Involvement of PorK, a component of the type IX secretion system, in Prevotella melaninogenica pathogenicity.

Prevotella melaninogenica is a gram-negative anaerobic commensal bacterium that resides in the human oral cavity and is isolated as a pathogen of suppurative diseases both inside and outside the mouth. However, little is known about the pathogenic factors of P. melaninogenica. The periodontal pathogens Porphyromonas gingivalis and Tanerella forsythia secrete virulence factors such as protease and bacterial cell surface proteins via a type IX secretion system (T9SS) that are involved in pathogenicity. P. melaninogenica also possesses all known orthologs of T9SS. In this study, a P. melaninogenica GAI 07411 mutant deficient in the orthologue of the T9SS-encoding gene, porK, was constructed. Hemagglutination and biofilm formation were decreased in the porK mutant. Furthermore, following growth on skim milk-containing medium, the diameters of the halos surrounding the porK mutant were smaller than those of the wild-type strain, suggesting a decrease in secretion of proteases outside the bacterium. To investigate this in detail, culture supernatants of wild-type and porK mutant strains were purified and compared by two-dimensional electrophoresis. In the mutant strain, fewer spots were detected, indicating fewer secreted proteins. In infection experiments, the mortality rate of mice inoculated with the porK mutant strain was significantly lower than in the wild-type strain. These results suggest that P. melaninogenica secretes potent virulence factors via the T9SS that contribute to its pathogenic ability.

Complete Genome Sequence of Streptococcus sp. Strain NPS 308.

Streptococcus sp. strain NPS 308, isolated from an 8-year-old girl diagnosed with infective endocarditis, likely presents a novel species of Streptococcus Here, we present a complete genome sequence of this species, which will contribute to better understanding of the pathogenesis of infective endocarditis.

Acute oral complications in a pediatric patient with acute lymphoid leukemia.

Pseudomonas aeruginosa is a low-virulence pathogen that can cause infection in immunocompromised patients. Among pediatric hematologists, it is known that careful attention should be paid to P. aeruginosa as the bacteria responsible for intraoral inflammation, and antibiotic therapy targeting P. aeruginosa is the first-line treatment during neutropenia in patients with hematological malignancy. Immunosuppressed patients, however, are at high risk of developing inflammation. Here, we report a case involving a 10-year-old patient with acute lymphoid leukemia (ALL), in which P. aeruginosa synergistically acted with pre-existing gingivitis to induce unusual oral necrotic lesions, leading to acute buccal cellulitis and pus discharge from external sinus tracts.

Dental manifestations of a pediatric patient with hyperimmunoglobulin e syndrome: a case report.

A 7-year-old girl with hyperimmunoglobulin E syndrome (HIES) presented to our clinic with tooth agenesis in both primary and permanent dentitions. The patient's serum immunoglobulin E level was elevated at 17,091 IU/ml, and her medical history indicated the occurrence of HIES, numerous skin abscesses, and recurrent infection by bacteria and/or fungi such as Candida from birth. She also suffered from heart disease. Dental manifestations included extensive caries, impaired root resorption of primary mandibular central incisors and absence of primary mandibular canines and permanent mandibular lateral incisors. Intraoral phenotypes in HIES patients have already been reported in detail, but no previous report has described abnormalities in the number of primary teeth in HIES patients. The purpose of this report was to describe the dental manifestations in the primary dentition of a hyperimmunoglobulin E syndrome patient and to emphasize the importance of preventive dental management from early childhood in compromised children, such as those with HIES.

Phylogenetic analyses and detection of viridans streptococci based on sequences and denaturing gradient gel electrophoresis of the rod shape-determining protein gene.

BACKGROUND: Population analysis of viridans streptococci is important because these species are associated with dental caries, bacteremia, and subacute endocarditis, in addition to being important members of the human oral commensal microbiota. DESIGN: In this study, we phylogenetically analyzed the rod shape-determining protein gene (rodA), which is associated with cellular morphology, cell division, and sensitivity for antibiotics, and demonstrated that the diversity of the rodA gene is sufficient to identify viridans streptococci at the species level. Moreover, we developed a more convenient denaturing gradient gel electrophoresis (DGGE) method based on the diversity of the rodA gene (rodA-DGGE) for detecting nine dominant streptococcal species in human saliva, namely, Streptococcus sanguinis, Streptococcus oralis, Streptococcus mitis, Streptococcus parasanguinis, Streptococcus gordonii, Streptococcus vestibularis, Streptococcus salivarius, Streptococcus mutans, and Streptococcus sobrinus. RESULTS: This rodA-DGGE method proved useful in detecting viridans streptococci without cultivation, isolation, and phenotypic characterization. CONCLUSION: Analysis of the oral microbiota by rodA-DGGE offers a higher resolution than the conventional DGGE using 16S rDNA and may be an alternative in the microbial diagnosis of streptococcal infection.

Amelogenin binds to both heparan sulfate and bone morphogenetic protein 2 and pharmacologically suppresses the effect of noggin.

Enamel matrix derivative (EMD) is widely considered useful to promote tissue regeneration during periodontal treatment. It has been reported that the main constituent of EMD is amelogenin and that the BMP-like and TGF-beta-like activity of EMD promotes osteogenesis. However, it remains unclear whether those activities are dependent on amelogenin or another growth factor contained in EMD. We performed two-dimensional SDS-PAGE analysis of EMD, as well as Western blot analyses using anti-amelogenin, anti-BMP2/4, and anti-TGF-beta1 antibodies, and amino acid sequencing. Our results revealed that a large number of splicing forms of amelogenin, BMP2/4, and other unknown molecules were involved in EMD, though TGF-beta1 was not. In addition, we have evaluated intracellular signaling of ERK1/2 and Smad1/5/8, binding potential and alkaline phosphatase activity and have explored the potential regulatory relationship between amelogenin and BMP. Amelogenin bound to BMP2 as well as heparin/heparan sulfate. Thus, it was suggested that BMP2/4 carried over in EMD during processing promote binding activity and phosphorylate Smad1/5/8 in osteoblasts. On the other hand, amelogenin did not phosphorylate Smad1/5/8, but rather ERK1/2. Further, high-density amelogenin reduced the inhibition of alkaline phosphatase activity by noggin, though amelogenin did not have antagonistic properties against BMP. Together with the above findings, our findings suggest that the BMP2/4 contaminated during the purification process of EMD because of the avidity of amelogenin plays an important role in signaling pathway of calcification.

Amelogenin is a negative regulator of osteoclastogenesis via downregulation of RANKL, M-CSF and fibronectin expression in osteoblasts.

Amelogenin is a novel enamel matrix protein. Knockout mice showed enhanced osteoclast formation and resorption of tooth cementum. This study investigated the effects of amelogenin on osteoclastogenesis. In co-cultures with calvaria osteoblasts and purified bone marrow cells, amelogenin inhibited osteoclastogenesis dramatically. Furthermore, amelogenin inhibited the expression of receptor activator of nuclear factor kappaB ligand (RANKL), macrophage-colony stimulating factor (M-CSF) and fibronectin in osteoblasts, while RANKL expression was induced by fibronectin and inhibited by treatment with fibronectin small interfering RNA. These results suggest that the inhibitory effects of amelogenin on osteoclastogenesis lead to downregulation of RANKL, M-CSF and fibronectin production in osteoblasts.

Surface-expressed TLR6 participates in the recognition of diacylated lipopeptide and peptidoglycan in human cells.

Recognition of microbial components by TLR2 requires cooperation with other TLRs. TLR6 has been shown to be required for the recognition of diacylated lipoproteins and lipopeptides derived from mycoplasma and to activate the NF-kappaB signaling cascade in conjunction with TLR2. Human TLR2 is expressed on the cell surface in a variety of cells, including monocytes, neutrophils, and monocyte-derived, immature dendritic cells (iDCs), whereas the expression profile of TLR6 in human cells remains obscure. In this study we produced a function-blocking mAb against human TLR6 and analyzed TLR6 expression in human blood cells and cell lines and its participation in ligand recognition. TLR6 was expressed, although at a lower level than TLR2, on the cell surface in monocytes, monocyte-derived iDCs, and neutrophils, but not on B, T, or NK cells. Confocal microscopic analysis revealed that TLR6 was colocalized with TLR2 at the plasma membrane of monocytes. Importantly, TLR2/6 signaling did not require endosomal maturation, and anti-TLR6 mAb inhibited cytokine production in monocytes and iDCs stimulated with synthetic macrophage-activating lipopeptide-2 or peptidoglycan, indicating that TLR6 recognized diacylated lipopeptide and peptidoglycan at the cell surface. In addition, TLR2 mutants C30S and C36S (Cys(30) and Cys(36) in TLR2 were substituted with Ser), which were expressed intracellularly in HEK293 cells, failed to induce NF-kappaB activation upon macrophage-activating lipopeptide-2 stimulation even in the presence of TLR6. Thus, coexpression of TLR2 and TLR6 at the cell surface is crucial for recognition of diacylated lipopeptide and peptidoglycan and subsequent cellular activation in human cells.

Inhibition of murine osteosarcoma cell proliferation by glucocorticoid.

The effects of glucocorticoid (GC) on the proliferation of Dunn Osteosarcoma (OS) cells were examined under in vitro culture conditions. Dexamethasone (Dex) inhibited the proliferation of Dunn OS cells in a dose-dependent manner, while the addition of anti-GC, RU486, to the culture medium in part recovered Dex-induced growth inhibition. The number of maximum binding sites (Bmax) and the dissociation constant (Kd) value of glucocorticoid receptor (GR) in Dunn OS cells were 19,560 sites/cell and 5.2 +/- 0.8 nM, respectively. RU486 competed with labeled Dex against GR at a concentration of 10(-6) M. Western blot analysis of [3H]Dex-mesylate-labeled cell homogenate and immunohistochemical staining against GR further confirmed the presence of GR. Dex treatment of Dunn OS cells resulted in apoptosis with the characteristic internucleosomal DNA cleavage shown by the DNA ladder pattern in agarose gel electrophoresis. These data demonstrate that GC inhibits the proliferation of Dunn OS cells via GR, for which one possible mechanism in vitro is induction of apoptosis.