Role of IL-beta converting enzyme on the induction of apoptosis mediated by the infection of periodontopathic bacteria infection

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We have previously reported the evidence for apoptosis in the mouse macrophage cell line J774.1 by the periodontopathic bacterium Actinobacillus actinomycetemcomitans. In this study, we examined the role of protein kinases in the induction of apoptosis in A.actinomycetemcomitans-infected J774.1 cells. After J774.1 cells were precultured with protein kinase C (PKC) activator, J774.1 cells infected with A.actinomycetemcomitans showed the increased percentage of apoptotic cells. On the contrary, PKA activator do not mimic the effect of PKC activator. In addition, PKC inhibitors suppressed apoptotic cell death in J774.1 cells infected with A.actinomycetemcomitans. The results presented here suggest that the signals through PKC may play crucial roles in the modulation of apoptosis in macrophages infected with A.actinomycetemcomitans. Next, we examined the role of caspases, interleukin-1beta (IL-1beta) converting enzyme family proteases, in the regulation of apoptosis in infected J774.1 cells. TWo peptide inhibitors of caspases, benzyloxycarbonyl-Val-Ala-Asp (OMe)-fluoromethyl ketone (Z-VAD-FMK ; caspase-1 inhibitor)and benzyloxycarbonyl-Asp-Glu-Val-ASP (OMe)-fluoromethyl ketone (DEVD-FMK ; caspase-3 inhibitor) inhibited the induction of apoptosis in J774.1 cells infected with A.actinomycetemcomitans. Furhtermore, Z-VAD-FMK suppressed the production of IL-1beta from A.actinomycetemcomitans-infected J774.1 cells. When endogenous caspase-3 activity of J774.1 cells were analyzed, caspase-3 activity was markedly increased after A.actinomycetemcomitans infection. In addition, Z-VAD-FMK and DEVD-FMK suppressed caspase-3 activity of J774.1 cells infected with A.actinomycetemcomitans. These findings suggest that caspase-1 and-3 are involved in the regulation of apoptosis in macrophages infected with A.actinomycetemcomitans.