Highly purified lipoteichoic acid induced pro-inflammatory signalling in primary culture of rat microglia through Toll-like receptor 2: selective potentiation of nitric oxide production by muramyl dipeptide

J Neurochem. 2006 Oct;99(2):596-607. doi: 10.1111/j.1471-4159.2006.04085.x. Epub 2006 Jul 31.


In contrast to the role of lipopolysaccharide from Gram-negative bacteria, the role of Gram-positive bacterial components in inducing inflammation in the CNS remains controversial. We studied the potency of highly purified lipoteichoic acid and muramyl dipeptide isolated from Staphylococcus aureus to activate primary cultures of rat microglia. Exposure of pure microglial cultures to lipoteichoic acid triggered a significant time- and dose-dependent production of pro-inflammatory cytokines (tumour-necrosis factor-alpha, interleukin-1beta, interleukin-6) and nitric oxide. Muramyl dipeptide strongly and selectively potentiated lipoteichoic acid-induced inducible nitric oxide synthase expression and nitric oxide production. However, it did not have any significant influence on the production of pro-inflammatory cytokines. As bacterial components are recognised by the innate immunity through Toll-like receptors (TLRs) we showed that lipoteichoic acid was recognised in microglia by the TLR2 and lipopolysaccharide by the TLR4, as cells isolated from mice lacking TLR2 or TLR4 did not produce pro-inflammatory cytokines and nitric oxide upon lipoteichoic acid or lipopolysaccharide stimulation, respectively. Lipoteichoic acid-induced glia activation was mediated by p38 and ERK1/2 MAP kinases, as pretreatment with inhibitor of p38 or ERK1/2 decreased lipoteichoic acid-induced cytokine release, iNOS mRNA expression and nitric oxide production. The observed pro-inflammatory response induced by lipoteichoic acid-activated microglia could play a major role in the inflammatory response of CNS induced by Gram-positive bacteria.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acetylmuramyl-Alanyl-Isoglutamine / immunology
  • Acetylmuramyl-Alanyl-Isoglutamine / metabolism
  • Acetylmuramyl-Alanyl-Isoglutamine / pharmacology*
  • Animals
  • Animals, Newborn
  • Cells, Cultured
  • Central Nervous System Bacterial Infections / immunology*
  • Central Nervous System Bacterial Infections / metabolism
  • Cytokines / immunology
  • Cytokines / metabolism
  • Dose-Response Relationship, Drug
  • Encephalitis / immunology
  • Encephalitis / metabolism
  • Encephalitis / physiopathology
  • Enzyme Inhibitors / pharmacology
  • Extracellular Signal-Regulated MAP Kinases / drug effects
  • Extracellular Signal-Regulated MAP Kinases / metabolism
  • Inflammation Mediators / immunology
  • Inflammation Mediators / metabolism
  • Inflammation Mediators / pharmacology
  • Lipopolysaccharides / immunology
  • Lipopolysaccharides / pharmacology*
  • Microglia / drug effects
  • Microglia / immunology*
  • Microglia / metabolism
  • Nitric Oxide / metabolism*
  • Nitric Oxide Synthase Type II / drug effects
  • Nitric Oxide Synthase Type II / genetics
  • Nitric Oxide Synthase Type II / immunology
  • Rats
  • Signal Transduction / drug effects
  • Signal Transduction / immunology
  • Teichoic Acids / immunology
  • Teichoic Acids / pharmacology*
  • Time Factors
  • Toll-Like Receptor 2 / drug effects
  • Toll-Like Receptor 2 / metabolism*
  • Toll-Like Receptor 4 / drug effects
  • Toll-Like Receptor 4 / immunology
  • Toll-Like Receptor 4 / metabolism
  • p38 Mitogen-Activated Protein Kinases / drug effects
  • p38 Mitogen-Activated Protein Kinases / metabolism


  • Cytokines
  • Enzyme Inhibitors
  • Inflammation Mediators
  • Lipopolysaccharides
  • Teichoic Acids
  • Tlr2 protein, rat
  • Tlr4 protein, rat
  • Toll-Like Receptor 2
  • Toll-Like Receptor 4
  • Nitric Oxide
  • Acetylmuramyl-Alanyl-Isoglutamine
  • lipoteichoic acid
  • Nitric Oxide Synthase Type II
  • Extracellular Signal-Regulated MAP Kinases
  • p38 Mitogen-Activated Protein Kinases