P2Y2 Receptor Modulates Leukocyte‐Endothelium Interaction

Abstract

Nucleotide P2Y2 receptor (P2Y2R) plays important roles in inflammation. The leukocyte‐endothelium interaction is essential for leukocyte recruitment at the site of tissue damage or injury. Little is known about the role of P2Y2R in the regulation of in vivo leukocyte‐endothelium interaction. This study tested the hypothesis that P2Y2R mediates leukocyte‐endothelium interaction using the cremaster muscle. Leukocytes were labeled with Rhodamine 6G injected via tail vein. Leukocyte rolling and stable adhesion were analyzed using a semi‐automatic leukocyte tracking method. P2Y2R activation by UTP increased leukocyte rolling (EC50 = 4.7 ± 1.4 x 10−7 M) and adhesion (EC50= 4.3 ± 1.3 x 10−6 M) in a concentration‐dependent manner in C57BL/6 wild‐type (WT) mice (n=3). UTP (10−5 M) induced sustained increases in both leukocyte rolling and adhesion in WT mice (n=7–19, P<0.05) over 60 min. P2Y2R knockout (P2Y2R−/−) mice exhibited a 2‐fold increase in baseline leukocyte rolling (rolling fraction=37.8%, n=8, p < 0.001) compared to WT mice (rolling fraction=16.2%, n=12) and stayed at the high basal level without changes in rolling following stimulation of UTP (10−5 M) over 60 min. Baseline leukocyte adhesion in P2Y2R−/− mice was 1.5‐fold increase (15 ± 4 adherent cells.100 μm−1, n=12, p < 0.001) compared with WT mice (9 ± 4 adherent cells·100 μm−1; n=19). There was no change in leukocyte adhesion from the baseline in response to UPT (10−5 M) stimulation in P2Y2R−/− mice (n=5–12). We conclude that P2Y2R prevents in vivo leukocyte rolling and adhesion under resting condition while activation P2Y2R by UTP increases both leukocyte rolling and adhesion.Support or Funding InformationMissouri State University