Mitochondrial Iron Overload And Friedreich's Ataxia: The Role Of Frataxin In Iron And Haem Metabolism
Funder
National Health and Medical Research Council
Funding Amount
$285,990.00
Summary
Friedreich's ataxia (FA) is due to the lack of a protein known as frataxin. Recent studies using Baker's yeast have shown that the deletion of frataxin results in the accumulation of toxic iron in the mitochondrion. More recently, a variety of studies have shown that FA patients have iron loading within their cells. The iron build-up may cause severe damage. At present, the role of frataxin in mammalian mitochondrial iron metabolism is unknown. Our preliminary studies demonstrate that frataxin i ....Friedreich's ataxia (FA) is due to the lack of a protein known as frataxin. Recent studies using Baker's yeast have shown that the deletion of frataxin results in the accumulation of toxic iron in the mitochondrion. More recently, a variety of studies have shown that FA patients have iron loading within their cells. The iron build-up may cause severe damage. At present, the role of frataxin in mammalian mitochondrial iron metabolism is unknown. Our preliminary studies demonstrate that frataxin is down-regulated by either erythroid differentiation or the haem precursor protoporphyrin IX (Becker and Richardson, submitted). These data strongly suggest a role for frataxin in iron metabolism. In the present study we will continue to assess if frataxin plays a role in the way cells handle iron. Using a unique model of mitochondrial iron overload developed in my lab (Richardson et al. (1996) BLOOD 87:3477), we will extensively investigate the iron metabolism of the mitochondrion in order to determine the function of frataxin and its role in Friedreich's ataxia. In addition, we have developed a series of new drugs known as iron chelators that can enter the mitochondrion due to their high lipid solubility (Becker and Richardson 1999 J. Lab. Clin. Med. 134:510). These latter drugs are far more effective than the chelator currently used to treat iron overload, desferrioxamine (DFO). Indeed, our chelators have been designed to result in high iron chelation efficacy but low toxicity (see Becker and Richardson, 1999). This exciting research may be crucial in understanding the development of FA and in creating new therapies such as the use of iron chelators.Read moreRead less
Mitochondrial Iron Overload And Friedreich's Ataxia: The Role Of Frataxin In Iron And Haem Metabolism
Funder
National Health and Medical Research Council
Funding Amount
$606,000.00
Summary
Friedreich's ataxia (FA) is due to the lack of a protein known as frataxin. A variety of studies using Baker's yeast and conditional frataxin knockout (KO) mice have shown that deletion of frataxin leads to the accumulation of toxic iron in their mitochondrion. More recently, a variety of studies have shown that FA patients have iron-loading within their mitochondrion. Iron in the highly redox active environment of the mitochondrion could contribute to the generation of cytotoxic radicals that c ....Friedreich's ataxia (FA) is due to the lack of a protein known as frataxin. A variety of studies using Baker's yeast and conditional frataxin knockout (KO) mice have shown that deletion of frataxin leads to the accumulation of toxic iron in their mitochondrion. More recently, a variety of studies have shown that FA patients have iron-loading within their mitochondrion. Iron in the highly redox active environment of the mitochondrion could contribute to the generation of cytotoxic radicals that cause severe damage. Further, cells deficient in frataxin are sensitive to oxidant stress and Fe chelators rescue oxidant-mediated death of cells from FA patients. Indeed, free radical scavengers have shown to be of use in the treatment of this disease. Studies in DR's lab during this NHMRC grant have shown that frataxin is down-regulated by erythroid differentiation or the haem precursor, protoporphyrin IX (BLOOD 2002;99:3813-22). These data indicate a role for frataxin in Fe metabolism and the pathogenesis of FA. In this study we will continue to examine the role of frataxin in the way cells handle Fe using experimental models developed under the current NHMRC grant. These include transfected cell lines with low frataxin expression generated using an expression vector containing anti-sense frataxin cDNA. Further we obtained the frataxin conditional KO mouse and generated a breeding colony. These animals display many of the pathological features of FA and are the best current model of the disease. Indeed, they will be critical for assessing the role of frataxin in Fe metabolism and as a model to test the ability of Fe-binding drugs to prevent the pathology observed. We designed lipid-soluble chelators that can enter the mitochondrion to bind Fe (Biochim Biophys Acta 2001;1536:133-140) and these ligands will be tested to prevent disease progression in the KO mice. This exciting research is crucial for understanding the pathogenesis of FA and in creating new therapies.Read moreRead less
A NOVEL MOUSE MODEL TO INVESTIGATE THE MECHANISMS OF VIRUS-INDUCED ARTHRITIS
Funder
National Health and Medical Research Council
Funding Amount
$336,000.00
Summary
We have developed a novel animal model by which to study arthritic disease caused by insect-transmitted viruses known as arboviruses. The existence of this model and novel reagents provides an excellent opportunity to further explore the basic mechanisms of infectious disease in a complete functioning animal, rather than specific cultured cells. The study will use modern approaches in molecular and cellular biology to achieve this goal. The production by our immune systems of soluble mediators ( ....We have developed a novel animal model by which to study arthritic disease caused by insect-transmitted viruses known as arboviruses. The existence of this model and novel reagents provides an excellent opportunity to further explore the basic mechanisms of infectious disease in a complete functioning animal, rather than specific cultured cells. The study will use modern approaches in molecular and cellular biology to achieve this goal. The production by our immune systems of soluble mediators (cytokines-chemokines) and antibodies is an overwhelming positive aspect of our physiological response to infection by microbes. Protection from disease by these immune compounds can happen naturally, or the body's ability to produce these factors can be exploited to our benefit via the administration of vaccines. However, these factors can also be detrimental to the host contributing to severe disease. For instance, work performed almost 40 years ago showed for the first time that under particular conditions, antibodies against viruses can enhance infection, instead of inhibiting infection as normally seen. In the intervening years work by scientists all over the world has associated antibody-dependent enhancement (ADE) of infection to many types of viruses; ADE is even thought to be a risk factor to serious disease with dengue virus, and has been shown in vitro for the AIDS virus and Ebola virus. We have recently discovered a molecular mechanism which explains how antibody enhances viral infection in vitro. In studies on immune cells infected with Ross River Virus (RRV) we found that infection helped by antibody resulted in the specific disruption to the production of cellular chemicals which are toxic to viruses. Are these mechanisms of antibody-enhanced infection also found in animals? Will such mode of infection cause enhanced disease and tissue pathology (arthritis) in animals?Read moreRead less
Development Of Iron Chelators For The Treatment Of Friedreichs Ataxia And The Role Of Frataxin In Iron Metabolism
Funder
National Health and Medical Research Council
Funding Amount
$550,987.00
Summary
Friedreich's ataxia (FA) is a neuro- and cardio-degenerative disease where there is an accumulation of toxic Fe in the mitochondrion. Excitingly, work from our current NHMRC grant showed iron plays a significant role in FA pathology. Importantly, we developed new drugs (Fe chelators) which rescue the cardiac pathology of FA in an animal model. Studies will now assess if our drugs prevent the neurodegeneration of FA in another animal model. This work could lead to novel therapies for FA.
Role Of Transition Metal Ions And Redox Activity In The Development Of Atherosclerotic Plaques
Funder
National Health and Medical Research Council
Funding Amount
$196,018.00
Summary
Metal ions such as iron and copper have been reproted to be present in the lesions present in diseased human arteries and it has been suggested that these metal ions contribute to the development of atherosclerosis (hardening of the arteries) via their ability to catalyse the formation of highly reactive molecualr fragments called free radicals. Though metal ions are known to catalyse such reactions in test-tube experiments, both the presence of metal ions in diseased arteries and their ability ....Metal ions such as iron and copper have been reproted to be present in the lesions present in diseased human arteries and it has been suggested that these metal ions contribute to the development of atherosclerosis (hardening of the arteries) via their ability to catalyse the formation of highly reactive molecualr fragments called free radicals. Though metal ions are known to catalyse such reactions in test-tube experiments, both the presence of metal ions in diseased arteries and their ability to generate free radicals is controversial. This study will employ a novel, minimally-invasive, technique to assess the nature and quantity of metal ions present in well-defined human and animal lesions at different stages of lesion development. The ability of these metal ions to catalyse free radical formation from components present in the artery wall will also be assessed. The release of these metal ions from the artery wall to added organic molecules will be assessed as this might minimise their potential to cause damage, and provide a possible therapeutic strategy. These studies will therefore provide valuable information as to the significance and role of reactive metal ions in the development of human artery disease and the possible prevention, or minimisation, of such processes.Read moreRead less
Epimutations As Germ-line Defects In Hereditary Cancer Syndromes
Funder
National Health and Medical Research Council
Funding Amount
$385,925.00
Summary
Traditionally familial cancers were thought to be caused and inherited by spelling mistakes within the genetic code of cancer prevention genes. Our group has found that a 'chemical coat' around the MLH1 gene, causing it to be switched off, can also be inherited in some cases of bowel cancer, without any mistakes within the gene's code. We will determine if this 'coat' causes other types of cancer and if this runs in families. We also hope to find out how the coat is formed and may be reversed.