Melbourne Medical School Collected Works - Research Publications
Permanent URI for this collection
Search Results
1 - 10 of 101
-
ItemEpigenetic Changes in Diabetes and Cardiovascular Risk(LIPPINCOTT WILLIAMS & WILKINS, 2016-05-27)Cardiovascular complications remain the leading causes of morbidity and premature mortality in patients with diabetes mellitus. Studies in humans and preclinical models demonstrate lasting gene expression changes in the vasculopathies initiated by previous exposure to high glucose concentrations and the associated overproduction of reactive oxygen species. The molecular signatures of chromatin architectures that sensitize the genome to these and other cardiometabolic risk factors of the diabetic milieu are increasingly implicated in the biological memory underlying cardiovascular complications and now widely considered as promising therapeutic targets. Atherosclerosis is a complex heterocellular disease where the contributing cell types possess distinct epigenomes shaping diverse gene expression. Although the extent that pathological chromatin changes can be manipulated in human cardiovascular disease remains to be established, the clinical applicability of epigenetic interventions will be greatly advanced by a deeper understanding of the cell type-specific roles played by writers, erasers, and readers of chromatin modifications in the diabetic vasculature. This review details a current perspective of epigenetic mechanisms of macrovascular disease in diabetes mellitus and highlights recent key descriptions of chromatinized changes associated with persistent gene expression in endothelial, smooth muscle, and circulating immune cells relevant to atherosclerosis. Furthermore, we discuss the challenges associated with pharmacological targeting of epigenetic networks to correct abnormal or deregulated gene expression as a strategy to alleviate the clinical burden of diabetic cardiovascular disease.
-
ItemStimulating the Release of Exosomes Increases the Intercellular Transfer of Prions(ELSEVIER, 2016-03-04)Exosomes are small extracellular vesicles released by cells and play important roles in intercellular communication and pathogen transfer. Exosomes have been implicated in several neurodegenerative diseases, including prion disease and Alzheimer disease. Prion disease arises upon misfolding of the normal cellular prion protein, PrP(C), into the disease-associated isoform, PrP(Sc). The disease has a unique transmissible etiology, and exosomes represent a novel and efficient method for prion transmission. The precise mechanism by which prions are transmitted from cell to cell remains to be fully elucidated, although three hypotheses have been proposed: direct cell-cell contact, tunneling nanotubes, and exosomes. Given the reported presence of exosomes in biological fluids and in the lipid and nucleic acid contents of exosomes, these vesicles represent an ideal mechanism for encapsulating prions and potential cofactors to facilitate prion transmission. This study investigates the relationship between exosome release and intercellular prion dissemination. Stimulation of exosome release through treatment with an ionophore, monensin, revealed a corresponding increase in intercellular transfer of prion infectivity. Conversely, inhibition of exosome release using GW4869 to target the neutral sphingomyelinase pathway induced a decrease in intercellular prion transmission. Further examination of the effect of monensin on PrP conversion revealed that monensin also alters the conformational stability of PrP(C), leading to increased generation of proteinase K-resistant prion protein. The findings presented here provide support for a positive relationship between exosome release and intercellular transfer of prion infectivity, highlighting an integral role for exosomes in facilitating the unique transmissible nature of prions.
-
ItemSecreted primary human malignant mesothelioma exosome signature reflects oncogenic cargo(NATURE PORTFOLIO, 2016-09-08)Malignant mesothelioma (MM) is a highly-aggressive heterogeneous malignancy, typically diagnosed at advanced stage. An important area of mesothelioma biology and progression is understanding intercellular communication and the contribution of the secretome. Exosomes are secreted extracellular vesicles shown to shuttle cellular cargo and direct intercellular communication in the tumour microenvironment, facilitate immunoregulation and metastasis. In this study, quantitative proteomics was used to investigate MM-derived exosomes from distinct human models and identify select cargo protein networks associated with angiogenesis, metastasis, and immunoregulation. Utilising bioinformatics pathway/network analyses, and correlation with previous studies on tumour exosomes, we defined a select mesothelioma exosomal signature (mEXOS, 570 proteins) enriched in tumour antigens and various cancer-specific signalling (HPGD/ENO1/OSMR) and secreted modulators (FN1/ITLN1/MAMDC2/PDGFD/GBP1). Notably, such circulating cargo offers unique insights into mesothelioma progression and tumour microenvironment reprogramming. Functionally, we demonstrate that oncogenic exosomes facilitate the migratory capacity of fibroblast/endothelial cells, supporting the systematic model of MM progression associated with vascular remodelling and angiogenesis. We provide biophysical and proteomic characterisation of exosomes, define a unique oncogenic signature (mEXOS), and demonstrate the regulatory capacity of exosomes in cell migration/tube formation assays. These findings contribute to understanding tumour-stromal crosstalk in the context of MM, and potential new diagnostic and therapeutic extracellular targets.
-
ItemPodoplanin is a component of extracellular vesicles that reprograms cell-derived exosomal proteins and modulates lymphatic vessel formation(IMPACT JOURNALS LLC, 2016-03-29)Podoplanin (PDPN) is a transmembrane glycoprotein that plays crucial roles in embryonic development, the immune response, and malignant progression. Here, we report that cells ectopically or endogenously expressing PDPN release extracellular vesicles (EVs) that contain PDPN mRNA and protein. PDPN incorporates into membrane shed microvesicles (MVs) and endosomal-derived exosomes (EXOs), where it was found to colocalize with the canonical EV marker CD63 by immunoelectron microscopy. We have previously found that expression of PDPN in MDCK cells induces an epithelial-mesenchymal transition (EMT). Proteomic profiling of MDCK-PDPN cells compared to control cells shows that PDPN-induced EMT is associated with upregulation of oncogenic proteins and diminished expression of tumor suppressors. Proteomic analysis of exosomes reveals that MDCK-PDPN EXOs were enriched in protein cargos involved in cell adhesion, cytoskeletal remodeling, signal transduction and, importantly, intracellular trafficking and EV biogenesis. Indeed, expression of PDPN in MDCK cells stimulated both EXO and MV production, while knockdown of endogenous PDPN in human HN5 squamous carcinoma cells reduced EXO production and inhibited tumorigenesis. EXOs released from MDCK-PDPN and control cells both stimulated in vitro angiogenesis, but only EXOs containing PDPN were shown to promote lymphatic vessel formation. This effect was mediated by PDPN on the surface of EXOs, as demonstrated by a neutralizing specific monoclonal antibody. These results contribute to our understanding of PDPN-induced EMT in association to tumor progression, and suggest an important role for PDPN in EV biogenesis and/or release and for PDPN-EXOs in modulating lymphangiogenesis.
-
ItemErratum: Factors determining the stability, size distribution, and cellular accumulation of small, monodisperse chitosan nanoparticles as candidate vectors for anticancer drug delivery: application to the passive encapsulation of [(14)C]-doxorubicin [Corrigendum].(Informa UK Limited, 2016)[This corrects the article on p. 67 in vol. 8, PMID: 26715842.].
-
ItemBrain-derived neurotrophic factor genetic polymorphism (rs6265) is protective against chemotherapy-associated cognitive impairment in patients with early-stage breast cancer.(Oxford University Press (OUP), 2016-02)BACKGROUND: Brain-derived neurotrophic factor (BDNF), a neurotrophin that regulates neuronal function and development, is implicated in several neurodegenerative conditions. Preliminary data suggest that a reduction of BDNF concentrations may lead to postchemotherapy cognitive impairment. We hypothesized that a single nucleotide polymorphism (rs6265) of the BDNF gene may predispose patients to cognitive impairment. This study aimed to evaluate the effect of BDNF gene polymorphism on chemotherapy-associated cognitive impairment. METHODS: Overall, 145 patients receiving chemotherapy for early-stage breast cancer (mean age: 50.8 ± 8.8 y; 82.1% Chinese) were recruited. Patients' cognitive functions were assessed longitudinally using the validated Functional Assessment of Cancer Therapy-Cognitive Function (v.3) and an objective computerized tool, Headminder. Genotyping was performed using Sanger sequencing. Logistic regression was used to evaluate the association between BDNF Val66Met polymorphism and cognition after adjusting for ethnicity and clinically important covariates. RESULTS: Of the 145 patients, 54 (37%) reported cognitive impairment postchemotherapy. The Met/Met genotype was associated with statistically significant lower odds of developing cognitive impairment (odds ratio [OR] = 0.26; 95% CI: 0.08-0.92; P = .036). The Met carriers were less likely to experience impairment in the domains of verbal fluency (OR = 0.34; 95% CI: 0.12-0.90; P = .031) and multitasking ability (OR = 0.37; 95% CI: 0.15-0.91; P = .030) compared with the Val/Val homozygote. No associations were observed between Headminder and the BDNF Val66Met polymorphism. CONCLUSIONS: This is the first study to provide evidence that carriers of the BDNF Met allele are protected against chemotherapy-associated cognitive impairment. Further studies are required to validate the findings.
-
ItemEchocardiographic screening for non-ischaemic stage B heart failure in the community(WILEY, 2016-11)AIMS: Incident heart failure (HF) continues to pose a common and serious problem. We sought to examine the value of echocardiographic predictors of new HF in a community-based elderly population at risk for HF, independent of and incremental to clinical evaluation. METHODS AND RESULTS: Asymptomatic patients ≥65 years old, with ≥1 HF risk factor (hypertension, type 2 diabetes, or obesity) were recruited from the community; patients with valve disease, reduced ejection fraction (EF), and atrial fibrillation (AF) were excluded. Patients underwent standard clinical evaluation including calculation of the Charlson co-morbidity score and a comprehensive echocardiography including global longitudinal strain (GLS). Functional capacity was assessed by 6 min walk test. New HF and cardiovascular death were assessed after a mean follow-up of 14 ± 4 months by three independent cardiologists using Framingham criteria. Of 410 subjects (median age 70 years; 48% men), the prevalence of stage B HF was 13% [by LV hypertrophy (LVH)], 12% (by abnormal E/e'), 33% (by impaired GLS), and 31% [by left atrial enlargement (LAE)]. New HF symptoms developed in 49, and 2 died of cardiovascular causes, giving an event rate of 104/1000 person-years. These patients were older (P = 0.012), had a higher Charlson co-morbidity score (P < 0.001), larger LV mass and left atrium, higher E/e', and lower GLS (P < 0.05). LAE, LVH, abnormal GLS, and E/e' were independent predictors of new HF. In sequential models, LV mass and GLS added incremental information to clinical parameters. GLS significantly reclassified individuals (P = 0.002), but no reclassification improvement was identified using LV mass index, E/e', and left atrial volume index. CONCLUSION: Echocardiographic assessment (especially GLS and LV mass) provides incremental value in predicting incident HF.
-
ItemSex differences in response to miRNA-34a therapy in mouse models of cardiac disease: identification of sex-, disease- and treatment-regulated miRNAs(WILEY, 2016-10-15)KEY POINTS: MicroRNA (miRNA)-based therapies are in development for numerous diseases, including heart disease. Currently, very limited basic information is available on the regulation of specific miRNAs in male and female hearts in settings of disease. The identification of sex-specific miRNA signatures has implications for translation into the clinic and suggests the need for customised therapy. In the present study, we found that a miRNA-based treatment inhibiting miRNA-34a (miR-34a) was more effective in females in a setting of moderate dilated cardiomyopathy than in males. Furthermore, the treatment showed little benefit for either sex in a setting of more severe dilated cardiomyopathy associated with atrial fibrillation. The results highlight the importance of understanding the effect of miRNA-based therapies in cardiac disease settings in males and females. ABSTRACT: MicroRNA (miRNA)-34a (miR-34a) is elevated in the diseased heart in mice and humans. Previous studies have shown that inhibiting miR-34a in male mice in settings of pathological cardiac hypertrophy or ischaemia protects the heart against progression to heart failure. Whether inhibition of miR-34a protects the female heart is unknown. Furthermore, the therapeutic potential of silencing miR-34a in settings of dilated cardiomyopathy (DCM) and atrial fibrillation (AF) has not been assessed previously. In the present study, we examined the effect of silencing miR-34a in males and females in (1) a model of moderate DCM and (2) a model of severe DCM with AF. The cardiac disease models were administered with a locked nucleic acid-modified oligonucleotide (LNA-antimiR-34a) at 6-7 weeks of age when the models display cardiac dysfunction and conduction abnormalities. Cardiac function and morphology were measured 6 weeks after treatment. In the present study, we show that inhibition of miR-34a provides more protection in the DCM model in females than males. Disease prevention in LNA-antimiR-34a treated DCM female mice was characterized by attenuated heart enlargement and lung congestion, lower expression of cardiac stress genes (B-type natriuretic peptide, collagen gene expression), less cardiac fibrosis and better cardiac function. There was no evidence of significant protection in the severe DCM and AF model in either sex. Sex- and treatment-dependent regulation of miRNAs was also identified in the diseased heart, and may explain the differential response of males and females. These studies highlight the importance of examining the impact of miRNA-based drugs in both sexes and under different disease conditions.
-
ItemBiostatistical analysis of quantitative immunofluorescence microscopy images(WILEY, 2016-12)Semiquantitative immunofluorescence microscopy has become a key methodology in biomedical research. Typical statistical workflows are considered in the context of avoiding pseudo-replication and marginalising experimental error. However, immunofluorescence microscopy naturally generates hierarchically structured data that can be leveraged to improve statistical power and enrich biological interpretation. Herein, we describe a robust distribution fitting procedure and compare several statistical tests, outlining their potential advantages/disadvantages in the context of biological interpretation. Further, we describe tractable procedures for power analysis that incorporates the underlying distribution, sample size and number of images captured per sample. The procedures outlined have significant potential for increasing understanding of biological processes and decreasing both ethical and financial burden through experimental optimization.
-
ItemMore than skin deep. Ten year follow-up of delayed cutaneous adverse drug reactions (CADR)(WILEY, 2016-10)AIMS: To determine the gaps in practice regarding appropriate ADR documentation and risk communication for patients diagnosed with severe cutaneous adverse drug reactions (CADR). METHODS: This was a retrospective observational cohort study conducted using hospital coding and databases to identify inpatients diagnosed with CADR from January 2004 to August 2014. Hospital discharge summaries, ADR reports and pharmacy dispensing records were reviewed for ADR documentation. Patients still living in Australia and who did not opt out of being contacted were invited to be surveyed by telephone to determine their understanding of recommendations, re-exposure rates and long-term effects. RESULTS: Of 85 patients identified, median age was 59 (IQR 44-72) years and 47.1% were male. The most common diagnosis was TENS (49.4%). Ten patients (11.8%) died as inpatients. Of the 81 patients with a drug-related causality, 47 (58%) had appropriate documentation in all three required medical record platforms. Of the 56 eligible patients, 38 (67.9%) were surveyed; 13% had no information provided upon discharge and 26.3% patients had a mismatch in knowledge of implicated medications. No surveyed patient had a relapse of CADR, but 23.7% had a subsequent unrelated allergic reaction. Thirteen patients (34.2%) reported long-term effects. CONCLUSIONS: We found gaps in the accuracy of ADR documentation and communication of risk at discharge, which indicated risks to patient safety. Electronic systems are being developed to improve documentation. Written information about CADR is being provided at discharge to improve patient understanding and knowledge.