Mycobacterium tuberculosis-infected human monocytes down-regulate microglial MMP-2 secretion in CNS tuberculosis via TNFα, NFκB, p38 and caspase 8 dependent pathways

J Neuroinflammation. 2011 May 11:8:46. doi: 10.1186/1742-2094-8-46.

Abstract

Tuberculosis (TB) of the central nervous system (CNS) is a deadly disease characterized by extensive tissue destruction, driven by molecules such as Matrix Metalloproteinase-2 (MMP-2) which targets CNS-specific substrates. In a simplified cellular model of CNS TB, we demonstrated that conditioned medium from Mycobacterium tuberculosis-infected primary human monocytes (CoMTb), but not direct infection, unexpectedly down-regulates constitutive microglial MMP-2 gene expression and secretion by 72.8% at 24 hours, sustained up to 96 hours (P < 0.01), dependent upon TNF-α. In human CNS TB brain biopsies but not controls the p38 pathway was activated in microglia/macrophages. Inhibition of the p38 MAP kinase pathway resulted in a 228% increase in MMP-2 secretion (P < 0.01). In contrast ERK MAP kinase inhibition further decreased MMP-2 secretion by 76.6% (P < 0.05). Inhibition of the NFκB pathway resulted in 301% higher MMP-2 secretion than CoMTb alone (P < 0.01). Caspase 8 restored MMP-2 secretion to basal levels. However, this caspase-dependent regulation of MMP-2 was independent of p38 and NFκB pathways; p38 phosphorylation was increased and p50/p65 NFκB nuclear trafficking unaffected by caspase 8 inhibition. In summary, suppression of microglial MMP-2 secretion by M.tb-infected monocyte-dependent networks paradoxically involves the pro-inflammatory mediators TNF-α, p38 MAP kinase and NFκB in addition to a novel caspase 8-dependent pathway.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anti-Inflammatory Agents, Non-Steroidal / metabolism
  • Caspase 8 / metabolism*
  • Culture Media, Conditioned / chemistry
  • Extracellular Signal-Regulated MAP Kinases / metabolism
  • Humans
  • Matrix Metalloproteinase 2 / genetics
  • Matrix Metalloproteinase 2 / metabolism*
  • Microglia / cytology
  • Microglia / metabolism
  • Monocytes / cytology
  • Monocytes / metabolism*
  • Monocytes / microbiology*
  • Mycobacterium tuberculosis / metabolism
  • Mycobacterium tuberculosis / pathogenicity
  • NF-kappa B / metabolism*
  • Sesquiterpenes / metabolism
  • Sesquiterpenes, Guaiane
  • Signal Transduction / physiology
  • Tuberculosis, Central Nervous System / metabolism*
  • Tuberculosis, Central Nervous System / microbiology
  • Tumor Necrosis Factor-alpha / metabolism*
  • p38 Mitogen-Activated Protein Kinases / metabolism*

Substances

  • Anti-Inflammatory Agents, Non-Steroidal
  • Culture Media, Conditioned
  • NF-kappa B
  • Sesquiterpenes
  • Sesquiterpenes, Guaiane
  • Tumor Necrosis Factor-alpha
  • helenalin
  • Extracellular Signal-Regulated MAP Kinases
  • p38 Mitogen-Activated Protein Kinases
  • Caspase 8
  • Matrix Metalloproteinase 2