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Mechanisms of group B streptococcal-induced apoptosis of murine macrophages

Glen C Ulett1, Kirsteen H Maclean, Sunitha Nekkalapu

  • 1Department of Infectious Diseases, St. Jude Children's Research Hospital, Memphis, TN 38105, USA.

Journal of Immunology (Baltimore, Md. : 1950)
|August 6, 2005
PubMed

Insights

Group B Streptococcus agalactiae (GBS) triggers macrophage apoptosis, a key bacterial virulence factor. Inhibiting caspase-3 shows potential for therapeutic intervention in GBS infections.

Area of Science:

  • Microbiology
  • Immunology
  • Cell Biology

Background:

  • Group B Streptococcus agalactiae (GBS) infection can lead to macrophage apoptosis.
  • This apoptosis is a significant virulence mechanism for GBS, aiding immune suppression and persistence.
  • The precise molecular mechanisms driving GBS-induced apoptosis remain largely unelucidated.

Purpose of the Study:

  • To investigate the mechanisms by which GBS induces apoptosis in murine macrophages.
  • To identify key apoptotic regulators and pathways involved in GBS pathogenesis.

Main Methods:

  • Murine macrophages were infected with GBS.
  • Changes in the regulation and localization of apoptotic proteins (Bad, 14-3-3, Omi/HtrA2) were analyzed.
  • Mitochondrial cytochrome c release and caspase activation (caspase-9, caspase-3) were assessed.
  • The effect of caspase-3 inhibition on GBS-induced apoptosis was evaluated.

Main Results:

  • GBS infection induced unique alterations in the apoptotic regulators Bad, 14-3-3, and Omi/high-temperature requirement A2 (Omi/HtrA2) in murine macrophages.
  • GBS promoted the release of cytochrome c from mitochondria.
  • Activation of caspase-9 and caspase-3 was observed following GBS infection.
  • Pharmacological inhibition of caspase-3 significantly reduced GBS-induced macrophage apoptosis.

Conclusions:

  • GBS utilizes a distinct apoptotic pathway involving specific regulators and caspase activation to induce macrophage death.
  • Modulating effector caspase activity presents a potential therapeutic strategy against GBS infections.

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