Myeloid differentiation protein 2 facilitates pollen- and cat dander–induced innate and allergic airway inflammation

Abstract

Background The NHANES study identified several pollens and cat dander among the most common allergens that induce allergic sensitization and allergic diseases. We recently reported that ragweed pollen extract (RWPE) requires TLR4 to stimulate CXCL-mediated innate neutrophilic inflammation that facilitates allergic sensitization and airway inflammation. Myeloid differentiation protein-2 (MD2) is a TLR4 coreceptor, but its role in pollen and cat dander-induced innate and allergic inflammation has not been critically evaluated. Objective To elucidate the role of MD2 in inducing pollen and cat dander-induced innate and allergic airway inflammation. Methods TCMNull (TLR4Null, CD14Null, MD2Null), TLR4Hi, TCMHi cells and human bronchial epithelial cells with siRNA-induced downregulation of MD2 were stimulated with RWPE, other pollen allergic extracts, or cat dander extract (CDE), and activation of NF-κB and/or secretion of the NF-κB-dependent CXCL8 were quantified. Wild type (WT) mice or mice with siRNA knockdown of lung MD2 were challenged intranasally with RWPE or CDE, and innate and allergic inflammation were quantified. Results RWPE stimulated MD2-dependent NF-κB activation and CXCL secretion. Likewise, Bermuda, rye, timothy, pigweed, Russian thistle, cottonwood, walnut and CDE stimulated MD2-dependent CXCL secretion. RWPE and CDE challenge induced MD2-dependent, CD14-independent innate neutrophil recruitment. RWPE induced MD2-dependent allergic sensitization and airway inflammation. Conclusions MD2 plays an important role in induction of allergic sensitization to cat dander and common pollens relevant to human allergic diseases.

Excision release of 5?hydroxycytosine oxidatively induced DNA base lesions from the lung genome by cat dander extract challenge stimulates allergic airway inflammation

“…To test this hypothesis, we performed a CDE multiple-challenge model (Figure S1C). 9,10 As expected, these challenges induced allergic inflammation in WT mice (Figure 4A-G). This was characterized by an increase in total cells (Figure 4A), eosinophils (Figure 4B), and neutrophils (Figure 4C) in BALF, stimulation of mucin in airway epithelial cells (Figure 4D,E), increase in serum levels of cat dander-specific IgE (Figure 4F), and increase in BALF levels of IL5, IL13, IL33, and TSLP at 72 hours post-challenge (Figure 4G).…”

“…Because RWPE induces the TLR4/MD2-dependent CXCL chemo-kine pathway that almost entirely mediates innate neutrophil recruitment and allergic inflammation, 9,10 we initially examined the contribution of TLR4 in CDE-induced innate neutrophilic inflammation. Compared to WT mice, a single CDE challenge (CDE single-challenge model, Figure S1A) in Tlr4KO elicited 50% less innate neutrophil recruitment (Figure 1A).…”

“…9,10 In some experiments, WT mice were challenged with five intranasal low doses of CDE (1 μg/60 μL) with or without 5-OH-Cyt on days 0, 1, 2, 3, 4, and, 11 and sacrificed after 72 hours post-challenge (Figure S1C). …”

“…Two investigators who were blinded to the treatment groups assessed mucin production using a minor modification of a method reported 9,10 on a subjective scale of 0, 1, 2, 3, and 4 corresponding to none, mild, moderate, marked, or severe mucin deposition, respectively. The data were expressed as mean of score recorded by two blinded investigators.…”

“…8 We reported that RWPE stimulates Toll-like receptor 4 (TLR4) and myeloid differentiation protein-2 (MD2)-dependent NF-kB activation mediated recruitment of ROS-generating neutrophils to the lungs. 9,10 Repeated challenge with RWPE shifts the immune response to a TLR4-dependent allergic inflammation. 9 Adoptive transfer of purified neutrophils together with RWPE reconstitutes allergic inflammation in Tlr4KO mice.…”