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Sulforaphane Protects the Liver against CdSe Quantum Dot-Induced Cytotoxicity.

Wang W, He Y, Yu G, Li B, Sexton DW, Wileman T, Roberts AA, Hamilton CJ, Liu R, Chao Y, Shan Y, Bao Y - PLoS ONE (2015)

Bottom Line: Wortmannin inhibition of SFN-induced autophagy significantly suppressed the protective effect of SFN on CdSe QD-induced cell death.CdSe QDs caused significant liver damage in mice, and this was decreased by SFN treatment.In conclusion, SFN attenuated the cytotoxicity of CdSe QDs in both human hepatocytes and in the mouse liver, and this protection was associated with the induction of Nrf2 pathway and autophagy.

View Article: PubMed Central - PubMed

Affiliation: Norwich Medical School, University of East Anglia, Norwich, Norfolk, United Kingdom.

ABSTRACT
The potential cytotoxicity of cadmium selenide (CdSe) quantum dots (QDs) presents a barrier to their use in biomedical imaging or as diagnostic and therapeutic agents. Sulforaphane (SFN) is a chemoprotective compound derived from cruciferous vegetables which can up-regulate antioxidant enzymes and induce apoptosis and autophagy. This study reports the effects of SFN on CdSe QD-induced cytotoxicity in immortalised human hepatocytes and in the livers of mice. CdSe QDs induced dose-dependent cell death in hepatocytes with an IC50 = 20.4 μM. Pre-treatment with SFN (5 μM) increased cell viability in response to CdSe QDs (20 μM) from 49.5 to 89.3%. SFN induced a pro-oxidant effect characterized by depletion of intracellular reduced glutathione during short term exposure (3-6 h), followed by up-regulation of antioxidant enzymes and glutathione levels at 24 h. SFN also caused Nrf2 translocation into the nucleus, up-regulation of antioxidant enzymes and autophagy. siRNA knockdown of Nrf2 suggests that the Nrf2 pathway plays a role in the protection against CdSe QD-induced cell death. Wortmannin inhibition of SFN-induced autophagy significantly suppressed the protective effect of SFN on CdSe QD-induced cell death. Moreover, the role of autophagy in SFN protection against CdSe QD-induced cell death was confirmed using mouse embryonic fibroblasts lacking ATG5. CdSe QDs caused significant liver damage in mice, and this was decreased by SFN treatment. In conclusion, SFN attenuated the cytotoxicity of CdSe QDs in both human hepatocytes and in the mouse liver, and this protection was associated with the induction of Nrf2 pathway and autophagy.

No MeSH data available.


Related in: MedlinePlus

Intracellular GSH levels and susceptibility to CdSe QD-induced cytotoxicity.(A) Effect of SFN on intracellular GSH levels. HHL-5 cells were exposed to SFN (2.5, 5 and 10 μM) with DMSO (0.1%) as a control for 0, 3, 6, 12 and 24 h. The levels of intracellular GSH were measured by an HPLC assay. Data are shown as means ± SEM (n = 3). (B) Effect of SFN and BSO pre-treatment on CdSe QD-induced cytotoxicity. HHL-5 cells were pre-treated with SFN (5 μM) and/or BSO (100 μM) for 24 h, and then incubated with 20 μM CdSe QDs for another 24 h. Cytotoxicity was measured by MTT assay, and data shown as means ± SD (n = 6). *P<0.05, **P<0.01.
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pone.0138771.g003: Intracellular GSH levels and susceptibility to CdSe QD-induced cytotoxicity.(A) Effect of SFN on intracellular GSH levels. HHL-5 cells were exposed to SFN (2.5, 5 and 10 μM) with DMSO (0.1%) as a control for 0, 3, 6, 12 and 24 h. The levels of intracellular GSH were measured by an HPLC assay. Data are shown as means ± SEM (n = 3). (B) Effect of SFN and BSO pre-treatment on CdSe QD-induced cytotoxicity. HHL-5 cells were pre-treated with SFN (5 μM) and/or BSO (100 μM) for 24 h, and then incubated with 20 μM CdSe QDs for another 24 h. Cytotoxicity was measured by MTT assay, and data shown as means ± SD (n = 6). *P<0.05, **P<0.01.

Mentions: GSH is the most important and abundant endogenous antioxidant in mammals and its regulation represents an important research topic in chemoprevention [29]. Synthesis of the rate-limiting enzyme for glutathione synthesis, glutamate cysteine ligase (GCL), is regulated partly by the Keap1-Nrf2-antioxidant response element (ARE) pathway [30]. GSH has been shown to protect against cadmium-induced toxicity in cultured Chinese hamster cells [31]. In this study, SFN caused a dose dependent biphasic depletion and repletion of intracellular reduced GSH. SFN induced a pro-oxidant effect characterized by depletion of intracellular glutathione during short term exposure (3–6 h), followed by an antioxidant effect with up-regulation of glutathione at 24 h. The concentration of reduced GSH in control HHL-5 cells at time 0 was 51.0 nmol/mg protein. When cells were treated with 5 μM SFN for up to 24 h, the GSH level decreased to 33.6 nmol/mg protein at 3 h, 40.9 nmol/mg protein at 6 h, then the GSH levels increased to 89.5 and 113.5 nmol/mg protein at 12 and 24 h respectively, which were 1.7-, 2.2- fold of the control (Fig 3A). Moreover, at 10 μM SFN treatment the GSH levels decreased to 23.5 nmol/mg protein (46% of the control) at 3 h, 25.8 nmol/mg protein (50.6% of the control) at 6 h, whereas at 24 h the GSH level increased to 131.6 nmol/mg protein (2.6-fold of the control). However, when cells were pre-treated with L-buthionine S,R-sulfoximine (BSO) (100 μM, 24 h), a specific inhibitor of GCL, the toxicity of CdSe QDs was enhanced (cell viability from 63% decreased to 4.2%), and the protective effect of SFN pre-treatment on CdSe QD toxicity was completely abolished (Fig 3B). These data suggest that GSH exerts an important protective role in CdSe QD-mediated cell death.


Sulforaphane Protects the Liver against CdSe Quantum Dot-Induced Cytotoxicity.

Wang W, He Y, Yu G, Li B, Sexton DW, Wileman T, Roberts AA, Hamilton CJ, Liu R, Chao Y, Shan Y, Bao Y - PLoS ONE (2015)

Intracellular GSH levels and susceptibility to CdSe QD-induced cytotoxicity.(A) Effect of SFN on intracellular GSH levels. HHL-5 cells were exposed to SFN (2.5, 5 and 10 μM) with DMSO (0.1%) as a control for 0, 3, 6, 12 and 24 h. The levels of intracellular GSH were measured by an HPLC assay. Data are shown as means ± SEM (n = 3). (B) Effect of SFN and BSO pre-treatment on CdSe QD-induced cytotoxicity. HHL-5 cells were pre-treated with SFN (5 μM) and/or BSO (100 μM) for 24 h, and then incubated with 20 μM CdSe QDs for another 24 h. Cytotoxicity was measured by MTT assay, and data shown as means ± SD (n = 6). *P<0.05, **P<0.01.
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pone.0138771.g003: Intracellular GSH levels and susceptibility to CdSe QD-induced cytotoxicity.(A) Effect of SFN on intracellular GSH levels. HHL-5 cells were exposed to SFN (2.5, 5 and 10 μM) with DMSO (0.1%) as a control for 0, 3, 6, 12 and 24 h. The levels of intracellular GSH were measured by an HPLC assay. Data are shown as means ± SEM (n = 3). (B) Effect of SFN and BSO pre-treatment on CdSe QD-induced cytotoxicity. HHL-5 cells were pre-treated with SFN (5 μM) and/or BSO (100 μM) for 24 h, and then incubated with 20 μM CdSe QDs for another 24 h. Cytotoxicity was measured by MTT assay, and data shown as means ± SD (n = 6). *P<0.05, **P<0.01.
Mentions: GSH is the most important and abundant endogenous antioxidant in mammals and its regulation represents an important research topic in chemoprevention [29]. Synthesis of the rate-limiting enzyme for glutathione synthesis, glutamate cysteine ligase (GCL), is regulated partly by the Keap1-Nrf2-antioxidant response element (ARE) pathway [30]. GSH has been shown to protect against cadmium-induced toxicity in cultured Chinese hamster cells [31]. In this study, SFN caused a dose dependent biphasic depletion and repletion of intracellular reduced GSH. SFN induced a pro-oxidant effect characterized by depletion of intracellular glutathione during short term exposure (3–6 h), followed by an antioxidant effect with up-regulation of glutathione at 24 h. The concentration of reduced GSH in control HHL-5 cells at time 0 was 51.0 nmol/mg protein. When cells were treated with 5 μM SFN for up to 24 h, the GSH level decreased to 33.6 nmol/mg protein at 3 h, 40.9 nmol/mg protein at 6 h, then the GSH levels increased to 89.5 and 113.5 nmol/mg protein at 12 and 24 h respectively, which were 1.7-, 2.2- fold of the control (Fig 3A). Moreover, at 10 μM SFN treatment the GSH levels decreased to 23.5 nmol/mg protein (46% of the control) at 3 h, 25.8 nmol/mg protein (50.6% of the control) at 6 h, whereas at 24 h the GSH level increased to 131.6 nmol/mg protein (2.6-fold of the control). However, when cells were pre-treated with L-buthionine S,R-sulfoximine (BSO) (100 μM, 24 h), a specific inhibitor of GCL, the toxicity of CdSe QDs was enhanced (cell viability from 63% decreased to 4.2%), and the protective effect of SFN pre-treatment on CdSe QD toxicity was completely abolished (Fig 3B). These data suggest that GSH exerts an important protective role in CdSe QD-mediated cell death.

Bottom Line: Wortmannin inhibition of SFN-induced autophagy significantly suppressed the protective effect of SFN on CdSe QD-induced cell death.CdSe QDs caused significant liver damage in mice, and this was decreased by SFN treatment.In conclusion, SFN attenuated the cytotoxicity of CdSe QDs in both human hepatocytes and in the mouse liver, and this protection was associated with the induction of Nrf2 pathway and autophagy.

View Article: PubMed Central - PubMed

Affiliation: Norwich Medical School, University of East Anglia, Norwich, Norfolk, United Kingdom.

ABSTRACT
The potential cytotoxicity of cadmium selenide (CdSe) quantum dots (QDs) presents a barrier to their use in biomedical imaging or as diagnostic and therapeutic agents. Sulforaphane (SFN) is a chemoprotective compound derived from cruciferous vegetables which can up-regulate antioxidant enzymes and induce apoptosis and autophagy. This study reports the effects of SFN on CdSe QD-induced cytotoxicity in immortalised human hepatocytes and in the livers of mice. CdSe QDs induced dose-dependent cell death in hepatocytes with an IC50 = 20.4 μM. Pre-treatment with SFN (5 μM) increased cell viability in response to CdSe QDs (20 μM) from 49.5 to 89.3%. SFN induced a pro-oxidant effect characterized by depletion of intracellular reduced glutathione during short term exposure (3-6 h), followed by up-regulation of antioxidant enzymes and glutathione levels at 24 h. SFN also caused Nrf2 translocation into the nucleus, up-regulation of antioxidant enzymes and autophagy. siRNA knockdown of Nrf2 suggests that the Nrf2 pathway plays a role in the protection against CdSe QD-induced cell death. Wortmannin inhibition of SFN-induced autophagy significantly suppressed the protective effect of SFN on CdSe QD-induced cell death. Moreover, the role of autophagy in SFN protection against CdSe QD-induced cell death was confirmed using mouse embryonic fibroblasts lacking ATG5. CdSe QDs caused significant liver damage in mice, and this was decreased by SFN treatment. In conclusion, SFN attenuated the cytotoxicity of CdSe QDs in both human hepatocytes and in the mouse liver, and this protection was associated with the induction of Nrf2 pathway and autophagy.

No MeSH data available.


Related in: MedlinePlus