Fetal factors disrupt placental and maternal iron homeostasis in murine ß-thalassemia.

Pregnancy rates in ß-thalassemia are increasing but the risk of complications is higher; thus, better understanding of maternal and fetal iron homeostasis in this disorder is needed. HbbTh3/+ (Th3/+) mice model human ß-thalassemia. Both the murine and human diseases are characterized by low hepcidin, high iron absorption, and tissue iron overload, with concurrent anemia. We hypothesized that disordered iron metabolism in pregnant Th3/+ mice would negatively affect their unborn offspring. The experimental design included these groups: wild-type (WT) dams carrying WT fetuses (WT1); WT dams carrying WT and Th3/+ fetuses (WT2); Th3/+ dams carrying WT and Th3/+ fetuses (Th3/+); and age-matched, nonpregnant adult females. Serum hepcidin was low, and mobilization of splenic and hepatic storage iron was enhanced in all 3 groups of experimental dams. Intestinal 59Fe absorption was lower in Th3/+ dams (as compared with WT1/2 dams) but splenic 59Fe uptake was higher. Th3/+ dams had hyperferremia, which led to fetal and placenta iron loading, fetal growth restriction, and placentomegaly. Notably, Th3/+ dams loaded Th3/+ and WT fetuses, with the latter situation more closely mirroring human circumstances when mothers with thalassemia have relatively unaffected (thalassemia trait) offspring. Iron-related oxidative stress likely contributed to fetal growth impairment; enhanced placental erythropoiesis is a probable cause of placental enlargement. Moreover, high fetal liver iron transactivated Hamp; fetal hepcidin downregulated placental ferroportin expression, limiting placental iron flux and thus mitigating fetal iron loading. Whether gestational iron loading occurs in human thalassemic pregnancy, when blood transfusion can further elevate serum iron, is worth consideration.

Feasibility of behavioral activation group therapy in reducing depressive symptoms and improving quality of life in patients with depression: the BRAVE pilot trial.

BACKGROUND: Depression impacts the lives of millions of people worldwide. Behavioral activation (BA), derived from cognitive behavioral therapy, has the potential for improving depressive symptoms in patients with depression. Studies evaluating the effectiveness of BA specifically in the context of group therapy programs in a hospital setting for patients with depression are limited. In this study, we report findings from a pilot trial evaluating group BA for major depressive disorder. OBJECTIVE: The objectives of this pilot trial are to assess the potential of a full trial of BA group therapy in a large-scale tertiary care setting and to provide preliminary information about possible results regarding mood symptoms and quality of life in adults with depression. METHODS: Using a parallel single-cohort pragmatic pilot randomized controlled trial design, we evaluated the potential of conducting a large trial of BA effectiveness among adults with depression. Participants were randomized to the intervention (BA in addition to usual care) or control (support group in addition to usual care) groups and were assessed weekly for 18 consecutive weeks. Participants randomized to intervention underwent 28 2-h group BA therapy visits administered by trained therapists and completed assessments to examine treatment outcomes. Feasibility was measured in terms of enrollment rates (min. 20%), completion rates of study (min. 80%), and completion rates of weekly measurement scales (min. 80%). The reporting of this pilot trial is in accordance with the CONSORT extension for randomized pilot and feasibility trials. RESULTS: We randomized 20 individuals of mean age of 48.8 years (standard deviation = 9.7) with a DSM-5 diagnosis of major depressive disorder to intervention (n = 10) or control (n = 10) groups. Based on our feasibility criteria, our recruitment rate was excellent (20/27; 74%), study completion was found to be a moderate (80% of the total participants in both arms completed the study; BA = 100%, control = 60%), and completeness of measurements on a weekly basis was adequate overall (82%; BA = 86%, control = 79%). CONCLUSIONS: The study has demonstrated the potential feasibility to perform a larger scale trial upon modifications to the control group to avoid the low rate of study completion (60%) in this group. TRIAL REGISTRATION: ClinicalTrials NCT02045771, Registered January 22, 2014.

A direct comparison of divalent metal-ion transporter (DMT1) and hinokitiol, a potential small molecule replacement.

Hinokitiol, a natural lipophilic chelator, appears capable of replacing several iron transporters after they have been genetically ablated. Divalent metal-ion transporter (DMT1) is the major iron importer in enterocytes and erythroblasts. We have compared DMT1 and hinokitiol in multiple fashions to learn if the smaller molecule is a suitable substitute using two HEK293 cell lines engineered to overexpress different isoforms of DMT1. Both the macromolecule and the lipophilic chelator enable import of ferrous ions into HEK293 cells. Hinokitiol also mediates ferric ion import but DMT1 cannot do so. While DMT1 can also import Mn2+ ions, hinokitiol lacks this ability. The Michaelis-Menten analysis for kinetics of macromolecular catalysis is also suitable for hinokitiol-supported iron import. To compare hinokitiol to DMT1 relative to other metal ions that DMT1 can transport, we employed an organic extraction procedure with which we initially matched the results obtained for Fe2+, Fe3+ and Mn2+, and then showed that multiple other cations were unlikely to enter via hinokitiol. The small chelator thus shares some functional properties with DMT1, but distinct difference were also noted.

Impact of a structured, group-based running programme on clinical, cognitive and social function in youth and adults with complex mood disorders: a 12-week pilot study.

BACKGROUND: Individuals with mood disorders often report lingering health-related quality of life (HRQOL) and social and cognitive impairments even after mood symptoms have improved. Exercise programmes improve mood symptoms in patients, but whether exercise improves functional outcomes in patients with difficult-to-treat mood disorders remains unknown. DESIGN: We evaluated the impact of a 12-week structured running programme on cognitive, social and quality-of-life outcomes in participants with difficult-to-treat mood disorders. METHODS: In a prospective, open-label study, patients referred to the St Joseph's Healthcare Hamilton Team Unbreakable running programme for youth and adults with mood disorders completed a comprehensive assessment battery before and after the 12-week exercise intervention. RESULTS: We collected preintervention and postintervention data from 18 participants who improved on the general health, vitality, role of emotions, social functioning and mental health (all p≤0.01) HRQOL subscales. Performance improved on cognitive tests that assessed working memory and processing speed (p≤0.04); there were no improvements in complex executive functioning tasks. Regression analyses indicated that younger age, shorter illness duration and reduced bodily pain predicted social and cognitive outcomes. CONCLUSION: Participation in a group-based, structured running programme was associated with improved HRQOL and social and cognitive function.

Effects of a 12-week running programme in youth and adults with complex mood disorders.

OBJECTIVE: Although numerous studies suggest a salutary effect of exercise on mood, few studies have explored the effect of exercise in patients with complex mental illness. Accordingly, we evaluated the impact of running on stress, anxiety and depression in youth and adults with complex mood disorders including comorbid diagnoses, cognitive and social impairment and high relapse rates. METHODS: Participants were members of a running group at St Joseph Healthcare Hamilton's Mood Disorders Program, designed for clients with complex mood disorders. On a weekly basis, participants completed Cohen's Perceived Stress Scale, Beck Depression Inventory (BDI) and Beck Anxiety Inventory (BAI) questionnaires, providing an opportunity to evaluate the effect of running in this population. RESULTS: Data collected for 46 participants from April 2012 to July 2015 indicated a significant decrease in depression (p<0.0001), anxiety (p<0.0001) and stress (p=0.01) scores. Whereas younger participant age, younger age at onset of illness and higher perceived levels of friendship with other running group members (ps≤0.04) were associated with lower end-of-study depression, anxiety and stress scores, higher attendance was associated with decreasing BDI and BAI (ps≤0.01) scores over time. CONCLUSIONS: Aerobic exercise in a supportive group setting may improve mood symptoms in youth and adults with complex mood disorders, and perceived social support may be an important factor in programme's success. Further research is required to identify specifically the mechanisms underlying the therapeutic benefits associated with exercise-based therapy programmes.

A role for divalent metal transporter (DMT1) in mitochondrial uptake of iron and manganese.

Much of iron and manganese metabolism occurs in mitochondria. Uptake of redox-active iron must be tightly controlled, but little is known about how metal ions enter mitochondria. Recently, we established that the divalent metal transporter 1 (DMT1) is present in the outer mitochondrial membrane (OMM). Therefore we asked if it mediates Fe2+ and Mn2+ influx. Mitochondria were isolated from HEK293 cells permanently transfected with inducible rat DMT1 isoform 1 A/+IRE (HEK293-rDMT1). Fe2+-induced quenching of the dye PhenGreen™SK (PGSK) occurred in two phases, one of which reflected OMM DMT1 with stronger Fe2+ uptake after DMT1 overexpression. DMT1-specific quenching showed an apparent affinity of ~1.5 µM for Fe2+and was blocked by the DMT1 inhibitor CISMBI. Fe2+ influx reflected an imposed proton gradient, a response that was also observed in purified rat kidney cortex (rKC) mitochondria. Non-heme Fe accumulation assayed by ICPOES and stable 57Fe isotope incorporation by ICPMS were increased in HEK293-rDMT1 mitochondria. HEK293-rDMT1 mitochondria displayed higher 59Fe2+ and 54Mn2+ uptake relative to controls with 54Mn2+ uptake blocked by the DMT1 inhibitor XEN602. Such transport was defective in rKC mitochondria with the Belgrade (G185R) mutation. Thus, these results support a role for DMT1 in mitochondrial Fe2+ and Mn2+ acquisition.

Acceptability of the Fitbit in behavioural activation therapy for depression: a qualitative study.

INTRODUCTION: Major depressive disorder is characterised by low mood and poor motivation. Literature suggests that increased physical activity has positive effects on alleviating depression. Fitness-tracking devices may complement behavioural activation (BA) therapy to improve physical activity and mental health in patients with depression. OBJECTIVES: To understand patients' perceived benefit from the Fitbit and explore themes associated with patient experiences. To compare perceived benefit, patient factors, Fitbit usage and Beck's Depression Inventory (BDI) scores. METHODS: Semistructured interviews were conducted with patients (n=36) who completed a 28-week BA group programme in a mood disorders outpatient clinic. All patients were asked to carry a Fitbit One device. We conducted thematic analyses on the interviews and exploratory quantitative analyses on patient characteristics, Fitbit usage, steps recorded, perceived benefit and BDI scores. FINDINGS: Twenty-three patients found the Fitbit helpful for their physical activity. Themes of positive experiences included self-awareness, peer motivation and goal-setting opportunities. Negative themes included inconvenience, inaccuracies and disinterest. Age, baseline and change in BDI scores, prior physical activity goals and familiarity with technology were not associated with perceived benefit from the Fitbit or usage. Perceived benefit was significantly (p<0.01) associated with usage. CONCLUSIONS: Overall, the Fitbit is an acceptable tool to complement BA therapy for patients with depression. Many positive themes were concordant with current literature; however, patients also reported negative aspects that may affect use. CLINICAL IMPLICATIONS: Clinicians and researchers should consider both strengths and limitations of activity trackers when implementing them to motivate patients with depression. TRIAL REGISTRATION NUMBER: NCT02045771; Pre-results.

Behavioral activation group therapy for reducing depressive symptoms and improving quality of life: a feasibility study.

BACKGROUND: Depression is associated with a loss of productivity and noticeable personal, social, and economic decline; it affects more than 350 million people worldwide. Behavioral activation (BA), derived from cognitive behavioral therapy, has drawn increasingly more interest as a means of treatment for major depressive disorder due to its relative cost-effectiveness and efficacy. In this study, we disseminate findings from a feasibility study evaluating barriers to implementing a group BA program for major depressive disorder. The purpose of this feasibility study is to assess both patient and clinician perceptions on components of a group-based behavioral activation (BA) program. In particular, this feasibility study provides in-depth evaluation of the acceptability of BA prior to the design and implementation of a randomized trial to investigate BA effectiveness. Findings from this study directly informed decisions regarding the design and implementation of BA during the pilot trial. Specific components of BA were assessed and modified based on the results of this study. METHODS: This qualitative study was completed through the Mood Disorders Program at St. Joseph's Healthcare Hamilton. The authors of this study used data from two focus group sessions, one consisting of an interdisciplinary group of clinicians working in the Mood Disorders Program, and the other of registered outpatients of the Mood Disorders Program with a confirmed clinical diagnosis of depression. The benefits of offering this program in a group format, mainly social skill development opportunities and the use of technology such as activity tracking device, smart phones, and tablets during the therapy sessions, are a major focus of both the clinician and patient groups. Both groups emphasized the importance of offering sustainable activation. RESULTS: Differences in opinions existed between staff and patient groups regarding the use of technology in the program, though ultimately it was agreed upon that technology could be useful as a therapeutic aid. All participants agreed that behavioral activation was essential to the development of positive habits and routines necessary for recovery from depression. Patients agreed the program looked sustainable and stressed the potential benefit for improving depressive symptoms. CONCLUSIONS: Discussions from clinician and patient-centered focus groups directly informed decisions regarding the design and implementation of BA during the pilot trial. Specific components of BA were assessed and modified based on the results of this study. These findings provide insight for clinicians providing behavioral activation programming, and will serve as a framework for the development of the Out of the Blues program, a group-based BA program to be piloted in the Mood Disorders Program at St. Joseph's Healthcare Hamilton. TRIAL REGISTRATION: Clinical Trials registration number NCT02045771.

A pragmatic pilot randomized trial to investigate the effectiveness of behavioural activation group therapy in reducing depressive symptoms and improving quality of life in patients with depression: the BRAVE pilot trial protocol.

BACKGROUND: Depression is a common disorder with a lifetime prevalence of 16 %. Despite the availability of several treatment options for depression, many patients do not respond to treatment and develop chronic illness associated with several secondary comorbidities. Behavioural activation (BA) is a simple therapy that has the potential for improving symptoms of depression and quality of life in patients with depression. The effectiveness of BA has not, however, been tested in a group format for patients with moderate to severe depression attending a specialized mood disorders tertiary care setting. Group format has the advantage of treating more patients at the same time especially in resource-limited settings. The primary objective of this pilot study is to test the feasibility of a main trial by assessing the recruitment and retention rates, average group size, completion of data and resources needed and receive the participants' feedback on the intervention. The secondary objective is to explore the change in mood and quality of life measures in adults with depression receiving BA. METHODS/DESIGN: Using a pragmatic pilot randomized controlled trial design, we will test the feasibility of a large trial to assess the effectiveness of BA added to usual care compared to a depression support group with usual care. Participants will be randomized after obtaining informed written consent to one of two study arms. Face-to-face group therapy will be provided in a hospital setting by trained therapists. Intervention and control groups will be seen twice weekly for 10 weeks and then once weekly for further 8 weeks. Participants will be completing mood symptom scales, quality of life questionnaires and anthropometric measures and provide blood samples for future analysis of biomarkers of response to treatment. During the pilot study we will also solicit participants' feedback and experience regarding the number, frequency and contents of the sessions as well as to explore participant perceptions of barriers or benefits associated with the BA program. DISCUSSION: The pilot study will help to inform a larger trial and assist in modifying the intervention based on patients' feedback. TRIAL REGISTRATION: Clinicaltrials.gov Identifier NCT02045771. Hamilton Integrated Research Ethics Board (HiREB) number: 14-042.

Mitochondria represent another locale for the divalent metal transporter 1 (DMT1).

The divalent metal transporter (DMT1) is well known for its roles in duodenal iron absorption across the apical enterocyte membrane, in iron efflux from the endosome during transferrin-dependent cellular iron acquisition, as well as in uptake of non-transferrin bound iron in many cells. Recently, using multiple approaches, we have obtained evidence that the mitochondrial outer membrane is another subcellular locale of DMT1 expression. While iron is of vital importance for mitochondrial energy metabolism, its delivery is likely to be tightly controlled due to iron's damaging redox properties. Here we provide additional support for a role of DMT1 in mitochondrial iron acquisition by immunofluorescence colocalization with mitochondrial markers in cells and isolated mitochondria, as well as flow cytometric quantification of DMT1-positive mitochondria from an inducible expression system. Physiological consequences of mitochondrial DMT1 expression are discussed also in consideration of other DMT1 substrates, such as manganese, relevant to mitochondrial antioxidant defense.

Evidence for mitochondrial localization of divalent metal transporter 1 (DMT1).

In mammalian cells, mitochondria receive most incoming iron, yet no entry pathway for iron at the outer mitochondrial membrane (OMM) has been characterized. Our results show that the divalent metal transporter 1 (DMT1) occurs in the OMM. Immunoblots detected DMT1 in mitochondria from a pneumocyte cell model in their OMM. Using the split-ubiquitin yeast 2-hybrid system, we found that cytochrome c oxidase subunit II (COXII) and the translocase of OMM 6-kDa subunit (Tom6) homologue interact with DMT1. COXII coimmunoprecipitates with DMT1. There are 4 DMT1 isoforms that differ at the N and C termini. Using HEK293 cells that inducibly express all of the 4 ends of DMT1, we found all of them in the OMM, as detected by immunoblots after cell fractionation, and in isolated mitochondria, as detected by immunofluorescence. Immunoblot analysis of purified cell fractions from rat renal cortex confirmed and extended these results to the kidney, which expressed high levels of DMT1. Immunogold labeling detected DMT1 colocalization in mitochondria with the voltage-dependent anion-selective channel protein-1, which is expressed in the OMM. We suggest that DMT1 not only exports iron from endosomes, but also serves to import the metal into the mitochondria.

Divalent metal transporter 1 (Dmt1) mediates copper transport in the duodenum of iron-deficient rats and when overexpressed in iron-deprived HEK-293 cells.

Intracellular copper-binding proteins (metallothionein I/II) and a copper exporter (Menkes copper-transporting ATPase) are upregulated in duodenal enterocytes from iron-deficient rats, consistent with copper accumulation in the intestinal mucosa. How copper enters enterocytes during iron deficiency is, however, not clear. Divalent metal transporter 1 (Dmt1), the predominant iron importer in the mammalian duodenum, also transports other metal ions, possibly including copper. Given this possibility and that Dmt1 expression is upregulated by iron deprivation, we sought to test the hypothesis that Dmt1 transports copper during iron deficiency. Two model systems were utilized: the Belgrade (b) rat, expressing mutant Dmt1, and an inducible Dmt1-overexpression cell culture system. Mutant rats (b/b) were fed a semipurified, AIN93G-based control diet and phenotypically normal littermates (+/b) were fed control or iron-deficient diets for ~14 wk. An everted gut sleeve technique and a colorimetric copper quantification assay were utilized to assess duodenal copper transport. The control diet-fed +/b rats had normal hematological parameters, whereas iron-deprived +/b and b/b rats were iron deficient and Dmt1 mRNA and protein levels increased. Importantly, duodenal copper transport was similar in the control +/b and b/b rats; however, it significantly increased (~4-fold) in the iron-deprived +/b rats. Additional experiments in Dmt1 overexpressing HEK-293 cells showed that copper ((64)Cu) uptake was stimulated (∼3-fold) in the presence of an iron chelator. Dmt1 transcript stabilization due to a 3' iron-responsive element was also documented, likely contributing to increased transport activity. In summary, these studies suggest that Dmt1 enhances copper uptake into duodenal enterocytes during iron deprivation.

Isoform specific regulation of divalent metal (ion) transporter (DMT1) by proteasomal degradation.

Divalent metal ion transporter (DMT1) is the major transporter for iron entrance into mammalian cells and iron exit from endosomes during the transferrin cycle. Four major mRNA isoforms correspond to four protein isoforms, differing at 5'/3' and N-/C-termini, respectively. Isoforms are designated 1A versus 1B reflecting where transcription starts or +iron responsive element (+IRE) versus -IRE reflecting the presence/absence of an IRE in the 3' end of the mRNA. These differences imply regulation at transcriptional and posttranscriptional levels. Many proteins are degraded by a ubiquitination-dependent mechanism. Two different ubiquitin ligases (E3s) appear to be involved in DMT1 ubiquitination: Parkin or neuronal precursor cell-expressed developmentally downregulated 4 (Nedd4) family E3s which often utilize Nedd4 family interacting protein-1 and -2 (Ndfip1 and 2) to ubiquitinate their substrate proteins. Prior data suggest that Parkin ubiquitinates 1B DMT1 but not 1A DMT1 while Nedd4/Ndfips ligate ubiquitin to DMT1 in the duodenum where 1A/+IRE DMT1 predominates. Our assay for whether these systems target DMT1 depends on two HEK293 cell lines that express permanently transfected 1A/+IRE DMT1 or 1B/-IRE DMT1 after induction by doxycycline. Transient transfection with a Parkin construct before induction diminishes 1B/-IRE DMT1 detected by immune-blots but not 1A/+IRE DMT1. Mutant Parkin serves as a control that does not affect DMT1 levels. Thus DMT1 regulation in an isoform specific fashion can occur by ubiquitination and the events involved have implications for DMT1 function and disease processes.

Cellular iron transport.

Iron has a split personality as an essential nutrient that also has the potential to generate reactive oxygen species. We discuss how different cell types within specific tissues manage this schizophrenia. The emphasis in enterocytes is on regulating the body's supply of iron by regulating transport into the blood stream. In developing red blood cells, adaptations in transport manage the body's highest flux of iron. Hepatocytes buffer the body's stock of iron. Macrophage recycle the iron from effete red cells among other iron management tasks. Pneumocytes provide a barrier to prevent illicit entry that, when at risk of breaching, leads to a need to handle the dangers in a fashion essentially shared with macrophage. We also discuss or introduce cell types including renal cells, neurons, other brain cells, and more where our ignorance, currently still vast, needs to be removed by future research.

Divalent metal transporter 1 (DMT1) contributes to neurodegeneration in animal models of Parkinson's disease.

Dopaminergic cell death in the substantia nigra (SN) is central to Parkinson's disease (PD), but the neurodegenerative mechanisms have not been completely elucidated. Iron accumulation in dopaminergic and glial cells in the SN of PD patients may contribute to the generation of oxidative stress, protein aggregation, and neuronal death. The mechanisms involved in iron accumulation also remain unclear. Here, we describe an increase in the expression of an isoform of the divalent metal transporter 1 (DMT1/Nramp2/Slc11a2) in the SN of PD patients. Using the PD animal model of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) intoxication in mice, we showed that DMT1 expression increases in the ventral mesencephalon of intoxicated animals, concomitant with iron accumulation, oxidative stress, and dopaminergic cell loss. In addition, we report that a mutation in DMT1 that impairs iron transport protects rodents against parkinsonism-inducing neurotoxins MPTP and 6-hydroxydopamine. This study supports a critical role for DMT1 in iron-mediated neurodegeneration in PD.

Induction of arachidonate 12-lipoxygenase (Alox15) in intestine of iron-deficient rats correlates with the production of biologically active lipid mediators.

To identify novel genes associated with iron metabolism, we performed gene chip studies in two models of iron deficiency: iron-deprived rats and rats deficient in the principal intestinal iron transporter, divalent metal transporter 1 (i.e., Belgrade rats). Affymetrix rat genome gene chips were utilized (RAE230) with cRNA samples derived from duodenum and jejunum of experimental and control animals. Computational analysis and statistical data reduction identified 29 candidate genes, which were induced in both models of iron deficiency. Gene ontology analysis showed enrichment for genes related to lipid homeostasis, and one gene related to this physiological process, a leukocyte type, arachidonate 12-lipoxygenase (Alox15), was selected for further examination. TaqMan real-time PCR studies demonstrated strong induction of Alox15 throughout the small and large intestine, and in the liver of iron-deficient rats. Polyclonal antibodies were developed and utilized to demonstrate that proteins levels are significantly increased in the intestinal epithelium of iron-deprived rats. HPLC analysis revealed altered intestinal lipid metabolism indicative of Alox15 activity, which resulted in the production of biologically active lipid molecules (12-HETE, 13-HODE, and 13-HOTE). The overall effect is a perturbation of intestinal lipid homeostasis, which results in the production of lipids essentially absent in the intestine of control rats. We have thus provided mechanistic insight into the alteration in lipid metabolism that occurs during iron deficiency, in that induction of Alox15 mRNA expression may be the primary event. The resulting lipid mediators may be related to documented alterations in villus structure and cell proliferation rates in iron deficiency, or to structural alterations in membrane lipid composition.

Lung injury after ozone exposure is iron dependent.

We tested the hypothesis that oxidative stress and biological effect after ozone (O3) exposure are dependent on changes in iron homeostasis. After O3 exposure, healthy volunteers demonstrated increased lavage concentrations of iron, transferrin, lactoferrin, and ferritin. In normal rats, alterations of iron metabolism after O3 exposure were immediate and preceded the inflammatory influx. To test for participation of this disruption in iron homeostasis in lung injury following O3 inhalation, we exposed Belgrade rats, which are functionally deficient in divalent metal transporter 1 (DMT1) as a means of iron uptake, and controls to O3. Iron homeostasis was disrupted to a greater extent and the extent of injury was greater in Belgrade rats than in control rats. Nonheme iron and ferritin concentrations were higher in human bronchial epithelial (HBE) cells exposed to O3 than in HBE cells exposed to filtered air. Aldehyde generation and IL-8 release by the HBE cells was also elevated following O3 exposure. Human embryonic kidney (HEK 293) cells with elevated expression of a DMT1 construct were exposed to filtered air and O3. With exposure to O3, elevated DMT1 expression diminished oxidative stress (i.e., aldehyde generation) and IL-8 release. We conclude that iron participates critically in the oxidative stress and biological effects after O3 exposure.

Loss of rapid transferrin receptor recycling due to a mutation in Sec15l1 in hbd mice.

The hbd (hemoglobin deficit) mutation affects iron trafficking in murine reticulocytes. It is due to a deletion that eliminates exon 8 of Sec15l1, the homolog of a gene that encodes an exocyst component in yeast. We tested the hypothesis that the mutation causes defective slow or rapid receptor recycling by measuring endocytosis and exocytosis of transferrin by hbd reticulocytes. Endocytosis and initial iron incorporation were relatively unaffected, but exocytosis was unexpectedly slowed. These data indicate that rapid transferrin recycling is defective after pSec15l1 has mutated.

Comparison of mammalian cell lines expressing distinct isoforms of divalent metal transporter 1 in a tetracycline-regulated fashion.

DMT1 (divalent metal transporter; also known as SLC11A2, DCT1 or Nramp2) is responsible for ferrous iron uptake in the duodenum, iron exit from endosomes during the transferrin cycle and some transferrin-independent iron uptake in many cells. Four protein isoforms differ by starting in exon 1A or 2 and ending with alternative peptides encoded by mRNA that contains or lacks an IRE (iron responsive element; +/-IRE). We have compared 1A/+IRE and 2/-IRE DMT1 during regulated ectopic expression. HEK-293-F (human embryonic kidney-293-fast growing variant) cells were stably transfected with each construct expressed from a tetracycline-regulated CMV promoter. Reverse transcriptase-PCR analysis showed that construct expression responded to doxycycline. Immunofluorescence staining of cells, using antibodies specific for DMT1 isoforms, confirmed an increase in expression in the plasma membrane and cytosolic vesicles after doxycycline treatment, but with isoform specific distributions. Immunoblotting also revealed stimulation of expression. Nevertheless, both DMT1 isoforms performed similarly in assays for functional properties based on 54Mn2+ and 59Fe2+ uptake. Mn incorporation after doxycycline treatment was approximately 10-fold greater than that of untreated cells, while expression in the untreated cells was approximately 5-fold greater than in the untransfected cells. Uptake of Mn depended on addition of doxycycline, with half maximal response at approximately 1 nM doxycycline. Doxycycline-stimulated Mn and Fe uptake was linear with time for 10 min but not over longer periods. Transport exhibited a pH optimum at approximately 5.5 and dependence on incubation temperature and Mn or Fe concentration. The new cell lines should prove useful for research on metal homoeostasis, toxicological studies and efforts to identify distinctive properties of the isoforms.