Asthma is a chronic disease of airway hyper-responsiveness, airway inflammation and episodic bronchoconstriction. With asthma forecasted to increase by an additional 100 million cases by 2025, there is a critical and immediate need to address new asthma therapies. Guidelines for asthma treatment in the emergency department conditionally recommend intravenous magnesium sulfate (MgSO4). However, some investigations have failed to demonstrate beneficial effects. Ethical constraints limit evaluation of the bronchodilatory effects of MgSO4 alone in patients with acute asthma exacerbation, independent of other conventional therapeutics. To address this ethical dilemma, this study consisted of two phases: 1) quantification of the independent pulmonary effect of three doubling doses of MgSO4 in the spontaneous equine model of asthma during naturally occurring exacerbations of bronchoconstriction, and 2) evaluation of arterial blood gas parameters in response to administration of MgSO4 at a dose identified in phase 1 that yielded greatest efficacy without deleterious side effects.

Pasture-associated severe equine asthma (EPA) is a progressive condition affecting horses in the southeastern United States. Pulmonary function testing with methacholine challenge (MC) provides a definitive diagnosis by eliciting airway hyper-responsiveness. Most horses require extensive conditioning to accept the instrumentation. Our hypothesis was that MC protocols designed to elicit airway hyper-responsiveness would yield equivalent results in the presence and absence of sedation. Sedated and unsedated MCs were performed on 8 EPA-affected horses, with each horse acting as its own control. Acepromazine was superior to xylazine/butorphanol, resulting in sedation and data collection. Based on American Thoracic Society guidelines, an acceptable ability to detect differences in lung resistance is less than a twofold difference in the provocative concentration of methacholine that elicited a 40% increase in lung resistance (PC40RL). Significant differences in PC40RL were not detected. Validation of a sedation protocol for use in MC will expand the application of this diagnostic.

No description available.

No description available.

No description available.

No description available.

No description available.

Pulmonary surfactant is synthesized in the alveoli and lines the respiratory epithelium of the airways. Phospholipids, the main component of surfactant, confer it its ability to lower surface tension and to prevent alveolar collapse. Airway surfactant helps maintain smaller airway patency, improves muco-ciliary clearance, decreases bronchoconstriction, and modulates pulmonary immunity. Surfactant alterations in human asthma are therefore believed to contribute to the severity of airway obstruction. The goal of our first study was to characterize surfactant phospholipid composition and function in healthy horses, and to investigate the influence of age and bronchoalveolar lavage fluid (BALF) sample characteristics on surfactant. For that purpose, BALF was collected from 17 healthy horses and evaluated for BALF recovery percentage, cell count, and cell differential. BALF was separated into crude surfactant pellets (CSP) and supernatant and was analyzed for phospholipid content, protein content, phospholipid composition, and surface tension. Interestingly, phospholipid (surfactant) content in CSP significantly decreased with age. BALF recovery percentage, nucleated cell count, and cytological profile did not affect surfactant composition or function. The hypothesis of our second study was that surfactant alterations in RAO-affected horses are related to clinical stage of RAO. The objectives were 1) to compare surfactant phospholipid composition and function between Non-RAO and RAO horses at clinical stages and 2) to investigate relationships between surfactant alterations and variables assessing clinical stage of RAO. Seven horses with confirmed RAO and seven Non-RAO horses were evaluated in pairs (RAO/Non-RAO) at baseline, during exposure to hay, and post-exposure. Assessments included: clinical scoring, measure of maximal change in pleural pressure (ΔPplmax), airway endoscopy, and BALF cell counts and differentials. Samples were processed and analyzed as described above. Phospholipid levels in BALF were significantly lower in RAO versus Non-RAO horses, even in the absence of clinical signs. In the group of RAO horses, phospholipid content was significantly lower during exposure versus baseline. Furthermore, exposure to hay led to an increase in the protein versus phospholipid ratio in BALF from RAO horses. No significant differences were found in BALF protein content, phospholipid composition, or surface tension between or within groups of horses. Phosphatidylglycerol percentage had a tendency to be lower in RAO horses with higher clinical scores. Supernatant protein content was related to BALF neutrophilia in RAO crisis and overall ΔPplmax . In conclusion, our study demonstrated that surfactant alterations in RAO horses are present in remission and are exacerbated following exposure to hay. It is conceivable that a lower amount of surfactant in bronchioli of RAO horses may contribute to the horses' propensity to develop airway obstruction, mucous accumulation, and bronchial hyperresponsiveness. This may be exacerbated during crisis by a relatively higher protein versus phospholipid ratio. Furthermore, a progressive decrease of surfactant levels in older horses may contribute to a worsening of clinical signs in older RAO-affected horses. / Ph. D.

Human airway epithelial cells (HAECs) play a pivotal role in creating a mechanical barrier to prevent environmental insults from entering deeper into the lung tissue and in facilitating host defence against pathogens and allergens by producing immune mediators and recruiting inflammatory cells. ABCF1, is a unique member of the ABC transporter family that it is highly expressed in the airway epithelium, however, its function in HAECs is currently not known.In this thesis, we explored the role of ABCF1 as a dsDNA viral sensor in HAECs. Our findings demonstrated that while ABCF1 is required for an immune response to a double-stranded DNA (dsDNA) viral mimic, VACV-70, our transcriptomic analysis suggested a role in pro-inflammatory responses downstream of toll-like receptors (TLR) 3 and 4 signalling pathways. We followed this outcome by investigating ABCF1 in mediating pro-inflammatory responses to TNF-α and Poly(I:C) through A20, NF-κB and IRF-3 regulated signalling pathways. Our study demonstrated that Poly(I:C) and TNF-α induced IL-8 are regulated by ABCF1 through pathways independent of NF-κB, and IRF-3 activation, although the exact mechanism remains unclear. The next approach was to run a hypothesis-free in silico investigation of the ABCF1 protein-protein interaction (PPI) network using publicly available databases and Gene Ontology (GO) term enrichment analysis. Following our in silico results of ABCF1 protein interactors, we validated a novel interaction of ABCF1 and SYK in human airway epithelial cells following Poly(I:C) stimulation. We have demonstrated that silencing ABCF1 under stimulation by VACV-70, TNF-α and Poly(I:C) in HAECs affects the induction of immune mediators, and a candidate protein interaction partner, SYK, is involved in immune signalling, however its exact mechanism is not defined. We propose that further insights into the functions of ABCF1 may aid in understanding how HAECs maintain mucosal immune homeostasis. / Thesis / Doctor of Philosophy (Medical Science) / The human lungs are exposed to over 10,000 litres of air each day from normal respiration, and it is the first point of contact between the outside environment and the internal anatomy. The cells on the surface of the air passages in the lungs are called human airway epithelial cells (HAECs), and they represent a critical defence against inhaled foreign objects that may include air pollution, allergens, bacteria, and viruses. HAECs have a group of proteins called ABC transporters, that are capable of different activities that are essential for maintaining normal lung health. One unique ABC transporter called ABCF1 was found to regulate defences against viral and bacterial infections in non-lung cells. It is unclear whether ABCF1 has the same function and protective capacity in HAECs. In this Ph.D. thesis, we investigated how ABCF1 functions in HAECs to detect and respond to respiratory infections. By understanding how ABCF1 is involved in protecting the lungs against these infections, novel treatments can be developed to minimize morbidity and mortality in both healthy and vulnerable individuals. In our studies, we evaluated the changes in the response of HAECs that had normal or absent levels of the ABCF1 gene under conditions that resemble an infection. We used computational tools to help us investigate the proteins that interact with ABCF1 and predict their potential function. Our studies have concluded that ABCF1 does have a protective capacity in HAECs, however, we have yet to elucidate how and what other proteins are involved to help it function.

Doctor of Philosophy / Department of Human Nutrition / Craig A. Harms / The overall aim of this dissertation was to ascertain the influences of lifestyle factors on airway health in children and young adults. In Study 1 (Chapter 2) the effect of a high-fat meal on airway inflammation and hyper-responsiveness was examined. Results revealed a post-prandial increase (p<0.05) in total cholesterol (~4%), triglycerides (~93%), and exhaled nitric oxide (a marker of airway inflammation, ~19%) two-hours following a high-fat meal (74.2±4.1g fat). These novel findings suggest that a high-fat meal may contribute to impaired airway function. In study 2 (Chapter 3) we assessed the role of body fat and physical activity (PA) on airway health in prepubescent children. This study revealed that children with higher-body-fat levels (>21%), who were not meeting current PA recommendations, experienced greater (p<0.05) amounts of post-exercise airway narrowing (FEV1, forced expiratory volume in 1-second, ~11%), as compared to children with lower-body-fat (<21%), who were meeting PA guidelines. These findings suggest that elevated adiposity and low PA levels may place children at risk for development of asthma and asthma-like symptoms. In study 3 (Chapter 4), based on study 2 results, we assessed the impact of 8 weeks of high-intensity interval training on airway health in children who were not meeting PA guidelines. We determined that high-intensity training significantly increased V02max (~24%), and decreased total cholesterol (~11%) and LDL cholesterol (~35%). Additionally, we found improvements (p<0.05) in ∆FEV1 both post-exercise (pre: -7.6±2.2%, post: -1.3±1.8%) and post-eucapnic voluntary hyperventilation (pre: -6.7±2.2%, post: -1.4±1.5%) with training. Further, Lower-body-fat and higher V02max subjects experienced significantly greater improvement in ∆FEV1 following training than higher-body-fat and lower V02max subjects (r=-0.80, r=0.73, respectively). These results suggest that in children, high-intensity training can ameliorate the negative health consequences of inactivity. However, increased body fat, and low V02max levels may constrain these improvements. This series of studies underscores the importance of dietary habits, body composition, and PA for airway health in children and young adults. These findings may be useful in determining policies and practices impacting children’s health, and could facilitate protocol development for prevention of asthma-like symptoms.