Growing knowledge: using stem cells to study developmental neurotoxicity

Altered Offspring Immunity in Maternal Parasitic Infections

Maternal infection during pregnancy is known to alter the development and function of offspring's immune system, leading to inappropriate immune responses to common childhood infections and immunizations. Although this is an expanding field, maternal parasitic infections remain understudied. Millions of women of reproductive age are currently at risk for parasitic infection, whereas many pregnant, chronically infected women are excluded from mass drug administration due partially to a lack of resources, as well as fear of unknown adverse fetal developmental outcomes. In areas endemic for multiple parasitic infections, such as sub-Saharan Africa, there are increased rates of morbidity and mortality for various infections during early childhood in comparison with nonendemic areas. Despite evidence supporting similar immunomodulatory effects between various parasite species, there is no clear mechanistic understanding of how maternal infection reprograms offspring immunity. This brief review will compare the effects of selected maternal parasitic infections on offspring immunity.

Machine learning to predict developmental neurotoxicity with high-throughput data from 2D bio-engineered tissues

There is a growing need for fast and accurate methods for testing developmental neurotoxicity across several chemical exposure sources. Current approaches, such as in vivo animal studies, and assays of animal and human primary cell cultures, suffer from challenges related to time, cost, and applicability to human physiology. Prior work has demonstrated success employing machine learning to predict developmental neurotoxicity using gene expression data collected from human 3D tissue models exposed to various compounds. The 3D model is biologically similar to developing neural structures, but its complexity necessitates extensive expertise and effort to employ. By instead focusing solely on constructing an assay of developmental neurotoxicity, we propose that a simpler 2D tissue model may prove sufficient. We thus compare the accuracy of predictive models trained on data from a 2D tissue model with those trained on data from a 3D tissue model, and find the 2D model to be substantially more accurate. Furthermore, we find the 2D model to be more robust under stringent gene set selection, whereas the 3D model suffers substantial accuracy degradation. While both approaches have advantages and disadvantages, we propose that our described 2D approach could be a valuable tool for decision makers when prioritizing neurotoxicity screening.

Mitochondrial Stress Response in Neural Stem Cells Exposed to Electronic Cigarettes

Stem cells provide a sensitive model to study exposure to toxicants, such as cigarette smoke. Electronic cigarettes (ECs) are popular nicotine delivery devices, often targeted to youth and pregnant mothers. However, little is known about how chemicals in ECs might affect neural stem cells, and in particular their mitochondria, organelles that maintain cell functionality and health. Here we show that the mechanism underlying EC-induced stem cell toxicity is stress-induced mitochondrial hyperfusion (SIMH), a transient survival response accompanied by increased mitochondrial oxidative stress. We identify SIMH as a survival response to nicotine, now widely available in EC refill fluids and in pure form for do-it-yourself EC products. These observed mitochondrial alterations combined with autophagy dysfunction to clear damaged mitochondria could lead to faulty stem cell populations, accelerate cellular aging, and lead to acquired mitochondriopathies. Any nicotine-containing product may likewise stress stem cells with long-term repercussions for users and passively exposed individuals. VIDEO ABSTRACT.

Diesel, children and respiratory disease

Air pollution generated in urban areas is a global public health burden since half of the world's population live in either cities, megacities or periurban areas. Its direct effects include initiating and exacerbating disease, with indirect effects on health mediated via climate change putting the basic needs of water, air and food at risk.

Placental Nitrosative Stress and Exposure to Ambient Air Pollution During Gestation: A Population Study

The placenta plays a crucial role in fetal growth and development through adaptive responses to perturbations of the maternal environment. We investigated the association between placental 3-nitrotyrosine (3-NTp), a biomarker of oxidative stress, and exposure to air pollutants during various time windows of pregnancy. We measured the placental 3-NTp levels of 330 mother-newborn pairs enrolled in the Environmental Influence on Ageing in Early Life (ENVIRONAGE) Study, a Belgian birth cohort study (2010-2013). Daily concentrations of particulate matter with an aerodynamic diameter ≤2.5 µm (PM2.5), black carbon (BC), and nitrogen dioxide were interpolated for each mother's residence using a spatiotemporal interpolation method. Placental 3-NTp levels, adjusted for covariates, increased by 35.0% (95% confidence interval (CI): 13.9, 60.0) for each interquartile-range increment in entire-pregnancy PM2.5 exposure. The corresponding estimate for BC exposure was 13.9% (95% CI: -0.21, 29.9). These results were driven by the first (PM2.5: 29.0% (95% CI: 4.9, 58.6); BC: 23.6% (95% CI: 4.4, 46.4)) and second (PM2.5: 39.3% (95% CI: 12.3, 72.7)) gestational exposure windows. This link between placental nitrosative stress and exposure to fine particle air pollution during gestation is in line with experimental evidence on cigarette smoke and diesel exhaust exposure. Further research is needed to elucidate potential health consequences experienced later in life through particle-mediated nitrosative stress incurred during fetal life.

Traffic-related air pollution and brain development

Automotive traffic-related air pollution (TRP) imposes an increasing health burden with global urbanization. Gestational and early child exposure to urban TRP is associated with higher risk of autism spectrum disorders and schizophrenia, as well as low birth weight. While cardio-respiratory effects from exposure are well documented, cognitive effects are only recently becoming widely recognized. This review discusses effects of TRP on brain and cognition in human and animal studies. The mechanisms underlying these epidemiological associations are studied with rodent models of pre- and neonatal exposure to TRP, which show persisting inflammatory changes and altered adult behaviors and cognition. Some behavioral and inflammatory changes show male bias. Rodent models may identify dietary and other interventions for neuroprotection to TRP.

Environmental toxicity and poor cognitive outcomes in children and adults

Extensive literature has already documented the deleterious effects of heavy metal toxins on the human brain and nervous system. These toxins, however, represent only a fraction of the environmental hazards that may pose harm to cognitive ability in humans. Lead and mercury exposure, air pollution, and organic compounds all have the potential to damage brain functioning yet remain understudied. In order to provide comprehensive and effective public health and health care initiatives for prevention and treatment, we must first fully understand the potential risks, mechanisms of action, and outcomes surrounding exposure to these elements in the context of neurocognitive ability. This article provides a review of the negative effects on cognitive ability of these lesser-studied environmental toxins, with an emphasis on delineating effects observed in child versus adult populations. Possible differential effects across sociodemographic populations (e.g., urban versus rural residents; ethnic minorities) are discussed as important contributors to risk assessment and the development of prevention measures. The public health and clinical implications are significant and offer ample opportunities for clinicians and researchers to help combat this growing problem.

Increased accumulation of magnetic nanoparticles by magnetizable implant materials for the treatment of implant-associated complications

Background

In orthopaedic surgery, accumulation of agents such as anti-infectives in the bone as target tissue is difficult. The use of magnetic nanoparticles (MNPs) as carriers principally enables their accumulation via an externally applied magnetic field. Magnetizable implants are principally able to increase the strength of an externally applied magnetic field to reach also deep-seated parts in the body. Therefore, the integration of bone-addressed therapeutics in MNPs and their accumulation at a magnetic orthopaedic implant could improve the treatment of implant related infections. In this study a martensitic steel platelet as implant placeholder was used to examine its accumulation and retention capacity of MNPs in an in vitro experimental set up considering different experimental frame conditions as magnet quantity and distance to each other, implant thickness and flow velocity.

Results

The magnetic field strength increased to approximately 112% when a martensitic stainless steel platelet was located between the magnet poles. Therewith a significantly higher amount of magnetic nanoparticles could be accumulated in the area of the platelet compared to the sole magnetic field. During flushing of the tube system mimicking the in vivo blood flow, the magnetized platelet was able to retain a higher amount of MNPs without an external magnetic field compared to the set up with no mounted platelet during flushing of the system. Generally, a higher flow velocity led to lower amounts of accumulated MNPs. A higher quantity of magnets and a lower distance between magnets led to a higher magnetic field strength. Albeit not significantly the magnetic field strength tended to increase with thicker platelets.

Conclusion

A martensitic steel platelet significantly improved the attachment of magnetic nanoparticles in an in vitro flow system and therewith indicates the potential of magnetic implant materials in orthopaedic surgery. The use of a remanent magnetic implant material could improve the efficiency of capturing MNPs especially when the external magnetic field is turned off thus facilitating and prolonging the effect. In this way higher drug levels in the target area might be attained resulting in lower inconveniences for the patient.

Biodistribution and toxicity of pegylated single wall carbon nanotubes in pregnant mice

BACKGROUND

Single wall carbon nanotubes (SWCNTs) are considered promising nanoparticles for industrial and biomedical applications; however their potential toxicity in several biological systems, including the feto-placental unit, has been demonstrated. Functionalization of SWCNTs with polyethylene glycol chains (PEG-SWCNTs) dramatically reduces their toxicity, and for this reason PEG-SWCNTs are candidates for biomedical applications. However, no data are available on their safety for the developing embryo, in spite of the clinical and social relevance of this topic. The purpose of this study is therefore to investigate the safety of PEG-SWCNTs for their use as biomedical carriers in pregnancy.

METHODS

For toxicological studies, amino-functionalized PEG-SWCNT were intravenously injected in CD1 pregnant mice at different doses (range 0.1-30 μg/mouse), in single or multiple administrations. For biodistribution studies, fluorescently labeled PEG-SWCNTs were obtained by acylation of terminal PEG amino groups with near infrared emitting fluorochromes (PEG-SWCNT-750) and injected at the dosage of 10 μg/mouse, at either day 5.5 (when the placenta is still developing) or day 14.5 of gestation (when the maturation of the placenta is complete).

RESULTS

We found no adverse effects both on embryos and dams up to the dose of 10 μg/mouse. At the dose of 30 μg/mouse, occasional teratogenic effects, associated with placental damage, were detected both when administered as a single bolus (1 out of 10 dams; 1 malformed embryo) or as multiple doses (2 out of 10 dams; 5 malformed embryos). The difference in the prevalence of dams with malformed embryos between the 30 μg exposed group and controls approached the statistical significance (p = 0.06). Hepatic damage in dams was seen only in the multiple exposure group (4 out of 10; p = 0.04 when compared with the single exposure group or controls). PEG-SWCNT-750 reached the conceptus when administered early in pregnancy. At later stages, PEG-SWCNT-750 were detected in the placenta and the yolk sac, but not in the embryo.

CONCLUSIONS

PEG-SWCNTs may cause occasional teratogenic effects in mice beyond a threshold dose. Such effect might depend on their ability to reach the feto-placenta unit. Although not automatically transferable to humans, these data should be considered if exposing women during pregnancy.

Titanium dioxide nanoparticles: a review of current toxicological data

Titanium dioxide (TiO2) nanoparticles (NPs) are manufactured worldwide in large quantities for use in a wide range of applications. TiO2 NPs possess different physicochemical properties compared to their fine particle (FP) analogs, which might alter their bioactivity. Most of the literature cited here has focused on the respiratory system, showing the importance of inhalation as the primary route for TiO2 NP exposure in the workplace. TiO2 NPs may translocate to systemic organs from the lung and gastrointestinal tract (GIT) although the rate of translocation appears low. There have also been studies focusing on other potential routes of human exposure. Oral exposure mainly occurs through food products containing TiO2 NP-additives. Most dermal exposure studies, whether in vivo or in vitro, report that TiO2 NPs do not penetrate the stratum corneum (SC). In the field of nanomedicine, intravenous injection can deliver TiO2 nanoparticulate carriers directly into the human body. Upon intravenous exposure, TiO2 NPs can induce pathological lesions of the liver, spleen, kidneys, and brain. We have also shown here that most of these effects may be due to the use of very high doses of TiO2 NPs. There is also an enormous lack of epidemiological data regarding TiO2 NPs in spite of its increased production and use. However, long-term inhalation studies in rats have reported lung tumors. This review summarizes the current knowledge on the toxicology of TiO2 NPs and points out areas where further information is needed.

Human pluripotent stem cells in pharmacological and toxicological screening: new perspectives for personalized medicine

Human stem cells provide an important novel tool for generating in vitro pharmacological and toxicological test systems. In the development of new targeted therapies, as well as in critical safety issues, including hepato-, neuro- and cardio-toxicity, animal-based tests are mostly unsatisfactory, whereas the use of in vitro model systems is limited by the unavailability of relevant human tissues. Human embryonic stem cell lines may fill this gap and offer an advantage over primary cultures as well as tissue-derived (adult) stem cells. Human embryonic stem cells represent an unlimited source for the production of differentiated somatic progenies and allow various stable genetic manipulations. As a new opening in personalized medicine test systems, the generation of induced pluripotent stem cell lines and their derivatives can provide patient- and disease-specific cellular assays for drug development and safety assessments. This article reviews promising human stem cell applications in pharmacological and toxicological screenings, focusing on the implications for personalized medicine.