that SExos deliver arginase 1 to endothelial cells, representing a novel cellular mechanism during development of diabetic endothelial dysfunction. The results expand the scope of blood-borne substances that monitor vascular homeostasis.