Role and regulation of MKP-1 in airway inflammation

Mitogen-activated protein kinase (MAPK) phosphatase 1 (MKP-1) is a protein with anti-inflammatory properties and the archetypal member of the dual-specificity phosphatases (DUSPs) family that have emerged over the past decade as playing an instrumental role in the regulation of airway inflammation. Not only does MKP-1 serve a critical role as a negative feedback effector, controlling the extent and duration of pro-inflammatory MAPK signalling in airway cells, upregulation of this endogenous phosphatase has also emerged as being one of the key cellular mechanism responsible for the beneficial actions of clinically-used respiratory medicines, including beta(2)-agonists, phosphodiesterase inhibitors and corticosteroids. Herein, we review the role and regulation of MKP-1 in the context of airway inflammation. We initially outline the structure and biochemistry of MKP-1 and summarise the multi-layered molecular mechanisms responsible for MKP-1 production more generally. We then focus in on some of the key in vitro studies in cell types relevant to airway disease that explain how MKP-1 can be regulated in airway inflammation at the transcriptional, post-translation and post-translational level. And finally, we address some of the potential challenges with MKP-1 upregulation that need to be explored further to fully exploit the potential of MKP-1 to repress airway inflammation in chronic respiratory disease

Targeting mitogen-activated protein kinase phosphatase-1 (MKP-1): Structure-based design of MKP-1 inhibitors and upregulators

Mitogen-activated protein kinase phosphatases (MKPs) are dual specificity protein phosphatases (DUSPs) that dephosphorylate both phospho-tyrosine and phospho-threonine residues on mitogen-activated protein kinases (MAPKs). Because the MAPK family of signalling molecules (phospho-p38 MAPK, c-Jun N-terminal kinase (JNK) and extracellular signal-regulated kinase (ERK)) play essential roles in cell signalling pathways that regulate cell growth and inflammation, controlling MAPK-mediated pathways is a therapeutically attractive strategy. While small molecule MAPK inhibitors have utility, in this review we will focus on exploring the potential of targeting the endogenous MAPK deactivator - MKP-1. Importantly, there is a strong justification for developing both inhibitors and upregulators of MKP-1 because of the diverse roles played by MAPKs in disease: for example, in cancer, MKP-1 inhibitors may prove beneficial, as MKP-1 is overexpressed and is considered responsible for the failure of JNK-driven apoptotic pathways induced by chemotherapeutics; conversely, in inflammatory diseases such as asthma and arthritis, MKP-1 reduces MAPKmediated signalling and developing novel ligands to upregulate MKP-1 levels would be a therapeutically attractive anti-inflammatory strategy. Thus, in this review we utilise MKP-1 homology modeling to highlight the structural features of MKP-1 inhibitors that permit potent and selective inhibition, and to provide insights into the structural requirements for selective MKP-1 upregulators. © 2012 Bentham Science Publishers

Antiproliferative and antimigratory actions of synthetic long chain n-3 monounsaturated fatty acids in breast cancer cells that overexpress cyclooxygenase-2

Cyclooxygenase-2 (COX-2) is overexpressed in many human cancers and converts the n-6 polyunsaturated fatty acid (PUFA) arachidonic acid to prostaglandin E2 (PGE2), which drives tumorigenesis; in contrast, n-3 PUFA inhibit tumorigenesis. We tested the hypothesis that these antitumor actions of n-3 PUFA may involve the n-3 olefinic bond. n-3 Monounsaturated fatty acids (MUFAs) of chain length C16-C22 were synthesized and evaluated in MDA-MB-468 breast cancer cells that stably overexpressed COX-2 (MDA-COX-2 cells). Longer chain (C19-C22) n-3 MUFAs inhibited proliferation, activated apoptosis, decreased PGE2 formation, and decreased cell invasion; C16-C18 analogues were less active. Molecular modeling showed that interactions of Arg120, Tyr355, and several hydrophobic amino acid residues in the COX-2 active site with C19-C22 MUFA analogues were favored. Thus, longer-chain n-3 MUFAs may be prototypes of novel anticancer agents that decrease the formation of PGE2 in tumor cells that contain high levels of COX-2. © 2012 American Chemical Society