Oral Exposure to the Amino Acid Glycine Inhibits the Onset of Allergic Disorders

Background: The non-essential amino acid glycine (Gly) has been shown to act as an anti-inflammatory trigger in animal models of ischemic perfusion, post-operative inflammation, periodontal disease, arthritis and obesity (inflammation and Th1/Th17 models).  Gly exerts its actions by binding to a glycine-gated chloride channel (GlyR) which has been demonstrated on neurons, as well as on immune cells (macrophages, polymorphonuclear neutrophils and lymphocytes).  The present study aims to evaluate the effect of Gly on allergy development using an experimental model of cow’s milk allergy (Th2 model).

Methods: Female C3H/HeOuJ mice were supplemented with or without Gly by oral gavage (50 or 100 mg/mouse) 4 hours before sensitization with the cow's milk protein whey, using cholera toxin as adjuvant.  Acute allergic skin responses and systemic anaphylaxis were assessed after intradermal allergen challenge in the ear.  Mouse mast cell protease-1 (mMCP-1) and whey specific IgE levels were assessed one hour after an oral allergen challenge.

Results: Intake of Gly significantly opposed allergy development in a concentration dependant manner as indicated by a reduction in; acute allergic skin response (63:40:30 µm whey-induced ear-swelling), anaphylaxis (127:107:89 AUC), serum mMCP-1 (1244:109:66 µg mMCP1/ml) and, serum levels of whey specific IgE (785:318:155 AU IgE/ml). All results are depicted in the following order; allergic control: 50 mg Gly: 100 mg Gly.

Conclusion: The present study indicates, for the first time, that oral intake of the free amino acid glycine protects against whey induced allergy development. Additional studies are warranted to elucidate the underlying mechanisms involved and to demonstrate effectiveness in humans.