Change search
ReferencesLink to record
Permanent link

Direct link
The cytolethal distending toxin induces receptor activator of NF-κB ligand expression in human gingival fibroblasts and periodontal ligament cells
Umeå University, Faculty of Medicine, Odontology, Oral Cell Biology. Umeå University, Faculty of Medicine, Odontology, Oral Microbiology.
Umeå University, Faculty of Medicine, Odontology, Periodontology.
Show others and affiliations
2005 (English)In: Infection and Immunity, ISSN 0019-9567, Vol. 73, no 1, 342-351 p.Article in journal (Refereed) Published
Abstract [en]

Actinobacillus actinomycetemcomitans is associated with localized aggressive periodontitis, a disease characterized by rapid loss of the alveolar bone surrounding the teeth. Receptor activator of NF-kappaB Ligand (RANKL) and osteoprotegerin (OPG) are two molecules that regulate osteoclast formation and bone resorption. RANKL induces osteoclast differentiation and activation, whereas OPG blocks this process by acting as a decoy receptor for RANKL. The purpose of this study was to investigate the effect of A. actinomycetemcomitans on the expression of RANKL and OPG in human gingival fibroblasts and periodontal ligament cells. RANKL mRNA expression was induced in both cell types challenged by A. actinomycetemcomitans extract, whereas OPG mRNA expression remained unaffected. Cell surface RANKL protein was also induced by A. actinomycetemcomitans, whereas there was no change in OPG protein secretion. A cytolethal distending toxin (Cdt) gene-knockout strain of A. actinomycetemcomitans did not induce RANKL expression, in contrast to its wild-type strain. Purified Cdt from Haemophilus ducreyi alone, or in combination with extract from the A. actinomycetemcomitans cdt mutant strain, induced RANKL expression. Pretreatment of A. actinomycetemcomitans wild-type extract with Cdt antiserum abolished RANKL expression. In conclusion, A. actinomycetemcomitans induces RANKL expression in periodontal connective tissue cells. Cdt is crucial for this induction and may therefore be involved in the pathological bone resorption during the process of localized aggressive periodontitis.

Place, publisher, year, edition, pages
2005. Vol. 73, no 1, 342-351 p.
URN: urn:nbn:se:umu:diva-18058DOI: 10.1128/IAI.73.1.342-351.2005PubMedID: 15618171OAI: diva2:157731
Available from: 2007-12-13 Created: 2007-12-13 Last updated: 2009-12-08Bibliographically approved
In thesis
1. Cellular and molecular responses of periodontal connective tissue cells to Actinobacillus actinomycetemcomitans cytolethal distending toxin
Open this publication in new window or tab >>Cellular and molecular responses of periodontal connective tissue cells to Actinobacillus actinomycetemcomitans cytolethal distending toxin
2004 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Actinobacillus actinomycetemcomitans is present in elevated proportions and numbers in dental bacterial biofilms of patients with localized aggressive periodontitis. This variant of periodontal disease, occurring in adolescents and young adults, is characterized by rapid and severe destruction of the connective tissues and bone supporting the teeth, eventually culminating in tooth loss. The cytolethal distending toxin (Cdt) is a newly discovered bacterial protein toxin, uniquely present in A. actinomycetemcomitans among all known to-date oral bacterial species. The Cdt has the capacity to inhibit mammalian cell growth, but its putative role in the pathogenesis of the disease is unclear. The aim of this in vitro work has been to study the effects of A. actinomycetemcomitans on periodontal connective tissue cell cultures, and to evaluate the possible involvement of its Cdt.

A. actinomycetemcomitans inhibited the proliferation of gingival and periodontal ligament fibroblasts, as a result of a combined arrest at the G1 and G2/M phases of the cell cycle. This growth inhibition was non-lethal and the cells remained metabolically active, although their DNA synthesis was reduced. The intoxicated cells exhibited increased size and irregular structure, characterized by distension and elongation. This cellular enlargement occurred in both G1 and G2/M phase arrested cells. The Cdt of A. actinomycetemcomitans was responsible for the observed growth inhibition, as well as the concomitant morphological alterations.

The possible induction of inflammatory cytokines related to bone resorption was investigated in response to A. actinomycetemcomitans, and the involvement of Cdt was evaluated. Extensive focus was given to the study of receptor activator of NF-κB ligand (RANKL) expression, a membrane-bound ligand that signals osteoclast progenitors to differentiate and fuse into mature osteoclasts, activating bone resorption. It was demonstrated that A. actinomycetemcomitans induced RANKL mRNA and protein expression in the cells studied, but did not affect the expression of its decoy receptor, osteoprotegerin. This induction was solely attributed to its Cdt, as demonstrated by the use of a cdt-knockout A. actinomycetemcomitans strain, purified recombinant Cdt, and antibodies blocking the Cdt. In addition, this event was not mediated by pro-inflammatory cytokines known to stimulate RANKL. Interleukin-6 mRNA and protein expression were also enhanced by A. actinomycetemcomitans, but Cdt had limited involvement in this enhancement.

In conclusion, two distinct mechanisms by which A. actinomycetemcomitans Cdt may be involved in the pathogenesis of localized aggressive periodontitis are proposed. Firstly, the growth arrest of the resident fibroblasts may impair the physiological connective tissue remodelling equilibrium and lead to connective tissue attachment loss. Secondly, the induction of RANKL by these cells, residing in the proximity of the alveolar bone, may locally stimulate osteoclastogenesis and promote alveolar bone resorption. This work also provides further insights to the understanding of Cdt mechanisms of action, contributing to the global characterization of the toxin’s virulence.

Place, publisher, year, edition, pages
Umeå: Odontologi, 2004. 49 p.
Umeå University odontological dissertations, ISSN 0345-7532 ; 88
Medical sciences, Actinobacillus actinomycetemcomitans, cytolethal distending toxin, periodontal connective tissue cells, localized aggressive periodontitis, growth arrest, bone resorption, receptor activator of NF-κB ligand, osteoprotegerin, pro-inflammatory cytokines, MEDICIN OCH VÅRD
National Category
Medical and Health Sciences
Research subject
urn:nbn:se:umu:diva-345 (URN)91-7305-746-0 (ISBN)
Public defence
2004-12-10, Sal 933, 3A, Norrlands Universitessjukhus, Umeå, 13:00 (English)
Available from: 2004-11-01 Created: 2004-11-01 Last updated: 2009-08-24Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full textPubMed

Search in DiVA

By author/editor
Johansson, AndersLerner, Ulf
By organisation
Oral Cell BiologyOral MicrobiologyPeriodontology
In the same journal
Infection and Immunity

Search outside of DiVA

GoogleGoogle Scholar
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Altmetric score

Total: 58 hits
ReferencesLink to record
Permanent link

Direct link