Unlike for human monocytes after LPS activation, release of TNF-α by THP-1 cells is produced by a TACE catalytically different from constitutive TACE

PLoS One. 2012;7(3):e34184. doi: 10.1371/journal.pone.0034184. Epub 2012 Mar 30.

Abstract

Background: Tumor necrosis factor-alpha (TNF-α) is a pro-inflammatory cytokine today identified as a key mediator of several chronic inflammatory diseases. TNF-α, initially synthesized as a membrane-anchored precursor (pro-TNF-α), is processed by proteolytic cleavage to generate the secreted mature form. TNF-α converting enzyme (TACE) is currently the first and single protease described as responsible for the inducible release of soluble TNF-α.

Methodology/principal findings: Here, we demonstrated the presence on THP-1 cells as on human monocytes of a constitutive proteolytical activity able to cleave pro-TNF-α. Revelation of the cell surface TACE protein expression confirmed that the observed catalytic activity is due to TACE. However, further studies using effective and innovative TNF-α inhibitors, as well as a highly selective TACE inhibitor, support the presence of a catalytically different sheddase activity on LPS activated THP-1 cells. It appears that this catalytically different TACE protease activity might have a significant contribution to TNF-α release in LPS activated THP-1 cells, by contrast to human monocytes where the TACE activity remains catalytically unchanged even after LPS activation.

Conclusions/significance: On the surface of LPS activated THP-1 cells we identified a releasing TNF-α activity, catalytically different from the sheddase activity observed on human monocytes from healthy donors. This catalytically-modified TACE activity is different from the constitutive shedding activity and appears only upon stimulation by LPS.

MeSH terms

  • ADAM Proteins / metabolism*
  • ADAM17 Protein
  • Animals
  • Benzoquinones / pharmacology
  • Cell Line
  • Cell Membrane / metabolism
  • Chronic Disease
  • Enzyme-Linked Immunosorbent Assay / methods
  • Flow Cytometry / methods
  • Humans
  • Hydroxamic Acids / pharmacology
  • Inflammation
  • Inhibitory Concentration 50
  • Lipopolysaccharides / metabolism*
  • Mice
  • Microscopy, Confocal / methods
  • Monocytes / cytology*
  • Peptide Hydrolases / metabolism
  • Recombinant Proteins / metabolism
  • Sulfonamides / pharmacology
  • Triterpenes / pharmacology
  • Tumor Necrosis Factor-alpha / metabolism*

Substances

  • 2-(1-(hydroxycarbamoyl)-4-phenyl-3-butenyl)-2'-isobutyl-2'-(methanesulfonyl)-4-methylvalerohydrazide
  • Benzoquinones
  • Hydroxamic Acids
  • Lipopolysaccharides
  • Recombinant Proteins
  • Sulfonamides
  • Triterpenes
  • Tumor Necrosis Factor-alpha
  • Peptide Hydrolases
  • ADAM Proteins
  • ADAM17 Protein
  • ADAM17 protein, human
  • Adam17 protein, mouse
  • celastrol
  • thymoquinone