Metabolic Signaling and Spatial Interactions in the Oral Polymicrobial Community.

Oral supra- and subgingival biofilms are complex communities in which hundreds of bacteria, viruses, and fungi reside and interact. In these social environments, microbes compete and cooperate for resources, such as living space and nutrients. The metabolic activities of bacteria can transform their microenvironment and dynamically influence the fitness and growth of cohabitating organisms. Biofilm communities are temporally and spatially organized largely due to cell-to-cell communication, which promotes synergistic interactions. Metabolic interactions maintain biofilm homeostasis through mutualistic cross-feeding, metabolic syntrophy, and cross-respiration. These interactions include reciprocal metabolite exchanges that promote the growth of physiologically compatible bacteria, processive catabolism of complex substrates, and unidirectional interactions that are globally important for the polymicrobial community. Additionally, oral bacterial interactions can lead to detoxification of oxidative compounds, which will provide protection to the community at large. It has also been established that specific organisms provide terminal electron acceptors to partner species that result in a shift from fermentation to respiration, thus increasing ATP yields and improving fitness. Indeed, many interspecies relationships are multidimensional, and the net outcome can be spatially and temporally dependent. Cross-kingdom interactions also occur as oral yeast are antagonistic to some oral bacteria, while numerous mutualistic interactions contribute to yeast-bacterial colonization, fitness in the oral community, and the pathogenesis of caries. Consideration of this social environment reveals behaviors and phenotypes that are not apparent through the study of microbes in isolation. Here, we provide a comprehensive overview of the metabolic interactions that shape the oral microbial community.

Avoidance learning and classical eyeblink conditioning as model systems to explore a learning diathesis model of PTSD.

Experiencing a trauma is necessary, but not sufficient, for the development of post-traumatic stress disorder (PTSD) in that most individuals who experience a trauma do not go on to develop PTSD. This suggests that identifiable vulnerabilities (i.e., diatheses) exist that increase the risk for the development of PTSD. One such factor is the personality temperament of behavioral inhibition (BI). Organisms that exhibit BI were studied in the context of avoidance learning and classical eyeblink conditioning. We present a body of evidence supporting a learning diathesis model in which behaviorally inhibited organisms exhibit enhanced acquisition and resistance to extinction in these tasks. Vulnerable individuals show learning-related enhancements when the learning situation involves some degree of uncertainty. We review the known brain circuitry involved in classical eyeblink conditioning in the context of the learning diathesis model. Finally, the data reviewed here demonstrate the value of studying vulnerability factors in humans and a rodent model using cerebellar-dependent learning tasks for understanding the acquisition and endurance of PTSD symptomatology.

Transcriptome analysis of Porphyromonas gingivalis and Acinetobacter baumannii in polymicrobial communities.

Acinetobacter baumannii is a nosocomial, opportunistic pathogen that causes several serious conditions including meningitis, septicemia, endocarditis, and pneumonia. It can be found in the oral biofilm, which may be a reservoir for pneumonia and chronic obstructive pulmonary disease. Subgingival colonization by A. baumannii is associated with chronic and aggressive periodontitis as well as refractory periodontal disease. Porphyromonas gingivalis, a keystone periodontal pathogen localized to subgingival plaque, is also implicated in several chronic conditions including aspiration pneumonia. Although both bacteria are found together in subgingival plaque and can cause multiple polymicrobial infections, nothing is known about the interactions between these two important human pathogens. In this study, we used RNA sequencing to understand the transcriptional response of both species as they adapt to heterotypic communities. Among the differentially regulated genes were those encoding a number of important virulence factors for both species including adhesion, biofilm formation, and protein secretion. Additionally, the presence of A. baumannii increased the abundance of P. gingivalis in model dual-species communities. Collectively these results suggest that both P. gingivalis and A. baumannii adapt to each other and have synergistic potential for increased pathogenicity. In identifying the mechanisms that promote pathogenicity and refractory disease, novel approaches to mitigate polymicrobial synergistic interactions may be developed to treat or prevent associated diseases.

Plasminogen binding and degradation by Treponema denticola: Identification of the plasminogen binding interface on the FhbB protein.

Treponema denticola is a proteolytic-anaerobic spirochete whose abundance in the subgingival crevice correlates with periodontal disease severity. Treponema denticola evades serum-mediated killing through the binding of factor H (FH), a negative regulator of the complement system. The T. denticolaFH receptor has been identified as FhbB, an 11.4kDa immunodominant lipoprotein. Three distinct subfamilies of FhbB proteins have been delineated and designated as FhbB1, FhbB2 and FhbB3. In this study we demonstrate that all FhbB variants bind human plasminogen (Plg). Competitive binding analyses revealed that FH and Plg do not compete for binding. Binding studies with FhbB135405 site-directed amino acid substitution mutants demonstrated that the interaction domains for FH and Plg on FhbB are separable. Inhibition of Plg-FhbB binding by ε-aminocaproic acid (a lysine analog) indicates that binding is mediated by electrostatic interactions that presumably occur with Lys binding sites contained within Plg "Kringle" domains 1, 2, 4 or 5. Similar to that demonstrated for FH, Plg can also serve as a substrate for the T. denticola protease, dentilisin. The in vivo consequences of dentilisin-mediated cleavage of Plg remained to be determined. The data presented demonstrate that FhbB is a multi-functional protein that may contribute to virulence through several mechanisms including immune evasion, manipulation of the host immune response, adherence or tissue invasion.

Structure-function aspects of the Porphyromonas gingivalis tyrosine kinase Ptk1.

The development of synergistically pathogenic communities of Porphyromonas gingivalis and Streptococcus gordonii is controlled by a tyrosine-phosphorylation-dependent signaling pathway in P. gingivalis. The Ptk1 bacterial tyrosine (BY) kinase of P. gingivalis is required for maximal community development and for the production of extracellular polysaccharide. We show that the consensus BY kinase Walker A and B domains, the RK cluster, and the YC domain of Ptk1 are necessary for autophosphorylation and for substrate phosphorylation. Mass spectrometry showed that six tyrosine residues in a 16-amino-acid C-terminal region were phosphorylated in recombinant (r) Ptk1. Complementation of a ptk1 mutant with the wild-type ptk1 allele in trans restored community development between P. gingivalis and S. gordonii, and extracellular polysaccharide production by P. gingivalis. In contrast, complementation of Δptk1 with ptk1 containing a mutation in the Walker A domain failed to restore community development or extracellular polysaccharide production. rPtk1 was capable of phosphorylating the tyrosine phosphatase Ltp1 and the transcriptional regulator CdhR, both of which are involved in the development of P. gingivalis communities with S. gordonii.

The Treponema denticola AtcR LytTR domain-containing response regulator interacts with three architecturally distinct promoter elements: implications for understanding the molecular signaling mechanisms that drive the progression of periodontal disease.

Treponema denticola is an oral spirochete and periopathogen that transitions from low abundance in healthy subgingival crevices to high abundance in periodontal pockets. The T. denticola response regulator AtcR harbors the relatively rare, LytTR DNA-binding domain. LytTR domain containing response regulators control critical transcriptional responses required for environmental adaptation. Using a multi-step bioinformatics approach, 26 strong lytTR recognition motifs were identified in the genome of T. denticola strain 35405. Electrophoretic mobility shift assays demonstrated that AtcR binds to these recognition motifs. High specificity-high affinity complexes formed with phosphorylated AtcR. The LytTR recognition sequences were found to exist in three distinct promoter architectures designated as LytTR1, LytTR2 and LytTR3 promoters. LytTR1 and LytTR2 promoters harbor σ(54) binding sites. The functional diversity of the proteins encoded by the putative AtcR regulon suggests that AtcR sits at the top of a regulatory cascade that plays a central role in facilitating T. denticola's ability to adapt to changing environmental conditions and thrive in periodontal pockets.

Analysis of the complement sensitivity of oral treponemes and the potential influence of FH binding, FH cleavage and dentilisin activity on the pathogenesis of periodontal disease.

Treponema denticola, a periopathogen, evades complement-mediated killing by binding the negative complement regulatory protein factor H (FH) to its surface via the FhbB protein. Paradoxically, bound FH is cleaved by T. denticola's dentilisin protease, a process hypothesized to trigger localized dysregulation of complement activation in periodontal pockets. The ability of other oral treponemes to evade complement-mediated killing and bind and cleave FH has not been assessed. In this report, we demonstrate that representative isolates of Treponema socranskii, Treponema medium, Treponema pectinovorum and Treponema maltophilum are also serum resistant, whereas Treponema vincentii and Treponema amylovorum are serum sensitive. Although T. denticola's ability to evade complement-mediated killing is strictly dependent on FH binding, other serum-resistant treponemal species lack FhbB and do not bind FH, indicating an FH-independent mechanism of complement evasion. To assess the influence of FhbB sequence variation on FH binding and cleavage by T. denticola, fhbB sequences were determined for 30 isolates. Three distinct phyletic types were identified. All T. denticola strains bound FH and were serum resistant, but differences in binding kinetics, dentilisin activity and FH cleavage ability were observed. Based on these analyses, we hypothesize that the composition of the T. denticola population is a determining factor that influences the progression and severity of periodontal disease.

Sequence divergence in the Treponema denticola FhbB protein and its impact on factor H binding.

Treponema denticola is an anaerobic spirochete whose abundance in the subgingival crevice correlates with the development and severity of periodontal disease. The ability of T. denticola to survive and thrive in the hostile environment of the periodontal pocket is due, at least in part, to its ability to bind factor H (FH), a negative regulator of the alternative complement pathway. The FH binding protein of T. denticola has been identified as FhbB and its atomic structure has been determined. The interaction of FH with T. denticola is unique in that FH bound to the cell surface is cleaved by the T. denticola protease, dentilisin. It has been postulated that FH cleavage by T. denticola leads to immune dysregulation in periodontal pockets. In this study, we conduct a comparative assessment of the sequence, properties, structure and ligand binding kinetics of the FhbB proteins of strains 33521 and 35405. The biological outcome of the interaction of these strains with FH could differ significantly as 33521 lacks dentilisin activity. The data presented here offer insight into our understanding of the interactions of T. denticola with the host and its potential to influence disease progression.

Identification of the primary mechanism of complement evasion by the periodontal pathogen, Treponema denticola.

Treponema denticola, a periodontal pathogen, binds the complement regulatory protein Factor H (FH). Factor H binding protein B (FhbB) is the sole FH binding protein produced by T. denticola. The interaction of FhbB with FH is unique in that FH is bound to the cell and then cleaved by the T. denticola protease, dentilisin. A ∼ 50-kDa product generated by dentilisin cleavage is retained at the cell surface. Until this study, a direct role for the FhbB-FH interaction in complement evasion and serum sensitivity had not been demonstrated. Here we assess the serum resistance of T. denticola strain 35405 (Td35405wt) and isogenic mutants deficient in dentilisin (Td35405-CCE) and FhbB production (Td35405ΔfhbB), respectively. Both dentilisin and FhbB have been postulated to be key virulence factors that mediate complement evasion. Consistent with conditions in the subgingival crevice, an environment with a significant concentration of complement, Td35405wt was resistant to serum concentrations as high as 25%. Deletion of fhbB (Td35405ΔfhbB), which resulted in the complete loss of FH binding ability, but not inactivation of dentilisin activity (Td35405-CCE), rendered T. denticola highly sensitive to 25% human serum with 80% of the cells being disrupted after 4 h of incubation. Heat treatment of the serum to inactivate complement confirmed that killing was mediated by complement. These results indicate that the FH-FhbB interaction is required for serum resistance whereas dentilisin is not. This report provides new insight into the novel complement evasion mechanisms of T. denticola.

Expression of the Cydia pomonella granulovirus iap3 gene.

The IAP3 protein of Cydia pomonella granulovirus (CpGV) was the first identified member of the baculovirus IAP family of proteins, which have been shown to block apoptosis in diverse systems. However, little is known of the expression and subcellular localisation of CpGV IAP3 during a viral infection. This study examined IAP3 in cells infected by CpGV and in cells infected by an Autographa californica nucleopolyhedrovirus (AcMNPV) recombinant that carried the CpGV iap3 gene. The levels of iap3 specific transcripts were monitored and production of the protein was assessed using an IAP3-specific antiserum. The data showed that iap3 is expressed during both early and late phases of infection, with a switch occurring from distal early transcription start sites to proximal late start sites. Protein levels are highest after DNA replication. IAP3 is localised exclusively in the cytoplasm. Subcellular fractionation experiments demonstrated that the protein is present in both soluble and membrane-bound cytosolic fractions. The membrane-bound fraction includes IAP3 that is associated with the mitochondria. However, the data do not support the hypothesis that release of cytochrome C from the mitochondria is involved in baculovirus-induced apoptosis.

Differential association of the codon 72 p53 and GSTM1 polymorphisms on histological subtype of non-small cell lung carcinoma.

Traditionally, non-small cell lung cancer (NSCLC) has been evaluated as a unique entity in genotyping studies. However, recent biological data suggest that different NSCLC subtypes, specifically adenocarcinomas (AC) and squamous cell carcinomas (SCC), differentially alter cancer behavior. Several studies have associated a p53 polymorphism at codon 72 with NSCLC susceptibility. This study investigated whether different p53 genotypes altered the overall risk of developing AC versus SCC. Polymorphisms in metabolizing enzymes, together with prolonged exposure to tobacco carcinogens, can result in accumulation of DNA damage; these effects may potentiate the effects of subtle differences in p53 function. Thus, interactions between polymorphisms of p53 and either GSTM1 or GSTT1 were also evaluated. We analyzed 1168 incident lung cancer cases and 1256 control subjects using multiple logistic regression. Histological data were available for 1144 cases (98%): 585 with AC, 284 with SCC, and 275 with other histological subtypes (large cell, small cell, mixed, and other). An increase in the NSCLC risk posed by the p53 Pro allele (versus Arg/Arg) was seen in AC compared with controls [adjusted odds ratio (OR), 1.36; 95% confidence interval (CI), 1.1-1.7] but not in SCC (adjusted OR, 1.04; 95% CI, 0.8-1.4). Among AC and SCC cancer patients, individuals with the GSTM1-null genotype had an OR of 1.80 (95% CI, 1.1-2.8; case-only analysis) of having AC versus SCC if they also carried a p53 Pro allele. We conclude that different genotype combinations of p53 and GSTM1 increase the risk of developing specific histological subtypes of NSCLC.

Health-Related quality-of-life and quality-days incrementally gained in symptomatic nonerosive GERD patients treated with lansoprazole or ranitidine.

Eight-hundred forty-nine patients with symptomatic nonerosive GERD from two clinical trials of lansoprazole 15 mg daily (LAN 15) and lansoprazole 30 mg daily (LAN 30) vs ranitidine 150 mg twice a day (RAN 150) completed a health-related quality-of-life (HRQoL) questionnaire at baseline and four and eight weeks after treatment. The questionnaire included the Short-Form 12, GERD symptoms, eating symptoms, social restrictions, problems with sleep, work disability, treatment satisfaction, and associated importance weights items. Both LAN groups reported greater, although not significant, improvement from baseline to week 8 versus RAN 150 in the majority of HRQoL scales. Treatment satisfaction was significantly higher at week 8 in both LAN groups. Quality-days incrementally gained analysis showed that both LAN groups gained significantly more quality days than RAN 150. Patients taking lansoprazole 15 or 30 mg daily reported better outcomes than those receiving ranitidine 150 twice a day over the eight-week study.

Long-term mortality benefit with abciximab in patients undergoing percutaneous coronary intervention.

OBJECTIVES: The goal of this study was to test: 1) if platelet glycoprotein IIb/IIIa (GP IIb/IIIa) blockade with abciximab bolus plus 12-h infusion reduces mortality after percutaneous coronary intervention (PCI); 2) if prevention of early myocardial infarction (MI) after PCI is a mechanism for reducing mortality; and 3) for risk factors for mortality after PCI. BACKGROUND: Studies of PCI suggest that MI after intervention is predictive of mortality. Abciximab, a platelet GP IIb/IIIa receptor inhibitor, has consistently reduced the incidence of MI among PCI patients in several trials. The presumed mechanism is prevention of platelet thrombus associated with vessel wall injury and downstream embolization into the microcirculation. METHODS: In eight trials, 5,154 patients were randomized to a regimen comprising conventional therapy plus a bolus of abciximab within 1 h before PCI followed by a 12-h infusion; 4,136 controls were randomized to conventional therapy alone. Patient follow-up from six months to three years was available. Survival differences are examined using proportional hazards regression and survival curves. RESULTS: A hazard ratio of 0.71 (95% confidence interval 0.57 to 0.89; p = 0.003) suggests a mortality benefit with abciximab. The absolute reduction in mortality was estimated to be 0.5% through 30 days, 0.7% through six months, 0.9% through one year and 1.8% through three years. Early MI explained 18% of the observed mortality benefit at one year. Multivariate regression suggests that patients with advanced cardiovascular disease may derive the greatest mortality benefit from abciximab. CONCLUSIONS: The evidence from 9,290 randomized PCI patients shows a mortality benefit provided by abciximab bolus plus 12-h infusion.

The interaction between microsomal epoxide hydrolase polymorphisms and cumulative cigarette smoking in different histological subtypes of lung cancer.

Microsomal epoxide hydrolase (mEH) is involved in the metabolism of environmental and tobacco carcinogens. Smaller studies found inconsistent results in the relationship between mEH polymorphisms and lung cancer risk. We investigated the two polymorphisms of mEH in 974 Caucasian lung cancer patients and 1142 controls using PCR-RFLP techniques. The results were analyzed using generalized additive models and logistic regression, adjusting for relevant covariates. There was no overall relationship between mEH genotypes and lung cancer risk. The adjusted odds ratio (OR) of the very low activity genotype versus that of other genotypes combined was 1.00 [95% confidence interval (CI), 0.74-1.34]. However, gene-environment interaction analyses revealed that the ORs decreased as cumulative smoking (defined as square root of pack-years) increased. When pack-years = 0, the OR was 1.89 (95% CI, 1.08-3.28). When pack-years = 28.5, the OR was 1.00 (95% CI, 0.76-1.32), and when pack-years = 80, the OR decreased to 0.65 (95% CI, 0.42-1.00). When cases were stratified according to histological subtypes, the interaction between mEH genotype and cumulative smoking was statistically significant (P < 0.01) for the 222 squamous cell carcinoma cases, whereas it was not significant (P = 0.18) for the 432 adenocarcinoma cases. In conclusion, cumulative cigarette smoking plays a pivotal role in the association between mEH polymorphisms and lung cancer risk, altering the direction of risk (in the case of the very low activity genotype) from a risk factor in nonsmokers to a relatively protective factor in heavy smokers.

The NAD(P)H:quinone oxidoreductase 1 gene polymorphism and lung cancer: differential susceptibility based on smoking behavior.

We conducted a hospital-based case-control study of 814 lung cancer patients and 1123 controls to examine the association of the NAD(P)H: quinone oxidoreductase 1 (NQO1) gene polymorphism with lung cancer susceptibility. Using PCR-RFLP genotyping assay techniques, we analyzed DNA samples to detect the variant forms of the NQO1 gene in exon 6 on chromosome 16q. We examined the relationship between lung cancer odds and NQO1 genotypes after adjusting for age, gender, and smoking behavior using generalized additive modeling. We found no overall association between NQO1 genotypes and lung cancer susceptibility, regardless of age, gender, family history of cancer, or histological cell type. However, our data demonstrated that in both former and current smokers, there was an association between NQO1 genotypes and lung cancer susceptibility that was dependent upon cigarette smoking duration and smoking intensity. For both current and former smokers, smoking intensity was more important in predicting cancer risk than smoking duration for all of the genotypes. Among former smokers, individuals with the T/T genotype were predicted to have a greater cancer risk than those with the C/C genotype for smoking durations up to 37 years. The predicted cancer risk for former smokers with the C/T versus T/T genotype depended on both smoking intensity and smoking duration. Our results support the concept that differential susceptibility to lung cancer is a function of both an inheritable trait in NQO1 metabolism and individual smoking characteristics.

Birth and first-year costs for mothers and infants attributable to maternal smoking.

Maternal smoking during pregnancy has been linked to high costs. This study estimates the magnitude of excess costs attributable to smoking during pregnancy for mothers and infants. The model estimates smoking-attributable costs for 11 infant and maternal conditions. From a claims database of 7784 mothers and 7901 infants who had deliveries during 1996, we estimated total cost over the infants' first year of life for each mother and infant and identified each complication of interest, based on ICD-9 codes. The average cost for smokers and non-smokers could not be computed directly because smoking status is not available in claims data. Therefore, the population attributable risk percentage (PAR%) due to smoking for each complication was identified from the literature. Multiple linear regression was used to provide estimates of the incremental cost associated with each smoking-related complication. The total cost attributable to smoking was computed as a function of the incremental cost of each complication and the PAR% for each complication. The conditions associated with the largest incremental costs compared to patients without those conditions were abruptio placenta ($23,697) and respiratory distress syndrome ($21,944). Because they were more common, the conditions with the largest smoking-attributable cost were low birth weight ($914) and lower respiratory infection ($428). The sum of the additional costs attributable to smoking for all conditions yielded a total in the first year after birth ranging from $1142 to $1358 per smoking pregnant woman. It was concluded that maternal smoking during pregnancy results in an economic burden to payers and society. These estimates may be useful in formal cost-effectiveness evaluations of individual smoking cessation strategies.

Recurrent ischemia after thrombolysis for acute myocardial infarction.

BACKGROUND: Reliable predictors have yet to be found for recurrent ischemia after thrombolysis for acute myocardial infarction (AMI), nor do we know whether early angiography can herald recurrent ischemia. This study sought to investigate the relationship between recurrent ischemia and cardiac procedures after thrombolysis for AMI. METHODS: The Global Utilization of Streptokinase and Tissue Plasminogen Activator for Occluded Coronary Arteries (GUSTO-I) trial prospectively studied recurrent ischemia, which was defined as the presence of angina and changes in hemodynamics or the electrocardiogram. Cox regression analysis was used to identify predictors of recurrent ischemia. Other variables examined included time to coronary angiography and revascularization. RESULTS: Of 21,772 US GUSTO-I patients, 6313 (29%) had recurrent ischemia before discharge. Women (hazard ratio [HR] 1.25, 95% confidence interval [CI] 1.17-1.33) and patients with hypercholesterolemia (HR 1.14, 95% CI 1.07-1.22) or prior angina (HR 1.40, 95% CI 1.32-1.49) had a higher likelihood of recurrent ischemia. Current smoking and hours to thrombolysis were inversely related to recurrent ischemia (HR 0.86, 95% CI 0.81-0.92, HR 0.97, 95% CI 0.95- 0.99, respectively). Patients who underwent angiography before recurrent ischemia had a marginally increased risk of ischemia within 12 hours after angiography (HR 1.2, 95% CI 1.1-1.4); ultimately, they had a considerably lower risk 1 week after angiography than did patients without angiography (HR 0.57, 95% CI 0.45-0.72). CONCLUSIONS: Female sex, hypercholesterolemia, prior angina, and nonsmoking status weakly predict recurrent ischemia. Early coronary angiography reduces recurrent ischemia, probably because high-risk patients are identified and revascularized.

Use of an asbestos exposure score and the presence of pleural and parenchymal abnormalities in a lung cancer case series.

To assess whether there was an association between asbestos exposure and abnormalities on chest x-rays or CT scans, chest radiographs and CT scans of 103 asbestos-exposed patients with known lung cancer were reviewed for pleural or parenchymal abnormalities. Asbestos exposure was assessed using an asbestos exposure index that integrated time and intensity of reported exposure via a weighting scheme. Chest CT scans were clearly more sensitive in detecting pleural or parenchymal abnormalities than were standard PA chest x-rays. Furthermore, there was a significant correlation between higher asbestos exposure index scores and abnormalities on CT scans. Multivariable logistic regression models were used to investigate the relationship between the asbestos exposure index score and pleural or parenchymal abnormalities after adjusting for gender, pack-years of smoking, and cell type. None of these variables was associated with abnormalities on chest x-rays or CT scans. An asbestos exposure score > 10 was associated with pleural or parenchymal abnormalities (OR = 4.93; 95%CI 1.05-23.12). The results suggest that assessment of asbestos exposures by means of an algorithm-based index can classify the exposures accurately for epidemiologic studies.