MAP Kinase Phosphatase-2 Plays a Critical Role in Response to Infection by Leishmania mexicana

Mashael S Al-Mutairi,James Alexander,Clare E Bryant,Magdalena Kurnik,Juliane Schroeder,Laurence C Cadalbert,Robin Plevin,Muhannad Shweash,Callum M Sloss,H Adrienne Mcgachy,Ingrid Müller

doi:10.1371/journal.ppat.1001192

Abstract

In this study we generated a novel dual specific phosphatase 4 (DUSP4) deletion mouse using a targeted deletion strategy in order to examine the role of MAP kinase phosphatase-2 (MKP-2) in immune responses. Lipopolysaccharide (LPS) induced a rapid, time and concentration-dependent increase in MKP-2 protein expression in bone marrow-derived macrophages from MKP-2+/+ but not from MKP-2−/− mice. LPS-induced JNK and p38 MAP kinase phosphorylation was significantly increased and prolonged in MKP-2−/− macrophages whilst ERK phosphorylation was unaffected. MKP-2 deletion also potentiated LPS-stimulated induction of the inflammatory cytokines, IL-6, IL-12p40, TNF-α, and also COX-2 derived PGE2 production. However surprisingly, in MKP-2−/− macrophages, there was a marked reduction in LPS or IFNγ-induced iNOS and nitric oxide release and enhanced basal expression of arginase-1, suggesting that MKP-2 may have an additional regulatory function significant in pathogen-mediated immunity. Indeed, following infection with the intracellular parasite Leishmania mexicana, MKP-2−/− mice displayed increased lesion size and parasite burden, and a significantly modified Th1/Th2 bias compared with wild-type counterparts. However, there was no intrinsic defect in MKP-2−/− T cell function as measured by anti-CD3 induced IFN-γ production. Rather, MKP-2−/− bone marrow-derived macrophages were found to be inherently more susceptible to infection with Leishmania mexicana, an effect reversed following treatment with the arginase inhibitor nor-NOHA. These findings show for the first time a role for MKP-2 in vivo and demonstrate that MKP-2 may be essential in orchestrating protection against intracellular infection at the level of the macrophage.

Highlights

The mitogen-activated protein (MAP) kinase phosphatases (MKPs) are a family of dual specific phosphatases which regulate the functional activity of the major MAP kinase subfamilies through tyrosine and threonine dephosphorylation [1]
We found that the macrophages with no MAP kinase phosphatase-2 (MKP-2) fought off Leishmania poorly and mice deficient in MKP-2 had a modified immune response favouring the growth of the parasite
In macrophages derived from MKP-22/2 mice, we find that its deletion results in enhanced Jun N-terminal kinase (JNK) and p38 MAP kinase activation but not, as expected, increased extracellular regulated kinase (ERK) phosphorylation

Summary

Introduction

The mitogen-activated protein (MAP) kinase phosphatases (MKPs) are a family of dual specific phosphatases which regulate the functional activity of the major MAP kinase subfamilies through tyrosine and threonine dephosphorylation [1]. The action of one or more MKP is essential for the tight regulation of MAP kinase activity and subsequent functional responses mediated by a vast array of extracellular stimuli [1]. A number of MKPs have been implicated in the regulation of disease. Recent evidence implicates a role in the regulation of immune responses [4]. Deletion of MKP-1 [5] and PAC-1 [6] have been shown to both enhance and reduce LPS mediated cellular responses respectively, whilst MKP-5 is thought to regulate adaptive immunity via effects upon T-cells [7]. One of the main anti-inflammatory effects of dexamethasone is attributed to the induction of MKP-1 and the subsequent inhibition of p38 MAP kinase [8]

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Discussion

Conclusion