The influence of apical periodontitis on the concentration of inflammatory mediators in peripheral blood plasma and the metagenomic profiling of endodontic infections: Study design and protocol

Increased systemic inflammation has been identified in presence of oral disease, specifically endodontic disease. It is important to investigate whether treatment of the oral disease ameliorates systemic inflammation. Furthermore, there is no information about the extent to which different microorganisms may trigger inflammatory response.

Objectives

Primarily (i) to compare the plasma concentrations of inflammatory mediators of apical periodontitis (AP) subjects to controls, (ii) to evaluate whether elimination of the endodontic infection reduces systemic inflammation (iii) to investigate the microbiome of root canal infections. Secondarily i) to correlate the inflammatory mediator data with the microbiome data to investigate whether the type of infection influences the type and severity of the inflammatory condition ii) to examine patterns in the inflammatory mediator data before and after tooth extraction in order to establish a biomarker signature of AP/oral disease.

This is a multi-centre prospective case-control intervention study. The cohort will consist of 30 healthy human volunteers with one or two teeth with a root-tip inflammation and 30 matched healthy controls. Peripheral blood will be drawn at 6 time points, 3 before and 3 after the extraction of the tooth with apical periodontitis. The teeth will be pulverized, DNA extraction and sequencing will be performed.

This study aims to compare the concentration of inflammatory blood plasma proteins in between AP-subjects and controls at different time points before and after the tooth extraction in a systematic and complete way. Additionally the composition of the root canal microbiome in association with the inflammatory response of the host will be assessed.

Stem cell-like populations and immunoregulatory molecules in periodontal granulation tissue

BACKGROUND AND OBJECTIVES

Determine the presence of mesenchymal stem cells (MSCs) in healthy periodontal tissue and periodontal granulation tissue (GT) and explore associations between immuno-regulatory molecules and selected subgingival microorganisms.

MATERIAL AND METHODS

Mesenchymal stem cells were isolated, propagated and characterised by flow cytometry from a region of healthy gingival tissue and inflamed GT of 10 systemically healthy non-smokers with chronic periodontitis. Tissue levels of immunoregulatory molecules were determined by qPCR and Gingival Crevicular Fluid (GCF) levels by ELISA. Subgingival plaque levels of periodontal pathogens were determined by qPCR RESULTS: Cells with MSC-properties were isolated from both inflamed GT and healthy gingival (G) tissue. A pro-inflammatory process predominated in GT which was partly reflected in GCF and putative periodontal pathogens were higher at diseased sites. However, there was no significant difference in surface levels of mesenchymal (CD90, CD73, CD146, CD271, STRO-1), endothelial (CD105, CD106), hematopoietic (CD34, CD45) and embryonic (SSEA-4) stem cell markers between MSCs isolated from GT and G tissue.

CONCLUSION

Periodontal lesions, albeit inflamed, retain healing potential as inferred by the presence of MSC-like cells with similar immunophenotypic characteristics to those found in healthy periodontal tissue. Therefore, there might be merits for healing in preserving sufficient GT in-situ during periodontal surgery.

Diamond burs versus curettes in root planing: a randomized clinical trial

BACKGROUND

This study compares diamond burs and curettes by clinical, microbiological, biochemical and scanning electron microscopic parameters and treatment time data in the non-surgical periodontal treatment of patients with chronic periodontitis.

METHODS

Two quadrants of each of the 12 patients received root planing with diamond burs, whereas the other two quadrants were treated with curettes. Clinical periodontal measurements were recorded at baseline and then 1, 3 and 6 months after completion of non-surgical periodontal treatment. Subgingival plaque and gingival crevicular fluid samples were obtained at baseline and 1-month control. Twenty-one hopeless teeth received root planing with diamond burs or curettes or no treatment and then extracted for microscopic evaluations.

RESULTS

Clinical periodontal parameters improved similarly with both treatment modalities. Microbiological analyses revealed similar findings for the bacterial load (16S gene copy numbers) and ratio of each bacterium to the total bacterial count at baseline and 1-month control. Cytokine levels in the gingival crevicular fluid samples exhibited differences between the two treatments. Scanning electron microscopic analyses indicated that diamond burs were better in terms of calculus removal and loss of tooth substance indices but roughness index values were better for curettes.

CONCLUSIONS

Diamond burs provide findings comparable with curettes in root planing.

Gingival Toll-like receptor and cytokine messenger RNA levels in equine periodontitis and oral health

REASONS FOR PERFORMING STUDY

Equine periodontitis is a common and painful condition. However, the disease often goes unnoticed by owners and is thus a major welfare concern. The aetiopathogenesis of the condition remains poorly understood and has been investigated in few studies. The innate immune system is known to play an important role in human periodontitis, but its role in equine periodontitis has not been examined.

OBJECTIVES

To quantify the messenger (m)RNA levels of Toll-like receptors (TLRs) and cytokines in gingival tissue from orally healthy horses and those affected by periodontitis.

STUDY DESIGN

Observational study.

METHODS

Gingival tissue samples were taken post-mortem from 13 horses with no clinical signs of oral disease and 20 horses with periodontitis. mRNA levels of TLR2, TLR4 and TLR9 and cytokines interleukin-1β (IL-1β), tumour necrosis factor-α (TNF-α), IL-4, IL-6, IL-10, IL-12, IL-17 and interferon-γ (IFN-γ) were determined using quantitative real-time PCR. The statistical significance of results was assessed using appropriate t tests.

RESULTS

mRNA levels of all TLRs and cytokines were upregulated in equine periodontitis. Significant increases in mRNA levels of TLR2, TLR9, IL-4, IL-10, IL-12 (P≤0.05) and IFN-γ (P≤0.01) were observed for both unweighted and age-weighted analyses of diseased gingival tissue samples compared with healthy gingival samples. In comparisons of samples of periodontitis lesions with healthy gingival control samples from the same horse, significant increases in mRNA levels of TLR4, TLR9, IL-10, IFN-γ (P≤0.05), TLR2, IL-1β and IL-12p35 (P≤0.01) were observed.

CONCLUSIONS

This study has provided an initial insight into the involvement of the immune system in equine periodontitis. Increased mRNA levels of TLR2, TLR4 and TLR9 indicate substantial microbial challenge in diseased gingival tissue. A mixed Th1/Th2/Th17 cytokine response is produced in equine periodontitis. Further studies are required to more fully characterise the role of the innate immune system in this disease.

The epithelial cell response to health and disease associated oral biofilm models

Background and Objective

Different bacteria differentially stimulate epithelial cells. Biofilm composition and viability are likely to influence the epithelial response. In vitro model systems are commonly used to investigate periodontitis‐associated bacteria and their interactions with the host; therefore, understanding factors that influence biofilm–cell interactions is essential. The present study aimed to develop in vitro monospecies and multispecies biofilms and investigate the epithelial response to these biofilms.

Material and Methods

Bacterial biofilms were cultured in vitro and then either live or methanol‐fixed biofilms were co‐cultured with epithelial cells. Changes in epithelial cell viability, gene expression and cytokine content of culture supernatants were evaluated.

Results

Bacterial viability was better preserved within mixed‐species biofilm culture than within single‐species biofilm culture. Both mixed‐ and single‐species biofilms stimulated increased expression of mRNA for interleukin 8 (IL8), C‐X‐C motif chemokine ligand 3 (CXCL3), C‐X‐C motif chemokine ligand 1 (CXCL1), interleukin 1 (IL1), interleukin 6 (IL6), colony‐stimulating factor 2 (CSF2) and tumour necrosis factor (TNF), and the response was greatest in response to mixed‐species biofilms. Following co‐culture, cytokines detected in the supernatants included IL‐8, IL‐6, granulocyte colony‐stimulating factor and granulocyte–macrophage colony‐stimulating factor, with the greatest release of cytokines found following co‐culture with methanol‐fixed, mixed‐species biofilms.

Conclusions

These data show that epithelial cells generate a distinct cytokine gene‐ and protein‐expression signature in response to live or fixed, single‐ or multispecies biofilms.

IL-33 Exacerbates Periodontal Disease through Induction of RANKL

Cytokines mediate the balance between protective and destructive immunity in periodontitis. We sought to investigate the role of IL-33 in periodontitis. The expression of IL-33 in gingival tissue from healthy controls (n = 10) and patients with chronic periodontitis (n = 17) was investigated. Based on a murine model of periodontal disease, the function of IL-33 was determined first by administration of exogenous IL-33 and second by inhibition of IL-33 signaling using mice deficient in the IL-33 receptor ST2. Alveolar bone level, serum antibody, and lymphocyte responses were assessed in the murine model. Expression of IL-33 and ST2 was elevated in gingival tissues from patients with chronic periodontitis as compared with healthy tissues (P < 0.05). Similarly, Il33 expression was higher in periodontal tissues of Porphyromonas gingivalis-infected mice as compared with sham-infected controls (P < 0.05). IL-33 treatment of P. gingivalis-infected mice significantly exacerbated alveolar bone loss when compared with infection or IL-33 treatment alone (P < 0.001). Conversely, P. gingivalis infection-induced alveolar bone loss was attenuated in mice lacking ST2. The percentages of T and B lymphocytes expressing nuclear factor κB ligand (RANKL) in the gingival tissues and T lymphocytes expressing RANKL in the cervical draining lymph nodes were higher in IL-33-treated P. gingivalis-infected mice versus phosphate buffered saline-treated P. gingivalis-infected controls (all P < 0.001). Targeting the RANKL pathway by osteoprotegerin administration abrogated periodontal bone destruction in P. gingivalis-infected, IL-33-treated mice. These data demonstrate a previously unrecognized role for IL-33 in exacerbating bone loss in a RANKL-dependent manner in the context of bacterial infection and suggest that this pathway may be amenable to manipulation as a novel therapeutic target in periodontitis.

Salivary antimicrobial proteins associate with age-related changes in streptococcal composition in dental plaque

Secretion of antimicrobial proteins (AMPs) and salivary antibodies can modify biofilm formation at host body surfaces. In adolescents, associations have been reported between dental caries and salivary AMPs. AMPs demonstrate direct antimicrobial effects at high concentrations, and at lower more physiological concentrations they mediate changes in host cell defenses, which may alter the local environment and indirectly shape local biofilm formation. The expression of salivary AMPs in preschool children, at an age when the oral bacteria are known to change, has not been investigated. We sought to investigate salivary AMP expression in the context of previously well-documented changes in the oral cavities of this age group including salivary immunoglobulin A (IgA), oral bacteria and dental caries. Dental plaque and saliva were collected from 57 children aged 12-24 months at baseline, of whom 23 children were followed-up at 3 years of age. At each time, saliva was assessed for LL37, human neutrophil peptides 1-3, calprotectin, lactoferrin, salivary IgA, total plaque bacteria and Streptococcus mutans. Over time, concentrations of AMPs, S. mutans and bacteria-specific salivary IgA increased. Caries experience was also recorded when children were 3 years old. Concentrations of AMPs were highest in the saliva of 3-year-old children with the greatest burden of S. mutans. These data suggest that salivary AMPs are variable over time and between individuals, and are linked with bacterial colonization. At follow up, the majority of children remained caries free. Larger longitudinal studies are required to confirm whether salivary AMP levels are predictive of caries and whether their modulation offers therapeutic benefit.

Increased plasma levels epithelial cell-derived neutrophil-activating peptide 78/CXCL5 in periodontitis patients undergoing supportive therapy

AIM

To investigate the influence of cigarette smoking on plasma epithelial cell-derived neutrophil-activating peptide-78 (CXCL5/ENA-78) and interleukin-6 (IL-6) in supportive therapy periodontitis patients.

MATERIALS AND METHODS

Plasma concentrations of CXCL5/ENA-78 and IL-6 were evaluated in 167 systemically healthy subjects (54 smokers and 113 non-smokers) divided into four groups: non-smokers with periodontitis (n=90), smokers with periodontitis (n=49), healthy non smokers (n=23) and healthy smokers (n=5).

RESULTS

Clinical probing depth (CPD) of smokers with periodontitis were significantly greater than those of non-smoking patients (p<0.05). Although clinical attachment loss (CAL) and the number of deep sites affected were greater in the smokers with periodontitis, these differences were not significant. Periodontitis patients had significantly higher plasma IL-6 and ENA-78 than healthy subjects (p<0.05). There was no significant difference in IL-6 between smokers and non-smokers with periodontitis but CXCL5/ENA-78 concentrations were significantly greater in smokers with periodontitis (p=0.006). Plasma CXCL5/ENA-78 correlated with CPD, CAL and tobacco consumption (all p<0.05).

CONCLUSION

Plasma CXCL5/ENA-78 concentrations are a good systemic indicator of the inflammatory process and disease severity in subjects with periodontitis and in addition are potential indicator of inflammatory effects of cigarette smoking. Further studies are required to elucidate the biological mechanisms underlining this increase in CXCL5/ENA-78.

Stimulants of Toll-like receptors 2 and 4 are elevated in saliva of periodontitis patients compared with healthy subjects

AIM

Because the absorption of stimulants of Toll-like receptor (TLR)2 and TLR4 from the gastrointestinal tract into the circulation has been proposed to promote the development of atherosclerosis and insulin resistance, we aimed to quantify the abundance of stimulants of TLR2 and TLR4 in human saliva.

METHODS

A recently developed bioassay based upon measurement of NF-κB activation in TLR-deficient human embryonic kidney (HEK)-293 cells transfected with human TLR2 or TLR4 and calibrated with synthetic bacterial lipopeptide (Pam(3) CSK(4) ) or Escherichia coli lipopolysaccharide (LPS), was used to establish the normal range of TLR stimulants in saliva of 20 healthy subjects and 20 subjects with periodontal disease.

RESULTS

Median soluble stimulants of TLR2 and TLR4 were significantly higher in saliva of periodontitis patients compared with saliva of healthy subjects; 3450 versus 77 ng/ml Pam(3) CSK(4) equivalents (p<0.0001) and 138 versus 7 ng/ml LPS equivalents, respectively (p<0.0001). Salivary TLR stimulant levels remained relatively stable in healthy subjects over several days. Six strains of oral Gram-negative bacteria, including Tannerella forsythensis, Lysobacter enzymogenes, Prevotella intermedia, Prevotella oris and Porphyromonas gingivalis, from a panel of nine examined did not stimulate TLR4-dependent signalling.

CONCLUSIONS

Elevated salivary TLR stimulants may represent a novel mechanism by which periodontitis increases the risk of developing cardiovascular disease and insulin resistance.

Gingival epithelial cells heterozygous for Toll-like receptor 4 polymorphisms Asp299Gly and Thr399ile are hypo-responsive to Porphyromonas gingivalis

The Toll-like receptor (TLR)4 is the major sensor for bacterial lipopolysaccharide and its two common co-segregating polymorphisms, Asp299Gly and Thr399Ile, which occur at a frequency of between 6 and 10%, have been associated with infectious diseases, LPS hypo-responsiveness and cardiovascular disease. Porphyromonas gingivalis is a Gram-negative bacterium implicated in chronic periodontitis and is a known TLR4 and TLR2 agonist. We obtained two gingival epithelial cell primary cultures from subjects heterozygous for the TLR4 polymorphism Asp299Gly and compared response characteristics with similar cells from patients (four) with the wild-type TLR4 genes. Cytokine responses and transcriptome profiles of gingival epithelial cell primary culture cells to TNFalpha challenge were similar for all primary epithelial cell cultures. P. gingivalis challenge, however, gave markedly different responses for Asp299Gly heterozygous and wild-type epithelial cell cultures. The epithelial cells heterozygous for the TLR4 polymorphism Asp299Gly were functionally hypo-responsive, evidenced by differences in BD-2 mRNA expression, mRNA response profile by microarray analysis and by pro-inflammatory and chemokine cytokines at the protein and mRNA level. These findings emphasize variance in human epithelial cell TLRs, linked with Asp299Gly carriage, which results in a hypo-responsive epithelial cell phenotype less susceptible to Gram-negative diseases and associated systemic conditions.

The systemic immune response is more prominent than the mucosal immune response in the pathogenesis of periodontal disease

BACKGROUND/AIM

The diseased periodontium appears to express features of a systemic and a mucosal immune response. Our aims were to determine differences in immunoglobulin expression between gingivitis and periodontitis lesions and to ascertain whether immune and inflammatory cells were recruited into the diseased periodontium by the mucosal addressin adhesion molecule (MAdCAM-1).

METHODS

In situ hybridization and immunohistochemistry were used to detect the expression of chemokines, adhesion molecules and immunoglobulins in tissue sections of gingival and granulation tissues excised from periodontitis-affected sites and of healthy tissue and gingivitis-affected tissue excised during crown-lengthening procedures.

RESULTS

Greater numbers of plasma cells were observed in periodontitis gingival/granulation tissue lesions compared with gingivitis lesions. While IgA1 were predominant in all lesions, IgA2 and J-chain expressing plasma cells were present in increased proportions in gingival tissues compared with granulation tissue. Intracellular adhesion molecule-1 (ICAM-1) was higher in periodontitis than in gingivitis and interleukin-8 mRNA was higher in lesions with a pronounced neutrophil infiltrate. Vascular cell adhesion molecule-1 (VCAM-1) localized to the deep connective tissue and indicated the presence of a systemic type of immune response in this region. Periodontal tissues (n=71 biopsies) did not appear to express MAdCAM-1, in positive control sections of small intestine where it was detected.

CONCLUSION

Overall, the systemic-type immune response is predominant, and although the mucosal immune response is minor and limited to the superficial tissues it may have an important role in the host defense to periodontal pathogens.

Clinical, pathological and immunological aspects of periodontal disease

The inflammatory and immune responses during the development and progression of periodontitis are reviewed. Susceptibility to periodontitis may be related to whether plasma cells predominate in the tissues of an individual, or a site, in response to the microbial insult from dental plaque. The tendency for an individual or site to form an extensive plasma cell infiltrate may indicate an inability to defend against periodontopathogenic bacteria and thus a predisposition to periodontitis. Selected pertinent areas of current interest in cellular and humoral immunology are considered within the periodontal context. These topical issues include (a) homing of immune and inflammatory cells to target tissues; (b) the local proliferation and synthetic activity of immune and inflammatory cells; (c) the cytokine profile of the inflammatory and immune cells; and (d) the immunoglobulin subclasses of locally produced antibodies.

Anti-inflammatory cytokine IL-10 and T cell cytokine profile in periodontitis granulation tissue

Th2 cells are more abundant than Th1 cells in periodontitis lesions, but the relative importance of the Th1 and Th2 subsets in periodontal disease is not understood. In addition, the role of proinflammatory and anti-inflammatory cytokines in this disease process is unclear. Biopsies were obtained from 10 patients with early onset periodontitis (EOP) and 10 patients with adult periodontitis (AP). From all of the patients in the AP group we were able to obtain and section the gingival tissue to serve as controls. We used polyclonal monospecific antibodies to detect cells expressing IL-2, IL-4, IL-6, IL-10 and IL-15, tumour necrosis factor (TNF-alpha) and interferon-gamma (IFN-gamma) in formalin-fixed, paraffin-embedded sections of granulation tissue from periodontitis lesions. We also employed a series of oligonucleotide probes to detect cells expressing the cytokine transcripts in the same tissue biopsies. Cells that expressed IL-4 or IL-6 were more numerous than cells expressing either IL-2 or IFN-gamma. Th2 cells were more numerous in EOP and AP tissues. IL-15 substitutes for IL-2 in a number of biological activities related to the Th1 immune response, and interestingly, in periodontal lesions the IL-15-expressing cells outnumbered IL-2-expressing cells, suggesting that this is the pattern of immune regulation by T cells in the periodontium. The functional balance in the T cell subsets detected by their cytokine profiles underlies the importance of the anti-inflammatory mechanisms taking place in the diseased tissue. The numbers of inflammatory leucocytes that express the anti-inflammatory cytokine IL-10 are much more widely distributed than those that express the proinflammatory cytokines IL-6 and TNF-alpha. This study suggests that large numbers of infiltrating inflammatory cells as well as accessory cells are involved in the down-regulation of the inflammatory and immune response in periodontitis.

Inducible nitric oxide synthase expression in periodontitis

Recently, nitric oxide (NO) has been shown to be vital in inflammatory processes. Nitric oxide synthase (NOS) exists in three different isoforms, two constitutively produced with physiological roles, and an inducible form, iNOS, which is involved in inflammation. This study examined the localisation of iNOS in biopsies from patients with periodontitis using immunohistochemistry, and compared these with healthy tissue biopsies. Biopsies were obtained from 16 periodontitis patients undergoing periodontal surgery and from clinically healthy tissues of 5 patients having crown lengthening procedures. The periodontitis diseased tissue demonstrated a greater level of iNOS expression than the healthy tissue. The source of iNOS in the periodontal tissues was determined by our monoclonal antibody to be the macrophage, with the endothelial cells also contributing. A role for NO in the inflammatory response of periodontal tissues is suggested, but the precise role requires further elucidation.

Cytokine responses of oral epithelial cells to Porphyromonas gingivalis infection

Accumulating evidence indicates that epithelia are not merely mechanical barriers but also important elements of the innate immune system. The present study was performed to examine cytokine responses of oral epithelial cells after infection with the periodontal pathogen Porphyromonas gingivalis. The KB-cell line and primary cultures of periodontal pocket epithelium were infected with P. gingivalis for assessment of bacterial invasion by an antibiotic protection assay, and examination of expression of interleukin-1 beta, interleukin-6, interleukin-8, and tumor necrosis factor-alpha by in situ hybridization and immunohistochemistry. We observed that P. gingivalis induces a strong cytokine response, positively correlated with the adhesive/invasive potential of the infecting strain, in both KB cells and primary cultures. These findings indicate that the epithelial cells of the periodontal pocket are an integral part of the immune system, eliciting cytokine responses to a bacterial challenge. In this context, the adhesive/invasive phenotype of P. gingivalis appears to contribute to pathogenicity.

Cytokine expression in periapical granulation tissue as assessed by immunohistochemistry

The aims of this study were to investigate the expression of pro-inflammatory, anti-inflammatory and immune-related cytokines present in periapical lesions. We investigated the expression of cytokines: namely interleukins IL-2, IL-4, IL-6, IL-10 and interferon-gamma (IFN-gamma) in formalin-fixed, paraffin-embedded sections of periapical granulation tissue. The study samples were biopsies from 24 patients with periapical lesions: 12 with periapical granulomas and 12 patients with radicular cysts. Immunohistochemistry was also performed on tonsillar tissue which served as a control. We utilised a set of specific monoclonal antibodies and polyclonal monospecific antibodies to detect cells that expressed the different cytokines within the tissues. We also considered the nature of the periapical immune response by investigation of the T-helper 1 (Th-1) and T-helper 2 (Th-2) lymphocyte subsets using their cytokine profile, i.e., Th-1: IL-2 and IFN-gamma and Th-2: IL-4, IL-5 and IL-6. Only a few cells were weakly positive for the IL-2 protein in each of the tissue sections. Cells that expressed IL-4 or IL-6 were far more numerous than cells that expressed either IL-2 or IFN-gamma. Thus, we demonstrated a greater number of Th-2 cells in periapical lesions. This relative ratio of the T-cell subsets underlines the importance of the anti-inflammatory mechanisms taking place in the diseased tissue manifested by the wide array of IL-10-expressing cells: B cells, T suppressor cells (CD8 (+)) and tissue macrophages. The numbers of inflammatory cells expressing the anti-inflammatory molecules far outnumbered the cells that expressed pro-inflammatory cytokines. Thus, the downregulation of the inflammatory response and the predominant Th-2 or humoral immune response in periapical periodontitis may be important features that dictate the outcome of the disease process in the periapical lesion.

Cell division, synthetic capacity and apoptosis in periodontal lesions analysed by in situ hybridisation and immunohistochemistry

In this study, we investigated the synthetic and proliferative activity of infiltrating mononuclear cells in sections of granulation tissue from periodontitis lesions in both adult periodontitis (AP) and early onset periodontitis (EOP) patients. We also investigated the role of apoptosis in the remodelling of the inflamed tissue. We utilised a Ki-67 antigen specific antibody and a histone messenger RNA (mRNA) probe to detect cells undergoing cell division in the sections. Oligonucleotide probes for 28S ribosomal RNA and for the detection of poly A mRNA were utilised to detect cells with synthetic capacity. Apoptosis was determined using terminal transferase labelling of fragmented DNA with Biotin labelled dUTP. Biopsies of granulation tissue were obtained from 9 AP patients, from 10 EOP patients and for comparative purposes, biopsies of gingival tissue from 4 patients with AP. There were no differences regarding the relative proportions of cells with synthetic capacity or in the numbers of dividing cells in the periodontitis tissue sections. However, we observed an increase in the number of dividing cells in the AP granulation tissues compared to the AP gingival sections and that these cells were predominantly fibroblast like in appearance. Apoptotic cells consisted mainly of connective tissue cells; mainly fibroblasts with few if any leukocytes being apoptotic other than polymorphonuclear leukocytes. Only a few cyto-phagocytic macrophages were ever observed in the gingival and granulation tissues. We conclude that the turnover of infiltrating leukocytes in inflamed periodontal tissue is low, that they probably arrive at this site by recruitment from distant lymph nodes, and that neither cell division nor programmed cell death significantly alter the numbers of inflammatory cells. On the other hand, fibroblast apoptosis and cell division occur within the periodontium as these are typical processes in the normal turnover and remodelling of these tissues.

Humoral immune responses in periodontal disease may have mucosal and systemic immune features

The humoral immune response, especially IgG and IgA, is considered to be protective in the pathogenesis of periodontal disease, but the precise mechanisms are still unknown. Immunoglobulins arriving at the periodontal lesion are from both systemic and local tissue sources. In order to understand better the local immunoglobulin production, we examined biopsy tissue from periodontitis lesions for the expression of IgM, IgG, IgA, IgE and in addition the IgG and IgA subclasses and J-chain by in situ hybridization. Tissues examined were superficial inflamed gingiva and the deeper granulation tissue from periodontal sites. These data confirm that IgM, and IgG and IgA subclass proteins and J-chain can be locally produced in the periodontitis tissues. IgG1 mRNA-expressing cells were predominant in the granulation tissues and in the gingiva, constituting approx. 65% of the total IgG-expressing plasma cells. There was a significantly increased proportion of IgA-expressing plasma cells in the gingiva compared with the granulation tissue (P < 0.01). Most of the IgA-expressing plasma cells were IgA1, but a greater proportion expressed IgA2 mRNA and J-chain mRNA in the gingival tissues (30.5% and 7.5%, respectively) than in the periodontal granulation tissues (19% and 0-4%, respectively). The J-chain or dimeric IgA2-expressing plasma cells were located adjacent to the epithelial cells, suggesting that this tissue demonstrates features consistent with a mucosal immune response. Furthermore, we were able to detect the secretory component in gingival and junctional epithelial cells, demonstrating that the periodontal epithelium shares features with mucosal epithelium. In contrast, deeper tissues had more plasma cells that expressed IgM, and less expressing IgA, a response which appears more akin to the systemic immune response. In conclusion, this study suggests that immune mechanisms involved in the pathogenesis of periodontitis may involve features of both the mucosal and systemic immune systems, dependent on tissue location.

Relative proportions of mononuclear cell types in periodontal lesions analyzed by immunohistochemistry

In this study, we investigated the relative proportions of infiltrating mononuclear inflammatory cells in sections of granulation tissue from periodontitis lesions in both adult periodontitis (AP) and early onset periodontitis (EOP) patients. We utilised a set of cluster of differentiation (CD) antigen-specific monoclonal antibodies to detect different cell types within the tissues. These included anti-CD 20 (B cells), anti-CD 3 (pan T cells) and anti-CD 45RO (memory T cells), anti-CD 4 (helper T cells) anti-CD 8 (suppressor T cells) and anti-CD 68 (monocyte/macrophage). Biopsies of granulation tissue were obtained from 9 patients with adult periodontitis (AP), from 10 patients with early onset periodontitis (EOP) and for comparative purposes, biopsies of gingival tissue from 4 patients with AP. A significantly greater number of T cells (p < 0.05) were observed in EOP and gingival sections than in AP sections. In addition, a greater number of B cells were observed in the granulation tissues than in the gingiva (p < 0.05). The relative numbers of B cells (CD 20). T cells (CD 3) and macrophages (CD 68) were expressed as a percentage of their combined total for each of the patient groups and indicated that the proportion of B lymphocytes was greater in AP sections than in EOP or gingival sections (p < 0.02). The proportion of T cells was lower in the AP periodontitis sections than in the EOP periodontitis sections (p < 0.05). There were no significant differences in the proportion of macrophages between the 3 categories of tissue specimens. The relative ratios of B cells (CD 20) to T cells (CD 3) and B cells (CD 20) to memory T cells (CD 45RO) and macrophages (CD 68) to T cells (CD 3) and memory T cells (CD 45RO) were analyzed and indicated that there was a significant increase in the B to T cell ratio in AP sections compared to EOP and gingival sections (p < 0.02). There was also a significant increase in the macrophage to T cell ratio in AP sections as indicated by CD 68 to CD 3 ratios (p < 0.05). There were no differences regarding the relative proportions of memory T cells or in the ratios of CD 4+ to CD 8+ T cells in the different disease categories. In conclusion, these differences in the relative proportions of B cells, T cells and macrophages may reflect a difference in the immunopathology of AP and EOP.

Relative distribution of plasma cells expressing immunoglobulin G subclass mRNA in human dental periapical lesions using in situ hybridization

Immunoglobulin G (IgG)-producing plasma cells are the predominant immunoglobulin secreting plasma cells in human dental periapical lesions, compared with immunoglobulin A- and immunoglobulin M-producing plasma cells. In this study, the cells expressing mRNA, that encoded the distinct IgG subclasses, were detected using an in situ hybridization technique in 25 periapical lesions. These lesions consisted of 14 periapical granulomas and 11 radicular cysts. Four oligonucleotide probes were chemically synthesized from IgG subclass-specific hinge region genes to ensure specificity of the probes. Plasma cells expressing mRNA, which coded for the IgG subclasses, were detected in formalin-fixed/paraffin wax-embedded sections. Background staining was negligible in all of the sections tested. The in situ hybridization method used in this study was both specific and sensitive for the detection of mRNA encoding each of the four distinct IgG subclasses, whereas the cells retained good morphology. The relative proportions of plasma cells expressing each of the IgG subclass-specific mRNAs in both granulomas and cysts were as follows: IgG1 (57.4 and 55.5%); IgG2 (34.1 and 34.6%); IgG3 (4.0 and 4.3%); and IgG4 (4.0 and 5.5%). There were no significant differences between the percentages of plasma cells expressing each of the IgG subclass mRNAs between the two types of lesions. IgG1 producing plasma cells comprised the highest proportion of IgG-producing plasma cells in both types of periapical lesion. IgG2-producing plasma cells were next in abundance, followed by plasma cells for either IgG3 or IgG4, which were in roughly equivalent numbers.

Localization of Bunyamwera bunyavirus G1 glycoprotein to the Golgi requires association with G2 but not with NSm

The Bunyamwera bunyavirus (BUN) M RNA genome segment encodes three proteins, two glycoproteins termed G1 and G2 and a non-structural protein called NSm, in the form of a polyprotein precursor that is co-translationally cleaved to give the mature proteins. Indirect immunofluorescence experiments have shown that these proteins localize to the Golgi complex in BUN-infected cells. We have used a recombinant vaccinia virus (vTF7-3), which expresses bacteriophage T7 RNA polymerase, to drive the expression of plasmids containing either the entire BUN M segment cDNA or fragments that encode the G1, G2 and NSm proteins separately under control of the T7 promoter. After transfection of these plasmids into vTF7-3-infected cells, correctly sized and processed proteins were detected by immunoprecipitation with BUN-specific antibodies. Immunofluorescence experiments showed that G1, G2 and NSm localized to the Golgi when transiently expressed from the full-length cDNA. When G2 or NSm were expressed separately they also localized to the Golgi, but when G1 was expressed alone a staining pattern typical for the endoplasmic reticulum was obtained. However coexpression of G2 and G1 from independent plasmids resulted in G1 localizing to the Golgi. In contrast translocation of G1 to the Golgi was not observed when G1 was coexpressed with NSm, although NSm itself was still detected in the Golgi. Similar results were obtained when the proteins were expressed from transfected plasmids containing the G2-, NSm- or G1-coding sequences under control of the cytomegalovirus immediate-early promoter. The localization of G1 to the Golgi when coexpressed with G2 was confirmed by the loss of endoglycosidase H (endo H) sensitivity of G1 after approximately 60 min in a pulse-chase experiment; G1 remained sensitive to endo H when expressed either alone or in combination with NSm. These results suggest that G2 contains the Golgi targeting and/or retention signals and that G1 has to interact with this protein to localize to this cellular compartment.

Effect of interferon-gamma on complement gene expression in different cell types

We have studied the expression of the complement components C2, C3, factor B, C1 inhibitor (C1-inh), C4-binding protein (C4-bp) and factor H in human peripheral blood monocytes, skin fibroblasts, umbilical vein endothelial cells (HUVEC) and the human hepatoma cell line G2 (Hep G2) in the absence and the presence of interferon-gamma (IFN-gamma). E.l.i.s.a. performed on culture fluids, run-on transcription assays, Northern blot and double-dilution dot-blot techniques confirmed that monocytes expressed all six components, whereas fibroblasts, HUVEC and HepG2 each expressed five of the six components. Fibroblasts and HUVEC did not synthesize C4-bp, and Hep G2 did not produce factor H. In addition to these differences, the synthesis rates of C3, C1-inh and factor H were not the same in all cell types. However, the synthesis rates of C2 and factor B were similar in all four cell types. The half-lives of the mRNAs were shorter in monocytes than in other cell types. Monocyte factor H mRNA had a half-life of 12 min in monocytes, compared with over 3 h in fibroblasts and HUVEC. The instability of factor H mRNA in monocytes may contribute to their low factor H secretion rate. IFN-gamma produced dose-dependent stimulation of C2, factor B, C1-inh, C4-bp and factor H synthesis by all cell types expressing these proteins, but decreased C3 synthesis in all four cell types. Cell-specific differences in the response to IFN-gamma were observed. The increased rates of transcription of the C1-inh and factor H genes in HUVEC were greater than in other cell types, while the increased rate of transcription of the C2, factor B and C1-inh genes in Hep G2 cells was less than in other cell types. IFN-gamma did not affect the stability of C3, factor H or C4 bp mRNAs, but increased the stability of factor B and C1-inh mRNAs and decreased the stability of C2 mRNA. Although these changes occurred in all four cell types studied, the half-life of C1-inh mRNA in monocytes was increased almost 4-fold, whereas the increases in the other cell types were less than 30%. These data show that the constitutive synthesis rates of complement components may vary in the different cell types. They also show that the degree of change in synthesis rates in response to IFN-gamma in each of the cell types often varies due to differences in transcriptional response, sometimes in association with changes in mRNA stability.

An RNA splice site mutation in the C1-inhibitor gene causes type I hereditary angio-oedema

Restriction fragment length polymorphism analysis, the polymerase chain reaction and nucleotide sequencing have been used to characterise a single base substitution (G----T) at nucleotide 8863 in the C1-inhibitor gene. This destroys the 5' donor splice site recognition motif of the sixth intron. Family studies suggest that the mutation is responsible for type I hereditary angio-oedema in a studied kindred.

Modulation of complement gene expression by glucocorticoids

The addition of dexamethasone, prednisolone or cortisol (in order of efficacy) to human monocytes in culture produced dose-related increases in the synthesis rates of the complement components C1 inhibitor (C1-inh), factor B (B) and C2. In contrast, concentrations of C3 and lysozyme in the culture supernatants were decreased. Indomethacin stimulated synthesis of C1-inh, C2 and B, but had little effect on synthesis of C3 or lysozyme. The simultaneous addition of cycloheximide (2.5 micrograms/ml) abrogated the effects of dexamethasone on synthesis of C2, B and C1-inh, but the effect of indomethacin on the synthesis of these components was unchanged. These data suggest that protein synthesis is required for the effects of glucocorticoids on the synthesis of C2, B and C1-inh to occur. Dexamethasone and indomethacin increased the abundances of C1-inh mRNA, B mRNA and C2 mRNA in parallel with changes in the synthesis rates of these proteins. The changes in mRNA abundance were not transcriptional, but were shown to be due to increased mRNA stability. In contrast, dexamethasone decreased the expression of C3 and lysozyme by decreasing the rate of transcription of these genes. Indomethacin had no effect on transcription of the C3 and lysozyme genes. The half-lives of C3 mRNA, lysozyme mRNA and actin mRNA were not altered by dexamethasone or indomethacin. It is concluded that the effects of glucocorticoids on monocyte synthesis of C2, B and C1-inh are due to increased mRNA stability and may be related to inhibition of prostaglandin synthesis, as these effects are similar to those produced by indomethacin. The effects of dexamethasone on the synthesis of C3 and lysozyme differ from those on C2, B and C1-inh as they depend upon a decrease in gene transcription, which is not affected by indomethacin.

Human complement factor H. Tissue specificity in the expression of three different mRNA species

Using cDNA clones H-19 and H-46, we have shown previously that three different mRNA species (4.3 kb, 1.8 kb and 1.4 kb) for complement factor H are expressed constitutively in human liver. Here we report data suggesting that the expression of these different factor-H mRNA species is regulated by tissue-specific control mechanisms. Total RNA and poly(A)-enriched RNA from various human tissues (heart, lung, temporal cortex, kidney, spleen, bone marrow and muscle) various cell lines (HepG2, HepG3, HepG4, Hep3B, H-4, Jurkat, Molt4, H-9, KHos24Os, A-431, U937, Mono Mac 6 and Raji) and from primary cultures of peripheral blood monocytes, fibroblasts and human umbilical vein endothelial cells (HUVEC) were investigated for the expression of factor-H mRNA. In RNA preparations from extrahepatic tissue, factor-H mRNA was only detected in biopsies from the lung. Using 20 micrograms total RNA isolated from all 13 cell lines it was not possible to detect any factor-H mRNA, while mRNA for factor H was expressed in monocytes, HUVEC and fibroblasts. When expressed in extrahepatic tissues, only the 4.3-kb and the 1.8-kb mRNA species were detected, while the 1.4-kb mRNA is expressed abundantly in liver. Interferon-gamma did not induce the expression of factor-H mRNA in any of the cell lines tested. On the other hand, tumour necrosis factor-alpha induced the expression of the 4.3-kb mRNA species in U937 cells. In HUVEC and fibroblasts the relative quantities of the 4.3-kb and the 1.8-kb mRNA species and the regulatory effects of interferon-gamma, interleukin-1, dexamethasone and retinoic acid on their expression showed significant tissue specificity.

Interferon-mediated transcriptional and post-transcriptional modulation of complement gene expression in human monocytes

The addition of lymphoblastoid interferon alpha, fibroblast interferon beta and recombinant interferon gamma to in vitro monocyte cultures produced dose-dependent increases in transcription rates of the genes encoding the second component of complement (C2), factor B (B) and C1 inhibitor, and the abundance of their respective mRNA. Interferon gamma was the most effective at stimulating transcription of the C1-inhibitor gene whereas interferons alpha and beta were more effective at increasing the transcription of the C2 and B genes. Transcription of the C3 gene was reduced by interferon gamma. None of these cytokines altered the level of transcription of the actin gene. Interferon-induced changes in the levels of transcription of the C2, B and C1-inhibitor genes occurred rapidly, with significant changes occurring within 30 min of exposure to these cytokines. Within 4 h of removal of the interferons from the culture fluid, the level of transcription of the C1-inhibitor, C2, B and C3 genes returned to control values, as did abundance of C2, B and C3 mRNA. However, the abundance of C1-inhibitor mRNA remained elevated in interferon-gamma-treated monocytes. Combinations of interferons produced less than additive effects on the stimulation of the transcription of C2, B and C1-inhibitor genes, whereas measurements of C1-inhibitor mRNA and B mRNA showed that interferon gamma acted synergistically with interferon gamma to increase the abundance of the mRNA. Their effects on C2 mRNA abundance were less than additive. The half-lives of C1-inhibitor, C2, B and C3 mRNA were not altered by interferon alpha, whereas interferon gamma shortened the half-life of C2 mRNA by approximately 50%, and prolonged the half-lives of B and C1-inhibitor mRNA approximately twofold and fivefold, respectively. The half-life of C3 mRNA was unaltered by either interferon. These results show that the large increase in C1-inhibitor synthesis which occurs in interferon-gamma-treated monocytes, is due to a combination of increased transcription and increased C1-inhibitor mRNA stability. They also suggest that the synergistic effects of interferon alpha together with interferon gamma on C1-inhibitor and factor B synthesis is also dependent upon increased transcription and increased mRNA stability.

Interferon-induced transcriptional and post-transcriptional modulation of factor H and C4 binding-protein synthesis in human monocytes

Cultured human monocytes synthesize factor H (H) and C4 binding protein (C4-bp), as assessed by measuring their presence in culture fluids, and demonstrating the presence of their corresponding mRNAs in total monocyte RNA by Northern blot analysis and by nuclear run-on experiments. H mRNA (4.3 kb and 1.8 kb) could only be detected when cycloheximide (2.5 micrograms/ml) was present in monocyte culture fluid. Recombinant interferon-gamma (IFN-gamma) and lymphoblastoid interferon-alpha (IFN-alpha) produce dose-related increases in the synthesis of H and C4-bp and in the abundance of C4-bp mRNA (2.5 kb). Increased abundance of H mRNA was also seen when cycloheximide (2.5 micrograms/ml) was present in the cultures. Both cytokines increased the transcription rates of the H and C4-bp genes. These changes in transcription were rapid, with significant increases being observed within 30 min of exposure. Following the removal of the cytokines from the cultures the transcription rates of both genes returned to control levels within 4 h. The effects of combining IFN-alpha and IFN-gamma on H and C4-bp transcription rates, mRNA abundances and protein secretion rates were not quantitatively additive. The half-life of H mRNA in monocytes was 15 min, whereas that of C4-bp mRNA was 2 h 45 min. Neither half-life was altered by IFN-gamma.

Modulation by interferons of the expression of monocyte complement genes

Interferons-alpha, -beta and -gamma (IFNs-alpha, -beta and -gamma) stimulated the synthesis of the second complement component (C2), Factor B (B) and C1 inhibitor (C1-inh) by human monocytes in vitro. The degree of increase of the secretion rates of C2, B and C1-inh was dose-dependent and proportional to increases in the abundances of their respective mRNAs. IFN-gamma was the most effective at stimulating monocyte C1-inh synthesis, whereas IFN-alpha and IFN-beta were marginally more effective at stimulating monocyte C2 and B synthesis. Kinetic studies showed that the effect of the IFNs was rapid, with maximum stimulation occurring within 1-2 h for all three proteins. After the removal of IFNs from cultures the C1-inh mRNA abundance remained elevated for over 24 h in IFN-gamma-treated monocytes but returned to control levels within 8 h in IFN-alpha-treated and IFN-beta-treated monocytes. The abundances of C2 mRNA and B mRNA also returned to basal values within 8 h after removal of any of the three cytokines from the cultures. Both IFN-alpha and IFN-beta acted synergistically with IFN-gamma to stimulate synthesis of C1-inh and B. This synergistic effect only occurred when the cytokines were present in the cultures simultaneously. The effects of IFN-gamma plus IFN-alpha or IFN-beta on C2 synthesis appeared to be additive rather than synergistic. IFN-gamma inhibited synthesis of C3 by monocytes, but IFN-alpha and IFN-beta had no effect on the synthesis of this protein. Furthermore, none of the three cytokines had any effect on the expression of actin mRNA in monocytes.

Regulation of hepatic synthesis of C3 and C4 during the acute-phase response in the rat

Following the i.p. injection of casein, rats showed increased serum levels of C4 and C3. C4 levels peaked on day 2 and returned to normal by day 4, while C3 levels peaked on day 3 before returning to normal on day 4. These changes were paralleled by changes in the hepatocyte synthesis rates of these two proteins. Macrophages, isolated from the peritoneal cavities of rats on days 1 to 7 (day-1 to day-7 macrophages) following i.p. injection of casein, were cultured in vitro, and the peritoneal macrophage-conditioned media (PMCM) assayed for their abilities to stimulate synthesis of C4 and C3 by hepatocytes from control rats. Day-2 PMCM selectively stimulated synthesis of C4, while day-3 and day-4 PMCM selectively stimulated C3 synthesis. These activities were called C4-hepatocyte stimulating factor (C4-HSF) and C3-HSF, respectively. The addition of anti-interleukin (IL) 1, tumor necrosis factor (TNF)-alpha, TNF-beta, IL 6 or interferon (IFN)-gamma antibodies to day-2 PMCM did not affect C4-HSF activity, and none had any effect on C3-HSF activity in day-4 PMCM. However, the addition of anti-IL 1 to day-4 PMCM resulted in the re-expression of C4-HSF activity as well as loss of thymocyte proliferative activity. C4-HSF activity could also be detected in day-4 PMCM by separating it from IL 1 activity using gel filtration chromatography. Furthermore the addition of recombinant IL 1 beta to day-2 PMCM prevented the expression of C4-HSF activity. Thus IL 1 appears to play a regulatory role in the acute-phase response in the rat, by preventing the expression of C4-HSF activity. The identities of C4-HSF activity and C3-HSF are still unknown but we believe that C3-HSF activity could be IL 6 as it has a similar molecular weight (30 kDa) and purified human IL 6 was more effective than IL 1, TNF-alpha or TNF-beta in stimulating C3 synthesis by rat hepatocytes. C4-HSF activity appears to be a property of a previously undescribed cytokine. It is not IL 1 alpha or beta, TNF-alpha or -beta, IL 6 or IFN-gamma.

Monocyte C1-inhibitor synthesis in patients with C1-inhibitor deficiency

Monocytes of seven out of eight patients with type 1 C1-inhibitor (C1-inh) deficiency (HAE) produced 40% as much C1-inh as monocytes from normal donors (controls). In contrast, monocytes from three patients with type 2 and three patients with acquired C1-inh deficiency produced similar amounts of C1-inh as controls. Recombinant gamma-interferon (gamma-interferon 10 ng/ml) stimulated C1-inh production of C1-inh (eight-10-fold) by control and patients' monocytes. Monocytes from patients with type 1 HAE contained 40% the level of C1-inh messenger ribonucleic acid (mRNA) found in control monocytes. Gamma-interferon increased the abundance of C1-inh mRNA by the same extent in both control and patients' monocytes. C1-inh protein and mRNA were undetectable in the monocytes of one patient, unless stimulated by gamma-interferon. Under these conditions, his monocytes produced comparable amounts of C1-inh (protein and mRNA) as gamma-interferon-stimulated monocytes of the other type 1 HAE patients. The data suggest that in most type 2 HAE patients there is a lesion in the C1-inh gene such that mRNA is transcribed by a single allele.

Prostaglandins and prostaglandin synthetase inhibitors regulate the synthesis of complement components by human monocytes

The addition of prostaglandins E2 (PGE2), PGD2, PGI2, 6-keto PGF1 alpha and thromboxane B2 (TXB2) to human monocyte cultures, inhibited the production of the second component of complement (C2). PGF2 alpha did not significantly affect C2 production. As the former compounds, but not the latter increase intracellular cAMP, it was thought that the effect was mediated by this action. The addition of cyclo-oxygenase and lipoxygenase inhibitors to monocyte cultures enhanced the synthesis of complement components and other proteins in a dose-dependent fashion: cyclo-oxygenase inhibitors being more potent in this regard than lipoxygenase inhibitors. The enhancing effect of cyclo-oxygenase inhibitors paralleled their ability to inhibit cyclo-oxygenase activity. The enhancement of C2 synthesis by the addition of cyclo-oxygenase and lipoxygenase inhibitors was reversed by the addition of PGs to the cultures. It is concluded that the production of PG by monocytes could provide an endogenous mechanism to control the synthesis of complement components and other proteins.