Presence of functional TLR2 and TLR4 on human adipocytes.
In addition to the well-known role of adipose tissue in energy metabolism, it has recently been demonstrated that this tissue can secrete a large array of molecules, including inflammatory cytokines. Furthermore, recent studies suggest that adipose cells can behave as immune cells. Therefore, the aim of this study was to determine the presence of the two most prominent 'pattern recognition receptors' for bacterial and fungal cell wall components, TLR2 and TLR4 on human adipose cells, as well as to assess their functionality. We demonstrated that TLR2 and TLR4 were expressed at relatively high levels (compared to a monocyte cell line) on the surface of human adipose cells. Stimulation of human adipocytes with lipopolysaccharide (LPS), or with lipoteichoic acid (LTA), two specific ligands of TLR4 and TLR2, respectively, induced a strong increase in TNFalpha production. The specificity of the response was demonstrated by the use of anti-TLR4 and anti-TLR2 blocking antibodies, which were able to decrease LPS- or LTA-induced TNFalpha secretion. Thus, it is clear that these receptors are functional in human adipocytes. This study adds weight to the argument that human fat tissue plays a potential role in innate immunity.
Bès-Houtmann
Sandrine
S
Laboratoire de Biochimie et de Génétique Moléculaire (EA2526), Université de la Réunion, Saint Denis, Ile de la Réunion, France. sandrine.houtmann@univ-reunion.fr
Roche
Régis
R
Hoareau
Laurence
L
Gonthier
Marie-Paule
MP
Festy
Franck
F
Caillens
Henri
H
Gasque
Philippe
P
Lefebvre d'Hellencourt
Christian
C
Cesari
Maya
M
D017667:Adipocytes / Q000166:cytology / Q000276:immunology* / Q000378:metabolism*; D000328:Adult; D005260:Female; D006801:Humans; D007113:Immunity, Innate; D008070:Lipopolysaccharides / Q000276:immunology / Q000378:metabolism; D008875:Middle Aged; D013682:Teichoic Acids / Q000276:immunology / Q000378:metabolism; D051195:Toll-Like Receptor 2 / Q000276:immunology / Q000302:isolation & purification / Q000378:metabolism*; D051197:Toll-Like Receptor 4 / Q000276:immunology / Q000302:isolation & purification / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000819:agonists / Q000276:immunology / Q000378:metabolism*
D008070:Lipopolysaccharides; C495342:TLR2 protein, human; C495345:TLR4 protein, human; D013682:Teichoic Acids; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D014409:Tumor Necrosis Factor-alpha; C009900:lipoteichoic acid