Browsing by Author "Giembycz, Mark A"

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    A bronchoprotective role for Rgs2 in a murine model of lipopolysaccharide-induced airways inflammation
    (2018-10-01) George, Tresa; Chakraborty, Mainak; Giembycz, Mark A; Newton, Robert
    Abstract Background Asthma exacerbations are associated with the recruitment of neutrophils to the lungs. These cells release proteases and mediators, many of which act at G protein-coupled receptors (GPCRs) that couple via Gq to promote bronchoconstriction and inflammation. Common asthma therapeutics up-regulate expression of the regulator of G protein signalling (RGS), RGS2. As RGS2 reduces signaling from Gq-coupled GPCRs, we have defined role(s) for this GTPase-activating protein in an acute neutrophilic model of lung inflammation. Methods Wild type and Rgs2−/− C57Bl6 mice were exposed to nebulized lipopolysaccharide (LPS). Lung function (respiratory system resistance and compliance) was measured using a SCIREQ flexivent small animal ventilator. Lung inflammation was assessed by histochemistry, cell counting and by cytokine and chemokine expression in bronchoalveolar lavage (BAL) fluid. Results Lipopolysaccharide inhalation induced transient airways hyperreactivity (AHR) and neutrophilic lung inflammation. While AHR and inflammation was greatest 3 h post-LPS exposure, BAL neutrophils persisted for 24 h. At 3 h post-LPS inhalation, multiple inflammatory cytokines (CSF2, CSF3, IL6, TNF) and chemokines (CCL3, CCL4, CXCL1, CXCL2) were highly expressed in the BAL fluid, prior to declining by 24 h. Compared to wild type counterparts, Rgs2−/− mice developed significantly greater airflow resistance in response to inhaled methacholine (MCh) at 3 h post-LPS exposure. At 24 h post-LPS exposure, when lung function was recovering in the wild type animals, MCh-induced resistance was increased, and compliance decreased, in Rgs2−/− mice. Thus, Rgs2−/− mice show AHR and stiffer lungs 24 h post-LPS exposure. Histological markers of inflammation, total and differential cell counts, and major cytokine and chemokine expression in BAL fluid were similar between wild type and Rgs2−/− mice. However, 3 and 24 h post-LPS exposure, IL12B expression was significantly elevated in BAL fluid from Rgs2−/− mice compared to wild type animals. Conclusions While Rgs2 is bronchoprotective in acute neutrophilic inflammation, no clear anti-inflammatory effect was apparent. Nevertheless, elevated IL12B expression in Rgs2−/− animals raises the possibility that RGS2 could dampen Th1 responses. These findings indicate that up-regulation of RGS2, as occurs in response to inhaled corticosteroids and long-acting β2-adrenoceptor agonists, may be beneficial in acute neutrophilic exacerbations of airway disease, including asthma.
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    Comparative and functional analysis of β-adrenoceptors in human myometrium
    (2018-01) Albadri, Randa G. A.; Giembycz, Mark A; Slater, Donna M.; Cole, William C.; Klein, Claudia; von der Weid, Pierre-Yves
    There are three subtypes of the β-adrenoceptors (β1, β2 and β3). All the β-adrenoceptor subtypes couple to Gαs subunit of G protein. All the β-adrenoceptor subtypes couple mainly to Gαs subunit of G protein. β2-adrenoceptor agonists have been used clinically to suppress myometrial contractions during the management of preterm labour. β2-adrenoceptor agonists lose their effectiveness in a short time and their use causes several side effects. Evidence in the literature supports the expression of functional β2- and β3-adrenoceptors in the lower pregnant human myometrial tissues. However, no definitive understanding in terms of regional and temporal expression and function of the β-adrenoceptors in the uterus was obtained by reviewing the literature. Experiments of this work have confirmed the expression of the three β-adrenoceptor subtypes in term pregnant (upper and lower) human myometrial tissues by real-time RT-PCR analysis. Poor antibody specificity was an obstacle to determine and localize the β-adrenoceptor proteins in the myometrium by immunohistochemistry. β2- and β3-adrenoceptor agonists did not affect the expression of CRISPLD2, RGS2 and NA4A3 in primary MSM cells after 2 and 6 h of incubation. Further research must be done to determine and localize the expression of the β-adrenoceptors in the myometrium.