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Molecular mechanism of DNA damage induced by titanium dioxide nanoparticles in toll-like receptor 3 or 4 expressing human hepatocarcinoma cell lines.

El-Said KS, Ali EM, Kanehira K, Taniguchi A - J Nanobiotechnology (2014)

Bottom Line: Our results showed evidence for elevated oxidative stress, including the generation of reactive oxygen species (ROS), with increased hydrogen peroxide levels, decreased glutathione peroxidase, and reduced glutathione and activated caspase-3 levels in cells exposed for 48 h to 10 μg/ml TiO2 NPs.These effects were enhanced by TLR4 and reduced by TLR3 over-expression.Our results indicated that TiO2 NPs induced ROS, and the above molecules are implicated in the genotoxicity induced by TiO2 NPs.

View Article: PubMed Central - PubMed

Affiliation: Cell-Material Interaction Group, Biomaterial Unit, Nano-Bio Field, Interaction Center for Material Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), Tsukuba, Japan. SAMYELSAIDALI.Karim@nims.go.jp.

ABSTRACT

Background: Titanium dioxide nanoparticles (TiO2 NPs) are widely used in the biological sciences. The increasing use of TiO2 NPs increases the risk of humans and the environment being exposed to NPs. We previously showed that toll-like receptors (TLRs) play an important role in the interactions between NPs and cells. Our previous results indicated that TLR4 increased the DNA damage response induced by TiO2 NPs, due to enhanced NP uptake into the cytoplasm, whereas TLR3 expression decreased the DNA damage response induced by TiO2 NPs because of NP retention in the endosome. In this study, we explored the molecular mechanism of the DNA damage response induced by TiO2 NPs using TLR3 or TLR4 transfected cells. We examined the effect of TLR3 or TLR4 over-expression on oxidative stress and the effect of DNA damage induced by TiO2 NPs on gene expression levels.

Results: Our results showed evidence for elevated oxidative stress, including the generation of reactive oxygen species (ROS), with increased hydrogen peroxide levels, decreased glutathione peroxidase, and reduced glutathione and activated caspase-3 levels in cells exposed for 48 h to 10 μg/ml TiO2 NPs. These effects were enhanced by TLR4 and reduced by TLR3 over-expression. Seventeen genes related to DNA double-strand breaks and apoptosis were induced, particularly IP6K3 and ATM.

Conclusion: Our results indicated that TiO2 NPs induced ROS, and the above molecules are implicated in the genotoxicity induced by TiO2 NPs.

No MeSH data available.


Related in: MedlinePlus

Reduced glutathione (GSH) levels in TiO2NP-exposed HepG2 cells with and without TLR3 or TLR4 transfection. The transfected cells were exposed to 10 μg/ml TiO2 NPs for 48 h. Each plot was produced from at least 3 replicate measurements. All values are presented as mean ± S.D. (n ≥3), (*P <0.05).
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Fig4: Reduced glutathione (GSH) levels in TiO2NP-exposed HepG2 cells with and without TLR3 or TLR4 transfection. The transfected cells were exposed to 10 μg/ml TiO2 NPs for 48 h. Each plot was produced from at least 3 replicate measurements. All values are presented as mean ± S.D. (n ≥3), (*P <0.05).

Mentions: GPX catalyzes the reduction of hydroperoxides, including H2O2, using GSH tripeptide as a hydrogen donor. In order to confirm the elevated H2O2 levels, we measured GPX activity and GSH levels. The results showed that TiO2 NP treatment inhibited GPX enzyme activity in HepG2 cells by 1.6 and 3.6 fold in the absence and presence of TLR4 transfection, respectively, when compared to control cells. Over-expression of TLR3 with TiO2 NP exposure resulted in a 1.3 fold decrease in GPX activity compared to control cells (Figure 3). Similarly, TLR4 over-expression exacerbated TiO2 NP-induced reductions in GSH levels, while TLR3 over-expression appeared to reduce the effects of TiO2 NP exposure (Figure 4). These results showed that reduced GPX detoxification of H2O2 is involved in the oxidative stress response stimulated by TiO2 NPs, regardless of TLR3 or TLR4 over-expression, and confirmed the accumulation of H2O2 due to inhibition of the antioxidants GPX and GSH.Figure 3


Molecular mechanism of DNA damage induced by titanium dioxide nanoparticles in toll-like receptor 3 or 4 expressing human hepatocarcinoma cell lines.

El-Said KS, Ali EM, Kanehira K, Taniguchi A - J Nanobiotechnology (2014)

Reduced glutathione (GSH) levels in TiO2NP-exposed HepG2 cells with and without TLR3 or TLR4 transfection. The transfected cells were exposed to 10 μg/ml TiO2 NPs for 48 h. Each plot was produced from at least 3 replicate measurements. All values are presented as mean ± S.D. (n ≥3), (*P <0.05).
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4260178&req=5

Fig4: Reduced glutathione (GSH) levels in TiO2NP-exposed HepG2 cells with and without TLR3 or TLR4 transfection. The transfected cells were exposed to 10 μg/ml TiO2 NPs for 48 h. Each plot was produced from at least 3 replicate measurements. All values are presented as mean ± S.D. (n ≥3), (*P <0.05).
Mentions: GPX catalyzes the reduction of hydroperoxides, including H2O2, using GSH tripeptide as a hydrogen donor. In order to confirm the elevated H2O2 levels, we measured GPX activity and GSH levels. The results showed that TiO2 NP treatment inhibited GPX enzyme activity in HepG2 cells by 1.6 and 3.6 fold in the absence and presence of TLR4 transfection, respectively, when compared to control cells. Over-expression of TLR3 with TiO2 NP exposure resulted in a 1.3 fold decrease in GPX activity compared to control cells (Figure 3). Similarly, TLR4 over-expression exacerbated TiO2 NP-induced reductions in GSH levels, while TLR3 over-expression appeared to reduce the effects of TiO2 NP exposure (Figure 4). These results showed that reduced GPX detoxification of H2O2 is involved in the oxidative stress response stimulated by TiO2 NPs, regardless of TLR3 or TLR4 over-expression, and confirmed the accumulation of H2O2 due to inhibition of the antioxidants GPX and GSH.Figure 3

Bottom Line: Our results showed evidence for elevated oxidative stress, including the generation of reactive oxygen species (ROS), with increased hydrogen peroxide levels, decreased glutathione peroxidase, and reduced glutathione and activated caspase-3 levels in cells exposed for 48 h to 10 μg/ml TiO2 NPs.These effects were enhanced by TLR4 and reduced by TLR3 over-expression.Our results indicated that TiO2 NPs induced ROS, and the above molecules are implicated in the genotoxicity induced by TiO2 NPs.

View Article: PubMed Central - PubMed

Affiliation: Cell-Material Interaction Group, Biomaterial Unit, Nano-Bio Field, Interaction Center for Material Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), Tsukuba, Japan. SAMYELSAIDALI.Karim@nims.go.jp.

ABSTRACT

Background: Titanium dioxide nanoparticles (TiO2 NPs) are widely used in the biological sciences. The increasing use of TiO2 NPs increases the risk of humans and the environment being exposed to NPs. We previously showed that toll-like receptors (TLRs) play an important role in the interactions between NPs and cells. Our previous results indicated that TLR4 increased the DNA damage response induced by TiO2 NPs, due to enhanced NP uptake into the cytoplasm, whereas TLR3 expression decreased the DNA damage response induced by TiO2 NPs because of NP retention in the endosome. In this study, we explored the molecular mechanism of the DNA damage response induced by TiO2 NPs using TLR3 or TLR4 transfected cells. We examined the effect of TLR3 or TLR4 over-expression on oxidative stress and the effect of DNA damage induced by TiO2 NPs on gene expression levels.

Results: Our results showed evidence for elevated oxidative stress, including the generation of reactive oxygen species (ROS), with increased hydrogen peroxide levels, decreased glutathione peroxidase, and reduced glutathione and activated caspase-3 levels in cells exposed for 48 h to 10 μg/ml TiO2 NPs. These effects were enhanced by TLR4 and reduced by TLR3 over-expression. Seventeen genes related to DNA double-strand breaks and apoptosis were induced, particularly IP6K3 and ATM.

Conclusion: Our results indicated that TiO2 NPs induced ROS, and the above molecules are implicated in the genotoxicity induced by TiO2 NPs.

No MeSH data available.


Related in: MedlinePlus