Amelioration of titanium dioxide nanoparticles-induced liver injury in mice: possible role of some antioxidants

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.

Quercetin Mitigates Oxidative Stress, Inflammation, Apoptosis, and Histopathological Alterations Induced by Chronic Titanium Dioxide Nanoparticle Exposure in the Rat Spleen

Titanium dioxide nanoparticles (nano-TiO2) have become widespread but are accompanied by various health concerns. Quercetin (QT), a naturally occurring flavonoid in fruits and vegetables, exhibits potent antioxidant properties. This research examined the toxic impacts of nano-TiO2 on the structure and function of the spleen in adult male rats and assessed the possible protective effects of QT. A set of randomly grouped rats was established, consisting of a control group, a QT group (50 mg/kg/day), a nano-TiO2 group (300 mg/kg/day), and a QT-nano-TiO2 group. These substances were orally administered to the respective groups for 90 days. Nano-TiO2 significantly induced oxidative stress in the spleen, leading to reduced levels of serum immunoglobulins. Additionally, there was a notable increase in the expression of apoptotic markers and proinflammatory cytokines. These biochemical disturbances were accompanied by morphological changes in the spleens of rats exposed to nano-TiO2. However, coadministration of QT and nano-TiO2 effectively mitigated most nano-TiO2-induced alterations in the spleen, including apoptotic and proinflammatory responses, antioxidant imbalance, serum immunoglobulin levels, and histopathological changes. It can be concluded that QT has the potential to function as a protective agent against the detrimental impacts of nano-TiO2 on the spleen by improving the antioxidant defense mechanism and modulating the apoptotic and inflammatory responses.

Dental Implants and Implant Coatings: A Focus on Their Toxicity and Safety

Dental implants are medical devices that are surgically inserted into the patient's jawbone by an orthodontist to act as roots of missing teeth. After the implantation, the maxilla or mandible integrates with the surface of the dental implant. This process, called "osseointegration," is an important period to ensure the long-term use of dental implants and prevent implant failures. Metal implants are the most used implant materials. However, they have disadvantages such as corrosion, metal ion release from metal implant surfaces and associated toxicity. To avoid these adverse effects and improve osseointegration, alternative dental implant materials such as ceramics, polymers, composites, and novel surface modification technologies have been developed. The safety of these materials are also of concern for toxicologists. This review will give general information about dental implant materials, osseointegration and successful implantation process. Moreover, we will focus on the new surface coatings materials for of dental implants and their toxicity and safety concerns will be discussed.

Long Non-Coding RNA Expression Profile Alteration Induced by Titanium Dioxide Nanoparticles in HepG2 Cells

The liver is considered the major target organ affected by oral exposure to titanium dioxide nanoparticles (TiO₂ NPs), but the mechanism of hepatotoxicity is not fully understood. This study investigated the effect of TiO₂ NPs on the expression profile of long non-coding RNA (lncRNA) in hepatocytes and tried to understand the potential mechanism of hepatotoxicity through bioinformatics analysis. The human hepatocellular carcinoma cells (HepG2) were treated with TiO₂ NPs at doses of 0-200 μg/mL for 48 h and then RNA sequencing was implemented. The differential lncRNAs between the control and TiO₂ NPs-treated groups were screened, then the lncRNA-mRNA network and enrichment pathways were analyzed via multivariate statistics. As a result, 46,759 lncRNAs were identified and 129 differential lncRNAs were screened out. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis showed that the targeted mRNAs of those differential lncRNAs were enriched in the Hedgehog signaling pathway, Vasopressin-regulated water reabsorption, and Glutamatergic synapse. Moreover, two lncRNA-mRNA networks, including lncRNA NONHSAT256380.1-JRK and lncRNA NONHSAT173563.1-SMIM22, were verified by mRNA detection. This study demonstrated that an alteration in the lncRNA expression profile could be induced by TiO₂ NPs and epigenetics may play an important role in the mechanism of hepatotoxicity.

Impact of chitosan administration on titanium dioxide nanoparticles induced testicular dysfunction

The potential reproductive toxic effects of oral TiO₂ NPs in adult male rats as well as the possible alleviation of chitosan administration was investigated. Animals were allocated to four groups; the first group received deionized water and was assigned as a control group. In the second group, rats received chitosan at a dose of 5 mg/kg BW/day. The third group was designed for administration of TiO₂ NPs at a dose of 150 mg/kg BW/day (1/80 LD₅₀). Rats in the fourth group received both TiO₂ NPs and chitosan. After 14 days, TiO₂ NPs induced testicular lipid peroxidation as well as oxidative stress. Nano-titanium significantly upregulated genes that encode apoptosis and inflammation in testicular tissue. Moreover, it induced histological alteration in the testicular structure with impairment in spermatogenesis via reduction of PCNA immune-staining. Chitosan administration significantly improved the activities of testicular GPx, SOD, and CAT enzymes. In addition, it significantly down-regulated the relative expressions of pro-apoptotic and pro-inflammatory testicular genes. Chitosan was able to improve the testicular architecture as well as spermatogenesis. The current study revealed the capability of chitosan to ameliorate nano-titanium induced testicular toxicity. Thus, attention should be given to the extensive consumption of nano-titanium particles.

Adverse Outcome Pathways Associated with the Ingestion of Titanium Dioxide Nanoparticles-A Systematic Review

Titanium dioxide nanoparticles (TiO₂-NPs) are widely used, and humans are exposed through food (E171), cosmetics (e.g., toothpaste), and pharmaceuticals. The oral and gastrointestinal (GIT) tract are the first contact sites, but it may be systemically distributed. However, a robust adverse outcome pathway (AOP) has not been developed upon GIT exposure to TiO₂-NPs. The aim of this review was to provide an integrative analysis of the published data on cellular and molecular mechanisms triggered after the ingestion of TiO₂-NPs, proposing plausible AOPs that may drive policy decisions. A systematic review according to Prisma Methodology was performed in three databases of peer-reviewed literature: Pubmed, Scopus, and Web of Science. A total of 787 records were identified, screened in title/abstract, being 185 used for data extraction. The main endpoints identified were oxidative stress, cytotoxicity/apoptosis/cell death, inflammation, cellular and systemic uptake, genotoxicity, and carcinogenicity. From the results, AOPs were proposed where colorectal cancer, liver injury, reproductive toxicity, cardiac and kidney damage, as well as hematological effects stand out as possible adverse outcomes. The recent transgenerational studies also point to concerns with regard to population effects. Overall, the findings further support a limitation of the use of TiO₂-NPs in food, announced by the European Food Safety Authority (EFSA).

Ameliorative Effect of Pomegranate Peel Extract (PPE) on Hepatotoxicity Prompted by Iron Oxide Nanoparticles (Fe2O3-NPs) in Mice

An evaluation of the ameliorative effect of pomegranate peel extract (PPE) in counteracting the toxicity of iron oxide nanoparticles (Fe₂O₃-NPs) that cause hepatic tissue damage is focused on herein. Forty male albino mice were haphazardly grouped into four groups as follows: the first control group was orally gavage daily with physiological saline; the second group received 100 mg/kg of PPE by the oral route day after day; the third group received 30 mg/kg Fe₂O₃-NPs orally; and the fourth group received both PPE and Fe₂O₃-NPs by the oral route, the same as the second and third sets. Later, after the completion of the experiment, we collected the liver, blood, and bone marrow of bone specimens that were obtained for further laboratory tests. For instance, exposure to Fe₂O₃-NPs significantly altered serum antioxidant biomarkers by decreasing the levels of total antioxidant capacity (TAC), catalase (CAT), and glutathione s-transferase (GST). Additionally, it caused changes in the morphology of hepatocytes, hepatic sinusoids, and inflammatory Kupffer cells. Furthermore, they significantly elevated the number of chromosomal aberrations including gaps, breaks, deletions, fragments, polyploidies, and ring chromosomes. Moreover, they caused a significant overexpression of TIMP-1, TNF-α, and BAX mRNA levels. Finally, the use of PPE alleviates the toxicity of Fe₂O₃-NPs that were induced in the hepatic tissues of mice. It is concluded that PPE extract has mitigative roles against the damage induced by Fe₂O₃-NPs, as it serves as an antioxidant and hepatoprotective agent. The use of PPE as a modulator of Fe₂O₃-NPs' hepatotoxicity could be considered as a pioneering method in the use of phytochemicals against the toxicity of nanoparticles.

Improvement of the antioxidant activity of thyme essential oil against biosynthesized titanium dioxide nanoparticles-induced oxidative stress, DNA damage, and disturbances in gene expression in vivo

BACKGROUND

Titanium dioxide nanoparticles (TiO₂-NPs) are widely utilized in medicine and industry; however, their safety in biological organisms is still unclear. In this study, we determined the bioactive constitutes of thyme essential oil (TEO) and utilized the nanoemulsion technique to improve its protective efficiency against oxidative stress, genotoxicity, and DNA damage of biosynthesized titanium dioxide nanoparticles (TiO₂-NPs).

METHODS

TEO nanoemulsion (TEON) was prepared using whey protein isolate (WPI). Sixty male Sprague-Dawley rats were divided into six groups and treated orally for 21 days including the control group, TEO, or TEON- treated groups (5 mg/kg b.w), TiO₂-NPs-treated group (50 mg/kg b.w) and the groups received TiO₂-NPs plus TEO or TEON. Blood and tissues samples were collected for different assays.

RESULTS

The GC-MS analysis identified 17 bioactive compounds in TEO and thymol and carvacrol were the major compounds. TEON was irregular with average particles size of 230 ± 3.7 nm and ζ-potential of -24.17 mV. However, TiO2-NPs showed a polygonal shape with an average size of 50 ± 2.4 nm and ζ-potential of -30.44 mV. Animals that received TiO2-NPs showed severe disturbances in liver and kidney indices, lipid profile, oxidant/antioxidant indices, inflammatory cytokines, gene expressions, increased DNA damage, and pathological changes in hepatic tissue. Both TEO and TEON showed potential protection against these hazards and TEON was more effective than TEO.

CONCLUSION

The nanoemulsion of TEO enhances the oil bioactivity, improves its antioxidant characteristics, and protects against oxidative damage and genotoxicity of TiO2-NPs.

Vitamin Supplementation Protects against Nanomaterial-Induced Oxidative Stress and Inflammation Damages: A Meta-Analysis of In Vitro and In Vivo Studies

The extensive applications of nanomaterials have increased their toxicities to human health. As a commonly recommended health care product, vitamins have been reported to exert protective roles against nanomaterial-induced oxidative stress and inflammatory responses. However, there have been some controversial conclusions in regards to this field of research. This meta-analysis aimed to comprehensively evaluate the roles and mechanisms of vitamins for cells and animals exposed to nanomaterials. Nineteen studies (seven in vitro, eleven in vivo and one in both) were enrolled by searching PubMed, EMBASE, and Cochrane Library databases. STATA 15.0 software analysis showed vitamin E treatment could significantly decrease the levels of oxidants [reactive oxygen species (ROS), total oxidant status (TOS), malondialdehyde (MDA)], increase anti-oxidant glutathione peroxidase (GPx), suppress inflammatory mediators (tumor necrosis factor-α, interleukin-6, C-reactive protein, IgE), improve cytotoxicity (manifested by an increase in cell viability and a decrease in pro-apoptotic caspase-3 activity), and genotoxicity (represented by a reduction in the tail length). These results were less changed after subgroup analyses. Pooled analysis of in vitro studies indicated vitamin C increased cell viability and decreased ROS levels, but its anti-oxidant potential was not observed in the meta-analysis of in vivo studies. Vitamin A could decrease MDA, TOS and increase GPx, but its effects on these indicators were weaker than vitamin E. Also, the combination of vitamin A with vitamin E did not provide greater anti-oxidant effects than vitamin E alone. In summary, we suggest vitamin E alone supplementation may be a cost-effective option to prevent nanomaterial-induced injuries.

Nanomaterials: The New Antimicrobial Magic Bullet

Bacterial infections are a significant cause of mortality and morbidity worldwide, despite decades of use of numerous existing antibiotics and constant efforts by researchers to discover new antibiotics. The emergence of infections associated with antibiotic-resistant bacterial strains, has amplified the pressure to develop additional bactericidal therapies or new unorthodox approaches that can deal with antimicrobial resistance. Nanomaterial-based strategies, particularly those that do not rely on conventional small-molecule antibiotics, offer promise in part due to their ability to dodge existing mechanisms used by drug-resistant bacteria. Therefore, the use of nanomaterial-based formulations has attracted attention in the field of antibiotic therapy. In this Review, we highlight novel and emerging nanomaterial-based formulations along with details about the mechanisms by which nanoparticles can target bacterial infections and antimicrobial resistance. A detailed discussion about types and the activities of nanoparticles is presented, along with how they can be used as either delivery systems or as inherent antimicrobials, or a combination of both. Lastly, we highlight some toxicological concerns for the use of nanoparticles in antibiotic therapies.

Chitosan attenuated the neurotoxicity-induced titanium dioxide nanoparticles in brain of adult rats

In the current study, we aimed to investigate the neurotoxic effect of oral titanium dioxide nanoparticles (TiO₂ NPs) as well as the possible neuroprotective effect of carboxymethyl chitosan in adult rats for 14 days. The results revealed that TiO₂ NPs inhibited the activity of the acetylcholine esterase enzyme and the levels of serotonin, dopamine, and norepinephrine neurotransmitters. Additionally, it induced neuro-oxidative stress and neuroinflammation via an elevation in MDA levels and IL-6, while GSH concentration, as well as GPx and GST activities, were decreased. TiO₂ NPs induced neuronal apoptosis through upregulation of the expression of caspase-8 and -9 that was further confirmed by increasing caspases-3 and -8 proteins in the hippocampus, cerebral cortex, and cerebellum. The expression of the immediate-early gene BDNF was increased in response to TiO₂ NPs, while that of Arc was reduced. Chitosan significantly attenuated the TiO₂ NPs-induced neurotoxicity regarding AChE, serotonin, MDA, GSH, GPx, GST, IL-6, caspases-8, -9, and -3. Chitosan inhibited the expression of Arc and alleviated the effect of TiO₂ NPs on BDNF expression. Collectively, TiO₂ NPs induced neurotoxicity via their action on vital neuronal biomarkers that might in turn cause brain dysfunction. Despite the neuroprotection of chitosan, its inhibitory effect on Arc expression should be considered.

Advances in genotoxicity of titanium dioxide nanoparticles in vivo and in vitro

Titanium dioxide nanoparticles (TiO₂ NPs) are currently one of the most widely used nanomaterials. Due to an increasing scope of applications, the exposure of humans to TiO₂ NP is inevitable, such as entering the body through the mouth with food additives or drugs, invading the damaged skin with cosmetics, and entering the body through the respiratory tract during the process of production and handling. Compared with TiO₂ coarse particles, TiO₂ NPs have stronger conductivity, reaction activity, photocatalysis, and permeability, which may lead to greater toxicity to organisms. Given that TiO₂ was classified as a category 2B carcinogen (possibly carcinogenic to humans), the genotoxicity of TiO₂ NPs has become the focus of attention. There have been a series of previous studies investigating the potential genotoxicity of TiO₂ NPs, but the existing research results are still controversial and difficult to conclude. More than half of studies have shown that TiO₂ NPs can cause genotoxicity, suggesting that TiO₂ NPs are likely to be genotoxic to humans. And the genotoxicity of TiO₂ NPs is closely related to the exposure concentration, mode and time, and experimental cells/animals as well as its physicochemical properties (crystal type, size, and shape). This review summarized the latest research progress of related genotoxic effects through in vivo studies and in vitro cell tests, hoping to provide ideas for the evaluation of TiO₂ NPs genotoxicity.

Moroccan Bee Bread Improves Biochemical and Histological Changes of the Brain, Liver, and Kidneys Induced by Titanium Dioxide Nanoparticles

Titanium dioxide nanoparticles (TiO2) were used in various fields such as food industry, cosmetics, medicine, and agriculture. Despite the many advantages of nanotechnology, the adverse effects of nanoparticles are inevitable. The present study was conducted to evaluate the protective effect of bee bread on titanium dioxide (TiO2) nanoparticle toxicity. Male rats were randomly divided into four groups: Group 1 received daily by gavage (10 mL/kg bw) of distilled water, Group 2 received bee bread ethanolic extract (100 mg/kg bw), Group 3 received TiO2 (100 mg/kg bw) and distilled water (10 mL/kg bw), and Group 4 received TiO2 (100 mg/kg bw) and bee bread ethanolic extract (100 mg/kg bw). All treatments were given daily by gavage during 30 days. At the end of the experiment period, blood samples were collected to analyze fasting blood glucose, lipid profile (TC, TG, LDL-C, HDL-C, and VLDL-C), liver enzymes (AST, ALT, and LDH), total protein, urea, albumin, creatinine, sodium, potassium, and chloride ions. In addition, histological examinations of the kidneys, liver, and brain were investigated. The results showed that the subacute administration of TiO2 alone (100 mg/kg bw) had induced hyperglycemia (309 ± 5 mg/dL) and elevation of hepatic enzyme levels, accompanied by a change in both lipid profile and renal biomarkers as well as induced congestion and dilatation in the hepatic central vein and congestion in kidney and brain tissues. However, the cotreatment with bee bread extract restored these biochemical parameters and attenuated the deleterious effects of titanium nanoparticles on brain, liver, and kidney functions which could be due to its rich content on functional molecules. The findings of this paper could make an important contribution to the field of using bee bread as a detoxifying agent against titanium dioxide nanoparticles and other xenobiotics.

Innovations in nanoscience for the sustainable development of food and agriculture with implications on health and environment

A rapid increase in world population is leading to the rise in global demand of food and agriculture (agri) products. Nanotechnology and its applications have emerged as one of the most pioneering and promising technology for transforming conventional food and agri industries, with the aim of sustainable farming, improving the food security, quality and safety which could revolutionize the food and agri industries. Current developments in nanotechnology have led to the new paths progressively and bringing the radical changes the way food is perceived throughout the farming, transportation, processing, packaging, storage, monitoring and consumption. This review brings the current updates on novel nanomaterials in food and agri industries. Emphasis is given on the importance of nanotechnological applications, offering complete food solutions from farm to fork; including nutraceutical and functional foods, improving bioavailability, efficiency, nutritional status, nano-additives, food texture, color, taste and packaging. Agricultural sector also witnessed several nano-based products, such as nano-fertilizer, nano-pesticide, nano growth promoters and many more for the development of sustainable farming and crop improvement. Despite of numerous advantages of nanotechnology, there are still toxicity challenges, safety concerns, which needs to be addressed and demands transformations in regulatory policies. Rapid development is projected to transform several foods and agri sectors, with rapid increase in market stake and investment. Government agencies, private research centers as well as academicians are also coming together to explore the benefits of nanotechnology to improve food scarcity in the coming years.

Eugenol attenuates TiO2 nanoparticles-induced oxidative damage, biochemical toxicity and DNA damage in Wistar rats: an in vivo study

Titanium dioxide nanoparticles (TiO2 NPs) are widely used in food, edible dyes, and other commercial products. Human exposure to TiO2 NPs has raised concerns regarding their toxic potential. Various studies have evaluated the TiO2 NPs-induced toxicity, oxidative damage to the cellular components, and genotoxicity. In the present study, we examined whether co-treatment with the dietary antioxidant eugenol can attenuate or protect against TiO2 NPs-induced toxicity. We exposed the adult male Wistar rats to TiO2 NPs (150 mg/kg body weight) by intraperitoneal injection (i.p.) either alone or as co-treatment with eugenol (1-10 mg/kg body weight) once a day for 14 days. The untreated rats were supplied saline and served as control. Titanium (Ti) accumulation in various tissues was analyzed by inductively coupled plasma mass spectrometry. Serum levels of liver and kidney biomarkers and oxidative stress markers in the liver, kidney, and spleen were determined. A significant increase in hydrogen peroxide level confirmed that oxidative stress occurred in these tissues. TiO2 NPs induced oxidation of lipids, and decreased glutathione level and antioxidant enzyme activity in the kidney, liver, and spleen of treated rats. TiO2 NPs also increased the serum levels of alanine aminotransferase, alkaline phosphatase, aspartate aminotransferase, albumin, and total cholesterol and decreased the blood urea nitrogen, uric acid, and total bilirubin in serum, which indicates oxidative damage to the liver and kidney. In eugenol and TiO2 NPs co-treated rats, all these changes were mitigated. Single-cell gel electrophoresis (comet assay) of lymphocytes showed longer comet tail length in TiO2 NPs-treated groups, indicating DNA damage while tail length was reduced in eugenol and TiO2 NPs co-treated groups. Thus, it seems that eugenol can be used as a chemoprotective agent against TiO2 NPs-induced toxicity.

Safety assessment of titanium dioxide (E171) as a food additive

The present opinion deals with an updated safety assessment of the food additive titanium dioxide (E 171) based on new relevant scientific evidence considered by the Panel to be reliable, including data obtained with TiO2 nanoparticles (NPs) and data from an extended one-generation reproductive toxicity (EOGRT) study. Less than 50% of constituent particles by number in E 171 have a minimum external dimension < 100 nm. In addition, the Panel noted that constituent particles < 30 nm amounted to less than 1% of particles by number. The Panel therefore considered that studies with TiO2 NPs < 30 nm were of limited relevance to the safety assessment of E 171. The Panel concluded that although gastrointestinal absorption of TiO2 particles is low, they may accumulate in the body. Studies on general and organ toxicity did not indicate adverse effects with either E 171 up to a dose of 1,000 mg/kg body weight (bw) per day or with TiO2 NPs (> 30 nm) up to the highest dose tested of 100 mg/kg bw per day. No effects on reproductive and developmental toxicity were observed up to a dose of 1,000 mg E 171/kg bw per day, the highest dose tested in the EOGRT study. However, observations of potential immunotoxicity and inflammation with E 171 and potential neurotoxicity with TiO2 NPs, together with the potential induction of aberrant crypt foci with E 171, may indicate adverse effects. With respect to genotoxicity, the Panel concluded that TiO2 particles have the potential to induce DNA strand breaks and chromosomal damage, but not gene mutations. No clear correlation was observed between the physico-chemical properties of TiO2 particles and the outcome of either in vitro or in vivo genotoxicity assays. A concern for genotoxicity of TiO2 particles that may be present in E 171 could therefore not be ruled out. Several modes of action for the genotoxicity may operate in parallel and the relative contributions of different molecular mechanisms elicited by TiO2 particles are not known. There was uncertainty as to whether a threshold mode of action could be assumed. In addition, a cut-off value for TiO2 particle size with respect to genotoxicity could not be identified. No appropriately designed study was available to investigate the potential carcinogenic effects of TiO2 NPs. Based on all the evidence available, a concern for genotoxicity could not be ruled out, and given the many uncertainties, the Panel concluded that E 171 can no longer be considered as safe when used as a food additive.

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.

Protective Effects of Idebenone against Sepsis Induced Acute Lung Damage

BACKGROUND/AIMS

Sepsis is an uncontrolled systemic infection, withcomplex pathophysiology that may result in acute lung organ damage and cause multiple organ failure. Although much research has been conducted to illuminate sepsis's complex pathophysiology, sepsis treatment protocols are limited, and sepsis remains an important cause of mortality andmorbidity in intensive care units.Various studies have shown that idebenone (IDE) possesses strong antioxidant properties, which inhibit lipid peroxidation and protect cells from oxidative damage. The present study aimed to evaluate the protective effects of IDE against lung injury in a cecal ligation and puncture (CLP)-induced sepsis rat model.

METHODS

Male albino Wistar rats were used. The animals were divided into a healthy control (no treatment), CLP, IDE control (200 mg/kg), and CLP + IDE subgroups (50 mg/kg, 100 mg/kg, and 200 mg/kg), with nine rats in each group.IDE was administered 1 h after CLP induction.To evaluate the protective effects of IDE, lung tissues were collected 16 h after sepsis for biochemical, immunohistochemical staining, and histopathological examination.

RESULTS

IDE significantly ameliorated sepsis-induced disturbances in oxidative stress-related factors, with its effects increasing in accordance with the dose.IDE also abolished histopathological changes in lung tissues associated with CLP.Furthermore, interleukin 1 beta (IL-1β)and tumor necrosis factor-alpha (TNF-α) immunopositivity markedly decreased in the septic rats following IDE treatment.

CONCLUSIONS

IDE largely mitigated the inflammatory response in sepsis-induced lung injury by decreasing free radicals and preventing lipid peroxidation. The results suggest that IDE may represent a potential novel therapeutic drug for sepsis treatment.

C-reactive Protein Signaling and Chromosomal Abnormalities in Nanotoxicity Induced via Different Doses of TiO2 (80 nm) Boost Liver Function

The wide application of nanotechnology merits the need to clarify their nanotoxicity. In vivo studies have raised concerns about the toxicity of titanium dioxide nanoparticles (TiO₂ NPs), but there are limited data on chromosomal abnormalities induced in hepatic tissue. In this article, the toxicity of three IP doses of TiO₂ NPs (80 nm) (50, 250, and 500 mg/kg) through three time intervals (up to 7, 15, and 45 days) on liver tissue was assessed. Hepatic catalase (CAT), glutathione (GSH), nitric oxide (NOx), and malondialdehyde (MDA) levels varied with the administered dose and exposure time of TiO₂ NPs. As a result, TiO₂ NPs caused a statistically significant decrease in hepatic CAT and GSH activities and a significant alleviation in MDA and NOx levels (p < 0.05), suggesting that the liver exposed to these various doses of TiO₂ NPs suffered from severe oxidative stress. The extent of depletion of antioxidant enzymes and the elevation of MDA and NOx in the liver exposed to the highest dose and duration of TiO₂ NPs 500 mg for 45 days was the greatest, suggesting that the toxicity might be dose and time dependent. Further, C-reactive protein (CRP) as an inflammatory marker was also alleviated, in addition to the apparent chromosomal aberration and liver pathologies including necrotic and fibrotic hepatocytes after exposure to 250 and 500 mg/kg of TiO₂ NPs for 14 and 45 days that were deduced. Hence, nanotechnology-based industries are growing rapidly leading to large-scale production of engineered nanoparticles. They contribute to increased chances of human NPs exposure and health risk.

Tissue-specific oxidative stress and element distribution after oral exposure to titanium dioxide nanoparticles in rats

Dietary and environmental exposure to titanium dioxide nanoparticles (TiO2 NPs) can cause low-dose and long-term oral exposure in the population, posing a potential adverse health risk. Oxidative stress is considered to be the primary effect of TiO2 NPs through biological interaction. In the present study, we conducted an animal experiment to investigate the element distribution and oxidative stress in Sprague-Dawley rats after oral exposure to TiO2 NPs at daily doses of 0, 2, 10, and 50 mg kg-1 for 90 days. Through the detection of Ti element content in various tissues, limited absorption and distribution of TiO2 NPs in rats was found. However, orally ingested TiO2 NPs still induced tissue-specific oxidative stress and imbalance of elements. Liver tissue was the most sensitive tissue to TiO2 NP-induced oxidative stress, showing decreased reduced glutathione (GSH), increased oxidized glutathione (GSSG) and decreased ratio of GSH/GSSG as well as accumulation of lipid peroxidation (malondialdehyde, MDA) in liver tissues of rats after TiO2 NP exposure (10 and 50 mg kg-1). Meanwhile, oral exposure to TiO2 NPs caused a significant reduction in metal elements such as Mg, Ca and Co in various tissues. Through bioinformatics analysis, the tissue specificity and correlation between the imbalance of elements and oxidative stress were statistically confirmed, but it was difficult to understand the causal relationship. Disorder of element distribution and oxidative stress may lead to a series of subsequent adverse health effects and the tissue specificity would partly explain the target effects of TiO2 NPs.

Possible effects of titanium dioxide particles on human liver, intestinal tissue, spleen and kidney after oral exposure

Recent studies reported adverse liver effects and intestinal tumor formation after oral exposure to titanium dioxide (TiO₂). Other oral toxicological studies, however, observed no effects on liver and intestine, despite prolonged exposure and/or high doses. In the present assessment, we aimed to better understand whether TiO₂ can induce such effects at conditions relevant for humans. Therefore, we focused not only on the clinical and histopathological observations, but also used Adverse Outcome Pathways (AOPs) to consider earlier steps (Key Events). In addition, aiming for a more accurate risk assessment, the available information on organ concentrations of Ti (resulting from exposure to TiO₂) from oral animal studies was compared to recently reported concentrations found in human postmortem organs. The overview obtained with the AOP approach indicates that TiO₂ can trigger a number of key events in liver and intestine: Reactive Oxygen Species (ROS) generation, induction of oxidative stress and inflammation. TiO₂ seems to be able to exert these early effects in animal studies at Ti liver concentrations that are only a factor of 30 and 6 times higher than the median and highest liver concentration found in humans, respectively. This confirms earlier conclusions that adverse effects on the liver in humans as a result of (oral) TiO₂ exposure cannot be excluded. Data for comparison with Ti levels in human intestinal tissue, spleen and kidney with effect concentrations were too limited to draw firm conclusions. The Ti levels, though, are similar or higher than those found in liver, suggesting these tissues may be relevant too.

Prophylactic administration of carnosine and melatonin abates the incidence of apoptosis, inflammation, and DNA damage induced by titanium dioxide nanoparticles in rat livers

Although titanium dioxide nanoparticles (TDO-ns) are extensively used in the food, medicine, and cosmetic industries, discussions about the possible hazards of nanomaterials are just beginning to emerge. This study aimed to detect the inflammatory stress, oxidative stress, and apoptotic cell death induced in the livers of rats exposed to TDO-ns (600 mg/kg, particle size ≤ 100 nm). Furthermore, the modulation of these toxic effects by two potent naturally occurring antioxidants, carnosine (Carno) or melatonin (Melato), was evaluated. The co-administration of carnosine or melatonin to rats intoxicated with TDO-ns significantly attenuated the increases in serum tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), C-reactive protein (CRP), immunoglobulin G (IgG), vascular endothelial growth factor (VEGF), nitric oxide (NO), and alanine aminotransferase (ALT) levels. The two agents markedly ameliorated hepatic DNA damage and the alterations in hepatic malondialdehyde (MDA), glutathione (GSH), cytochrome P450, caspase-3, total phospholipid, phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, sphingomyelin, and triglyceride (TG) levels. These results support the use of Carno or Melato as prophylactic agents against TDO-ns-induced liver damage.

In vivo evaluation of oxidative stress and biochemical alteration as biomarkers in glass clover snail, Monacha cartusiana exposed to zinc oxide nanoparticles

Oxidative stress is considered a main commonly reported mechanism of nanoparticles toxicity, so this study aimed to evaluate oxidative stress and biochemical alterations in the haemolymph and digestive gland of snail, Monacha cartusiana exposed to sublethal concentrations of zinc oxide nanoparticles (ZnONPs) for 14 days (d). The results indicated that, ZnONPs induced significant increases in lipid peroxidation (LPO) and lactate dehydrogenase (LDH) in treated animals and did not return to normal levels after recover period. A significant decline of glutathione peroxidase (GPx), glutathione-S-transferase (GST) activities, and glutathione (GSH) content in the haemolymph and digestive gland of snails was observed when compared with control. A significant increase was observed in catalase (CAT), alanine aminotransferase (ALT), and aspartate aminotransferase (AST) activities of treated animals. In general, nano-materials are able to induce oxidative stress in exposed animals. The present findings indicate that, alterations of antioxidant enzyme activities, increase of LPO, LDH, and reducing of GSH content and GST, GPx activities are recognized to oxidative stress and cell damage. This species could be considered a good bioindicator to assess nano-materials exposure.

The NRF2 Signaling Network Defines Clinical Biomarkers and Therapeutic Opportunity in Friedreich's Ataxia

Friedreich’s ataxia (FA) is a trinucleotide repeats expansion neurodegenerative disorder, for which no cure or approved therapies are present. In most cases, GAA trinucleotide repetitions in the first intron of the FXN gene are the genetic trigger of FA, determining a strong reduction of frataxin, a mitochondrial protein involved in iron homeostasis. Frataxin depletion impairs iron–sulfur cluster biosynthesis and determines iron accumulation in the mitochondria. Mounting evidence suggests that these defects increase oxidative stress susceptibility and reactive oxygen species production in FA, where the pathologic picture is worsened by a defective regulation of the expression and signaling pathway modulation of the transcription factor NF-E2 p45-related factor 2 (NRF2), one of the fundamental mediators of the cellular antioxidant response. NRF2 protein downregulation and impairment of its nuclear translocation can compromise the adequate cellular response to the frataxin depletion-dependent redox imbalance. As NRF2 stability, expression, and activation can be modulated by diverse natural and synthetic compounds, efforts have been made in recent years to understand if regulating NRF2 signaling might ameliorate the pathologic defects in FA. Here we provide an analysis of the pharmaceutical interventions aimed at restoring the NRF2 signaling network in FA, elucidating specific biomarkers useful for monitoring therapeutic effectiveness, and developing new therapeutic tools.

The Toxicity Of Metallic Nanoparticles On Liver: The Subcellular Damages, Mechanisms, And Outcomes

Metallic nanoparticles (MNPs) are new engineering materials with broad prospects for biomedical applications; thus, their biosafety has drawn great concern. The liver is the main detoxification organ of vertebrates. However, many issues concerning the interactions between MNPs and biological systems (cells and tissues) are unclear, particularly the toxic effects of MNPs on hepatocytes and other liver cells. Numerous researchers have shown that some MNPs can induce decreased cell survival rate, production of reactive oxygen species (ROS), mitochondrial damage, DNA strand breaks, and even autophagy, pyroptosis, apoptosis, or other forms of cell death. Our review focuses on the recent researches on the liver toxicity of MNPs and its mechanisms at cellular and subcellular levels to provide a scientific basis for the subsequent hepatotoxicity studies of MNPs.

Evaluation of immunologic and intestinal effects in rats administered an E 171-containing diet, a food grade titanium dioxide (TiO2)

The toxicity of dietary E 171, a food grade titanium dioxide was evaluated. A recent study reported rats receiving E 171 in water developed inflammation and aberrant crypt foci (ACF) in the gastrointestinal tract. Here, rats received food containing E 171 (7 or 100 days). The 100-day study included feeding E 171 after dimethylhydrazine (DMH) or vehicle only pretreatment. Food consumption was similar between treatment groups with maximum total cumulative E 171 exposure being 2617 mg/kg in 7 days and 29,400 mg/kg in 100 days. No differences were observed due to E 171 in the percentage of dendritic, CD4+ T or Treg cells within Peyer's patches or the periphery, or in cytokine production in plasma, sections of jejunum, and colon in 7- or 100-day E 171 alone fed rats. Differences were observed for IL-17A in colon (400 ppm E 171 + DMH) and IL-12p70 in plasma (40 ppm E 171 + DMH). E 171 had no effect on histopathologic evaluations of small and large intestines, liver, spleen, lungs, or testes, and no effects on ACF, goblet cell numbers, or colonic gland length. Dietary E 171 administration (7- or 100-day), even at high doses, produced no effect on the immune parameters or tissue morphology.

NLRP3 inflammasome, oxidative stress, and apoptosis induced in the intestine and liver of rats treated with titanium dioxide nanoparticles: in vivo and in vitro study

Purpose

This study evaluated the effects of titanium dioxide nanoparticles (TiO₂ NPs) on liver and intestine of normal rats.

Methods

Male rats were divided into four groups as follows: 1) control rats, 2) control rats that orally received 10 mg/kg TiO₂ NPs, 3) control rats that orally received 50 mg/kg TiO₂ NPs, and 4) control rats that orally received 100 mg/kg TiO₂ NPs. After 30 days, the NLRP3 inflammasome pathway (NLRP3, caspase-1, and IL-1β), antioxidant pathway (superoxide dismutase [SOD], glutathione peroxidase [GPx], and catalase [CAT]), inflammatory pathway (inducible nitric oxide synthase [iNOS] and tumor necrosis factor-α [TNF-α]), and the apoptosis pathway (p53, Bax, Bcl-2, and caspase-3) were determined in the intestine and liver of the rats. H&E and Masson’s trichrome (MT) staining as well as TUNEL assay were used to examine the liver and the intestine. Biochemical factors, cytotoxicity, ROS generation, and apoptosis rate were also determined in HepG2 and Caco-2 cells.

Results

TiO₂ NPs in a dose-dependent manner increased cytotoxicity, oxidative stress, and apoptosis rate in Caco-2 and HepG2 cells. The administration of TiO₂ NPs significantly reduced antioxidant enzyme activity and gene expressions (SOD, CAT, and GPx) as well as glutathione (GSH) levels and total antioxidant capacity (TAC) in a dose-dependent manner. TiO₂ NPs also induced the apoptosis pathway and inflammatory pathway gene expressions and caspase-3 activity in the intestine and liver. TUNEL assay was in agreement with gene expressions. TiO₂ NPs also led to morphological changes in the liver and intestine.

Conclusion

TiO₂ NPs could have cytotoxic effects on the intestine and liver structure and function by inducing oxidative stress, inflammation, and apoptosis.

Toxicity and mechanisms of action of titanium dioxide nanoparticles in living organisms

Titanium dioxide nanoparticles (TiO₂ NPs) are one of the most widely used nanomaterials in the consumer products, agriculture, and energy sectors. Their large demand and widespread applications will inevitably cause damage to organisms and ecosystems. A better understanding of TiO₂ NP toxicity in living organisms may promote risk assessment and safe use practices of these nanomaterials. This review summarizes the toxic effects of TiO₂ NPs on multiple taxa of microorganisms, algae, plants, invertebrates, and vertebrates. The mechanism of TiO₂ NP toxicity to organisms can be outlined in three aspects: The Reactive Oxygen Species (ROS) produced by TiO₂ NPs following the induction of electron-hole pairs; cell wall damage and lipid peroxidation of the cell membrane caused by NP-cell attachment by electrostatic force owing to the large surface area of TiO₂ NPs; and TiO₂ NP attachment to intracellular organelles and biological macromolecules following damage to the cell membranes.

Critical review of the safety assessment of titanium dioxide additives in food

Nanomaterial engineering provides an important technological advance that offers substantial benefits for applications not only in the production and processing, but also in the packaging and storage of food. An expanding commercialization of nanomaterials as part of the modern diet will substantially increase their oral intake worldwide. While the risk of particle inhalation received much attention, gaps of knowledge exist regarding possible adverse health effects due to gastrointestinal exposure. This problem is highlighted by pigment-grade titanium dioxide (TiO2), which confers a white color and increased opacity with an optimal particle diameter of 200-300 nm. However, size distribution analyses showed that batches of food-grade TiO2 always comprise a nano-sized fraction as inevitable byproduct of the manufacturing processes. Submicron-sized TiO2 particles, in Europe listed as E 171, are widely used as a food additive although the relevant risk assessment has never been satisfactorily completed. For example, it is not possible to derive a safe daily intake of TiO2 from the available long-term feeding studies in rodents. Also, the use of TiO2 particles in the food sector leads to highest exposures in children, but only few studies address the vulnerability of this particular age group. Extrapolation of animal studies to humans is also problematic due to knowledge gaps as to local gastrointestinal effects of TiO2 particles, primarily on the mucosa and the gut-associated lymphoid system. Tissue distributions after oral administration of TiO2 differ from other exposure routes, thus limiting the relevance of data obtained from inhalation or parenteral injections. Such difficulties and uncertainties emerging in the retrospective assessment of TiO2 particles exemplify the need for a fit-to-purpose data requirement for the future evaluation of novel nano-sized or submicron-sized particles added deliberately to food.

Titanium dioxide nanoparticles induce in vitro autophagy

Aim:

Concerns about the possible toxicity to environment and human health of titanium dioxide nanoparticles (TiO2 NPs) are increasing. The aim of this study was to investigate the relationship between toxicology and autophage in vitro.

Methods:

RAW 264.7 cells were exposed to five concentrations (50, 100, 200, 300, and 400 μg/mL) and two particle size of TiO2 NPs (30 and 100 nm) for 24 h.

Results:

The results showed that TiO2 NPs decreased cell viability, phagocytic rate, and phagocytic index in a concentration-dependent manner, thereby inducing autophagy. TiO2 NPs-induced autophagy was indicated by monodansyl cadaverine staining and transmission electron microscopy. TiO2 NPs-induced messenger RNA expression of autophagy-related proteins LC3 and Beclin-1 was also significantly increased compared with those of the unexposed control cells. LC3 and Beclin-1 protein expression levels were markedly increased with the increase of TiO2 NPs concentrations.

Conclusion:

These results suggest the possibility that TiO2 NPs-induced toxicology probably plays a key role in autophagy in RAW 264.7 cells, and further exhaustive research on the harmful effects of these NPs in relevant organisms is needed for their safe application.

Hepatoprotective effect of thymol against subchronic toxicity of titanium dioxide nanoparticles: Biochemical and histological evidences

The study was aimed to investigate the protective action of thymol against nano titanium dioxide (nano-TiO₂) induced hepatotoxicity in rats. To achieve this purpose, the rats were divided into four groups (n = 6) including control, nano-TiO₂ (100 mg/kg), nano-TiO₂ + thymol (10 mg/kg) and nano-TiO₂ + thymol (30 mg/kg). Intragastric (IG) administration of nano-TiO₂ for 60 consecutive days caused widespread histological changes and significantly induced oxidative stress in the liver tissues as manifested by the rise in serum transaminase activities accompanied by marked decline of enzymatic (catalase, superoxide dismutase and glutathione peroxidase) and non-enzymatic (ferric reducing antioxidant power and glutathione) antioxidant levels, and rise of malondialdehyde levels in liver tissue. Pretreatment with thymol (IG) prior to nano-TiO₂ administration significantly ameliorated all of biochemical and histopathological alterations in a dose-dependent manner. In conclusion, thymol effectively protects against nano-TiO₂-induced hepatotoxicity in rats by its antioxidant properties.

Ameliorative effects of thymoquinone on titanium dioxide nanoparticles induced acute toxicity in rats

Although the nanoparticles had a beneficial activity, it had also adverse effects as a result of generation of oxidative stress. The current study aimed to assess the ameliorative effect of thymoquinone (TQ) on titanium dioxide nanoparticles (TiO₂ NPs) induced acute toxicity in male rats. Forty-eight male rats were distributed into four equal groups (12 rats each). Group (1) received single oral dose of TiO₂ NPs (300 mg/kg), Group (2) received TiO₂ NPs and TQ (20 mg/kg), Group (3) received TQ and group (4) received only the vehicle and served as control group. TiO₂ NPs intoxicated group showed increased the level of lipid peroxidation product (LPO), aspartate aminotransferase (AST) and alanine aminotransferase (ALT) and decreased the level of antioxidants and testosterone. Vascular and degenerative changes in the liver and testes were observed by light microscopy as well as presence of TiO₂ NPs in the lysosomes by electron microscopy. Treatment with TQ revealed improvement of the biochemical parameters, histology and ultrastructure of the liver and testes. It was concluded that acute intoxication of rats with TiO₂ NPs induced adverse effect in the liver and testes. Administration of TQ has an ameliorative effect against oxidative stress induced by TiO₂ NPs intoxication.

Therapeutic effect of carnosine in rat model of experimental liver carcinogenesis

The possible anticancer effect of carnosine versus doxorubicin was investigated against hepatocellular carcinoma (HCC) induced by trichloroacetic acid (TCA) (500mg/kg/day, p.o., for 5days) in rats. Following induction of HCC, rats treated with either carnosine (10mg/kg/day, i.p.), or doxorubicin (2.5mg/kg, i.p., once weekly), for 2 weeks. Carnosine significantly decreased serum alanine aminotransferase, and hepatic lipid peroxidation, nitric oxide, tumor necrosis factor-α, and nuclear factor-κB p65 unit, and significantly increased liver total antioxidant status in TCA-challenged rats. The effects of doxorubicin on oxidative, nitrative, and inflammatory biomarkers were less significant than carnosine. However, both carnosine and doxorubicin significantly induced liver tissue apoptotic biomarkers, Bax, cytosolic cytochrome C, and caspase-3, in a comparable manner. Additionally, carnosine and doxorubicin reduced the histopathological dysplastic changes, and alpha-fetoprotein expression in liver of rats with HCC. It was concluded that carnosine significantly protected against TCA-induced liver carcinogenesis in rats, through its antioxidant, antinitrative, and anti-inflammatory effects, and induction of apoptosis.

The role of antioxidants in attenuation of Caenorhabditis elegans lethality on exposure to TiO2 and ZnO nanoparticles

The exponential increase in the usage of engineered nanoparticles (ENPs) has raised global concerns due to their potential toxicity and environmental impacts. Nano-TiO₂ and nano-ZnO have been extensively used in various applications. Thus, there is a need for determining the toxic potentials of ENPs as well as, to develop the possible attenuation method for ENPs toxicity. Both in the in vitro and in vivo systems, exposure to the majority of ENPs have shown Reactive Oxygen Species (ROS) generation, which leads to oxidative stress mediated inflammation, genotoxicity, and cytotoxicity. Hence, with the rationale of determining easy and economical protection against ENPs exposure, the amelioration effect of the antioxidants (curcumin and vitamin-C) against the nano-TiO₂ and nano-ZnO induced ROS and lethality were investigated in Caenorhabditis elegans. We not only employed pre-treatment and along with treatment approach, but also determined the effect of antioxidants at different time points of treatment. Our study revealed that both the antioxidants efficiently ameliorate nanoparticles induced ROS as well as lethality in worms. Further, the pretreatment approach was more effective than the along with treatment. Therefore, our study indicates the possibility of evading the nanotoxicity by incorporating curcumin and vitamin-C in everyday diet.

Reduction of oxidative damages induced by titanium dioxide nanoparticles correlates with induction of the Nrf2 pathway by GSPE supplementation in mice

Titanium dioxide nanoparticles (TiO₂ NPs) are widely used to additives in cosmetics, pharmaceuticals, paints and foods. Recent studies have demonstrated that TiO₂ NPs increased the risk of cancer and the mechanism might relate with oxidative stress. Grape seed procyanidin extract (GSPE) is a natural compound which has been demonstrated to possess a wide array of pharmacological and biochemical actions, including anti-inflammatory, anti-carcinogenic, and antioxidant properties. Our data show that GSPE prevents the changes of histopathology and biomarkers in heart, liver and kidney that occur in mice exposed to TiO₂ NPs. After pretreatment with GSPE, the DNA damage, reactive oxygen species (ROS) generation and malondialdehyde (MDA) content in mice exposed to TiO₂ NPs had statistically significant decreases in dose dependent manners. GSPE increased the expression of nuclear factor erythroid 2 (NF-E2)-related factor 2 (Nrf2), NAD(P)H dehydrogenase[quinine] 1(NQO1), heme oxygenase 1 (HO-1) and glutamate-cysteine ligase catalytic subunit (GCLC). We conclude that grape seed procyanidin extract prevents the majority of tissue and molecular damage resulting from nanoparticle treatment. The protective effect of GSPE may be due to its strong antioxidative activities which related with the activated Nrf2 and its down-regulated genes including NQO1, HO-1 and GCLC.

Progress of in vivo studies on the systemic toxicities induced by titanium dioxide nanoparticles

Titanium dioxide nanoparticles (TiO2 NPs) are inorganic materials with a diameter of 1-100 nm. In recent years, TiO2 NPs have been used in a wide range of products, including food, toothpaste, cosmetics, medicine, paints and printing materials, due to their unique properties (high stability, anti-corrosion, and efficient photocatalysis). Following exposure via various routes including inhalation, injection, dermal deposition and gastrointestinal tract absorption, NPs can be found in various organs in the body potentially inducing toxic effects. Thus more attention to the safety of TiO2 NPs is necessary. Therefore, the present review aims to provide a comprehensive evaluation of the toxic effects induced by TiO2 NPs in the lung, liver, stomach, intestine, kidney, spleen, brain, hippocampus, heart, blood vessels, ovary and testis of mice and rats in in vivo experiments, and evaluate their potential toxic mechanisms. The findings will provide an important reference for human risk evaluation and management following TiO2 NP exposure.

Contribution of oxidative stress to TiO2 nanoparticle-induced toxicity

With the rapid development of nanotechnology, titanium dioxide nanoparticles (TNPs) are widely used in many fields. People in such workplaces or researchers in laboratories are at a higher risk of being exposed to TNPs, so are the consumers. Moreover, increasing evidence revealed that the concentrations of TNPs are elevated in animal organs after systematic exposure and such accumulated TNPs could induce organ dysfunction. Although cellular responses such as oxidative stress, inflammatory response, apoptosis, autophagy, signaling pathways, and genotoxic effects contribute to the toxicity of TNPs, the interrelationship among them remains obscure. Given the pivotal role of oxidative stress, we summarized relevant articles covering the involvement of oxidative stress in TNPs' toxicity and found that TNP-induced oxidative stress might play a central role in toxic mechanisms. However, available data are far from being conclusive and more investigations should be performed to further confirm whether the toxicity of TNPs might be attributed in part to the cascades of oxidative stress. Tackling this uncertain issue may help us to comprehensively understand the interrelationship among toxic cellular responses induced by TNPs and might shed some light on methods to alleviate toxicity of TNPs.

Risk assessment of titanium dioxide nanoparticles via oral exposure, including toxicokinetic considerations

Titanium dioxide white pigment consists of particles of various sizes, from which a fraction is in the nano range (<100 nm). It is applied in food as additive E 171 as well as in other products, such as food supplements and toothpaste. Here, we assessed whether a human health risk can be expected from oral ingestion of these titanium dioxide nanoparticles (TiO₂ NPs), based on currently available information. Human health risks were assessed using two different approaches: Approach 1, based on intake, i.e. external doses, and Approach 2, based on internal organ concentrations using a kinetic model in order to account for accumulation over time (the preferred approach). Results showed that with Approach 1, a human health risk is not expected for effects in liver and spleen, but a human health risk cannot be excluded for effects on the ovaries. When based on organ concentrations by including the toxicokinetics of TiO₂ NPs (Approach 2), a potential risk for liver, ovaries and testes is found. This difference between the two approaches shows the importance of including toxicokinetic information. The currently estimated risk can be influenced by factors such as absorption, form of TiO₂, particle fraction, particle size and physico-chemical properties in relation to toxicity, among others. Analysis of actual particle concentrations in human organs, as well as organ concentrations and effects in liver and the reproductive system after chronic exposure to well-characterized TiO₂ (NPs) in animals are recommended to refine this assessment.

Protective effects of thymoquinone and avenanthramides on titanium dioxide nanoparticles induced toxicity in Sprague-Dawley rats

The protective effect of thymoquinone (TQ), the major active ingredient of Nigella sativa seeds, and avenanthramides (AVA) enriched extract of oats on titanium dioxide naonparticles (TiO₂ NPs) induced toxicity and oxidative stress in Sprague-Dawley (SD) rats was investigated. Sixty rats were divided into 6 equal groups. The first, second, third, fourth and fifth groups received TiO₂ NPs, TiO₂ NPs and TQ, TiO₂ NPs and AVA, TQ only, or AVA only for 6 weeks. The sixth group served as the control. Exposure to TiO₂ NPs resulted in increased liver enzyme markers, oxidative stress indices, tumor necrosis factor alpha (TNF-α) and DNA damage. Histopathological alterations were also observed in the liver, brain, lung, kidney, heart and testes. Co-administration of TQ and AVA with TiO₂ NPs decreased the level of liver enzymes, oxidative stress, TNF-α and DNA damage. Furthermore, TQ and AVA increased the total antioxidant and glutathione (GSH) levels. In conclusion, TiO₂ NPs induce hazardous effects in different organs and are closely related to oxidative stress. TQ and AVA have antioxidative and anti-inflammatory effect against the detrimental effect of TiO₂ NPs.