Genome-Wide DNA Methylation Variations upon Exposure to Engineered Nanomaterials and Their Implications in Nanosafety Assessment

Genome-wide DNA methylation sequencing reveals the involvement of ferroptosis in hepatotoxicity induced by dietary exposure to food-grade titanium dioxide

BACKGROUND

Following the announcement by the European Food Safety Authority that the food additive titanium dioxide (E 171) is unsafe for human consumption, and the subsequent ban by the European Commission, concerns have intensified over the potential risks E 171 poses to human vital organs. The liver is the main organ for food-grade nanoparticle metabolism. It is increasingly being found that epigenetic changes may play an important role in nanomaterial-induced hepatotoxicity. However, the profound effects of E 171 on the liver, especially at the epigenetic level, remain largely unknown.

METHODS

Mice were exposed orally to human-relevant doses of two types of E 171 mixed in diet for 28 and/or 84 days. Conventional toxicology and global DNA methylation analyses were performed to assess E 171-induced hepatotoxicity and epigenetic changes. Whole genome bisulfite sequencing and further ferroptosis protein detection were used to reveal E 171-induced changes in liver methylation profiles and toxic mechanisms.

RESULTS

Exposed to E 171 for 28 and/or 84 days resulted in reduced global DNA methylation and hydroxymethylation in the liver of mice. E 171 exposure for 84 days elicited inflammation and damage in the mouse liver, whereas 28-day exposure did not. Whole-genome DNA methylation sequencing disclosed substantial methylation alterations at the CG and non-CG sites of the liver DNA in mice exposed to E 171 for 84 days. Mechanistic analysis of the DNA methylation alterations indicated that ferroptosis contributed to the liver toxicity induced by E 171. E 171-induced DNA methylation changes triggered NCOA4-mediated ferritinophagy, attenuated the protein levels of GPX4, FTH1, and FTL in the liver, and thereby caused ferroptosis.

CONCLUSIONS

Long-term oral exposure to E 171 triggers hepatotoxicity and induces methylation changes in both CG and non-CG sites of liver DNA. These epigenetic alterations activate ferroptosis in the liver through NCOA4-mediated ferritinophagy, highlighting the role of DNA methylation and ferroptosis in the potential toxicity caused by E 171 in vivo.

Epigenetics and environmental health

Epigenetic modifications including DNA methylation, histone modifications, chromatin remodeling, and RNA modifications complicate gene regulation and heredity and profoundly impact various physiological and pathological processes. In recent years, accumulating evidence indicates that epigenetics is vulnerable to environmental changes and regulates the growth, development, and diseases of individuals by affecting chromatin activity and regulating gene expression. Environmental exposure or induced epigenetic changes can regulate the state of development and lead to developmental disorders, aging, cardiovascular disease, Alzheimer's disease, cancers, and so on. However, epigenetic modifications are reversible. The use of specific epigenetic inhibitors targeting epigenetic changes in response to environmental exposure is useful in disease therapy. Here, we provide an overview of the role of epigenetics in various diseases. Furthermore, we summarize the mechanism of epigenetic alterations induced by different environmental exposures, the influence of different environmental exposures, and the crosstalk between environmental variation epigenetics, and genes that are implicated in the body's health. However, the interaction of multiple factors and epigenetics in regulating the initiation and progression of various diseases complicates clinical treatments. We discuss some commonly used epigenetic drugs targeting epigenetic modifications and methods to prevent or relieve various diseases regulated by environmental exposure and epigenetics through diet.

Nanomedomics

Nanomaterials have attractive physicochemical properties. A variety of nanomaterials such as inorganic, lipid, polymers, and protein nanoparticles have been widely developed for nanomedicine via chemical conjugation or physical encapsulation of bioactive molecules. Superior to traditional drugs, nanomedicines offer high biocompatibility, good water solubility, long blood circulation times, and tumor-targeting properties. Capitalizing on this, several nanoformulations have already been clinically approved and many others are currently being studied in clinical trials. Despite their undoubtful success, the molecular mechanism of action of the vast majority of nanomedicines remains poorly understood. To tackle this limitation, herein, this review critically discusses the strategy of applying multiomics analysis to study the mechanism of action of nanomedicines, named nanomedomics, including advantages, applications, and future directions. A comprehensive understanding of the molecular mechanism could provide valuable insight and therefore foster the development and clinical translation of nanomedicines.

Maternal exposure to E 551 during pregnancy leads to genome-wide DNA methylation changes and metabolic disorders in the livers of pregnant mice and their fetuses

The widespread use of nanoparticles in the food industry has raised concerns regarding their potential adverse effects on human health, particularly in vulnerable populations, including pregnant mothers and fetuses. However, studies evaluating the reproductive and developmental toxicity of food-grade nanomaterials are limited. This study investigated the potential risks of prenatal dietary exposure to food-grade silica nanoparticles (E 551) on maternal health and fetal growth using conventional toxicological and epigenetic methods. The results showed that prenatal exposure to a high-dose of E 551 induces fetal resorption. Moreover, E 551 significantly accumulates in maternal and fetal livers, triggering a hepatic inflammatory response. At the epigenetic level, global DNA methylation is markedly altered in the maternal and fetal livers. Genome-wide DNA methylation sequencing revealed affected mCG, mCHG, and mCHH methylation landscapes. Subsequent bioinformatic analysis of the differentially methylated genes suggests that E 551 poses a risk of inducing metabolic disorders in maternal and fetal livers. This is further evidenced by impaired glucose tolerance in pregnant mice and altered expression of key metabolism-related genes and proteins in maternal and fetal livers. Collectively, the results of this study highlighted the importance of epigenetics in characterizing the potential toxicity of maternal exposure to food-grade nanomaterials during pregnancy.

Maternal exposure to sunlight-irradiated graphene oxide induces neurodegeneration-like symptoms in zebrafish offspring through intergenerational translocation and genomic DNA methylation alterations

The physiochemical properties of graphene oxide may be affected by sunlight irradiation. However, the underlying mechanisms that alter the properties and subsequent intergenerational effects are not sufficiently investigate. Epigenetics is an early sensitive marker for the intergenerational effects of nanomaterial exposure due to the epigenetic memory. In this study, we investigate changes in the physicochemical properties and the intergenerational effects of maternal exposure to simulated sunlight-irradiated polyethyleneimine-functionalized graphene oxide (SL-PEI-GO). Results show that the physicochemical properties of polyethyleneimine-functionalized graphene oxide (PEI-GO) can be altered significantly by the oxidation of carbon atoms with unpaired electrons present in the defects and on the edges of PEI-GO by sunlight. First, the positive charges, sharp edges, defects and disordered structures of SL-PEI-GO make it translocate from maternal zebrafish to offspring, thus catalyzing the production of reactive oxygen species and damaging mitochondria directly. In addition, changes in DNA methylation reduce the expression of protocadherin1a, protocadherin19 and cadherin4, thus destroying cell membrane integrity, cell adhesion and Ca2+ binding. The alteration of DNA methylation induced by maternal exposure activates the Ca2+-CaMKK-brsk2a pathway, which catalyzes the phosphorylation of Tau and eventually results in the appearance of neurodegeneration-like symptoms, including the loss of neurons and neurobehavioral disorders. This study demonstrates that maternal exposure to SL-PEI-GO induces clear neurodegeneration-like symptoms in offspring through both the intergenerational translocation of nanomaterials and differential DNA methylation. These findings may provide new insights into the health risks of nanomaterials altered by nature conditions.

Silver Nanoparticles Induced Changes in DNA Methylation and Histone H3 Methylation in a Mouse Model of Breast Cancer

The importance of epigenetic changes as a measurable endpoint in nanotoxicological studies is getting more and more appreciated. In the present work, we analyzed the epigenetic effects induced by citrate- and PEG-coated 20 nm silver nanoparticles (AgNPs) in a model consisting of 4T1 breast cancer tumors in mice. Animals were administered with AgNPs intragastrically (1 mg/kg b.w. daily-total dose 14 mg/kg b.w.) or intravenously (administration twice with 1 mg/kg b.w.-total dose 2 mg/kg b.w.). We observed a significant decrease in 5-methylcytosine (5-mC) level in tumors from mice treated with citrate-coated AgNPs regardless of the route of administration. For PEG-coated AgNPs, a significant decrease in DNA methylation was observed only after intravenous administration. Moreover, treatment of 4T1 tumor-bearing mice with AgNPs decreased histone H3 methylation in tumor tissue. This effect was the most pronounced for PEG-coated AgNPs administered intravenously. No changes in histone H3 Lys9 acetylation were observed. The decrease in methylation of DNA and histone H3 was accompanied by changes in expression of genes encoding chromatin-modifying enzymes (Setd4, Setdb1, Smyd3, Suv39h1, Suv420h1, Whsc1, Kdm1a, Kdm5b, Esco2, Hat1, Myst3, Hdac5, Dnmt1, Ube2b, and Usp22) and genes related to carcinogenesis (Akt1, Brca1, Brca2, Mlh1, Myb, Ccnd1, and Src). The significance of the observed changes and the mechanisms responsible for their development are unclear, and more research in this area is warranted. Nevertheless, the present work points to the epigenetic effects as an important level of interaction between nanomaterials and biological systems, which should always be taken into consideration during analysis of the biological activity of nanomaterials and development of nanopharmaceuticals.

Transformation, Absorption and Toxicological Mechanisms of Silver Nanoparticles in the Gastrointestinal Tract Following Oral Exposure

Oral exposure is known as the primary way for silver nanoparticles (AgNPs), which are commonly used as food additives or antibacterial agents in commercial products, to enter the human body. Although the health risk of AgNPs has been a concern and extensively researched over the past few decades, there are still numerous knowledge gaps that need to be filled to disclose what AgNPs experience in the gastrointestinal tract (GIT) and how they cause oral toxicity. In order to gain more insight into the fate of AgNPs in the GIT, the main gastrointestinal transformation of AgNPs, including aggregation/disaggregation, oxidative dissolution, chlorination, sulfuration, and corona formation, is first described. Second, the intestinal absorption of AgNPs is presented to show how AgNPs interact with epithelial cells and cross the intestinal barrier. Then, more importantly, we make an overview of the mechanisms underlying the oral toxicity of AgNPs in light of recent advances as well as the factors affecting the nano-bio interactions in the GIT, which have rarely been thoroughly elaborated in published literature. At last, we emphatically discuss the issues that need to be addressed in the future to answer the question "How does oral exposure to AgNPs cause detrimental effects on the human body?".

Nanomedicine for drug resistant pathogens and COVID-19 using mushroom nanocomposite inspired with bacteriocin – A Review

Multidrug resistant (MDR) pathogens have become a major global health challenge and have severely threatened the health of society. Current conditions have gotten worse as a result of the COVID-19 pandemic, and infection rates in the future will rise. It is necessary to design, respond effectively, and take action to address these challenges by investigating new avenues. In this regard, the fabrication of metal NPs utilized by various methods, including green synthesis using mushroom, is highly versatile, cost-effective, eco-compatible, and superior. In contrast, biofabrication of metal NPs can be employed as a powerful weapon against MDR pathogens and have immense biomedical applications. In addition, the advancement in nanotechnology has made possible to modify the nanomaterials and enhance their activities. Metal NPs with biomolecules composite to prevents their microbial adhesion and kills the microbial pathogens through biofilm formation. Bacteriocin is an excellent antimicrobial peptide that works well as an augmentation substance to boost the antimicrobial effects. As a result, we concentrate on the creation of new, eco-compatible mycosynthesized metal NPs with bacteriocin nanocomposite via electrostatic, covalent, or non-covalent bindings. The synergistic benefits of metal NPs with bacteriocin to combat MDR pathogens and COVID-19, as well as other biomedical applications, are discussed in this review. Moreover, the importance of the adverse outcome pathway (AOP) in risk analysis of manufactured metal nanocomposite nanomaterial and their future possibilities also discussed.

The critical role of epigenetic mechanisms involved in nanotoxicology

Over the past decades, nanomaterials (NMs) have been widely applied in the cosmetic, food, engineering, and medical fields. Along with the prevalence of NMs, the toxicological characteristics exhibited by these materials on health and the environment have gradually attracted attentions. A growing number of evidences have indicated that epigenetics holds an essential role in the onset and development of various diseases. NMs could cause epigenetic alterations such as DNA methylation, noncoding RNA (ncRNA) expression, and histone modifications. NMs might alternate either global DNA methylation or the methylation of specific genes to affect the biological function. Abnormal upregulation or downregulation of ncRNAs might also be a potential mechanism for the toxic effects caused by NMs. In parallel, the phosphorylation, acetylation, and methylation of histones also take an important part in the process of NMs-induced toxicity. As the adverse effects of NMs continue to be explored, mechanisms such as chromosomal remodeling, genomic imprinting, and m⁶ A modification are also gradually coming into the limelight. Since the epigenetic alterations often occur in the early development of diseases, thus the relevant studies not only provide insight into the pathogenesis of diseases, but also screen for the prospective biomarkers for early diagnosis and prevention. This review summarizes the epigenetic alterations elicited by NMs, hoping to provide a clue for nanotoxicity studies and security evaluation of NMs. This article is categorized under: Toxicology and Regulatory Issues in Nanomedicine > Toxicology of Nanomaterials.

Early Epigenetic Responses in the Genomic DNA Methylation Fingerprints in Cells in Response to Sublethal Exposure of Silver Nanoparticles

With the rapid development of nanotechnology and nanoscience, nanosafety assessment has raised public concern. Although many studies have illustrated that nanomaterials could lead to genotoxicity, the early alterations of DNA methylation with nanomaterials under low-dose exposure have not been completely clear. In this study, we investigated the potential effect and molecular mechanism of AgNPs on the alternation of DNA methylation fingerprints in HEK293T cells under sublethal exposure. Intriguingly, silver nanoparticle treatment increased 5-mC level and changed methylation-related enzyme contents. Mechanistically, we scrutinized the changes in the molecular signaling and biological functions by means of MeDIP-Seq and RNA-seq. Our results revealed that AgNPs might undermine a number of vital regulatory networks including the metabolic processes, biological regulation and other cellular processes. More specifically at the DNA methylation fingerprints, there were 12 up-regulated and simultaneous hypomethylated genes, and 22 down-regulated and concomitant hypermethylated genes in HEK293T cells responding to AgNPs. Notably, these genes were primarily involved in lipid metabolism and ion metabolism. Together, these responsive genes might be used as early sensitive indicators for the variations of early epigenetic integrity through changing the DNA methylation fingerprints, as reflective of biological risk and toxicity of silver nanoparticles under realistic exposure scenarios.

Nanosafety: An Evolving Concept to Bring the Safest Possible Nanomaterials to Society and Environment

The use of nanomaterials has been increasing in recent times, and they are widely used in industries such as cosmetics, drugs, food, water treatment, and agriculture. The rapid development of new nanomaterials demands a set of approaches to evaluate the potential toxicity and risks related to them. In this regard, nanosafety has been using and adapting already existing methods (toxicological approach), but the unique characteristics of nanomaterials demand new approaches (nanotoxicology) to fully understand the potential toxicity, immunotoxicity, and (epi)genotoxicity. In addition, new technologies, such as organs-on-chips and sophisticated sensors, are under development and/or adaptation. All the information generated is used to develop new in silico approaches trying to predict the potential effects of newly developed materials. The overall evaluation of nanomaterials from their production to their final disposal chain is completed using the life cycle assessment (LCA), which is becoming an important element of nanosafety considering sustainability and environmental impact. In this review, we give an overview of all these elements of nanosafety.

RNA m6A Alterations Induced by Biomineralization Nanoparticles: A Proof-of-Concept Study of Epitranscriptomics for Nanotoxicity Evaluation

Although various strategies have been included in nanotoxicity evaluation, epitranscriptomics has rarely been integrated into this field. In this proof-of-concept study, N6-methyladenosine (m⁶A) changes of mRNA in HEK293T cells induced by three bovine serum albumin (BSA)-templated Au, CuS and Gd₂O₃ nanoparticles are systematically explored, and their possible biological mechanisms are preliminarily investigated. It has been found that all the three BSA-templated nanoparticles can reduce m⁶A levels, and the genes with reduced m⁶A are enriched for TGF-beta signaling, which is critical for cell proliferation, differentiation and apoptosis. Further results indicate that abnormal aggregation of m⁶A-related enzymes at least partly account for the nanoparticle-induced epitranscriptomic changes. These findings demonstrate that epitranscriptomics analysis can provide an unprecedented landscape of the biological effect induced by nanomaterials, which should be involved in the nanotoxicity evaluation to promote the potential clinical translation of nanomaterials.

Intracellular Exposure Dose-Associated Susceptibility of Steatotic Hepatocytes to Metallic Nanoparticles

Non-alcoholic fatty liver disease (NAFLD), mainly characterized by the accumulation of excess fat in hepatocytes, is the most prevalent liver disorder afflicting ~25% of adults worldwide. In vivo studies have shown that adult rodents with NAFLD were more sensitive to metallic nanoparticles (MNPs) than healthy MNPs. However, due to the complex interactions between various cell types in a fatty liver, it has become a major challenge to reveal the toxic effects of MNPs to specific types of liver cells such as steatotic hepatocytes. In this study, we reported the susceptibility of steatotic hepatocytes in cytotoxicity and the induction of oxidative stress to direct exposures to MNPs with different components (silver, ZrO₂, and TiO₂ NPs) and sizes (20-30 nm and 125 nm) in an oleic acid (OA) -induced steatotic HepG2 (sHepG2) cell model. Furthermore, the inhibitory potential of MNPs against the process of fatty acid oxidation (FAO) were obvious in sHepG2 cells, even at extremely low doses of 2 or 4 μg/mL, which was not observed in non-steatotic HepG2 (nHepG2) cells. Further experiments on the differential cell uptake of MNPs in nHepG2 and sHepG2 cells demonstrated that the susceptibility of steatotic hepatocytes to MNP exposures was in association with the higher cellular accumulation of MNPs. Overall, our study demonstrated that it is necessary and urgent to take the intracellular exposure dose into consideration when assessing the potential toxicity of environmentally exposed MNPs.

Multifunctional Ginger Nanofiber Hydrogels with Tunable Absorption: The Potential for Advanced Wound Dressing Applications

In this study, ginger residue from juice production was evaluated as a raw material resource for preparation of nanofiber hydrogels with multifunctional properties for advanced wound dressing applications. Alkali treatment was applied to adjust the chemical composition of ginger fibers followed by TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl radical)-mediated oxidation prior to nanofiber isolation. The effect of alkali treatment on hydrogel properties assembled through vacuum filtration without addition of any chemical cross-linker was evaluated. An outstanding absorption ability of 6200% combined with excellent mechanical properties, tensile strength of 2.1 ± 0.2 MPa, elastic modulus of 15.3 ± 0.3 MPa, and elongation at break of 25.1%, was achieved without alkali treatment. Furthermore, the absorption capacity was tunable by applying alkali treatment at different concentrations and by adjusting the hydrogel grammage. Cytocompatibility evaluation of the hydrogels showed no significant effect on human fibroblast proliferation in vitro. Ginger essential oil was used to functionalize the hydrogels by providing antimicrobial activity, furthering their potential as a multifunctional wound dressing.

Genome-Wide DNA Methylation Alterations and Potential Risk Induced by Subacute and Subchronic Exposure to Food-Grade Nanosilica in Mice

The intensive application of nanomaterials in the food industry has raised concerns about their potential risks to human health. However, limited data are available on the biological safety of nanomaterials in food, especially at the epigenetic level. This study examined the implications of two types of synthetic amorphous silica (SAS), food-grade precipitated silica (S200) and fumed silica Aerosil 200F (A200F), which are nanorange food additives. After 28-day continuous and intermittent subacute exposure to these SAS via diet, whole-genome methylation levels in mouse peripheral leukocytes and liver were significantly altered in a dose- and SAS type-dependent manner, with minimal toxicity detected by conventional toxicological assessments, especially at a human-relevant dose (HRD). The 84-day continuous subchronic exposure to all doses of S200 and A200F induced liver steatosis where S200 accumulated in the liver even at HRD. Genome-wide DNA methylation sequencing revealed that the differentially methylated regions induced by both SAS were mainly located in the intron, intergenic, and promoter regions after 84-day high-dose continuous exposure. Bioinformatics analysis of differentially methylated genes indicated that exposure to S200 or A200F may lead to lipid metabolism disorders and cancer development. Pathway validation experiments indicated both SAS types as potentially carcinogenic. While S200 inhibited the p53-mediated apoptotic pathway in mouse liver, A200F activated the HRAS-mediated MAPK signaling pathway, which is a key driver of hepatocarcinogenesis. Thus, caution must be paid to the risk of long-term exposure to food-grade SAS, and epigenetic parameters should be included as end points during the risk assessment of food-grade nanomaterials.

Postchronic Single-Walled Carbon Nanotube Exposure Causes Irreversible Malignant Transformation of Human Bronchial Epithelial Cells through DNA Methylation Changes

As environmental pollutants and possible carcinogens, carbon nanotubes (CNTs) have recently been found to induce carcinogenesis and tumor metastasis after long-term pulmonary exposure. However, whether CNT-induced carcinogenesis can be inherited and last for generations remains unclear. Herein, postchronic single-walled carbon nanotubes (SWCNTs) exposed human lung cell model (BEAS-2B cells) are established to investigate SWCNT-induced carcinogenesis. At a tolerated sublethal dose level, postchronic SWCNT exposure significantly increases the migration and invasion abilities of BEAS-2B cells, leading to malignant cell transformation. Notably, the malignant transformation of BEAS-2B cells is irreversible within a 60 day recovery period after SWCNT exposure, and the malignant transformation activities of cells gradually increase during the recovery period. Moreover, these transformed cells promote carcinogenesis in vivo, accompanied by a raised level of biomarkers of lung adenocarcinoma. Further mechanism analyses reveal that postchronic exposure to SWCNTs causes substantial DNA methylation and transcriptome dysregulation of BEAS-2B cells. Subsequent enrichment and clinical database analyses reveal that differentially expressed/methylated genes of BEAS-2B cells are enriched in cancer-related biological pathways. These results not only demonstrate that postchronic SWCNT-exposure-induced carcinogenesis is heritable but also uncover a mechanism from the perspective of DNA methylation.

Too small to matter? Physicochemical transformation and toxicity of engineered nTiO2, nSiO2, nZnO, carbon nanotubes, and nAg

Engineered nanomaterials (ENMs) refer to a relatively novel class of materials that are increasingly prevalent in various consumer products and industrial applications - most notably for their superlative physicochemical properties when compared with conventional materials. However, consumer products inevitably degrade over the course of their lifetime, releasing ENMs into the environment. These ENMs undergo physicochemical transformations and subsequently accumulate in the environment, possibly leading to various toxic effects. As a result, a significant number of studies have focused on identifying the possible transformations and environmental risks of ENMs, with the objective of ensuring a safe and responsible application of ENMs in consumer products. This review aims to consolidate the results from previous studies related to each stage of the pathway of ENMs from being embodied in a product to disintegration/transformation in the environment. The scope of this work was defined to include the five most prevalent ENMs based on recent projected production market data, namely: nTiO₂, nSiO₂, nZnO, carbon nanotubes, and nAg. The review focuses on: (i) models developed to estimate environmental concentrations of ENMs; (ii) the possible physicochemical transformations; (iii) cytotoxicity and genotoxicity effects specific to each ENM selected; and (iv) a discussion to identify potential gaps in the studies conducted and recommend areas where further investigation is warranted.

MicroRNA Response and Toxicity of Potential Pathways in Human Colon Cancer Cells Exposed to Titanium Dioxide Nanoparticles

Titanium dioxide nanoparticles (TiO₂-NPs) are widely used for biomedical and food applications, the toxicity of TiO₂-NPs in vivo and in vitro has been elucidated, but the underlying cytotoxicity of TiO₂-NPs against microRNA remains largely unknown. The purpose of this study was to analyze microRNA profiling induced by TiO₂-NPs against NCM460 and HCT116 cell lines. Comparative analysis identified 34 and 24 microRNAs were significantly altered in the TiO₂-NPs treated cells at concentrations of 3 μg/mL and 30 μg/mL, respectively. Functional classification demonstrated that a large proportion of genes involved in metabolism, human disease, and environmental information process were significantly upregulated by TiO₂-NPs. Bioinformatics analysis suggested that microRNA 378 might be an early indicator of cellular response to exogenous stimuli with apoptotic signals. Furthermore, TiO₂-NPs significantly altered the expression of microRNA 378b and 378g in HCT116 and NCM460 cell lines at different concentrations from 3 to 6 μg/mL. These concentrations elicit high-sensitivity of stimuli response in colon cancer cells when exposed to the slight doses of TiO₂-NPs. Our study indicated that microRNAs 378b and 378g may play an important role in TiO₂-NPs-mediated colonic cytotoxicity, which may provide a valuable insight into the molecular mechanisms of potential risks in colitis and colon cancer.

Silver nanoparticles compromise the development of mouse pubertal mammary glands through disrupting internal estrogen signaling

Despite numerous studies on the environmental health and safety (EHS) of silver nanoparticles (AgNPs), most studies looked into their gross toxicities with rather limited understanding on their labyrinthine implicit effects on the target sites, such as the endocrine system. Burgeoning evidence documents the disrupting effects of AgNPs on endocrine functions; however, little research has been invested to recognize the potential impacts on the mammary gland, a susceptible estrogen-responsive organ. Under this setting, we here aimed to scrutinize AgNP-induced effects on the development of pubertal mammary glands at various concentrations that bear significant EHS relevance. We unearthed that AgNPs could accumulate in mouse mammary glands and result in a decrease in the percentage of ducts and terminal ducts in the adult mice after chronic exposure. Strikingly, smaller sized AgNPs showed greater capability to alter the pubertal mammary development than larger sized particles. Intriguingly, mechanistic investigation revealed that the reduction of epithelial proliferation in response to AgNPs was ascribed to reduced ERα expression, which, at least partially, accounted for diseased epithelial morphology in mammary glands. Meanwhile, the decline in fibrous collagen deposition around the epithelium was found to contribute to the compromised development of mammary glands under the exposure of AgNPs. Moreover, as an extension of the mechanism, AgNPs diminished serum levels of estradiol in exposed animals. Together, these results uncovered a novel toxicity feature of AgNPs: compromised development of mouse pubertal mammary glands through the endocrine-disrupting actions. This study would open a new avenue to unveil the EHS impacts of AgNPs.

Continued Efforts on Nanomaterial-Environmental Health and Safety Is Critical to Maintain Sustainable Growth of Nanoindustry

Nanotechnology is enjoying an impressive growth and the global nanotechnology industry is expected to exceed US$ 125 billion by 2024. Based on these successes, there are notions that enough is known and efforts on engineered nanomaterial environmental health and safety (nano-EHS) research should be put on the back burner. However, there are recent events showing that it is not the case. The US Food and Drug Administration found ferumoxytol (carbohydrate-coated superparamagnetic iron oxide nanoparticle) for anemia treatment could induce lethal anaphylactic reactions. The European Union will categorize TiO2 as a category 2 carcinogen due to its inhalation hazard and France banned use of TiO2 (E171) in food from January 1, 2020 because of its carcinogenic potential. Although nanoindustry is seemingly in a healthy state, growth could be hindered for the lack of certainty and more nano-EHS research is needed for the sustainable growth of nanoindustry. Herein, the current knowledge gaps and the way forward are elaborated.

Anticancer Effects of Zinc Oxide Nanoparticles Through Altering the Methylation Status of Histone on Bladder Cancer Cells

Purpose

Zinc oxide nanoparticles (nZnO) have been widely used in the medicine field. Numerous mechanistic studies for nZnO’s anticancer effects are merely performed under high concentration exposure. However, possible anticancer mechanisms of epigenetic dysregulation induced by low doses of nZnO are unclear.

Methods

nZnO were characterized and bladder cancer T24 cells were treated with nZnO for 48 hrs at different exposure concentrations. Cell cycle, apoptosis, cell migration and invasion were determined. We performed qRT-PCR, Western blot and chromatin immunoprecipitation to detect the mRNA and protein levels of signaling pathway cascades for histone modification.

Results

In this study, we investigated the potential anticancer effects and mechanisms of nZnO on histone modifications in bladder cancer T24 cells upon low-dose exposure. Our findings showed that low concentrations of nZnO resulted in cell cycle arrest at S phase, facilitated cellular late apoptosis, repressed cell invasion and migration after 48 hrs exposure. These anticancer effects could be attributed to increased RUNX3 levels resulting from reduced H3K27me³ occupancy on the RUNX3 promoter, as well as decreased contents of histone methyltransferase EZH2 and the trimethylation of histone H3K27. Our findings reveal that nZnO are able to enter into the cytoplasm and nucleus of T24 cells. Additionally, both particles and ions from nZnO may jointly contribute to the alteration of histone methylation. Moreover, sublethal nZnO-conducted anticancer effects and epigenetic mechanisms were not associated with oxidative stress or DNA damage.

Conclusion

We reveal a novel epigenetic mechanism for anticancer effects of nZnO in bladder cancer cells under low-dose exposure. This study will provide experimental basis for the toxicology and cancer therapy of nanomaterials.

Graphene Oxide Causes Disordered Zonation Due to Differential Intralobular Localization in the Liver

The liver is the primary organ to sequester nanodrugs, representing a substantial hurdle for drug delivery and raising toxicity concerns. However, the mechanistic details underlying the liver sequestration and effects on the liver are still elusive. The difficulty in studying the liver lies in its complexity, which is structured with stringently organized anatomical units called lobules. Graphene oxide (GO) has attracted attention for its applications in biomedicine, especially as a nanocarrier; however, its sequestration and effects in the liver, the major enrichment and metabolic organ, are less understood. Herein, we unveiled the differential distribution of GO in lobules in the liver, with a higher amount surrounding portal triad zones than the central vein zones. Strikingly, liver zonation patterns also changed, as reflected by changes in vital zonated genes involved in hepatocyte integrity and metabolism, leading to compromised hepatic functions. RNA-Seq and DNA methylation sequencing analyses unraveled that GO-induced changes in liver functional zonation could be ascribed to dysregulation of key signaling pathways governing liver zonation at not only mRNA transcriptions but also DNA methylation imprinting patterns, partially through TET-dependent signaling. Together, this study reveals the differential GO distribution pattern in liver lobules and pinpoints the genetic and epigenetic mechanisms in GO-induced liver zonation alterations.

Metallic Fingerprints of Carbon: Label-Free Tracking and Imaging of Graphene in Plants

Detection and quantification of carbon nanomaterials are extremely challenging, especially under the background interference of carbon. Here, we propose a new label-free method to quantify, track, and in situ image graphene and graphene oxide (GO) in plants based on their inherent metallic impurities as fingerprints. We show the ubiquity and high stability of inherent metallic fingerprints of graphene and GO obtained from different exposure routes under the natural environments, which enables the materials to be easily quantified and in situ imaged by high-sensitivity (laser ablation) inductively coupled plasma mass spectrometry. The method was applied to investigate the uptake and spatial distribution of graphene and GO in soybean plants. The plants were cultivated in graphene or GO solutions for 7 days, and the indicative elements (Ni or Mn) in different parts of plants were monitored and imaged. We found that graphene and GO showed different distribution patterns in plants (the highest uptake percentages in root up to 14.4% for graphene and 47.8% for GO), and high concentration of material exposure might cause excessive accumulation of materials in roots which blocked their further transport to the other parts of plants. The present method is more straightforward, accessible, and economical than normally used isotopic or metal-labeling methods. It also avoids the uncertainties or alterations of properties caused by the labeling process and thus has great promise in analysis and risk assessment of carbon nanomaterials.

Construction of cellulose nanofibers/quaternized chitin/organic rectorite composites and their application as wound dressing materials

Traumatic injury is a major cause of mortality, and poor wound healing affects millions of people. Thus, the development of effective wound dressings is essential for speeding up wound healing and decreasing mortality. In this study, a suspension of carboxylated brown algae cellulose nanofibers (BACNFs) with a high aspect ratio was freeze dried to prepare a sponge. The sponge showed high porosity and water absorption capacity; thus, it can absorb wound exudates when used as a wound dressing. In addition, quaternized β-chitin (QC) with antibacterial properties was intercalated into the interlayer space of the organic rectorite (OREC) via electrostatic interactions to obtain composite suspensions (QCRs) with improved antimicrobial activity compared to that of QC alone. Subsequently, the BACNF sponge was soaked in the QCR suspension to absorb QCRs via electrostatic interactions and hydrogen bonding from which cellulose nanofiber/quaternized chitin/organic rectorite composite (BACNF/QCR) sponges were constructed via freeze-drying. The in vivo animal tests demonstrated that the BACNF/QCR sponges rapidly induced hemostasis in a rat tail amputation test, making them superior to the traditional hemostatic materials. Furthermore, BACNFs/QCRs could substantially promote collagen synthesis and neovascularization, thereby accelerating wound healing 3 days earlier than gauze. This multi-functional biomedical material, fabricated using natural substances, shows great potential to be used for wound healing.

Insights into the epigenetic effects of nanomaterials on cells

With the development of nanotechnology, nanomaterials are increasingly being applied in health fields, such as biomedicine, pharmaceuticals, and cosmetics. Concerns have therefore been raised over their toxicity and numerous studies have been carried out to assess their safety. Most studies on the toxicity and therapeutic mechanisms of nanomaterials have revealed the effects of nanomaterials on cells at the transcriptome and proteome levels. However, epigenetic modifications, for example DNA methylation, histone modification, and noncoding RNA expression induced by nanomaterials, which play an important role in the regulation of gene expression, have not received sufficient attention. In this review, we therefore state the importance of studying epigenetic effects induced by nanomaterials; then we review the progress of nanomaterial epigenetic research in the assessment of toxicity, therapeutic, and other mechanisms. We also clarify the possible study directions for future nanomaterial epigenetic research. Finally, we discuss the future development and challenges of nanomaterial epigenetics that must still be addressed. We hope to understand the potential toxicity of nanomaterials and clearly understand the therapeutic mechanism through a thorough investigation of nanomaterial epigenetics.

Structural transformation and potential toxicity of iron-based deposits in drinking water distribution systems

Discoloration events in drinking water distribution systems (DWDSs) are usually considered an aesthetic issue rather than a health concern, and the potential toxicity of the iron-based particles resuspended from deposits in DWDSs has not been a focus. More importantly, it has not been recognized that the iron-based particles may have structural transformation under the complex condition in DWDSs which would further increase their adverse effects. In the present study, iron particle-dominated loose deposits, which were collected from a real DWDSs through pipe flushing, were firstly found to possess obvious toxicity to human liver cells. To further evaluate the potential harms of the deposits, FeOOH crystals (which is one of the most representative components in the deposits of DWDSs) were grown with different types of coexisting matters which may emerge in DWDSs. Results showed that the FeOOH had obvious structure transformation with coexisting matters which further influenced their toxicity: the samples with sharp surfaces had higher toxicity than those with smooth surfaces. Interestingly, although the FeOOH particles formed with perfluorooctanoic acid (FeOOH-PFOA) did not have the sharpest surface or smallest particle size among all the samples, they demonstrated the highest toxicity with strong generation of reactive oxygen species. Experimental and theoretical studies verified that PFOA induced the electron migration around Fe in FeOOH-PFOA particles. The FeOOH-PFOA not only was able to capture electrons directly from DNA, but also generated ROS from O₂ using DNA as an electron donor which might greatly enhance the oxidative damage to cells. This study would broaden the understanding of the potential harms of deposits in DWDSs.

DNA Methylation Regulates Corneal Epithelial Wound Healing by Targeting miR-200a and CDKN2B

Purpose

DNA methylation is a key epigenetic modification involved in various biological processes and diseases. Corneal epithelial wound healing (CEWH) is essential for restoring corneal integrity and transparency after injury. However, the role of DNA methylation in CEWH remains elusive. Here, we investigate the function and underlying mechanism of DNA methylation in regulating CEWH.

Methods

Dot blots and global methylation assays determined DNA methylation levels during CEWH. Quantitative RT-PCR and Western blot analysis examined the expression of DNA methyltransferases (DNMTs), cyclin-dependent kinase inhibitor 2B (CDKN2B), and miR-200a during CEWH, respectively. MTS assays and flow cytometry were used to analyze human corneal epithelial cell (HCEC) proliferation and cell cycle, respectively. The in vitro scratch wound assay assessed HCEC migration and an in vivo murine corneal epithelial debridement model evaluated wound healing. Using bisulfite sequencing PCR, we determined the DNA methylation status of the candidate genes. Transfection of miR-200a mimic or inhibitor assessed the function of miR-200a in HCECs. Rescue experiments were performed to clarify the correlation between DNMT1 and miR-200a/CDKN2B during CEWH.

Results

DNMT1 and DNMT3B expression was significantly upregulated during CEWH, resulting in a significant global DNA hypermethylation. DNMT1 downregulation dramatically delayed CEWH in vivo, and suppressed HCEC proliferation and migration. MiR-200a inhibited HCEC migration. Furthermore, miR-200a and CDKN2B were identified as molecular targets of DNA methylation and as having a causal connection with DNMT1.

Conclusions

DNMT1-mediated DNA hypermethylation can enhance the process of CEWH by directly targeting miR-200a and CDKN2B. This insight pinpoints novel potential drug targets for promoting CEWH.

Tetrahedral DNA Nanomaterial Regulates the Biological Behaviors of Adipose-Derived Stem Cells via DNA Methylation on Dlg3

As a simple and classical three-dimensional shape, tetrahedral DNA nanostructures (TDNs) can provide robust properties for better stability and can serve as a versatile platform for biosensing and drug delivery. More in-depth, its safety should be assessed by sensitive detection methods. However, the effect of TDNs at the epigenetic level has not received much attention. Here, DNA methylation alteration in adipose-derived stem cells (ASCs) after exposure to TDNs was comprehensively evaluated. The results from reduced representation bisulfite sequencing, bisulfite-specific polymerase chain reaction, and further gene function analysis revealed that TDNs induced a few differentially methylated regions where negatively correlated gene expressions occur. Moreover, TDNs facilitated ASC proliferation and attenuated apoptosis via DNA hypermethylation of the Dlg3 gene promotor. This study may help pave the way for potential applications with the nanosafety of TDNs and offer deep insights into the proliferation promotion effect and antiapoptosis ability of TDNs.

Involvement of telomerase activity inhibition and telomere dysfunction in silver nanoparticles anticancer effects

AIM

To investigate the possible mechanisms of telomerase and telomere underlying the anticancer effects of silver nanoparticles (AgNPs).

MATERIALS & METHODS

25nm polyvinylpyrrolidone-coated AgNPs were used. The telomerase activity and telomere function were evaluated. The anticancer effects of AgNPs were gauged with cell viability assay under different statement of telomerase and telomere.

RESULTS & CONCLUSION

AgNPs could inhibit telomerase activity and lead to telomere shortening and dysfunction. Overexpression of telomerase attenuated the anticancer activity of AgNPs, whereas downregulation of telomerase activity or dysfunction of the telomere enhanced the cytotoxicity of AgNPs in HeLa cells. Our findings provided strong evidence that the anticancer effects of AgNPs were mediated via interference with the telomerase/telomere.

Multi-omics analysis of ten carbon nanomaterials effects highlights cell type specific patterns of molecular regulation and adaptation

New strategies to characterize the effects of engineered nanomaterials (ENMs) based on omics technologies are emerging. However, given the intricate interplay of multiple regulatory layers, the study of a single molecular species in exposed biological systems might not allow the needed granularity to successfully identify the pathways of toxicity (PoT) and, hence, portraying adverse outcome pathways (AOPs). Moreover, the intrinsic diversity of different cell types composing the exposed organs and tissues in living organisms poses a problem when transferring in vivo experimentation into cell-based in vitro systems. To overcome these limitations, we have profiled genome-wide DNA methylation, mRNA and microRNA expression in three human cell lines representative of relevant cell types of the respiratory system, A549, BEAS-2B and THP-1, exposed to a low dose of ten carbon nanomaterials (CNMs) for 48 h. We applied advanced data integration and modelling techniques in order to build comprehensive regulatory and functional maps of the CNM effects in each cell type. We observed that different cell types respond differently to the same CNM exposure even at concentrations exerting similar phenotypic effects. Furthermore, we linked patterns of genomic and epigenomic regulation to intrinsic properties of CNM. Interestingly, DNA methylation and microRNA expression only partially explain the mechanism of action (MOA) of CNMs. Taken together, our results strongly support the implementation of approaches based on multi-omics screenings on multiple tissues/cell types, along with systems biology-based multi-variate data modelling, in order to build more accurate AOPs.

Preliminary investigation on cytotoxicity of fluorinated polymer nanoparticles

As well-known persistent organic pollutants (POPs), organofluorine pollutants such as perfluorooctane sulfonate (PFOS) have been proven to be bioaccumulated and harmful to health. However, toxicological assessment of organofluorinated nanoparticles, which have emerged as a novel tool for biomedical and industrial applications, is lacking, to the best of our knowledge. To assess the biological effects and health risk of fluorinated nanoparticles, trifluoroethyl aryl ether-based fluorinated poly(methyl methacrylate) nanoparticles (PTFE-PMMA NPs) were synthesized with various fluorine contents (PTFE-PMMA-1 NPs 12.0wt.%, PTFE-PMMA-2 NPs 6.1wt.% and PTFE-PMMA-3 NPs 5.0wt.%), and their cytotoxicity was investigated in this study. The in vitro experimental results indicated that the cytotoxicity of PTFE-PMMA NPs was mild, and was closely related to their fluorine (F) contents and F-containing side chains. Specifically, the cytotoxicity of PTFE-PMMA NPs decreased with increasing F content and F-containing side chains. After exposure to PTFE-PMMA NPs at a sublethal dose (50μg/mL) for 24hr, the phospholipid bilayer was damaged, accompanied by increasing permeability of the cell membrane. Meanwhile, the intracellular accumulation of reactive oxygen species (ROS) occurred, resulting in the increase of DNA damage, cell cycle arrest and cell death. Overall, the PTFE-PMMA NPs were found to be relatively safe compared with typical engineered nanomaterials (ENMs), such as silver nanoparticles and graphene oxide, for biomedical and industrial applications.

Long non-coding RNA MT1DP shunts the cellular defense to cytotoxicity through crosstalk with MT1H and RhoC in cadmium stress

Metallothioneins (MTs) are known to protect cells against oxidative stress, especially providing protection against cadmium (Cd) toxicity in hepatocytes. There are various gene variants and pseudogenes for MTs; however, there is little understanding on the functions of those non-coding MT members that are known to be expressed as long non-coding RNAs (lncRNAs) nowadays. Different from most protein-coding MT members, MT1DP was here found that remarkably induced to provoke cytotoxicity in hepatocytes in response to Cd treatment. MT1DP exerted such a pro-apoptotic function in Cd-treated hepatocytes through interacting with two partners: RhoC and MT1H. On one hand, MT1DP interacted with RhoC protein to increase the latter’s stability by preventing lysosome-dependent protein degradation. Therefore, upon Cd stress, MT1DP/RhoC complex was quickly reinforced to activate RhoC-CCN1/2-AKT signaling and potentiate Ca²⁺ influx, leading to enhanced Cd uptake and elevated Cd toxicity. On the other hand, MT1H, a protein-coding member of the MT family with little known function, was found to quickly respond to Cd exposure along with MT1DP. Mechanistically, MT1H and MT1DP were uncovered to mutually protect each other through a reciprocal ceRNA mechanism, building up a positive feedback loop to enforce MT1DP-conducted signaling upon Cd exposure. Moreover, MT1DP was found to contribute much more to the activation of RhoC-CCN1/2-AKT signaling than MT1H. Considered together, we here unveiled a mystery whether a pseudogene within the MT family, MT1DP, has actual biological functions in regulating Cd-induced cellular defense. Our findings unearthed an important role of pseudogene MT1DP in calibrating the cellular machinery to switch the cellular defense to cytotoxicity through crosslinking an interplay between its two partners, namely MT1H and RhoC, under cadmium stress.

Graphene Oxide Induced Perturbation to Plasma Membrane and Cytoskeletal Meshwork Sensitize Cancer Cells to Chemotherapeutic Agents

The outstanding physicochemical properties endow graphene materials (e.g., graphene oxide, GO) with beneficial potentials in diverse biomedical fields such as bioimaging, drug delivery, and biomolecular detection. GO recently emerged as a chemosensitizer; however, the detailed molecular basis underlying GO-conducted sensitization and corresponding biological effects are still elusive. Based on our recent findings that GO treatment at sublethal concentrations could impair the general cellular priming state, including disorders of plasma membrane and cytoskeleton construction, we aimed here to explore the mechanism of GO as a sensitizer to make cancer cells more susceptible to chemotherapeutic agents. We discovered that GO could not only compromise plasma membrane and cytoskeleton in J774A.1 macrophages and A549 lung cancer cells at sublethal concentrations without incurring significant cell death but also dampen a number of biological processes. Using the toxicogenomics approaches, we laid out the gene expression signature affected by GO and further defined those genes involved in membrane and cytoskeletal impairments responding to GO. The mechanistic investigation uncovered that the interactions of GO-integrin occurred on the plasma membrane and consequently activated the integrin-FAK-Rho-ROCK pathway and suppressed the expression of integrin, resulting in compromised cell membrane and cytoskeleton and a subsequent cellular priming state. By making use of this mechanism, the efficacy of chemotherapeutic agents (e.g., doxorubicin and cisplatin) could be enhanced by GO pretreatment in killing cancer cells. This study unveiled a feature of GO in cancer therapeutics: sensitizing cancer cells to chemotherapeutic agents by undermining the resistance capability of tumor cells against chemotherapeutic agents, at least partially, by compromising plasma membrane and cytoskeleton meshwork.

Presence and formation of fluorescence carbon dots in a grilled hamburger

Carbon nanoparticles in a grilled hamburger were discovered, which showed different structures and properties at various heating temperatures.