McMaster University MASTER OF SCIENCE (2019) Hamilton, Ontario (Medical Sciences) TITLE: Modulation of cyclic adenosine monophosphate for potentiation of long-acting β2-agonist and glucocorticoids in human airway epithelial cells AUTHOR: Yechan Kim, B.HSc. (McMaster University) SUPERVISOR: Dr. Jeremy Alexander Hirota NUMBER OF PAGES: xiv, 81 / In Canada, asthma is the third most common chronic disease resulting in 250 premature deaths annually and related healthcare expenses exceeding $2.1 billion/year. It is estimated that around 50-80% of asthma exacerbations are due to viral infections. Despite an advanced understanding on how to treat and manage the symptoms of asthma, current therapy is sub-optimal in 35-50% of moderate-severe asthmatics around the world resulting in lung inflammation, persistent impairment of lung function, and increased risk of mortality. Combination of long-acting β2 agonists (LABA) for bronchodilation and glucocorticoids (GCS) to control lung inflammation represent the dominant strategy for the management of asthma. Increasing intracellular cyclic adenosine monophosphate (cAMP) beyond existing combination LABA/GCS are likely to be beneficial for the management of difficult to control asthmatics that are hypo-responsive to mainstay therapy. In human airway epithelial cells (HAEC), cAMP is either exported by transporters or broken down by enzymes, such as phosphodiesterase 4 (PDE4). We have demonstrated that HAEC express ATP Binding Cassette Transporter C4 (ABCC4), an extracellular cAMP transporter. We also show that ABCC4 and PDE4 inhibition can potentiate LABA/GCS anti-inflammatory responses in a human epithelial cell line in a cAMP-dependent mechanism validating the pursuit of novel ABCC4 inhibitors as a cAMP elevating agent for asthma. / Thesis / Master of Science in Medical Sciences (MSMS) / Asthma is a common chronic lung disease characterized by narrow and inflamed airways that cause breathing difficulties. Current management includes the combination of bronchodilators, to relax the airway, and steroids, to decrease inflammation. Unfortunately, this combination therapy is suboptimal in 35-50% of users, increasing the risk of asthma attacks, hospitalization rate, and health care costs. Recently, there have been studies theorizing that we can improve the therapy’s ability to decrease inflammation by increasing cAMP, an important molecule for biological activities. We tested this claim by blocking the breakdown and export of cAMP to increase its levels and measured inflammatory cytokines, molecules that direct the action of immune cells. Our results show that in a model of viral infection, administering the combination therapy while increasing cAMP levels can further decrease inflammatory cytokines prompting further investigation for its potential implication in the clinic.

Cystic fibrosis (CF) is the most common genetic disease affecting Canadian newborns (1 in 3,850) and is caused by mutations in the CF transmembrane conductance regulator (CFTR) gene. This gene encodes for CFTR, a phosphorylation-dependent ion channel localized at the apical membrane. Phosphorylation of CFTR by the cyclic adenosine monophosphate (cAMP)-dependent enzyme protein kinase A activates its activity, facilitating the transport of chloride and bicarbonate ions across the epithelial membrane. CFTR contributes to ion and airway surface liquid regulation, crucial for maintaining host defenses. The inheritance of CFTR mutations leads to a variety of respiratory complications, including impaired mucociliary clearance, excessive mucus production, persistent airway infections, and heightened inflammation, ultimately causing lung damage. While there is currently no cure for CF, the development of CFTR modulators, targeting the defective CFTR protein directly, has significantly improved the quality of life for many CF patients. Despite these advancements, many patients remain unresponsive to current treatment options. It has been well-established that combination therapies outperform monotherapies, emphasizing the need for alternative or complementary therapeutic strategies for CF management. Furthermore, CFTR dysfunction extends beyond CF and has been implicated in other respiratory diseases, such as chronic obstructive pulmonary disease, which is primarily linked to tobacco smoke exposure. This Ph.D. thesis explores a complementary therapeutic approach, targeting proteins within the CFTR-containing macromolecular signaling complex to elevate intracellular cAMP levels, thereby enhancing CFTR function. We hypothesized that synergistic use of cAMP modulators, alongside CFTR modulators, will serve as an effective therapeutic strategy for CF and other respiratory diseases. Collectively, our studies highlight the potential of cAMP and CFTR modulation as a therapeutic strategy for improving the treatment of CF and other respiratory diseases, warranting further investigation, offering insights for future studies, and contributes to the ongoing pursuit of improved combination treatments. / Dissertation / Doctor of Philosophy (PhD) / Cystic fibrosis (CF) is the most common genetic condition affecting Canadian newborns, caused by inheritance of mutations in the CF transmembrane conductance regulator (CFTR) gene. These mutations result in respiratory issues, including breathlessness, excess mucus, and susceptibility to infections, causing lung damage and premature death. Despite progress in CF drug development, some patients remain unresponsive to existing drug combinations, highlighting the need for new combinations to improve the quality of life for all CF patients. CFTR function is also compromised in other respiratory diseases like chronic obstructive pulmonary disease, a lung disease that shares many characteristics with CF and is mainly caused by tobacco smoke exposure. This Ph.D. thesis explores the effectiveness of a new drug strategy targeting proteins interacting with CFTR. By investigating drugs to complement existing treatments, we aim to improve CFTR function. This research offers a promising strategy to improve treatment for CF and other respiratory diseases.