Protective Roles for RGS2 in a Mouse Model of House Dust Mite-Induced Airway Inflammation

Abstract

The GTPase-accelerating protein, regulator of G-protein signalling 2 (RGS2) reduces signalling from G-protein-coupled receptors (GPCRs) that signal via Gαq. In humans, RGS2 expression is up-regulated by inhaled corticosteroids (ICSs) and long-acting β2-adrenoceptor agonists (LABAs) such that synergy is produced in combination. This may contribute to the superior clinical efficacy of ICS/LABA therapy in asthma relative to ICS alone. In a murine model of house dust mite (HDM)-induced airways inflammation, three weeks of intranasal HDM (25 μg, 3×/week) reduced lung function and induced granulocytic airways inflammation. Compared to wild type animals, Rgs2-/- mice showed airways hyperresponsiveness (increased airways resistance and reduced compliance). While HDM increased pulmonary inflammation observed on hematoxylin and eosin-stained sections, there was no difference between wild type and Rgs2-/- animals. HDM-induced mucus hypersecretion was also unaffected by RGS2 deficiency. However, inflammatory cell counts in the bronchoalveolar lavage fluid of Rgs2-/- animals were significantly increased (57%) compared to wild type animals and this correlated with increased granulocyte (neutrophil and eosinophil) numbers. Likewise, cytokine and chemokine (IL4, IL17, IL5, LIF, IL6, CSF3, CXCLl, CXCL10 and CXCL11) release was increased by HDM exposure. Compared to wild type, Rgs2-/- animals showed a trend towards increased expression for many cytokines/chemokines, with CCL3, CCL11, CXCL9 and CXCL10 being significantly enhanced. As RGS2 expression was unaffected by HDM exposure, these data indicate that RGS2 exerts tonic bronchoprotection in HDM-induced airways inflammation. Modest anti-inflammatory and anti-remodelling roles for RGS2 are also suggested. If translatable to humans, therapies that maximize RGS2 expression may prove advantageous.

Glucocorticoid-Driven Transcriptomes in Human Airway Epithelial Cells: Commonalities, Differences and Functional Insight from Cell Lines and Primary Cells

“…Likewise, other GO terms indicate positive effects on proliferation and negative effects on apoptosis. Of the four genes associated with GO terms for signaling, one of these, RGS2, a positive regulator of GTPase activity, promotes inactivation of signaling from many pro-asthma G-protein coupled receptors (GPCRs) and is implicated in the therapeutic benefits of glucocorticoids in the airways [33][34][35][36]. ERRFI1 and IRS2 relate to tyrosine kinase-linked and insulin signaling, while the fourth signaling gene, RGCC, is a regulator of the cell cycle and is therefore also likely to operate alongside other genes involved in proliferation and/or apoptosis.…”

A bronchoprotective role for Rgs2 in a murine model of lipopolysaccharide-induced airways inflammation

“…In prior studies, we found no differences in the total or differential BAL fluid cell counts between naïve, non-inflamed, wild type and Rgs2 − / − animals [ 26 , 28 ]. In each case, wild type or Rgs2 − / − animals, the total cell counts were essentially identical and consisted of macrophage.…”

“…Breeding from heterozygous Rgs2 − / + pairs to produce wild type and Rgs2 − / − knockout littermates allowed lung function to be compared between wild type and Rgs2 − / − animals. In prior studies [ 26 , 28 ], we found that control animals, without any pro-inflammatory insult, showed AHR due to Rgs2 loss. In the current study, N = 6 wild type and N = 3 Rgs2 − / − animals were subjected to PBS exposure and lung function was examined.…”

“…** P < 0.01, *** P < 0.001. b Wild type (wt) ( N = 6) and Rgs2 −/− ( N = 3) mice were exposed to aerosolized PBS (20 ml) for 30 min prior to lung function analysis at 3 h. Resistance and compliance were measured following inhaled challenge with nebulized PBS and PBS containing increasing concentrations of MCh. To enable definitive analysis of Rgs2 loss in naïve (non-inflamed) animals, the current data were combined with that for previously analysed PBS exposed/naïve mice [ 26 , 28 ]. Data (wild type, N = 26; Rgs2 − / − , N = 23) are plotted as cm H 2 O/s/ml (resistance) or ml/cm H 2 O (compliance) as mean ± SE.…”

β2-Adrenoceptor Function in Asthma

“…This hypothesis was later confirmed by the same authors who used knockout animals to demonstrate the bronchoprotective role of RGS2 in a murine model of house dust mite-induced allergic inflammation. Interestingly, the authors also found that the presence of RGS2 was required to suppress allergen-associated pulmonary inflammation including production of different chemokines such as CCL3, CCL11, CXCL9 and CXCL10 (George et al, 2017). Combined therapy also inhibits features of ASM remodelling where low doses of fluticasone synergized with fenoterol to suppress PDGFinduced proliferation and hypocontractility in bovine tracheal smooth muscle cells (Dekkers et al, 2012).…”