UVM Theses and Dissertations
Format:
Print
Author:
Martin, Rebecca
Dept./Program:
Cell and Molecular Biology Program
Year:
2013
Degree:
Ph. D.
Abstract:
Severe, steroid-resistant asthma comprises 5-7% of patients with asthma. This population would benefit from more comprehensive clinical characterization, including the identification of functionally relevant biomarkers. Biomarkers of severe asthma include serum amyloid A (SAA), interleukin (IL)-1[beta], and IL-17, and likely contribute to asthma pathogenesis. Because traditional animal models of asthma are Th2 driven, they do not reflect the phenotypic variability observed in clinical asthma. Newly developed models better represent nonclassical asthma phenotypes and explore the role of non-Th2 driven pathology. For example, the adoptive transfer of in vitro polarized Thl7 cells generates steroid resistant allergic airway disease following antigen exposure. Other models employ more physiologically relevant sensitizing agents, such as nitrogen dioxide (NO₂)-promoted allergic airway disease.
NO₂ is an environmental pollutant and an endogenously-generated oxidant, associated with the development, severity and exacerbation of asthma. NO₂ exposure is capable of allergically sensitizing mice to the innocuous inhaled antigen ovalbumin (OVA), promoting neutrophil and eosinophil recruitment and a mixed Th2/ThI7 response following antigen challenge. This response requires the presence of CD11 cells (dendritic cells; DCs). At the time of sensitization, NO₂ promotes the airway epithelial expression of Saa3, a candidate mediator of promoting the Th17 response. We have previously determined that recombinant SAA (rSAA) is sufficient to sensitize mice to OVA, which requires the inflammasome scaffold nucleotide-binding oligomerization domain, leucine rich repeat and pyrin domain 3 (NLRP3)/caspase-1 inflammasome, and the IL-1 receptor (IL-1R).
RSAA-exposed DCs secrete Th17 polarizing cytokines, and CD4 T-cells polyclonally stimulated in the presence of conditioned media from SAA-exposed DCs produce IL-17, demonstrating the capacity for SAA to signal through antigen presenting cells in the generation of a Th17 response. In further characterizing the Th17 response in NO₂-promoted allergic airway disease, we identify the IL-17A-producing cells as predominately CD4⁺ T-cell receptor[beta] (TCR[beta])⁺ Th17 cells. The generation of the Thl7 response requires IL-1R, and Caspase-1, but not Nlrp3. Furthermore, intranasal administration of IL-IP and inhalation of antigen was sufficient to promote neutrophil recruitment to the airway and IL-17A production by CD4⁺ TCR[beta]⁺ Th17 cells subsequent to antigen challenge. These data implicate a role for caspase-1 and IL-1[beta] in the IL-1R-dependent Th17 response manifest in NO₂-promoted allergic airway disease.
We hypothesized that the IL-1R-dependent Th17 response contributes to pulmonary inflammation and airway hyperresponsiveness (AHR) in NO₂ in NO₂-promoted allergic airway disease and exhibits steroid resistant cytokine production. While IL-17A neutralization at the time of antigen challenge or genetic deficiency in IL-1R resulted in decreased neutrophil recruitment, following antigen challenge, neither IL-17A neutralization nor genetic deficiency in IL-I R protected mice against the development of AHR. In vitro treatment of lung cells from NO₂-allergically inflammed mice with dexamethasone during antigen restimulation inhibited Th17 cytokine production, whereas Th17 cytokine production by lung cells from recipient mice of in vitro polarized Th17 OTII T-cells was resistant. Thus, the IL-1R/Th17 axis does not contribute to AHR development in NO₂-promoted allergic airway disease, and the endogenously generated Th17 response is qualitatively distinct from that generated following TH17 adoptive transfer. Furthermore, the Th17 response is not a single immune response, but rather a functionally divergent response that is contingent on the experimental conditions in which it is generated. In other words, the model determines the pathogenic contribution of the immune response, particularly the Th17 response.
Many variables combine to create a unique model, including those chosen to address the hypothesis, such as sensitization method, and variables that are hypothesis-independent, as is often the mouse substrain. The manifestation of asthma-like disease in animal models results from a complex interaction between genetic and environmental factors. In this way, animal models resemble the complex nature of clinical asthma. The proposal for asthma entotyping, categorizing based on underlying pathophysiologic mechanisms, offers a new, stratified approach for the management and treatment of patients with asthma. By characterizing and validating animal models of asthma in a similar context, based on the contributing pathophysiology, asthma endotypes and animal models can be aligned, resulting in a stratified.
NO₂ is an environmental pollutant and an endogenously-generated oxidant, associated with the development, severity and exacerbation of asthma. NO₂ exposure is capable of allergically sensitizing mice to the innocuous inhaled antigen ovalbumin (OVA), promoting neutrophil and eosinophil recruitment and a mixed Th2/ThI7 response following antigen challenge. This response requires the presence of CD11 cells (dendritic cells; DCs). At the time of sensitization, NO₂ promotes the airway epithelial expression of Saa3, a candidate mediator of promoting the Th17 response. We have previously determined that recombinant SAA (rSAA) is sufficient to sensitize mice to OVA, which requires the inflammasome scaffold nucleotide-binding oligomerization domain, leucine rich repeat and pyrin domain 3 (NLRP3)/caspase-1 inflammasome, and the IL-1 receptor (IL-1R).
RSAA-exposed DCs secrete Th17 polarizing cytokines, and CD4 T-cells polyclonally stimulated in the presence of conditioned media from SAA-exposed DCs produce IL-17, demonstrating the capacity for SAA to signal through antigen presenting cells in the generation of a Th17 response. In further characterizing the Th17 response in NO₂-promoted allergic airway disease, we identify the IL-17A-producing cells as predominately CD4⁺ T-cell receptor[beta] (TCR[beta])⁺ Th17 cells. The generation of the Thl7 response requires IL-1R, and Caspase-1, but not Nlrp3. Furthermore, intranasal administration of IL-IP and inhalation of antigen was sufficient to promote neutrophil recruitment to the airway and IL-17A production by CD4⁺ TCR[beta]⁺ Th17 cells subsequent to antigen challenge. These data implicate a role for caspase-1 and IL-1[beta] in the IL-1R-dependent Th17 response manifest in NO₂-promoted allergic airway disease.
We hypothesized that the IL-1R-dependent Th17 response contributes to pulmonary inflammation and airway hyperresponsiveness (AHR) in NO₂ in NO₂-promoted allergic airway disease and exhibits steroid resistant cytokine production. While IL-17A neutralization at the time of antigen challenge or genetic deficiency in IL-1R resulted in decreased neutrophil recruitment, following antigen challenge, neither IL-17A neutralization nor genetic deficiency in IL-I R protected mice against the development of AHR. In vitro treatment of lung cells from NO₂-allergically inflammed mice with dexamethasone during antigen restimulation inhibited Th17 cytokine production, whereas Th17 cytokine production by lung cells from recipient mice of in vitro polarized Th17 OTII T-cells was resistant. Thus, the IL-1R/Th17 axis does not contribute to AHR development in NO₂-promoted allergic airway disease, and the endogenously generated Th17 response is qualitatively distinct from that generated following TH17 adoptive transfer. Furthermore, the Th17 response is not a single immune response, but rather a functionally divergent response that is contingent on the experimental conditions in which it is generated. In other words, the model determines the pathogenic contribution of the immune response, particularly the Th17 response.
Many variables combine to create a unique model, including those chosen to address the hypothesis, such as sensitization method, and variables that are hypothesis-independent, as is often the mouse substrain. The manifestation of asthma-like disease in animal models results from a complex interaction between genetic and environmental factors. In this way, animal models resemble the complex nature of clinical asthma. The proposal for asthma entotyping, categorizing based on underlying pathophysiologic mechanisms, offers a new, stratified approach for the management and treatment of patients with asthma. By characterizing and validating animal models of asthma in a similar context, based on the contributing pathophysiology, asthma endotypes and animal models can be aligned, resulting in a stratified.