DOI
https://doi.org/10.25772/AJ4E-9507
Defense Date
2008
Document Type
Dissertation
Degree Name
Doctor of Philosophy
Department
Pharmaceutics
First Advisor
MASAHIRO SAKAGAMI
Abstract
Lung cellular disposition and anti-inflammatory pharmacology of inhaled corticosteroids (ICSs) is complex, comprised of a cascade of aerosol deposition and dissolution, followed by cellular uptake for local pharmacological action. This project hypothesized that the kinetics of dissolution for certain ICS aerosols generated from inhaler products were kinetically rate-determined for their cellular uptake and local pharmacological action. A novel dissolution testing system was developed to determine the dissolution kinetics for the ICS aerosols. A total of 5 ICSs aerosols generated from 6 inhaler products were collected in 2.1-3.3 or 4.7-5.8 µm of aerodynamic diameters at 0.7-19.8 µg on filter membranes by impaction using the Andersen cascade impactor. The filter membrane was then placed on the donor side of the transwell insert, with its face down, and the ICS dissolution in the limited 40 µL of the donor fluid was monitored over time. The dissolution kinetics overall conformed to the rank order of the aqueous solubility, while also being affected by ICS aerosol’s mass, size, formulation and dosage forms. For the readily soluble triamcinolone acetonide (TA), the kinetics was first-order, reaching ≥89 % dissolution in 5 h. In contrast, for the least soluble fluticasone propionate (FP), the kinetics was zero-order, reaching only 3 % dissolution in 10 h. The project then developed an air-interface culture of human bronchial epithelial cell line, Calu-3. Well-differentiated monolayers were formed with sufficiently “tight” barrier for restrictive solute diffusion while their mucosal surface was maintained semi-dry with 39.7±12.1 µL of the mucosal lining fluid in the 4.5 cm2 transwells. These monolayers were transfected with reporter plasmid of pNFκB-Luc to assess in vitro anti-inflammation via repression of pro-inflammatory NFκB by direct FP or TA aerosol deposition. The FP aerosols at 0.9 µg successfully exhibited significant 35.7±6.3 % repression. Notably, however, an identical ~0.5 µg of FP and TA aerosols caused comparable 15.5±2.2 and 10.4±2.6 % repression, respectively, despite FP’s 10-fold greater “intrinsic” anti-inflammatory potency over TA, reported in the literature. This was attributed to FP’s slow dissolution resulting in only 4.7 % cellular uptake, compared to 32.6 % for the TA aerosols. Hence, the FP aerosols were shown to be rate-determined by dissolution on the lung cell surface, resulting in reduced anti-inflammatory actions, which was not the case for the readily soluble TA aerosols.
Rights
© The Author
Is Part Of
VCU University Archives
Is Part Of
VCU Theses and Dissertations
Date of Submission
December 2008