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Published on: August 7, 2012
Adenosine A2A receptor activation reduces hepatic ischemia reperfusion injury by inhibiting CD1d-dependent NKT cell
Courtney M Lappas1, Yuan-Ji Day, Melissa A Marshall
1Department of Pharmacology, University of Virginia, Charlottesville, VA 2290, USA.
Abstract:
Ischemia reperfusion injury results from tissue damage during ischemia and ongoing inflammation and injury during reperfusion. Liver reperfusion injury is reduced by lymphocyte depletion or activation of adenosine A2A receptors (A2ARs) with the selective agonist 4-{3-[6-amino-9-(5-ethylcarbamoyl-3,4-dihydroxy-tetrahydro-furan-2-yl)-9H-purin-2-yl]- prop-2-ynyl}-cyclohexanecarboxylic acid methyl ester (ATL146e). We show that NKT cells are stimulated to produce interferon (IFN)-gamma by 2 h after the initiation of reperfusion, and the use of antibodies to deplete NK1.1-positive cells (NK and NKT) or to block CD1d-mediated glycolipid presentation to NKT cells replicates, but is not additive to, the protection afforded by ATL146e, as assessed by serum alanine aminotransferase elevation, histological necrosis, neutrophil accumulation, and serum IFN-gamma elevation. Reduced reperfusion injury observed in RAG-1 knockout (KO) mice is restored to the wild-type (WT) level by adoptive transfer of NKT cells purified from WT or A2AR KO mice but not IFN-gamma KO mice. Additionally, animals with transferred A2AR-/- NKT cells are not protected from hepatic reperfusion injury by ATL146e. In vitro, ATL146e potently inhibits both anti-CD3 and alpha-galactosylceramide-triggered production of IFN-gamma by NKT cells. These findings suggest that hepatic reperfusion injury is initiated by the CD1d-dependent activation of NKT cells, and the activation of these cells is inhibited by A2AR activation.
Insights
Hepatic reperfusion injury involves NKT cell activation, which can be inhibited by adenosine A2A receptor (A2AR) agonists like ATL146e. This suggests a new therapeutic target for reducing liver damage during reperfusion.
Area of Science:
- Immunology
- Hepatology
- Pharmacology
Background:
- Ischemia reperfusion injury (IRI) causes significant tissue damage, particularly in the liver, due to inflammation during reperfusion.
- Adenosine A2A receptors (A2ARs) and lymphocyte depletion have shown promise in reducing liver IRI.
- NKT cells play a role in IRI, producing interferon-gamma (IFN-γ) upon activation.
Purpose of the Study:
- To investigate the role of NKT cells in hepatic IRI.
- To determine if A2AR activation inhibits NKT cell function and reduces liver IRI.
- To elucidate the mechanism by which ATL146e protects against liver IRI.
Main Methods:
- Utilized RAG-1 knockout mice and adoptive transfer of NKT cells.
- Employed antibodies to deplete NK1.1-positive cells and block CD1d-mediated presentation.
- Assessed liver injury markers including serum alanine aminotransferase, histological necrosis, neutrophil accumulation, and serum IFN-γ levels.
- Performed in vitro assays to measure IFN-γ production by NKT cells upon stimulation.
Main Results:
- NKT cells produced IFN-γ within 2 hours of reperfusion.
- Depletion of NK1.1+ cells or blockade of CD1d-mediated presentation mimicked the protective effects of ATL146e.
- ATL146e inhibited IFN-γ production by NKT cells both in vivo and in vitro.
- Protection was lost in A2AR knockout mice receiving NKT cells, and ATL146e did not protect A2AR-/- NKT cell recipients.
- Adoptive transfer of NKT cells from IFN-γ knockout mice did not restore reperfusion injury in RAG-1 KO mice.
Conclusions:
- Hepatic IRI is initiated by CD1d-dependent NKT cell activation.
- A2AR activation inhibits NKT cell-mediated IFN-γ production, offering a protective mechanism against liver IRI.
- Targeting A2ARs represents a potential therapeutic strategy for mitigating liver IRI.
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