Kynurenic Acid Triggers Firm Arrest of Leukocytes to Vascular Endothelium under Flow Conditions

• Published in: The Journal of biological chemistry Vol. 284; no. 29; pp. 19189 - 19195
• Main Authors: Barth, Marita C., Ahluwalia, Neil, Anderson, Thomas J.T., Hardy, Gregory J., Sinha, Sumita, Alvarez-Cardona, Jose A., Pruitt, Ivy E., Rhee, Eugene P., Colvin, Richard A., Gerszten, Robert E.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 17-07-2009; American Society for Biochemistry and Molecular Biology
• Subjects: CD18 Antigens - metabolism; Cell Adhesion - drug effects; Cell Line; Dose-Response Relationship, Drug; Endothelial Cells - cytology; Endothelial Cells - drug effects; Endothelial Cells - metabolism; Excitatory Amino Acid Antagonists - pharmacology; Fibronectins - metabolism; Gene Expression - drug effects; Humans; Integrin beta1 - metabolism; Intercellular Adhesion Molecule-1 - metabolism; Kynurenic Acid - chemistry; Kynurenic Acid - pharmacology; Leukocytes, Mononuclear - cytology; Leukocytes, Mononuclear - drug effects; Leukocytes, Mononuclear - metabolism; Molecular Basis of Cell and Developmental Biology; Molecular Structure; Receptors, G-Protein-Coupled - genetics; Reverse Transcriptase Polymerase Chain Reaction; Rheology; RNA Interference
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M109.024042

Recent studies have demonstrated that kynurenic acid (KYNA), a compound produced endogenously by the interferon-γ-induced degradation of tryptophan by indoleamine 2,3-dioxygenase, activates the previously orphaned G protein-coupled receptor, GPR35. This receptor is expressed in immune tissues, although its potential function in immunomodulation remains to be explored. We determined that GPR35 was most highly expressed on human peripheral monocytes. In an in vitro vascular flow model, KYNA triggered the firm arrest of monocytes to both fibronectin and ICAM-1, via β1 integrin- and β2 integrin-mediated mechanisms, respectively. Incubation of monocytes with pertussis toxin prior to use in flow experiments significantly reduced the KYNA-induced monocyte adhesion, suggesting that adhesion is triggered by a Gi-mediated process. Furthermore, KYNA-triggered adhesion of monocytic cells was reduced by short hairpin RNA-mediated silencing of GPR35. Although GPR35 is expressed at slightly lower levels on neutrophils, KYNA induced firm adhesion of these cells to an ICAM-1-expressing monolayer as well. KYNA also elicited neutrophil shedding of surface L-selectin, another indicator of leukocyte activation. Taken together, these data suggest that KYNA could be an important early mediator of leukocyte recruitment.