Allergic sensitization: screening methods

Experimental in silico, in vitro, and rodent models for screening and predicting protein sensitizing potential are discussed, including whether there is evidence of new sensitizations and allergies since the introduction of genetically modified crops in 1996, the importance of linear versus conformational epitopes, and protein families that become allergens. Some common challenges for predicting protein sensitization are addressed: (a) exposure routes; (b) frequency and dose of exposure; (c) dose-response relationships; (d) role of digestion, food processing, and the food matrix; (e) role of infection; (f) role of the gut microbiota; (g) influence of the structure and physicochemical properties of the protein; and (h) the genetic background and physiology of consumers. The consensus view is that sensitization screening models are not yet validated to definitively predict the de novo sensitizing potential of a novel protein. However, they would be extremely useful in the discovery and research phases of understanding the mechanisms of food allergy development, and may prove fruitful to provide information regarding potential allergenicity risk assessment of future products on a case by case basis. These data and findings were presented at a 2012 international symposium in Prague organized by the Protein Allergenicity Technical Committee of the International Life Sciences Institute’s Health and Environmental Sciences Institute

Low-dose tributyltin exposure induces an oxidative stress-triggered JNK-related pancreatic β-cell apoptosis and a reversible hypoinsulinemic hyperglycemia in mice

Abstract Tributyltin (TBT), an endocrine disrupting chemical, can be found in food (particular in fish and seafood) and drinking water by contamination. Here, we elucidated the effects and possible mechanisms of low-dose TBT on the growth and function of pancreatic β-cells and glucose metabolism in mice. Submicromolar-concentration of TBT significantly induced β-cell cytotoxicity and apoptosis, which were accompanied by poly (ADP-ribose) polymerase cleavage and mitogen-activated protein kinases-JNK and ERK1/2 phosphorylation. TBT could also suppress the glucose-stimulated insulin secretion in β-cells and isolated mouse islets. TBT increased reactive oxygen species production. TBT-induced β-cell cytotoxicity and apoptosis were significantly prevented by antioxidant N-acetylcysteine (NAC) and JNK inhibitor SP600125, but not ERK1/2 inhibitor PD98059 and p38 inhibitor SB203580. Both NAC and SP600125 inhibited JNK phosphorylation and reduced cell viability in TBT-treated β-cells. Four-week exposure of TBT (0.25 mg/kg) to mice revealed the decreased plasma insulin, increased blood glucose and plasma malondialdehyde, suppressed islet insulin secretion, and increased islet caspase-3 activity, which could be reversed by NAC treatment. After removing the TBT exposure for 2 weeks, the TBT-induced glucose metabolism alteration was significantly reversed. These results suggest that low-dose TBT can induce β-cell apoptosis and interfere with glucose homeostasis via an oxidative stress-related pathway

Effects of transforming growth factor-beta and formula feeding on systemic immune responses to dietary beta-lactoglobulin in allergy-prone rats

Early nutritional events have the potential to affect health outcomes in later life including the development of allergy. Food allergy is usually the first manifestation of allergy. Breast-feeding has been associated with a protective effect against the development of allergy, but the evidence is contradictory and the mechanisms involved are not clear. We hypothesize that milk cytokines, such as transforming growth factor beta (TGF-beta), play a role in regulating immune responses to dietary antigens. Using a rat pup model of gastrostomy feeding, the immune response profile, at weaning and post-weaning, of allergy-prone Brown Norway rats fed formula supplementation with TGF-beta was assessed. We show that feeding formula to allergy-prone rat pups results in increased total IgE immunoglobulin, beta-lactoglobulin (BLG) IgG1 antibody, and mucosal mast cell activation, as measured by serum rat mast cell protease II (RMCPII) levels in the gut. Supplementation of formula with physiological levels of TGF-beta down-regulated the BLG IgG1 response as well as total IgE and mucosal mast cell activation. Supplementation of formula also resulted in an increase in Th1 cytokines, interleukin (IL)-18, IL-12p40, IL-12p35, and interferon gamma (IFN-gamma) and an increase in IL-10. In conclusion, TGF-beta supplementation of formula moved the immune response profile of allergy prone (Th2 type) rat pups toward a Th1 profile in the suckling period. Importantly, this immune profile persisted after weaning when TGF-beta was no longer present in the diet