PubMed Health⌕ Search

Biomedical subjects

M Cottin

Publications and source records attributed to M Cottin.

11 recordsLinked to original sources
PubMed2002

Use of human reconstituted epidermis Episkin for assessment of weak phototoxic potential of chemical compounds.

BACKGROUND/PURPOSE: Drug-induced phototoxicity is a non-immunological inflammatory skin reaction, caused by concurrent topical or systemic exposure to a specific molecule and ultraviolet radiation. Most of phototoxic compounds absorb energy particularly from UVA light leading to activated derivatives, which can induce cellular damage. This type of adverse cutaneous response can be reproduced, in vitro, using human skin models. In this study, we investigated the ability of human reconstituted epidermis Episkin to assess skin phototoxicity of weak phototoxic compounds such as 6-methylcoumarin and ofloxacin, compared to a strong one, chlorpromazine, and two negative controls (sodium dodecyl sulphate (SDS), sulisobenzone). METHODS: : After 1 h incubation with five test concentrations of each chemical compound, epidermis was then exposed or not to UVA at a non-cytotoxic dose (50 J/cm2). 18 h after UVA exposure, cellular damage was evaluated measuring cytotoxicity by MTT conversion test; in addition, pro-inflammatory mediator IL-1alpha release was also investigated. RESULTS: Topical pretreatment of Episkin, with weak phototoxic compounds induced, after UVA exposure, a dose-dependent decrease in cell viability, in concordance with an increasing IL-1alpha release. Moreover, compared to chlorpromazine, the lower IL-1alpha release observed with 6-methylcoumarin and ofloxacin could be linked to their weak phototoxic potential. CONCLUSION: Human reconstituted epidermis Episkin can be useful to study in vitro the onset of cutaneous phototoxic reactions and particularly to identify weak phototoxic compounds.

Dermatitis, Phototoxic↗
PubMed2002

Improvement of the experimental setup to assess cutaneous bioavailability on human skin models: dynamic protocol.

Human skin models, such as EpiDerm and Episkin, are not easily mounted into static or dynamic diffusion cells that are commonly used to perform bioavailability studies with human skin ex vivo. For various reasons, such as fragility, small sample size, and other morphological constraints, skin absorption studies with human skin models are often carried out on the delimited skin surface obtained by gluing a ring onto the reconstituted epidermis and manually exchanging the receptor solution. However, such an experimental setup is prone to artifacts. Discontinuous removal of the receptor fluid leads to alternating sink conditions, and an area of application smaller than the area in contact with the receptor fluid, as well as imperfect seal of the glued ring, may result in inaccurate penetration rates. Human skin models were shown to be relatively easily mounted into In-Line cells (PermeGear Inc.), vertical diffusion cells which appear to be appropriately designed for such a purpose. In-Line cells allowed accurate determination of solute penetration as well as automated sampling of receptor fluid. Excised human skin can be mounted into these cells as well, making it possible to compare penetration rates through different types of skin samples under identical conditions. Using mannitol as a reference compound, penetration profiles and epidermal distribution similar to those obtained with human skin ex vivo were obtained both with EpiDerm and Episkin. Under the present conditions, human skin models were more permeable to mannitol than excised human skin, which was only slightly permeable to mannitol. Due to these experimental innovations and to the good agreement with the absorption characteristics through human skin ex vivo, EpiDerm and Episkin seem to be promising human skin models for testing the cutaneous bioavailability of topical products in vitro.

Biological Availability↗
PubMed2000

Contact sensitizers specifically increase MHC class II expression on murine immature dendritic cells.

Contact sensitivity is a T-cell-mediated immune disease that can occur when low-molecular-weight chemicals penetrate the skin. In vivo topical application of chemical sensitizers results in morphological modification of Langerhans cells (LC). Moreover, within 18 h, LC increase their major histocompatibility complex (MHC) class II antigens expression and migrate to lymph nodes where they present the sensitizer to T lymphocytes. We wanted to determine if such an effect could also be observed in vitro. However, because of the high genetic diversity encountered in humans, assays were performed with dendritic cells (DC) obtained from a Balb/c mouse strain. The capacity of a strong sensitizer, DNBS (2,4-dinitrobenzene sulfonic acid), to modulate the phenotype of bone marrow-derived DC in vitro, was investigated. A specific and marked increase of MHC class II molecules expression was observed within 18 h. To eliminate the use of animals in sensitization studies, the XS52 DC line was tested at an immature stage. A 30-min contact with the strong sensitizers DNBS and oxazolone, or the moderate mercaptobenzothiazole, resulted in upregulation of MHC class II molecules expression, analyzed after 18-h incubation. This effect was not observed with irritants (dimethyl sulfoxide and sodium lauryl sulfate) nor with a neutral molecule (sodium chloride). These data suggested the possibility of developing an in vitro model for the identification of the sensitizing potential of chemicals, using a constant and non animal-consuming material.

Animal Testing Alternatives↗
PubMed1997

Evaluation of eye irritation potential: statistical analysis and tier testing strategies.

Eye irritation testing, specifically the Draize test, has been the centre of controversy for many reasons. Several alternatives, based on the principles of reduction, refinement and replacement, have been proposed and are being used by the industry and government authorities. However, no universally applicable, validated non-animal alternative(s) is currently available. This report presents a statistical analysis and two testing approaches: the partial least squares multivariate statistical analysis of de Silva and colleagues from France, the tier-testing approach for regulatory purposes described by Gerner and colleagues from Germany, and the three-step tier-testing approach of the US Interagency Regulatory Alternatives Group described by Gupta and Hill. These approaches were presented as three separate papers at the November 1993 Interagency Regulatory Alternatives Group (IRAG) Workshop on Eye Irritation Testing; they have been summarized and combined into the following three-part report. The first part (de Silva et al.) presents statistical techniques for establishing test batteries of in vitro alternatives to the eye irritation test. The second (Gerner et al.) and third (Gupta and Hill) parts are similar in that they stage assessment of information by using a combination of screening information and animal testing to effect reductions in animal use and distress.

Animal Testing Alternatives↗
PubMed1997

IRAG working group 3. Cell function-based assays. Interagency Regulatory Alternatives Group.

Cell function-based tests measure responses of cells at sublytic concentrations of test agents. The fluorescein leakage assay measures effects of substances on the barrier function of epithelial monolayers or multilayers (MDCK or NHEK cells) as in vitro models of corneal epithelial function. Two IRAG data submissions suggest that the fluorescein leakage assay shows promise as a screening test for surfactants and alcohols. The test method requires further optimization, standardization and evaluation to fully determine its utility as an in vitro ocular irritancy test. The silicon microphysiometer test measures effects of test substances on the metabolic rate of cells; although a large number of cell types have been evaluated, L929 cells have been used for irritancy screening. Three IRAG data submissions on the silicon microphysiometer test showed strong in vivo/in vitro correlations for surfactants and surfactant-based personal care and household cleaning products in a range of mild to moderate ocular irritancy. This and published information support the reproducibility of the method and its use as an ocular irritancy screening test for aqueous-soluble liquid, surfactant-based formulations.

Animal Testing Alternatives↗
PubMed1995

Synthesis, structure-activity relationships, and pharmacological evaluation of pyrrolo[3,2,1-ij]quinoline derivatives: potent histamine and platelet activating factor antagonism and 5-lipoxygenase inhibitory properties. Potential therapeutic application in asthma.

A series of pyrrolo[3,2,1-ij]quinoline derivatives was synthesized and evaluated for their in vitro and in vivo activities against histamine, platelet activating factor (PAF), and leukotrienes which are recognized to be of importance in asthma. The structure-activity relationship studies have shown that the optimum moiety on the 1-position of the pyrroloquinoline nucleus is a 2-[4-(4-methyl-2-pyridinyl)-1-piperazinyl]ethyl chain in conjunction with a methyl group on the 2-position for potent antagonism of both histamine and PAF. The introduction of substituents on the 8- and 4-positions was also investigated in order to increase the potency of 5-lipoxygenase inhibition while retaining or improving the activities against histamine and PAF. This series is exemplified by 4-n-butyl-5,6-dihydro-8-hydroxy-2-methyl-1- [2-[4-(4-methyl-2-pyridinyl)-1-piperazinyl]ethyl]-4H-pyrrolo[3,2,1- ij]quinoline (24, KC 11404) which was found to be active against all three of the selected mediators. Compound 24 was found to be orally active in guinea pig models against the histaminic phase of antigen-induced bronchospasm and PAF-induced bronchoconstriction (ED50 = 1.9 and 2.1 mumol/kg, respectively). When tested against the leukotriene-dependent phase of the antigen-induced bronchoconstriction, compound 24 showed the same potency as zileuton.

Animals↗
PubMed1992

In vitro methods: their relevance and complementarity in ocular safety assessment.

Ocular irritation includes a wide variety of mechanisms some of which can be explored by in vitro methods. For example, the effects on epithelial cells that constitute the outer layers of both the conjunctiva and the cornea may result in direct cytotoxicity or impairment of cellular functions -such as impermeability-, phenomena that can be explored in vitro. Irritancy may also involve inflammation of the conjunctival connective tissue and of the corneal stroma with its vascular and cellular features; effects on the stroma can lead to the opacification of the cornea; this last phenomenon may be the consequence of mechanisms such as modification of the structure of proteins or changes in stroma hydration which in particular is closely related to corneal endothelium metabolic activity. Recovery after eye injury depends partly on the extent of ocular damage and on the residual mitotic activity of the remaining cells. We have studied 41 surfactants, lotions and shampoos in 6 to 8 in vitro methods each one exploring one or two endpoints that could be linked to the ocular irritancy phenomena described above. In vivo ocular irritancy data for these materials from previous studies were compared to in vitro results. The results obtained show that -among the techniques that were investigated and for the categories of substances that were studied- the Het-CAM test and more particularly the endpoint that is related to vascular effects gives the best assessment of acute ocular irritancy (Spearman's rho coefficients between in vivo and in vitro data greater than 0.90); however, cell culture methods, especially one based on short contact time between cells and products and on evaluation of early toxic effects, also proved interesting (Spearman's rho coefficients between in vivo and in vitro data greater than 0.85). Moreover, the isolated cornea opacity and permeability test gave complementary information more related to recovery from surfactant-induced damage. These encouraging results lead us to consider in vitro ocular safety assessment with optimism for the categories of products investigated.

Allantois↗
PubMedDate not supplied

Contact sensitizers decrease 33D1 expression on mature Langerhans cells.

Langerhans cells play a critical role in allergic contact hypersensitivity. In vivo, these cells capture xenobiotics that penetrate the skin and transport them through the lymphatic vessels into regional lymph nodes for presentation to T cells. During this migration step, Langerhans cells become mature dendritic cells according to their phenotype and their high immunostimulatory capacity. In vitro, when isolated from the skin and cultured for 3 days, Langerhans cells undergo similar phenotypic and functional maturation. In this study, the capacity of sensitizers, irritants and neutral chemicals to modulate the surface marker expression and morphology of pure mature murine Langerhans cells in vitro was examined. Contact with 4 sensitizers (2,4-dinitrobenzenesulfate, 4-ethoxymethylene-2-phenyl-2-oxazolin-5-one, p-phenylenediamine, mercaptobenzo-thiazole) resulted in a rapid, specific, marked fall in 33D1 expression, a murine specific dendritic cell marker. No effect was observed with 2 neutral chemicals (sodium chloride, methyl nicotinate) or 2 irritants (dimethyl sulfoxide, benzalkonium chloride). Nevertheless, sodium lauryl sulfate, a very irritant detergent, altered morphology and down-regulated all membrane markers. These preliminary data suggest that in vitro modulation of 33D1 expression by strong sensitizers may be an approach to the development of an in vitro model for the identification of chemicals that have the potential to cause skin sensitization and to distinguish them as far as possible from irritants.

Animals↗
PubMedDate not supplied

[Anxiolytic efficacy and tolerance of tetrabamate in anxious patients abusing alcohol. Multicenter double-blind versus placebo study].

The anxiolytic efficacy of tetrabamate was evaluated in 68 out-patients presenting an anxiety state with alcohol abuse according to DSM III criteria. The study followed a double-blind placebo-controlled design with parallel groups and lasted for 21 days. Anxiety was evaluated by the Hamilton anxiety scale, Norris visual analog scales, and the Hopkins Symptom Check List, along with the investigator's assessment. Safety was evaluated in terms of somatic symptoms (CHESS 84) and the physician's overall evaluation. The anxiolytic activity of tetrabamate (three 300 mg tablets/day) was significantly greater than that of placebo from seventh day on. There were no statistically significant differences in safety profile between tetrabamate and placebo. Moreover, in the tetrabamate group the significantly greater improvement in the scores of somatic symptoms indicates that the compound caused no notable adverse effects and its activity on somatic complaints (psychopathologic and/or toxic).

Alcoholism↗