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Biomedical subjects

Jean-Pierre Lepoittevin

Publications and source records attributed to Jean-Pierre Lepoittevin.

At least 19 recordsLinked to original sources

Synthesis and reactivity toward nucleophilic amino acids of 2,5-[13C]-dimethyl-p-benzoquinonediimine.

2,5-[(13)C]-Dimethyl-p-benzoquinonediimine was synthesized, and its reactivity toward several nucleophilic amino acids was studied by associated (13)C and (1)H{(13)C} NMR spectroscopies, combined with HPLC in tandem with mass spectrometry. A classical electrophile-nucleophile mechanism was observed for the reaction with N-acetyl-Cys. Adducts resulted from the reaction of the amino acid thiol group with the benzoquinonediimine electrophilic positions 3 and 6 as well as with the nitrogen atom of the imino group. However, N-acetyl-Trp and N-acetyl-Lys were chemically modified in the presence of 2,5-[(13)C]-dimethyl-p-benzoquinonediimine through the involvement of oxido-reduction processes. Heteronuclear (1)H{(13)C} NMR experiments allowed the identification of known oxidation intermediates derived from N-acetyl-Trp, indicating the oxidative strength of the reaction media. An adduct resulted from the reaction between the reduced form of the benzoquinonediimine and N-acetyl-formylkynurenine, which is the most known oxidation derivative of N-acetyl-Trp. In the case of N-acetyl-Lys, 4-amino-2,5-dimethyl-[(13)C]-formanilide and its derivative with N-acetyl-Lys at position 4 were obtained. A reaction mechanism was suggested in which the epsilon-NH(2) of the amino acid reacted on the electrophilic diimine to form an enamine adduct, which could then induce an oxidative deamination of N-acetyl-Lys. Further oxido-reduction mechanisms on the N-acetyl-alpha-aminoadipate-delta-semialdehyde formed might afford N,N-acetyl-formyl glutamic semialdehyde, which was considered as the powerful reactive species toward the reduced form of 2,5-[(13)C]-dimethyl-p-benzoquinonediimine. In the presence of N-acetyl-Tyr or N-acetyl-Met, the hydrolysis of the diimine parent compound was preferred, followed by a reduction to the hydroquinone form. In this study, we have thus shown that p-benzoquinonediimines, the first oxidation derivatives of allergenic p-amino aromatic compounds, can react with nucleophilic residues on amino acids through a set of complex mechanisms and must be seriously considered as potential candidates for the formation of antigenic structures responsible for allergic contact dermatitis.

Amino Acids↗

Comparison of elicitation potential of chloroatranol and atranol--2 allergens in oak moss absolute.

Chloroatranol and atranol are degradation products of chloroatranorin and atranorin, respectively, and have recently been identified as important contact allergens in the natural fragrance extract, oak moss absolute. Oak moss absolute is widely used in perfumery and is the cause of many cases of fragrance allergic contact dermatitis. Chloroatranol elicits reactions at very low levels of exposure. In oak moss absolute, chloroatranol and atranol are present together and both may contribute to the allergenicity and eliciting capacity of the natural extract. In this study, 10 eczema patients with known sensitization to chloroatranol and oak moss absolute were tested simultaneously to a serial dilution of chloroatranol and atranol in ethanol, in equimolar concentrations (0.0034-1072 microM). Dose-response curves were estimated and analysed by logistic regression. The estimated difference in elicitation potency of chloroatranol relative to atranol based on testing with equimolar concentrations was 217% (95% confidence interval 116-409%). Both substances elicited reactions at very low levels of exposure. It is concluded that the differences in elicitation capacity between the 2 substances are counterbalanced by exposure being greater to atranol than to chloroatranol and that both substances contribute to the clinical problems seen in oak moss absolute-sensitized individuals.

Adult↗

Identification of carbon-centred radicals derived from linalyl hydroperoxide, a strong skin sensitizer: a possible route for protein modifications.

Few studies are reported on the formation of reactive carbon-centred radical species from toxic xenobiotics. In this paper the formation of carbon radicals derived from the skin sensitizer linalyl hydroperoxide is described using radical trapping and EPR studies. Radical trapping used TMIO as scavenger agent and light, heat or TPP-Fe(3+) as radical inducers. EPR spin trapping was based on the use of the parent alcohol, generating the same allyloxyl radical than the hydroperoxide by photolysis of the corresponding nitrite formed with t-BuONO, also playing the role of the spin trap. It is suggested that the generation of these carbon radical species could play an important role for the binding of the hydroperoxide with skin proteins to form antigenic structures, the first step of the skin sensitization mechanism.

Carbon↗

Patch testing with a new fragrance mix - reactivity to the individual constituents and chemical detection in relevant cosmetic products.

UNLABELLED: A new fragrance mix (FM II), with 6 frequently used chemicals not present in the currently used fragrance mix (FM I), was evaluated in 6 dermatological centres in Europe, as previously reported. In this publication, test results with the individual constituents and after repeated open application test (ROAT) of FM II are described. Furthermore, cosmetic products which had caused a contact dermatitis in patients were analysed for the presence of the individual constituents. In 1701 patients, the individual constituents of the medium (14%) and the highest (28%) concentration of FM II were simultaneously applied with the new mix at 3 concentrations (break-down testing for the lowest concentration of FM II (2.8%) was performed only if the mix was positive). ROAT was performed with the concentration of the FM II which had produced a positive or doubtful (+ or ?+) patch test reaction. Patients' products were analysed for the 6 target compounds by gas chromatography-mass spectrometry (GC-MS). RESULTS: 50 patients (2.9%) showed a positive reaction to 14% FM II and 70 patients (4.1%) to 28% FM II. 24/50 (48%) produced a positive reaction to 1 or more of the individual constituents of 14% FM II and 38/70 (54.3%) to 28% FM II, respectively. If doubtful reactions to individual constituents are included, the break-down testing was positive in 74% and 70%, respectively. Patients with a positive reaction to 14% FM II showed a higher rate of reactions to the individual constituent of the 28% FM II: 36/50 (72%). Positive reactions to individual constituents in patients negative to FM II were exceedingly rare. If doubtful reactions are regarded as negative, the sensitivity, specificity, positive predictive value and negative predictive value for the medium concentration of FM II towards at least 1 individual constituent was 92.3% (exact 95% confidence interval 74.9-99.1%), 98.4% (97.7-99.0%), 48% (33.7-62.6%) and 99.9% (99.6-"100.0%), respectively. For the high concentration, the figures were very similar. The frequency of positive reactions to the individual constituents in descending order was the same for both FM II concentrations: hydroxyisohexyl 3-cyclohexene carboxaldehyde (Lyral) > citral > farnesol > citronellol > alpha-hexyl-cinnamic aldehyde (AHCA). No unequivocally positive reaction to coumarin was observed. Lyral) was the dominant individual constituent, with positive reactions in 36% of patients reacting to 14% FM II and 37.1% to 28% FM II. 5/11 patients developed a positive ROAT after a median of 7 days (range 2-10). The 5 patients with a doubtful or negative reaction to 28% FM II were all ROAT negative except 1. There were 7 patients with a certain fragrance history and a positive reaction to either 28% or 14% FM II but a negative reaction to FM I. Analysis with GC-MS in a total of 24 products obtained from 12 patients showed at least 1-5 individual constituents per product: Lyral (79.2%), citronellol (87.5%), AHCA (58.3%), citral (50%) and coumarin (50%). The patients were patch test positive to Lyral, citral and AHCA. In conclusion, patients with a certain fragrance history and a negative reaction to FM I can be identified by FM II. Testing with individual constituents is positive in about 50% of cases reacting to either 14% or 28% FM II.

Acrolein↗

Patch testing with a new fragrance mix detects additional patients sensitive to perfumes and missed by the current fragrance mix.

The currently used 8% fragrance mix (FM I) does not identify all patients with a positive history of adverse reactions to fragrances. A new FM II with 6 frequently used chemicals was evaluated in 1701 consecutive patients patch tested in 6 dermatological centres in Europe. FM II was tested in 3 concentrations - 28% FM II contained 5% hydroxyisohexyl 3-cyclohexene carboxaldehyde (Lyral), 2% citral, 5% farnesol, 5% coumarin, 1% citronellol and 10%alpha-hexyl-cinnamic aldehyde; in 14% FM II, the single constituents' concentration was lowered to 50% and in 2.8% FM II to 10%. Each patient was classified regarding a history of adverse reactions to fragrances: certain, probable, questionable, none. Positive reactions to FM I occurred in 6.5% of the patients. Positive reactions to FM II were dose-dependent and increased from 1.3% (2.8% FM II), through 2.9% (14% FM II) to 4.1% (28% FM II). Reactions classified as doubtful or irritant varied considerably between the 6 centres, with a mean value of 7.2% for FM I and means ranging from 1.8% to 10.6% for FM II. 8.7% of the tested patients had a certain fragrance history. Of these, 25.2% were positive to FM I; reactivity to FM II was again dose-dependent and ranged from 8.1% to 17.6% in this subgroup. Comparing 2 groups of history - certain and none - values for sensitivity and specificity were calculated: sensitivity: FM I, 25.2%; 2.8% FM II, 8.1%; 14% FM II, 13.5%; 28% FM II, 17.6%; specificity: FM I, 96.5%; 2.8% FM II, 99.5%; 14% FM II, 98.8%; 28% FM II, 98.1%. 31/70 patients (44.3%) positive to 28% FM II were negative to FM I, with 14% FM II this proportion being 16/50 (32%). In the group of patients with a certain history, a total of 7 patients were found reacting to FM II only. Conversely, in the group of patients without any fragrance history, there were significantly more positive reactions to FM I than to any concentration of FM II. In conclusion, the new FM II detects additional patients sensitive to fragrances missed by FM I; the number of false-positive reactions is lower with FM II than with FM I. Considering sensitivity, specificity and the frequency of doubtful reactions, the medium concentration, 14% FM II, seems to be the most appropriate diagnostic screening tool.

Acrolein↗

Deodorants: an experimental provocation study with isoeugenol.

Axillary dermatitis is common and overrepresented in people with contact allergy to fragrances. Many people suspect their deodorants to be the incriminating products. In order to investigate the significance of isoeugenol in deodorants for the development of axillary dermatitis when used by people with and without contact allergy to isoeugenol, patch tests with deodorants and ethanol solutions with isoeugenol, as well as repeated open application tests (ROAT) with roll-on deodorants with and without isoeugenol at various concentrations, were performed in 35 dermatitis patients, 10 without and 25 with contact allergy to isoeugenol. A positive ROAT was observed only in patients hypersensitive to isoeugenol (P<0.001) and only in the axilla to which the deodorants containing isoeugenol had been applied (P<0.001). Deodorants containing isoeugenol in the concentration range of 0.0063-0.2% used 2 times daily on healthy skin can thus elicit axillary dermatitis within a few weeks in people with contact allergy to isoeugenol.

Adult↗

Development of a peptide reactivity assay for screening contact allergens.

Allergic contact dermatitis resulting from skin sensitization is a common occupational and environmental health problem. In recent years, the local lymph node assay (LLNA) has emerged as a practical option for assessing the skin sensitization potential of chemicals. In addition to accurate identification of skin sensitizers, the LLNA can also provide a reliable measure of relative sensitization potency; information that is pivotal in successful management of human health risks. However, even with the significant animal welfare benefits provided by the LLNA, there is still interest in the development of nonanimal test methods for skin sensitization testing. One characteristic of a chemical allergen is its ability to react with proteins prior to the induction of skin sensitization. The majority of chemical allergens is electrophilic and as such reacts with nucleophilic amino acids like cysteine or lysine. In order to determine if reactivity correlates with sensitization potential, 38 chemicals representing allergens of different potencies (weak to extreme) and nonsensitizers were evaluated for their ability to react with glutathione or three synthetic peptides containing either cysteine, lysine, or histidine. Following a 15-min reaction time for glutathione or a 24 h reaction period for the three synthetic peptides, the samples were analyzed by HPLC. UV detection was used to monitor the depletion of glutathione or the peptide following reaction. The results demonstrate that a significant correlation (Spearman correlation) exists between allergen potency and the depletion of glutathione (p = 0.001), lysine (p = 0.025), and cysteine (p = 0.020), but not histidine. The peptide with the highest sensitivity was cysteine (80.8%) whereas histidine was the least sensitive (11.5%). The data presented show that measuring peptide reactivity has utility for screening chemicals for their skin sensitization potency and thus potential for reducing our reliance on animal test methods.

Algorithms↗

Synthesis and photocytotoxic activity of new alpha-methylene-gamma-butyrolactone-psoralen heterodimers.

The synthesis of a new alpha-methylene-gamma-butyrolactone-psoralen heterodimer 2 is reported. Its photoantiproliferative activity and skin phototoxicity were compared with that of 5-methoxypsoralen (5-MOP) and another heterodimer 1. Both derivatives show a significant phototoxicity toward malignant cell lines including melanoma cells A375 compared to their intrinsic cytotoxicity in the dark. Both compounds were found to be nonphototoxic on mice skin and therefore could be active potential drugs in photochemotherapy.

Animals↗

A liquid chromatography-mass spectrometric method for the determination of oak moss allergens atranol and chloroatranol in perfumes.

This paper describes a validated liquid chromatographic-tandem mass spectrometric method for quantitative analysis of the potential oak moss allergens atranol and chloroatranol in perfumes and similar products. The method employs LC-MS-MS with electrospray ionization (ESI) in negative mode. The compounds are analysed by selective reaction monitoring (SRM) of 2 or 3 ions for each compound in order to obtain high selectivity and sensitivity. The method has been validated for the following parameters: linearity; repeatability; recovery; limit of detection; and limit of quantification. The limits of detection, 5.0 ng/mL and 2.4 ng/mL, respectively, for atranol and chloroatranol, achieved by this method allowed identification of these compounds at concentrations below those causing allergic skin reactions in oak-moss-sensitive patients. The recovery of chloratranol from spiked perfumes was 96+/-4%. Low recoveries (49+/-5%) were observed for atranol in spiked perfumes, indicating ion suppression caused by matrix components. The method has been applied to the analysis of 10 randomly selected perfumes and similar products.

Allergens↗

Effect of glutathione on the covalent binding of the 13C-labeled skin sensitizer 5-chloro-2-methylisothiazol-3-one to human serum albumin: identification of adducts by nuclear magnetic resonance, matrix-assisted laser desorption/ionization mass spectrometry, and nanoelectrospray tandem mass spectrometry.

The covalent binding of 4-[(13)C]- and 5-[(13)C]-5-chloro-2-methylisothiazol-3-one (MCI) toward human serum albumin (HSA) was followed by (13)C and (1)H[(13)C] NMR spectroscopy. MCI was found to react with histidine through an addition-elimination at position 5, leading to stable substitution adducts, and with lysine to form open adducts of the thioamide or amide type. No other modification could be detected on either cysteine or tyrosine. In the presence of glutathione (GSH), we observed an increased covalent binding to lysine residues. This could be explained by the rapid reaction of GSH with MCI to form a chlorothioacyl intermediate very reactive toward primary amino groups of lysine residues. To further confirm these observations and map covalent binding sites, HSA samples modified by MCI with or without GSH were analyzed by matrix-assisted laser desorption/ionization mass spectrometry of tryptic digests and electrospray tandem mass spectrometry of modified peptides purified by reverse phase HPLC. About 80% of the HSA sequence was mapped, and several modified peptides were identified. When HSA was incubated with MCI without GSH, three peptides modified at histidine residues were characterized while when HSA was incubated in the presence of GSH, five peptides modified at histidine and lysine residues were identified. These experiments confirmed that modifications on lysine residues were of the amide and thioamide types. Observed modifications were in accordance with mass increases corresponding to structures identified by NMR, and an extra adduct corresponding to a double modification of His 338 was observed. Comparison of HSA-MCI and HSA-MCI-GSH samples confirmed that the presence of GSH increased the modification of lysine residues.

Binding Sites↗

Further evaluation of quantitative structure--activity relationship models for the prediction of the skin sensitization potency of selected fragrance allergens.

Fragrance substances represent a very diverse group of chemicals; a proportion of them are associated with the ability to cause allergic reactions in the skin. Efforts to find substitute materials are hindered by the need to undertake animal testing for determining both skin sensitization hazard and potency. One strategy to avoid such testing is through an understanding of the relationships between chemical structure and skin sensitization, so-called structure-activity relationships. In recent work, we evaluated 2 groups of fragrance chemicals -- saturated aldehydes and alpha,beta-unsaturated aldehydes. Simple quantitative structure-activity relationship (QSAR) models relating the EC3 values [derived from the local lymph node assay (LLNA)] to physicochemical properties were developed for both sets of aldehydes. In the current study, we evaluated an additional group of carbonyl-containing compounds to test the predictive power of the developed QSARs and to extend their scope. The QSAR models were used to predict EC3 values of 10 newly selected compounds. Local lymph node assay data generated for these compounds demonstrated that the original QSARs were fairly accurate, but still required improvement. Development of these QSAR models has provided us with a better understanding of the potential mechanisms of action for aldehydes, and hence how to avoid or limit allergy. Knowledge generated from this work is being incorporated into new/improved rules for sensitization in the expert toxicity prediction system, deductive estimation of risk from existing knowledge (DEREK).

Aldehydes↗

Content of oak moss allergens atranol and chloroatranol in perfumes and similar products.

Chloroatranol and atranol have been identified as the main allergens in the fragrance material of botanical origin, oak moss absolute. A previous study has shown that nearly all individuals sensitized to chloroatranol will elicit to 5 microg/ml. in a repeated open application test and that 50% will get a reaction to 0.15 micro g/ml under patch test conditions. Thus, chloroatranol is known as a potent allergen. The aim of the current investigation was to quantify exposure to chloroatranol and the chemically related substance atranol in some popular perfumes, eaux de parfum and eaux de toilette available on the European market. In total, 31 products were analysed by liquid chromatography-electrospray ionization-tandemmass spectrometry (LC-ESI-MS-MS) for their contents of atranol and chloroatranol. The 2 substances were found in 87% (n = 27) of the products. The median concentration of atranol in perfumes was 0.502 micro g/ml and 0.012 micro g/ml in eaux de toilette, and 0.235 micro g/ml and 0.006 micro g/ml for chloroatranol, respectively, in perfumes and eaux de toilette. Chloroatranol was found at a maximum concentration of 53 micro g/ml and atranol at one of 190 micro g/ml. The wide exposure to oak moss allergens, together with significant amounts of these potent allergens in at least half of perfumes and some eaux de toilettes explains the high frequencies of oak moss absolute allergy. It is suggested that regulations should be introduced aimed directly at these substances, and not just at oak moss absolute.

Allergens↗

Contact allergy to oak moss: search for sensitizing molecules using combined bioassay-guided chemical fractionation, GC-MS, and structure-activity relationship analysis.

In addition to pure synthetic fragrance materials several natural extracts are still in use in the perfume industry. Among them oak moss absolute, prepared from the lichen Evernia prunastri (L.) Arch., is considered a major contact sensitizer and is therefore included in the fragrance mix used for diagnosing perfume allergy. The process of preparing oak moss absolute has changed during recent years and, even though several potential sensitizers have been identified from former benzene extracts, its present constituents and their allergenic status are not clear. In the study reported here, we applied a method developed for the identification of contact allergens present in natural complex mixtures to oak moss absolute. The method is based on the combination of bioassay-guided chemical fractionation, gas chromatography-mass spectrometry analysis and structure-activity relationship studies. Our first results showed that atranol and chloroatranol, formed by transesterification and decarboxylation of the lichen depsides, atranorin and chloroatranorin, during the preparation of oak moss absolute, are strong elicitants in most patients sensitized to oak moss. Methyl-beta-orcinol carboxylate, a depside degradation product and the most important monoaryl derivative of oak moss from an olfactory standpoint, was also found to elicit a reaction in most patients.

Allergens↗

Air oxidation of 17-hydroxycorticosteroids catalyzed by cupric acetate: formation of hemiacetal dimers.

Hydrocortisone, cortexolone, hydrocortisone-17-butyrate, and budesonide were oxidized into alpha-ketoaldehydes by air exposure in the presence of Cu(OAc)(2). When free hydroxyl functions were present at position 17, hydrocortisone and cortexolone, the formed oxidation products, were identified as hemiacetal dimeric structures involving the free hydroxyl functions at position 17 and the newly formed aldehydes at position 21. Dimeric structures were established by using 1H913C0 correlations (HSQC and HMBC) and 1H-1H correlations (COSY and ROESY). The hemiacetal function was further confirmed by reaction of the dimer formed from hydrocortisone with two equivalents of 3-methyl-2-benzotriazolinone hydrazine (MTBH), giving quantitatively two equivalents of the 3-methyl-2-benzotriazolinone hydrazone of 21-dehydrohydrocortisone. When no free hydroxyl function was present as in the case of hydrocortisone-17-butyrate and budesonide, the expected alpha-ketoaldehydes were obtained.

17-Hydroxycorticosteroids↗

Studies of chemical selectivity of hapten, reactivity, and skin sensitization potency. 3. Synthesis and studies on the reactivity toward model nucleophiles of the 13C-labeled skin sensitizers, 5-chloro-2-methylisothiazol-3-one (MCI) and 2-methylisothiazol-3-one (MI).

The skin sensitizers, 5-chloro-2-methylisothiazol-3-one (MCI) and 2-methylisothiazol-3-one (MI), have been synthesized isotopically labeled with (13)C at all carbon positions. The reactivity of 3-[(13)C]-, 4-[(13)C]-, and 5-[(13)C]MCI and MI toward a series of model nucleophiles for protein amino acid residues, i.e., butylamine, imidazole, sodium propanethiolate, and sodium phenoxide, was followed by (13)C and (1)H[(13)C] NMR spectroscopy. While MCI was found to react quantitatively with sodium propanethiolate and butylamine and significantly with imidazole and sodium phenoxide, MI reacted only with sodium propanethiolate. Reaction of MCI with nonthiol nucleophiles proceeded through an initial addition-elimination at position 5, leading to stable substitution adducts in the case of imidazole and sodium phenoxide. In the case of butylamine, the initial adduct was subjected to extra reactions at the sulfur atom through a cleavage of the S-N bond, leading to open adducts of the thioamide or amide type. Experiments carried out with N-acetyl-Cys, in excess or in deficiency, indicated that thiol nucleophiles reacted first at the sulfur atom through a cleavage of the S-N bond followed by extra nucleophilic reactions leading to open adducts of the mercaptothioester or mercaptoester type. Reaction of MCI with thiol nucleophiles gave products consistent with the formation of a reactive thioacyl chloride intermediate able to react with other nucleophiles present in the reaction medium. As a consequence, N-acetyl-Cys was found to be able to activate MCI toward N(alpha)-acetyl-Lys under physiological conditions to form adducts of the thioamide or amide type. Thus MCI, a strong sensitizer, and MI, a weak sensitizer, were found to react with different nucleophiles through different mechanisms. Although both MCI and MI can react with thiol nucleophiles, only MCI is capable of significantly reacting with amino nucleophiles of the Lys or His type. Moreover, MCI could be activated by a prior reaction with thiols.

Carbon Isotopes↗

Chloroatranol, an extremely potent allergen hidden in perfumes: a dose-response elicitation study.

Oak moss absolute is a long-known, popular natural extract widely used in perfumes. It is reported as the cause of allergic reactions in a significant number of those with perfume allergy. Oak moss absolute has been the target of recent research to identify its allergenic components. Recently, chloroatranol, a hitherto unknown fragrance allergen, was identified in oak moss absolute. The objective was to assess the clinical importance of chloroatranol as a fragrance allergen by characterizing its elicitation profile. 13 patients previously showing a positive patch test to oak moss absolute and chloroatranol were included, together with a control group of 10 patients without sensitization to either of the 2 materials. A serial dilution patch test was performed on the upper back with concentrations ranging from 200 to 0.0063 p.p.m. of chloroatranol in ethanol. Simultaneously, the participant performed an open test simulating the use of perfumes on the volar aspect of the forearms in a randomized and double-blinded design. A solution with 5 p.p.m. chloroatranol was used for 14 days, and, in case of no reaction, the applications were continued for another 14 days with a solution containing 25 p.p.m. All test subjects (13/13) developed an allergic reaction at the site of application of the solution containing chloroatranol. Among them, 12/13 (92%) gave a positive reaction to the 5 p.p.m. solution and 1 to 25 p.p.m. None of the controls reacted (P < 0.001). The use test was terminated at median day 4. The dose eliciting a reaction in 50% of the test subjects at patch testing was 0.2 p.p.m. In conclusion, the hidden exposure to a potent allergen widely used in perfumes has caused a highly sensitized cohort of individuals. Judged from the elicitation profile, chloroatranol is the most potent allergen present in consumer products today.

Adult↗