Corticosteroids and β₂‐agonists upregulate mitogen‐activated protein kinase phosphatase 1: in vitro mechanisms

Abstract

BACKGROUND AND PURPOSEAirway remodelling is a consequence of long-term inflammation and MAPKs are key signalling molecules that drive pro-inflammatory pathways. The endogenous MAPK deactivator -MAPK phosphatase 1 (MKP-1) -is a critical negative regulator of the myriad pro-inflammatory pathways activated by MAPKs in the airway. EXPERIMENTAL APPROACHHerein we investigated the molecular mechanisms responsible for the upregulation of MKP-1 in airway smooth muscle (ASM) by the corticosteroid dexamethasone and the b2-agonist formoterol, added alone and in combination. KEY RESULTSMKP-1 is a corticosteroid-inducible gene whose expression is enhanced by long-acting b2-agonists in an additive manner. Formoterol induced MKP-1 expression via the b2-adrenoceptor and we provide the first direct evidence (utilizing overexpression of PKIa, a highly selective PKA inhibitor) to show that PKA mediates b2-agonist-induced MKP-1 upregulation. Dexamethasone activated MKP-1 transcription in ASM cells via a cis-acting corticosteroid-responsive region located between -1380 and -1266 bp of the MKP-1 promoter. While the 3′-untranslated region of MKP-1 contains adenylate + uridylate elements responsible for regulation at the post-transcriptional level, actinomycin D chase experiments revealed that there was no increase in MKP-1 mRNA stability in the presence of dexamethasone, formoterol, alone or in combination. Rather, there was an additive effect of the asthma therapeutics on MKP-1 transcription. CONCLUSIONS AND IMPLICATIONSTaken together, these studies allow us a greater understanding of the molecular basis of MKP-1 regulation by corticosteroids and b2-agonists and this new knowledge may lead to elucidation of optimized corticosteroid-sparing therapies in the future. AbbreviationsAd5, adenoviral serotype 5; ASM, airway smooth muscle; CREB, cyclic-AMP response element binding protein; GC, glucocorticoid; GRE, GC-responsive element; H-89, N-[2-(p-bromocinnamylamino)ethyl]-5-isoquinolinesulfonamide dihydrochloride; MKP-1, MAPK phosphatase 1; MOI, multiplicity of infection; 3'-UTR, 3′-untranslated region

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

“…Given the relatively low efficacy as a cAMP-inducer in ASM cells, therefore RNO (at 1000 nM) only minimally increased formoterol-induced MKP-1 mRNA expression and protein upregulation and the impact was not significant. Consequently, TNF-induced IL- (12)), as well as steroids (dexamethasone (11,14), fluticasone: (12, 14)). Together cAMP-elevating agents and steroids can act in an additive manner to increase MKP-1 upregulation and we have shown this with steroids and LABA added in combination (11,12 ).…”

“…Our previous studies in ASM cells have confirmed that stimuli that increase cAMP induce expression of the cAMP-dependent anti-inflammatory protein MKP-1 (5,(11)(12)(13). Because RNO (at 1000 nM) increased cAMP production in response to formoterol, we hypothesized that RNO will augment MKP-1 expression in response to the long-acting β2-agonist in ASM cells.…”

Superiority of Combined Phosphodiesterase PDE3/PDE4 Inhibition over PDE4 Inhibition Alone on Glucocorticoid- and Long-Acting β2-Adrenoceptor Agonist–Induced Gene Expression in Human Airway Epithelial Cells

“…Indeed, the dual-specificity mitogen-activated protein kinase (MAPK) phosphatase, dual-specificity phosphatase 1 (DUSP1), is induced by glucocorticoids to switch off MAPK signaling and thereby reduce inflammatory gene expression (Clark et al, 2008). Since the effect of LABAs and glucocorticoids on DUSP1 expression appears additive Manetsch et al, 2012), this offers some explanation for the effects of combination therapy. Notwithstanding effects on DUSP1 expression, synergistic enhancement of glucocorticoid-dependent transcription by the cAMP/protein kinase A (PKA) pathway is well established (Rangarajan et al, 1992;Nordeen et al, 1993).…”

Temporal regulation of cytokine mRNA expression by tristetraprolin: dynamic control by p38 MAPK and MKP-1

“…MKP-1 is a MAPK deactivator with multiple modes of anti-inflammatory action: it is an endogenous protein that functions as a negative feedback effector to repress MAPK-mediated proinflammatory signaling and cytokine secretion (7,19), and it can be upregulated by anti-asthma medicines such as ␤ 2 -agonists and corticosteroids (8,20,21,27,28), serving as an important way in which these front-line asthma medicines achieve their anti-inflammatory function.…”