Human Oral Exposure Research Articles

Human Oral Exposure to Nano- and Microplastics and Plastic Additives in Barcelona, Spain: a series of single-case studies

Human Oral Exposure to Nano- and Microplastics and Plastic Additives in Barcelona, Spain: a series of single-case studies

Physicochemical Transformations of Silver Nanoparticles in the Oro-Gastrointestinal Tract Mildly Affect Their Toxicity to Intestinal Cells In Vitro: An AOP-Oriented Testing Approach.

The widespread use of silver nanoparticles (Ag NPs) in food and consumer products suggests the relevance of human oral exposure to these nanomaterials (NMs) and raises the possibility of adverse effects in the gastrointestinal tract. The aim of this study was to investigate the toxicity of Ag NPs in a human intestinal cell line, either uncoated or coated with polyvinylpyrrolidone (Ag PVP) or hydroxyethylcellulose (Ag HEC) and digested in simulated gastrointestinal fluids. Physicochemical transformations of Ag NPs during the different stages of in vitro digestion were identified prior to toxicity assessment. The strategy for evaluating toxicity was constructed on the basis of adverse outcome pathways (AOPs) showing Ag NPs as stressors. It consisted of assessing Ag NP cytotoxicity, oxidative stress, genotoxicity, perturbation of the cell cycle and apoptosis. Ag NPs caused a concentration-dependent loss of cell viability and increased the intracellular level of reactive oxygen species as well as DNA damage and perturbation of the cell cycle. In vitro digestion of Ag NPs did not significantly modulate their toxicological impact, except for their genotoxicity. Taken together, these results indicate the potential toxicity of ingested Ag NPs, which varied depending on their coating but did not differ from that of non-digested NPs.

Microplastics in Widely Used Polypropylene-Made Food Containers.

As a potential threat to human health, ingestion of microplastics (MPs) has become of concern. Limited studies have carefully characterized the occurrence of MPs in polypropylene-made takeout food containers (TOFCs), which have been widely used in China. In this study, TOFC samples (n = 210) were collected from seven Chinese cities (Hangzhou, Guangzhou, Shanghai, Xining, Chengdu, Qingdao, and Dalian) and analyzed for MPs. All the TOFC samples contained MPs, with an abundance of 3−43 items/TOFC. The TOFCs from Chengdu (25 items/TOFC) contained the highest mean abundance of MPs, which is significantly (p < 0.01) higher than that from Shanghai (8.7 items/TOFC). Fiber accounted for 66−87% of the total for the shape of the MPs in the TOFCs from the different Chinese cities. Most of the MPs in the TOFCs from the different cities had a size of 201−500 μm and accounted for a mean 34−42% of the total MPs in the TOFCs. The major color type of the MPs in the TOFCs was transparent, accounting for a mean 39 (Qingdao)−73% (Hangzhou) of the total MPs. Polymer compositions of the MPs in the TOFCs were consistently dominated by polypropylene, which represented a mean 56−73% of the total MPs. The estimated daily intake of MPs for the general Chinese population through using TOFCs was in the range of 0.042−0.14 items/kg bw/day. To our knowledge, this is the most comprehensive study investigating the occurrence of MPs in TOFCs from China, which contributes to a better understanding of the sources of human oral exposure to MPs.

Toxicological Assessment of Cellulose Nanomaterials: Oral Exposure.

Cellulose nanomaterials (CNMs) have emerged recently as an important group of sustainable bio-based nanomaterials (NMs) with potential applications in multiple sectors, including the food, food packaging, and biomedical fields. The widening of these applications leads to increased human oral exposure to these NMs and, potentially, to adverse health outcomes. Presently, the potential hazards regarding oral exposure to CNMs are insufficiently characterised. There is a need to understand and manage the potential adverse effects that might result from the ingestion of CNMs before products using CNMs reach commercialisation. This work reviews the potential applications of CNMs in the food and biomedical sectors along with the existing toxicological in vitro and in vivo studies, while also identifying current knowledge gaps. Relevant considerations when performing toxicological studies following oral exposure to CNMs are highlighted. An increasing number of studies have been published in the last years, overall showing that ingested CNMs are not toxic to the gastrointestinal tract (GIT), suggestive of the biocompatibility of the majority of the tested CNMs. However, in vitro and in vivo genotoxicity studies, as well as long-term carcinogenic or reproductive toxicity studies, are not yet available. These studies are needed to support a wider use of CNMs in applications that can lead to human oral ingestion, thereby promoting a safe and sustainable-by-design approach.

Pro-inflammatory effects of silver nanoparticles in the intestine.

Nanotechnology is a promising technology of the twenty-first century, being a rapidly evolving field of research and industrial innovation widely applied in our everyday life. Silver nanoparticles (AgNP) are considered the most commercialized nanosystems worldwide, being applied in diverse sectors, from medicine to the food industry. Considering their unique physical, chemical and biological properties, AgNP have gained access into our daily life, with an exponential use in food industry, leading to an increased inevitable human oral exposure. With the growing use of AgNP, several concerns have been raised, in recent years, about their potential hazards to human health, more precisely their pro-inflammatory effects within the gastrointestinal system. Therefore a review of the literature has been undertaken to understand the pro-inflammatory potential of AgNP, after human oral exposure, in the intestine. Despite the paucity of information reported in the literature about this issue, existing studies indicate that AgNP exert a pro-inflammatory action, through generation of oxidative stress, accompanied by mitochondrial dysfunction, interference with transcription factors and production of cytokines. However, further studies are needed to elucidate the mechanistic pathways and molecular targets involved in the intestinal pro-inflammatory effects of AgNP.

Investigation of the genotoxicity of digested titanium dioxide nanomaterials in human intestinal cells

The widespread use of titanium dioxide nanomaterials (TiO2 NMs) in food and consumer products such as toothpaste or food contact materials, suggests the relevance of human oral exposure to these nanomaterials (NMs) and raises the possibility of adverse effects in the gastrointestinal tract (GIT).We previously showed that the in vitro digestion of TiO2 NMs may increase their toxicity in intestinal cells. In this work, we analyzed the genotoxicity and the intracellular reactive oxygen species induction by physiologically relevant concentrations of three different TiO2 NMs (NM-102, NM-103 and NM-105) in Caco-2 and HT29-MTX-E12 intestinal cells, while considering the potential influence of the digestion process in the NMs’ physiochemical characteristics. The results evidenced a DNA-damaging effect dependent on the NM, more relevant for the rutile/anatase NM-105, possibly due to its lower hydrodynamic size in the cells medium. In addition, the results of the micronucleus assay suggest effects on chromosomal integrity, an indicator of cancer risk, in the HT29-MTX-E12 cells, for all the tested TiO2 NMs, especially after the in vitro digestion. This work supports the evidence for concerns on the use of TiO2 NMs as a food additive, recently reported by EFSA, and for their use in applications in consumer products that may drive human exposure through ingestion.

In vitro toxicity evaluation of graphene oxide and reduced graphene oxide on Caco-2 cells

Graphene derivatives are expected to have a great impact in a wide range of applications, among them as food packaging materials. This is one of the sources of potential human oral exposure to them. However, studies devoted to investigating their putative toxic effects at the intestinal level are underrepresented in the scientific literature. Thus, this study aimed to investigate the in vitro toxicity of reduced graphene oxide (rGO) and graphene oxide (GO) in the human intestinal Caco-2 cell line. rGO and GO were firstly characterized and later, cell viability was assessed after exposure to 0–250 µg/mL rGO/GO for 24 and 48 h. Internalization was evidenced for both materials using transmission electron microscopy. A mean effective concentration (24 h) of 176.3 ± 7.6 µg/mL for cytotoxicity was obtained for rGO, whereas GO did not induce any change at the concentration range evaluated. However, both of them altered oxidative stress biomarkers, causing increased reactive oxygen species (ROS) and depletion of the glutathione content (GSH) after exposures up to 24 h. Further studies, particularly with rGO, are required to elucidate their toxicity profile in experimental models relevant for oral exposures.

Biosafety-inspired structural optimization of triazolium ionic liquids based on structure-toxicity relationships

Ionic liquids (ILs), owing to their low vapor pressure and excellent solvating ability, are being increasingly applied in various industries to replace highly toxic organic solvents. They mainly pollute aquatic environment and soils, directly endangering eco-environment and human health. Therefore, it is critical to understand and optimize structural motifs of ILs with reduced toxicity. Considering human oral exposure is the major route, our investigations employed a human cell panel (modeling oral exposures) including human stomach (GES-1), intestinal (FHC), liver (HepG2) and kidney (HEK293) cells using a series of experimental and computational approaches to explore the cytotoxicity and molecular mechanism of ILs. We discovered that the cytotoxicity of triazolium and imidazolium ILs was human cell line-dependent with cytotoxicity in an order of FHC > GES-1 > HepG2 > HEK293. For this reason, a toxicity assay using a single cell line was highly inappropriate. Compared to anions (Br-, OTs-, OTMBS-) we tested, the cation of ILs played a major role in causing cytotoxicity. Ionic liquids with cations having longer hydrophobic sidechains (IL09 vs. IL01) readily insert into cell membranes with enhanced membrane and lipidomic perturbations, induce cytotoxicity by triggering cell cycle arrest and apoptosis. Reducing sidechain length and incorporating three nitrogen atoms (triazolium) instead of two (imidazolium) in the cation core alleviated cytotoxicity by reducing cell membrane perturbations and cell function interference. These findings provide important guiding principles for the design of the next-generation of “green” and safe ILs.

Using chemical structure information to develop predictive models for in vitro toxicokinetic parameters to inform high-throughput risk-assessment

The toxicokinetic (TK) parameters fraction of the chemical unbound to plasma proteins and metabolic clearance are critical for relating exposure and internal dose when building in vitro-based risk assessment models. However, experimental toxicokinetic studies have only been carried out on limited chemicals of environmental interest (~1000 chemicals with TK data relative to tens of thousands of chemicals of interest). This work evaluated the utility of chemical structure information to predict TK parameters in silico; development of cluster-based read-across and quantitative structure–activity relationship models of fraction unbound or fub (regression) and intrinsic clearance or Clint (classification and regression) using a dataset of 1487 chemicals; utilization of predicted TK parameters to estimate uncertainty in steady-state plasma concentration (Css); and subsequent in vitro–in vivo extrapolation analyses to derive bioactivity-exposure ratio (BER) plot to compare human oral equivalent doses and exposure predictions using androgen and estrogen receptor activity data for 233 chemicals as an example dataset. The results demonstrate that fub is structurally more predictable than Clint. The model with the highest observed performance for fub had an external test set RMSE/σ = 0.61 and R2 = 0.57, for Clint classification had an external test set accuracy = 73.2%, and for intrinsic clearance regression had an external test set RMSE/σ = 0.92 and R2 = 0.16. This relatively low performance is in part due to the large uncertainty in the underlying Clint data. We show that Css is relatively insensitive to uncertainty in Clint. The models were benchmarked against the ADMET Predictor software. Finally, the BER analysis allowed identification of 14 out of 136 chemicals for further risk assessment demonstrating the utility of these models in aiding risk-based chemical prioritization.

Long-term simulation of lead concentrations in agricultural soils in relation to human adverse health effects

Lead (Pb) exposure of consumers and the environment has been reduced over the past decades. Despite all measures taken, immission of Pb onto agricultural soils still occurs, with fertilizer application, lead shot from hunting activities, and Pb from air deposition representing major sources. Little is known about the intermediate and long-term consequences of these emissions. To gain more insight, we established a mathematical model that considers input from fertilizer, ammunition, deposition from air, uptake of Pb by crops, and wash-out to simulate the resulting Pb concentrations in soil over extended periods. In a further step, human oral exposure by crop-based food was simulated and blood concentrations were derived to estimate the margin of exposure to Pb-induced toxic effects. Simulating current farming scenarios, a new equilibrium concentration of Pb in soil would be established after several centuries. Developmental neurotoxicity represents the most critical toxicological effect of Pb for humans. According to our model, a Pb concentration of ~ 5 mg/kg in agricultural soil leads to an intake of approximately 10 µg Pb per person per day by the consumption of agricultural products, the dose corresponding to the tolerable daily intake (TDI). Therefore, 5 mg Pb/kg represents a critical concentration in soil that should not be exceeded. Starting with a soil concentration of 0.1 mg/kg, the current control level for crop fields, our simulation predicts periods of ~ 50 and ~ 175 years for two Pb immission scenarios for mass of Pb per area and year [scenario 1: ~ 400 g Pb/(ha × a); scenario 2: ~ 175 g Pb/(ha × a)], until the critical concentration of ~ 5 mg/kg Pb in soil would be reached. The two scenarios, which differ in their Pb input via fertilizer, represent relatively high but not unrealistic Pb immissions. From these scenarios, we calculated that the annual deposition of Pb onto soil should remain below ~ 100 g/(ha × a) in order not to exceed the critical soil level of 5 mg/kg. We propose as efficient measures to reduce Pb input into agricultural soil to lower the Pb content of compost and to use alternatives to Pb ammunition for hunting.

Establishing a macrophage model with relevance for oral methacrylate monomer exposures: Attenuated Staphylococcus aureus-induced cytokine release from human macrophages

BackgroundLeakage of unpolymerized methacrylate monomers after placement of methacrylate-containing polymeric dental materials leads to human exposure. Based on studies using murine macrophages and LPS from Escherichia coli (E. coli), dental monomers like 2-hydroxyethyl methacrylate (HEMA) are known to inhibit lipopolysaccharide (LPS) induced cytokine release. The aim of this study was to establish a model system with relevance for human oral monomer exposure using exposure to live gram-positive bacteria, and to confirm the HEMA-induced effects on cytokine release in this model. MethodsThe human THP-1 monocyte cell line was differentiated to macrophages using phorbol 12-myristate 13-acetate (PMA), before exposure to 0.5–2mM HEMA and live Staphylococcus aureus (S. aureus) in various multiplicity of infections (MOI). Cytokine release and cytotoxicity were determined after (i) 2–24h pre-exposure to HEMA followed by 2–4h S. aureus exposure and (ii) 2–4h simultaneous exposure. The 24h pre-exposure regime was also tested in primary human airway macrophages and for phagocytosis of S. aureus in THP-1 macrophages. ResultsHEMA attenuated the cytokine release more strongly in the pre-exposure than combined exposure regime, with a maximal reduction of 95% in the S. aureus-induced cytokine release. A MOI of 0.1 (corresponding to a bacteria-macrophage ratio of 1:10) was determined to be optimal in the THP-1 macrophages as it induced sufficient cytokine release and negligible cytotoxicity. Attenuated release of S. aureus-induced interleukin (IL)-1β after HEMA exposure was confirmed in primary airway macrophages, while HEMA increased the phagocytosis of S. aureus in THP-1 cells. ConclusionThe model was successfully established and attenuated bacteria-induced cytokine release after HEMA exposure confirmed.

Effect of Perinatal Exposure to Low Dose Bisphenol A on Hepatic and Renal Tissues of Male Albino Rat Offspring: Histological, Immunohistochemical and Morphometric Studies

Introduction: Bisphenol A (BPA) is one of the environmental endocrine disrupting chemicals with worldwide human oral exposure. Guideline studies established a no observed adverse effect level (NOAEL) at 5 mg/kg body weight /day. Aim of The Work: to assess the hazards of oral maternal intake to low dose of BPA below NOAEL during pregnancy and lactation, on hepatic and renal tissues of male albino rat offspring through histological, immunohistochemical and morphometric studies. Material and Methods: Thirty pregnant albino rats were equally divided into three groups; group A did not receive any treatment, group B received 1mL corn oil orally once daily by gastric tube, group C received 200 μg/kg bw /day of BPA (dissolved in 1mL corn oil) by gastric tube once daily from 6th day of gestation until weaning. Forty male rat pups from each group were subdivided into four subgroups according to the age of sacrifice (1st, 3rd, 6th and 9th) postnatal weeks (PW). After weaning, treatment was stopped. Livers and kidneys' specimens were collected and prepared for histological, immunohistochemical, morphometric studies and statistical analysis. Results: Multiple histological degenerative changes in the hepatic and renal tissues of male albino rat offspring were observed after oral administration of low dose BPA to their mothers. These changes were obvious at 1st PW and progressed to become massive and extensive at 3rd and 6th PW then became less severe at 9th PW in spite of the cessation of BPA treatment at weaning. These results were confirmed by immunohistochemical and statistical studies. Conclusion: Perinatal maternal intake to low dose of BPA below the dose of NOAEL, induced histopathological changes in livers and kidneys of male albino rat offspring. These changes may be considered as indicator for possibility of neoplastic liability.

In vitro intestinal toxicity of copper oxide nanoparticles in rat and human cell models

Human oral exposure to copper oxide nanoparticles (NPs) may occur following ingestion, hand-to-mouth activity, or mucociliary transport following inhalation. This study assessed the cytotoxicity of Cupric (II) oxide (CuO) and Cu2O-polyvinylpyrrolidone (PVP) coated NPs and copper ions in rat (intestine epithelial cells; IEC-6) and human intestinal cells, two- and three-dimensional models, respectively. The effect of pretreatment of CuO NPs with simulated gastrointestinal (GI) fluids on IEC-6 cell cytotoxicity was also investigated. Both dose- and time-dependent decreases in viability of rat and human cells with CuO and Cu2O-PVP NPs and Cu2+ ions was observed. In the rat cells, CuO NPs had greater cytotoxicity. The rat cells were also more sensitive to CuO NPs than the human cells. Concentrations of H2O2 and glutathione increased and decreased, respectively, in IEC-6 cells after a 4-h exposure to CuO NPs, suggesting the formation of reactive oxygen species (ROS). These ROS may have damaged the mitochondrial membrane of the IEC-6 cells causing a depolarization, as a dose-related loss of a fluorescent mitochondrial marker was observed following a 4-h exposure to CuO NPs. Dissolution studies showed that Cu2O-PVP NPs formed soluble Cu whereas CuO NPs essentially remained intact. For GI fluid-treated CuO NPs, there was a slight increase in cytotoxicity at low doses relative to non-treated NPs. In summary, copper oxide NPs were cytotoxic to rat and human intestinal cells in a dose- and time-dependent manner. The data suggests Cu2O-PVP NPs are toxic due to their dissolution to Cu ions, whereas CuO NPs have inherent cytotoxicity, without dissolving to form Cu ions.

Oral exposure to low dose bisphenol A aggravates allergic airway inflammation in mice.

Bisphenol A (BPA) is widely used in many consumer products and has adverse effects on human health including allergic diseases. We investigated the effects of low dose BPA, comparable to actual human oral exposure, on allergic asthma in mice. C3H/HeJ male mice were fed a chow diet containing BPA (equivalent to 0.09, 0.90, or 9.01 μg/kg/day) and were intratracheally administered ovalbumin (OVA, 1 μg/animal) every two weeks from 5-11 weeks of age. All doses of BPA plus OVA enhanced pulmonary inflammation and airway hyperresponsiveness, and increased lung mRNA levels of Th2 cytokine/chemokine, and serum OVA-specific IgE and IgG1 compared to OVA alone, with greater effects observed in the middle- and high-dose BPA plus OVA groups. Furthermore, high-dose BPA with OVA decreased lung mRNA levels of ERβ and AR compared with OVA. Furthermore, BPA enhanced OVA-restimulated cell proliferation and protein levels of IL-4 and IL-5 in mediastinal lymph node (MLN) cells in OVA-sensitized mice. In bone marrow (BM) cells, middle-dose BPA with OVA increased Gr-1 expression. In conclusion, oral exposure to low-dose BPA at levels equivalent to human exposure can aggravate allergic asthmatic responses through enhancement of Th2-skewed responses, lung hormone receptor downregulation, and MLN and BM microenvironment change.

Investigation of the in vitro genotoxicity of two rutile TiO2 nanomaterials in human intestinal and hepatic cells and evaluation of their interference with toxicity assays

TiO2 nanomaterials (NM) have a wide range of industrial applications, including their use in food products. The incorporation of these NMs in consumer products represents a clear concern for public health safety agencies and consumers, and further investigation of the potential impact of these products on human health is necessary. Indeed, since human oral exposure to TiO2 NMs is expected to increase in the years to come, there exist legitimate concerns about the risk assessment of these nanomaterials present in food products. A considerable amount of studies investigating the adverse effects of TiO2 NMs have focused on the genotoxic effects of these NMs, and more recently they have been classified by the International Agency for Research on Cancer (IARC) as carcinogen group 2B following inhalation studies (IARC, 2010). While numerous data are available for anatase or mixes of anatase/rutile forms, the toxicity and the genotoxicity of rutile TiO2 NMs have been rarely investigated. The aim of our study was therefore to investigate the cytotoxic and genotoxic effects of two rutile TiO2 NMs, differing in surface coating, NM103 (hydrophobic) and NM104 (hydrophilic), on intestinal and hepatic cell models. Following 3 or 24 h treatments with concentrations of TiO2 NMs from 1.2 to 80 μg/cm2, we have assessed the genotoxicity of these NMs with γH2AX, alkaline comet assay and micronucleus (MN) assays. Cellular viability and effects on oxidative stress were also evaluated. Although TEM imaging demonstrated the presence of the two TiO2 NMs within the cytoplasm, no significant cytotoxic or genotoxic were observed in either cell model. We have also evaluated and taken into account a variety of potential sources of interference of NMs with cellular assays. TiO2 NMs present in the cytoplasm introduce uncertainty in the scoring of micronuclei, and therefore this assay is not recommended for the evaluation of the genotoxicity of TiO2 NMs, or other NMs demonstrating similar interference. The unique properties of TiO2 NMs introduce additional complexity for genotoxicity testing, and caution must be taken in order to obtain reliable results necessary for accurate hazard assessment.

In vitro and in vivo genotoxicity of nano aluminum, aluminum oxide and aluminum chloride: A comparative study

Volume 280, Supplement 1, Pages S1-S346 (20 October 2017) Abstracts of the 53rd Congress of the European Societies of Toxicology (EUROTOX)Bratislava, Slovakia, 10th–13th September, 2017 Edited by Mumtaz Iscan and Helena Kandarova P-03-02-16 Aluminum on different forms is found in several goods: food addi- tives, medication, beverage, water treatment as well as cooking utensils. EFSA has established a tolerable weekly intake (TWI) of 1 mg/kg bw for human oral exposure (EFSA, 2008). Since the 2000s, due to the increasing use of nanoparticles (NP), aluminum NPs are expected to be more largely involved in human exposure although their effects on human health has not been fully characterized. Nevertheless, aluminum was depicted to cross epithelial barriers and to include neurotoxicity and embryotoxic- ity. As aluminum NPs may not behave as Al ions, their toxic effects must be investigated. In this study, we investigated the genotoxicity of Al, Al 2 O 3 NPs and the ionic form AlCl 3 on intestine, the contact organ fol- lowing oral exposure, and on liver, the main target organ for Al accumulation using both the alkaline comet assay and the Fpg- modified comet assay for highlighting potential oxidative damage. We observed DNA damage on the human intestinal Caco2 and hepatic HepaRG cells (exposure from 0.6 to 256 g/cm 2 ). How- ever, no genotoxicity was detected in duodenum and liver of male Sprague Dawley rats after 3 gavages as well as after 28 days oral treatment with 6, 12 and 25 mg/kg bw/day. This project was funded by Agence Nationale de la Recherche (ANR-13-IS10-0005-01).

Health-based ingestion exposure guidelines for Vibrio cholerae: Technical basis for water reuse applications

U.S. military and allied contingency operations are increasingly occurring in locations with limited, unstable or compromised fresh water supplies. Non-potable graywater reuse is currently under assessment as a viable means to increase mission sustainability while significantly reducing the resources, logistics and attack vulnerabilities posed by transport of fresh water. Development of health-based (non-potable) exposure guidelines for the potential microbial components of graywater would provide a logical and consistent human-health basis for water reuse strategies. Such health-based strategies will support not only improved water security for contingency operations, but also sustainable military operations.Dose-response assessment of Vibrio cholerae based on adult human oral exposure data were coupled with operational water exposure scenario parameters common to numerous military activities, and then used to derive health risk-based water concentrations. The microbial risk assessment approach utilized oral human exposure V. cholerae dose studies in open literature. Selected studies focused on gastrointestinal illness associated with experimental infection by specific V. cholerae serogroups most often associated with epidemics and pandemics (O1 and O139). Nonlinear dose-response model analyses estimated V. cholerae effective doses (EDs) aligned with gastrointestinal illness severity categories characterized by diarrheal purge volume. The EDs and water exposure assumptions were used to derive Risk-Based Water Concentrations (CFU/100mL) for mission-critical illness severity levels over a range of water use activities common to military operations.Human dose-response studies, data and analyses indicate that ingestion exposures at the estimated ED1 (50CFU) are unlikely to be associated with diarrheal illness while ingestion exposures at the lower limit (200CFU) of the estimated ED10 are not expected to result in a level of diarrheal illness associated with degraded individual capability. The current analysis indicates that the estimated ED20 (approximately 1000CFU) represents initiation of a more advanced stage of diarrheal illness associated with clinical care.

The aflatoxin B1‐fumonisin B1 toxicity in BRL‐3A hepatocytes is associated to induction of cytochrome P450 activity and arachidonic acid metabolism

Human oral exposure to aflatoxin B1 (AFB1 ) and fumonisin B1 (FB1 ) is associated with increased hepatocellular carcinoma. Although evidence suggested interactive AFB1 -FB1 hepatotoxicity, the underlying mechanisms remain mostly unidentified. This work was aimed at evaluating the possible AFB1 -FB1 interplay to induce genetic and cell cycle toxicities in BRL-3A rat hepatocytes, reactive oxygen species (ROS) involvement, and the AFB1 metabolizing pathways cytochrome P450 (CYP) and arachidonic acid (ArAc) metabolism as ROS contributors. Flow cytometry of stained BRL-3A hepatocytes was used to study the cell cycle (propidium iodide), ROS intracellular production (DCFH-DA, HE, DAF-2 DA), and phospholipase A activity (staining with bis-BODIPY FL C11-PC). The CYP1A activity was assessed by the 7-ethoxyresorufin-O-deethylase (EROD) assay. Despite a 48-h exposure to FB1 (30μM) not being genotoxic, the AFB1 (20μM)-induced micronucleus frequency was overcome by the AFB1 -FB1 mixture (MIX), presumably showing toxin interaction. The mycotoxins blocked G1/S-phase, but only MIX caused cell death. Overall, the oxidative stress led these alterations as the pretreatment with N-acetyl-l-cysteine reduced such toxic effects. While AFB1 had a major input to the MIX pro-oxidant activity, with CYP and ArAc metabolism being ROS contributors, these pathways were not involved in the FB1 -elicited weak oxidative stress. The MIX-induced micronucleus frequency in N-acetyl-l-cysteine pretreated cells was greater than that caused by AFB1 without antioxidants, suggesting enhanced AFB1 direct genotoxicity probably owing to the higher CYP activity and ArAc metabolism found in MIX. The metabolic pathways modulation by AFB1 -FB1 mixtures could raise its hepatocarcinogenic properties.

Oral uptake of nanoparticles: human relevance and the role of in vitro systems.

Nanoparticles (NPs) present in environment, consumer and health products, food and medical applications lead to a high degree of human exposure and concerns about potential adverse effects on human health. For the general population, the exposure through contact with the skin, inhalation and oral uptake are most relevant. Since in vivo testing is only partly able to study the effects of human oral exposure, physiologically relevant in vitro systems are being developed. This review compared the three routes taking into account the estimated concentration, size of the exposed area, morphology of the involved barrier and translocation rate. The high amounts of NPs in food, the large absorption area and the relatively high translocation rate identified oral uptake as most important portal of entry for NPs into the body. Changes of NP properties in the physiological fluids, mechanisms to cross mucus and epithelial barrier, and important issues in the use of laboratory animals for oral exposure are mentioned. The ability of in vitro models to address the varying conditions along the oro-gastrointestinal tract is discussed, and requirements for physiologically relevant in vitro testing of orally ingested NPs are listed.

Toxicity Evaluation of Bisphenol A Administered by Gavage to Sprague Dawley Rats From Gestation Day 6 Through Postnatal Day 90

Bisphenol A (BPA) is a high production volume industrial chemical to which there is widespread human oral exposure. Guideline studies used to set regulatory limits detected adverse effects only at doses well above human exposures and established a no-observed-adverse-effect level (NOAEL) of 5 mg/kg body weight (bw)/day. However, many reported animal studies link BPA to potentially adverse effects on multiple organ systems at doses below the NOAEL. The primary goals of the subchronic study reported here were to identify adverse effects induced by orally (gavage) administered BPA below the NOAEL, to characterize the dose response for such effects and to determine doses for a subsequent chronic study. Sprague Dawley rat dams were dosed daily from gestation day 6 until the start of labor, and their pups were directly dosed from day 1 after birth to termination. The primary focus was on seven equally spaced BPA doses (2.5-2700 μg/kg bw/day). Also included were a naïve control, two doses of ethinyl estradiol (EE2) to demonstrate the estrogen responsiveness of the animal model, and two high BPA doses (100,000 and 300,000 μg/kg bw/day) expected from guideline studies to produce adverse effects. Clear adverse effects of BPA, including depressed gestational and postnatal body weight gain, effects on the ovary (increased cystic follicles, depleted corpora lutea, and antral follicles), and serum hormones (increased serum estradiol and prolactin and decreased progesterone), were observed only at the two high doses of BPA. BPA-induced effects partially overlapped those induced by EE2, consistent with the known weak estrogenic activity of BPA.