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

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.