| 1. |
- Bauer, Brigitte, 1978, et al.
(författare)
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Modification and expulsion of keratins by human epidermal keratinocytes upon hapten exposure in vitro.
- 2011
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Ingår i: Chemical research in toxicology. - : American Chemical Society (ACS). - 1520-5010 .- 0893-228X. ; 24:5, s. 737-43
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Tidskriftsartikel (refereegranskat)abstract
- Allergic contact dermatitis is the most prevalent form of human immunotoxicity. It is caused by reactive low molecular weight chemicals, that is, haptens, coming in contact with the skin where hapten-peptide complexes are formed, activating the immune system. By using sensitizing fluorescent thiol-reactive haptens, that is, bromobimanes, we show how keratinocytes respond to hapten exposure in vitro and reveal, for the first time in a living system, an exact site of haptenation. Rapid internalization and reaction of haptens with keratin filaments were visualized. Subsequently, keratinocytes respond in vitro to hapten exposure by release of membrane blebs, which contain haptenated keratins 5 and 14. Particularly, cysteine 54 of K5 was found to be a specific target. A mechanism is proposed where neoepitopes, otherwise hidden from the immune system, are released after hapten exposure via keratinocyte blebbing. The observed expulsion of modified keratins by keratinocytes in vitro might play a role during hapten sensitization in vivo and should be subject to further investigations.
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| 2. |
- Evenbratt, Hanne, 1980, et al.
(författare)
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In vivo study of an instantly formed lipid-water cubic phase formulation for efficient topical delivery of aminolevulinic acid and methyl-aminolevulinate
- 2013
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Ingår i: International Journal of Pharmaceutics. - : Elsevier BV. - 0378-5173 .- 1873-3476. ; 452:1-2, s. 270-275
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate a rapidly formed cubic liquid crystalline phase, i.e. typically 1 g cubic phase in less than 1 min confirmed by X-ray diffraction, consisting of an ether lipid, 1-glyceryl monooleyl ether (GME), an aprotic solvent (propylene glycol or pentane-1,5-diol) and water. The efficacy of the cubic formulation was tested in vivo by administrating formulations containing 3% (w/w) of the HCl salts of delta-aminolevulinic acid (ALA) or methylaminolevulinate (MAL) to hairless mice. The endogenous formation of protoporphyrin IX (PpIX) was monitored spectrophotometrically as a marker for cellular uptake of active compound. As reference, a commercial product containing 16% (w/w) MAL in an oil-in-water emulsion (Metvix (R)), and a cubic phase based on an ester lipid (glyceryl monooleate, GMO), previously shown to facilitate topical delivery of both ALA and MAL, were applied. It was found that in general the cubic phases gave rise to higher fluorescence levels than the mice exposed to the commercial product. The instantly formed cubic formulations based on GME demonstrated the same efficiency as the GMO based formulations. The results imply that instantly formed cubic formulations opens up new opportunities, particularly for transdermal drug delivery of substances subject to stability problems in, e. g. aqueous environments.
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| 3. |
- Samuelsson, Kristin, 1979, et al.
(författare)
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Diphenylthiourea, a common rubber chemical, is bioactivated to potent skin sensitizers
- 2011
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Ingår i: Chemical Research in Toxicology. - : American Chemical Society (ACS). - 0893-228X .- 1520-5010. ; 24:1, s. 35-44
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Tidskriftsartikel (refereegranskat)abstract
- Diphenylthiourea (DPTU) is a known skin sensitizer commonly used as a vulcanization accelerator in the production of synthetic rubber, for example, neoprene. The versatile usage of neoprene is due to the multifaceted properties of the material; for example, it is stretchable, waterproof, and chemical- and abrasion-resistant. The wide application of neoprene has resulted in numerous case reports of dermatitis patients allergic to DPTU. The mechanism by which DPTU works as a contact allergen has not been described; thus, the aim of the present study was to investigate if DPTU is a prohapten that can be activated by skin metabolism. The metabolic activation and covalent binding of (14)C-labeled DPTU to proteins were tested using a skinlike cytochrome P450 (P450) cocktail containing the five most abundant P450s found in human skin (CYP1A1, 1B1, 2B6, 2E1, and 3A5) and human liver microsomes. The incubations were carried out in the presence or absence of the metabolite trapping agents glutathione, methoxylamine, and benzylamine. The metabolism mixtures were analyzed by LC-radiochromatography, LC-MS, and LC-MS/MS. DPTU was mainly metabolically activated to reactive sulfoxides resulting in desulfurated adducts in both enzymatic systems used. Also, phenylisothiocyanate and phenylisocyanate were found to be metabolites of DPTU. The sensitizing capacity of the substrate (DPTU) and three metabolites was tested in the murine local lymph node assay. Two out of three metabolites tested were strong skin sensitizers, whereas DPTU itself, as previously known, was negative using this mouse model. In conclusion, DPTU forms highly reactive metabolites upon bioactivation by enzymes present in the skin. These metabolites are able to induce skin sensitization and are probable causes for DPTU allergy. To increase the possibilities of diagnosing contact allergy to DPTU-containing items, we suggest that suitable metabolites of DPTU should be used for screening testing.
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| 4. |
- Simonsson, Carl, 1976, et al.
(författare)
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A study of the enhanced sensitizing capacity of a contact allergen in lipid vesicle formulations.
- 2011
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Ingår i: Toxicology and applied pharmacology. - : Elsevier BV. - 1096-0333 .- 0041-008X. ; 252:3, s. 221-7
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Tidskriftsartikel (refereegranskat)abstract
- The growing focus on nanotechnology and the increased use of nano-sized structures, e.g. vesicles, in topical formulations has led to safety concerns. We have investigated the sensitizing capacity and penetration properties of a fluorescent model compound, rhodamine B isothiocyanate (RBITC), when administered in micro- and nano-scale vesicle formulations. The sensitizing capacity of RBITC was studied using the murine local lymph node assay (LLNA) and the skin penetration properties were compared using diffusion cells in combination with two-photon microscopy (TPM). The lymph node cell proliferation, an indicator of a compounds sensitizing capacity, increased when RBITC was applied in lipid vesicles as compared to an ethanol:water (Et:W) solution. Micro-scale vesicles showed a slightly higher cell proliferative response compared to nano-scale vesicles. TPM imaging revealed that the vesicle formulations improved the skin penetration of RBITC compared to the Et:W solution. A strong fluorescent region in the stratum corneum and upper epidermis implies elevated association of RBITC to these skin layers when formulated in lipid vesicles. In conclusion, the results indicate that there could be an elevated risk of sensitization when haptens are delivered in vehicles containing lipid vesicles. Although the size of the vesicles seems to be of minor importance, further studies are needed before a more generalized conclusion can be drawn. It is likely that the enhanced sensitizing capacity is a consequence of the improved penetration and increased formation of hapten-protein complexes in epidermis when RBITC is delivered in ethosomal formulations.
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| 5. |
- Simonsson, Carl, 1976, et al.
(författare)
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Caged fluorescent haptens reveal the generation of cryptic epitopes in allergic contact dermatitis.
- 2011
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Ingår i: The Journal of investigative dermatology. - : Elsevier BV. - 1523-1747 .- 0022-202X. ; 131:7, s. 1486-93
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Tidskriftsartikel (refereegranskat)abstract
- Allergic contact dermatitis (ACD) is the most prevalent form of human immunotoxicity. It is caused by skin exposure to haptens, i.e., protein-reactive, low-molecular-weight chemical compounds, which form hapten-protein complexes (HPCs) in the skin, triggering the immune system. These immunogenic HPCs are elusive. In this study a series of thiol-reactive caged fluorescent haptens, i.e., bromobimanes, were deployed in combination with two-photon fluorescence microscopy, immunohistochemistry, and proteomics to identify possible hapten targets in proteins in human skin. Key targets found were the basal keratinocytes and the keratins K5 and K14. Particularly, cysteine 54 of K5 was found to be haptenated by the bromobimanes. In addition, elevated levels of anti-keratin antibodies were found in the sera of mice exposed to bromobimanes in vivo. The results indicate a general mechanism in which thiol-reactive haptens generate cryptic epitopes normally concealed from the immune system. In addition, keratinocytes and keratin seem to have an important role in the mechanism behind ACD, which is a subject for further investigations.
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| 6. |
- Simonsson, Carl, 1976, et al.
(författare)
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The pilosebaceous unit-a phthalate-induced pathway to skin sensitization
- 2012
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Ingår i: Toxicology and Applied Pharmacology. - : Elsevier BV. - 0041-008X. ; 264:1, s. 114-120
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Tidskriftsartikel (refereegranskat)abstract
- Allergic contact dermatitis (ACD) is caused by low-molecular weight compounds called haptens. It has been shown that the potency of haptens can depend on the formulation in which they are applied on the skin. Specifically the sensitization potency of isothiocyanates, a group of haptens which can be released from e.g. adhesive tapes and neoprene materials, increases with the presence of phthalates; however, the underlying mechanisms are not clear. A better understanding of the mechanisms governing the potency of haptens is important, e.g. to improve the risk assessment and the formulation of chemicals in consumer products. In this study we have explored phthalate-induced effects on the sensitization potency, skin distribution, and reactivity of fluorescent model isothiocyanate haptens using non-invasive two-photon microscopy to provide new insights regarding vehicle effects in ACD. The data presented in this paper indicate that the sensitization potency of isothiocyanates increases when applied in combination with dibutylphthalate due to a specific uptake via the pilosebaceous units. The results highlight the importance of shunt pathways when evaluating the bioavailability of skin sensitizers. The findings also indicate that vehicle-dependent hapten reactivity towards stratum corneum proteins regulates the bioavailability, and thus the potency, of skin sensitizers. (C) 2012 Elsevier Inc. All rights reserved.
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