Pro-inflammatory effects of different MWCNTs dispersions in p16(INK4A)-deficient telomerase-expressing human keratinocytes but not in human SV-40 immortalized sebocytes

We tested whether multi-walled carbon nanotubes (MWCNTs) induce oxidative stress and a pro-inflammatory response in human N-hTERT telomerase-immortalized keratinocytes, in human SZ95 SV-40 immortalized sebocytes and in in vitro reconstructed epidermises. MWCNTS were tested in various dispersion states, from raw and agglomerated particles to isolated entities obtained by sonication in the presence of dispersive agents (hydroxypropylcellulose and Pluronic F108). It was observed that: (a) Contrary to individualized MWCNTs, agglomerated particles prepared by suspension into pure water increased the intracellular levels of reactive oxygen species as well as the expression and secretion of interleukin-8 in N-hTERT cells; (b) the inflammatory signature of MWCNTs in N-hTERT cells, drawn by transcriptomic analysis with low-density microfluidic cards, included various other cytokines such as interleukin-6 or C-C motif ligand 3; (c) the pro-inflammatory effects of MWCNTs, as assessed by interleukin-8 transcript level and protein release, were not observed in SZ95 cells; and (d) the secretion of interleukins-1α and -8 from in vitro reconstructed epidermal tissues, used as specific markers for skin irritation and sensitization, was unaffected in presence of MWCNTs, confirming that the cornified layer is an efficient barrier against MWCNTs.

Pharmacokinetics and Metabolism of 14C-Brivaracetam, a Novel SV2A Ligand, in Healthy Subjects

This study was designed to investigate the human absorption, disposition, and mass balance of (14)C-brivaracetam, a novel high affinity SV2A ligand with potent anticonvulsant activity. Six healthy male subjects received a single p.o. dose of (14)C-brivaracetam (150 mg, 82 microCi, or 3.03 MBq). Serial blood and complete urine and feces were collected until 144 h postdose. Expired air samples were obtained until 24 h. Brivaracetam was rapidly absorbed, with C(max) of 4 mug/ml occurring within 1.5 h of dosing. Unchanged brivaracetam amounted to 90% of the total plasma radioactivity, suggesting a modest first-pass effect. Plasma protein binding of radioactivity was low (17.5%). Urinary excretion exceeded 90% after 2 days, and the final mass balance reached 96.8% of the radioactivity in urine and 0.7% in feces. Only 8.6% of the radioactive dose was recovered in urine as unchanged brivaracetam, the remainder being identified as non-cytochrome P450 (P450)- and P450-dependent biotransformation products resulting from hydrolysis of the amide moiety (M9, 34.2%), hydroxylation of the n-propyl side chain (M1b, 15.9%), and a combination of these two pathways leading to the hydroxy acid (M4b, 15.2%). Minor amounts of taurine and glucuronic acid conjugates and other oxidized derivatives were also identified. Brivaracetam is completely absorbed, is weakly bound to plasma proteins, extensively biotransformed through several metabolic pathways, and eliminated renally.

Modelling the human epidermis in vitro: tools for basic and applied research

Culture models of tissues and organs are valuable tools developed by basic research that help investigation of the body functions. Modelling is aimed at simplifying experimental procedures in order to better understand biological phenomena, and consequently, when sufficiently characterized, culture models can also be utilized with high potential in applied research. In skin biology and pathology, the development of cultures of keratinocytes as monolayers has allowed the elucidation of most functional and structural characteristics of the cell type. Beside the multiple great successes that have been obtained with this type of culture, this review draws attention on several neglected characteristics of monolayer cultures. The more sophisticated models created in order to reconstruct the fully differentiated epidermis have followed the monolayers. The epidermal reconstruction produces all typical layers found in vivo and thus makes the model much less simple, but only this kind of model allows the study of full differentiation in keratinocyte and production of the cornified barrier. In addition to its interest in basic research, the reconstructed epidermis is currently gaining a lot of interest for applied research, particularly as an alternative to laboratory animals in the chemical and cosmetic industry. Today several commercial providers propose reconstructed skin or epidermis, but in vitro assays on these materials are still under development. In order to be beneficial at long term, the validation of assays must be performed on a material whose availability will not be interrupted. We warn here providers and customers that the longevity of in vitro assays will be guaranteed only if these assays are done with well-described models, prepared according to published procedures, and must consider having a minimum of two independent simultaneous producers of similar material.

A simple reconstructed human epidermis: preparation of the culture model and utilization in in vitro studies

The preparation of a reconstructed human epidermis is described with examples of its utilization in in vitro studies. The model was obtained by culturing normal human keratinocytes at high cell density for 14 days in serum-free and high calcium (1.5 m M) medium on an inert polycarbonate filter at the air-liquid interface. These stratified cultures showed histological features similar to those observed in vivo in the epidermis: a proliferating basal layer and differentiating spinous, granular, and cornified layers. Electron microscopy illustrated lamellar bodies, junctions and keratohyalin granules. Immunofluorescent localization of epidermal markers (keratins 14 and 10, involucrin and filaggrin) revealed typical differentiation. This in vitro reconstructed tissue was used in studies of toxic effects of chemicals. The modelled tissue showed progressive cytotoxicity of a skin irritant (benzalkonium chloride) and a sensitizer (dinitrochlorobenzene) as assessed by MTT assay. Moreover, differential release of interleukin-1alpha and interleukin-8 were measured after 20 h of incubation allowing the irritant to be distinguished from the sensitizer. Permeation studies indicated efficient barrier function of the reconstructed epidermis, as well as metabolizing properties towards hormones. This model can be custom-made and is potentially useful for studies involving keratinocytes in the epidermis, in basic science, dermatology or toxicology.

Analysis of interleukin-1alpha (IL-1alpha) and interleukin-8 (IL-8) expression and release in in vitro reconstructed human epidermis for the prediction of in vivo skin irritation and/or sensitization

In the present study, reconstructed human epidermis (RHE) was used as an in vitro model to discriminate 1-chloro-2,4-dinitrobenzene (DNCB), nickel sulfate (NiSO(4)), oxazolone (OXA), 2,4-dinitrofluorobenzene (DNFB) and 2,4,6-trinitrobenzenesulfonic acid (TNBS) as skin sensitizers from benzalkonium chloride (BC), benzoic acid (BA) and sodium lauryl sulfate (SLS) as skin irritants. Our criteria were (a) the differential IL-1alpha and IL-8 synthesis and release (b) cytotoxicity assessment by MTT assay. When the RHE are topically treated with the sensitizers, very low levels of extra- and intracellular IL-1alpha are observed although they induce significant cytotoxicity. In contrast, they exhibit a sharp maximum of IL-8 release. In the presence of the tested irritants, we observe the inverse cytokine release profile, although they induce dose-dependent cytotoxicity profiles similar to those observed with the sensitizers. Finally, IL-1alpha mRNA upregulation is observed after topical application of both sensitizers and irritants, but only the latter significantly increase extracellular IL-1alpha. In conclusion, our results suggest that the associated determination of IL-8, with IL-1alpha, and MTT conversion are at least necessary to discriminate and classify, in a single assay, irritant and sensitizing agents and represent a potential in vitro alternative to two classical in vivo assays.

Follow-up to the ECVAM prevalidation study on in vitro tests for acute skin irritation. The European Centre for the Validation of Alternative Methods Skin Irritation Task Force report 2

The European Centre for the Validation of Alternative Methods (ECVAM) Skin Irritation Task Force was established in 1996, to review the status of the development and validation of alternative tests for skin irritation and corrosion, and to identify appropriate non-animal tests for predicting human skin irritation that were sufficiently well-developed to be prevalidated and validated by ECVAM. The EpiDerm method, based on a reconstituted human skin model, was proposed as being sufficiently well advanced to enter a prevalidation (PV) study. Based on a review of test protocols, prediction models (PMs), and data submitted by test developers on ten specified chemicals, with 20% sodium lauryl sulphate as a reference standard, the task force recommended the inclusion of four other tests: EPISKIN and PREDISKIN, based on reconstituted human epidermis or on human skin; the non-perfused pig-ear test, based on pig skin; and the skin integrity function test (SIFT), with ex vivo mouse skin. The prevalidation study on these methods was funded by ECVAM, and took place during 1999-2000. The outcome of the PV study was that none of the methods was ready to enter a formal validation study, and that the protocols and PMs of the methods had to be improved in order to increase their predictive abilities. Improved protocols and PMs for the EpiDerm and EPISKIN methods, the pig ear test, and the SIFT were presented at an extended Task Force meeting held in May 2001. It was agreed that, in the short term, the performance of the revised and harmonised EpiDerm and EPISKIN methods, as well as the modified SIFT, should be evaluated in a further study with a new set of 20 test chemicals. In addition, it was decided that the SIFT and the pig ear test would be compared to see if common endpoints (transepidermal water loss, methyl green-pyronine stain) could be identified.

A European Interlaboratory Evaluation Study of an In Vitro Ocular Irritation Model (Skin2™ Model ZK1100) using 15 Chemicals and 3 Shampoos

The aim of this interlaboratory study was to ascertain the feasibility of the use of the in vitro Skin2™ Model ZK1100 kit as a tissue substrate for cytotoxicity studies.

Eighteen compounds — 15 raw chemicals and 3 finished products (commercial shampoos) — were tested in four different laboratories on two separate occasions, and the data obtained were compared with the data available in the literature on eye irritancy potential.

The kit was easy to manage, and no technical difficulties were encountered in the estimation of MTT reduction, LDH and PGE2 release in the medium. Similar MTT50 values were recorded in two independent experiments in each laboratory, and the rankings of irritation potency within the same chemical class were comparable. Both LDH and PGE2 were important parameters to be taken into account along with MTT50 values in establishing the irritation potential of some categories of compounds.

Eicosanoids modulate CR1- and Fc-dependent bacterial phagocytosis

It is known that macrophages produce large amounts of eicosanoids during phagocytosis and that pharmacological concentrations of prostaglandin E2 (PGE2) inhibit phagocytosis in several models. However, the physiological effect on phagocytosis of endogenous prostaglandins, produced during CR1- or FcR-mediated bacterial phagocytosis, remains unclear. In this study, we show that indomethacin inhibits the CR1- but not the FcR-dependent phagocytosis of bacteria by rat peritoneal cells in the same range of concentrations that inhibit the synthesis of PGE2, PGI2 and thromboxane A2. An exogenous supply of PGE2 and PGE1 (10(-10) to 10(-8) M) restored the CR1-mediated phagocytosis; higher concentrations were inhibitory. Our data indicate that PGE2 and/or PGI2, produced by rat peritoneal cells, are involved in CR1-dependent bacterial phagocytosis.

Macrophage heterogeneity in prostaglandins and thromboxane synthesis: differential activation by Fc- and C3b-dependent bacterial phagocytosis

Resident peritoneal macrophages, obtained from rats, were separated into subpopulations by centrifugation on a Percoll discontinuous density gradient. Nine fractions of pure macrophages were isolated. Each subpopulation was studied for Fc- and C3b-dependent bacterial phagocytosis and assayed for the related synthesis of PGE2, TxA2 and PGI2, measured by their stable metabolites TxB2 and 6-Keto-PGF1. The results show that with decreasing density, which corresponds to a greater maturity, the production of PGE2 increases and that of TxB2 and 6-Keto-PGF1 decreases. The cells of low density were mostly stimulated by IgG-opsonized bacteria, whereas those of high density responded preferentially to C3b- opsonized bacteria. This pattern is roughly similar to the one characterizing the phagocytosis via these two receptors although the correlation is not absolute. It can be concluded that enzymes involved in the metabolism of arachidonic acid, as well as receptors for C3b and IgG, are differentially expressed among resident macrophage subpopulations and thus during macrophage maturation.

Role of vitamin E in the protection of the resident macrophage membrane against oxidative damage

The variation in tocopherol content of resident peritoneal rat macrophages was investigated during an oxidative stress provided by superoxide anions. Fluorometric measurements showed that phagocytic cells contain 298 +/- 18 ng vit.E/mg prot. The vitamin E level remains nearly constant during 1 h of incubation: 266 +/- 46 ng vit.E/mg prot. HPLC control at 37 degrees C validates our fluorometric measurement. Superoxide anions (O2-.) synthesis was activated by phorbol myristate acetate (PMA) (0.5 microgram/ml), after 1 h of incubation a decrease of 40% of the macrophage tocopherol level was observed and assessed by HLPC control. No tocopherolquinone (TQ) was detected. To clarify this point, tocopherol oxidation was followed spectrophotometrically. Results did not show any appearance of TQ at 265 nm but appearance of a peak at 307 mm. This our results show for the first time that macrophages possess vitamin E which plays a partial role in the protection of their plasma membrane. The lack of detection of TQ is of interest and the study of this unidentified product of oxidation should help us to understand the exact metabolism of vitamin E.