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P2X receptor characterization and IL‐1/IL‐1Ra release from human endothelial cells
Author(s) -
Wilson H L,
Varcoe R W,
Stokes L,
Holland K L,
Francis S E,
Dower S K,
Surprenant A,
Crossman D C
Publication year - 2007
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1038/sj.bjp.0707213
Subject(s) - umbilical vein , cytokine , receptor , receptor antagonist , flow cytometry , inflammation , interleukin , interleukin 8 , intracellular , microbiology and biotechnology , biology , pharmacology , chemistry , immunology , antagonist , in vitro , biochemistry
Background and purpose: The pro‐inflammatory cytokine, interleukin‐1β (IL‐1β), has been implicated in the pathogenesis of atherosclerosis, potentially via its release from vascular endothelium. Endothelial cells (EC) synthesize IL‐1β in response to inflammatory stimuli, but the demonstration and mechanism of release of IL‐1 from ECs remains unclear. In activated monocytes, efficient release of bioactive IL‐1β occurred via activation of ATP‐gated P2X 7 receptors (P2X 7 Rs). Activation of P2X 7 R in ECs from human umbilical vein (HUVECs) released IL‐1 receptor antagonist (IL‐1Ra). The purpose of this study was to provide a quantitative investigation of P2XR expression and function, in parallel with IL‐1β and IL‐1Ra synthesis, processing and release, in HUVECs under pro‐inflammatory conditions. Experimental approach: Quantitative RT‐PCR, immunoblotting, ELISA, flow cytometry, and whole‐cell patch clamp recordings were used to determine protein expression and receptor function. IL‐8‐luciferase‐reporter was used as an IL‐1 sensitive bioassay. Key results: HUVECs expressed P2X 4 R and P2X 7 R subtypes and both were significantly up‐regulated under inflammatory conditions. P2X 7 R currents were increased 3‐fold by inflammatory stimuli, whereas no P2X 4 R‐mediated currents were detected. Caspase‐1, but not IL‐1β, was present intracellularly under basal conditions; inflammatory stimuli activated the synthesis of intracellular pro‐IL‐1β and increased caspase‐1 levels. Activation of P2X 7 Rs resulted in low‐level release of bioactive IL‐1β and simultaneous release of IL‐1Ra. The net biological effect of release was anti‐inflammatory. Conclusions and implications: Endothelial P2X 7 Rs induced secretion of both pro‐ and anti‐inflammatory IL‐1 receptor ligands, the balance of which may provide a means for altering the inflammatory state of the arterial vessel wall. British Journal of Pharmacology (2007) 151 , 96–108. doi: 10.1038/sj.bjp.0707213