Understanding buckwheat allergies for the management of allergic reactions in humans and animals.

Buckwheat allergy is an immediate hypersensitivity reaction that includes anaphylaxis mediated by specific IgE antibodies. Several IgE-binding proteins in common buckwheat have been reported to be possible clinically relevant buckwheat allergens. Although common buckwheat is popularly consumed in Asia, buckwheat allergy is becoming a serious problem not only in Asia but also in Europe. In addition, common buckwheat has also been found to be a causative agent of allergic symptoms in animals. In recent years, in addition to conventional food allergy testing methods, the development of component-resolved diagnosis (CRD) has improved the diagnostic accuracy of food allergy. The identification of allergens is essential for the construction of CRD. In this review, we introduce the different types of buckwheat allergens and discuss how each buckwheat allergen contributes to the diagnosis of buckwheat allergy. We also present the analysis of buckwheat allergen that will help reduce the allergenicity of common buckwheat and reduce buckwheat allergen molecules. These findings may be beneficial in overcoming buckwheat allergies in humans and animals.

Inter-laboratory optimization of protein extraction, separation, and fluorescent detection of endogenous rice allergens.

In rice, several allergens have been identified such as the non-specific lipid transfer protein-1, the α-amylase/trypsin-inhibitors, the α-globulin, the 33 kDa glyoxalase I (Gly I), the 52-63 kDa globulin, and the granule-bound starch synthetase. The goal of the present study was to define optimal rice extraction and detection methods that would allow a sensitive and reproducible measure of several classes of known rice allergens. In a three-laboratory ring-trial experiment, several protein extraction methods were first compared and analyzed by 1D multiplexed SDS-PAGE. In a second phase, an inter-laboratory validation of 2D-DIGE analysis was conducted in five independent laboratories, focusing on three rice allergens (52 kDa globulin, 33 kDa glyoxalase I, and 14-16 kDa α-amylase/trypsin inhibitor family members). The results of the present study indicate that a combination of 1D multiplexed SDS-PAGE and 2D-DIGE methods would be recommended to quantify the various rice allergens.

Establishment of monoclonal antibodies of BW10kDa distinguish it from Fag e 2 related to anaphylaxis.

BW10kDa, which is a buckwheat (BW) allergen, belongs to the 2S-albumin protein family, akin to Fag e 2. Detailed analyses of BW10kDa were lacking until this study. Herein, we conducted these analyses using monoclonal antibodies (mAbs) to recombinant BW10kDa (rBW10kDa). We successfully generated anti-rBW10kDa mAbs capable of distinguishing between Fag e 2 and BW10kDa. These mAbs were categorised into two types (type 1 and type 2) based on their reactivity to BW plant seed extracts in western blot analyses. Type 1 mAbs revealed two bands (15 kDa and 10 kDa), while type 2 mAbs showed a single band (15 kDa). Spot analyses using these mAbs confirmed that type 1 mAbs recognised epitopes near the C-terminal region, with the 10 kDa band representing the C-terminal subunit cleaved by protease. The mAbs targeting rBW10kDa enabled to assess the concentration of BW10kDa in wild type and also in diagnostic buckwheat extracts.

Proteomic analysis of known and candidate rice allergens between non-transgenic and transgenic plants.

Salt-soluble proteins extracted from non-transgenic and transgenic rice were evaluated for the presence of known and potential allergens by proteomic techniques. The salt-soluble proteins were extracted, separated by 1D and 2D electrophoresis, and analyzed by Western blotting. 1D immunoblot analysis with patients' sera revealed few qualitative differences between the IgE-binding proteins of the non-transgenic and transgenic rice. 1D immunoblot with antigen-specific-animal sera revealed no qualitative or quantitative differences in two known allergens, RAG2 and glyoxalase I, between non-transgenic and transgenic rice. Multiple spots containing known and novel IgE-binding proteins were detected among the salt-soluble proteins of non-transgenic rice by 2D immunoblotting. Two globulin-like proteins, a 52 kDa protein and a 63 kDa protein, were identified as novel IgE-binding proteins that are candidates for rice allergens. These globulin-like proteins were homologous to Cupin superfamily allergens. Quantitative analysis of 19, 52, and 63 kDa globulins with protein-specific-animal sera showed no significant differences in the expression of these proteins between the transgenic rice and non-transgenic rice. These results indicate that none of the known or novel endogenous IgE-binding proteins detected in this study appear to be altered by genetic modification.

Identification of an IgE-binding epitope of a major buckwheat allergen, BWp16, by SPOTs assay and mimotope screening.

BACKGROUND: The buckwheat 16-kDa protein (BWp16), as reported in our previous study, is a major allergen in buckwheat; however, the IgE-binding epitopes of BWp16 have not as yet been identified. METHODS: We screened candidates for IgE-binding epitopes on BWp16 by using arrays of overlapping peptides synthesized on activated cellulose membranes (SPOTs membrane). The mimotope method was also used to analyze IgE-binding epitopes of BWp16. Nine single alanine (Ala) mutants of BWp16 expressed in Escherichia coli were used to confirm the epitopes of BWp16. The IgE-binding activity of single Ala mutants of BWp16 was determined by ELISA with mouse anti-BWp16 polyclonal antiserum or ELISA inhibition with sera from buckwheat allergic patients. RESULTS: The SPOTs assay identified amino acid residues 99-110, i.e. EGVRDLKELPSK, as a candidate for the linear IgE-binding epitope of BWp16. The mimotope method indicated that peptides similar to EGVRDLKE were candidate sequences for epitopes of BWp16. Ala scanning of rBWp16 revealed that all EGVRDLKE peptides containing a single amino acid mutation had weaker IgE-binding activity than rBWp16 WT. An ELISA inhibition assay for rBWp16 WT revealed the inhibitory effect of rBWp16 D103A to be less than that of rBWp16 WT. CONCLUSIONS: We identified the peptide EGVRDLKE as a very likely candidate for the IgE-binding epitope of BWp16, and Asp103 as the critical amino acid in BWp16. This is the first report on the identification of IgE-binding epitopes of BWp16. Our findings will contribute to the production of BWp16 hypoallergens, and to allergen-specific immunotherapy for buckwheat allergy.

Immunoproteomic and two-dimensional difference gel electrophoresis analysis of Arabidopsis dehydration response element-binding protein 1A (DREB1A)-transgenic potato.

To produce crops that are more tolerant to stresses such as heat, cold, and salt, transgenic plants have been produced those express stress-associated proteins. In this study, we used immunoproteomic and two-dimensional difference gel electrophoresis (2D-DIGE) methods to investigate the allergenicity of transgenic potatoes expressing Arabidopsis DREB1A (dehydration responsive element-binding protein 1A), driven by the rd29A promoter or the 35S promoter. Immunoproteomic analysis using sera from potato-allergic patients revealed several immunoglobulin E (IgE)-binding protein spots. The patterns of protein binding were almost the same between transgenic and non-transgenic potatoes. The IgE-binding proteins in potato were identified as patatin precursors, a segment of serine protease inhibitor 2, and proteinase inhibitor II by matrix assisted laser desorption/ionization-time of flight (MALDI-TOF) MS/MS. 2D-DIGE analysis revealed several differences in protein expression between non-transgenic potato and transgenic potato; those showing increased expression in transgenic potatoes were identified as precursors of patatin, a major potato allergen, and those showing decreased expression in transgenic potatoes were identified as lipoxygenase and glycogen (starch) synthase. These results suggested that transgenic potatoes may express slightly higher levels of allergens, but their IgE-binding patterns were almost the same as those of control potatoes. Further research on changes in protein expressions in response to environmental factors is required to confirm whether the differences observed in this study are due to gene transfection, rather than environmental factors.

Novel method to detect a construct-specific sequence of the acetolactate synthase gene in genetically-modified flax CDC Triffid (FP967).

During the fall of 2009, a trace of unauthorized genetically modified (GM) flax (Linum usitatissimum L.) line, CDC Triffid, which is resistant to sulfonylurea herbicides, was detected in many countries including Japan. A method to reliably identify the CDC Triffid line was urgently required. We developed a novel construct-specific real-time polymerase chain reaction (PCR) method to identify the mutant acetolactate synthase gene in the CDC Triffid line. We confirmed that the method can detect 0.001% GM flax in DNA mixing solution. The study shows that the developed method is specific, sensitive and reliable way to monitor a trace of CDC Triffid.

2D-DIGE analysis of rice proteins from different cultivars.

The 2D-DIGE (2-Dimensional Fluorescence Difference Gel Electrophoresis) method was applied to proteomic phenotyping of natural variants in 10 varieties of rice (Nipponbare, Koshihikari, Sasanishiki, Akitakomachi, Hitomebore, Hinohikari, Kasalath, Rexark, Bleiyo, Cho-ko) from the world rice collection (WRC) in the GenBank of the National Institute of Agrobiological Sciences (NIAS), Japan. Salt-soluble protein extracts of Nipponbare brown rice were labeled with Cy2 fluorochrome and used as an internal standard. Protein extracts from nine other rice varieties were labeled with Cy3 or Cy5 fluorochrome and applied to 2D-PAGE (13cm gel length) analysis. Approximately 700 spots of rice proteins were observed. Fluorescence intensities of each of these spots for the nine rice varieties were expressed as relative ratios to that of Nipponbare. Statistical analysis revealed the spot numbers of five Japanese rice varieties above threshold five (relative ratio of each variety to Nipponbare exceeded 5-fold or was less than 1/5) to be less than three, while those of four varieties from other countries were more than five (especially, Kasalath which was 29 and Bleiyo which was 23). The 2D-DIGE method seems to be useful for analyzing natural varieties of different cultivars and also for comparing the expression of allergen proteins.

Purification, crystallization and preliminary X-ray analysis of a deletion mutant of a major buckwheat allergen.

A 16 kDa buckwheat protein (BWp16) is a major allergen responsible for immediate hypersensitivity reactions including anaphylaxis. A deletion mutant of BWp16 (rBWp16DeltaN) was overproduced and purified and was shown to be immunologically active. A three-wavelength MAD data set was collected from a crystal of selenomethionine-labelled rBWp16DeltaN. The crystal belonged to the triclinic space group P1, with unit-cell parameters a = 28.39, b = 31.54, c = 32.20 A, alpha = 111.92, beta = 108.91, gamma = 98.74 degrees . One monomer was expected to be present in the asymmetric unit based on the calculated Matthews coefficient of 1.76 A(3) Da(-1).

Comparative study of GH-transgenic and non-transgenic amago salmon (Oncorhynchus masou ishikawae) allergenicity and proteomic analysis of amago salmon allergens.

Genetically modified (GM) foods are beneficial from the standpoint of ensuring a constant supply of foodstuffs, but they must be tested for safety before being released on the market, including by allergenicity tests to ensure that they do not contain new allergens or higher concentrations of known allergens than the same non-GM foods. In this study we used GM-amago salmon into which a growth hormone gene had been introduced and compared the allergens contained in the GM and the non-GM-amago salmons. We used a combination of Western blotting with allergen-specific antibodies and a proteomic analysis of their allergens with patients' sera, a so-called allergenome analysis, to analyze allergens. Western blotting with specific antibodies showed no increase in the content of the known allergens fish parvalbumin and fish type-I collagen in GM-amago salmon, in comparison with their content in non-GM-amago salmon. The allergenome analysis of two fish-allergic patients allowed us to identify several IgE-binding proteins in amago salmon, including parvalbumin, triose-phosphate isomerase, fructose-bisphosphate aldolase A, and serum albumin, and there were no qualitative differences in these proteins between GM and non-GM-amago salmons. These results indicate that amago salmon endogenous allergen expression does not seem to be altered by genetic modification.

Analysis of the distribution of rice allergens in brown rice grains and of the allergenicity of products containing rice bran.

To understand the allergenicity of rice bran, the distribution of rice allergens in brown rice grains was analysed and the allergenicity of cosmetics and health foods containing rice bran determined. RAG2 and a 19-kDa globulin were localized in polished rice, while a 52-kDa globulin was localized in rice bran. The 52-kDa globulin was also identified as the most likely causative allergen of rice bran allergy. Several products containing intact rice bran were found to contain the 52-kDa globulin. Our study provides the first data regarding cosmetics and health foods containing potential rice bran allergens. Western blot analysis using a rice-bran-allergic patient's plasma showed that 52-kDa globulin was detected as an IgE-binding protein of rice bran and some rice bran-containing cosmetics and health foods. Our results indicate that patients with rice bran allergy need to be careful about using products containing intact rice bran as a constituent.

Oral Immunotherapy with a Phosphorylated Hypoallergenic Allergen Ameliorates Allergic Responses More Effectively Than Intact Allergen in a Murine Model of Buckwheat Allergy.

SCOPE: Buckwheat is a common food allergen frequently consumed in Asian countries, with Fag e 1 and Fag e 2 being the major buckwheat allergens. The purpose of this study is to prepare an oral immunotherapy agent by attenuating these allergens via phosphorylation. The immunomodulatory effects of phosphorylated Fag e 2 (P-Fag e 2) in a mouse model of buckwheat allergy are evaluated. METHODS AND RESULTS: Phosphorylated Fag e 1 (P-Fag e 1) and P-Fag e 2 are prepared by dry-heating in the presence of pyrophosphate. Subsequent dot-blot analysis using serum from food-allergic patient indicates that both proteins exhibit reduced allergenicity upon phosphorylation. Mice subjected to oral administration of P-Fag e 2 for 6 weeks exhibit decreased specific serum IgE and increased specific IgA after Fag e 2 sensitization compared to the sham-treated mice. Moreover, the Peyer's patches (PP) of phosphorylated antigen-fed mice show decreased IL-4 production and induction of T follicular helper (Tfh) cells. Increased production of IL-6 is observed in the CD11c+ cells isolated from the PPs of P-Fag e 2-fed mice. CONCLUSION: These results indicate that attenuated allergens can suppress Th2-induced allergic responses via induction of Tfh cells, which are regulated by IL-6 secreted from dendritic cells.

Relationship between electronic structure and cytotoxic activity of azulenequinones and trihaloacetylazulenes.

The relationship between the structure and cytotoxic activity of azulenequinones and trihaloacetylazulenes was investigated based on theoretical calculations. Four different dipole moments (mu(G), mu(ESP-G), mu(W) and mu(ESP-W)) and heats of formation (DeltaH(f)) of the azulenequinones [1-27] and trihaloacetylazulenes [28a,b-40a,b] were separately calculated in gas phase and aqueous solution using the conductor-like screening model/parametric method 3 (COSMO/PM3) method. The cytotoxic activity of azulenequinones was well correlated to DeltaDeltaH(f) HOMO energy and mu(ESP-w). The cytotoxic activity of trihaloacetylazulenes was correlated to DeltaDeltaH(f) LUMO energy and mu(ESP-W). QSAR may be applicable to predict the cytotoxicity of azulenequinones and trihaloacetylazulenes.

Tumor-specificity and apoptosis-inducing activity of stilbenes and flavonoids.

A total of eleven stilbenes [1-6] and flavonoids [7-11] were investigated for their tumor- specific cytotoxicity and apoptosis-inducing activity, using four human tumor cell lines (squamous cell carcinoma HSC-2, HSC-3, submandibular gland carcinoma HSG and promyelocytic leukemia HL-60) and three normal human oral cells (gingival fibroblast HGF, pulp cell HPC, periodontal ligament fibroblast HPLF). All of the compounds, especially sophorastilbene A [1], (+)-alpha-viniferin [2], piceatannol [5], quercetin [9] and isoliquiritigenin [10], showed higher cytotoxicity against the tumor cell lines than normal cells, yielding tumor-specific indices of 3.6, 4.7, >3.5, >3.3 and 4.0, respectively. Among the seven cell lines, HSC-2 and HL-60 cells were the most sensitive to the cytotoxic action of these compounds. Sophorastilbene A [1], piceatannol [5], quercetin [9] and isoliquiritigenin [10] induced internucleosomal DNA fragmentation and activation of caspases -3, -8 and -9 dose-dependently in HL-60 cells. (+)-alpha-Viniferin [2] showed similar activity, but only at higher concentrations. All the compounds failed to induce DNA fragmentation and activated caspases to much lesser extents in HSC-2 cells. Western blot analysis showed that sophorastilbene A [1], piceatannol [5] and quercetin [9] did not induce any consistent changes in the expression of pro-apoptotic proteins (Bax, Bad) and antiapoptotic protein (Bcl-2) in HL-60 and HSC-2 cells. An undetectable expression of Bcl-2 protein in control and drug-treated HSC-2 cells may explain the relatively higher sensitivity of this cell line to stilbenes and flavonoids.

Changes in fluoride sensitivity during in vitro senescence of normal human oral cells.

We have previously reported that sodium fluoride (NaF) showed slightly higher cytotoxicity against human oral tumor cell lines than normal human oral cells. Possible changes in the NaF sensitivity of three normal human oral cell types (gingival fibroblast HGF, pulp cell HPC, periodontal ligament fibroblast HPLF) during in vitro ageing were investigated in the present study. When these cells were subcultured at 1:4 split ratio every week, their saturation density declined with increasing population doubling level (PDL), and they ceased to divide when they reached 20 PDL. Mitochondrial function, evaluated by MTT stainability per cell basis, was elevated at the terminal phase. NaF dose-dependently reduced the viable cell number, but did not show any beneficial (growth promoting) effect (so-called "hormesis") at lower concentrations. NaF produced large DNA fragments, without induction of internucleosomal DNA fragmentation, possibly due to weak activation of caspases -3, -8 and -9. Higher concentrations of NaF were required to reduce the number of viable senescent cells than younger cells, indicating that cells become resistant to cytotoxicity of NaF with in vitro ageing.

Immunological characterization and mutational analysis of the recombinant protein BWp16, a major allergen in buckwheat.

Buckwheat allergy is one of the most critical diseases manifested by severe and dangerous symptoms in Japan and other countries. We previously isolated the cDNA encoding protein BWp16, a member of the 2S albumin family with a conserved motif of 8 cysteine (Cys) residues. Comparison of the deduced amino acid sequences of BWp16 and related proteins in the 2S albumin family showed similarities between BWp16 and BW 8-kDa from buckwheat, Ara h 6 from peanuts and Ric c 1 from castor bean. Purified recombinant BWp16 (rBWp16) expressed in Escherichia coli was recognized by >80% of sera from patients with positive for IgE binding to buckwheat. Mutational analysis of rBWp16 revealed that 7 out of 10 mutants in the Cys residues showed weaker IgE binding to patient's serum than wild-type rBWp16 (rBWp16 WT). Mutations of Cys65 and Cys66 in rBWp16 decreased the pepsin digestibility of the protein, and an ELISA inhibition assay revealed a weaker inhibitory effect of rBWp16 C65S than that of rBWp16 WT. These results suggest that the Cys residues, especially Cys65, are involved in the allergenicity of rBWp16. Our findings provide new evidence for the role of Cys residues in 2S albumin family proteins and open the door to the production of hypoallergens and application to safe diagnostic methods and allergen-specific immunotherapy of buckwheat allergy.

AREB1 is a transcription activator of novel ABRE-dependent ABA signaling that enhances drought stress tolerance in Arabidopsis.

ABSCISIC ACID-RESPONSIVE ELEMENT BINDING PROTEIN1 (AREB1) (i.e., ABF2) is a basic domain/leucine zipper transcription factor that binds to the abscisic acid (ABA)-responsive element (ABRE) motif in the promoter region of ABA-inducible genes. Here, we show that expression of the intact AREB1 gene on its own is insufficient to lead to expression of downstream genes under normal growth conditions. To overcome the masked transactivation activity of AREB1, we created an activated form of AREB1 (AREB1DeltaQT). AREB1DeltaQT-overexpressing plants showed ABA hypersensitivity and enhanced drought tolerance, and eight genes with two or more ABRE motifs in the promoter regions in two groups were greatly upregulated: late embryogenesis abundant class genes and ABA- and drought stress-inducible regulatory genes. By contrast, an areb1 null mutant and a dominant loss-of-function mutant of AREB1 (AREB1:RD) with a repression domain exhibited ABA insensitivity. Furthermore, AREB1:RD plants displayed reduced survival under dehydration, and three of the eight greatly upregulated genes were downregulated, including genes for linker histone H1 and AAA ATPase, which govern gene expression and multiple cellular activities through protein folding, respectively. Thus, these data suggest that AREB1 regulates novel ABRE-dependent ABA signaling that enhances drought tolerance in vegetative tissues.

A novel subgroup of bZIP proteins functions as transcriptional activators in hypoosmolarity-responsive expression of the ProDH gene in Arabidopsis.

A 6-bp sequence, ACTCAT, acts as a cis-acting element involved in hypoosmolarity- and proline-responsive expression of an Arabidopsis proline dehydrogenase (ProDH) gene. Search of the database for plant cis-acting elements revealed that the ACTCAT sequence is similar to the GCN4 motif [ATGA(C/G)TCAT] that is recognized by bZIP transcription factors. To identify transcription factor(s) for regulation of ProDH, we examined whether Arabidopsis bZIPs function as transcription factors for the ACTCAT sequence. Transient expression analysis revealed that the four proteins in Group S bZIPs, AtbZIP11/ATB2, AtbZIP44, AtbZIP2/GBF5 and AtbZIP53, formed an ATB2 subgroup that activated expression of the GUS reporter gene driven by the ACTCAT sequence while other bZIPs and different families of plant transcription factors did not. The transactivation activity of the ATB2 subgroup was enhanced in a hypoosmotic condition. In a gel mobility shift assay, the recombinant proteins of the ATB2 subgroup specifically bound to the ACTCAT sequence. RNA gel blot analysis indicated that the expression of AtbZIP2/GBF5 and AtbZIP53, as well as that of ProDH, is induced by hypoosmolarity. Moreover, we showed that the sGFP::AtbZIP11/ATB2 fusion protein is localized in the nucleus. These results suggest that the ATB2 subgroup functions as a transcriptional activator for hypoosmolarity-inducible ProDH in Arabidopsis:

ACTCAT, a novel cis-acting element for proline- and hypoosmolarity-responsive expression of the ProDH gene encoding proline dehydrogenase in Arabidopsis.

Proline (Pro) is one of the most widely distributed osmolytes in water-stressed plants. We previously isolated from Arabidopsis a gene encoding Pro dehydrogenase (ProDH), a mitochondrial enzyme involved in the first step of the conversion of Pro to glutamic acid. The ProDH gene in Arabidopsis is up-regulated by rehydration after dehydration but is down-regulated by dehydration. ProDH is also induced by L-Pro and hypoosmolarity. The induction of ProDH expression under rehydration seems to be caused by both accumulated Pro and hypoosmolarity. We analyzed a DNA region that is located 5' to the transcription start site (a promoter region) of ProDH to identify cis-acting elements involved in L-Pro-induced and hypoosmolarity-induced expression in transgenic tobacco (Nicotiana tabacum) and Arabidopsis plants. We found that a 9-bp sequence, ACTCATCCT, in the ProDH promoter is necessary for the efficient expression of ProDH in response to L-Pro and hypoosmolarity. Moreover, ACTCAT is a core cis-acting element, which we have called Pro- or hypoosmolarity-responsive element (PRE), that is necessary for L-Pro-responsive and hypoosmolarity-responsive expression of ProDH. Microarray and RNA gel-blot analyses showed that 21 L-Pro-inducible genes have the PRE sequences in their promoter regions. These results indicate that the PRE sequence play an important role in the L-Pro-responsive gene expression.

Monitoring expression profiles of Arabidopsis gene expression during rehydration process after dehydration using ca 7000 full-length cDNA microarray.

Plants respond and adapt to drought stress in order to survive under stress conditions. Several genes that respond to drought at the transcriptional level have been described, but there are few reports on genes involved in the recovery from dehydration. Analysis of rehydration-inducible genes should help not only to understand the molecular mechanisms of stress responses in higher plants, but also to improve the stress tolerance of crops by gene manipulation. We used a full-length cDNA microarray containing ca. 7000 Arabidopsis full-length cDNAs and identified 152 rehydration-inducible genes. Venn diagram analysis showed relationship of the rehydration-inducible genes to proline-inducible and water-treatment-inducible genes. Among the 152 rehydration-inducible genes, 58 genes contained the ACTCAT sequence involved in proline- and hypoosmolarity-inducible gene expression in their promoter regions, suggesting that ACTCAT sequence is a major cis-acting element involved in rehydration-inducible gene expression, and that some novel cis-acting elements are involved in rehydration-inducible gene expression. Functional analysis of rehydration-inducible and rehydration-repressed genes revealed their functions not only in the release from a stressed status but also in the recovery of growth in plants.