Abstract
BackgroundWe revealed in previous studies that nitration of food proteins reduces the risk of de novo sensitization in a murine food allergy model. In contrast, in situations with preformed specific IgE antibodies, in vitro experiments suggested an increased capacity of effector cell activation by nitrated food proteins.ObjectiveThe aim of this study was to investigate the influence of protein nitration on the effector phase of food allergy.DesignBALB/c mice were immunized intraperitoneally (i.p.) with the milk allergen β-lactoglobulin (BLG) or the egg allergen ovomucoid (OVM), followed by intragastric (i.g.) gavages to induce a strong local inflammatory response and allergen-specific antibodies. Subsequently, naïve and allergic mice were intravenously (i.v.) challenged with untreated, sham-nitrated or nitrated BLG or OVM. Anaphylaxis was monitored by measuring core body temperature and determination of mouse mast cell protease-1 (mMCP-1) levels in blood.ResultsA significant drop of body temperature accompanied with significantly elevated concentrations of the anaphylaxis marker mMCP-1 were only observed in BLG allergic animals challenged with nitrated BLG and not in OVM allergic mice challenged with nitrated OVM. SDS-PAGE and circular dichroism analysis of the differentially modified allergens revealed an effect of nitration on the secondary protein structure exclusively for BLG together with enhanced protein aggregation.ConclusionOur data suggest that nitration affects differently the food allergens BLG and OVM. In the case of BLG, structural changes favored dimerization possibly explaining the increased anaphylactic reactivity in BLG allergic animals.
Highlights
Food allergies are on the rise and have become a significant health problem in Europe [1]
A significant drop of body temperature accompanied with significantly elevated concentrations of the anaphylaxis marker mouse mast cell protease-1 (mMCP-1) were only observed in BLG allergic animals challenged with nitrated BLG and not in OVM allergic mice challenged with nitrated OVM
Nitrated OVA proteins significantly increased the mediator release of rat basophil leukemia (RBL) cells, passively sensitized with serum of allergic mice. These data indicated that nitrated food proteins influenced the effector phase of allergy, in which the so-called effector cells, such as mast cells, basophils and eosinophils can be activated by the cross link of allergen specific IgE on their surface and can lead to a mediator release, such as histamine, which mediates the allergic response
Summary
Food allergies are on the rise and have become a significant health problem in Europe [1]. Nitration of proteins, which is the addition of a nitro group to the aromatic ring of a tyrosine residue, has been discribed to increase allergenicity [7] Pollutants, such as NOx and ozone [8], were discovered to chemically alter airborne proteins by nitration [7] affecting protein conformation and T-cell as well as Bcell epitopes [6,9]. Nitrated OVA proteins significantly increased the mediator release of rat basophil leukemia (RBL) cells, passively sensitized with serum of allergic mice These data indicated that nitrated food proteins influenced the effector phase of allergy, in which the so-called effector cells, such as mast cells, basophils and eosinophils can be activated by the cross link of allergen specific IgE on their surface and can lead to a mediator release, such as histamine, which mediates the allergic response. In situations with preformed specific IgE antibodies, in vitro experiments suggested an increased capacity of effector cell activation by nitrated food proteins
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