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Neutrophil-derived 5'-adenosine monophosphate promotes endothelial barrier function via CD73-mediated conversion to
P F Lennon1, C T Taylor, G L Stahl
1Center for Experimental Therapeutics and Reperfusion Injury, Department of Anesthesia, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA.
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.
Insights
Activated neutrophils release 5'-adenosine monophosphate (AMP) and adenosine, which enhance endothelial barrier function. This mechanism may limit fluid loss during inflammation and neutrophil migration.
Area of Science:
- Immunology
- Vascular Biology
- Cell Biology
Background:
- Inflammation involves neutrophil migration across blood vessels, potentially disrupting vascular barrier function and causing fluid leakage.
- Mechanisms that limit fluid loss during neutrophil-endothelial interactions are not well understood.
Purpose of the Study:
- To investigate innate mechanisms that dampen fluid loss during neutrophil-endothelial interactions.
- To identify soluble mediators released by activated neutrophils that modulate endothelial barrier function.
Main Methods:
- Utilized an in vitro endothelial paracellular permeability model.
- Analyzed cell-free supernatants from activated neutrophils using biophysical and biochemical methods.
- Assessed the effects of 5 eal-adenosine monophosphate (AMP) and adenosine on endothelial barrier function in human umbilical vein endothelial cells and human microvascular endothelial cells.
Main Results:
- Activated neutrophils released 5 eal-AMP and adenosine, which decreased endothelial paracellular permeability.
- Exposure to 5 eal-AMP and adenosine increased endothelial barrier function in a dose-dependent manner.
- 5 eal-AMP's effect was dependent on endothelial CD73 activity, converting it to adenosine, which activated the A2B receptor and increased intracellular cAMP.
Conclusions:
- Activated neutrophils release soluble mediators, including 5 eal-AMP and adenosine, that enhance endothelial barrier function.
- This pathway may limit excessive fluid extravasation during inflammation.
- Neutrophil-derived mediators contribute to endothelial resealing during transendothelial migration.