PIM2 Induced COX-2 and MMP-9 Expression in Macrophages Requires PI3K and Notch1 Signaling

Peter Sommer,Kushagra Bansal,Germain Puzo,Nisha Kapoor,Kithiganahalli Narayanaswamy Balaji,Martine Gilleron,Yeddula Narayana

doi:10.1371/journal.pone.0004911

Abstract

Activation of inflammatory immune responses during granuloma formation by the host upon infection of mycobacteria is one of the crucial steps that is often associated with tissue remodeling and breakdown of the extracellular matrix. In these complex processes, cyclooxygenase-2 (COX-2) plays a major role in chronic inflammation and matrix metalloproteinase-9 (MMP-9) significantly in tissue remodeling. In this study, we investigated the molecular mechanisms underlying Phosphatidyl-myo-inositol dimannosides (PIM2), an integral component of the mycobacterial envelope, triggered COX-2 and MMP-9 expression in macrophages. PIM2 triggers the activation of Phosphoinositide-3 Kinase (PI3K) and Notch1 signaling leading to COX-2 and MMP-9 expression in a Toll-like receptor 2 (TLR2)-MyD88 dependent manner. Notch1 signaling perturbations data demonstrate the involvement of the cross-talk with members of PI3K and Mitogen activated protein kinase pathway. Enforced expression of the cleaved Notch1 in macrophages induces the expression of COX-2 and MMP-9. PIM2 triggered significant p65 nuclear factor -κB (NF-κB) nuclear translocation that was dependent on activation of PI3K or Notch1 signaling. Furthermore, COX-2 and MMP-9 expression requires Notch1 mediated recruitment of Suppressor of Hairless (CSL) and NF-κB to respective promoters. Inhibition of PIM2 induced COX-2 resulted in marked reduction in MMP-9 expression clearly implicating the role of COX-2 dependent signaling events in driving the MMP-9 expression. Taken together, these data implicate PI3K and Notch1 signaling as obligatory early proximal signaling events during PIM2 induced COX-2 and MMP-9 expression in macrophages.

Highlights

Mycobacterium tuberculosis, the causative agent of pulmonary tuberculosis, infects one-third of the world’s population [1]
We examined the molecular details of Phosphatidyl-myo-inositol mannosides-2 (PIM2) induced signaling events that are leading to the expression of COX-2 and matrix metalloproteinase-9 (MMP-9)
PIM2 treatment of mouse peritoneal macrophages triggers the expression of COX-2 and Matrix metalloproteinases (MMPs)-9 both at mRNA and protein levels (Figure 1A–B)

Summary

Introduction

Mycobacterium tuberculosis, the causative agent of pulmonary tuberculosis, infects one-third of the world’s population [1]. Mycobacterial species are known to induce MMP-9 expression and MMP-9 induction in macrophages is suggested to involve Cyclooxygenase-2 (COX-2) dependent signaling events [9]. COX2 is a key enzyme that catalyzes the rate-limiting step in the inducible secretion of Prostaglandin E2 (PGE2) [10]. In this perspective, studies have suggested that MMP-9 expression in macrophages was induced by Prostaglandin E2, and inhibition of COX-2 resulted in inhibition of mycobacterium triggered MMP-9 expression [9]. COX-2 dependent PGE2 production appears to be an important factor in driving the MMP9 expression, a step critical for the breakdown of the ECM components during formation of granulomas. In addition to many species of mycobacteria, the mycobacterial antigens are known to trigger the inducible expression of COX-2 and MMP-9 [9,13,14,15]

Methods

Results

Conclusion