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Peripheral Effects of Iron Deficiency
Abstract
• Clinical manifestations of iron deficiency were described since 1500 bc and were well known in 16th and 17th century Europe as part of the disease “chlorosis”.
• The major cause of iron deficiency is blood loss, commonly from the gastro-intestinal tract in adults.
• The hematologic changes characteristic of iron deficiency include hypochromic and microcytic anemia.
• The tongue and mouth, hypopharynx and esophagus, stomach, nails, and hair are common epithelial tissues affected by iron deficiency.
• Glossitis, cheilitis, koilonychia, dysphagia, and pica are the signs and symptoms commonly associated with iron deficiency and iron deficiency anemia.
A case study of a female patient, diagnosed with iron deficiency anemia, was unresponsive to oral iron treatment and only partially responsive to parenteral iron therapy, a clinical profile resembling the iron-refractory iron deficiency anemia (IRIDA) disorder. However, the patient failed to exhibit microcytic phenotype, one of the IRIDA hallmarks. Biochemical assays revealed that serum iron, hepcidin, interluekin 6, and transferrin saturation were within the normal range of references or were comparable to her non-anemic offspring. Iron contents in serum and red blood cells and hemoglobin levels were measured, which confirmed the partial improvement of anemia after parenteral iron therapy. Strikingly, serum transferrin receptor in patient was almost undetectable, reflecting the very low activity of bone-marrow erythropoiesis. Our data demonstrate that this is not a case of systemic iron deficiency, but rather cellular iron deficit due to the low level of transferrin receptor, particularly in erythroid tissue.
SYNOPSIS
This study includes all white and Aboriginal children under the age of 5 years admitted to the Bourke District Hospital over a 12 month period. 15% of all white children and 72% of all Aboriginal children in the Bourke shire were admitted to hospital on at least one occasion; Aboriginal children had proportionately 10 times the number of hospital admissions on a population basis.
The amyloid beta-peptide (A beta) that accumulates as insoluble plaques in the brain in Alzheimer's disease can be directly neurotoxic and can increase neuronal vulnerability to excitotoxic insults. The mechanism of A beta toxicity is unclear but is believed to involve generation of reactive oxygen species (ROS) and loss of calcium homeostasis. We now report that exposure of cultured rat hippocampal neurons to A beta 1-40 or A beta 25-35 causes a selective reduction in Na+/K(+)-ATPase activity which precedes loss of calcium homeostasis and cell degeneration. Na+/K(+)-ATPase activity was reduced within 30 min of exposure to A beta 25-35 and declined to less than 40% of basal level by 3 hr. A beta did not impair other Mg(2+)-dependent ATPase activities or Na+/Ca2+ exchange. Experiments with ouabain, a specific inhibitor of the Na+/K(+)-ATPase, demonstrated that impairment of this enzyme was sufficient to induce an elevation of [Ca2+]i and neuronal injury. Impairment of Na+/K(+)-ATPase activity appeared to be causally involved in the elevation of [Ca2+]i and neurotoxicity since suppression of Na+ influx significantly reduced A beta- and ouabain-induced [Ca2+]i elevation and neuronal death. Neuronal degeneration induced by ouabain appeared to be of an apoptotic form as indicated by nuclear condensation and DNA fragmentation. The antioxidant free radical scavengers vitamin E and propylgallate significantly attenuated A beta-induced impairment of Na+/K(+)-ATPase activity, elevation of [Ca2+]i and neurotoxicity, suggesting a role for ROS. Finally, exposure of synaptosomes from postmortem human hippocampus to A beta resulted in a significant and specific reduction in Na+/K(+)-ATPase and Ca(2+)-ATPase activities, without affecting other Mg(2+)-dependent ATPase activities or Na+/Ca2+ exchange. These data suggest that impairment of ion-motive ATPases may play a role in the pathogenesis of neuronal injury in Alzheimer's disease.
Under conditions of iron overload, which are now reaching epidemic proportions worldwide, iron-overload cardiomyopathy is the most important prognostic factor in patient survival. We hypothesize that in iron-overload disorders, iron accumulation in the heart depends on ferrous iron (Fe2+) permeation through the L-type voltage-dependent Ca2+ channel (LVDCC), a promiscuous divalent cation transporter. Iron overload in mice was associated with increased mortality, systolic and diastolic dysfunction, bradycardia, hypotension, increased myocardial fibrosis and elevated oxidative stress. Treatment with LVDCC blockers (CCBs; amlodipine and verapamil) at therapeutic levels inhibited the LVDCC current in cardiomyocytes, attenuated myocardial iron accumulation and oxidative stress, improved survival, prevented hypotension and preserved heart structure and function. Consistent with the role of LVDCCs in myocardial iron uptake, iron-overloaded transgenic mice with cardiac-specific overexpression of the LVDCC alpha1-subunit had twofold higher myocardial iron and oxidative stress levels, as well as greater impairment in cardiac function, compared with littermate controls; LVDCC blockade was again protective. Our results indicate that cardiac LVDCCs are key transporters of iron into cardiomyocytes under iron-overloaded conditions, and potentially represent a new therapeutic target to reduce the cardiovascular burden from iron overload.
AIMSTo define the normal ranges and investigate associated factors for haemoglobin and ferritin in British children at 12 and 18 months of age, and to estimate correlations between both haemoglobin and ferritin concentrations at 8, 12, and 18 months of age.SUBJECTS AND METHODS
Subjects were part of the “children in focus” sample, randomly selected from the Avon longitudinal study of pregnancy and childhood. Capillary blood samples were taken from 940 children at 12 months and 827 children at 18 months of age.RESULTSHaemoglobin was distributed normally and ferritin was distributed log normally at 12 and 18 months of age. Ninety five per cent reference ranges were established from empirical centiles of haemoglobin and ferritin. Haemoglobin concentrations at 18 months were associated with sex and maternal education. Concentrations of ferritin at 12 and 18 months of age were associated with birth weight and current weight. Girls at 12 months, but not at 18 months, had 8% higher ferritin concentrations than boys. Haemoglobin and ferritin concentrations were significantly correlated over time (8–12 months:rHb = 0.26,rFer = 0.46; 12–18 months:rHb = 0.37,rFer = 0.34; 8–18 months:rHb = 0.22,rFer = 0.24).CONCLUSION
Iron stores are depleted by rapid growth in infancy. A definition of anaemia based on the fifth centile gives cut off points at 12 and 18 months of age of haemoglobin < 100 g/l, and for iron deficiency of ferritin < 16 μg/l and < 12 μg/l, respectively. Because children below the fifth centile at one time point differ from those six months later, it is unclear whether screening would be effective.
Lewy bodies and Lewy neurites are the defining neuropathological characteristics of Parkinson’s disease and dementia with
Lewy bodies. They are made of abnormal filamentous assemblies of unknown composition. We show here that Lewy bodies and Lewy
neurites from Parkinson’s disease and dementia with Lewy bodies are stained strongly by antibodies directed against amino-terminal
and carboxyl-terminal sequences of α-synuclein, showing the presence of full-length or close to full-length α-synuclein. The
number of α-synuclein-stained structures exceeded that immunoreactive for ubiquitin, which is currently the most sensitive
marker of Lewy bodies and Lewy neurites. Staining for α-synuclein thus will replace staining for ubiquitin as the preferred
method for detecting Lewy bodies and Lewy neurites. We have isolated Lewy body filaments by a method used for the extraction
of paired helical filaments from Alzheimer’s disease brain. By immunoelectron microscopy, extracted filaments were labeled
strongly by anti-α-synuclein antibodies. The morphologies of the 5- to 10-nm filaments and their staining characteristics
suggest that extended α-synuclein molecules run parallel to the filament axis and that the filaments are polar structures.
These findings indicate that α-synuclein forms the major filamentous component of Lewy bodies and Lewy neurites.
The purpose of this study was to characterize red blood cell (RBC) deformability by iron deficiency. We measured RBC deformability to ektacytometry, a laser diffraction method for determining the elongation of suspended red cells subjected to shear stress. Isotonic deformability of RBC from iron-deficient human subjects was consistently and significantly lower than that of normal controls. In groups of rats with severe and moderate dietary iron deficiency, RBC deformability was also reduced in proportion to the severity of iron deficiency. At any given shear stress value, deformability of resealed RBC ghosts from both iron-deficient humans and rats was lower than that of control ghosts. However, increase of applied shear stress resulted in progressive increase in ghost deformation, indicating that ghost deformability was primarily limited by membrane stiffness rather than by reduced surface area-to-volume ratio. This was consistent with the finding that iron-deficient cells had a normal membrane surface area. In addition, the reduced mean corpuscular hemoglobin concentration (MCHC) and buoyant density of the iron-deficient rat cells indicated that a high hemoglobin concentration was not responsible for impaired whole cell deformability. Biochemical studies of rat RBC showed increased membrane lipid and protein crosslinking and reduced intracellular cation content, findings that are consistent with in vivo peroxidative damage. RBC from iron-deficient rats incubated in vitro with hydrogen peroxide showed increased generation of malonyldialdehyde, an end-product of lipid peroxidation, compared to control RBC. Taken together, these findings suggest that peroxidation could contribute in part to increased membrane stiffness in iron- deficient RBC. This reduced membrane deformability may in turn contribute to impaired red cell survival in iron deficiency.
The coefficient of variation (CV) of red cell size, as measured by electronic red cell sizing (erythrography), was less than 14.0% in 20 normal subjects. In 22 of 25 patients with beta-thalassemia minor and microcytosis (mean corpuscular volume [MCV] less than 70 fl), CV was less than 14.0%; in the other 3, CV was 14.0%--14.9%. In 53 patients with iron deficiency anemia and MCV less than 70 fl, CV always was greater than 14.0%. In 7 patients with alpha-thalassemia minor and MCV less than 70 fl, CV was less than 14.0% in all 7. Among patients with microcytosis, erythrography appears to be an excellent technique for rapidly distinguishing between iron deficiency and alpha or beta thalassemia minor.
The level of serum ferritin is a reliable indicator of body iron stores. Exceptions include liver disease, malignant diseases, and treatment of iron-deficiency anemia. The latter was noted in iron- deficient infants who showed a rise of serum ferritin to normal levels in the first week of treatment. To evaluate this in adults, 14 patients with iron-deficiency anemia were studied prior to and after beginning treatment with oral ferrous sulfate in standard dose, 300 mg t.i.d., or double dose, 600 mg t.i.d. Serum ferritin was assayed by radioimmunoassay. No rise occurred in the first 3 wk in 5 patients treated with standard dose, although hematologic response occurred. With double dose, 7 of 9 showed a ferritin rise in 2 days with return to subnormal levels within 6 days of discontinuing iron. This study indicates that standard treatment of iron deficiency anemia in adults does not cause a rise in serum ferritin until hemoglobin levels are normal. The early rise seen with double dose is most likely due to absorption of iron in excess of utilization for erythropoiesis resulting in temporary storage. When iron is discontinued, stores are rapidly depleted as reflected by the prompt decrease in serum ferritin.
Using blinded procedures, determine the relation between serum ferritin levels and severity of subjective and objective symptoms of the restless legs syndrome (RLS) for a representative patient sample covering the entire adult age range.
All patient records from the past 4 years were retrospectively reviewed to obtain data from all cases with RLS. All patients were included who had ferritin levels obtained at about the same time as a polysomnogram (PSG), met diagnostic criteria for RLS, and were not on iron or medications that would reduce the RLS symptoms at the time of the PSG.
Sleep Disorders Center.
27 (18 females, 9 males), aged 29-81 years.
None.
Measurements included clinical ratings of RLS severity and PSG measures of sleep efficiency and periodic limb movements (PLMS) in sleep with and without arousal. Lower ferritin correlated significantly to greater RLS severity and decreased sleep efficiency. All but one patient with severe RLS had ferritin levels < or = 50 mcg/l. Patients with lower ferritin (< or = 50 mcg/l) also showed significantly more PLMS with arousal than did those with higher ferritin, but the PLMS/hour was not significantly related to ferritin. This last finding may be due to inclusion of two 'outliers' or because of severely disturbed sleep of the more severe RLS patients.
These data are consistent with those from a prior unblinded study and suggest that RLS patients will have fewer symptoms if they have ferritin levels greater than 50 mcg/l.
Restlesslegs syndrome (RLS), although long ignored and still much underdiagnosed,disrupts the life and sleep considerably of those who have it. Recent clinicaland basic research provides for better definition and pathophysiologicunderstanding of the disorder. The body of knowledge about this disorder hasbeen expanding rapidly during the past decade and it has altered our conceptsof this disorder. This review of RLS covers history, diagnosis, morbidity ofsleep disturbance, relation to periodic limb movements in both sleep andwaking, secondary causes, severity assessment methods, phenotypes for possiblegenetic patterns, epidemiology, pathophysiology, and medical treatmentconsiderations. The emphasis on pathophysiology includes consideration ofcentral nervous system localization, neurotransmitter and other systemsinvolved, and the role of iron metabolism. Studies to date support theauthors’ recently advanced iron–dopamine model ofRLS.
Mild-to-moderate thrombocytopenia has been reported as an occasional finding in patients with iron deficiency. The present case describes a multiparous woman who presented with increased menorrhagia, severe anemia (3.0 g/dl) and thrombocytopenia (9,000 platelets/mm3). Her bone marrow examination showed iron deficiency, megakaryocytopenia, and erythroid hypoplasia but no other evidence of a primary marrow disorder. Her symptoms, the thrombocytopenia and the megakaryocytopenia, resolved with iron replacement. This case demonstrates the profound degree to which thrombopoiesis can be affected in iron deficiency.
Background. Optimal response to recombinant human erythropoietin (rHuEpo) in haemodialysis (HD) patients requires provision of sufficient
available iron. However, a balance between iron requirements and supplements remains a challenge in clinical practice. Reticulocyte
parameters, i.e. reticulocyte haemoglobin content (CHr) and reticulocytes in a high‐fluorescence intensity region (HFR), have
been shown to be accurate predictors of iron‐deficient erythropoiesis as compared with traditional markers. Therefore, the
aim of this study was to appraise the diagnostic power of these two parameters in the early prediction of response to intravenous
iron (IVFE) medications in HD patients receiving rHuEpo.
Methods. Sixty‐five HD patients with a serum ferritin level of <500 µg/l and on rHuEpo therapy for >6 months were enrolled for IVFE
supplementation (100 mg iron saccharate three times a week for 4 weeks, then 100 mg every 2 weeks for 5 months). Haemoglobin,
haematocrit, serum ferritin, transferrin saturation, reticulocyte count, percentage of hypochromic red cells, CHr and HFR
were measured before and following iron supplementation. Response was defined as a rise in haematocrit of >3% and/or a reduction
in rHuEpo dose of >30% over the baseline values at the end of the study.
Results. Forty‐two patients had a dramatic response to IVFE therapy with a 13.5% increase in mean haematocrit and a 38% reduction
in rHuEpo dose at the end of the study (P<0.001). This paralleled a statistically significant rise in CHr and HFR (P<0.001). Univariate analyses showed that ferritin (P<0.010) and CHr (P<0.001) at baseline, changes in CHr (ΔCHr2W, P<0.001) and HFR (ΔHFR2W, P<0.010) at 2 weeks, as well as changes in CHr (ΔCHr4W, P<0.001) and HFR (ΔHFR4W, P<0.001) at 4 weeks, strongly correlated with response to IVFE supplementation. Stepwise discriminant analysis disclosed that
ΔCHr4W in conjunction with ΔHFR4W exhibited an r2 value of 0.531 (P<0.001) to predict response to IVFE therapy. Analyses by receiver operating characteristic curves and logistic regression
further revealed that ΔCHr4W at a cut‐off value of >1.2 pg and ΔHFR4W of >500/µl were more specific to the status of iron‐deficient erythropoiesis following IVFE medications. Combined use of
the two cut‐off values allowed for the highest accuracy in the early prediction of the response to IVFE therapy, with a sensitivity
of 96% and a specificity of 100%.
Conclusions. Our study shows that changes in CHr and HFR at either 2 or 4 weeks are superior to the conventional erythrocyte and iron
metabolism indices and may serve as reliable parameters to detect iron‐deficient erythropoiesis in HD patients undergoing
rHuEpo therapy. During aggressive IVFE treatment, early identification of non‐responsiveness and subsequent discontinuation
of treatment can avoid the inadvertent iron‐related toxicity due to over‐treatment.
In the past seven years numerous genes that influence iron homeostasis have been discovered. Dr. Beutler provides a brief overview of these genes, genes that encode HFE, DMT-1, ferroportin, transferrin receptor 2, hephaestin, and hepcidin to lay the groundwork for a discussion of the various clinical forms of iron storage disease and how they differ from one another.
In Section I, Dr. Beutler also discusses the types of hemochromatosis that exist as acquired and as hereditary forms. Acquired hemochromatosis occurs in patients with marrow failure, particularly when there is active ineffective erythropoiesis. Hereditary hemochromatosis is most commonly due to mutations in the HLA-linked HFE gene, and hemochromatosis clinically indistinguishable from HFE hemochromatosis is the consequence of mutations in three transferrin receptor-2 gene. A more severe, juvenile form of iron storage disease results from mutations of the gene encoding hepcidin or of a not-yet-identified gene on chromosome 1q. Autosomal dominant iron storage disease is a consequence of ferroportin mutations, and a polymorphism in the ferroportin gene appears to be involved in the African iron overload syndrome.
Evidence regarding the biochemical and clinical penetrance of hemochromatosis due to mutations of the HFE gene is rapidly accumulating. These studies, emanating from several centers in Europe and the United States, all agree that the penetrance of hemochromatosis is much lower than had previously been thought. Probably only 1% of homozygotes develop clinical findings. The implications of these new findings for the management of hemochromatosis will be discussed.
In Section II, Dr. Victor Hoffbrand discusses the management of iron storage disease by chelation therapy, treatment that is usually reserved for patients with secondary hemochromatosis such as occurs in the thalassemias and in patients with transfusion requirements due to myelodysplasia and other marrow failure states. Tissue iron can be estimated by determining serum ferritin levels, measuring liver iron, and by measuring cardiac iron using the MRI-T2* technique. The standard form of chelation therapy is the slow intravenous or subcutaneous infusion of desferoxamine. An orally active bidentate iron chelator, deferiprone, is now licensed in 25 countries for treatment of patients with thalassemia major. Possibly because of the ability of this compound to cross membranes, it appears to have superior cardioprotective properties. Agranulocytosis is the most serious complication of deferiprone therapy and occurs in about 1% of treated patients. Deferiprone and desferoxamine can be given together or on alternating schedules. A new orally active chelating agent ICL 670 seems promising in early clinical studies.
In Section III, Dr. James Cook discusses the most common disorder of iron homeostasis, iron deficiency. He will compare some of the standard methods for identifying iron deficiency, the hemoglobin level, transferrin saturation, and mean corpuscular hemoglobin and compare these with some of the newer methods that have been introduced, specifically the percentage of hypochromic erythrocytes and reticulocyte hemoglobin content. The measurement of storage iron is achieved by measuring serum ferritin levels. The soluble transferrin receptor is a truncated form of the cellular transferrin receptor and the possible value of this measurement in the diagnosis of iron deficiency will be discussed. Until recently iron dextran was the only parental iron preparation available in the US. Sodium ferric gluconate, which has been used extensively in Europe for many years, is now available in the United States. It seems to have a distinct advantage over iron dextran in that anaphylactic reactions are much less common with the latter preparation.
Iron-deficiency anemia occurs at all ages, but its pathogenesis is different in childhood and adult life. Excretion of iron is negligible. In the growing child, the needs of an expanding red cell mass require appreciable absorption of dietary iron, and the anemic child will usually be found to have a diet insufficient in iron-containing foods. In adult life, a constant amount of iron is present in the red cell mass, and an additional supply, available for hemoglobin production if needed, is stored in the tissues. Once iron stores are accrued, the adult is virtually independent of dietary iron, and iron deficiency develops only after chronic blood loss.Pathogenesis
Iron balance during the first year is diagramed in Figure 1. An average newborn infant has a blood volume of 250 ml., of which 150 ml. represents red cells.1 In the first year, the blood volume increases to 750 ml., and
In 100 hospitalized older patients with iron-deficiency anemia, the mean corpuscular hemoglobin concentration (MCHC) varied with the degree of anemia, but the degree of poikilocytosis and cell size did not; in 21 patients mean corpuscular volumes (MCV's) were normal or above normal. Nucleated red blood cells (RBC's) were seen on the blood smears of 22 patients. Platelet counts often were considerably increased. Diameters of primitive bonemarrow erythroblasts were smaller than those of normal persons. Chronic, occult bleeding from the gastrointestinal tract was the usual cause of iron loss. More than 12 different gastrointestinal lesions were found in this group; no one type of lesion predominated. In 21 patients no source of blood loss could be found.
Most discussions of iron therapy include a statement about the ineffectiveness of iron ingested simultaneously with antacids. This study was designed to determine whether or not antacids inhibit iron absorption. A small-dose iron tolerance test was used to compare absorption of iron with and without various antacids. Liquid antacid containing aluminum hydroxide and magnesium hydroxide did not significantly decrease iron absorption. Sodium bicarbonate and calcium carbonate caused the plasma iron increase to be 50% and 67% less than the control values, respectively. However, when calcium carbonate was present in a multivitamin-plus-minerals tablet, the plasma iron change was not significantly different from control trials. Presumably the competitive binding of iron by ascorbic acid in the vitamin pill allowed uninhibited absorption of the iron. Our results suggest that certain antacids may be combined with iron therapy without reducing the efficacy of the iron.
(JAMA 1986;255:1468-1470)
Previously we have shown that cell death in the substantia nigra (SN) in Parkinson's disease (PD) is associated with an increase in iron content but a decrease in the level of the iron-binding protein ferritin. Alterations in other metal ion levels were also observed; copper levels were reduced, whereas zinc levels were increased. The importance of these changes in iron, ferritin, and other metal ions in the pathophysiology of PD depends on whether they are specific to the illness. We measured levels of iron, copper, zinc, manganese, and ferritin in postmortem tissue from patients with progressive supranuclear palsy (PSP) and multiple system atrophy (MSA) (which shows pathology in the SN and striatum) and Huntington's disease (HD) (which shows pathological changes in the striatum, compared with control subjects). Total iron levels were elevated in areas of the basal ganglia showing pathological changes in these disorders. In particular, total iron content was increased in SN in PD, PSP, and MSA, but not in HD. Total iron levels in the striatum (caudate nucleus and/or putamen) were increased in PSP, MSA, and HD, but not in PD. There were no consistent alterations in manganese levels in the basal ganglia in any of the diseases studied. Copper levels were decreased in the SN in PD and in the cerebellum in PSP, and were elevated in the putamen and possibly the SN in HD. Zinc levels were only increased in PD in the SN, the caudate nucleus, and the putamen.(ABSTRACT TRUNCATED AT 250 WORDS)
The effects of systemically administered interleukin-1beta (1.0 microg) on in vivo variations of monoamines was assessed in several brain regions. Administration of the cytokine provoked a modest increase of extracellular 5-HIAA and HVA from the nucleus accumbens, and 5-HIAA from the hippocampus. Following mild neurogenic stressor (application of a series of air puffs), a still greater increase of accumbal 5-HIAA and HVA was evident, a transient increase of hippocampal 5-HT was noted and the 5-HIAA increases were augmented. Additionally, while the air puff stress was without effect on DOPAC and HVA in the prefrontal cortex of saline treated rats, a significant rise of these metabolites was apparent in rats treated with the cytokine. It appears that interleukin-1 administration may have effects on forebrain monoamines, and also results in greater neuronal reactivity to mild neurogenic stressors. This study reveals that although effects of neurogenic stressors (air puffs) and cytokine (somatic stressor) may share some similarities (e.g., HPA activation), the pattern of central neurochemical changes elicited by the cytokine could be distinguished from that induced by a more neurogenic stressor (air puffs), and that these effects showed selective synergism. These data also lend support to the contention that neurogenic stressors may have a much greater impact on central neurotransmission under conditions of immune activation.
In our books Fraústo da Silva and I have looked at living systems from a chemical element analysis point of view and in recent papers we have looked at evolution in the same way. In this paper I wish to continue this approach looking at the brain and describing its compartmentalised zones from knowledge of chemistry, especially that of particular elements. We have already given some indication of the way this might be done in our third book.
‘Mobilized pools’ of metal ions are important in accelerating damaging free radical reactions. A major part of extracellular antioxidant defence is to keep ionic iron largely sequestered in proteins. Metal-chelating agents can inhibit radical reactions in vivo and in vitro.
1. Oxygen is a toxic gas - an introductionto oxygen toxicity and reactive species 2. The chemistry of free radicals and related 'reactive species' 3. Antioxidant defences Endogenous and Diet Derived 4. Cellular responses to oxidative stress: adaptation, damage, repair, senescence and death 5. Measurement of reactive species 6. Reactive species can pose special problems needing special solutions. Some examples. 7. Reactive species can be useful some more examples 8. Reactive species can be poisonous: their role in toxicology 9. Reactive species and disease: fact, fiction or filibuster? 10. Ageing, nutrition, disease, and therapy: A role for antioxidants?
Interleukin (IL)-6 is a potent activator of the human hypothalamic- pituitary-adrenal axis. After chronic administration of IL-6 in hu- mans, there is a substantial elevation of cortisol, whereas ACTH levels are blunted. Thus, we investigated whether IL-6 and/or the IL-6 receptor (IL-6R) are expressed in the human adrenal gland and whether IL-6 could cause the release of steroid hormones by a direct action on adrenal cells in primary culture. The expression of IL-6 and IL-6R was investigated with RT-PCR and immunohistochemistry, and the effects on human adrenal steroidogenesis were tested with IL-6 in vitro. To avoid effects mediated by macrophages, we depleted adrenal primary cultures from macrophages using specific mouse antihuman CD68 and sheep antimouse IgG conjugated magnetic beads. The results showed that: 1) IL-6 and IL-6R are expressed in adrenal cell cultures, including all cell types and those depleted of macrophages; 2) IL-6R is mainly expressed in the zona reticularis and the inner zona fasciculata; positive signals from the zona glomerulosa and the medulla occurred in single cells; and 3) IL-6 regulates adrenal synthesis of mineralocorticoids, glucocorticoids, and androgens in vitro, dependent on time and dose, in the absence of macrophages. After 24 h, aldosterone secretion increased to 172 6 28% SEM, cortisol to 177 6 27% SEM, and dehydroepiandrosterone to 153 6 20% SEM of basal secretion. These findings, in combination with previous inves- tigations, suggest that IL-6 exerts its acute action via the hypothal- amus and the pituitary. In the adrenal gland, however, IL-6 seems to be a long-term regulator of stress response, integrating the responses of all cortical zones to stimuli from the immune and endocrine system. (J Clin Endocrinol Metab 82: 2343-2349, 1997)
Iron deficiency in rats produces numerous alterations in brain metabolism as assessed by in vitro techniques. We used a new method of in vivo microdialysis to study the effect of acute iron deficiency anemia on rat brain monoamine metabolism. This method was used to sample extracellular fluid from an implanted microdialysis probe in the caudate putamen from freely moving animals. Method validation experiments showed that steady-state levels of dopamine, norepinephrine, and their metabolites were obtained only after 5 to 7 days of surgical recovery and with prior perfusion of the brain region. Caudate putamen dopamine was significantly increased 30% and 40% in fasted light-exposed and 2-hr-fed dark-exposed iron deficient anemic rats (hemoglobin <6 g/dL), respectively, relative to control rats. Dihydroxyphenyl acetic acid and homovanillic acid concentrations were unaffected by iron deficiency in the fasted state. These metabolites, along with dopamine, increased significantly (50 to 82%) in iron deficient rats with exposure to darkness and food while control rats' metabolites did not change. The present study documents that iron deficiency is associated with altered in vivo brain monoamine metabolism in the steady state and in response to the environmental stimuli of food and darkness. While these data are supportive of the previous in vitro demonstrations of down-regulation of dopamine D2 receptors, they also suggest that uptake and processing of monoamines is significantly perturbed by iron deficiency.
Missense mutations at the α-synuclein gene have been associated with familial parkinsonism. We report that the phenotype of a kindred (Family H) with autosomal dominant, levodopa-responsive parkinsonism maps to chromosomal region 4q21-23 and that affected members of this kindred harbor a previously reported mutation (G209A) in exon 4 of the α-synuclein gene. We assessed the expression of the G209A allele in lymphoblastoid cell lines established from 12 individuals heterozygous for the G209A allele. The expression of this allele is either absent or significantly reduced in 7 affected heterozygotes and in 3 asymptomatic heterozygotes who are older than the mean age at disease diagnosis for their generation. In contrast, it is expressed in 1 affected and 1 unaffected heterozygote. The unaffected heterozygote is younger than the mean age at disease diagnosis for their generation. The lack of or significantly reduced expression of the G209A allele in affected heterozygotes suggests that the timing of reduced expression may be critical for disease onset. If so, the parkinsonian phenotype may arise from haploinsufficiency at the α-synuclein gene at a time point before symptom onset. In conclusion, reduced α-synuclein gene expression may be important in the pathogenesis of parkinsonism.
IL-18 was originally described as a cytokine which induced IFN-γ production by established Th1 cells in an IL-12-independent manner. However, subsequent studies demonstrated that exogenous IL-18 in the absence of IL-12 failed to drive Th1 differentiation of naive cells and induced IFN-γ from established Th1 cells only in combination with IL-12. We have examined the role of endogenous IL-18 in controlling Th1 lineage commitment. When naive TCR-transgenic T cells were stimulated with antigen, anti-IL-18 antibodies resulted in partial inhibition of IFN-γ production, but did not inhibit Th1 differentiation. To distinguish whether the inhibitory effect of anti-IL-18 antibodies was mediated directly by blocking IFN-γ production or indirectly by blocking IL-12Rβ2 up-regulation, naive T cells from IL-12 − / − mice were stimulated with anti-CD3 and IL-18. These cells failed to produce IFN-γ, but markedly up-regulated IL-12Rβ2 expression. We propose that the major effect of IL-18 on Th1 development is mediated by up-regulation of IL-12Rβ2 expression, thereby enhancing IL-12-mediated signaling. The enhancement of IL-12Rβ2 expression by IL-18 may be particularly important for the differentiation of foreign antigen- or autoantigen-specific Th1 cells when the stimulatory concentration of IL-12 in the microenvironment is just below the threshold required for Th1 development.
An imaging protocol for a quantitative estimation of disease-induced variations in brain iron is proposed and then validated, first, on a phantom and second, on a group of 11 healthy volunteers. The relative estimate of brain iron is achieved from a rate difference image that measures the enhancement, δR2app, of the transverse relaxation rate of water protons brought about by the heterogeneous accumulation of iron in the glial cells. At 1.5 T, the phantom study demonstrates, over the range 0-6 A/m, a linear dependence of δR2app on the magnetization difference between micro-spheres and a paramagnetic gel, with a sensitivity of ∼2 s−1 A−1 m. In the group of healthy volunteers (mean age 33 ± 7 years) devoid of disease-related or appreciable age-related accumulations of iron, the precision of δR2app was still sufficient to distinguish the globus pallidus and the putamen from all of the other iron-containing brain structures in a manner that was significant at the 99% confidence level.
: To examine risk factors for poor iron status in British toddlers.
: National Diet and Nutrition Survey (NDNS) of children aged 1.5-4.5 years.
: Mainland Britain, 1992/93.
: Of the 1859 children whose parents or guardians were interviewed, a weighed dietary intake was provided for 1675, and a blood sample obtained from 1003.
: Mean haemoglobin (Hb) and ferritin levels were significantly lower in younger (1.5-2.5 years) than in older (3.5-4.5 years) children, with boys having significantly lower ferritin levels than girls. Poor iron status ferritin <10 microg l-1, or low values for both indices) was associated with lower socioeconomic and employment status. Iron status was directly associated with meat and fruit consumption and inversely with that of milk and milk products, after adjustment for age and gender. The latter association remained significant after further adjustment for sociodemographic variables, energy intake and body weight. Children consuming >400 g day-1 of milk and cream were less likely to consume foods in other groups, with those also consuming little meat, fish, fruit and nuts at greatest risk of poor iron status. Few associations were observed between poor iron status and individual nutrient intakes, and iron status was not associated with either iron intake or with consumption of a vegetarian diet.
: Overdependence on milk, where it displaces iron-rich or iron-enhancing foods, may put toddlers at increased risk of poor iron status. However, this becomes non-significant when moderate-to-high amounts of foods known to enhance iron status (e.g. meat and/or fruit) are also consumed. Milk consumption in this age group should ideally be part of a mixed and balanced diet including all food groups, and particularly lean meat (or other iron-rich or fortified foods) and fruit. This is particularly relevant for households of lower socioeconomic and employment status.
Transgenic mice, named GFAP-IL6, that express interleukin-6 in astrocytes in the central nervous system (CNS) have a constitutive blood-brain barrier (BBB) defect and develop a progressive neurodegenerative disease. Based on ultrastructural observations showing electron-dense pigment in the brain of the GFAP-IL6 mice, we hypothesized that iron metabolism was altered in the brains of these animals. Enhanced histochemical methods revealed abnormal iron deposition in the cerebellum from 1 month of age that worsened with progression of the disease. Immunohistochemical analysis of iron-binding proteins (IBP) showed increased ferritin immunoreactivity and a decreased signal from the transferrin receptor in symptomatic animals. Atomic absorption spectroscopy revealed a 40% increase of total iron concentration in the cerebellum at the symptomatic stage. In order to obtain evidence that accumulation of this oxidizing metal was toxic, we looked for the presence of oxidative damage. Using the MAL-2 antibody, extensive lipid peroxidation (LP) was detected in the neocortex and the cerebellum in symptomatic animals. Ultrastructural analysis indicated lipofuscin deposition at the sites of neuro-axonal degeneration and abnormal iron deposition. These results suggest that the IL6-induced BBB defect precipitates iron accumulation in the GFAP-IL6 mouse brain and that subsequent IBP regulation mediates protective responses. As these defenses become overwhelmed, the iron overload seems to promote LP, which may contribute to the neurodegeneration that ensues. This transgenic mouse model of IL6-mediated neurodegeneration provides a unique opportunity to examine several aspects of iron metabolism in the brain, including its entry at the site of the BBB, its distribution through the IBP, and its mechanisms of toxicity.
Dopamine-β-hydroxylase(DBH), the enzyme that catalyzes the conversion of dopamine to norepinephrine, is localized in the vesicles
containing catecholamine in sympathetic nerves. This enzyme is released with norepinephrine when the nerves to the guinea
pig vas deferens are stimulated in vitro, and the amount of enzyme discharged increases as the length of stimulation periods
increases. The amount of DBH released is proportional to the amount of norepinephrine released, and the ratio of norepinephrine
to DBH discharged into the incubation medium is similar to that in the soluble portion of the contents of the synaptic vesicles
from the vas deferens. These data are compatible with the release of the neurotransmitter norepinephrine and DBH from symnpathetic
nerves by a process of exocytosis.
Plasma levels of penicillamine, urinary recovery of penicillamine and its oxidized metabolites, and urinary excretion of copper were examined afier single 500-mg oral doses of penicillamine to six healthy men. Penicillamine was given after an overnight fast, a standard breakfast, and after antacid and ferrous sulfate. Following the fasting dose, the mean peak plasma level of 3.05 g/ml developed at 3.8 hr and the drug was cleared from plasma with a t½ of 2.1 hr. Penicillamine levels were reduced to 52%, 35%, and 66% of those from the fasting dose after food, ferrous sulfate, and antacid. The rates of penicillamine appearance and disappearance from plasma were essentially treatment independent. There were good correlations between urinary recovery of total penicillamine (r = 0.875), between urinary copper excretion (r = 0.758) and the penicillamine plasma concentration AUCs. The availability of oral penicillamine is very susceptible to interactions with other substances. Further studies may be necessary to assess the full clinical significance of these interactions.
Fibrillar α-synuclein is a component of the Lewy body, the characteristic neuronal inclusion of the Parkinson's disease (PD) brain. Both α-synuclein mutations linked to autosomal dominant early-onset forms of PD promote the in vitro conversion of the natively unfolded protein into ordered prefibrillar oligomers, suggesting that these protofibrils, rather than the fibril itself, may induce cell death. We report here that protofibrils differ markedly from fibrils with respect to their interactions with synthetic membranes. Protofibrillar α-synuclein, in contrast to the monomeric and the fibrillar forms, binds synthetic vesicles very tightly via a β-sheet-rich structure and transiently permeabilizes these vesicles. The destruction of vesicular membranes by protofibrillar α-synuclein was directly observed by atomic force microscopy. The possibility that the toxicity of α-synuclein fibrillization may derive from an oligomeric intermediate, rather than the fibril, has implications regarding the design of therapeutics for PD.
Objective An evaluation of the effectiveness and acceptability of a screening programme for anaemia linked to routine child health surveillance.
Design A community-based study of the screening process with re-evaluation after treatment and again 9 months later, supported by a questionnaire study of the opinions of GPs, health visitors and parents.
Setting Child Health clinics and GP surgeries in an area of Birmingham with high levels of deprivation and ethnic minority groups.
Subjects All 625 children turning 21 months of age during a 2-month period who were resident in the study area.
Main outcome measures Attendance for screening, haemoglobin result, compliance with medication, and post-treatment haemoglobin.
Results Sixty-three per cent of the target population attended for blood screening. 46% of 365 children tested were anaemic (Hb < 110 g/L). The thumb-prick blood test was acceptable to children, parents and health visitors. Two months of iron therapy was effective in raising haemoglobin by a mean of 15.5 g/l, but one-third of cases were noncompliant with oral iron. At 30 months of age, haemoglobin tended to fall in those previously not anaemic at 21 months from a mean of 122.2 to 115.5 g/l, and 33% who had been successfully treated later relapsed.
Conclusions The effectiveness of the programme from the public health perspective was reduced by nonattendance. Nevertheless, it could identify and treat anaemic children successfully. Despite shortcomings, we feel that screening is a useful adjunct to ongoing primary prevention of anaemia.
A major pathological feature of Alzheimer's disease (AD) is the presence of a high density of amyloid plaques in the brain tissue of patients. The plaques are predominantly composed of human β-amyloid peptide βA4, a 40-mer whose neurotoxicity is related to its aggregation. Certain metals have been proposed as risk factors for AD, but the mechanism by which the metals may exert their effects is unclear. Radioiodinated human βA4 has been used to assess the effects of various metals on the aggregation of the peptide in dilute solution (10-10M). In physiological buffers, 10-3M calcium, cobalt, copper, manganese, magnesium, sodium, or potassium had no effect on the rate of βA4 aggregation. In sharp contrast, aluminum, iron, and zinc under the same conditions strongly promoted aggregation (rate enhancement of 100–1,000-fold). The aggregation of βA4 induced by aluminum and iron is distinguishable from that induced by zinc in terms of rate, extent, pH and temperature dependence. These results suggest that high concentrations of certain metals may play a role in the pathogenesis of AD by promoting aggregation of βA4.
Accumulation and toxic conversion to protofibrils of α-synuclein has been associated with neurological disorders such as Parkinson's disease (PD), Lewy body disease, multiple system atrophy, neurodegeneration with brain iron accumulation type 1, and Alzheimer's disease. In recent years, modeling these disorders in transgenic (tg) mice and flies has helped improve understanding of the pathogenesis of these diseases and has established the basis for the development of new experimental treatments. Overexpression of α-synuclein in tg mice in a region- and cell-specific manner results in degeneration of selective circuitries accompanied by motor deficits and inclusion formation similar to what is found in PD and related disorders. Furthermore, studies in singly and doubly tg mice have shown that toxic conversion and accumulation can be accelerated by α-synuclein mutations associated with familial parkinsonism, by amyloid β peptide 1–42 (Aβ 1–42), and by oxidative stress. In contrast, molecular chaperones such as Hsp70 and close homologues such as α-synuclein have been shown to suppress toxicity. Similar studies are underway to evaluate the effects of other modifying genes that might play a role in α-synuclein ubiquitination. Among them considerable interest has been placed on the role of molecules associated with familial parkinsonism (Parkin, UCHL-1). Furthermore, studying the targeted overexpression of α-synuclein and other modifier genes in the nigrostriatal and limbic system by using regulatable promoters, lentiviral vectors, and siRNA will help improve understanding of the molecular mechanisms involved in selective neuronal vulnerability, and it will aid the development of new treatments.
Tryptophan hydroxylase requires Fe2+ for in vitro enzyme activity. In this study, the intracellular activity of tryptophan hydroxylase was assessed by applying 3-hydroxybenzylhydrazine (NSD-1015), an inhibitor of aromatic l-amino acid decarboxylase, to monolayer cultures of RBL2H3 cells, a serotonin producing mast cell line. The effect of manipulating intracellular ‘free’ iron levels on enzyme activity was analyzed by administration of iron chelators. Desferrioxamine (DFO) suppressed the intracellular enzyme activity. Salicylaldehyde isonicotinoyl hydrazone (SIH) also suppressed enzyme activity, but stimulated it when administered in the Fe-bound form. Hemin also stimulated enzyme activity, which progressively increased over several hours to more than sixfold the initial level. DFO and SIH inhibited the hemin stimulatory effect when administered simultaneously with hemin. Both suppression and stimulation with these chelators took place without a significant decrease or increase in the amount of enzyme. These results indicate that there was an inadequate supply of Fe2+ in the cells to support full activity of tryptophan hydroxylase.