Heterogeneity in the immune response to serotype b LPS of Actinobacillus actinomycetemcomitans in inbred strains of mice

Kato, Tsuyoshi

doi:10.1016/s0928-8244(00)00134-6

Cited by 13 publications

(13 citation statements)

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“…The genetic control of immune responses against periodontopathic bacteria has been studied by several groups (Watanabe, Marsh and Ivany, 1989; Shimauchi, Ogawa and Hamada, 1991; Honma et al , 1997). We investigated a variety of humoral immune responses to A. actinomycetemcomitans LPS and the production of cytokines in inbred strains of mice; our results suggest that there is a genetic control of responses to periodontopathic bacterial LPS (Kato et al , 2000a). It is well known that periodontopathic bacterial LPSs are able to induce several cytokines, including inflammatory ones, and possibly to affect the cytokine network.…”

Section: Role Of Periodontopathic Bacterial Lipopolysaccharidesmentioning

confidence: 99%

Involvement of periodontopathic biofilm in vascular diseases

2003

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Oral bacteria inhabit biofilms, which are firm clusters adhering in layers to surfaces and are not easily eliminated by immune responses and are resistant to antimicrobial agents. Dental plaque is one such biofilm. In the past 10 years, subgingival plaque bacteria forming biofilms have been increasingly reported to be involved in systemic diseases. A close relationship between microbial infections and vascular disease has also been reported in the past two decades. The present review discusses the significance of the ecologic characteristics of biofilms formed by periodontopathic bacteria in order to further clarify the associations between periodontal disease and systemic disease. We focus on the relationships between periodontal disease-associated bacteria forming biofilms and vascular diseases including atherosclerosis and carotid coronary stenotic artery disease, and we discuss the direct and indirect effects on vascular diseases of lipopolysaccharides as well as heat shock proteins produced by periodontopathic bacteria.

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Section: Role Of Periodontopathic Bacterial Lipopolysaccharidesmentioning

confidence: 99%

Involvement of periodontopathic biofilm in vascular diseases

2003

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“…actinomycetemcomitans is a capnophilic gram-negative bacterium that is associated with various forms of early-onset periodontal diseases (60,73,74), endocarditis (7), and subcutaneous abscesses (46). The mechanisms of A. actinomycetemcomitans pathogenesis are not well understood, but the organism expresses a variety of potential virulence-associated factors, e.g., a collagenase (51), lipopolysaccharide (32,34), and GroEL-like proteins (26), that may stimulate the breakdown of the extracellular matrix and the induction of bone resorption. A. actinomycetemcomitans also produces several toxins which target various components of the immune system and may play a role in modulating the host response.…”

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confidence: 99%

luxSandarcBControl Aerobic Growth ofActinobacillus actinomycetemcomitansunder Iron Limitation

2003

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LuxS is responsible for the production of autoinducer 2 (AI-2), which functions in Vibrio harveyi as a quorum-sensing signal that controls the cell density-dependent expression of the lux operon. In nonluminescent organisms, the physiologic role of AI-2 is not clear. We report that inactivation of luxS in Actinobacillus actinomycetemcomitans JP2 results in reduced growth of the mutant, but not the wild-type organism, under aerobic, iron-limited conditions. Stunted cultures of the luxS mutant A. actinomycetemcomitans JP2-12 grew to high cell density when subcultured under iron-replete conditions. In addition, the mutant strain grew to high cell density under iron limitation after transformation with a plasmid containing a functional copy of luxS. Results of real-time PCR showed that A. actinomycetemcomitans JP2-12 exhibited significantly reduced expression of afuA (eightfold), fecBCDE (10-fold), and ftnAB (>50-fold), which encode a periplasmic ferric transport protein, a putative ferric citrate transporter, and ferritin, respectively. The expressions of putative receptors for transferrin, hemoglobin, and hemophore binding protein were also reduced at more modest levels (two-to threefold). In contrast, expressions of sidD and frpB (encoding putative siderophore receptors) were increased 10-and 3-fold, respectively, in the luxS mutant. To better understand the mechanism of the AI-2 response, the A. actinomycetemcomitans genome was searched for homologs of the V. harveyi signal transduction proteins, LuxP, LuxQ, LuxU, and LuxO. Interestingly, ArcB was found to be most similar to LuxQ sensor/kinase. To determine whether arcB plays a role in the response of A. actinomycetemcomitans to AI-2, an arcB-deficient mutant was constructed. The isogenic arcB mutant grew poorly under anaerobic conditions but grew normally under aerobic iron-replete conditions. However, the arcB mutant failed to grow aerobically under iron limitation, and reverse transcriptase PCR showed that inactivation of arcB resulted in decreased expression of afuA and ftnAB. Thus, isogenic luxS and arcB mutants of A. actinomycetemcomitans exhibit similar phenotypes when cultured aerobically under iron limitation, and both mutants exhibit reduced expression of a common set of genes involved in the transport and storage of iron. These results suggest that LuxS and ArcB may act in concert to control the adaptation of A. actinomycetemcomitans to iron-limiting conditions and its growth under such conditions.

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“…However, the organism produces an array of potential virulence factors that may contribute to pathogenesis. For example, the breakdown of the extracellular matrix and the induction of bone resorption that occur in periodontitis may be facilitated by expression of collagenase (38), lipopolysaccharide (28), and GroEL-like proteins (20). A. actinomycetemcomitans expresses various adherence factors (34) (including fimbriae [39]), invades human epithelial cells (33,45), produces several toxins which target various components of the immune system, and may play a role in modulating the host response by killing cells of the lymphocytic and monomyelocytic lineages.…”

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Intra- and Interspecies Regulation of Gene Expression byActinobacillus actinomycetemcomitansLuxS

et al. 2001

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The cell density-dependent control of gene expression is employed by many bacteria for regulating a variety of physiological functions, including the generation of bioluminescence, sporulation, formation of biofilms, and the expression of virulence factors. Although periodontal organisms do not appear to secrete acyl-homoserine lactone signals, several species, e.g., Porphyromonas gingivalis, Prevotella intermedia, and Fusobacterium nucleatum, have recently been shown to secrete a signal related to the autoinducer II (AI-2) of the signal system 2 pathway in Vibrio harveyi. Here, we report that the periodontal pathogen Actinobacillus actinomycetemcomitans expresses a homolog of V. harveyi luxS and secretes an AI-2-like signal. Cell-free conditioned medium from A. actinomycetemcomitans or from a recombinant Escherichia coli strain (E. coli AIS) expressing A. actinomycetemcomitans luxS induced luminescence in V. harveyi BB170 >200-fold over controls. AI-2 levels peaked in mid-exponential-phase cultures of A. actinomycetemcomitans and were significantly reduced in late-log-and stationary-phase cultures. Incubation of early-log-phase A. actinomycetemcomitans cells with conditioned medium from A. actinomycetemcomitans or from E. coli AIS resulted in a threefold induction of leukotoxic activity and a concomitant increase in leukotoxin polypeptide. In contrast, no increase in leukotoxin expression occurred when cells were exposed to sterile medium or to conditioned broth from E. coli AIS ؊ , a recombinant strain in which luxS was insertionally inactivated. A. actinomycetemcomitans AI-2 also induced expression of afuA, encoding a periplasmic iron transport protein, approximately eightfold, suggesting that LuxS-dependent signaling may play a role in the regulation of iron acquisition by A. actinomycetemcomitans. Finally, A. actinomycetemcomitans AI-2 added in trans complemented a luxS knockout mutation in P. gingivalis by modulating the expression of the luxS-regulated genes uvrB and hasF in this organism. Together, these results suggest that LuxS-dependent signaling may modulate aspects of virulence and the uptake of iron by A. actinomycetemcomitans and induce responses in other periodontal organisms in mixed-species oral biofilm.

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Heterogeneity in the immune response to serotype b LPS of Actinobacillus actinomycetemcomitans in inbred strains of mice

Cited by 13 publications

References 13 publications

Involvement of periodontopathic biofilm in vascular diseases

Involvement of periodontopathic biofilm in vascular diseases

luxSandarcBControl Aerobic Growth ofActinobacillus actinomycetemcomitansunder Iron Limitation

Intra- and Interspecies Regulation of Gene Expression byActinobacillus actinomycetemcomitansLuxS

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