Nuoya Yin

Graphene oxide induces toll-like receptor 4 (TLR4)-dependent necrosis in macrophages.

Graphene and graphene-based nanomaterials display novel and beneficial chemical, electrical, mechanical, and optical characteristics, which endow these nanomaterials with promising applications in a wide spectrum of areas such as electronics and biomedicine. However, its toxicity on health remains unknown and is of great concern. In the present study, we demonstrated that graphene oxide (GO) induced necrotic cell death to macrophages. This toxicity is mediated by activation of toll-like receptor 4 (TLR4) signaling and subsequently in part via autocrine TNF-α production. Inhibition of TLR4 signaling with a selective inhibitor prevented cell death nearly completely. Furthermore, TLR4-deficient bone marrow-derived macrophages were resistant to GO-triggered necrosis. Similarly, GO did not induce necrosis of HEK293T/TLR4-null cells. Macrophagic cell death upon GO treatment was partially attributed to RIP1-RIP3 complex-mediated programmed necrosis downstream of TNF-α induction. Additionally, upon uptake into macrophages, GO accumulated primarily in cytoplasm causing dramatic morphologic alterations and a significant reduction of the macrophagic ability in phagocytosis. However, macrophagic uptake of GO may not be required for induction of necrosis. GO exposure also caused a large increase of intracellular reactive oxygen species (ROS), which contributed to the cause of cell death. The combined data reveal that interaction of GO with TLR4 is the predominant molecular mechanism underlying GO-induced macrophagic necrosis; also, cytoskeletal damage and oxidative stress contribute to decreased viability and function of macrophages upon GO treatment.

Silver Nanoparticle Exposure Attenuates the Viability of Rat Cerebellum Granule Cells through Apoptosis Coupled to Oxidative Stress

The impact of silver nanoparticles (AgNPs) on the central nervous system is a topic with mounting interest and concern and the facts remain elusive. In the current study, the neurotoxicity of commercial AgNPs to rat cerebellum granule cells (CGCs) and the corresponding molecular mechanism are closely investigated. It is demonstrated that AgNPs induce significant cellular toxicity to CGCs in a dose-dependent manner without damaging the cell membrane. Flow cytometry analysis with the Annexin V/propidium iodide (PI) staining indicates that the apoptotic proportion of CGCs upon treatment with AgNPs is greatly increased compared to the negative control. Moreover, the activity of caspase-3 is largely elevated in AgNP-treated cells compared to the negative control. AgNPs are demonstrated to induce oxidative stress, reflected by the massive generation of reactive oxygen species (ROS), the depletion of antioxidant glutathione (GSH), and the increase of intracellular calcium. Histological examination suggests that AgNPs provoke destruction of the cerebellum granular layer in rats with concomitant activation of caspase-3, in parallel to the neurotoxicity of AgNPs observed in vitro. Taken together, it is demonstrated for the first time that AgNPs substantially impair the survival of primary neuronal cells through apoptosis coupled to oxidative stress, depending on the caspase activation-mediated signaling.

Silver nanoparticles induced neurotoxicity through oxidative stress in rat cerebral astrocytes is distinct from the effects of silver ions

The rapid development of silver nanoparticles (AgNPs) based products has raised increasing concerns in view of their potential hazardous risks to the environment and human health. The roles of the released silver ions in AgNPs induced cytotoxicities are being hotly debated. Using rat cerebral astrocytes, the neurotoxicological effects of AgNPs and silver ions were investigated. Acute toxicity based on Alamar Blue assay showed that silver ions were considerably more toxic than AgNPs. Comparative studies indicated that AgNPs increased caspase activities and induced cell apoptosis under cytotoxic level of exposures, while silver ions compromised cell membrane integrity and dominantly caused cell necrosis. Cellular internalization of silver provided the basis for the cytotoxicities of these two silver species. In contrast to silver ions, intracellular reactive oxygen species (ROS) generation occurred in time- and concentration-dependent manners in astrocytes upon AgNPs stimulation, which caused subsequent c-Jun N-terminal kinases (JNK) phosphorylation and promoted the programmed cell death. Non-cytotoxic level of AgNPs exposure increased multiple cytokines secretion from the astrocytes, indicating that AgNPs were potentially involved in neuroinflammation. This effect was independent of silver ions as well. The distinct toxicological effects caused by AgNPs and silver ions provided the solid proofs for the particle-specific effects which should be concerned regarding the accurate assessment of AgNPs exposure risks.

Assessment of Bisphenol A (BPA) neurotoxicity in vitro with mouse embryonic stem cells

The adverse effects of environmental pollution on our well-being have been intensively studied with many in vitro and in vivo systems. In our group, we focus on stem cell toxicology due to the multitude of embryonic stem cell (ESC) properties which can be exerted in toxicity assays. In fact, ESCs can differentiate in culture to mimic embryonic development in vivo, or specifically to virtually any kind of somatic cells. Here, we used the toxicant Bisphenol A (BPA), a chemical known as a hazard to infants and children, and showed that our stem cell toxicology system was able to efficiently recapitulate most of the toxic effects of BPA previously detected by in vitro system or animal tests. More precisely, we demonstrated that BPA affected the proper specification of germ layers during our in vitro mimicking of the embryonic development, as well as the establishment of neural ectoderm and neural progenitor cells.

Vitamin E attenuates silver nanoparticle-induced effects on body weight and neurotoxicity in rats.

Silver nanoparticles (AgNPs) are one of the most commonly used nanomaterials; however, it remains unclear whether AgNPs induce neurotoxicity. Here, we investigated the potential neurological effects of AgNPs and the neuroprotective effect of vitamin E (VE). We found that intranasal instillation of AgNPs in neonatal Sprague-Dawley rats caused significant body weight loss. Moreover, histological examinations revealed activation of neuroglial cells with concomitant destruction of the granular layer of the cerebellum. Furthermore, western blot analyses showed an increase in the levels of the glial fibrillary acidic protein (GFAP), a marker of astrocyte activation. These observations suggest that AgNPs have significant neurotoxic effects on the rat cerebellum. Strikingly, oral administration of VE counterbalanced the toxic effects triggered by AgNPs. Taken together, our findings suggest that nasal administration of AgNPs may produce neurotoxicity in rats, and that VE supplementation attenuates these effects.

The ex vivo and in vivo biological performances of graphene oxide and the impact of surfactant on graphene oxide's biocompatibility.

Graphene oxide (GO) displays promising properties for biomedical applications including drug delivery and cancer therapeutics. However, GO exposure also raises safety concerns such as potential side effects on health. Here, the biological effects of GO suspended in phosphate buffered saline (PBS) with or without 1% nonionic surfactant Tween 80 were investigated. Based on the ex vivo experiments, Tween 80 significantly affected the interaction between GO and peripheral blood from mice. GO suspension in PBS tended to provoke the aggregation of diluted blood cells, which could be prevented by the addition of Tween 80. After intravenous administration, GO suspension with or without 1% Tween 80 was quickly eliminated by the mononuclear phagocyte system. Nevertheless, GO suspension without Tween 80 showed greater accumulation in lungs than that containing 1% Tween 80. In contrast, less GO was found in livers for GO suspension compared to Tween 80 assisted GO suspension. Organs including hearts, livers, lungs, spleens, kidneys, brains, and testes did not reveal histological alterations. The indexes of peripheral blood showed no change upon GO exposure. Our results together demonstrated that Tween 80 could greatly alter GOs biological performance and determine the pattern of its biodistribution in mice.

Effects of polycyclic musks HHCB and AHTN on steroidogenesis in H295R cells.

1,3,4,6,7,8-Hexahydro-4,6,6,7,8,8-hexamethylcyclopenta-(γ)-2-benzopyran (HHCB) and 7-acetyl-1,1,3,4,4,6-hexamethyl-1,2,3,4-tetrahydronaphthalene (AHTN) are widely used in personal care products. Previous studies showed that HHCB and AHTN can be found in various environmental matrices and have potential endocrine disrupting effects. However, the effects on adrenocortical function of HHCB and AHTN are not fully understood. This study evaluated the influences of HHCB and AHTN on seven steroid hormones (progesterone, aldosterone, cortisol, 17α-OH-progesterone, androstenedione, 17β-estradiol, and testosterone) and 10 genes involved in steroidogenic pathways (HMGR, StAR, CYP11A1, 3βHSD2, CYP17, CYP21, CYP11B1, CYP11B2, 17βHSD, and CYP19) using the H295R cell line in the absence and presence of 8-Br-cAMP. MC2R transcription on the cell membrane was also examined to further investigate the effects of HHCB and AHTN on adrenal steroidogenesis. The results demonstrated that HHCB and AHTN could inhibit progesterone and cortisol production mainly by the suppression of 3βHSD2 and CYP21. Meanwhile, high concentrations of AHTN can affect the sensitivity of H295R cells to ACTH by disrupting MC2R transcription. Overall, the results indicate that high concentrations of HHCB and AHTN can affect steroidogenesis in vitro using the H295R cell line.

The Rise of Stem Cell Toxicology

T field of environmental toxicology has been challenged in the last few decades by the exponential discovery of novel persistent pollutants and the relative lack of knowledge of their hazardousness to human health. At the same time, there has been increasing awareness of the urgency and necessity of innovative, validated, and comprehensive assays to collect toxicity data more relevant to humans. Since the onset of toxicology science, we have heavily relied on animal tests. Although these in vivo experiments have been refined in recent years, they are still expensive, labor intensive, time-consuming, and accompanied by ethical issues. More importantly, Russell and Burch’s “high fidelity fallacy” theory postulates that toxicity assays with animals are not always applicable to human health due to interspecies variations, even when primates are used. A prototypical example is the case of the drug thalidomide, proven to be highly teratogenic in humans even though it had passed all animal tests. This led to the introduction of in vitro tests as alternatives to in vivo animal experiments (reviewed in ref 2). In particular, the culture of human cells for toxicity tests, more directly relevant to human health, has been the primary solution to the obvious fact that humans cannot be used for in vivo studies. However, the direct derivation of some types of primary human cells, can be extremely invasive or simply impossible, and even if successful, the ability of primary cells to be cultured and expanded in vitro is limited. Conversely, immortalized or cancer cell lines can be readily grown and amplified in dishes; nevertheless, they may no longer be representative of the cells of origin because of accumulating mutations or altered cell functions, for example. Collectively, these issues can greatly affect the generation and interpretation of toxicity data. However, as described below, new stem cell technologies for the in vitro analyses of pollutants’ potential hazardousness, allow scientists to move past these problems. The first successful derivation of human embryonic stem cells (hESCs), and the discovery of human induced pluripotent stem cells (iPSCs), have intrigued the scientific community because of their potential to immensely advance many research fields. In particular, these breakthroughs are revolutionizing the field of toxicology in such a way that we need to create a new branch defined as “stem cell toxicology” that encompasses the thorough investigation of the adverse effects of substances on living organisms exclusively using stem cells. Though this approach may seem limited, it is important to remember that pluripotent stem cells have the capacity to proliferate indefinitely in culture, and the ability to differentiate into all cell types of an adult organism. These properties therefore make them ideal for human toxicological studies on various cell or tissue types. For instance, ESCs and iPSCs can be used to evaluate acute toxicity, and although other cultured cells types may be suitable for this type of assay, pluripotent stem cells have often been demonstrated to be more sensitive than somatic cells. The effects of a test material on fetal development can also be assessed with stem cells by looking at any abnormal differentiation phenotype. For example, ESCs can differentiate in vitro as three-dimensional aggregates called embryoid bodies (EBs), which mimic early embryonic developmental stages in vivo. This is the so-called embryonic/developmental toxicity assay. A third type of toxicity assay where stem cells are very useful is the cell function assay. Pluripotent stem cells are first differentiated into adult stem cells or progenitor cells, and then into particular types of terminally differentiated somatic cells. Subsequently, their cellular functions are assessed upon treatment with a chemical. This is particularly important when the primary cells are very difficult to derive directly from animals or humans. All of these assays are reviewed in. A growing concern about pollution is its relationship to human reproduction. With pluripotent stem cells, we are able to investigate in vitro the potential effects of pollutants on our ability to reproduce. In fact, murine ESCs can first be differentiated toward epiblast stem cells (EpiSCs), and then to germ cells. Similarly, hESCs can be differentiated toward primordial germ cell-like cells. We can then test whether these germ cells function correctly under various conditions. In conclusion, stem cell toxicology allows for the concurrent assessment of many forms of toxicity including acute, embryonic, developmental, organ, reproductive, and functional. It also provides a unique and widely applicable system for

Characterization of Three Tetrabromobisphenol-S Derivatives in Mollusks from Chinese Bohai Sea: A Strategy for Novel Brominated Contaminants Identification

Identification of novel brominated contaminants in the environment, especially the derivatives and byproducts of brominated flame retardants (BFRs), has become a wide concern because of their adverse effects on human health. Herein, we qualitatively and quantitatively identified three byproducts of tetrabromobisphenol-S bis(2,3-dibromopropyl ether) (TBBPS-BDBPE), including TBBPS mono(allyl ether) (TBBPS-MAE), TBBPS mono(2-bromoallyl ether) (TBBPS-MBAE) and TBBPS mono(2,3-dibromopropyl ether) (TBBPS-MDBPE) as novel brominated contaminants. Meanwhile, the mass spectra and analytical method for determination of TBBPS-BDBPE byproducts were presented for the first time. The detectable concentrations (dry weight) of TBBPS-MAE, TBBPS-MBAE and TBBPS-MDBPE were in the ranges 28–394 μg/g in technical TBBPS-BDBPE and 0.1–4.1 ng/g in mollusks collected from the Chinese Bohai Sea. The detection frequencies in mollusk samples were 5%, 39%, 95% for TBBPS-MAE, TBBPS-MBAE and TBBPS-MDBPE, respectively, indicating their prevailing in the environment. The results showed that they could be co-produced and leaked into the environment with production process, and might be more bioaccumulative and toxic than TBBPS-BDBPE. Therefore, the production and use of TBBPS derivatives lead to unexpected contamination to the surrounding environment. This study also provided an effective approach for identification of novel contaminants in the environment with synthesized standards and Orbitrap high resolution mass spectrometry.

TBBPA and Its Alternatives Disturb the Early Stages of Neural Development by Interfering with the NOTCH and WNT Pathways

Tetrabromobisphenol A (TBBPA), as well as its alternatives Tetrabromobisphenol S (TBBPS) and Tetrachlorobisphenol A (TCBPA), are widely used halogenated flame retardants. Their high detection rates in human breast milk and umbilical cord serum have raised wide concerns about their adverse effects on human fetal development. In this study, we evaluated the cytotoxicity and neural developmental toxicity of TBBPA, TBBPS, and TCBPA with a mouse embryonic stem cell (mESC) system, at human body fluid and environmental relevant doses. All the three compounds showed similar trends in their cytotoxic effects. However, while TBBPA and TBBPS stimulated ESC neural differentiation, TCBPA significantly inhibited neurogenesis. Mechanistically, we demonstrated that, as far as the NOTCH (positive regulator) and WNT (negative regulator) pathways were concerned, TBBPA only partially and slightly disturbed them, whereas TBBPS significantly inhibited the WNT pathway, and TCBPA down-regulated the expression of NOTCH effectors but increased the WNT signaling, actions which both inhibited neural specification. In conclusion, our findings suggest that TBBPS and TCBPA may not be safe alternatives to TBBPA, and their toxicity need to be comprehensively evaluated.