Interleukin-13 (IL-13) has been implicated as a critical inducer of a number of features of allergy and asthma including the induction of nonspecific airway hyperresponsiveness (AHR), eosinophilic inflammatory response, eotaxin production, excess mucus formation, and fibrosis. Determining the mechanism(s) of AHR, a hallmark of asthma, is crucial to our understanding of both the pathogenesis and successful treatment of asthma. After carrying out initial experiments to determine the effect of IL-13-induced AHR on murine and rat tracheal rings, mice tissues were chosen for subsequent experiments due to their consistent results and the fact that the mouse genetic map was completed in 1996, which will enable subsequent gene therapy work. Human and mouse share a high percentage of their genes with an average of 85% homology. Numerous IL-13 signalling studies have concentrated on the JAK/STAT6 pathway. IL-13 also activates phosphoinositide 3-kinase (PI3K) and downstream effector molecules. In experiments presented in this thesis pharmacological and genetic approaches implicate the involvement of PI3K and its individual isoform PI3Kδ in IL-13 induced AHR in vitro and this involvement was confirmed using a small interference RNA (siRNA) technology approach. However, IL-13 induced an early activation of PI3K, whereas increased responsiveness was not observed until overnight incubation. Arginase I induction was demonstrated to be another PI3K-dependent potential mechanism of IL-13-induced hyperresponsiveness. The epithelium is also implicated in IL-13-induced hyperresponsiveness, however, the induction of arginase I was demonstrated in both intact and denuded epithelium tracheal rings. The siRNA approach was also employed in 9HTEo-, A549 and BEAS-2B cell lines using different transfecting agents. From these findings, it is concluded that class IA p110δ could be a useful target for the treatment of asthma by preventing IL-13-induced airway smooth muscle hyperresponsiveness and also that arginase I may be involved in IL-13-induced hyperresponsiveness through PI3K- and epithelial-dependent pathways.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:500756 |
| Date | January 2008 |
| Creators | Farghaly, Hanan |
| Contributors | Blagbrough, Ian |
| Publisher | University of Bath |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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