Actinobacillus actinomycetemcomitans toxin induces both cell cycle arrest in the G2/M phase and apoptosis

Masahiro Ohguchi, Akira Ishisaki, Nobuo Okahashi, Masanori Koide, Takeyoshi Koseki, Kenji Yamato, Toshihide Noguchi, Tatsuji Nishihara

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42 Citations (Scopus)

Abstract

We found that the culture supernatant of the periodontopathic bacterium Actinobacillus actinomycetemcomitans had a cytotoxic effect on several cell lines. In this study, we purified the toxin from the culture supernatant of A. actinomycetemcomitans Y4 by a four-step procedure: ammonium sulfate precipitation, POROS HQ/M column chromatography, polymyxin B matrix column chromatography, and Mono-Q column chromatography. The purified toxin gave two major bands of protein with molecular masses of 80 and 85 kDa upon sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The mechanism of cell death of the B-cell hybridoma cell line HS-72 was examined by observing changes in nuclear morphology, an increase in the proportion of fragmented DNA, and the typical ladder pattern of degraded chromosomal DNA, indicating the induction of apoptosis. Overexpression of human Bcl-2 suppressed apoptosis in HS-72 cells, indicating that the toxin from A. actinomycetemcomitans induces apoptosis by a Bcl-2-inhibitable mechanism. Flow cytometric analysis revealed that the toxin caused cell cycle arrest in the G2/M phase and apoptosis in HS-72 cells. In addition, aurintricarboxylic acid, a DNA endonuclease inhibitor, markedly decreased the percentage of apoptotic cells but had no effect on cell cycle arrest in the G2/M phase. Taken together, these findings suggest that the toxin from A. actinomycetemcomitans could mediate the development of periodontal diseases through cell cycle arrest in the G2/M phase and apoptosis in B lymphocytes of periodontal tissue.

Original languageEnglish
Pages (from-to)5980-5987
Number of pages8
JournalInfection and immunity
Volume66
Issue number12
DOIs
Publication statusPublished - 1998 Dec

ASJC Scopus subject areas

  • Parasitology
  • Microbiology
  • Immunology
  • Infectious Diseases

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