Temporal activation of anti- and pro-apoptotic factors in human gingival fibroblasts infected with the periodontal pathogen, Porphyromonas gingivalis: potential role of bacterial proteases in host signalling.
BACKGROUND
Porphyromonas gingivalis is the foremost oral pathogen of adult periodontitis in humans. However, the mechanisms of bacterial invasion and the resultant destruction of the gingival tissue remain largely undefined.


RESULTS
We report host-P. gingivalis interactions in primary human gingival fibroblast (HGF) cells. Quantitative immunostaining revealed the need for a high multiplicity of infection for optimal infection. Early in infection (2-12 h), P. gingivalis activated the proinflammatory transcription factor NF-kappa B, partly via the PI3 kinase/AKT pathway. This was accompanied by the induction of cellular anti-apoptotic genes, including Bfl-1, Boo, Bcl-XL, Bcl2, Mcl-1, Bcl-w and Survivin. Late in infection (24-36 h) the anti-apoptotic genes largely shut down and the pro-apoptotic genes, including Nip3, Hrk, Bak, Bik, Bok, Bax, Bad, Bim and Moap-1, were activated. Apoptosis was characterized by nuclear DNA degradation and activation of caspases-3, -6, -7 and -9 via the intrinsic mitochondrial pathway. Use of inhibitors revealed an anti-apoptotic function of NF-kappa B and PI3 kinase in P. gingivalis-infected HGF cells. Use of a triple protease mutant P. gingivalis lacking three major gingipains (rgpA rgpB kgp) suggested a role of some or all these proteases in myriad aspects of bacteria-gingival interaction.


CONCLUSIONS
The pathology of the gingival fibroblast in P. gingivalis infection is affected by a temporal shift from cellular survival response to apoptosis, regulated by a number of anti- and pro-apoptotic molecules. The gingipain group of proteases affects bacteria-host interactions and may directly promote apoptosis by intracellular proteolytic activation of caspase-3.
Urnowey
Sonya
S
Department of Biochemistry and Molecular Biology, University of South Alabama, College of Medicine, 307 University Blvd,, Mobile, Alabama 36688-0002, USA. spu301@jaguar1.usouthal.edu
Ansai
Toshihiro
T
Bitko
Vira
V
Nakayama
Koji
K
Takehara
Tadamichi
T
Barik
Sailen
S
D017209:Apoptosis / Q000502:physiology*; D002478:Cells, Cultured; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism / Q000382:microbiology*; D015964:Gene Expression Regulation, Bacterial; D005881:Gingiva / Q000166:cytology*; D006801:Humans; D010447:Peptide Hydrolases / Q000378:metabolism*; D016966:Porphyromonas gingivalis / Q000201:enzymology* / Q000235:genetics / Q000502:physiology*; D015398:Signal Transduction
D010447:Peptide Hydrolases