Mycobacterium tuberculosis Infection and Tissue Factor Expression in Macrophages

Deepak Kaushal,Ramakrishna Vankayalapati,L Vijaya Mohan Rao,Usha R Pendurthi,Hema Kothari

doi:10.1371/journal.pone.0045700

Deepak Kaushal, Ramakrishna Vankayalapati + Show 3 more

Open Access

https://doi.org/10.1371/journal.pone.0045700

Copy DOI

Abstract

A number of earlier studies reported the occurrence of thrombotic complications, particularly disseminated intravascular coagulation and deep vein thrombosis, in tuberculosis (TB) patients. The aberrant expression of tissue factor (TF), the primary activator of coagulation cascade, is known to be responsible for thrombotic disorders in many diseases including bacterial infections. Further, expression of TF by cells of the monocyte/macrophage lineage is also shown to contribute to the development and progression of local and systemic inflammatory reactions. In the present study, we have investigated whether Mycobacterium tuberculosis (Mtb) infection induces TF expression in macrophages, and various host and pathogenic factors responsible for TF expression. We have tested the effect of live virulent Mtb H37Rv, gamma-irradiated Mtb H37Rv (γ-Mtb) and various components derived from Mtb H37Rv on TF expression in macrophages. The data presented in the manuscript show that both live virulent Mtb and γ-Mtb treatments markedly increased TF activity in macrophages, predominantly in the CD14+ macrophages. Detailed studies using γ-Mtb showed that the increased TF activity in macrophages following Mtb treatment is the result of TF transcriptional activation. The signaling pathways of TF induction by Mtb appears to be distinct from that of LPS-induced TF expression. Mtb-mediated TF expression is dependent on cooperation of CD14/TLR2/TLR4 and probably yet another unknown receptor/cofactor. Mtb cell wall core components, mycolyl arabinogalactan peptidoglycan (mAGP), phosphatidylinositol mannoside-6 (PIM6) and lipomannan (LM) were identified as factors responsible for induction of TF in the order of mAGP>PIM6>LM. A direct contact between bacteria and macrophage and not Mtb-released soluble factors is critical for TF induction by Mtb. In summary, our data show that Mtb induces TF expression in macrophages and Mtb signaling pathways that elicit TF induction require cooperation of multiple receptors, co-receptors/co-factors including Toll-like receptors. The importance of TF in granuloma formation and containment of Mtb is discussed.

Highlights

Activation of extrinsic coagulation cascade initiated by tissue factor (TF) is a critical step in the pathogenesis of various thrombotic disorders [1,2]
LPS CD14+ and CD16+ monocyte-derived macrophages (MDMs) were treated for varying time periods with c-Mycobacterium tuberculosis (Mtb) (10 mg/ml) or LPS (100 ng/ml) and TF expression in MDMs was evaluated by measuring TF procoagulant activity in the cell lysates
The time course for TF activity increase was similar in both CD14+ and CD16+ macrophages, the level of induction was 100 times higher in CD14+ MDMs in comparison to that observed in CD16+ macrophages (Fig. 1B)

Summary

Introduction

Activation of extrinsic coagulation cascade initiated by tissue factor (TF) is a critical step in the pathogenesis of various thrombotic disorders [1,2]. A number of studies have reported the occurrence of thrombotic complications in TB patients, disseminated intravascular coagulation (DIC) and deep vein thrombosis (DVT) [27,28,29,30,31,32]. It is unclear how tuberculosis infection causes thrombotic complications in some patients as mycobacteria are not known to produce endotoxins or exotoxins that are known to initiate the clotting cascade. Earlier studies have reported that cell wall components of Mycobacterium species induced TF expression in macrophages, but these studies were limited to the use of derivatives from non-virulent Mycobacterium species. [33,35,36]

Methods

Results

Conclusion