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Actinobacillus actinomycetemcomitans induces apoptosis in human monocytic THP-1 cells

Satsuki Kato1, Norihiko Sugimura1, Keisuke Nakashima1

  • 1Department of Periodontology and Endodontology, School of Dentistry, Health Sciences University of Hokkaido, 1757 Kanazawa, Ishikari-Tobetsu, Hokkaido 061-0293, Japan 2Department of Oral Microbiology, Kyusyu Dental College, Fukuoka 803-8580, Japan.

Journal of Medical Microbiology
|February 17, 2005
PubMed

Insights

Actinobacillus actinomycetemcomitans infection triggers apoptosis in human immune cells, involving p38 MAPK and tumor necrosis factor alpha. This process may contribute to periodontal disease progression.

Area of Science:

  • Immunology
  • Cell Biology
  • Microbiology

Background:

  • Actinobacillus actinomycetemcomitans infection induces apoptosis in specific cell lines.
  • Mitogen-activated protein kinase (MAPK) family members regulate apoptosis.
  • MAPK signaling pathways are crucial in cellular responses to stress and growth factors.

Purpose of the Study:

  • To determine if human immune cells undergo apoptosis upon A. actinomycetemcomitans infection.
  • To investigate the involvement of the MAPK family in this apoptotic process.

Main Methods:

  • Human monocytic THP-1 cells were infected with A. actinomycetemcomitans.
  • Apoptosis was assessed by monitoring lactate dehydrogenase release and DNA fragmentation.
  • Agarose gel electrophoresis was used to confirm DNA fragmentation patterns.
  • p38 MAPK activity and tumor necrosis factor alpha (TNF-alpha) levels were measured.
  • The effects of a p38 inhibitor and an anti-TNF-alpha antibody were evaluated.

Main Results:

  • A. actinomycetemcomitans infection induced apoptosis in THP-1 cells, evidenced by DNA fragmentation.
  • p38 MAPK activity and TNF-alpha levels increased post-infection.
  • Inhibition of p38 MAPK or TNF-alpha reduced cell death and TNF-alpha levels.
  • Exogenous TNF-alpha did not induce apoptosis in uninfected cells.
  • Anti-TNF-alpha antibody decreased p38 MAPK activity.

Conclusions:

  • A. actinomycetemcomitans infection causes apoptosis in human immune cells (THP-1).
  • p38 MAPK is directly involved in mediating this apoptosis.
  • TNF-alpha appears to play an indirect role, potentially by enhancing p38 MAPK activity.
  • This A. actinomycetemcomitans-induced apoptosis may be significant in the initiation and progression of periodontal diseases.

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