Extracellular nucleotide inhibits cell proliferation and negatively regulates Toll-like receptor 4 signalling in human progenitor endothelial cells.
Extracellular nucleotides mediate a wide range of physiological effects by interacting with plasma membrane P2 purinergic receptors. P2 receptors are expressed in certain kinds of stem cells, and function to induce cytokine expression and to modulate cell proliferation. We have analysed the expression and the function of P2 receptors in human umbilical cord blood-derived EPCs (endothelial progenitor cells). EPCs expressed P2X4,6,7 and P2Y2,4,11,13,14 receptors and extracellular ATP inhibited EPCs proliferation. As in a previous study, EPCs expressed functional TLR4 (Toll-like receptor 4) and activation of TLR4 by LPS (lipopolysaccharide) evoked a pro-inflammatory immune response. When human EPCs were stimulated with LPS and nucleotides, ATP or UTP inhibited the expression of pro-inflammatory cytokines including MCP-1 (monocyte chemoattractant protein-1), IFNα (interferon α), TNFα (tumour necrosis factor α) and adhesion molecule VCAM-1 (vascular cell adhesion molecule 1) induced by LPS. ATP and UTP also down-regulated the gene expression of TLR4, CD14 and MyD88 (myeloid differentiation factor 88), a TLR adaptor molecule, and protein expression of CD14 and MyD88. Moreover, the phosphorylation of NF-κB (nuclear factor κB) p65 induced by TLR4 activation was inhibited partly by ATP or UTP at concentrations of 1-5 μM. These results suggest that extracellular nucleotides negatively regulate EPCs proliferation and TLR4 signalling.
*Department of Geriatric Cardiology, Xiangya Hospital, Central South University, Changsha 410008, People's Republic of China.
Zhilin
Z
Xiao
Mei
M
Yang
Li
L
Fang
Qingshan
Q
Lv
Qing
Q
He
Minjie
M
Deng
Xueting
X
Liu
Xiaobin
X
Chen
Meifang
M
Chen
Xiumei
X
Xie
Jinyue
J
Hu
D000255:Adenosine Triphosphate / Q000494:pharmacology*; D049109:Cell Proliferation / Q000187:drug effects; D016207:Cytokines / Q000235:genetics / Q000378:metabolism; D015536:Down-Regulation; D015870:Gene Expression / Q000187:drug effects; D006801:Humans; D018950:Lipopolysaccharide Receptors / Q000378:metabolism; D008070:Lipopolysaccharides / Q000633:toxicity; D053594:Myeloid Differentiation Factor 88 / Q000378:metabolism; D010766:Phosphorylation; D018048:Receptors, Purinergic P2 / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D013234:Stem Cells / Q000166:cytology / Q000378:metabolism*; D051197:Toll-Like Receptor 4 / Q000235:genetics / Q000378:metabolism*; D051996:Transcription Factor RelA / Q000378:metabolism; D014470:Umbilical Cord / Q000166:cytology; D014544:Uridine Triphosphate / Q000494:pharmacology*
D016207:Cytokines; D018950:Lipopolysaccharide Receptors; D008070:Lipopolysaccharides; D053594:Myeloid Differentiation Factor 88; D018048:Receptors, Purinergic P2; D051197:Toll-Like Receptor 4; D051996:Transcription Factor RelA; D000255:Adenosine Triphosphate; D014544:Uridine Triphosphate