Screening of anti-allergy Lactobacillus and its effect on allergic reactions in BALB/c mice sensitized by soybean protein

Molecular Cloning, Prokaryotic Expression, and Immunological Characterization of β-Enolase from Grass Carp (Ctenopharyngodon idella)

β-Enolase is a cross-allergen commonly found in fungi, plants, and aquatic products. Although studies on the allergenicity of fish enolase have been reported in recent years, they are still limited to a few species of marine fish. Therefore, the detection of freshwater fish in the food industry requires more studies of the molecular characterization as well as the allergenicity of enolase. In this study, the nucleotide sequence of β-enolase from grass carp was obtained by molecular cloning technology. Structural domain analysis showed that it contained the characteristic structural domains of the enolase superfamily, and homology analysis indicated that enolases are highly conserved evolutionarily. Recombinant β-enolase was obtained by prokaryotic expression, and its allergenicity was assessed by β-enolase-sensitized mice, which confirmed the ability of β-enolase to trigger an allergic response and cause a rise in Th1 and Th2 immune responses in mice. These results suggest that β-enolase could be used as a characterizing substance for the detection of fish allergens in the food industry as well as the preparation of drugs for allergy-related studies.

Effects of medicine food homologous materials on food allergy-associated factors: intestinal oxidative stress, intestinal inflammation and Th2 immune response

BACKGROUND

Food allergies could be regulated via Th1/Th2 balance, intestinal oxidative stress and inflammation, which were considered as food allergy-associated factors. Medicine-food homologous materials (MFHM) were considered as a significant factor with respect to preventing human diseases. To evaluate the associations between MFHM and food allergy-associated factors, two types of MFHM with the remarkable function of anti-oxidation and anti-inflammation, Gardeniae fructus (Gar) and Sophorae glos (Sop), were chosen.

RESULTS

By constructing an H2O2-induced oxidative stress model of Caco-2 cells and an intestinal inflammatory cell model of Caco-2 cells with tumor necrosis factor-α and interleukin (IL)-13, the contents of anti-oxidative enzymes (SOD and GSH), inflammatory factor (IL-8) and tight junction proteins (zonula occludens-1, occludin and claudin-1) in Caco-2 cells were determined. Moreover, the anti-allergic effects of digestive Sop and Gar were evaluated by measuring the levels of Th1/Th2/Treg cytokines in the spleen cells of sensitized mice. The results showed that the SOD and GSH were obviously increased and the gene and protein expression of IL-8 and claudin-1 were improved with the incubation of digested Sop. Th2 cytokine was reduced and Th1/Th2 balance was promoted on coincubation with ovalbumin (OVA) and digested Sop in the splenocytes. However, the digested Gar had no effect.

CONCLUSION

The digested Sop not only had suppressive effects on intestinal oxidative stress and inflammation, but also had regulative effects on Th1/Th2 balance. This finding demonstrated that not all of the MFHM with anti-oxidant and anti-inflammatory effects have anti-allergic activities. The present study may be contributing toward establishing a screening model to identify the anti-allergic MFHM. © 2024 Society of Chemical Industry.

Transglutaminase-Cross-Linked Tofu Suppressed Soybean-Induced Allergic Reactions by Enhancing Intestinal Mucosa Immune Tolerance

Currently, food allergies are closely related to intestinal health, and ensuring the integrity and health of intestinal mucosa could reduce the incidence of food allergies. In this study, a soybean-allergic mouse model was used to explore the mechanism of intestinal mucosa immune response induced by enzyme-cross-linked tofu. The effects of enzyme-cross-linked tofu on intestinal mucosal immunity in mice were determined by hematoxylin-eosin (HE) staining and flow cytometry. Our results reveled that the MTG-cross-linked tofu reduced the reactivity of the intestinal mucosal immune system, which mainly manifested as a decrease in the dendritic cell (DC) levels of mesenteric lymph nodes (MLNs), increasing the Th1 cells and Tregs in Peyer's patch (PP) nodes and MLNs, and inhibiting the Th2 cells. Compared with soy protein, enzyme-cross-linked tofu had less damage to the small intestinal tract of mice. Therefore, the above-mentioned results fully revealed that the enzyme-cross-linked tofu promoted the transformation of intestinal mucosal immune cells, shifted the Th1/Th2 balance toward Th1, and reduced its sensitization effect.

Covalent conjugation with quercetin mitigates allergenicity of the bee pollen allergen Bra c p in a murine model

Profilin family members are highly conserved food allergens that can cause widespread cross-allergic reactions. Our previous research has demonstrated that the covalent conjunction with quercetin can disrupt the conformational epitopes of a profilin allergen, Bra c p. In this study, we further investigated the intrinsic molecular mechanisms using molecular dynamics simulations. Moreover, the allergenic potential of Bra c p and its conjugate with quercetin was assessed in BALB/c mice. The results showed that continuous interaction with quercetin increased the molecular motion of Bra c p, causing changes to its α-helices and exposing hydrophobic residues which altered antigenic epitopes. Additionally, mice treated with Bra c p-quercetin conjugate showed reduced allergic reactions compared to those treated with Bra c p alone by regulating purine metabolism, calcium signaling, and CD4+CD25+ Tregs proportion. Quercetin conjugation decreases the allergenicity of Bra c p, providing a scientific foundation for reducing the profilin allergens in food.

Allergenicity of alternative proteins: research hotspots, new findings, evaluation strategies, regulatory status, and future trends: a bibliometric analysis

As the world population rises, the demand for protein increases, leading to a widening gap in protein supply. There is an unprecedented interest in the development of alternative proteins, but their allergenicity has raised consumer concerns. This review aims to highlight and correlate the current research status of allergenicity studies on alternative proteins based on previously published studies. Current research keywords, hotspots and trends in alternative protein sensitization were analyzed using a mixed-method approach that combined bibliometric analysis and literature review. According to the bibliometric analysis, current research is primarily focused on food science, agriculture, and immunology. There are significant variations in the type and amount of allergens found in alternative proteins. A significant amount of research has been focused on studying plant-based proteins and the cross-reactivity of insect proteins. The allergenicity of alternative proteins has not been studied extensively or in depth. The allergenicity of other alternative proteins and the underlying mechanisms warrant further study. In addition, the lack of a standardized allergy assessment strategy calls for additional efforts by international organizations and collaborations among different countries. This review provides new research and regulatory perspectives for the safe utilization of alternative proteins in human food systems.

In Vitro Evaluation of Intestinal Transport and High-Density Fermentation of Lactobacillus acidophilus

Lactobacillus acidophilus strains have limiting factors such as low cell density and complex nutritional requirements in industrial production, which greatly restricts their industrial application. In this study, fermentation conditions for L. acidophilus were optimized and transcriptomic analysis used to understand growth mechanisms under high-density fermentation conditions. We found that L. acidophilus IMAU81186 has strong tolerance to gastrointestinal juice. In addition, its optimal culture conditions were 3% inoculum (v/v); culture temperature 37 °C; initial pH 6.5; and medium composition of 30.18 g/L glucose, 37.35 g/L soybean peptone, 18.68 g/L fish peptone, 2.46 g/L sodium citrate, 6.125 g/L sodium acetate, 2.46 g/L K2HPO4, 0.4 g/L MgSO4·7H2O,0.04 g/L MnSO4·5H2O, 0.01 g/L serine, and 0.3 g/L uracil. After optimization, viable counts of IMAU81186 increased by 7.03 times. Differentially expressed genes in IMAU81186 were analyzed at different growth stages using transcriptomics. We found that a single carbon source had limitations in improving the biomass of the strain, and terP and bfrA were significantly down-regulated in the logarithmic growth period, which may be due to the lack of extracellular sucrose. After optimizing the carbon source, we found that adding 12 g/L sucrose to the culture medium significantly increased cell density.

Probiotics: mechanism of action, health benefits and their application in food industries

Probiotics, like lactic acid bacteria, are non-pathogenic microbes that exert health benefits to the host when administered in adequate quantity. Currently, research is being conducted on the molecular events and applications of probiotics. The suggested mechanisms by which probiotics exert their action include; competitive exclusion of pathogens for adhesion sites, improvement of the intestinal mucosal barrier, gut immunomodulation, and neurotransmitter synthesis. This review emphasizes the recent advances in the health benefits of probiotics and the emerging applications of probiotics in the food industry. Due to their capability to modulate gut microbiota and attenuate the immune system, probiotics could be used as an adjuvant in hypertension, hypercholesterolemia, cancer, and gastrointestinal diseases. Considering the functional properties, probiotics are being used in the dairy, beverage, and baking industries. After developing the latest techniques by researchers, probiotics can now survive within harsh processing conditions and withstand GI stresses quite effectively. Thus, the potential of probiotics can efficiently be utilized on a commercial scale in food processing industries.

Tyndallized Bacteria Preferentially Induce Human Macrophage M1 Polarization: An Effect Useful to Balance Allergic Immune Responses and to Control Infections

Macrophage polarization is a dynamic process through which macrophages acquire specific features whose extremes are represented by M1 and M2 polarization. Interleukin (IL)-6, IL-1β, IL-12 and IL-8 belong to M1 macrophages while transforming growth factor-beta (TGF-β belongs to M2 cytokines. M2 polarization prevalence is observed in allergic diseases. Tyndallization is a thermal process able to inactivate microorganisms and to allow their use for chronic respiratory disease treatment via immune response modulation. The present study explores the effects of a blend of tyndallized bacteria (TB) on macrophage polarization. THP-1-derived macrophages were exposed to different concentrations of TB (106, 5 × 106, 107, 5 × 107, 108 CFU/mL) and then cell viability and TB phagocytosis, and IL-8, IL-1β, IL-6, IL-12 and TGF-β1 gene expression and release were assessed. TB were tolerated, phagocyted and able to increase IL-8, IL-1β and IL-6 gene expression and release IL-12 gene expression, as well as decrease TGF-β1 gene expression and release. The effects on IL-8, IL-6 and TGF-β1 release were confirmed in human monocyte-derived macrophages (hMDMs) exposed to TB. In conclusion, TB promote M1 polarization, and this mechanism might have valuable potential in controlling allergic diseases and infections, possibly preventing disease exacerbations.

Effects of Lactobacillus on the Differentiation of Intestinal Mucosa Immune Cells and the Composition of Gut Microbiota in Soybean-Sensitized Mice

In the early stage of this study, three strains of Lactobacillus with anti-soybean allergy potential were screened: Lactobacillus acidophilus CICC 6081, Lactobacillus delbrueckii subsp. Bulgaricus CICC 6103 and Lactobacillus plantarum subsp. Plantarum CICC 20988. The aim of this study was to analyze the desensitization effect of three strains of Lactobacillus administered by gavage to soybean-allergic mice through the differentiation of immune cells in intestinal lymph nodes and the changes to gut microbiota. The results showed that the three strains of Lactobacillus could stimulate the proliferation of dendritic cells (DCs) and regulate the balance of Th1/Th2 differentiation in the MLNs and PPs of soybean-allergic mice. Furthermore, the Th17/Tregs cell-differentiation ratio in the MLNs of the Lactobacillus-treated mice was significantly lower than that of the allergic mice (p < 0.05). Compared to the control group, the Shannon, Sobs and Ace indexes of intestinal microbiota in the allergic mice were significantly increased (p < 0.05), and the proportion of Clostridiales was significantly higher (p < 0.05), which was reversed by Lactobacillus gavage. In conclusion, the three strains of Lactobacillus can inhibit the intestinal mucosal immune response and regulate gut microbiota balance in soybean-allergic mice.

Evaluation of the potential anti-soybean allergic activity of different forms of Lactobacillus delbrueckii subsp. bulgaricus based on cell model in vitro

Live, inactivated Lactobacillus or their metabolites have various beneficial functions, which may alleviate food allergy. This study aimed to investigate the intervention effects of three forms of Lactobacillus delbrueckii subsp. bulgaricus (Ld) on cell degranulation, intestinal barrier function, and intestinal mucosal immunity against soybean allergy. First, the intervention effect of Ld on cell degranulation was investigated using the KU812 cell degranulation model. Then, the Caco-2 cell inflammation model was used to evaluate their anti-inflammatory capacity, and the cell monolayer model was constructed to test the protective effects of different forms of Ld on the intestinal barrier. Finally, mesenteric lymph node (MLN) cells from mice were used to assess the ability of different forms of Ld to regulate the balance of cytokines associated with food allergy in the immune tissue of the intestinal mucosa. Results showed that live bacteria and heat-inactivated bacteria could inhibit the degranulation of KU812 cells, mainly by significantly inhibiting the release of histamine, IL-6 and TNF-α. Both live bacteria and heat-inactivated bacteria could also suppress the increase of IL-6 and IL-8 in Caco-2 cells induced by lipopolysaccharide (LPS). The culture supernatant of bacteria and live bacteria showed better ability to maintain the integrity and permeability of the intestinal epithelial barrier. In addition, heat-inactivated bacteria could return the values of IFN-γ and IL-10 to normal levels and restore the balance of IFN-γ/IL-4, thereby reversing the immune deviation of MLN cells. Therefore, three forms of Ld have potential for the treatment of soybean allergy.

Effect of Structural Targeted Modifications on the Potential Allergenicity of Peanut Allergen Ara h 2

Protein structure affects allergenicity, and critical structural elements, especially conformational epitopes that determine allergenicity, have attracted a great deal of interest. In this study, we aimed to identify the localized structure that affects the potential allergenicity of protein by making targeted modifications of Ara h 2 and comparing the structure and allergenicity of mutants with those of the wide-type allergen. The structures of the allergen and its mutants were characterized by circular dichroism and ultraviolet absorption spectroscopy and simulated by molecular dynamics. The allergenicity was assessed by Western blotting, an indirect competitive enzyme-linked immunosorbent assay, a cell model, and a mouse model. Then, the structures that affect allergenicity were analyzed and screened. Our results showed that mutations in amino acids changed the nearby localized structure and the overall structures. The structural changes affected the IgE binding capacity of the allergen and reduced its potential allergenicity. The solvent accessible surface area (SASA) of aromatic residues was positively correlated with the IgE binding capacity. The integrity of the disulfide bond is also critical for the binding of IgE to allergens. Interestingly, different mutations induced similar electrostatic potential and allergenicity changes, such as localized structure R⁶²DPYSPSQDPYSPS⁷⁵. In conclusion, the disulfide bond and the SASA of aromatic residues are important for the allergenicity of Ara h 2. The localized structure R⁶²DPYSPSQDPYSPS⁷⁵ is also crucial for the allergenicity of Ara h 2.

Polygonatum sibiricum saponin Exerts Beneficial Hypoglycemic Effects in Type 2 Diabetes Mice by Improving Hepatic Insulin Resistance and Glycogen Synthesis-Related Proteins

Type 2 diabetes mellitus (T2DM) is a systemic metabolic disorder characterized by insulin deficiency and insulin resistance. Recently, it has become a significant threat to public health. Polygonatum sibiricum saponin (PSS) has potential hypoglycemic effects, but its specific mechanism needs further study. In this study, PSS significantly decreased the level of blood glucose, water intake, and the organ index in diabetic mice. Meanwhile, PSS effectively reduced the content of total triglyceride (TG), total cholesterol (TCHO), low-density lipoprotein cholesterol (LDL-C), alanine aminotransferase (ALT), and aspartate aminotransferase (AST) in the blood, and increased the content of high-density lipoprotein cholesterol (HDL-C). This suggests that PSS could reduce the content of blood lipids and initially improve the damage of hepatocytes. We found that PSS alleviated hepatic insulin resistance, repaired islet beta cells, and enabled insulin to play its biological role normally. It also improved oral glucose tolerance and abated serum lipopolysaccharide (LPS) and glycosylated hemoglobin (HbA1c) levels in T2DM mice. Furthermore, studies have found that PSS increased the content of phosphorylated protein kinase B (AKT), thereby promoting the effect of glucose transporter 4 (GLUT-4), and activating glycogen synthase kinase 3beta (GSK-3β) and glycogen synthase (GS) proteins to promote hepatic glycogen synthesis. Finally, we found that PSS could promote the growth of beneficial bacteria such as Bifidobacterium and Lactobacillus, reduce the growth of harmful bacteria such as Enterococcus and Enterobacter, and preliminarily improve the composition of important bacteria in the intestine. These studies indicate that PSS has an excellent hypoglycemic effect, which provides a potential new treatment for T2DM and guidance for more in-depth research.

Sialic acid and food allergies: The link between nutrition and immunology

Food allergies (FA), a major public health problem recognized by the World Health Organization, affect an estimated 3%-10% of adults and 8% of children worldwide. However, effective treatments for FA are still lacking. Recent advances in glycoimmunology have demonstrated the great potential of sialic acids (SAs) in the treatment of FA. SAs are a group of nine-carbon α-ketoacids usually linked to glycoproteins and glycolipids as terminal glycans. They play an essential role in modulating immune responses and may be an effective target for FA intervention. As exogenous food components, sialylated polysaccharides have anti-FA effects. In contrast, as endogenous components, SAs on immunoglobulin E and immune cell surfaces contribute to the pathogenesis of FA. Given the lack of comprehensive information on the effects of SAs on FA, we reviewed the roles of endogenous and exogenous SAs in the pathogenesis and treatment of FA. In addition, we considered the structure-function relationship of SAs to provide a theoretical basis for the development of SA-based FA treatments.

Gut microbiota: A target for prebiotics and probiotics in the intervention and therapy of food allergy

Food allergy has become a major public health problem all over the world. Evidence showed that allergic reactions induced by food proteins often lead to disturbances in the gut microbiota (symbiotic bacteria). Gut microbiota plays an important role in maintaining the balance between intestinal immune tolerance and allergic reactions. Dietary intervention has gradually become an important method for the prevention and treatment of allergic diseases, and changing the composition of gut microbiota through oral intake of prebiotics and probiotics may serve as a new effective adjuvant treatment measure for allergic diseases. In this paper, the main mechanism of food allergy based on intestinal immunity was described firstly. Then, the clinical and experimental evidence showed that different prebiotics and probiotics affect food allergy by changing the structure and composition of gut microbiota was summarized. Moreover, the molecular mechanism in which the gut microbiota and their metabolites may directly or indirectly regulate the immune system or intestinal epithelial barrier function to affect food immune tolerance of host were also reviewed to help in the development of food allergy prevention and treatment strategies based on prebiotics and probiotics.