Role of pattern recognition receptors in organic dust-induced airway inflammation

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 DESCRIPTION (provided by applicant): Chronic inhalation of organic dusts causes significant airway inflammatory diseases including asthma, bronchitis, and chronic obstructive pulmonary disease, particularly in agriculture-exposed persons. This population is also at increased risk of adverse systemic consequences including high rates of musculoskeletal disorders and fractures. To provide mechanistic insights and inform future therapeutic and/or prevention strategies, we developed and have utilized an animal inflammatory lung injury model following exposure to complex organic dusts from large animal farm confinements. During the previous funding period, we initiated a paradigm shift in this field by finding that gram-positive bacterial peptidoglycan (PGN), as opposed to gram- negative lipopolysaccharide (LPS), is a predominant driver of lung inflammatory consequences, with a strong role demonstrated for the Toll-like receptor 2 (TLR2) signaling pathway. We also defined roles for other pattern-recognition receptor pathways, but the strongest phenotype discovered was for the common TLR/IL-1R adaptor protein, MyD88, which forms the basis of this competitive renewal. Furthermore, our research evolved to understand the systemic consequences of these inhalant exposures on bone homeostasis. Importantly, using state-of-the-art micro-CT imaging we uncovered significant bone deterioration following treatment with organic dust exposures. This established, for the first time, an animal model connecting inhalant lung injury to bone disease. Importantly, our new preliminary studies support that inhalant organic dust exposures engage the lung-bone inflammatory axis through TLR/MyD88 signaling and downstream IL-6 effector pathways, which could be targeted to reduce disease burden. Using this innovative experimental model systems combined with our novel observations and preliminary data, we hypothesize that TLR/MyD88-dependent pathways are central in regulating the crosstalk between lung injury and systemic bone loss induced by organic dust inhalant exposures via downstream cytokine effectors. The goal of our research proposal is to investigate mechanisms, biomarkers, and therapeutic approaches in a relevant animal model that can be later translated to humans. In Aim 1, we will expand upon our findings of a central role for MyD88 to establish how MyD88- dependent signaling pathways function in the lung to govern airway inflammatory responses to organic dust exposures. Understanding the mechanistic signals and lung cell biology regulating airway and lung parenchyma pathology may guide future therapeutic strategies. In Aim 2, we will delineate the potential mechanisms governing the crosstalk between the lung-bone inflammatory-axis to explain how lung injury induced following inhalation of organic dusts and its microbial components mediate systemic bone loss through focused efforts on key TLR/MyD88 signaling pathway. In Aim 3, we will target the downstream TLR/MyD88- mediated systemic IL-6 effector response as a pre-clinical, translatable approach to reduce bone deterioration induced by organic dust inhalant exposures.