The molecular and cellular mechanisms of the STAT3 mutation-mediated pulmonary disorder in Autosomal Dominant Hyper IgE Syndrome (AD-HIES)

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Abstract: Autosomal Dominant Hyper IgE Syndrome (AD-HIES) is a rare genetic disease characterized by elevated IgE, eosinophilia, eczema, recurrent skin infections, and pneumonia. AD-HIES is most frequently caused by mutations in the STAT3 gene, leading to impaired TH17 cell differentiation and recurrent pulmonary infections, a major cause of morbidity and mortality in AD-HIES patients. Airway mucus obtained from AD- HIES patients is abnormally thick (hyperconcentrated), viscous, and adherent. The abnormal mucus properties are associated with chronic inflammation and mucus obstruction, resembling features observed in cystic fibrosis (CF) and primary ciliary dyskinesia (PCD). In CF and PCD, loss of the CFTR or motile cilia, respectively, leads to hyperconcentrated mucus, impaired mucociliary clearance (MCC), and chronic infection, suggesting candidate pathways for the pathogenesis of AD-HIES lung disease. Our preliminary in vitro and in vivo studies suggest both pathways are defective in AD-HIES: (1) CFTR transcription and function are downregulated; and (2) expression of ciliary shaft dyneins are also downregulated. These data led us to test the hypothesis that defective STAT3 perturbs mucus clearance in AD-HIES lungs. Three Aims are prepared to test this hypothesis. Specific Aim 1: STAT3 regulates CFTR-mediated airway surface hydration and mucus concentration. We will measure nasal PD, sweat chloride values in AD-HIES patients in vivo, and CFTR activity in vitro using primary AD-HIES human bronchial epithelial (HBE) cultures at baseline and after exposure to inflammatory stimuli. Therapeutic approaches aimed to improve CFTR expression and function will be assessed in AD-HIES HBE cells. Specific Aim 2: STAT3 is required for ciliated cell genesis, function, and mucociliary transport. We will image motile cilia ultrastructure in freshly collected nasal scrapes by TEM. Ciliary beat frequency and direction, waveform patterns, regulation of ATP/adenosine concentrations, and mucus clearance rate in the AD-HIES HBE cells will be measured. Therapies aimed to restore MCC and mucus hydration will be assessed for their efficacy in AD-HIES HBE cells. Specific Aim 3: AD-HIES is associated with airway mucus plugging and heterogeneous ventilation that can be quantified using advanced CT and MRI imaging techniques. To quantify the muco-obstructive phenotype in AD-HIES patients in vivo, we will perform quantitative imaging analyses by conventional CT, regional ultra- high resolution CT scan, and high-performance low field MRI to measure mucus plug, airway trapping and gas exchange distribution. This collaborative project combines the strengths of the NHLBI, NIAID, NIH Clinical Center, Johns Hopkins CF Center and UNC’s Marsico Lung Institute, to study AD-HIES lung disease. Data derived from this application should identify the molecular and cellular mechanism(s) of STAT3 in regulating MCC-mediated innate host defense, optimal imaging modalities for detecting mucus obstruction in AD-HIES subjects, and novel therapeutic options for restoring mucus clearance in AD-HIES subjects.