The P2Y2 Nucleotide Receptor Mediates Tissue Factor Expression in Human Monocytes

Abstract

Recently we reported that in human coronary artery endothelial cells, activation of the P2Y2 receptor induces up‐regulation of tissue factor (TF), a key initiator of the coagulation cascade. However, it has been shown by others that monocyte TF is more important than endothelial TF in terms of provoking pro‐thrombotic state. Thus, we aimed to study whether human monocytes express P2Y2 receptor and its role in control of TF expression. RT‐PCR and receptor activity assays revealed that among the eight P2Y nucleotide receptors, the P2Y2 subtype was selectively and functionally expressed in human monocytic THP‐1 cells. Consistent with this, stimulation of the THP‐1 cells by ATP or UTP at micromolar concentration dramatically increased TF protein expression measured by Western blotting, which was abolished by AR‐C118925XX, a selective P2Y2 receptor antagonist, suggesting a key role for P2Y2 receptor. In addition, UTP or ATP treatment induced a rapid accumulation of TF mRNA, which was maximal at 2h and preceded with an increased TF pre‐mRNA, indicating enhanced TF gene transcription. However, we also observed a significant increase in TF mRNA stability after UTP and ATP treatment. Furthermore, activation of the monocyte P2Y2 receptor by a low dose of UTP or ATP (1μM) significantly activated the MAPK pathways including ERK1/2, JNK, and p38, along with their downstream transcription factors including c‐Jun, c‐Fos and ATF‐2, whereas blocking the ERK1/2, JNK or p38 pathways respectively, all significantly suppressed P2Y2 receptor‐mediated TF expression. These findings demonstrate for the first time that the P2Y2 receptor mediates TF expression in human monocytes through new mechanisms involving ERK1/2, JNK and p38, and that both transcriptional and posttranscriptional mechanisms contribute to a pro‐thrombotic status in monocytes through the P2Y2‐TF axis, highlighting monocyte P2Y2 receptor may be a new drug target for the prevention and/or treatment of relevant thrombotic diseases.Support or Funding InformationSupported by NIH funding 1R01HL125279‐01A1 (JS)