Loss of IL-4Rα-mediated PI3K signaling accelerates the progression of IgE/mast cell-mediated reactions

IL-4 receptor alpha signaling alters oral food challenge and immunotherapy outcomes in mice

BACKGROUND

Food allergy diagnosis and management causes a number of social and emotional challenges for individuals with food allergies and their caregivers. This has led to increased interest in developing approaches to accurately predict food allergy diagnosis, severity of food allergic reactions, and treatment outcomes. However, the utility of these approaches is somewhat conflicting.

OBJECTIVE

We sought to develop and utilize a murine model that mimics the disease course of food allergy diagnosis and treatment in humans and to identify biomarkers that predict reactivity during food challenge (FC) and responsiveness during oral immunotherapy (OIT) and how these outcomes are modified by genetics.

METHODS

Skin-sensitized intestinal IL-9 transgenic (IL9Tg) and IL9Tg mice backcrossed onto the IL-4RαY709F background received a single intragastric exposure of egg antigen (ovalbumin), underwent oral FC and OIT; food allergy severity, mast cell activation, and ovalbumin-specific IgE levels were examined to determine the predictability of these outcomes in determining reactivity and treatment outcomes.

RESULTS

Subcutaneous sensitization and a single intragastric allergen challenge of egg antigen to BALB/c IL9Tg mice and Il4raY709F IL9Tg induced a food allergic reaction. Enhanced IL-4Rα signaling altered the symptoms induced by the first oral exposure, decreased the cumulative antigen dose, increased the severity of reaction during oral FC, and altered the frequency of adverse events and OIT outcomes. Biomarkers after first oral exposure indicated that only the severity of the initial reaction significantly correlated with cumulative dose of oral FC.

CONCLUSION

Collectively, these data indicate that single nucleotide polymorphisms in IL-4Rα can alter clinical symptoms of food allergic reactions, severity, and reactive dose during FC and OIT, and that severity of first reaction can predict the likelihood of reaction during FC in mice with IL-4Rα gain of function.

Dysregulation of intestinal epithelial CFTR-dependent Cl- ion transport and paracellular barrier function drives gastrointestinal symptoms of food-induced anaphylaxis in mice

Food-triggered anaphylaxis can encompass a variety of systemic and intestinal symptoms. Murine-based and clinical studies have revealed a role for histamine and H1R and H2R-pathway in the systemic response; however, the molecular processes that regulate the gastrointestinal (GI) response are not as well defined. In the present study, by utilizing an IgE-mast cell (MC)-dependent experimental model of oral antigen-induced anaphylaxis, we define the intestinal epithelial response during a food-induced anaphylactic reaction. We show that oral allergen-challenge stimulates a rapid dysregulation of intestinal epithelial transcellular and paracellular transport that was associated with the development of secretory diarrhea. Allergen-challenge induced (1) a rapid intestinal epithelial Cftr-dependent Cl- secretory response and (2) paracellular macromolecular leak that was associated with modification in epithelial intercellular junction proteins claudin-1, 2, 3 and 5, E-cadherin and desmosomal cadherins. OVA-induced Cftr-dependent Cl- secretion and junctional protein degradation was rapid occurring and was sustained for 72 h following allergen-challenge. Blockade of both the proteolytic activity and Cl- secretory response was required to alleviate intestinal symptoms of food-induced anaphylaxis. Collectively, these data suggest that the GI symptom of food-induced anaphylactic reaction, secretory diarrhea, is a consequence of CFTR-dependent Cl- secretion and proteolytic activity.

Lipopolysaccharide suppresses IgE-mast cell-mediated reactions

BACKGROUND

Clinical and experimental analyses have identified a central role for IgE/FcεRI/mast cells in promoting IgE-mediated anaphylaxis. Recent data from human studies suggest that bacterial infections can alter susceptibility to anaphylaxis.

OBJECTIVE

We examined the effect of LPS exposure on the induction of IgE-mast cell (MC) mediated reactions in mice.

METHODS

C57BL/6 WT, tlr4-/- and IL10-/- mice were exposed to LPS, and serum cytokines (TNF and IL-10) were measured. Mice were subsequently treated with anti-IgE, and the symptoms of passive IgE-mediated anaphylaxis, MC activation, Ca2+ -mobilization and the expression of FcεRI on peritoneal MCs were quantitated.

RESULTS

We show that LPS exposure of C57BL/6 WT mice constraints IgE-MC-mediated reactions. LPS-induced suppression of IgE-MC-mediated responses was TLR-4-dependent and associated with increased systemic IL-10 levels, decreased surface expression of FcεRI on MCs and loss of sensitivity to IgE activation. Notably, LPS-induced desensitization of MCs was short term with MC sensitivity to IgE reconstituted within 48 hours, which was associated with recapitulation of FcεRI expression on the MCs. Mechanistic analyses revealed a requirement for IL-10 in LPS-mediated decrease in MC FcεRI surface expression.

CONCLUSIONS & CLINICAL RELEVANCE

Collectively, these studies suggest that LPS-induced IL-10 promotes the down-regulation of MC surface FcεRI expression and leads to desensitization of mice to IgE-mediated reactions. These studies indicate that targeting of the LPS-TLR-4-IL-10 pathway may be used as a therapeutic approach to prevent adverse IgE-mediated reactions.

The vascular endothelial specific IL-4 receptor alpha-ABL1 kinase signaling axis regulates the severity of IgE-mediated anaphylactic reactions

BACKGROUND

Severe IgE-mediated, food-induced anaphylactic reactions are characterized by pulmonary venous vasodilatation and fluid extravasation, which are thought to lead to the life-threatening anaphylactic phenotype. The underlying immunologic and cellular processes involved in driving fluid extravasation and the severe anaphylactic phenotype are not fully elucidated.

OBJECTIVE

We sought to define the interaction and requirement of IL-4 and vascular endothelial (VE) IL-4 receptor α chain (IL-4Rα) signaling in histamine-abelson murine leukemia viral oncogene homology 1 (ABL1)-mediated VE dysfunction and fluid extravasation in the severity of IgE-mediated anaphylactic reactions in mice.

METHODS

Mice deficient in VE IL-4Rα and models of passive and active oral antigen- and IgE-induced anaphylaxis were used to define the requirements of the VE IL-4Rα and ABL1 pathway in severe anaphylactic reactions. The human VE cell line (EA.hy926 cells) and pharmacologic (imatinib) and genetic (short hairpin RNA knockdown of IL4RA and ABL1) approaches were used to define the requirement of this pathway in VE barrier dysfunction.

RESULTS

IL-4 exacerbation of histamine-induced hypovolemic shock in mice was dependent on VE expression of IL-4Rα. IL-4- and histamine-induced ABL1 activation in human VE cells and VE barrier dysfunction was ABL1-dependent. Development of severe IgE-mediated hypovolemia and shock required VE-restricted ABL1 expression. Treatment of mice with a history of food-induced anaphylaxis with the ABL kinase inhibitor imatinib protected the mice from severe IgE-mediated anaphylaxis.

CONCLUSION

IL-4 amplifies IgE- and histamine-induced VE dysfunction, fluid extravasation, and the severity of anaphylaxis through a VE IL-4Rα/ABL1-dependent mechanism. These studies implicate an important contribution by the VE compartment in the severity of anaphylaxis and identify a new pathway for therapeutic intervention of IgE-mediated reactions.