House dust mites (HDMs) are known to trigger chronic inflammation through Toll-like receptors (TLRs) and their signalling cascades. In this study, we found that TLR2 ligation by HDMs induced the activation of dual oxidase 2 (Duox2) and nuclear factor-jB (NF-jB), leading to the production of proinflammatory cytokines in human keratinocytes. Stimulation of human keratinocytes with HDMs resulted in increases in interleukin-8 (IL-8) and chemokine (C–C motif) ligand 20 (CCL20) levels. However, pro-inflammatory cytokine production was abolished in keratinocytes transfected with TLR2 siRNA, indicating that HDM-induced cytokine production was mediated via TLR2 signalling. We also examined the function of Duox1/2 isozymes, which are primarily expressed in keratinocytes, in HDM-mediated pro-inflammatory cytokine production. Human keratinocytes transfected with control siRNA or Duox1 siRNA showed no inhibition of IL-8 or CCL20 production in response to HDMs, whereas the silencing of Duox2 expression resulted in a failure to induce cytokine production. Moreover, the phosphorylation and nuclear localization of RelA/p65, a component of NF-jB, were induced by HDMs in human keratinocytes. Transfection of human keratinocytes with TLR2 siRNA or Duox2 siRNA resulted in the complete abolishment of RelA/p65 nuclear localization in response to HDMs. Taken together, these results indicate that the HDM-dependent TLR2-Duox2 signalling axis indeed promotes NF-jB activation, which induces IL-8 and CCL20 production and mediates epidermal keratinocyte inflammation.
Bibliographical noteFunding Information:
This work was supported by the National Research Foundation of Korea (NRF) (grant No. 2012R1A5A1048236), by the Bio & Medical Technology Development Program (No. 2012M3A9B4028785) and by a Redoxomics Grant (grant 2012M3A.
© 2015 John Wiley & Sons A/S.
- Dual oxidase 2
- House dust mite
- Nuclear factor-jB
- Reactive oxygen species
- Toll-like receptors