THE REGULATORY MECHANISM OF HAEM OXYGENASE PROTECTION AGAINST PHOTOIMMUNOSUPPRESSION AND SKIN CANCER
Funder
National Health and Medical Research Council
Funding Amount
$439,500.00
Summary
Current dogma holds that UVA radiation adds to UVB damage in the skin. However we have identified a window of UVA doses, easily achievable from daytime sunlight exposure, that do not cause sunburn and are not immunosuppressive, but that significantly attenuate the damaging effects of UVB. In mice the mechanism partially depends on the UVA-upregulated cytokine interferon-gamma, and strongly on the UVA-inducible antioxidant enzyme haem oxygenase-1 (HO-1). This project aims to establish how the HO- ....Current dogma holds that UVA radiation adds to UVB damage in the skin. However we have identified a window of UVA doses, easily achievable from daytime sunlight exposure, that do not cause sunburn and are not immunosuppressive, but that significantly attenuate the damaging effects of UVB. In mice the mechanism partially depends on the UVA-upregulated cytokine interferon-gamma, and strongly on the UVA-inducible antioxidant enzyme haem oxygenase-1 (HO-1). This project aims to establish how the HO-1 gene is regulated by UVA. Available data from cultured human skin cells suggest that HO-1 is UVA-inducible in fibroblasts but not keratinocytes, whereas we found both cell types respond in mouse skin, keratinocytes most actively. We will ascertain whether a species difference, or an anomaly in cultured cells, underlies these discrepancies. With human skin grafted onto immunodeficient SCID mice, we will study impaired immune function, an important prerequisite for cancer, compared with mouse skin in vivo. Using molecular biology techniques with this model, we will monitor the activity of the transcription factor Bach 1, known to bind to the DNA of the HO-1 promoter region to repress the gene normally, but reversibly by haem-binding, and the corresponding activity of HO-1, during immunoprotective (UVA exposure, haem elevated) conditions. Immunoprotection may result from binding by Bach 1 of haem released from microsomal proteins by UVA, its release from DNA and thus derepression of HO-1. We will seek evidence of a role for skin cytokines in modifying Bach 1 binding, and for Bach 1 and HO-1 actions during photocarcinogenesis induction with chronic UV exposure. The significance of the outcome of the studies will be in understanding how a natural ameliorating pathway induced by UVA radiation could be utilised for superior photoprotection strategies for skin cancer susceptible humans.Read moreRead less
Role Of Placental Heme-oxygenase Pathway In Regulating Preterm Neonatal Cardiovascular Function
Funder
National Health and Medical Research Council
Funding Amount
$176,719.00
Summary
Babies born prematurely are more likely to experience problems as a result of being born early with males doing worse than females. The mechanisms causing this difference are unknown. The control of blood flow in the placenta and fetus is essential for normal growth and development. This project will investigate the influence of duration of pregnancy, gender, and exposure to antenatal steroids on pathways that control blood flow in the placenta and the newborn in babies born after prematurely.
Potential Novel Pharmacological Strategies To Prevent Atherosclerotic Plaque Rupture
Funder
National Health and Medical Research Council
Funding Amount
$1,584,568.00
Summary
Most heart attacks are the consequence of the acute rupture of plaques in arteries that supply our heart with oxygen and nutrients. Current standard tests cannot distinguish plaques that likely rupture from plaques that do not rupture. Similarly, little is known about the processes that determine whether a plaque is vulnerable to rupture or stable. The current project examines the involvement of two processes - either alone or in combination - in determining plaque stability/vulnerability.
The Mechanism Of Intestinal Haem Iron Absorption And Characterization Of A Novel Haem-binding Protein
Funder
National Health and Medical Research Council
Funding Amount
$537,773.00
Summary
Iron is essential for normal health as many important proteins in the body require iron to function properly (e.g. haemoglobin). However, too much iron can be toxic, so the body must keep its iron content within defined limits. The amount of iron in the body is determined at the point of absorption from the diet in the small intestine. If too little iron is absorbed, then anaemia can result. If too much iron is absorbed, as is the case in the common disease haemochromatosis (with approximately 1 ....Iron is essential for normal health as many important proteins in the body require iron to function properly (e.g. haemoglobin). However, too much iron can be toxic, so the body must keep its iron content within defined limits. The amount of iron in the body is determined at the point of absorption from the diet in the small intestine. If too little iron is absorbed, then anaemia can result. If too much iron is absorbed, as is the case in the common disease haemochromatosis (with approximately 1 in 200 Australians at risk) then the body becomes iron loaded and various organs, particularly the liver, can become damaged. An understanding of how iron is absorbed will place us in a much better position to treat diseases such as this. Iron is present in the diet in two forms - inorganic iron and haem iron. Inorganic iron is the main form of iron in foods of plant origin while most haem iron comes from meat. In a typical diet 80-90% of the iron is inorganic iron and only 10-20% is haem. Despite this, 30-50% of the iron taken into the body comes from haem, so haem iron absorption is particularly efficient. While we have learned a great deal about the mechanims by which inorganic iron is absorbed in recent years, we know very little about the absorption of haem iron, so that is the focus of this project. We will study the pathway by which haem enters the body, how this process is regulated, and the characteristics of haem binding to the cells lining the small intestine. These cells are responsible for the uptake of all nutrients from the diet. In particular, we will examine the biology of a recently identified protein known as HCP1. Preliminary evidence suggests that HCP1 could be the main protein enabling haem to be taken up by intestinal cells. These studies will enhance our knowledge of an important nutritional pathway and improve our capacity to treat diseases such as haemochromatosis where iron absorption is defective.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
Defining Iron And Haem-induced Pro-carcinogenic Pathways Of Colorectal Cancer
Funder
National Health and Medical Research Council
Funding Amount
$566,277.00
Summary
Colorectal cancer is very common in Western society. Population studies have reported that high consumption iron-containing foods and red meat, the latter being a source of both haem and iron, are risk factors for colorectal cancer. This study will identify the levels of dietary haem and iron that promote colorectal cancer development. Also, it will determine the mechanisms and relative contribution of iron and haem to pro-carcinogenic pathways that result in colorectal cancer.
COX-2 INHIBITORS AS A CAUSE OF HEART AND RENAL FAILURE
Funder
National Health and Medical Research Council
Funding Amount
$271,610.00
Summary
Non-steroid anti-inflammatory drugs (NSAIDs) have pain-killing and anti-inflammatory properties. For many years Australia had a higher use of these drugs than other countries. The drugs are quite toxic, and in susceptible individuals may cause ulceration and bleeding from the stomach and duodenum, kidney damage and fluid congestion leading to heart failure. Each of these conditions carries a high morbidity, particularly in the elderly. Because of concerns about toxicity, the use of NSAIDs in Aus ....Non-steroid anti-inflammatory drugs (NSAIDs) have pain-killing and anti-inflammatory properties. For many years Australia had a higher use of these drugs than other countries. The drugs are quite toxic, and in susceptible individuals may cause ulceration and bleeding from the stomach and duodenum, kidney damage and fluid congestion leading to heart failure. Each of these conditions carries a high morbidity, particularly in the elderly. Because of concerns about toxicity, the use of NSAIDs in Australia fell during the 1990s by around 40%. Newer allegedly safer forms of NSAIDs called COX-2 inhibitors have been introduced into the Australian market. The first 2 drugs to be marketed are called Celebrex and Vioxx. These drugs appear to be safer for the stomach and duodenum, but the true effects on the kidney and heart are as yet unclear. COX-2 inhibitors have been very widely used with over 1.7 million prescriptions issued since their listing on the Pharmaceutical Benefits Scheme in August 2000. Most of this use appears to be in addition to prescribing of the older NSAIDs rather than as a replacement for them. The purpose of this study is to compare the safety of the new COX-2 inhibitors with that of the older NSAIDs. We are interested in how often they cause renal failure and heart failure. The investigators will use well-established research methods to estimate the risk of heart failure and kidney failure with these drugs in the Australian community. Data from the study will form the basis of clinical practice guidelines for the safe use of these drugs in Australia.Read moreRead less
Self-limiting Anti-inflammatory Actions Of Glucocorticoids In Asthma
Funder
National Health and Medical Research Council
Funding Amount
$377,036.00
Summary
Asthma is a disease characterised by excessive narrowing of the airway tubes resulting in difficulty exhaling air from the lungs. Symptoms of asthma include coughing, wheezing, shortness of breath and difficulty in breathing. Asthma affects almost 1 in 5 Australians and is especially prevelant in children. One in every three Australians will suffer from symptoms of asthma at some time in their life and despite current therapy, asthma is responsible for the deaths of more than 700 Australians eve ....Asthma is a disease characterised by excessive narrowing of the airway tubes resulting in difficulty exhaling air from the lungs. Symptoms of asthma include coughing, wheezing, shortness of breath and difficulty in breathing. Asthma affects almost 1 in 5 Australians and is especially prevelant in children. One in every three Australians will suffer from symptoms of asthma at some time in their life and despite current therapy, asthma is responsible for the deaths of more than 700 Australians every year. Airway tubes of asthmatics have more and larger contractile muscle cells lining the tubes. This increase in muscle mass results from chemicals that are released from white blood cells that migrate into the airway tubes during and after asthma attacks. This thickening slows airflow through the airway tubes because the muscle mass bulges into the holes of the tubes and when the muscle shortens the total diameter of the tubes decrease. We have recently shown that steroids used by asthmatics to treat the white blood cell contribution to the disease can reduce the growth of airway muscle. However, when the muscle has been pretreated with factors that are present in the inflamed airway, the anti-growth effects of steroids are prevented. This effect of the steroids is due to reduced production of a substance called prostaglandin E2 which can also reduce the growth of muscle. Thus, whilst steroids may help in treating some of the symptoms of asthma, they may be suboptimal in the treatment of muscle thickening and other aspects of the disease which involve cell division and multiplication. Our specific question in the next phase of this research is whether steroid inhibition of the release of prostaglandins compromises the useful actions of steroids on the growth of the airway tubes. The findings of this proposed study will provide new information on the role of steroids in asthma and may lead to better therapeutic strategies for the treatment of severe asthma.Read moreRead less