Increased Level of α2,6-Sialylated Glycans on HaCaT Cells Induced by Titanium Dioxide Nanoparticles under UV Radiation.

Yuanyuan Ren,Runqing Geng,Xin Liu,Xiangliang Yang,Qunwei Lu,Wei Liu,Rong Rao,Xi Tan

doi:10.3390/nano8040253

Abstract

As one of the most widely used nanomaterials, the safety of nano-TiO2 for human beings has raised concern in recent years. Sialylation is an important glycosylation modification that plays a critical role in signal transduction, apoptosis, and tumor metastasis. The aim of this work was to investigate the cytotoxicity and phototoxicity of nano-TiO2 with different crystalline phases for human skin keratinocytes (HaCaT cells) under ultraviolet (UV) irradiation and detect sialic acid alterations. The results showed that the mixture of crystalline P25 had the highest cytotoxicity and phototoxicity, followed by pure anatase A25, whereas pure rutile R25 had the lowest cytotoxicity and phototoxicity. A25 and R25 had no effects on the expression of sialic acids on HaCaT cells. However, HaCaT cells treated with P25 and UV showed an increased level of alterations in α2,6-linked sialic acids, which was related to the level of reactive oxygen species (ROS) generated by nano-TiO2 and UV. The abundance of α2,6-linked sialic acids increased as ROS production increased, and vice versa. Antioxidant vitamin C (VC) reversed the abnormal expression of α2,6-linked sialic acids caused by nano-TiO2 and protected cells by eliminating ROS. These findings indicate that nano-TiO2 can alter the sialylation status of HaCaT cells under UV irradiation in a process mediated by ROS.

Highlights

Nanoparticles and nanotechnology are being developed rapidly and are increasingly encountered during the course of daily life
Cells treated with UV and nano-TiO2 showed enhanced reactivity with Sambucus nigra agglutinin (SNA) and increased binding with α2,6-linked sialic acid. These changes were related to reactive oxygen species (ROS) generated by nano-TiO2 and UV, which led to changes in sialic acids. These findings suggest that sialic acid expression plays an important role in the toxic effects of nano-TiO2 on the skin
Nano-TiO2 can be found in the forms of aerosols, suspensions or emulsions, which can cause toxic effects via inhalation and dermal exposure [34]

Summary

Introduction

Nanoparticles and nanotechnology are being developed rapidly and are increasingly encountered during the course of daily life. Studies of the potential health risk of nano-TiO2 for humans have revealed that the toxicity of nano-TiO2 is dependent on the size, shape, and crystalline phase of the particles, as well as their distribution in the body [4,5,6]. Under UV irradiation, electrons in the nano-TiO2 valence band absorb photon energy and jump to the conduction band, leaving valence band holes that extract electrons from water or hydroxyl ions and generate reactive oxygen species (ROS), which are cytotoxic and genotoxic [8,9]. The phototoxicity and degree of damage associated with nano-TiO2 are dependent on the crystalline phase, size and concentration of the nanoparticles [4,10]. ROS damage cells, tissues, and organisms by causing lipid peroxidation, altering the abundance of proteins, producing DNA mutations, and triggering apoptosis [12,13,14,15]

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