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The effects of repeated Toll-like receptors 2 and 4 stimulation in COPD alveolar macrophages

Simon R Lea1, Sophie L Reynolds1, Manminder Kaur1

  • 1Division of Infection, Immunity and Respiratory Medicine, School of Biological Sciences, Faculty of Biology, Medicine and Health, Manchester Academic Health Science Centre, The University of Manchester, Manchester University NHS Foundation Trust, Manchester.

International Journal of Chronic Obstructive Pulmonary Disease
|March 15, 2018
PubMed
Abstract

Insights

Toll-like receptor (TLR) tolerance develops in COPD macrophages with repeated stimulation by the same ligand, but sequential stimulation with different TLR ligands amplifies cytokine production, potentially worsening inflammation.

Area of Science:

  • Immunology
  • Respiratory Medicine

Background:

  • Chronic Obstructive Pulmonary Disease (COPD) involves progressive airway inflammation and increased alveolar macrophages.
  • Bacterial colonization in COPD frequently triggers Toll-like receptors (TLRs), exacerbating inflammation.
  • Understanding macrophage responses to repetitive TLR stimulation is crucial for COPD pathogenesis.

Purpose of the Study:

  • To investigate the impact of repetitive Toll-like receptor (TLR) stimulation on alveolar macrophages from COPD patients.
  • To determine if sequential stimulation with different TLR ligands induces tolerance or immune response amplification.

Main Methods:

  • Alveolar macrophages from COPD patients and smokers were stimulated with TLR4 (LPS) or TLR2 (Pam3CSK4) agonists.
  • Cells were subjected to repetitive 24-hour stimulation periods.
  • Cytokine protein release and gene expression were analyzed.

Main Results:

  • Repetitive stimulation with the same TLR ligand (LPS or Pam3CSK4) induced tolerance in selected cytokines (TNF-α, CCL5, IL-10) but not others (IL-6, CXCL8).
  • Sequential stimulation of COPD macrophages with TLR4 followed by TLR2 agonists enhanced cytokine production.
  • CXCL8 production remained unaltered after repetitive stimulation with the same TLR ligand.

Conclusions:

  • TLR tolerance in COPD alveolar macrophages is ligand-specific and affects only certain cytokines.
  • Unchanged CXCL8 production following repetitive TLR stimulation may contribute to elevated levels in COPD.
  • Sequential TLR4 and TLR2 stimulation amplifies cytokine release, potentially explaining excessive bacterial-induced inflammation in COPD.
Keywords:
COPDalveolar macrophagestolerance

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