Knockout Mice Reveal a Role for P2Y₆ Receptor in Macrophages, Endothelial Cells, and Vascular Smooth Muscle Cells

Abstract

P2Y receptors are G-protein-coupled receptors activated by extracellular nucleotides. The P2Y 6 receptor is selectively activated by UDP, and its transcript has been detected in numerous organs, including the spleen, thymus, intestine, blood leukocytes, and aorta. To investigate the biological functions of this receptor, we generated P2Y 6 -null mice by gene targeting. The P2Y 6 knockout (KO) mice are viable and are not distinguishable from the wild-type (WT) mice in terms of growth or fertility. In thioglycollate-elicited macrophages, the production of inositol phosphate in response to UDP stimulation was lost, indicating that P2Y 6 is the unique UDP-responsive receptor expressed by mouse macrophages. Furthermore, the amount of interleukin-6 and macrophage-inflammatory protein-2, but not tumor necrosis factor-␣, released in response to lipopolysaccharide stimulation was significantly enhanced in the presence of UDP, and this effect was lost in the P2Y 6 KO macrophages. The endothelium-dependent relaxation of the aorta by UDP was abolished in KO P2Y 6 mice. The contractile effect of UDP on the aorta, observed when endothelial nitric-oxide synthase is blocked, was also abolished in P2Y 6 -null mice. In conclusion, we generated P2Y 6 -deficient mice and have shown that these mice have a defective response to UDP in macrophages, endothelial cells, and vascular smooth muscle cells. These observations might be relevant to several physiopathological conditions such as atherosclerosis or hypertension.

Myogenic tone in mouse mesenteric arteries: evidence for P2Y receptor-mediated, Na+, K+, 2Cl− cotransport-dependent signaling

“…Unlike UTP, ATP affected VSMC contractions via transient activation of Ca 2+ influx through P2X ion channels and independently of E m modulation [44]. Finally, the slow kinetic of MT development in mesenteric arteries is consistent with the presence of P2Y 6 receptors in endothelial cells triggering NOmediated vasorelaxation [45] and suppressing the rapid phase of vasoconstriction evoked by interaction of UTP/ UDP with VSMC P2Y 6 receptors. The data considered above are consistent with the signaling mechanism presented schematically in Figure 7.…”

Concomitant activation of P2Y2 and P2Y6 receptors on monocytes is required for TLR1/2‐induced neutrophil migration by regulating IL‐8 secretion

“…Studies suggest that the chemokine MIP-2 is a mouse counterpart of IL-8. Interestingly, Bar et al [25] showed that UDP via P2Y 6 activation potentiates LPS-induced release of MIP-2 from WT mouse peritoneal macrophages and that this effect is absent in P2Y 6 deficient macrophages. The authors however did not test whether LPS or other PAMP such Pam 3 CSK 4 -induced MIP-2 release was nucleotide-dependent and whether UDP would also synergize with these molecules.…”

The P2 receptor antagonist PPADS abrogates LPS-induced neutrophil migration in the murine air pouch via inhibition of MIP-2 and KC production

“…It is therefore possible that PPADS and UTP acted on distinct P2 receptors. PPADS can inhibit various P2 receptors including P2X (North and Surprenant, 2000) whereas UTP can activate P2Y 2 , P2Y 4 , and also P2Y 6 in mice (Abbracchio et al, 2006;Bar et al, 2008;SuarezHuerta et al, 2001). Noteworthy, PPADS does not inhibit neutrophil migration due to Pam 3 CSK 4 and flagellin (Fig.…”

“…These nucleotides are natural agonists of P2Y 2 (UTP) and P2Y 6 (in mouse activated by either UDP or UTP; Bar et al, 2008;Kauffenstein et al, in press) receptors that have been shown to control neutrophil migration in vivo and in vitro Chen et al, 2006;Inoue et al, 2008;Kukulski et al, 2007). UTP is also a ligand of P2Y 4 receptor which is highly sensitive to PPADS.…”