Effect of stretch on the bronchial epithelium
This thesis describes the use of a model of cell deformation to measure the effect of stretch on mediator release or expression by airway epithelial cells, and to assess the method of mechanotransduction in these cells. Cells were cyclically stretched using the Flexercell system delivering biaxial stretch. IL-8 release by BEAS 2B cells was increased by cytokine stimulation and stretch, in a dose, time and rate dependent manner, whereas RANTES levels in the cell supernatant and cell surface ICAM-1 expression decreased after stretch. 30% elongation at 20 cycles/minute for 24 hours increased IL-8 levels by over 100% (p<0.01). Changes in IL-8 and RANTES RNA correlated with the effect on protein levels. Stretch did not adversely effect cell viability. The novel use of primary bronchial epithelial cells in stretch experiments is reported, with, in contrast to the BEAS 2B cell line, no effect of stretch on IL-8 release by these cells.;To interpret how the cells were sensing the stretch stimulus, signalling via integrins was blocked using an inhibitor of Rho (R&barbelow;as Homologous) associated kinases, which inhibited the effect of stretch on IL-8 release by the BEAS 2B cells, but not the effect on RANTES release or ICAM-1 expression. Blocking individual integrins did not affect the stretch response. Paxillin was visualised by indirect immunofluorescence to study the effect of stretch on the distribution of focal contacts and the organisation of the actin cytoskeleton. This demonstrated that stretch caused dramatic disassembly of focal adhesions and resulted in the redistribution of paxillin to the peri-nuclear region.