Nucleotide metabolism and cell-cell interactions

Area of Science:

• Immunology
• Vascular Biology
• Cellular Biology

Background:

• Neutrophil transmigration (TEM) is crucial for inflammation but can compromise vascular barrier integrity, leading to edema.
• Neutrophil-endothelial cell interactions are key regulators of inflammatory responses and vascular permeability.
• Existing knowledge lacks understanding of endogenous mechanisms that mitigate vascular leak during TEM.

Purpose of the Study:

• To investigate innate mechanisms by which neutrophils and endothelial cells interact to dampen vascular leak during inflammation.
• To elucidate the role of adenine nucleotides and their metabolites in regulating vascular barrier function during neutrophil emigration.

Main Methods:

• Observation of polymorphonuclear leukocyte (PMN) activation and release of adenine nucleotides (ATP, AMP).
• Analysis of endothelial cell-surface enzyme metabolism of ATP and AMP via ecto-apyrase (CD39) and 5'-ecto-nucleotidase (CD73).
• Assessment of adenosine receptor activation and its downstream effects on endothelial cyclic AMP levels and junctional integrity.

Main Results:

• Activated PMNs release adenosine triphosphate (ATP) and adenosine monophosphate (AMP).
• Endothelial enzymes CD39 and CD73 metabolize released ATP and AMP into adenosine.
• Generated adenosine activates endothelial receptors, increasing cyclic AMP and resealing endothelial junctions, thus enhancing vascular barrier function.

Conclusions:

• Neutrophil-derived adenine nucleotides, metabolized by endothelial cells, activate an endogenous pathway to restore vascular barrier function.
• This neutrophil-endothelial crosstalk mechanism limits intravascular fluid loss and edema during inflammatory responses.
• The process acts as a self-limiting mechanism, with neutrophils effectively 'closing the door' after transmigration.