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. 2021 Aug 31;10(5):1045–1051. doi: 10.1093/toxres/tfab085

Effect of titanium dioxide nanoparticles on DNA methylation of human peripheral blood mononuclear cells

Mohammad Malakootian 1, Alireza Nasiri 2, Alvaro R Osornio-Vargas 3, Maryam Faraji 4,5,✉
PMCID: PMC8557643  PMID: 34733489

Abstract

The aim of the current study was to investigate the effect of well-characterized TiO2 nanoparticles on DNA methylation of peripheral blood mononuclear cells (PBMCs) in vitro. Maximum non-toxic concentration of nanoparticles for PBMCs was determined by MTT assay. The effect of TiO2 nanoparticles at concentrations of 25–100 μg/ml on DNA methylation of PBMCs was investigated by measuring the %5-mC alterations through an ELISA assay. The physicochemical analysis showed that the TiO2 nanoparticles were crystalline, pure and in the anatase phase. Peaks related to Ti-O tensile vibrations were observed in the range of 1510 cm−1. The size of nanoparticles was in the range of 39–74 nm with an average hydrodynamic diameter of 43.82 nm. According to the results of the MTT test, 100 μg/ml was found to be maximum non-toxic concentration. The %5-mC in treated PBMCs revealed that TiO2 nanoparticles could lead to DNA hypomethylation in PBMCs. The %5-mC difference compared with the negative control was found to be 2.07 ± 1.02% (P = 0.03). The difference of %5-mC between the 25 and 100 μg/ml concentration of nanoparticles was statistically significant (P = 0.02). The results of the current study show that the TiO2 nanoparticles cause DNA hypomethylation in PBMCs in a dose-response manner. Therefore, it is recommended to evaluate the effects of cytotoxicity and epigenotoxicity of commonly used nanoparticles before their use.

Keywords: titanium dioxide nanoparticles, DNA methylation, epigenetic genotoxicity

Introduction

In the last decade, nanoparticles have been widely used in commercial and medical products, such as electronics, computers, cosmetics, edible dyes and clothing, causing human exposure to nanomaterials [1, 2]. TiO2 nanoparticles are widely used as photocatalyst, in cosmetics as a pigment, and UV absorber, in solar cells to convert solar energy, and as a material in memristors [3]. Nanoparticles can permeate to the respiratory tracts and blood circulation due to the physicochemical properties included small size, high ratio of surface area to volume, solubility and shape. Therefore, they can affect blood cells and cause adverse effects in organs, tissues and cells. Nanoparticles can affect the antioxidant defense system due to the reaction to proteins and enzymes within mammalian cells. They produce reactive oxygen species (ROS) and induce inflammatory reactions, mitochondrial degradation, apoptosis and necrosis [4, 5]. Some mechanisms have been proposed to describe the toxic effects of nanoparticles. The production of ROS and oxidative stress have been considered as the most important mechanisms. ROS, included hydrogen peroxide, superoxide, hydroxyl and other oxygen radicals, can oxidize DNA, proteins and lipids. There is ample evidence indicating that ROS production results in cell death in a variety of cells treated with nanoparticles [6]. Oxidative stress can lead to epigenetic changes in DNA levels [1]. Epigenetic mechanisms modify chromatin constituents altering gene expression patterns and cellular functions such as DNA repair and cell proliferation. Mechanisms include cytosine methylation and hydroxymethylation, histone modification and microRNAs [7]. DNA methylation is known to be the most frequently surveyed epigenetic mechanism. It represents the covalent addition of a methyl group at carbon 5 of cytosine, resulting in 5-methylcytosine (5-mC). They occur at CpG dinucleotides that clustered in the CpG islands [8]. Increasing or decreasing the methylated spots in DNA affects gene expression and leads to genomic instability. Hypermethylation silences gene expression; in contrast, hypomethylation increases gene transcription and expression. A disruption of the DNA methylation pattern leads to the suppression of gene expression and associates with autoimmune diseases and asthma [7]. Changes in methylation patterns in specific genes and the whole genome associate with various cancers. These include hypermethylation of tumor suppressor genes, hypomethylation of tumorigenic genes and global methylation [8]. Some studies have been explored the effect of different nanoparticles on the epigenetic modifications in multiple human cell lines and animal models. Gong et al. investigated the effect of SiO2 nanoparticles on DNA methylation and histone modifications in the skin keratinocyte cell line (HaCaT), finding PARP-1 hypomethylation, microRNAs modifications and global hypomethylation [12]. The effect of gold nanoparticles on lung fibroblast cell line (MRC5) was studied by Ng et al. reporting changes in the microRNAs (miR155) and chromatin condensation [9]. Patil et al. studied the epigenetic changes induced in vitro by the exposure of TiO2 and ZnO nanoparticles to lung fibroblast (MRC5). The results of the study reported a significant change in the response of cells to metal oxide nanoparticles [10]. Pogribna et al. investigated the effect of TiO2 nanoparticles on the DNA methylation of different cell lines. The results of the study showed a decrease in DNA methylation in the treated cell lines [5]. In a study of the effect of Maghemite nanoparticles on epigenetic alterations in human submandibular gland cells by Bonadio et al., increase in ROS production and change in global DNA methylation in cells treated by nanoparticles have been reported [4]. Halappanavar et al. investigated the effects of TiO2 nanoparticles using an animal model. In this study, changes were observed in the microRNAs (miR-449a, -1, -135b) [11].

To the best of our knowledge, the present study is a novel study to explore the effect of TiO2 nanoparticles on DNA methylation in peripheral blood mononuclear cells (PBMCs) through analyzing 5-mC. Whole blood is composed of diverse cell types, and the global methylation profile is different in each one of the blood cell types is different from the other [12]. That is why in the current study, we centered on PBMCs to control for these differences. The aim of the current study was to: (i) characterize the TiO2 nanoparticles used, (ii) analyze the toxicity of the TiO2 on the PBMCs through MTT method and (iii) examine epigenotoxic effects of TiO2 on the global DNA methylation (%5-mC) in human PBMCs.

Materials and Methods

The study stages were as follows: (i) characterization of the TiO2 nanoparticles, (ii) blood sampling and PBMCs isolation, (iii) toxicity analysis, (iv) PBMCs treatment, (v) DNA methylation analysis and (vi) statistical analysis of data. We showed study stages in detail in Fig. 1.

Figure 1.

Figure 1

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Study stages.

Chemicals

Suppliers of chemicals were: TiO2 nanoparticles, MTT (3-(4, 5-dimethylthiazol-2-yl)-2, 5 diphenyltetrazolium bromide) and dimethylsulfoxide (DMSO) from Sigma Chemical Company, St. Louis, MO, USA; Ca2+/Mg2+–free PBS and Ficoll–Hypaque solution from Biosera, France; RPMI-1640 culture medium from Gibco BRL, San Diego, CA.

Characterization of the TiO2 nanoparticles

TiO2 nanoparticles were obtained from Sigma-Aldrich Company. The company provided the following physical characteristics, particle size (100 nm), specific surface area (14 m2/g), melting point (350°C) and density (4.26 g/ml at 25°C). We conducted further characterization using: powder X-ray diffraction (XRD: Philips, model XPERT PW 3040/60); scanning electron microscopy (SEM: KYKY-EM 3200); Fourier Transform Infrared Spectroscopy (FTIR, Bruker Tensor 27) and Dynamic Light Scattering (DLS, Zetasizer Nano-Malvern, model ZEN3600).

Blood sampling and PBMCs isolation

The ethics committee of the Kerman University of Medical Sciences approved this study (IR.KMU.REC.1398.281). Volunteers filled written informed consent before initiating the study. Ten males (18–24 years old) were enrolled in the current study. Inclusion criteria were described in the previous studies [12, 13]. The whole blood samples from individual donors were put into the heparinized tubes and processed within 2 h. Isolation of PBMCs was carried out by the method of the Ficoll–Hypaque gradient described in the previous studies [12, 14, 15]. The viability of the isolated PBMCs was obtained to be over 95%. Finally, the cells were stored in an incubator at 37°C with 5% (v/v) CO2/air.

Toxicity analysis

MTT method was used to assess the toxicity of TiO2 nanoparticles on the PBMCs. Detail of the MTT method was described in the previous studies [12, 15]. Briefly, extracted PBMCs were seeded in the 96-well plate, 200 000 cells in each well, in 100 mL RPMI-1640 culture medium. Plates were incubated at 37°C with 5% (v/v) CO2. After incubation, treatment of cells with suspension of nanoparticles was done at several concentrations (0 as the negative control, 25, 50, 100, 150 and 200 μg/ml) in triplicate. Then, treated cells were incubated for 24 h. After addition of MTT solution at the concentration of 0.5 mg/ml plates were incubated for 4 h. During the cellular metabolism, the byproduct of MTT was produced as the insoluble formazan crystals. DMSO in the volume of 150 μl was applied to dissolved formazan crystals. The absorbance OD in each well was read by a microplate reader (Bio-Tek Instruments, Winooski, VT, USA) at 570 nm. Concentration of nanoparticles that caused cell viability >80% was considered as a non-toxic concentration [10, 16, 17].

PBMCs treatment

For cell treatment, 500 000 cells/ml were cultured in RPMI-1640 culture medium in an incubator at 37°C with 5% (v/v) CO2/air for 24 h. Suspension of TiO2 was made in culture medium at the concentrations of 25, 50 and 100 μg/ml which were non-toxic concentrations according to the MTT test results. Furthermore, treatment of PBMCs from individual donors with TiO2 suspensions was separately done for 4 h. After time elapsed, PBMCs were separated from the supernatant after centrifugation of contents of each wells at 5000 rpm for 8 min and maintained at −20°C. PBMCs without exposure to the TiO2 nanoparticles were used as the negative control samples in all experiments.

DNA methylation analysis

Extraction of genomic DNA of PBMCs and the measurement of its concentration at 260 nm were done by the method described in the previous studies using the QIAamp DNA blood mini kit (Qiagen, Hilden, Germany) and Nanodrop spectrophotometer (NanoDrop Technologies, Wilmington, DE, USA), respectively [12, 14]. Then, extracted DNA (100 ng) was used to investigate %5-mC through the measurement of global %5-mC by the enzyme-linked immunosorbent assay (ELISA) method with a 5-mC DNA ELISA kit (Zymo Research, Orange, CA, USA) with a detection limit .5% per 100 ng single-stranded DNA [12, 14]. DNA methylation analysis was done in duplicate.

Statistical analysis of data

The effect of TiO2 nanoparticles at several concentrations on the difference of cell viability percent and %5-mC with the negative control was analyzed using R software version 3.6.2 [18, 19]. A P-value of <0.05 defined as the level of significance. Analysis of variance (ANOVA) test and post-hoc test of TukeyHSD were used to compare of the averages of %5-mC and viability percent between different TiO2 concentrations. Results were reported based on mean ± standard deviation. Cytotoxicity graph was made in GraphPad Prism software version 8 (San Diego, CA, USA).

Results and Discussion

TiO2 characteristics

The results of TiO2 characterization are summarized in Table 1. The graphs of XRD, SEM, FTIR and DLS are presented in Figs 2–5, respectively.

Table 1.

The results of titanium dioxide nanoparticles (TiO2) characterization

Characteristics Value
SEM 39–74 nm
DLS 43.82 nm
PDI 1.67
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Figure 2.

Figure 2

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XRD pattern of TiO2 nanoparticles, spectra recorded in a Philips, model XPERT PW 3040/60 (Cu Kα radiation, λ 1.56) at 45 kV and 30 mA; diffracted intensities from 10° to 90° 2θ angles.

Figure 5.

Figure 5

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Results of DLS analysis of TiO2 nanoparticles.

XRD analysis confirmed the crystalline structure of TiO2 after comparing the peak structure with the standard peak. The presence of a peak at 2θ = 25° and its relatively low width (Fig. 2) confirmed the TiO2 crystal structure in the anatase phase, which is consistent with the results from other studies [3, 20]. The peaks indicated that the TiO2 structure was in line with standard spectra.

Morphology and geometric particle size of TiO2 nanoparticle were investigated through the SEM analysis. SEM image in Fig. 3 revealed the nanoparticles that to be in a size range of 39–74 nm, which corresponded to the specifications provided by the supplier.

Figure 3.

Figure 3

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Scanning electron microscope (SEM) image of TiO2 nanoparticles captured using an KYKY-EM 3200, 26 kV, 40 kX SEM.

The chemical structure of TiO2 nanoparticles was investigated using FTIR. Based on the results of the FTIR analysis in Fig. 4, the broad peak in the range of 3406 cm−1 could be related to the tensile vibrations of OH obtained from the moisture absorbed on the surface of TiO2. The weak peak in 1637 cm−1 may be associated to the Ti-OH bending vibrations. The peak in the range of 700–500 cm−1 was due to Ti-O tensile vibrations.

Figure 4.

Figure 4

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Fourier Transform Infrared Spectra (FTIR) of TiO2 nanoparticles recorded over the range of 500–3500 cm−1 using an FTIR spectrometer, Bruker Tensor 27.

The size distribution of TiO2 nanoparticles and the polydispersity index (PDI) value were determined by DLS method. According to the results of DLS analysis in Fig. 5, the maximum size distribution of TiO2 nanoparticles was found to be 24.8%, with an average hydrodynamic diameter of 43.82 nm. Therefore, it can be concluded that at least 24.8% of the nanoparticles had a hydrodynamic diameter of ~44 nm. PDI was obtained to be 1.67. PDI more than one showed that the suspension was unstable with a tendency to make aggregates [20].

Cytotoxic effect of TiO2 nanoparticles on PBMCs

The cytotoxicity of nanoparticles on PBMCs was determined through the MTT test at the TiO2 concentration range of 25–200 μg/ml. Based on the results of the cytotoxicity test (Fig. 6), 100 μg/ml did not alter cell viability by >20%. As a result, it could be considered as the maximum non-toxic concentration of TiO2 for future analyses. Based on the mean difference of cell viability at different concentrations of nanoparticles, it could be stated that there is a significant difference between cytotoxicity effects of TiO2 nanoparticles at different concentrations (P < 0.001). Except for 0 and 25; 0 and 50; 25 and 50; and 50 and 100 μg/ml, significant differences were observed between the other two concentrations.

Figure 6.

Figure 6

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Results of toxicity test on PBMCs exposed to the TiO2 concentrations of 25–200 μg/ml by the MTT assay. Each bar illustrates the mean and SD (n = 3). Except for 0 and 25; 0 and 50; 25 and 50; and 50 and 100 μg/ml, significant differences were observed between the other two concentrations.

In the study of Ghosh et al. on the toxicity of TiO2 nanoparticles at concentrations of 0–100 μg/ml on lymphocyte cells, the maximum and minimum toxicity level of nanoparticles was observed at concentrations of 25 and 50 μg/ml, respectively [20]. Patil et al. assessed the cytotoxicity of TiO2 and ZnO nanoparticles on the lung fibroblast cells at the concentrations of 0–8 μg/ml in three-time points of 24, 48 and 72 h. They found that TiO2 nanoparticles were more toxic than ZnO. In this study, 1 μg/ml was reported as the maximum concentration without any toxic effect for both types of nanoparticles [10]. Differences in the level of non-toxic concentrations in several studies could be attributed to differences in the type of cells studied.

The significant dose-related decrease in MTT signal could be attributed to impaired dehydrogenase activity and decreased reduction rates of the tetrazolium salts. The results of the cytotoxicity test provided evidence for altered mitochondrial activity of PBMCs treated by nanoparticles [12, 15].

Results of %5-mC

Exposure of PBMCs with the nanoparticles at several concentrations (25, 50 and 100 μg/ml) showed that %5-mC decreased in treated cells compared with the negative control samples (Table 2). The observed %5-mC difference was totally found to be −2.07 ± 1.02%. TiO2 nanoparticles caused epigenetic alterations and DNA hypomethylation even at the non-toxic concentrations. Similar studies showed that nanoparticles at non-toxic levels could modify histone methylation effecting gene expression [10, 21]. Recently, there are a lot of reports on the epigenetic modifications of nanoparticles at the non-toxic concentrations [2]. In various in vitro studies, the production of oxidative stress, activation of inflammatory pathways, cytotoxicity, genotoxicity and methylation have been reported as the biological effects of engineered nanoparticles [22–26]. Pogribna et al. investigated the effect of TiO2 nanoparticles on DNA methylation of different cell lines. They reported decreased DNA methylation in all cell lines exposed to the nanoparticles [5]. An increase in ROS production and alteration in global DNA methylation in human submandibular gland cells exposed to maghemite nanoparticles have been reported in the study of Bonadio et al. [4]. The cytotoxicity and DNA damage caused by TiO2 and ZnO nanoparticles have been considered in a human lung carcinoma cell line (A549) by Freire et al. Both ZnO and TiO2 NPs increased ROS and decreased GSH/GSSG ratio and found inside the cells, within membrane-bound vesicles [27].

Table 2.

Descriptive statistics for difference of %5-mC in various TiO2 concentration

TiO2 concentration (μg/ml) Total
25 50 100
Difference of %5-mC
Min −2.85 −2.95 −3.50 −3.50
First quartile −2.35 −2.75 −3.25 −2.93
Median −1.40 −2.00 −3.15 −2.30
Mean −1.55 −2.00 −2.67 −2.07
Standard deviation 1.00 0.90 0.91 1.02
Third quartile −.73 −1.53 −2.30 −1.42
Max −.10 −.10 −.75 −.10
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There were no significant differences between treated and control cells in the DNA methylation status in the study by Brzóska et al. on the DNA methylation status of genes related to inflammation and apoptosis as well as the expression of miRNAs related to the silver (AgNPs), gold (AuNPs) and superparamagnetic iron oxide nanoparticles (SPIONs) in HepG2 cells [28].

Increase the levels of oxidative stress can damage the body’s antioxidant system. Glutathione S-transferases (GSTs) and glutathione (GSH) are important elements in the antioxidant mechnisms [7]. The major role of GSTs is to detoxify xenobiotic compounds by catalyzing nucleophilic substitutions in carbon electrophilic, sulfur or nitrogen atoms of xenobiotic compounds by GSH, which ultimately prevents the reaction of these compounds with important cellular proteins and nucleic acid [29]. GSH is considered as the major antioxidant compound in organisms that can maintain important cellular components. Damage to important cellular components is caused by radicals, peroxides and heavy metals [30]. Measurement of GSH has been also introduced as an indicator of oxidative stress conditions [10]. GSH is produced by cysteine and from the transsulfuration pathway. The GSH production pathway is associated with S-adenosylmethionine (SAM) biosynthesis. Since SAM is the most important donor of methyl in methyl transferases, therefore, its level is a key factor in determining the status of DNA methylation [31]. Under oxidative stress conditions induced by nanoparticles, increasing the need for GSH decreases SAM production and ultimately causes DNA hypomethylation [32].

The results of the ANOVA test showed that the difference of %5-mC obtained from various nanoparticle concentrations was statistically significant (P = 0.02). Difference of %5-mC at the concentrations of 25 and 100 μg/ml was significantly obtained using TukeyHSD test (P = 0.02) (Fig. 7). There was no significant difference at other concentrations. The dose–response curve of the concentration of nanoparticles and %5-mC showed a negative dose–response relationship in the PBMCs samples of every 10 individuals (Fig. 8). Lung fibroblast cells were treated by TiO2 and ZnO nanoparticles in the study of Patil et al. In this study, it was reported that global DNA methylation and the activity of methylation-generating enzyme namely methyltransferase reduced in the exposed cells. The decrease in the rate of biological reactions had a direct relationship with the concentration of nanoparticles [10].

Figure 7.

Figure 7

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The results of TukeyHSD test of %5-mC difference in studied concentrations of TiO2 nanoparticles. Each bar illustrates the mean and SD (n = 3).

Figure 8.

Figure 8

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The dose–response curve of the concentration of TiO2 nanoparticles and %5-mC in 10 donors.

Conclusions

In the current study, the effect of TiO2 nanoparticles on DNA methylation of PBMCs was investigated in vitro. The TiO2 nanoparticles used in this study were in the range of 39–74 nm, pure, in the anatase phase with the crystalline structure. The maximum size distribution of TiO2 nanoparticles was 24.8%, with an average hydrodynamic diameter of 43.82 nm. The results showed that the exposure of PBMCs to TiO2 nanoparticles in the range of concentration from 25 to 100 μg/ml resulted in the DNA hypomethylation reactions. Difference of %5-mC at several concentrations of TiO2 was found to be significant (P = 0.02). There was a negative dose–response relationship between TiO2 concentration and %5-mC. Therefore, it could be stated that exposure to the TiO2 metal nanoparticles causes epigenetic alterations and DNA hypomethylation methylation. Abnormalities in the methylation pattern are associated with uncontrolled cell proliferation, abnormal cell cycle arrest and apoptosis, which all of these alterations are considered as the risk factors for cancer, malignant tumors and metastases. Therefore, the health effects of these nanoparticles must be considered in before their use. Also, nanoparticles should be applied with greater caution.

Author’s contribution

M.M. and M.F. investigated methylation. A.N. contributed the nanoparticle characteristics and A.O. drafted the manuscript and contributed to data analysis. All authors read and approved the final manuscript.

Acknowledgments

The authors acknowledged the Iran National Science Foundation (INSF) for financially supports (grant number 97023002) and Kerman University of Medical Sciences for technically supports.

Contributor Information

Mohammad Malakootian, Environmental Health Engineering Research Center, Kerman University of Medical Sciences, Kerman, Iran.

Alireza Nasiri, Environmental Health Engineering Research Center, Kerman University of Medical Sciences, Kerman, Iran.

Alvaro R Osornio-Vargas, Department of Pediatrics, University of Alberta, 3-591 Edmonton Clinic Health Academy, Edmonton T6G 1C9, Canada.

Maryam Faraji, Environmental Health Engineering Research Center, Kerman University of Medical Sciences, Kerman, Iran; Department of Environmental Health Engineering, Faculty of Public Health, Kerman University of Medical Sciences, Kerman, Iran.

Competing financial interests

The authors declare that they have no competing financial interests.

References

  • 1. Chibber  S, Ansari  SA, Satar  R. New vision to CuO, ZnO, and TiO 2 nanoparticles: their outcome and effects. J Nanopart Res  2013;15:1492. [Google Scholar]
  • 2. Patil-Rajpathak  Y, Patil  N. Epigenetic toxicity of nanoparticles. In: Advances in Bioengineering. Singapore: Springer, 2020. 10.1007/978-981-15-2063-1_7. [DOI] [Google Scholar]
  • 3. Malakootian  M, Nasiri  A, Amiri  Gharaghani M. Photocatalytic degradation of ciprofloxacin antibiotic by TiO2 nanoparticles immobilized on a glass plate. Chem Eng Commun  2020;207:56–72. [Google Scholar]
  • 4. Bonadio  RS, da  Cunha  MCPC, Longo  JPF  et al.  Exposure to maghemite nanoparticles induces epigenetic alterations in human submandibular gland cells. J Nanosci Nanotechnol  2020;20:1454–62. [DOI] [PubMed] [Google Scholar]
  • 5. Pogribna  M, Koonce  NA, Mathew  A  et al.  Effect of titanium dioxide nanoparticles on DNA methylation in multiple human cell lines. Nanotoxicology  2020;14(4):534–553. doi: 10.1080/17435390.2020.1723730. [DOI] [PubMed] [Google Scholar]
  • 6. Rezaei  S, Naddafi  K, Hassanvand  MS  et al.  Physiochemical characteristics and oxidative potential of ambient air particulate matter (PM10) during dust and non-dust storm events: a case study in Tehran, Iran. J Environ Health Sci Eng  2018;16:147–158. 10.1007/s40201-018-0303-9. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 7. De Prins  S, Koppen  G, Jacobs  G  et al.  Influence of ambient air pollution on global DNA methylation in healthy adults: a seasonal follow-up. Environ Int  2013;59:418–24. [DOI] [PubMed] [Google Scholar]
  • 8. Terry  MB, Delgado-Cruzata  L, Vin-Raviv  N, Wu  HC, Santella  RM. DNA methylation in white blood cells: association with risk factors in epidemiologic studies. Epigenetics  2011;6:828–37. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 9. Ng  C-T, Dheen  ST, Yip  W-CG, Ong  C-N, Bay  B-H, Yung  L-YL. The induction of epigenetic regulation of PROS1 gene in lung fibroblasts by gold nanoparticles and implications for potential lung injury. Biomaterials  2011;32:7609–15. [DOI] [PubMed] [Google Scholar]
  • 10. Patil  NA, Gade  W, Deobagkar  DD. Epigenetic modulation upon exposure of lung fibroblasts to TiO2 and ZnO nanoparticles: alterations in DNA methylation. Int J Nanomedicine  2016;11:4509. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 11. Halappanavar  S, Jackson  P, Williams  A, Jensen  KA, Hougaard  KS, Vogel  U, et al.  Pulmonary response to surface-coated nanotitanium dioxide particles includes induction of acute phase response genes, inflammatory cascades, and changes in microRNAs: a toxicogenomic study. Environ Mol Mutagen  2011;52:425–39. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 12. Faraji  M, Pourpak  Z, Naddafi  K  et al.  Effects of airborne particulate matter (PM10) from dust storm and thermal inversion on global DNA methylation in human peripheral blood mononuclear cells (PBMCs) in vitro. Atmos Environ  2018;195:170–8. [Google Scholar]
  • 13. Faraji  M, Pourpak  Z, Naddafi  K, Nodehi  RN, Nicknam  MH, Shamsipour  M, et al.  Chemical composition of PM 10 and its effect on in vitro hemolysis of human red blood cells (RBCs): a comparison study during dust storm and inversion. J Environ Health Sci Eng  2019;17:493–502. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 14. Faraji  M, Pourpak  Z, Naddafi  K  et al.  An in vitro method to survey DNA methylation in peripheral blood mononuclear cells (PBMCs) treated by airborne particulate matter (PM10). MethodsX  2018;5:1508–14. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 15. Faraji  M, Nodehi  RN, Naddafi  K, Pourpak  Z, Alizadeh  Z, Rezaei  S, et al.  Cytotoxicity of airborne particulate matter (PM10) from dust storm and inversion conditions assessed by MTT assay. J Air Pollut Health  2018;3:135–42. [Google Scholar]
  • 16. Ko  M-J, Ahn  J-I, Shin  H-J, Kim  H-S, Chung  H-J, Jeong  H-S. Gene expression analysis for statin-induced cytotoxicity from rat primary hepatocytes. Genomics Inform  2010;8:41–9. [Google Scholar]
  • 17. Ahmed  M, Jamil  K. Cytotoxicity of neoplastic drugs Gefitinib, Cisplatin, 5-FU, Gemcitabine, and Vinorelbine on human cervical cancer cells (HeLa). Biol Med  2011;3:60–71. [Google Scholar]
  • 18. Sarkar  D. Lattice: Multivariate Data Visualization with R. Springer Science & Business Media, 2008.
  • 19. Venables  WN, Ripley  BD. Modern Applied Statistics with S-PLUS. Springer Science & Business Media, 2003.
  • 20. Ghosh  M, Chakraborty  A, Mukherjee  A. Cytotoxic, genotoxic and the hemolytic effect of titanium dioxide (TiO2) nanoparticles on human erythrocyte and lymphocyte cells in vitro. J Appl Toxicol  2013;33:1097–110. [DOI] [PubMed] [Google Scholar]
  • 21. Qian  Y, Zhang  J, Hu  Q  et al.  Silver nanoparticle-induced hemoglobin decrease involves alteration of histone 3 methylation status. Biomaterials  2015;70:12–22. [DOI] [PubMed] [Google Scholar]
  • 22. Costa  PM, Fadeel  B. Emerging systems biology approaches in nanotoxicology: Towards a mechanism-based understanding of nanomaterial hazard and risk. Toxicol Appl Pharmacol  2016;299:101–11. [DOI] [PubMed] [Google Scholar]
  • 23. Hardy  TM, Tollefsbol TO . Epigenetic diet: impact on the epigenome and cancer. Epigenomics  2011;3:503–18. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 24. Khanna  P, Ong  C, Bay  BH, Baeg  GH. Nanotoxicity: an interplay of oxidative stress, inflammation and cell death. Nanomaterials  2015;5:1163–80. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 25. Lozano-Fernández  T, Ballester-Antxordoki  L, Pérez-Temprano  N, Rojas  E, Sanz  D, Iglesias-Gaspar  M, et al.  Potential impact of metal oxide nanoparticles on the immune system: the role of integrins, L-selectin and the chemokine receptor CXCR4. Nanomedicine  2014;10:1301–10. [DOI] [PubMed] [Google Scholar]
  • 26. Sarkar  A, Ghosh  M, Sil  PC. Nanotoxicity: oxidative stress mediated toxicity of metal and metal oxide nanoparticles. J Nanosci Nanotechnol  2014;14:730–43. [DOI] [PubMed] [Google Scholar]
  • 27. Freire  K, Ordóñez Ramos  F, Soria  DB, Pabón Gelves  E, Di Virgilio  AL. Cytotoxicity and DNA damage evaluation of TiO2 and ZnO nanoparticles. Uptake in lung cells in culture. Toxicol Res  2021;10:192–202. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 28. Brzóska  K, Grądzka  I, Kruszewski  M. Silver, gold, and iron oxide nanoparticles alter miRNA expression but do not affect DNA methylation in HepG2 cells. Materials  2019;12:1038. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 29. Josephy  PD. Genetic variations in human glutathione transferase enzymes: significance for pharmacology and toxicology. Hum Genom Proteom  2010;2010:876940. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 30. Pompella  A, Corti  A. the changing faces of glutathione, a cellular protagonist. Front Pharmacol  2015;6:98. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 31. Ji  H, Hershey  GKK. Genetic and epigenetic influence on the response to environmental particulate matter. J Allergy Clin Immunol  2012;129:33–41. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 32. Lee  D-H, Jacobs  Jr  DR, Porta  M. Hypothesis: a unifying mechanism for nutrition and chemicals as lifelong modulators of DNA hypomethylation. Environ Health Perspect  2009;117:1799. [DOI] [PMC free article] [PubMed] [Google Scholar]

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