Melbourne Dental School - Research Publications
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ItemAdolescent temperament dimensions as stable prospective risk and protective factors for salivary C-reactive protein(WILEY, 2018-02)OBJECTIVE: Temperament has associations with later physical health outcomes, yet there is a dearth of research exploring the connection between temperament and mechanisms that have known associations with these health outcomes. Recent research has delineated a connection between personality and inflammation during adulthood, but this association has not yet been studied in adolescent samples. DESIGN: We investigated whether stable adolescent temperament (averaged over two years), specifically effortful control and negative emotionality, provided a more robust prediction of inflammation as measured by salivary C-reactive protein (sCRP), than depressive symptoms. METHODS: Temperament and depressive symptoms were measured in a sample of sixty-three adolescents (37 males) when they were approximately 12 years old (mean age = 12.30, SD = 0.69) and again when they were approximately 14 years old (mean age = 14.84, SD = 0.49). Levels of sCRP were determined approximately 7 months later (mean = 6.77, SD = 2.99) when participants were approximately 15 years old (mean age = 15.49, SD = 0.49). RESULTS: Regression analyses revealed that effortful control (EC) was significantly associated with lower sCRP levels, while higher negative emotionality (NE) was significantly associated with higher sCRP levels. Furthermore, these associations were larger than those for depressive symptoms and were differentially impacted by the addition of covariates. Implications for the role of stable risk and protective factors in inflammatory processes are discussed. CONCLUSIONS: These findings are the first to show associations between adolescent temperament and inflammation. Furthermore, these findings extend previous personality research to temperamental research in a younger sample of adolescents. Statement of contribution What is already known? There is a large extant literature on the association between depressive symptoms and inflammation. There is a smaller extant literature on the association between personality and inflammation. No studies have examined how adolescent temperament traits may relate to inflammation. What does this study add? Longitudinal data collection over the course of 3 years in an adolescent sample. Addresses the question of whether temperament factors relate to inflammation. Temperament provides a more robust predictor of later inflammation than depressive symptoms.
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ItemPeripheral memory T-cell profile is modified in patients undergoing periodontal management(WILEY, 2021-02)AIMS: T-cells are known to have a role in periodontitis, however, the effect of periodontal therapy on peripheral memory T-cells is unclear. This study evaluated variation in peripheral memory T-cells and red complex bacteria in sub-gingival plaque in patients undergoing periodontal management. METHODS: Peripheral blood mononuclear cells and sub-gingival plaque were collected from 54 periodontitis patients at baseline, 3-, 6- and 12-months post-therapy and 40 healthy controls. Periodontitis patients were divided into treatment outcome (TxO) groups based on prevalence of sites with probing depth ≥5 mm as good (<10% of sites), moderate (10-20%) or poor (>20%) at study conclusion. Naïve (TN -CCR7+ CD45RA+ ), central memory (TCM -CCR7+ CD45RA- ), effector memory (TEM -CCR7- CD45RA- ) and effector memory T-cells re-expressing CD45RA (TEMRA -CCR7- CD45RA+ ) were phenotyped using flow cytometry in CD4+ , CD8+ , CD4+ CD8+ and CD4- CD8- T-cells and red complex bacteria were quantified using qPCR. RESULTS: At baseline, periodontitis subjects had significantly greater mean probing depths and Porphyromonas gingivalis proportions, lower TN but higher CD4+ TCM , CD8+ TCM , CD4+ CD8+ TEM and CD4- CD8- TEM cell proportions compared to health. Periodontal therapy decreased mean probing depths, P. gingivalis proportions, TEM and CD4+ and CD8+ TCM cells, but increased TN and CD4+ and CD8+ TEMRA cells. The T-cell profile in the good TxO group showed therapy-related changes in CD4+ TEM , and CD8+ TN and TEM cells, whereas, no changes were observed in the poor TxO group. CONCLUSION: Management and the reduction in red complex bacteria were associated with changes in peripheral memory T-cells in periodontitis.
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ItemPeripheral T helper cell profiles during management of periodontitis(WILEY, 2021-01)AIM: Periodontitis has been associated with other systemic diseases with underlying inflammation responsible for the shared link. This study evaluated longitudinal variation in peripheral T helper cells in periodontitis patients undergoing management over 1 year. MATERIALS AND METHODS: Periodontal parameters and peripheral blood mononuclear cells (PBMCs) were collected from 54 periodontitis patients at baseline, and 3-, 6- and 12-months post-treatment and 40 healthy controls. IFN-γ+ , IL-4+ , IL-17+ and Foxp3+ and their double-positive expression were identified in CD4+ and TCRαβ+ cells using flow cytometry. PBMCs were incubated with P. gingivalis, and IFN-γ, IL-4, IL-17 and IL-10 in cell supernatant were measured by ELISA. Cells and cytokines were also assessed based on clinical response to treatment where good (<10% of sites), moderate (10-20%) and poor (>20%) treatment outcome (TxO) groups had probing depths of ≥5 mm at study conclusion. RESULTS: IFN-γ+ cells were lower at baseline, and 3- and 6-months compared to health, whereas Foxp3+ cells were increased at 12-months compared to all preceding timepoints and health. The good TxO group showed treatment-related variation in IFN-γ+ and Foxp3+ cells, whereas the poor TxO group did not. IFN-γ and IL-17 cytokine expression in cell supernatants was significantly lower at baseline compared to health, and IFN-γ and IL-10 showed treatment-related decrease. CONCLUSION: This study suggests that IFN-γ+ and Foxp3+ cells may have a role in the systemic compartment in periodontitis. Periodontal management has local and systemic effects, and thus, assessment and management of periodontitis should form an integral part of overall systemic health.
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ItemPeripheral neutrophil phenotypes during management of periodontitis(WILEY, 2021-01)BACKGROUND AND OBJECTIVES: Neutrophils are emerging as a key player in periodontal pathogenesis. The surface expression of cellular markers enables functional phenotyping of neutrophils which have distinct roles in disease states. This study aimed to evaluate the effect of periodontal management on neutrophil phenotypes in peripheral blood in periodontitis patients over one year. MATERIALS AND METHODS: Peripheral blood and the periodontal parameters, mean probing depth and percentage of sites with bleeding on probing (%BOP), were collected from 40 healthy controls and 54 periodontitis patients at baseline and 3-, 6- and 12- months post-treatment. Flow cytometry was used to identify CD11b+ , CD16b+ , CD62L- and CD66b+ expression on neutrophils, neutrophil maturation stages as promyelocytes (CD11b- CD16b- ), metamyelocytes (CD11b+ CD16b- ) and mature neutrophils (CD11b+ CD16b+ ), and suppressive neutrophil phenotype as bands (CD16dim CD62Lbright ), normal neutrophils (CD16bright CD62Lbright ) and suppressive neutrophils (CD16bright CD62Ldim ). RESULTS: CD62L- expression decreased with treatment. No differences were observed in neutrophil maturation stages in health or disease upon treatment. Suppressive and normal neutrophils showed a reciprocal relationship, where suppressive neutrophils decreased with treatment and normal neutrophils increased with treatment. In addition, %BOP was associated with suppressive neutrophils. CONCLUSION: This study demonstrates that management of periodontitis significantly modifies distinct neutrophil phenotypes in peripheral blood. Suppressive neutrophils may play a role in the pathogenesis of periodontitis. However, their exact role is unclear and requires further investigation.
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ItemAssociations Between Observed Parenting Behavior and Adolescent Inflammation Two and a Half Years Later in a Community Sample(AMER PSYCHOLOGICAL ASSOC, 2017-07)OBJECTIVE: Family environments have an effect on physical health during adolescence, and a possible underlying mechanism is inflammation. However, little is known about the association between observed parenting behaviors and immune system functioning. The current study examined whether positive and negative emotional parental behaviors observed during family interactions were associated with inflammation in adolescents. METHOD: Sixty-one parent-adolescent dyads (37 male adolescents, 60.6%; 15 male parents, 24.6%) were observed during 2 laboratory-based interaction tasks designed to elicit positive and conflictual emotional behaviors, respectively. Frequency of aggressive and positive parental behavior was coded. Adolescents were followed up approximately 2.5 years later and salivary concentrations of the inflammatory biomarker C-reactive protein (sCRP) were measured. RESULTS: Controlling for BMI and depressive symptoms, lower sCRP was associated both with greater frequency of positive parental behaviors, t = -3.087, p = .003 and less frequency of aggressive parental behavior (t = 2.087, p = .041) in the conflictual task. Trend associations between positive behavior during the positive task and lower sCRP were also found. CONCLUSIONS: This is the first study to show that observed positive parenting is associated with lower levels of inflammation in adolescents. (PsycINFO Database Record
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ItemNo Preview AvailableBacterial Fluorescent-dextran Diffusion Assay(Bio-Protocol, LLC, 2014)
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ItemOxantel Disrupts Polymicrobial Biofilm Development of Periodontal Pathogens(AMER SOC MICROBIOLOGY, 2014-01)Bacterial pathogens commonly associated with chronic periodontitis are the spirochete Treponema denticola and the Gram-negative, proteolytic species Porphyromonas gingivalis and Tannerella forsythia. These species rely on complex anaerobic respiration of amino acids, and the anthelmintic drug oxantel has been shown to inhibit fumarate reductase (Frd) activity in some pathogenic bacteria and inhibit P. gingivalis homotypic biofilm formation. Here, we demonstrate that oxantel inhibited P. gingivalis Frd activity with a 50% inhibitory concentration (IC50) of 2.2 μM and planktonic growth of T. forsythia with a MIC of 295 μM, but it had no effect on the growth of T. denticola. Oxantel treatment caused the downregulation of six P. gingivalis gene products and the upregulation of 22 gene products. All of these genes are part of a regulon controlled by heme availability. There was no large-scale change in the expression of genes encoding metabolic enzymes, indicating that P. gingivalis may be unable to overcome Frd inhibition. Oxantel disrupted the development of polymicrobial biofilms composed of P. gingivalis, T. forsythia, and T. denticola in a concentration-dependent manner. In these biofilms, all three species were inhibited to a similar degree, demonstrating the synergistic nature of biofilm formation by these species and the dependence of T. denticola on the other two species. In a murine alveolar bone loss model of periodontitis oxantel addition to the drinking water of P. gingivalis-infected mice reduced bone loss to the same level as the uninfected control.
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ItemA therapeutic Porphyromonas gingivalis gingipain vaccine induces neutralising IgG1 antibodies that protect against experimental periodontitis(SPRINGERNATURE, 2016-12-01)Porphyromonas gingivalis infected mice with an established P. gingivalis-specific inflammatory immune response were protected from developing alveolar bone resorption by therapeutic vaccination with a chimera (KAS2-A1) immunogen targeting the major virulence factors of the bacterium, the gingipain proteinases. Protection was characterised by an antigen-specific IgG1 isotype antibody and Th2 cell response. Adoptive transfer of KAS2-A1-specific IgG1 or IgG2 expressing B cells confirmed that IgG1-mediated protection. Furthermore, parenteral or intraoral administration of KAS2-A1-specific polyclonal antibodies protected against the development of P. gingivalis-induced bone resorption. The KAS2-A1-specific antibodies neutralised the gingipains by inhibiting: proteolytic activity, binding to host cells/proteins and co-aggregation with other periodontal bacteria. Combining key gingipain sequences into a chimera vaccine produced an effective therapeutic intervention that protected against P. gingivalis-induced periodontitis.
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ItemStreptococcus mutans biofilm disruption by κ-casein glycopeptide(ELSEVIER SCI LTD, 2013-06)UNLABELLED: Caseinomacropeptide (CMP), the variably phosphorylated and glycosylated forms of the bovine milk protein fragment, κ-casein(106-169), is produced during cheese production and has been shown to have a range of antibacterial bioactivities. OBJECTIVES: To characterise the biofilm disruptive component of CMP and compare its activity with the known antimicrobial agents chlorhexidine and zinc ions. METHODS: Streptococcus mutans biofilms were grown in flow cells with an artificial saliva medium containing sucrose and treated with CMP and the glycosylated forms of κ-casein(106-169) (κ-casein glycopeptide, KCG). The biofilms were imaged using confocal laser scanning microscopy (CLSM) and quantified by COMSTAT software analysis. A static biofilm assay and flow cytometric analysis were used to examine the mechanism of action of chlorhexidine and a combination of KCG with the known antimicrobial agent ZnCl2 (KCG-Zn). RESULTS: CLSM analysis showed that S. mutans produced robust, structured biofilms with an average thickness of 7.37μm and a biovolume of 3.88μm(3)/μm(2) substratum after 16h of incubation in the flow cell system. A single application of 10mg/mL CMP that contained 2.4mg/mL KCG significantly reduced total biofilm biovolume and average biofilm thickness by 53% and 61%, respectively. This was statistically the same as a 2.4mg/mL KCG treatment that reduced the total biovolume and average thickness by 59% and 69%, respectively, suggesting the KCG was the biofilm disruptive component of CMP. Chlorhexidine treatment (0.1%) caused similar effects in the flow cell model. KCG-Zn caused significantly more disruption of the biofilms than either KCG or ZnCl2 treatment alone. In a static biofilm model chlorhexidine was shown to work by disrupting bacterial membrane integrity whilst KCG-Zn had no effect on membrane integrity. CONCLUSIONS: KCG and KCG-Zn may have potential as natural biofilm disruptive agents.
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ItemA Rapid and Quantitative Flow Cytometry Method for the Analysis of Membrane Disruptive Antimicrobial Activity(PUBLIC LIBRARY SCIENCE, 2016-03-17)We describe a microbial flow cytometry method that quantifies within 3 hours antimicrobial peptide (AMP) activity, termed Minimum Membrane Disruptive Concentration (MDC). Increasing peptide concentration positively correlates with the extent of bacterial membrane disruption and the calculated MDC is equivalent to its MBC. The activity of AMPs representing three different membranolytic modes of action could be determined for a range of Gram positive and negative bacteria, including the ESKAPE pathogens, E. coli and MRSA. By using the MDC50 concentration of the parent AMP, the method provides high-throughput, quantitative screening of AMP analogues. A unique feature of the MDC assay is that it directly measures peptide/bacteria interactions and lysed cell numbers rather than bacteria survival as with MIC and MBC assays. With the threat of multi-drug resistant bacteria, this high-throughput MDC assay has the potential to aid in the development of novel antimicrobials that target bacteria with improved efficacy.