Enkephalin Metabolism In Cardiac Ischemia, Heart Failure And Cardiac Surgery
Funder
National Health and Medical Research Council
Funding Amount
$327,037.00
Summary
It has recently been discovered in animal studies that heart muscle can make its own opioid proteins. Previously, it was thought that only nerves made and released opioids. We have recently found that a class of opioids called enkephalins are made and then depleted from the heart during the stress of oxygen and nutrient deprivation. Enkephalins have been found to have potent metabolic effects on the heart. Previous work has shown that opioids can protect the heart against injury incurred during ....It has recently been discovered in animal studies that heart muscle can make its own opioid proteins. Previously, it was thought that only nerves made and released opioids. We have recently found that a class of opioids called enkephalins are made and then depleted from the heart during the stress of oxygen and nutrient deprivation. Enkephalins have been found to have potent metabolic effects on the heart. Previous work has shown that opioids can protect the heart against injury incurred during disease that restricts energy and oxygen supply to the blood vessels and heart. We wish to demonstrate this for the first time in human heart, and we will explore whether the production of enkephalins is altered by the stresses of cardiac surgery and heart failure. Understanding how the human heart attempts to protect itself in disease and how enkephalins work under these conditions, may prove valuable in the development of new drug therapy with synthetic drugs which mimic the action of enkephalins for heart protection during cardiac surgery, heart transplantation and ischemic heart disease. We will test whether specific enkephalins may be used to improve donor heart viability for transplantation by improving the duration and quality of preservation during storage. Understanding what happens to enkephalin production and metabolism in the failing hearts of patients may allow us to find new therapeutic targets in heart failure.Read moreRead less
This project studies the mechanisms involved in rejection of skin and heart grafts using a novel model to track the behaviour of individual graft-reactive white blood cells. We will test two promising new techniques to limit graft rejection: using drugs to inhibit the entry of graft-reactive cells into the graft, and administering cells with the ability to suppress the function of graft-reactive cells. This work will help us to design new therapies to prevent heart graft rejection.
Regulation Of The Cardiac Sodium/proton Exchanger During Ischaemia, Reperfusion And Preconditioning
Funder
National Health and Medical Research Council
Funding Amount
$101,000.00
Summary
Heart attacks are currently treated with drugs to dissolve the clot in the coronary artery or by catheterisation with the aim of restoring blood flow to the ischaemic heart muscle. If restoration of blood flow occurs soon after the heart attack, the ischaemic region can recover completely. However if treatment is delayed, the ischaemic region may not recover. This project concerns the mechanisms that are involved in the myocardial damage which occurs after moderate periods of ischaemia. A transp ....Heart attacks are currently treated with drugs to dissolve the clot in the coronary artery or by catheterisation with the aim of restoring blood flow to the ischaemic heart muscle. If restoration of blood flow occurs soon after the heart attack, the ischaemic region can recover completely. However if treatment is delayed, the ischaemic region may not recover. This project concerns the mechanisms that are involved in the myocardial damage which occurs after moderate periods of ischaemia. A transport protein, the sodium-proton exchanger, is involved in recovery and if its action is blocked with an inhibitory drug, recovery of the ischaemic myocardium is improved. However clinical trials of the drug in humans have given variable results. We are investigating the regulation of this exchanger and believe that such information is essential to the efficient use of the inhibitory drugs in humans and may identify other pathways to improving recovery after ischaemia.Read moreRead less
CD39 Protects Against Renal Ischaemic-reperfusion Injury
Funder
National Health and Medical Research Council
Funding Amount
$441,584.00
Summary
In many medical settings, such as heart attacks, strokes, transplantation, heart surgery, shock and infection, the blood supply to an organ may be compromised resulting in damage. The cessation of blood flow depletes the organ of oxygen and generates a number of toxic changes. Re-establishing blood flow to the organ is essential to prevent further damage, however the reestablishment of blood flow itself can be harmful to the organ. The return of blood flow, oxygen and energy can actually promote ....In many medical settings, such as heart attacks, strokes, transplantation, heart surgery, shock and infection, the blood supply to an organ may be compromised resulting in damage. The cessation of blood flow depletes the organ of oxygen and generates a number of toxic changes. Re-establishing blood flow to the organ is essential to prevent further damage, however the reestablishment of blood flow itself can be harmful to the organ. The return of blood flow, oxygen and energy can actually promote more widespread injury - a process known as ischaemia-reperfusion injury (IRI). A greater understanding of IRI should aid in the development of drugs that minimise its impact. The overall aim of this work is to examine the role of a molecule - CD39 - in IRI. This molecule is ideally situated to minimise injury - it is located on cells that line blood vessels and, as such, is able to directly neutralise toxins released in response to this injury. We, therefore, believe that it will be protective in this setting. We have developed animals that express this molecule and have preliminary results to suggest that these animals are protected in experimental models of IRI as well as in several other models including heart transplantation surgery; processes that share many features with IRI. Moreover, mice deplete of this molecule are prone to more severe IRI. We aim to investigate this by using animals both lacking and expressing CD39. Blood flow to the kidneys will be interrupted for 30 minutes and kidney function assessed at 24 and 48 hours. We will then delve into the potential mechanisms underpinning IRI by determining whether the kidney itself or the blood cells afford protection, which has direct clinical implications.Read moreRead less
Intravascular Coagulopathy In Discordant Xenotransplantation
Funder
National Health and Medical Research Council
Funding Amount
$447,750.00
Summary
The successful treatment of many conditions in which the relevant organ has failed completely and irreversibly is to replace that organ with a new one ie. to perform a transplant. It is well known that there are far fewer organs available for transplantation than the number needed. This means that for those conditions where a supportive treatment is available, eg. the artificial kidney, patients must be maintained by that method, however for other organs such as hearts, lungs and livers, there i ....The successful treatment of many conditions in which the relevant organ has failed completely and irreversibly is to replace that organ with a new one ie. to perform a transplant. It is well known that there are far fewer organs available for transplantation than the number needed. This means that for those conditions where a supportive treatment is available, eg. the artificial kidney, patients must be maintained by that method, however for other organs such as hearts, lungs and livers, there is no mechanical substitute. If these patients do not receive a transplant, they die. A solution to this problem is to use organs from animals. This is called xenotransplantation. The pig is the most suitable donor, however despite many similarities to humans which make it suitable, there are many differences which are still to be overcome before clinical application is possible. These differences are at a very fine molecular level and prevent the normal integration of the organ into the new recipient. The result is that the new organ is rejected within minutes. This process is called hyperacute rejection and by research into its mechanism it was found to be due to just a few differences. We and others have genetically modified pigs so that they have the human components and this has completely prevented this form of rejection. However,we have found a second barrier which causes a rejection response after a few days. It is now known that a major component of the cause of this second barrier is a few differences in the clotting system. We propose to make further genetic modifications which we think will prevent this rejection. This project proposes to examine various genetic modifications and test their effect in small animal models before going on to make and test pigs in which human anti-clotting genes have been inserted. . If we are successful, the possibility of replacing failed human organs with animal organs will be a step closer.Read moreRead less
Intravascular Coagulopathy In Discordant Xenotransplantation
Funder
National Health and Medical Research Council
Funding Amount
$227,036.00
Summary
The successful treatment of many conditions in which the relevant organ has failed completely and irreversibly, is to replace that organ with a new one ie. to perform a transplant. It is well known that there are far fewer organs available for transplantation than the number needed. This means that for those conditions where a supportive treatment is available, eg. the artificial kidney, patients must be maintained by that method, however for other organs such as hearts, lungs and livers, there ....The successful treatment of many conditions in which the relevant organ has failed completely and irreversibly, is to replace that organ with a new one ie. to perform a transplant. It is well known that there are far fewer organs available for transplantation than the number needed. This means that for those conditions where a supportive treatment is available, eg. the artificial kidney, patients must be maintained by that method, however for other organs such as hearts, lungs and livers, there is no mechanical substitute. If these patients do not receive a transplant, they die. A solution to this problem is to use organs from animals. This is called xenotransplantation. The pig is the most suitable donor, however despite many similarities to humans which make it suitable, there are many differences which are still to be overcome before we can use xenotransplants clinically. These differences are at a very fine molecular level and prevent the normal integration of the organ into the new recipient. The result is that the new organ is rejected within minutes. This process is called hyperacute rejection and by research into its mechanism it was found to be due to just a few differences. We and others have genetically modified pigs so that they have the human genes and this has completely prevented this form of rejection. However,we have found a second barrier which causes a rejection response after a few days. It is now known that a major component of the cause of this second barrier is a few differences in the clotting system. We propose to make further genetic modifications which we think will prevent this rejection. This project proposes to examine various genetic modifications and test their effect in small animal models before going on to make and test pigs into which human genes have been inserted. If we are successful, the possibility of replacing failed human organs with animal organs will be a step closer.Read moreRead less
Molecular Cloning And Expression Of Cytokine Genes Related To Induction Of Allograft Transplantation Tolerance In Rats
Funder
National Health and Medical Research Council
Funding Amount
$212,371.00
Summary
Cytokines are soluble proteins produced by leucocytes, and in many cases other cell types, which act as chemical communicators between cells, but not as effector molecules in their own right. Most of the cytokines are growth or differentiation factors and they generally act on cells within the haematopoietic system. In this grant application we will focus on the production of cytokines and antibodies to these cytokines, that are likely to be important in organ transplantation tolerance or organ ....Cytokines are soluble proteins produced by leucocytes, and in many cases other cell types, which act as chemical communicators between cells, but not as effector molecules in their own right. Most of the cytokines are growth or differentiation factors and they generally act on cells within the haematopoietic system. In this grant application we will focus on the production of cytokines and antibodies to these cytokines, that are likely to be important in organ transplantation tolerance or organ rejection. We would like to synthesize these cytokines using molecular biological techniques. These biological materials will be used to treat animals and study their biological effect on transplanted graft survival. If the cytokine treatment does prolong graft survival, what is the mechanisms involved in the immune responses will be further studied. Our aim is to develop strategies that couold be applied to help pateints with organ transplants and receive most specific therapies.Read moreRead less
Adenosine A1 And A3 Receptor Mediated Cardioprotection In Ischaemic Myocardium
Funder
National Health and Medical Research Council
Funding Amount
$265,698.00
Summary
Damage to the heart from coronary vascular disease causes significant morbidity and mortality in Australia. Indeed, ischaemic injury represents the single greatest cause of premature death. Moreover, due to the increasing age of our population the problem is growing - coronary artery disease affects 50% of those older than 65, contributing to an increased incidence of angina pectoris, myocardial infarction, arrhythmia, congestive heart failure, and sudden death. Protective strategies have been, ....Damage to the heart from coronary vascular disease causes significant morbidity and mortality in Australia. Indeed, ischaemic injury represents the single greatest cause of premature death. Moreover, due to the increasing age of our population the problem is growing - coronary artery disease affects 50% of those older than 65, contributing to an increased incidence of angina pectoris, myocardial infarction, arrhythmia, congestive heart failure, and sudden death. Protective strategies have been, and continue to be, developed to reduce the extent of tissue damage and minimise prolonged reductions in heart function. The success of these interventions has been mixed. This research project takes the novel approach of identifying the true roles of two receptors present in the heart (the adenosine A1 and A3 receptors) which may play a crucial role in enhancing tolerance of the heart to disease and injury. We currently do not fully understand the roles of these receptors, although preliminary findings suggest they can exert powerful protective effects during disease conditions. From a fundamental viewpoint, identifying the roles of these two receptors will significantly advance our understanding of the mechanisms of injury and protection in the heart. From a therapeutic viewpoint, this study will take us closer to the potential use of adenosine receptor-based therapy in protecting the heart from ischaemic injury.Read moreRead less
Heartbeats are considered to arise through specialised pacemaker cells establishing rhythmically generated (i.e. pacemaker) action potentials, which then trigger propagating action potentials in heart muscle causing contraction and pumping of blood. This research proposal aims to challenge the physical model that is used to describe this pacemaker process and resultant heart conduction. Our reasons for doing this derive from our discovery of an alternative pacemaker-conduction mechanism, which w ....Heartbeats are considered to arise through specialised pacemaker cells establishing rhythmically generated (i.e. pacemaker) action potentials, which then trigger propagating action potentials in heart muscle causing contraction and pumping of blood. This research proposal aims to challenge the physical model that is used to describe this pacemaker process and resultant heart conduction. Our reasons for doing this derive from our discovery of an alternative pacemaker-conduction mechanism, which we have shown to operate in various smooth muscles. This mechanism, termed store-based pacemaking, is entirely different to the currently held cardiac model but could readily achieve the same outcome. We will investigate the hypotheses that this pacemaker mechanism is also fundamental to mammalian heart pacemaking and conduction. Positive support for our hypotheses, as indicated by our findings on amphibian hearts and from pilot findings, may severely challenge the present model for cardiac pacemaking. Such an outcome will have major ramifications on present interpretation of cardiac function in health and disease and will be particularly important to interpretation of disorders associated with cardiac arrhythmias and heart conduction.Read moreRead less
Noncontact Biventricular Mapping And Intramural Ablation In A Chronic Ovine Model Of Septal Ventricular Tachycardia
Funder
National Health and Medical Research Council
Funding Amount
$519,279.00
Summary
Ventricular tachycardia (VT), an abnormal rhythm originating from the bottom portion of the heart is the major cause of sudden death in the community. Medications are not reliably effective. Expensive (costing about $40,000 every 5 years) implanted defibrillators are very effective in terminating VT, but frequently require painful shocks. Patients who require frequent treatment from their defibrillators are considered for mapping and ablation. About half of the patients with VT have the arrhythm ....Ventricular tachycardia (VT), an abnormal rhythm originating from the bottom portion of the heart is the major cause of sudden death in the community. Medications are not reliably effective. Expensive (costing about $40,000 every 5 years) implanted defibrillators are very effective in terminating VT, but frequently require painful shocks. Patients who require frequent treatment from their defibrillators are considered for mapping and ablation. About half of the patients with VT have the arrhythmia originating from the septum (heart muscle separating the two bottom portions of the heart). This area of the heart is difficult to map from an electrical point of view. A new type of mapping system called the Ensite 3000 system enables acquisition of 3,300 virtual electrical signals from within a heart chamber using an electrode array that does not have to be in direct contact with the heart muscle surface. Our evaluation of the Ensite system in one chamber of the heart has found it to be very good in identifying areas of abnormal electrical activity. It is possible that simultaneous mapping from both sides of the septum using Ensite might be useful in mapping VT originating from the septum. Destruction of the abnormal area, once identified, is generally done using a catheter, but is limited by its ability to destroy targets deep in the heart tissue. We have designed and developed a catheter that is equipped with a needle at its tip that can create deeper lesions. In this study we will be evaluating mapping using the Ensite electrodes in both ventricles in a chronic sheep model with VT originating from the septum. The Ensite mapping will be validated with detailed contact (conventional) mapping. The prototype catheter will be used to destroy the site of origin of VT, once identified. This study should enable more effective treatment of patients with VT and improve their quality of life.Read moreRead less