Dongming Lin

Periodontal Disease and Coronary Heart Disease A Reappraisal of the Exposure

Background—Results from studies relating periodontal disease to cardiovascular disease have been mixed. Residual confounding by smoking and use of clinical measures of periodontal disease rather than measures of infection have been 2 major criticisms. The aims of this study were to investigate relationships between prevalent coronary heart disease (CHD) and 2 exposures, (1) clinical periodontal disease and (2) IgG antibodies to 17 oral organisms, and to evaluate the role of smoking in these relationships. Methods and Results—Our study is based on a subset of participants in the Atherosclerosis Risk in Communities (ARIC) Study, who received a complete periodontal examination during visit 4 (1996–1998). The exposures were periodontal status and serum IgG antibody levels against 17 periodontal organisms, and the outcome was prevalent CHD at visit 4. Multivariable analyses indicate that periodontal status is not significantly associated with CHD in either ever smokers or never smokers. Similar analyses evaluating antibodies indicate that high antibodies (above the median) to Treponema denticola (odds ratio [OR]=1.7; 95% CI, 1.2 to 2.3), Prevotella intermedia (OR=1.5; 95% CI, 1.1 to 2.0), Capnocytophaga ochracea (OR=1.5; 95% CI, 1.1 to 2.1), and Veillonella parvula (OR=1.7; 95% CI, 1.2 to 2.3) are significantly associated with CHD among ever smokers, whereas Prevotella nigrescens (OR=1.7; 95% CI, 1.1 to 2.6), Actinobacillus actinomycetemcomitans (OR=1.7; 95% CI, 1.2 to 2.7), and Capnocytophaga ochracea (OR=2.0; 95% CI, 1.3 to 3.0) were associated with CHD among never smokers. Conclusions—Clinical signs of periodontal disease were not associated with CHD, whereas systemic antibody response was associated with CHD in ever smokers and never smokers. These findings indicate that the quality and quantity of the host response to oral bacteria may be an exposure more relevant to systemic atherothrombotic coronary events than clinical measures.

Porphyromonas gingivalis Infection during Pregnancy Increases Maternal Tumor Necrosis Factor Alpha, Suppresses Maternal Interleukin-10, and Enhances Fetal Growth Restriction and Resorption in Mice

ABSTRACT Epidemiological studies have shown a potential association between maternal periodontitis and pregnancy complications. We used a pregnant murine model to study the effect of infection with the periodontal pathogen Porphyromonas gingivalis on pregnancy outcomes. Female BALB/c mice were inoculated with heat-killed P. gingivalis (109 CFU) in a subcutaneous chamber and mated 2 weeks later. At gestation day (GD) 7.5, mice were challenged with live P. gingivalis (107 CFU) (n = 20) or broth (control; n = 8) and sacrificed at GD 16.5. Fetal growth restriction (FGR, <0.46 g) was defined as fetuses with weights 2 standard deviations (SD) smaller than controls (0.56 ± 0.05 g [mean ± SD]). Among the 20 challenged mice, 8 had both normal-weight (0.51 ± 0.11 g) and FGR (0.34 ± 0.1 g) fetuses within the same litter. All other challenged dams had normal-weight fetuses (0.57 ± 0.04 g). Maternal liver, uterus, and spleen samples were examined for P. gingivalis DNA using a PCR technique. Of the eight challenged mice with FGR fetuses, three had PCR signals for P. gingivalis in liver and uterus, but not in the spleen. Liver, uterus, and spleen were negative for P. gingivalis DNA among all other challenged and control mice. In serum of dams with FGR fetuses, tumor necrosis factor alpha levels were elevated significantly, while interluekin-10 levels were significantly reduced compared to levels in dams with normal fetuses. P. gingivalis-specific serum immunoglobulin G levels were significantly elevated in dams with FGR fetuses compared to dams without any FGR fetuses. These data demonstrate that P. gingivalis-induced murine FGR is associated with systemic dissemination of the organism and activated maternal immune and inflammatory responses.

Bacterial Infection Promotes DNA Hypermethylation

Maternal oral infection, caused by bacteria such as C. rectus or P. gingivalis, has been implicated as a potential source of placental and fetal infection and inflammatory challenge, which increases the relative risk for pre-term delivery and growth restriction. Intra-uterine growth restriction has also been reported in various animal models infected with oral organisms. Analyzing placental tissues of infected growth-restricted mice, we found down-regulation of the imprinted Igf2 gene. Epigenetic modification of imprinted genes via changes in DNA methylation plays a critical role in fetal growth and development programming. Here, we assessed whether C. rectus infection mediates changes in the murine placenta Igf2 methylation patterns. We found that infection induced hypermethylation in the promoter region-P0 of the Igf2 gene. This novel finding, correlating infection with epigenetic alterations, provides a mechanism linking environmental signals to placental phenotype, with consequences for development.

Porphyromonas gingivalis Infection in Pregnant Mice Is Associated with Placental Dissemination, an Increase in the Placental Th1/Th2 Cytokine Ratio, and Fetal Growth Restriction

ABSTRACT Our previous animal studies showed that maternal Porphyromonas gingivalis infection in a subcutaneous chamber is associated with hepatic and uterine translocation, as well as systemic induction of maternal inflammatory responses, both of which were associated with fetal growth restriction (FGR). However, P. gingivalis-challenged dams had fetuses with either FGR (2 standard deviations below mean weight of nonchallenged dams) or normal weight. Therefore, the objective of this study was to determine whether maternal infection with P. gingivalis compromises normal fetal development via direct placental invasion and induction of fetus-specific placental immune responses characterized by a proinflammatory Th1-type cytokine profile. P. gingivalis-specific DNA was detected in placentas and fetuses of FGR and normal littermates from P. gingivalis-infected dams. Th1- and Th2-type cytokine mRNA as well as tumor necrosis factor alpha and transforming growth factor β2 mRNA were examined in placental tissue by using reverse transcription-PCR to determine Th1/Th2 ratios. For eight litters containing both normal-weight and FGR fetuses, P. gingivalis DNA was detected only in the placentas of FGR fetuses. All fetuses and all amniotic fluid samples from infected and control dams were negative for P. gingivalis DNA. mRNA levels of gamma interferon and interleukin-2 (IL-2) were significantly increased in placentas of FGR fetuses, while expression of IL-10 was significantly decreased in the same group. These data indicate that, in P. gingivalis-challenged dams, within each litter there is placenta-specific translocation of P. gingivalis that results in growth restriction of the targeted fetus, which is associated with a shift in the placental Th1/Th2 cytokine balance.

Effects of maternal Campylobacter rectus infection on murine placenta, fetal and neonatal survival, and brain development

BACKGROUND Maternal periodontal infection has been associated with increased risk of prematurity and low birthweight. Infection and inflammatory pathways that mediate prematurity have also been implicated in neonatal developmental impairments. The objective of this study was to determine whether maternal Campylobacter rectus infection that induces fetal growth restriction in a mouse model also compromises neonatal pup survival, growth, and neurodevelopment. METHODS Timed pregnant mice were challenged with C. rectus on gestation day 7.5. One group of animals was sacrificed on embryonic day 16.5 for placental histology and measurement of fetal brain mRNA expression of tumor necrosis factor (TNF)-α and interferon (IFN)-γ. Another group of animals was allowed to deliver to follow pup survival, growth, and brain structure at day 9. RESULTS C. rectus challenge resulted in abnormal placental architecture with inflammation and a 2.8-fold increase in fetal brain expression of IFN-γ (P = 0.04). Pup birthweight was unaffected by C. rectus exposure, but lethality was 3.9-fold higher after 1 week. Ultrastructurally, the 9-day neonatal brain tissue displayed cellular and myelin alterations consistent with white matter damage. CONCLUSIONS Maternal C. rectus infection induces placental inflammation and decidual hyperplasia as well as concomitant increase in fetal brain IFN-γ. Maternal infection increased pup mortality, and preliminary findings demonstrate ultrastructural changes in the hippocampal region of the neonatal brain, in a manner analogous to the effects of maternal infection on white matter damage seen in humans. Thus, the threat of maternal oral infectious exposure during pregnancy may not be limited to the duration of gestation, but may also potentially affect perinatal neurological growth and development.