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γ-Tocotrienol prevents 5-FU-induced reactive oxygen species production in human oral keratinocytes through the stabilization of 5-FU-induced activation of Nrf2.

Takano H, Momota Y, Kani K, Aota K, Yamamura Y, Yamanoi T, Azuma M - Int. J. Oncol. (2015)

Bottom Line: When cells were treated with 5-FU alone, significant growth inhibition was observed as compared to untreated cells.Simultaneous treatment of cells with these agents resulted in the significant recovery of cell growth, owing to the suppression of ROS generation by γ-tocotrienol.In addition, expression of Nrf2-dependent antioxidant genes, such as heme oxygenase-1 (HO-1) and quinone oxidoreductase-1 (NQO-1), was significantly augmented by treatment of cells with both agents.

View Article: PubMed Central - PubMed

Affiliation: Department of Oral Medicine, Institute of Health Biosciences, The University of Tokushima Graduate Faculty of Dentistry, Tokushima, Japan.

ABSTRACT

Unlabelled: Chemotherapy-induced oral mucositis is a common adverse event in patients with oral squamous cell carcinoma, and is initiated through a variety of mechanisms, including the generation of reactive oxygen species (ROS). In this study, we examined the preventive effect of γ-tocotrienol on the 5-FU-induced ROS production in human oral keratinocytes (RT7). We treated RT7 cells with 5-FU and γ-tocotrienol at concentrations of 10 µg/ml and 10 nM, respectively. When cells were treated with 5-FU alone, significant growth inhibition was observed as compared to untreated cells. This inhibition was, in part, due to the ROS gene-rated by 5-FU treatment, because N-acetyl cysteine (NAC), a ROS scavenger, significantly ameliorated the growth of RT7 cells. γ-tocotrienol showed no cytotoxic effect on the growth of RT7 cells. Simultaneous treatment of cells with these agents resulted in the significant recovery of cell growth, owing to the suppression of ROS generation by γ-tocotrienol. Whereas 5-FU stimulated the expression of NF-E2-related factor 2 (Nrf2) protein in the nucleus up to 12 h after treatment of RT7 cells, γ-tocotrienol had no obvious effect on the expression of nuclear Nrf2 protein. Of note, the combined treatment with both agents stabilized the 5-FU-induced nuclear Nrf2 protein expression until 24 h after treatment. In addition, expression of Nrf2-dependent antioxidant genes, such as heme oxygenase-1 (HO-1) and

Nad(p)h: quinone oxidoreductase-1 (NQO-1), was significantly augmented by treatment of cells with both agents. These findings suggest that γ-tocotrienol could prevent 5-FU-induced ROS generation by stabilizing Nrf2 activation, thereby leading to ROS detoxification and cell survival in human oral keratinocytes.

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Effects of γ-tocotrienol on the growth and production of reactive oxygen species (ROS) in RT7 cells. (A) Cells were grown for 3 days in 96-well plates containing medium supplemented with 5-FU (10 μg/ml, △), γ-tocotrienol (γT3, 10 nM, ●), or both (▲). γ-tocotrienol treatment significantly restored the 5-FU-induced growth inhibition in RT7 cells. (B) Effect of γ-tocotrienol on the generation of 5-FU-induced ROS. γ-tocotrienol (γT3, 10 nM) significantly suppressed the production of ROS at 48 h after treatment with 5-FU (10 μg/ml). Statistically significant at *P<0.05 and **P<0.01 (Mann-Whitney U test).
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f3-ijo-46-04-1453: Effects of γ-tocotrienol on the growth and production of reactive oxygen species (ROS) in RT7 cells. (A) Cells were grown for 3 days in 96-well plates containing medium supplemented with 5-FU (10 μg/ml, △), γ-tocotrienol (γT3, 10 nM, ●), or both (▲). γ-tocotrienol treatment significantly restored the 5-FU-induced growth inhibition in RT7 cells. (B) Effect of γ-tocotrienol on the generation of 5-FU-induced ROS. γ-tocotrienol (γT3, 10 nM) significantly suppressed the production of ROS at 48 h after treatment with 5-FU (10 μg/ml). Statistically significant at *P<0.05 and **P<0.01 (Mann-Whitney U test).

Mentions: The growth response of RT7 cells to γ-tocotrienol (10 nM) was investigated by MTT assay for 3 days. As can be seen in Fig. 3A, γ-tocotrienol alone did not affect RT7 cell growth when compared to the growth of the control cells. Whether or not γ-tocotrienol can restore the suppressive effect of 5-FU on RT7 cell growth was also examined. The dose of γ-tocotrienol (10 nM) that did not affect cell growth when used alone resulted in an enhanced recovery of cell growth when used in combination with 5-FU. In addition, although 5-FU alone stimulated the generation of ROS in RT7 cells, combined treatment with 5-FU and γ-tocotrienol significantly inhibited the production of ROS at 48 h (Fig. 3B).


γ-Tocotrienol prevents 5-FU-induced reactive oxygen species production in human oral keratinocytes through the stabilization of 5-FU-induced activation of Nrf2.

Takano H, Momota Y, Kani K, Aota K, Yamamura Y, Yamanoi T, Azuma M - Int. J. Oncol. (2015)

Effects of γ-tocotrienol on the growth and production of reactive oxygen species (ROS) in RT7 cells. (A) Cells were grown for 3 days in 96-well plates containing medium supplemented with 5-FU (10 μg/ml, △), γ-tocotrienol (γT3, 10 nM, ●), or both (▲). γ-tocotrienol treatment significantly restored the 5-FU-induced growth inhibition in RT7 cells. (B) Effect of γ-tocotrienol on the generation of 5-FU-induced ROS. γ-tocotrienol (γT3, 10 nM) significantly suppressed the production of ROS at 48 h after treatment with 5-FU (10 μg/ml). Statistically significant at *P<0.05 and **P<0.01 (Mann-Whitney U test).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4356501&req=5

f3-ijo-46-04-1453: Effects of γ-tocotrienol on the growth and production of reactive oxygen species (ROS) in RT7 cells. (A) Cells were grown for 3 days in 96-well plates containing medium supplemented with 5-FU (10 μg/ml, △), γ-tocotrienol (γT3, 10 nM, ●), or both (▲). γ-tocotrienol treatment significantly restored the 5-FU-induced growth inhibition in RT7 cells. (B) Effect of γ-tocotrienol on the generation of 5-FU-induced ROS. γ-tocotrienol (γT3, 10 nM) significantly suppressed the production of ROS at 48 h after treatment with 5-FU (10 μg/ml). Statistically significant at *P<0.05 and **P<0.01 (Mann-Whitney U test).
Mentions: The growth response of RT7 cells to γ-tocotrienol (10 nM) was investigated by MTT assay for 3 days. As can be seen in Fig. 3A, γ-tocotrienol alone did not affect RT7 cell growth when compared to the growth of the control cells. Whether or not γ-tocotrienol can restore the suppressive effect of 5-FU on RT7 cell growth was also examined. The dose of γ-tocotrienol (10 nM) that did not affect cell growth when used alone resulted in an enhanced recovery of cell growth when used in combination with 5-FU. In addition, although 5-FU alone stimulated the generation of ROS in RT7 cells, combined treatment with 5-FU and γ-tocotrienol significantly inhibited the production of ROS at 48 h (Fig. 3B).

Bottom Line: When cells were treated with 5-FU alone, significant growth inhibition was observed as compared to untreated cells.Simultaneous treatment of cells with these agents resulted in the significant recovery of cell growth, owing to the suppression of ROS generation by γ-tocotrienol.In addition, expression of Nrf2-dependent antioxidant genes, such as heme oxygenase-1 (HO-1) and quinone oxidoreductase-1 (NQO-1), was significantly augmented by treatment of cells with both agents.

View Article: PubMed Central - PubMed

Affiliation: Department of Oral Medicine, Institute of Health Biosciences, The University of Tokushima Graduate Faculty of Dentistry, Tokushima, Japan.

ABSTRACT

Unlabelled: Chemotherapy-induced oral mucositis is a common adverse event in patients with oral squamous cell carcinoma, and is initiated through a variety of mechanisms, including the generation of reactive oxygen species (ROS). In this study, we examined the preventive effect of γ-tocotrienol on the 5-FU-induced ROS production in human oral keratinocytes (RT7). We treated RT7 cells with 5-FU and γ-tocotrienol at concentrations of 10 µg/ml and 10 nM, respectively. When cells were treated with 5-FU alone, significant growth inhibition was observed as compared to untreated cells. This inhibition was, in part, due to the ROS gene-rated by 5-FU treatment, because N-acetyl cysteine (NAC), a ROS scavenger, significantly ameliorated the growth of RT7 cells. γ-tocotrienol showed no cytotoxic effect on the growth of RT7 cells. Simultaneous treatment of cells with these agents resulted in the significant recovery of cell growth, owing to the suppression of ROS generation by γ-tocotrienol. Whereas 5-FU stimulated the expression of NF-E2-related factor 2 (Nrf2) protein in the nucleus up to 12 h after treatment of RT7 cells, γ-tocotrienol had no obvious effect on the expression of nuclear Nrf2 protein. Of note, the combined treatment with both agents stabilized the 5-FU-induced nuclear Nrf2 protein expression until 24 h after treatment. In addition, expression of Nrf2-dependent antioxidant genes, such as heme oxygenase-1 (HO-1) and

Nad(p)h: quinone oxidoreductase-1 (NQO-1), was significantly augmented by treatment of cells with both agents. These findings suggest that γ-tocotrienol could prevent 5-FU-induced ROS generation by stabilizing Nrf2 activation, thereby leading to ROS detoxification and cell survival in human oral keratinocytes.

Show MeSH
Related in: MedlinePlus