Abstract
Hydrochloric acid (HCl)-treated wheat protein (HWP) is widely used in various products, including foods, cosmetics and shampoos. Recently, immediate hypersensitivity towards facial soap containing HWP has been reported. HCl treatment of protein causes hydrolysis not only of main-chain amide bonds (peptide-bond hydrolysis) but also of side-chain ones (deamidation). We have already reported that gliadin, the main allergen in wheat, reduces allergenicity and increases digestibility by deamidation, indicating that deamidation and peptide-bond hydrolysis are effective to reduce the allergenicity of wheat protein. However, transdermally administered HWP is assumed to induce sensitization to orally administered wheat protein even in those who have been taking wheat products daily before sensitization. The present study was conducted to examine which structural change is responsible for the induction of cutaneous sensitization by comparing the allergenicity of deamidated and/or peptide-bond-hydrolyzed wheat gliadin. Because we have developed a deamidation method without causing peptide-bond hydrolysis, only deamidated wheat gliadin is available. Therefore, after deamidated-only, hydrolyzed-only, and deamidated and hydrolyzed gliadins were transdermally administered to mice for several weeks, the corresponding gliadin was intraperitoneally administered and allergenicity was evaluated. Transdermal administration of deamidated and hydrolyzed gliadin induced severe allergic reaction, while that of deamidated-only and hydrolyzed-only gliadin showed almost no allergic response. This result indicates that both deamidation and peptide-bond hydrolysis are necessary to increase the allergenic potency of transdermally administered wheat gliadin.
Highlights
Wheat is one of the most important cereals, as a carbohydrate source and as a source of food with unique texture [1]
The abundance ratios of peptides with molecular weights lower than 10 kDa in UG, DG, HG, and Hydrolyzed and deamidated gliadin (HDG) were 0%,
The abundance ratios of peptides with molecular weight higher than 100 kDa in UG, DG, HG, and HDG were 44%, 45%, 0%, and 31%, respectively, which was consistent with the inverse order of degree of peptide-bond hydrolysis of gliadins
Summary
Wheat is one of the most important cereals, as a carbohydrate source and as a source of food with unique texture [1]. The unique functional properties of wheat are mostly attributed to wheat protein, which enhances the cohesiveness, viscoelasticity, extensibility, expandability, emulsifiability and foamability of the food to which it is added [1,2]. These properties of wheat protein are useful for cosmetics such as soaps, shampoos, hair conditioners, skin moisturizers and facial creams to meet specified usages required [3]. 86% of all wheat proteins, gliadin content being about 40%, and glutenin content being about 46% [4], and is often used for cosmetics after treatment with an acid like hydrochloric acid (HCl) [5]. Regarding patients with wheat-dependent, exercise-induced anaphylaxis (WDEIA), certain tandem sequencing sites with glutamine residues in gluten and gliadin, such as QQQPP [11], QQIPQQQ, QQLPQQQ, QQFPQQQ, QQSPEQQ, QQSPQQQ, QQYPQQQ, and PYPP [12], have been identified as the primary structure of immunoglobulin (Ig) E-binding epitopes
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