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J Med Microbiol 56 (2007), 1399-1404; DOI: 10.1099/jmm.0.47193-0
© 2007 Society for General Microbiology
ISSN 1473-5644

Role of caspases in cleavage of lamin A/C and PARP during apoptosis in macrophages infected with a periodontopathic bacterium

Toshinori Okinaga1, Hironori Kasai2, Toshiyuki Tsujisawa1 and Tatsuji Nishihara1

1 Department of Health Promotion, Division of Infections and Molecular Biology, Kyushu Dental College, 2-6-1 Manazuru, Kokurakita-ku, Kitakyushu 803-8580, Japan

2 Department of Cariology and Periodontology, Division of Periodontology, Kyushu Dental College, 2-6-1 Manazuru, Kokurakita-ku, Kitakyushu 803-8580, Japan

Correspondence
Tatsuji Nishihara
tatsujin{at}kyu-dent.ac.jp

Received 29 January 2007
Accepted 25 June 2007

The periodontopathic bacterium Actinobacillus actinomycetemcomitans has been implicated in the pathogenesis of periodontal diseases. It has been reported previously that infection with the organism induced apoptosis in the mouse macrophage cell line J774.1. In the present study, the role of caspases during apoptosis in A. actinomycetemcomitans-infected J774.1 cells was examined. A large number of apoptotic cells was detected by flow cytometric analysis in infected J774.1 cells; however, inhibitors of caspase-9, -6 and -3/7 completely blocked the induction of apoptosis. Expression of the cleaved forms of caspase-6 and -7 was detected during apoptosis in infected J774.1 cells. Immunoblot analysis revealed that the caspase-9 inhibitor blocked expression of the cleaved forms of caspase-6 and -7, whilst the caspase-3 inhibitor blocked expression of the cleaved form of caspase-7, but not caspase-6. It is known that lamin A/C and poly(ADP-ribose) polymerase (PARP) are essential nuclear components for maintaining normal cell function and viability, and both were found to be cleaved in the infected J774.1 cells. Immunoblot analysis also revealed that the caspase-6 inhibitor blocked the cleavage of lamin A/C, whilst the caspase-3/7 inhibitor blocked the cleavage of PARP. Taken together, these results suggest that activation of caspases and the subsequent cleavage of lamin A/C and PARP are involved in the morphological changes of apoptotic macrophages infected with A. actinomycetemcomitans.

Abbreviations: PARP, poly(ADP-ribose) polymerase; PI, propidium iodide.






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