Calcium-Sensing Receptor Contributes to Hyperoxia Effects on Human Fetal Airway Smooth Muscle.

Supplemental O (hyperoxia), necessary for maintenance of oxygenation in premature infants, contributes to neonatal and pediatric airway diseases including asthma. Airway smooth muscle (ASM) is a key resident cell type, responding to hyperoxia with increased contractility and remodeling [proliferation, extracellular matrix (ECM) production], making the mechanisms underlying hyperoxia effects on ASM significant. Recognizing that fetal lungs experience a higher extracellular Ca ([Ca]) environment, we previously reported that the calcium sensing receptor (CaSR) is expressed and functional in human fetal ASM (fASM).

Class C GPCRs in the airway.

Understanding and targeting of GPCRs remain a critical aspect of airway pharmacology and therapeutics for diseases such as asthma or COPD. Most attention has been on the large Class A GPCRs towards improved bronchodilation and blunting of remodeling. Better known in the central or peripheral nervous system, there is increasing evidence that Class C GPCRs which include metabotropic glutamate and GABA receptors, the calcium sensing receptor, sweet/umami taste receptors and a number of orphan receptors, can contribute to airway structure and function.

Prostaglandin E, but not cAMP nor β-agonists, induce tristetraprolin (TTP) in human airway smooth muscle cells.

Tristetraprolin (TTP) is an anti-inflammatory molecule known to post-transcriptionally regulate cytokine production and is, therefore, an attractive drug target for chronic respiratory diseases driven by inflammation, such as asthma and chronic obstructive pulmonary disease. Our recent in vitro studies in primary human airway smooth (ASM) cells have confirmed the essential anti-inflammatory role played by TTP as a critical partner in a cytokine regulatory network. However, several unanswered questions remain.

Doxofylline does not increase formoterol-induced cAMP nor MKP-1 expression in ASM cells resulting in lack of anti-inflammatory effect.

The xanthine doxofylline has been examined in clinical trials and shown to have efficacy and greater tolerability than theophylline in asthma and chronic obstructive pulmonary disease. The 'novofylline' doxofylline has demonstrated bronchodilatory and anti-inflammatory actions in in vivo and ex vivo experimental models of respiratory disease. However, there are limited studies in vitro.

Roflumilast N-Oxide in Combination with Formoterol Enhances the Antiinflammatory Effect of Dexamethasone in Airway Smooth Muscle Cells.

Roflumilast is an orally active phosphodiesterase 4 inhibitor approved for use in chronic obstructive pulmonary disease. Roflumilast N-oxide (RNO) is the active metabolite of roflumilast and has a demonstrated antiinflammatory impact in vivo and in vitro. To date, the effect of RNO on the synthetic function of airway smooth muscle (ASM) cells is unknown.

The phosphorylated form of FTY720 activates PP2A, represses inflammation and is devoid of S1P agonism in A549 lung epithelial cells.

Protein phosphatase 2A (PP2A) activity can be enhanced pharmacologically by PP2A-activating drugs (PADs). The sphingosine analog FTY720 is the best known PAD and we have shown that FTY720 represses production of pro-inflammatory cytokines responsible for respiratory disease pathogenesis. Whether its phosphorylated form, FTY720-P, also enhances PP2A activity independently of the sphingosine 1-phosphate (S1P) pathway was unknown.

TLR2 ligation induces corticosteroid insensitivity in A549 lung epithelial cells: Anti-inflammatory impact of PP2A activators.

Corticosteroids are effective anti-inflammatory therapies widely utilized in chronic respiratory diseases. But these medicines can lose their efficacy during respiratory infection resulting in disease exacerbation. Further in vitro research is required to understand how infection worsens lung function control in order to advance therapeutic options to treat infectious exacerbation in the future.

Theophylline Represses IL-8 Secretion from Airway Smooth Muscle Cells Independently of Phosphodiesterase Inhibition. Novel Role as a Protein Phosphatase 2A Activator.

Theophylline is an old drug experiencing a renaissance owing to its beneficial antiinflammatory effects in chronic respiratory diseases, such as asthma and chronic obstructive pulmonary disease. Multiple modes of antiinflammatory action have been reported, including inhibition of the enzymes that degrade cAMP-phosphodiesterase (PDE). Using primary cultures of airway smooth muscle (ASM) cells, we recently revealed that PDE4 inhibitors can potentiate the antiinflammatory action of β2-agonists by augmenting cAMP-dependent expression of the phosphatase that deactivates mitogen-activated protein kinase (MAPK)-MAPK phosphatase (MKP)-1.

Repression of breast cancer cell growth by proteasome inhibitors in vitro: impact of mitogen-activated protein kinase phosphatase 1.

Mitogen activated protein kinase phosphatase-1 (MKP-1) has emerged as an important protein mediating breast cancer oncogenesis and chemoresistance to cancer chemotherapies, especially proteasome inhibitors. In this in vitro study, we utilized the breast cancer epithelial cell lines MCF-7 and MDA-MB-231, in comparison to MCF-10A control cells, to examine the impact of MKP-1 on breast cancer cell growth and repression by proteasome inhibitors. We confirm that proteasome inhibitors MG-132 and bortezomib induce MKP-1 protein upregulation and we show that one of the ways in which bortezomib increases MKP-1 in breast cancer cells, in addition to inhibition of ubiquitin-proteasome system, is via upregulation of MKP-1 mRNA expression in p38 MAPK-mediated manner.

Inhibitors of Phosphodiesterase 4, but Not Phosphodiesterase 3, Increase β2-Agonist-Induced Expression of Antiinflammatory Mitogen-Activated Protein Kinase Phosphatase 1 in Airway Smooth Muscle Cells.

β2-agonists are principally used in asthma to provide bronchodilation; however, they also have antiinflammatory properties, due, in part, to their ability to up-regulate mitogen-activated protein kinase phosphatase (MKP) 1 in a cAMP-dependent manner. Phosphodiesterases (PDEs) are attractive targets for potentiating the antiinflammatory response. There are 11 subfamilies of PDE enzymes; among these, inhibition of PDE3 and PDE4 are the main targets for airway smooth muscle (ASM).

Long-acting β2-agonists increase fluticasone propionate-induced mitogen-activated protein kinase phosphatase 1 (MKP-1) in airway smooth muscle cells.

Mitogen-activated protein kinase phosphatase 1 (MKP-1) represses MAPK-driven signalling and plays an important anti-inflammatory role in asthma and airway remodelling. Although MKP-1 is corticosteroid-responsive and increased by cAMP-mediated signalling, the upregulation of this critical anti-inflammatory protein by long-acting β2-agonists and clinically-used corticosteroids has been incompletely examined to date. To address this, we investigated MKP-1 gene expression and protein upregulation induced by two long-acting β2-agonists (salmeterol and formoterol), alone or in combination with the corticosteroid fluticasone propionate (abbreviated as fluticasone) in primary human airway smooth muscle (ASM) cells in vitro.

Sphingosine 1-phosphate induces MKP-1 expression via p38 MAPK- and CREB-mediated pathways in airway smooth muscle cells.

Sphingosine 1-phosphate (S1P), a bioactive sphingolipid elevated in asthmatic airways, is increasingly recognized as playing an important role in respiratory disease. S1P activates receptor-mediated signaling to modulate diverse cellular functions and promote airway inflammation. Although many of the stimulatory pathways activated by S1P have been delineated, especially mitogen-activated protein kinases (MAPK), the question of whether S1P exerts negative feedback control on its own signaling cascade via upregulation of phosphatases remains unexplored.