Evaluation of in vitro cytotoxicity and paracellular permeability of intact monolayers with mouse embryonic stem cells

Cosm-nutraceutical nanovesicles for acne treatment: Physicochemical characterization and exploratory clinical experimentation

The full exploration of the 'nutraceuticals' therapeutic potential in cosmetics has been hindered by their poor stratum corneum permeation. Therefore, the aim of the present study was to formulate a nutraceutical; quercetin, in novel vitamin C based nanovesicles (aspasomes), and to explore their beneficial effects in the treatment of acne. Aspasomes were characterized for their particle size, zeta potential, entrapment efficiency (EE%), 3-months storage stability, skin deposition/permeation, antioxidant potential, and morphology. Aspasomes antibacterial efficacy on Propionibacterium acnes using the zone of inhibition assay was also tested, whilst their safety on skin fibroblastic cells was assessed in vitro using 3T3 CCL92 cell lines. An exploratory clinical trial was conducted in acne patients, and the percentage reduction of inflammatory, non-inflammatory and total acne lesions was taken as the evaluation criterion. Results revealed that quercetin-loaded aspasomes displayed a desirable nanometer size (125-184 nm), negative charge with good storage stability, and high skin deposition reaching 40%. Aspasomes managed to preserve the antioxidant activity of quercetin, and exhibited a significantly higher antibacterial effect (15 ± 1.53 mm) against Propionibacterium acnes than quercetin alone (8.25 ± 2.08 mm), and were safe on skin fibroblastic cells. Upon clinical examination in 20 acne patients (14 females, 6 males), quercetin aspasomes exhibited reduction percentages of 77.9%, 11.8% and 55.3% for inflammatory lesions, comedones and total lesions respectively. This opens vast applications of the presented formulation in the treatment of other oxidative skin diseases, and delineates the nutraceuticals and nanoformulations prepared from natural materials as promising dermatological treatment modes.

Toxicity of antimony, copper, cobalt, manganese, titanium and zinc oxide nanoparticles for the alveolar and intestinal epithelial barrier cells in vitro

Heavy metals are found naturally on Earth and exposure to them in the living environment is increasing as a consequence of human activity. The toxicity of six different metal oxide nanoparticles (NP) at different points in time was compared using resazurin assay. After incubating Caco2 and A549 cells with 100 μg/mL of Sb₂O₃, Mn₃O₄ and TiO₂ nanoparticles (NPs) for 24 h no toxic effects were observed while Co₃O₄ and ZnO NPs had moderate effects and CuO NPs were toxic below 100 μg/mL (24 h EC₂₅ = 11 for A549 and 71 μg/mL for Caco2). The long-term monitoring (up to 9 days) of cells to NPs revealed that the toxic effects of Mn₃O₄ and Sb₂O₃ NPs remarkably increased over time. The 9 day EC₅₀ values for Sb₂O₃ NPs were 22 and 48 μg/mL for A549 and Caco2 cells; and for Mn₃O₄ NPs were 47 and 29 μg/mL for A549 and Caco2 cells, respectively. In general, the sensitivity of the cell lines in the resazurin assay was comparable. Trans epithelial electrical resistance (TEER) measurements were performed for both cell types exposed to Co₃O₄, Sb₂O₃ and CuO NPs. In TEER assay, the Caco2 cells were more susceptible to the toxic effects of these NPs than A549 cells, where the most toxic NPs were the Sb₂O₃ NPs: the permeability of the Caco2 cell layer exposed to 10 μg/mL Sb₂O₃ NPs already increased after 24 h of exposure.

Cadmium affects mitotically inherited histone modification pathways in mouse embryonic stem cells

The fetal basis of adult disease (FeBAD) theorizes that embryonic challenges initiate pathologies in adult life through epigenetic modification of gene expression. In addition, inheritance of H3K27 methylation marks, especially in vitro, is still controversial. Metals, such as Cd, are known to affect differentiation, DNA repair and epigenetic status in mES cells. We tested the premise that Cd exerts differential toxicity in mouse embryonic stem (mES) cells by targeting total histone protein (THP) production early in stem cell development, while affecting H3K27-mono-methylation (H3K27me(1)) in latter stages of differentiation. The inability of mES cells to recover from Cd insult at concentrations greater than IC50 indicates that maximum cytotoxicity occurs during initial hours of exposure. Moreover, as a measure of chromatin stability, low dose acute Cd exposure lowers THP production. The heritable effects of Cd exposure on cell proliferation, chromatin stability and transcription observed through several cell population doublings were detected only during alternate passages on days 3, 7, and 11, presumably due to slower maturation of histone methylation marks. These findings demonstrate a selective disruption of chromatin structure following acute Cd exposure, an effect not seen in developmentally mature cells. Hence, we present that acute Cd toxicity is cumulative and disrupts DNA repair, while concurrently affecting cell cycle progression, chromatin stability and transcriptional state in mES cells.

Undifferentiated murine embryonic stem cells used to model the effects of the blue-green algal toxin cylindrospermopsin on preimplantation embryonic cell proliferation

Undifferentiated mouse embryonic stem cell (mES) proliferation in vitro resembles aspects of in vivo pre-implantation embryonic development. mES were used to assess the embryo-toxicity of cylindrospermopsin (CYN), a water contaminant with an Australian Drinking Water Guideline (ADWG) of 1 μg/L. mES exposed to 0-1 μg/mL CYN for 24-168 h were subjected to an optimised crystal violet viability assay. mES exposed to retinoic acid ± 1 μg/L CYN differentiated into neural-like cells confirmed by morphological examination and RT-PCR for Oct4, Brachyury and Nestin. The CYN No Observed Effect Concentration (OEC) was 0.5 μg/mL, the Lowest OEC was 1 μg/mL (p < 0.001, n = 3), and the IC50 was 0.86 μg/mL after 24 h. The ADWG 1 μg/L CYN did not affect differentiation or proliferation after 72 h, but decreased proliferation after 168 h (p < 0.05). We conclude that higher algal bloom-associated CYN concentrations have the potential to impair in vivo pre-implantation development, and the mES crystal violet assay has broad application to screening environmental toxins.

Metformin increases mitochondrial energy formation in L6 muscle cell cultures

A popular hypothesis for the action of metformin, the widely used anti-diabetes drug, is the inhibition of mitochondrial respiration, specifically at complex I. This is consistent with metformin stimulation of glucose uptake by muscle and inhibition of gluconeogenesis by liver. Yet, mitochondrial inhibition is inconsistent with metformin stimulation of fatty acid oxidation in both tissues. In this study, we measured mitochondrial energy production in intact cells adapting an in vivo technique of phosphocreatine (PCr) formation following energy interruption ("PCr recovery") to cell cultures. Metformin increased PCr recovery from either dinitrophenol (DNP) or azide in L6 cells. We found that metformin alone had no effect on cell viability as measured by total ATP concentration, trypan blue exclusion, or 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide reduction. However, treatments with low concentrations of DNP or azide reversibly decreased ATP concentration. Metformin increased 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide reduction during recovery from either agent. Viability measured by trypan blue exclusion indicated that cells were intact under these conditions. We also found that metformin increased free AMP and, to a smaller extent, free ADP concentrations in cells, an action that was duplicated by a structurally unrelated AMP deaminase inhibitor. We conclude that, in intact cells, metformin can lead to a stimulation of energy formation, rather than an inhibition.

Water-soluble organic solubilizers for in vitro drug delivery studies with respiratory epithelial cells: selection based on various toxicity indicators

The aim of this study was to use different toxicity indices to investigate the effect of N, N-Dimethylacetamide (DMA), Polyethylene glycol 400 (PEG 400), Methyl-Pyrrolidone/aromatic hydrocarbon (MPH), Cremophor((R)) EL, and Dimethylsulfoxide (DMSO) on Calu-3 cells. Membrane perturbation and cytotoxicity were investigated using lactate dehydrogenase (LDH), 3-[4, 5-Dimethylthiazol-2-yl]-2, 5-diphenyl tetrazolinium bromide (MTT), transepithelial electrical resistance (TEER) assessment, sodium fluorescein (SF) permeation, and phalloidin actin staining. The MDH activity of cells treated with DMSO (<or= 4.0 v/v), Cremophor EL (<or= 10% v/v), and PEG 400 (<or= 10% v/v) was not significantly altered (p > 0.5). Similarly, DMSO (<or= 8.0% v/v), Cremophor((R)) EL (<or= 16.0% v/v) and PEG 400 (<or= 32.0% v/v) had no significant effect on LDH (p > 0.05). Conversely, MPH and DMA at very low concentrations (<or= 0.25% v/v) induced cell toxicity. However, up to 2.0% v/v MPH and (DMA) had no effect on TEER and SF permeation. No obvious change in actin staining was observed for DMSO (15%), Cremophor((R)) EL (15%), and MPA (1%). However, the actin architecture for cells treated with DMA (1%) and PEG 400 (15%) appeared significantly different from control. Based on this study Cremophor (<or= 10%), PEG 400 (<or= 5%), and DMSO (<or= 5%), and low concentrations of DMA and MPA (<or= 0.25%) were suitable for in vitro studies with Calu-3 cells.

Effect of metals on β-actin and total protein synthesis in cultured human intestinal epithelial cells

INTRODUCTION

As an important structural protein, β-actin is associated with anchoring of tight junctions (TJs) to the cell scaffold. Caco-2 cells, an immortal intestinal epithelial cell line, rely on β-actin to form intact monolayers with high transepithelial electrical resistance in cell culture inserts.

METHODS

We examined the effect of six metals on expression of β-actin mRNA and β-actin synthesis, on total and net production of newly synthesized proteins, on paracellular transport of TJ markers, and on cell viability in confluent monolayers. [(3)H]-glycine and [(3)H]-tyrosine were used as indicators of newly synthesized proteins in the absence or presence of increasing concentrations of arsenic, cadmium, copper, manganese, mercury and nickel. The monolayers were exposed to 24-h single exposures as well as continuous daily repeated doses of metals for 48-h and 96-h.

RESULTS

Results suggest that decreases in newly synthesized proteins, in which β-actin represents about 10%, correlated with 2- to 5-fold higher expression of β-actin mRNA for the higher concentrations of metals. Interestingly, IC(50)s calculated for each chemical for 24-h acute and 48- and 96-h repeated dosing experiments, using the MTT viability assay and paracellular permeability markers, decreased newly synthesized and total proteins to 10% and 40% of control, respectively.

DISCUSSION

Overall, the results indicate that, at equivalent concentrations, the metals affect β-actin mRNA and newly synthesized proteins before cell viability and paracellular permeability are compromised. Consequently the results help in elucidating mechanisms of metal cytotoxicity that lead to understanding the relationship between tight junction integrity, paracellular transport, and cell viability.

Validating and troubleshooting ocular in vitro toxicology tests

In vitro organotypic models for testing ocular irritants have warranted sufficient interest as methods to replace in vivo ocular testing. The in vitro organotypic models claim to maintain short-term normal physiological and biochemical functions of the mammalian cornea in an isolated system. In these test methods, damage by the test substance is assessed by quantitative measurements of changes in corneal opacity and permeability using opacitometry and spectrophotometry, respectively. Both measurements are used quantitatively for irritancy classification for prediction of the in vivo ocular irritation potential of a test substance. Examples of organotypic models that incorporate these criteria include: the bovine corneal opacity and permeability (BCOP) assay, the isolated chicken eye (ICE) test method and the isolated rabbit eye (IRE) assay. A fourth method, the hen's egg test-chorioallantoic membrane (HET-CAM) assay, differs in the evaluation criteria but is also normally included among this class of in vitro protocols. Each of these protocols is discussed in detail as representative candidate in vitro methods for assessing ocular irritation and corrosion. The methodologies, protocol details, applications, and their validation status are discussed. A brief historical perspective of the development of original in vitro ocular testing models is also mentioned. More importantly, improving and troubleshooting the current techniques, in order to present the models as stand-alone in vitro tools for ocular toxicity assessment, is emphasized.