Yoji Murayama

A Proposed Model Linking Inflammation to Obesity, Diabetes, and Periodontal Infections

BACKGROUND Obesity is an important risk factor for diabetes, cardiovascular disease, and periodontal disease. Adipocytes appear to secrete proinflammatory cytokines which may be the molecules linking the pathogenesis of these diseases. We evaluated the relationship between obesity, periodontal disease, and diabetes mellitus insulin resistance as well as the plasma levels of tumor necrosis factor alpha (TNFα) and its soluble receptors (sTNFα) to assess the relationship of inflammation to obesity, diabetes, and periodontal infections. METHODS The relationship between periodontal disease, obesity, and insulin resistance was examined in the Third National Health and Nutrition Examination Survey (NHANES III). In a population of 12,367 non-diabetic subjects, the variable body mass index (BMI) was used as an assessment of obesity and periodontal disease was assessed by mean clinical attachment loss. The plasma levels of TNFα and sTNFα were assessed in subsets of 1,221 adults from Erie County, New York, who represented the highest and lowest quartile of BMI. These subjects had extensive periodontal and medical evaluations. RESULTS In the NHANES III portion of the study, BMI was positively related to severity of periodontal attachment loss (P <0.001). Weighted multiple logistic regressions showed that this relationship is likely mediated by insulin resistance, since overweight individuals (with BMI ≥27 kg/m2 ) with high levels of insulin resistance (IR) exhibited an odds ratio of 1.48 (95% confidence interval 1.13 - 1.93) for severe periodontal disease as compared to overweight subjects with low IR. In the Erie County adult population, the highest levels of TNFα and sTNFα receptors were found in those individuals in the highest quartile of BMI. A positive correlation of TNFα levels with periodontal disease was found only in those in the lowest quartile of BMI. CONCLUSIONS Obesity is a significant predictor of periodontal disease and insulin resistance appears to mediate this relationship. Furthermore, obesity is associated with high plasma levels of TNFα and its soluble receptors, which in turn may lead to a hyperinflammatory state increasing the risk for periodontal disease and also accounting in part for insulin resistance. Further studies of the molecular basis of insulin resistance and its relationship to diabetes, periodontal disease, and obesity are necessary to fully test the hypothesis that adipocyte production of proinflammatory cytokines is a pathogenic factor linking obesity to diabetes and periodontal infections.

Serum Immunoglobulin G Antibody To Periodontal Bacteria

The purpose of this study was to assess the serum antibody levels to periodontal bacteria in patients with periodontal disease, and to explore the diagnostic uses of the serum antibody assessment and its potential as a therapeutic guide. One hundred twenty-nine patients were clinically examined for the type and extent of periodontal destruction and serum IgG antibody levels to Actinobacillus actinomycetemcomitans (Aa), Actinomyces israelii (Ai), A. viscosus (Av), Bacteroides asaccharolyticus (Ba), B. corporis (Bc), B. denticola (Bd), B. gingivalis (Bg), B. intermedius (Bi), B. loescheii (BI), Capnocytophaga gingivalis (Cg), C. ochracea (Co), and Fusobacterium nucleatum (Fn). Clinical and serological data were subjected to correlation analyses. A small group of patients was monitored during the progress of periodontal treatments. The IgG antibody levels were assessed with an enzyme-linked immunosorbent assay (ELISA). Significantly elevated IgG antibody levels were manifested to Aa, Ai, Bg, and Fn in all forms of periodontal disease, additionally to Cg and Co in juvenile periodontitis, and to Bi in adult periodontitis. There were some correlations between a few clinical parameters and the antibody levels. Successful periodontal treatment significantly decreased the antibody levels to all of the micro-organisms; however, during periodontal treatment, there were no marked differences between pre- and post-treatment levels. The antibody reactivities to the periodontopathic micro-organisms may be of diagnostic and predictive value in patients.

Molecular characterization of low-molecular-weight component protein, Flp, in Actinobacillus actinomycetemcomitans fimbriae.

Fimbriae preparation from Actinobacillus actinomycetemcomitans was found to contain an abundant low‐molecular‐weight protein (termed Flp) with an apparent molecular mass of approximately 6.5 kDa, in addition to a small amount of 54‐kDa protein. Immunogold electron microscopy localized the Flp protein at the bacterial fimbriae but not at the cell surface. The DNA fragment including the flp gene was cloned from A. actinomycetemcomitans 304‐a and its nucleotide sequence was determined. An open reading frame of the flp gene was composed of 225 bp encoding a protein of 75 amino acids. Comparison of the translated amino acid sequence with the sequence of native Flp determined by Edman degradation indicated that the N‐terminal part of 26 amino acids is leader peptide. The N‐terminal sequence of mature Flp exhibited some similarity to type‐IV pilin. Furthermore, the processing site of premature Flp is also similar to that of type‐IV prepilin, and a gene encoding a protein homologous to type‐IV prepilin‐like protein leader peptidase was found downstream of the flp gene. These findings indicate that Flp is the major component protein of A. actinomycetemcomitans fimbriae.

Effect of connective tissue growth factor (CCN2/CTGF) on proliferation and differentiation of mouse periodontal ligament-derived cells

BackgroundCCN2/CTGF is known to be involved in tooth germ development and periodontal tissue remodeling, as well as in mesenchymal tissue development and regeneration. In this present study, we investigated the roles of CCN2/CTGF in the proliferation and differentiation of periodontal ligament cells (murine periodontal ligament-derived cell line: MPL) in vitro.ResultsIn cell cultures of MPL, the mRNA expression of the CCN2/CTGF gene was stronger in sparse cultures than in confluent ones and was significantly enhanced by TGF-β. The addition of recombinant CCN2/CTGF (rCCN2) to MPL cultures stimulated DNA synthesis and cell growth in a dose-dependent manner. Moreover, rCCN2 addition also enhanced the mRNA expression of alkaline phosphatase (ALPase), type I collagen, and periostin, the latter of which is considered to be a specific marker of the periosteum and periodontium; whereas it showed little effect on the mRNA expression of typical osteoblastic markers, e.g., osteopontin and osteocalcin. Finally, rCCN2/CTGF also stimulated ALPase activity and collagen synthesis.ConclusionThese results taken together suggest important roles of CCN2/CTGF in the development and regeneration of periodontal tissue including the periodontal ligament.

A microbiological and immunological study of endodontic-periodontic lesions

The microflora and humoral immune response in tissue from the periodontal pockets and root canals of five teeth with endodontic-periodontic lesions were examined. We found more microbes in the periodontal pockets than in the root canals. The flora in the periodontal pockets was dominated by rods and motile organisms, whereas that in the root canals was largely rods and cocci. We detected no spirochetes in the root canals. The cultivable microflora in the periodontal pockets comprised a high number of different species of bacteria, whereas those in the root canals included only a small number of species. There was no correlation between microbial isolates and antibody titer in the apical tissues or periodontal pockets. We conclude from these studies that the microflora of infected root canals is simple and limited, and that the local humoral immune response does not seem to affect the pathogenesis of disease directly.

Cathepsin-L, a Key Molecule in the Pathogenesis of Drug-Induced and I-Cell Disease-Mediated Gingival Overgrowth: A Study with Cathepsin-L-Deficient Mice

Drug-induced gingival overgrowth, the chronic side effect of calcium antagonists, is frequently seen due to the increase in patients with hypertension, although the etiology of the disease is largely unknown. I-cell disease, which accompanies gingival overgrowth, is characterized by a deficiency in UDP-N-acetyl-glucosamine and is classified as one of the lysosomal storage diseases. Here, we hypothesized that a common mechanism may underlie the etiology of gingival overgrowth seen in patients treated with calcium antagonist and in patients with I-cell disease. A calcium antagonist, nifedipine, specifically suppressed cathepsin-L activity and mRNA expression, but not that of cathepsin-B in cultured gingival fibroblasts. The activity of cathepsin-L was suppressed up to 50% at 24 hours after treatment of the cells with the reagent. The selective suppression of cathepsin-L activity appeared not to be dependent on Ca(2+), since treatment of the cells with thapsigargin suppressed both cathepsin-B and -L activity. Mice deficient in the cathepsin-L gene manifested enlarged gingivae. Histological observation of the gingivae demonstrated typical features of acanthosis, a phenotype very similar to that of experimentally induced gingival overgrowth. Since cathepsin-L deficiency was reported to be associated with thickening of the skin, impaired cathepsin-L activity may play a key role in the establishment of skin and gingival abnormalities seen in I-cell disease. In addition, reduced cathepsin-L activity may play an important role in inducing drug-induced gingival overgrowth.

Impairment of Gingival Fibroblast Adherence by IL-6/sIL-6R

Interleukin-6 (IL-6) binds to human gingival fibroblasts (HGF) in the presence of a soluble form of IL-6 receptor (sIL-6R). We investigated the effects of IL-6 on the functions of HGF in the presence of sIL-6R. HGF changed their morphology from spindle-shaped to round, and detached from the culture dish by stimulation with IL-6/sIL-6R. In this condition, a signal transducer gpl30 and a transcription factor Stat3 were phosphorylated, resulting in activation of transcription factors Stat3 and C/EBPβ. Cytoskeletal β-actin and adhesion molecule integrin-a5, a subunit of α5β1 integrin (VLA-5), were found to possess potential binding domains for these transcription factors in their promoters. Accumulation of (3-actin and integrin-a5 mRNA decreased, contrary to the expectation of the induction of gene transcription. Furthermore, the decrease in their mRNAs was associated with reduced expression of both actin and VLA-5 proteins. These results suggest that the expression of VLA-5 and actin was down-regulated in HGF through an IL-6 signaling pathway, resulting in impairment of HGF adherence.

Induction of Intracellular Interleukin-1 β Signals via Type II Interleukin-1 Receptor in Human Gingival Fibroblasts

The type II interleukin-1 receptor (IL-1RII) has been thought to be incapable of transducing signals to cells because of its short intracellular domain, while type I IL-1 receptor (IL-1RI) does transduce signals. Since over-expression of IL-1RII has been demonstrated to inhibit cytokine production in the fibroblastic cell line, it has been proposed to use IL-1RII to prevent IL-1-induced inflammation in connective tissue. In this study, trace amounts of IL-1RII mRNA expression were detected in human gingival fibroblasts (HGFs), which are affected by cytokines in inflammatory periodontal disease. Cloning of the cDNA encoding IL-1RII expressed in HGFs revealed 3 amino acid substitutions in the extracellular domain, when compared with the 408 residues predicted from human B-cells. Over-expression of IL-1RII on HGFs by gene transfer down-regulated the expression of IL-1β mRNA and IL-6 mRNA in response to IL-1β stimulation, while the expression of IL-8 mRNA was not affected. In the IL-1RII-transfected HGFs, phosphorylation of 25-and 74-kDa proteins was up-regulated upon IL-1β stimulation in the transfected HGFs. The phosphorylation of these proteins was suppressed by the addition of a neutralizing antibody against IL-1RII. These results suggest that the IL-1RII may regulate HGFs expression of cytokine mRNA upon IL-1β stimulation, possibly by altering the IL-1RI-dependent signals.

Cell Surface-Associated Enolase in Actinobacillus actinomycetemcomitans

Cell surface‐associated materials of Actinobacillus actinomycetemcomitans were extracted by a short incubation of the cell suspension in a Tris‐buffered saline in the presence and absence of a restriction enzyme, EcoRI. The supernatants (which we termed EcoRI extract and surface extract, respectively) contained a number of extracellularly released proteins. Of these proteins, four major proteins were identified by N‐terminal sequencing to be the 34 and 39 kDa outer membrane proteins, the GroEL‐like protein, and a 47 kDa protein homologous to Haemophilus influenzae enolase. Enolase activity was found in the extracts and its relative amount of activity in the EcoRI extract from a culture of the mid‐exponential growth phase was estimated as 5.7% of total enzyme activity. In contrast, the relative amount of activity of another cytosolic enzyme, lactate dehydrogenase, was extremely low in the extracts and also in the culture supernatant. These results suggest the external localization of enolase in this bacterium.

Tumor Necrosis Factor-α (TNF-α)-Induced and Interleukin-1β (IL-1β)-Induced Shedding of TNF Receptors from Gingival Fibroblasts

Tumor necrosis factor-α (TNF-α) exerts its functions by binding two different receptors (TNFR55 and TNFR75). Both TNFR55 and TNFR75 exist in cell-associated and soluble forms. Soluble TNF receptors (sTNFR), sTNFR55 and sTNFR75, are proteolytically shed upon inflammatory stimuli and then modulate various TNF-α bioactivities. As human gingival fibroblasts (HGF) can be potential targets for TNF-α in inflamed gingiva, we hypothesized that HGF partially modulate the cellular responses to TNF-α by regulating their own TNFR. In this study, the kinetics of expression of cell-associated and soluble forms of both receptors from cultured HGF in response to proinflammatory cytokines TNF-α and interleukin-1β (IL-1β) were investigated in vitro. Both TNF-α and IL-1β upregulated the gene expression of TNFR75 and did not affect that of TNFR55. TNF-α and IL-1β decreased binding of [125I]TNF-α to HGF. Moreover, TNF-α and IL-1β upregulated the release of sTNFR75 from HGF but not that of sTNFR55. These results suggest that HG...