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

Abstract

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. We show that S1P rapidly and robustly upregulates mRNA and protein expression of the MAPK deactivator-MAPK phosphatase 1 (MKP-1). Utilizing the pivotal airway structural cell, airway smooth muscle (ASM), we confirm that S1P activates all members of the MAPK family and, in part, S1P upregulates MKP-1 expression in a p38 MAPK-dependent manner. MKP-1 is a cAMP response element binding (CREB) protein-responsive gene and here, we reveal for the first time that an adenylate cyclase/PKA/CREB-mediated pathway also contributes to S1P-induced MKP-1. Thus, by increasing MKP-1 expression via parallel p38 MAPK- and CREB-mediated pathways, S1P temporally regulates MAPK signaling pathways by upregulating the negative feedback controller MKP-1. This limits the extent and duration of pro-inflammatory MAPK signaling and represses cytokine secretion in ASM cells. Taken together, our results demonstrate that S1P stimulates both kinases and the phosphatase MKP-1 to control inflammation in ASM cells and may provide a greater understanding of the molecular mechanisms responsible for the pro-asthmatic functions induced by the potent bioactive sphingolipid S1P in the lung.

Effect of the Plant Derivative Compound A on the Production of Corticosteroid-Resistant Chemokines in Airway Smooth Muscle Cells

“…We here found that CpdA-induced up-regulation of the antiinflammatory protein MKP-1 was crucial for the inhibition of cytokine-induced CXCL10 (Figure 7). Previous studies have confirmed the antiinflammatory potential of GC-inducible MKP-1 in human ASM cells (26,31,36). Our data strongly implicate MKP-1-sensitive MAPK pathways in the regulation of CXCL10 in ASM cells.…”

“…We did confirm that CpdA had no transactivation potential by its failure to induce the GILZ gene (Figure 3). The transient induction by CpdA of MKP-1, another GC-inducible early gene, can be easily explained by the implication of GRa-independent mechanisms because MKP-1 up-regulation in ASM could be induced by TNF-a (36), sphingosine 1-phosphate (26), and b2 agonists (37). We found that induction of MKP-1 was also seen at the protein level.…”

“…Previous studies have convincingly demonstrated the antiinflammatory action of MKP-1 in ASM cells (26,31). To determine the role of MKP-1 in our model of cytokineinduced GC insensitivity, we tested whether knocking down MKP-1 would affect the antiinflammatory action of CpdA.…”

“…Immunoblot analyses of IRF-1 or MKP-1 were performed as described previously (25,26) using the anti-IRF-1 (C-20) and MKP-1 (C-19)-specific antibodies (Santa Cruz Biotechnology, Dallas, TX). To ensure equal loading, the membranes were stripped and reprobed with anti-b-actin antibody (C-4) (Santa Cruz Biotechnology).…”

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.…”