NO negatively regulates cell surface expression of CD73 in sheared endothelial cells

Abstract

Both NO and adenosine produced from eNOS and cell surface CD73 in endothelial cells (EC), respectively, are potent vasodilator and anti‐inflammatory molecules. Adenosine increases eNOS expression and activity in EC. We examined if NO regulates cell surface expression of CD73 in EC under shear stress.In human coronary artery EC, 24‐hour exposure to laminar shear stress (LS; 15 dyne/cm2) increased CD73 mRNA expression (2.1±0.3‐fold vs. static condition, p<0.05, n=10–17), whereas oscillatory shear (OS; ± 5 dyne/cm2) had no effect (0.9±0.2 fold, n=6). However, there was no difference in total CD73 protein levels between LS and OS, since LS caused cleavage of CD73 into the medium (static 22±0.3 and LS 37±0.2‐fold increase vs. fresh medium density, n=4) leading to less surface CD73 expression. Addition of an NO donor DETA‐NONOate abolished surface CD73. This was consistent with less surface expression of CD73 in LS‐exposed regions of mouse aortas than in OS‐regions. On the other hand, an NOS inhibitor LNAME augmented the mRNA up‐regulation (3.7±1.1 fold, n=5) and total and surface protein expressions in LS‐exposed EC. This was consistent with increased CD73 protein expression in eNOS−/− mouse aortas.These results indicate that NO negatively regulates EC surface expression of CD73 by down‐regulating the mRNA expression and by facilitating cleavage of surface CD73 protein under LS.