Vascular
inflammation is an important factor in the pathophysiology of
cardiovascular diseases, such as
atherosclerosis. Changes in the extracellular
nucleotide and in particular
adenosine catabolism may alter a chronic
inflammation and endothelial activation. This study aimed to evaluate the relation between vascular ecto-
adenosine deaminase (eADA) activity and endothelial activation in humans and to analyze the effects of LPS-mediated
inflammation on this activity as well as mechanisms of its increase. Moreover, we investigated a therapeutic potential of ADA inhibition by deoxycofromycin (dCF) for endothelial activation. We demonstrated a positive correlation of vascular eADA activity and ADA1
mRNA expression with endothelial activation parameters in humans with
atherosclerosis. The activation of vascular eADA was also observed under LPS stimulation in vivo along with endothelial activation, an increase in markers of
inflammation and alterations in the
lipid profile of a rat model. Ex vivo and in vitro studies on human specimen demonstrated that at an early stage of vascular pathology, eADA activity originated from activated endothelial cells, while at later stages also from an inflammatory infiltrate. We proposed that LPS-stimulated increase in endothelial
adenosine deaminase activity could be a result of IL-6/JAK/STAT pathway activation, since the lack of
IL-6 in mice was associated with lower vascular and plasma eADA activities. Furthermore, the inhibitors of JAK/STAT pathway decreased LPS-stimulated
adenosine deaminase activity in endothelial cells. We demonstrated that cell surface eADA activity could be additionally regulated by transcytosis pathways, as exocytosis inhibitors including
lipid raft inhibitor, methyl-β-
cyclodextrin decreased LPS-induced eADA activity. This suggests that
cholesterol-dependent
protein externalization mediated by
lipid rafts could be an important factor in the eADA increase. Moreover, endocytosis inhibitors and exocytosis activators increased this activity on the cell surface. Furthermore, the inhibition of
adenosine deaminase in endothelial cells in vitro attenuated LPS-mediated
IL-6 release and soluble
ICAM-1 and
VCAM-1 concentration in the incubation medium through the restoration of the extracellular
adenosine pool and
adenosine receptor-dependent pathways. This study demonstrated that the vascular endothelial eADA activity remains under control of inflammatory mediators acting through JAK/STAT pathway that could be further modified by dyslipidemic-dependent exocytosis and transcytosis pathways. Inhibition of eADA blocked endothelial activation suggesting a crucial role of this
enzyme in the control of vascular
inflammation. This supports the concept of eADA targeted vascular protection
therapy.