|Cancer||Cell death||Cell cycle||Cytoskeleton||Exo/endocytosis||Differentiation||Division||Organelles||Signalling||Stem cells||Trafficking|
Extracellular nucleotide inhibits cell proliferation and negatively regulates Toll-like receptor 4 signalling in human progenitor endothelial cells
Zhilin Xiao*, Mei Yang*, Li Fang*, Qingshan Lv*, Qing He†, Minjie Deng†, Xueting Liu†, Xiaobin Chen*, Meifang Chen*, Xiumei Xie*1 and Jinyue Hu†1
*Department of Geriatric Cardiology, Xiangya Hospital, Central South University, Changsha 410008, People's Republic of China, and †Central Laboratory, Renmin Hospital, Wuhan University, Wuhan 430060, People's Republic of China
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.
Key words: ATP, endothelial progenitor cell (EPC), P2Y2, proliferation, Toll-like receptor 4 (TLR4) signalling, UTP
Abbreviations: CCK-8, cell counting kit-8, Dil-LDL, 1,1′-dioctadecyl-3,3,3′,3′-tetramethylindocarbocyanine-labelled acetylated LDL, EPC, endothelial progenitor cell, ERK, extracellular-signal-regulated kinase, GAPDH, glyceraldehyde-3-phosphate dehydrogenase, ICAM-1, intercellular adhesion molecule 1, IFNα, interferon α, IL-1β, interleukin-1β, LDL, low-density lipoprotein, LPS, lipopolysaccharide, MCP-1, monocyte chemoattractant protein-1, MyD88, myeloid differentiation factor 88, NF-κB, nuclear factor κB, PRR, pattern recognition receptors, RT–PCR, reverse transcription–PCR, TLR, Toll-like receptor, TNFα, tumour necrosis factor α, UDP, uridine diphosphate, VCAM-1, vascular cell adhesion molecule 1
1Correspondence may be addressed to either of these authors (email email@example.com or firstname.lastname@example.org).
Received 24 February 2011/19 September 2011; accepted 2 February 2012
Published as Cell Biology International Immediate Publication 2 February 2012, doi:10.1042/CBI20110111
© The Author(s) Journal compilation © 2012 International Federation for Cell Biology