Toll-Like Receptor 4 (TLR4) expression and stimulation in a model of intervertebral disc inflammation and degeneration

Spine (Phila Pa 1976). 2013 Jul 15;38(16):1343-51. doi: 10.1097/BRS.0b013e31826b71f4.


Study design: We measured the expression and responses of Toll-Like Receptor 4 (TLR4) activation in the intervertebral disc (IVD) in vitro and in vivo. We hypothesize that stimulation of the IVD with the TLR4 ligand lipopolysaccharide (LPS) results in upregulation of a coordinated set of proinflammatory mediators and inhibition of matrix expression, both consistent with a molecular profile of degeneration.

Objective: To characterize early inflammatory and morphological changes induced by TLR4 activation in the IVD.

Summary of background data: TLR4 is a pattern recognition receptor activated in innate immunity that has been implicated in disease mechanisms of inflammatory cartilaginous degeneration. However, no study to date has examined the expression and responses of TLR4 in the IVD.

Methods: IVD cells were stimulated with LPS in a dose-dependent manner, and inflammatory cytokine levels were measured by quantitative reverse transcription-polymerase chain reaction. Histological and inflammatory changes due to in vivo injection of LPS into the rat caudal IVD were measured by enzyme-linked immunosorbent assay and immunoblotting.

Results: Baseline TLR4 expression in IVD tissue varied according to cell type. LPS stimulation resulted in significant increases in tumor necrosis factor α (TNF)-α, interleukin (IL)-1β, IL-6, and nitric oxide levels and significant inhibition in aggrecan and collagen-2. Intradiscal injection of LPS was found to cause moderate degenerative changes in the IVD, with increases in tissue levels of IL-1β, TNF-α, high mobility group box 1 protein (HMGB1), and macrophage migration inhibitory factor (MIF).

Conclusion: This study provides the first evidence that IVD cells express TLR4 and are responsive to TLR4 activation by upregulating a coordinated set of inflammatory cytokines. This study suggests that intradiscal injection of LPS offers a model for triggering inflammation of the IVD, demonstrating that inflammatory insults alone may potentially trigger degenerative changes of the IVD.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cattle
  • Cells, Cultured
  • Cytokines / genetics*
  • Cytokines / metabolism
  • Gene Expression / drug effects*
  • Immunoblotting
  • Inflammation / genetics
  • Inflammation / metabolism
  • Inflammation Mediators / metabolism*
  • Interleukin-1beta / genetics
  • Interleukin-1beta / metabolism
  • Interleukin-6 / genetics
  • Interleukin-6 / metabolism
  • Intervertebral Disc / cytology
  • Intervertebral Disc / drug effects*
  • Intervertebral Disc / metabolism
  • Intervertebral Disc Degeneration / genetics
  • Intervertebral Disc Degeneration / metabolism
  • Lipopolysaccharides / pharmacology*
  • Male
  • Rats
  • Rats, Sprague-Dawley
  • Reverse Transcriptase Polymerase Chain Reaction
  • Toll-Like Receptor 4 / genetics*
  • Toll-Like Receptor 4 / metabolism
  • Tumor Necrosis Factor-alpha / genetics
  • Tumor Necrosis Factor-alpha / metabolism


  • Cytokines
  • Inflammation Mediators
  • Interleukin-1beta
  • Interleukin-6
  • Lipopolysaccharides
  • Toll-Like Receptor 4
  • Tumor Necrosis Factor-alpha