Compositional characterisation of human respiratory tract lining fluids for the design of disease specific simulants

Student thesis: Doctoral ThesisDoctor of Philosophy

Abstract

The respiratory tract lining fluid (RTLF) is the first physical interface with which inhaled materials and aerosolised drugs come into contact in the airways. Surrounding the underlying epithelial cells, the RTLFs are composed of a thin amphipathic layer, providing crucial physiological and protective roles across the airways. The aim of this thesis was to investigate the composition of this extracellular compartment using human lavage samples from healthy volunteers, asthmatics and patients with Chronic Obstructive Pulmonary Disease (COPD) to guide the development of a series of lung lining fluid simulants for the testing of inhaled drugs. Analysis across nasal, bronchial and alveolar compartments revealed marked compositional differences throughout the respiratory tract in healthy individuals, with significant differences also observed with age, smoking status and the presence of established respiratory disease. Within the asthmatic group I observed evidence of an impaired microbicidal defense network at the air-lung interface, with significant depression of innate immunity proteins in the bronchial RTLFs associated with elevated concentrations of bacterial cell wall components. In the lavage samples obtained from healthy aged populations a general dysregulation of immunity and inflammatory processes was observed, alongside a pro-oxidant shift in the redox balance. In COPD, characteristic pathological changes were identified, from evidence of chronic inflammation, to protease-antiprotease imbalance and oxidative stress. In addition, I obtained preliminary evidence of dysregulated metal homeostasis, superimposed on compositional protein signatures characteristic of normal physiologic ageing. Clear differences in the composition of the RTLF could be attributed to smoking; with the greatest number of proteins identified (234) in the RTLFs of COPD smokers, in stark contrast to only 58 proteins accounted for within the COPD ex-smoking proteome. This extensive characterization of the RTLFs was used to successfully develop a physiologically representative ‘base model’; the suitability of which was assessed in a series of preliminary studies, focusing on particle and cellular interactions (nanoparticle characterization and biocompatibility with in vitro cell lines). These fundamental applications will be significant in evolving both understanding the behaviour of inhaled particles at the surface of the lung and improving the biopharmaceutical screening of aerosolized medicines.
Date of Award2015
Original languageEnglish
Awarding Institution
  • King's College London
SupervisorIan Mudway (Supervisor)

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