Neutrophil-derived 5′-Adenosine Monophosphate Promotes Endothelial Barrier Function via CD73-mediated Conversion to Adenosine and Endothelial A2B Receptor Activation

Abstract

During episodes of inflammation, polymorphonuclear leukocyte (PMN) transendothelial migration has the potential to disturb vascular barrier function and give rise to intravascular fluid extravasation and edema. However, little is known regarding innate mechanisms that dampen fluid loss during PMN-endothelial interactions. Using an in vitro endothelial paracellular permeability model, we observed a PMN-mediated decrease in endothelial paracellular permeability. A similar decrease was elicited by cell-free supernatants from activated PMN (FMLP 10−6 M), suggesting the presence of a PMN-derived soluble mediator(s). Biophysical and biochemical analysis of PMN supernatants revealed a role for PMN-derived 5′-adenosine monophosphate (AMP) and its metabolite, adenosine, in modulation of endothelial paracellular permeability. Supernatants from activated PMN contained micromolar concentrations of bioactive 5′-AMP and adenosine. Furthermore, exposure of endothelial monolayers to authentic 5′-AMP and adenosine increased endothelial barrier function more than twofold in both human umbilical vein endothelial cells and human microvascular endothelial cells. 5′-AMP bioactivity required endothelial CD73-mediated conversion of 5′-AMP to adenosine via its 5′-ectonucleotidase activity. Decreased endothelial paracellular permeability occurred through adenosine A2B receptor activation and was accompanied by a parallel increase in intracellular cAMP. We conclude that activated PMN release soluble mediators, such as 5′-AMP and adenosine, that promote endothelial barrier function. During inflammation, this pathway may limit potentially deleterious increases in endothelial paracellular permeability and could serve as a basic mechanism of endothelial resealing during PMN transendothelial migration.

IFN‐β regulates CD73 and adenosine expression at the blood–brain barrier

“…CD73 is a key regulator of extracellular ATP metabolism and inflammation as it shifts the balance from pro-inflammatory ATP and prothrombotic ADP to anti-inflammatory adenosine by converting AMP into adenosine. Adenosine is a known anti-inflammatory agent, which promotes endothelial integrity and has neuroprotective properties [17,[22][23][24].…”

“…CD73 modulates the extent of immune and inflammatory responses in vitro and in vivo. These effects are mediated via its enzymatic capability to hydrolyse adenosine monophosphate 5 0 -AMP into adenosine, an immunomodulatory purine compound [16][17][18].We have recently shown that CD73 is upregulated on vascular endothelium in a time-and dose-dependent manner after treatment with type-I IFN-a in vitro and in vivo [19], but how IFN-b affects CD73 in brain EC and in the context of MS has never been studied before. As adenosine, the end product of the CD73 catalytic reaction, has both anti-inflammatory and neuroprotective effects, we hypothesized that IFN-b might also exert some of its beneficial effects on MS-disease pathology by regulating CD73-mediated adenosine production.…”

“…CD73 modulates the extent of immune and inflammatory responses in vitro and in vivo. These effects are mediated via its enzymatic capability to hydrolyse adenosine monophosphate 5 0 -AMP into adenosine, an immunomodulatory purine compound [16][17][18].…”

Endotoxin Activation of Macrophages Does Not Induce ATP Release and Autocrine Stimulation of P2 Nucleotide Receptors

“…This suggests that nucleotides used for purinergic regulation of macrophages at an inflammatory locus are released from other cells, such as neutrophils, damaged tissues, or bacteria. Neutrophils have been reported to release relatively high amounts of nucleotides during activation by formyl peptides (45). A recent study also described the release of ATP from J774 macrophage cultures infected with Mycobacterium tuberculosis (8).…”

Role of A2A‐adenosine receptor activation for ATP‐mediated coronary vasodilation in guinea‐pig isolated heart

“…Guibert et al (1998) reported that inhibition of ectonucleotidase activity reduced the A 2A -AdoR-mediated dilation of endothelium-denuded portal vein strips caused by ATP. Similarly, inactivation of ectonucleotidase by monoclonal antibodies reduced the A 2B -AdoRmediated decrease of endothelial permeability caused by adenine nucleotides (Lennon et al, 1998). Furthermore, administration of the ecto-5'-nucleotidase inhibitor AOPCP reduced the formation of adenosine from exogenously administered ATP by the isolated perfused guinea-pig heart (Borst & Schrader, 1991).…”