EP₂ and EP₄ receptor antagonists: Impact on cytokine production and β₂‐adrenergic receptor desensitization in human airway smooth muscle

Abstract

Prostaglandin E2 (PGE2) is a key prostanoid known to have both proinflammatory and anti‐inflammatory impact in the context of chronic respiratory diseases. We hypothesize that these opposing effects may be the result of different prostanoid E (EP) receptor‐mediated signaling pathways. In this study, we focus on two of the four EP receptors, EP2 and EP4, as they are known to induce cyclic adenosine monophosphate (cAMP)‐dependent signaling pathways. Using primary human airway smooth muscle (ASM) cells, we first focussed on the PGE2‐induced production of two cAMP‐dependent proinflammatory mediators: interleukin 6 (IL‐6) and cyclo‐oxygenase 2 production. We show that PGE2‐induced IL‐6 protein secretion occurs via an EP2‐mediated pathway, in a manner independent of receptor‐mediated effects on messenger RNA (mRNA) expression and temporal activation kinetics of the transcription factor cAMP response element binding. Moreover, stimulation of ASM with PGE2 did not establish a positive, receptor‐mediated, feedback loop, as mRNA expression for EP2 and EP4 receptors were not upregulated and receptor antagonists were without effect. Our studies revealed that the EP2, but not the EP4, receptor is responsible for β2‐adrenergic desensitization induced by PGE2. We demonstrate that PGE2‐induced heterologous receptor desensitization responsible for tachyphylaxis to short‐ (salbutamol) or long‐ (formoterol) β2‐agonists (measured by cAMP release) can be reversed by the EP2 receptor antagonist PF‐04418948. Importantly, this study highlights that inhibiting the EP2 receptor restores β2‐adrenergic receptor function in vitro and offers an attractive novel therapeutic target for treating infectious exacerbations in people suffering from chronic respiratory diseases in the future.

Prostaglandin E2 breaks down pericyte–endothelial cell interaction via EP1 and EP4-dependent downregulation of pericyte N-cadherin, connexin-43, and R-Ras

“…We treated pericytes with specific inhibitors targeting EP receptors. We found that a cocktail of EP1/2/4 specific inhibitors [66][67][68][69][70][71] prior to PGE2 treatment allows pericytes to resume the morphology of untreated control cells (Fig. 4c) and intimately associate with ECs in 3-D coculture, thus restoring their capacity to form endothelial cords (Fig.…”

Role of prostaglandin E2 in tissue repair and regeneration

“…The EP2 and EP4 receptors coupled to Gs activate adenylate cyclase (AC) and increase cAMP production, whereas the EP3 receptor inhibits cAMP signaling. EP receptors, selective agonists, or antagonists were used to amplify or antagonize PGE2 signal effects 15 - 18 . It's reported that solute carrier organic anion transporter family member 2A1 (SLCO2A1), known as prostaglandin transporter (PGT), is responsible for transporting extracellular PGE2 into the cell and performs a function in the intracellular activity of PGE2 13 , 19 .…”

Parkinsonian Neurotoxins Impair the Pro-inflammatory Response of Glial Cells

“…The range of concentrations used in these studies are higher than that used in neuronal cultures (0.1–500 μM MPP+ and 10 nM-1 μM rotenone; Gao et al, 2003; Henze et al, 2005; Klintworth et al, 2009; Bournival et al, 2012; Jin et al, 2012; Du et al, 2014). Some authors have reported no alterations (Klintworth et al, 2009; Ferger et al, 2010; Jin et al, 2012), but others have shown the induction of pro-inflammatory markers in the MPP+- and rotenone-treated microglial cultures (Du et al, 2014; Zhang et al, 2014; Liang et al, 2015; Zhou et al, 2016). Differences in the pattern of neurotoxin treatment (concentration and duration of the treatment) and the cell types used (primary cultures and cell lines from different species) may partially account for the differences observed.…”

“…However, as MPP+- and rotenone-damaged neurons induce reactive microgliosis, which has a neurotoxic effect, it is difficult to establish the contribution of a direct effect of the toxins on glial cells in the neurotoxicity observed. In fact, although the neurotoxic effect of MPP+ and rotenone has been widely described using in vivo and in vitro experimental approaches, their direct effects on glial cells remain poorly characterized (Gao et al, 2003; Klintworth et al, 2009; Bournival et al, 2012; Du et al, 2014; Chen et al, 2015; Zhou et al, 2016). Most of the studies performed until now using glial cell cultures have tested whether these neurotoxins induce a pro-inflammatory phenotype in the microglial cells, and the results obtained are controversial.…”

“…Either no direct effect of MPP+ on microglial cell function (Gao et al, 2003; Jin et al, 2012), or an increase in the expression of pro-inflammatory markers in microglial cells after MPP+ exposure (Bournival et al, 2012; Chen et al, 2015) has been reported. Similarly, either an increase in the expression of pro-inflammatory factors (Gao et al, 2013; Yuan et al, 2013; Du et al, 2014) or no direct effect on the production of inflammatory factors (Klintworth et al, 2009) has been observed in rotenone-treated microglial cell cultures.…”