Unraveling the neurotoxicity of titanium dioxide nanoparticles: focusing on molecular mechanisms

Development of nanomedicines for the treatment of Alzheimer's disease: Raison d'être, strategies, challenges and regulatory aspects

Alzheimer's disease (AD) is a chronic neurodegenerative disorder characterized by progressive loss of memory. Presently, AD is challenging to treat with current drug therapy as their delivery to the brain is restricted by the presence of the blood-brain barrier. Nanomedicines, due to their size, high surface volume ratio, and ease of tailoring drug release characteristics, showed their potential to treat AD. The nanotechnology-based formulations for brain targeting are expected to enter the market in the near future. So, regulatory frameworks are required to ensure the quality, safety, and effectiveness of the nanomedicines to treat AD. In this review, we discuss different strategies, in-vitro blood-brain permeation models, in-vivo permeation assessment, and regulatory aspects for the development of nanomedicine to treat AD.

Neurotoxic effects of heavy metal pollutants in the environment: Focusing on epigenetic mechanisms

The pollution of heavy metals (HMs) in the environment is a significant global environmental issue, characterized by its extensive distribution, severe contamination, and profound ecological impacts. Excessive exposure to heavy metal pollutants can damage the nervous system. However, the mechanisms underlying the neurotoxicity of most heavy metals are not completely understood. Epigenetics is defined as a heritable change in gene function that can influence gene and subsequent protein expression levels without altering the DNA sequence. Growing evidence indicates that heavy metals can induce neurotoxic effects by triggering epigenetic changes and disrupting the epigenome. Compared with genetic changes, epigenetic alterations are more easily reversible. Epigenetic reprogramming techniques, drugs, and certain nutrients targeting specific epigenetic mechanisms involved in gene expression regulation are emerging as potential preventive or therapeutic tools for diseases. Therefore, this review provides a comprehensive overview of epigenetic modifications encompassing DNA/RNA methylation, histone modifications, and non-coding RNAs in the nervous system, elucidating their association with various heavy metal exposures. These primarily include manganese (Mn), mercury (Hg), lead (Pb), cobalt (Co), cadmium (Cd), nickel (Ni), sliver (Ag), toxic metalloids arsenic (As), and etc. The potential epigenetic mechanisms in the etiology, precision prevention, and target therapy of various neurodevelopmental disorders or different neurodegenerative diseases are emphasized. In addition, the current gaps in research and future areas of study are discussed. From a perspective on epigenetics, this review offers novel insights for prevention and treatment of neurotoxicity induced by heavy metal pollutants.

Nanoparticles and neurodegeneration: Insights on multiple pathways of programmed cell death regulated by nanoparticles

Currently, nanoparticles (NPs) are extensively applied in the diagnosis and treatment of neurodegenerative diseases (NDs). With the rapid development and increasing exposure to the public, the potential neurotoxicity associated with NDs caused by NPs has attracted the researchers' attentions but their biosafety assessments are still far behind relevant application studies. Based on recent research, this review aims to conduct a comprehensive and systematic analysis of neurotoxicity induced by NPs. The 191 studies selected according to inclusion and exclusion criteria were imported into the software, and the co-citations and keywords of the included literatures were analyzed to find the breakthrough point of previous studies. According to the available studies, the routes of NPs entering into the normal and injured brain were various, and then to be distributed and accumulated in living bodies. When analyzing the adverse effects induced by NPs, we focused on multiple programmed cell deaths (PCDs), especially ferroptosis triggered by NPs and their tight connection and crosstalk that have been found playing critical roles in the pathogenesis of NDs and their underlying toxic mechanisms. The activation of multiple PCD pathways by NPs provides a scientific basis for the occurrence and development of NDs. Furthermore, the adoption of new methodologies for evaluating the biosafety of NPs would benefit the next generation risk assessment (NGRA) of NPs and their toxic interventions. This would help ensure their safe application and sustainable development in the field of medical neurobiology.

The use of nanoparticles in the treatment of infectious diseases and cancer, dental applications and tissue regeneration: a review

The emergence of nanotechnology as a field of study can be traced back to the 1980s, at which point the means to artificially produce, control, and observe matter on a nanometer level was made viable. Recent advancements in technology have enabled us to extend our reach to the nanoscale, which has presented an unparalleled opportunity to directly target biomolecular interactions. As a result of these developments, there is a drive to arise intelligent nanostructures capable of overcoming the obstacles that have impeded the progress of conventional pharmacological methodologies. After four decades, the gradual amalgamation of bio- and nanotechnologies is initiating a revolution in the realm of disease detection, treatment, and monitoring, as well as unsolved medical predicaments. Although a significant portion of research in the field is still confined to laboratories, the initial application of nanotechnology as treatments, vaccines, pharmaceuticals, and diagnostic equipment has now obtained endorsement for commercialization and clinical practice. The current issue presents an overview of the latest progress in nanomedical strategies towards alleviating antibiotic resistance, diagnosing and treating cancer, addressing neurodegenerative disorders, and an array of applications, encompassing dentistry and tuberculosis treatment. The current investigation also scrutinizes the deployment of sophisticated smart nanostructured materials in fields of application such as regenerative medicine, as well as the management of targeted and sustained release of pharmaceuticals and therapeutic interventions. The aforementioned concept exhibits the potential for revolutionary advancements within the field of immunotherapy, as it introduces the utilization of implanted vaccine technology to consistently regulate and augment immune functions. Concurrently with the endeavor to attain the advantages of nanomedical intervention, it is essential to enhance the unceasing emphasis on nanotoxicological research and the regulation of nanomedications' safety. This initiative is crucial in achieving the advancement in medicine that currently lies within our reach.

Multigenerational inheritance of breathing deficits following perinatal exposure to titanium dioxide nanoparticles in the offspring of mice

BACKGROUND

The utilization of titanium dioxide nanoparticles (TIO2NPs) has experienced a significant surge in recent decades, and these particles are now commonly found in various everyday consumer products. Due to their small size, TIO2NPs can penetrate biological barriers and elicit adverse interactions with biological tissues. Notably, exposure of pregnant females to TIO2NPs during the perinatal period has been shown to disrupt the growth of offspring. Furthermore, this exposure induces epigenetic modifications in the DNA of newborns, suggesting the possibility of multigenerational effects. Thus, perinatal exposure to TIO2NPs may induce immediate metabolic impairments in neonates, which could be transmitted to subsequent generations in the long term.

RESULTS

In this study, we utilized perinatal exposure of female mice to TIO2NPs through voluntary food intake and observed impaired metabolism in newborn male and female F1 offspring. The exposed newborn mice exhibited reduced body weight gain and a slower breathing rate compared to non-exposed animals. Additionally, a higher proportion of exposed F1 newborns experienced apneas. Similar observations were made when the exposure was limited to the postnatal period, highlighting lactation as a critical period for the adverse effects of TIO2NPs on postnatal metabolism. Importantly, the breathing deficits induced by TIO2NPs were transmitted from F1 females to the subsequent F2 generation. Moreover, re-exposure of adult F1 females to TIO2NPs exacerbated the breathing deficits in newborn F2 males.

CONCLUSIONS

Our findings demonstrate that perinatal exposure to TIO2NPs disrupts postnatal body weight gain and respiration in the offspring, and these deficits are transmissible to future generations.

Characterization of oxidative damage induced by nanoparticles via mechanism-driven machine learning approaches

The wide application of TiO₂-based engineered nanoparticles (nTiO₂) inevitably led to release into aquatic ecosystems. Importantly, increasing studies have emphasized the high risks of nTiO₂ to coastal environments. Bivalves, the representative benthic filter feeders in coastal zones, acted as important roles to assess and monitor the toxic effects of nanoparticles. Oxidative damage was one of the main toxic mechanisms of nTiO₂ on bivalves, but the experimental variables/nanomaterial characteristics were diverse and the toxicity mechanism was complex. Therefore, it was very necessary to develop machine learning model to characterize and predict the potential toxicity. In this study, thirty-six machine learning models were built by nanodescriptors combined with six machine learning algorithms. Among them, random forest (RF) - catalase (CAT), k-neighbors classifier (KNN) - glutathione peroxidase (GPx), neural networks - multilayer perceptron (ANN) - glutathione s-transferase (GST), random forest (RF) - malondialdehyde (MDA), random forest (RF) - reactive oxygen species (ROS), and extreme gradient boosting decision tree (XGB) - superoxide dismutase (SOD) models performed good with high accuracy and balanced accuracy for both training sets and external validation sets. Furthermore, the best model revealed the predominant factors (exposure concentration, exposure periods, and exposure matrix) influencing the oxidative stress induced by nTiO₂. These results showed that high exposure concentrations and short exposure-intervals tended to cause oxidative damage to bivalves. In addition, gills and digestive glands could be vulnerable to nTiO₂-induced oxidative damage as tissues/organs differences were the important factors controlling MDA activity. This study provided insights into important nano-features responsible for the different indicators of oxidative stress and thereby extended the application of machine learning approaches in toxicological assessment for nanoparticles.

A perspective on persistent toxicants in veterans and amyotrophic lateral sclerosis: identifying exposures determining higher ALS risk

Multiple studies indicate that United States veterans have an increased risk of developing amyotrophic lateral sclerosis (ALS) compared to civilians. However, the responsible etiological factors are unknown. In the general population, specific occupational (e.g. truck drivers, airline pilots) and environmental exposures (e.g. metals, pesticides) are associated with an increased ALS risk. As such, the increased prevalence of ALS in veterans strongly suggests that there are exposures experienced by military personnel that are disproportionate to civilians. During service, veterans may encounter numerous neurotoxic exposures (e.g. burn pits, engine exhaust, firing ranges). So far, however, there is a paucity of studies investigating environmental factors contributing to ALS in veterans and even fewer assessing their exposure using biomarkers. Herein, we discuss ALS pathogenesis in relation to a series of persistent neurotoxicants (often emitted as mixtures) including: chemical elements, nanoparticles and lipophilic toxicants such as dioxins, polycyclic aromatic hydrocarbons and polychlorinated biphenyls. We propose these toxicants should be directly measured in veteran central nervous system tissue, where they may have accumulated for decades. Specific toxicants (or mixtures thereof) may accelerate ALS development following a multistep hypothesis or act synergistically with other service-linked exposures (e.g. head trauma/concussions). Such possibilities could explain the lower age of onset observed in veterans compared to civilians. Identifying high-risk exposures within vulnerable populations is key to understanding ALS etiopathogenesis and is urgently needed to act upon modifiable risk factors for military personnel who deserve enhanced protection during their years of service, not only for their short-term, but also long-term health.

Nanoparticles in Combating Neuronal Dysregulated Signaling Pathways: Recent Approaches to the Nanoformulations of Phytochemicals and Synthetic Drugs Against Neurodegenerative Diseases

As the worldwide average life expectancy has grown, the prevalence of age-related neurodegenerative diseases (NDDs) has risen dramatically. A progressive loss of neuronal function characterizes NDDs, usually followed by neuronal death. Inflammation, apoptosis, oxidative stress, and protein misfolding are critical dysregulated signaling pathways that mainly orchestrate neuronal damage from a mechanistic point. Furthermore, in afflicted families with genetic anomalies, mutations and multiplications of α-synuclein and amyloid-related genes produce some kinds of NDDs. Overproduction of such proteins, and their excessive aggregation, have been proven in various models of neuronal malfunction and death. In this line, providing multi-target therapies carried by novel delivery systems would pave the road to control NDDs through simultaneous modulation of such dysregulated pathways. Phytochemicals are multi-target therapeutic agents, which employ several mechanisms towards neuroprotection. Besides, the blood-brain barrier (BBB) is a critical issue in managing NDDs since it inhibits the accessibility of drugs to the brain in sufficient concentration. Besides, discovering novel delivery systems is vital to improving the efficacy, bioavailability, and pharmacokinetic of therapeutic agents. Such novel formulations are also employed to improve the drug's biodistribution, allow for the co-delivery of several medicines, and offer targeted intracellular delivery against NDDs. The present review proposes nanoformulations of phytochemicals and synthetic agents to combat NDDs by modulating neuroinflammation, neuroapoptosis, neuronal oxidative stress pathways and protein misfolding.

TGF-β1/SMADs signaling involved in alleviating inflammation induced by nanoparticulate titanium dioxide in BV2 cells

There are increasing safety concerns accompanying the widespread use of nanoparticulate titanium dioxide (nano-TiO₂). It has been demonstrated that nano-TiO₂ can cross the blood-brain barrier and enter the brain, causing damage to the nervous system, consisting mainly of neuroinflammation and neuronal apoptosis. Several studies have linked the TGF-β1/SMADs signaling to the development of inflammatory response in various organs. However, no studies have connected the induction of microglial inflammation by nano-TiO₂ to this signaling. Therefore, this study aimed to investigate the role of TGF-β1/SMADs signaling in microglia inflammatory response induced by nano-TiO₂. The results showed that nano-TiO₂ increased the secretions of pro-inflammatory cytokines (IL-1α, IL-6, and TNF-α) and decreased the expressions of TGF-β1 and SMAD1/2/3 proteins in BV2 cells. When TGF-β1/SMADs signaling was inhibited, the inflammatory effect induced by nano-TiO₂ increased, suggesting a suppressive effect of this signaling on the inflammation. In addition, exogenous TGF-β1 upregulated the expressions of TGF-β1 and SMADs1/2/3 proteins as well as decreased the secretions of pro-inflammatory cytokines (IL-1α, IL-6, and TNF-α) compared to BV2 cells treated with only nano-TiO₂. Our results suggest that nano-TiO₂ may inhibit the TGF-β1/SMADs signaling by suppressing the intracellular secretion of active TGF-β1, leading to microglial activation and the induction or exacerbation of inflammatory responses.

Nanobiotechnological advancements in agriculture and food industry: Applications, nanotoxicity, and future perspectives

The high demand for sufficient and safe food, and continuous damage of environment by conventional agriculture are major challenges facing the globe. The necessity of smart alternatives and more sustainable practices in food production is crucial to confront the steady increase in human population and careless depletion of global resources. Nanotechnology implementation in agriculture offers smart delivery systems of nutrients, pesticides, and genetic materials for enhanced soil fertility and protection, along with improved traits for better stress tolerance. Additionally, nano-based sensors are the ideal approach towards precision farming for monitoring all factors that impact on agricultural productivity. Furthermore, nanotechnology can play a significant role in post-harvest food processing and packaging to reduce food contamination and wastage. In this review, nanotechnology applications in the agriculture and food sector are reviewed. Implementations of nanotechnology in agriculture have included nano- remediation of wastewater for land irrigation, nanofertilizers, nanopesticides, and nanosensors, while the beneficial effects of nanomaterials (NMs) in promoting genetic traits, germination, and stress tolerance of plants are discussed. Furthermore, the article highlights the efficiency of nanoparticles (NPs) and nanozymes in food processing and packaging. To this end, the potential risks and impacts of NMs on soil, plants, and human tissues and organs are emphasized in order to unravel the complex bio-nano interactions. Finally, the strengths, weaknesses, opportunities, and threats of nanotechnology are evaluated and discussed to provide a broad and clear view of the nanotechnology potentials, as well as future directions for nano-based agri-food applications towards sustainability.

Toxicity of Nanoparticles in Biomedical Application: Nanotoxicology

Nanoparticles are of great importance in development and research because of their application in industries and biomedicine. The development of nanoparticles requires proper knowledge of their fabrication, interaction, release, distribution, target, compatibility, and functions. This review presents a comprehensive update on nanoparticles' toxic effects, the factors underlying their toxicity, and the mechanisms by which toxicity is induced. Recent studies have found that nanoparticles may cause serious health effects when exposed to the body through ingestion, inhalation, and skin contact without caution. The extent to which toxicity is induced depends on some properties, including the nature and size of the nanoparticle, the surface area, shape, aspect ratio, surface coating, crystallinity, dissolution, and agglomeration. In all, the general mechanisms by which it causes toxicity lie on its capability to initiate the formation of reactive species, cytotoxicity, genotoxicity, and neurotoxicity, among others.

How can exposure to engineered nanomaterials influence our epigenetic code? A review of the mechanisms and molecular targets

Evidence suggests that engineered nanomaterials (ENM) can induce epigenetic modifications. In this review, we provide an overview of the epigenetic modulation of gene expression induced by ENM used in a variety of applications: titanium dioxide (TiO₂), silver (Ag), gold (Au), silica (SiO₂) nanoparticles and carbon-based nanomaterials (CNM). Exposure to these ENM can trigger alterations in cell patterns of DNA methylation, post-transcriptional histone modifications and expression of non-coding RNA. Such effects are dependent on ENM dose and physicochemical properties including size, shape and surface chemistry, as well as on the cell/organism sensitivity. The genes affected are mostly involved in the regulation of the epigenetic machinery itself, as well as in apoptosis, cell cycle, DNA repair and inflammation related pathways, whose long-term alterations might lead to the onset or progression of certain pathologies. In addition, some DNA methylation patterns may be retained as a form of epigenetic memory. Prenatal exposure to ENM may impair the normal development of the offspring by transplacental effects and/or putative transmission of epimutations in imprinting genes. Thus, understanding the impact of ENM on the epigenome is of paramount importance and epigenetic evaluation must be considered when assessing the risk of ENM to human health.

Emerging Nanotechnology for Treatment of Alzheimer's and Parkinson's Disease

The prevalence of the two most common neurodegenerative diseases, Parkinson's disease (PD) and Alzheimer's Disease (AD), are expected to rise alongside the progressive aging of society. Both PD and AD are classified as proteinopathies with misfolded proteins α-synuclein, amyloid-β, and tau. Emerging evidence suggests that these misfolded aggregates are prion-like proteins that induce pathological cell-to-cell spreading, which is a major driver in pathogenesis. Additional factors that can further affect pathology spreading include oxidative stress, mitochondrial damage, inflammation, and cell death. Nanomaterials present advantages over traditional chemical or biological therapeutic approaches at targeting these specific mechanisms. They can have intrinsic properties that lead to a decrease in oxidative stress or an ability to bind and disaggregate fibrils. Additionally, nanomaterials enhance transportation across the blood-brain barrier, are easily functionalized, increase drug half-lives, protect cargo from immune detection, and provide a physical structure that can support cell growth. This review highlights emergent nanomaterials with these advantages that target oxidative stress, the fibrillization process, inflammation, and aid in regenerative medicine for both PD and AD.

Nanoparticle delivery system, highly active antiretroviral therapy, and testicular morphology: The role of stereology

The conjugation of nanoparticles (NPs) with antiretroviral drugs is a drug delivery approach with great potential for managing HIV infections. Despite their promise, recent studies have highlighted the toxic effects of nanoparticles on testicular tissue and their impact on sperm morphology. This review explores the role of stereological techniques in assessing the testicular morphology in highly active antiretroviral therapy (HAART) when a nanoparticle drug delivery system is used. Also, NPs penetration and pharmacokinetics concerning the testicular tissue and blood-testis barrier form the vital part of this review. More so, various classes of NPs employed in biomedical and clinical research to deliver antiretroviral drugs were thoroughly discussed. In addition, considerations for minimizing nanoparticle-drugs toxicity, ensuring enhanced permeability of nanoparticles, maximizing drug efficacy, ensuring adequate bioavailability, and formulation of HAART-NPs fabrication are well discussed.

Linking emerging contaminants exposure to adverse health effects: Crosstalk between epigenome and environment

Environmental epigenetic findings shed new light on the roles of epigenetic regulations in environmental exposure-induced toxicities or disease susceptibilities. Currently, environmental emerging contaminants (ECs) are in focus for further investigation due to the evidence of human exposure in addition to their environmental occurrences. However, the adverse effects of these environmental ECs on health through epigenetic mechanisms are still poorly addressed in many aspects. This review discusses the epigenetic mechanisms (DNA methylation, histone modifications, and microRNA expressions) linking ECs exposure to health outcomes. We emphasized on the recent literature describing how ECs can dysregulate epigenetic mechanisms and lead to downstream health outcomes. These up-to-date research outputs could provide novel insights into the toxicological mechanisms of ECs. However, the field still faces a demand for further studies on the broad spectrum of health effects, synergistic/antagonistic effects, transgenerational epigenetic effects, and epidemiologic and demographic data of ECs.

Nec-1 Attenuates Neurotoxicity Induced by Titanium Dioxide Nanomaterials on Sh-Sy5y Cells Through RIP1

Titanium dioxide nanomaterials are applied in numerous fields due to their splendid physicochemical characteristics, which in turn poses a potential threat to human health. Recently, numerous in vivo studies have revealed that titanium dioxide nanoparticles (TNPs) can be transported into animal brains after exposure through various routes. Absorbed TNPs can accumulate in the brain and may disturb neuronal cells, leading to brain dysfunction. In vitro studies verified the neurotoxicity of TNPs. The mechanisms underlying the neurotoxicity of TNPs remains unclear. Whether necroptosis is involved in the neurotoxicity of TNPs is unknown. Therefore, we performed an in vitro study and found that TNPs induced inflammatory injury in SH-SY5Y cells in a dose-dependent way, which was mitigated by necrostatin-1 (Nec-1) pretreatment. Since receptor-interacting protein kinase 1 (RIP1) is reported to be the target of Nec-1, we silenced it by siRNA. We exposed mutant and wild-type cells to TNPs and assessed inflammatory injury. Silencing RIP1 expression inhibited inflammatory injury induced by TNPs exposure. Taken together, Nec-1 ameliorates the neurotoxicity of TNPs through RIP1. However, more studies should be performed to comprehensively assess the correlation between the neurotoxicity of TNPs and RIP1.

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.

Analyzing nanoparticle-induced neurotoxicity: A bibliometric analysis

BACKGROUND

In recent years, nanoparticles have been widely used in many fields, ranging from cosmetics, agriculture, environment, and biomedical areas. The increasing use of nanoproducts induces a potential increasing exposure to human body, and then, unknown pathological consequences could increase.

METHODS

The database was searched from 2008 to 2018 by the Web of Science Core Collection. The bibliometric methods, CiteSpace and HistCite, were used for analysis and visualization of the data.

RESULTS

The 2932 publications were analyzed and the annual publications grew from 78 to 512 in a decade. The United States and China mainly contribute to this research area, which accounted for 29.5% and 22.9%, respectively. PLoS One, Scientific Reports, and Nanoscale were the three journals that published the most articles. Keyword analysis indicated that the major research direction was the mechanisms of nanoneurotoxicity, which included oxidative stress, inflammation, astrocyte activation, and the fibrillation of amyloid β protein.

CONCLUSION

This bibliometric study revealed that nanoneurotoxicity was still a research hot topic and could be a promising area of research in the next few years. Nanoparticles play a role in neurodegenerative diseases by inducing reactive oxygen species production, inflammation, alterations of gene expression, and signal pathways.

Biphasic adverse effect of titanium nanoparticles on testicular function in mice

The male reproductive system is being recognized as toxic targets of nanoparticles including titanium dioxide nanoparticles (TiNP). Most of these reports are, however, obtained from the results of long-term exposure of TiNP. In this study, we diversely examined the acute effects of TiNP on the male reproductive system. Male C57BL/6J mice were administered a single intravenous injection of TiNP (10, 50 mg/kg), and were sacrificed at 1, 3, and 9 days post-injection. Testicular functions (estimated by sperm motility and sperm number) were measured via computer-assisted sperm analysis (CASA). Results indicated that sperm motility was significantly reduced from 1 day following TiNP injection (in both dose), and this reduction persisted up to 9 days post-TiNP injection (10 mg/kg injection group). Interestingly, we observed no significant decrease in sperm numbers in both the testis and the cauda epididymis in either treatment groups during the course of the experiment. Therefore, we hypothesized that TiNP may target the mature spermatozoa. In addition, sperm suspensions directly incubated with TiNP showed reduced sperm motility, [³H]-thymidine incorporation, and ATP level. Our results indicated that TiNP possesses “biphasic effects”; the obstacles to mature sperms (short term effect) in addition to the impairment in testis (long-term effect).

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.

The neurotoxicity induced by engineered nanomaterials

Engineered nanomaterials (ENMs) have been widely used in various fields due to their novel physicochemical properties. However, the use of ENMs has led to an increased exposure in humans, and the safety of ENMs has attracted much attention. It is universally acknowledged that ENMs could enter the human body via different routes, eg, inhalation, skin contact, and intravenous injection. Studies have proven that ENMs can cross or bypass the blood-brain barrier and then access the central nervous system and cause neurotoxicity. Until now, diverse in vivo and in vitro models have been developed to evaluate the neurotoxicity of ENMs, and oxidative stress, inflammation, DNA damage, and cell death have been identified as being involved. However, due to various physicochemical properties of ENMs and diverse study models in existing studies, it remains challenging to establish the structure-activity relationship of nanomaterials in neurotoxicity. In this paper, we aimed to review current studies on ENM-induced neurotoxicity, with an emphasis on the molecular and cellular mechanisms involved. We hope to provide a rational material design strategy for ENMs when they are applied in biomedical or other engineering applications.

Hepatic and Renal Toxicity Induced by TiO2 Nanoparticles in Rats: A Morphological and Metabonomic Study

Titanium dioxide (TiO₂) nanoparticles (NPs) are produced abundantly and are frequently used as a white pigment in the manufacture of paints, foods, paper, and toothpaste. Despite the wide ranges of uses, there is a lack of information on the impact of NPs on animal and human health. In the present study, rats were exposed to different doses of TiO₂ nanoparticles and sacrificed, respectively, 4 days, 1 month, and 2 months after treatment. Dosage of TiO₂ in tissues was performed by ICP-AES and revealed an important accumulation of TiO₂ in the liver. The nanoparticles induced morphological and physiological alterations in liver and kidney. In the liver, these alterations mainly affect the hepatocytes located around the centrilobular veins. These cells were the site of an oxidative stress evidenced by immunocytochemical detection of 4-hydroxynonenal (4-HNE). Kupffer cells are also the site of an important oxidative stress following the massive internalization of TiO₂ nanoparticles. Enzymatic markers of liver and kidney functions (such as AST and uric acid) are also disrupted only in animals exposed to highest doses. The metabonomic approach allowed us to detect modifications in urine samples already detectable after 4 days in animals treated at the lowest dose. This metabonomic pattern testifies an oxidative stress as well as renal and hepatic alterations.

Neurotoxicity of Nanomaterials: An Up-to-Date Overview

The field of nanotechnology, through which nanomaterials are designed, characterized, produced, and applied, is rapidly emerging in various fields, including energy, electronics, food and agriculture, environmental science, cosmetics, and medicine. The most common biomedical applications of nanomaterials involve drug delivery, bioimaging, and gene and cancer therapy. Since they possess unique properties which are different than bulk materials, toxic effects and long-term impacts on organisms are not completely known. Therefore, the purpose of this review is to emphasize the main neurotoxic effects induced by nanoparticles, liposomes, dendrimers, carbon nanotubes, and quantum dots, as well as the key neurotoxicology assays to evaluate them.

Impact of Nanoparticles on Brain Health: An Up to Date Overview

Nanoparticles are zero-dimensional nanomaterials and, based on their nature, they can be categorized into organic, inorganic, and composites nanoparticles. Due to their unique physical and chemical properties, nanoparticles are extensively used in a variety of fields, including medicine, pharmaceutics, and food industry. Although they have the potential to improve the diagnosis and treatment of brain diseases, it is fundamentally important to develop standardized toxicological studies, which can prevent the induction of neurotoxic effects. The focus of this review is to emphasize both the beneficial and negative effects of nanoparticles on brain health.

Morphological alterations induced by the exposure to TiO2 nanoparticles in primary cortical neuron cultures and in the brain of rats

Nowadays, nanoparticles (NPs) of titanium dioxide (TiO₂) are abundantly produced. TiO₂ NPs are present in various food products, in paints, cosmetics, sunscreens and toothpastes. However, the toxicity of TiO₂ NPs on the central nervous system has been poorly investigated until now. The aim of this study was to evaluate the toxicity of TiO₂ NPs on the central nervous system in vitro and in vivo. In cell cultures derived from embryonic cortical brain of rats, a significant decrease in neuroblasts was observed after 24 to 96 h of incubation with TiO₂ NPs (5 to 20 μg/ml). This phenomenon resulted from an inhibition of neuroblast proliferation and a concomitant increase in apoptosis. In the same time, a gliosis, characterized by an increase in proliferation of astrocytes and the hypertrophy of microglial cells, occurred. The phagocytosis of TiO₂ NPs by microgliocytes was also observed. In vivo, after intraperitoneal injection, the TiO₂ NPs reached the brain through the blood brain barrier and the nanoparticles promoted various histological injuries such as cellular lysis, neuronal apoptosis, and inflammation. A reduction of astrocyte population was observed in some brain area such as plexiform zone, cerebellum and subependymal area. An oxidative stress was also detected by immunohistochemistry in neurons of hippocampus, cerebellum and in subependymal area. In conclusion, our study demonstrated clearly the toxic impact of TiO₂ NPs on rat brain and neuronal cells and pointed about not yet referenced toxicity impacts of TiO2 such as the reduction of neuroblast proliferation both in vitro and in vivo.

Titanium dioxide nanoparticle stimulating pro-inflammatory responses in vitro and in vivo for inhibited cancer metastasis

AIMS

The interaction of engineered nanoparticles (NPs) with the immune system and the possibility of inflammation induction are of particularly interest. Titanium dioxide nanoparticles (TiO₂ NPs) are one of the most popular manufactured nanomaterials. In this study, we focused on the immune-modulatory effect of commercial P-25 TiO₂ NPs in vivo and in vitro and their crucial role in cancer metastasis.

MAIN METHODS

The female C57BL/6 mice were injected into abdominal cavity with PBS or P-25 TiO₂ to investigate the immune-modulatory function of P-25. And breast cancer cells were intravenously (i.v.) injected into mouse to establish the liver and lung cancer metastasis model. Peritoneal macrophage was used to investigate the macrophage polarization in vitro.

KEY FINDINGS

Results showed us that peritoneal macrophage exposed to P-25 TiO₂ NPs displayed activated M1 macrophage response, as evidenced by the increased mRNA expression of interleukin-1β (IL1β), IL6, TNFα, CCR7 and inducible nitric oxide synthase (iNOS). After exposure of TiO₂ NPs in vivo for 21 days, the body weights of mice decreased significantly, which were accompanied by an infiltration of immune cells in liver and spleen in 20 mg/kg BW treated group. Importantly, the production of pro-inflammatory cytokines in liver, spleen and the serum were amplified, which indicated the tissue and systemic inflammation induced by TiO₂ NPs. In addition, the activation of immune response induced by P-25 TiO₂ NPs was correlated with their ability to inhibit cancer metastasis.

SIGNIFICANCE

Our results delineated the stimulating pro-inflammatory response induced by P-25 TiO₂ NPs and their outcome in vivo for cancer metastasis.

High sensitivity of testicular function to titanium nanoparticles

Titanium dioxide nanoparticles (TiNPs) present toxicity in organs such as the liver, lung, and intestine. The testis has also been reported as a target organ of TiNPs. We recently reported that TiNPs had no genotoxic effect in the liver and bone marrow, while showing clear testicular dysfunction. In this paper, therefore, we systematically compared the sensitivity of hepatic function using biochemical markers and testicular function against TiNPs. Male C57BL/6J mice were injected intravenously with TiNPs (Aeroxide-P25, at doses of 0.1, 1, 2, and 10 mg/kg body weight) once per week for 4 consecutive weeks. Mice were sacrificed three days after the last injection. Body weights, liver weights, and testicular-related organ weights were not found to be changed by TiNP treatment. Moreover, TiNPs caused no hepatic damage, as evaluated by alanine aminotransferase and aspartate aminotransferase indexes. The testicular function, however, was clearly impaired by TiNP treatment; reduction in two sperm motion parameters (motile percent and progressive percent) and sperm numbers in cauda epididymides was seen. We observed Ti accumulation in the liver but not in the testis, as well as no change in plasma levels of sex hormones related to spermatogenesis. Our findings indicate that the testis is highly sensitive to TiNPs, as compared to the liver. We believe that, when considering the biological effects of TiNPs, testicular function (especially motility ability) may be a sensitive indicator.

Neurotoxic effect of active ingredients in sunscreen products, a contemporary review

Sunscreen application is the main strategy used to prevent the maladies inflicted by ultraviolet (UV) radiation. Despite the continuously increasing frequency of sunscreen use worldwide, the prevalence of certain sun exposure-related pathologies, mainly malignant melanoma, is also on the rise. In the past century, a variety of protective agents against UV exposure have been developed. Physical filters scatter and reflect UV rays and chemical filters absorb those rays. Alongside the evidence for increasing levels of these agents in the environment, which leads to indirect exposure of wildlife and humans, recent studies suggest a toxicological nature for some of these agents. Reviews on the role of these agents in developmental and endocrine impairments (both pathology and related mechanisms) are based on both animal and human studies, yet information regarding the potential neurotoxicity of these agents is scant. In this review, data regarding the neurotoxicity of several organic filters: octyl methoxycinnamate, benzophenone-3 and −4, 4-methylbenzylidene camphor, 3-benzylidene camphor and octocrylene, and two allowed inorganic filters: zinc oxide and titanium dioxide, is presented and discussed. Taken together, this review advocates revisiting the current safety and regulation of specific sunscreens and investing in alternative UV protection technologies.

The effect of titanium dioxide nanoparticles on neuroinflammation response in rat brain

Titanium dioxide nanoparticles (TiO₂ NPs) are widely used for their whiteness and opacity in several applications such as food colorants, drug additives, biomedical ceramic, and implanted biomaterials. Research on the neurobiological response to orally administered TiO₂ NPs is still limited. In our study, we investigate the effects of anatase TiO₂ NPs on the brain of Wistar rats after oral intake. After daily intragastric administration of anatase TiO₂ NPs (5-10 nm) at 0, 50, 100, and 200 mg/kg body weight (BW) for 60 days, the coefficient of the brain, acethylcholinesterase (AChE) activities, the level of interleukin 6 (IL-6), and the expression of glial fibrillary acidic protein (GFAP) were assessed to quantify the brain damage. The results showed that high-dose anatase TiO₂ NPs could induce a downregulated level of AChE activities and showed an increase in plasmatic IL-6 level as compared to the control group accompanied by a dose-dependent decrease inter-doses, associated to an increase in the cerebral IL-6 level as a response to a local inflammation in brain. Furthermore, we observed elevated levels of immunoreactivity to GFAP in rat cerebral cortex. We concluded that oral intake of anatase TiO₂ NPs can induce neuroinflammation and could be neurotoxic and hazardous to health.