Brain Iron Deficiency Research Articles

Brain iron deficiency and periodic limb movement disorder with parasomnias

Brain iron deficiency and periodic limb movement disorder with parasomnias

Brain Iron Dysregulation in Iron Deficiency Anemia-Related Restless Leg Syndrome Revealed by Neuron-Derived Extracellular Vesicles: A Case-Control Study.

Brain iron deficiency (ID) and, to a degree, systemic ID have been implicated in restless leg syndrome (RLS) pathogenesis. Previously, we found increased ferritin in neuron-derived extracellular vesicles (NDEVs) in RLS, suggesting a mechanism for depleting intracellular iron by secreting ferritin-loaded NDEVs. In this study, we hypothesized that increased NDEV ferritin occurs even in RLS accompanied by systemic ID and that neuronal intracellular iron depletion in RLS also manifests as NDEV abnormalities in other iron regulatory proteins, specifically, decreased transferrin receptor (TfR) and increased ferroportin. To address these hypotheses, we studied 71 women with ID anemia, 36 with RLS, and 35 without RLS. Subjects with RLS again showed higher NDEV ferritin and also decreased TfR, suggesting diminished neuronal capacity for iron uptake. Findings inform a more complete understanding of the pathogenic role of neuronal iron homeostasis and dissociate it from peripheral ID. ANN NEUROL 2024;96:560-564.

A randomized double-blind pilot study to evaluate the efficacy, safety, and tolerability of intravenous iron versus oral iron for the treatment of restless legs syndrome in patients with iron deficiency anemia.

Restless legs syndrome (RLS) is a neurological disorder that can have a profound effect on sleep and quality of life. Idiopathic RLS is associated with brain iron insufficiency despite normal peripheral iron stores. There is, however, a five- to six-fold increase in prevalence of RLS in patients with iron deficiency anemia (IDA). Several open-label trials have demonstrated symptomatic improvement in RLS following treatment of IDA using oral or intravenous iron supplementation. To date, there have been no randomized double-blind controlled trials of intravenous iron compared with oral iron for the treatment of RLS patients with IDA. In the current study, oral ferrous sulfate and ferumoxytol were compared for efficacy and speed of response for treatment of RLS occurring in patients with IDA. The planned recruitment for this study was 70 patients with RLS and IDA, to be randomly assigned 1:1 to oral or intravenous iron, using double-blind, double-dummy procedures. At Week 6, the primary outcomes of Clinical Global Impression-Improvement score and change from baseline in the International Restless Legs Syndrome Study Group rating scale score were assessed. Due to challenges, performing the clinical trial during the COVID-19 pandemic, final-week data were found missing for 30 patients. As a result, in order to maintain the prespecified statistical analysis, an additional 30 patients were recruited. Both IV and oral iron were associated with a marked improvement in RLS symptoms, with no statistically significant difference between treatment groups. No serious adverse events were observed in either treatment group.

Cellular iron depletion enhances behavioral rhythm by limiting brain Per1 expression in mice.

Disturbances in the circadian rhythm are positively correlated with the processes of aging and related neurodegenerative diseases, which are also associated with brain iron accumulation. However, the role of brain iron in regulating the biological rhythm is poorly understood. In this study, we investigated the impact of brain iron levels on the spontaneous locomotor activity of mice with altered brain iron levels and further explored the potential mechanisms governing these effects invitro. Our results revealed that conditional knockout of ferroportin 1 (Fpn1) in cerebral microvascular endothelial cells led to brain iron deficiency, subsequently resulting in enhanced locomotor activity and increased expression of clock genes, including the circadian locomotor output cycles kaput protein (Clock) and brain and muscle ARNT-like 1 (Bmal1). Concomitantly, the levels of period circadian regulator 1 (PER1), which functions as a transcriptional repressor in regulating biological rhythm, were decreased. Conversely, the elevated brain iron levels in APP/PS1 mice inhibited autonomous rhythmic activity. Additionally, our findings demonstrate a significant decrease in serum melatonin levels in Fpn1cdh5 -CKO mice compared with the Fpn1flox/flox group. In contrast, APP/PS1 mice with brain iron deposition exhibited higher serum melatonin levels than the WT group. Furthermore, in the human glioma cell line, U251, we observed reduced PER1 expression upon iron limitation by deferoxamine (DFO; iron chelator) or endogenous overexpression of FPN1. When U251 cells were made iron-replete by supplementation with ferric ammonium citrate (FAC) or increased iron import through transferrin receptor 1 (TfR1) overexpression, PER1 protein levels were increased. Additionally, we obtained similar results to U251 cells in mouse cerebellar astrocytes (MA-c), where we collected cells at different time points to investigate the rhythmic expression of core clock genes and the impact of DFO or FAC treatment on PER1 protein levels. These findings collectively suggest that altered iron levels influence the circadian rhythm by regulating PER1 expression and thereby modulating the molecular circadian clock. In conclusion, our study identifies the regulation of brain iron levels as a potential new target for treating age-related disruptions in the circadian rhythm.

Restless legs syndrome.

Restless legs syndrome (RLS) is a common sensorimotor disorder causing significant distress and is commonly seen in the primary care setting. This article outlines the epidemiology, pathophysiology, diagnosis and management of RLS, with a focus on the primary care setting. RLS is a clinical diagnosis, although mimics exist. Brain iron deficiency, dopaminergic dysfunction and genetics underpin the poorly understood pathophysiology of this common condition. After repleting iron stores, reviewing any exacerbating medications and attending to non-pharmacological management options, there are pharmacological options that prove to be effective, although with class-specific effects that need to be considered.

Brain Iron Metabolism, Redox Balance and Neurological Diseases.

The incidence of neurological diseases, such as Parkinson's disease, Alzheimer's disease and stroke, is increasing. An increasing number of studies have correlated these diseases with brain iron overload and the resulting oxidative damage. Brain iron deficiency has also been closely linked to neurodevelopment. These neurological disorders seriously affect the physical and mental health of patients and bring heavy economic burdens to families and society. Therefore, it is important to maintain brain iron homeostasis and to understand the mechanism of brain iron disorders affecting reactive oxygen species (ROS) balance, resulting in neural damage, cell death and, ultimately, leading to the development of disease. Evidence has shown that many therapies targeting brain iron and ROS imbalances have good preventive and therapeutic effects on neurological diseases. This review highlights the molecular mechanisms, pathogenesis and treatment strategies of brain iron metabolism disorders in neurological diseases.

Change of iron content in brain regions after intravenous iron therapy in restless legs syndrome: quantitative susceptibility mapping study.

The pathomechanism of restless legs syndrome (RLS) is related to brain iron deficiency and iron therapy is effective for RLS; however, the effect of iron therapy on human brain iron state has never been studied with magnetic resonance imaging. This study aimed to investigate the change of brain iron concentrations in patients with RLS after intravenous iron therapy using quantitative susceptibility mapping (QSM). We enrolled 31 RLS patients and 20 healthy controls. All participants underwent initial baseline (t0) assessment using brain magnetic resonance imaging, serum iron status, and sleep questionnaires including international RLS Study Group rating scale (IRLS). RLS patients underwent follow-up tests at 6 and 24 weeks (t1 and t2) after receiving 1000 mg ferric carboxymaltose. Iron content of region-of-interest on QSM images was measured for 13 neural substrates using the fixed-shaped method. RLS symptoms evaluated using IRLS were significantly improved after iron treatment (t0: 29.7 ± 6.5, t1: 19.5 ± 8.5, t2: 21.3 ± 10.1; p < .001). There was no significant difference in susceptibility values between the controls and RLS patients at t0. In the caudate nucleus, putamen, and pulvinar thalamus of RLS patients, the QSM values differed significantly for three timepoints (p = .035, .048, and .032, respectively). The post-hoc analysis revealed that the QSM values increased at t1 in the caudate nucleus (66.8 ± 18.0 vs 76.4 ± 16.6, p = .037) and decreased from t1 to t2 in the putamen (69.4 ± 16.3 vs 62.5 ± 13.6, p = .025). Changes in the QSM values for the pulvinar and caudate nuclei at t1 were positively and negatively correlated with symptomatic improvement, respectively (r = 0.361 and -0.466, respectively). Intravenous iron treatment results in changes in brain iron content which correlate to reductions in RLS severity. This suggests a connection between symptom improvement and the associated specific brain regions constituting the sensorimotor network.

Effects of iron-deficient diet on sleep onset and spinal reflexes in a rodent model of Restless Legs Syndrome.

Restless Legs Syndrome (RLS) is a common sensorimotor and a sleep disorder that affects 2.5-10% of the European and North American populations. RLS is also often associated with periodic leg movements during sleep (PLMS). Despite ample evidence of genetic contributions, the underlying mechanisms that elicit the sensory and motor symptoms remain unidentified. Clinically, RLS has been correlated with an altered central iron metabolism, particularly in the brain. While several animal models have been developed to determine the outcome of an altered iron homeostasis on brain function, the potential role of an altered iron homeostasis on sleep and sensorimotor circuits has not yet been investigated. Here, we utilize a mouse model to assess the effects of an iron-deficient (ID) but non-anemic state on sleep time and episodes, and sensorimotor reflexes in male and female mice. We found that animals on the ID diet displayed an increased expression of the transferrin receptor in the spinal cord, confirming the results of previous studies that focused only on the impact of ID in the brain. We also demonstrate that the ID diet reduced hematocrit levels compared to controls but not into the anemic range, and that animals on the ID diet exhibited RLS-like symptoms with regard to sleep onset and spinal cord reflex excitability. Interestingly, the effects on the spinal cord were stronger in females than in males, and the ID diet-induced behaviors were rescued by the return of the animals to the control diet. Taken together, these results demonstrate that diet-induced ID changes to CNS function are both inducible and reversible, and that they mimic the sleep and sensorimotor RLS symptoms experienced in the clinic. We therefore propose replacing the commonly used phrase "brain iron deficiency" (BID) hypothesis in the RLS research field with the term "iron deficiency in the central nervous system" (ID-CNS), to include possible effects of altered iron levels on spinal cord function.

Restless legs syndrome in patients with epilepsy: risk analysis, polysomnography, and quality of life evaluation.

Restless legs syndrome (RLS) is a circadian rhythm related sensorimotor disorder due to brain iron deficiency, with lesion sites at the putamen and substantia nigra. However, epilepsy is a disease with abnormal electric discharge from the cortex and can be triggered with iron disequilibrium. We designed a case-control study to discover the association between epilepsy and RLS. A total of 24 patients with epilepsy and RLS and 72 patients with epilepsy without RLS were included. Most of the patients underwent polysomnography and video electroencephalogram tests and took sleep questionnaires. We collected information on seizure characteristics, including general or focal onset, epileptogenic focus, current antiseizure medications, medically responsive epilepsy or refractory epilepsy, and nocturnal attacks. The sleep architectures of the two groups were compared. We analyzed the risk factors for RLS using multivariate logistic regression. Among the patients with epilepsy, the occurrence of RLS was associated with refractory epilepsy (OR 6.422, p = 0.002) and nocturnal seizures (OR 4.960, p = 0.005). Sleep parameters were not significantly associated with RLS status. Quality of life was significantly impaired in the group with RLS in both the physical and mental domains. Refractory epilepsy and nocturnal seizures were strongly correlated with RLS in patients with epilepsy. RLS should be considered a predictable comorbidity in patients with epilepsy. The management of RLS not only led to better control of the patient's epilepsy but also improved their quality of life.

The divergent effects of astrocyte ceruloplasmin on learning and memory function in young and old mice

Ceruloplasmin (CP) plays an important role in maintaining iron homeostasis. Cp gene knockout (Cp-/-) mice develop a neurodegenerative disease with aging and show iron accumulation in the brain. However, iron deficiency has also been observed in 3 M Cp-/- mice. The use of systemic Cp gene knockout is insufficient to reveal specific functions for CP in the central nervous system. Considering recent discoveries that astrocytes synthetize the majority of brain CP, we generated astrocyte conditional Cp knockout (CpGfapcKO) mice, and found that iron contents decreased in the cerebral cortex and hippocampus of young (6 M) and old (18 M) CpGfapcKO mice. Further experiments revealed that 6 M CpGfapcKO mice exhibited impaired learning and memory function, while 18 M CpGfapcKO mice exhibited improved learning and memory function. Our study demonstrates that astrocytic Cp deletion blocks brain iron influx through the blood-brain-barrier, with concomitantly increased iron levels in brain microvascular endothelial cells, resulting in brain iron deficiency and down-regulation of ferritin levels in neurons, astrocytes, microglia and oligodendrocytes. At the young age, the synapse density, synapse-related protein levels, 5-hydroxytryptamine and norepinephrine, hippocampal neurogenesis and myelin formation were all decreased in CpGfapcKO mice. These changes affected learning and memory impairment in young CpGfapcKO mice. In old CpGfapcKO mice, iron accumulation with aging was attenuated, and was accompanied by the alleviation of the ROS-MAPK-apoptosis pathway, Tau phosphorylation and β-amyloid aggregation, thus delaying age-related memory decline. Overall, our results demonstrate that astrocytic Cp deletion has divergent effects on learning and memory function via different regulatory mechanisms induced by decreased iron contents in the brain of mice, which may present strategies for the prevention and treatment of dementia.

Striatal mechanism of the restless legs syndrome.

Brain iron deficiency has been reported to be associated with the restless legs syndrome (RLS). However, 30%-50% of RLS patients do not respond to iron therapy, indicating that mechanisms other than brain iron deficiency may also participate in this disease. The striatum is known to be involved in the modulation of motor activity. We speculated that dysfunction of the striatum may induce RLS. Two groups, wild-type (WT) and iron-deficient (ID) rats were used. Each group was divided into two subgroups, control and N-methyl-d-aspartate striatal-lesioned. After baseline recording, striatal-lesioned wild-type (WT-STL) and striatal-lesioned iron-deficient (ID-STL) rats were given pramipexole and thioperamide injections. Iron-deficient and ID-STL rats were then given a standard rodent diet for 4 weeks, and their sleep and motor activity were recorded. WT-STL rats showed periodic leg movements (PLM) in wake, an increase in PLM in slow wave sleep (SWS), a decrease in rapid-eye-movement sleep, and a decrease in the daily average duration of episodes in SWS. The sleep-wake pattern and motor activity did not differ between ID and ID-STL rats. Thioperamide or pramipexole injection decreased PLM in sleep and in wake in WT-STL rats and ID-STL rats. Unlike ID rats, whose motor hyperactivity can be reversed by iron replacement, PLM in wake and in sleep in ID-STL rats were not fully corrected by iron treatment. Lesions of the striatum generate RLS-like activity in rats. Dysfunction of the striatum may be responsible for failure to respond to iron treatment in some human RLS patients.

Brain Iron Deficiency Changes the Stoichiometry of Adenosine Receptor Subtypes in Cortico-Striatal Terminals: Implications for Restless Legs Syndrome.

Brain iron deficiency (BID) constitutes a primary pathophysiological mechanism in restless legs syndrome (RLS). BID in rodents has been widely used as an animal model of RLS, since it recapitulates key neurochemical changes reported in RLS patients and shows an RLS-like behavioral phenotype. Previous studies with the BID-rodent model of RLS demonstrated increased sensitivity of cortical pyramidal cells to release glutamate from their striatal nerve terminals driving striatal circuits, a correlative finding of the cortical motor hyperexcitability of RLS patients. It was also found that BID in rodents leads to changes in the adenosinergic system, a downregulation of the inhibitory adenosine A1 receptors (A1Rs) and upregulation of the excitatory adenosine A2A receptors (A2ARs). It was then hypothesized, but not proven, that the BID-induced increased sensitivity of cortico-striatal glutamatergic terminals could be induced by a change in A1R/A2AR stoichiometry in favor of A2ARs. Here, we used a newly developed FACS-based synaptometric analysis to compare the relative abundance on A1Rs and A2ARs in cortico-striatal and thalamo-striatal glutamatergic terminals (labeled with vesicular glutamate transporters VGLUT1 and VGLUT2, respectively) of control and BID rats. It could be demonstrated that BID (determined by measuring transferrin receptor density in the brain) is associated with a selective decrease in the A1R/A2AR ratio in VGLUT1 positive-striatal terminals.

Quantitative susceptibility mapping reveals brain iron deficiency in children with attention-deficit/hyperactivity disorder: a whole-brain analysis.

To quantitatively measure and compare the whole-brain iron deposition between attention-deficit/hyperactivity disorder (ADHD) patients and typically developing (TD) children using the quantitative susceptibility mapping (QSM) technique. This study was approved by the institutional review board of our institution (No. [2019]328). Fifty-one patients between 6 and 14years with clinical diagnosis of ADHD and 51 age- and gender-paired TD children were enrolled. For each participant, the 3D T1 and multi-echo GRE sequence were performed to acquire the whole-brain data with 3.0-T MRI. The QSM maps were calculated using STISuite toolbox. After normalizing the QSM images to MNI space, the voxel-based analysis was used to compare the iron content between the two groups. Pearson's correlation test was used to assess the associations between the iron content and the score of the tablet-PC-based cancellation test, which was done to evaluate the attention concentration level. Iron deficiency was observed in several brain regions in children with ADHD, including bilateral striatums, anterior cingulum, olfactory gyrus, and right lingual gyri. In further correlation analysis, the left anterior cingulum was found to show positive correlation with the symptom severity (r = 0.326, p < 0.05). Our study demonstrated that the iron deficiency in several brain regions might be related with ADHD, which might be valuable for further studies. And QSM might have the potential efficacy in the auxiliary diagnosis of ADHD. • Iron deficiency was observed in several brain regions in children with ADHD, which include bilateral striatums, the critical regions in the dopaminergic transmitter system. • The iron content in the left ACG may have association with the symptom severity of ADHD. • QSM might have the potential efficacy in the auxiliary diagnosis of ADHD.

Revisiting brain iron deficiency in restless legs syndrome using magnetic resonance imaging

Study objectivesStudies on brain iron content in restless legs syndrome (RLS) using magnetic resonance imaging (MRI) are heterogeneous. In this study, we sought to leverage the availability of a large dataset including a range of iron-sensitive MRI techniques to reassess the association between brain iron content and RLS with added statistical power and to compare these results to previous studies. MethodsThe relaxation rates R2, R2′, and R2* and quantitative susceptibility are MRI parameters strongly correlated to iron content. In general, these parameters are sensitive to magnetic field variations caused by iron particles. These parameters were quantified within iron-rich brain regions using a fully automatized approach in a cohort of 72 RLS patients and individually age and gender-matched healthy controls identified from an existing dataset acquired at the Sleep Laboratory of the Department of Neurology, Medical University of Innsbruck. 3 T-MRI measures were corrected for age and volume of the segmented brain nuclei and results were compared with previous findings in a meta-analysis. ResultsIn our cohort, RLS patients had increased R2* signal in the caudate and increased quantitative susceptibility signal in the putamen and the red nucleus compared to controls, suggesting increased iron content in these areas. The meta-analysis revealed no significant pooled effect across all brain regions. Furthermore, potential publication bias was identified for the substantia nigra. ConclusionsNormal and increased iron content of subcortical brain areas detected in this study is not in line with the hypothesis of reduced brain iron storage, but favors CSF investigations and post mortem studies indicating alteration of brain iron mobilization and homeostasis in RLS.

Dose- and sex-dependent effects of phlebotomy-induced anemia on the neonatal mouse hippocampal transcriptome.

Background:Phlebotomy-induced anemia (PIA) is universal and variable in degree among preterm infants and may contribute to neurodevelopmental risk. In mice, PIA causes brain tissue hypoxia, iron deficiency, and long-term sex-dependent neurobehavioral abnormalities. The neuroregulatory molecular pathways disrupted by PIA underlying these effects are unknown.Methods:Male and female pups were phlebotomized daily from postnatal day (P)3-P14 via facial venipuncture to target hematocrits of 25% (moderate, mPIA) and 18% (severe, sPIA). P14 hippocampal RNA from non-bled control and PIA mice was sequenced by Next-Generation Sequencing to identify differentially-expressed-genes (DEGs) that were analyzed using Ingenuity Pathway Analysis.Results:mPIA females showed the least DEGs (0.5% of >22,000 genes) whereas sPIA females had the most (8.6%), indicating a dose-dependent effect. mPIA and sPIA males showed similar changes in gene expression (5.3% and 4.7%, respectively), indicating a threshold effect at mPIA. The pattern of altered genes induced by PIA indicate sex-specific and anemia-dose-dependent effects with increased pro-inflammation in females and decreased neurodevelopment in males.Conclusion:These gene-expression changes may underlie the reduced recognition memory function in male and abnormal social-cognitive behavior in female adult mice following neonatal PIA. These results parallel clinical studies demonstrating sex-specific behavioral outcomes as a function of neonatal anemia.

Restless legs syndrome.

Restless legs syndrome (RLS) is a common sensorimotor disorder characterized by an urge to move that appears during rest or is exacerbated by rest, that occurs in the evening or night and that disappears during movement or is improved by movement. Symptoms vary considerably in age at onset, frequency and severity, with severe forms affecting sleep, quality of life and mood. Patients with RLS often display periodic leg movements during sleep or resting wakefulness. RLS is considered to be a complex condition in which predisposing genetic factors, environmental factors and comorbidities contribute to the expression of the disorder. RLS occurs alone or with comorbidities, for example, iron deficiency and kidney disease, but also with cardiovascular diseases, diabetes mellitus and neurological, rheumatological and respiratory disorders. The pathophysiology is still unclear, with the involvement of brain iron deficiency, dysfunction in the dopaminergic and nociceptive systems and altered adenosine and glutamatergic pathways as hypotheses being investigated. RLS is poorly recognized by physicians and it is accordingly often incorrectly diagnosed and managed. Treatment guidelines recommend initiation of therapy with low doses of dopamine agonists or α2δ ligands in severe forms. Although dopaminergic treatment is initially highly effective, its long-term use can result in a serious worsening of symptoms known as augmentation. Other treatments include opioids and iron preparations.

Quantitative synthetic MRI reveals grey matter abnormalities in children with drug-naïve attention-deficit/hyperactivity disorder.

To investigate the quantitative profiles of brain grey matter (GM) in pediatric drug-naïve ADHD patients using synthetic magnetic resonance imaging (SyMRI). A total of 37 drug-naïve pediatric ADHD and 27 age- and gender-matched healthy controls (HC) were enrolled in this study. Each subject underwent both SyMRI and conventional 3D T1-FSPGR scans. Quantitative parameters, T1 and T2 maps, were extracted from the SyMRI data. Between-group quantitative maps were compared using a general linear model analysis. Pearson correlation analysis was conducted to assess the association between significantly altered MR indices and clinical measurements in ADHD. Compared with the HC group, altered T1 and T2 relaxometry times in the ADHD group were mainly distributed in GM regions of the cerebellum, attention and execution control network, default mode network, and limbic areas. Moreover, the T1 value of the right cerebellum 8 was negatively correlated with the attention concentration level in ADHD (R = 0.140, P = 0.0225). With regards to T2 map, the associations were observed between the attention level of ADHD patients and left fusiform gyrus (R = 0.251, P = 0.0016), and right cerebellum crus2 (R = 0.142, P = 0.0214). Altered T1, T2 values found in specific regions of GM, including cerebellum, attention and execution control network, default mode network, and limbic areas, may reveal widespread micromorphology changes, i.e., brain iron deficiency, low myelin content, and enlarged vascular interstitial space in ADHD patients. Thus, T1, T2 values might be promising imaging markers for future ADHD studies.

Akathisia and Restless Legs Syndrome

Akathisia is an urgent need to move that is associated with treatment with dopamine receptor blocking agents (DRBAs) and with restless legs syndrome (RLS). The pathogenetic mechanism of akathisia has not been resolved. This article proposes that it involves an increased presynaptic dopaminergic transmission in the ventral striatum and concomitant strong activation of postsynaptic dopamine D1 receptors, which form complexes (heteromers) with dopamine D3 and adenosine A1 receptors. It also proposes that in DRBA-induced akathisia, increased dopamine release depends on inactivation of autoreceptors, whereas in RLS it depends on a brain iron deficiency–induced down-regulation of striatal presynaptic A1 receptors.

Brain iron deficiency and affected contextual fear memory in mice with conditional Ferroportin1 ablation in the brain.

Fear memory is a pivotal biological function by which organisms can predict possible danger to avoid or reduce harm. However, dysregulation of fear memory processing may lead to pathological fear or anxiety and produce serious clinical symptoms, such as post-traumatic stress disorder (PTSD). Iron deficiency (ID) is reported to inhibit the initiation of fear memory. In our study, we found that ferroportin1 (FPN1), the only known cellular iron export protein in mammals, and ablation in neurons and astrocytes caused iron deficiency in the cortex and hippocampus. However, little is known about its role in the development of fear memory. Moreover, direct evidence of the role of FPN1, or the related molecular mechanisms of such a role, in balancing brain iron homeostasis, especially in neuronal cells, is lacking. Herein, we deleted Fpn1 in mouse neurons, using Nestin-cre transgenic mice, and explored the impact on neuronal iron recycling and brain iron homeostasis in the cortex and hippocampus. We investigated the response of the mice to contextual fear and found that formation of fear memory was impeded after neuronal FPN1 depletion. We also found that FPN1 ablation in neurons and astrocytes caused an atypical expression of iron metabolism-related proteins in these two regions: decreased expression of DMT1, Ft-H, and Ft-L, and increased TfR1 expression. In addition, the decreased FPN1 in brain microvascular endothelial cells (BMVECs) also shed light on the cause of the decreased iron delivery to the brain through the blood-brain barrier (BBB). Our research highlights the major role played by FPN1 in brain iron homeostasis and identifies a potential target for the treatment of PTSD.

0796 Dipyridamole for the Treatment of RLS: Preliminary Results of a Cross-Over, Placebo-Controlled, Double-Blind Trial

Abstract Introduction Recent animal models of restless legs syndrome (RLS) suggest that brain iron deficiency is associated with a hypoadenosinergic state, with downregulation of adenosine A1 receptors (A1R) in the striatum. Dipyridamole is a non-selective inhibitor of ENT1/ENT2 (the main reuptake mechanism of adenosine) and increases thereby extracellular adenosine. We hypothesized that treatment with dipyridamole would improve RLS symptoms more than placebo. Methods We performed a randomized, double-blind, placebo-controlled clinical trial on 15 previously untreated idiopathic RLS patients that underwent a two week treatment with either 300 mg dipyridamol or placebo (randomized for the order of treatments), following a cross-over design. Treatment started with a dose of 100 mg/day, followed by a forced up-titration to 200 mg on day 4, and to 300 mg on day 7. Severity was assessed at baseline, day 7 and day 14 of each treatment condition by means of the IRLS and CGI scales. The primary endpoint was therapeutic response (50% improvement in IRLS total score). Results Fifteen patients (nine women), never before treated with dopaminergic agents, completed both arms of the study. Mean age was 60,2 (±7,1), and the mean duration of illness was 6,03 (±3,1) yrs. IRLS score improved during treatment with dipyridamole from a mean (±S.D.) of 24,36 (±3,3) to 9,78 (±3,4), in contrast to a change from 23,9 (±3,8) to 16,6 (±3,7) under placebo (p&amp;lt; 0.05). Corresponding improvements on the CGI were 61,3% and 11,8% for dipyridamole and placebo, respectively. 7/ 15 patients improved by more than 50% during treatment with dipyridamole vs. 4/15 under placebo. Main side effects were abdominal cramps, diarrhea, dizziness, and flushing. Conclusion These preliminary results suggest that dipyridamole is an effective agent on RLS symptoms. It also provides evidence of hypoadenosinergic mechanisms playing a central role in RLS. Support No funding was provided for this investigation.