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Titanium dioxide induces apoptotic cell death through reactive oxygen species-mediated Fas upregulation and Bax activation.

Yoo KC, Yoon CH, Kwon D, Hyun KH, Woo SJ, Kim RK, Lim EJ, Suh Y, Kim MJ, Yoon TH, Lee SJ - Int J Nanomedicine (2012)

Bottom Line: In line with these results, knockdown of either Fas or Bax with specific siRNA significantly inhibited TiO(2)-induced apoptotic cell death.These results indicate that sub-100 nm sized TiO(2) treatment under ultraviolet A irradiation induces apoptotic cell death through reactive oxygen species-mediated upregulation of the death receptor, Fas, and activation of the preapoptotic protein, Bax.Elucidating the molecular mechanisms by which nanosized particles induce activation of cell death signaling pathways would be critical for the development of prevention strategies to minimize the cytotoxicity of nanomaterials.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Molecular Biochemistry, Department of Chemistry, Hanyang University, Seoul, Republic of Korea.

ABSTRACT

Background: Titanium dioxide (TiO(2)) has been widely used in many areas, including biomedicine, cosmetics, and environmental engineering. Recently, it has become evident that some TiO(2) particles have a considerable cytotoxic effect in normal human cells. However, the molecular basis for the cytotoxicity of TiO(2) has yet to be defined.

Methods and results: In this study, we demonstrated that combined treatment with TiO(2) nanoparticles sized less than 100 nm and ultraviolet A irradiation induces apoptotic cell death through reactive oxygen species-dependent upregulation of Fas and conformational activation of Bax in normal human cells. Treatment with P25 TiO(2) nanoparticles with a hydrodynamic size distribution centered around 70 nm (TiO(2) (P25-70)) together with ultraviolet A irradiation-induced caspase-dependent apoptotic cell death, accompanied by transcriptional upregulation of the death receptor, Fas, and conformational activation of Bax. In line with these results, knockdown of either Fas or Bax with specific siRNA significantly inhibited TiO(2)-induced apoptotic cell death. Moreover, inhibition of reactive oxygen species with an antioxidant, N-acetyl-L-cysteine, clearly suppressed upregulation of Fas, conformational activation of Bax, and subsequent apoptotic cell death in response to combination treatment using TiO(2) (P25-70) and ultraviolet A irradiation.

Conclusion: These results indicate that sub-100 nm sized TiO(2) treatment under ultraviolet A irradiation induces apoptotic cell death through reactive oxygen species-mediated upregulation of the death receptor, Fas, and activation of the preapoptotic protein, Bax. Elucidating the molecular mechanisms by which nanosized particles induce activation of cell death signaling pathways would be critical for the development of prevention strategies to minimize the cytotoxicity of nanomaterials.

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TiO2 sensitizes normal cells to ultraviolet A irradiation leading to apoptotic cell death (A and B) Measurement of cell death by FACS analysis after propidium iodide staining. (A) Treatment of Chang cells with TiO2 in combination with UVA irradiation caused cell death in proportion to the size of TiO2 (TiO2P25–70, TiO2P25–130, TiO2P25–300), while treatment with TiO2 alone did not induce cell death. (B) Treatment of WI-38 and MCF10A cells with TiO2P25–70 in combination with ultraviolet A irradiation caused cell death, while treatment with either TiO2 or ultraviolet A alone did not induce cell death.Abbreviations: UVA, ultraviolet A; WI-38, normal lung fibroblast cell line; MCF10A, normal breast epithelial cell line.
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f3-ijn-7-1203: TiO2 sensitizes normal cells to ultraviolet A irradiation leading to apoptotic cell death (A and B) Measurement of cell death by FACS analysis after propidium iodide staining. (A) Treatment of Chang cells with TiO2 in combination with UVA irradiation caused cell death in proportion to the size of TiO2 (TiO2P25–70, TiO2P25–130, TiO2P25–300), while treatment with TiO2 alone did not induce cell death. (B) Treatment of WI-38 and MCF10A cells with TiO2P25–70 in combination with ultraviolet A irradiation caused cell death, while treatment with either TiO2 or ultraviolet A alone did not induce cell death.Abbreviations: UVA, ultraviolet A; WI-38, normal lung fibroblast cell line; MCF10A, normal breast epithelial cell line.

Mentions: In previous studies, TiO2 has been excited by ultraviolet irradiation and showed cellular toxicity.18 Because treatment with TiO2 nanoparticles at a concentration of 150 ppm did not induce cell death, we went on to investigate the synergistic effect of TiO2 nanoparticles and ultraviolet irradiation on cell death in a Chang line. To examine this possibility, we treated the Chang cells with TiO2 nanoparticles (TiO2P25–70, TiO2P25–130, and TiO2P25–300) in combination with ultraviolet A irradiation (0.75 J/hour), cultured the cells for 24 hours, and then measured cell death by flow cytometry with propidium iodide staining. As shown in Figure 3A, treatment with TiO2 at a concentration of 150 ppm, at which there was no significant cell death (Figure S1), in combination with ultraviolet A, induced cell death in Chang cells in a size-dependent manner; almost 20% of Chang cells underwent cell death within 24 hours after combined treatment with TiO2P25–70 and ultraviolet A irradiation; 50% and 80% underwent cell death after treatment with TiO2P25–130 and TiO2P25–300 in combination with ultraviolet A irradiation, respectively (Figure 3A). However, treatment with TiO2 at 150 ppm or ultraviolet A irradiation alone did not cause significant cell death. In addition, combined treatment with TiO2 and ultraviolet A irradiation induced cell death in normal breast epithelial cells (MCF-10A) and lung fibroblasts (WI38, Figure 3B). Thereafter, we used TiO2 nanoparticles at a concentration of 150 ppm in all experiments. Also, although all three fractions of TiO2 showed cellular toxicity, we undertook further investigations of the mechanism of nanotoxicity only with the smallest sized nanoparticles, ie, the TiO2P25–70 fraction, because this fraction may minimize the influence of increased cellular exposure via gravitational settling of the nanoparticles as well as the toxicity mechanisms caused by the heavily agglomerated micron-sized particles.


Titanium dioxide induces apoptotic cell death through reactive oxygen species-mediated Fas upregulation and Bax activation.

Yoo KC, Yoon CH, Kwon D, Hyun KH, Woo SJ, Kim RK, Lim EJ, Suh Y, Kim MJ, Yoon TH, Lee SJ - Int J Nanomedicine (2012)

TiO2 sensitizes normal cells to ultraviolet A irradiation leading to apoptotic cell death (A and B) Measurement of cell death by FACS analysis after propidium iodide staining. (A) Treatment of Chang cells with TiO2 in combination with UVA irradiation caused cell death in proportion to the size of TiO2 (TiO2P25–70, TiO2P25–130, TiO2P25–300), while treatment with TiO2 alone did not induce cell death. (B) Treatment of WI-38 and MCF10A cells with TiO2P25–70 in combination with ultraviolet A irradiation caused cell death, while treatment with either TiO2 or ultraviolet A alone did not induce cell death.Abbreviations: UVA, ultraviolet A; WI-38, normal lung fibroblast cell line; MCF10A, normal breast epithelial cell line.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3298386&req=5

f3-ijn-7-1203: TiO2 sensitizes normal cells to ultraviolet A irradiation leading to apoptotic cell death (A and B) Measurement of cell death by FACS analysis after propidium iodide staining. (A) Treatment of Chang cells with TiO2 in combination with UVA irradiation caused cell death in proportion to the size of TiO2 (TiO2P25–70, TiO2P25–130, TiO2P25–300), while treatment with TiO2 alone did not induce cell death. (B) Treatment of WI-38 and MCF10A cells with TiO2P25–70 in combination with ultraviolet A irradiation caused cell death, while treatment with either TiO2 or ultraviolet A alone did not induce cell death.Abbreviations: UVA, ultraviolet A; WI-38, normal lung fibroblast cell line; MCF10A, normal breast epithelial cell line.
Mentions: In previous studies, TiO2 has been excited by ultraviolet irradiation and showed cellular toxicity.18 Because treatment with TiO2 nanoparticles at a concentration of 150 ppm did not induce cell death, we went on to investigate the synergistic effect of TiO2 nanoparticles and ultraviolet irradiation on cell death in a Chang line. To examine this possibility, we treated the Chang cells with TiO2 nanoparticles (TiO2P25–70, TiO2P25–130, and TiO2P25–300) in combination with ultraviolet A irradiation (0.75 J/hour), cultured the cells for 24 hours, and then measured cell death by flow cytometry with propidium iodide staining. As shown in Figure 3A, treatment with TiO2 at a concentration of 150 ppm, at which there was no significant cell death (Figure S1), in combination with ultraviolet A, induced cell death in Chang cells in a size-dependent manner; almost 20% of Chang cells underwent cell death within 24 hours after combined treatment with TiO2P25–70 and ultraviolet A irradiation; 50% and 80% underwent cell death after treatment with TiO2P25–130 and TiO2P25–300 in combination with ultraviolet A irradiation, respectively (Figure 3A). However, treatment with TiO2 at 150 ppm or ultraviolet A irradiation alone did not cause significant cell death. In addition, combined treatment with TiO2 and ultraviolet A irradiation induced cell death in normal breast epithelial cells (MCF-10A) and lung fibroblasts (WI38, Figure 3B). Thereafter, we used TiO2 nanoparticles at a concentration of 150 ppm in all experiments. Also, although all three fractions of TiO2 showed cellular toxicity, we undertook further investigations of the mechanism of nanotoxicity only with the smallest sized nanoparticles, ie, the TiO2P25–70 fraction, because this fraction may minimize the influence of increased cellular exposure via gravitational settling of the nanoparticles as well as the toxicity mechanisms caused by the heavily agglomerated micron-sized particles.

Bottom Line: In line with these results, knockdown of either Fas or Bax with specific siRNA significantly inhibited TiO(2)-induced apoptotic cell death.These results indicate that sub-100 nm sized TiO(2) treatment under ultraviolet A irradiation induces apoptotic cell death through reactive oxygen species-mediated upregulation of the death receptor, Fas, and activation of the preapoptotic protein, Bax.Elucidating the molecular mechanisms by which nanosized particles induce activation of cell death signaling pathways would be critical for the development of prevention strategies to minimize the cytotoxicity of nanomaterials.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Molecular Biochemistry, Department of Chemistry, Hanyang University, Seoul, Republic of Korea.

ABSTRACT

Background: Titanium dioxide (TiO(2)) has been widely used in many areas, including biomedicine, cosmetics, and environmental engineering. Recently, it has become evident that some TiO(2) particles have a considerable cytotoxic effect in normal human cells. However, the molecular basis for the cytotoxicity of TiO(2) has yet to be defined.

Methods and results: In this study, we demonstrated that combined treatment with TiO(2) nanoparticles sized less than 100 nm and ultraviolet A irradiation induces apoptotic cell death through reactive oxygen species-dependent upregulation of Fas and conformational activation of Bax in normal human cells. Treatment with P25 TiO(2) nanoparticles with a hydrodynamic size distribution centered around 70 nm (TiO(2) (P25-70)) together with ultraviolet A irradiation-induced caspase-dependent apoptotic cell death, accompanied by transcriptional upregulation of the death receptor, Fas, and conformational activation of Bax. In line with these results, knockdown of either Fas or Bax with specific siRNA significantly inhibited TiO(2)-induced apoptotic cell death. Moreover, inhibition of reactive oxygen species with an antioxidant, N-acetyl-L-cysteine, clearly suppressed upregulation of Fas, conformational activation of Bax, and subsequent apoptotic cell death in response to combination treatment using TiO(2) (P25-70) and ultraviolet A irradiation.

Conclusion: These results indicate that sub-100 nm sized TiO(2) treatment under ultraviolet A irradiation induces apoptotic cell death through reactive oxygen species-mediated upregulation of the death receptor, Fas, and activation of the preapoptotic protein, Bax. Elucidating the molecular mechanisms by which nanosized particles induce activation of cell death signaling pathways would be critical for the development of prevention strategies to minimize the cytotoxicity of nanomaterials.

Show MeSH