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Autoregulation mechanism of human neutrophil apoptosis during bacterial infection

Marcos G Ocaña1, Víctor Asensi, Angel H Montes

  • 1Biochemistry and Molecular Biology Department, Oviedo University Medical School, Hospital Central de Asturias, Oviedo, Spain.

Molecular Immunology
|November 21, 2007
PubMed

Insights

Bacterial infections like osteomyelitis delay neutrophil apoptosis, a key immune cell. This study reveals that cytokines produced by infected neutrophils protect them from programmed cell death, potentially aiding infection resolution.

Area of Science:

  • Immunology
  • Cell Biology
  • Microbiology

Background:

  • Neutrophils (PMN) are crucial phagocytes in host defense against bacteria.
  • Neutrophil apoptosis is a critical process for their clearance.
  • Delayed neutrophil apoptosis is observed in human osteomyelitis.

Purpose of the Study:

  • To investigate apoptosis modulation in human neutrophils infected with Staphylococcus aureus or Escherichia coli.
  • To understand the role of cytokines and protein expression in bacterial-induced apoptosis inhibition.

Main Methods:

  • Flow cytometry with propidium iodide and annexin V staining.
  • Detection of cytokine secretion (IL-6, TNF-alpha, IL-1 beta).
  • Analysis of anti-apoptotic (Bcl-xL) and pro-apoptotic (Bax-alpha) protein expression.

Main Results:

  • Bacterial infection, LPS, or LTA inhibited neutrophil apoptosis.
  • Infected neutrophils secreted IL-6, TNF-alpha, and IL-1 beta, which protected against apoptosis.
  • Increased Bcl-xL and decreased Bax-alpha expression were observed, altering the Bax-alpha/Bcl-xL ratio.

Conclusions:

  • Neutrophil apoptosis is inhibited during bacterial infection via autocrine cytokine production.
  • The modulation of Bax-alpha/Bcl-xL ratio plays a role in this anti-apoptotic effect.
  • This mechanism may contribute to resolving bacterial osteomyelitis.

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