Iron and atherosclerosis: inhibition by the iron chelator deferiprone (L1)

Iron and atherosclerosis: Lessons learned from rabbits relevant to human disease

The role of iron in promoting atherosclerosis, and hence the cardiovascular, neurodegenerative and other diseases that result from atherosclerosis, has been fiercely controversial. Many studies have been carried out on various rodent models of atherosclerosis, especially on apoE-knockout (apoE-/-) mice, which develop atherosclerosis more readily than normal mice. These apoE-/- mouse studies generally support a role for iron in atherosclerosis development, although there are conflicting results. The purpose of the current article is to describe studies on another animal model that is not genetically manipulated; New Zealand White (NZW) rabbits fed a high-cholesterol diet. This may be a better model than the apoE-/- mice for human atherosclerosis, although it has been given much less attention. Studies on NZW rabbits support the view that iron promotes atherosclerosis, although some uncertainties remain, which need to be resolved by further experimentation.

The Vital Role Played by Deferiprone in the Transition of Thalassaemia from a Fatal to a Chronic Disease and Challenges in Its Repurposing for Use in Non-Iron-Loaded Diseases

The iron chelating orphan drug deferiprone (L1), discovered over 40 years ago, has been used daily by patients across the world at high doses (75-100 mg/kg) for more than 30 years with no serious toxicity. The level of safety and the simple, inexpensive synthesis are some of the many unique properties of L1, which played a major role in the contribution of the drug in the transition of thalassaemia from a fatal to a chronic disease. Other unique and valuable clinical properties of L1 in relation to pharmacology and metabolism include: oral effectiveness, which improved compliance compared to the prototype therapy with subcutaneous deferoxamine; highly effective iron removal from all iron-loaded organs, particularly the heart, which is the major target organ of iron toxicity and the cause of mortality in thalassaemic patients; an ability to achieve negative iron balance, completely remove all excess iron, and maintain normal iron stores in thalassaemic patients; rapid absorption from the stomach and rapid clearance from the body, allowing a greater frequency of repeated administration and overall increased efficacy of iron excretion, which is dependent on the dose used and also the concentration achieved at the site of drug action; and its ability to cross the blood-brain barrier and treat malignant, neurological, and microbial diseases affecting the brain. Some differential pharmacological activity by L1 among patients has been generally shown in relation to the absorption, distribution, metabolism, elimination, and toxicity (ADMET) of the drug. Unique properties exhibited by L1 in comparison to other drugs include specific protein interactions and antioxidant effects, such as iron removal from transferrin and lactoferrin; inhibition of iron and copper catalytic production of free radicals, ferroptosis, and cuproptosis; and inhibition of iron-containing proteins associated with different pathological conditions. The unique properties of L1 have attracted the interest of many investigators for drug repurposing and use in many pathological conditions, including cancer, neurodegenerative conditions, microbial conditions, renal conditions, free radical pathology, metal intoxication in relation to Fe, Cu, Al, Zn, Ga, In, U, and Pu, and other diseases. Similarly, the properties of L1 increase the prospects of its wider use in optimizing therapeutic efforts in many other fields of medicine, including synergies with other drugs.

Deferiprone: A Forty-Year-Old Multi-Targeting Drug with Possible Activity against COVID-19 and Diseases of Similar Symptomatology

The need for preparing new strategies for the design of emergency drug therapies against COVID-19 and similar diseases in the future is rather urgent, considering the high rate of morbidity and especially mortality associated with COVID-19, which so far has exceeded 18 million lives. Such strategies could be conceived by targeting the causes and also the serious toxic side effects of the diseases, as well as associated biochemical and physiological pathways. Deferiprone (L1) is an EMA- and FDA-approved drug used worldwide for the treatment of iron overload and also other conditions where there are no effective treatments. The multi-potent effects and high safety record of L1 in iron loaded and non-iron loaded categories of patients suggests that L1 could be developed as a “magic bullet” drug against COVID-19 and diseases of similar symptomatology. The mode of action of L1 includes antiviral, antimicrobial, antioxidant, anti-hypoxic and anti-ferroptotic effects, iron buffering interactions with transferrin, iron mobilizing effects from ferritin, macrophages and other cells involved in the immune response and hyperinflammation, as well as many other therapeutic interventions. Similarly, several pharmacological and other characteristics of L1, including extensive tissue distribution and low cost of production, increase the prospect of worldwide availability, as well as many other therapeutic approach strategies involving drug combinations, adjuvant therapies and disease prevention.

The Emerging Role of Ferroptosis in Cardiovascular Diseases

Ferroptosis is one type of programmed cell death discovered in recent years, which is characterized by iron-dependent lipid peroxidation and participating in iron, lipid and antioxidant metabolism. Ferroptosis is different from the traditional cell death types such as apoptosis, necroptosis and autophagy in morphology, biochemistry and genetics. Cardiovascular diseases are considered as an important cause of death from non-communicable diseases in the global population and poses a serious threat to human health. Apoptosis has long been thought to be the major type of cardiomyocyte death, but now ferroptosis has been shown to play a major role in cardiovascular diseases as well. This review will discuss related issues such as the mechanisms of ferroptosis and its effects on the occurrence and development of cardiovascular diseases, aiming to provide a novel target for the prevention and treatment of cardiovascular diseases.

The Fungal Iron Chelator Desferricoprogen Inhibits Atherosclerotic Plaque Formation

Hemoglobin, heme and iron are implicated in the progression of atherosclerosis. Therefore, we investigated whether the hydrophobic fungal iron chelator siderophore, desferricoprogen (DFC) inhibits atherosclerosis. DFC reduced atherosclerotic plaque formation in ApoE^-/- mice on an atherogenic diet. It lowered the plasma level of oxidized LDL (oxLDL) and inhibited lipid peroxidation in aortic roots. The elevated collagen/elastin content and enhanced expression of adhesion molecule VCAM-1 were decreased. DFC diminished oxidation of Low-density Lipoprotein (LDL) and plaque lipids catalyzed by heme or hemoglobin. Formation of foam cells, uptake of oxLDL by macrophages, upregulation of CD36 and increased expression of TNF-α were reduced by DFC in macrophages. TNF-triggered endothelial cell activation (vascular cell adhesion molecule-1 (VCAM-1), intercellular adhesion molecules (ICAMs), E-selectin) and increased adhesion of monocytes to endothelium were attenuated. The increased endothelial permeability and intracellular gap formation provoked by TNF-α was also prevented by DFC. DFC acted as a cytoprotectant in endothelial cells and macrophages challenged with a lethal dose of oxLDL and lowered the expression of stress-responsive heme oxygenase-1 as sublethal dose was employed. Saturation of desferrisiderophore with iron led to the loss of the beneficial effects. We demonstrated that DFC accumulated within the atheromas of the aorta in ApoE^-/- mice. DFC represents a novel therapeutic approach to control the progression of atherosclerosis.

DIBc, a nanochelating-based nano metal-organic framework, shows anti-diabetic effects in high-fat diet and streptozotocin-induced diabetic rats

Aims

Despite daily increase in diabetic patients in the world, currently approved medications for this disease, at best, only reduce its progression speed. Using novel technologies is a solution for synthetizing more efficient medicines. In the present study, we evaluated anti-diabetic effects of DIBc, a nano metal–organic framework, which is synthetized based on nanochelating technology.

Methods

High-fat diet and streptozotocin-induced diabetic rats were treated by DIBc or metformin for 6 weeks.

Results

DIBc decreased plasma glucose, triglyceride, cholesterol, high-density lipoprotein, and low-density lipoprotein compared with diabetic and metformin groups. In DIBc-treated rats, significant homeostasis model assessment of insulin resistance index, malondialdehyde, and tumor necrosis factor-α decrease was observed. H&E staining showed increased islet number and area in DIBc-treated rats compared with diabetic controls.

Conclusion

The results showed anti-diabetic effects of nanochelating-based framework. So DIBc, as a nano structure, has the capacity to be evaluated in future studies as a novel anti-diabetic agent.

Long-term donors versus non-donor men: Iron metabolism and the atherosclerotic process

BACKGROUND AND AIMS

The increased iron level and the labile iron pool (LIP) in circulating monocytes are connected to a higher frequency of cardiovascular events.

METHODS

The study investigates the relationship between LIP in circulating monocytes and markers of iron metabolism and atherosclerosis (inflammation, oxidative stress, endothelial dysfunction and arterial elasticity) in long-term blood donors and non-donor volunteers.

RESULTS

We found that donors had significantly higher LIP values than the control group (1.89 ± 0.47 μM vs. 1.50 ± 0.41 μM, p = 0.007). Despite the observed tendency for the donor group to have higher blood pressure, cholesterol, glucose and HOMAR-IR (homeostasis model assessment of insulin resistance), the groups did not differ in inflammatory markers, markers of endothelial dysfunction and markers of impaired arterial elasticity. The donor group had significant changes in iron metabolism (higher serum Fe, ceruloplasmin, and TfR/Ft ratio (transferrin receptor/ferritin ratio) and lower hepcidin, ferritin, and CD163), indicating depletion of body iron stores and activation of iron turnover.

CONCLUSIONS

LIP seems to be a good marker of iron turnover activity in these individuals despite the lack of a decrease in the hemoglobin concentration. We did not find a significant correlation between LIP levels and atherosclerosis progression in the two groups. However, further studies are needed to assess long-term donorship as a protective factor against atherosclerosis.

Deferiprone inhibits iron overload-induced tissue factor bearing endothelial microparticle generation by inhibition oxidative stress induced mitochondrial injury, and apoptosis

Iron overload-induced cardiovascular toxicity is one of the most common causes of morbidity and mortality in beta-thalassemia major patients. We have previously shown that iron overload-induced systemic arterial changes characterized by endothelial dysfunction are associated with increased endothelial microparticle (EMP) release. In this study, we further demonstrate how EMP release is associated with iron-induced mitochondrial injury and apoptosis of endothelial cells. Iron increased the production of reactive oxygen species (ROS) and calcium influx into mitochondria [Ca²⁺]_m. Iron also disturbed mitochondrial respiration function and eventually led to loss of mitochondrial membrane potential (ΔΨ_m). A significant increase in apoptotic cells and EMPs were found under iron treatment. EMPs contained tissue factor (TF), which has potential clinical impact on thromboembolic phenomenon. Then, we investigated the salvaging effect of deferiprone (L1) on endothelial cell damage and EMP release. We found that L1 could inhibit iron-induced ROS generation, and decrease mitochondrial damage with the resultant effect of less endothelial cell apoptosis and EMP release. L1 could protect endothelial cells from iron-induced toxic effects and minimize EMP release, which could be potentially helpful in a subgroup of thalassemia patients who have increased thromboembolic complications.

The role of iron in the pathogenesis of atherosclerosis

Ferritin and increased iron stores first appeared on the list of cardiovascular risk factors more than 30 years ago and their causal role in the pathogenesis of atherosclerosis has been heavily discussed since the early 1990s. It seems that besides traditional factors such as hyperlipoproteinemia, hypertension, diabetes mellitus, obesity, physical inactivity, smoking and family history, high iron stores represent an additional parameter that could modify individual cardiovascular risk. The role of iron in the pathogenesis of atherosclerosis was originally primarily associated with its ability to catalyze the formation of highly reactive free oxygen radicals and the oxidation of atherogenic lipoproteins. Later, it became clear that the mechanism is more complex. Atherosclerosis is a chronic fibroproliferative inflammatory process and iron, through increased oxidation stress as well as directly, can control both native and adaptive immune responses. Within the arterial wall, iron affects all of the cell types that participate in the atherosclerotic process (monocytes/macrophages, endothelial cells, vascular smooth muscle cells and platelets). Most intracellular iron is bound in ferritin, whereas redox-active iron forms labile iron pool. Pro-inflammatory and anti-inflammatory macrophages within arterial plaque differ with regard to the amount of intracellular iron and most probably with regard to their labile iron pool. Yet, the relation between plasma ferritin and intracellular labile iron pool has not been fully clarified. Data from population studies document that the consumption of meat and lack of physical activity contribute to increased iron stores. Patients with hereditary hemochromatosis, despite extreme iron storage, do not show increased manifestation of atherosclerosis probably due to the low expression of hepcidin in macrophages.

Transferrin Saturation: A Body Iron Biomarker

Iron is an essential element for several metabolic pathways and physiological processes. The maintenance of iron homeostasis within the human body requires a dynamic and highly sophisticated interplay of several proteins, as states of iron deficiency or excess are both potentially deleterious to health. Among these is plasma transferrin, which is central to iron metabolism not only through iron transport between body tissues in a soluble nontoxic form but also through its protective scavenger role in sequestering free toxic iron. The transferrin saturation (TSAT), an index that takes into account both plasma iron and its main transport protein, is considered an important biochemical marker of body iron status. Its increasing use in many health systems is due to the increased availability of measurement methods, such as calorimetry, turbidimetry, nephelometry, and immunochemistry to estimate its value. However, despite its frequent use in clinical practice to detect states of iron deficiency or iron overload, careful attention should be paid to the inherent limitations of the test especially in certain settings such as inflammation in order to avoid misinterpretation and erroneous conclusions. Beyond its usual clinical use, an emerging body of evidence has linked TSAT levels to major clinical outcomes such as cardiovascular mortality. This has the potential to extend the utility of TSAT index to risk stratification and prognostication. However, most of the current evidence is mainly driven by observational studies where the risk of residual confounding cannot be fully eliminated. Indeed, future efforts are required to fully explore this capability in well-designed clinical trials or prospective large-scale cohorts.

Effects of Environmental Pollutants on Cellular Iron Homeostasis and Ultimate Links to Human Disease

Chronic disease has increased in the past several decades, and environmental pollutants have been implicated. The magnitude and variety of diseases may indicate the malfunctioning of some basic mechanisms underlying human health. Environmental pollutants demonstrate a capability to complex iron through electronegative functional groups containing oxygen, nitrogen, or sulfur. Cellular exposure to the chemical or its metabolite may cause a loss of requisite functional iron from intracellular sites. The cell is compelled to acquire further iron critical to its survival by activation of iron-responsive proteins and increasing iron import. Iron homeostasis in the exposed cells is altered due to a new equilibrium being established between iron-requiring cells and the inappropriate chelator (the pollutant or its catabolite). Following exposure to environmental pollutants, the perturbation of functional iron homeostasis may be the mechanism leading to adverse biological effects. Understanding the mechanism may lead to intervention methods for this major public health concern.

Serum hepcidin predicts uremic accelerated atherosclerosis in chronic hemodialysis patients with diabetic nephropathy

BACKGROUND

Hepcidin, as a regulator of body iron stores, has been recently discovered to play a critical role in the pathogenesis of anemia of chronic disease. Atherosclerotic cardiovascular disease is the most common complication and the leading cause of death in chronic hemodialysis (CHD) patients. In the current study, we aimed to explore the relationship between serum hepcidin and uremic accelerated atherosclerosis (UAAS) in CHD patients with diabetic nephropathy (CHD/DN).

METHODS

A total of 78 CHD/DN and 86 chronic hemodialyzed nondiabetic patients with chronic glomerulonephritis (CHD/non-DN) were recruited in this study. The level of serum hepcidin-25 was specifically measured by liquid chromatography-tandem mass spectrometry. Serum levels of interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) were measured by enzyme-linked immunosorbent assay.

RESULTS

High serum level of hepcidin-25 was seen in CHD patients. Serum hepcidin-25 in CHD/DN was significantly higher than that in CHD/non-DN patients. Serum hepcidin-25 was positively correlated with ferritin, high-sensitivity C-reactive protein (hs-CRP), TNF-α, and IL-6 in CHD/DN patients. CHD/DN patients exhibited higher common carotid artery intima media thickness (CCA-IMT), hs-CRP, and hepcidin-25 levels than that in CHD/non-DN patients. Moreover, in CHD/DN patients, CCA-IMT was positively correlated with serum hepcidin, hs-CRP, and low-density lipoprotein-cholesterol. On multiple regression analysis, serum hepcidin and hs-CRP level exhibited independent association with IMT in CHD/DN patients.

CONCLUSIONS

These findings suggest possible linkage between iron metabolism and hepcidin modulation abnormalities that may contribute to the development of UAAS in CHD/DN patients.

Deferasirox-induced cytogenetic responses

Deferasirox (commercially formulated as Exjade(®)) is one of the effective iron chelators used in treatment of iron overload diseases. In this study the effect of this substance for chromosome aberration, sister chromatid exchange and mitotic index was studied by in vitro (by using human peripheral lymphocytes) and in vivo (by using rat) analysis. Deferasirox increased the sister chromatid exchange frequency in all tested concentrations and periods in vitro. Also, in the presence of metabolic activator, the substance led to a statistically significant increase in the sister chromatid exchange frequencies only at high concentration. While in in vitro analysis the substance significantly increased abnormal cell percentages in all concentrations, in in vivo study the substance increased chromosome aberrations only in two concentrations at 12h treatment. In the cultured lymphocytes, deferasirox showed cytotoxicity by significantly reducing proliferation index and mitotic index values. While in the presence of metabolic activation it did not affect the proliferation index frequency, it had a stimulant effect on the mitotic index frequency. Deferasirox reduced significantly the mitotic index value in the bone marrow cells especially in high concentration and short treatment period (12h).

Serum ferritin is an important inflammatory disease marker, as it is mainly a leakage product from damaged cells

"Serum ferritin" presents a paradox, as the iron storage protein ferritin is not synthesised in serum yet is to be found there. Serum ferritin is also a well known inflammatory marker, but it is unclear whether serum ferritin reflects or causes inflammation, or whether it is involved in an inflammatory cycle. We argue here that serum ferritin arises from damaged cells, and is thus a marker of cellular damage. The protein in serum ferritin is considered benign, but it has lost (i.e. dumped) most of its normal complement of iron which when unliganded is highly toxic. The facts that serum ferritin levels can correlate with both disease and with body iron stores are thus expected on simple chemical kinetic grounds. Serum ferritin levels also correlate with other phenotypic readouts such as erythrocyte morphology. Overall, this systems approach serves to explain a number of apparent paradoxes of serum ferritin, including (i) why it correlates with biomarkers of cell damage, (ii) why it correlates with biomarkers of hydroxyl radical formation (and oxidative stress) and (iii) therefore why it correlates with the presence and/or severity of numerous diseases. This leads to suggestions for how one might exploit the corollaries of the recognition that serum ferritin levels mainly represent a consequence of cell stress and damage.

Iron-induced fibrin in cardiovascular disease

Accumulating evidence within the last two decades indicates the association between cardiovascular disease (CVD) and chronic inflammatory state. Under normal conditions fibrin clots are gradually degraded by the fibrinolytic enzyme system, so no permanent insoluble deposits remain in the circulation. However, fibrinolytic therapy in coronary and cerebral thrombosis is ineffective unless it is installed within 3-5 hours of the onset. We have shown that trivalent iron (FeIII) initiates a hydroxyl radical-catalyzed conversion of fibrinogen into a fibrin-like polymer (parafibrin) that is remarkably resistant to the proteolytic dissolution and thus promotes its intravascular deposition. Here we suggest that the persistent presence of proteolysis-resistant fibrin clots causes chronic inflammation. We study the effects of certain amphiphilic substances on the iron- and thrombin-induced fibrinogen polymerization visualized using scanning electron microscopy. We argue that the culprit is an excessive accumulation of free iron in blood, known to be associated with CVD. The only way to prevent iron overload is by supplementation with iron chelating agents. However, administration of free radical scavengers as effective protection against persistent presence of fibrin-like deposits should also be investigated to contribute to the prevention of cardiovascular and other degenerative diseases.

SPION primes THP1 derived M2 macrophages towards M1-like macrophages

Potentially, cellular iron regulates functional plasticity in macrophages yet; interaction of functionally polarized macrophages with iron-oxide nanoparticles has never been studied. We found that monocyte differentiation alters cellular ferritin and cathepsin L levels and induces functional polarization in macrophages. Iron in super paramagnetic iron-oxide nanoparticle (SPION) induces a phenotypic shift in THP1 derived M2 macrophages towards a high CD86+ and high TNF α+ macrophage subtype. This phenotypic shift was accompanied by up-regulated intracellular levels of ferritin and cathepsin L in M2 macrophages, which is a characteristic hallmark of M1 macrophages. Atherogenic oxysterols reduce phagocytic activity in macrophage subtypes, and thus these cells may escape detection by iron-oxide nanoparticles (INPs) in-vivo.

Iron, human growth, and the global epidemic of obesity

Iron is an essential nutrient utilized in almost every aspect of cell function and its availability has previously limited life. Those same properties which allow iron to function as a catalyst in the reactions of life also present a threat via generation of oxygen-based free radicals. Accordingly; life exists at the interface of iron-deficiency and iron-sufficiency. We propose that: (1) human life is no longer positioned at the limits of iron availability following several decades of fortification and supplementation and there is now an overabundance of the metal among individuals of many societies; (2) this increased iron availability exerts a positive effect on growth by targeting molecules critical in regulating the progression of the cell cycle; there is increased growth in humans provided greater amounts of this metal; and indices of obesity can positively correlate with body stores of iron; and (3) diseases of obesity reflect this over-abundance of iron. Testing potential associations between iron availability and both obesity and obesity-related diseases in populations will be difficult since fortification and supplementation is so extensively practiced.

Hydroxyl radical-modified fibrinogen as a marker of thrombosis: the role of iron

Excessive free iron in blood and in organ tissues (so called iron overload) has been observed in degenerative diseases such as atherosclerosis, cancer, neurological, and certain autoimmune diseases, in which fibrin-like deposits are also found. Although most of the body iron is bound to hemoglobin and myoglobin in a divalent ferrous form, a certain amount of iron exists in blood as a trivalent (ferric) ion. This particular chemical state of iron has been shown to be toxic to the human body when not controlled by endogenous and/or dietary chelating agents. Experiments described in this paper show for the first time that ferric ions (Fe(3+)) can generate hydroxyl radicals without participation of any redox agent, thus making it a special case of the Fenton reaction. Ferric chloride was also demonstrated to induce aggregation of purified fibrinogen at the same molar concentrations that were used for the generation of hydroxyl radicals. Iron-aggregated fibrinogen, by contrast to native molecule, could not be dissociated into polypeptide subunit chains as shown in a polyacrylamide gel electrophoresis. The mechanism of this phenomenon is very likely based on hydroxyl radical-induced modification of fibrinogen tertiary structure with the formation of insoluble aggregates resistant to enzymatic and chemical degradations. Soluble modified fibrinogen species can be determined in blood of thrombotic patients by the reaction with protamine sulfate and/or by scanning electron microscopy. In view of these findings, it is postulated that iron-induced alterations in fibrinogen structure is involved in pathogenesis of certain degenerative diseases associated with iron overload and persistent thrombosis. It is concluded that the detection of hydroxyl radical-modified fibrinogen may be utilized as a marker of a thrombotic condition in human subjects.

Deferiprone reduces amyloid-β and tau phosphorylation levels but not reactive oxygen species generation in hippocampus of rabbits fed a cholesterol-enriched diet

Accumulation of amyloid-β (Aβ) peptide and the hyperphosphorylation of tau protein are major hallmarks of Alzheimer's disease (AD). The causes of AD are not well known but a number of environmental and dietary factors are suggested to increase the risk of developing AD. Additionally, altered metabolism of iron may have a role in the pathogenesis of AD. We have previously demonstrated that cholesterol-enriched diet causes AD-like pathology with iron deposition in rabbit brain. However, the extent to which chelation of iron protects against this pathology has not been determined. In this study, we administered the iron chelator deferiprone in drinking water to rabbits fed with a 2% cholesterol diet for 12 weeks. We found that deferiprone (both at 10 and 50 mg/kg/day) significantly decreased levels of Aβ40 and Aβ42 as well as BACE1, the enzyme that initiates cleavage of amyloid-β protein precursor to yield Aβ. Deferiprone also reduced the cholesterol diet-induced increase in phosphorylation of tau but failed to reduce reactive oxygen species generation. While deferiprone treatment was not associated with any change in brain iron levels, it was associated with a significant reduction in plasma iron and cholesterol levels. These results demonstrate that deferiprone confers important protection against hypercholesterolemia-induced AD pathology but the mechanism(s) may involve reduction in plasma iron and cholesterol levels rather than chelation of brain iron. We propose that adding an antioxidant therapy to deferiprone may be necessary to fully protect against cholesterol-enriched diet-induced AD-like pathology.

Hepcidin as well as TNF-α are significant predictors of arterial stiffness in patients on maintenance hemodialysis

BACKGROUND

Dysregulated iron metabolism has been suspected to be linked to anemia of chronic disease and to cardiovascular disease (CVD). For the purpose of clarifying the factors affecting arterial stiffness, we evaluated the relationship between iron metabolism, brachial-ankle (ba)-pulse wave velocity (PWV) and several risk factors for CVD in maintenance hemodialysis (MHD) patients.

METHODS

A total of 168 MHD patients were recruited, and the levels of iron parameters, hepcidin, CVD risk factors and ba-PWV were evaluated. The level of serum hepcidin-25 was specifically measured by liquid chromatography-tandem mass spectrometry.

RESULTS

Serum levels of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6) and hepcidin were higher in MHD patients, which was consistent with results from our previous study. ba-PWV significantly correlated with age (P < 0.01, R = 0.34), total cholesterol (T-CHO; P = 0.02, R = 0.21), TNF-α (P < 0.01, R = 0.24) and hepcidin (P < 0.01, R = 0.25) but not with other iron parameters and CVD risk factors. According to multiple regression analysis, age (β = 0.30), T-CHO (β = 0.24) TNF-α (β = 0.19) and hepcidin (β = 0.23) were selected as the significant predictors of ba-PWV in MHD patients.

CONCLUSION

Serum levels of both hepcidin and TNF-α are independently associated with arterial stiffness in MHD patients, suggesting that microinflammation and iron metabolism might affect the integrity of arterial walls.

Towards a unifying, systems biology understanding of large-scale cellular death and destruction caused by poorly liganded iron: Parkinson's, Huntington's, Alzheimer's, prions, bactericides, chemical toxicology and others as examples

Exposure to a variety of toxins and/or infectious agents leads to disease, degeneration and death, often characterised by circumstances in which cells or tissues do not merely die and cease to function but may be more or less entirely obliterated. It is then legitimate to ask the question as to whether, despite the many kinds of agent involved, there may be at least some unifying mechanisms of such cell death and destruction. I summarise the evidence that in a great many cases, one underlying mechanism, providing major stresses of this type, entails continuing and autocatalytic production (based on positive feedback mechanisms) of hydroxyl radicals via Fenton chemistry involving poorly liganded iron, leading to cell death via apoptosis (probably including via pathways induced by changes in the NF-κB system). While every pathway is in some sense connected to every other one, I highlight the literature evidence suggesting that the degenerative effects of many diseases and toxicological insults converge on iron dysregulation. This highlights specifically the role of iron metabolism, and the detailed speciation of iron, in chemical and other toxicology, and has significant implications for the use of iron chelating substances (probably in partnership with appropriate anti-oxidants) as nutritional or therapeutic agents in inhibiting both the progression of these mainly degenerative diseases and the sequelae of both chronic and acute toxin exposure. The complexity of biochemical networks, especially those involving autocatalytic behaviour and positive feedbacks, means that multiple interventions (e.g. of iron chelators plus antioxidants) are likely to prove most effective. A variety of systems biology approaches, that I summarise, can predict both the mechanisms involved in these cell death pathways and the optimal sites of action for nutritional or pharmacological interventions.

Iron behaving badly: inappropriate iron chelation as a major contributor to the aetiology of vascular and other progressive inflammatory and degenerative diseases

BACKGROUND

The production of peroxide and superoxide is an inevitable consequence of aerobic metabolism, and while these particular 'reactive oxygen species' (ROSs) can exhibit a number of biological effects, they are not of themselves excessively reactive and thus they are not especially damaging at physiological concentrations. However, their reactions with poorly liganded iron species can lead to the catalytic production of the very reactive and dangerous hydroxyl radical, which is exceptionally damaging, and a major cause of chronic inflammation.

REVIEW

We review the considerable and wide-ranging evidence for the involvement of this combination of (su)peroxide and poorly liganded iron in a large number of physiological and indeed pathological processes and inflammatory disorders, especially those involving the progressive degradation of cellular and organismal performance. These diseases share a great many similarities and thus might be considered to have a common cause (i.e. iron-catalysed free radical and especially hydroxyl radical generation).The studies reviewed include those focused on a series of cardiovascular, metabolic and neurological diseases, where iron can be found at the sites of plaques and lesions, as well as studies showing the significance of iron to aging and longevity. The effective chelation of iron by natural or synthetic ligands is thus of major physiological (and potentially therapeutic) importance. As systems properties, we need to recognise that physiological observables have multiple molecular causes, and studying them in isolation leads to inconsistent patterns of apparent causality when it is the simultaneous combination of multiple factors that is responsible.This explains, for instance, the decidedly mixed effects of antioxidants that have been observed, since in some circumstances (especially the presence of poorly liganded iron) molecules that are nominally antioxidants can actually act as pro-oxidants. The reduction of redox stress thus requires suitable levels of both antioxidants and effective iron chelators. Some polyphenolic antioxidants may serve both roles.Understanding the exact speciation and liganding of iron in all its states is thus crucial to separating its various pro- and anti-inflammatory activities. Redox stress, innate immunity and pro- (and some anti-)inflammatory cytokines are linked in particular via signalling pathways involving NF-kappaB and p38, with the oxidative roles of iron here seemingly involved upstream of the IkappaB kinase (IKK) reaction. In a number of cases it is possible to identify mechanisms by which ROSs and poorly liganded iron act synergistically and autocatalytically, leading to 'runaway' reactions that are hard to control unless one tackles multiple sites of action simultaneously. Some molecules such as statins and erythropoietin, not traditionally associated with anti-inflammatory activity, do indeed have 'pleiotropic' anti-inflammatory effects that may be of benefit here.

CONCLUSION

Overall we argue, by synthesising a widely dispersed literature, that the role of poorly liganded iron has been rather underappreciated in the past, and that in combination with peroxide and superoxide its activity underpins the behaviour of a great many physiological processes that degrade over time. Understanding these requires an integrative, systems-level approach that may lead to novel therapeutic targets.

Diabetes and the heart: could the diabetic myocardium be protected by preconditioning?

Both type 1 and type 2 diabetes (insulin-dependent and non-insulin dependent diabetes, respectively) are associated with increased risk for microvascular and macrovascular complications including retinopathy, neuropathy, nephropathy and atherosclerosis. Type 2 diabetes markedly increases the risk for cardiovascular morbidity and mortality, which has major public health implications. In this review, molecular mechanisms pertaining to diabetes-induced heart pathology are addressed.

Macrophage iron, hepcidin, and atherosclerotic plaque stability

Hepcidin has emerged as the key hormone in the regulation of iron balance and recycling. Elevated levels increase iron in macrophages and inhibit gastrointestinal iron uptake. The physiology of hepcidin suggests an additional mechanism by which iron depletion could protect against atherosclerotic lesion progression. Without hepcidin, macrophages retain less iron. Very low hepcidin levels occur in iron deficiency anemia and also in homozygous hemochromatosis. There is defective retention of iron in macrophages in hemochromatosis and also evidently no increase in atherosclerosis in this disorder. In normal subjects with intact hepcidin responses, atherosclerotic plaque has been reported to have roughly an order of magnitude higher iron concentration than that in healthy arterial wall. Hepcidin may promote plaque destabilization by preventing iron mobilization from macrophages within atherosclerotic lesions; the absence of this mobilization may result in increased cellular iron loads, lipid peroxidation, and progression to foam cells. Marked downregulation of hepcidin (e.g., by induction of iron deficiency anemia) could accelerate iron loss from intralesional macrophages. It is proposed that the minimally proatherogenic level of hepcidin is near the low levels associated with iron deficiency anemia or homozygous hemochromatosis. Induced iron deficiency anemia intensely mobilizes macrophage iron throughout the body to support erythropoiesis. Macrophage iron in the interior of atherosclerotic plaques is not exempt from this process. Decreases in both intralesional iron and lesion size by systemic iron reduction have been shown in animal studies. It remains to be confirmed in humans that a period of systemic iron depletion can decrease lesion size and increase lesion stability as demonstrated in animal studies. The proposed effects of hepcidin and iron in plaque progression offer an explanation of the paradox of no increase in atherosclerosis in patients with hemochromatosis despite a key role of iron in atherogenesis in normal subjects.

Iron enhances endothelial cell activation in response to Cytomegalovirus or Chlamydia pneumoniae infection

BACKGROUND

Chronic inflammation has been implemented in the pathogenesis of inflammatory diseases like atherosclerosis. Several pathogens like Chlamydia pneumoniae (Cp) and cytomegalovirus (CMV) result in inflammation and thereby are potentially artherogenic. Those infections could trigger endothelial activation, the starting point of the atherogenic inflammatory cascade. Considering the role of iron in a wide range of infection processes, the presence of iron may complicate infection-mediated endothelial activation.

MATERIALS AND METHODS

Endothelial intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1) and endothelial selectin (E-selectin) expression were measured using flow cytometry, as an indication of endothelial activation. Cytotoxicity was monitored using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Immunostaining was applied to measure Cp and CMV infectivity to endothelial cells.

RESULTS

An increased number of infected endothelial cells in a monolayer population leads to a raised expression of adhesion molecules of the whole cell population, suggesting paracrine interactions. Iron additively up-regulated Cp-induced VCAM-1 expression, whereas synergistically potentiated Cp-induced ICAM-1 expression. Together with CMV, iron also enhanced ICAM-1 and VCAM-1 expression. These iron effects were observed without modulation of the initial infectivity of both microorganisms. Moreover, the effects of iron could be reversed by intracellular iron chelation or radical scavenging, conforming modulating effects of iron on endothelial activation after infections.

CONCLUSIONS

Endothelial response towards chronic infections depends on intracellular iron levels. Iron status in populations positive for Cp or CMV infections should be considered as a potential determinant for the development of atherosclerosis.

Therapeutic potential of iron chelators in diseases associated with iron mismanagement

A considerable array of diseases are now recognized to be associated with misplacement of iron. Excessive deposits of the metal in sensitive tissue sites can result in formation of destructive hydroxyl radicals as well as in stimulation of growth of neoplastic and microbial cell invaders. To counteract potential iron damage, hosts employ the iron chelators, transferrin and lactoferrin. These proteins have been recently developed into pharmaceutical products. Additionally, a variety of low molecular mass iron chelators are being used/tested to treat whole body iron loading, and specific diseases for which the metal is a known or suspected risk factor.

Iron chelators may help prevent photoaging

For years, cosmetic ingredients for anti-aging treatments have attracted consumers. Skin aging is accelerated by reactive oxygen species (ROS), generated by exposure to solar ultraviolet radiation (UVR), in a process known as photoaging. Because cutaneous iron catalyses ROS generation, it is thought to play a key role in photoaging. Iron is essential to almost all forms of life. However, excess iron is potentially toxic as its catalytic activity induces the generation of ROS. Iron-catalysed ROS generation is involved in numerous pathological conditions, including cutaneous damage. When skin is directly exposed to UVR, cutaneous intracellular catalytic iron levels increase because of the release of iron from iron-binding proteins such as ferritin. Consequently, the subsequent ROS generation may overwhelm cutaneous defense systems such as the cellular iron sequestration and ROS scavenging capacity. The harmful role of excess cutaneous iron implies that there may be a potential for topical iron chelator treatments. We now consider cutaneous photodamage skin photoaging as the result of iron-catalysed ROS generation and discuss preventative strategies based on iron chelators.

Zinc supplementation decreases the development of atherosclerosis in rabbits

Developing atherosclerotic plaques in cholesterol-fed rabbits are enriched in iron but depleted in zinc. In order to examine further the role of zinc, New Zealand White rabbits were fed a high-cholesterol 1% (w/w) diet with zinc (1 g/kg) supplementation for 8 weeks. After the 8-week period, the average atherosclerotic lesion cross-sectional areas in the aortas of the animals fed with the zinc supplement were significantly decreased (1.0 mm2) compared with lesion areas of the animals fed only on the high-cholesterol diet (3.1 mm2). Using nuclear microscopy, a technique for mapping and measuring trace elements in tissue sections, lesion zinc levels (24 ppm) were observed to be unchanged in the zinc-fed rabbits compared to controls. However, average lesion Fe levels in the zinc-fed group were measured at 32 ppm, whereas in the control group the average Fe levels were significantly higher at 43 ppm (P = 0.03). Our data support the concept that zinc may have an antiatherogenic effect by decreasing iron levels in the lesion, possibly leading to inhibition of iron-catalyzed free radical reactions.

Iron Chelation Suppresses Ferritin Upregulation and Attenuates Vascular Dysfunction in the Aorta of Angiotensin II–Infused Rats

Objective— We have investigated whether long-term administration of angiotensin (Ang) II causes ferritin induction and iron accumulation in the rat aorta, and their possible relation to regulatory effects on gene expression and vascular function in Ang II-infused animals.

Methods and Results— Sprague-Dawley rats were given Ang II for 7 days via subcutaneously implanted osmotic minipumps. Ang II infusion caused a >20-fold increase in ferritin protein expression over control values. Immunohistochemistry showed that Ang II infusion markedly increased the ferritin expression in the aortic endothelial and adventitial cells, with some of the latter being identified as monocytes/macrophages. Prussian blue staining showed that stainable iron was observed in the adventitial layer of aorta from Ang II-infused animals, but not in the endothelial layer. Chelation of iron suppressed aortic induction of ferritin and also the oxidative stress markers, heme oxygenase-1 and 4-hydroxynonenal-modified protein adducts. In addition, iron chelation attenuated Ang II-induced impairment of aortic relaxations in response to acetylcholine and sodium nitroprusside and suppressed upregulation of mRNA levels of monocyte chemoattractant protein-1. Iron chelation also partially attenuated the medial thickening and perivascular fibrosis induced by Ang II infusion for 4 weeks.

Conclusion— Ang II infusion caused ferritin induction and iron deposition in the aortas. These phenomena might have a role in the regulation of gene expression, impairment of vascular function, and arterial remodeling induced by Ang II, which are presumably mediated in part by enhancement of oxidative stress.

Ferritin in atherosclerosis

Iron, an essential element for many important cellular functions in all living organisms, can catalyze the formation of potentially toxic free radicals. Excessive iron is sequestered by ferritin in a nontoxic and readily available form in a cell. Ferritin is composed of 24 subunits of different proportions of two functionally distinct subunits: ferritin H and L. The former is involved in ferroxidase activity necessary for iron uptake and oxidation of ferrous iron, while the latter is involved in nucleation of the iron core. The expression of ferritin is under delicate control and is regulated at both the transcriptional and posttranscriptional levels by iron, cytokines and oxidative stress. Elevated ferritin levels are associated with an increased risk of atherosclerotic coronary artery disease (CAD), the leading cause of death and illness in developed countries. Serum ferritin levels are a good indicator of iron stores in the body. In fact, epidemiological studies have suggested that elevated serum ferritin levels are associated with an increased risk of CAD and myocardial infarction (MI), though inconsistent results were obtained in some other studies. Moreover, recent proteomics and molecular biology studies have shown that ferritin levels in arteries are increased in diseased tissues, which further supports the link of ferritin to CAD/MI. Future studies will determine whether increased ferritin levels can serve as a distinct biomarker for the incidence of CAD/MI and distinguish whether increased ferritin levels are a cause of CAD or a consequence of the disease process.

Potential risk for infection and atherosclerosis due to iron therapy

Iron is an essential nutrient, but carries potential risks. Iron therapy not only affects the functions of leukocytes, endothelial cells, and cytokine production, but also causes oxidative stress and can support bacterial growth. Intravenous iron therapy may result in nontransferrin-bound iron. This may act as a catalytic agent in the formation of hydroxyl radicals, and thus potentially contribute to cell damage and atherosclerosis. Potential long-term complications of intravenous iron therapy in end-stage renal disease patients include atherosclerosis and infection, particularly in patients with iron overload.

Labile plasma iron in iron overload: redox activity and susceptibility to chelation

Plasma non-transferrin-bound-iron (NTBI) is believed to be responsible for catalyzing the formation of reactive radicals in the circulation of iron overloaded subjects, resulting in accumulation of oxidation products. We assessed the redox active component of NTBI in the plasma of healthy and beta-thalassemic patients. The labile plasma iron (LPI) was determined with the fluorogenic dihydrorhodamine 123 by monitoring the generation of reactive radicals prompted by ascorbate but blocked by iron chelators. The assay was LPI specific since it was generated by physiologic concentrations of ascorbate, involved no sample manipulation, and was blocked by iron chelators that bind iron selectively. LPI, essentially absent from sera of healthy individuals, was present in those of beta-thalassemia patients at levels (1-16 microM) that correlated significantly with those of NTBI measured as mobilizer-dependent chelatable iron or desferrioxamine chelatable iron. Oral treatment of patients with deferiprone (L1) raised plasma NTBI due to iron mobilization but did not lead to LPI appearance, indicating that L1-chelated iron in plasma was not redox active. Moreover, oral L1 treatment eliminated LPI in patients. The approach enabled the assessment of LPI susceptibility to in vivo or in vitro chelation and the potential of LPI to cause tissue damage, as found in iron overload conditions.

Benefits and risks of deferiprone in iron overload in Thalassaemia and other conditions: comparison of epidemiological and therapeutic aspects with deferoxamine

Deferiprone is the only orally active iron-chelating drug to be used therapeutically in conditions of transfusional iron overload. It is an orphan drug designed and developed primarily by academic initiatives for the treatment of iron overload in thalassaemia, which is endemic in the Mediterranean, Middle East and South East Asia and is considered an orphan disease in the European Union and North America. Deferiprone has been used in several other iron or other metal imbalance conditions and has prospects of wider clinical applications. Deferiprone has high affinity for iron and interacts with almost all the iron pools at the molecular, cellular, tissue and organ levels. Doses of 50-120 mg/kg/day appear to be effective in bringing patients to negative iron balance. It increases urinary iron excretion, which mainly depends on the iron load of patients and the dose of the drug. It decreases serum ferritin levels and reduces the liver and heart iron content in the majority of chronically transfused iron loaded patients at doses >80 mg/kg/day. It is metabolised to a glucuronide conjugate and cleared through the urine in the metabolised and a non-metabolised form, usually of a 3 deferiprone: 1 iron complex, which gives the characteristic red colour urine. Peak serum levels of deferiprone are observed within 1 hour of its oral administration and clearance from blood is within 6 hours. There is variation among patients in iron excretion, the metabolism and pharmacokinetics of deferiprone. Deferiprone has been used in more than 7500 patients aged from 2-85 years in >50 countries, in some cases daily for >14 years. All the adverse effects of deferiprone are considered reversible, controllable and manageable. These include agranulocytosis with frequency of about 0.6%, neutropenia 6%, musculoskeletal and joint pains 15%, gastrointestinal complains 6% and zinc deficiency 1%. Discontinuation of the drug is recommended for patients developing agranulocytosis. Deferiprone is of similar therapeutic index to subcutaneous deferoxamine but is more effective in iron removal from the heart, which is the target organ of iron toxicity and mortality in iron-loaded thalassaemia patients. Deferiprone is much less expensive to produce than deferoxamine. Combination therapy of deferoxamine and deferiprone has been used in patients not complying with subcutaneous deferoxamine or experiencing toxicity or not excreting sufficient amounts of iron with use of either drug alone. New oral iron-chelating drugs are being developed, but even if successful these are likely to be more expensive than deferiprone and are not likely to become available in the next 5-8 years. About 25% of treated thalassaemia patients in Europe and more than 50% in India are using deferiprone. For most thalassaemia patients worldwide who are not at present receiving any form of chelation therapy the choice is between deferiprone and fatal iron toxicity.

Iron chelators for the treatment of iron overload disease: relationship between structure, redox activity, and toxicity

The success of the iron (Fe) chelator desferrioxamine (DFO) in the treatment of beta-thalassemia is limited by its lack of bioavailability. The design and characterization of synthetic alternatives to DFO has attracted much scientific interest and has led to the discovery of orally active chelators that can remove pathological Fe deposits. However, chelators that access intracellular Fe pools can be toxic by either inhibiting Fe-containing enzymes or promoting Fe-mediated free radical damage. Interestingly, toxicity does not necessarily correlate with Fe-binding affinity or with chelation efficacy, suggesting that other factors may promote the cytopathic effects of chelators. In this review, we discuss the interactions of chelators and their Fe complexes with biomolecules that can lead to toxicity and tissue damage.

Role of iron in atherosclerosis

The importance of iron in injury is derived from the ease with which iron is reversibly oxidized and reduced and thus able to participate in the generation of powerful oxidant species, such as hydroxyl radical, and in lipid peroxidation. There is compelling mechanistic evidence for the potential role of iron in atherosclerosis: the role of iron in oxidizing low-density lipoprotein (LDL), iron chelators prevent endothelial cell damage by oxidized LDL, the ability of iron to cause endothelial cell damage, and iron chelators prevent endothelial cell dysfunction and vascular smooth muscle proliferation. In addition to these effects, important in atherosclerosis, ample experimental evidence suggests a role of iron in myocardial reperfusion injury. Epidemiological data have provided conflicting results, with several studies reporting an association between iron stores and progression of carotid atherosclerosis or acute myocardial infarction, whereas others argue against such an association. However, the availability of catalytic iron and the susceptibility of an individual may be more important than overall iron body status. Studies that address these issues, as well as those designed to establish cause and effect, are needed before one can reach meaningful conclusions about the role of iron in atherosclerosis and the therapeutic implications for patients.

Slowed progression or elimination of atherosclerosis by low-frequency electrical impulses

BACKGROUND

In our previous investigations we showed that electrical impulses (EI) can prevent the development of atherosclerosis if they began simultaneously with high cholesterol diet (HCD) or in the early stages of atherosclerosis (after three weeks of HCD only). In this investigation we demonstrated the slow progression or elimination of atherosclerosis by low-frequency EI in case of moderate atherosclerosis (after eight weeks of HCD).

METHODS

Series I rabbits (control group) were fed HCD for eight weeks. Series II rabbits were fed HCD for eight weeks and were then switched to normal diet for eight weeks (no EI). Series III rabbits were fed HCD for eight weeks and then switched to a normal diet with simultaneous EI (applied near the abdominal aorta) for eight weeks (3 V, 30 single impulses per minute, 24 hours/day). After euthanization, the level of atherosclerosis, percentage of surface area involved in the atherosclerosis process, and an atherosclerosis score were calculated in the aortic arch, thoracic and abdominal aorta.

RESULTS

Statistically significant differences were seen in the level of atherosclerosis in the abdominal aorta between series III animals (0.4 +/- 0.2) and the other two groups: 1.5 +/- 0.4 in series I (HCD only), 1.2 +/- 0.3 in series II (HCD then normal diet). Gross examination of the surface also revealed statistically significant differences (p < 0.05) in the percentage of atherosclerosis between the control series I (30.1 +/- 4.1%) and series II (21.3 +/- 3.6%), compared with series III (5.5 +/- 5.4%). In addition, the atherosclerosis score was also significantly different: 45.8 +/- 3.9 in series I, 25.2 +/- 6.9 in series II, and 2.2 +/- 2.0 in series III (p < 0.05).

CONCLUSION

Our study showed that, when applied near the abdominal aorta, low-frequency electrical impulses decrease atherosclerotic deposition in the abdominal aorta.

The iron hypothesis of atherosclerosis and its clinical impact

The iron hypothesis as an alternative explanation for the gender difference in the incidence and mortality of atherosclerosis has provoked increased debates and public health concerns. In this review we summarize the historical and recent literature on the iron hypothesis and discuss several related clinical issues and their implications. Apart from misconstruction of study populations, lack of a good method to reflect the iron contents of tissues may be the major factor for causing inconsistent results from epidemiological studies. Published data from 11 countries clearly indicate that the mortality from cardiovascular diseases is correlated with liver iron. We propose that redox-active iron in tissue is the atherogenic portion of total iron stores. Recently developed magnetic resonance imaging techniques in combination with Fe chelators may allow future studies to examine this component of body iron in lesions and the whole body. Several clinical situations characterized by increased iron stores have been proposed as 'human models' suitable for further tests of the iron hypothesis. Patients with end-stage renal disease may be the most unique cohort, having significant increases in their iron stores, low-density lipoprotein (LDL) oxidation, and cardiovascular events. Other patient groups may be well suited for specific studies of different atherogenic events. With a better understanding of iron-driven oxidative damage, well controlled and effectively designed studies on these models will finally bring us to the truth of the iron hypothesis.

Insight into the mechanism of trypanosome lytic factor-1 killing of Trypanosoma brucei brucei

It has been known for almost a century that normal human serum can lyse the extracellular blood parasite Trypanosoma brucei brucei. This process is a result of a non-immune killing factor in human sera known as trypanosome lytic factor (TLF). In this work, we demonstrate that killing of T. b. brucei by trypanosome lytic factor-1 (TLF-1) in vitro is inhibited by the lipophyllic iron chelator, LI, the lipophyllic antioxidant DPPD, and the protease inhibitors antipain and E64. Thus TLF-1 killing likely requires iron, oxidants, and serine and cysteine proteases. Furthermore, we demonstrate that TLF-1 mediated lysis causes measurable peroxidation in T. brucei lipids via a reaction that is inhibited by DPPD, weak bases, and human haptoglobin. We hypothesize that TLF-1 lysis requires intracellular factors within the trypanosome including high intracellular H2O2 and high polyenoic lipid concentrations, lysosomal acidification and proteases, and intracellular iron sources. The data presented supports the hypothesis that the combination of these factors with TLF-1 inside the lysosome results in lysosomal membrane breakdown, release of the lysosomal contents, and subsequent autodigestion of the cell.

EDTA bis-(ethyl phenylalaninate): a novel transition metal-ion chelating hydroxyl radical scavenger with a potential anti-inflammatory role

Conjugation of ethylenediaminetetraacetic acid (EDTA) to ethyl phenylalaninate generates a novel radical scavenging metal-ion chelator EDTA bis-(ethyl phenylalaninate) (EBEP). The oxidation products o-, m- and p-tyrosine were isolated from hydrolysed, aqueous and aerated solutions containing EBEP, Fe(II) and H(2)O(2). Data obtained demonstrate the potential of EBEP to act as a radical scavenging, iron-ion chelating antioxidant under physiologically relevant conditions.

Different susceptibility to oxidation of proline and arginine residues of apolipoprotein B-100 among subspecies of low density lipoproteins

gamma-Glutamyl semialdehyde is a primary oxidation product of apolipoprotein (apo) B-100 proline (Pro) and arginine (Arg) side chain residues. By reduction gamma-glutamyl semialdehyde forms 5-hydroxy-2-aminovaleric acid (HAVA). Here we describe the application of sensitive and specific HAVA measurement to characterize the formation of gamma-glutamyl semialdehyde in several domains of apoB-100 in LDL(1) (S(f) 7-12) and LDL(2) (S(f) 0-7) subfractions subjected to oxidative damage in the presence of iron in vitro. Results suggest that susceptibility of apoB-100 Pro and Arg residues toward oxygen radicals drastically changes along the lipoprotein metabolic cascade.

Measurement of 5-hydroxy-2-aminovaleric acid as a specific marker of iron-mediated oxidation of proline and arginine side-chain residues of low-density lipoprotein apolipoprotein B-100

An alteration of apolipoprotein (apo) B-100 structure by direct oxidative modification is supposed to be an important mechanism involved in atherogenesis. There is difficulty in quantifying this type of modification owing to a lack of specific assays. We evaluated a methodology based on the oxidation of protein arginine and proline to gamma-glutamyl semialdehyde which by reduction forms 5-hydroxy-2-aminovaleric acid (HAVA). We determined HAVA by using derivatization to N(O)-ethoxycarbonyl ethyl esters and gas chromatography-mass spectrometry in different low-density lipoprotein preparations subjected to oxidative damage in the presence of iron. Results suggest that apoB-100 proline and arginine residues are highly reactive toward oxygen radicals ex vivo. Femtomole levels of HAVA can be reproducible measured. HAVA determination compares well with the measurement of carbonyl group formation used as a generally accepted but nonspecific index of protein oxidation. Thus, HAVA could prove to be a sensitive assay for studying specific modification of apoB-100.

Deferiprone: a review of its clinical potential in iron overload in beta-thalassaemia major and other transfusion-dependent diseases

Patients with beta-thalassaemia and other transfusion-dependent diseases develop iron overload from chronic blood transfusions and require regular iron chelation to prevent potentially fatal iron-related complications. The only iron chelator currently widely available is deferoxamine, which is expensive and requires prolonged subcutaneous infusion 3 to 7 times per week or daily intramuscular injections. Moreover, some patients are unable to tolerate deferoxamine and compliance with the drug is poor in many patients. Deferiprone is the most extensively studied oral iron chelator to date. Non-comparative clinical studies mostly in patients with beta-thalassaemia have demonstrated that deferiprone 75 to 100 mg/kg/day can reduce iron burden in regularly transfused iron-overloaded patients. Serum ferritin levels are generally reduced in patients with very high pretreatment levels and are frequently maintained within an acceptable range in those who are already adequately chelated. Deferiprone is not effective in all patients (some of whom show increases in serum ferritin and/or liver iron content, particularly during long term therapy). This may reflect factors such as suboptimal dosage and/or severe degree of iron overload at baseline in some instances. Although few long term comparative data are available, deferiprone at the recommended dosage of 75 mg/kg/day appears to be less effective than deferoxamine; however, compliance is superior with deferiprone, which may partly compensate for this. Deferiprone has additive, or possibly synergistic, effects on iron excretion when combined with deferoxamine. The optimum dosage and long term efficacy of deferiprone, and its effects on survival and progression of iron-related organ damage, remain to be established. The most important adverse effects in deferiprone-treated patients are arthropathy and neutropenia/agranulocytosis. Other adverse events include gastrointestinal disturbances, ALT elevation, development of antinuclear antibodies and zinc deficiency. With deferiprone, adverse effects occur mostly in heavily iron-loaded patients, whereas with deferoxamine adverse effects occur predominantly when body iron burden is lower.

CONCLUSION

Deferiprone is the most promising oral iron chelator under development at present. Further studies are required to determine the best way to use this new drug. Although it appears to be less effective than deferoxamine at the recommended dosage and there are concerns regarding its tolerability, it may nevertheless offer a therapeutic alternative in the management of patients unable or unwilling to receive the latter drug. Deferipone also shows promise as an adjunct to deferoxamine therapy in patients with insufficient response and may prove useful as a maintenance treatment to interpose between treatments.

Cholesterol-lowering nature of unsaturated fat in rats may be due to its inability to increase hepatic iron

The present investigation was conducted to determine whether the cholesterol-raising properties of saturated fat and cholesterol-lowering properties of unsaturated fat are associated with levels of hepatic iron. The magnitude of hepatic iron retention was manipulated by feeding rats diets that were either copper-deficient or -adequate, iron-adequate or -supplemented, and contained either beef tallow or corn oil. Weanling male Sprague-Dawley rats were randomly divided into eight dietary groups according to the type of dietary fat (beef tallow or corn oil) and level of dietary copper (0.74 or 6.9 microg Cu/g diet) or iron (44.4 or 86.7 microg Fe/g diet). Beef tallow and copper deficiency alone increased hepatic iron levels, which in turn were associated with increased plasma cholesterol. When the three dietary factors were combined, ie, iron, beef tallow, and copper deficiency, they induced the highest magnitude of hepatic iron retention, which in turn was associated with the highest concentration of plasma cholesterol. In contrast, when hepatic iron retention was not increased, such as by feeding a diet containing corn oil or by consumption of a copper-adequate diet, plasma cholesterol was not elevated. Based on these data, it is suggested that nutrients that have the ability to increase hepatic iron have the potential to increase plasma cholesterol.