Abstract
We have previously reported that the periodontopathic bacterium Actinobacillus actinomycetemcomitans infection induces apoptosis in the mouse macrophage cell line J774.1. In the present study, we examined the involvement of cytochrome c and caspases in the induction of apoptosis in A. actinomycetemcomitans-infected J774.1 cells. After J774.1 cells were infected with A. actinomycetemcomitans, the expression levels of cytochrome c, caspase-9 and caspase-3 were examined by immunoblot analysis. Cytochrome c was released from mitochondria into the cytoplasm, when A. actinomycetemcomitans-infected J774.1 cells were cultured for 6 h. Both caspase-9 and caspase-3 were found to be cleaved to active form in J774.1 cells infected with A. actinomycetemcomitans. In addition, phosphorylated p53 was detected in J774.1 cells after 30 h of A. actinomycetemcomitans infection. These findings suggest that apoptosis in J774.1 cells infected with A. actinomycetemcomitans is regulated by cytochrome c relased from mitochondria into cytoplasm and subsequent activation of caspases via p53 dependent pathway.
