How can 1 + 1 = 3? β2-adrenergic and glucocorticoid receptor agonist synergism in obstructive airway diseases

Independent roles of beta-adrenergic and glucocorticoid receptors in systemic and pulmonary effects of ozone

Background: The release of catecholamines is preceded by glucocorticoids during a stress response. We have shown that ozone-induced pulmonary responses are mediated through the activation of stress hormone receptors.Objective: To examine the interdependence of beta-adrenergic (βAR) and glucocorticoid receptors (GRs), we inhibited βAR while inducing GR or inhibited GR while inducing βAR and examined ozone-induced stress response.Methods: Twelve-week-old male Wistar-Kyoto rats were pretreated daily with saline or propranolol (PROP; βAR-antagonist; 10 mg/kg-i.p.; starting 7-d prior to exposure) followed-by saline or dexamethasone (DEX) sulfate (GR-agonist; 0.02 mg/kg-i.p.; starting 1-d prior to exposure) and exposed to air or 0.8 ppm ozone (4 h/d × 2-d). In a second experiment, rats were similarly pretreated with corn-oil or mifepristone (MIFE; GR-antagonist, 30 mg/kg-s.c.) followed by saline or clenbuterol (CLEN; β₂AR-agonist; 0.02 mg/kg-i.p.) and exposed.Results: DEX and PROP + DEX decreased adrenal, spleen and thymus weights in all rats. DEX and MIFE decreased and increased corticosterone, respectively. Ozone-induced pulmonary protein leakage, inflammation and IL-6 increases were inhibited by PROP or PROP + DEX and exacerbated by CLEN or CLEN + MIFE. DEX and ozone-induced while MIFE reversed lymphopenia (MIFE > CLEN + MIFE). DEX exacerbated while PROP, MIFE, or CLEN + MIFE inhibited ozone-induced hyperglycemia and glucose intolerance. Ozone inhibited glucose-mediated insulin release.Conclusions: In summary, 1) activating βAR, even with GR inhibition, exacerbated and inhibiting βAR, even with GR activation, attenuated ozone-induced pulmonary effects; and 2) activating GR exacerbated ozone systemic effects, but with βAR inhibition, this exacerbation was less remarkable. These data suggest the independent roles of βAR in pulmonary and dependent roles of βAR and GR in systemic effects of ozone.

Beta-2-adrenoreceptor polymorphism at position 16 determines the clinical severity of chronic obstructive pulmonary disease

The Arg/Arg homozygosity at codon 16 of the beta-2-adrenoreceptor (ADRB2) gene has been thought to predispose asthma patients to a poorer therapeutic response to beta-2-mimetics, or to worse control of the disease. In contrast, the results of the studies analysing the effect of ADRB2 polymorphisms on the response to beta-2-adrenoreceptor agonists in chronic obstructive pulmonary disease (COPD) patients are sparse and inconclusive. The aim of this research was to verify if p.Arg16Gly (c.46A > G) and p.Gly27Glu (c.79G > C) single nucleotide polymorphisms (SNPs) exert a negative effect on the selected clinical indicators of COPD. The SNPs of the ADRB2 were identified by multiplex allele-specific PCR on DNA isolated from the venous blood leukocytes of 92 patients with stable grade COPD. In addition, all of the patients were asked about the course of COPD during the 12 months preceding the study, including the frequency of exacerbations requiring hospitalisation, the number of antibiotic therapy courses given due to the lower respiratory tract infection, and the number of courses of systemic corticosteroid therapy administered due to the exacerbation of COPD. Arg/Arg homozygotes at codon 16 required at least two courses of antibiotic therapy administered as a result of a lower respiratory tract infection significantly more frequently than carriers of other polymorphic variants of the ADRB2. Moreover, they were the only ones who required three or more courses of corticosteroid therapy due to COPD exacerbation. No significant relationships were observed between the polymorphism at codon 27 and the analysed clinical indicators of COPD severity. These data suggested that Arg/Arg homozygosity at codon 16 of the ADRB2 gene predisposes patients to a clinically more severe course of COPD.

Effect of budesonide and azelastine on histamine signaling regulation in human nasal epithelial cells

Both glucocorticoids and H1-antihistamines are widely used on patients with airway diseases. However, their direct effects on airway epithelial cells are not fully explored. Therefore, we use the primary culture of human nasal epithelial cells (HNEpC) to delineate in vitro mucosal responses to above two drugs. HNEpC cells were cultured with/without budesonide and azelastine. The growth rate at each group was recorded and measured as population double time (PDT). The histamine1-receptor (H1R), muscarinic1-receptor (M1R) and M3R were measured using immunocytochemistry and western blotting after 7-days treatment. Then, we used histamine and methacholine to stimulate the mucus secretion from HNEpC and observed the MUC5AC expression in culture supernatants. Concentration-dependent treatment-induced inhibition of HNEpC growth rate was observed. Cells incubated with azelastine proliferated significantly slower than that with budesonide and the combined use of those drugs led to significant PDT prolong. The immunocytochemistry showed the H1R, M1R and M3R were obviously located in the cell membrane without apparent difference after treatment. However, western blotting showed that budesonide can significantly up-regulate the H1R, M1R and M3R level while azelastine had opposite effects. Histamine and methacholine stimulated MUC5AC secretion was greater in cells treated with budesonide but was lesser in those treated with azelastine, as compared to controls. Our data suggest that both budesonide and azelastine can significantly inhibit HNEpC proliferation, and therefore, be helpful in against airway remodeling. Long-term use of budesonide might amplify histamine signaling and result in airway hyperreactivity to stimulants by enhancing H1R, M1R and M3R expression while azelastine can oppose this effect. Therefore, combined use of those two drugs in patients with chronic inflammatory airway diseases may be an ideal option.

Why use long acting bronchodilators in chronic obstructive lung diseases? An extensive review on formoterol and salmeterol

Long-acting β2-adrenoceptor agonists, formoterol and salmeterol, represent a milestone in the treatments of chronic obstructive lung diseases. Although no specific indications concerning the choice of one molecule rather than another are provided by asthma and COPD guidelines, they present different pharmacological properties resulting in distinct clinical employment possibilities. In particular, salmeterol has a low intrinsic efficacy working as a partial receptor agonist, while formoterol is a full agonist with high intrinsic efficacy. From a clinical perspective, in the presence of low β2-adrenoceptors availability, like in inflamed airways, a full agonist can maintain its bronchodilatory and non-smooth muscle activities while a partial agonist may be less effective. Furthermore, formoterol presents a faster onset of action than salmeterol. This phenomenon, combined with the molecule safety profile, leads to a prompt amelioration of the symptoms, and allows using this drug in asthma as an "as needed" treatment in patients already on regular treatment. The fast onset of action and the full agonism of formoterol need to be considered in order to select the best pharmacological treatment of asthma and COPD.

Steroids and antihistamines synergize to inhibit rat's airway smooth muscle contractility

Both glucocorticoids and H1-antihistamines were widely used on patients with allergic rhinitis (AR) and obstructive airway diseases. However, their direct effects on airway smooth muscle were not fully explored. In this study, we tested the effectiveness of prednisolone (Kidsolone) and levocetirizine (Xyzal) on isolated rat trachea submersed in Kreb's solution in a muscle bath. Changes in tracheal contractility in response to the application of parasympathetic mimetic agents were measured. The following assessments of the drug were performed: (1) effect on tracheal smooth muscle resting tension; (2) effect on contraction caused by 10(-6) M methacholine; (3) effect of the drug on electrical field stimulation (EFS) induced tracheal smooth muscle contractions. The result revealed sole use of Kidsolone or Xyzal elicited no significant effect or only a little relaxation response on tracheal tension after methacholine treatment. The tension was 90.5 ± 7.5 and 99.5 ± 0.8 % at 10(-4) M for Xyzal and 10(-5) M for Kidsolone, respectively. However, a dramatically spasmolytic effect was observed after co-administration of Kidsolone and Xyzal and the tension dropped to 67.5 ± 13.6 %, with statistical significance (p < 0.05). As for EFS-induced contractions, Kidsolone had no direct effect but Xyzal could inhibit it, with increasing basal tension. In conclusion, using glucocorticoids alone had no spasmolytic effect but they can be synergized with antihistamines to dramatically relax the trachea smooth muscle within minutes. Therefore, for AR patients with acute asthma attack, combined use of those two drugs is recommended.

Dexamethasone in the presence of desipramine enhances MAPK/ERK1/2 signaling possibly via its interference with β-arrestin

Antidepressant medication is the standard treatment for major depression disorder (MDD). However, the response to these treatments is often incomplete and many patients remain refractory. In the present study, we show that the glucocorticoid receptor (GR) agonist dexamethasone (DEX) increased MAPK/ERK1/2 signaling in the presence of the noradrenergic antidepressant, desipramine (DMI), while no such effect was induced by DEX or DMI alone in human neuroblastoma SH-SY5Y cells. This enhancement was dependent on the activation of both α(2) adrenergic receptors (AR) and GR. The timing of MAPK/ERK1/2 activation as well as DEX-induced reduction in membranous α(2) AR suggests the involvement of a β-arrestin-dependent mechanism. In line with the latter, DEX increased cytosolic and decreased membranous levels of β-arrestin. Concomitantly, DEX induced a time-dependent increase in cytosolic α(2) AR-β-arrestin interaction and a decrease in β-arrestin interaction with Mdm2 E3 ubiquitin ligase. All of these effects of DEX were prevented by the GR antagonist RU486. Our data suggest an additional intracellular role for DEX, in which activation of GR interferes with the trafficking and degradation of β-arrestin-α2c-AR complex. We suggest that such an interaction in the presence of DMI can enhance MAPK/ERK1/2 signaling, a key player in neural plasticity and neurogenesis processes, which is impaired in MDD, while stimulated by antidepressants.

Distinct PKA and Epac compartmentalization in airway function and plasticity

Asthma and chronic obstructive pulmonary disease (COPD) are obstructive lung diseases characterized by airway obstruction, airway inflammation and airway remodelling. Next to inflammatory cells and airway epithelial cells, airway mesenchymal cells, including airway smooth muscle cells and (myo)fibroblasts, substantially contribute to disease features by the release of inflammatory mediators, smooth muscle contraction, extracellular matrix deposition and structural changes in the airways. Current pharmacological treatment of both diseases intends to target the dynamic features of the endogenous intracellular suppressor cyclic AMP (cAMP). This review will summarize our current knowledge on cAMP and will emphasize on key discoveries and paradigm shifts reflecting the complex spatio-temporal nature of compartmentalized cAMP signalling networks in health and disease. As airway fibroblasts and airway smooth muscle cells are recognized as central players in the development and progression of asthma and COPD, we will focus on the role of cAMP signalling in their function in relation to airway function and plasticity. We will recapture on the recent identification of cAMP-sensing multi-protein complexes maintained by cAMP effectors, including A-kinase anchoring proteins (AKAPs), proteins kinase A (PKA), exchange protein directly activated by cAMP (Epac), cAMP-elevating seven-transmembrane (7TM) receptors and phosphodiesterases (PDEs) and we will report on findings indicating that the pertubation of compartmentalized cAMP signalling correlates with the pathopysiology of obstructive lung diseases. Future challenges include studies on cAMP dynamics and compartmentalization in the lung and the development of novel drugs targeting these systems for therapeutic interventions in chronic obstructive inflammatory diseases.

Glucocorticoids regulate arrestin gene expression and redirect the signaling profile of G protein-coupled receptors

G protein-coupled receptors (GPCRs) compose the largest family of cell surface receptors and are the most common target of therapeutic drugs. The nonvisual arrestins, β-arrestin-1 and β-arrestin-2, are multifunctional scaffolding proteins that play critical roles in GPCR signaling. On binding of activated GPCRs at the plasma membrane, β-arrestins terminate G protein-dependent responses (desensitization) and stimulate β-arrestin-dependent signaling pathways. Alterations in the cellular complement of β-arrestin-1 and β-arrestin-2 occur in many human diseases, and their genetic ablation in mice has severe consequences. Surprisingly, however, the factors that control β-arrestin gene expression are poorly understood. We demonstrate that glucocorticoids differentially regulate β-arrestin-1 and β-arrestin-2 gene expression in multiple cell types. Glucocorticoids act via the glucocorticoid receptor (GR) to induce the synthesis of β-arrestin-1 and repress the expression of β-arrestin-2. Glucocorticoid-dependent regulation involves the recruitment of ligand-activated glucocorticoid receptors to conserved and functional glucocorticoid response elements in intron-1 of the β-arrestin-1 gene and intron-11 of the β-arrestin-2 gene. In human lung adenocarcinoma cells, the increased expression of β-arrestin-1 after glucocorticoid treatment impairs G protein-dependent activation of inositol phosphate signaling while enhancing β-arrestin-1-dependent stimulation of the MAPK pathway by protease activated receptor 1. These studies demonstrate that glucocorticoids redirect the signaling profile of GPCRs via alterations in β-arrestin gene expression, revealing a paradigm for cross-talk between nuclear and cell surface receptors and a mechanism by which glucocorticoids alter the clinical efficacy of GPCR-based drugs.