Mechanisms underlying the association between periodontitis and atherosclerotic disease.

Atherosclerosis is central to the pathology of cardiovascular diseases, a group of diseases in which arteries become occluded with atheromas that may rupture, leading to different cardiovascular events, such as myocardial infarction or ischemic stroke. There is a large body of epidemiologic and animal model evidence associating periodontitis with atherosclerotic disease, and many potential mechanisms linking these diseases have been elucidated. This chapter will update knowledge on these mechanisms, which generally fall into 2 categories: microbial invasion and infection of atheromas; and inflammatory and immunologic. With respect to the invasion and infection of atheromas, it is well established that organisms from the subgingival biofilm can enter the circulation and lodge in most distant tissues. Bacteremias resulting from oral interventions, and even oral hygiene activities, are well documented. More recently, indirect routes of entry of oral organisms (via phagocytes or dendritic cells) have been described for many oral organisms, into many tissues. Such organisms include the periodontal pathogens Porphyromonas gingivalis, Aggregatibacter actinomycetemcomitans, Prevotella intermedia, Tannerella forsythia, and Fusobacterium nucleatum. Intracellular survival of these organisms with dissemination to distant sites (The Trojan Horse approach) has been described. Their relative contribution to atheroma formation and progression has been studied mainly in experimental research, with results demonstrating that these organisms can invade endothelial cells and phagocytic cells within the atheroma, leading to pathogenic changes and progression of the atheroma lesion. The second category of mechanisms potentially linking periodontitis to atherosclerosis includes the dumping of inflammatory mediators originating from periodontal lesions into the systemic circulation. These inflammatory mediators, such as C-reactive protein, matrix metalloproteinases, fibrinogen, and other hemostatic factors, would further accelerate atheroma formation and progression, mainly through oxidative stress and inflammatory dysfunction. Moreover, direct effects on lipid oxidation have also been described. In summary, the evidence supports the concept that periodontitis enhances the levels of systemic mediators of inflammation that are risk factors for atherosclerotic diseases.

Spontaneous preterm birth: advances toward the discovery of genetic predisposition.

Evidence from family and twin-based studies provide strong support for a significant contribution of maternal and fetal genetics to the timing of parturition and spontaneous preterm birth. However, there has been only modest success in the discovery of genes predisposing to preterm birth, despite increasing sophistication of genetic and genomic technology. In contrast, DNA variants associated with other traits/diseases have been identified. For example, there is overwhelming evidence that suggests that the nature and intensity of an inflammatory response in adults and children are under genetic control. Because inflammation is often invoked as an etiologic factor in spontaneous preterm birth, the question of whether spontaneous preterm birth has a genetic predisposition in the case of pathologic inflammation has been of long-standing interest to investigators. Here, we review various genetic approaches used for the discovery of preterm birth genetic variants in the context of inflammation-associated spontaneous preterm birth. Candidate gene studies have sought genetic variants that regulate inflammation in the mother and fetus; however, the promising findings have often not been replicated. Genome-wide association studies, an approach to the identification of chromosomal loci responsible for complex traits, have also not yielded compelling evidence for DNA variants predisposing to preterm birth. A recent genome-wide association study that included a large number of White women (>40,000) revealed that maternal loci contribute to preterm birth. Although none of these loci harbored genes directly related to innate immunity, the results were replicated. Another approach to identify DNA variants predisposing to preterm birth is whole exome sequencing, which examines the DNA sequence of protein-coding regions of the genome. A recent whole exome sequencing study identified rare mutations in genes encoding for proteins involved in the negative regulation (dampening) of the innate immune response (eg, CARD6, CARD8, NLRP10, NLRP12, NOD2, TLR10) and antimicrobial peptide/proteins (eg, DEFB1, MBL2). These findings support the concept that preterm labor, at least in part, has an inflammatory etiology, which can be induced by pathogens (ie, intraamniotic infection) or "danger signals" (alarmins) released during cellular stress or necrosis (ie, sterile intraamniotic inflammation). These findings support the notion that preterm birth has a polygenic basis that involves rare mutations or damaging variants in multiple genes involved in innate immunity and host defense mechanisms against microbes and their noxious products. An overlap among the whole exome sequencing-identified genes and other inflammatory conditions associated with preterm birth, such as periodontal disease and inflammatory bowel disease, was observed, which suggests a shared genetic substrate for these conditions. We propose that whole exome sequencing, as well as whole genome sequencing, is the most promising approach for the identification of functionally significant genetic variants responsible for spontaneous preterm birth, at least in the context of pathologic inflammation. The identification of genes that contribute to preterm birth by whole exome sequencing, or whole genome sequencing, promises to yield valuable population-specific biomarkers to identify the risk for spontaneous preterm birth and potential strategies to mitigate such a risk.

Inflammatory mechanisms linking periodontal diseases to cardiovascular diseases.

AIMS: In this article, inflammatory mechanisms that link periodontal diseases to cardiovascular diseases are reviewed. METHODS: This article is a literature review. RESULTS: Studies in the literature implicate a number of possible mechanisms that could be responsible for increased inflammatory responses in atheromatous lesions due to periodontal infections. These include increased systemic levels of inflammatory mediators stimulated by bacteria and their products at sites distant from the oral cavity, elevated thrombotic and hemostatic markers that promote a prothrombotic state and inflammation, cross-reactive systemic antibodies that promote inflammation and interact with the atheroma, promotion of dyslipidemia with consequent increases in pro-inflammatory lipid classes and subclasses, and common genetic susceptibility factors present in both disease leading to increased inflammatory responses. CONCLUSIONS: Such mechanisms may be thought to act in concert to increase systemic inflammation in periodontal disease and to promote or exacerbate atherogenesis. However, proof that the increase in systemic inflammation attributable to periodontitis impacts inflammatory responses during atheroma development, thrombotic events or myocardial infarction or stroke is lacking.

Anti-cardiolipin from periodontitis patients induces MCP-1 production by human umbilical vein endothelial cells.

AIM: Periodontal diseases are associated with a variety of systemic diseases, including cardiovascular disease and stroke, and patients with periodontitis demonstrate elevated levels of anti-cardiolipin antibodies. We sought to determine if anti-cardiolipin antibodies from periodontitis patients induced monocyte chemotactic protein-1 production by human vascular endothelial cells. MATERIALS AND METHODS: IgG was purified from sera from 53 subjects, including chronic and aggressive periodontitis patients and periodontally healthy controls, with elevated or normal IgG anti-cardiolipin levels. In addition, anti-cardiolipin antibodies were specifically removed from some sera by immunoabsorption. RESULTS: We found that, irrespective of diagnostic category, IgG from subjects with elevated anti-cardiolipin induced significantly greater monocyte chemotactic protein-1 production by human vascular endothelial cells than IgG from those subjects with normal anti-cardiolipin titres. Removal of anti-cardiolipin from IgG preparations from periodontitis patients significantly reduced their ability to induce monocyte chemotactic protein-1. CONCLUSIONS: Since elevated titres of anti-cardiolipin are found in a significantly greater proportion of patients with periodontitis than in periodontally healthy individuals, and these antibodies activate endothelial cells to produce monocyte chemotactic protein-1, they may explain some of the associations noted between periodontal infections and systemic conditions.

Anticardiolipin (aCL) in sera from periodontitis subjects activate Toll-like receptor 4 (TLR4).

Anticardiolipin antibodies (aCL) have been reported to be present in 15-20% of sera from subjects with periodontitis at concentrations exceeding those found in 95% of the healthy adult population. These antibodies, albeit at concentrations exceeding those generally found in periodontitis subjects, are typically present in patients with the antiphospholipid syndrome (APS), an autoimmune disease characterized by thrombosis and recurrent pregnancy loss. aCL from APS patients are proinflammatory and can activate trophoblasts, macrophages, and platelets via cell-surface interactions with their target antigen beta-2-glycoprotein-I (ß2GPI). ß2GPI is an anionic phospholipid-binding serum protein that can associate with toll-like receptors (TLR's) on the cell-surface, leading to cell activation following interaction with autoimmune aCL. We examined an expanded series of 629 sera from clinically characterized subjects for aCL content, and observed that 14-19% of these sera contained elevated (>95th %-tile) levels of aCL. We purified IgG from 16 subjects with elevated or normal levels of aCL and examined their ability to activate TLR2- or TLR4-transfected human embryonic kidney (HEK) cells, and observed that IgG from periodontitis patients with elevated aCL activated HEK-TLR4 cells, but not HEK-TLR2 cells. Prior removal of aCL by immunoabsorption significantly reduced the ability of IgG preparations from these sera to activate TLR4. Further experiments using a human first trimester trophoblastic cell line (HTR8 sv/neo) revealed that aCL from periodontitis patients stimulated IL-8 production, which was profoundly decreased if aCL was removed by immunoabsorption or if HTR8 sv/neo were pretreated with blocking anti-TLR4 antibodies. Thus, it appears that aCL from periodontitis patients can be proinflammatory, activating cells via TLR4. Since these antibodies are likely produced via molecular mimicry due to similarities between oral bacterial antigens and ß2GPI, the data indicate that circulating serum aCL may induce or influence inflammatory responses at sites distant from the oral cavity.

Clinical crown length of the maxillary anterior teeth preorthodontics and postorthodontics.

BACKGROUND: Prevalence information on excessive gingival display in postorthodontic patients is limited. By studying the size relationship of the clinical crowns of teeth, in an orthodontic population, we can begin to quantify their need for periodontal plastic surgery. METHODS: Preorthodontic and postorthodontic crown dimensions were measured on 200 plaster models, and after 5 years, 31 of the subjects were recalled to repeat the measurements in a clinical examination. The measurements included clinical crown lengths and widths of the six anterior teeth, and these values were compared to known ideals. RESULTS: This study revealed a significant increase in the length of the maxillary anterior crowns over the three examinations, yet these values were still approximately 1.5 mm shorter than ideal. The mean crown width-to-length ratio was 87% to 88% for maxillary central incisors, clearly above the accepted "ideal." In addition, 61% to 71% of maxillary central incisors exceeded allowable crown width-to-length ratios, and 61% of subjects displayed asymmetry in gingival architecture. CONCLUSIONS: Although this study only examined one aspect of excessive gingival display, to our knowledge it is the first study to show that in a predominantly young, postorthodontic population, the prevalence of non-ideal width-to-length ratios is >65% and the presence of asymmetry is >60%. Therefore, close interaction between the periodontist and the orthodontist is necessary to diagnose these conditions to provide patients with all options for improving their smile.

Anti-cardiolipin and increased serum adhesion molecule levels in patients with aggressive periodontitis.

BACKGROUND: We observed that a significant proportion of patients with periodontitis have elevated serum levels of beta2-glycoprotein-I-dependent anti-cardiolipin (anti-CL). These prothrombotic autoantibodies, commonly found to be elevated in patients with systemic lupus erythematosus and the antiphospholipid syndrome, are associated with adverse pregnancy outcomes, such as fetal involution, prematurity, and low birth weight, and with cardiovascular sequelae, such as atherosclerosis, stroke, and myocardial infarction. Anti-CL is known to promote vascular inflammation and thrombosis. METHODS: We measured serum levels of markers of vascular inflammation, including soluble intercellular adhesion molecule (sICAM)-1, soluble vascular cell adhesion molecule (sVCAM)-1, and sE-selectin, in 190 subjects with generalized aggressive or chronic periodontitis and in 90 periodontally healthy subjects. RESULTS: sVCAM-1 and sE-selectin levels were significantly higher in patients with elevated anti-CL (>15 U/ml). This relationship also was observed in the never-smoker subset of subjects, even after correction for demographic and periodontal variables. Within the diagnostic categories, sICAM-1, sVCAM-1, and sE-selectin were significantly higher in generalized aggressive periodontitis patients who had elevated anti-CL compared to those with normal anti-CL. Statistical correction for demographic and periodontal variables indicated that elevated anti-CL remained significantly associated with increased sVCAM-1 and sE-selectin in generalized aggressive periodontitis patients. CONCLUSIONS: Systemic markers of vascular inflammation in patients with aggressive periodontitis are associated with elevated levels of anti-CL. We hypothesize that a subset of periodontitis patients with elevated antiphospholipid antibodies could represent a subgroup at increased risk for obstetrical and cardiovascular sequelae.

C-reactive protein levels in patients with aggressive periodontitis.

BACKGROUND: Sera from patients with periodontal infections contain elevated levels of C-reactive protein (CRP) compared to periodontally healthy individuals. Most studies to date have included patients with chronic periodontitis, and few investigators have studied CRP levels in subjects with aggressive periodontitis (AgP). The purpose of this study was to determine the relative levels of serum CRP in AgP patients and periodontally healthy subjects and to examine patients' characteristics that might account for intergroup differences. METHODS: Serum samples were collected from 93 patients with generalized AgP (GAgP), from 97 patients with localized AgP (LAgP), and from 91 healthy controls (non-periodontitis [NP]). Periodontal examination consisted of plaque index, gingival index, probing depth, bleeding index, and attachment loss measurements. Current smoking was assessed by determination of serum cotinine levels by enzyme-linked immunosorbent assay (ELISA), and serum CRP levels were determined using a high-sensitivity ELISA assay. RESULTS: The three groups were significantly different from one another (P <0.0001). The 95% confidence interval for serum CRP concentrations were as follows: NP, 0.65919 (0.4901 to 0.8869); LAgP, 1.10138 (0.8265 to 1.468); and GAgP, 2.05318 (1.5313 to 2.7538) mg/l. CRP levels in both LAgP and GAgP subjects were significantly greater than those in NP subjects, and levels in GAgP were significantly greater than those in LAgP. Following adjustment of the data for periodontal and demographic variables and current smoking, both mean probing depth and periodontal diagnosis remained correlated with CRP levels. CONCLUSIONS: Patients with AgP have statistically significant elevations in serum CRP levels compared to subjects without periodontitis. Elevated CRP in these subjects might represent a contribution of periodontal infections to systemic inflammation in relatively young individuals.

Quantitative measures of aggressive periodontitis show substantial heritability and consistency with traditional diagnoses.

BACKGROUND: Aggressive periodontitis (AgP) research nearly always classifies subjects into traditional discrete categories of localized or generalized, based upon degree of attachment loss (AL) and types of affected teeth. Since AL is continuous and quantitative, however, useful information is lost. We developed quantitative measures of AgP, compared these to traditional methods, and estimated heritabilities in families. METHODS: We examined 237 healthy, 169 localized AgP, and 204 generalized AgP subjects. We used the site of maximum AL of each tooth to calculate means for each subject for different groups of teeth. We also applied principal components analysis (PCA) to condense variation among 28 teeth into three orthogonal (uncorrelated) variables. We used discriminant function analysis (DFA) to evaluate how well the quantitative measures match with traditional classifications. Quantitative trait heritabilities were estimated by variance components. RESULTS: PCA clustered first molars, incisors, and the other teeth into three groups. DFA showed that quantitative measures classified subjects consistent with traditional methods (87% to 94% agreement). Heritabilities ranged from 13.7% (P = 0.10) to 30.0% (P = 0.008) for quantitative measures, with highest values obtained for first molars. A combination of the principal component variables most heavily weighted on first molars and incisors gave the best model of disease susceptibility, with good separation of healthy versus diseased subjects, independent of disease extent or severity. CONCLUSIONS: Quantitative measures may provide improved precision and power for many kinds of periodontal research. Our finding of significant heritability supports their use in gene mapping studies of AgP susceptibility.

Prostaglandin E2-mediated regulation of immunoglobulin G2 via interferon gamma.

BACKGROUND: Patients with localized aggressive periodontitis (LAgP) produce elevated levels of IgG2 both in vivo and in vitro. Responses to the periodontitis-associated pathogens Actinobacillus actinomycetemcomitans and Porphyromonas gingivalis are dominated by IgG2, and these IgG2 responses are associated with reduced extent and severity of disease. Little is known about regulation of the IgG2 subclass, although prostaglandin E2 (PGE2) (a mediator known to polarize responses toward Th-2) and interferon (IFN)-gamma (a Th-1 mediator) both promote IgG2 production. This unusual relationship prompted the hypothesis that, in certain circumstances, PGE2 enhances rather than inhibits IFN-gamma production. METHODS: To test this hypothesis, indomethacin (IND)-treated peripheral blood mononuclear cell (PBL) cultures from healthy volunteers were stimulated with pokeweed mitogen (PWM), and the cultures were manipulated by adding PGE2, rIFN-gamma, rIL-Ialpha, rIL-1beta, rIL-6, or rIL-12. Production of IgG1, IgG2, IFN-gamma, and PGE2 was monitored by enzyme-linked immunosorbent assay. RESULTS: Indomethacin treatment inhibited IgG1 and IgG2 production, and PGE2 restored both immunoglobulins in PWM-stimulated cultures. Remarkably, addition of IFN-gamma also restored IND-suppressed IgG2 but not IgG1. In contrast, addition of rIL (interleukin)-1alpha, rIL-1beta, rIL-6, or rIL-12 did not restore IgG2 responses. Furthermore, IND suppressed IFN-gamma production and PGE2 increased IFN-gamma levels. Kinetic studies indicate that PGE2 production occurred on the first day of culture, followed by IFN-gamma two days later. CONCLUSIONS: These findings support the concept that in certain circumstances, PGE2 production can lead to increased IFN-gamma and that this IFN-gamma selectively promotes IgG2 responses. These data suggest that the elevated PGE2 observed in LAgP patients may contribute to increased IFN-gamma production and help explain elevated IgG2 responses.

Locally produced anti-phosphorylcholine and anti-oxidized low-density lipoprotein antibodies in gingival crevicular fluid from aggressive periodontitis patients.

BACKGROUND: Sera from patients with periodontal attachment loss contain higher concentrations of IgG anti-phosphorylcholine (anti-PC) than sera from healthy subjects. Furthermore, a large proportion of plaque bacteria bear PC-containing surface antigens, implicating the oral flora as a source of immunogen for anti-PC. Additionally, anti-PC is cross-reactive with a variety of oral bacterial antigens and human antigens such as oxidized low-density lipoprotein (oxLDL). We hypothesized that, if the oral flora is a source of PC antigens, then we should be able to detect local anti-PC and anti-oxLDL production in gingival crevicular fluid (GCF). METHODS: To test this, we collected 66 GCF samples from 15 patients with aggressive periodontitis and examined both the GCF samples and serum samples for their content of IgG anti-PC, IgG anti-LDL, and IgG anti-oxLDL by enzyme-linked immunosorbent assay. We also determined levels of anti-tetanus toxoid (anti-TT) as a non-oral antigen control. Serum and GCF concentrations of serum albumin (HSA) were also determined for use as a dilution marker. A conservative GCF:serum antibody ratio of greater than 1.5 was considered to be evidence of local antibody production. RESULTS: For the non-oral antigen TT, only one out of 62 samples contained locally produced antibody. Eight out of 64 samples (7 from a single subject) demonstrated local production of anti-LDL. In contrast, 28 out of 66 samples demonstrated local production of anti-PC, and 47 out of 66 samples contained locally produced anti-oxLDL. It was observed that A. actinomycetemcomitans strains containing or devoid of PC could absorb anti-oxLDL from human sera. Although there was a correlation between the ratios of anti-PC and anti-oxLDL (Spearman's rho = 0.35, P = 0.0037), local production of both antibodies was found in only 17 out of 65 samples, indicating that these antibodies are not always reflective of reactivity to the same antigens. CONCLUSION: The local production of anti-PC and anti-oxLDL further implicates the oral flora as a source of antigen that may mediate immune reactions of relevance to cardiovascular and other systemic diseases.

Serum anticardiolipin concentrations in patients with chronic periodontitis following scaling and root planing.

BACKGROUND: Anticardiolipin antibodies (antiCl), present in some patients with autoimmune disease, are associated with thrombosis, fetal loss, and other conditions. A significant proportion of patients with chronic periodontitis (CP) test positive for antiCl, likely because some periodontal pathogens contain antigens homologous to the target antigen of antiCl on the serum protein ß-2 glycoprotein-I (ß2GPI) and thus can induce antiCl by molecular mimicry. The authors hypothesized that treatment of periodontitis by scaling and root planing (SRP) could therefore decrease serum titers of antiCl in patients with CP. METHODS: Thirty patients with CP received complete periodontal examinations at baseline including assessment of probing depth, attachment loss, gingival index, and plaque index. SRP was performed in two sessions at 2-week intervals. Eight weeks later, patients were reexamined. Blood samples were taken at baseline, 2 weeks after the initial therapy appointment, and 8 weeks after the completion of treatment for assessment of immunoglobulin (Ig)G and IgM antiCl levels. RESULTS: All periodontal parameters improved significantly. Consistent with previous observations, five (16.7%) of the 30 patients exhibited elevated levels of IgG or IgM antiCl at baseline. Following treatment, the concentrations of IgG and IgM antiCl remained unchanged for the entire cohort of 30 patients. However, in the five patients with elevated antiCl at baseline, IgM antiCl concentrations decreased significantly (P = 0.0008) owing to therapy, while IgG antiCl did not. CONCLUSION: The oral microflora is a likely source of antigen inducing antiCl in CP, since IgM antiCl levels can be reduced in the short term with conservative therapy.

Inflammatory mechanisms linking periodontal diseases to cardiovascular diseases.

AIMS: In this article, inflammatory mechanisms that link periodontal diseases to cardiovascular diseases are reviewed. METHODS: This article is a literature review. RESULTS: Studies in the literature implicate a number of possible mechanisms that could be responsible for increased inflammatory responses in atheromatous lesions due to periodontal infections. These include increased systemic levels of inflammatory mediators stimulated by bacteria and their products at sites distant from the oral cavity, elevated thrombotic and hemostatic markers that promote a prothrombotic state and inflammation, cross-reactive systemic antibodies that promote inflammation and interact with the atheroma, promotion of dyslipidemia with consequent increases in pro-inflammatory lipid classes and subclasses, and common genetic susceptibility factors present in both disease leading to increased inflammatory responses. CONCLUSIONS: Such mechanisms may be thought to act in concert to increase systemic inflammation in periodontal disease and to promote or exacerbate atherogenesis. However, proof that the increase in systemic inflammation attributable to periodontitis impacts inflammatory responses during atheroma development, thrombotic events or myocardial infarction or stroke is lacking.

Birth weight of infants of mothers with aggressive periodontitis.

BACKGROUND: It was hypothesized that if periodontal infections predispose low birth weights and premature birth, then such outcomes should be apparent when the mother has aggressive periodontitis (AgP). METHODS: Birth weight data were collected by questionnaire from females with AgP, their periodontally healthy siblings, and unrelated periodontally healthy women. Both prospective and retrospective birth outcome data were used. Because many of the periodontal evaluations were performed after the births, there were incomplete data regarding most of the risk factors for low birth weight. We determined associations between mothers' periodontal diagnoses and clinical variables and the reported birth weights. RESULTS: There were no significant differences in mean birth weights of babies born to control subjects or AgP patients. This was true whether all the births were considered or only those reported <1 or 2 years before periodontal examination. For periodontally healthy controls, 13.2% of babies born to siblings of AgP patients and 12.8% of babies born to unrelated mothers weighed <2,500 g, whereas 9.9% of those born to mothers with generalized AgP and 10.3% of those born to mothers with localized AgP weighed <2,500 g. CONCLUSIONS: Because of the relative rarity of AgP in the population, and attendant difficulties in performing a prospective study of its association with pregnancy outcomes, we used a compromised approach using prospective data as well as weaker retrospective data assuming that disease onset was likely before the births. Our results, within the limitations of this approach, indicate no evidence that AgP in the mother predisposes low birth weights. AgP has many unique biologic characteristics that differentiate it from chronic forms of periodontal disease, and the possible lack of its association with birth weight may be another such characteristic.

Endocarditis-associated oral streptococci promote rapid differentiation of monocytes into mature dendritic cells.

Endocarditis is frequently attributable to oral streptococci, but mechanisms of pathogenesis are not well understood, although monocytes appear to be important. High titers of interleukin-12 (IL-12) are produced by peripheral blood mononuclear cells (PBMC) after engaging Streptococcus mutans, but monocytes in developing endocardial vegetations tend to disappear rather than become macrophages. These data prompted the hypothesis that streptococcus-infected monocytes differentiate into short-lived IL-12-producing dendritic cells (DCs) rather than macrophages. PBMC from healthy subjects were stimulated with six isolates of oral streptococci, three nonstreptococcal oral bacteria, or IL-4 plus granulocyte-macrophage colony-stimulating factor, and the appearance of cells with markers typical of mature DCs (CD83(+), CD86(+), CD11c(+), and CD14(-)) was monitored. Supernatant fluids from the PBMC cultures were harvested and IL-12 p70 levels were determined. S. mutans-stimulated monocytes were analyzed for their ability to elicit allogeneic mixed-lymphocyte reactions. All streptococci examined, except one strain of Streptococcus oralis (35037), rapidly induced up-regulation of CD83 and CD86 and a loss of CD14 in the CD11c(+) monocyte population within 20 h. Induction of IL-12 was CD14 dependent and correlated with streptococcal isolates that promoted the DC phenotype. Major histocompatibility complex (MHC) class II expression was up-regulated by S. mutans, and these cells were short-lived and elicited potent allogeneic mixed-lymphocyte reactions typical of DCs. In summary, monocytes stimulated with endocarditis-associated oral streptococci rapidly exhibited the DC phenotype and functions. These data suggest that the initiation of bacterial endocarditis by oral streptococci may involve monocyte-to-DC differentiation, and this may help explain the low levels of macrophages in the site.

Altered lipoprotein subclass distribution and PAF-AH activity in subjects with generalized aggressive periodontitis.

In this study, we examined whether the documented increase of plasma triglycerides in patients with generalized aggressive periodontitis (GAgP) is associated with changes in lipoprotein subclass distribution and/or LDL-associated platelet-activating factor acetylhydrolase (PAF-AH) activity. Lipoprotein subclasses were analyzed in whole plasma samples using nuclear magnetic resonance methods. Compared with subjects without periodontitis (NP subjects; n = 12), GAgP subjects (n = 12) had higher plasma levels of large, medium, and small VLDL (35.0 +/- 6.7 vs. 63.1 +/- 9.6 nmol/l; P = 0.025), higher levels of intermediate density lipoprotein (24.8 +/- 11.6 vs. 87.2 +/- 16.6 nmol/l; P = 0.006), lower levels of large LDL (448.3 +/- 48.5 vs. 315.8 +/- 59.4 nmol/l; P = 0.098), and higher levels of small LDL (488.2 +/- 104.2 vs. 946.7 +/- 151.6 nmol/l; P = 0.021). The average size of LDL from NP and GAgP subjects was 21.4 +/- 0.2 and 20.6 +/- 0.3 nm, respectively (P = 0.031). Compared with NP subjects, GAgP subjects had a greater number of circulating LDL particles (961.3 +/- 105.3 vs. 1,349.0 +/- 133.2 nmol/l; P = 0.032). Differences in the plasma levels of large, medium, and small HDL were not statistically significant. NP and GAgP subjects had similar plasma levels of total LDL-associated PAF-AH activity; however, LDL of GAgP subjects contained less PAF-AH activity per microgram of LDL protein (1,458.0 +/- 171.0 and 865.2 +/- 134 pmol/min/microg; P = 0.014). These results indicate that, in general, GAgP subjects have a more atherogenic lipoprotein profile and lower LDL-associated PAF-AH activity than NP subjects. These differences may help explain the increased risk of GAgP subjects for cardiovascular disease.

Opsonization of Actinobacillus actinomycetemcomitans by immunoglobulin G antibody reactive with phosphorylcholine.

We used two strains of Actinobacillus actinomycetemcomitans, one bearing phosphorylcholine (PC) (strain D045D-40) and one devoid of PC antigens (strain DB03A-42), as well as a nonencapsulated strain of Streptococcus pneumoniae (strain 39937), to examine the opsonic properties of physiological concentrations (

Differential expression of platelet-activating factor acetylhydrolase in macrophages and monocyte-derived dendritic cells.

Although macrophages (Mphi) and monocyte-derived dendritic cells (MDDC) come from a common precursor, they are distinct cell types. This report compares the two cell types with respect to the metabolism of platelet-activating factor (PAF), a biologically active lipid mediator. These experiments were prompted by our studies of localized juvenile periodontitis, a disease associated with high IgG2 production and a propensity of monocytes to differentiate into MDDC. As the IgG2 Ab response is dependent on PAF, and MDDC selectively induce IgG2 production, we predicted that PAF levels would be higher in MDDC than in Mphi. To test this hypothesis, human MDDC were prepared by treating adherent monocytes with IL-4 and GM-CSF, and Mphi were produced by culture in M-CSF. Both Mphi and MDDC synthesized PAF; however, MDDC accumulated significantly more of this lipid. We considered the possibility that PAF accumulation in MDDC might result from reduced turnover due to lower levels of PAF acetylhydrolase (PAFAH), the enzyme that catabolizes PAF. Although PAFAH increased when monocytes differentiated into either cell type, MDDC contained significantly less PAFAH than did Mphi and secreted almost no PAFAH activity. The reduced levels of PAFAH in MDDC could be attributed to lower levels of expression of the enzyme in MDDC and allowed these cells to produce PGE(2) in response to exogenous PAF. In contrast, Mphi did not respond in this manner. Together, these data indicate that PAF metabolism may impinge on regulation of the immune response by regulating the accessory activity of MDDC.

Delineation of the role of platelet-activating factor in the immunoglobulin G2 antibody response.

Localized aggressive periodontitis (LAgP) is a chronic inflammatory disease characterized by severe destruction of periodontal tissues surrounding the first molars and incisors. LAgP subjects produce large amounts of immunoglobulin G2 (IgG2) antibody against oral pathogens, and this response is inversely correlated with the severity of disease. We previously demonstrated that platelet-activating factor (PAF) is required for optimal IgG2 responses. The present investigation was designed to determine the mechanism of IgG2 induction by PAF. Exogenous PAF acetylhydrolase suppressed approximately 80% of pokeweed mitogen-stimulated IgG2 production, confirming that PAF is essential for optimal responses. PAF-activated leukocytes produced gamma interferon (IFN-gamma), a Th1 cytokine that has been associated with IgG2 responses in previous studies. The monocyte-derived cytokines interleukin-12 (IL-12) and IL-18 are upstream of IFN-gamma production, and IgG2 production was suppressed by neutralizing antibodies against these proteins. In addition, PAF induced monocyte-derived dendritic cells (DC) but not macrophages (MPhi) to secrete IL-12 and IL-18. This observation was interesting because monocyte differentiation in LAgP subjects is skewed to the DC phenotype. Although other investigators have implicated IFN-gamma in IgG2 production, its precise role in this response is controversial. Our studies suggest that IFN-gamma induces isotype switching to IgG2 but only in concert with the Th2 cytokine IL-4. Thus, it appears that the unique PAF metabolism of LAgP monocytes or DC promotes Th1 responses that are essential for optimal IgG2 antibody production. As IgG2 antibodies opsonize oral bacteria and promote their clearance and destruction, these alterations in PAF metabolism may be essential for limiting disease severity in LAgP patients.

Antibody reactive with Porphyromonas gingivalis hemagglutinin in chronic and generalized aggressive periodontitis.

BACKGROUND: Porphyromonas gingivalis, a black-pigmented, gram-negative anaerobe, is found in periodontitis lesions and its presence in subgingival plaque significantly increases the risk for periodontitis. We have previously shown that patients with aggressive forms of periodontitis that are seropositive for P. gingivalis have less attachment loss than those that are seronegative. This suggests that antibody reactive with antigens of P. gingivalis may be protective and decrease disease severity and extent. Recent studies in the murine abscess model and in the host antibody response in chronic periodontitis patients suggest that antibody reactive with P. gingivalis hemagglutinin may be an important protective antibody response. OBJECTIVES: In this study, we tested the hypothesis that there was a significant relationship between antibody reactive with P. gingivalis hemagglutinin and measures of periodontal attachment loss. METHODS: We determined the immunoglobulin G (IgG) antibody concentration reactive with recombinant P. gingivalis hemagglutinin in 117 chronic periodontitis and 90 generalized aggressive periodontitis patients. We also determined the IgG subclass distribution for antibody reactive with P. gingivalis hemagglutinin. RESULTS AND CONCLUSIONS: We found IgG reactive with P. gingivalis hemagglutinin in both chronic periodontitis and generalized aggressive periodontitis patients. Most of this IgG antibody was of the IgG1 and IgG3 subclasses. Antibody reactive with P. gingivalis hemagglutinin, however, did not have a significant relationship with measures of periodontal attachment loss.