Pulmonary infection with hypervirulent Mycobacteria reveals a crucial role for the P2X7 receptor in aggressive forms of tuberculosis

PLoS Pathog. 2014 Jul 3;10(7):e1004188. doi: 10.1371/journal.ppat.1004188. eCollection 2014 Jul.

Abstract

The purinergic P2X7 receptor (P2X7R) is a sensor of extracellular ATP, a damage-associated molecule that is released from necrotic cells and that induces pro-inflammatory cytokine production and cell death. To investigate whether the innate immune response to damage signals could contribute to the development of pulmonary necrotic lesions in severe forms of tuberculosis, disease progression was examined in C57BL/6 and P2X7R-/- mice that were intratracheally infected with highly virulent mycobacterial strains (Mycobacterium tuberculosis strain 1471 of the Beijing genotype family and Mycobacterium bovis strain MP287/03). The low-dose infection of C57BL/6 mice with bacteria of these strains caused the rapid development of extensive granulomatous pneumonia with necrotic areas, intense bacillus dissemination and anticipated animal death. In contrast, in P2X7R-/- mice, the lung pathology presented with moderate infiltrates of mononuclear leukocytes without visible signs of necrosis; the disease attenuation was accompanied by a delay in mortality. In vitro, the hypervirulent mycobacteria grew rapidly inside macrophages and induced death by a P2X7R-dependent mechanism that facilitated the release of bacilli. Furthermore, these bacteria were resistant to the protective mechanisms elicited in macrophages following extracellular ATP stimulation. Based on this study, we propose that the rapid intracellular growth of hypervirulent mycobacteria results in massive macrophage damage. The ATP released by damaged cells engages P2X7R and accelerates the necrotic death of infected macrophages and the release of bacilli. This vicious cycle exacerbates pneumonia and lung necrosis by promoting widespread cell destruction and bacillus dissemination. These findings suggest the use of drugs that have been designed to inhibit the P2X7R as a new therapeutic approach to treat the aggressive forms of tuberculosis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphate / immunology
  • Animals
  • Humans
  • Macrophages* / immunology
  • Macrophages* / microbiology
  • Macrophages* / pathology
  • Mice
  • Mice, Knockout
  • Mycobacterium bovis / immunology
  • Mycobacterium bovis / pathogenicity
  • Mycobacterium tuberculosis / immunology*
  • Mycobacterium tuberculosis / pathogenicity*
  • Receptors, Purinergic P2X7* / genetics
  • Receptors, Purinergic P2X7* / immunology
  • Tuberculosis, Pulmonary* / genetics
  • Tuberculosis, Pulmonary* / immunology
  • Tuberculosis, Pulmonary* / pathology

Substances

  • Receptors, Purinergic P2X7
  • Adenosine Triphosphate

Grant support

This work was supported by the Fundação de Amparo à Pesquisa do Estado de São Paulo-FAPESP grant 2010/51150-4 (to MRDL), the Conselho Nacional de Desenvolvimento Cientifico e Tecnológico -CNPq grant 471869/2010-4 (to MRDL), the CNPq Universal grant 473453/2011-8 (to EBL), the Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro-FAPERJ grant E-26/110.623/2011(to EBL) and the MCT/CNPq/MS-DECIT 25/2006 (to EBL). EPA was supported by an award from FAPESP (number: 2010/19246-1). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.