Microtubules Are Associated with Intracellular Movement and Spread of the Periodontopathogen Actinobacillus actinomycetemcomitans

Abstract

Actinobacillus actinomycetemcomitans SUNY 465, the invasion prototype strain, enters epithelial cells by an actin-dependent mechanism, escapes from the host cell vacuole, and spreads intracellularly and to adjacent epithelial cells via intercellular protrusions. Internalized organisms also egress from host cells into the assay medium via protrusions that are associated with just a single epithelial cell. Here we demonstrate that agents which inhibit microtubule polymerization (e.g., colchicine) and those which stabilize polymerized microtubules (e.g., taxol) both increase markedly the number of intracellular A. actinomycetemcomitansorganisms. Furthermore, both colchicine and taxol prevented the egression of A. actinomycetemcomitans from host cells into the assay medium. Immunofluorescence microscopy revealed that protrusions that mediate the bacterial spread contain microtubules.A. actinomycetemcomitans SUNY 465 and 652, strains that are both invasive and egressive, interacted specifically with the plus ends (growing ends) of the filaments of microtubule asters in a KB cell extract. By contrast, neither A. actinomycetemcomitans 523, a strain that is invasive but not egressive, nor Haemophilus aphrophilus, a noninvasive oral bacterium with characteristics similar to those of A. actinomycetemcomitans, bound to microtubules. Together these data suggest that microtubules function in the spread and movement of A. actinomycetemcomitans and provide the first evidence that host cell dispersion of an invasive bacterium may involve the usurption of host cell microtubules.

Desulfovibrio spp. survive within KB cells and modulate inflammatory responses

“…Among periodontopathogens, P. gingivalis and F. nucleatum have been shown to enter epithelial cells via both a microtubule-dependent and actin-dependent mechanism (Lamont et al, 1995;Han et al, 2000). It has also been reported that a few strains of A. actinomycetemcomitans utilize microtubule-dependent mode of invasion whereas most strains use an actin-dependent mode of entry into epithelial cells (Brissette & Fives-Taylor, 1999;Meyer et al, 1999). In the present study, treatment with nocodazole, a microtubule-destabilizing agent, resulted in a significant inhibition of bacterial invasion whereas internalization was enhanced in cells pretreated with cytochalasin D. These data suggest that internalization of all three Desulfovibrio strains tested was microtubule-dependent.…”

Efficacy of Antibiotics Against Periodontopathogenic Bacteria Within Epithelial Cells: An In Vitro Study

“…This pathogen is known to replicate within 30 minutes after entry into an epithelial cell, then to excite the host cell and spread to the adjacent epithelial cells. 10,24 However, the bacterium does not seem to persist within the epithelial cells and the pathogenic effect may be related to the fact that the mere contact with the epithelial cells provokes the release of proinflammatory interleukin (IL)-6 and interleukin-8 and stimulates the specific and unspecific immune response. 11,25,26 The tested antibiotics showed limited effectiveness against P. gingivalis, which is known to persist within the epithelial cells.…”

Microorganisms as risk indicators for periodontal disease

“…In a human epidermoid carcinoma cell line (KB), invasion is initiated by the contact of A. actinomycetemcomitans with microvilli. Once in the cell, A. actinomycetemcomitans SUNY 465 can spread intracellularly by utilizing host cell microtubules (41). Recently, A. actinomycetemcomitans, among the other periodontal pathogens discussed in this review, have been detected in human buccal epithelial cells.…”