Korean J Dermatol.  2006 Jan;44(1):15-21.

Expression of Toll-like Receptor 4 on Human Keratinocytes by Lipoteichoic Acid

• Park YM
• Kwon HJ
• Kang YS
• Koo JK
• Kim MY
• Kim HO
• Song PI
• Armstrong
• Ansel JC

Abstract

BACKGROUND: We have recently shown that lipopolysaccharide (LPS), a major biologically active component of Gram-negative bacteria, mediate the activation of human keratinocytes by CD14 and Toll-like receptor (TLR 4). However, the mechanism of activation of keratinocytes by Gram-positive bacterial toxins remains unclear.
OBJECTIVE
We investigated the mechanism of activation of human keratinocytes by lipoteichoic acid (LTA), a main stimulatory component of Gram-positive bacteria.
METHODS
The effects of LTA on CD14, TLR2 and TLR4 mRNA expression were measured by quantitative RT-PCR in cultured human keratinocytes. To determine whether the effects of LTA on CD14, TLR2 and TLR4 expressions of the human keratinocytes were biologically functional, NF-kappaB nuclear translocation and IL-1alpha secretion were measured by immunofluorescence staining and ELISA, respectively. Furthermore, to determine whether these effects by LTA were specific for CD14, TLR2 and TLR4, some cells were pretreated with anti-CD14, anti-TLR2, or anti-TLR2 monoclonal antibodies prior to the addition of LTA.
RESULTS
TLR4 mRNA expression on keratinocytes was augmented by exposure to LTA. LTA binding to keratinocytes resulted in NF-kappaB nuclear translocation and secretion of interleukin-1alpha. These responses by LTA were effectively abrogated by preincubating cells with anti-TLR4 monoclonal antibody, but not with anti-CD14 or anti- TLR2 monoclonal antibodies.
CONCLUSION
These results indicate that, similar to LPS, LTA induces activation of human keratinocytes mainly through TLR4, however, in contrast to LPS signaling, LTA-induced keratinocyte activation is CD14-independent.

Keyword

Human keratinocytes; Lipoteichoic acid; Toll-like receptor 4; CD14

MeSH Terms

Antibodies, Monoclonal
Bacterial Toxins
Enzyme-Linked Immunosorbent Assay
Fluorescent Antibody Technique
Gram-Negative Bacteria
Gram-Positive Bacteria
Humans*
Interleukin-1alpha
Keratinocytes*
NF-kappa B
RNA, Messenger
Toll-Like Receptor 4*
Toll-Like Receptors*
Antibodies, Monoclonal
Bacterial Toxins
Interleukin-1alpha
NF-kappa B
RNA, Messenger
Toll-Like Receptor 4
Toll-Like Receptors