Detection of a fibroblast proliferation inhibitory factor from Capnocytophaga sputigena

Capnocytophaga granulosa and Capnocytophaga haemolytica: novel species in subgingival plaque

BACKGROUND

The oral cavity accommodates one of the most diverse microfloras in the human body. Knowledge of this microflora, and of the periodontal microflora in particular, proves crucial towards an understanding of the bacterial-host interactions which lead to the development of infectious inflammatory periodontal diseases. Capnocytophaga species have been implicated as putative periodontal pathogens. To date, only 3 members of this genus (C. gingivalis, C. ochracea and C. sputigena) have been isolated from subgingival plaque.

AIM

This communication reports the isolation of 2 recently-speciated strains, namely C. granulosa and C. haemolytica, from subgingival plaque collected from adult periodontitis patients.

MATERIAL AND METHODS

Subgingival plaque was collected from 29 patients with chronic adult periodontitis. Plaque samples were inoculated onto fastidious anaerobe agar and incubated anaerobically for 5 days. Routine identification of clinical isolates was performed by 16S rRNA PCR-RFLP analysis, using Cfo I as restriction enzyme and corroborated by 16S rRNA gene sequencing.

RESULTS

16 of 29 patients (55%) tested positive for either C. granulosa and or C. haemolytica. A total of 70 isolates (63 C. granulosa and 7 C. haemolytica) were cultivated from subgingival plaque. 15 (51%) patients tested positive for C. granulosa, and 3 (10%) patients tested positive for C. haemolytica.

CONCLUSION

This is the 1st report which recounts the presence of C. granulosa and C. haemolytica in subgingival plaque. Further research is required to establish the relative proportions of these species subgingivally in health and disease.

Evidence for genetic control of changes in f-actin polymerization caused by pathogenic microorganisms: in vitro assessment using gingival fibroblasts from human twins

Attachment to and migration upon a substratum, as well as other functions of connective tissue cells, are regulated mainly by cytoplasmic structural proteins, particularly filamentous actin (f-actin). Pathogenic microorganisms exert negative effects on cytoskeletal proteins. In the present study, normal gingival fibroblasts from 10 sets of human twins (6 fraternal, DZ; 4 identical, MZ) were exposed to soluble extracts from Porphyromonas gingivalis or Fusobacterium nucleatum, then f-actin was stained using FITC-labeled phalloidin. Cells were examined under fluorescence, and a computer-assisted image analyzer quantitated f-actin polymerization as fluorescence intensity on a per-cell basis. Intraclass correlation coefficients for f-actin in MZ/MZ vis-a-vis DZ/DZ paired cell cultures were determined to assess the possible heritability of responses to the microorganism preparations. F-actin labeling was significantly different between control cultures and those exposed to the extracts. Both F. nucleatum and P. gingivalis effected f-actin and fibroblast morphology. When the data were adjusted for gender and age effects, and for differences in control f-actin levels, fibroblasts from MZ twin pairs were moderately similar in both absolute and relative responses to bacterial challenges; cells from DZ twins showed little similarity when response was measured on the absolute scale, and moderate similarity using the relative scale.

Serum antibody responses in human periodontitis to cellular components of Capnocytophaga

Serum levels of IgM, IgG and IgG-antibody subclasses directed against cell envelopes, lipopolysaccharides and cytoplasmic fractions from Capnocytophaga sputigena, C. gingivalis and C. ochracea were examined in age-, race- and sex-matched periodontally healthy (n = 25) subjects and subjects with adult periodontitis (n = 25). The envelopes and cytoplasmic fractions were obtained by ballistic disintegration of the cells and ultracentrifugation. Cell envelopes were treated with DNase, RNase and lysozyme. Lipopolysaccharides were obtained by hot phenol-water extraction and treated with DNase and RNase. The relative levels of the antibodies in response to the cell fractions were measured by the streptavidinbiotin micro enzyme-linked immunosorbent assay. Both groups showed IgM and IgG antibodies to each fraction of the three Capnocytophaga species, but the frequency of positive IgG subclass responses varied. The IgG4 responses were lower than the other subclasses. There were no significant differences between the IgM antibody levels of the two groups. However, the adult periodontitis group had significantly lower IgG antibody titres to the cell envelopes and cytoplasmic fractions of C. gingivalis and C. ochracea, and lipopolysaccharide of C. gingivalis. These results were reflected in the depressed levels of IgG1 and/or IgG2 to these cellular fractions from the same bacterial species. The adult periodontitis group also showed a lower level of IgG1 to the cytoplasmic fractions of C. sputigena without any depression in the total IgG antibody level. There were no significant differences between the groups in IgG3 and IgG4 antibody levels to any of the cellular fractions.(ABSTRACT TRUNCATED AT 250 WORDS)

Isolation and characterization of enzymes hydrolyzing chymotrypsin synthetic substrate (Enzyme I) and trypsin synthetic substrate (Enzyme II) from the envelope of Capnocytophaga gingivalis

Enzymes hydrolyzing chymotrypsin synthetic substrate and trypsin synthetic substrate, referred to as Enzyme I and Enzyme II, respectively, were found in the envelope fraction of Capnocytophaga gingivalis (ATCC 33624). Detergent extraction of both enzymes were purified by gel filtration, ion exchange chromatography, and affinity chromatography. The Enzyme I was a serine-containing metallo enzyme with a molecular mass of 77 kDa. The molecular mass of the Enzyme II was 83 kDa, and it was inhibited by tosyl-L-lysine chloromethyl ketone and leupeptin, and thus may be related to trypsin.

The comparative cytotoxicity of periodontal bacteria

The direct cytotoxicity of sonic extracts (SE) from nine periodontal bacteria for human gingival fibroblasts (HGF) was compared. Equivalent dosages (in terms of protein concentration) of SE were used to challenge HGF cultures. The cytotoxic potential of each SE was assessed by its ability to (1) inhibit HGF proliferation, as measured by direct cell counts; (2) inhibit 3H-thymidine incorporation in HGF cultures; or (3) cause morphological alterations of the cells in challenged cultures. The highest concentration (500 micrograms SE protein/ml) of any of the SEs used to challenge the cells was found to be markedly inhibitory to the HGFs by all three of the criteria of cytotoxicity. At the lowest dosage tested (50 micrograms SE protein/ml); only SE from Actinobacillus actinomycetemcomitans, Bacteroides gingivalis, and Fusobacterium nucleatum caused a significant effect (greater than 90% inhibition or overt morphological abnormalities) in the HGFs as determined by any of the criteria employed. SE from Capnocytophaga sputigena, Eikenella corrodens, or Wolinella recta also inhibited cell proliferation and thymidine incorporation at this dosage; however, the degree of inhibition (5-50%) was consistently, clearly less than that of the first group of three organisms named above. The SE of the three other organisms tested (Actinomyces odontolyticus, Bacteroides intermedius, and Streptococcus sanguis) had little or no effect (0-10% inhibition) at this concentration. The data suggest that the outcome of the interaction between bacterial components and normal resident cells of the periodontium is, at least in part, a function of the bacterial species.

Effect of lipopolysaccharide on proteoglycan synthesis by adult human gingival fibroblasts in vitro

The effect of lipopolysaccharide preparations from Salmonella enteritidis, Bacteroides gingivalis, and Actinobacillus actinomycetemcomitans on human gingival fibroblasts was studied. Lipopolysaccharide from all sources inhibited fibroblast proliferation in the concentration range of 0.5 to 50 micrograms/ml, with the lipopolysaccharide from A. actinomycetemcomitans having the strongest inhibitory effect. Assessment of the effect of lipopolysaccharide on gingival fibroblast metabolism indicated both total protein and proteoglycan synthesis to be inhibited with increasing concentrations of lipopolysaccharide. As for the antiproliferative effect, lipopolysaccharide from A. actinomycetemcomitans had the greatest inhibitory effect on cell synthetic activity. This inhibitory effect was determined by pulse-chase experiments to be a true depression in synthesis. Furthermore, the effect was independent of lipopolysaccharide-induced changes in cell proliferation and prostaglandin synthesis. This study confirmed the toxic effect of lipopolysaccharide on fibroblasts and, in particular, indicated that various lipopolysaccharide preparations vary in their potency to influence cell proliferation and extracellular matrix synthesis.

Characterization and cross-reactivity of rabbit antisera to plaque toxins

The effects of heat labile, high molecular weight water-soluble toxins from bacterial plaque on HL60 promyelocytic cells were examined. On gel filtration, four inhibitors of HL60 cell growth and two inhibitors of HeLa cell growth (PT1, PT2) were detected. The first and third HL60 cell inhibitors corresponded to the two HeLa cell inhibitors. The last eluted HL60 cell inhibitor (plaque leukotoxin, PL) did not inhibit HeLa cell growth. Anti-PT2 antibodies reduced the activity of enriched PT2 by 20-50%, but all other antisera tested exhibited no effect. Anti-PL antibodies detected antigens from Actinobacillus actinomycetemcomitans, although anti-A. actinomycetemcomitans and anti-Capnocytophaga sputigena antibodies did not react with plaque extract. These findings suggest that the plaque toxins examined in this study were probably not derived from these two bacteria.

Inhibition of gingival fibroblast growth by Bacteroides gingivalis

Human gingival fibroblasts were exposed in culture to cell extracts of different black-pigmented Bacteroides species, and their growth was monitored by determining thymidine uptake and counting cells. Of the Bacteroides species tested (B. gingivalis, B. asaccharolyticus, and B. intermedius), B. gingivalis gave the extract with the strongest inhibitory effect on fibroblast thymidine uptake. Linear inhibition reaching 80% of the control level was obtained with a dose of 100 micrograms of B. gingivalis extract protein per ml. The effect of B. asaccharolyticus resembled that of B. gingivalis, but even at the highest dose tested B. intermedius had only a slight inhibitory effect. When fibroblasts were counted after 2- and 4-day exposures to B. gingivalis extracts, a clear depression in the number of fibroblasts was found. The effects of extracts obtained from early and late growth phases of B. gingivalis cultures were similar. A fraction of B. gingivalis consisting essentially of lipopolysaccharides (LPSs) was obtained by degrading the extract proteins with proteinase K. Silver staining of polyacrylamide gels revealed a LPS pattern with a molecular mass ranging from 37 to 60 kilodaltons. This LPS-rich fraction caused inhibition of thymidine uptake by gingival fibroblasts similar to that caused by the native extract alone. Thus, the inhibition of gingival fibroblast growth by B. gingivalis appeared to be LPS mediated. This inhibitory effect of B. gingivalis on oral fibroblast growth may be a virulence factor of this bacterium.

Effects of extracellular products of a presumed gingival pathogen, the bacterium Peptostreptococcus 84H14S, on cultured human fibroblasts and HeLa cells

Culture fluids from this microorganism, fibroblasts and HeLa cells contained potent factors which inhibited thymidine uptake in HeLa cells. The outcome of heating the culture fluid and fractionating it by gel filtration suggested that this was not due to bacterial hyaluronidase activity. Purified peptostreptococcal hyaluronidase and several commercially-available mucopolysaccharidases also did not inhibit thymidine uptake.

The role for butyrate and propionate in mediating HeLa-cells growth inhibition by human dental plaque fluid from adult periodontal disease

To determine to what extent propionate and butyrate, secreted in vitro by various oral bacteria, account for the growth-inhibiting activity of plaque fluid in gingivitis in the absence or presence of chronic periodontitis, the fluid phase of plaque from each of these disease forms was obtained by homogenizing the bacteria with 0.13 M NaCl, centrifuging the mixture and Millipore-filter-sterilizing the plaque-fluid-extract supernatant. Toxins were detected and measured by growth inhibition of HeLa cells grown in minimal Eagle medium supplemented with calf serum and antibiotics. Samples of butyrate, propionate or plaque-fluid extract were added and inhibition of growth was determined relative to control cultures. The toxins in each extract were characterized by their stability to heat, freeze-drying and elution on gel filtration. Butyrate and propionate contents were measured with a Hewlett-Packard 5880A gas chromatograph. The plaque-fluid extracts from each group had similar contents of butyrate, but most of the activity was due to heat-sensitive high mol. wt components. Butyrate and propionate accounted for only 5 to 15 per cent of the total activity. High mol. wt exotoxins, rather than butyrate or propionate, were the most prominent and freeze-drying-stable tissue-destructive agents in the plaque fluid from subjects with or without periodontitis.

Inhibition of [3H]-thymidine uptake in human gingival fibroblasts by extracts from human dental plaque, oral bacteria of the Streptococcus and Actinomyces species

Extracts from human dental plaque, Streptococcus mutans, Streptococcus salivarius, Streptococcus faecalis, Streptococcus sanguis, Actinomyces israelli and Actinomyces odontolyticus inhibited [3H]-thymidine uptake by primary human gingival fibroblast cell lines as previous work has shown in respect of HeLa cells. The results show that a variety of oral bacteria, not usually considered to be periodontal pathogens, elaborate factors that adversely affect fibroblasts.

Capnocytophaga ochracea infection: two cases and a review of the published work

Bacteria of the genus Capnocytophaga are recently recognised pathogens which may cause oral disease and subsequent septicaemia in the immunocompromised host. We present two cases of infection caused by Capnocytophaga ochracea; a soft tissue infection in an immunologically normal patient and an episode of septicaemia in a child with leukaemia. The microbiology, pathogenicity, and antimicrobial susceptibility of the genus capnocytophaga are reviewed.

Suppression of fibroblast proliferation by oral spirochetes

Soluble sonic extracts of several strains of Treponema denticola and Treponema vincentii were examined for their abilities to alter proliferation of both murine and human fibroblasts. We found that sonic extracts of all tested strains of T. denticola caused a dose-dependent inhibition of murine and human fibroblast proliferation when assessed by both DNA synthesis ([3H]thymidine incorporation) and direct cell counts. T. vincentii had only a minimal inhibitory effect at comparable doses. No inhibition was observed when sonic extracts were added simultaneously with [3H]thymidine, indicating that suppression was not due to the presence of excessive amounts of cold thymidine in the extract, nonspecific effects on thymidine utilization by the cells (transport and incorporation), or degradation of label. RNA ([3H]uridine incorporation) and protein ([3H]leucine incorporation) synthesis were similarly altered after exposure to the T. denticola sonic extracts. There was no effect on cell viability as measured by trypan blue exclusion. Inhibition could be reversed by extensive washing of the cells within the first few hours of exposure to sonic extracts. Preliminary characterization and purification indicated that the inhibitory factor(s) is not endotoxin since it is heat labile, and elutes in a single, well-defined peak on a Sephadex G-150 chromatography column corresponding to a molecular weight of approximately 50,000. Since oral spirochetes have been implicated in the pathogenesis of periodontal disorders, it is possible that they contribute to the disease process by inhibition of fibroblast growth and therefore may, at least in part, account for the loss of collagen seen in diseased tissue.

Septic arthritis involving Capnocytophaga ochracea

Septic arthritis of the knee developed in a 21-month-old child. The causative organism, isolated from two separate arthrocenteses, was identified as Capnocytophaga ochracea morphologically and by biochemical reactions. Previous human infections (bacteremias) have occurred in granulocytopenic hosts with concomitant oral pathology including periodontitis and gingivitis. No abnormalities of oral hygiene were present in this patient, and granulocyte numbers were normal or elevated. Eradication of the infection was accomplished with 8 weeks of antibiotic therapy combined with surgical drainage. Septic arthritis expands the spectrum of infections reported to be caused by Capnocytophaga spp.

The periodontal microflora of juvenile diabetics. Culture, immunofluorescence, and serum antibody studies

These studies demonstrate a unique constellation of organisms populating the subgingival area in periodontitis lesions of patients with juvenile or insulin-dependent diabetes mellitus (IDDM). The cultivable microflora was predominated by Capnocytophaga and anaerobic vibrios in the patients studied. In some patients, Actinobacillus actinomycetemcomitans were also found. This distinguishes the subgingival flora of IDDM patients suffering from periodontitis from that of patients with localized juvenile periodontitis (LJP), and that of adult periodontitis patients. In LJP most patients harbor both A actinomycetemcomitans and Capnocytophaga subgingivally; and in periodontitis lesions from nondiabetic adults, black-pigmented Bacteroides such as B gingivalis or B melaninogenicus subspecies intermedius are often found. Antibiotic susceptibility patterns suggest that penicillin or tetracycline or its analogs such as minocycline may be effective against the predominant cultivable microflora in periodontal lesions of IDDM patients; however, individual patients may harbor flora with significant resistance to these antibiotics.

Ultrastructural studies of the effect of human leukocyte extracts on periodontopathic bacteria

Human gingival crevicular exudate (GE) and leukocyte extracts (LE) were previously shown to be able to release the bulk of radioactivity from a variety of 14C-labeled oral bacteria. The present study demonstrates that the release of radiolabel by these enzymatic agents from two periodontopathic bacteria (Actinobacillus actinomycetemcomitans strain Y4 and Capnocytophaga sputigena strain 4) is accompanied by both cell wall and cytoplasmatic damage. The possible role of bacterial products released by lysosomal enzymes, present in the gingival crevice, is discussed.

Effect of human leukocyte extracts and gingival exudate on periodontopathic bacteria

The effect of leukocyte hydrolytic enzymes on periodontopathic bacteria was examined in vitro. A frozen and thawed extract of human peripheral blood leukocytes (LE) and human gingival crevicular exudate (GE) were shown to be able to cause the release of 50% of the radioactivity from a leukotoxic strain of Actinobacillus actinomycetemcomitans (Aa Y4), labeled by 14C. A nonleukotoxic strain (Aa 653) was shown to be more susceptible to both LE and GE, up to 68% of the total radioactivity was solubilized by LE at pH 7.4. Both bacterial strains were found to be resistant to the activity of lysozyme, but highly susceptible to lysolecithin and mixtures of lysolecithin and lysozyme or LE. Capnocytophaga sputigena strain 4 was also found to be partially susceptible to the effect of LE and GE. The possible role of leukocyte hydrolytic enzymes in bacteriolysis and release of bacterial products in relation to periodontal disease is discussed.

Cytotoxicity of the bacterium Actinobacillus actinomycetemcomitans extracts in human gingival fibroblasts

Filter-sterilized sonic extracts (SE) of strains of Actinobacillus actinomycetemcomitans were shown to inhibit the proliferation of human gingival fibroblasts in vitro. The inhibition was dose-dependent: a 50 per cent inhibitory dose of 2 micrograms protein/ml was found for A. actinomycetemcomitans strain Y4. The inhibitory activity could be neutralized by homologous antiserum and was heat inactivated by temperatures of 80 degrees C or greater. The fibroblast-inhibitory activity was present in SEs of both leukotoxic-producing and non-leukotoxic strains of A. actinomycetemcomitans, suggesting that a separate agent is responsible for leukotoxicity and fibroblast inhibition. A short (10 min) exposure of the fibroblasts to the A. actinomycetemcomitans SE was sufficient to inhibit irreversibly cell proliferation, provided that serum was present at the time that the cells were exposed to the SE. SE-challenged fibroblasts exhibited a marked decrease in the rate of DNA synthesis, but no inhibition of RNA or protein synthesis. Although the SE-treated cells did not proliferate, they appeared to remain intact and viable; and displayed no gross morphological alterations.

Inhibition of fibroblast proliferation by Actinobacillus actinomycetemcomitans

We have examined soluble sonic extracts of Actinobacillus actinomycetemcomitans for their ability to alter human and murine fibroblast proliferation. We found that extracts of all A. actinomycetemcomitans strains examined (both leukotoxic and nonleukotoxic) caused a dose-dependent inhibition of both murine and human fibroblast proliferation as assessed by DNA synthesis ([3H]thymidine incorporation). Addition of sonic extract simultaneously with [3H]thymidine had no effect on incorporation, indicating that suppression was not due to the presence of excessive amounts of cold thymidine. Inhibition of DNA synthesis was also paralleled by decreased RNA synthesis ([3H]uridine incorporation) and by a decrease in cell growth as assessed by direct cell counts; there was no effect on cell viability. The suppressive factor(s) is heat labile; preliminary purification and characterization studies indicate that it is a distinct and separate moiety from other A. actinomycetemcomitans mediators previously reported, including leukotoxin, immune suppressive factor, and endotoxin. Although it is not clear how A. actinomycetemcomitans acts to cause disease, we propose that one aspect of the pathogenicity of this organism rests in its ability to inhibit fibroblast growth, which in turn could contribute to the collagen loss associated with certain forms of periodontal disease, in particular juvenile periodontitis.

Immunological activities of Capnocytophaga cellular components

Whole cells of a clinical isolate (strain S-3) of the genus Capnocytophaga were divided into cell envelope (CE) and cytoplasm (CP) fractions by mechanical disintegration followed by differential centrifugation, and a part of the CE fraction was further fractionated by sodium dodecyl sulfate (SDS) treatment into the peptidoglycan and SDS-supernatant fractions. The other part of the CE was extracted with butanol-water or hot phenol-water to isolate butanol-lipopolysaccharide and phenol-lipopolysaccharide, respectively. All of the test fractions except CP exhibited multifold immunomodulating activities, namely, the adjuvant activities to cellular as well as humoral immune responses against ovalbumin in guinea pigs, the mitogenicity on splenocytes of guinea pigs and BALB/c mice (but not on their thymocytes), the stimulation of guinea pig peritoneal macrophages (in terms of increased glucosamine uptake), and the activation of the human complement system through alternative as well as classical pathways. In addition, the test fractions other than the CP evoked dermatoxic reactions on rabbit skin with characteristic variations among them. The immunomodulating activities of SDS-supernatant were noteworthy in view of the fact that this fraction was essentially free of muramic acid and diaminopimelic acid and did not cause the gelation of horseshoe crab amoebocyte lysate except when it was used at the very high dose, suggesting that there was practically no contamination by peptidoglycans and lipopolysaccharides in the SDS-supernatant.

API ZYM system for identification of Bacteroides spp., Capnocytophaga spp., and spirochetes of oral origin

A total of 80 oral strains of Bacteroides gingivalis, B. asaccharolyticus, B. melaninogenicus subsp. intermedius, B. melaninogenicus subsp. melaninogenicus, Capnocytophaga, Treponema denticola, and T. vincentii were characterized with the API ZYM system for 19 enzyme activities. Comparison of anaerobic and aerobic incubation with nine reference strains of these organisms showed no important differences. The key differential tests for black-pigmented Bacteroides strains and treponemes of oral origin were trypsin, alpha-glucosidase, and N-acetyl-beta-glucosaminidase. All Capnocytophaga strains produced distinctive aminopeptidase activities but varied in their glycosidic capabilities. The presence of a trypsin-like activity in B. gingivalis, T. denticola, and a group of Capnocytophaga strains may contribute to tissue destruction in periodontal disease.

Biological and chemical characterization of endotoxin from Capnocytophaga sputigena

An endotoxin was isolated from Capnocytophaga sputigena strain 4 by a modification of the hot phenol-water method. The extraction procedure yielded a lipopolysaccharide which accounted for approximately 1.5% of the dry weight of the cells. The material was composed of 18.6% lipid (as C(15) fatty acid), 46.5% neutral sugar including 9.6% hexose, 18.3% 6-deoxy sugar, 1.0% 2-keto-3-deoxy sugar, and 4.8% heptose. Hexosamine, protein, and phosphorus were found in quantities amounting to 9.0, 2.9, and 2.0% of the dry weight, respectively. No pentose or nucleic acid was detected. Acid hydrolysis resulted in the release of the constituent sugars and the formation of an insoluble precipitate. The lipopolysaccharide was tested for numerous biological activities characteristic of endotoxins. The pyrogenicity was relatively low; the fever index 40 was 17 mug, and 10 mug was required to give the characteristic biphasic fever response. The toxicity of the extract was very low, with a 50% chicken embryo lethal dose of 15.6 mug and a 50% mouse embryo lethal dose of greater than 8 mg. Similarly, the C. sputigena endotoxin had modest effects on leukocytes when compared with endotoxin standards from other organisms. The extract exhibited little or no mitogenicity when tested on mouse spleen lymphocytes. It was not toxic to human peripheral polymorphonuclear leukocytes and caused the release of only a small (13%) portion of lysosomal enzymes. Although the C. sputigena lipopolysaccharide caused significant activation of mouse peritoneal macrophages, the dose required was twice that of an Escherichia coli endotoxic standard. However, the Limulus amoebocyte lysate clotting activity of the lipopolysaccharide was comparable to that of an Serratia marcescens lipopolysaccharide standard, and passive hemagglutination tests revealed that 1 mug of the lipopolysaccharide was capable of sensitizing 1 ml of a 2% sheep erythrocyte suspension for agglutination with an antiserum prepared against C. sputigena whole cells.