TY - BOOK
T1 - The influence of PAR activators on allergen-induced pulmonary eosinophilia and hyperresponsiveness in mice
AU - De Campo, Benjamin
PY - 2007
Y1 - 2007
N2 - [Truncated abstract] Protease-activated receptors (PARs) are widely expressed throughout the body and can influence the activity of many cell types. In the airways, the role of PARs has been unclear. This thesis specifically aims to contribute to the body of knowledge relating to airway PARs by assessing the interaction between allergic pulmonary inflammation and PAR activation in mice by utilising both standard and novel experimental techniques. To go some way towards achieving this aim, the effects of PAR activation on airway smooth muscle (ASM) tone, and allergen-induced airway eosinophilia and hyperresponsiveness were observed and the results examined in context with allergic asthma, a disease which is at least in part, characterised by increased ASM tone, pulmonary eosinophilia and hyperresponsiveness. The veracity of this comparison was increased by the employment of two different allergic models, one in which mice were sensitised and briefly challenged with ovalbumin (OVA), termed "acute allergic", and one in which mice were sensitised and chronically challenged with OVA, termed "chronic allergic". To date, four subtypes of PAR receptor, named PAR1, PAR2, PAR3 and PAR4 have been cloned and characterised. In mice, peptide activators of PAR1, PAR2 and PAR4 have been demonstrated to modulate both airway smooth muscle (ASM) tone in vitro and airway responsiveness to methacholine in vivo but little is known about whether inflammation might influence these effects. This thesis initially examined the effect of both acute and chronic pulmonary allergy on tracheal smooth muscle (SM) tone in vitro via organ bathing techniques, and airway responsiveness to methacholine challenge in vivo via lung function recording (LFR). Interestingly, both organ bath studies and LFR revealed significant functional changes in response to pulmonary allergy. ... Bronchoalveolar lavage (BAL) and lung function recording (LFR) were performed 48 hours post-administration. Under these conditions, both the number of BAL eosinophils recovered and airway resistance to methacholine was significantly attenuated (compared to mice that received the inactive control peptide LSIGRL-NH2 with OVA). Consistent with our hypothesis, pre-treatment with the cyclooxygenase (COX) inhibitors indomethacin and nimesulide significantly inhibited the effects of SLIGRL-NH2, and concomitant administration of PGE2 with OVA to OVA-sensitised mice mimicked the actions of SLIGRL-NH2. Thus, we report that SLIGRL-NH2 induced a COX-sensitive reduction in allergic airway eosinophilia and hyperresponsiveness in mice, probably via the generation of PGE2. To follow on from initial studies, this thesis examined whether SLIGRL-NH2 inhibits OVA-induced eosinophil accumulation in the airways by modulating adhesion molecule interactions. To this end, a novel method of isolating eosinophils from the whole blood of interleukin-5 (IL-5) transgenic mice was successfully developed. Recipient mice were anaesthetised, their trachea was surgically exposed and fluorescently-labelled donor eosinophils were injected intravenously (i.v.). Using a direct-view confocal (DVC) microscope, the rolling and adhesion of donor eosinophils in the airways of mice was observed and reported for the first time.
AB - [Truncated abstract] Protease-activated receptors (PARs) are widely expressed throughout the body and can influence the activity of many cell types. In the airways, the role of PARs has been unclear. This thesis specifically aims to contribute to the body of knowledge relating to airway PARs by assessing the interaction between allergic pulmonary inflammation and PAR activation in mice by utilising both standard and novel experimental techniques. To go some way towards achieving this aim, the effects of PAR activation on airway smooth muscle (ASM) tone, and allergen-induced airway eosinophilia and hyperresponsiveness were observed and the results examined in context with allergic asthma, a disease which is at least in part, characterised by increased ASM tone, pulmonary eosinophilia and hyperresponsiveness. The veracity of this comparison was increased by the employment of two different allergic models, one in which mice were sensitised and briefly challenged with ovalbumin (OVA), termed "acute allergic", and one in which mice were sensitised and chronically challenged with OVA, termed "chronic allergic". To date, four subtypes of PAR receptor, named PAR1, PAR2, PAR3 and PAR4 have been cloned and characterised. In mice, peptide activators of PAR1, PAR2 and PAR4 have been demonstrated to modulate both airway smooth muscle (ASM) tone in vitro and airway responsiveness to methacholine in vivo but little is known about whether inflammation might influence these effects. This thesis initially examined the effect of both acute and chronic pulmonary allergy on tracheal smooth muscle (SM) tone in vitro via organ bathing techniques, and airway responsiveness to methacholine challenge in vivo via lung function recording (LFR). Interestingly, both organ bath studies and LFR revealed significant functional changes in response to pulmonary allergy. ... Bronchoalveolar lavage (BAL) and lung function recording (LFR) were performed 48 hours post-administration. Under these conditions, both the number of BAL eosinophils recovered and airway resistance to methacholine was significantly attenuated (compared to mice that received the inactive control peptide LSIGRL-NH2 with OVA). Consistent with our hypothesis, pre-treatment with the cyclooxygenase (COX) inhibitors indomethacin and nimesulide significantly inhibited the effects of SLIGRL-NH2, and concomitant administration of PGE2 with OVA to OVA-sensitised mice mimicked the actions of SLIGRL-NH2. Thus, we report that SLIGRL-NH2 induced a COX-sensitive reduction in allergic airway eosinophilia and hyperresponsiveness in mice, probably via the generation of PGE2. To follow on from initial studies, this thesis examined whether SLIGRL-NH2 inhibits OVA-induced eosinophil accumulation in the airways by modulating adhesion molecule interactions. To this end, a novel method of isolating eosinophils from the whole blood of interleukin-5 (IL-5) transgenic mice was successfully developed. Recipient mice were anaesthetised, their trachea was surgically exposed and fluorescently-labelled donor eosinophils were injected intravenously (i.v.). Using a direct-view confocal (DVC) microscope, the rolling and adhesion of donor eosinophils in the airways of mice was observed and reported for the first time.
KW - Proteolytic enzymes
KW - Physiological effect
KW - Eosinophil
KW - Protease-activated receptor
M3 - Doctoral Thesis
ER -