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Reproductive toxicity and gender differences induced by cadmium telluride quantum dots in an invertebrate model organism

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ABSTRACT

Sexual glands are key sites affected by nanotoxicity, but there is no sensitive assay for measuring reproductive toxicity in animals. The aim of this study was to investigate the toxic effects of cadmium telluride quantum dots (CdTe-QDs) on gonads in a model organism, Bombyx mori. After dorsal vein injection of 0.32 nmol of CdTe-QDs per individual, the QDs passed through the outer membranes of gonads via the generation of ROS in the membranes of spermatocysts and ovarioles, as well as internal germ cells, thereby inducing early germ cell death or malformations via complex mechanisms related to apoptosis and autophagy through mitochondrial and lysosomal pathways. Histological observations of the gonads and quantitative analyses of germ cell development showed that the reproductive toxicity was characterized by obvious male sensitivity. Exposure to QDs in the early stage of males had severe adverse effects on the quantity and quality of sperm, which was the main reason for the occurrence of unfertilized eggs. Ala- or Gly-conjugated QDs could reduce the nanotoxicity of CdTe-QDs during germ cell development and fertilization of their offspring. The results demonstrate that males are preferable models for evaluating the reproductive toxicity of QDs in combined in vivo/in vitro investigations.

No MeSH data available.


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(A)Location of the gonads in silkworm larva. QDs were found in the testes (B) and ovaries (C) by the characteristic green fluorescent. Fifth instar larvae received vascular injection of 0.32 nmol CdTe QDs per larva (10 μL at 32 μM per individual) at 48 h after molting, whereas the control organisms (CK) were injected with the same volume of pure water. The gonads were removed randomly from male larvae at 24 h and female larvae at 48 h after exposure to QDs. WL + FL, merged images showing white light and fluorescent light. FL, fluorescent light. The green fluorescence of QDs was observed at an emission wavelength of 530 nm using a fluorescence microscope (Olympus BX51, Tokyo, Japan). Bar = 100 μm.
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f1: (A)Location of the gonads in silkworm larva. QDs were found in the testes (B) and ovaries (C) by the characteristic green fluorescent. Fifth instar larvae received vascular injection of 0.32 nmol CdTe QDs per larva (10 μL at 32 μM per individual) at 48 h after molting, whereas the control organisms (CK) were injected with the same volume of pure water. The gonads were removed randomly from male larvae at 24 h and female larvae at 48 h after exposure to QDs. WL + FL, merged images showing white light and fluorescent light. FL, fluorescent light. The green fluorescence of QDs was observed at an emission wavelength of 530 nm using a fluorescence microscope (Olympus BX51, Tokyo, Japan). Bar = 100 μm.

Mentions: In our previous study, we showed that QDs can rapidly enter circulating blood cells in silkworms after dorsal vein injection of 0.08 or 0.32 nmol CdTe QDs per larva (10 μL at 8 μM or 32 μM per individual), thereby reducing the capacity for hematopoiesis6. In the present study, a similar dorsal vein injection method was used to expose silkworm hemolymph to 0.32 nmol CdTe QDs per larva (10 μL at 32 μM per individual). The characteristic green fluorescence of QDs was detected in the testes at 24 h after injection (Fig. 1B). Similar results were also obtained in the ovaries at 48 h after injection (Fig. 1B). The transfer of QDs from the hemolymph circulation system to the reproductive system emphasizes the utility of this system for studying potentially reprotoxic effects. We further investigated the effects of modifying the surfaces of QDs with amino acids on their transfer into the reproductive system. They found that the characteristic green fluorescence of QDs was detected in the testes and ovaries at 12 h after exposure to 0.64 nmol CdTe QDs, QDs-Ala or QDs-Gly (10 μL at 64 μM per individual), but the proportion of glands that exhibited weak fluorescence in the QDs-Ala or QDs-Gly treatment groups was higher than that in the QDs group (Fig. S1), thereby implying that Ala- or Gly-capped CdTe QDs may reduce the transfer and accumulation of QDs to the gonads.


Reproductive toxicity and gender differences induced by cadmium telluride quantum dots in an invertebrate model organism
(A)Location of the gonads in silkworm larva. QDs were found in the testes (B) and ovaries (C) by the characteristic green fluorescent. Fifth instar larvae received vascular injection of 0.32 nmol CdTe QDs per larva (10 μL at 32 μM per individual) at 48 h after molting, whereas the control organisms (CK) were injected with the same volume of pure water. The gonads were removed randomly from male larvae at 24 h and female larvae at 48 h after exposure to QDs. WL + FL, merged images showing white light and fluorescent light. FL, fluorescent light. The green fluorescence of QDs was observed at an emission wavelength of 530 nm using a fluorescence microscope (Olympus BX51, Tokyo, Japan). Bar = 100 μm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5037452&req=5

f1: (A)Location of the gonads in silkworm larva. QDs were found in the testes (B) and ovaries (C) by the characteristic green fluorescent. Fifth instar larvae received vascular injection of 0.32 nmol CdTe QDs per larva (10 μL at 32 μM per individual) at 48 h after molting, whereas the control organisms (CK) were injected with the same volume of pure water. The gonads were removed randomly from male larvae at 24 h and female larvae at 48 h after exposure to QDs. WL + FL, merged images showing white light and fluorescent light. FL, fluorescent light. The green fluorescence of QDs was observed at an emission wavelength of 530 nm using a fluorescence microscope (Olympus BX51, Tokyo, Japan). Bar = 100 μm.
Mentions: In our previous study, we showed that QDs can rapidly enter circulating blood cells in silkworms after dorsal vein injection of 0.08 or 0.32 nmol CdTe QDs per larva (10 μL at 8 μM or 32 μM per individual), thereby reducing the capacity for hematopoiesis6. In the present study, a similar dorsal vein injection method was used to expose silkworm hemolymph to 0.32 nmol CdTe QDs per larva (10 μL at 32 μM per individual). The characteristic green fluorescence of QDs was detected in the testes at 24 h after injection (Fig. 1B). Similar results were also obtained in the ovaries at 48 h after injection (Fig. 1B). The transfer of QDs from the hemolymph circulation system to the reproductive system emphasizes the utility of this system for studying potentially reprotoxic effects. We further investigated the effects of modifying the surfaces of QDs with amino acids on their transfer into the reproductive system. They found that the characteristic green fluorescence of QDs was detected in the testes and ovaries at 12 h after exposure to 0.64 nmol CdTe QDs, QDs-Ala or QDs-Gly (10 μL at 64 μM per individual), but the proportion of glands that exhibited weak fluorescence in the QDs-Ala or QDs-Gly treatment groups was higher than that in the QDs group (Fig. S1), thereby implying that Ala- or Gly-capped CdTe QDs may reduce the transfer and accumulation of QDs to the gonads.

View Article: PubMed Central - PubMed

ABSTRACT

Sexual glands are key sites affected by nanotoxicity, but there is no sensitive assay for measuring reproductive toxicity in animals. The aim of this study was to investigate the toxic effects of cadmium telluride quantum dots (CdTe-QDs) on gonads in a model organism, Bombyx mori. After dorsal vein injection of 0.32 nmol of CdTe-QDs per individual, the QDs passed through the outer membranes of gonads via the generation of ROS in the membranes of spermatocysts and ovarioles, as well as internal germ cells, thereby inducing early germ cell death or malformations via complex mechanisms related to apoptosis and autophagy through mitochondrial and lysosomal pathways. Histological observations of the gonads and quantitative analyses of germ cell development showed that the reproductive toxicity was characterized by obvious male sensitivity. Exposure to QDs in the early stage of males had severe adverse effects on the quantity and quality of sperm, which was the main reason for the occurrence of unfertilized eggs. Ala- or Gly-conjugated QDs could reduce the nanotoxicity of CdTe-QDs during germ cell development and fertilization of their offspring. The results demonstrate that males are preferable models for evaluating the reproductive toxicity of QDs in combined in vivo/in vitro investigations.

No MeSH data available.


Related in: MedlinePlus