Project Summary Cystic Fibrosis (CF) and nonCF bronchiectasis (NCFB) are characterized by thickened respiratory secretions, chronic lung infection and neutrophilic inflammation. A host of epidemiologic data demonstrates that females with CF suffer from increased pulmonary exacerbations, earlier colonization with bacteria such as Pseudomonas aeruginosa (PsA) and decreased life expectancy relative to males with CF. Similarly, NCFB is more common in females and associated with worse outcomes in females relative to males, but the etiology behind these sex disparities is unclear. A leading candidate to explain this disparity is an estrogen-dependent effect on inflammation and immunity given that our work and the work of others demonstrates higher sputum inflammatory markers and increased pulmonary exacerbations at times of high estrogen levels (ovulation) in females with CF. Moreover, we found that suppressing endogenous 17β-estradiol with hormonal contraception improved these markers of health. Our central hypothesis is that estrogen causes dysregulated neutrophil function and inflammation leading to a sex difference in lung disease and outcomes in people with CF and NCFB. CF respiratory disease is characterized by a sustained influx of neutrophils into the lungs in response to bacterial infection and inflammation. A major mechanism for neutrophil killing is the release of web-like neutrophil extracellular traps (NETs) that trap and kill a variety of microbes. Although NET formation is an important event in innate immunity, excess NETs can be detrimental by producing pro-inflammatory stimuli and proteases that amplify lung damage. Our preliminary studies show that: (1) neutrophils from females with CF and NCFB kill less PsA than neutrophils from males; (2) estrogen decreases neutrophil killing and upregulates NETosis and inflammatory mediator release. We aim to answer several key questions including: (1) what estrogen receptor is driving the estrogen effect on neutrophils (2) what other downstream pathways are involved (3) what is the context of these findings in cis and transgender individuals (4) Are the findings unique to CF or applicable to other chronic inflammatory airway diseases such as non-CF bronchiectasis (NCFB). The expected outcome of this research is a comprehensive understanding of how estrogen mediates functional activity of the neutrophil and the pathways involved that can reveal therapeutic targets, including the potential use of nebulized estrogen receptor antagonists to combat the disproportionate chronic inflammatory process present in cis and trans women with CF. The long-term goal of our lab is to understand the mechanisms leading to sex and gender differences in CF and to develop novel therapies to narrow the disparity. The objective of this proposal is to understand the estrogen- specific effect on neutrophil dysregulation and inflammation. The impact of this proposal is significant because it may lead to treatments that can ...