Arsenic mobilizes Langerhans cell migration and induces Th1 response in epicutaneous protein sensitization via CCL21: a plausible cause of decreased Langerhans cells in arsenic-induced intraepithelial carcinoma.

Arsenic, still a significant environmental threat in several regions in the world, induces various cancers, including lungs, skin, and bladder. Arsenic-induced Bowen's disease (As-BD) is generally an indolent cutaneous intraepithelial carcinoma in susceptible people. Patients with As-BD have been found to have attenuated contact hypersensitivity. Skin samples collected from these patients have reduced numbers of Langerhans cells (LCs), the major epidermal antigen presenting cells expressing Langerins. This study uses an epicutaneous protein sensitization model to investigate the mechanism through which LCs are decreased in As-BD. It further investigates the possibility that arsenic alters LC migration and polarizes Th responses. To do this, we patch-sensitized Balb/c mice or DT-treated Langerin-DTR mice (conditional depletion of Langerin(+) cells) with OVA or PBS, and fed them water containing 300 ppb arsenic or regular water for 200 μl for five days. Ninety-six hours after OVA sensitization, Langerin(+)EpCAM(+) cells in arsenic-treated WT mice were significantly increased in draining lymph nodes and decreased in epidermis without changes in the dermis. Lymph node cells from arsenic-treated WT mice were found to proliferate more than lymph node cells from control PBS-treated mice after OVA challenge in vitro. They also secreted more IFN-γ and IL-12, but not IL-4, IL-13, or IL-17. However, cell proliferation and the induction of IFN-γ by arsenic were found to be abolished in DT-treated Langerin-DTR mice. The expressions of CCL21 and CXCL12 were also increased in lymph nodes from arsenic-treated WT mice. The administration of a neutralizing antibody against CCL21, but not CXCL12, abolished the increase of LCs in lymph nodes in vivo. The results of this study, the first to study oral arsenic polarization of Th1 responses in epicutaneous protein sensitization through CCL21-mediated LC migration, suggest the chronicity of As-BD without invasion might result from enhanced Th1 responses and altered LC migrations by arsenic.

Lee CH ，Hong CH ，Yu CL ，Wang LF ，Clausen BE ，Liao WT ，Huang SK ，Chen GS ，Yu HS ... -  《-》

Langerhans cell-like dendritic cells stimulated with an adjuvant direct the development of Th1 and Th2 cells in vivo.

It is well known that Langerhans cells (LCs) work as the primary orchestrators in the polarization of immune responses towards a T helper type 1 (Th1) or Th2 milieu. In this study, we attempted to generate LCs from murine bone marrow cells and elicit a Th1- or Th2-prone immune response through the LCs after stimulation with Th1 or Th2 adjuvant. LCs were generated from murine bone marrow cells using granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin (IL)-4 and transforming growth factor (TGF)-β, and were obtained as I-A(d) positive cells. Mice were primed with Th1/Th2 adjuvant- and ovalbumin (OVA)-pulsed LCs and then given a booster injection of OVA 2 days later via the hind footpad. Five days after the OVA injection, the cytokine response in the draining popliteal lymph nodes was investigated by reverse transcription-polymerase chain reaction (RT-PCR) flow cytometry and enzyme-linked immunosorbent assay (ELISA). The generated LCs expressed typical LC surface markers, E-cadherin and Langerin, and were classified accordingly as LC-like dendritic cells (LDCs). Administration of Th1 adjuvant, cytosine-phosphate-guanosine (CpG)-DNA- and OVA-pulsed LDCs into the hind footpads of mice induced a Th1-prone immune response, as represented by up-regulation of IFN-γ production and down-regulation of IL-4 production in the lymph node cells. Conversely, Th2 adjuvant, histamine-pulsed LDCs induced a Th2-prone immune response, as represented by up-regulation of IL-4 production and down-regulation of IFN-γ production. These results suggest that LDCs may be used as a substitute for LCs and have the ability to induce the development of Th1 and Th2 cells in vivo. Our experimental system would therefore be useful for screening of inhibitors of Th1/Th2 differentiation in order to control allergic disease.

Matsui K ，Mori A ，Ikeda R 《-》

STAT3-dependent VEGF production from keratinocytes abrogates dendritic cell activation and migration by arsenic: a plausible regional mechanism of immunosuppression in arsenical cancers.

Arsenic remains an important environmental hazard that causes several human cancers. Arsenic-induced Bowen's disease (As-BD), a skin carcinoma in situ, is the most common arsenical cancer. While great strides have been made in our understanding of arsenic carcinogenesis, how host immunity contributes to this process remains unknown. Patients with As-BD have an impaired contact hypersensitivity response. Although impaired T cell activation has been well-documented in arsenical cancers, how dendritic cell (DC), the key cell regulating innate immunity, regulates the immune response in arsenical cancers remains unclear. Using myeloid derived DC (MDDC) from patients with As-BD and normal controls as well as bone marrow derived DC (BMDC) from mice fed with or without arsenic, we measured the migration of DC. As-BD patients showed an impaired CCL21-mediated MDDC migration in vitro. Arsenic-fed mice had defective DC migration toward popliteal lymph nodes when injected with allogenic BMDCs via foot pad. Using skin from As-BD and normal controls, we found an increased expression of STAT3, a transcriptional factor contributing to impaired DC activation. Arsenic induced STAT3 activation and the production of VEGF in keratinocytes. The increase in VEGF was blocked by inhibiting STAT3 with RNA interference or pharmaceutically with JSI-124. While VEGF by itself minimally induced the expression of CD86 and MHC-II in MDDC, arsenic induced-MDDC activation was abolished by VEGF pretreatment. We concluded that the STAT3-VEGF axis in keratinocytes inhibits DC migration in the microenvironment of As-BD, indicating that cellular interactions play an important role in regulating the disease course of arsenical cancers.

Hong CH ，Lee CH ，Chen GS ，Chang KL ，Yu HS ... -  《-》

Visualization and characterization of migratory Langerhans cells in murine skin and lymph nodes by antibodies against Langerin/CD207.

Stoitzner P ，Holzmann S ，McLellan AD ，Ivarsson L ，Stössel H ，Kapp M ，Kämmerer U ，Douillard P ，Kämpgen E ，Koch F ，Saeland S ，Romani N ... -  《-》

Selective AhR knockout in langerin-expressing cells abates Langerhans cells and polarizes Th2/Tr1 in epicutaneous protein sensitization.

Hong CH ，Lin SH ，Clausen BE ，Lee CH ... -  《-》