Florey Department of Neuroscience and Mental Health - Research Publications
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ItemNovel approaches to alcohol rehabilitation: Modification of stress-responsive brain regions through environmental enrichment(PERGAMON-ELSEVIER SCIENCE LTD, 2019-02-01)Relapse remains the most prominent hurdle to successful rehabilitation from alcoholism. The neural mechanisms underlying relapse are complex, but our understanding of the brain regions involved, the anatomical circuitry and the modulation of specific nuclei in the context of stress and cue-induced relapse have improved significantly in recent years. In particular, stress is now recognised as a significant trigger for relapse, adding to the well-established impact of chronic stress to escalate alcohol consumption. It is therefore unsurprising that the stress-responsive regions of the brain have also been implicated in alcohol relapse, such as the nucleus accumbens, amygdala and the hypothalamus. Environmental enrichment is a robust experimental paradigm which provides a non-pharmacological tool to alter stress response and, separately, alcohol-seeking behaviour and symptoms of withdrawal. In this review, we examine and consolidate the preclinical evidence that alcohol seeking behaviour and stress-induced relapse are modulated by environmental enrichment, and these are primarily mediated by modification of neural activity within the key nodes of the addiction circuitry. Finally, we discuss the limited clinical evidence that stress-reducing approaches such as mindfulness could potentially serve as adjunctive therapy in the treatment of alcoholism. This article is part of the Special Issue entitled "Neurobiology of Environmental Enrichment".
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ItemHPA axis regulation and stress response is subject to intergenerational modification by paternal trauma and stress(ACADEMIC PRESS INC ELSEVIER SCIENCE, 2019-09-01)There is increasing evidence that one's risk for psychiatric disturbances and metabolic syndromes is influenced by their parents' own health history, lifestyle and living environment. For example, paternal high fat diet is strongly linked to neuroendocrine dysregulation in offspring and increased risk for diabetes. The potential intergenerational impact of paternal stress has only just begun to emerge, with the initial evidence suggestive of greater risk for anxiety-related disorders. The hypothalamic-pituitary-adrenal (HPA)-axis is a key neuroendocrine signalling system involved in physiological homeostasis and stress response. In individuals, dysregulation of this system is closely associated with behavioral deficits and mood disorders. Various preclinical models of paternal stress have demonstrated robust behavioral shifts but little is known about the intergenerational modification of HPA axis function. This review will present evidence drawn from a range of laboratory mouse and rat models that the intergenerational influence of paternal stress on offspring behavioral phenotypes involve some level of HPA axis dysregulation. It makes the case that further investigations to comprehensively profile HPA axis function in offspring generations is warranted.
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ItemScavenger Receptor Class A1 Mediates Uptake of Morpholino Antisense Oligonucleotide into Dystrophic Skeletal Muscle.(Elsevier BV, 2019-03-01)Exon skipping using phosphorodiamidate morpholino oligomers (PMOs) is a promising treatment strategy for Duchenne muscular dystrophy (DMD). The most significant limitation of these clinically used compounds is their lack of delivery systems that target muscles; thus, cell-penetrating peptides are being developed to enhance uptake into muscles. Recently, we reported that uptake of peptide-conjugated PMOs into myofibers was mediated by scavenger receptor class A (SR-A), which binds negatively charged ligands. However, the mechanism by which the naked PMOs are taken up into fibers is poorly understood. In this study, we found that PMO uptake and exon-skipping efficiency were promoted in dystrophin-deficient myotubes via endocytosis through a caveolin-dependent pathway. Interestingly, SR-A1 was upregulated and localized in juxtaposition with caveolin-3 in these myotubes and promoted PMO-induced exon skipping. SR-A1 was also upregulated in the skeletal muscle of mdx52 mice and mediated PMO uptake. In addition, PMOs with neutral backbones had negative zeta potentials owing to their nucleobase compositions and interacted with SR-A1. In conclusion, PMOs with negative zeta potential were taken up into dystrophin-deficient skeletal muscle by upregulated SR-A1. Therefore, the development of a drug delivery system targeting SR-A1 could lead to highly efficient exon-skipping therapies for DMD.
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ItemNo Preview AvailableEvaluating retinal biomarkers in a mouse model of Parkinson's disease(Association for Research in Vision and Ophthalmology, 2019-07-01)Purpose : The retina, an accessible outpouching of the central nervous system, may manifest cortical changes that occur with Parkinson’s disease (PD), lending itself as a potential biomarker. PD is characterised by reduced dopamine levels, a neurotransmitter found in amacrine cells. Human PD patients have also shown structural changes in the outer retina. This work aims to determine if retinal function and structure are altered in a murine model of PD and whether deficits can be ameliorated with L-DOPA treatment. Methods : A PD model was induced in adult C57BL6/J mice using MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, 4x i.p. injections, 20mg/kg) and vehicle control and examined at day 21 and 45. Another MPTP group was administered L-DOPA (L-3,4-dihydroxyphenylalanine 0.2 mg/ml) or control in their drinking water and assessed at day 45 (n=12–15/group). In ketamine:xylazine anaesthetised (80:10mg/kg) mice full-field dark- and light-adapted electroretinography (ERG) was assessed to target dopamine-related responses. Optical coherence tomography (OCT) was used to quantify thickness of retinal layers. Retinal and cortical tissue were collected for immunohistochemical assessment of changes in tyrosine hydroxylase (TH)and imaged using confocal microscopy. Data (mean±SEM) were compared using unpaired ANOVA and t-tests as appropriate. Results : At day 21 no retinal changes were found. At day 45 dark and light adapted ERGs showed slower amacrine cell responses (oscillatory potential, p<0.05), a finding which reversed with L-DOPA treatment (p<0.05). Other components of the ERG were unchanged. TH staining showed a trend towards decreased retinal levels in MPTP mice but this did not reach significance (p=0.10). Reduced levels of TH were found in the ventral hippocampus of MPTP mice compared with control (p<0.05). OCT revealed thinning of the outer plexiform layer at day 45, and the L-DOPA group exhibited a thinning of the outer nuclear layer (p<0.05). Conclusions : This study shows for the first time that the MPTP model recapitulates key dopaminergic changes previously reported in humans. In particular, electroretinographic changes that correspond with dopaminergic retinal cells occur in the Parkinson’s model and reverse with therapeutic treatment. Structural thinning of the outer retinal layers also occur, which parallels some human findings. This work paves the way for retinal measures as preclinical screening tools in drug development.
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ItemProgressive impairments in executive function in the APP/PS1 model of Alzheimer’s disease as measured by translatable touchscreen testing( 2019-08-21)Executive function deficits in Alzheimer’s disease (AD) occur early in disease progression and may be predictive of cognitive decline. However, no preclinical studies have identified deficits in rewarded executive function in the commonly used APP/PS1 mouse model. To address this, we assessed 12-26 month old APP/PS1 mice on rewarded reversal and/or extinction tasks. 16-month-old, but not 13- or 26-month-old, APP/PS1 mice showed an attenuated rate of extinction. Reversal deficits were seen in 22-month-old, but not 13-month-old APP/PS1 animals. We then confirmed that impairments in reversal were unrelated to previously reported visual impairments in both AD mouse models and humans. Age, but not genotype, had a significant effect on markers of retinal health, indicating the deficits seen in APP/PS1 mice were directly related to cognition. This is the first characterisation of rewarded executive function in APP/PS1 mice, and has great potential to facilitate translation from preclinical models to the clinic.
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ItemNo Preview AvailableMETHYLOME-WIDE ASSOCIATION STUDIES FOR MAJOR DEPRESSIVE DISORDER IN BLOOD OVERLAP WITH METHYLATION RESULTS FROM BRAIN AND LARGE-SCALE GWAS(ELSEVIER SCIENCE BV, 2019-01-01)Background: Epigenetic modifications such as DNA methy- lation provide stability and diversity to the cellular phenotype and aberrant methylation has been implicated in processes underlying psychiatric disorders. Therefore, studies combining DNA methylation and genotype information provide a promis- ing approach to study disorders where genotype information alone has failed to reveal the full etiology. Methods: We applied an optimized MBD-seq protocol to assay the complete CpG methylome in cases with Major Depressive Disorder (MDD) and controls using blood samples (N=1,132) from Netherlands Study of Depression and Anxiety and brain samples (N=64) from the Victorian Brain Bank Network. Data were analyzed with RaMWAS, a novel Biocon- ductor package specifically designed for Methylome-Wide Association Studies (MWAS). To study the overlap between top MWAS findings in blood and brain, we used a permutation based enrichment test (shiftR) that accounted for the depen- dency between adjacent CpG sites. Furthermore, we utilized the methylation data in combination with existing genotype information from the same individuals in a MWAS of CpGs created or destroyed by SNPs. Next, we tested whether top results from this CpG-SNP MWAS overlapped with recent large- scale GWAS to identify robust associations with genomic loci of importance for MDD etiology Results: The MWAS in blood identified five methylome- wide significant sites (P o 5 10-8) from three distinct loci and 472 nominally significant (P o 1 10-5) CpG sites. To study the robustness of the overall MWAS signal, we used an “in-sample” replication based on k-fold cross validation. Results showed that the findings replicated (P = 4.0 10- 10). When we compared blood and brain we found that top blood MWAS findings were significantly enriched for top CpGs in the brain MWAS (P = 5.4 10-3). The MWAS of CpG-SNPs identified 32 nominally significant sites and in- sample replication showed that the signal replicated (P = 2.2 10-8). Finally, the top CpG-SNP MWAS showed a consistent trend towards enrichment in all tested large- scale GWAS, with the most significant enrichment observed for the 23andMe study (P = 4.9 10-3). This overlap involved 55 genes that were overrepresented (P o 0.01) in 12 level-5 gene ontology terms, of which a major portion was related to neuronal regulation, function and development. Discussion: This work involves the largest MWAS for MDD performed to date. Our integrated analysis with brain tissue, genotype information and GWAS results highlighted biological functions of potential value for MDD etiology. Part of the associated methylation marks in blood overlapped with MWAS finding in brain. As blood can easily be collected in a clinical setting, these loci may be of direct value as potential diagnostic biomarkers for MDD.
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ItemNo Preview AvailableEpigenetic aging in major depressive disorder(ELSEVIER, 2019-01-01)Major depressive disorder (MDD) is associated with increased risk of mortality and aging-related diseases [1–3]. The authors examined whether MDD is associated with higher epigenetic aging (EA) [4] in blood as measured by DNA methylation (DNAm) patterns, whether clinical characteristics of MDD have a further impact on these patterns, and whether findings replicate in brain tissue. DNAm age was estimated using all methylation sites in blood of 811 depressed patients and 319 control subjects from the Netherlands Study of Depression and Anxiety. The residuals of the DNAm age estimates regressed on chronological age were calculated to indicate EA. MDD diagnosis and clinical characteristics were assessed with questionnaires and psychiatric interviews. Analyses were adjusted for sociodemographic characteristics, lifestyle, and health status. Postmortem brain samples of 74 depressed patients and 64 control subjects were used for replication. Pathway enrichment analysis was conducted using ConsensusPathDB to gain insight into the biological processes underlying EA in blood and brain. Significantly higher EA was observed in MDD patients compared with control subjects, with a significant dose effect with increasing symptom severity in the overall sample. In the depression group, EA was positively and significantly associated with childhood trauma score. The case-control difference was replicated in an independent dataset of postmortem brain samples. The top significantly enriched Gene Ontology terms included neuronal processes. As compared with control subjects, MDD patients exhibited higher EA in blood and brain tissue, suggesting that they are biologically older than their corresponding chronological age. This effect was even more profound in the presence of childhood trauma.
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ItemNovel insights into stroke pain beliefs and perceptions(TAYLOR & FRANCIS LTD, 2019-12-12)BACKGROUND: Chronic pain is common following stroke, yet its characteristics are poorly understood. OBJECTIVES: To characterize the beliefs and perceptions of people with stroke who experience chronic pain and compare these to a non-stroke population with chronic pain. METHOD: An online survey of the Pain Beliefs and Perceptions Inventory for stroke and non-stroke individuals with chronic pain. Pain beliefs and perceptions, including perceived causes of pain, were compared across the two groups. RESULTS: A total of 223 participants completed all questions. The stroke group (N = 106) reported significantly higher pain intensities (p = <0.001) than the non-stroke group (N = 117). In addition, they identified the stroke as the primary cause of their pain, whereas the non-stroke group identified a body injury as the primary cause. When compared to the non-stroke group, people with stroke were more likely to report their pain as being constant (p = <0.001), demonstrate a lack of understanding regarding cause(s) of their pain (p = <0.001), believe less that their actions contribute to their pain (p = <0.001), and have greater belief that their pain is permanent (p = <0.001). CONCLUSION: These findings emphasize differences in the beliefs and perceptions associated with pain after stroke, supporting the value of targeted attention from research and therapy perspectives. Significant differences in the pain experienced by stroke and non-stroke groups may reflect a poor understanding of chronic pain following stroke. Future educational programs for stroke survivors should be tailored. Targets for future educational interventions are identified and include causes of pain, an understanding of its behavior and potential for improved prognosis.
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ItemCarotid endarterectomy: the change in practice over 11years in a stroke centre(WILEY, 2019-04-01)BACKGROUND: Recent research evidence has impacted the practice of carotid endarterectomy (CEA). We aim to characterize changes in the practice and outcome of CEA over time in a single large-volume stroke centre. METHODS: All patients who underwent CEA from 2004 to 2014 and carotid angioplasty and stenting (CAS) from 2003 to 2008 at an Australian metropolitan tertiary stroke centre hospital were included. Clinical data were analysed to identify time trends in choice of intervention, patient selection, preoperative imaging utilization, surgical timing and outcome. RESULTS: There were 510 CEAs performed during 2004-2014 and 95 CASs during 2003-2008. The proportion of patients undergoing CEA compared to CAS increased from 60% to 90% from 2004 to 2008 (P < 0.001). CAS patients were more likely to have cardiac co-morbidities. From 2004 to 2014, the proportion of CEA patients aged ≥80 years increased (P = 0.001) and the proportion of asymptomatic patients decreased (P = 0.003) over time. Median time from symptom onset to surgery decreased from 52 days (Q1: 25, Q3: 74) in 2004 to 8 days (Q1: 5, Q3: 37) in 2014 (P < 0.001). Use of preoperative ultrasonography decreased whilst CT angiography and the number of imaging modalities applied to each patient increased over time (P < 0.001). Overall, 5.9% of CEAs were complicated by death, stroke or acute myocardial infarction with no significant change over time. CONCLUSION: The trends in CEA practice at our centre align with international trends and guidelines. This study provides a representative indicator of Australian hospital practice, and illustrates how evidence from research is translated into clinical care.
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ItemNo Preview AvailableComparing Participation Outcome Over Time Across International Stroke Cohorts: Outcomes and Methods(W B SAUNDERS CO-ELSEVIER INC, 2019-11-01)OBJECTIVE: To enable a direct comparison of participation levels in the first year post-stroke, assessed by different outcome measures internationally. DESIGN: Two prospective stroke cohort studies following persons from stroke onset to 12 months post-stroke. SETTING: Community. PARTICIPANTS: Persons with stroke (N=495), not living at a nursing home, from Australia STroke imAging pRevention and Treatment-Prediction and Prevention to Achieve optimal Recovery Endpoints after stroke (START-PrePARE; n=100) and the Netherlands (Restore4stroke; n=395). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Activity Card Sort-Australia and Utrecht Scale for Evaluation of Rehabilitation-Participation. Activity domains were matched across measures to find common denominators and original scoring methods were recoded, hereby enabling a direct comparison of retained activities. RESULTS: Ninety-one (START-PrePARE) and 218 (Restore4stroke) persons with stroke were included for analyses. No major differences in background characteristics were observed between the cohorts; the Dutch cohort suffered from slightly more severe stroke. A higher level of participation was observed (radar charts) in the first months post-stroke for the Australian cohort than in the Dutch cohort, especially for unpaid work (P<.003). At 12 months post-stroke, participation levels were similar, without significant differences in retained activities using the defined common denominators (P>.003). CONCLUSIONS: An international comparison of actual activities that persons re-engage in in the first year post-stroke was achieved using a new method and recoding of data. High levels of participation were observed in both cohorts. Unpaid work showed different frequencies at 2-3 months, contributing to different trajectories over time across cultures. Important insights were gained. Although valuable information is inevitably lost with recoding, the approach may assist future studies on the harmonization of data across cohorts, particularly for 1 of the key outcomes of stroke: participation.