Melbourne Dental School - Research Publications
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ItemThe 'Danse Macabre'-Neutrophils the Interactive Partner Affecting Oral Cancer Outcomes(FRONTIERS MEDIA SA, 2022-06-16)Over the past few decades, tremendous advances in the prevention, diagnosis, and treatment of cancer have taken place. However for head and neck cancers, including oral cancer, the overall survival rate is below 50% and they remain the seventh most common malignancy worldwide. These cancers are, commonly, aggressive, genetically complex, and difficult to treat and the delay, which often occurs between early recognition of symptoms and diagnosis, and the start of treatment of these cancers, is associated with poor prognosis. Cancer development and progression occurs in concert with alterations in the surrounding stroma, with the immune system being an essential element in this process. Despite neutrophils having major roles in the pathology of many diseases, they were thought to have little impact on cancer development and progression. Recent studies are now challenging this notion and placing neutrophils as central interactive players with other immune and tumor cells in affecting cancer pathology. This review focuses on how neutrophils and their sub-phenotypes, N1, N2, and myeloid-derived suppressor cells, both directly and indirectly affect the anti-tumor and pro-tumor immune responses. Emphasis is placed on what is currently known about the interaction of neutrophils with myeloid innate immune cells (such as dendritic cells and macrophages), innate lymphoid cells, natural killer cells, and fibroblasts to affect the tumor microenvironment and progression of oral cancer. A better understanding of this dialog will allow for improved therapeutics that concurrently target several components of the tumor microenvironment, increasing the possibility of constructive and positive outcomes for oral cancer patients. For this review, PubMed, Web of Science, and Google Scholar were searched for manuscripts using keywords and combinations thereof of "oral cancer, OSCC, neutrophils, TANs, MDSC, immune cells, head and neck cancer, and tumor microenvironment" with a focus on publications from 2018 to 2021.
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ItemNo Preview AvailableArticle Development and application of Diels-Alder adducts displaying AIE properties(ELSEVIER, 2022-02-16)
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ItemThe Potential of Calcium Phosphate Nanoparticles as Adjuvants and Vaccine Delivery Vehicles(FRONTIERS MEDIA SA, 2021-12-22)Vaccination is one of the most efficacious and cost-effective ways to protect people from infectious diseases and potentially cancer. The shift in vaccine design from disrupted whole pathogens to subunit antigens has brought attention on to vaccine delivery materials. For the last two decades, nanotechnology-based vaccines have attracted considerable attention as delivery vehicles and adjuvants to enhance immunogenicity, exemplified with the current COVID vaccines. The nanoparticle vaccines display unique features in protecting antigens from degradation, controlled antigen release and longer persisting immune response. Due to their size, shape and surface charge, they can be outstanding adjuvants to achieve various immunological effects. With the safety and biodegradable benefit of calcium phosphate nanoparticles (CaP NPs), they are an efficient carrier for vaccine design and adjuvants. Several research groups have studied CaP NPs in the field of vaccination with great advances. Although there are several reports on the overview of CaP NPs, they are limited to the application in biomedicine, drug delivery, bone regeneration and the methodologies of CaP NPs synthesis. Hence, we summarised the basic properties of CaP NPs and the recent vaccine development of CaP NPs in this review.
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ItemC-terminus amidation influences biological activity and membrane interaction of maculatin 1.1(SPRINGER WIEN, 2021-04-23)Cationic antimicrobial peptides have been investigated for their potential use in combating infections by targeting the cell membrane of microbes. Their unique chemical structure has been investigated to understand their mode of action and optimize their dose-response by rationale design. One common feature among cationic AMPs is an amidated C-terminus that provides greater stability against in vivo degradation. This chemical modification also likely modulates the interaction with the cell membrane of bacteria yet few studies have been performed comparing the effect of the capping groups. We used maculatin 1.1 (Mac1) to assess the role of the capping groups in modulating the peptide bacterial efficiency, stability and interactions with lipid membranes. Circular dichroism results showed that C-terminus amidation maintains the structural stability of the peptide (α-helix) in contact with micelles. Dye leakage experiments revealed that amidation of the C-terminus resulted in higher membrane disruptive ability while bacteria and cell viability assays revealed that the amidated form displayed higher antibacterial ability and cytotoxicity compared to the acidic form of Mac1. Furthermore, 31P and 2H solid-state NMR showed that C-terminus amidation played a greater role in disturbance of the phospholipid headgroup but had little effect on the lipid tails. This study paves the way to better understand how membrane-active AMPs act in live bacteria.
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ItemEvaluation of Potential DnaK Modulating Proline-Rich Antimicrobial Peptides Identified by Computational Screening(FRONTIERS MEDIA SA, 2022-04-13)The day is rapidly approaching where current antibiotic therapies will no longer be effective due to the development of multi-drug resistant bacteria. Antimicrobial peptides (AMPs) are a promising class of therapeutic agents which have the potential to help address this burgeoning problem. Proline-rich AMPs (PrAMPs) are a sub-class of AMPs, that have multiple modes of action including modulation of the bacterial protein folding chaperone, DnaK. They are highly effective against Gram-negative bacteria and have low toxicity to mammalian cells. Previously we used an in silico approach to identify new potential PrAMPs from the DRAMP database. Four of these peptides, antibacterial napin, attacin-C, P9, and PP30, were each chemically assembled and characterized. Together with synthetic oncocin as a reference, each peptide was then assessed for antibacterial activity against Gram-negative/Gram-positive bacteria and for in vitro DnaK modulation activity. We observed that these peptides directly modulate DnaK activity independently of eliciting or otherwise an antibiotic effect. Based on our findings, we propose a change to our previously established PrAMP definition to remove the requirement for antimicrobial activity in isolation, leaving the following classifiers: >25% proline, modulation of DnaK AND/OR the 70S ribosome, net charge of +1 or more, produced in response to bacterial infection AND/OR with pronounced antimicrobial activity.
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ItemThe Potential of Modified and Multimeric Antimicrobial Peptide Materials as Superbug Killers(FRONTIERS MEDIA SA, 2022-01-10)Antimicrobial peptides (AMPs) are found in nearly all living organisms, show broad spectrum antibacterial activity, and can modulate the immune system. Furthermore, they have a very low level of resistance induction in bacteria, which makes them an ideal target for drug development and for targeting multi-drug resistant bacteria 'Superbugs'. Despite this promise, AMP therapeutic use is hampered as typically they are toxic to mammalian cells, less active under physiological conditions and are susceptible to proteolytic degradation. Research has focused on addressing these limitations by modifying natural AMP sequences by including e.g., d-amino acids and N-terminal and amino acid side chain modifications to alter structure, hydrophobicity, amphipathicity, and charge of the AMP to improve antimicrobial activity and specificity and at the same time reduce mammalian cell toxicity. Recently, multimerisation (dimers, oligomer conjugates, dendrimers, polymers and self-assembly) of natural and modified AMPs has further been used to address these limitations and has created compounds that have improved activity and biocompatibility compared to their linear counterparts. This review investigates how modifying and multimerising AMPs impacts their activity against bacteria in planktonic and biofilm states of growth.
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ItemEnhancing proline-rich antimicrobial peptide action by homodimerization: influence of bifunctional linker(ROYAL SOC CHEMISTRY, 2022-02-01)Antimicrobial peptides (AMPs) are host defense peptides, and unlike conventional antibiotics, they possess potent broad spectrum activities and, induce little or no antimicrobial resistance. They are attractive lead molecules for rational development to improve their therapeutic index. Our current studies examined dimerization of the de novo designed proline-rich AMP (PrAMP), Chex1-Arg20 hydrazide, via C-terminal thiol addition to a series of bifunctional benzene or phenyl tethers to determine the effect of orientation of the peptides and linker length on antimicrobial activity. Antibacterial assays confirmed that dimerization per se significantly enhances Chex1-Arg20 hydrazide action. Greatest advantage was conferred using perfluoroaromatic linkers (tetrafluorobenzene and octofluorobiphenyl) with the resulting dimeric peptides 6 and 7 exhibiting potent action against Gram-negative bacteria, especially the World Health Organization's critical priority-listed multidrug-resistant (MDR)/extensively drug-resistant (XDR) Acinetobacter baumannii as well as preformed biofilms. Mode of action studies indicated these lead PrAMPs can interact with both outer and inner bacterial membranes to affect the membrane potential and stress response. Additionally, 6 and 7 possess potent immunomodulatory activity and neutralise inflammation via nitric oxide production in macrophages. Molecular dynamics simulations of adsorption and permeation mechanisms of the PrAMP on a mixed lipid membrane bilayer showed that a rigid, planar tethered dimer orientation, together with the presence of fluorine atoms that provide increased bacterial membrane interaction, is critical for enhanced dimer activity. These findings highlight the advantages of use of such bifunctional tethers to produce first-in-class, potent PrAMP dimers against MDR/XDR bacterial infections.
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ItemTumor Associated Macrophages: Origin, Recruitment, Phenotypic Diversity, and Targeting(FRONTIERS MEDIA SA, 2021-12-20)The tumor microenvironment (TME) is known to have a strong influence on tumorigenesis, with various components being involved in tumor suppression and tumor growth. A protumorigenic TME is characterized by an increased infiltration of tumor associated macrophages (TAMs), where their presence is strongly associated with tumor progression, therapy resistance, and poor survival rates. This association between the increased TAMs and poor therapeutic outcomes are stemming an increasing interest in investigating TAMs as a potential therapeutic target in cancer treatment. Prominent mechanisms in targeting TAMs include: blocking recruitment, stimulating repolarization, and depletion methods. For enhancing targeting specificity multiple nanomaterials are currently being explored for the precise delivery of chemotherapeutic cargo, including the conjugation with TAM-targeting peptides. In this paper, we provide a focused literature review of macrophage biology in relation to their role in tumorigenesis. First, we discuss the origin, recruitment mechanisms, and phenotypic diversity of TAMs based on recent investigations in the literature. Then the paper provides a detailed review on the current methods of targeting TAMs, including the use of nanomaterials as novel cancer therapeutics.
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ItemAdolescent temperament dimensions as stable prospective risk and protective factors for salivary C-reactive protein(WILEY, 2018-02-01)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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ItemC-Terminal Modification and Multimerization Increase the Efficacy of a Proline-Rich Antimicrobial Peptide(WILEY-V C H VERLAG GMBH, 2017-01-05)Two series of branched tetramers of the proline-rich antimicrobial peptide (PrAMP), Chex1-Arg20, were prepared to improve antibacterial selectivity and potency against a panel of Gram-negative nosocomial pathogens including Escherichia coli, Klebsiella pneumoniae, Acinetobacter baumannii and Pseudomonas aeruginosa. First, tetramerization was achieved by dithiomaleimide (DTM) conjugation of two C-terminal-cysteine bearing dimers that also incorporated C-terminal peptide chemical modification. DTM-linked tetrameric peptides containing a C-terminal hydrazide moiety on each dimer exhibited highly potent activities in the minimum inhibitory concentration (MIC) range of 0.49-2.33 μm. A second series of tetrameric analogues with C-terminal hydrazide modification was prepared by using alternative conjugation linkers including trans-1,4-dibromo-2-butene, α,α'-dibromo-p-xylene, or 6-bismaleimidohexane to determine the effect of length on activity. Each displayed potent and broadened activity against Gram-negative nosocomial pathogens, particularly the butene-linked tetrameric hydrazide. Remarkably, the greatest MIC activity is against P. aeruginosa (0.77 μm/8 μg mL-1 ) where the monomer is inactive. None of these peptides showed any cytotoxicity to mammalian cells up to 25 times the MIC. A diffusion NMR study of the tetrameric hydrazides showed that the more active antibacterial analogues were those with a more compact structure having smaller hydrodynamic radii. The results show that C-terminal PrAMP hydrazidation together with its rational tetramerization is an effective means for increasing both diversity and potency of PrAMP action.