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Screening Bioactive Nanoparticles in Phagocytic Immune Cells for Inhibitors of Toll-like Receptor Signaling
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Dysfunctional mitochondria contain endogenous high-affinity human Toll-like receptor 4 (TLR4) ligands and induce

Sally A Nicholas1, Karen Coughlan, Inna Yasinska

  • 1Medway School of Pharmacy, University of Kent, United Kingdom.

The International Journal of Biochemistry & Cell Biology
|January 26, 2011
PubMed

Insights

Mitochondria from damaged cells trigger inflammation via Toll-like receptor 4 (TLR4) activation, similar to bacterial LPS. These findings reveal new insights into cellular damage and immune responses.

Area of Science:

  • Immunology
  • Cell Biology
  • Molecular Biology

Background:

  • Mitochondria share features with prokaryotes and accumulate endogenous Toll-like receptor 4 (TLR4) ligands, like heat shock proteins.
  • Toll-like receptor 4 (TLR4) recognizes bacterial lipopolysaccharide (LPS) and endogenous ligands, playing roles in autoimmunity and regeneration.

Purpose of the Study:

  • To investigate the pro-inflammatory potential of mitochondria from dysfunctional cells.
  • To determine if mitochondria-derived ligands activate Toll-like receptor 4 (TLR4) and induce inflammatory responses.

Main Methods:

  • Mitochondria extracts from hydrogen peroxide-treated cells were used to stimulate human THP-1 myeloid leukemia cells.
  • Inflammatory markers including hypoxia-inducible factor 1 alpha (HIF-1α), IL-6, and TNF-α were measured.
  • Toll-like receptor 4 (TLR4) neutralizing antibodies, ELISA, and surface plasmon resonance were employed.

Main Results:

  • Mitochondria extracts from dysfunctional cells induced a potent pro-inflammatory response, activating HIF-1α and cytokine release (IL-6, TNF-α).
  • This response mimicked LPS-induced inflammation and was significantly stronger than that from normal mitochondria.
  • Toll-like receptor 4 (TLR4) mediated the response, as evidenced by antibody neutralization and conserved signaling pathways.
  • Binding assays confirmed endogenous TLR4 ligands in mitochondria extracts, with higher affinity from dysfunctional mitochondria.

Conclusions:

  • Mitochondria from damaged cells release endogenous ligands that activate Toll-like receptor 4 (TLR4), driving pro-inflammatory responses.
  • This mechanism highlights a novel pathway linking cellular damage to innate immunity activation.

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