Possible involvement of toll-like receptor 4 in endothelial cell activation of larger vessels in response to lipopolysaccharide.
Toll-like receptors (TLRs) serve as recognition and signaling elements for bacterial substances. To examine the role of TLRs in endothelial cells of larger vessels in lipopolysaccharide (LPS)-induced signaling, the expression and function of TLRs in human umbilical vein endothelial cells (HUVEC) were analyzed. A high level of TLR4 mRNA expression was found in HUVEC, human peripheral blood mononuclear cells (PBMC) and human monocyte cell line THP-1 cells. Little or no TLR2 mRNA expression was observed in HUVEC. In contrast, strong TLR2 mRNA expression was observed in PBMC and THP-1 cells. Moderate and high levels of TLR1 mRNA expression were found in HUVEC, PBMC and THP-1 cells, respectively. TLR3 mRNA expression was moderate in PBMC but weak in HUVEC and THP-1 cells. Little or no TLR5 and RP105 mRNA expression was observed in HUVEC, whereas a moderate level was detected in PBMC and THP-1 cells. The LPS-induced E-selectin expression in HUVEC was significantly inhibited by pretreatment with an anti-TLR4 mAb. Preincubation of HUVEC with an anti- TLR4 mAb significantly reduced the LPS-induced IL-6 production. LPS induced E-selectin and IL-6 production by HUVEC only in the presence of human serum, suggesting the involvement of soluble CD14. Anti-CD14 mAb strongly inhibited the LPS-induced E-selectin and IL-6 production by HUVEC. The inhibition with the concomitant treatment with anti-TLR4 and anti-CD14 mAbs was stronger than that with anti-CD14 mAb only, although it was slight. These results show that TLR4 in the presence of soluble CD14 plays a major role in the signaling of LPS in endothelial cells of larger vessels.
Hijiya
Naoki
N
Department of Pathology, Oita Medical University, Oita, Japan. hijiya@oita-med.ac.jp
Miyake
Kensuke
K
Akashi
Sachiko
S
Matsuura
Keiko
K
Higuchi
Yasunori
Y
Yamamoto
Shunsuke
S
D015152:Blotting, Northern; D002478:Cells, Cultured; D017931:DNA Primers / Q000737:chemistry; D004305:Dose-Response Relationship, Drug; D029721:Drosophila Proteins; D019040:E-Selectin / Q000235:genetics / Q000378:metabolism; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D007963:Leukocytes, Mononuclear / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D009000:Monocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012475:Salmonella / Q000276:immunology; D015398:Signal Transduction; D051194:Toll-Like Receptor 1; D051195:Toll-Like Receptor 2; D051196:Toll-Like Receptor 3; D051197:Toll-Like Receptor 4; D051198:Toll-Like Receptor 5; D051193:Toll-Like Receptors; D014471:Umbilical Veins / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*
D017931:DNA Primers; D029721:Drosophila Proteins; D019040:E-Selectin; D008070:Lipopolysaccharides; D008562:Membrane Glycoproteins; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; C495342:TLR2 protein, human; C495344:TLR3 protein, human; C495345:TLR4 protein, human; C495346:TLR5 protein, human; D051194:Toll-Like Receptor 1; D051195:Toll-Like Receptor 2; D051196:Toll-Like Receptor 3; D051197:Toll-Like Receptor 4; D051198:Toll-Like Receptor 5; D051193:Toll-Like Receptors