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Gold nanoparticles induce heme oxygenase-1 expression through Nrf2 activation and Bach1 export in human vascular endothelial cells.

Lai TH, Shieh JM, Tsou CJ, Wu WB - Int J Nanomedicine (2015)

Bottom Line: The AuNPs enhanced Nrf2 protein levels but did not affect Nrf2 mRNA expression.Although N-acetylcysteine inhibited the AuNP-induced Nrf2 nuclear translocation, the AuNPs did not promote intracellular reactive oxygen species production or endoplasmic reticulum stress in the ECs.Knockdown of Nrf2 expression by RNA interference significantly inhibited AuNP-induced HO-1 expression at the protein and mRNA levels.

View Article: PubMed Central - PubMed

Affiliation: School of Medicine, Fu-Jen Catholic University, New Taipei City, Taiwan ; Department of Obstetrics and Gynecology, Cathay General Hospital, Taipei, Taiwan ; Institute of Systems Biology and Bioinformatics, National Central University, Jhongli City, Taiwan.

ABSTRACT
It has been reported that increased levels and activity of the heme oxygenase-1 (HO-1) protein ameliorate tissue injuries. In the present study, we investigated the effects and mechanisms of action of gold nanoparticles (AuNPs) on HO-1 protein expression in human vascular endothelial cells (ECs). The AuNPs induced HO-1 protein and mRNA expression in a concentration- and time-dependent manner. The induction was reduced by the thiol-containing antioxidants, including N-acetylcysteine and glutathione, but not by the non-thiol-containing antioxidants and inhibitors that block the enzymes for intracellular reactive oxygen species generation. The AuNPs enhanced Nrf2 protein levels but did not affect Nrf2 mRNA expression. In response to the AuNP treatment, the cytosolic Nrf2 translocated to the nucleus, and, concomitantly, Bach1 exited the nucleus and its tyrosine phosphorylation increased. The chromatin immunoprecipitation assay revealed that the translocated Nrf2 bound to the antioxidant-response element located in the E2 enhancer region of the HO-1 gene promoter and acted as a transcription factor. Although N-acetylcysteine inhibited the AuNP-induced Nrf2 nuclear translocation, the AuNPs did not promote intracellular reactive oxygen species production or endoplasmic reticulum stress in the ECs. Knockdown of Nrf2 expression by RNA interference significantly inhibited AuNP-induced HO-1 expression at the protein and mRNA levels. In summary, AuNPs enhance the levels and nuclear translocation of the Nrf2 protein and Bach1 export/tyrosine phosphorylation, leading to Nrf2 binding to the HO-1 E2 enhancer promoter region to drive HO-1 expression in ECs. This study, together with our parallel findings, demonstrates that AuNPs can act as an HO-1 inducer, which may partially contribute to their anti-inflammatory bioactivity in human vascular ECs.

No MeSH data available.


Related in: MedlinePlus

Effect of the AuNPs on intracellular ROS production and ER stress-related protein expression.Notes: (A) CM-H2 DCFDA-loaded endothelial cells were treated with H2O2 (100 μM), vehicle, or the AuNPs (2 ppm) for the indicated time intervals. Intracellular ROS production was measured by fluorometry (n=4). (B) The cells were treated with thapsigargin, vehicle (ddH2O), or the AuNPs for the indicated time intervals; the ER stress-related protein expression was determined by Western blotting (n=3).Abbreviations: AuNPs, gold nanoparticles; ER, endoplasmic reticulum; ROS, reactive oxygen species.
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f6-ijn-10-5925: Effect of the AuNPs on intracellular ROS production and ER stress-related protein expression.Notes: (A) CM-H2 DCFDA-loaded endothelial cells were treated with H2O2 (100 μM), vehicle, or the AuNPs (2 ppm) for the indicated time intervals. Intracellular ROS production was measured by fluorometry (n=4). (B) The cells were treated with thapsigargin, vehicle (ddH2O), or the AuNPs for the indicated time intervals; the ER stress-related protein expression was determined by Western blotting (n=3).Abbreviations: AuNPs, gold nanoparticles; ER, endoplasmic reticulum; ROS, reactive oxygen species.

Mentions: It has been reported that modification of one or more critical cysteine residues in Keap1 represents a likely chemico-biological trigger for the activation of Nrf2.12 To determine whether AuNPs are a stressor, we examined ROS production and ER stress in the ECs upon the AuNP treatment. As shown in Figure 6A, the AuNPs did not cause intracellular ROS production, which was in contrast to the exogenous H2O2. The AuNPs also did not induce ER stress in the ECs. However, thapsigargin, a compound known to cause ER stress by emptying the ER of calcium ions, decreased calnexin and increased the BiP and PDI proteins after 4 hours of treatment (Figure 6B).


Gold nanoparticles induce heme oxygenase-1 expression through Nrf2 activation and Bach1 export in human vascular endothelial cells.

Lai TH, Shieh JM, Tsou CJ, Wu WB - Int J Nanomedicine (2015)

Effect of the AuNPs on intracellular ROS production and ER stress-related protein expression.Notes: (A) CM-H2 DCFDA-loaded endothelial cells were treated with H2O2 (100 μM), vehicle, or the AuNPs (2 ppm) for the indicated time intervals. Intracellular ROS production was measured by fluorometry (n=4). (B) The cells were treated with thapsigargin, vehicle (ddH2O), or the AuNPs for the indicated time intervals; the ER stress-related protein expression was determined by Western blotting (n=3).Abbreviations: AuNPs, gold nanoparticles; ER, endoplasmic reticulum; ROS, reactive oxygen species.
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4590552&req=5

f6-ijn-10-5925: Effect of the AuNPs on intracellular ROS production and ER stress-related protein expression.Notes: (A) CM-H2 DCFDA-loaded endothelial cells were treated with H2O2 (100 μM), vehicle, or the AuNPs (2 ppm) for the indicated time intervals. Intracellular ROS production was measured by fluorometry (n=4). (B) The cells were treated with thapsigargin, vehicle (ddH2O), or the AuNPs for the indicated time intervals; the ER stress-related protein expression was determined by Western blotting (n=3).Abbreviations: AuNPs, gold nanoparticles; ER, endoplasmic reticulum; ROS, reactive oxygen species.
Mentions: It has been reported that modification of one or more critical cysteine residues in Keap1 represents a likely chemico-biological trigger for the activation of Nrf2.12 To determine whether AuNPs are a stressor, we examined ROS production and ER stress in the ECs upon the AuNP treatment. As shown in Figure 6A, the AuNPs did not cause intracellular ROS production, which was in contrast to the exogenous H2O2. The AuNPs also did not induce ER stress in the ECs. However, thapsigargin, a compound known to cause ER stress by emptying the ER of calcium ions, decreased calnexin and increased the BiP and PDI proteins after 4 hours of treatment (Figure 6B).

Bottom Line: The AuNPs enhanced Nrf2 protein levels but did not affect Nrf2 mRNA expression.Although N-acetylcysteine inhibited the AuNP-induced Nrf2 nuclear translocation, the AuNPs did not promote intracellular reactive oxygen species production or endoplasmic reticulum stress in the ECs.Knockdown of Nrf2 expression by RNA interference significantly inhibited AuNP-induced HO-1 expression at the protein and mRNA levels.

View Article: PubMed Central - PubMed

Affiliation: School of Medicine, Fu-Jen Catholic University, New Taipei City, Taiwan ; Department of Obstetrics and Gynecology, Cathay General Hospital, Taipei, Taiwan ; Institute of Systems Biology and Bioinformatics, National Central University, Jhongli City, Taiwan.

ABSTRACT
It has been reported that increased levels and activity of the heme oxygenase-1 (HO-1) protein ameliorate tissue injuries. In the present study, we investigated the effects and mechanisms of action of gold nanoparticles (AuNPs) on HO-1 protein expression in human vascular endothelial cells (ECs). The AuNPs induced HO-1 protein and mRNA expression in a concentration- and time-dependent manner. The induction was reduced by the thiol-containing antioxidants, including N-acetylcysteine and glutathione, but not by the non-thiol-containing antioxidants and inhibitors that block the enzymes for intracellular reactive oxygen species generation. The AuNPs enhanced Nrf2 protein levels but did not affect Nrf2 mRNA expression. In response to the AuNP treatment, the cytosolic Nrf2 translocated to the nucleus, and, concomitantly, Bach1 exited the nucleus and its tyrosine phosphorylation increased. The chromatin immunoprecipitation assay revealed that the translocated Nrf2 bound to the antioxidant-response element located in the E2 enhancer region of the HO-1 gene promoter and acted as a transcription factor. Although N-acetylcysteine inhibited the AuNP-induced Nrf2 nuclear translocation, the AuNPs did not promote intracellular reactive oxygen species production or endoplasmic reticulum stress in the ECs. Knockdown of Nrf2 expression by RNA interference significantly inhibited AuNP-induced HO-1 expression at the protein and mRNA levels. In summary, AuNPs enhance the levels and nuclear translocation of the Nrf2 protein and Bach1 export/tyrosine phosphorylation, leading to Nrf2 binding to the HO-1 E2 enhancer promoter region to drive HO-1 expression in ECs. This study, together with our parallel findings, demonstrates that AuNPs can act as an HO-1 inducer, which may partially contribute to their anti-inflammatory bioactivity in human vascular ECs.

No MeSH data available.


Related in: MedlinePlus