P2Y2 Receptor Biased Signaling in Control of Vascular Inflammation

Abstract

Vascular inflammation plays a critical role in the pathogenesis of endotoxic shock and sepsis. Bacterial endotoxins like lipopolysaccharide (LPS) are biologically active substances that initiate the inflammatory response in vascular endothelial cells (ECs) and blood cells including monocytes/macrophages. Progression of sepsis involves the amplification of the inflammatory response due to the overwhelming production of many inflammatory mediators including GM-CSF, TNF-α, and extracellular nucleotides. One of the potential new therapeutic strategies for sepsis is to limit the degree of endothelial inflammation. Although the pro-inflammatory effect of the nucleotide P2Y2 receptor (P2Y2R) has been intensively investigated, accumulating evidence indicates that P2Y2R may also play a protective role in inflammation. For example, the P2Y receptor ligand 2-MeS-ATP was reported to protect mice from endotoxic death, the exact receptor mechanism(s) remains unclear. In addition, our previous founding in HCAEC show that P2Y2R mediated different anti-inflammatory signaling to control TF transcription, which inspired us to find ligands to select target anti-inflammatory pathway. Further, we presented interesting data indicating that activation of the P2Y2R induced a hypothetical new effector protein termed p25 in HCAEC. Based on these original findings, therefore we hypothesized that manipulating P2Y2R biased signaling (tissue bias and pathway bias) is a new strategy in control of pro-inflammatory and pro-thrombotic gene expression through transcriptional and translational mechanisms. In this dissertation, we assessed signaling pathway bias for P2Y2R function in suppression of inflammatory gene transcription in cultured primary human cells and cells isolated from P2Y2R-null mice; determined tissue/cell-specific bias for P2Y2R signaling in control of inflammatory gene expression; and characterized a putative new post-P2Y2R signaling molecule p25. The dissertation revealed P2Y2R biased signaling, a new mechanism that has the potential to produce new therapeutic drugs in combating inflammatory and thrombotic diseases such as sepsis. In addition, identification strategies of a new signaling or effector protein p25 may open a new window in the field of membrane receptor biology. Further understanding the role of p25 may also establish a new therapeutic target for relevant diseases.