Chemical chaperone TUDCA selectively inhibits production of allergen-specific IgE in a low-dose model of allergy

The cellular response to endoplasmic reticulum (ER) stress accompanies plasma cell maturation and is one of triggers and cofactors of the local inflammatory response. Chemical chaperones, low-molecular substances that eliminate pathological ER stress, are proposed as means of treating pathologies associated with ER stress. The aim of this study was to evaluate the effect and mechanisms of influence of chemical chaperones on the humoral response in a low-dose model of allergy. The allergic immune response was induced in BALB/c mice by repeated administration of ovalbumin at a dose of 100 ng for 6 weeks. Some animals were injected with both the antigen and the chemical chaperones, TUDCA (tauroursodeoxycholic acid) or 4-PBA (4-phenylbutyrate). Administration of TUDCA, but not 4-PBA, suppressed production of allergen-specific IgE (a 2.5-fold decrease in titer). None of the chemical chaperones affected the production of specific IgG1. The effect of TUDCA was associated with suppression of the switch to IgE synthesis in regional lymph nodes. This phenomenon was associated with suppressed expression of genes encoding cytokines involved in type 2 immune response, especially Il4 and Il9, which in turn could be caused by suppression of IL-33 release. In addition, TUDCA significantly suppressed expression of the cytokine APRIL, and to a lesser extent, BAFF. Thus, TUDCA inhibition of the allergy-specific IgE production is due to suppression of the release of IL-33 and a decrease in the production of type 2 immune response cytokines, as well as suppression of the expression of the cytokines APRIL and BAFF.