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Characterization of the proteinase-dependent cytotoxicity of Porphyromonas gingivalis
1Department of Oral Biology, Faculty of Odontology, University of Umeå, Sweden. anders.johansson@oralbio.umu.se
Abstract:
Cytotoxicity of proteins from Porphyromonas gingivalis towards gingival fibroblasts and epithelial cells was studied by methods measuring vital dye uptake, DNA synthesis, release of cytoplasmic components, and apoptosis. Microscopic examination of the cells was also performed for detection of morphological changes. Experiments were made with dialyzed culture supernatants of P. gingivalis as well as supernatant fractions obtained by isoelectric focusing. The main cell damage observed was rounding of the cells and detachment from each other and the underlying surface. The cell-damaging activity correlated with the cystein-dependent proteolytic activity of the various supernatant preparations as well as with the occurrence of gelatinolytic protein bands with molecular weights previously reported for the cysteine proteinases gingipains R and K of P. gingivalis. The activity was abolished by heat treatment or by the addition of cysteine proteinase inhibitors. The results indicate that the main cytotoxic effect towards fibroblasts and epithelial cells is degradation of the intercellular matrix. The gingipains released in P. gingivalis culture supernatants are the responsible factors for this degradation.
Insights
Porphyromonas gingivalis proteins, specifically gingipains, cause cell damage by degrading the intercellular matrix. This leads to fibroblast and epithelial cell death, contributing to periodontal disease.
Area of Science:
- Microbiology
- Cell Biology
- Periodontology
Background:
- Porphyromonas gingivalis is a key pathogen in periodontitis.
- Bacterial virulence factors contribute to host tissue damage.
Purpose of the Study:
- To investigate the cytotoxic effects of P. gingivalis proteins on gingival cells.
- To identify the specific bacterial factors responsible for cytotoxicity.
Main Methods:
- Assessing cell viability using vital dye uptake and DNA synthesis assays.
- Measuring release of cytoplasmic components and detecting apoptosis.
- Microscopic analysis of morphological changes in treated cells.
- Isoelectric focusing of bacterial culture supernatants to isolate protein fractions.
Main Results:
- P. gingivalis proteins induced cell rounding and detachment.
- Cytotoxicity correlated with cysteine-dependent proteolytic activity.
- Gelatinolytic bands matched the molecular weights of gingipains R and K.
- Cell damage was abolished by heat or protease inhibitors.
Conclusions:
- Gingipains are the primary factors causing cytotoxicity in P. gingivalis supernatants.
- Degradation of the intercellular matrix is the main mechanism of cell damage.
- These findings elucidate a key mechanism in P. gingivalis-mediated tissue destruction.