Eilstein Joan, Giménez-Arnau Elena, Duché Daniel, Rousset Françoise, Lepoittevin Jean-Pierre
Laboratoire de Dermatochimie, Université Louis Pasteur (CNRS-UMR 7177), Clinique Dermatologique CHU, 1 Place de l'Hôpital, 67091 Strasbourg, France.
Chem Res Toxicol. 2006 Sep;19(9):1248-56. doi: 10.1021/tx0601408.
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.
合成了2,5-[(13)C]-二甲基对苯醌二亚胺，并通过相关的(13)C和(1)H{(13)C}核磁共振光谱，结合串联质谱的高效液相色谱法，研究了其与几种亲核氨基酸的反应活性。观察到与N-乙酰半胱氨酸反应的经典亲电-亲核机制。加合物是由氨基酸硫醇基团与苯醌二亚胺亲电位置3和6以及亚氨基的氮原子反应形成的。然而，在2,5-[(13)C]-二甲基对苯醌二亚胺存在下，N-乙酰色氨酸和N-乙酰赖氨酸通过氧化还原过程发生化学修饰。异核(1)H{(13)C}核磁共振实验能够鉴定出源自N-乙酰色氨酸的已知氧化中间体，表明反应介质的氧化强度。加合物是由苯醌二亚胺的还原形式与N-乙酰甲酰犬尿氨酸反应形成的，N-乙酰甲酰犬尿氨酸是N-乙酰色氨酸最著名的氧化衍生物。就N-乙酰赖氨酸而言，得到了4-氨基-2,5-二甲基-[(13)C]-甲酰苯胺及其在第4位与N-乙酰赖氨酸的衍生物。提出了一种反应机制，其中氨基酸的ε-NH(2)与亲电二亚胺反应形成烯胺加合物，然后烯胺加合物可诱导N-乙酰赖氨酸的氧化脱氨。在形成的N-乙酰-α-氨基己二酸-δ-半醛上进一步的氧化还原机制可能产生N,N-乙酰甲酰谷氨酸半醛，其被认为是对2,5-[(13)C]-二甲基对苯醌二亚胺还原形式具有强大反应活性的物种。在N-乙酰酪氨酸或N-乙酰甲硫氨酸存在下，二亚胺母体化合物优先水解，随后还原为对苯二酚形式。在本研究中，我们因此表明，作为变应原性对氨基芳香化合物的首批氧化衍生物，对苯醌二亚胺可通过一系列复杂机制与氨基酸上的亲核残基反应，并且必须被认真视为形成导致过敏性接触性皮炎的抗原结构的潜在候选物。
