POSSIBLE INVOLVEMENT OF PROTEIN-KINASE-C IN APOPTOTIC CELL-DEATH OF MACROPHAGES INFECTED WITH ACTINOBACILLUS-ACTINOMYCETEMCOMITANS

We have previously reported the evidence for apoptosis in the mouse ma crophage cell line J774.1 by the periodontopathic bacterium Actinobaci llus actinomycetemcomitans. In this study, we examined the role of pro tein kinases in the induction of apoptosis in A. actinomycetemcomitans -infected J774.1 cells by the MTT assay, fluorescence microscopy and f low cytometric analysis. After J774.1 cells were precultured with prot ein kinase C (PKC) activator, phorbol 12-myristate 13-acetate (PMA), J 774.1 cells infected with A. actinomycetemcomitans showed the increase d percentage of apoptotic cells. On the contrary, protein kinase A (PK A) activators, such as forskolin and dibutyryl cAMP, do not mimic the effect of PMA. PKC inhibitors, such as staurosporine, calphostin C, ch elerythrine chloride, and H7 were found to suppress apoptotic cell dea th in J774.1 cells infected with A. actinomycetemcomitans. However, HA 1004, known as PKA inhibitor, had no effect on apoptosis in infected macrophages. The results presented here suggest that the signals throu gh PKC may play crucial roles in the modulation of apoptosis in macrop hages infected with A. actinomycetemcomitans. (C) 1998 Federation of E uropean Microbiological Societies. Published by Elsevier Science B.V.