Antagonistic Skin Toxicity of Co-Exposure to Physical Sunscreen Ingredients Zinc Oxide and Titanium Dioxide Nanoparticles.

Being the main components of physical sunscreens, zinc oxide nanoparticles (ZnO NPs) and titanium dioxide nanoparticles (TiO2 NPs) are often used together in different brands of sunscreen products with different proportions. With the broad use of cosmetics containing these nanoparticles (NPs), concerns regarding their joint skin toxicity are becoming more and more prominent. In this study, the co-exposure of these two NPs in human-derived keratinocytes (HaCaT) and the in vitro reconstructed human epidermis (RHE) model EpiSkin was performed to verify their joint skin effect. The results showed that ZnO NPs significantly inhibited cell proliferation and caused deoxyribonucleic acid (DNA) damage in a dose-dependent manner to HaCaT cells, which could be rescued with co-exposure to TiO2 NPs. Further mechanism studies revealed that TiO2 NPs restricted the cellular uptake of both aggregated ZnO NPs and non-aggregated ZnO NPs and meanwhile decreased the dissociation of Zn2+ from ZnO NPs. The reduced intracellular Zn2+ ultimately made TiO2 NPs perform an antagonistic effect on the cytotoxicity caused by ZnO NPs. Furthermore, these joint skin effects induced by NP mixtures were validated on the epidermal model EpiSkin. Taken together, the results of the current research contribute new insights for understanding the dermal toxicity produced by co-exposure of different NPs and provide a valuable reference for the development of formulas for the secure application of ZnO NPs and TiO2 NPs in sunscreen products.

TRPM2 expression levels are associated with histological grading in patients with tongue squamous cell carcinoma.

Tongue squamous cell carcinoma (TSCC) accounts for a large proportion of cases of head and neck cancer. Transient receptor potential melastatin 2 (TRPM2) is a non­selective cation channel sensitive to oxidative stress. High TRPM2 expression has been reported in various types of cancer, including neuroblastoma, glioblastoma, non­small cell lung cancer and breast cancer. However, whether expression levels of TRPM2 are associated with aggressive clinical features in TSCC remains unclear. A total of 26 clinical sample tissues with TSCC were collected in the present study. The expression levels of the TRPM2 channel were determined by immunohistochemistry, western blot, and qPCR analysis. The content of malondialdehyde (MDA) and the activity of superoxide dismutase (SOD) were measured to reveal oxidative stress levels in TSCC tissues with different degrees of differentiation. The protein expression levels of caspase­8, Bcl­xL, Bax, caspase­9, cleaved caspase­9, caspase­3, cleaved caspase­3, poly [ADP­ribose] polymerase (PARP) and cleaved PARP were detected by western blot analysis. Analysis of the tissue specimens from 26 patients with TSCC showed that TRPM2 was not upregulated in all specimens. Notably, the expression levels of TRPM2 were associated with the histological grading of different tissues. The specimens with low TRPM2 expression were significantly associated with moderate or poor differentiation (P=0.003), and exhibited increased lipid peroxidation level and decreased SOD activity. Furthermore, the altered expression of pro­ and anti­apoptotic proteins indicated a significant upregulation of apoptosis in TSCC tissues with low TRPM2 expression. These results suggested that low TRPM2 expression in TSCC may inhibit the ability of cells to adapt to or resist the oxidative stress, resulting in increased susceptibility to apoptosis. Therefore, the oxidative stress­sensitive TRPM2 channel may serve as a potent biomarker, and the present study provides insights into the underlying mechanisms of tumor cell differentiation.

Silica nanoparticles induce lung inflammation in mice via ROS/PARP/TRPM2 signaling-mediated lysosome impairment and autophagy dysfunction.

BACKGROUND: Wide applications of nanoparticles (NPs) have raised increasing concerns about safety to humans. Oxidative stress and inflammation are extensively investigated as mechanisms for NPs-induced toxicity. Autophagy and lysosomal dysfunction are emerging molecular mechanisms. Inhalation is one of the main pathways of exposing humans to NPs, which has been reported to induce severe pulmonary inflammation. However, the underlying mechanisms and, more specifically, the interplays of above-mentioned mechanisms in NPs-induced pulmonary inflammation are still largely obscure. Considered that NPs exposure in modern society is often unavoidable, it is highly desirable to develop effective strategies that could help to prevent nanomaterials-induced pulmonary inflammation. RESULTS: Pulmonary inflammation induced by intratracheal instillation of silica nanoparticles (SiNPs) in C57BL/6 mice was prevented by PJ34, a poly (ADP-ribose) polymerase (PARP) inhibitor. In human lung bronchial epithelial (BEAS-2B) cells, exposure to SiNPs reduced cell viability, and induced ROS generation, impairment in lysosome function and autophagic flux. Inhibition of ROS generation, PARP and TRPM2 channel suppressed SiNPs-induced lysosome impairment and autophagy dysfunction and consequent inflammatory responses. Consistently, SiNPs-induced pulmonary inflammation was prevented in TRPM2 deficient mice. CONCLUSION: The ROS/PARP/TRPM2 signaling is critical in SiNPs-induced pulmonary inflammation, providing novel mechanistic insights into NPs-induced lung injury. Our study identifies TRPM2 channel as a new target for the development of preventive and therapeutic strategies to mitigate nanomaterials-induced lung inflammation.