Cardiopulmonary effects induced by occupational exposure to titanium dioxide nanoparticles

Worse pulmonary function in association with cumulative exposure to nanomaterials. Hints of a mediation effect via pulmonary inflammation

BACKGROUND

Today, nanomaterials are broadly used in a wide range of industrial applications. Such large utilization and the limited knowledge on to the possible health effects have raised concerns about potential consequences on human health and safety, beyond the environmental burden. Given that inhalation is the main exposure route, workers exposed to nanomaterials might be at risk of occurrence of respiratory morbidity and/or reduced pulmonary function. However, epidemiological evidence regarding the association between cumulative exposure to nanomaterials and respiratory health is still scarce. This study focused on the association between cumulative exposure to nanomaterials and pulmonary function among 136 workers enrolled in the framework of the European multicentric NanoExplore project.

RESULTS

Our findings suggest that, independently of lifelong tobacco smoking, ethnicity, age, sex, body mass index and physical activity habits, 10-year cumulative exposure to nanomaterials is associated to worse FEV1 and FEF25 - 75%, which might be consistent with the involvement of both large and small airway components and early signs of airflow obstruction. We further explored the hypothesis of a mediating effect via airway inflammation, assessed by interleukin (IL-)10, IL-1β and Tumor Necrosis Factor alpha (TNF-α), all quantified in the Exhaled Breath Condensate of workers. The mediation analysis results suggest that IL-10, TNF-α and their ratio (i.e., anti-pro inflammatory ratio) may fully mediate the negative association between cumulative exposure to nanomaterials and the FEV1/FVC ratio. This pattern was not observed for other pulmonary function parameters.

CONCLUSIONS

Safeguarding the respiratory health of workers exposed to nanomaterials should be of primary importance. The observed association between cumulative exposure to nanomaterials and worse pulmonary function parameters underscores the importance of implementing adequate protective measures in the nanocomposite sector. The mitigation of harmful exposures may ensure that workers can continue to contribute productively to their workplaces while preserving their respiratory health over time.

Research advance of occupational exposure risks and toxic effects of semiconductor nanomaterials

In recent years, semiconductor nanomaterials, as one of the most promising and applied classes of engineered nanomaterials, have been widely used in industries such as photovoltaics, electronic devices, and biomedicine. However, occupational exposure is unavoidable during the production, use, and disposal stages of products containing these materials, thus posing potential health risks to workers. The intricacies of the work environment present challenges in obtaining comprehensive data on such exposure. Consequently, there remains a significant gap in understanding the exposure risks and toxic effects associated with semiconductor nanomaterials. This paper provides an overview of the current classification and applications of typical semiconductor nanomaterials. It also delves into the existing state of occupational exposure, methodologies for exposure assessment, and prevailing occupational exposure limits. Furthermore, relevant epidemiological studies are examined. Subsequently, the review scrutinizes the toxicity of semiconductor nanomaterials concerning target organ toxicity, toxicity mechanisms, and influencing factors. The aim of this review is to lay the groundwork for enhancing the assessment of occupational exposure to semiconductor nanomaterials, optimizing occupational exposure limits, and promoting environmentally sustainable development practices in this domain.

Assessing the inhaled dose of nanomaterials by nanoparticle tracking analysis (NTA) of exhaled breath condensate (EBC) and its relationship with lung inflammatory biomarkers

The widespread and increasing use of nanomaterials has resulted in a higher likelihood of exposure by inhalation for nanotechnology workers. However, tracking the internal dose of nanoparticles deposited at the airways level, is still challenging. To assess the suitability of particle number concentration determination as biomarker of internal dose, we carried out a cross sectional investigation involving 80 workers handling nanomaterials. External exposure was characterized by portable counters of particles DISCminiTM (Testo, DE), allowing to categorize 51 workers as exposed and 29 as non-exposed (NE) to nanoparticles. Each subject filled in a questionnaire reporting working practices and health status. Exhaled breath condensate was collected and analysed for the number of particles/ml as well as for inflammatory biomarkers. A clear-cut relationship between the number of airborne particles in the nano-size range determined by the particle counters and the particle concentration in exhaled breath condensate (EBC) was apparent. Moreover, inflammatory cytokines (IL-1β, IL-10, and TNF-α) measured in EBC, were significantly higher in the exposed subjects as compared to not exposed. Finally, significant correlations were found between external exposure, the number concentration of particles measured by the nanoparticle tracking analysis (NTA) and inflammatory cytokines. As a whole, the present study, suggests that NTA can be regarded as a reliable tool to assess the inhaled dose of particles and that this dose can effectively elicit inflammatory effects.

Hepatotoxicity of titanium dioxide nanoparticles

The food additive E171 (titanium dioxide, TiO2), is widely used in foods, pharmaceuticals and cosmetics. It is a fine white powder, with at least one third of its particles sized in the nanoparticulate (˂100 nm range, TiO2 NPs). The use of E171 is controversial as its relevant risk assessment has never been satisfactorily accomplished. In vitro and in vivo studies have shown dose-dependent toxicity in various organs including the liver. TiO2 NPs have been shown to induce inflammation, cell death and structural and functional changes within the liver. The toxicity of TiO2 NPs in experimental models varies between organs and according to their physiochemical characteristics and parameters such as dosage and route of administration. Among these factors, ingestion is the most significant exposure route, and the liver is a key target organ. The aim of this review is to highlight the reported adverse effects of orally administered TiO2 NPs on the liver and to discuss the controversial state of its toxicity.

Biomarkers of exposure and effect in human biomonitoring of metal-based nanomaterials: their use in primary prevention and health surveillance

Metal-based nanomaterials (MNMs) have gained particular interest in nanotechnology industry. They are used in various industrial processes, in biomedical applications or to improve functional properties of several consumer products. The widescale use of MNMs in the global consumer market has resulted in increases in the likelihood of exposure and risks to human beings. Human exposure to MNMs and assessment of their potential health effects through the concomitant application of biomarkers of exposure and effect of the most commonly used MNMs were reviewed in this paper. In particular, interactions of MNMs with biological systems and the nanobiomonitoring as a prevention tool to detect the early damage caused by MNMs as well as related topics like the influence of some physicochemical features of MNMs and availability of analytical approaches for MNMs testing in human samples were summarized in this review. The studies collected and discussed seek to increase the current knowledge on the internal dose exposure and health effects of MNMs, highlighting the advantages in using biomarkers in primary prevention and health surveillance.

Toxicity of Metal Oxide Nanoparticles: Looking through the Lens of Toxicogenomics

The impact of solubility on the toxicity of metal oxide nanoparticles (MONPs) requires further exploration to ascertain the impact of the dissolved and particulate species on response. In this study, FE1 mouse lung epithelial cells were exposed for 2-48 h to 4 MONPs of varying solubility: zinc oxide, nickel oxide, aluminum oxide, and titanium dioxide, in addition to microparticle analogues and metal chloride equivalents. Previously published data from FE1 cells exposed for 2-48 h to copper oxide and copper chloride were examined in the context of exposures in the present study. Viability was assessed using Trypan Blue staining and transcriptomic responses via microarray analysis. Results indicate material solubility is not the sole property governing MONP toxicity. Transcriptional signaling through the 'HIF-1α Signaling' pathway describes the response to hypoxia, which also includes genes associated with processes such as oxidative stress and unfolded protein responses and represents a conserved response across all MONPs tested. The number of differentially expressed genes (DEGs) in this pathway correlated with apical toxicity, and a panel of the top ten ranked DEGs was constructed (Hmox1, Hspa1a, Hspa1b, Mmp10, Adm, Serpine1, Slc2a1, Egln1, Rasd1, Hk2), highlighting mechanistic differences among tested MONPs. The HIF-1α pathway is proposed as a biomarker of MONP exposure and toxicity that can help prioritize MONPs for further evaluation and guide specific testing strategies.

Co-exposure to iron, copper, zinc, selenium and titanium is associated with the prevention of gastric precancerous lesions

Gastric cancer is the third leading cause of cancer death, and gastric precancerous lesions (GPLs) are an important stage in the transformation of normal gastric mucosa to gastric cancer. Matched for age and sex, a total of 316 subjects were eventually included from our prospective observation population (including 1007 patients with GPLs and 762 normal controls), and a questionnaire survey was conducted. In total, 10 plasma elements (iron, copper, zinc, selenium, rubidium, strontium, titanium, aluminum, vanadium and arsenic) were measured by applying inductively coupled plasma‒mass spectrometry (ICP‒MS). A multivariate conditional logistic regression model and Bayesian kernel logistic regression model (BKMR) were used to analyze the association between plasma element concentrations and GPLs. In the multimetal model, plasma titanium concentrations were significantly and positively associated with the prevalence of GPLs, with a fourth-quartile OR of 11.56 ([95% CI]: [2.78-48.13]). Plasma selenium and copper were negatively correlated with GPLs, with the highest quartiles of selenium and copper having an OR of 0.03 ([95% CI]: [0.01-0.15]; P < 0.001) and 0.24 ([95% CI]: [0.07-0.82]), respectively. In the BKMR model, there was a significant negative combined correlation of five metals on GPLs: iron, copper, zinc, selenium, and titanium. The results of this study showed that plasma concentrations of selenium and copper were negatively correlated with GPLs, while plasma concentrations of titanium were positively correlated with GPLs, and the combined action of the five elements was negatively correlated with GPLs.

Effect biomarkers of nanoparticle-exposed workers: A scoping review

The widespread and increasing use of engineered nanomaterials (i.e., particulate materials measuring 1-100 nanometers (nm) in at least one dimension) poses a potential health and safety risk to exposed workers. The unique properties of nanomaterials have made nanomaterials useful in multiple industries. However, their production and use may compromise worker health, presenting an emerging occupational health hazard, the acute and chronic effects of which have not been fully assessed. In this scoping review, we critically assess the literature on biomarkers of effect from nanoparticles and discuss the utility of biomonitoring as a means of assessing the physiological effects of nanoparticle exposure among nanotechnology workers. Multiple databases were queried based on select inclusion and exclusion criteria according to PRISMA guidelines, and articles were independently screened by two topic experts. Of 286 articles initially retrieved, 28 were included after screening and eligibility. The reviewed articles indicated that sensitive effect biomarkers could reflect early health effects of exposure to nanoparticles in the workplace and may be useful for monitoring toxicological effects and associated risks.

Characterisation of engineered titanium dioxide nanoparticles in selected food

Titanium dioxide (TiO2), an E171 manufacturer-made food additive, is extensively utilised as a colourant in drug and a food products. Some studies showed that most of confectionary and food items contain inexplicable particles. The aim of this article is to determine the size and structure of TiO2 nanoparticles in different food products. Ten food samples, including coffee cream, white chocolate concentrate, frosting, gum, yoghurt candy, hard candies and chewy candies, were investigated for this purpose. The crystalline structure and particle size of TiO2 were determined by Powder X-ray Diffraction (PXRD) and Transmission Electron Microscopy (TEM). TEM images revealed that a few of the extracted nanoparticles had a rod-like shape, but most were spherical. Also, the size of the TiO2 particle had a wide distribution between 12 and 450 nm. Thus, to avoid human health risk, crucial factors such as size, and shape should be considered and regulated by food authorities.

Occupational exposure to nanomaterials and biomarkers in exhaled air and urine: Insights from the NanoExplore international cohort

The current evidence on nanomaterial toxicity is mostly derived from experimental studies making it challenging to translate it into human health risks. We established an international cohort (N = 141 workers) within the EU-LIFE project "NanoExplore" to address possible health effects from occupational exposures to nanomaterials. We used a handheld direct-reading optical particle counter to measure airborne nanoparticle number concentrations (PNC) and lung-deposited surface areas (LDSAs). Airborne particles were characterized by TEM and SEM-EDAX. We assessed oxidative/nitrosative stress with a panel of biomarkers in exhaled breath condensate (EBC) (8-isoprostane, malondialdehyde, nitrotyrosine), inflammation (high-sensitivity C reactive protein (hs-CRP), IL-1β, TNF-α, IL-10) and KL-6 (considered as biomarker of interstitial lung fibrosis) and urine (total antioxidant power (TAP), 8-isoprostane, and malondialdehyde). Exhaled breath sampled in gas-sampling bags were assessed for oxidative potential. These biomarkers were quantified pre-shift at the beginning of the workweek and post-shift the 4th day. Relationships between airborne nanoparticle concentration and biomarkers were assessed by multiple linear regression with log-transformed exposure and biomarker concentrations adjusted for potential confounders. We found a positive dose-response relationship for three inflammation biomarkers (IL-10, IL-1β and TNF-α) in EBC with both PNC and LDSA. A negative dose-response relationship was observed between PNC and TAP. This study suggests that occupational exposures to nanoparticles can affect the oxidative balance and the innate immunity in occupationally exposed workers. However, owing to the intrinsic variability of biomarkers, the observed changes along with their health significance should be assessed in a long-term perspective study.

Titanium dioxide nanoparticles: revealing the mechanisms underlying hepatotoxicity and effects in the gut microbiota

Numerous studies in recent years have questioned the safety of oral exposure to titanium dioxide nanoparticles (TiO2 NPs). TiO2 NPs are not only likely to accumulate in the gastrointestinal tract, but they are also found to penetrate the body circulation and reach distant organs. The liver, which is considered to be a target organ for nanoparticles, is of particular concern. TiO2 NPs accumulate in the liver and cause oxidative stress and inflammatory reactions, resulting in pathological damage. The impact of TiO2 NPs on liver aspartate aminotransferase (AST) and alanine aminotransferase (ALT) was studied using a meta-analysis. According to the findings, TiO2 NPs exposure can cause an elevation in AST and ALT levels in the blood. Furthermore, TiO2 NPs are eliminated mostly through feces, and their lengthy residence in the gut exposes them to microbiota. The gut microbiota is also dysbiotic due to titanium dioxide's antibacterial capabilities. This further leads to changes in the amount of microbiota metabolites, which can reach the liver with blood circulation and trigger hepatotoxicity through the gut-liver axis. This review examines the gut-liver axis to assess the effects of gut microbiota dysbiosis on the liver to provide suggestions for assessing the gut-hepatotoxicity of TiO2 NPs.

Immunomodulatory and antioxidant effect of green synthesized titanium dioxide nanoparticles on pregnant female albino rats and their fetuses

Titanium dioxide nanoparticles (TiO2 NPs) are one of the various nanoparticles that have been increasingly commonly used in vital sectors. This study was aimed at evaluating the effects of prenatal exposure to the chemical TiO2 NPs (CHTiO2 NPs) and green-synthesized TiO2 NPs (GTiO2 NPs) on immunological and oxidative status as well as lungs and spleen. Fifty pregnant female albino rats were divided into five groups of ten rats each: control, CHTiO2 NPs-treated groups orally received 100 and 300 mg/kg CHTiO2 NPs, and GTiO2 NPs-treated groups received 100 and 300 mg/kg GTiO2 NPs, respectively, daily for 14 days. The serum level of proinflammatory cytokines IL-6, oxidative stress markers (MDA and NO), and antioxidant biomarkers (SOD and GSH-PX) were assayed. Spleen and lungs were collected from pregnant rats and fetuses for histopathological examinations. The results showed a significant increase in IL-6 levels in treated groups. In the CHTiO2 NPs-treated groups, there was a significant increase in MDA activity and a significant decrease in GSH-Px and SOD activities, revealing its oxidative effect, while GSH-Px and SOD activities significantly increased in the 300 GTiO2 NPs-treated group, confirming the antioxidant effect of green-synthesized TiO2 NPs. Histopathological findings of the spleen and lungs of the CHTiO2 NPs-treated group revealed severe congestion and thickening of the blood vessels, while those of the GTiO2 NPs-treated group revealed mild tissue alterations. It could be deduced that green synthesized titanium dioxide nanoparticles have immunomodulatory and antioxidant effects on pregnant female albino rats and their fetuses, with an ameliorated impact on the spleen and lung compared to chemical titanium dioxide nanoparticles.

A harmonized protocol for an international multicenter prospective study of nanotechnology workers: the NanoExplore cohort

Nanotechnology applications are fast-growing in many industrial fields. Consequently, health effects of engineered nanomaterials (ENMs) should be investigated. Within the EU-Life project NanoExplore, we developed a harmonized protocol of an international multicenter prospective cohort study of workers in ENM-producing companies. This article describes the development of the protocol, sample size calculation, data collection and management procedures and discusses its relevance with respect to research needs. Within this protocol, workers' ENM exposure will be assessed over four consecutive working days during the initial recruitment campaign and the subsequent follow-up campaigns. Biomonitoring using noninvasive sampling of exhaled breath condensate (EBC), exhaled air, and urine will be collected before and after 4-day exposure monitoring. Both exposure and effect biomarkers, will be quantified along with pulmonary function tests and diagnosed diseases reported using a standardized epidemiological questionnaire available in four languages. Until now, this protocol was implemented at seven companies in Switzerland, Spain and Italy. The protocol is well standardized, though sufficiently flexible to include company-specific conditions and occupational hygiene measures. The recruitment, to date, of 140 participants and collection of all data and samples, enabled us launching the first international cohort of nanotechnology workers. All companies dealing with ENMs could join the NanoExplore Consortium, apply this harmonized protocol and enter in the cohort, concieved as an open cohort. Its protocol meets all requirements of a hypotheses-driven prospective study, which will assess and reassess effects of ENM exposure on workers' health by updating the follow-up of the cohort. New hypothesis could be also considered.

Activation of KLF6 by titanate nanofibers and regulatory roles of KLF6 on ATF3 in the endothelial monolayer and mouse aortas

Although titanium (Ti)-based nanomaterials (NMs) were traditionally considered as biologically inert materials, it was recently reported that Ti-based NMs induce adverse vascular effects by inhibiting Kruppel-like factor 2 (KLF2) and/or KLF4, vasoprotective KLFs with well-documented regulatory activity in NO signaling. However, the potential roles of other KLFs are not clear. KLF6 was recently identified as an important KLF involved in regulating endothelial dysfunction, inflammation, and angiogenesis, therefore, this study investigated the influence of titanate nanofibers (TiNFs) on KLF6-mediated events. Ingenuity pathway analysis (IPA) showed that TiNFs altered the expression of a panel of KLF6-related genes: KLF6-mediated gene ontology (GO) terms were altered, categories including cytokine-mediated signaling pathways, transcription factor (TF) functions and membrane-bound organelles. Additionally, RT-PCR confirmed that TiNFs increased KLF6 activating transcription factor 3 (ATF3), a TF involved in endoplasmic reticulum (ER) stress, and ELISA confirmed the increase of soluble monocyte chemotactic protein 1 (sMCP-1), a KLF6-related inflammatory cytokine. Interestingly, the activation of klf6, atf3 and C-C motif chemokine ligand 2 (ccl2; mcp-1 encoding gene) was observed in aortas of mice following one-time intravenous injection but not intratracheal instillation of TiNFs (100 μg per mouse), indicating a need for direct contact with NMs to activate klf6-mediated pathways in vivo. In endothelial cells, KLF6 knockdown inhibited the expression of ATF3 but not CCL2, suggesting the regulatory role of KLF6 in ATF3 expression. Overall, this study uncovered a previously unknown role of KLF6 in TiNF-induced vascular effects both in vitro and in vivo.

Nano-Calcium Carbonate Affect the Respiratory and Function Through Inducing Oxidative Stress: A Cross-sectional Study Among Occupational Exposure of Workers and a Further Research for Underlying Mechanisms

OBJECTIVE

The aim of the study is to investigate whether nano-calcium carbonate (nano-CaCO 3 ) occupational exposure could induce adverse health effects in workers.

METHODS

A cross-sectional study was conducted in a nano-CaCO 3 manufacturing plant in China. Then, we have studied the dynamic distribution of nano-CaCO 3 in nude mice and examined the oxidative damage biomarkers of subchronic administrated nano-CaCO 3 on Sprague-Dawley rats.

RESULTS

The forced vital capacity (%) and the ratio of FEV1 to FVC is the rate of one second of workers were significantly decreased than unexposed individuals. Dynamic imaging in mice of fluorescence labeled nano-CaCO 3 showed relatively high uptake and slow washout in lung. Similar to population data, the decline in serum glutathione level and elevation in serum MDA were observed in nano-CaCO 3 -infected Sprague-Dawley rats.

CONCLUSIONS

We found that nano-CaCO 3 exposure may result in the poor pulmonary function in workers and lead to the changes of oxidative stress indexes.

Multi-instrument assessment of fine and ultrafine titanium dioxide aerosols

The measurement of fine (diameter: 100 nanometers-2.5 micrometers) and ultrafine (UF: < 100 nanometers) titanium dioxide (TiO2) particles is instrument dependent. Differences in measurements exist between toxicological and field investigations for the same exposure metric such as mass, number, or surface area because of variations in instruments used, operating parameters, or particle-size measurement ranges. Without appropriate comparison, instrument measurements create a disconnect between toxicological and field investigations for a given exposure metric. Our objective was to compare a variety of instruments including multiple metrics including mass, number, and surface area (SA) concentrations for assessing different concentrations of separately aerosolized fine and UF TiO2 particles. The instruments studied were (1) DustTrak™ DRX, (2) personal DataRAMs™ (PDR), (3) GRIMMTM, and (4) diffusion charger (DC). Two devices of each field-study instrument (DRX, PDR, GRIMM, and DC) were used to measure various metrics while adjusting for gravimetric mass concentrations of fine and UF TiO2 particles in controlled chamber tests. An analysis of variance (ANOVA) was used to apportion the variance to inter-instrument (between different instrument-types), inter-device (within instrument), and intra-device components. Performance of each instrument-device was calculated using root mean squared error compared to reference methods: close-faced cassette and gravimetric analysis for mass and scanning mobility particle sizer (SMPS) real-time monitoring for number and SA concentrations. Generally, inter-instrument variability accounted for the greatest (62.6% or more) source of variance for mass, and SA-based concentrations of fine and UF TiO2 particles. However, higher intra-device variability (53.7%) was observed for number concentrations measurements with fine particles compared to inter-instrument variability (40.8%). Inter-device variance range(0.5-5.5%) was similar for all exposure metrics. DRX performed better in measuring mass closer to gravimetric than PDRs for fine and UF TiO2. Number concentrations measured by GRIMMs and SA measurements by DCs were considerably (40.8-86.9%) different from the reference (SMPS) method for comparable size ranges of fine and UF TiO2. This information may serve to aid in interpreting assessments in risk models, epidemiologic studies, and development of occupational exposure limits, relating to health effect endpoints identified in toxicological studies considering similar instruments evaluated in this study.

The effect and underlying mechanisms of titanium dioxide nanoparticles on glucose homeostasis: A literature review

Titanium dioxide (TiO₂ ) is used extensively as a white pigment in the food industry, personal care, and a variety of products of everyday use. Although TiO₂ has been categorized as a bioinert material, recent evidence has demonstrated different toxicity profiles of TiO₂ nanoparticles (NPs) and a potential health risk to humans. Studies indicated that titanium dioxide enters the systemic circulation and accumulates in the lungs, liver, kidneys, spleen, heart, and central nervous system and may cause oxidative stress and tissue damage in these vital organs. Recently, some studies have raised concerns about the possible detrimental effects of TiO₂ NPs on glucose homeostasis. However, the findings should be interpreted with caution due to the methodological issues. This article aims to evaluate current evidence regarding the effects of TiO₂ NPs on glucose homeostasis, including possible underlying mechanisms. Furthermore, the limitations of current studies are discussed, which may provide a comprehensive understanding and new perspectives for future studies in this field.

Oxidative Stress and Inflammatory Biomarkers for Populations with Occupational Exposure to Nanomaterials: A Systematic Review and Meta-Analysis

Exposure to nanomaterials (NMs) is suggested to have the potential to cause harmful health effects. Activations of oxidative stress and inflammation are assumed as main contributors to NM-induced toxicity. Thus, oxidative stress- and inflammation-related indicators may serve as biomarkers for occupational risk assessment. However, the correlation between NM exposure and these biomarkers remains controversial. This study aimed to perform a meta-analysis to systematically investigate the alterations of various biomarkers after NM exposure. Twenty-eight studies were found eligible by searching PubMed, EMBASE and Cochrane Library databases. The pooled results showed NM exposure was significantly associated with increases in the levels of malonaldehyde (MDA) [standardized mean difference (SMD) = 2.18; 95% confidence interval (CI), 1.50-2.87], 4-hydroxy-2-nonhenal (HNE) (SMD = 2.05; 95% CI, 1.13-2.96), aldehydes C6-12 (SMD = 3.45; 95% CI, 2.80-4.10), 8-hydroxyguanine (8-OHG) (SMD = 2.98; 95% CI, 2.22-3.74), 5-hydroxymethyl uracil (5-OHMeU) (SMD = 1.90; 95% CI, 1.23-2.58), o-tyrosine (o-Tyr) (SMD = 1.81; 95% CI, 1.22-2.41), 3-nitrotyrosine (3-NOTyr) (SMD = 2.63; 95% CI, 1.74-3.52), interleukin (IL)-1β (SMD = 1.76; 95% CI, 0.87-2.66), tumor necrosis factor (TNF)-α (SMD = 1.52; 95% CI, 1.03-2.01), myeloperoxidase (MPO) (SMD = 0.25; 95% CI, 0.16-0.34) and fibrinogen (SMD = 0.11; 95% CI, 0.02-0.21), and decreases in the levels of glutathione peroxidase (GPx) (SMD = -0.31; 95% CI, -0.52--0.11) and IL-6 soluble receptor (IL-6sR) (SMD = -0.18; 95% CI, -0.28--0.09). Subgroup analysis indicated oxidative stress biomarkers (MDA, HNE, aldehydes C6-12, 8-OHG, 5-OHMeU, o-Tyr, 3-NOTyr and GPx) in exhaled breath condensate (EBC) and blood samples were strongly changed by NM exposure; inflammatory biomarkers (IL-1β, TNF-α, MPO, fibrinogen and IL-6sR) were all significant in EBC, blood, sputum and nasal lavage samples. In conclusion, our findings suggest that these oxidative stress and inflammatory indicators may be promising biomarkers for the biological monitoring of occupationally NM-exposed workers.

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.

TiO2 Nanoparticles and Their Effects on Eukaryotic Cells: A Double-Edged Sword

Nanoparticulate TiO₂ (TiO₂ NPs) is a widely used material, whose potential toxicity towards eukaryotic cells has been addressed by multiple studies. TiO₂ NPs are considered toxic due to their production of reactive oxygen species (ROS), which can, among others, lead to cellular damage, inflammatory responses, and differences in gene expression. TiO₂ NPs exhibited toxicity in multiple organs in animals, generating potential health risks also in humans, such as developing tumors or progress of preexisting cancer processes. On the other hand, the capability of TiO₂ NPs to induce cell death has found application in photodynamic therapy of cancers. In aquatic environments, much has been done in understanding the impact of TiO₂ on bivalves, in which an effect on hemocytes, among others, is reported. Adversities are also reported from other aquatic organisms, including primary producers. These are affected also on land and though some potential benefit might exist when it comes to agricultural plants, TiO₂ can also lead to cellular damage and should be considered when it comes to transfer along the food chain towards human consumers. In general, much work still needs to be done to unravel the delicate balance between beneficial and detrimental effects of TiO₂ NPs on eukaryotic cells.

Relationship between maternal exposure to heavy metal titanium and offspring congenital heart defects in Lanzhou, China: A nested case-control study

Background

Previous studies have found that exposure to heavy metals increased the incidence of congenital heart defects (CHDs). However, there is a paucity of information about the connection between exposure to titanium and CHDs. This study sought to examine the relationship between prenatal titanium exposure and the risk of CHDs in offspring.

Methods

We looked back on a birth cohort study that was carried out in our hospital between 2010 and 2012. The associations between titanium exposure and the risk of CHDs were analyzed by using logistic regression analysis to investigate titanium concentrations in maternal whole blood and fetal umbilical cord blood.

Results

A total of 97 case groups and 194 control groups were included for a nested case-control study. The [P₅₀ (P₂₅, P₇₅)] of titanium were 371.91 (188.85, 659.15) μg/L and 370.43 (264.86, 459.76) μg/L in serum titanium levels in pregnant women and in umbilical cord serum titanium content in the CHDs group, respectively. There was a moderate positive correlation between the concentration of titanium in pregnant women's blood and that in umbilical cord blood. A higher concentrations of maternal blood titanium level was associated with a greater risk of CHDs (OR 2.706, 95% CI 1.547–4.734), the multiple CHDs (OR 2.382, 95% CI 1.219–4.655), atrial septal defects (OR 2.367, 95% CI 1.215–4.609), and patent ductus arteriosus (OR 2.412, 95% CI 1.336–4.357). Dramatically higher concentrations of umbilical cord blood levels had an increased risk of CHDs and different heart defects.

Conclusion

Titanium can cross the placental barrier and the occurrence of CHDs may be related to titanium exposure.

Lycopene Alleviates Titanium Dioxide Nanoparticle-Induced Testicular Toxicity by Inhibiting Oxidative Stress and Apoptosis in Mice

PURPOSE

The research was carried out to investigate the possible ameliorative effect of lycopene on TiO₂ NPs-induced male reproductive toxicity and explore the possible mechanism.

METHODS

Ninety-six healthy male Institute of Cancer Research (ICR) mice were equally divided into eight groups (control group, 50 mg/kg TiO₂ NPs group, 5 mg/kg LYC group, 20 mg/kg LYC group, 40 mg/kg LYC group, 50 mg/kg TiO₂ NPs + 5 mg/kg LYC group, 50 mg/kg TiO₂ NPs + 20 mg/kg LYC group, 50 mg/kg TiO₂ NPs + 40 mg/kg LYC group), and the mice were treated by intragastric administration every day for 30 days in this research. Sperm parameters, testicular histopathology, oxidant and antioxidant enzymes, and cell apoptosis-related protein expression in the testicular tissue were analyzed.

RESULTS

The results showed that TiO₂ NPs exposure significantly decreased sperm count and motility, and TiO₂ NPs also increased sperm malformation in the epididymis; these characteristics were improved when co-administration with LYC. Testicular histopathological lesions like disorder of germ cells arrange, detachment, atrophy, and vacuolization were observed after TiO₂ NPs exposure, and these abnormalities were effectively ameliorated by co-administration with LYC. Oxidative stress was induced by TiO₂ NPs exposure as evidenced by increased the level of MDA and decreased the activity of SOD as well as the level of anti-O₂^-, and these alterations were effectively prevented by co-administration with LYC. LYC also alleviated TiO₂ NPs-induced germ cell apoptosis by inhibiting mitochondrial apoptotic pathway, as shown by the upregulation of Bcl-2, the downregulation of Bax, Cleaved Caspase 3, and Cleaved Caspase 9.

CONCLUSION

LYC could ameliorate TiO₂ NPs-induced testicular damage via inhibiting oxidative stress and apoptosis, which could be used to alleviate the testicular toxicity associated with TiO₂ NPs intake.

A Biomonitoring Pilot Study in Workers from a Paints Production Plant Exposed to Pigment-Grade Titanium Dioxide (TiO2)

Among particulate matter composing paints, titanium dioxide (TiO2) forms about 20% of the final suspension. Although TiO2 is broadly used in many applications, TiO2 powders represent an established respiratory hazard for workers with long-term exposure. In 35 workers of a paints production plant (15 exposed and 20 not exposed), we assessed pro-inflammatory cytokines (IL-1β, TNF-α, IL-10, IL-17), surfactant protein D (SP-D) and Krebs von den Lungen-6 glycoprotein (KL-6) in exhaled breath condensate (EBC). In urine samples, we measured 8-isoprostane (Isop) and Malondialdehyde (MDA) as biomarkers of oxidative stress, and Titanium (Ti-U) as a biomarker of exposure. Health status, habits and occupational history were recorded. Airborne respirable dusts and Ti were quantified. Particle number concentration and average diameter (nm) were detected by a NanoTracer™ monitoring device. Ti was measurable in filters collected at the respiratory breathing zone (0.11−0.44 µg/m3 8-h TWA). IL-1β and IL-10 values were significantly higher in exposed workers, whereas SP-D was significantly lower (p < 0.001). KL-6 was significantly higher in workers than in controls (p < 0.01). MDA levels were significantly increased in exposed workers and were positively correlated with Ti-U. Exposure to TiO2 in paint production is associated with the subtle alterations of lung pathobiology. These findings suggest the need for an integrated approach relying on both personal exposure and biomarker assessment to improve the hazard characterisation in occupational settings.

The distribution and structural fingerprints of metals from particulate matters (PM) deposited in human lungs

This work investigated the distribution and chemical fingerprints of 24 metals in particulate matter (PM) deposited in nonoccupational human lungs. Metals in the pulmonary PM can be grouped by the mean concentration as > 5 × 10³ μg/g (Al/Fe/Ca/Mg/Zn), 1-5 × 10³ μg/g (Ti/Ba/Pb/Mn), 0.2-1 × 10³ μg/g (Cu/Cr/As/V) and < 100 μg/g (Ni/Sn/Cd/Sb). Three parameters (LF_L, LR, EF_P) were defined to predict different metal leaching behaviors. The leaching factor (LF_L) of metals was 10-60 for Pb/Sb/Cd/Co/Cu and decreased to 1-2 for Ni/Cr/Mg/Al/Fe. Metals showed a divergent extent of lung retention (LR), including high retention (LR>10, Al/Cd/Cr/Ba/Ni/Ti/Sn/V/Sb), moderate retention (2 <LR<10, Pb/Mn/Fe), minor retention (1 < LR <2, Cu/Co), and negligible retention (LR<1, Ca/Mg/Zn). V and Ti were found to be mainly from indoor PM sources and deserve a close attention in healthy individuals. C-, Al- and Ti-rich fine particles were the most common pulmonary particles imaged by spherical aberration-corrected scanning transmission electron microscopy (Cs-STEM). These data establish a foundation for classification and further risk assessment of the metal species in pulmonary PM.

Association between Heavy Metal Exposure and Dyslipidemia among Korean Adults: From the Korean National Environmental Health Survey, 2015-2017

Cardiovascular disease (CVD) is a leading cause of death in Korea. Dyslipidemia, characterized by the presence of abnormal lipid levels, has been suggested as an early diagnostic and preventable factor for CVD. Recent studies have shown that exposure to lead (Pb), cadmium (Cd), and mercury (Hg) affects lipid metabolism. This study aimed to verify the association between heavy metal concentrations and serum lipid profiles in the general population. A representative sample of 2591 Korean adults from the Korean National Environmental Health Survey (2015−2017) was analyzed. The associations between heavy metals [Blood Pb (BPb), blood Hg (BHg), urinary Hg (UHg), urinary Cd (UCd)] and serum lipid profiles [total cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterol (LDL-C), non-low level of high-density lipoprotein cholesterol (Non-HDL-C)] were assessed using regression analysis. After adjusting for demographic and socioeconomic factors, the proportional changes in serum lipid levels were significantly associated with increases in BPb, BHg, and UHg levels (p for trend < 0.05). Overall, BPb, BHg, and Uhg levels positively correlated with dyslipidemia, whereas UCd levels did not show a significant association. Our results suggest that heavy metal exposure, at low levels, may contribute to an increased prevalence of dyslipidemia in Korean adults.

TiO2 nanosheets promote the transformation of vascular smooth muscle cells into foam cells in vitro and in vivo through the up-regulation of nuclear factor kappa B subunit 2

Titanium dioxide (TiO₂) nanomaterials have been shown to promote atherosclerosis through endothelial dysfunction. This study investigated the toxicity of TiO₂ nanosheets (NSs) to vascular smooth muscle cells (VSMCs), one of the pivotal cells involved in all stages of atherosclerosis. Only a high concentration of TiO₂ NSs (128 μg/mL) modestly induced cytotoxicity by decreasing thiols. RNA-sequencing data revealed that 64 μg/mL TiO₂ NSs significantly down-regulated 94 genes and up-regulated 174 genes, respectively. Gene ontology (GO) terms and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways related to SMC function and lipid metabolism were altered. TiO₂ NSs increased nuclear factor kappa B subunit 2 (NFKB2), which led to a decrease in VSMC marker actin alpha 2, smooth muscle (ACTA2). On the other hand, macrophage marker CD36 and fatty acid synthase (FASN) proteins were increased. Additionally, TiO₂ NSs induced inflammatory cytokines and lipid accumulation, and these effects were curtailed by NFKB inhibitor - triptolide. Furthermore, repeated TiO₂ NS injection (5 mg/kg BW, once a day for 5 continuous days) into ICR mice led to increased NFKB2, CD36 and FASN, with a decreased ACTA2. Our results suggested that TiO₂ NSs promoted the transformation of VSMCs into foam cells through the up-regulation of NFKB2.

Role of necroptosis of alveolar macrophages in acute lung inflammation of mice exposed to titanium dioxide nanoparticles

Titanium dioxide (TiO₂) nanoparticles are indispensable for daily life but induce acute inflammation, mainly via inhalation exposure. TiO₂ nanoparticles can be phagocytosed by alveolar macrophages (AMs) in vivo and cause necroptosis of exposed cells in vitro. However, the relationship between localization of TiO₂ nanoparticles in the lungs after exposure and their biological responses including cell death and inflammation remains unclear. This study was conducted to investigate the intra/extracellular localization of TiO₂ nanoparticles in murine lungs at 24 h after intratracheal exposure to rutile TiO₂ nanoparticles and subsequent local biological reactions, specifically necroptosis of AMs and lung inflammation. We found that TiO₂ exposure induced leukocyte migration into the alveolar region and increased the secretion of C-C motif ligand (CCL) 3 in the bronchoalveolar lavage (BAL) fluid. A combination of Raman spectroscopy and staining of cell and tissue samples confirmed that AMs phagocytose TiO₂. AMs that phagocytosed TiO₂ nanoparticles showed necroptosis, characterized by the expression of phosphorylated mixed lineage kinase domain-like protein and translocation of high mobility group box-1 from the cell nucleus to the cytoplasm. In primary cultured AMs, TiO₂ also induced necroptosis and increased the secretion of CCL3. Necroptosis inhibitors suppressed the increase in CCL3 secretion in both the BAL fluid and culture supernatant of AMs and suppressed the increase in leukocytes in the BAL fluid. These data suggest that necroptosis of AMs that phagocytose TiO₂ nanoparticles is involved as part of the mechanism by which TiO₂ induces acute lung inflammation.

Toxic Metals and Subclinical Atherosclerosis in Carotid, Femoral, and Coronary Vascular Territories: The Aragon Workers Health Study

OBJECTIVE

Studies evaluating the association of metals with subclinical atherosclerosis are mostly limited to carotid arteries. We assessed individual and joint associations of nonessential metals exposure with subclinical atherosclerosis in 3 vascular territories. Approach and Results: One thousand eight hundred seventy-three Aragon Workers Health Study participants had urinary determinations of inorganic arsenic species, barium, cadmium, chromium, antimony, titanium, uranium, vanadium, and tungsten. Plaque presence in carotid and femoral arteries was determined by ultrasound. Coronary Agatston calcium score ≥1 was determined by computed tomography scan. Median arsenic, barium, cadmium, chromium, antimony, titanium, uranium, vanadium, and tungsten levels were 1.83, 1.98, 0.27, 1.18, 0.05, 9.8, 0.03, 0.66, and 0.23 μg/g creatinine, respectively. The adjusted odds ratio (95% CI) for subclinical atherosclerosis presence in at least one territory was 1.25 (1.03-1.51) for arsenic, 1.67 (1.22-2.29) for cadmium, and 1.26 (1.04-1.52) for titanium. These associations were driven by arsenic and cadmium in carotid, cadmium and titanium in femoral, and titanium in coronary territories and mostly remained after additional adjustment for the other relevant metals. Titanium, cadmium, and antimony also showed positive associations with alternative definitions of increased coronary calcium. Bayesian Kernel Machine Regression analysis simultaneously evaluating metal associations suggested an interaction between arsenic and the joint cadmium-titanium exposure.

CONCLUSIONS

Our results support arsenic and cadmium and identify titanium and potentially antimony as atherosclerosis risk factors. Exposure reduction and mitigation interventions of these metals may decrease cardiovascular risk in individuals without clinical disease.

Centrality of Myeloid-Lineage Phagocytes in Particle-Triggered Inflammation and Autoimmunity

Exposure to exogenous particles found as airborne contaminants or endogenous particles that form by crystallization of certain nutrients can activate inflammatory pathways and potentially accelerate autoimmunity onset and progression in genetically predisposed individuals. The first line of innate immunological defense against particles are myeloid-lineage phagocytes, namely macrophages and neutrophils, which recognize/internalize the particles, release inflammatory mediators, undergo programmed/unprogrammed death, and recruit/activate other leukocytes to clear the particles and resolve inflammation. However, immunogenic cell death and release of damage-associated molecules, collectively referred to as "danger signals," coupled with failure to efficiently clear dead/dying cells, can elicit unresolved inflammation, accumulation of self-antigens, and adaptive leukocyte recruitment/activation. Collectively, these events can promote loss of immunological self-tolerance and onset/progression of autoimmunity. This review discusses critical molecular mechanisms by which exogenous particles (i.e., silica, asbestos, carbon nanotubes, titanium dioxide, aluminum-containing salts) and endogenous particles (i.e., monosodium urate, cholesterol crystals, calcium-containing salts) may promote unresolved inflammation and autoimmunity by inducing toxic responses in myeloid-lineage phagocytes with emphases on inflammasome activation and necrotic and programmed cell death pathways. A prototypical example is occupational exposure to respirable crystalline silica, which is etiologically linked to systemic lupus erythematosus (SLE) and other human autoimmune diseases. Importantly, airway instillation of SLE-prone mice with crystalline silica elicits severe pulmonary pathology involving accumulation of particle-laden alveolar macrophages, dying and dead cells, nuclear and cytoplasmic debris, and neutrophilic inflammation that drive cytokine, chemokine, and interferon-regulated gene expression. Silica-induced immunogenic cell death and danger signal release triggers accumulation of T and B cells, along with IgG-secreting plasma cells, indicative of ectopic lymphoid tissue neogenesis, and broad-spectrum autoantibody production in the lung. These events drive early autoimmunity onset and accelerate end-stage autoimmune glomerulonephritis. Intriguingly, dietary supplementation with ω-3 fatty acids have been demonstrated to be an intervention against silica-triggered murine autoimmunity. Taken together, further insight into how particles drive immunogenic cell death and danger signaling in myeloid-lineage phagocytes and how these responses are influenced by the genome will be essential for identification of novel interventions for preventing and treating inflammatory and autoimmune diseases associated with these agents.

Comparison of P25 and nanobelts on Kruppel-like factor-mediated nitric oxide pathways in human umbilical vein endothelial cells

Recently, we reported that titanium dioxide (TiO₂ ) materials activated endothelial cells via Kruppel-like factor (KLF)-mediated nitric oxide (NO) dysfunction, but the roles of physical properties of materials are not clear. In this study, we prepared nanobelts from P25 particles and compared their adverse effects to human umbilical vein endothelial cells (HUVECs). TiO₂ nanobelts had belt-like morphology but comparable surface areas as P25 particles. When applied to HUVECs, P25 particles or nanobelts did not induce cytotoxicity, although nanobelts were much more effective to increase intracellular Ti element concentrations compared the same amounts of P25 particles. Only nanobelts significantly induced THP-1 adhesion onto HUVECs. Consistently, nanobelts were more significant to induce the expression of intracellular adhesion molecule-1 (ICAM1) and the release of soluble ICAM-1 (sICAM-1), indicating that nanobelts were more potent to induce endothelial activation in vitro. As the mechanisms for endothelial activation, both P25 and nanobelts reduced the generation of intracellular NO as well as the expression of NO regulators KLF2 and KLF4. Combined, the results from this study indicated that the different morphologies of P25 particles and nanobelts only changed their internalization into HUVECs but showed minimal impact on KLF-mediated NO signaling pathways.

Toxicity risks of occupational exposure in 3D printing and bioprinting industries: A systematic review

3-Dimensional (3D) printing and bioprinting are the new technologies. In 3D printing, synthetic polymers such as acrylonitrile, butadiene, and styrene, polylactic acid, nylon, and some metals are used as feedstocks. During 3D printing, volatile organic compounds (VOCs) and nanoparticles can be released. In the bioprinting process, natural polymers are most commonly used. All of these materials have direct and indirect toxic effects in exposed people. Therefore, the aim of this study was to provide a comprehensive review of toxicity risks due to occupational exposure to pollutants in the 3D printing and bioprinting industries. The Cochrane review method was used as a guideline for systematic review. Articles were searched in the databases including PubMed, Scopus, Web of Science, and Google Scholar. This systematic review showed that VOCs and ultra-fine particles are often released in fused deposition modeling and selective laser sintering, respectively. Asthma, chronic obstructive pulmonary disease, allergic rhinitis, and DNA damage were observed in occupational exposure to synthetic polymers. Metal nanoparticles can induce adverse health effects on the respiratory and nervous systems. This study emphasized the need to further study the toxicity of 3D printing and bioprinting-induced air pollutants. Also, consideration of safety and health principles is necessary in 3D printing and bioprinting workplaces.

Effect of Nano-Titanium Dioxide on Blood-Testis Barrier and MAPK Signaling Pathway in Male Mice

Some studies have found that nano-sized titanium dioxide (nano-TiO₂) has adverse effects on the male reproductive system. Blood-testis barrier (BTB), as one of the tightest blood-tissue restriction, is crucial to the male reproductive system. However, the potential effects on BTB and signaling pathway changes in testis tissue induced by nano-TiO₂ remain poorly understood. Therefore, in this study, 60 Institute of Cancer Research mice were divided randomly into four groups (per group = 15). The mice of four groups were intragastrically administered with 0, 10, 50, and 100 mg/kg BW nano-TiO₂ respectively for 30 days to analyze the changes of BTB structure, BTB-related proteins, and MAPK signal pathways. Besides, testosterone level, estradiol level, and sperm parameter (sperm count, sperm motility, and sperm malformation rate) changes were also studied in this research. The results indicated that nano-TiO₂ could induce the BTB structural damage and accompanied by the BTB main protein (ZO-1, Claudin-11, and F-actin) elevation of irritability. Nano-TiO₂ could also activate the MAPK signaling pathways (p38, JNK, and ERK) of mice testis tissue. The testosterone and estradiol levels in serum reduced. Besides when the mice were administered with nano-TiO₂, we also found the sperm motility rate decreased, and sperm malformation increased. The above changes may be associated with BTB damage and the activation of MAPK signaling pathways, thereby causing male reproductive dysfunction.

The genotoxic effects in the leukocytes of workers handling nanocomposite materials

The extensive development of nanotechnologies and nanomaterials poses a number of questions to toxicologists about the potential health risks of exposure to nanoparticles (NP). In this study, we analysed DNA damage in the leukocytes of 20 workers who were long-term exposed (18 ± 10 years) to NP in their working environment. Blood samples were collected in September 2016, before and after a shift, to assess (i) the chronic effects of NP on DNA (pre-shift samples) and (ii) the acute effects of exposure during the shift (the difference between pre- and post-shift samples). The samples from matched controls were taken in parallel with workers before the shift. Leukocytes were isolated from heparinised blood on a Ficoll gradient. The enzyme-modified comet assay (DNA formamido-pyrimidine-glycosylase and endonuclease III) demonstrated a considerable increase of both single- and double-strand breaks in DNA (DNA-SB) and oxidised bases when compared with the controls (2.4× and 2×, respectively). Acute exposure induced a further increase of DNA-SB. The welding and smelting of nanocomposites represented a higher genotoxic risk than milling and grinding of nanocomposite surfaces. Obesity appeared to be a factor contributing to an increased risk of oxidative damage to DNA. The data also indicated a higher susceptibility of males vs. females to NP exposure. The study was repeated in September 2017. The results exhibited similar trend, but the levels of DNA damage in the exposed subjects were lower compared to previous year. This was probably associated with lower exposure to NP in consequence of changes in nanomaterial composition and working operations. The further study involving also monitoring of personal exposures to NP is necessary to identify (i) the main aerosol components responsible for genotoxic effects in workers handling nanocomposites and (ii) the primary cause of gender differences in response to NP action.

Long-Term Exposure to Nanosized TiO2 Triggers Stress Responses and Cell Death Pathways in Pulmonary Epithelial Cells

There is little in vitro data available on long-term effects of TiO₂ exposure. Such data are important for improving the understanding of underlying mechanisms of adverse health effects of TiO₂. Here, we exposed pulmonary epithelial cells to two doses (0.96 and 1.92 µg/cm²) of TiO₂ for 13 weeks and effects on cell cycle and cell death mechanisms, i.e., apoptosis and autophagy were determined after 4, 8 and 13 weeks of exposure. Changes in telomere length, cellular protein levels and lipid classes were also analyzed at 13 weeks of exposure. We observed that the TiO₂ exposure increased the fraction of cells in G1-phase and reduced the fraction of cells in G2-phase, which was accompanied by an increase in the fraction of late apoptotic/necrotic cells. This corresponded with an induced expression of key apoptotic proteins i.e., BAD and BAX, and an accumulation of several lipid classes involved in cellular stress and apoptosis. These findings were further supported by quantitative proteome profiling data showing an increase in proteins involved in cell stress and genomic maintenance pathways following TiO₂ exposure. Altogether, we suggest that cell stress response and cell death pathways may be important molecular events in long-term health effects of TiO₂.

Metabolomics screening of serum biomarkers for occupational exposure of titanium dioxide nanoparticles

Although nanotoxicology studies have shown that respiratory exposure of titanium dioxide nanoparticles (TiO₂ NPs) could induce adverse health effects, limited biomarkers associated with occupational exposure of TiO₂ NPs were reported. The purpose of this study is to screen serum biomarkers among workers occupationally exposed to TiO₂ NPs using metabolomics. Compared with the control group, a total of 296 serum metabolites were differentially expressed in the TiO₂ NPs-exposed group, of which the relative expression of 265 metabolites increased, and the remaining 31 decreased. Three machine learning methods including random forest (RF), support vector machines (SVM), and boruta screened eight potential biomarkers and simultaneously selected a metabolite, Liquoric acid. Through multiple linear regression analysis to adjust the influence of confounding factors such as gender, age, BMI, smoking and drinking, occupational exposure to TiO₂ NPs was significantly related to the relative expression of the eight potential biomarkers. Meanwhile, the receiver operating characteristic curves (ROCs) of these potential biomarkers had good sensitivity and specificity. These potential biomarkers were related to lipid peroxidation, and had biological basis for occupational exposure to TiO₂ NPs. Therefore, it was demonstrated that the serum metabolites represented by Liquoric acid were good biomarkers of occupational exposure to TiO₂ NPs.

Genotoxicity Evaluation of Titanium Dioxide Nanoparticles In Vitro: a Systematic Review of the Literature and Meta-analysis

With the wide use of titanium dioxide nanoparticles (TiO₂-NPs), the genotoxicity of TiO₂-NPs, which is a factor for safety assessment, has attracted people's attention. However, their genotoxic effects in vitro remain controversial due to inconsistent reports. Therefore, a systematic review was conducted followed by a meta-analysis to reveal whether TiO₂-NPs cause genotoxicity in vitro. A total of 59 studies were identified in this review through exhaustive database retrieval and exclusion. Meta-analysis results were presented based on different evaluation methods. The results showed that TiO₂-NP exposure considerably increased the percentage of DNA in tail and olive tail moment in comet assay. Gene mutation assay revealed that TiO₂-NPs could also induce gene mutation. However, TiO₂-NP exposure had no effect on micronucleus (MN) formation in the MN assay. Subgroup analysis showed that normal cells were more vulnerable to toxicity induced by TiO₂-NPs. Moreover, mixed form and small particles of TiO₂-NPs increased the percentage of DNA in tail. In addition, short-term exposure could detect more DNA damage. The size, coating, duration, and concentration of TiO₂-NPs influenced MN formation. This study presented that TiO₂-NP exposure could cause genotoxicity in vitro. The physicochemical properties of TiO₂-NPs and experimental protocols influence the genotoxic effects in vitro. Comet and gene mutation assays may be more sensitive to the detection of TiO₂-NP genotoxic effects.

Potential roles of Kruppel-like factors in mediating adverse vascular effects of nanomaterials: A review

The development of nanotechnology leads to the exposure of human beings to nanomaterials (NMs), and there is a health concern about the adverse vascular effects of NMs. Current data from epidemiology, controlled human exposure, and animal studies suggested that exposure to NMs could induce cardiopulmonary effects. In support of in vivo findings, in vitro studies showed that direct contact of vascular cells with NMs could induce endothelial cell (EC) activation and promote macrophage foam cell formation, although only limited studies showed that NMs could damage vascular smooth muscle cells and promote their phenotypic switch. It has been proposed that NMs induced adverse vascular effects via different mechanisms, but it is still necessary to understand the upstream events. Kruppel-like factors (KLFs) are a set of C2H2 zinc finger transcription factors (TFs) that can regulate various aspects of vascular biology, but currently, the roles of KLF2 in mediating the adverse vascular effects of NMs have gained little attention by toxicologists. This review summarized current knowledge about the adverse vascular effects of NMs and proposed the potential roles of KLFs in mediating these effects based on available data from toxicological studies as well as the current understanding about KLFs in vascular biology. Finally, the challenges in investigating the role of KLFs in vascular toxicology were also summarized. Considering the important roles of KLFs in vascular biology, further studies are needed to understand the influence of NMs on KLFs and the downstream events.

Protective Effect of Lactobacillus rhamnosus GG on TiO2 Nanoparticles-Induced Oxidative Stress Damage in the Liver of Young Rats

The potential toxicity of titanium dioxide nanoparticles (TiO₂ NPs) to mammals has become a widespread concern. Young individuals exposed to TiO₂ NPs have a higher risk than adults. In this study, the protective effects of Lactobacillus rhamnosus GG (LGG) on liver toxicity in young rats induced by TiO₂ NPs were explored. Results show that the four-week-old rats that underwent LGG after the oral intake of TiO₂ NPs could prevent weight loss, reduce hematological indicators (WBC and NEUT) and serum biochemical indicators (AST, ALT, AST/ALT, and ALP). Moreover, it alleviated the pathological damage of the liver (as indicated by the disordered hepatocytes, more eosinophilic, ballooning degeneration, and accompany with blood cells), but it did not reduce the Ti contents in the liver. In addition, RT-qPCR results indicated that LGG restored the expression of anti-oxidative stress-related genes, such as SOD1, SOD2, CAT, HO-1, GSH, GCLC, and GCLM in the liver. In summary, the hepatotoxicity of TiO₂ NPs in young rats is closely related to oxidative stress, and the antioxidant effect of LGG might protect the harmful effects caused by TiO₂ NPs.

Exploring urine biomarkers of early health effects for occupational exposure to titanium dioxide nanoparticles using metabolomics

Many experimental studies have demonstrated that titanium dioxide nanoparticles (TiO2 NPs) could induce adverse health effects in vivo and in vitro. But epidemiological evidence and biomarkers related to early health effects are still lacking. This study aimed to explore biomarkers in the urine samples of workers occupationally exposed to a relatively low concentration of TiO2 NPs. A cross-sectional study was conducted in Jinan, China, involving 132 employees of a TiO2 NP manufacturing plant, among which the exposed group and control group were 1 : 1 matched by confounding factors such as gender, age, BMI, smoking and drinking. Untargeted metabolomics was performed in urine samples using high performance liquid chromatography-mass spectrometry (HPLC-MS) technology. The differential metabolites between the TiO2 NP exposed group and the control group were analyzed and then screened for potential biomarkers using bioinformatics methods. Metabolomics found a total of 1760 differentially expressed metabolites in the TiO2 NP exposed group, of which 60 differential metabolites were simultaneously confirmed by one-dimensional and multi-dimensional statistical analysis. Among these 60 differential metabolites, the relative expression of 27 metabolites increased, and the remaining 33 decreased. Pathway enrichment analysis further found that the metabolic pathway of long chain acyl-coa dehydrogenase deficiency (Lcad) was significantly enriched. Ten differential metabolites were selected as potential biomarkers of occupational exposure to TiO2 NPs using machine learning methods, including dibenzyl ether, quassimarin, tryptophan, etc. The receiver operating characteristic curves (ROCs) of these potential biomarkers showed good sensitivity and specificity. These potential biomarkers also had biological basis for occupational exposure to TiO2 NPs. Therefore, urine metabolites represented by dibenzyl ether are considered as good biomarkers of early health effects for occupational exposure to TiO2 NPs.

Biomaterials for Three-Dimensional Cell Culture: From Applications in Oncology to Nanotechnology

Three-dimensional cell culture has revolutionized cellular biology research and opened the door to novel discoveries in terms of cellular behavior and response to microenvironment stimuli. Different types of 3D culture exist today, including hydrogel scaffold-based models, which possess a complex structure mimicking the extracellular matrix. These hydrogels can be made of polymers (natural or synthetic) or low-molecular weight gelators that, via the supramolecular assembly of molecules, allow the production of a reproducible hydrogel with tunable mechanical properties. When cancer cells are grown in this type of hydrogel, they develop into multicellular tumor spheroids (MCTS). Three-dimensional (3D) cancer culture combined with a complex microenvironment that consists of a platform to study tumor development and also to assess the toxicity of physico-chemical entities such as ions, molecules or particles. With the emergence of nanoparticles of different origins and natures, implementing a reproducible in vitro model that consists of a bio-indicator for nano-toxicity assays is inevitable. However, the maneuver process of such a bio-indicator requires the implementation of a repeatable system that undergoes an exhaustive follow-up. Hence, the biggest challenge in this matter is the reproducibility of the MCTS and the associated full-scale characterization of this system's components.

Genotoxicity and Immunotoxicity of Titanium Dioxide-Embedded Mesoporous Silica Nanoparticles (TiO2@MSN) in Primary Peripheral Human Blood Mononuclear Cells (PBMC)

Background: TiO₂ nanoparticles (TiO₂ NPs) are the nanomaterial most produced as an ultraviolet (UV) filter. However, TiO₂ is a semiconductor and, in nanoparticle size, is a strong photocatalyst, raising concerns about photomutagenesis. Mesoporous silica nanoparticles (MSN) were synthetized incorporating TiO₂ NPs (TiO₂@MSN) to develop a cosmetic UV filter. The aim of this study was to assess the toxicity of TiO₂@MSN, compared with bare MSN and commercial TiO₂ NPs, based on several biomarkers. Materials and Methods: Human peripheral blood mononuclear cells (PBMC) were exposed to TiO₂@MSN, bare MSN (network) or commercial TiO₂ NPs for comparison. Exposed PBMC were characterized for cell viability/apoptosis, reactive oxygen species (ROS), nuclear morphology, and cytokines secretion. Results: All the nanoparticles induced apoptosis, but only TiO₂ NPs (alone or assembled into MSN) led to ROS and micronuclei. However, TiO₂@MSN showed lower ROS and cytotoxicity with respect to the P25. Exposure to TiO₂@MSN induced Th2-skewed and pro-fibrotic responses. Conclusions: Geno-cytotoxicity data indicate that TiO₂@MSN are safer than P25 and MSN. Cytokine responses induced by TiO₂@MSN are imputable to both the TiO₂ NPs and MSN, and, therefore, considered of low immunotoxicological relevance. This analytical assessment might provide hints for NPs modification and deep purification to reduce the risk of health effects in the settings of their large-scale manufacturing and everyday usage by consumers.

Assessment of the Influence of Crystalline Form on Cyto-Genotoxic and Inflammatory Effects Induced by TiO2 Nanoparticles on Human Bronchial and Alveolar Cells

Titanium dioxide nanoparticles (TiO₂NPs) are increasingly used in consumer products, industrial and medical applications, raising concerns on their potential toxicity. The available in vitro and in vivo studies on these NPs show controversial results. Crystalline structure is the physicochemical characteristic that seems to influence mainly TiO₂NPs toxicity, so its effect needs to be further studied. We aimed to study whether and how crystalline form influences potential cyto-genotoxic and inflammatory effects induced by two commercial TiO₂NPs (TiO₂-A, mainly anatase; TiO₂-B, mainly rutile) in human alveolar A549 and bronchial BEAS-2B cells exposed to 1–40 µg/mL. Cell viability (WST-1), membrane damage (LDH release), IL-6, IL-8 and TNF-α release (ELISA) and direct/oxidative DNA damage (fpg-comet assay) were evaluated. Physicochemical characterization included analysis of crystalline form (TEM and XRD), specific surface area (BET), agglomeration (DLS) and Z-potential (ELS). Our results show that TiO₂-A NPs induce in BEAS-2B cytotoxicity and a slight inflammation and in A549 slight oxidative effects, whereas TiO₂-B NPs induce genotoxic/oxidative effects in both cell lines, revealing different toxicity mechanisms for the two tested NPs. In conclusion, our study confirms the influence of crystalline form on cellular response, also demonstrating the suitability of our in vitro model to screen early TiO₂NPs effects.

Environmental titanium exposure and reproductive health: Risk of low birth weight associated with maternal titanium exposure from a nested case-control study in northern China

Titanium (Ti) is commonly used in additives in the form of titanium dioxide (TiO₂). However, our understanding of the effect of Ti on reproductive health remains limited. This nested case-control study, performed in a Ti mining exposure field, investigated the association between maternal blood Ti concentration and the risk of low birth weight (LBW), as well as the potential biological mechanism. A total of 45 women who delivered LBW infants (cases) and 352 women with normal birth weight infants (controls) were included. We collected maternal peripheral blood samples in the first or early second trimester to measure Ti concentration in serum (Ti^sr) and blood cells (Ti^bc), as well as inflammatory, lipid, and oxidative stress biomarkers thereof. The demographic characteristics of the women included in the study were also obtained. The results showed that the median total blood Ti concentration (Ti^tb) in the case group was significantly higher than that in the control group (134 vs. 129 ng/mL, P = 0.039). A higher Ti^tb level was associated with a greater risk of LBW [odds ratio = 2.62; 95% confidence interval (CI): 1.16-5.90], but no such association was observed for Ti^sr or Ti^bc after adjusting for potential confounders. The serum lipid biomarkers TC, TG, and total lipids (TL) were all negatively associated with Ti^sr and Ti^tb. Serum 8-OHdG was positively associated with Ti^bc. We concluded that a high Ti^tb during early pregnancy may increase the risk of LBW. Lipid metabolism and oxidative stress may play an important role in the adverse health effects associated with Ti exposure. Thus, our results merit more attention to the probable adverse effects of titanium exposure during pregnancy.

Low-level environmental lead and cadmium exposures and dyslipidemia in adults: Findings from the NHANES 2005-2016

BACKGROUND

Previous experimental and occupational health studies have shown the toxic effects of relatively high-level cadmium and lead on lipid metabolism. However, limited studies investigated the relationships between serum lipid levels and exposure to low-level lead and cadmium in adults.

OBJECTIVE

To investigate the associations between lead and cadmium levels in blood and dyslipidemia in adults.

METHODS

A retrospective cross-sectional study of 7,457 adults aged 20-79 years who were recruited in the National Health and Nutrition Examination Survey (NHANES, 2005-2016) was conducted. Multivariate linear and logistic regressions were used to examine the associations of blood lead and cadmium levels with serum lipid profiles and risk of dyslipidemia, respectively.

RESULTS

The weighted geometric means [95% confidence intervals (CIs)] of lead and cadmium in blood were 1.23 (1.21, 1.25) μg/dL and 0.36 (0.35, 0.37) μg/L, respectively. Blood lead was significantly associated with serum total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), non-high-density lipoprotein cholesterol (non-HDL-C), and apolipoprotein B (Apo B) levels after adjusting for covariates. Compared with the adults in the lowest blood lead quartile (≤0.76 μg/dL), those in the highest lead quartile (>1.90 μg/dL) had higher risks of elevated TC (OR = 1.88, 95% CI: 1.59-2.22), non-HDL-C (OR = 1.59, 95% CI: 1.33-1.91), LDL-C (OR = 1.68, 95% CI: 1.41-1.99) and Apo B (OR = 2.00, 95% CI: 1.46-2.73). However, the single effect of cadmium exposure and the joint effect of lead and cadmium exposures on dyslipidemia were not observed.

CONCLUSION

Blood lead well below the current recommended level was positively associated with the risk of dyslipidemia in adults, while the low-level cadmium exposure currently observed in adults did not show any significant associations with lipid levels.

Occupational exposure to graphene and silica nanoparticles. Part II: pilot study to identify a panel of sensitive biomarkers of genotoxic, oxidative and inflammatory effects on suitable biological matrices

The available biomonitoring studies on workers producing/handling nanomaterials (NMs) focused on potential effects on respiratory, immune and cardio-vascular system. Aim of this study was to identify a panel of sensitive biomarkers and suitable biological matrices to evaluate particularly genotoxic and oxidative effects induced on workers unintentionally exposed to graphene or silica nanoparticles during the production process. These nanomaterials have been chosen for 'NanoKey' project, integrating the workplace exposure assessment (reported in part I) with the biomonitoring of exposed workers reported in the present work. Simultaneously to workplace exposure characterization, we monitored the workers using: Buccal Micronucleus Cytome (BMCyt) assay, fpg-comet test (lymphocytes), oxidized DNA bases 8-oxoGua, 8-oxoGuo and 8-oxodGuo measurements (urine), analysis of oxidative stress biomarkers in exhaled breath condensate (EBC), FENO measurement and cytokines release detection (serum). Since buccal cells are among the main targets of NM occupational exposure, particular attention was posed to the BMCyt assay that represents a noninvasive assay. This pilot study, performed on 12 workers vs.11 controls, demonstrates that BMCyt and fpg-comet assays are the most sensitive biomarkers of early, still reparable, genotoxic and oxidative effects. The findings suggest that these biomarkers could represent useful tools for the biomonitoring of workers exposed to nanoparticles, but they need to be confirmed on a high number of subjects. However, such biomarkers don't discriminate the effects of NM from those due to other chemicals used in the NM production process. Therefore, they could be suitable for the biomonitoring of workers exposed to complex scenario, including nanoparticles exposure.

Presence of Titanium and Toxic Effects Observed in Rat Lungs, Kidneys, and Central Nervous System in vivo and in Cultured Astrocytes in vitro on Exposure by Titanium Dioxide Nanorods

Background

Non-spherical titanium dioxide (TiO₂) nanoparticles have been increasingly applied in various biomedical and technological fields. Their toxicological characterization is, however, less complete than that of roundish nanoparticles.

Materials and Methods

Anatase form TiO₂ nanorods, ca. 15x65 nm in size, were applied to cultured astrocytes in vitro and to the airways of young adult Wistar rats in vivo in 5, 10, and 8 mg/kg BW dose for altogether 28 days. Presence of nanorods and cellular damage was investigated in the astrocytes and in rat lungs and kidneys. Functional damage of the nervous system was studied by electrophysiological methods.

Results

The treated astrocytes showed loss of viability without detectable apoptosis. In rats, TiO₂ nanorods applied to the airways reached the blood and various organs including the lungs, kidneys, and the central nervous system. In lung and kidney samples, nanorods were observed within (partly damaged) phagolysosomes and attached to organelles, and apoptotic cell death was also detected. In cortical and peripheral electrophysiological activity, alterations corresponding to energy shortage (resulting possibly from mitochondrial damage) and astrocytic dysfunction were detected. Local titanium levels and relative weight of the investigated organs, apoptotic cell death in the lungs and kidneys, and changes in the central and peripheral nervous activity were mostly proportional to the applied doses, and viability loss of the cultured astrocytes was also dose-dependent, suggesting causal relationship of treatments and effects.

Conclusion

Based on localization of the visualized nanorods, on neuro-functional changes, and on literature data, the toxic mechanism involved mitochondrial damage, oxidative stress, and apoptotic cell death. These indicate potential human toxicity and occupational risk in case of exposure to rod-shaped TiO₂ nanoparticles.

Oxidative stress induced by occupational exposure to nanomaterials: a systematic review

The rapid growth of nanotechnology has increased the occupational exposure to nanomaterials. On the other hand, a growing body of evidence considers exposure to these materials to be hazardous. Therefore, it is necessary to examine the effects of occupational exposure to these materials by different methods. Biological monitoring, especially the investigation of oxidative stress induced by exposure to nanomaterials, can provide useful information for researchers. This study systematically reviews studies that have investigated oxidative stress caused by occupational exposure to nanomaterials. The search was conducted on the PubMed, Scopus and Web of Science databases. Of the 266 studies we obtained in our initial search, eventually 11 were included in our study. There is currently no specific biomarker for investigating oxidative stress induced by exposure to nanomaterials. Therefore, the reviewed studies have used different biomarkers in different biological fluids for this purpose. Also, the methods of assessing occupational exposure to nanomaterials in the investigated studies were very diverse. Given the approach of the investigated studies to biomarkers and exposure assessment methods, finding a specific biomarker for investigating exposure to nanomaterials seems unattainable. But reaching a group of biomarkers, to assess exposure to nanomaterials seems more applicable and achievable.

Duration-dependent effects induced by titanium dioxide nanoparticles on pancreas of adult male albino rats (histological and biochemical study)

Titanium dioxide nanoparticles (TiO2NPs) have been widely used in numerous applications and enter the human body through different routes. This study aimed to investigate the effect of intraperitoneal TiO2NPs on the histological and biochemical structure of rat pancreas. Fifty adult male albino rats were divided into four groups. Group I (control) was equally divided into two subgroups. Groups II, III, and IV: rats received intraperitoneal TiO2NPs for 7, 14, and 45 days, respectively. Blood samples were taken for the estimation of blood glucose, serum insulin, serum α-amylase, and lipase activity levels. Sections of the pancreas were processed for light, electron microscope examination, and immunohistochemical detection of insulin protein. Other parts were exposed to Real-Time Polymerase Chain Reaction for Bax, Bcl-2, SOD, and GST mRNA gene expression. Results showed pancreatic tissue damage, including acinar and islet cells, which became worse with increased duration of exposure to TiO2NPs. Decreased immune expression of the insulin protein together with decreased serum insulin and increased blood glucose levels indicated the alteration of β cells. Decreased serum α-amylase and lipase activities indicated alteration of acinar cells. Increased Bax and decreased Bcl-2 mRNA expression levels showed the apoptotic effect of TiO2NPs caused by oxidative stress and evidenced by a significant reduction in the mRNA expression of SOD and GST in a duration-dependent manner. In conclusion: the present study stated that TiO2NPs exposure for long durations had toxic effects on both exocrine and endocrine pancreas mediated by apoptotic and oxidative stress pathways.