Non-enterobacterial endotoxins stimulate human coronary artery but not venous endothelial cell activation via Toll-like receptor 2.
OBJECTIVE
To determine whether non-enterobacterial endotoxins, which are likely to constitute the majority of the circulating endotoxin pool, may stimulate coronary artery endothelial cell activation.


RESULTS
Interleukin-8 secretion, monocyte adhesion, and E-selectin expression were measured in human umbilical vein endothelial cells (HUVECs) and coronary artery endothelial cells (HCAECs) challenged in vitro with highly purified endotoxins of common host colonisers Escherichia coli, Porphyromonas gingivalis, Pseudomonas aeruginosa, and Bacteroides fragilis. HCAECs but not HUVECs expressed Toll-like receptor (TLR)-2 and were responsive to non-enterobacterial endotoxins. Transfection of TLR-deficient HEK-293 cells with TLR2 or TLR4/MD2 revealed that while E. coli endotoxin utilised solely TLR4 to signal, the endotoxins, deglycosylated endotoxins (lipid-A), and whole heat-killed bacteria of the other species stimulated TLR2-but not TLR4-dependent cell-signalling. Blockade of TLR2 with neutralizing antibody prevented HCAEC activation by non-enterobacterial endotoxins. Comparison of each endotoxin with E. coli endotoxin in limulus amoebocyte lysate assay revealed that the non-enterobacterial endotoxins are greatly underestimated by this assay, which has been used in all previous studies to estimate plasma endotoxin concentrations.


CONCLUSIONS
Circulating non-enterobacterial endotoxins may be an underestimated contributor to endothelial activation and atherosclerosis in individuals at risk of increased plasma endotoxin burden.
Erridge
Clett
C
Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, 204 George Street, Glasgow, G1 1XW, UK. clett.eridge@strath.ac.uk
Spickett
Corinne M
CM
Webb
David J
DJ
D000704:Analysis of Variance; D001441:Bacteroides fragilis / Q000378:metabolism; D002460:Cell Line; D002478:Cells, Cultured; D003331:Coronary Vessels; D042783:Endothelial Cells / Q000187:drug effects / Q000276:immunology / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D004926:Escherichia coli / Q000378:metabolism; D006801:Humans; D016209:Interleukin-8 / Q000032:analysis; D008033:Limulus Test; D008050:Lipid A / Q000032:analysis / Q000302:isolation & purification / Q000494:pharmacology*; D016966:Porphyromonas gingivalis / Q000378:metabolism; D011550:Pseudomonas aeruginosa / Q000378:metabolism; D013268:Stimulation, Chemical; D051194:Toll-Like Receptor 1 / Q000378:metabolism; D051195:Toll-Like Receptor 2 / Q000378:metabolism; D051216:Toll-Like Receptor 6 / Q000378:metabolism; D051193:Toll-Like Receptors / Q000378:metabolism*; D014162:Transfection / Q000379:methods; D014471:Umbilical Veins
D016209:Interleukin-8; D008050:Lipid A; D051194:Toll-Like Receptor 1; D051195:Toll-Like Receptor 2; D051216:Toll-Like Receptor 6; D051193:Toll-Like Receptors