Inhibition of autoimmune neuropathological process by treatment with an iron-chelating agent

The role of iron metabolism in the pathogenesis and treatment of multiple sclerosis

Multiple sclerosis is a severe demyelinating disease mediated by cells of the innate and adaptive immune system, especially pathogenic T lymphocytes that produce the pro-inflammatory cytokine granulocyte-macrophage colony stimulating factor (GM-CSF). Although the factors and molecules that drive the genesis of these cells are not completely known, some were discovered and shown to promote the development of such cells, such as dietary factors. In this regard, iron, the most abundant chemical element on Earth, has been implicated in the development of pathogenic T lymphocytes and in MS development via its effects on neurons and glia. Therefore, the aim of this paper is to revise the state-of-art regarding the role of iron metabolism in cells of key importance to MS pathophysiology, such as pathogenic CD4+ T cells and CNS resident cells. Harnessing the knowledge of iron metabolism may aid in the discovery of new molecular targets and in the development of new drugs that tackle MS and other diseases that share similar pathophysiology.

Mechanisms of Intranasal Deferoxamine in Neurodegenerative and Neurovascular Disease

Identifying disease-modifying therapies for neurological diseases remains one of the greatest gaps in modern medicine. Herein, we present the rationale for intranasal (IN) delivery of deferoxamine (DFO), a high-affinity iron chelator, as a treatment for neurodegenerative and neurovascular disease with a focus on its novel mechanisms. Brain iron dyshomeostasis with iron accumulation is a known feature of brain aging and is implicated in the pathogenesis of a number of neurological diseases. A substantial body of preclinical evidence and early clinical data has demonstrated that IN DFO and other iron chelators have strong disease-modifying impacts in Alzheimer’s disease (AD), Parkinson’s disease (PD), ischemic stroke, and intracranial hemorrhage (ICH). Acting by the disease-nonspecific pathway of iron chelation, DFO targets each of these complex diseases via multifactorial mechanisms. Accumulating lines of evidence suggest further mechanisms by which IN DFO may also be beneficial in cognitive aging, multiple sclerosis, traumatic brain injury, other neurodegenerative diseases, and vascular dementia. Considering its known safety profile, targeted delivery method, robust preclinical efficacy, multiple mechanisms, and potential applicability across many neurological diseases, the case for further development of IN DFO is considerable.

Potential role of iron in repair of inflammatory demyelinating lesions

Inflammatory destruction of iron-rich myelin is characteristic of multiple sclerosis (MS). Although iron is needed for oligodendrocytes to produce myelin during development, its deposition has also been linked to neurodegeneration and inflammation, including in MS. We report perivascular iron deposition in multiple sclerosis lesions that was mirrored in 72 lesions from 13 marmosets with experimental autoimmune encephalomyelitis. Iron accumulated mainly inside microglia/macrophages from 6 weeks after demyelination. Consistently, expression of transferrin receptor, the brain's main iron-influx protein, increased as lesions aged. Iron was uncorrelated with inflammation and postdated initial demyelination, suggesting that iron is not directly pathogenic. Iron homeostasis was at least partially restored in remyelinated, but not persistently demyelinated, lesions. Taken together, our results suggest that iron accumulation in the weeks after inflammatory demyelination may contribute to lesion repair rather than inflammatory demyelination per se.

Dexras1 Deletion and Iron Chelation Promote Neuroprotection in Experimental Optic Neuritis

Dysregulation of iron metabolism, and resultant cytotoxicity, has been implicated in the pathogenesis of multiple sclerosis (MS) and other neurodegenerative processes. Iron accumulation promotes cytotoxicity through various mechanisms including oxidative stress and glutamate toxicity, and occurs in both MS patients and in the experimental autoimmune encephalomyelitis (EAE) model of MS. Divalent Metal Transporter1, a major iron importer in cells, is stimulated by signaling of Dexras1, a small G protein member of the Ras family. Dexras1 is activated by S-nitrosylation by nitric oxide (NO) produced by either inducible nitric oxide synthase in activated microglia/macrophages or neuronal nitric oxide synthase in neurons. Here we show Dexras1 exacerbates oxidative stress-induced neurodegeneration in experimental optic neuritis, an inflammatory demyelinating optic nerve condition that occurs in MS and EAE. Dexras1 deletion, as well as treatment with the iron chelator deferiprone, preserves vision and attenuates retinal ganglion cell (RGC) and axonal loss during EAE optic neuritis. These results suggest that iron entry triggered by NO-activated Dexras1 signaling is a potential mechanism of neuronal death in experimental optic neuritis. The current data suggest modulation of Dexras1 signaling and iron chelation are potential novel treatment strategies for optic neuritis and MS, and possibly other optic neuropathies as well.

[Anemia and dysregulation of iron metabolism in multiple sclerosis]

Anemia is one of the common diseases comorbid with multiple sclerosis (MS). This article reviews the prevalence and types of anemia in MS patients. It has been shown that anemia is often accompanied by a decrease in serum iron level. The authors present the data on iron metabolism in patients with MS and MRI findings concerning deposits of iron in the gray matter of the brain. The causal relationship between abnormalities in iron metabolism and MS remains unclear; this study allows to approach the understanding of the MS pathogenesis and to increase the efficacy of therapy for this disease.

Cisplatin-Induced Nephrotoxicity; Protective Supplements and Gender Differences

Cisplatin (CDDP) has been widely used as a chemotherapeutic agent for solid tumors. The most common side effect of CDDP is nephrotoxicity, and many efforts have been made in the laboratory and the clinic to employ candidate adjuvants to CDDP to minimize this adverse influence. Many synthetic and herbal antioxidants as well as trace elements have been investigated for this purpose in recent years and a variety of positive and negative results have been yielded. However, no definitive supplement has so far been proposed to prevent CDDP-induced nephrotoxicity; however, this condition is gender related and the sex hormone estrogen may protect the kidney against CDDP damage. In this review, the results of research related to the effect of different synthetic and herbal antioxidants supplements are presented and discussed with suggestions included for future work.

Iron in the Brain: An Important Contributor in Normal and Diseased States

Iron is essential for normal neurological function because of its role in oxidative metabolism and because it is a cofactor in the synthesis of neurotransmitters and myelin. In the past several years, there has been increased attention to the importance of oxidative stress in the central nervous system. Iron is the most important inducer of reactive oxygen species, therefore, the relation of iron to neurodegenerative processes is more appreciated today than it was a few years ago. Nevertheless, despite this increased attention and awareness, our knowledge of iron metabolism in the brain at the cellular and molecular levels is still limited. Iron is distributed in a heterogeneous fashion among the different regions and cells of the brain. This regional and cellular heterogeneity is preserved across many species. Brain iron concentrations are not static; they increase with age and in many diseases and decrease when iron is deficient in the diet. In infants and children, insufficient iron in the diet is associated with decreased brain iron and with changes in behavior and cognitive functioning. Abnormal iron accumulation in the diseased brain areas and, in some cases, alterations in iron-related proteins have been reported in many neurodegenerative diseases, including Hallervorden-Spatz syndrome, Alzheimer’s disease, Parkinson’s disease, and Friedreich’s ataxia. There is strong evidence for iron-mediated oxidative damage as a primary contributor to cell death in these disorders. Demyelinating diseases, such as multiple sclerosis, especially warrant study in relation to iron availability. Myelin synthesis and maintenance have a high iron requirement, thus, oligodendrocytes must have a relatively high and constant supply of iron. However, the high oxygen utilization, high density of lipids, and high iron content of white matter all combine to increase the risk of oxidative damage. We review here the current knowledge of the normal metabolism of iron in the brain and the suspected role of iron in neuropathology.

Hypoxic Adaptation in the Nervous System: Promise for Novel Therapeutics for Acute and Chronic Neurodegeneration

Homeostasis is the process by which cells adapt to stress and prevent or repair injury. Unique programs have evolved to sense and activate these homeostatic mechanisms and as such, homeostatic sensors may be potent therapeutic targets. The hypoxic response mediated by hypoxia inducible factor (HIF) downstream of oxygen sensing by HIF prolyl 4-hydroxylases (PHDs) has been well-studied, revealing cell-type specific regulation of HIF stability, activity, and transcriptional targets. HIF's paradoxical roles in nervous system development, physiology, and pathology arise from its complex roles in hypoxic adaptation and normoxic biology. Understanding how to engage the hypoxic response so as to recapitulate the protective mechanism of ischemic preconditioning is a high priority. Indeed, small molecules that activate the hypoxic response provide broad neuroprotection in several clinically relevant injury models. Screens for PHD inhibitors have identified novel therapeutics for neuroprotection that are ready to proceed to clinical trials for ischemic stroke. Better understanding the mechanisms of how to engage hypoxic adaption without altering development or physiology may identify additional novel therapeutic targets for diverse acute and chronic neuropathologies.

Oxidative tissue injury in multiple sclerosis is only partly reflected in experimental disease models

Recent data suggest that oxidative injury may play an important role in demyelination and neurodegeneration in multiple sclerosis (MS). We compared the extent of oxidative injury in MS lesions with that in experimental models driven by different inflammatory mechanisms. It was only in a model of coronavirus-induced demyelinating encephalomyelitis that we detected an accumulation of oxidised phospholipids, which was comparable in extent to that in MS. In both, MS and coronavirus-induced encephalomyelitis, this was associated with massive microglial and macrophage activation, accompanied by the expression of the NADPH oxidase subunit p22phox but only sparse expression of inducible nitric oxide synthase (iNOS). Acute and chronic CD4⁺ T cell-mediated experimental autoimmune encephalomyelitis lesions showed transient expression of p22phox and iNOS associated with inflammation. Macrophages in chronic lesions of antibody-mediated demyelinating encephalomyelitis showed lysosomal activity but very little p22phox or iNOS expressions. Active inflammatory demyelinating lesions induced by CD8⁺ T cells or by innate immunity showed macrophage and microglial activation together with the expression of p22phox, but low or absent iNOS reactivity. We corroborated the differences between acute CD4⁺ T cell-mediated experimental autoimmune encephalomyelitis and acute MS lesions via gene expression studies. Furthermore, age-dependent iron accumulation and lesion-associated iron liberation, as occurring in the human brain, were only minor in rodent brains. Our study shows that oxidative injury and its triggering mechanisms diverge in different models of rodent central nervous system inflammation. The amplification of oxidative injury, which has been suggested in MS, is only reflected to a limited degree in the studied rodent models.

Hemoglobin as a source of iron overload in multiple sclerosis: does multiple sclerosis share risk factors with vascular disorders?

Although iron is known to be essential for the normal development and health of the central nervous system, abnormal iron deposits are found in and around multiple sclerosis (MS) lesions that themselves are closely associated with the cerebral vasculature. However, the origin of this excess iron is unknown, and it is not clear whether this is one of the primary causative events in the pathogenesis of MS, or simply another consequence of the long-lasting inflammatory conditions. Here, applying a systems biology approach, we propose an additional way for understanding the neurodegenerative component of the disease caused by chronic subclinical extravasation of hemoglobin, in combination with multiple other factors including, but not limited to, dysfunction of different cellular protective mechanisms against extracellular hemoglobin reactivity and oxidative stress. Moreover, such considerations could also shed light on and explain the higher susceptibility of MS patients to a wide range of cardiovascular disorders.

Iron chelation and multiple sclerosis

Histochemical and MRI studies have demonstrated that MS (multiple sclerosis) patients have abnormal deposition of iron in both gray and white matter structures. Data is emerging indicating that this iron could partake in pathogenesis by various mechanisms, e.g., promoting the production of reactive oxygen species and enhancing the production of proinflammatory cytokines. Iron chelation therapy could be a viable strategy to block iron-related pathological events or it can confer cellular protection by stabilizing hypoxia inducible factor 1α, a transcription factor that normally responds to hypoxic conditions. Iron chelation has been shown to protect against disease progression and/or limit iron accumulation in some neurological disorders or their experimental models. Data from studies that administered a chelator to animals with experimental autoimmune encephalomyelitis, a model of MS, support the rationale for examining this treatment approach in MS. Preliminary clinical studies have been performed in MS patients using deferoxamine. Although some side effects were observed, the large majority of patients were able to tolerate the arduous administration regimen, i.e., 6-8 h of subcutaneous infusion, and all side effects resolved upon discontinuation of treatment. Importantly, these preliminary studies did not identify a disqualifying event for this experimental approach. More recently developed chelators, deferasirox and deferiprone, are more desirable for possible use in MS given their oral administration, and importantly, deferiprone can cross the blood-brain barrier. However, experiences from other conditions indicate that the potential for adverse events during chelation therapy necessitates close patient monitoring and a carefully considered administration regimen.

Hypoxia-inducible factor prolyl hydroxylases as targets for neuroprotection by "antioxidant" metal chelators: From ferroptosis to stroke

Neurologic conditions including stroke, Alzheimer disease, Parkinson disease, and Huntington disease are leading causes of death and long-term disability in the United States, and efforts to develop novel therapeutics for these conditions have historically had poor success in translating from bench to bedside. Hypoxia-inducible factor (HIF)-1α mediates a broad, evolutionarily conserved, endogenous adaptive program to hypoxia, and manipulation of components of the HIF pathway is neuroprotective in a number of human neurological diseases and experimental models. In this review, we discuss molecular components of one aspect of hypoxic adaptation in detail and provide perspective on which targets within this pathway seem to be ripest for preventing and repairing neurodegeneration. Further, we highlight the role of HIF prolyl hydroxylases as emerging targets for the salutary effects of metal chelators on ferroptosis in vitro as well in animal models of neurological diseases.

In vitro ischemia suppresses hypoxic induction of hypoxia-inducible factor-1α by inhibition of synthesis and not enhanced degradation

Hypoxia-inducible factor (HIF) mediates a broad, conserved adaptive response to hypoxia, and the HIF pathway is a potential therapeutic target in cerebral ischemia. This study investigated the mechanism by which in vitro ischemia (oxygen-glucose deprivation; OGD) affects canonical hypoxic HIF-1α stabilization. We validated the use of a reporter containing the oxygen-dependent degradation domain of HIF-1α fused to firefly luciferase (ODD-luc) to monitor quantitatively distinct biochemical events leading to hypoxic HIF-1α expression or stabilization in a human neuroblastoma cell line (SH-SY5Y). When OGD was imposed following a 2-hr hypoxic stabilization of ODD-luc, the levels of the reporter were reduced, consistent with prior models proposing that OGD enhances HIF prolylhydroxylase (PHD) activity. Surprisingly, PHD inhibitors and proteasome inhibitors do not stabilize ODD-luc in OGD. Furthermore, OGD does not affect the half-life of ODD-luc protein following hypoxia, suggesting that OGD abrogates hypoxic HIF-1α induction by reducing HIF-1α synthesis rather than by enhancing its degradation. We observed ATP depletion under OGD vs. hypoxia and propose that ATP depletion enhances translational suppression, overcoming the selective synthesis of HIF concurrent with global decreases in protein synthesis in hypoxia. Taken together, these findings biochemically characterize a practical reporter for monitoring HIF-1α levels and support a novel model for HIF regulation in an in vitro model of human ischemia.

Pathogenic implications of iron accumulation in multiple sclerosis

Iron, an essential element used for a multitude of biochemical reactions, abnormally accumulates in the CNS of patients with multiple sclerosis (MS). The mechanisms of abnormal iron deposition in MS are not fully understood, nor do we know whether these deposits have adverse consequences, that is, contribute to pathogenesis. With some exceptions, excess levels of iron are represented concomitantly in multiple deep gray matter structures often with bilateral representation, whereas in white matter, pathological iron deposits are usually located at sites of inflammation that are associated with veins. These distinct spatial patterns suggest disparate mechanisms of iron accumulation between these regions. Iron has been postulated to promote disease activity in MS by various means: (i) iron can amplify the activated state of microglia resulting in the increased production of proinflammatory mediators; (ii) excess intracellular iron deposits could promote mitochondria dysfunction; and (iii) improperly managed iron could catalyze the production of damaging reactive oxygen species (ROS). The pathological consequences of abnormal iron deposits may be dependent on the affected brain region and/or accumulation process. Here, we review putative mechanisms of enhanced iron uptake in MS and address the likely roles of iron in the pathogenesis of this disease.

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.

The iron chelator, desferrioxamine, reduces inflammation and atherosclerotic lesion development in experimental mice

Vascular inflammation and monocyte recruitment are initiating events in atherosclerosis that have been suggested to be caused, in part, by iron-mediated oxidative stress and shifts in the intracellular redox environment of vascular cells. Therefore, the objective of this study was to investigate whether the intracellular iron chelator, desferrioxamine (DFO), reduces inflammation and atherosclerosis in experimental mice. Treatment of C57BL/6J mice with DFO (daily intraperitoneal injection of 100 mg/kg body weight for two weeks) strongly inhibited lipopolysaccharide-induced increases of soluble cellular adhesion molecules and monocyte chemoattractant protein-1 (MCP-1) in the serum and activation of the redox-sensitive transcription factors, nuclear factor-kappaB and activator protein-1, in the aorta. Furthermore, treatment of apolipoprotein E-deficient (apoE-/-) mice with DFO (100 mg/kg, intraperitoneal, daily for 10 weeks) attenuated aortic atherosclerotic lesion development by 26% (P < 0.05). DFO treatment of apoE-/- mice also lowered serum levels of MCP-1 and gene expression of proinflammatory and macrophage markers in the aorta and heart, in parallel with increased protein expression of the transferrin receptor in the heart and liver. In contrast, DFO treatment had no effect on serum cholesterol and triglyceride levels. These data show that DFO inhibits inflammation and atherosclerosis in experimental mice, providing the proof-of-concept for an important role of iron in atherogenesis. Whether eliminating excess iron is a useful adjunct for the prevention or treatment of atherosclerosis in humans remains to be investigated.

Deep gray matter T2 hypointensity correlates with disability in a murine model of MS

Advanced MRI studies demonstrated several diffuse non-lesional features in multiple sclerosis, including changes detectable in gray matter areas. Standard T2 weighted MRI scans of deep gray matter structures, including the thalamus, caudate, putamen, dentate nuclei often demonstrate hypointensity. T2 hypointensity has been shown to correlate with cognitive, neuropsychiatric and motor dysfunction. The exact pathogenesis of this MRI phenomenon remains unknown. In this manuscript, we demonstrate the first known MS animal model of deep gray matter T2 hypointensity. In TMEV infected SJL/J mice, gradual development of thalamic T2 hypointensity was noted over the disease course. Quantitative analysis of the hypointensity demonstrated a strong correlation between the degree of T2 hypointensity and rotarod detectable disability. We propose that this model will allow mechanistic studies investigating the pathogenesis and significance of deep gray matter T2 hypointensity in MS.

Quantitative assessment of iron accumulation in the deep gray matter of multiple sclerosis by magnetic field correlation imaging

BACKGROUND AND PURPOSE

Deposition of iron has been recognized recently as an important factor of pathophysiologic change including neurodegenerative processes in multiple sclerosis (MS). We propose that there is an excess accumulation of iron in the deep gray matter in patients with MS that can be measured with a newly developed quantitative MR technique--magnetic field correlation (MFC) imaging.

MATERIALS AND METHODS

With a 3T MR system, we studied 17 patients with relapsing-remitting MS and 14 age-matched healthy control subjects. We acquired MFC imaging using an asymmetric single-shot echo-planar imaging sequence. Regions of interest were selected in both deep gray matter and white matter regions, and the mean MFC values were compared between patients and controls. We also correlated the MFC data with lesion load and neuropsychologic tests in the patients.

RESULTS

MFC measured in the deep gray matter in patients with MS was significantly higher than that in the healthy controls (P < or = .03), with an average increase of 24% in the globus pallidus, 39.5% in the putamen, and 30.6% in the thalamus. The increased iron deposition measured with MFC in the deep gray matter in the patients correlated positively with the total number of MS lesions (thalamus: r = 0.61, P = .01; globus pallidus: r = 0.52, P = .02). A moderate but significant correlation between the MFC value in the deep gray matter and the neuropsychologic tests was also found.

CONCLUSION

Quantitative measurements of iron content with MFC demonstrate increased accumulation of iron in the deep gray matter in patients with MS, which may be associated with the disrupted iron outflow pathway by lesions. Such abnormal accumulation of iron may contribute to neuropsychologic impairment and have implications for neurodegenerative processes in MS.

Iron in chronic brain disorders: imaging and neurotherapeutic implications

Iron is important for brain oxygen transport, electron transfer, neurotransmitter synthesis, and myelin production. Though iron deposition has been observed in the brain with normal aging, increased iron has also been shown in many chronic neurological disorders including Alzheimer's disease, Parkinson's disease, and multiple sclerosis. In vitro studies have demonstrated that excessive iron can lead to free radical production, which can promote neurotoxicity. However, the link between observed iron deposition and pathological processes underlying various diseases of the brain is not well understood. It is not known whether excessive in vivo iron directly contributes to tissue damage or is solely an epiphenomenon. In this article, we focus on the imaging of brain iron and the underlying physiology and metabolism relating to iron deposition. We conclude with a discussion of the potential implications of iron-related toxicity to neurotherapeutic development.

Deferiprone, an orally deliverable iron chelator, ameliorates experimental autoimmune encephalomyelitis

The iron chelator, Desferal, suppressed disease activity of experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis (MS), and it has been tested in pilot trials for MS. The administration regimen of Desferal is cumbersome and prone to complications. Orally-deliverable, iron chelators have been developed that circumvent these difficulties, and the objective of this study was to test an oral chelator in EAE. SJL mice with active EAE were randomly assigned to receive deferiprone (150 mg/kg) or vehicle (water) 2×/day via gavage. EAE mice given deferiprone had significantly less disease activity and lower levels of inflammatory cell infiltrates (revealed by H&E staining) than EAE mice administered vehicle. T-cell infiltration, assessed by anti-CD3 immunohistochemical staining, also was reduced, although not significantly. Splenocytes cultured from naïve SJL mice were stimulated with anti-CD3 and anti-CD28 with or without 250 μM deferiprone. While ~39% of costimulated splenocytes without deferiprone underwent division, only ~2.8% of costimulated splenocytes with deferiprone divided and the latter cells were only 53% as viable as the former. Deferiprone had no effect on proliferation or viability of cells that were not costimulated. In summary, deferiprone effectively suppressed active EAE disease and it inhibited T-cell function. Multiple Sclerosis 2007; 13: 1118—1126. http://msj.sagepub.com

Iron chelator induces THP-1 cell differentiation potentially by modulating intracellular glutathione levels

Iron chelators have been implicated to modulate certain inflammatory mediators and regulate inflammatory processes. Here we report that iron chelator deferoxamine (DFO) induces differentiation of monocytic THP-1 cells into functional macrophages. DFO rapidly phosphorylated both extracellular signal-regulated kinase (ERK) and p38 kinase. Blockade of ERK signaling by the MEK1/2 inhibitor PD098059 abolished DFO-induced class A scavenger receptor (SR-A) expression and phagocytic activity, indicating that ERK cascades mediate the induction of THP-1 differentiation. In contrast, in cells treated with the p38 inhibitor SB203580 or transfected with the dominant-negative variant of p38 kinase, DFO-mediated ERK activation became more prominent, and the induction of SR-A expression and phagocytic activity were significantly increased. Interestingly, differentiation by DFO was associated with decrease in cellular glutathione (GSH) level. Both MAPK inhibitors did not influence the GSH level; however, treatment with ferric citrate (Fe3+) or N-acetyl-cysteine, a major precursor of GSH, markedly recovered GSH level to a normal extent, along with the significant decrease of differentiation. Collectively, these results indicate that oxidative stress by DFO and the resulting activation of ERK cascade play dominant roles in the process of THP-1 differentiation, while p38 acts as a negative signal transmitter.

Hypoxia-inducible factor prolyl 4-hydroxylase inhibition. A target for neuroprotection in the central nervous system

Hypoxia-inducible factor (HIF) prolyl 4-hydroxylases are a family of iron- and 2-oxoglutarate-dependent dioxygenases that negatively regulate the stability of several proteins that have established roles in adaptation to hypoxic or oxidative stress. These proteins include the transcriptional activators HIF-1alpha and HIF-2alpha. The ability of the inhibitors of HIF prolyl 4-hydroxylases to stabilize proteins involved in adaptation in neurons and to prevent neuronal injury remains unclear. We reported that structurally diverse low molecular weight or peptide inhibitors of the HIF prolyl 4-hydroxylases stabilize HIF-1alpha and up-regulate HIF-dependent target genes (e.g. enolase, p21(waf1/cip1), vascular endothelial growth factor, or erythropoietin) in embryonic cortical neurons in vitro or in adult rat brains in vivo. We also showed that structurally diverse HIF prolyl 4-hydroxylase inhibitors prevent oxidative death in vitro and ischemic injury in vivo. Taken together these findings identified low molecular weight and peptide HIF prolyl 4-hydroxylase inhibitors as novel neurological therapeutics for stroke as well as other diseases associated with oxidative stress.

Quantifying immunohistochemical staining of phospho-eIF2alpha, heme oxygenase-2 and NADPH cytochrome P450 reductase in oligodendrocytes during experimental autoimmune encephalomyelitis

As a consequence of inflammation associated with multiple sclerosis and its animal model, experimental autoimmune encephalomyelitis (EAE), stress responses are induced in many cells within the CNS, however, those that occur within the primary pathological target, the oligodendrocyte, are not fully established. Recently, we found that phosphorylated eukaryotic initiation factor-2alpha (eIF2alpha), an inhibitor of protein translation associated with the stress response, is expressed in a greater number of oligodendrocytes in EAE animals compared to controls. However, since numerous oligodendrocytes in control animals also expressed phospho-eIF2alpha, a method was developed to detect expression levels within oligodendrocytes that did not rely on the number of oligodendrocytes that were stained. This method utilized a high dilution of the primary antibody so that the staining density was kept below a maximum plateau which could eliminate expression differences. Furthermore, the staining density within oligodendrocytes, as determined by image analysis, was corrected by the background density or that within neurons. In either case, the density of staining was greater in oligodendrocytes from EAE animals versus controls. The expression of heme oxygenase-2 and NADPH cytochrome P450 reductase also were examined, but unlike phospho-eIF2alpha, neither was increased in oligodendrocytes from EAE animals compared to controls. In summary, a protocol involving a high dilution of primary antibody and image analysis revealed that the expression of phospho-eIF2alpha within oligodendrocytes was increased in EAE animals compared to control animals.

Cytokine toxicity to oligodendrocyte precursors is mediated by iron

Inflammatory processes play a key role in the pathogenesis of a number of common neurodegenerative disorders such as Alzheimer's disease (AD), Parkinson's disease (PD), and multiple sclerosis (MS). Abnormal iron accumulation is frequently noted in these diseases and compelling evidence exists that iron is involved in inflammatory reactions. Histochemical stains for iron repeatedly demonstrate that oligodendrocytes, under normal conditions, stain more prominently than any other cell type in the brain. Therefore, we examined the hypothesis that cytokine toxicity to oligodendrocytes is iron mediated. Oligodendrocytes in culture were exposed to interferon-gamma (IFN-gamma), interleukin-1beta (IL-1beta), and tumor necrosis factor-alpha (TNF-alpha). Toxicity was observed in a dose-dependent manner for IFN-gamma and TNF-alpha. IL-1beta was not toxic in the concentrations used in this study. The toxic concentration of IFN-gamma, and TNF-alpha was lower if the cells were iron loaded, but iron loading had no effect on the toxicity of IL-1beta. These data provide insight into the controversy regarding the toxicity of cytokines to oligodendrocytes by revealing that iron status of these cells will significantly impact the outcome of cytokine treatment. The exposure of oligodendrocytes to cytokines plus iron decreased mitochondrial membrane potential but activation of caspase 3 is limited. The antioxidant, TPPB, which targets mitochondria, protected the oligodendrocytes from the iron-mediated cytotoxicity, providing further support that mitochondrial dysfunction may underlie the iron-mediated cytokine toxicity. Therapeutic strategies involving anti-inflammatory agents have met with limited success in the treatment of demyelinating disorders. A better understanding of these agents and the contribution of cellular iron status to cytokine toxicity may help develop a more consistent intervention strategy.

The Role of Iron in the Pathogenesis of Experimental Allergic Encephalomyelitis and Multiple Sclerosis

Multiple sclerosis (MS) and its animal model, experimental allergic encephalomyelitis (EAE), are autoimmune disorders resulting in demyelination in the central nervous system (CNS). Pathologically, the blood-brain barrier becomes damaged, macrophages and T cells enter into the CNS, oligodendrocytes and myelin are destroyed, astrocytes and microglia undergo gliosis, and axons become transected. Data from several biochemical and pharmacological studies indicate that free radicals participate in the pathogenesis of EAE, and iron has been implicated as the catalyst leading to their formation. The primary focus of this article is the examination of the role of iron in the pathogenesis of MS and EAE. Particular attention will be paid to the role and distribution of iron and proteins involved with iron metabolism (e.g., transferrin, ferritin, heme oxygenase-1, etc.) in normal and disease states of myelin. Furthermore, therapeutic interventions aimed at iron, iron-binding proteins, and substrates or products of iron-catalyzed reactions leading to free radical production will be discussed.

The cardioprotector dexrazoxane augments therapeutic efficacy of mitoxantrone in experimental autoimmune encephalomyelitis

The present study investigates the immunological effects of a combination treatment of mitoxantrone and the cardioprotector dexrazoxane in experimental autoimmune encephalomyelitis (EAE). Mitoxantrone, an anthracycline-derived immunosuppressive drug has been approved recently for treatment of very active multiple sclerosis (MS). Its prolonged use is limited due to its cardiotoxic properties. Dexrazoxane (DZR (S)-(+)-1,2-bis (3,5.dioxopiperazinyl)propane, ICRF-187) is an iron III chelator which in animal models and in cancer patients reduces anthracycline and mitoxantrone induced cardiotoxicity when given immediately before these agents. We examined the immunological effects of dexrazoxane in combination with mitoxantrone in experimental autoimmune encephalomyelitis (EAE) in Lewis rats. EAE was induced by active immunization with myelin basic protein (MBP) or by adoptive transfer of MBP specific T cells (AT-EAE). The clinical course, spinal cord pathology, activity of metalloproteinases (MMP-2 and MMP-9) and T cell apoptosis were assessed. Monotherapy with DZR ameliorated slightly the course of actively induced EAE and AT-EAE. The combination of DZR and mitoxantrone was superior to mitoxantrone given alone. Clinical amelioration ran in parallel with the marked reduction of inflammatory infiltration which was nearly abolished by the combination treatment. DZR did not affect the activity of metalloproteinase 9 and did not increase the proportion of apoptotic lymph node cells ex vivo or T cells in situ. We conclude that in addition to its cardioprotective role, DZR augments mitoxantrone-mediated immunosuppressive effects in animal models of human central nervous system (CNS) autoimmune disease. Clinical trials in MS patients are warranted to evaluate the unexpected immunosuppressive efficacy of DZR as add-on treatment.

Activation of histamine H2 receptors ameliorates experimental allergic encephalomyelitis

Experimental allergic encephalomyelitis (EAE), a model of multiple sclerosis, is an autoimmune, demyelinating disease of the CNS. Pro-inflammatory cytokines (e.g. tumour necrosis factor-alpha (TNF-alpha) and interleukin (IL)-12) and reactive oxygen species are implicated in promoting EAE. Since histamine H(2) receptor activation suppresses production of O(2)*-, TNF-alpha, and IL-12 by inflammatory cells, we tested the hypothesis that dimaprit, an H(2) agonist, would reduce the clinical severity and pathology of EAE. Dimaprit treatment significantly reduced clinical signs compared to vehicle in both C57BL/6 and iNOS deficient EAE mice. Furthermore, dimaprit significantly reduced CNS staining for lectin-positive macrophages and decreased extravasated albumin staining, an indicator of blood-brain barrier leakage. These data provide a rationale for exploring H2 receptor activation for therapeutic value in multiple sclerosis.

Iron and iron management proteins in neurobiology

The ability of the brain to store a readily bioavailable source of iron is essential for normal neurologic function because both iron deficiency and iron excess in the brain have serious neurologic consequences. The blood-brain barrier presents unique challenges to timely and adequate delivery of iron to the brain. The regional compartmentalization of neurologic function and a myriad of cell types provide additional challenges. Furthermore, iron-dependent events within the central nervous system (CNS) are age dependent (e.g., myelination) or region specific (e.g., dopamine synthesis). Thus the mechanisms for maintaining the delicate balance of CNS iron concentration must be considered on a region-specific and age-specific basis. Confounding factors that influence brain iron acquisition in addition to age-specific and region-specific requirements are dietary factors and disease. This article raises and addresses the novel concept of regional regulation of brain iron uptake by reviewing the developmental patterns of iron accumulation and expression of proteins responsible for maintaining iron homeostasis in a region-specific and cell-specific manner. Understanding these mechanisms is essential for generating insights into diseases such as Hallervorden-Spatz syndrome, in which excess iron accumulation in the brain plays a significant role in the disease process, and should also unveil windows of opportunity for replenishing the brain in a state of iron deficiency.

Myelin membranes isolated from rats intracranially injected with apotransferrin are more susceptible to in vitro peroxidation

Purified myelin obtained from 17 day old rats intracranially injected with aTf at 3 days of age was submitted to in vitro peroxidation using Fe + ascorbic acid (FeA) or Cu + H2O2 (CuH), to investigate the susceptibility of this membrane to in vitro metal catalyzed peroxidation. There was an increase in thiobarbituric acid-reactive-substances (TBARS) (60%) and in protein-associated carbonyls (PAC) (20%) in the myelin from aTf injected rats in comparison to myelin from controls, indicating a higher susceptibility to peroxidation. Desferoxamine (DFX) injected simultaneously with aTf did not change the response of myelin to aTf. CNS myelin is highly vulnerable to oxidative stress, and its susceptibility to peroxidation increases in myelin isolated from aTf injected rats. This increased liability to peroxidation as well as the previously reported aTf-dependent increment in certain myelin proteins and lipids and in the expression of specific myelin mRNAS, does not appear to be due to an increased amount of iron bound to the injected aTf. The changes in composition that we have previously reported could result in an abnormal myelin, allowing the peroxidative system to act upon the membrane more easily than in normal circumstances.

Protection from oxidative stress-induced apoptosis in cortical neuronal cultures by iron chelators is associated with enhanced DNA binding of hypoxia-inducible factor-1 and ATF-1/CREB and increased expression of glycolytic enzymes, p21(waf1/cip1), and erythropoietin

Iron chelators are pluripotent neuronal antiapoptotic agents that have been shown to enhance metabolic recovery in cerebral ischemia models. The precise mechanism(s) by which these agents exert their effects remains unclear. Recent studies have demonstrated that iron chelators activate a hypoxia signal transduction pathway in non-neuronal cells that culminates in the stabilization of the transcriptional activator hypoxia-inducible factor-1 (HIF-1) and increased expression of gene products that mediate hypoxic adaptation. We examined the hypothesis that iron chelators prevent oxidative stress-induced death in cortical neuronal cultures by inducing expression of HIF-1 and its target genes. We report that the structurally distinct iron chelators deferoxamine mesylate and mimosine prevent apoptosis induced by glutathione depletion and oxidative stress in embryonic cortical neuronal cultures. The protective effects of iron chelators are correlated with their ability to enhance DNA binding of HIF-1 and activating transcription factor 1(ATF-1)/cAMP response element-binding protein (CREB) to the hypoxia response element in cortical cultures and the H19-7 hippocampal neuronal cell line. We show that mRNA, protein, and/or activity levels for genes whose expression is known to be regulated by HIF-1, including glycolytic enzymes, p21(waf1/cip1), and erythropoietin, are increased in cortical neuronal cultures in response to iron chelator treatment. Finally, we demonstrate that cobalt chloride, which also activates HIF-1 and ATF-1/CREB in cortical cultures, also prevents oxidative stress-induced death in these cells. Altogether, these results suggest that iron chelators exert their neuroprotective effects, in part, by activating a signal transduction pathway leading to increased expression of genes known to compensate for hypoxic or oxidative stress.

Protection from oxidative stress-induced apoptosis in cortical neuronal cultures by iron chelators is associated with enhanced DNA binding of hypoxia-inducible factor-1 and ATF-1/CREB and increased expression of glycolytic enzymes, p21(waf1/cip1), and erythropoietin

Iron chelators are pluripotent neuronal antiapoptotic agents that have been shown to enhance metabolic recovery in cerebral ischemia models. The precise mechanism(s) by which these agents exert their effects remains unclear. Recent studies have demonstrated that iron chelators activate a hypoxia signal transduction pathway in non-neuronal cells that culminates in the stabilization of the transcriptional activator hypoxia-inducible factor-1 (HIF-1) and increased expression of gene products that mediate hypoxic adaptation. We examined the hypothesis that iron chelators prevent oxidative stress-induced death in cortical neuronal cultures by inducing expression of HIF-1 and its target genes. We report that the structurally distinct iron chelators deferoxamine mesylate and mimosine prevent apoptosis induced by glutathione depletion and oxidative stress in embryonic cortical neuronal cultures. The protective effects of iron chelators are correlated with their ability to enhance DNA binding of HIF-1 and activating transcription factor 1(ATF-1)/cAMP response element-binding protein (CREB) to the hypoxia response element in cortical cultures and the H19-7 hippocampal neuronal cell line. We show that mRNA, protein, and/or activity levels for genes whose expression is known to be regulated by HIF-1, including glycolytic enzymes, p21(waf1/cip1), and erythropoietin, are increased in cortical neuronal cultures in response to iron chelator treatment. Finally, we demonstrate that cobalt chloride, which also activates HIF-1 and ATF-1/CREB in cortical cultures, also prevents oxidative stress-induced death in these cells. Altogether, these results suggest that iron chelators exert their neuroprotective effects, in part, by activating a signal transduction pathway leading to increased expression of genes known to compensate for hypoxic or oxidative stress.

Demyelination: the role of reactive oxygen and nitrogen species

This review summarises the role that reactive oxygen and nitrogen species play in demyelination, such as that occurring in the inflammatory demyelinating disorders multiple sclerosis and Guillain-Barré syndrome. The concentrations of reactive oxygen and nitrogen species (e.g. superoxide, nitric oxide and peroxynitrite) can increase dramatically under conditions such as inflammation, and this can overwhelm the inherent antioxidant defences within lesions. Such oxidative and/or nitrative stress can damage the lipids, proteins and nucleic acids of cells and mitochondria, potentially causing cell death. Oligodendrocytes are more sensitive to oxidative and nitrative stress in vitro than are astrocytes and microglia, seemingly due to a diminished capacity for antioxidant defence, and the presence of raised risk factors, including a high iron content. Oxidative and nitrative stress might therefore result in vivo in selective oligodendrocyte death, and thereby demyelination. The reactive species may also damage the myelin sheath, promoting its attack by macrophages. Damage can occur directly by lipid peroxidation, and indirectly by the activation of proteases and phospholipase A2. Evidence for the existence of oxidative and nitrative stress within inflammatory demyelinating lesions includes the presence of both lipid and protein peroxides, and nitrotyrosine (a marker for peroxynitrite formation). The neurological deficit resulting from experimental autoimmune demyelinating disease has generally been reduced by trial therapies intended to diminish the concentration of reactive oxygen species. However, therapies aimed at diminishing reactive nitrogen species have had a more variable outcome, sometimes exacerbating disease.

Iron deposits in the central nervous system of SJL mice with experimental allergic encephalomyelitis

Iron has been proposed to promote oxidative tissue damage in multiple sclerosis (MS). In order to gain insights about how iron gets processed during MS, the deposition of iron was investigated in the CNS of mice with experimental allergic encephalomyelitis (EAE), which is a commonly used animal model of MS. Control mice (adjuvant only) and EAE mice (myelin basic protein plus adjuvant), were sacrificed at 4-8 days (preclinical phase), 10-13 days (clinical phase), or 18 days (recovery phase) post injection. Sections from the cerebrum, hindbrain, and cervical, thoracic and lumbar spinal cord were stained as previously described (J. Neurosci. Res. 29:413, 1991), and scored blindly for histopathological staining. There was minimal histopathological staining at any age in control animals or during the preclinical stage in EAE animals. At the clinical stage of EAE, stained pathological features (macrophages, extravasated RBC and granular staining) were significantly increased compared to the preclinical stage. In the recovery phase, macrophage and granular staining persisted but there was loss of extravasated RBC. Dual labeling studies revealed that granular deposits were present in astrocytes and in locations that appeared to be extracellular. In order to gain insights about the origin of iron deposits in EAE mice, additional studies were performed on brains of mice with extravasated blood lesions. These brains had granular, macrophage and RBC staining. Thus, each of the stained features in EAE animals could be due to the extravasation of blood which occurs in the SJL model of EAE, although some of the iron could have originated from myelin and oligodendrocytes damaged during EAE.

Adeno-associated viral-mediated catalase expression suppresses optic neuritis in experimental allergic encephalomyelitis

Suppression of oxidative injury by viral-mediated transfer of the human catalase gene was tested in the optic nerves of animals with experimental allergic encephalomyelitis (EAE). EAE is an inflammatory autoimmune disorder of primary central nervous system demyelination that has been frequently used as an animal model for the human disease multiple sclerosis (MS). The optic nerve is a frequent site of involvement common to both EAE and MS. Recombinant adeno-associated virus containing the human gene for catalase was injected over the right optic nerve heads of SJL/J mice that were simultaneously sensitized for EAE. After 1 month, cell-specific catalase activity, evaluated by quantitation of catalase immunogold, was increased approximately 2-fold each in endothelia, oligodendroglia, astrocytes, and axons of the optic nerve. Effects of catalase on the histologic lesions of EAE were measured by computerized analysis of the myelin sheath area (for demyelination), optic disc area (for optic nerve head swelling), extent of the cellular infiltrate, extravasated serum albumin labeled by immunogold (for blood-brain barrier disruption), and in vivo H2O2 reaction product. Relative to control, contralateral optic nerves injected with the recombinant virus without a therapeutic gene, catalase gene inoculation reduced demyelination by 38%, optic nerve head swelling by 29%, cellular infiltration by 34%, disruption of the blood-brain barrier by 64%, and in vivo levels of H2O2 by 61%. Because the efficacy of potential treatments for MS are usually initially tested in the EAE animal model, this study suggests that catalase gene delivery by using viral vectors may be a therapeutic strategy for suppression of MS.

Chemical analysis of multiple sclerosis lesions by FT-IR microspectroscopy

Fourier transform infrared microspectroscopy can be used to collect infrared spectra from microscopic regions of tissue sections. If spectra are collected along a grid pattern, then maps of chemical functional groups can be produced and correlated to tissue histopathology. In the present study, white matter from multiple sclerosis and control brains were examined. Mapping experiments were designed such that 17 spectra were collected at 200 microm intervals along a line that was partially or wholly within a multiple sclerosis lesion site or within a representative white matter region of control tissue. Data analysis was based on earlier in vitro studies which found that the carbonyl at 1740 cm(-1) increases when lipids become oxidized (Free Rad. Biol. Med. 16:591-601, 1994), and the amide I peak at approximately 1660 cm(-1) broadens when proteins become oxidized (FEBS Let. 362:165-170, 1995). The results indicated that the C=O to CH2 ratio (1740 cm(-1):1468 cm(-1)) was elevated at several collection points in lesion sites from multiple sclerosis brains compared to values from white matter of control brains. Inspection of the amide I peak at 1657 cm(-1) revealed that it was broadened towards 1652 cm(-1) in multiple sclerosis tissues but not control tissues. These results suggest that lipids and proteins could be oxidized at active multiple sclerosis lesion sites. The localization of these products to lesion sites supports a role for free radicals in the pathogenesis of multiple sclerosis.

Desferrioxamine suppresses experimental allergic encephalomyelitis induced by MBP in SJL mice

Data from several studies indicate that free radicals have a pathogenic role in experimental allergic encephalomyelitis (EAE). Iron can contribute to free radical damage by catalyzing the formation of hydroxyl radical, inducing secondary initiation of lipid peroxidation and by promoting the oxidation of proteins. The iron chelator, desferrioxamine, can limit these oxidative reactions and it can scavenge peroxynitrite independent of iron chelation. Two previous studies have examined the therapeutic value of desferrioxamine in EAE. One study observed an effect when disease was induced by spinal cord homogenates (J. Exp. Med. 160, p. 1532, 1984), but a second study found no therapeutic value of desferrioxamine for myelin basic protein (MBP)-induced EAE (J. Neuroimmunol. 17, p. 127, 1988). In the second study, the drug was only administered during the preclinical stages of disease. Since desferrioxamine scavenges free radicals and prevents their formation, we hypothesized that the drug should be given during the active stage of disease to have therapeutic value. We first demonstrated that the drug enters the CNS around inflammatory cells in EAE animals. In animals treated during the active stage of MBP-induced EAE, the clinical signs were significantly reduced compared to vehicle-treated animals. The iron-bound form of this drug, ferrioxamine, was without therapeutic value. A derivative of desferrioxamine, hydroxylethyl starch (HES)-desferrioxamine, has a greater plasma half-life than desferrioxamine and it was also tested. Although there was a suggestion of improvement in these animals, the effects were less than that observed for desferrioxamine which may be related to the greater molecular size of HES-desferrioxamine. In summary, these data suggest that chelation of iron is an effective therapeutic target for EAE.

Desferrioxamine in chronic progressive multiple sclerosis: a pilot study

Chronic progressive Multiple Sclerosis is refractory to many conventional treatments. We performed a pilot study testing desferroxamine (DFO) as a candidate in the treatment of chronic progressive Multiple Sclerosis. DFO was given daily by 8 h subcutaneous infusions at a dose of 2 grams daily for 7 days, followed by 1 gram daily for 7 days. Eighteen of 19 individuals completed the full dose of 21 grams. One patient was unable to complete the course due to nausea. No acute deterioration of neurological status was seen during the administration of DFO. No worsening of vision or hearing was noted except that the one patient who was unable to tolerate the medication had a transient reduction in hearing. All patients had a local redness at the injection site. None of the patients had any sudden worsening during or shortly after the treatment. This pilot study suggests that DFO is relatively well tolerated by Multiple Sclerosis patients when given in a short course of therapy.

Relationship of iron to oligodendrocytes and myelination

Oligodendrocytes are the predominant iron-containing cells in the brain. Iron-containing oligodendrocytes are found near neuronal cell bodies, along blood vessels, and are particularly abundant within white matter tracts. Iron-positive cells in white matter are present from birth and eventually reside in defined patches of cells in the adult. These patches of iron-containing cells typically have a blood vessel in their center. Ferritin, the iron storage protein, is also expressed early in development in oligodendrocytes in a regional and cellular pattern similar to that seen for iron. Recently, the functionally distinct subunits of ferritin have been analyzed; only heavy (H)-chain ferritin is found in oligodendrocytes early in development. H-ferritin is associated with high iron utilization and low iron storage. Consistent with the expression of H-ferritin is the expression of transferrin receptors (for iron acquisition) on immature oligodendrocytes. Transferrin protein accumulation and mRNA expression in the brain are both dependent on a viable population of oligodendrocytes and may have an autocrine function to assist oligodendrocytes in iron acquisition. Although apparently the majority of oligodendrocytes in white matter tracts contain ferritin, transferrin, and iron, not all of them do, indicating that there is a subset of oligodendrocytes in white matter tracts. The only known function of oligodendrocytes is myelin production, and both a direct and indirect relationship exists between iron acquisition and myelin production. Iron is directly involved in myelin production as a required co-factor for cholesterol and lipid biosynthesis and indirectly because of its requirement for oxidative metabolism (which occurs in oligodendrocytes at a higher rate than other brain cells). Factors (such as cytokines) and conditions such as iron deficiency may reduce iron acquisition by oligodendrocytes and the susceptibility of oligodendrocytes to oxidative injury may be a result of their iron-rich cytoplasm. Thus, the many known phenomena that decrease oligodendrocyte survival and/or myelin production may mediate their effect through a final common pathway that involves disruptions in iron availability or intracellular management of iron.

Effects of desferrioxamine on human cytomegalovirus replication and expression of HLA antigens and adhesion molecules in human vascular endothelial cells

Desferrioxamine (DFO), commonly used in therapy as a chelator of ferric ion in disorders of iron overload, is a potent inhibitor of human cytomegalovirus (HCMV) replication in cultured fibroblast cells. Moreover, DFO has immunomodulatory activity both in vitro and in vivo. We studied DFO effects on HCMV replication in cultured human endothelial cells and on the expression of several cell surface molecules, which mediate interactions of endothelial cells with other cell types in the immune system. The concentrations of DFO required for 50% reduction in the number of endothelial cells expressing HCMV late antigen, ranged for several HCMV strains from 5.2 to 8.8 microM. DFO concentrations ranging from 5 to 40 microM inhibited cellular DNA synthesis in a dose-dependent manner without any significant effects on the cell viability. DFO at 10 microM concentration suppressed expression of intercellular adhesion molecule-1 (ICAM-1) and endothelial leucocyte adhesion molecule-1 (ELAM-1), while it had no significant effect on the expression of vascular cell adhesion molecule-1 (VCAM-1). Expression of HLA class I and class II was not influenced by DFO treatment. The results showed that DFO is both effective in inhibition of HCMV replication and expression of ICAM-1 and ELAM-1 in endothelial cells, a combination that warrants attention to its potential use to prevent HCMV-induced allograft rejection in transplant recipients.

Suppression of hyperacute and passively transferred experimental autoimmune encephalomyelitis by the anti-oxidant, butylated hydroxyanisole

Butylated hydroxyanisole (BHA) was used to treat hyperacute, ordinary passive, and hyperacute passive experimental autoimmune encephalomyelitis (EAE) in the Lewis rat. The anti-oxidant, delivered via mini-osmotic pumps, reduced the incidence, severity and mortality in hyperacute EAE and also reduced the incidence, severity and duration of disease in passively induced EAE and hyperacute passive EAE. In all cases, cellular infiltration by both mononuclear and polymorphonuclear leukocytes were significantly reduced in treated rats. BHA appears therefore to act at the effector stage of EAE, reducing cellular infiltration in the brain and spinal cord and minimising clinical signs without blocking sensitisation or activation. This was supported by the finding that spleen cells from BHA-treated donors immunised for hyperacute EAE transferred disease at least as well as cells recovered from untreated donors.

Increased generation of superoxide radicals in the blood of MS patients

Increased generation of superoxide radical (O2-) in the blood stimulated with phorbol myristate acetate (PMA) has been found in multiple sclerosis (MS) patients. All the subjects studied were non-smokers and received the same hospital diet. In the MS group treated with prednisone superoxide radical generation was lower than in untreated patients, but was still above the level of O2- generation in controls. Plasma lipid peroxidation products, measured as thiobarbituric-reactive substances, were slightly elevated in both prednisone treated and non-treated MS patients in comparison with controls. Erythrocyte superoxide dismutase activity (SOD) was at the same level in MS and control groups. These results suggest that increased generation of reactive oxygen species may occur in MS patients during acute relapse. This phenomenon may be involved in the pathomechanism of demyelinating disorders.

The role of reactive oxygen species, antioxidants and phytopharmaceuticals in human immunodeficiency virus activity

Currently, several prominent researchers are investigating the role of reactive oxygen and free radicals in the activation of latent HIV in infected individuals. Early clinical applications of free radical scavengers and plant-based antioxidant systems have shown promise of efficacy in altering this process. This manuscript demonstrates a premise for the existence of 'oxidative stress' as an important element in HIV progression and a basis for the use of these phytopharmaceutical substances.

Antioxidants attenuate microvascular changes in the early phase of experimental pneumococcal meningitis in rats

BACKGROUND AND PURPOSE

We tested in a rat meningitis model 1) whether pneumococcal cell wall components are capable of producing changes in regional cerebral blood flow, brain water content, and intracranial pressure similar to those we have already observed after intracisternal inoculation of live pneumococci and 2) whether antioxidants would modulate these alterations in the early phase of meningitis.

METHODS

Regional cerebral blood flow as measured by laser Doppler flowmetry and intracranial pressure were monitored continuously for 4 hours after intracisternal challenge. Brain edema formation was assessed by brain water content determinations. We investigated the following groups: rats challenged intracisternally with the whole intact pneumococcal cell wall (n = 7) or the pneumococcal cell wall hydrolyzed by the M1-muramidase (n = 7); rats injected intracisternally with phosphate-buffered saline (n = 6); rats pretreated intravenously with superoxide dismutase conjugated with polyethylene glycol (10,000 units/kg) and injected intracisternally with cell wall components (n = 5) or phosphate-buffered saline (n = 6); rats injected intracisternally with phosphate-buffered saline and pretreated intravenously with polyethylene glycol (10% solution, 1.2 ml/kg, n = 5) or continuously treated with intravenous free superoxide dismutase (22,000 units/kg per hour, n = 6); and rats continuously treated intravenously with deferoxamine mesylate (10 mg/kg per hour) and injected intracisternally with cell wall components (n = 6) or phosphate-buffered saline (n = 7).

RESULTS

Both pneumococcal cell wall preparations produced a significant increase in regional cerebral blood flow, intracranial pressure, and brain water content. Conjugated superoxide dismutase as well as deferoxamine prevented the increase in intracranial pressure and brain water content. In addition, the increase in regional cerebral blood flow as observed in untreated, cell wall-challenged rats (baseline, 100%; 183.1 +/- 12.3% after 4 hours, mean +/- SEM) was significantly attenuated by administration of both conjugated superoxide dismutase (136.6 +/- 14.1%) and deferoxamine (149.8 +/- 8.2%) (p < 0.05). Polyethylene glycol-conjugated superoxide dismutase alone produced an increase in regional cerebral blood flow (125.6 +/- 8.7% after 4 hours). We found that polyethylene glycol per se accounts for this action.

CONCLUSIONS

These data show that pneumococcal cell wall components containing teichoic acid produce changes in regional cerebral blood flow, intracranial pressure, and brain water content and that oxygen radicals contribute to these pathophysiological alterations in the early phase of experimental pneumococcal meningitis.