Characterization of primary human leptomeningeal cells in 2D culture

Maintaining the integrity of brain barriers is critical for a healthy central nervous system. While extensive research has focused on the blood-brain barrier (BBB) of the brain vasculature and blood-cerebrospinal fluid barrier (BCSFB) of the choroid plexus, the barriers formed by the meninges have not received as much attention. These membranes create a barrier between the brain and cerebrospinal fluid (CSF), as well as between CSF and blood. Recent studies have revealed that this barrier has been implicated in the development of neurological and immunological disorders. In order to gain a deeper comprehension of the functioning and significance of the meningeal barriers, sophisticated models of these barriers, need to be created. The aim of this paper is to investigate the characteristics of commercially available primary leptomeningeal cells (LMCs) that form the meningeal barriers, in a cultured environment, including their morphology, proteomics, and barrier properties, and to determine whether passaging of these cells affects their behaviour in comparison to their in vivo state. The results indicate that higher passage numbers significantly alter the morphology and protein localisation and expression of the LMCs. Furthermore, the primary cell culture co-stained for S100A6 and E-cadherin suggesting it is a co-culture of both pial and arachnoid cells. Additionally, cultured LMCs showed an increase in vimentin and cytokeratin expression and a lack of junctional proteins localisation on the cell membrane, which could suggest loss of epithelial properties due to culture, preventing barrier formation. This study shows that the LMCs may be a co-culture of pial and arachnoid cells, that the optimal LMC passage range is between passages two and five for experimentation and that the primary human LMCs form a weak barrier when in culture.

The Functions of Cholera Toxin Subunit B as a Modulator of Silica Nanoparticle Endocytosis

The gastrointestinal tract is the main target of orally ingested nanoparticles (NPs) and at the same time is exposed to noxious substances, such as bacterial components. We investigated the interaction of 59 nm silica (SiO2) NPs with differentiated Caco-2 intestinal epithelial cells in the presence of cholera toxin subunit B (CTxB) and compared the effects to J774A.1 macrophages. CTxB can affect cellular functions and modulate endocytosis via binding to the monosialoganglioside (GM1) receptor, expressed on both cell lines. After stimulating macrophages with CTxB, we observed notable changes in the membrane structure but not in Caco-2 cells, and no secretion of the pro-inflammatory cytokine tumor necrosis factor-α (TNF-α) was detected. Cells were then exposed to 59 nm SiO2 NPs and CtxB sequentially and simultaneously, resulting in a high NP uptake in J774A.1 cells, but no uptake in Caco-2 cells was detected. Flow cytometry analysis revealed that the exposure of J774A.1 cells to CTxB resulted in a significant reduction in the uptake of SiO2 NPs. In contrast, the uptake of NPs by highly selective Caco-2 cells remained unaffected following CTxB exposure. Based on colocalization studies, CTxB and NPs might enter cells via shared endocytic pathways, followed by their sorting into different intracellular compartments. Our findings provide new insights into CTxB's function of modulating SiO2 NP uptake in phagocytic but not in differentiated intestine cells.

Heat-Labile Toxin from Enterotoxigenic Escherichia coli Causes Systemic Impairment in Zebrafish Model

Heat-labile toxin I (LT-I), produced by strains of enterotoxigenic Escherichia coli (ETEC), causes profuse watery diarrhea in humans. Different in vitro and in vivo models have already elucidated the mechanism of action of this toxin; however, their use does not always allow for more specific studies on how the LT-I toxin acts in systemic tracts and intestinal cell lines. In the present work, zebrafish (Danio rerio) and human intestinal cells (Caco-2) were used as models to study the toxin LT-I. Caco-2 cells were used, in the 62nd passage, at different cell concentrations. LT-I was conjugated to FITC to visualize its transport in cells, as well as microinjected into the caudal vein of zebrafish larvae, in order to investigate its effects on survival, systemic traffic, and morphological formation. The internalization of LT-I was visualized in 3 × 104 Caco-2 cells, being associated with the cell membrane and nucleus. The systemic traffic of LT-I in zebrafish larvae showed its presence in the cardiac cavity, yolk, and regions of the intestine, as demonstrated by cardiac edema (100%), the absence of a swimming bladder (100%), and yolk edema (80%), in addition to growth limitation in the larvae, compared to the control group. There was a reduction in heart rate during the assessment of larval survival kinetics, demonstrating the cardiotoxic effect of LT-I. Thus, in this study, we provide essential new depictions of the features of LT-I.

Biocompatibility analysis of high molecular weight chitosan obtained from Pleoticus muelleri shrimps. Evaluation in prokaryotic and eukaryotic cells

The search for the exploitation and recycling of biomaterials is increasing for reducing the use of non-renewable resources and minimizing environmental pollution caused by synthetic materials. In this context, Chitosan (CS) being a naturally occurring biopolymer becomes relevant. The aim of the present work was to explore the effects of High Molecular Weight CS (H-CS) from Argentinean shrimp's wastes in prokaryotic and eukaryotic in vitro cell cultures. Ultrastructure of H-CS was analysed by SEM and TEM. In vitro studies were performed in prokaryotic (Lactobacillus casei BL23) and eukaryotic (Caco-2, ARPE-19, EA.hy926 and 3T3-L1) culture cells. High performance microscopic techniques were applied to examine culture cells. No changes in morphology were found in any of the cell types. In addition, fluorescent-dyed H-CS revealed that eukaryotic cells could internalize it optimally. Viability was maintained and proliferation rate even increased for Caco-2, ARPE-19 and 3T3-L1 cells under H-CS treatment. Besides, viability was neither altered in L. casei nor in EA.hy926 cells after H-CS exposure. In conclusion, H-CS could be a suitable biopolymer to be exploited for biomedical or food industry applications.

Intact glycosphingolipidomic analysis of the cell membrane during differentiation yields extensive glycan and lipid changes

Glycosphingolipids (GSLs) are found in cellular membranes of most organisms and play important roles in cell-cell recognition, signaling, growth, and adhesion, among others. A method based on nanoflow high performance liquid chromatography-chip-quadrupole-time-of-flight mass spectrometry (nanoHPLC Chip-Q-TOF MS) was applied towards identifying and quantifying intact GSLs from a variety of samples, including cultured cell lines and animal tissue. The method provides the composition and sequence of the glycan, as well as variations in the ceramide portion of the GSL. It was used to profile the changes in the glycolipidome of Caco-2 cells as they undergo differentiation. A total of 226 unique GSLs were found among Caco-2 samples from five differentiation time-points. The method provided a comprehensive glycolipidomic profile of a cell during differentiation to yield the dynamic variation of intact GSL structures.

Relocation is the key to successful correlative fluorescence and scanning electron microscopy

In this chapter the authors report on an automated hardware and software solution enabling swift correlative sample array mapping of fluorescently stained molecules within cells and tissues across length scales. Samples are first observed utilizing wide-field optical and fluorescence microscopy, followed by scanning electron microscopy, using calibration points on a dedicated sample-relocation holder. We investigated HeLa cells in vitro, fluorescently labeled for monosialoganglioside one (GM-1), across both imaging platforms within tens of minutes of initial sample preparation. This resulted in a high-throughput and high spatially resolved correlative fluorescence and electron microscopy analysis and allowed us to collect complementary nanoscopic information on the molecular and structural composition of two differently distinct HeLa cell populations expressing different levels of GM-1. Furthermore, using the small zebrafish animal model Danio rerio, we showed the versatility and relocation accuracy of the sample-relocation holder to locate fluo-tagged macromolecular complexes within large volumes using long ribbons of serial tissue sections. The subsequent electron microscopy imaging of the tissue arrays of interest enabled the generation of correlated information on the fine distribution of albumin within hepatic and kidney tissue. Our approach underpins the merits that an automated sample-relocation holder solution brings in support of results-driven research, where relevant biological questions can be answered, and high-throughput data can be generated in a rigorous statistical manner.

The effect of a number of H9C2 rat cardiomyocytes passage on repeatability of cytotoxicity study results

The embryonic cardiomyocyte cell line H9C2 is commonly used in numerous in vitro studies, including cardiotoxicity analyses of new drugs. So far no results were published for studies on cell parameters variability during the cell line ageing process. For this reason the aim of the study was to evaluate the effect of a number of H9C2 rat embryonic cardiomyocytes passages on repeatability of study results for selected cytotoxicity parameters, with doxorubicin as a model toxic agent. The cultures were passaged twenty-five times. Cells from passage 1, 5, 10, 15, 20 and 25 were treated with doxorubicin for 24 h. Then drug cytotoxicity was evaluated with the MTT test and additionally the nuclear factor erythroid 2–related factor (Nrf2) gene expression was examined. The analysis of oxidative stress intensity and cell morphology was also assessed. The microscopic appearance of cells indicates that untreated cardiomyocytes morphology changes as well as sensitivity to toxic effects increases with the number of passages. Also an increase in oxidative stress in cells occurs with further passaging of cardiomyocytes. Statistical significance of differences in conducted tests results depended on doxorubicin concentration but in many cases the H9C2 line was found to be a reliable in vitro model only for the first five passages. For this reason it is important to take into consideration that further culturing of cardiomyocytes may not ensure repeatability of study results due to the culture ageing.

Efficient reprogramming of naïve-like induced pluripotent stem cells from porcine adipose-derived stem cells with a feeder-independent and serum-free system

Induced pluripotent stem cells (iPSCs) are somatic cells reprogrammed by ectopic expression of transcription factors or small molecule treatment, which resemble embryonic stem cells (ESCs). They hold great promise for improving the generation of genetically modified large animals. However, few porcine iPSCs (piPSCs) lines obtained currently can support development of cloned embryos. Here, we generated iPSCs from porcine adipose-derived stem cells (pADSCs), using drug-inducible expression of defined human factors (Oct4, Sox2, c-Myc and Klf4). Reprogramming of iPSCs from pADSCs was more efficient than from fibroblasts, regardless of using feeder-independent or feeder-dependent manners. By addition of Lif-2i medium containing mouse Lif, CHIR99021 and PD0325901 (Lif-2i), naïve-like piPSCs were obtained under feeder-independent and serum-free conditions. These successfully reprogrammed piPSCs were characterized by short cell cycle intervals, alkaline phosphatase (AP) staining, expression of Oct4, Sox2, Nanog, SSEA3 and SSEA4, and normal karyotypes. The resemblance of piPSCs to naïve ESCs was confirmed by their packed dome morphology, growth after single-cell dissociation, Lif-dependency, up-regulation of Stella and Eras, low expression levels of TRA-1-60, TRA-1-81 and MHC I and activation of both X chromosomes. Full reprogramming of naïve-like piPSCs was evaluated by the significant up-regulation of Lin28, Esrrb, Utf1 and Dppa5, differentiating into cell types of all three germ layers in vitro and in vivo. Furthermore, nuclear transfer embryos from naïve-like piPSCs could develop to blastocysts with improved quality. Thus, we provided an efficient protocol for generating naïve-like piPSCs from pADSCs in a feeder-independent and serum-free system with controlled regulation of exogenous genes, which may facilitate optimization of culture media and the production of transgenic pigs.

Dietary flavonoid genistein induces Nrf2 and phase II detoxification gene expression via ERKs and PKC pathways and protects against oxidative stress in Caco-2 cells

SCOPE

Flavonoids have well-known antioxidant, anti-inflammatory, and anti-cancer activities. Isoflavone genistein is considered a potent antioxidant agent against oxidative stress. Although several mechanisms have been proposed, a clear antioxidant mechanism of genistein is still remained to be answered.

METHODS AND RESULTS

In this study, we focused on the concerted effects on expression of Nrf2 and phase II enzyme pathway components. Transient transfection assays, RT-PCR and immunoblot analysis were performed to study its molecular mechanisms of action. In Caco-2 cells, treatment with genistein markedly attenuated H(2)O(2) -induced peroxide formation; this amelioration was reversed by buthionine sulfoximine(GCLC inhibitor) and zinc protoporphyrin(HO-1 inhibitor). Genistein increased HO-1 and GCLC mRNA and protein expression. Genistein treatment activated the ERK1/2 and PKC signaling pathway; therefore increased Nrf2 mRNA and protein expression. The roles of the ERK1/2 and PKC signaling pathway were determined using PD98059 (ERK1/2 inhibitor) and GF109203X (PKC inhibitor) and RNA interference directed against Nrf2. Both inhibitors and siNrf2 abolished genistein-induced HO-1 and GCLC protein expression. These results suggest the involvement of ERK1/2, PKC, and Nrf2 in inducing HO-1 and GCLC by genistein.

CONCLUSION

Our studies show that genistein up-regulated HO-1 and GCLC expression through the EKR1/2 and PKC /Nrf2 pathways during oxidative stress.

Acetyl salicylic acid induces damage to intestinal epithelial cells by oxidation-related modifications of ZO-1

Acetyl salicylic acid (ASA) is one of the most frequently prescribed medications for the secondary prevention of cardiovascular and cerebrovascular events. It has recently been reported to cause small intestinal mucosal injury at a considerably higher rate than previously believed. The aim of this study is to investigate the mechanism by which this occurs using an in vitro small intestine model focusing on the role of oxidative stress and cell permeability. Differentiated Caco-2 exhibits a phenotype similar to human small intestinal epithelium. We measured whether ASA induced the increase of differentiated Caco-2 permeability, the decrease of tight junction protein expression, the production of reactive oxygen species (ROS), and the expression of ROS-modified zonula occludens-1 (ZO-1) protein. In some experiments, Mn(III) tetrakis(1-methyl-4-pyridyl)porphyrin (MnTMPyP, a superoxide dismutase mimetic) was used. The nontoxic concentration of ASA decreased transepithelial electrical resistance and increased the flux of fluorescein isothiocyanate-conjugated dextran across Caco-2 in a time-dependent manner. The same concentration of ASA significantly decreased ZO-1 expression among TJ proteins as assessed by Western blot and immunocytochemistry and increased ROS production and the expression of oxidative stress-modified ZO-1 protein. However, MnTMPyP suppressed the ASA-induced increased intercellular permeability and the ASA-induced ROS-modified ZO-1 expression. Our findings indicate that ASA-induced ROS production can specifically modify the expression of ZO-1 protein and induce increased cell permeability, which may ultimately cause small intestinal mucosal injury.

Selenium and zinc internalized by Lactobacillus buchneri Lb26 (DSM 16341) and Bifidobacterium lactis Bb1 (DSM 17850): improved bioavailability using a new biological approach

BACKGROUND

Minerals, often referred to as micronutrients, are one of the 5 fundamental groups of nutrients needed to sustain life. Micronutrient malnutrition affects >50% of the worldwide population. In particular, zinc (Zn) deficiency is considered an emerging public health problem in India and in other developing countries. Selenium (Se) is another trace mineral essential for humans and animals. Dietary Se exists primarily as selenomethionine and selenocysteine. In addition, Se may be present in its inorganic form (selenite) in some vegetables. To increase the daily intake of these minerals, numerous food supplements containing different inorganic and organic forms of Zn or Se are commercially available. At any rate, it is quite well known that inorganic salts have a very low bioavailability. Organic salts, commonly based on gluconate, orotate, citrate, or other molecules, are characterized by a higher systemic effect. The innovative opportunity of using certain species of probiotics enriched with the 2 minerals could represent an interesting alternative to these preparations. Diet integration with bacteria able to internalize Zn and Se may embody a new application of probiotics.

METHODS

To overcome the difficulties of in vivo animal or human trials, in this work a cell culture model using Caco-2 cells in bicameral chambers (Transwell system) was developed and validated to quantify the bioavailability of some commercial forms of Se and Zn compared with the organic forms accumulated intracellularly by Lactobacillus buchneri Lb26 (DSM 16341) and Bifidobacterium lactis Bb1 (DSM 17850), respectively.

RESULTS

The experimental data collected demonstrated a significantly higher bioavailability of Se and Zn internalized by L. buchneri Lb26 (DSM 16341) and B. lactis Bb1 (DSM 17850), respectively, compared with the inorganic and even organic forms tested. In particular, the Se accumulated at the intracellular level by L. buchneri Lb26 proved to be 5.9, 9.4, and 65 times more absorbable than sodium selenite, seleno-L-methionine, and seleno-L-cysteine, respectively. In contrast, Zn internalized by B. lactis Bb1 showed an absorption that was >16 times higher by Caco-2 cells compared with zinc gluconate and a 31.5 times higher absorption compared with zinc sulfate. Most notably, Se and Zn internalized by the 2 probiotics studied are the only forms able to reach the Transwell basolateral compartment at a concentration higher than the concentration found in the apical compartment, therefore suggesting a considerably higher in vivo ability to be absorbed into the bloodstream. Both organic and inorganic forms of Se and Zn were predominantly found in the apical compartment, thus demonstrating their poor ability to diffuse into the cell and become bioavailable in all subcellular areas.

CONCLUSIONS

The opportunity of delivering minerals in a highly bioavailable form by means of a probiotic bacterium has not been deeply investigated to date. This is the first study reporting quantitative data on the bioavailability and percentage of absorption of minerals internalized by specific probiotics. The most noticeable aspect is the significantly higher absorption of both probiotic Se and Zn compared with their organic forms, with particular reference to seleno-L-methionine, seleno-L-cysteine, and zinc gluconate.

Imaging fluorescently labeled complexes by means of multidimensional correlative light and transmission electron microscopy: practical considerations

These days the common ground between structural biology and molecular biology continues to grow thanks to the biomolecular insights offered by correlative microscopy, even though the vision of combining insights from different imaging tools has been around for nearly four decades. The use of correlative imaging methods to dissect the cell's internal structure is progressing faster than ever as shown by the boom in the number of methodological approaches available for correlative microscopy studies, each designed to address a specific scientific question. In this chapter, we will present a relatively straightforward approach to combining information from fluorescence microscopy and electron microscopy at the supramolecular level. The method combines live-cell and/or confocal laser microscopy with classical sample preparation for transmission electron microscopy (TEM), thereby allowing the integration of dynamic details of subcellular processes with insights about the organelles and molecular machinery involved. We illustrate the applicability of this multidimensional correlative microscopy approach on cultured Caco-2 colorectal cancer cells exposed to fluorescently labeled cisplatin, and discuss how these methods can deepen our understanding of key cellular processes, such as drug uptake and cell fate.