John J.L. Jacobs

Stratum corneum cytokines and skin irritation response to sodium lauryl sulfate

Little is known about cytokines involved in chronic irritant contact dermatitis. Individual cytokine profiles might explain at least part of the differences in the individual response to irritation. Our objective was to investigate the relation between baseline stratum corneum (SC) cytokine levels and the skin response to a single and a repeated irritation test. This study also aimed to determine changes in SC cytokine levels after repeated irritation. Transepidermal water loss (TEWL) and erythema were measured in 20 volunteers after single 24‐hr exposure to 1% sodium lauryl sulfate (SLS), and during and after repeated exposure to 0.1% SLS over a 3‐week period. SC cytokine levels were measured from an unexposed skin site and from the repeatedly exposed site. Interleukin (IL)‐1α decreased by 30% after repeated exposure, while IL‐1RA increased 10‐fold and IL‐8 increased fourfold. Baseline IL‐1RA and IL‐8 values were predictors of TEWL and erythema after single exposure (r = 0.55–0.61). 6 subjects showed barrier recovery during repeated exposure. Baseline IL‐1RA and IL‐8 levels are likely to be indicators of higher skin irritability after single exposure to SLS. Barrier repair in some of the subjects might explain the lack of agreement between the TEWL response after single and repeated irritation.

Skin irritants and contact sensitizers induce Langerhans cell migration and maturation at irritant concentration

Abstract:  Skin irritants and contact allergens reduce the number of Langerhans cells (LCs). It has been assumed that this reduction is due their migration to the draining lymph node (LN) for initiating immune sensitization in a host. Skin irritation, however, as opposed to contact allergy is not considered to be an immunological disease. Nevertheless, skin irritants are also known for their adjuvant‐like effects on contact allergy, resulting in skin hypersensitivity reactions like toxic dermatitis. The human organotypic skin explant culture (hOSEC) model is used to study the characteristics of chemical‐induced migration of CD1a+ LCs out of the epidermis in relation to irritancy or toxicity. We analysed cells emigrating out of hOSEC for CD1a+ LCs, CD83+ mature dendritic cells (DCs) and CCR7+ LN homing cells. After exposure to a toxic concentration of a non‐immunogenic irritant, an increase of CD1a+CD83+ LCs was found in the culture medium. A non‐toxic concentration of an sensitizer induced an increase of CD1a+ cells. About 50% of skin emigrating CD1a+ LCs were CD83– (immature) but all were CCR7+. Skin irritation by both non‐allergenic and allergenic compounds induces LC migration and maturation. In contrast, only allergenic compounds induced LC migration with partial maturation at subtoxic concentration. This effectively demonstrates that irritation is physiologically needed stimuli for inducing LC maturation.

Genetic polymorphism of metabolic enzymes modifies the risk of chronic solvent-induced encephalopathy

In the present study, we investigate whether genetic polymorphism in enzymes involved in the metabolism of organic solvents influences susceptibility to chronic solvent encephalopathy (CSE), which is one of the major effects of long-term exposure to organic solvents. Polymorphisms in the genes encoding CYP1A1, CYP2E1, EPHX1, GSTM1, GSTT1 and GSTP1 enzymes were determined in a group of male CSE patients (N = 97) and controls (N = 214). The selection of the patients was based on a standard diagnostic protocol, including interviews, neuropsychological tests and questionnaires directed to somatic, cognitive and mood symptoms and exposure, in combination with well-defined decision rules. As controls, healthy workers of similar socio-economic background, without memory problems and with no known exposure to organic solvents, were included in the study. Comparing patients and controls, higher frequencies of the variant *5B allele of the CYP2E1 gene (OR: 5.8; 95% CI: 1.8-18.8) and of the variant GSTP1*C allele (OR: 0.40; 95% CI: 0.17-0.94) were found. Homozygous carriers of the exon 4 EPHX1 Arg139 variant allele had a lower risk (OR:0.25; 95% CI: 0.06-1.13). The present study indicates that genetic polymorphism of CYP2E1, EPHX1 and GSTP1 modify the risk of developing CSE.

An automated method for the quantification of immunostained human Langerhans cells.

Allergic contact dermatitis is a frequent and increasing health problem. For ethical reasons, the current animal tests used to screen for contact sensitizers should be replaced by in vitro alternatives. Contact sensitizers have been shown to accelerate Langerhans cell (LC) migration from human organotypic skin explant cultures (hOSECs) more rapidly than non-sensitizers and it has been proposed that the hOSEC model could be used to screen for sensitizers. However, chemically induced decreases in epidermal LC numbers need to be accurately quantified if the alterations in epidermal LC numbers are to form the basis of an alternative system for screening contact sensitizers in vitro. As manual counting of LCs is labour intensive and subject to intra- and inter-personal variation we developed an image analysis routine, using the Leica QWin image analysis software, to quantify LCs in situ using immunohistochemically stained skin sections. LCs can be identified using antibodies against the membrane molecule CD1a or the Lag antibody, which recognises cytoplasmic Birbeck granules. Quantification of epidermal LC number using the image analysis software had a much lower inter-person variation than when the same specimens were counted manually, using both the anti-Lag and CD1a antibodies. The software-aided quantification of epidermal LCs provides an accurate method for measuring chemically-induced changes in LC numbers.

Subtoxic concentrations of allergenic haptens induce LC migration and maturation in a human organotypic skin explant culture model: a novel method for identifying potential contact allergens

Abstract:  The accelerated migration of Langerhans cells (LCs) out of the epidermis and up‐regulation of maturation markers, upon treatment with subtoxic concentrations of chemicals, were used as the criteria to determine the potential of allergenic chemicals capable of inducing a hapten‐specific delayed‐type hypersensitivity reaction. Here we report the findings of a study in which seven chemicals, coded and tested in a blind fashion, were classified as contact allergens or non‐allergens using the human organotypic skin explant culture (hOSEC) model. All chemicals that were identified as a contact sensitizer on decoding induced a definite decrease in the number of CD1a and HLA‐DR‐positive epidermal LCs in the epidermis of the skin explants, as determined by both semiquantitative immunohistochemistry and quantitative flow cytometric analysis. A significant increase in the number of CD83+ cells was accompanied by up‐regulation of activation molecules in the epidermis of hOSEC exposed specifically to contact allergens. In contrast, there were only minor alterations in epidermal LC numbers, expression of CD83 and other activation markers by LCs when the biopsies were treated with non‐toxic concentrations of non‐allergenic irritants and vehicles. The data suggest that an increased epidermal LC migration and maturation accompanied by increased expression of activation markers could be used as end‐point determinants to screen allergens in a non‐animal alternative hOSEC model.