An Assessment of the Oral and Inhalation Acute Toxicity of Nickel Oxide Nanoparticles in Rats
Nickel oxide nanoparticles (NiO NPs) have been the focus of many toxicity studies. However, acute toxicity studies that identify toxicological dose descriptors, such as an LC50 or LD50, are lacking. In this paper, the acute toxicity of NiO NPs was evaluated in albino-derived Sprague-Dawley rats through OECD guideline studies conducted by both the oral and inhalation routes of exposure. The animals were assessed for mortality, body weight, behavioral observations, and gross necropsy. Results from previously conducted (unpublished) acute inhalation studies with larger NiO microparticles (MPs) are also included for comparison. Mortality, the primary endpoint in acute toxicity studies, was not observed for rats exposed to NiO NPs via either the oral or inhalation exposure routes, with a determined LD50 of >5000 mg/kg and an LC50 > 5.42 mg/L, respectively. Our results suggest that these NiO NPs do not exhibit serious acute toxicity in rats or warrant an acute toxicity classification under the current GHS classification criteria. This aligns with similar results for NiO MPs from this and previously published studies.
The Chemistry and Health Outcomes of Electronic Waste (E-Waste) Leachate: Exposure to E-Waste Is Toxic to Atlantic Killifish (Fundulus heteroclitus) Embryos
Although there is rising global concern over the environmental, ecological, and human health risks associated with the discharge of leachates from e-waste dumpsites into the aquatic ecosystems, little is known in this research area. Thus, for this study, we first defined the chemistry of the test leachate, followed by assessment of the leachate on the development of a model aquatic organism (Fundulus heteroclitus) used extensively as a bioassay organism in pollution studies. Chemical analyses revealed that levels of phosphate (20.03 mg/L), cadmium (Cd) (0.4 mg/L), lead (Pb) (0.2 mg/L), and chromium (Cr) (0.4 mg/L) were higher than the 2009 US EPA and the 2009 National Environmental Standards and Regulations Enforcement Agency (NESREA) permissible limits. Polycyclic aromatic hydrocarbon (PAH) burdens were dominated mainly by the high molecular weight congeners, specifically the âˆ‘4rings (73 µg/L). Total polychlorinated biphenyls (PCB) levels ranged from 0.00 to 0.40 µg/L with the âˆ‘deca PCBs reaching the highest concentration. For the biological studies, F. heteroclitus embryos (48-h post-fertilization) were divided randomly into groups and exposed to one of six e-waste leachate concentrations (10, 1, 0.1, 0.01, 0.001, 0.0001%). Significant differences (p â‰¤ 0.05) between treated and control groups were observed in standard and total length, and head size. Further analysis using Duncan"™s post-hoc test of multiple comparison also revealed specific differences within and between specific treatment groups. We conclude that e-waste leachate arising from indiscriminate dumping into aquatic ecosystems in Nigeria contains mixtures of toxic constituents that can threaten ecosystem and public health.
E-Cigarette Exposure During Fetal Development Alters Protein Transporters and Gene Expression Activity in Neural Pathways Associated With Obesity in Mice [Meeting Abstract]
Electronic cigarettes (E-cigs), battery-powered devices containing vegetable glycerin and propylene glycol (PG/VG) as humectants, along with nicotine and flavors, are the most commonly used nicotine product amongst adolescents and young adults. Despite the lack of safety data, pregnant cigarette smokers are also turning to e-cigs as a 'safer' smoking alternative. This study hypothesized that like cigarette smoking, maternal vaping during pregnancy increases the risk of childhood obesity in the offspring. Thus, C57BL/6 mice were exposed both prenatally (3h/d; 5d/wk for ~3-wk) and postnatally from PND 4-21 to e-cig aerosols (50:50 PG/VG) with and without nicotine (16 mg/mL) and alterations in transcriptional and inflammatory activity in hypothalamic metabolic pathways associated with obesity were investigated. At 1-mo-of-age, offspring from filtered air (FA) control and both treatment groups were sacrificed, the hypothalami collected and expression of transporters associated with obesity (i.e., Glucose 1,2,3,4, PPARgamma, and Leptin) analyzed by Western blot. Results here demonstrated a significant increase in glucose transporter 1-4 expression in both the PG/VG alone and PG/VG plus nicotine treatment groups compared to control levels. In addition, gene expression of PPARgamma, LepRb, MC4R, SLC2A1 were significantly increased (p<0.01) in these same 1-moold offspring compared to matched FA controls. Alternatively, no significant changes in AMPK and POMC expression was observed between and amongst treatment groups. These findings suggest that like traditional cigarettes, early life exposure to vaping aerosols (with and without nicotine) predispose the young offspring to obesity later in life via e-cig-induced alterations in the neural-obesity pathways
Toxicologic evaluation of a novel, highly soluble biotin salt, magnesium biotinate
A novel, highly soluble biotin salt, magnesium biotinate (MgB), was assessed for general and genetic toxicity using several toxicologic tests. This battery of tests included in vitro bacterial reverse mutation test, in vitro mammalian micronucleus assay, and oral acute, 14-day, and 90-day repeat-dose toxicity in Sprague-Dawley (SD) rats. The results of the in vitro studies indicate that MgB is not mutagenic, clastogenic, or aneugenic. The acute oral toxicity study established an LD50 â‰¥ 5000 mg MgB/kg. In the 14-day oral toxicity study, doses of MgB up to 2500 mg MgB/kg/day produced no clinical signs or mortality. In the 90-day oral toxicity study, administration of 600 mg MgB/kg/day resulted in no clinical signs and was determined to be the no-observed-adverse-effect-level (NOAEL), which equates to 39 g biotin/day for a 70 kg human. Since MgB is composed of 93% biotin, the 600 mg NOAEL equates to approximately 1.3 million times the current recommended daily allowance of 30 Î¼g biotin/day and 3,900 times supplement levels of 10 mg biotin/day. Based on the toxicologic profile and lack of findings in various in vitro and in vivo studies, MgB may be considered safe for long-term human use.
Prenatal Exposure to Electronic-Cigarette Aerosols Leads to Sex-Dependent Pulmonary Extracellular-Matrix Remodeling and Myogenesis in Offspring Mice
Electronic-cigarette (e-cig) vaping is a serious concern, as many pregnant women who vape consider it safe. However, little is known about the harmful effects of prenatal e-cig exposure on adult offspring, especially on extracellular-matrix (ECM) deposition and myogenesis in the lungs of offspring. We evaluated the biochemical and molecular implications of maternal exposure during pregnancy to e-cig aerosols on the adult offspring of both sexes, with a particular focus on pulmonary ECM remodeling and myogenesis. Pregnant CD-1 mice were exposed to e-cig aerosols with or without nicotine, throughout gestation, and lungs were collected from adult male and female offspring. Compared with the air-exposed control group, female mice exposed to e-cig aerosols, with or without nicotine, demonstrated increased lung protein abundance of LEF-1 (lymphoid enhancer-binding factor 1), fibronectin, and E-cadherin, whereas altered E-cadherin and PPARÎ³ (peroxisome proliferator-activated receptor Î³) levels were observed only in males exposed to e-cig aerosols with nicotine. Moreover, lipogenic and myogenic mRNAs were dysregulated in adult offspring in a sex-dependent manner. PAI-1 (plasminogen activator inhibitor-1), one of the ECM regulators, was significantly increased in females exposed prenatally to e-cig aerosols with nicotine and in males exposed to e-cig aerosols compared with control animals exposed to air. MMP9 (matrix metalloproteinase 9), a downstream target of PAI-1, was downregulated in both sexes exposed to e-cig aerosols with nicotine. No differences in lung histology were observed among any of the treatment groups. Overall, adult mice exposed prenatally to e-cig aerosols could be predisposed to developing pulmonary disease later in life. Thus, these findings suggest that vaping during pregnancy is unsafe and increases the propensity for later-life interstitial lung diseases.
Prenatal Exposure to Gutkha, a Globally Relevant Smokeless Tobacco Product, Induces Hepatic Changes in Adult Mice
Maternal exposures during pregnancy affect the onset and progression of adult diseases in the offspring. A prior mouse study indicated that maternal tobacco smoke exposure affects hepatic fibrosis in adult offspring. Gutkha, a broadly used smokeless tobacco (ST) product, is widely used by pregnant woman in many countries. The objective of this murine study was to evaluate whether oral maternal exposure to gutkha during pregnancy alters non-alcoholic fatty liver disease (NAFLD) in adult offspring: risk factors for the progression of NAFLD to cirrhosis in adults remain elusive. Buccal cavity 'painting' of pregnant mice with gutkha began on gestational days (GD) 2-4 and continued until parturition. Beginning at 12 weeks of age, a subset of offspring were transitioned to a high-fat diet (HFD). Results demonstrated that prenatal exposure to gutkha followed by an HFD in adulthood significantly increased the histologic evidence of fatty liver disease only in adult male offspring. Changes in hepatic fibrosis-related cytokines (interleukin (IL)-1b and IL-6) and in hepatic collagen mRNA expression were observed when comparing adult male offspring exposed to gutkha in utero to those not exposed. These findings indicate that maternal use of gutkha during pregnancy affects NAFLD in adult offspring in a sex-dependent manner.
Neuroinflammatory and Behavioral Outcomes Measured in Adult Offspring of Mice Exposed Prenatally to E-Cigarette Aerosols
BACKGROUND:In an effort to decrease the rates of smoking conventional tobacco cigarettes, electronic cigarettes (e-cigarettes) have been proposed as an effective smoking cessation tool. However, little is known about their toxicological impacts. This is concerning given that e-cigarette use is perceived as less harmful than conventional tobacco cigarettes during pregnancy for both the mother and fetus. OBJECTIVE:The goal of this study was to test the neurodevelopmental consequences of maternal e-cigarette use on adult offspring behavior and neuroimmune outcomes. METHODS: RESULTS: DISCUSSION/CONCLUSIONS:These findings support previous adverse findings of e-cigarette exposure on neurodevelopment in a mouse model and provide substantial evidence of persistent adverse behavioral and neuroimmunological consequences to adult offspring following maternal e-cigarette exposure during pregnancy. https://doi.org/10.1289/EHP6067.
Differential gene expression analysis in mouse placentae reveals association between preterm birth linked genes and PM2.5 exposure [Meeting Abstract]
Numerous epidemiological and animal studies have demonstrated that exposure to ambient fine particulate matter (<2.5mum in diameter [PM2.5]) during gestation is associated with adverse obstetric outcomes including preterm birth (PTB). Early delivery has been linked to several lifetime health consequences for offspring, including behavioral and psychological abnormalities and reduced immune and respiratory functions. In a previous study performed in this laboratory, B6C3F1 pregnant mice exposed to concentrated ambient PM (CAPs) by inhalation, demonstrated shortened (by 0.4 d) gestational duration compared to filtered air (FA) controls. The mechanisms underlying the association between PM2.5 and PTB are not currently well understood. Since the placenta provides a crucial link between the intrauterine environment and fetal growth/development, it is a major target of PM and key for studying the effects on birth outcomes. Therefore, in this study, placentae from the previously developed pregnant mouse model (n=6 each from CAPs and FA groups) were subjected to whole transcriptomic profiling by RNAseq. A bioinformatic RNAseq analysis workflow (tximport, Salmon and edgeR /limmavoom) was used to identify differentially expressed genes between treatment groups. The 648 genes from the curated dbPTB (database Preterm Birth) were used for a candidate gene approach and were examined using gene counts obtained from RNAseq. Following PM2.5 exposure, six PTB genes were downregulated in placentae (Ace, Ddah1, Col1a2, Chst15, Akap12, Ephx1) and one was upregulated (Chys3) (p<0.01). Gene Ontology demonstrated that these seven genes are involved in neutrophil-mediated immunity, arterial blood pressure regulation, amino acid binding, cell membrane function, metal ion binding, and aromatic compound catabolism among other functions that could be linked to PTB. Additional computational models, agnostically testing placenta transcriptome-wide differential gene expression, revealed additional genes that were differentially expressed between the two treatment groups. These findings suggest that PM exposure influences the placenta genome thereby mediating PTB. Identification of these differentially expressed genes may contribute to intervention strategies to mitigate these adverse effects
Enhanced cerebellar myelination with concomitant iron elevation and ultrastructural irregularities following prenatal exposure to ambient particulate matter in the mouse
Accumulating evidence indicates the developing central nervous system (CNS) is a target of air pollution toxicity. Epidemiological reports increasingly demonstrate that exposure to the particulate matter (PM) fraction of air pollution during neurodevelopment is associated with an increased risk of neurodevelopmental disorders (NDDs) such as autism spectrum disorder (ASD). These observations are supported by animal studies demonstrating prenatal exposure to concentrated ambient PM induces neuropathologies characteristic of ASD, including ventriculomegaly and aberrant corpus callosum (CC) myelination. Given the role of the CC and cerebellum in ASD etiology, this study tested whether prenatal exposure to concentrated ambient particles (CAPs) produced pathological features in offspring CC and cerebella consistent with ASD. Analysis of cerebellar myelin density revealed male-specific hypermyelination in CAPs-exposed offspring at postnatal days (PNDs) 11-15 without alteration of cerebellar area. Atomic absorption spectroscopy (AAS) revealed elevated iron (Fe) in the cerebellum of CAPs-exposed female offspring at PNDs 11-15, which connects with previously observed elevated Fe in the female CC. The presence of Fe inclusions, along with aluminum (Al) and silicon (Si) inclusions, were confirmed at nanoscale resolution in the CC along with ultrastructural myelin sheath damage. Furthermore, RNAseq and gene ontology (GO) enrichment analyses revealed cerebellar gene expression was significantly affected by sex and prenatal CAPs exposure with significant enrichment in inflammation and transmembrane transport processes that could underlie observed myelin and metal pathologies. Overall, this study highlights the ability of PM exposure to disrupt myelinogenesis and elucidates novel molecular targets of PM-induced developmental neurotoxicity.
An In Vitro Versus In Vivo Toxicogenomic Investigation of Prenatal Exposures to Tobacco Smoke
Approximately 1 million women smoke during pregnancy despite evidence demonstrating serious juvenile and/or adult diseases being linked to early-life exposure to cigarette smoke. Susceptibility could be determined by factors in previous generations, that is, prenatal or "maternal" exposures to toxins. Prenatal exposure to airborne pollutants such as mainstream cigarette smoke has been shown to induce early-life insults (i.e., gene changes) in Offspring that serve as biomarkers for disease later in life. In this investigation, we have evaluated genome-wide changes in the lungs of mouse Dams and their juvenile Offspring exposed prenatally to mainstream cigarette smoke. An additional lung model was tested alongside the murine model, as a means to find an alternative in vitro, human tissue-based replacement for the use of animals in medical research. Our toxicogenomic and bio-informatic results indicated that in utero exposure altered the genetic patterns of the fetus, which could put them at greater risk for developing a range of chronic illnesses in later life. The genes altered in the in vitro, cell culture model were reflected in the murine model of prenatal exposure to mainstream cigarette smoke. The use of alternative in vitro models derived from human medical waste tissues could be viable options to achieve human endpoint data and conduct research that meets the remits for scientists to undertake the 3Rs practices.