Yoon Hee Park

Effect of the size and surface charge of silica nanoparticles on cutaneous toxicity

Silica nanoparticles (NPs) are widely applied in many fields, such as chemical industry, medicine, cosmetics, and agriculture. However, the hazardous effects of silica NPs exposure are not completely understood. In this study, the two different sizes (20 nm and 100 nm) and different charges (negatively charged [NC] and weakly negatively charged [WNC]) of silica NPs were used. The present study investigated the cytotoxicity and reactive oxygen species (ROS) generation of silica NPs on keratinocytes. The phototoxicity test of silica NPs was performed on skin fibroblast cells. In addition, skin irritation and skin sensitization of silica NPs were studied on HSEM and mouse skin, respectively. The cell viability of NC 20 nm silica NPs was decreased. However, there are no cytotoxicity for NC 100 nm silica NPs and WNC silica NPs (20 and 100 nm). The results for silica NPs-induced ROS generation are consistent with the cytotoxicity test by silica NPs. Further, NC and WNC silica NPs induced no phototoxicity, acute cutaneous irritation, or skin sensitization. These results suggested that silica NPs-induced ROS generation was the determinant of cytotoxicity. This study showed that the smaller size (20 nm) of silica NPs had more toxicity than the larger size (100 nm) of silica NPs for NC silica NPs. Moreover, we observed an effect of surface charge in cytotoxicity and ROS generation, by showing that the NC silica NPs (20 nm) had more toxic than the WNC silica NPs (20 nm). These findings suggested that the surface charge of silica NPs might be the important parameter for silica NPs-induced toxicity. Further study is needed to assess the effect of surface modification of nanotoxicity.

Up-regulation of TNF-alpha secretion by cigarette smoke is mediated by Egr-1 in HaCaT human keratinocytes

Please cite this paper as: Up‐regulation of TNF‐alpha secretion by cigarette smoke is mediated by Egr‐1 in HaCaT human keratinocytes. Experimental Dermatology 2010; 19: e206–e212.

Assessment of dermal toxicity of nanosilica using cultured keratinocytes, a human skin equivalent model and an in vivo model.

Assessments of skin irritation potentials are important aspects of the development of nanotechnology. Nanosilica is currently being widely used for commercial purposes, but little literature is available on its skin toxicity and irritation potential. This study was designed to determine whether nanosilica has the potential to cause acute cutaneous toxicity, using cultured HaCaT keratinocytes (CHK), a human skin equivalent model (HSEM), and invivo model. Nanosilica was characterized by scanning electron microscopy. We evaluated the cytotoxic effects of nanosilica on CHKs and the HSEM. In addition, we also investigated whether two commercially available nanosilicas with different sizes (7 and 10-20 nm) have different effects. To confirm invitro results, we evaluated the irritation potentials of nanosilicas on rabbit skin. Nanosilicas reduced the cell viabilities of CHKs in a dose-dependent manner. However, the HSEM revealed no irritation at 500 microg/ml of nanosilica. Furthermore, this result concurred with Draize skin irritation test findings. The present study data indicate that nanosilica does not cause acute cutaneous irritation. Furthermore, this study shows that the HSEM used provides more useful screening data than the conventional cell culture model on the relative toxicities of NPs.

Analysis for the potential of polystyrene and TiO2 nanoparticles to induce skin irritation, phototoxicity, and sensitization.

The human skin equivalent model (HSEM) is well known as an attractive alternative model for evaluation of dermal toxicity. However, only limited data are available on the usefulness of a HSEM for nanotoxicity testing. This study was designed to investigate cutaneous toxicity of polystyrene and TiO2 nanoparticles using cultured keratinocytes, a HSEM, and an animal model. In addition, we also evaluated the skin sensitization potential of nanoparticles using a local lymph node assay with incorporation of BrdU. Findings from the present study indicate that polystyrene and TiO2 nanoparticles do not induce phototoxicity, acute cutaneous irritation, or skin sensitization. Results from evaluation of the HSEMs correspond well with those from animal models. Our findings suggest that the HSEM might be a useful alternative model for evaluation of dermal nanotoxicity.

ZnO nanoparticles induce TNF-α expression via ROS-ERK-Egr-1 pathway in human keratinocytes

BACKGROUND The area of nanotechnology continues to expand rapidly and zinc oxide (ZnO) nanoparticles (NPs) are widely being used in cosmetics and sunscreens. Although ZnO-NPs are considered materials that can potentially cause skin inflammation, the underlying mechanisms remain elusive. OBJECTIVE The aim of this study was to investigate the signaling pathways of a cutaneous inflammatory response induced by ZnO-NPs. ZnO-NPs increased the early growth response-1 (Egr-1) expression, promoter activity and its nuclear translocation in HaCaT cells. METHODS HaCaT cells and primary keratinocytes were exposed to ZnO NPs over a range of doses and time course. Protein levels and mRNA levels of Egr-1 and mitogen-activated protein kinase (MAPK) were measured by Western blot and ELISA, respectively. As an in vivo study, ZnO-NPs were applicated on mouse skin, and immunohistochemical stain with TNF-α and Egr-1 was done. RESULTS ZnO-NPs activated extracellular signal-regulated kinase (ERK) of MAPK pathways. The up-regulation of Egr-1 expression by ZnO-NPs stimulation was found to be inhibited by an ERK inhibitor, but by neither c-Jun-N-terminal kinase (JNK) nor p38 inhibitor. Antioxidative N-acetyl-cysteine (NAC) strongly inhibited the level of Egr-1 and phosphorylated ERK expression in ZnO-NPs treated cells. ZnO NPs also increased tumor necrosis factor (TNF)-α expression and secretion, which were inhibited by the blockade of Egr-1 expression. CONCLUSIONS The present study demonstrated that ZnO-NPs might induce inflammatory response via ROS-ERK-Egr-1 pathway in human keratinocytes.

UVB Induces HIF-1α-Dependent TSLP Expression via the JNK and ERK Pathways

Thymic stromal lymphopoietin (TSLP) may have a key role in the initiation and maintenance of allergic inflammatory diseases, including atopic dermatitis. The present study revealed that UVB radiation exposure could induce TSLP expression in human keratinocytes and a human skin equivalent model. In addition, we investigated the regulatory mechanism of UVB-induced TSLP expression in keratinocytes. TSLP expression was upregulated by transfection with pcDNA3-hypoxia-inducible factor (HIF)-1α (P402A and P564A), which stably expresses HIF-1α protein. UVB-induced TSLP induction in keratinocytes was suppressed in the treatment of mitogen-activated protein kinase inhibitors or small interfering RNAs against HIF-1α. The results of chromatin immunoprecipitation assays indicate the direct involvement of HIF-1α in UVB-mediated TSLP induction. Taken together, these findings indicate that UVB exposure may increase TSLP expression through a HIF-1α-dependent mechanism via the c-JUN N-terminal kinase and extracellular signal-regulated kinase pathways in human keratinocytes. Our data showed that UVB-induced TSLP might increase secretion of the T-helper type 2-attracting chemokine (c-c motif) ligand 17 by human dendritic cells. The present study suggests an important role of HIF-1α in UVB-mediated immune response in keratinocytes.

The potential for skin irritation, phototoxicity, and sensitization of ZnO nanoparticles

In spite of widely use of zinc oxide (ZnO) nanoparticles (NPs) in cosmetic industry and in our daily lives, insufficient studies have evaluated the potential of their toxic response. This study was conducted to investigate the potential of cytotoxicity induced by ZnO NPs, especially influences of the surface charge and different particle size. Assessment of potential of skin irritation was estimated using human skin equivalent model (HSEM), and an animal model. And the evaluation of skin phototoxicity was tested by the 3T3 neutral red uptake test. Lastly, the potential of skin sensitization was evaluated by a local lymph node assay (LLNA). The results from this study demonstrated that ZnO NPs are not dermal sensitizers and do not induce skin irritation. But they may produce phototoxicity.

Oxidative stress and apoptosis induced by ZnO nanoparticles in HaCaT cells

Zinc oxide (ZnO) nanoparticles (NPs) are used in the cosmetic industry in cosmetics and sunscreen. ZnO NPs have been reported to elicit various adverse cellular effects, including cytotoxicity. However, the underlying mechanisms of these adverse effects have not been fully characterized. To investigate the potential of cytotoxicity induced by ZnO NPs, we evaluated cytosolic reactive oxygen species levels in human keratinocyte HaCaT cells treated with ZnO NPs having different surface charges and particle sizes. A short period of treatment (30 min) with 100 nm ZnO NPs resulted in a greater increase of cytosolic ROS levels, compared to treatment with 20 nm ZnO NPs at the same concentration. During a long period of treatment (24 h) with ZnO NPs, intracellular ROS was increased in cells treated with 20 μg/mL 20 nm (+/−) charged ZnO. No significant difference according to differences in surface charge was observed. In addition, total levels of caspase-7 and PARP were decreased by ZnO NPs. These results demonstrated that ZnO NPs could induce ROS mediated apoptosis.

Vascular Endothelial Growth Factor Induces Endothelin-1 Production via Matrix Metalloproteinase-2 Rather than Endothelin-Converting Enzyme-1

Objective: To investigate the mechanism of vascular endothelial growth factor (VEGF)-induced endothelin-1 production in human umbilical vein endothelial cells (HUVECs). Methods: Endothelin-1 levels were measured in conditioned medium of women with preeclampsia HUVECs were treated with different concentrations of VEGF165 and at various time intervals. Next, we measured endothelin-1 levels after HUVECs were also incubated with VEGF and endothelin-converting enzyme-1 (ECE-1) inhibitor or tissue inhibitors of matrix metalloproteinase-2 (TIMP-2). Additionally, the circulating levels of total and free VEGF, matrix metalloproteinase-2 (MMP-2), and endothelin-1 were measured in 20 preeclamptic patients and 20 healthy pregnant controls. Results: HUVECs treated with VEGF increased their endothelin-1 production in a concentration and time-dependent manner. The production of endothelin-1 was inhibited by TIMP-2, but not by the ECE-1 inhibitor. Total VEGF, MMP-2, and endothelin-1 concentrations were higher in preeclampsia and showed significant positive correlations between them. Conclusion: These findings suggest that VEGF-induced endothelin-1 production might be mediated by MMP-2 rather than by ECE-1 upregulation.

A safety assessment of phototoxicity and sensitization of SiO2 nanoparticles

Despite widespread use of silicon dioxide (SiO2) NPs in industry and in our daily lives, no studies so far have evaluated the potential of their skin phototoxicity and sensitization. This study was designed to investigate the potential of phototoxicity and sensitization of SiO2 NPs. Assessment of the potential of skin phototoxicity was carried out using the 3T3 neutral red uptake test, an HSEM, and an animal model. The potential of skin sensitization was evaluated by a non-radioisotope local lymph node assay (non-RI LLNA). Findings from the present study suggest that the HSEM may be a reasonable model system for evaluation of skin phototoxicity of NPs. In addition, our data demonstrate that non-RI LLNA may be a useful method for identification of skin sensitization of NPs. In this study, we showed that SiO2 NPs do not induce phototoxicity or skin sensitization.