Project 2

University Of Iowa, Iowa City IA

Investigators

Abstract

PROJECT 2 – ABSTRACT/SUMMARY Primary ciliary dyskinesia (PCD) is a disease that causes mucus obstruction, inflammation, and infection of the pulmonary and nasal airways. Mutations in more than 50 different genes cause PCD by disrupting the activity of motile cilia that facilitate mucociliary transport. Much knowledge of PCD has come from studies identifying disease-causing mutations, characterizing structural cilia abnormalities, finding genotype-phenotype relationships, and studying the cell biology of cilia. But knowledge of the pathophysiology is limited, and we lack effective treatments. However, other than defective MCT, the impact of PCD on cellular functions remains generally unknown. The high energy required to power cilia beating comes from mitochondria producing ATP; thus, decreased ciliary beating and ATP consumption will alter mitochondrial-dependent metabolism. Here we focus on two goals: a) to use newborn PCD pigs to understand altered ciliated cell mitochondrial metabolism and thus uncover defects that are intrinsic to PCD ciliated cells and epithelia and b) to learn how those abnormalities contribute to neonatal respiratory distress in PCD and later disease. To achieve these goals, we will study a newly developed porcine model of PCD with a disrupted DNAI1 gene, strikingly impaired mucociliary transport, and the hallmark features of the human disease. Aim 1. Does PCD alter mitochondrial function and ROS production? Ciliated cells bunch mitochondria just beneath the apical membrane ensuring an optimal supply chain, placing a major ATP producer (mitochondria) near a required source material (O2) and a major consumer (cilia). This arrangement carries risks for superoxide (O2-) generation when ATP is not used. Our preliminary data suggest that impaired cilia beating initiates a cascading metabolic scenario that increases superoxide (O2-) production. Aim 2. Does disrupted ciliated cell metabolism impact respiratory host defense? Our preliminary data indicate that PCD mucus has a markedly increased viscoelasticity, and we will learn if PCD ciliated cells are a source of reactive oxygen species that modify the overlying mucus, increasing its viscoelasticity. Here we explore how the PCD mitochondrial metabolic abnormalities affect respiratory host defenses in a time window before major inflammation and infection take hold. Aim 3. Does hyperoxia exacerbate and hypoxia attenuate airway disease in PCD pigs? We will test the hypothesis that raising airway O2 levels will exacerbate mitochondrial defects and consequences, and conversely, lowering the O2 levels will mitigate the abnormalities. Testing this hypothesis in vitro in culture and in vivo in PCD pigs will provide an important link to the metabolic data in Aims 1 and 2. The results will also have critical translational implications, especially for PCD infants with neonatal respiratory distress. The studies will also provide a foundation for investigating disease pathogenesis, the groundwork for deciphering time-dependent adaptive changes, and the basis for developing newtherapies.