James Kirkpatrick

Inflammatory and cytotoxic responses of an alveolar-capillary coculture model to silica nanoparticles: Comparison with conventional monocultures

BackgroundTo date silica nanoparticles (SNPs) play an important role in modern technology and nanomedicine. SNPs are present in various materials (tyres, electrical and thermal insulation material, photovoltaic facilities). They are also used in products that are directly exposed to humans such as cosmetics or toothpaste. For that reason it is of great concern to evaluate the possible hazards of these engineered particles for human health. Attention should primarily be focussed on SNP effects on biological barriers. Accidentally released SNP could, for example, encounter the alveolar-capillary barrier by inhalation. In this study we examined the inflammatory and cytotoxic responses of monodisperse amorphous silica nanoparticles (aSNPs) of 30 nm in size on an in vitro coculture model mimicking the alveolar-capillary barrier and compared these to conventional monocultures.MethodsThus, the epithelial cell line, H441, and the endothelial cell line, ISO-HAS-1, were used in monoculture and in coculture on opposite sides of a filter membrane. Cytotoxicity was evaluated by the MTS assay, detection of membrane integrity (LDH release), and TER (Transepithelial Electrical Resistance) measurement. Additionally, parameters of inflammation (sICAM-1, IL-6 and IL-8 release) and apoptosis markers were investigated.ResultsRegarding toxic effects (viability, membrane integrity, TER) the coculture model was less sensitive to apical aSNP exposure than the conventional monocultures of the appropriate cells. On the other hand, the in vitro coculture model responded with the release of inflammatory markers in a much more sensitive fashion than the conventional monoculture. At concentrations that were 10-100fold less than the toxic concentrations the apically exposed coculture showed a release of IL-6 and IL-8 to the basolateral side. This may mimic the early inflammatory events that take place in the pulmonary alveoli after aSNP inhalation. Furthermore, a number of apoptosis markers belonging to the intrinsic pathway were upregulated in the coculture following aSNP treatment. Analysis of the individual markers indicated that the cells suffered from DNA damage, hypoxia and ER-stress.ConclusionWe present evidence that our in vitro coculture model of the alveolar-capillary barrier is clearly advantageous compared to conventional monocultures in evaluating the extent of damage caused by hazardous material encountering the principle biological barrier in the lower respiratory tract.

Comparative Studies on Vascular Endothelium in vitro

Recent studies have presented evidence that the processes of hypoxaemia and reperfusion are involved in several pathogenetic mechanisms of atherosclerotic lesions. The ability of hypoxaemia to activate circulating white blood cells (WBCs) and enhance WBC-endothelial cell (EC) interactions is suspected to be a major factor in deleterious processes in the blood vessel wall. Various groups have suggested that cell adhesion molecules (CAMs), such as ICAM-1, VCAM-1 and E-selectin and their leukocyte ligands are involved in intercellular activities of the relevant cell types. We studied the effects of different oxygen tensions, simulating normoxic conditions, hypoxia and hyperoxia in vitro with the help of an umbilical vein EC model in order to determine the effects of oxygenation on CAM presentation on vascular ECs with and without further cytokine and endotoxin (lipopolysaccharides; LPS) stimulation. Semi-quantitative analysis of ICAM-1, E-selectin and VCAM-1 was performed using cell enzyme immunoassay techniques. The presentation of ICAM-1, E-selectin and VCAM-1 remained on the whole unaffected by both hypoxia and hyperoxic conditioning after both 7 and 24 h. Stimulation of ICAM-1 by cytokines and LPS was only marginally influenced by the oxygen tension. Cytokine induction of E-selectin was not affected after 7 h and was even reduced under hypoxia, compared to the control culture after 24 h, while stimulation was increased by hyperoxia. VCAM-1 was reduced in both the hypoxic and hyperoxic culture, while being maximally stimulated by cytokines and LPS after 7 h. In general, an effect of hypoxia was not found without any further stimulation. Moreover, evidence is presented that reoxygenation might be the more important aspect in the mechanisms of ischaemia/reperfusion.

Predictive Toxicology of cobalt ferrite nanoparticles: comparative in-vitro study of different cellular models using methods of knowledge discovery from data

BackgroundCobalt-ferrite nanoparticles (Co-Fe NPs) are attractive for nanotechnology-based therapies. Thus, exploring their effect on viability of seven different cell lines representing different organs of the human body is highly important.MethodsThe toxicological effects of Co-Fe NPs were studied by in-vitro exposure of A549 and NCIH441 cell-lines (lung), precision-cut lung slices from rat, HepG2 cell-line (liver), MDCK cell-line (kidney), Caco-2 TC7 cell-line (intestine), TK6 (lymphoblasts) and primary mouse dendritic-cells. Toxicity was examined following exposure to Co-Fe NPs in the concentration range of 0.05 -1.2 mM for 24 and 72 h, using Alamar blue, MTT and neutral red assays. Changes in oxidative stress were determined by a dichlorodihydrofluorescein diacetate based assay. Data analysis and predictive modeling of the obtained data sets were executed by employing methods of Knowledge Discovery from Data with emphasis on a decision tree model (J48).ResultsDifferent dose–response curves of cell viability were obtained for each of the seven cell lines upon exposure to Co-Fe NPs. Increase of oxidative stress was induced by Co-Fe NPs and found to be dependent on the cell type. A high linear correlation (R2=0.97) was found between the toxicity of Co-Fe NPs and the extent of ROS generation following their exposure to Co-Fe NPs. The algorithm we applied to model the observed toxicity belongs to a type of supervised classifier. The decision tree model yielded the following order with decrease of the ranking parameter: NP concentrations (as the most influencing parameter), cell type (possessing the following hierarchy of cell sensitivity towards viability decrease: TK6 > Lung slices > NCIH441 > Caco-2u2009=u2009MDCK > A549 > HepG2u2009=u2009Dendritic) and time of exposure, where the highest-ranking parameter (NP concentration) provides the highest information gain with respect to toxicity. The validity of the chosen decision tree model J48 was established by yielding a higher accuracy than that of the well-known “naive bayes” classifier.ConclusionsThe observed correlation between the oxidative stress, caused by the presence of the Co-Fe NPs, with the hierarchy of sensitivity of the different cell types towards toxicity, suggests that oxidative stress is one possible mechanism for the toxicity of Co-Fe NPs.

The protein corona protects against size- and dose-dependent toxicity of amorphous silica nanoparticles.

Summary Besides the lung and skin, the gastrointestinal (GI) tract is one of the main targets for accidental exposure or biomedical applications of nanoparticles (NP). Biological responses to NP, including nanotoxicology, are caused by the interaction of the NP with cellular membranes and/or cellular entry. Here, the physico-chemical characteristics of NP are widely discussed as critical determinants, albeit the exact mechanisms remain to be resolved. Moreover, proteins associate with NP in physiological fluids, forming the protein corona potentially transforming the biological identity of the particle and thus, adding an additional level of complexity for the bio–nano responses. Here, we employed amorphous silica nanoparticles (ASP) and epithelial GI tract Caco-2 cells as a model to study the biological impact of particle size as well as of the protein corona. Caco-2 or mucus-producing HT-29 cells were exposed to thoroughly characterized, negatively charged ASP of different size in the absence or presence of proteins. Comprehensive experimental approaches, such as quantifying cellular metabolic activity, microscopic observation of cell morphology, and high-throughput cell analysis revealed a dose- and time-dependent toxicity primarily upon exposure with ASP30 (Ø = 30 nm). Albeit smaller (ASP20, Ø = 20 nm) or larger particles (ASP100; Ø = 100 nm) showed a similar zeta potential, they both displayed only low toxicity. Importantly, the adverse effects triggered by ASP30/ASP30L were significantly ameliorated upon formation of the protein corona, which we found was efficiently established on all ASP studied. As a potential explanation, corona formation reduced ASP30 cellular uptake, which was however not significantly affected by ASP surface charge in our model. Collectively, our study uncovers an impact of ASP size as well as of the protein corona on cellular toxicity, which might be relevant for processes at the nano–bio interface in general.

Nanostructured medical sutures with antibacterial properties

Bacterial repellence in suture materials is a desirable property that can potentially improve the healing process by preventing infection. We describe a method for generating nanostructures at the surface of commercial sutures of different composition, and their potential for preventing biofilm formation. We show how bacteria attachment is altered in the presence of nanosized topographies and identify optimum designs for preventing it without compromising biocompatibility and applicability in terms of nanostructure robustness or tissue friction. These studies open new possibilities for flexible and cost-effective realization of topography-based antibacterial coatings for absorbable biomedical textiles.

Increased Adhesion and Activation of Polymorphonuclear Neutrophil Granulocytes to Endothelial Cells under Heavy Metal Exposure in vitro

Heavy metals have been implicated in the mechanisms of endothelial damage. Influences of heavy metal ions on diverse cell types have been studied using a variety of in vitro and in vivo methods. Polymorphonuclear neutrophil granulocytes (PMNs) have physiological and pathological functions, including the modulation of adhesion to and destruction of endothelial cells (ECs). PMNs were studied during interaction with human umbilical vein ECs under exposure to zinc, nickel and cobalt using an in vitro model. We studied adhesion processes with the help of a computer-controlled image-analyzing system and examined the activation of PMNs by quantification of leukotriene B4 (LTB4) release. The biphasic effects of the evaluated heavy metals on PMN-EC adhesion, with stimulation at very high and very low molar concentrations, were observed. The release of LTB4 by PMNs increased during exposure to very low metal concentrations. The initiation of these important pathogenetic mechanisms of inflammation at very low metal ion concentrations, which give no morphological changes, must be regarded as potentially significant with respect to the toxic effects of heavy metals.

Expression of the apoptosis accelerator Bax in rheumatoid arthritis synovium

AbstractnObjective. The aim of this study was to analyze the expression of apoptosis-related molecules in rheumatoid arthritis (RA) synovium, with special emphasis on the apoptosis accelerator Bax.nMethods. Immunohistochemical analysis of Bax, Bcl-2, and Bcl-xL was performed in tissue specimens of patients with RA and compared to normal synovial tissue. Expression of Bax was additionally determined by double labeling with CD68, p53, and Ki-67 (clone MIB-1). Apoptotic cells were further identified by the terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling (TUNEL) method.nResults. In RA, expression of Bax was higher than in healthy controls and occurred in CD68-positive and -negative synoviocytes. Strong Bax staining was also found in chondrocytes at sites of cartilage degradation. Bax-positive synoviocytes could be detected with p53 and also with Ki-67. Bax and Bcl-xL were markedly colocalized in synovium. The TUNEL method revealed only few positive synoviocytes.nConclusions. The marked colocalization of Bax and antiapoptotic Bcl-xL as well as the low frequency of TUNEL-positive cells in RA synovium suggest that Bax activity is not sufficient to decrease synovial hyperplasia in RA. Apoptotic mechanisms in RA chondrocytes might also be important for the pathogenesis of joint damage.

ESEM evaluations of muscle/nanoparticles interface in a rat model

In order to examine the influence that shape and chemistry of different materials have on the incitement of a tissue reaction, we implanted five materials (the two metals Ni and Co, the two ceramics TiO2 and SiO2, and the polymer poly vinyl-chloride) as nanoparticles or bulk, in the dorsal muscles of 50 rats. After 6 or 12xa0months, rats were euthanized and the implanted materials were excised together with the surrounding tissue. After a first histological evaluation, the specimens were prepared for environmental scanning electron microscopy (ESEM) and for energy dispersive spectroscopy (EDS), in order to analyse the chemical composition of the implanted material after the biological interaction had occurred, and to evaluate the possible corrosion and diffusion of the materials at tissue interface. The results indicate that the metals at nanoscale size have a carcinogenic effect, while the bulk materials only induce a foreign-body reaction. The ESEM observations show a chemical transformation of the materials. Corrosion of the metals and subsequent recombination of the released ions in a sort of organic–inorganic crystals is showed and verified by the EDS analyses. Finally, our hypotheses of the involved pathological mechanism are suggested.

Spontaneous In Vivo Chondrogenesis of Bone Marrow-Derived Mesenchymal Progenitor Cells by Blocking Vascular Endothelial Growth Factor Signaling

Chondrogenic differentiation of bone marrow‐derived mesenchymal stromal/stem cells (MSCs) can be induced by presenting morphogenetic factors or soluble signals but typically suffers from limited efficiency, reproducibility across primary batches, and maintenance of phenotypic stability. Considering the avascular and hypoxic milieu of articular cartilage, we hypothesized that sole inhibition of angiogenesis can provide physiological cues to direct in vivo differentiation of uncommitted MSCs to stable cartilage formation. Human MSCs were retrovirally transduced to express a decoy soluble vascular endothelial growth factor (VEGF) receptor‐2 (sFlk1), which efficiently sequesters endogenous VEGF in vivo, seeded on collagen sponges and immediately implanted ectopically in nude mice. Although naïve cells formed vascularized fibrous tissue, sFlk1‐MSCs abolished vascular ingrowth into engineered constructs, which efficiently and reproducibly developed into hyaline cartilage. The generated cartilage was phenotypically stable and showed no sign of hypertrophic evolution up to 12 weeks. In vitro analyses indicated that spontaneous chondrogenic differentiation by blockade of angiogenesis was related to the generation of a hypoxic environment, in turn activating the transforming growth factor‐β pathway. These findings suggest that VEGF blockade is a robust strategy to enhance cartilage repair by endogenous or grafted mesenchymal progenitors. This article outlines the general paradigm of controlling the fate of implanted stem/progenitor cells by engineering their ability to establish specific microenvironmental conditions rather than directly providing individual morphogenic cues.

Thyroid disease in children and adolescents with PTEN hamartoma tumor syndrome (PHTS)

AbstractPatients with PTEN hamartoma tumor syndrome (PHTS) are at increased risk of developing benign and malignant tumors, including thyroid carcinoma. Benign thyroid lesions and single cases of thyroid carcinoma have been reported in children with PHTS. We conducted a retrospective, single-centered study including children and adolescents with a molecularly proven diagnosis of PTEN. Our cohort consists of 16 patients, with a mean age at diagnosis PHTS of 5.7xa0years. Twelve of 16 cases exhibited thyroid abnormalities (75%). In seven patients, thyroid abnormalities were already present at first ultrasound screening, in five cases they occurred during follow-up. Eight patients underwent thyroidectomy. Histopathology included nodular goiter, follicular adenoma, papillary microcarcinoma in a boy of six and follicular carcinoma in a girl of 13xa0years. Two patients had autoimmune thyroid disease.n Conclusion: Thyroid disease is common in children with PHTS. Physicians caring for patients with early thyroid abnormalities and additional syndromal features should be aware of PHTS as a potentially underlying disorder. Ultrasound screening should be performed immediately after diagnosis of PHTS and repeated yearly or more frequently. Because of possible early cancer development, we recommend early surgical intervention in the form of total thyroidectomy in cases of suspicious ultrasound findings.What is Known:• PHTS patients are at high risk of developing benign and malignant tumors.• Individual cases of thyroid carcinoma in children have been reported.What is New:• Thyroid disease is even more common in children with PHTS (75%) than previously expected.• Frequently thyroid disease is the first organ pathology requiring diagnostic workup and therefore children with PHTS should be examined for thyroid disease right after diagnosis and receive follow-up on a regular basis throughout life.