Analysis of the human periodontal ligament fibroblast response to the cytolethal distending toxin produced by actinobacillus actinomycetemcomitans.

A small number of diverse bacterial pathogens have been found to produce cytolethal distending toxin (CDT). Much evidence has been obtained to show that CDTs cause a variety of eukaryotic cells to become irreversibly blocked in the G2 phase of the cell cycle. Cells which are sensitive to CDT, such as Chinese hamster ovary (CHO) cells, die within a few days after exposure to the toxin. Recent research has shown that CDT is a potential virulence factor for Actinobacillus actinomycetemcomitans, a bacterial species associated with juvenile periodontitis (JP). This research investigates the effects A. actinomycetemcomitans CDT has on human periodontal ligament fibroblasts (HPDLFs). After HPDLFs were exposed to physiologic levels of CDT, cell viability was assessed utilizing an assay that measured the conversion of a tetrazolium compound into a soluble formazan product, which could be read on a spectrophotometer. Cell viability was also measured after exposure to CDT through trypan blue staining and the use of a hemocytometer. CHO cells were utilized as a parallel control to show that the CDT obtained from A. actinomycetemcomitans was active. The results obtained indicate that the HPDLFs are resistant to the cytolethal distending toxin. The possible resistance the HPDLFs have to the CDT may stem from the low turnover rate of the fibroblasts. However, further research must be completed on this topic.