Uptake and bioaccumulation of iron oxide nanoparticles (Fe3O4) in barley (Hordeum vulgare L.): effect of particle-size

Root-to-shoot translocation of nanoparticles (NPs) is a matter of interest due to their possible unprecedented effects on biota. Properties of NPs, such as structure, surface charge or coating, and size, determine their uptake by cells. This study investigates the size effect of iron oxide (Fe3O4) NPs on plant uptake, translocation, and physiology. For this purpose, Fe3O4 NPs having about 10 and 100 nm in average sizes (namely NP10 and NP100) were hydroponically subjected to barley (Hordeum vulgare L.) in different doses (50, 100, and 200 mg/L) at germination (5 days) and seedling (3 weeks) stages. Results revealed that particle size does not significantly influence the seedlings' growth but improves germination. The iron content in root and leaf tissues gradually increased with increasing NP10 and NP100 concentrations, revealing their root-to-shoot translocation. This result was confirmed by vibrating sample magnetometry analysis, where the magnetic signals increased with increasing NP doses. The translocation of NPs enhanced chlorophyll and carotenoid contents, suggesting their contribution to plant pigmentation. On the other hand, catalase activity and H2O2 production were higher in NP10-treated roots compared to NP100-treated ones. Besides, confocal microscopy revealed that NP10 leads to cell membrane damages. These findings showed that Fe3O4 NPs were efficiently taken up by the roots and transported to the leaves regardless of the size factor. However, small-sized Fe3O4 NPs may be more reactive due to their size properties and may cause cell stress and membrane damage. This study may help us better understand the size effect of NPs in nanoparticle-plant interaction.

Neurotoxicity of Titanium Dioxide Nanoparticles: A Comprehensive Review

The increasing use of titanium dioxide nanoparticles (TiO2 NPs) across various fields has led to a growing concern regarding their environmental contamination and inevitable human exposure. Consequently, significant research efforts have been directed toward understanding the effects of TiO2 NPs on both humans and the environment. Notably, TiO2 NPs exposure has been associated with multiple impairments of the nervous system. This review aims to provide an overview of the documented neurotoxic effects of TiO2 NPs in different species and in vitro models. Following exposure, TiO2 NPs can reach the brain, although the specific mechanism and quantity of particles that cross the blood-brain barrier (BBB) remain unclear. Exposure to TiO2 NPs has been shown to induce oxidative stress, promote neuroinflammation, disrupt brain biochemistry, and ultimately impair neuronal function and structure. Subsequent neuronal damage may contribute to various behavioral disorders and play a significant role in the onset and progression of neurodevelopmental or neurodegenerative diseases. Moreover, the neurotoxic potential of TiO2 NPs can be influenced by various factors, including exposure characteristics and the physicochemical properties of the TiO2 NPs. However, a systematic comparison of the neurotoxic effects of TiO2 NPs with different characteristics under various exposure conditions is still lacking. Additionally, our understanding of the underlying neurotoxic mechanisms exerted by TiO2 NPs remains incomplete and fragmented. Given these knowledge gaps, it is imperative to further investigate the neurotoxic hazards and risks associated with exposure to TiO2 NPs.

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).

Safety and Toxicity Implications of Multifunctional Drug Delivery Nanocarriers on Reproductive Systems In Vitro and In Vivo

In the recent past, nanotechnological advancements in engineered nanomaterials have demonstrated diverse and versatile applications in different arenas, including bio-imaging, drug delivery, bio-sensing, detection and analysis of biological macromolecules, bio-catalysis, nanomedicine, and other biomedical applications. However, public interests and concerns in the context of human exposure to these nanomaterials and their consequential well-being may hamper the wider applicability of these nanomaterial-based platforms. Furthermore, human exposure to these nanosized and engineered particulate materials has also increased drastically in the last 2 decades due to enormous research and development and anthropocentric applications of nanoparticles. Their widespread use in nanomaterial-based industries, viz., nanomedicine, cosmetics, and consumer goods has also raised questions regarding the potential of nanotoxicity in general and reproductive nanotoxicology in particular. In this review, we have summarized diverse aspects of nanoparticle safety and their toxicological outcomes on reproduction and developmental systems. Various research databases, including PubMed and Google Scholar, were searched for the last 20 years up to the date of inception, and nano toxicological aspects of these materials on male and female reproductive systems have been described in detail. Furthermore, a discussion has also been dedicated to the placental interaction of these nanoparticles and how these can cross the blood–placental barrier and precipitate nanotoxicity in the developing offspring. Fetal abnormalities as a consequence of the administration of nanoparticles and pathophysiological deviations and aberrations in the developing fetus have also been touched upon. A section has also been dedicated to the regulatory requirements and guidelines for the testing of nanoparticles for their safety and toxicity in reproductive systems. It is anticipated that this review will incite a considerable interest in the research community functioning in the domains of pharmaceutical formulations and development in nanomedicine-based designing of therapeutic paradigms.

Hippocampal toxicity of metal base nanoparticles. Is there a relationship between nanoparticles and psychiatric disorders?

Metal base nanoparticles are widely produced all over the world and used in many fields and products such as medicine, electronics, cosmetics, paints, ceramics, toys, kitchen utensils and toothpastes. They are able to enter the body through digestive, respiratory, and alimentary systems. These nanoparticles can also cross the blood brain barrier, enter the brain and aggregate in the hippocampus. After entering the hippocampus, they induce oxidative stress, neuro-inflammation, mitochondrial dysfunction, and gene expression alteration in hippocampal cells, which finally lead to neuronal apoptosis. Metal base nanoparticles can also affect hippocampal neurogenesis and synaptic plasticity that both of them play crucial role in memory and learning. On the one hand, hippocampal cells are severely vulnerable due to their high metabolic activity, and on the other hand, metal base nanoparticles have high potential to damage hippocampus through variety of mechanisms and affect its functions. This review discusses, in detail, nanoparticles' detrimental effects on the hippocampus in cellular, molecular and functional levels to reveal that according to the present information, which types of nanoparticles have more potential to induce hippocampal toxicity and psychiatric disorders and which types should be more evaluated in the future studies.

The effects of vitamin D on learning and memory of hypothyroid juvenile rats and brain tissue acetylcholinesterase activity and oxidative stress indicators

Apart from a role as a key regulator of calcium/phosphate homeostasis, vitamin D (Vit D) is suggested to be a potential player in nervous system growth and function. This study aimed to assess the impacts of Vit D administration on memory impairment, oxidative damage, and acetylcholinesterase (AchE) overactivity in hypothyroid juvenile rats. The animals were randomly grouped as (1) Control; (2) Hypothyroid; (3) Hypothyroid-Vit D100, and (4) Hypothyroid-Vit D 500. Propylthiouracil (PTU) was added to their drinking water (0.05%) for 6 weeks, and Vit D (100 or 500 IU/kg) treatment was performed daily by gavage. Morris water maze (MWM) and passive avoidance (PA) tests were performed. The brains were removed under deep anesthesia, then the hippocampal and cortical tissues were separated to assess biochemical parameters. Hypothyroidism was significantly associated with learning and memory impairment in MWM and PA tests. Hypothyroidism was also accompanied by an elevation in AChE activity and malondialdehyde (MDA) content and a reduced level of thiol content and superoxide dismutase (SOD) activity in the brain. Treatment with Vit D recovered hypothyroidism-induced cognitive impairment and improved memory performance in MWM and PA tasks. On the other hand, Vit D alleviated AChE activity and MDA level, whereas increased SOD activity and thiol content in the hippocampal and cortical tissues. In conclusion, these outcomes suggest an association between the oral administrations of Vit D and learning and memory improvement of hypothyroid rats, which was accompanied by decreasing AChE activity and brain tissue oxidative damage.

Combined molecular, structural and memory data unravel the destructive effect of tramadol on hippocampus

Tramadol is a synthetic analogue of codeine and stimulates neurodegeneration in several parts of the brain that leads to various behavioral impairments. Despite the leading role of hippocampus in learning and memory as well as decreased function of them under influence of tramadol, there are few studies analyzing the effect of tramadol administration on gene expression profiling and structural consequences in hippocampus region. Thus, we sought to determine the effect of tramadol on both PC12 cell line and hippocampal tissue, from gene expression changes to structural alterations. In this respect, we investigated genome-wide mRNA expression using high throughput RNA-seq technology and confirmatory quantitative real-time PCR, accompanied by stereological analysis of hippocampus and behavioral assessment following tramadol exposure. At the cellular level, PC12 cells were exposed to 600μM tramadol for 48 hrs, followed by the assessments of ROS amount and gene expression levels of neurotoxicity associated with neurodegenerative pathways such as apoptosis and autophagy. Moreover, the structural and functional alteration of the hippocampus under chronic exposure to tramadol was also evaluated. In this regard, rats were treated with tramadol at doses of 50 mg/kg for three consecutive weeks. In vitro data revealed that tramadol provoked ROS production and caused the increase in the expression of autophagic and apoptotic genes in PC12 cells. Furthermore, in-vivo results demonstrated that tramadol not only did induce hippocampal atrophy, but it also triggered microgliosis and microglial activation, causing upregulation of apoptotic and inflammatory markers as well as over-activation of neurodegeneration. Tramadol also interrupted spatial learning and memory function along with long-term potentiation (LTP). Taken all together, our data disclosed the neurotoxic effects of tramadol on both in vitro and in-vivo. Moreover, we proposed a potential correlation between disrupted biochemical cascades and memory deficit under tramadol administration.

Damage to the Blood Brain Barrier Structure and Function from Nano Titanium Dioxide Exposure Involves the Destruction of Key Tight Junction Proteins in the Mouse Brain

Numerous studies have proven that nano titanium dioxide (nano TiO₂) can accumulate in animal brains, where it damages the blood brain barrier (BBB); however, whether this process involves destruction of tight junction proteins in the mouse brain has not been adequately investigated. In this study, mice were exposed to nano TiO₂ for 30 consecutive days, and then we used transmission electron microscopy to observe the BBB ultrastructure and the Evans blue assay to evaluate the permeability of the BBB. Our data suggested that nano TiO₂ damaged the BBB ultrastructure and increased BBB permeability. Furthermore, we used immunofluorescence and Western blotting to examine the expression of key tight junction proteins, including Occludin, ZO-1, and Claudin-5 in the mouse brain. Our data showed that nano TiO₂ reduced Occludin, ZO-1 and Claudin-5 expression. Taken together, nano TiO₂-induced damage to the BBB structure and function may involve the destruction of key tight junction proteins.

Grape seed extract effects on hippocampal neurogenesis, synaptogenesis and dark neurons production in old mice. Can this extract improve learning and memory in aged animals?

BACKGROUND

During the elderly, hippocampal neurogenesis and synaptogenesis reduce and dark neurons (DNs) increase, leading to cognitive impairment. It is believed that natural products can protect the neural cells and system by protecting from damages or promoting regeneration. Therefore, the effects of grape seed extract (GSE) on the hippocampus of aged mice were investigated in this study.

METHODS

twelve old mice were divided into two groups of control and GSE. Animals in the GSE group received 300 mg/kg of GSE for eight weeks via gavage. At the end of treatment, cognition performance was evaluated by Morris water maze (MWM) and passive avoidance tests. Hippocampal neurogenesis, synaptogenesis and DNs production were evaluated with immunohistochemistry and histological evaluations on 5-micron coronal tissue sections.

RESULTS

The hippocampal mean number of double cortin positive cells (DCX⁺) per unit area, as well as synaptophysin expression in the GSE group, were significantly higher than the control group (p < 0.01). The frequency of DNs in the GSE group was lower than the control group (p < 0.05). Behavioral tests showed that GSE improves memory and learning performance.

CONCLUSION

Consuming GSE in the elderly can potentially alleviate the age-related reduction of hippocampal neurogenesis and synaptogenesis. It is also able to decrease hippocampal DNs production and increase memory and learning.

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.

The role of Tetrahydrocannabinol in inducing disrupted signaling cascades, hippocampal atrophy and memory defects

Tetrahydrocannabinol (THC), a major psychoactive constituent of marijuana, can substantially change the function of several brain areas, leading to behavioral impairment including memory and learning dysfunction. Given the importance of hippocampus as one of the chief parts of the brain involved in memory processing, the present study seeks to investigate structural and histological alterations in hippocampus as well as behavioral defects provoked by THC treatment. Besides, using genome-wide sequencing, we adopted a pathway-based approach to discover dysregulated molecular pathways. Our results demonstrated remarkable hippocampal atrophy, and also interrupted memory function and long term potentiation (LTP) under THC exposure. We also detected several dysregulated signaling pathways involved in synaptic plasticity as well as cell-cell interaction in the hippocampus of THC-treated rats. Overall, the results indicate a potential correlation between disrupted signaling cascades, hippocampal atrophy and memory defects caused by THC treatment.

Nano-scaled materials may induce severe neurotoxicity upon chronic exposure to brain tissues: A critical appraisal and recent updates on predisposing factors, underlying mechanism, and future prospects

Owing to their tremendous potential, the inference of nano-scaled materials has revolutionized many fields including the medicine and health, particularly for development of various types of targeted drug delivery devices for early prognosis and successful treatment of various diseases, including the brain disorders. Owing to their unique characteristic features, a variety of nanomaterials (particularly, ultra-fine particles (UFPs) have shown tremendous success in achieving the prognostic and therapeutic goals for early prognosis and treatment of various brain maladies such as Alzheimer's disease, Parkinson's disease, brain lymphomas, and other ailments. However, serious attention is needful due to innumerable after-effects of the nanomaterials. Despite their immense contribution in optimizing the prognostic and therapeutic modalities, biological interaction of nanomaterials with various body tissues may produce severe nanotoxicity of different organs including the heart, liver, kidney, lungs, immune system, gastro-intestinal system, skin as well as nervous system. However, in this review, we have primarily focused on nanomaterials-induced neurotoxicity of the brain. Following their translocation into different regions of the brain, nanomaterials may induce neurotoxicity through multiple mechanisms including the oxidative stress, DNA damage, lysosomal dysfunction, inflammatory cascade, apoptosis, genotoxicity, and ultimately necrosis of neuronal cells. Our findings indicated that rigorous toxicological evaluations must be carried out prior to clinical translation of nanomaterials-based formulations to avoid serious neurotoxic complications, which may further lead to develop various neuro-degenerative disorders.

Are Titania Photocatalysts and Titanium Implants Safe? Review on the Toxicity of Titanium Compounds

Titanium and its compounds are broadly used in both industrial and domestic products, including jet engines, missiles, prostheses, implants, pigments, cosmetics, food, and photocatalysts for environmental purification and solar energy conversion. Although titanium/titania-containing materials are usually safe for human, animals and environment, increasing concerns on their negative impacts have been postulated. Accordingly, this review covers current knowledge on the toxicity of titania and titanium, in which the behaviour, bioavailability, mechanisms of action, and environmental impacts have been discussed in detail, considering both light and dark conditions. Consequently, the following conclusions have been drawn: (i) titania photocatalysts rarely cause health and environmental problems; (ii) despite the lack of proof, the possible carcinogenicity of titania powders to humans is considered by some authorities; (iii) titanium alloys, commonly applied as implant materials, possess a relatively low health risk; (iv) titania microparticles are less toxic than nanoparticles, independent of the means of exposure; (v) excessive accumulation of titanium in the environment cannot be ignored; (vi) titanium/titania-containing products should be clearly marked with health warning labels, especially for pregnant women and young children; (vi) a key knowledge gap is the lack of comprehensive data about the environmental content and the influence of titania/titanium on biodiversity and the ecological functioning of terrestrial and aquatic ecosystems.

Engineered magnetic nanoparticles enhance chlorophyll content and growth of barley through the induction of photosystem genes

This study investigates the impact of an engineered magnetic nanoparticle (MNP) on a crop plant. For this purpose, a sonochemical synthetic approach was utilized in order to dope magnetic elements (Co and Nd) into technologically important iron oxide NPs. After being characterized by using TEM, SEM, and XRD instruments, the MNPs were hydroponically applied to barley plants with varying doses (from 125 to 1000 mg/L) both in germination (4 days) and early growing stages (3 weeks). Physiological responses, as well as expression of photosystem marker genes, were assessed. Compared to the untreated control, MNP treatment enhanced germination rate (~ 31%), tissue growth (8% in roots, 16% in shoots), biomass (~ 21%), and chlorophyll (a, b) (~ 20%), and carotenoids (~ 22%) pigments. In general, plants showed the highest growth enhancement at 125 or 250 mg/L treatment. However, higher doses diminished the growth indices. Compared to the control, the catalase activity was significantly reduced in the leaves (~ 33%, p < 0.005) but stimulated in the roots (~ 46%, p < 0.005). All tested photosystem marker genes (BCA, psbA, and psaA) were overexpressed in MNP-treated leaves than non-treated control. Moreover, the gene expressions were found to be proportionally increased with increasing MNP doses, indicating a positive correlation between MNPs and the photosynthetic machinery, which could contribute to the enhancement of plant growth.

Titanium dioxide nanoparticles via oral exposure leads to adverse disturbance of gut microecology and locomotor activity in adult mice

Titanium dioxide nanoparticles (TiO₂NPs) have been widely used as food additives in daily life. However, the impact of oral intake of TiO₂NPs on the nervous system is largely unknown. In this study, 7-week-old mice were treated with either vehicle or TiO₂NPs suspension solution at 150 mg/kg by intragastric administration for 30 days. Our results demonstrated that oral exposure to TiO₂NPs resulted in aberrant excitement of enteric neurons, although unapparent pathological changes were observed in gut. We also found the richness and evenness of gut microbiota were remarkably decreased and the gut microbial community compositions were significantly changed in the TiO₂NP-treated group as compared with vehicle controls. Interestingly, oral exposure to TiO₂NPs was capable to induce the inhibitory effects on locomotor activity, but it did not lead to significant change on the spatial learning and memory ability. We further revealed the mechanism that TiO₂NPs could specifically cause locomotor dysfunction by elevating the excitement of enteric neuron, which might spread to brain via gut-brain communication by vagal pathway. However, inflammation response, enteric neurotransmitter 5-HT and major gut peptides might not be involved in this pathological process. Together, these findings provide valuable insights into the novel mechanism of TiO₂NP-induced neurotoxicity. Understanding the microbiota-gut-brain axis will provide the foundation for potential therapeutic or prevention approaches against TiO₂NP-induced gut and brain-related disorders.

Translocation of transition metal oxide nanoparticles to breast milk and offspring: The necessity of bridging mother-offspring-integration toxicological assessments

Although infant nanomaterial exposure is a worldwide concern, breastfeeding transfer of transition metal-oxide nanoparticles to as well as their toxicity to offspring are still unclear. Breastfeeding transmits nutrition and immunity from mothers to their offspring; it also provides a portal for maternal toxins to enter offspring. Thus, a toxicology assessment of both mothers and their offspring should be established to monitor nanomaterial exposure during lactation. Here, we determined the effects of the exposure route on the biodistribution, biopersistence, and toxicology of nanoparticles (titanium dioxide, zinc oxide, and zirconium dioxide) in both mouse dams and their offspring. Oral and airway exposure routes were tested using gavage and intranasal administration, respectively. Biodistribution in the main organs (breast, liver, spleen, lung, kidney, intestine, and brain) and biopersistence in the blood and milk were determined using inductively coupled plasma mass spectrometry. Hematology and histomorphology analyses were performed to determine the toxicology of the nanoparticles. A reduced offspring body weight was found with the reduced nanoparticle size. Furthermore, both oral and airway exposure increased the nanoparticle concentrations in the main tissues and milk. More nanoparticles were transferred into maternal tissues and milk via airway exposure than via oral exposure. During the transfer of the metal from the exposed nanoparticles to milk, the immune cell pathway played a more important role in the airway route than in the oral exposure route. Finally, maternal exposure via both the oral and airway routes reduced the body weight and survival rate of their breastfeeding offspring, which could possibly be attributed to the toxicity of nanoparticles to blood cells and organs. In conclusion, maternal exposure to nanoparticles led to a reduced body weight and survival rate in breastfed offspring, and nanoparticle exposure via the airway route led to a higher immune response and tissue injury than that via the oral exposure route. This study suggests that the use of products containing metal nanoparticles in breastfeeding mothers and their offspring should be reconsidered to maintain a safe breastfeeding system.

Effects of oral exposure to titanium dioxide nanoparticles on gut microbiota and gut-associated metabolism in vivo

The antibacterial activity of titanium dioxide nanoparticles (TiO2 NPs) has been extensively documented and applied to food packaging or environmental protection. Ingestion of TiO2 NPs via dietary and environmental exposure may pose potential health risks by interacting with gut microbiota. We conducted an animal experiment to investigate the effects of oral exposure to TiO2 NPs on gut microbiota and gut-associated metabolism in Sprague-Dawley rats. Rats were administered with TiO2 NPs (29 ± 9 nm) orally at population-related exposure doses (0, 2, 10, 50 mg kg-1) daily for 30 days. Changes in the gut microbiota and feces metabolomics were analyzed through bioinformatics. TiO2 NPs caused significant changes of colon morphology in rats, manifested as pathological inflammatory infiltration and mitochondrial abnormalities. 16S rDNA sequencing analysis showed that the structure and composition of gut microbiota in rats were modulated after exposure to TiO2 NPs. Monitoring data demonstrated that differentially expressed bacterial strains were obtained until exposure for 14 days and 28 days, including increased L. gasseri, Turicibacter, and L. NK4A136_group and decreased Veillonella. Fecal metabolomics analysis showed that 25 metabolites and the aminoacyl-tRNA biosynthesis metabolic pathway have changed significantly in exposed rats. The increased metabolites were represented by N-acetylhistamine, caprolactam, and glycerophosphocholine, and the decreased metabolites were represented by 4-methyl-5-thiazoleethanol, l-histidine, and l-ornithine. Metabolic disorders of gut microbiota and subsequently produced lipopolysaccharides (LPS) led to oxidative stress and an inflammatory response in the intestine, which was considered to be a key and primary indirect pathway for toxicity induced by oral exposure to the TiO2 NPs. In conclusion, orally ingested TiO2 NPs could induce disorders of gut microbiota and gut-associated metabolism in vivo. The indirect pathway of oxidative stress and inflammatory response, probably due to dysbiosis of gut microbiota primarily, played an important role in the mechanisms of toxicity induced by oral exposure to TiO2 NPs. This may be a common mechanism of toxicity caused by oral administration of most nanomaterials, as they usually have potential antimicrobial activity.

The effect of titanium dioxide nanoparticles on mice midbrain substantia nigra

OBJECTIVES

Widely used Titanium dioxide nanoparticles (TiO2) enter into the body and cause various organ damages. Therefore, we aimed to study the effect of TiO2 on the substantia nigra of midbrain.

MATERIALS AND METHODS

40 male BALB/c mice were randomly divided into five groups: three groups received TiO2 at doses of 10, 25, and 50 mg/kg, the fourth group received normal saline for 45 days by gavage, and control group (without intervention). Then, Motor tests including pole and hanging tests were done to investigate motor disorders. The animal brain was removed for histological purposes. Accordingly, immunohistochemistry was performed to detect tyrosine hydroxylase positive cells, and then toluidine blue staining was done to identify dark neurons in the substantia nigra. Eventually, the total number of these neurons were counted using stereological methods in different groups.

RESULTS

The results showed that the time recorded for mice to turn completely downward on the pole in the TiO2-50 group increased and also the time recorded for animals to hang on the wire in the hanging test significantly decreased (P<0.05) in comparison with other groups. Also, the average number of tyrosine hydroxylase positive neurons in TiO2-25 and TiO2-50 groups significantly decreased as compared to the TiO2-10 and control groups (P<0.05). The total number of dark neurons in the TiO2-25 and TiO2-50 groups was substantially higher than the TiO2-10, control and normal saline groups (P<0.05).

CONCLUSION

Our findings indicated that TiO2, depending on dose, can cause the destruction of dopaminergic neurons and consequently increase the risk of Parkinson's disease.

Blood titanium level as a biomarker of orthopaedic implant wear

BACKGROUND

Joint replacement implants are usually manufactured from cobalt-chromium or titanium alloys. After the device is implanted, wear and corrosion generate metal particles and ions, which are released into local tissue and blood. The metal debris can cause a range of adverse local and systemic effects in patients.

RESEARCH PROBLEM

In the case of cobalt and chromium, a blood level exceeding 7 μg L^-1 indicates potential for local toxicity, and a failing implant. It has been repeatedly suggested in the literature that measurement of titanium could also be used to assess implant function. Despite an increasing interest in this biomarker, and growing use of titanium in orthopaedics, it is unclear what blood concentrations should raise concerns. This is partly due to the technical challenges involved in the measurement of titanium in biological samples.

AIM

This Review summarises blood/serum titanium levels associated with well-functioning and malfunctioning prostheses, so that the prospects of using titanium measurements to gain insights into implant performance can be evaluated.

CONCLUSION

Due to inter-laboratory analytical differences, reliable conclusions regarding "normal" and "abnormal" titanium levels in patients with orthopaedic implants are difficult to draw. Diagnosis of symptomatic patients should be based on radiographic evidence combined with blood/serum metal levels.

Retardation of Axonal and Dendritic Outgrowth Is Associated with the MAPK Signaling Pathway in Offspring Mice Following Maternal Exposure to Nanosized Titanium Dioxide

Exposure to nanosized titanium oxide (nano-TiO₂) has been proven to suppress brain growth in mouse offspring; however, whether retardation of axonal or dendritic outgrowth is associated with activation of the mitogen-activated protein kinase (MAPK) pathway remains unclear. In the present study, pregnant mice were exposed to nano-TiO₂ at 1.25, 2.5, and 5 mg/kg body weight, and the molecular mechanism of axonal or dendritic outgrowth retardation was investigated. The results suggested that nano-TiO₂ crossed the blood-fetal barrier and blood-brain barrier and deposited in the brain of offspring, which retarded axonal and dendritic outgrowth, including the absence of axonal outgrowth, and decreased dendritic filament length, dendritic branching number, and dendritic spine density. Importantly, maternal exposure to nano-TiO₂ increased phosphorylated (p)-extracellular signal-regulated kinase1/2 (ERK1/2, +24.35% to +59.4%), p-p38 (+60.82% to 181.85%), and p-c-jun N-terminal kinase (JNK, +28.28% to 97.28%) expression in the hippocampus of the offspring. These findings suggested that retardation of axonal and dendritic outgrowth in mouse offspring caused by maternal exposure to nano-TiO₂ may be related to excessive activation of the ERK1/2/MAPK signaling pathway. Therefore, the potential toxicity of nano-TiO₂ is a concern, especially in pregnant woman or children who are exposed to nano-TiO₂.

Impact of manganese ferrite (MnFe2O4) nanoparticles on growth and magnetic character of barley (Hordeum vulgare L.)

The main objective of this study was to assess the uptake and translocation of MnFe₂O₄ magnetic nanoparticles (MNPs) in hydroponically grown barley (Hordeum vulgare L.). Hydrothermally synthesized and well characterized MNPs (average crystallite size of 14.5 ± 0.5 nm) with varied doses (62.5, 125, 250, 500, and 1000 mg L^-1) were subjected to the plants at germination and early growing stages (three weeks). The tissues analyzed by vibrating-sample magnetometer (VSM) and transmission electron microscopy (TEM) revealed the uptake and translocation of MNPs, as well as their internalization in the leaf cells. Also, elemental analysis proved that manganese (Mn) and iron (Fe) contents were ∼7-9 times and ∼4-7 times higher in the leaves of MNPs-treated plants than the ones for non-treated control, respectively. 250 mg L^-1 of MNPs significantly (at least p < 0.05) promoted the fresh weight (FW, %10.25). However, higher concentrations (500 and 1000 mg L^-1) remarkably reduced the increase to %8 and %5, respectively, possibly due to the restricted water uptake. Also, catalase activity was increased from 91 (μM H₂O₂ min^-1 mg^-1) to 138 in leaves, and decreased to 66 in roots upon 1000 mg L^-1 of MNPs application. Chlorophyll and carotenoid contents were not significantly changed, except chlorophyll a (%6 increase at 1000 mg L^-1, p < 0.05). Overall, MnFe₂O₄ NPs were up-taken from the roots and migrated to the leaves which promoted the growth parameters of barley. Hence, MNPs can be suggested for barley breeding programs and can be proposed as effective delivery system for agrochemicals. However, the possible negative effect of MNPs due to its potential horizontal transfer from plants to animals via the food chain must be also considered.

Nano-TiO2 Inhibits Development of the Central Nervous System and Its Mechanism in Offspring Mice

Nano titanium dioxide (Nano-TiO₂) has been applied in food packaging systems and food additives, but it may cause potential neurotoxicity for human and animals. In our study, the effects of nano-TiO₂ exposure during pregnancy/lactation on the development of the central nervous system in offspring mice were examined and its molecular mechanism involving Rho family was investigated. Our findings showed that pregnancy/lactation exposure to nano-TiO₂ resulted in thinning of cerebral and cerebellar cortex, decrease in number of neurons per unit area of cerebrum, edema and nuclear condensation, dysplasia of neurites in hippocampal pyramidal cells, thinning in pyramidal cell layer in hippocampus, and decrease in learning and memory of offspring mice. Furthermore, expressions of Rac1 and Cdc42 involved in axon and dendritic development were decreased, whereas RhoA expression and ratio of RhoA/Rac1 were increased in offspring brain. It implies that exposure to nano-TiO₂ during pregnancy/lactation could result in brain retardation and cognitive impairment in offspring mice, which was closely related to alterations in the expression of Rho protein family. Therefore, application of nano-TiO₂ in daily life should be performed with caution.

Penetration, distribution and brain toxicity of titanium nanoparticles in rodents' body: a review

Titanium dioxide (TiO2) has been vastly used commercially, especially as white pigment in paints, colorants, plastics, coatings, cosmetics. Certain industrial uses TiO2 in diameter <100 nm. There are three common exposure routes for TiO2: (i) inhalation exposure, (ii) exposure via gastrointestinal tract, (iii) dermal exposure. Inhalation and gastrointestinal exposure appear to be the most probable ways of exposure, although nanoparticle (NP) penetration is limited. However, the penetration rate may increase substantially when the tissue is impaired. When TiO2 NPs migrate into the circulatory system, they can be distributed into all tissues including brain. In brain, TiO2 lead to oxidative stress mediated by the microglia phagocytic cells which respond to TiO2 NPs by the production and release of superoxide radicals that convert to multiple reactive oxygen species (ROS). The ROS production may also cause the damage of blood-brain barrier which then becomes more permeable for NPs. Moreover, several studies have showed neuron degradation and the impairment of spatial recognition memory and learning abilities in laboratory rodent exposed to TiO2 NPs.

Quantum dots cause acute systemic toxicity in lactating rats and growth restriction of offspring

The in vivo toxicity of QDs in animals has been broadly studied; however, their reproductive toxicity towards lactating rodents is currently unknown. This study therefore aims to assess the potential toxicity against dams and offspring after postnatal QD exposure at two doses (5 and 1 nmol per rat) and unravel whether QDs can translocate to pups via breastfeeding. The dose-dependent systemic toxicity of QDs in dams was observed by examining the body weight, hematology, biochemistry, histopathological changes, and sex hormone levels. It was found that the QDs primarily accumulated in the liver and spleen of dams at 1 day post injection (dpi), but the highest concentrations were found in the kidneys at 18 dpi. A few QDs were detected in breast milk and stomach and intestine of pups; this suggested that the QDs were transmitted to breast milk via blood circulation and then transferred to pups via breastfeeding. High-dose QDs induced severe growth inhibition and a 71.08% offspring mortality, while pups showed growth restriction within 90 dpi in the low-dose group. Moreover, the hematology, biochemistry, and histology results showed limited chronic toxicity against offspring in the long term. This study provides a theoretical foundation for the exposure assessment of nanomaterials in lactating animals and for the advancement of QDs in the biomedical field.

Inducible nitric oxide inhibitor aminoguanidine, ameliorated oxidative stress, interleukin-6 concentration and improved brain-derived neurotrophic factor in the brain tissues of neonates born from titanium dioxide nanoparticles exposed rats

Introduction: An interaction between oxidative stress, neuroinflammation, and nitric oxide (NO) has been suggested to have a role neurotoxicity. The aim of current research was to investigate the effect of aminoguanidine (AG) as an inducible NO synthase (iNOS) inhibitor, on brain-derived neurotrophic factor (BDNF), oxidative stress, and interleukin-6 (IL-6) concentrations in the brain tissues of neonates born from the rats exposed to titanium dioxide nanoparticles (TiO2 NPs) during gestation. Methods: The pregnant rats were grouped into three and received: (1) saline, (2) TiO2 (200 mg/kg, gavage), and (3) TiO2-AG [200 mg/kg intraperitoneal (IP)]. The treatment was started since the second gestation day up to the delivery time. The neonates born from the rats were deeply anesthetized, sacrificed, and the brains were collected for biochemical evaluations. Results: The neonates born from the rats exposed to TiO₂ showed a lower BDNF (p < .001) but a higher IL-6 (p < .01) concentrations in their hippocampal tissue. TiO₂ exposure also increased malondialdehyde (MDA) (p < .001) and NO metabolites (p < .001), while diminished thiol (p < .001), superoxide (SOD) (p < .001), and catalase (CAT) (p < .001) in all hippocampal, cortical, and cerebellar tissues. Administration of AG improved BDNF (p < .01) but attenuated IL-6 (p < .01) concentrations in the hippocampal tissue. AG also decreased MDA (p < .001) and NO metabolites (p < .01-p < .001), while increased thiol (p < .01-p < .001), SOD (p < .001), and CAT (p < .05-p < .001) in all cerebellar, hippocampal, cortical, and tissues. Conclusion: The results of the current research revealed that iNOS inhibitor AG, ameliorated oxidative stress, IL-6 concentration, and improved BDNF in the brain tissues of neonates born from TiO₂ NPs exposed rats.

The effects of tramadol administration on hippocampal cell apoptosis, learning and memory in adult rats and neuroprotective effects of crocin

Tramadol, a frequently used pain reliever drug, present neurotoxic effects associated to cognitive dysfunction. Moreover, crocin has been reported to have neuroprotective effects. The aim of this study was to assess crocin's capacity to protect learning, and memory abilities on tramadol-treated rats. A total of 35 rats were divided into five groups: Control, Saline, tramadol (50 mg/kg), tramadol + crocin(30 mg/kg), crocin groups and treated orally for 28 consecutive days. Morris water maze (MWM) and passive avoidance (PA) tests were done, followed by dissection of the rat's brains for toluidine blue and TUNEL staining. In MWM test, tramadol group spent lower time and traveled shorter distance in the target quadrant (Q1) (P < 0.05). On the other side, the traveled distance in tramadol-crocin group was higher than tramadol (P < 0.05). In PA test, both the delay for entering the dark, and the total time spent in the light compartment decreased in tramadol comparing to the control group (P < 0.05), while it increased in tramadol-crocin compared with the tramadol group (P < 0.05). In tramadol-treated animals, the dark neurons (DNs) and apoptotic cells in CA1, CA3 and DG increased (P < 0.05), while concurrent intake of crocin decreased the number of DNs and apoptotic cells in these areas (P < 0.05). Crocin was able to improve learning and memory of tramadol-treated rats and also decreased DNs and apoptotic cells in the hippocampus. Considering these results, the potential capacity of crocin for decreasing side effects of tramadol on the nervous system is suggested.

Neurobehavioral assessment of rats exposed to pristine polystyrene nanoplastics upon oral exposure

The increasing use of plastics has raised concerns about pollution of freshwater by these polymeric materials. Knowledge about their potential effects on environmental and public health is limited. Recent publications have suggested that the degradation of plastics will result in the release of nano-sized plastic particles to the environment. Therefore, it is of utmost importance to gain knowledge about whether and how nanoplastics affect living organisms. The present study aimed to analyse potential neurobehavioral effects of polystyrene nanoparticles (PS-NPs) after long-term exposure on rat. Potential effects of PS-NPs were investigated using four test dosages (1, 3, 6, and 10 mg PS-NPs/kg of body weight/day) administrated orally with adult Wistar male rats for five weeks. Neurobehavioral tests were chosen to assess a variety of behavioral domains. Particle diameters in test suspensions were determined through dynamic light scattering and showed an average hydrodynamic diameter of approximately 38.92 nm. No statistically significant behavioral effects were observed in all tests performed (p > 0.05). In the elevated plus maze, PS-NPs-exposed rats showed greater number of entries into open arms compared to controls. Also, PS-NPs had no significant influence on body weight of animals. Taking into account the subtle and transient nature of neurobehavioral consequences, however, these results underline the possibility of even pristine plastic nanoparticles to induce behavioral alteration in the rest of the food web, including for marine biota and humans. Indeed even though studied neurobehavioral effects in our study was not statistically significant, the observed subtle effects may be clinically considerable.

Nanoparticulate titanium dioxide-inhibited dendritic development is involved in apoptosis and autophagy of hippocampal neurons in offspring mice

Background: Numerous studies have demonstrated that, upon maternal exposure, nano-TiO2 can cross the placental barrier, accumulate in offspring animals, and cause neurotoxicity. However, the neurotoxic mechanisms are not fully understood. The aim of this study is to determine the effects of nano-TiO2 on the dendritic outgrowth of hippocampal neurons and confirm the role of apoptosis and excessive autophagy in the neurotoxicity of offspring mice caused by nano-TiO2, as well as its molecular mechanisms. Methods: Pregnant mice were intragastrically administered 1, 2, or 3 mg per kg body weight nano-TiO2 consecutively from prenatal day 7 to postpartum day 21. The ultrastructure, mitochondrial membrane potential (MMP), levels of reactive oxygen species (ROS) and peroxides, and ATP contents, along with the expression of apoptosis- and autophagy-related factors, were investigated. Results: The dendritic length of hippocampal neurons was lower in the group treated with nano-TiO2 than in the control group. Apoptosis, excessive autophagy, and nano-TiO2 aggregation in hippocampal neurons resulted from maternal exposure to nano-TiO2. Maternal exposure to nano-TiO2 also resulted in the over-production of ROS, increases in malondialdehyde and protein carbonylation, reductions in MMP and ATP contents, up-regulation of apoptosis- or autophagy-related factors including histone H2AX at serine 139 (γH2AX), cytochrome C (Cyt C), caspase 3, phosphoinositide 3-kinase (PI3K3C), Beclin 1, c-Jun, LC3I, LC3II, JNK and p-JNK expression, and an increase of LC3II/LC3I, as well as down-regulation of Bcl-2 expression in hippocampal neurons of offspring mice. Conclusions: Maternal exposure to nano-TiO2 inhibited the dendritic outgrowth of hippocampal neurons. This effect is closely associated with excessive autophagy, which is related to severe oxidative stress and alterations in the expressions of apoptosis- and autophagy-related factors in the hippocampal neurons of offspring mice, due to maternal exposure to nano-TiO2.

Current understanding of the toxicological risk posed to the fetus following maternal exposure to nanoparticles

INTRODUCTION

With the broad use of nanotechnology, the number and variety of nanoparticles that humans can be exposed to has further increased. Consequently, there is growing concern about the potential effect of maternal exposure to various nanoparticles during pregnancy on a fetus. However, the nature of this risk is not fully known. Areas covered: In this review, materno-fetal transfer of nanoparticles through the placenta is described. Both prenatal and postnatal adverse effects, such as fetal resorption, malformation and injury to various organs in mice exposed to nanoparticles are reviewed. The potential mechanisms of toxicity are also discussed. Expert opinion: The toxicology and safe application of recently developed nanoparticles has attracted much attention in the past few years. Although many studies have demonstrated the toxicology of nanoparticles in various species, only a small number of studies have examined the effect on a fetus after maternal exposure to nanoparticles. This is particularly important, because the developing fetus is especially vulnerable to the toxic effects of nanoparticles during fetal development due to the unique physical stage of the fetus. Nanoparticles may directly or indirectly impair fetal development and growth after maternal exposure to nanoparticles.

Central neurotoxicity induced by the instillation of ZnO and TiO2 nanoparticles through the taste nerve pathway

AIM

To explore whether nanoparticles (NPs) can be transported into the CNS via the taste nerve pathway.

MATERIALS & METHODS

ZnO and TiO₂ NPs were tongue-instilled to male Wistar rats. Toxicity was assessed by Zn/Ti biodistribution, histopathological examination, oxidative stress assay, quantitative reverse-transcriptase PCR analysis, learning and memory capabilities.

RESULTS

ZnO NPs and TiO₂ NPs significantly deposited in the nerves and brain, respectively. The histopathological examination indicated a slight injury in the cerebral cortex and hippocampus. Ultrastructural changes and an imbalanced oxidative stress were observed. The Morris water maze results showed that the learning and memory of rats were impaired.

CONCLUSION

NPs can enter the CNS via the taste nerve translocation pathway and induce a certain adverse effect.

Maternal exposure to nanosized titanium dioxide suppresses embryonic development in mice

Although nanoscale titanium dioxide (nano-TiO2) has been extensively used in industrial food applications and daily products for pregnant women, infants, and children, its potential toxicity on fetal development has been rarely studied. The main objective of this investigation was to establish the effects of maternal exposure of nano-TiO2 on developing embryos. Female imprinting control region mice were orally administered nano-TiO2 from gestational day 0 to 17. Our findings showed that Ti concentrations in maternal serum, placenta, and fetus were increased in nano-TiO2-exposed mice when compared to controls, which resulted in reductions in the contents of calcium and zinc in maternal serum, placenta, and fetus, maternal weight gain, placental weight, fetal weight, number of live fetuses, and fetal crown-rump length as well as cauda length, and caused an increase in the number of both dead fetuses and resorptions. Furthermore, maternal nano-TiO2 exposure inhibited development of the fetal skeleton, suggesting a significant absence of cartilage, reduced or absent ossification, and an increase in the number of fetuses with dysplasia, including exencephaly, spina bifida, coiled tail, scoliosis, rib absence, and sternum absence. These findings indicated that nano-TiO2 can cross the blood-fetal barrier and placental barrier, thereby delaying the development of fetal mice and inducing skeletal malformation. These factors may be associated with reductions in both calcium and zinc in maternal serum and the fetus, and both the placenta and embryos may be major targets of developmental toxicity following maternal exposure to nano-TiO2 during the prenatal period. Therefore, the application of nano-TiO2 should be carried out with caution.

Nanoparticles and female reproductive system: how do nanoparticles affect oogenesis and embryonic development

Along with the increasing application of nanoparticles (NPs) in many walks of life, environmental exposure to NPs has raised considerable health concerns. When NPs enter a pregnant woman’s body through inhalation, venous injection, ingestion or skin permeation, maternal toxic stress reactions such as reactive oxygen species (ROS), inflammation, apoptosis and endocrine dyscrasia are induced in different organs, particularly in the reproductive organs. Recent studies have shown that NPs disturb the developing oocyte by invading the protective barrier of theca cells, granulosa cell layers and zona pellucida. NPs disrupt sex hormone levels through the hypothalamic–pituitary-gonadal axis or by direct stimulation of secretory cells, such as granule cells, follicle cells, thecal cells and the corpus luteum. Some NPs can cross the placenta into the fetus by passive diffusion or endocytosis, which can trigger fetal inflammation, apoptosis, genotoxicity, cytotoxicity, low weight, reproductive deficiency, nervous damage, and immunodeficiency, among others. The toxicity of these NPs depend on their size, dosage, shape, charge, material and surface-coating. We summarize new findings on the toxic effect of various NPs on the ovary and on oogenesis and embryonic development. Meanwhile, we highlight the problems that need to be studied in the future. This manuscript will also provide valuable guidelines for protecting the female reproductive system from the toxicity of NPs and provide a certain reference value for NP application in the area of ovarian diseases.

Nanoparticulate TiO2 -mediated inhibition of the Wnt signaling pathway causes dendritic development disorder in cultured rat hippocampal neurons

Titanium dioxide nanoparticles (TiO₂ NPs) are increasingly used in daily life, in industry, and in environmental clearing, but their potential neurodevelopmental toxicity has been highly debated. In this study, we explored whether TiO₂ NPs inhibited development of dendritic morphology and identified possible molecular mechanisms associated with this inhibition in primary cultured rat hippocampal neurons. Results showed that TiO₂ NPs decreased neurite length, the number of branches and the spine density, and impaired mitochondrial function in the developing neurons. Furthermore, TiO₂ NPs significantly reduced the expression of several proteins involved in canonical Wnt3a/β-catenin signaling including Wnt3a, β-catenin, p-GSK-3β, and CyclinD1 and conversely, elevated GSK-3β expression. In addition to altering expression of proteins involved in canonical Wnt3a/β-catenin signaling, TiO₂ NPs decreased expression of proteins invovled in non-canonical Wnt signaling, including, MKLP1, CRMP3, ErbB4, and KIF17. Taken together, these results indicate that suppression of dendritic development caused by TiO₂ NPs is associated with inhibition of activation of the Wnt/β-catenin pathway or non-canonical Wnt pathway-induced expression of microtubule cytoskeletal components in the developing neurons. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 2139-2149, 2017.

Maternal exposure to titanium dioxide nanoparticles during pregnancy and lactation alters offspring hippocampal mRNA BAX and Bcl-2 levels, induces apoptosis and decreases neurogenesis

INTRODUCTION

The usage of Titanium dioxide nanoparticles (TiO₂-NPs) covers a vast area in different fields ranging from cosmetics and food to the production of drugs. Maternal exposure to TiO₂-NPs during developmental period has been associated with hippocampal injury and with a decrease in learning and memory status of the offspring. However, little is known about its injury mechanism. This paper describes the in vivo neurotoxic effects of TiO₂-NPs on rat offspring hippocampus during developmental period.

MATERIAL AND METHODS

Pregnant and lactating Wistar rats received intragastric TiO₂-NPs (100mg/kg body weight) daily from gestational day (GD) 2 to (GD) 21 and postnatal day (PD) 2 to (PD) 21 respectively. Animals in the control groups received an equal volume of distilled water via gavage. At the end of the treatment process, offspring were deeply anesthetized and sacrificed. Then brains of each group were collected and sections of the rat offspring's brains were stained using TUNEL staining (for detection of apoptotic cells) and immunostaining (for neurogenesis). Moreover, the right hippocampus (n=6 per each group) were removed from the right hemisphere for evaluating the expression of Bax and Bcl-2 level.

RESULTS

Results of histopatological examination by TUNEL staining showed that maternal exposure to TiO₂-NPs during pregnancy and lactation periods increased apoptotic cells significantly (P<0.01) in the offspring hippocampus. The immunolabeling of double cortin (DCX) protein as neurogenesis marker also showed that TiO₂-NPs reduced neurogenesis in the hippocampus of the offspring (P<0.05). Moreover, in comparison with the control group, the mRNA levels of Bax and Bcl-2 in the TiO₂-NPs group significantly increased and decreased, respectively (P<0.01).

CONCLUSION

These findings provide strong evidence that maternal exposure to TiO₂-NPs significantly impact hippocampal neurogenesis and apoptosis in the offspring. The potential impact of nanoparticle exposure for millions of pregnant mothers and their offspring across the world is potentially devastating.

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.

Health implications of engineered nanoparticles in infants and children

BACKGROUND

The nanotechnology boom and the ability to manufacture novel nanomaterials have led to increased production and use of engineered nanoparticles (ENPs). However, the increased use of various ENPs inevitably results in their release in or the contamination of the environment, which poses significant threats to human health. In recent years, extraordinary economic and societal benefits of nanoproducts as well as their potential risks have been observed and widely debated. To estimate whether ENPs are safe from the onset of their manufacturing to their disposal, evaluation of the toxicological effects of ENPs on human exposure, especially on more sensitive and vulnerable sectors of the population (infants and children) is essential.

DATA SOURCES

Papers were obtained from PubMed, Web of Science, and Google Scholar. Literature search words included: "nanoparticles", "infants", "children", "exposure", "toxicity", and all relevant cross-references.

RESULTS

A brief overview was conducted to 1) characterize potential exposure routes of ENPs for infants and children; 2) describe the vulnerability and particular needs of infants and children about ENPs exposure; 3) investigate the current knowledge about the potential health hazards of ENPs; and 4) provide suggestions for future research and regulations in ENP applications.

CONCLUSIONS

As the manufacturing and use of ENPs become more widespread, directed and focused studies are necessary to measure actual exposure levels and to determine adverse health consequences in infants and children.

Induction of size-dependent breakdown of blood-milk barrier in lactating mice by TiO2 nanoparticles

This study aims to investigate the potential nanotoxic effects of TiO₂ nanoparticles (TNPs) to dams and pups during lactation period. TiO₂ nanoparticles are accumulated in mammary glands of lactating mice after i.v. administration. This accumulation of TiO₂ NP likely causes a ROS-induced disruption of tight junction of the blood-milk barrier as indicated by the loss of tight junction proteins and the shedding of alveolar epithelial cells. Compared to larger TNPs (50 nm), smaller ones (8 nm) exhibit a higher accumulation in mammary glands and are more potent in causing perturbations to blood-milk barrier. An alarming finding is that the smaller TNPs (8 nm) are transferred from dams to pups through breastfeeding, likely through the disrupted blood-milk barrier. However, during the lactation period, the nutrient quality of milk from dams and the early developmental landmarks of the pups are not affected by above perturbations.

Effects of Nano-MnO2 on dopaminergic neurons and the spatial learning capability of rats

This study aimed to observe the effect of intracerebrally injected nano-MnO₂ on neurobehavior and the functions of dopaminergic neurons and astrocytes. Nano-MnO₂, 6-OHDA, and saline (control) were injected in the substantia nigra and the ventral tegmental area of Sprague-Dawley rat brains. The neurobehavior of rats was evaluated by Morris water maze test. Tyrosine hydroxylase (TH), inducible nitric oxide synthase (iNOS) and glial fibrillary acidic protein (GFAP) expressions in rat brain were detected by immunohistochemistry. Results showed that the escape latencies of nano-MnO₂ treated rat increased significantly compared with control. The number of TH-positive cells decreased, GFAP- and iNOS-positive cells increased significantly in the lesion side of the rat brains compared with the contralateral area in nano-MnO₂ group. The same tendencies were observed in nano-MnO₂-injected rat brains compared with control. However, in the the positive control, 6-OHDA group, escape latencies increased, TH-positive cell number decreased significantly compared with nano-MnO₂ group. The alteration of spatial learning abilities of rats induced by nano-MnO₂ may be associated with dopaminergic neuronal dysfunction and astrocyte activation.