Role of PCBs in breast cancer progression and metastasis in the mouse model.

<p>(A) A schematic of the mouse model used in this study. The details about the model are described in the <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0011272#s3" target="_blank"><i>Methods</i></a>. (B) The average weight of primary tumors in the PCB-treated mice and the vehicle control mice (n = 8).</p

The signaling stimulated by PCBs in MDA-MB-231 cells.

<p>(A) The relative ROCK activity and Western blot analysis of P-MLC in MDA-MB-231 cells treated with the PCB mix (30 nM) with or without the ROCK inhibitor, Y27632 (10 µM) for 24 hrs (n = 3). (B) ROS production in MDA-MB-231 cells upon PCB treatment. DCF fluorescence in cells were measured by FACS analysis after 6-hr PCB treatment with or without β-ME (14.3 µM) (n = 3). (C) The relative ROCK activity and Western blot analysis of P-MLC in cells upon PCB treatment for 6 hrs with or without β-ME (n = 3). *, P<0.05, compared with the vehicle control and the PCBs+β-ME group. The intensities of autoradiogram in Western blots were quantified with Image J (rsbweb.nih.gov/ij). The quantified data for P-MLC were normalized to those of GAPDH.</p

PCBs enhance cell migration in breast cancer cells.

<p>Cell motility was examined from a transwell migration assay in MCF-7 and MDA-MB-231 cells treated with the PCB mix at 30 or 60 nM for 24 hrs. After the DAPI staining (blue), two images were randomly taken from three individual replicates under a microscope, and transmigrated cells in the chamber filters in each image were counted. Representative images for MCF-7 (A) and MDA-MB-231 (B) cells are shown, and the numbers of transmigrated cells were quantified (n = 6). *, P<0.001, compared with the vehicle control and the 60 nM group.</p

The cytotoxicity induced by PCBs on MDA-MB-231 cells.

<p>(A) Phase-contrast images of cell morphology from MDA-MB-231 cells treated with/without the PCB mix at 60 nM for 24 hrs. Original maginification, ×200. (B) FACS analysis of apoptosis induced by PCBs at 60 nM for 24 hrs in MDA-MB-231 cells using FITC-Annexin V and PI stains. Early apoptotic cells (lower right), necrotic cells (upper left) and late apoptotic/necrotic cells (upper right) are shown as arrows indicate.</p

A schematic of PCB-induced signaling in breast cancer cells.

<p>At low concentrations, PCBs activate ROCK kinase activity to regulate the actin-myosin-dependent contraction by phosphorylating motor proteins, such as the regulatory MLC. The resulting effect of ROCK activation leads to increased cell motility and potentially metastasis. At high concentrations, PCBs cause cell death via apoptosis, which may be dependent on ROS or not.</p

PCBs enhance MDA-MB-231 breast cancer cell metastases <i>in vivo</i>.

<p>(A) The occurrence of metastases in all organs tested in the PCB-treated mice and vehicle control mice. Metastases were examined using the Xenogen 2000 and the IVIS software as previously described <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0011272#pone.0011272-Liu1" target="_blank">[16]</a>. (B) The quantified data of metastatic tumors (reflected by photon flux, photons/sec <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0011272#pone.0011272-Liu1" target="_blank">[16]</a>) in mouse skeleton (n = 4). (C) Representative images of metastases in mouse liver, lung and skeleton from the bioluminescent imaging.</p

Graphene Oxide Causes Disordered Zonation Due to Differential Intralobular Localization in the Liver

The liver is the primary organ to sequester nanodrugs, representing a substantial hurdle for drug delivery and raising toxicity concerns. However, the mechanistic details underlying the liver sequestration and effects on the liver are still elusive. The difficulty in studying the liver lies in its complexity, which is structured with stringently organized anatomical units called lobules. Graphene oxide (GO) has attracted attention for its applications in biomedicine, especially as a nanocarrier; however, its sequestration and effects in the liver, the major enrichment and metabolic organ, are less understood. Herein, we unveiled the differential distribution of GO in lobules in the liver, with a higher amount surrounding portal triad zones than the central vein zones. Strikingly, liver zonation patterns also changed, as reflected by changes in vital zonated genes involved in hepatocyte integrity and metabolism, leading to compromised hepatic functions. RNA-Seq and DNA methylation sequencing analyses unraveled that GO-induced changes in liver functional zonation could be ascribed to dysregulation of key signaling pathways governing liver zonation at not only mRNA transcriptions but also DNA methylation imprinting patterns, partially through TET-dependent signaling. Together, this study reveals the differential GO distribution pattern in liver lobules and pinpoints the genetic and epigenetic mechanisms in GO-induced liver zonation alterations

Computational Investigations of the Interaction between the Cell Membrane and Nanoparticles Coated with a Pulmonary Surfactant

When inhaled nanoparticles (NPs) come into the deep lung, they develop a biomolecular corona by interacting with the pulmonary surfactant. The adsorption of the phospholipids and proteins gives a new biological identity to the NPs, which may alter their subsequent interactions with cells and other biological entities. Investigations of the interaction between the cell membrane and NPs coated with such a biomolecular corona are important in understanding the role of the biofluids on cellular uptake and estimating the dosing capacity and the nanotoxicology of NPs. In this paper, using dissipative particle dynamics, we investigate how the physicochemical properties of the coating pulmonary surfactant lipids and proteins affect the membrane response for inhaled NPs. We pinpoint several key factors in the endocytosis of lipid NPs, including the deformation of the coating lipids, coating lipid density, and ligand–receptor binding strength. Further studies reveal that the deformation of the coating lipids consumes energy but on the other hand promotes the coating ligands to bind with receptors more tightly. The coating lipid density controls the amount of the ligands as well as the hydrophobicity of the lipid NPs, thus affecting the endocytosis kinetics through the specific and nonspecific interactions. It is also found that the hydrophobic surfactant proteins associated with lipids can accelerate the endocytosis process of the NPs, but the endocytosis efficiency mainly depends on the density of the coating surfactant lipids. These findings can help understand how the pulmonary surfactant alters the biocompatibility of the inhaled NPs and provide some guidelines in designing an NP complex for efficient pulmonary drug delivery

Multihierarchically Profiling the Biological Effects of Various Metal-Based Nanoparticles in Macrophages under Low Exposure Doses

Thus far, tremendous efforts have been made to understand the biosafety of metal-based nanoparticles (MNPs). Nevertheless, most previous studies focused on specific adverse outcomes of MNPs at unrealistically high concentrations with little relevance to the National Institute for Occupational Safety and Health (NIOSH) exposure thresholds, and failed to comprehensively evaluate their toxicity profiles. To address these challenges, we here endeavored to multihierarchically profile the hazard effects of various popularly used MNPs in macrophages under low exposure doses. At these doses, no remarkable cell viability drop and cell death were induced. However, a cellular antioxidant defense system was seen to be initiated in cells by all MNPs even at these low concentrations, albeit to a differential extent and through different pathways, as reflected by differential induction of the antioxidant enzymes and Nrf2 signaling. Regarding inflammation, rare earth oxide nanomaterials (REOs) except nCeO₂ greatly increased IL-1β secretion in a NLRP3 inflammasome-dependent manner. By contrast, six REOs, AgNP-5nm, nFe₂O₃, nFe₃O₄, and nZnO were found to elevate TNF-α concentration through post-transcriptional regulation. Moreover, all MNPs except nCeO₂ drastically altered cellular membrane/cytoskeleton meshwork, but leading to different outcomes, with condensed cellular size and reduced numbers of protrusions by REOs and elongated protrusions by other MNPs. Consequently, REOs (e.g., nDy₂O₃ and nSm₂O₃) impaired phagocytosis of macrophages, and other MNPs (such as AgNP-25nm and nZnO) reversely enhanced macrophagic phagocytosis. Alterations of membrane and cytoskeleton meshwork induced by these MNPs also caused disordered membrane potential and calcium ion flux. Collectively, our data profiled the biological effects of different MNPs in macrophages under low exposure doses, and deciphered a complex network that links multiparallel pathways and processes to differential adverse outcomes

Silver Nanoparticles Compromise Female Embryonic Stem Cell Differentiation through Disturbing X Chromosome Inactivation

The widespread use of silver nanoparticles (AgNPs) has raised substantial health risks to human beings. Despite a wealth of progress on toxicity studies, the understanding of the adverse effects on fetuses, embryos, and early stage cells is still rather limited, particularly under low-dose exposure settings. Moreover, nearly all previous studies ascribed AgNP-induced toxic effects to oxidative stress. Differently, we here unearthed a mechanism, namely, interruption of X chromosome inactivation (XCI) in female mouse embryonic stem cells (mESCs). Albeit with no observable cytotoxicity, significant differentiation retardation was found in female mESCs upon low-dose AgNP exposure. Mechanistic investigations uncovered expedited inactivation for the inactive X chromosome (Xi) and attenuated maintenance of the active X chromosome (Xa) state during mESC differentiation upon the challenge of low-dose AgNPs, indicative of disordered XCI. Thereby, a few X-linked genes (which are closely involved in orchestrating ESC differentiation) were found to be repressed, partially attributable to reinforced enrichment of histone modification (e.g., histone 3 lysine 27 trimethylation, H3K27me3) on their promoter regions, as the result of disordered XCI. In stark contrast to female mESCs, no impairment of differentiation was observed in male mESCs under low-dose AgNP exposure. All considered, our data unearthed that AgNPs at low concentrations compromised the differentiation program of female mESCs through disturbing XCI. Thus, this work would provide a model for the type of studies necessary to advance the understandings on AgNP-induced developmental toxicity