P2X receptor characterization and IL-1/IL-1Ra release from human endothelial cells.

Area of Science:

• Cardiovascular Biology
• Immunology
• Cellular Physiology

Background:

• Interleukin-1beta (IL-1beta) is implicated in atherosclerosis pathogenesis.
• Endothelial cells (ECs) synthesize IL-1beta, but its release mechanism from ECs is unclear.
• ATP-gated P2X7 receptors (P2X7Rs) mediate IL-1beta release in monocytes.

Purpose of the Study:

• Quantify P2XR expression and function in human umbilical vein endothelial cells (HUVECs).
• Investigate IL-1beta and IL-1 receptor antagonist (IL-1Ra) synthesis, processing, and release.
• Examine these processes under pro-inflammatory conditions.

Main Methods:

• Quantitative RT-PCR, immunoblotting, ELISA, flow cytometry, and whole-cell patch clamp recordings.
• Assessed protein expression and receptor function.
• Utilized an IL-8-luciferase-reporter bioassay for IL-1 sensitivity.

Main Results:

• HUVECs express P2X4R and P2X7R, both upregulated by inflammation.
• Inflammatory stimuli increased P2X7R currents but not P2X4R currents.
• Inflammatory stimuli activated intracellular pro-IL-1beta synthesis and increased caspase-1.
• P2X7R activation led to low-level release of bioactive IL-1beta and IL-1Ra.
• The net effect of this release was anti-inflammatory.

Conclusions:

• Endothelial P2X7Rs induce secretion of both pro- and anti-inflammatory IL-1 receptor ligands.
• The balance of released ligands may modulate the inflammatory state of the arterial vessel wall.