Interleukin-1 production after treatment with non-ionic surfactants in a murine keratinocytes cell line

Interleukin-1α and Interleukin-8 Release by Human Keratinocyte Cell Culture Treated with Surfactants

The effects of four cosmetic surfactants on interleukin (IL)-1α and IL-8 release from human keratinocytes were studied to investigate the feasibility of using these effects for the prediction of the irritation potential of chemicals. After exposure of cells to surfactants, the amounts of IL-1α and IL-8 released into culture medium were measured by ELISA. Cytotoxicity was evaluated by using the neutral red uptake (NRU) cytotoxicity assay. Cytokine release was increased 7–15 times by sodium lauryl sulphate (SLS), laurtrimonium chloride, cocamidopropyl betaine (CPB) and Oleth-5 at cytotoxic concentrations. IL-8 release was increased 3–4 times by SLS, CPB and Oleth-5 at subcytotoxic concentrations. After exposure to SLS, IL-1α was released within 1 hour, suggesting that IL-1α release is associated with membrane damage, whereas IL-8 release continued for 24 hours, suggesting that IL-8 was produced within the cells. Cytotoxicity tests and IL-8 release assays were also performed on seven other surfactants. The results show that moderate irritants CPB and PEG-4 dioleate, which have weak cytotoxic effects, significantly increased IL-8 release from human keratinocytes. It is suggested that measurement of IL-8 release is useful for predicting the irritation potential of chemicals which cannot be detected by using the NRU cytotoxicity assay.

Safety Assessment of Diethanolamides as Used in Cosmetics

Cocamide diethanolamine (DEA) and some of the other diethanolamides are mainly used as surfactant foam boosters or viscosity increasing agents in cosmetics, although a few are reported to be used as hair and skin conditioning agents, surfactant-cleansing or surfactant-emulsifying agents, or as an opacifying agent. The Cosmetic Ingredient Review (CIR) Expert Panel considered new data and information from previous CIR reports to assess the concerns about the potential for amidases in human skin to convert these diethanolamides into DEA and the corresponding fatty acids. The Expert Panel concluded that these diethanolamides are safe as used when formulated to be nonirritating and when the levels of free DEA in the diethanolamides do not exceed those considered safe by the Panel. The Panel also recommended that these ingredients not be used in cosmetic products in which N-nitroso compounds can be formed.

Use of a serum-free reconstituted epidermis as a skin pharmacological model

This study is aimed at assessing some of the possibilities offered by a new kind of three-dimensional skin culture in the field of toxicity and skin inflammation. The Reconstituted Epidermis used is presently the only skin model on the market in which normal human keratinocytes are allowed to grow and to differentiate in a chemically defined culture medium. The response of this original tissue to chemical (anionic and cationic surfactants) and physical (UVB radiation) insults was compared with human keratinocytes in monolayer culture and assessed through histological analysis, cell viability quantification and interleukin-1alpha (IL-1alpha) release measurement. For the surfactants and the UVB radiation a clear relationship was shown between the amount of IL-1alpha released and both the cell viability and the histological appearance of the skin. Sublethal doses of UV radiation induced exclusively an increase of intracellular amount of IL-1alpha, the magnitude of which seemed to be time dependent. The irritating potential of various kinds of cosmetic creams was then assessed using this skin model and compared with human irritation data. The intensity of erythema and oedema induced by a 48-hr human patch test was consistent with the amount of IL-1alpha secreted in the medium, the histological appearance of the Reconstituted Epidermis and the cell viability.

Assessment of potency of allergenic activity of low molecular weight compounds based on IL-1alpha and IL-18 production by a murine and human keratinocyte cell line

Assessment of allergenic potency of low molecular weight compounds is generally performed using animal models, such as the guinea pig maximisation test and the murine local lymph node assay (LLNA). Progress in unravelling the mechanisms of skin sensitisation, including effects on the production of cytokines by the different cell types of the skin, provides us with the opportunity to develop in vitro tests as an alternative to in vivo sensitisation testing. The aim of the present study was to establish an in vitro method to assess the potency of allergens, on the basis of their induction of cytokine production by murine and human keratinocytes. In the present study we used test systems comprised of the murine epidermal keratinocyte cell line HEL-30 and the human keratinocyte cell line HaCaT. We exposed these cell lines to the allergens ethyl-p-aminobenzoate (benzocaine), diethylamine (DEA), 2,4-dinitrochlorobenzene (DNCB), and phthalic anhydride (PA). IL-1alpha and IL-18 dose-response data were evaluated by non-linear regression analysis and at a stimulation index of 3 of cytokine production of treatment versus control, the corresponding allergen concentration was calculated. For HEL-30, for both cytokines DNCB showed the strongest potency followed in this order by PA, benzocaine, and DEA. This classification was similar to our previous findings obtained in the LLNA. For HaCaT, unfortunately, such ranking proved to be much less feasible. In conclusion, to assess the potency of allergens the murine keratinocyte cell line HEL-30 may be a useful in vitro test system, alternative to in vivo models, although this requires further testing using a much wider range of compounds.

Cyclosporin A exacerbates skin irritation induced by tributyltin by increasing nuclear factor kappa B activation

In searching for pharmacologic agents able to reduce xenobiotic-induced skin irritation, we found that cyclosporine A exacerbates the skin irritation induced by tributyltin. We previously demonstrated the involvement of interleukin-1 alpha and tumor necrosis factor alpha in tributyltin-induced skin irritation. Here, we show that cyclosporine A (28 mg per kg), at a dose that results in systemic immunosuppression, potentiates tributyltin-induced skin irritation through increased tumor necrosis factor alpha production, associated with increased tributyltin-induced activation of transcription factor nuclear factor kappa B in cyclosporine-A-treated mice. On the other hand, under the same experimental conditions, cyclosporine A prevented the elicitation phase of oxazolone-induced contact allergy, but was ineffective in preventing benzalkonium-chloride-induced skin irritation. Using a murine keratinocyte cell line (HEL30) we demonstrated, also in vitro, that the cyclosporine A potentiates tributyltin-induced nuclear factor kappa B activation and cytokine production, this being preceded by an increase in cellular oxidative activity, essential for nuclear factor kappa B activation, that is time and dose (0.1-10 microM) dependent. This effect was not exclusive to tributyltin but could be extended to other mitochondrial poisons such as sodium arsenate. It has been reported that cyclosporine A binds to cyclophilins. An 18-mer antisense phosphorothioate oligodeoxynucleotide was used to target mitochondrial cyclophilin D mRNA. After 24 h exposure to the oligonucleotide, the amount of cyclophilin D in the cells was decreased by 54% as judged by Western blot analysis. Cyclophilin D suppression prevented cyclosporine A potentiation of tributyltin-induced cellular oxidative activity, indicating the key role of the binding of cyclosporine A to mitochondrial cyclophilin D in mediating this effect.

Predictive value of in vitro model systems in toxicology

The application of in vitro model systems to evaluate the toxicity of xenobiotics has significantly enhanced our understanding of drug- and chemical-induced target toxicity. From a scientific perspective, there are several reasons for the popularity of in vitro model systems. From the public perspective, in vitro model systems enjoy increasing popularity because their application may allow a reduction in the number of live animals employed in toxicity testing. In this review, we present an overview of the use of in vitro model systems to investigate target organ toxicity of drugs and chemicals, and provide selective examples of these model systems to better understand cutaneous and ocular toxicity and the role of drug metabolism in the hepatotoxicity of selected agents. We conclude by examining the value and use of in vitro model systems in industrial development of new pharmaceutical agents.

Sodium arsenate induces overproduction of interleukin-1alpha in murine keratinocytes: role of mitochondria

It has recently been demonstrated that arsenic induces overexpression of keratinocyte-derived growth factors, which are likely to have a significant role in arsenic-induced skin hyperkeratoses and cancer. The mechanism(s) involved in this induction are, however, still elusive. The purpose of this study was to investigate the early intracellular events that follow in vitro treatment with sodium arsenate in a murine keratinocyte cell line (HEL30), which leads to cytokine overproduction. First, we observed that sodium arsenate induced a concentration-dependent production of interleukin-1alpha and a significant increase in cell proliferation, that could be suppressed by the addition of a neutralizing antibody against murine interleukin-1alpha, confirming the ability of arsenic to induce keratinocyte growth-promoting cytokines. Electron microscopic analysis revealed that arsenate induced a dramatic alteration in keratinocyte mitochondria. This effect could be prevented by rotenone pretreatment, which suggests the possible involvement of mitochondria-derived reactive oxygen species. Arsenic induced a concentration- and time-dependent increase in cellular oxidative activity, which was followed by activation of redox-sensitive transcription factors such as nuclear factor-kappaB and activator protein-1, that are essential for interleukin-1alpha synthesis. Prior treatment with rotenone or prolonged treatment with ethidium bromide, an inhibitor of mitochondrial DNA and RNA synthesis, to deplete cells of functional mitochondria, completely prevented sodium arsenate-induced interleukin-1alpha production, this indicates the pivotal role of these organelles in sodium arsenate-induced keratinocyte growth factors.

Selective induction of cell-associated interleukin-1alpha in murine keratinocytes by chemical allergens

Cytokines may be useful tools to discriminate between irritant and allergic contact dermatitis. In the mouse only, it has been demonstrated by other, that contact sensitizers up-regulated keratinocytes-derived interleukin-1alpha (IL-1), macrophage inflammatory protein-2 and interferon induced protein 10 mRNAs. The purpose of this study was to investigate the possibility to use in vitro IL-1 production by a murine keratinocyte cell line for preliminary screening of chemicals for their irritant and/or allergic potential. We investigated the effects of five relevant skin allergens (dinitrochlorobenzene, oxazolone, nickel sulfate, penicillin G and eugenol), two skin irritants (benzalkonium chloride, and methylsalicilate) and two compounds with no sensitizing activity (glycerol and ethanol) on IL-1 production in HEL30 cells. Twenty four hours following treatment, both IL-1 release in conditioned media and cell-associated IL-1 were measured by a specific sandwich ELISA. Under our experimental conditions, only contact sensitizers were able to increase in a dose dependent fashion cell-associated IL-1, confirming the in vivo findings. Both skin irritants and allergens induced the release of IL-1, because of the irritative properties of both chemicals, while ethanol and glycerol failed to induce changes in IL-1 production, confirming the specificity of the proposed test. Taken together, these data indicate that it may be realistic to consider potential skin allergens those chemicals which are able to increase cell-associated IL-1, to consider skin irritants those chemicals which induce only IL-1 release, and to exclude as potential allergens or irritants those chemicals which fail to induce changes in IL-1 production.

Role of mitochondria and calcium ions in tributyltin-induced gene regulatory pathways

Tributyltin (TBT) salts are potent skin irritants both in humans and rodents. Data in the literature indicate mitochondria as target of TBT effects. Here, we investigate the early intracellular molecular events that follow TBT treatment and the relevance of calcium ions and mitochondria in gene-regulatory signaling pathways. Confluent HEL30 cells were treated with increasing doses of TBT (0-5 microM). At different times thereafter, the level of intracellular Ca2+, the cellular oxidative activity, nuclear factor-kappaB (NF-kappaB) activation, and IL-1alpha production were measured. TBT induced a dose-related increase of intracellular Ca2+ that reached the plateau 4 min following treatment. The increase of intracellular Ca2+ was followed by an increase in cellular oxidative activity as measured by DCFH oxidation (15 min) that preceded NF-kappaB activation (30 min) and IL-1alpha production (4 hr). All these events can be almost completely abrogated by BAPTA, an intracellular Ca2+ chelator. Furthermore, the modulation of cellular oxidative activity induced by TBT observed with rotenone, an inhibitor of the electron entry from complex I to ubiquinone, or after prolonged treatment with ethidium bromide, an inhibitor of mitochondrial DNA and RNA synthesis, indicates mitochondria as an important intracellular source of reactive oxygen species. These findings indicate the rise in intracellular Ca2+ as the starting event and indicate the role of mitochondria as the source of second messenger molecules essential for TBT-induced NF-kappaB activation and IL-1alpha production.

Role of mitochondria in tributyltin-induced interleukin-1alpha production in murine keratinocytes

Tributyltin (TBT) salts are well known skin irritants in rodents and humans. TBT induced both the intracellular production of interleukin-1alpha (IL-1alpha) and its release into culture medium in a murine keratinocyte cell line (HEL30). Here, we report that mitochondria are important for TBT-induced IL-1alpha production. Confluent cells were treated with increasing concentrations of TBT (0--2.5 microM) or dimethylsulfoxide as vehicle control. At different times thereafter (0--24 h), nuclear extracts were analyzed for nuclear factor-(kappa)B (NF-(kappa)B) binding activity by electrophoretic mobility shift assay, and the released and cell-associated IL-1alpha was measured by enzyme-linked immunosorbent assay. TBT induced a direct and concentration-related activation of NF-(kappa)B, which peaked at 2 h and was blocked by pyrrolidinedithiocarbamate, a potent NF-(kappa)B inhibitor, and rotenone, an inhibitor of the electron entry from complex I to ubiquinone. Rotenone also induced a concentration-related inhibition of IL-1alpha synthesis induced by TBT, but rotenone did not completely abrogate TBT-induced IL-1alpha production, which suggests that other transcription factors may be involved in IL-1alpha production. Prolonged treatment with ethidium bromide, an inhibitor of mitochondrial DNA and RNA synthesis, was used to partially deplete cells of functional mitochondria. After 5 d of treatment, mitochondrial conversion of tetrazolium bromide to formazan was reduced by 50%, and IL-1alpha release was decreased by 65%, whereas no induction of intracellular IL-1alpha was observed. This effect was not due to inhibition of protein synthesis, because identical incorporation of [3H]leucine into protein in control and ethidium bromide-treated cells was identical. This impairment of mitochondrial metabolism inhibited NF-(kappa)B activation by TBT. These findings indicate that mitochondria may be the source of second messenger molecules important for TBT-induced IL-1alpha production.