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Synergistic effects induced by a low dose of diesel particulate extract and ultraviolet-A in Caenorhabditis elegans: DNA damage-triggered germ cell apoptosis.

Guo X, Bian P, Liang J, Wang Y, Li L, Wang J, Yuan H, Chen S, Xu A, Wu L - Chem. Res. Toxicol. (2014)

Bottom Line: Diesel exhaust has been classified as a potential carcinogen and is associated with various health effects.A previous study showed that the doses for manifesting the mutagenetic effects of diesel exhaust could be reduced when coexposed with ultraviolet-A (UVA) in a cellular system.Our results demonstrated that though coexposure of wild type worms at young adult stage to low doses of DPE (20 μg/mL) plus UVA (0.2, 0.5, and 1.0 J/cm2) did not affect worm development (mitotic germ cells and brood size), it resulted in a significant induction of germ cell death.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Ion Beam Bioengineering, Hefei Institutes of Physical Science, Chinese Academy of Sciences , P.O. Box 1138, Hefei, Anhui 230031, P.R. China.

ABSTRACT
Diesel exhaust has been classified as a potential carcinogen and is associated with various health effects. A previous study showed that the doses for manifesting the mutagenetic effects of diesel exhaust could be reduced when coexposed with ultraviolet-A (UVA) in a cellular system. However, the mechanisms underlying synergistic effects remain to be clarified, especially in an in vivo system. In the present study, using Caenorhabditis elegans (C. elegans) as an in vivo system we studied the synergistic effects of diesel particulate extract (DPE) plus UVA, and the underlying mechanisms were dissected genetically using related mutants. Our results demonstrated that though coexposure of wild type worms at young adult stage to low doses of DPE (20 μg/mL) plus UVA (0.2, 0.5, and 1.0 J/cm2) did not affect worm development (mitotic germ cells and brood size), it resulted in a significant induction of germ cell death. Using the strain of hus-1::gfp, distinct foci of HUS-1::GFP was observed in proliferating germ cells, indicating the DNA damage after worms were treated with DPE plus UVA. Moreover, the induction of germ cell death by DPE plus UVA was alleviated in single-gene loss-of-function mutations of core apoptotic, checkpoint HUS-1, CEP-1/p53, and MAPK dependent signaling pathways. Using a reactive oxygen species (ROS) probe, it was found that the production of ROS in worms coexposed to DPE plus UVA increased in a time-dependent manner. In addition, employing a singlet oxygen (1O2) trapping probe, 2,2,6,6-tetramethyl-4-piperidone, coupled with electron spin resonance analysis, we demonstrated the increased 1O2 production in worms coexposed to DPE plus UVA. These results indicated that UVA could enhance the apoptotic induction of DPE at low doses through a DNA damage-triggered pathway and that the production of ROS, especially (1)O2, played a pivotal role in initiating the synergistic process.

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ROS, especially 1O2, play a crucial rolein germ cell apoptosis induced by DPE (20 μg/mL) plus UVA (0.5J/cm2) . (A) The induction of germ cell apoptosis by DPEplus UVA was effectively rescued by NaN3, a specific 1O2 scavenger. (B) The in situ expressionof fluorescence was measured using DCF-DA (a molecular probe) in singlewhole worms. (C) The relative fluorescence was determined using Image-ProPlus, version 6.0. (D) Three-line ESR spectra of the 4-O-TEMPO signal.(E) Relative signal intensity of 4-O-TEMPO. All these results suggestedthat ROS, especially 1O2, play a pivotal rolein the induction of germ cell apoptosis by DPE plus UVA. Data werepooled from at least three independent experiments. All values arepresented as the means ± SE; n ≥ 40,and * represents P < 0.05.
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fig8: ROS, especially 1O2, play a crucial rolein germ cell apoptosis induced by DPE (20 μg/mL) plus UVA (0.5J/cm2) . (A) The induction of germ cell apoptosis by DPEplus UVA was effectively rescued by NaN3, a specific 1O2 scavenger. (B) The in situ expressionof fluorescence was measured using DCF-DA (a molecular probe) in singlewhole worms. (C) The relative fluorescence was determined using Image-ProPlus, version 6.0. (D) Three-line ESR spectra of the 4-O-TEMPO signal.(E) Relative signal intensity of 4-O-TEMPO. All these results suggestedthat ROS, especially 1O2, play a pivotal rolein the induction of germ cell apoptosis by DPE plus UVA. Data werepooled from at least three independent experiments. All values arepresented as the means ± SE; n ≥ 40,and * represents P < 0.05.

Mentions: ROS wasreported to activate the mitogen-activated protein kinases, and playedan important role in the induction of DNA damage.48,50 To find out the role of ROS in the induction of germ cell apoptosisby DPE plus UVA, the ROS quenchers, NaN3 and DMSO, wereemployed. As shown in Figure 8A, the inductionof germ cell apoptosis by coexposure to DPE (20 μg/mL) + UVA(0.5 J/cm2) was significantly inhibited in the presenceof NaN3 (in both cases, P < 0.05) butonly partially inhibited in the presence of DMSO (in both cases, P > 0.05). In addition, the production of ROS in individualworm coexposure to DPE plus UVA increased in a time-dependent mannerand reached the highest level at a time point of 24 h compared withthat of the control or single-treated populations and decreased afterward(Figure 8B and C).


Synergistic effects induced by a low dose of diesel particulate extract and ultraviolet-A in Caenorhabditis elegans: DNA damage-triggered germ cell apoptosis.

Guo X, Bian P, Liang J, Wang Y, Li L, Wang J, Yuan H, Chen S, Xu A, Wu L - Chem. Res. Toxicol. (2014)

ROS, especially 1O2, play a crucial rolein germ cell apoptosis induced by DPE (20 μg/mL) plus UVA (0.5J/cm2) . (A) The induction of germ cell apoptosis by DPEplus UVA was effectively rescued by NaN3, a specific 1O2 scavenger. (B) The in situ expressionof fluorescence was measured using DCF-DA (a molecular probe) in singlewhole worms. (C) The relative fluorescence was determined using Image-ProPlus, version 6.0. (D) Three-line ESR spectra of the 4-O-TEMPO signal.(E) Relative signal intensity of 4-O-TEMPO. All these results suggestedthat ROS, especially 1O2, play a pivotal rolein the induction of germ cell apoptosis by DPE plus UVA. Data werepooled from at least three independent experiments. All values arepresented as the means ± SE; n ≥ 40,and * represents P < 0.05.
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Related In: Results  -  Collection

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fig8: ROS, especially 1O2, play a crucial rolein germ cell apoptosis induced by DPE (20 μg/mL) plus UVA (0.5J/cm2) . (A) The induction of germ cell apoptosis by DPEplus UVA was effectively rescued by NaN3, a specific 1O2 scavenger. (B) The in situ expressionof fluorescence was measured using DCF-DA (a molecular probe) in singlewhole worms. (C) The relative fluorescence was determined using Image-ProPlus, version 6.0. (D) Three-line ESR spectra of the 4-O-TEMPO signal.(E) Relative signal intensity of 4-O-TEMPO. All these results suggestedthat ROS, especially 1O2, play a pivotal rolein the induction of germ cell apoptosis by DPE plus UVA. Data werepooled from at least three independent experiments. All values arepresented as the means ± SE; n ≥ 40,and * represents P < 0.05.
Mentions: ROS wasreported to activate the mitogen-activated protein kinases, and playedan important role in the induction of DNA damage.48,50 To find out the role of ROS in the induction of germ cell apoptosisby DPE plus UVA, the ROS quenchers, NaN3 and DMSO, wereemployed. As shown in Figure 8A, the inductionof germ cell apoptosis by coexposure to DPE (20 μg/mL) + UVA(0.5 J/cm2) was significantly inhibited in the presenceof NaN3 (in both cases, P < 0.05) butonly partially inhibited in the presence of DMSO (in both cases, P > 0.05). In addition, the production of ROS in individualworm coexposure to DPE plus UVA increased in a time-dependent mannerand reached the highest level at a time point of 24 h compared withthat of the control or single-treated populations and decreased afterward(Figure 8B and C).

Bottom Line: Diesel exhaust has been classified as a potential carcinogen and is associated with various health effects.A previous study showed that the doses for manifesting the mutagenetic effects of diesel exhaust could be reduced when coexposed with ultraviolet-A (UVA) in a cellular system.Our results demonstrated that though coexposure of wild type worms at young adult stage to low doses of DPE (20 μg/mL) plus UVA (0.2, 0.5, and 1.0 J/cm2) did not affect worm development (mitotic germ cells and brood size), it resulted in a significant induction of germ cell death.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Ion Beam Bioengineering, Hefei Institutes of Physical Science, Chinese Academy of Sciences , P.O. Box 1138, Hefei, Anhui 230031, P.R. China.

ABSTRACT
Diesel exhaust has been classified as a potential carcinogen and is associated with various health effects. A previous study showed that the doses for manifesting the mutagenetic effects of diesel exhaust could be reduced when coexposed with ultraviolet-A (UVA) in a cellular system. However, the mechanisms underlying synergistic effects remain to be clarified, especially in an in vivo system. In the present study, using Caenorhabditis elegans (C. elegans) as an in vivo system we studied the synergistic effects of diesel particulate extract (DPE) plus UVA, and the underlying mechanisms were dissected genetically using related mutants. Our results demonstrated that though coexposure of wild type worms at young adult stage to low doses of DPE (20 μg/mL) plus UVA (0.2, 0.5, and 1.0 J/cm2) did not affect worm development (mitotic germ cells and brood size), it resulted in a significant induction of germ cell death. Using the strain of hus-1::gfp, distinct foci of HUS-1::GFP was observed in proliferating germ cells, indicating the DNA damage after worms were treated with DPE plus UVA. Moreover, the induction of germ cell death by DPE plus UVA was alleviated in single-gene loss-of-function mutations of core apoptotic, checkpoint HUS-1, CEP-1/p53, and MAPK dependent signaling pathways. Using a reactive oxygen species (ROS) probe, it was found that the production of ROS in worms coexposed to DPE plus UVA increased in a time-dependent manner. In addition, employing a singlet oxygen (1O2) trapping probe, 2,2,6,6-tetramethyl-4-piperidone, coupled with electron spin resonance analysis, we demonstrated the increased 1O2 production in worms coexposed to DPE plus UVA. These results indicated that UVA could enhance the apoptotic induction of DPE at low doses through a DNA damage-triggered pathway and that the production of ROS, especially (1)O2, played a pivotal role in initiating the synergistic process.

Show MeSH
Related in: MedlinePlus