The Heart Research Institute

Sydney, Australia

The Heart Research Institute

Sydney, Australia
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Chan S.W.,The Heart Research Institute | Dunlop R.A.,The Heart Research Institute | Rowe A.,University of Sydney | Double K.L.,University of New South Wales | And 2 more authors.
Experimental Neurology | Year: 2012

Levodopa (l-dopa), a close structural analogue of the protein amino acid l-tyrosine, can substitute for l-tyrosine in protein synthesis and be mistakenly incorporated into newly synthesised proteins in vitro. We show that l- dopa-containing proteins are present in the brain in l-DOPA-treated Parkinson's disease patients and accumulate in specific brain regions. In vitro studies demonstrate that substitution of l-tyrosine residues in proteins with l-DOPA causes protein misfolding and promotes protein aggregation in SH-SY5Y neuroblastoma cells resulting in the appearance of autofluorescent bodies. We show that the presence of l-DOPA-containing proteins causes profound changes in mitochondria and stimulates the formation of autophagic vacuoles in cells. Unlike l-DOPA, which is toxic to cells through its ability to generate radicals, proteins containing incorporated l-DOPA are toxic to SH-SY5Y cells by a mechanism independent of oxidative stress and resistant to antioxidants. These data suggest that the accumulation of l-DOPA-containing proteins in vulnerable cells might negatively impact on cell function. © 2011 Elsevier Inc.

Mithieux S.M.,University of Sydney | Wise S.G.,The Heart Research Institute | Weiss A.S.,University of Sydney
Advanced Drug Delivery Reviews | Year: 2013

Tropoelastin dominates the physical performance of human elastic tissue as it is assembled to make elastin. Tropoelastin is increasingly appreciated as a protein monomer with a defined solution shape comprising modular, bridged regions that specialize in elasticity and cell attachment, which collectively participate in macromolecular assembly. This modular, multifaceted molecule is being exploited to enhance the physical performance and biological presentation of engineered constructs to augment and repair human tissues. These tissues include skin and vasculature, and emphasize how growing knowledge of tropoelastin can be powerfully adapted to add value to pre-existing devices like stents and novel, multi-featured biological implants. © 2012 Elsevier B.V.

Kappelle P.J.W.H.,University of Groningen | Lambert G.,The Heart Research Institute | Lambert G.,University of Nantes | Dullaart R.P.F.,University of Groningen
Atherosclerosis | Year: 2011

Purpose: Proprotein convertase subtilisin-kexin type 9 (PCSK9) promotes low density lipoprotein (LDL) receptor degradation, thereby providing a key pathway for LDL metabolism. PCSK9 mRNA expression may be upregulated by insulin in murine models. Here we examined effects of exogenous hyperinsulinemia on plasma PCSK9 levels in humans without and with type 2 diabetes mellitus. Methods: A 24. h moderately hyperinsulinemic glucose clamp (30. mU/kg/h) was performed in 8 healthy men and 8 male type 2 diabetic patients. Plasma PCSK9 was measured using a sandwich enzyme-linked immunosorbent assay. Results: Plasma LDL cholesterol and apolipoprotein B were lowered by insulin in healthy subjects and diabetic patients (p< 0.01 for all), whereas triglycerides were also decreased in healthy subjects (p< 0.01). Plasma PCSK9 levels remained unchanged in healthy subjects (median (interquartile range) change, -23 (-63 to 25) %, P = 0.50) and in diabetic patients (change, 4 (-17 to 44) %, P = 0.20). Individual absolute and relative changes in LDL cholesterol, apolipoprotein B and triglycerides after 24. h of insulin were unrelated to changes in PCSK9 (P> 0.15 for all). Conclusion: Plasma PCSK9 levels are not increased by exposure to moderate 24. h hyperinsulinemia in healthy and type 2 diabetic individuals. © 2010 Elsevier Ireland Ltd.

Di Bartolo B.A.,University of New South Wales | Kavurma M.M.,The Heart Research Institute | Kavurma M.M.,University of Sydney
Current Pharmaceutical Design | Year: 2014

Receptor activator of nuclear factor-κB ligand (RANKL) is a member of the tumour necrosis factor family important in bone remodelling. Recent evidence suggest that calcification in the vessel wall is equivalent to mechanisms mediating bone formation. This review highlights the role of RANKL in vascular arterial calcification. Here, the relationship between RANKL, osteoprotegerin (OPG) and tumour necrosis factor-related apoptosis-inducing ligand (TRAIL) is discussed. Furthermore, we focus on the regulatory mechanisms mediating RANKL gene expression and transcription in cells of the vessel wall. A better understanding of RANKL-mediated signalling may help develop more sophisticated cell-based therapies to inhibit calcification of the vessel wall. © 2014 Bentham Science Publishers.

Jansson P.J.,University of Sydney | Hawkins C.L.,The Heart Research Institute | Lovejoy D.B.,University of Sydney | Richardson D.R.,University of Sydney
Journal of Inorganic Biochemistry | Year: 2010

Iron chelation therapy was initially designed to alleviate the toxic effects of excess iron evident in iron-overload diseases. However, some iron chelator-metal complexes have also gained interest due to their high redox activity and toxicological properties that have potential for cancer chemotherapy. This communication addresses the conflicting results published recently on the ability of the iron chelator, Dp44mT, to induce hydroxyl radical formation upon complexation with iron (B.B. Hasinoff and D. Patel, J Inorg. Biochem. 103 (2009), 1093-1101). This previous study used EPR spin-trapping to show that Dp44mT-iron complexes were not able to generate hydroxyl radicals. Here, we demonstrate the opposite by using the same technique under very similar conditions to show the Dp44mT-iron complex is indeed redox-active and induces hydroxyl radical formation. This was studied directly in an iron(II)/H2O2 reaction system or using a reducing iron(III)/ascorbate system implementing several different buffers at pH 7.4. The demonstration by EPR that the Dp44mT-iron complex is redox-active confirms our previous studies using cyclic voltammetry, ascorbate oxidation, benzoate hydroxylation and a plasmid DNA strand-break assay. We discuss the relevance of the redox activity to the biological effects of Dp44mT. © 2010.

Barter P.,The Heart Research Institute
Atherosclerosis Supplements | Year: 2011

Evidence that low-density lipoprotein-cholesterol (LDL-C) causes cardiovascular disease (CVD) is overwhelming. It has also been proven beyond all doubt that lowering the level of LDL-C using statins reduces CV risk. However, many people remain at high risk even when their level of LDL-C has been reduced by aggressive treatment with statins. One reason for this residual risk can be a low level of high-density lipoprotein-cholesterol (HDL-C).The concentration of HDL-C is an independent, inverse predictor for CVD. This relationship is apparent even when treatment with statins has reduced the level of LDL-C to below 1.8 mmol/L (70 mg/dL). It has therefore been suggested that raising the level of HDL-C should be considered as a therapeutic strategy for reducing the residual CV risk that persists in some people, despite aggressive LDL-C lowering with statins. HDL particles have several functions with the potential to protect against arterial disease, the best known of which relates to their ability to promote cholesterol efflux from macrophages in the artery wall. However, HDLs have several additional protective properties that are independent of their involvement in cholesterol metabolism. For example, they have properties that reduce oxidation, vascular inflammation and thrombosis, improve endothelial function, promote endothelial repair, enhance insulin sensitivity and promote insulin secretion by pancreatic beta islet cells. There is also a large and compelling body of evidence in animal models showing that interventions that increase HDL levels are profoundly anti-atherogenic. Major causes of low HDL are abdominal obesity and type 2 diabetes, the worldwide incidences of which are increasing at alarming rates. Strategies to increase the concentration of HDL should begin with lifestyle changes such as weight reduction, increased physical activity and smoking cessation. However, compliance with such measures is frequently poor and pharmacological intervention may be required. Currently available HDL-raising medications include fibrates, niacin and statins. There is indisputable evidence that lowering LDL-C levels using statins translates into a large reduction in CV risk. There is also mounting evidence that increasing the level of HDL-C using statins contributes to an additional reduction in CV risk. For example, the increase in HDL-C levels that was associated with simvastatin treatment in the 4S study was a significant predictor for the reduction in CV events. Moreover, a meta-analysis of 1,455 patients in 4 coronary intravascular ultrasound imaging trials showed that both the achieved level of LDL-C and the increase in HDL-C concentration during statin treatment were significant independent predictors for coronary atheroma progression as assessed by coronary intravascular ultrasound. In conclusion, evidence suggests that low levels of HDL-C are associated with an increased CV risk even when LDL-C is reduced to below 1.7 mmol/L (70 mg/dL) with a statin. Moreover, there is mounting evidence that increasing the level of HDL-C has the capacity to reduce CV risk. Thus, there is a compelling case for targeting both the LDL and HDL fractions to reduce CV risk in people with dyslipidemia, high CV risk and low levels of HDL-C. © 2011 Elsevier Ireland Ltd.

Summers F.A.,The Heart Research Institute | Forsman Quigley A.,The Heart Research Institute | Hawkins C.L.,The Heart Research Institute | Hawkins C.L.,University of Sydney
Biochemical and Biophysical Research Communications | Year: 2012

Hypochlorous acid (HOCl) is a potent oxidant produced by the enzyme myeloperoxidase, which is released by neutrophils under inflammatory conditions. Although important in the immune system, HOCl can also damage host tissue, which contributes to the development of disease. HOCl reacts readily with free amino groups to form N-chloramines, which also cause damage in vivo, owing to the extracellular release of myeloperoxidase and production of HOCl. HOCl and N-chloramines react readily with cellular thiols, which causes dysfunction via enzyme inactivation and modulation of redox signaling processes. In this study, the ability of HOCl and model N-chloramines produced on histamine and ammonia at inflammatory sites, to oxidize specific thiol-containing proteins in human coronary artery endothelial cells was investigated. Using a proteomics approach with the thiol-specific probe, 5-iodoacetamidofluorescein, we show that several proteins including peptidylprolyl isomerase A (cyclophilin A), protein disulfide isomerase, glyceraldehyde-3-phosphate dehydrogenase and galectin-1 are particularly sensitive to oxidation by HOCl and N-chloramines formed at inflammatory sites. This will contribute to cellular dysfunction and may play a role in inflammatory disease pathogenesis. © 2012 Elsevier Inc.

Barter P.J.,The Heart Research Institute
Diabetes and Metabolism Journal | Year: 2011

Type 2 diabetes is commonly accompanied by a low level of high density lipoprotein cholesterol (HDL-C) that contributes to the increased cardiovascular risk associated with this condition. Given that HDLs have the ability to improve increase the uptake of glucose by skeletal muscle and to stimulate the secretion of insulin from pancreatic beta cells the possibility arises that a low HDL concentration in type 2 diabetes may also contribute to a worsening of diabetic control. Thus, there is a double case for raising the level of HDL-C in patients with type 2 diabetes: to reduce cardiovascular risk and to improve glycemic control. Approaches to raising HDL-C include lifestyle factors such as weight reduction, increased physical activity and stopping smoking. Of currently available drugs, the most effective is niacin. Newer formulations of niacin are reasonably well tolerated and have the ability to increase HDL-C by up to 30%. The effect of niacin on cardiovascular events in type 2 diabetes is currently being tested in a largescale clinical outcome trial. © 2011 Korean Diabetes Association.

Tso C.,The Heart Research Institute
PloS one | Year: 2012

Blood monocytes are known to express endothelial-like genes during co-culture with endothelium. In this study, the time-dependent change in the phenotype pattern of primary blood monocytes after adhering to endothelium is reported using a novel HLA-A2 mistyped co-culture model. Freshly isolated human PBMCs were co-cultured with human umbilical vein endothelial cells or human coronary arterial endothelial cells of converse human leukocyte antigen A2 (HLA-A2) status. This allows the tracking of the PBMC-derived cells by HLA-A2 expression and assessment of their phenotype pattern over time. PBMCs that adhered to the endothelium at the start of the co-culture were predominantly CD11b+ blood monocytes. After 24 to 72 hours in co-culture, the endothelium-adherent monocytes acquired endothelial-like properties including the expression of endothelial nitric oxide synthase, CD105, CD144 and vascular endothelial growth factor receptor 2. The expression of monocyte/macrophage lineage antigens CD14, CD11b and CD36 were down regulated concomitantly. The adherent monocytes did not express CD115 after 1 day of co-culture. By day 6, the monocyte-derived cells expressed vascular cell adhesion molecule 1 in response to tumour necrosis factor alpha. Up to 10% of the PBMCs adhered to the endothelium. These monocyte-derived cells contributed up to 30% of the co-cultured cell layer and this was dose-dependent on the PBMC seeding density. Human blood monocytes undergo rapid phenotype change to resemble endothelial cells after adhering to endothelium.

Dunn L.,The Heart Research Institute
Journal of visualized experiments : JoVE | Year: 2013

Wound healing and repair are the most complex biological processes that occur in human life. After injury, multiple biological pathways become activated. Impaired wound healing, which occurs in diabetic patients for example, can lead to severe unfavorable outcomes such as amputation. There is, therefore, an increasing impetus to develop novel agents that promote wound repair. The testing of these has been limited to large animal models such as swine, which are often impractical. Mice represent the ideal preclinical model, as they are economical and amenable to genetic manipulation, which allows for mechanistic investigation. However, wound healing in a mouse is fundamentally different to that of humans as it primarily occurs via contraction. Our murine model overcomes this by incorporating a splint around the wound. By splinting the wound, the repair process is then dependent on epithelialization, cellular proliferation and angiogenesis, which closely mirror the biological processes of human wound healing. Whilst requiring consistency and care, this murine model does not involve complicated surgical techniques and allows for the robust testing of promising agents that may, for example, promote angiogenesis or inhibit inflammation. Furthermore, each mouse acts as its own control as two wounds are prepared, enabling the application of both the test compound and the vehicle control on the same animal. In conclusion, we demonstrate a practical, easy-to-learn, and robust model of wound healing, which is comparable to that of humans.

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