Application of xCELLigence real-time cell analysis to the microplate assay for pertussis toxin induced clustering in CHO cells

REV-ERBα agonist SR10067 attenuates Th2 cytokine-mediated barrier dysfunction in human bronchial epithelial cells

Allergens and Th2 cytokines affect the homeostatic environment in the airways, leading to increased mucus production by goblet cells associated with altered adherens junctional complex (AJC) and tight junction (TJ) proteins responsible for maintaining epithelial barrier function. Circadian clock-dependent regulatory mechanisms such as inflammation and epithelial barrier function are gaining more attention due to their therapeutic potential against allergic inflammatory lung diseases. Currently, there are no studies to support whether REV-ERBα activation can attenuate Th2 cytokine-induced epithelial barrier dysfunction in human bronchial epithelial cells. We hypothesized that Th2 cytokine-induced epithelial barrier dysfunction may be protected by activating REV-ERBα. Treatment with Th2 cytokines or HDM significantly reduced the cell impedance, as confirmed by transepithelial electrical resistance (TEER). However, pre-treatment with SR10067 attenuated Th2 cytokine-induced barrier dysfunction, such as decreased permeability, improved TEER, localization of AJC and TJ proteins, and mRNA and protein levels of selected epithelial barrier and circadian clock targets. Overall, we showed for the first time that REV-ERBα activation regulates altered epithelial barrier function that may have direct implications for the treatment of asthma and other allergic diseases.

In vitro cytoxicity profile of e-cigarette liquid samples on primary human bronchial epithelial cells

Cigarette smoke is associated to severe chronic diseases. The most harmful components of cigarette smoke derive from the combustion process, which are significantly reduced in the electronic cigarette aerosol, thus providing a valid option in harm reduction strategies. To develop safer products, it is therefore necessary to screen electronic cigarette liquids (e-liquids) to meet high safety standards defined by government regulations. The aim of the present study was to evaluate the presence of metal- and plastic-derived contaminants in four different commercial e-liquids with high concentration of nicotine and their cytotoxic effect in normal human bronchial epithelial cells by a number of in vitro assays, in comparison with the 1R6F reference cigarette, using an air-liquid interface (ALI) exposure system. Moreover, we evaluated the effect of aerosol exposure on oxidative stress by measuring the production of reactive oxygen species and mitochondrial potential. Our results showed no contaminants in all e-liquids and a significantly reduced cytotoxic effect of e-liquid aerosol compared to cigarette smoke as well as a maintained mitochondria integrity. Moreover, no production of reactive oxygen species was detected with e-cigarette aerosol. In conclusion, these results support the reduced toxicity potential of e-cigs compared to tobacco cigarettes in an in vitro model resembling real life smoke exposure.

Cytotoxic effects of halophilic archaea metabolites on ovarian cancer cell lines

BACKGROUND

Ovarian cancer is one of the most frequent and deadly gynaecological cancers, often resistant to platinum-based chemotherapy, the current standard of care. Halophilic microorganisms have been shown to produce a large variety of metabolites, some of which show toxicity to various cancer cell lines. However, none have yet been shown to be active against ovarian cancer cells. Here, we examined the effects of metabolites secreted by the halophilic archaea Halorhabdus rudnickae and Natrinema salaciae on various cancer cell lines, including ovarian cancer cell lines.

RESULTS

1H NMR analyses of Hrd. rudnickae and Nnm. salaciae culture supernatants contain a complex mixture of metabolites that differ between species, and even between two different strains of the same species, such as Hrd. rudnickae strains 64T and 66. By using the MTT and the xCELLigence RTCA assays, we found that the secreted metabolites of all three halophilic strains expressed cytotoxicity to the ovarian cancer cell lines, especially A2780, as well as its cisplatin-resistant derivative A2780cis, in a dose-dependent manner. The other tested cell lines A549, HepG2, SK-OV-3 and HeLa were only minimally, or not at all affected by the archaeal metabolites, and this was only seen with the MTT assay.

CONCLUSIONS

The halophilic archaea Hrd. rudnickae and Nnm. salaciae, isolated from a Polish salt mine and Lake Medee in the Mediterranean Sea, respectively, secrete metabolites that are active against ovarian cancer cells, including those that are resistant to cisplatin. This opens potential new possibilities for the treatment of these frequent and deadly gynaecological cancers.

Netrin-1 Secreted by Human Osteoarthritic Articular Chondrocytes Promotes Angiogenesis in Vitro

OBJECTIVE

Netrin-1 expression in articular cartilage is correlated with osteoarthritic changes. We aimed to investigate the contribution of Netrin-1 secreted by human osteoarthritic articular chondrocytes to angiogenesis process in vitro.

DESIGN

Human articular chondrocytes were extracted from non-osteoarthritic (n = 10) and osteoarthritic (n = 22) joints obtained from surgical specimens and incubated for 24 hours. Medium conditioned by non-osteoarthritic and osteoarthritic articular chondrocytes were collected. Human umbilical vein endothelial cells (HUVEC) were treated with control and conditioned medium and assessed using assays for cell adherence, migration, and tube formation. Netrin-1 expression and secretion was compared between non-osteoarthritic and osteoarthritic chondrocytes by qPCR, Western blot, and ELISA. The role of chondrocyte-secreted Netrin-1 on HUVEC functions was assessed by immunological neutralization using an anti-Netrin-1 monoclonal antibody.

RESULTS

As compared with medium conditioned by non-osteoarthritic chondrocytes, medium conditioned by osteoarthritic chondrocytes permitted tube formation by HUVEC. Both non-osteoarthritic and osteoarthritic chondrocytes expressed Netrin-1 at the RNA and protein levels. At the RNA level, Netrin-1 expression did not differ between non-osteoarthritic and osteoarthritic chondrocytes. At the protein level, Netrin-1 appeared as a full protein of 64 kDa in non-osteoarthritic chondrocytes and as two cleaved proteins of 55 kDa and 64 kDa in osteoarthritic chondrocytes. Immunological neutralization of endogenous Netrin-1 reduced the pro-angiogenic and pro-inflammatory transcriptional profile of HUVEC treated with the medium conditioned by osteoarthritic chondrocytes, as well as their capacities to form tubes.

CONCLUSIONS

Medium conditioned by osteoarthritic chondrocytes permits tube formation by HUVEC in vitro. This permissive effect is mediated by Netrin-1.

A549 Cell-Covered Electrodes as a Sensing Element for Detection of Effects of Zn2+ Ions in a Solution

Electrochemical-based biosensors have the potential to be a fast, label-free, simple approach to detecting the effects of cytotoxic substances in liquid media. In the work presented here, a cell-based electrochemical biosensor was developed and evaluated to detect the cytotoxic effects of Zn²⁺ ions in a solution as a reference test chemical. A549 cells were attached to the surface of stainless-steel electrodes. After treatment with ZnCl₂, the morphological changes of the cells and, ultimately, their death and detachment from the electrode surface as cytotoxic effects were detected through changes in the electrical signal. Electrochemical cell-based impedance spectroscopy (ECIS) measurements were conducted with cytotoxicity tests and microscopic observation to investigate the behavior of the A549 cells. As expected, the Zn²⁺ ions caused changes in cell confluency and spreading, which were checked by light microscopy, while the cell morphology and attachment pattern were explored by scanning electron microscopy (SEM). The ECIS measurements confirmed the ability of the biosensor to detect the effects of Zn²⁺ ions on A549 cells attached to the low-cost stainless-steel surfaces and its potential for use as an inexpensive detector for a broad range of chemicals and nanomaterials in their cytotoxic concentrations.

Prevalidation of the cAMP-PTx reporter assay for quantitative assessment of pertussis toxin activity

Testing for inactivation of pertussis toxin and reversion to toxicity in aP vaccines has historically relied on the murine histamine sensitization test, that lacks mechanistic understanding, suffers from standardization problems and is associated with severe animal suffering. Though the regulatory requirements for in vivo testing of acellular pertussis (aP) vaccine products have been waived in Europe, it is still common practice globally. Easy and quantitative in vitro methods are therefore urgently needed. One of the alternatives under development is our reporter cell line - CHO-CRE cells - that carries a cAMP-reporter construct. After exposure to pertussis toxin, cells are stimulated with a low concentration of forskolin to allow detection of pertussis toxin dependent changes in intracellular cAMP levels. Here, the results of two prevalidation studies with purified pertussis toxin and pertussis toxin spiked aP vaccines are described that were performed according to the principles of the ICH Q2(R1) guidelines for a content assay. We confirmed the assay's specificity, accuracy, precision, linearity and range. The cAMP-PTx reporter assay allows for objective, reliable and quantitative assessment of pertussis toxin levels in aP vaccines and can thereby boost broad and global replacement of the histamine sensitization test.

Organic Electrochemical Transistors as Versatile Tool for Real-Time and Automatized Viral Cytopathic Effect Evaluation

In-vitro viral studies are still fundamental for biomedical research since studying the virus kinetics on cells is crucial for the determination of the biological properties of viruses and for screening the inhibitors of infections. Moreover, testing potential viral contaminants is often mandatory for safety evaluation. Nowadays, viral cytopathic effects are mainly evaluated through end-point assays requiring dye-staining combined with optical evaluation. Recently, optical-based automatized equipment has been marketed, aimed at the real-time screening of cell-layer status and obtaining further insights, which are unavailable with end-point assays. However, these technologies present two huge limitations, namely, high costs and the possibility to study only cytopathic viruses, whose effects lead to plaque formation and layer disruption. Here, we employed poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (Pedot:Pss) organic electrochemical transistors (OECTs) for the real-time, electrical monitoring of the infection of cytolytic viruses, i.e., encephalomyocarditis virus (EMCV), and non-cytolytic viruses, i.e., bovine coronavirus (B-CoV), on cells. OECT data on EMCV were validated using a commercially-available optical-based technology, which, however, failed in the B-CoV titration analysis, as expected. The OECTs proved to be reliable, fast, and versatile devices for viral infection monitoring, which could be scaled up at low cost, reducing the operator workload and speeding up in-vitro assays in the biomedical research field.

The CHO Cell Clustering Response to Pertussis Toxin: History of Its Discovery and Recent Developments in Its Use

Chinese hamster ovary (CHO) cells respond to pertussis toxin (PT) with a novel clustering pattern, which is dependent on biologically active PT. Since its description in 1983, this cellular response has been refined and used extensively for detection and quantification of PT activity, as well as anti-PT antibodies. There are limitations, however, in the use of this phenomenon as originally described. They are: (1) a subjective, observer-dependent scoring system; (2) the requirement for 16–24 h incubation in order for the response to be clearly detectable; and (3) apparent interference from non-toxin materials. To overcome these limitations, a number of alternative in vitro assays for PT, using CHO cells or other cell types, have been developed and are described elsewhere in this publication. In addressing the challenges associated with the CHO cell assay, we discovered that changes in the electrical impedance-based “normalized cell index” of PT-treated CHO cells obtained with the ACEA xCELLigence instrument enable objective detection/quantification of the PT-induced effect in as little as 3–4 h. To the best of our knowledge, the molecular basis for this intriguing response remains unknown. We present here electron microscopic (EM) images of control and PT-treated cells, which suggest some potential molecular mechanisms.

In Vivo Models and In Vitro Assays for the Assessment of Pertussis Toxin Activity

One of the main virulence factors produced by Bordetella pertussis is pertussis toxin (PTx) which, in its inactivated form, is the major component of all marketed acellular pertussis vaccines. PTx ADP ribosylates Gα_i proteins, thereby affecting the inhibition of adenylate cyclases and resulting in the accumulation of cAMP. Apart from this classical model, PTx also activates some receptors and can affect various ADP ribosylation- and adenylate cyclase-independent signalling pathways. Due to its potent ADP-ribosylation properties, PTx has been used in many research areas. Initially the research primarily focussed on the in vivo effects of the toxin, including histamine sensitization, insulin secretion and leukocytosis. Nowadays, PTx is also used in toxicology research, cell signalling, research involving the blood–brain barrier, and testing of neutralizing antibodies. However, the most important area of use is testing of acellular pertussis vaccines for the presence of residual PTx. In vivo models and in vitro assays for PTx often reflect one of the toxin’s properties or details of its mechanism. Here, the established and novel in vivo and in vitro methods used to evaluate PTx are reviewed, their mechanisms, characteristics and limitations are described, and their application for regulatory and research purposes are considered.