Peili Huang

Cytotoxicity and mitochondrial damage caused by silica nanoparticles.

Amorphous silica nanoparticles are widely applied in many fields. But the adverse effects of silica nanoparticle exposure were unclear. The present study investigated the cytotoxicity and mitochondrial damage of silica nanoparticles exposure in hepatocellular carcinoma cell line (HepG2). The cells were treated with 43 nm non-modified amorphous silica nanoparticles which dispersed in serum-free DMEM at concentrations of 0, 25, 50, 100 and 200 μg/mL for 3 and 24 h. The results showed that the silica nanoparticles could lead to increasing cellular reactive oxygen species (ROS) production for 3 and 24 h exposure. Moreover, the oxidative stress induced by the particles could play an important role of the mitochondrial membrane damage and the cell apoptosis. It indicated that apoptosis through mitochondrial pathway mediated by oxidative stress was a potential mechanism of cytotoxicity induced by silica nanoparticles. The particles could enter the cells through different pathways and dispersed in cytoplasm and deposited inside mitochondria. Mitochondria were the major organelles for the cytotoxicity of silica nanoparticles exposure. Mitochondrial damage was related to the oxidative stress and the direct injurious effect of nanoparticles. It can be considered as the potential mechanism for the cytotoxic effects of amorphous silica nanoparticles.

Size-dependent cytotoxicity of amorphous silica nanoparticles in human hepatoma HepG2 cells

The purpose of this study is to compare the potential cytotoxicity induced by amorphous silica particles with different sizes. The effects of one fine particle (498 nm) and three nanoparticles (68, 43, and 19 nm) on cultured human hepatoma (HepG2) cells were investigated by detecting morphological changes, cell viability, cytomembrane integrity, DNA damage, cell cycle distribution, and apoptosis after the cells were treated with 100 μg/mL of four silica particles for 24h. The results indicated that in HepG2 cells, the cytotoxicity generated by silica particles strongly depended on the particle size, and smaller silica particle possessed higher toxic effect. In order to further elucidate the possible mechanisms of cell injuries, intracellular reactive oxygen species (ROS) was measured. Increased ROS level was also observed in a size dependent way. However, the result showed the fine particle did not promote intracellular ROS level significantly, while cell injuries were detected in this treated group. Thus, our data demonstrated that exposure to different sizes of silica particles resulted in a size dependent cytotoxicity in cultured HepG2 cells, and ROS generation should be one possible damage pathway but might not be completely responsible for the toxic effect produced by silica particles.

Toxic Effect of Silica Nanoparticles on Endothelial Cells through DNA Damage Response via Chk1-Dependent G2/M Checkpoint

Silica nanoparticles have become promising carriers for drug delivery or gene therapy. Endothelial cells could be directly exposed to silica nanoparticles by intravenous administration. However, the underlying toxic effect mechanisms of silica nanoparticles on endothelial cells are still poorly understood. In order to clarify the cytotoxicity of endothelial cells induced by silica nanoparticles and its mechanisms, cellular morphology, cell viability and lactate dehydrogenase (LDH) release were observed in human umbilical vein endothelial cells (HUVECs) as assessing cytotoxicity, resulted in a dose- and time- dependent manner. Silica nanoparticles-induced reactive oxygen species (ROS) generation caused oxidative damage followed by the production of malondialdehyde (MDA) as well as the inhibition of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px). Both necrosis and apoptosis were increased significantly after 24 h exposure. The mitochondrial membrane potential (MMP) decreased obviously in a dose-dependent manner. The degree of DNA damage including the percentage of tail DNA, tail length and Olive tail moment (OTM) were markedly aggravated. Silica nanoparticles also induced G2/M arrest through the upregulation of Chk1 and the downregulation of Cdc25C, cyclin B1/Cdc2. In summary, our data indicated that the toxic effect mechanisms of silica nanoparticles on endothelial cells was through DNA damage response (DDR) via Chk1-dependent G2/M checkpoint signaling pathway, suggesting that exposure to silica nanoparticles could be a potential hazards for the development of cardiovascular diseases.

Silica nanoparticles enhance autophagic activity, disturb endothelial cell homeostasis and impair angiogenesis

BackgroundGiven that the effects of ultrafine fractions (<0.1 μm) on ischemic heart diseases (IHD) and other cardiovascular diseases are gaining attention, this study is aimed to explore the influence of silica nanoparticles (SiNPs)-induced autophagy on endothelial cell homeostasis and angiogenesis.Methods and resultsUltrastructural changes of autophagy were observed in both vascular endothelial cells and pericytes in the heart of ICR mice by TEM. Autophagic activity and impaired angiogenesis were further confirmed by the immunohistochemistry staining of LC3 and VEGFR2. In addition, the immunohistochemistry results showed that SiNPs had an inhibitory effect on ICAM-1 and VCAM-1, but no obvious effect on E-selectin in vivo. The disruption of F-actin cytoskeleton occurred as an initial event in SiNPs-treated endothelial cells. The depolarized mitochondria, autophagic vacuole accumulation, LC3-I/LC3-II conversion, and the down-regulation of cellular adhesion molecule expression were all involved in the disruption of endothelial cell homeostasis in vitro. Western blot analysis indicated that the VEGFR2/PI3K/Akt/mTOR and VEGFR2/MAPK/Erk1/2/mTOR signaling pathway was involved in the cardiovascular toxicity triggered by SiNPs. Moreover, there was a crosstalk between the VEGFR2-mediated autophagy signaling and angiogenesis signaling pathways.ConclusionsIn summary, the results demonstrate that SiNPs induce autophagic activity in endothelial cells and pericytes, subsequently disturb the endothelial cell homeostasis and impair angiogenesis. The VEGFR2-mediated autophagy pathway may play a critical role in maintaining endothelium and vascular homeostasis. Our findings may provide experimental evidence and explanation for cardiovascular diseases triggered by nano-sized particles.

Effects of lanthanum, cerium, and neodymium on the nuclei and mitochondria of hepatocytes: accumulation and oxidative damage.

The aim of this study was to investigate the contents of lanthanum (La), cerium (Ce), and neodymium (Nd) that accumulate in nuclei and mitochondria isolated from the liver and their corresponding potential oxidative damage effects on nuclei and mitochondria. Five-week-old male imprinting control region (ICR) mice were exposed to chlorides of La, Ce, or Nd by oral gavage with one of three doses: 10, 20, or 40 mg/kgBW/day for 6 weeks. The concentrations of administered elements in hepatocyte nuclei and mitochondria were determined with inductively coupled plasma-mass (ICP-MS) spectrometry. The accumulation of La, Ce, and Nd in hepatocyte nuclei and mitochondria gradually increased in a dose-dependent manner with exposure to the elements, although the concentrations of La, Ce, and Nd in hepatocyte mitochondria were lower than those in their counterpart nuclei. In hepatocyte nuclei, superoxide dismutase (SOD) and catalase (CAT) activities decreased, whereas glutathione peroxidase (GPx) activity, glutathione (GSH) and malondialdehyde (MDA) levels increased. In hepatocyte mitochondria, SOD, CAT, and GPx activities and GSH levels were significantly decreased, and MDA levels were significantly increased. These results suggest that La, Ce, and Nd presumably enter hepatocytes and mainly accumulate in the nuclei and induce oxidative damage in hepatic nuclei and mitochondria.

Differential toxicity of Mn2+ and Mn3+ to rat liver tissues: Oxidative damage, membrane fluidity and histopathological changes

Toxicity due to overexposure to manganese (Mn) is becoming increasingly prevalent. Mn-induced neurodegenerative toxicity has been demonstrated, but little is known concerning the adverse effects of the element on the liver. Under physiological conditions, manganese primarily exists as divalent manganese (Mn(2+)) and trivalent manganese (Mn(3+)). The present study was designed to evaluate and compare the effects of Mn(2+) and Mn(3+) on oxidative hepatic damage, membrane fluidity and histopathological changes in rats. Rats exposed to Mn(2+) or Mn(3+) (2.0mg Mn/kg body weight) showed significant inhibition of superoxide dismutase (SOD) and glutathione peroxidase (GPx) activity, as well as decreased levels of glutathione (GSH) and increased levels of malondialdehyde (MDA) in liver tissues. We also showed a significant inhibition of SOD activity and increased MDA levels in hepatocyte nuclei. We also observed reduced Na(+),K(+)-ATPase activity, increased MDA levels and decreased plasma membrane fluidity, which was accompanied by an increase of fluorescence anisotropy (r) values, in hepatic plasma membranes. In addition, Mn(2+) and Mn(3+) both caused histopathological changes, such as mononuclear cell infiltration, congestion, enlargement of the veins and sinusoids, hepatocellular damage, necrotic changes, mitochondrial hyperplasia, swelling and vacuolization, as determined by light and electron microscopy. Taken together, these data suggest that both Mn(2+) and Mn(3+) inhibit the normal physiological functioning of the liver. Under the experimental conditions used, the adverse effects of Mn(2+) were more severe than those of Mn(3+).

Manganese effects in the liver following subacute or subchronic manganese chloride exposure in rats.

Manganese (Mn) toxicity is most often found in mining and welding industry workers. Accumulation of manganese in the brain can result in a syndrome similar to that of Parkinsons disease. Observations on former Mn-alloy workers suggested that residual effects could last for years after exposure. The objective of this study was to assess effects of Mn in the liver of rats following subacute or subchronic exposure and after recovery. Male Sprague-Dawley rats were exposed to manganese chloride (MnCl(2)) for 30 days, 90 days, or for 90 days followed by a 30-day post-exposure recovery period. Results showed that MnCl(2) exposure resulted in liver injury in rats and the extent of injury correlated positively with exposure time. The effect in mitochondria was stronger than in the membrane or nucleus. Most of the changes in these biomarkers recovered when manganese exposure ceased.

Multinucleation and cell dysfunction induced by amorphous silica nanoparticles in an L-02 human hepatic cell line.

Silica nanoparticles (SNPs) are one of the most important nanomaterials, and have been widely used in a variety of fields. Therefore, their effects on human health and the environment have been addressed in a number of studies. In this work, the effects of amorphous SNPs were investigated with regard to multinucleation in L-02 human hepatic cells. Our results show that L-02 cells had an abnormally high incidence of multinucleation upon exposure to silica, that increased in a dose-dependent manner. Propidium iodide staining showed that multinucleated cells were arrested in G2/M phase of the cell cycle. Increased multinucleation in L-02 cells was associated with increased generation of cellular reactive oxygen species and mitochondrial damage on flow cytometry and confocal microscopy, which might have led to failure of cytokinesis in these cells. Further, SNPs inhibited cell growth and induced apoptosis in exposed cells. Taken together, our findings demonstrate that multinucleation in L-02 human hepatic cells might be a failure to undergo cytokinesis or cell fusion in response to SNPs, and the increase in cellular reactive oxygen species could be responsible for the apoptosis seen in both mononuclear cells and multinucleated cells.

Time-dependent toxicity of cadmium telluride quantum dots on liver and kidneys in mice: histopathological changes with elevated free cadmium ions and hydroxyl radicals

A complete understanding of the toxicological behavior of quantum dots (QDs) in vivo is of great importance and a prerequisite for their application in humans. In contrast with the numerous cytotoxicity studies investigating QDs, only a few in vivo studies of QDs have been reported, and the issue remains controversial. Our study aimed to understand QD-mediated toxicity across different time points and to explore the roles of free cadmium ions (Cd2+) and hydroxyl radicals (·OH) in tissue damage. Male ICR mice were administered a single intravenous dose (1.5 µmol/kg) of CdTe QDs, and liver and kidney function and morphology were subsequently examined at 1, 7, 14, and 28 days. Furthermore, ·OH production in the tissue was quantified by trapping · OH with salicylic acid (SA) as 2,3-dihydroxybenzoic acid (DHBA) and detecting it using a high-performance liquid chromatography fluorescence method. We used the induction of tissue metallothionein levels and 2,3-DHBA:SA ratios as markers for elevated Cd2+ from the degradation of QDs and ·OH generation in the tissue, respectively. Our experimental results revealed that the QD-induced histopathological changes were time-dependent with elevated Cd2+ and ·OH, and could recover after a period of time. The Cd2+ and ·OH exhibited delayed effects in terms of histopathological abnormalities. Histological assessments performed at multiple time points might facilitate the evaluation of the biological safety of QDs.

Development of magnetic separation and quantum dots labeled immunoassay for the detection of mercury in biological samples.

A rapid and sensitive immunoassays of mercury (Hg) in biological samples was developed using quantum dots (QDs) and magnetic beads (MBs) as fluorescent and separated probes, respectively. A monoclonal antibody (mAb) that recognizes an Hg detection antigen (BSA-DTPA-Hg) complex was produced by the injection of BALB/c mice with an Hg immunizing antigen (KLH-DTPA-Hg). Then the ascites monoclonal antibodies were purified. The Hg monoclonal antibody (Hg-mAb) is conjugated with MBs to separate Hg from biological samples, and the other antibody, which is associated with QDs, is used to detect the fluorescence. The Hg in biological samples can be quantified using the relationship between the QDs fluorescence intensity and the concentration of Hg in biological samples following magnetic separation. In this method, the detection linear range is 1-1000ng/mL, and the minimum detection limit is 1ng/mL. The standard addition recovery rate was 94.70-101.18%. The relative standard deviation values were 2.76-7.56%. Furthermore, the Hg concentration can be detected in less than 30min, the significant interference of other heavy metals can be avoided, and the simultaneous testing of 96 samples can be performed. These results indicate that the method could be used for rapid monitoring Hg in the body.