Electric fields sensitized KG-1 cells in responding to IL-18

Disruption of an epithelial barrier generates electric fields (EFs) instantly, which induces directed cell migration into wound site and promotes wound healing. Langerhans cells are dendritic cells (DCs) of epidermis and play a key role in regulation of inflammatory responses in wound healing. It is not know that how EFs act on DCs in modification of their responses to the cytokine stimulation. One of the important cytokines produced in skin wound is IL-18. IL-18 is constitutively expressed in skin keratinocytes and released instantly after skin is wounded for cell stimulation. Molecular evidences have convincingly showed that IL-18 binds to IL-18Rα and aggregates with IL-18Rβ is critical to trigger IL-18 signaling. KG-1 cell is a human monocytic cell line and able to differentiate into DC. KG-1 cells express higher 18Rα and β after TNFα stimulation and subsequently respond to IL-18 for IFN-γ production. Objective: The aim of this study is to investigate the molecular mechanism of EF modulated sensitization response of DCs toward IL-18 stimulation in vitro. Methods: In this study a modified transwell assay was used for KG-1 cells stimulation with a suboptimal dose of IL-18 in the presence of EFs. The IFN-γ production in cell culture supernatant was measured by ELISA. To study the molecular mechanism, we constructed IL-18Rα and β fused with GFP and RFP. The IL-18Rα and β chains co-localization was monitored in the presence of EFs. Results: 1). EFs promoted IFN-γ production in KG1 cells in responding to IL-18 stimulation. 2) EFs stimulation redistributes IL-18 receptors and increases co-localization of IL-18 receptor α and β. Conclusion: Skin immune cells can be potentially sensitized by wound-induced endogenous electric fields. Sensitization of DCs may have clinical implication in vaccination or cancer therapy.