Urotensin-II In Human Heart: Investigation Of Mechanisms Involved In Cardiac Function
Funder
National Health and Medical Research Council
Funding Amount
$255,990.00
Summary
The normal function of the body is maintained by naturally occurring compounds. Some for example affect the heart, fine tuning it to make it beat faster or slower, or beat with greater or less force when required in different situations in health and disease. We were the first to show just recently that a small protein which occurs naturally in the body, called urotensin-II can affect the way the heart beats. We showed that extremely tiny amounts increase the force of the heart beat. Our finding ....The normal function of the body is maintained by naturally occurring compounds. Some for example affect the heart, fine tuning it to make it beat faster or slower, or beat with greater or less force when required in different situations in health and disease. We were the first to show just recently that a small protein which occurs naturally in the body, called urotensin-II can affect the way the heart beats. We showed that extremely tiny amounts increase the force of the heart beat. Our findings indicate that urotensin-II is the most potent heart stimulator identified to date. In patients with heart failure, short term stimulation of heart contraction is beneficial, supplying the heart and other organs with vital oxygen and nutrients. However, in the long term excessive stimulation causes worsening of the patients condition. Very little is currently known about the way in which urotensin-II alters heart function. The goal of our study is to understand the mechanism involved in urotensin-II mediated effects on the heart. This will involve identifying the location of urotensin-II and its receptors in the heart, and determining what signalling changes occur after the interaction of urotensin-II with its receptors. Urotensin-II must first be cleaved from a larger drug. We will determine where in the heart this cleavage occurs and whether the process is crucial to the ability of urotensin-II to stimulate contraction of the heart. Since stimulators of heart contraction are detrimental to patients with heart failure in the long term, we will determine whether these patients have more urotensin-II in their blood than patients who do not have heart failure. If the levels of urotensin-II are higher in heart failure patients, it may indicate a need to interfere with the interaction of urotensin-II with its receptors.Read moreRead less
Single-Beat Preload Recruitable Stroke Work Measurement Of Cardiac Contractility In Three Mammalian Models.
Funder
National Health and Medical Research Council
Funding Amount
$241,980.00
Summary
The accurate measurement of the inherent pumping capacity of the heart muscle is difficult because (i) most measurements currently in use cannot accurately discriminate between the contribution of the heart muscle and that of the vascular system to the results obtained, and (ii) the measurements which can discriminate currently require invasive measurements and procedures that frequently restrict their use. The overall purpose of this proposal is to more rigorously validate a promising method we ....The accurate measurement of the inherent pumping capacity of the heart muscle is difficult because (i) most measurements currently in use cannot accurately discriminate between the contribution of the heart muscle and that of the vascular system to the results obtained, and (ii) the measurements which can discriminate currently require invasive measurements and procedures that frequently restrict their use. The overall purpose of this proposal is to more rigorously validate a promising method we have developed that will (i) make accurate assessment possible from a single cardiac beat in both experimental animals and human subjects; (ii) reduce the number of experimental animals required for such measurements by permitting sequential measurements in the same animals; (iii) make it possible to perform such measurements non-invasively in human subjects.Read moreRead less
Anthracyclines Disrupt Ca2+ Signalling In Cardiomyocytes: A Contribution To Cardiac Toxicity
Funder
National Health and Medical Research Council
Funding Amount
$525,620.00
Summary
Anthracyclines are one of the most effective drugs used in chemotherapy, but cause side effects resulting in serious heart problems which can be fatal. The link between anthracycline therapy and the problems they cause in the heart is not fully defined. We will investigate mechanisms leading to these side effects and define specific targets of anthracyclines in the heart. It is hoped this will lead to the design of new drugs which counteract the side effects of anthracycline treatment.
Clinical trials and experimental investigations have demonstrated that a diet rich in fish oil, containing high levels of omega 3 fatty acids, provides protection against arrhythmias and sudden cardiac death associated with heart failure. Surprisingly little is known about how these dietary omega 3 lipids alter the electrical and mechanical function of cardiac muscle cells when incorporated into the membrane of these cells. The goal of this study is to examine how experimental omega 3 diet treat ....Clinical trials and experimental investigations have demonstrated that a diet rich in fish oil, containing high levels of omega 3 fatty acids, provides protection against arrhythmias and sudden cardiac death associated with heart failure. Surprisingly little is known about how these dietary omega 3 lipids alter the electrical and mechanical function of cardiac muscle cells when incorporated into the membrane of these cells. The goal of this study is to examine how experimental omega 3 diet treatment can modify the heart muscle cell structure and function. In particular we will determine which cellular mechanisms may be important in conferring selective benefit of dietary intervention on pre-failing heart function. For this study we will use mice which exhibit signs of heart failure induced by hormone overproduction (angiotensin II) and by elevation of blood pressure (by surgical constriction). Mice will be fed omega-3 and omega-6 diets and experiments to investigate cardiac muscle cell structure and function will be carried out using a variety of electrical recording, microscopic and molecular biology techniques. Diet-induced changes in the capacity of the heart cells to regulate calcium will be investigated using cells loaded with fluroescent indicators. Single cell electrical recording techniques (patch clamp) will also be used in combination with ECG measurement to evaluate how arrhythmic activity arising from electrically and mechanically unstable cells can be suppressed by omega-3 diet intervention. Finally we will take the first step towards validating the rodent experimental findings in a clinical setting with measurements of calcium transporters and channel expression in human specimens from cardiac surgery patients.Read moreRead less
The Role Of Mechanoelectric Feedback In Cardiac Arrhythmogenesis
Funder
National Health and Medical Research Council
Funding Amount
$307,550.00
Summary
Arrhythmias are disruptions of the normal electrical rhythm of the heart, and can vary from asymptomatic to fatal. It used to be thought that the electrical and mechanical functions of the heart muscle were essentially separate: the electrical activity triggered contraction something like pulling the trigger of a gun- once events were in motion, the electrical events played no further role. However, in recent years it has become apparent that this is an over-simplification of the real situation. ....Arrhythmias are disruptions of the normal electrical rhythm of the heart, and can vary from asymptomatic to fatal. It used to be thought that the electrical and mechanical functions of the heart muscle were essentially separate: the electrical activity triggered contraction something like pulling the trigger of a gun- once events were in motion, the electrical events played no further role. However, in recent years it has become apparent that this is an over-simplification of the real situation. In fact, the electrical activity of the heart is influenced strongly by the degree and timing of stretch to which the heart muscle is subjected, a process called Mechano-electric feedback. Since it can be demonstrated in isolated tissues, mechano-electric feedback must be an intrinsic property of the heart muscle. It has been shown in isolated heart preparations that passive stretch produces electrical disturbances in the normal action potential shape and propagation and that these electrical disturbances can be powerful enough to generate severe arrhythmias. There are paralells in human diseases. For example, atrial arrhythmias are common in older people, and it seems that these may be due to chronic stretch of the atria, as a consequence of high blood pressure. In addition, in those patients recovering from a heart attack, it seems likely that the damaged part of the heart muscle subjects the surrounding tissue to unusual mechanical stresses, and may trigger arrhythmias. This project aims to investigate the mechanisms underlying this mechano-electric feedback, in an attempt to understand some types of arrhythmias. Using molecular biology techniques, we will look at the gene expression of a novel type of stretch-activated potassium channel in both healthy and diseased animal hearts, with the aim of seeing if changes in the level of expression of these channels is correlated with changes in the response of the heart to stretch.Read moreRead less
Regulation Of Calcium Release Channels (RyR2) In Healthy And Failing Hearts
Funder
National Health and Medical Research Council
Funding Amount
$337,632.00
Summary
In striated muscle, the sarcoplasmic reticulum (SR) is the calcium store from which calcium release through ryanodine receptors (RyR2) is the key determinate of muscle force. We will develop an understanding of the complex functional changes in RyR2 that underlie adaptation of the heart to physiological stress (exercise) and functional changes associated with mal-adaptation in heart failure.
Mechanisms Involved In Reduced Cardiac Contractility As A Consequence Of Growth Restriction During Fetal Development
Funder
National Health and Medical Research Council
Funding Amount
$317,810.00
Summary
Functional development of the heart muscle has been a focus of intense research over the last 40 years. Despite our current understanding of the changes in how excitation of the cardiomyocyte leads to contraction, a process broadly termed excitation-contrcation (E-C) coupling, a major model used to study paralells of human fetal development, the sheep, has not been examined in this context. As such, it remains unclear how E-C coupling evolves from the fetus to the adult. Understanding normal phy ....Functional development of the heart muscle has been a focus of intense research over the last 40 years. Despite our current understanding of the changes in how excitation of the cardiomyocyte leads to contraction, a process broadly termed excitation-contrcation (E-C) coupling, a major model used to study paralells of human fetal development, the sheep, has not been examined in this context. As such, it remains unclear how E-C coupling evolves from the fetus to the adult. Understanding normal physiology is imperative to subsequetly understand pathological states, such as interuterine growth restriction (IUGR). In Australia, the incidence of IUGR leading to low birth weight babies is 7%. IUGR is caused by maternal undernutrition, maternal smoking-drug use and placental insufficiency. It is associated with an increase in perinatal mortality, respiratory problems, SIDS and morbidity. Epidemiological studies show that low birth weight babies are also at an increased risk of cardiovascular disease, including heart failure, in adult life. To date, there is little information on the impact of fetal growth restriction on the normal development and function of the heart muscle. Understanding the impact of IUGR on heart muscle development will allow the elucidation of the underlying physiological mechanisms linking these two temporally distinct events. This mechanistic understanding will allow improved clinical management of those individuals at risk of cardiovascular disease in adult life arising from IUGR. It may also allow for early intervention strategies that can improve cardiovascular function. Therefore, we propose to examine both the normal developmental changes to E-C coupling so that we can understand how placental insufficiency leading to IUGR impairs normal heart muscle development. This will result in impaired function at a cellular level, which will ultimately manifest as an increased susceptibility of the heart to injury in later life.Read moreRead less