The activation of CD14, TLR4, and TLR2 by mmLDL induces IL-1β, IL-6, and IL-10 secretion in human monocytes and macrophages.
Atherosclerosis is considered a chronic inflammatory disease in which monocytes and macrophages are critical. These cells express CD14, toll-like receptor (TLR) 2, and TLR4 on their surfaces, are activated by minimally modified low-density lipoprotein (mmLDL) and are capable of secreting pro-inflammatory cytokines. The aim of this research was thus to demonstrate that the activation of CD14, TLR2, and TLR4 by mmLDL induces the secretion of cytokines.


METHODS
Human monocytes and macrophages were incubated with monoclonal antibodies specific for CD14, TLR4, and TLR2 prior to stimulation with mmLDL. Cytokine secretion was then compared to that observed upon mmLDL stimulation in untreated cells.


RESULTS
Stimulation with mmLDL induced the secretion of pro-inflammatory cytokines. Blocking CD14 in monocytes inhibited secretion of interleukin (IL)-1β (72%), IL-6 (58%) and IL-10 (63%), and blocking TLR4 inhibited secretion of IL-1β by 67%, IL-6 by 63% and IL-10 by 60%. Blocking both receptors inhibited secretion of IL-1β by 73%, IL-6 by 69% and IL-10 by 63%. Furthermore, blocking TLR2 inhibited secretion of IL-1β by 65%, IL-6 by 62% and IL-10 by 75%. In macrophages, we found similar results: blocking CD14 inhibited secretion of IL-1β by 59%, IL-6 by 52% and IL-10 by 65%; blocking TLR4 inhibited secretion of IL-1β by 53%, IL-6 by 63% and IL-10 by 61%; and blocking both receptors inhibited secretion of IL-1β by 69%, IL-6 by 67% and IL-10 by 65%. Blocking TLR2 in macrophages inhibited secretion of IL-1β by 57%, IL-6 by 40% and IL-10 by 72%.


CONCLUSIONS
Our study demonstrates that CD14, TLR4, and TLR2 participate in the immune response against mmLDL by inducing the production of pro-inflammatory cytokines in both monocytes and macrophages. These findings suggest that the activation of these receptors by mmLDL contributes to the inflammatory process of atherosclerosis.
Unidad de Investigación Médica en Inmunología, Hospital de Pediatría, Centro Médico Nacional Siglo XXI, IMSS, México DF, México.
Luis
L
Chávez-Sánchez
Karina
K
Chávez-Rueda
Maria Victoria
MV
Legorreta-Haquet
Edgar
E
Zenteno
Yadira
Y
Ledesma-Soto
Eduardo
E
Montoya-Díaz
Emiliano
E
Tesoro-Cruz
Alejandra
A
Madrid-Miller
Francisco
F
Blanco-Favela
D000906:Antibodies / Q000276:immunology / Q000494:pharmacology; D002454:Cell Differentiation; D002478:Cells, Cultured; D006801:Humans; D016753:Interleukin-10 / Q000378:metabolism*; D053583:Interleukin-1beta / Q000378:metabolism*; D015850:Interleukin-6 / Q000378:metabolism*; D007963:Leukocytes, Mononuclear / Q000187:drug effects / Q000378:metabolism*; D018950:Lipopolysaccharide Receptors / Q000276:immunology / Q000378:metabolism*; D008077:Lipoproteins, LDL / Q000494:pharmacology*; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism*; D051195:Toll-Like Receptor 2 / Q000276:immunology / Q000378:metabolism*; D051197:Toll-Like Receptor 4 / Q000276:immunology / Q000378:metabolism*; D020298:U937 Cells
D000906:Antibodies; D053583:Interleukin-1beta; D015850:Interleukin-6; D018950:Lipopolysaccharide Receptors; D008077:Lipoproteins, LDL; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; C099252:oxidized low density lipoprotein; D016753:Interleukin-10