Cooperative effects of UVA irradiation on TiO2 nanoparticles-induced cell death in mammalian skin epidermal cells

[Speaker] Yoshihiro Higuchi:1
[Co-author] Ayako Furukawa:1, Natsuki Kamimura:1, Rikako Ikeda:1, Yumi Nakashima:1
1:Faculty of Pharmaceutical Sciences, Suzuka University of Medical Sciences, Japan

Nanoparticles are widely used in industrial and medical applications. However, some reports have suggested that nanometer-sized particles are hazardous to the environment and human health. Titanium dioxide (TiO2) has long been considered a biologically inert metals. It is used in many types of products, including white pigments, sunscreens and implants. We have reported that nanometer sized TiO2 particles induce apoptosis associated with chromosomal DNA fragmentation and caspase-3 activation in leukemia L1210 cells. In this study, we investigated the cytotoxicity of TiO2 to mammalian cultured cells such as skin epidermal cells and an additional effect of ultraviolet type A (UVA) radiations under the existing of TiO2 and UVA.
We used nanometer-sized TiO 2 particles which were pretreated with polyacrylic acid and also used UVA lamp (wavelength 315~380 nm). FRSK rat epidermal cells were used in this study. The cell death was detected by MTT assay. FRSK cells were treated with TiO2 particles (0.8 mg/ml of culture medium) at 37 for 24 hr and then washed in TiO 2 and serum free medium. Furthermore, the cells were irradiated with UVA at appropriate doses and then incubated under culture conditions. After treatment, a cell death and a cellular glutathione (GSH) level of the cells were determined.
TiO2 or UVA alone induced approximately 80% and 60% of the control cells, respectively on cell survivals. The cell survival in the treatment by TiO2 and then UVA irradiation were induced to less than 5% in comparison with the control cells. Cellular GSH levels in the treated cells were decreased in corresponding with cell death and time intervals from the treatment.
In conclusion, TiO2 particles and UVA irradiation may enhance their cytotoxic actions through by cooperative actions in skin epidermal cells. However, the cooperative action mechanism is unclear.

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