Decreased transferrin receptor expression by neuromelanin cells in restless legs syndrome

Proteomic analysis of the cerebrospinal fluid of patients with restless legs syndrome/Willis-Ekbom disease

BACKGROUND

Restless Legs Syndrome/Willis-Ekbom Disease (RLS/WED) is a sensorimotor disorder that causes patients to experience overwhelming and distressing sensations in the legs compelling the patient to move their legs to provide relief. The purpose of this study was to determine if biomarkers in the cerebrospinal fluid can distinguish RLS/WED patients from neurological controls.

METHODS

We obtained CSF samples by lumbar puncture from 5 early-onset RLS/WED patients and 5 controls. We performed 2-dimensional difference in-gel electrophoresis (2D-DIGE). Proteins that were significantly altered were identified by Student's t-test. Protein spots that were differentially expressed (p ≤ 0.05, Av. Ratio ≥ 2.0) between RLS/WED and control CSF samples were identified using MALDI-TOF-MS. Statistical analyses of the validation immunoblot assays were performed using Student's t-test.

RESULTS

In this discovery study we identified 6 candidate CSF protein markers for early-onset RLS/WED. Four proteins (Cystatin C, Lipocalin-type Prostaglandin D2 Synthase, Vitamin D binding Protein, and β-Hemoglobin) were increased and 2 proteins (Apolipoprotein A1 and α-1-acid Glycoprotein) were decreased in RLS/WED patients.

CONCLUSIONS

Our results reveal a protein profile in the RLS/WED CSF that is consistent with clinical findings of disruptive sleep, cardiovascular dysfunction and painful symptoms. Moreover, protein profiles are consistent with neuropathological findings of activation of hypoxia inducible factor (HIF) pathways and alterations in dopaminergic systems. These data indicate the CSF of RLS/WED patients may provide information relevant to biological basis for RLS/WED, treatment strategies and potential new treatment targets.

Thalamic glutamate/glutamine in restless legs syndrome: increased and related to disturbed sleep

OBJECTIVE

To evaluate possible abnormal increase in thalamic glutamate/glutamine levels for restless legs syndrome (RLS) indicating increased glutamatergic activity producing arousal that at night disrupts and shortens sleep.

METHODS

(1)H MRS of the right thalamus was performed using a 1.5 T GE MRI scanner and the PROBE-P (PRESS) on 28 patients with RLS and 20 matched controls. The Glx signal (combination of mostly glutamate [Glu] and glutamine [Gln]) was assessed as a ratio to the total creatine (Cr). This study tested 2 primary hypotheses: 1) higher thalamic Glx/Cr for patients with RLS than controls; 2) thalamic Glx/Cr correlates with increased wake during the sleep period.

RESULTS

The Glx/Cr was higher for patients with RLS than controls (mean ± SD 1.20 ± 0.73 vs 0.80 ± 0.39, t = 2.2, p = 0.016) and correlated significantly with the wake time during the sleep period (r = 0.61, p = 0.007) and all other RLS-related polysomnographic sleep variables (p < 0.05) except for periodic leg movements during sleep (PLMS)/hour.

CONCLUSIONS

The primary findings introduce 2 new related dimensions to RLS: abnormalities in a major nondopaminergic neurologic system and the arousal disturbance of sleep. The strong relation of the arousal sleep disturbance to glutamate and the lack of relation to the PLMS motor features of RLS contrasts with the reverse for dopamine of a limited relation to arousal sleep disturbance but strong relation to PLMS. Understanding this dichotomy and the interaction of these 2 differing systems may be important for understanding RLS neurobiology and developing better treatments for RLS.

The sleep-immunity relationship

Research models show a strong interrelationship between sleep quality and immune function. The proinflammatory cytokines, interleukin-1, interleukin-6, and tumor necrosis factor α are classified as official sleep-regulatory substances. However, sleep-promoting properties are also possessed by several other immune and proinflammatory cellular classes. This article reviews the current physiologic evidence for the prominent somnogenic and sleep-regulatory properties inherent to these immune substances. Clinical examples of this relationship are discussed from the perspective of infectious and primarily immune-related conditions associated with significant sleep disruption and from the perspective of immune dysregulation associated with several primary sleep disorders.

Iron deficiency anemia in infancy exerts long-term effects on the tibialis anterior motor activity during sleep in childhood

OBJECTIVES

To explore the eventual connection between iron deficiency anemia (IDA) in infancy and altered leg movements during sleep in a 10-year follow-up study in children who did or did not have IDA in infancy.

SUBJECTS AND METHODS

Polysomnographic studies were performed in 32 10-year-old children (13 females and 19 males) who had IDA in infancy and 26 peers (10 females and 16 males) who were nonanemic controls. The time structure of their polysomnographically recorded leg movements (LM) was analyzed by means of an approach particularly able to consider their quantity, periodicity, and distribution during the night.

RESULTS

All LM indexes and those related to periodic LM during sleep (PLMS) were slightly higher in the former IDA group than in the control group, but not always significant. The Periodicity index during NREM sleep was higher and was reflected by a small but significant increase in PLMS separated by 10-50s intervals. PLMS index tended to be higher in former IDA children than in controls throughout the whole night.

CONCLUSION

The association between IDA in infancy, despite iron therapy, and PLMS in childhood could lead to new research in this area. Indeed, transient infantile IDA, a common nutritional problem among human infants, may turn out to be important for understanding the mechanisms of PLMS or restless legs syndrome, which are common in adulthood.

Control of sleep and wakefulness

This review summarizes the brain mechanisms controlling sleep and wakefulness. Wakefulness promoting systems cause low-voltage, fast activity in the electroencephalogram (EEG). Multiple interacting neurotransmitter systems in the brain stem, hypothalamus, and basal forebrain converge onto common effector systems in the thalamus and cortex. Sleep results from the inhibition of wake-promoting systems by homeostatic sleep factors such as adenosine and nitric oxide and GABAergic neurons in the preoptic area of the hypothalamus, resulting in large-amplitude, slow EEG oscillations. Local, activity-dependent factors modulate the amplitude and frequency of cortical slow oscillations. Non-rapid-eye-movement (NREM) sleep results in conservation of brain energy and facilitates memory consolidation through the modulation of synaptic weights. Rapid-eye-movement (REM) sleep results from the interaction of brain stem cholinergic, aminergic, and GABAergic neurons which control the activity of glutamatergic reticular formation neurons leading to REM sleep phenomena such as muscle atonia, REMs, dreaming, and cortical activation. Strong activation of limbic regions during REM sleep suggests a role in regulation of emotion. Genetic studies suggest that brain mechanisms controlling waking and NREM sleep are strongly conserved throughout evolution, underscoring their enormous importance for brain function. Sleep disruption interferes with the normal restorative functions of NREM and REM sleep, resulting in disruptions of breathing and cardiovascular function, changes in emotional reactivity, and cognitive impairments in attention, memory, and decision making.

Linking restless legs syndrome with Parkinson's disease: clinical, imaging and genetic evidence

Restless legs syndrome (RLS) and Parkinson's disease (PD) are both common neurological disorders. There has been much debate over whether an etiological link between these two diseases exists and whether they share a common pathophysiology. Evidence pointing towards a link includes response to dopaminergic agents in PD and RLS, suggestive of underlying dopamine dysfunction in both conditions. The extrastriatal dopaminergic system, in particular altered spinal dopaminergic modulation, may be variably involved in PD patients with RLS symptoms. In addition, there is now evidence that the nigrostriatal system, primarily involved in PD, is also affected in RLS. Furthermore, an association of RLS with the parkin mutation has been suggested. The prevalence of RLS has also been reported to be increased in other disorders of dopamine regulation. However, clinical association studies and functional imaging have produced mixed findings. Conflicting accounts of emergence of RLS and improvement in RLS symptoms after deep brain stimulation (DBS) also contribute to the uncertainty surrounding the issue. Among the strongest arguments against a common pathophysiology is the role of iron in RLS and PD. While elevated iron levels in the substantia nigra contribute to oxidative stress in PD, RLS is a disorder of relative iron deficiency, with symptoms responding to replacement therapy. Recent ultrasonography studies have suggested that, despite overlapping clinical features, the mechanisms underlying idiopathic RLS and RLS associated with PD may differ. In this review, we provide a concise summary of the clinical, imaging and genetic evidence exploring the link between RLS and PD.

Investigation of unmedicated early onset restless legs syndrome by voxel-based morphometry, T2 relaxometry, and functional MR imaging during the night-time hours

BACKGROUND AND PURPOSE

The pathophysiology of eRLS has not yet been elucidated. The purpose of the study was to assess, in patients with eRLS, the volume, iron content, and activation of the brain during night-time episodes of SLD and PLMs.

MATERIALS AND METHODS

Eleven right-handed unmedicated patients with eRLS (mean age, 55.3 ± 8.4 years; disease duration, 17.5 ± 14.05 years) and 11 matched control subjects were studied with a T1-weighted high-resolution 3D spoiled gradient-echo sequence used for VBM and a multisection spin-echo T2-weighted sequence used for T2 relaxometry. Additionally, a single-shot multisection gradient echo-planar sequence was used for fMRI. Brain activation was recorded during spontaneous SLD and PLMs. SPM software was used for analysis of the functional data.

RESULTS

The patients showed no regional brain volume change, but T2 relaxometry revealed decreased T2 relaxation time in the right globus pallidus internal and the STN, indicating increased iron content. The patients were observed to activate the following areas: in the left hemisphere, the primary motor and somatosensory cortex, the thalamus, the pars opercularis, and the ventral anterior cingulum; and in the right hemisphere, the striatum, the inferior and superior parietal lobules, and the dorsolateral prefrontal cortex. Bilateral activation was observed in the cerebellum, the midbrain, and the pons.

CONCLUSIONS

eRLS is associated with increased iron content of the globus pallidus internal and STN, suggesting dysfunction of the basal ganglia. Activation of the striatofrontolimbic area may represent the neurofunctional substrate mediating the repetitive compulsive movements seen in RLS.

[Frequently occurring sleep disorders]

Some sleep disorders are frequently found in the general population. The most common include restless legs syndrome, insomnia, and sleep apnea. These sleep disorders are well classified and can easily be diagnosed and treated. Since they are risk factors for cardiovascular and psychiatric disorders, early diagnosis and treatment are essential to prevent these sequelae. The impairments caused by these sleep disorders (e.g., due to daytime sleepiness, sleep disruption, or cognitive deficits) can result in a significant reduction in a person's quality of life. The diagnostic and therapeutic recommendations were taken from the S3 guideline "Nonrestorative sleep/sleep disorders" by the German Sleep Society. The levels of evidence were given according to the recommendations of the Oxford Centre for Evidence-based Medicine.

Association studies of variants in MEIS1, BTBD9, and MAP2K5/SKOR1 with restless legs syndrome in a US population

BACKGROUND

A genome-wide association study (GWAS) identified significant association between variants in MEIS1, BTBD9, and MAP2K5/SKOR1 and restless legs syndrome (RLS). However, many independent replication studies are needed to unequivocally establish a valid genotype-phenotype association across various populations. To further validate the GWAS findings, we investigated three variants, rs2300478 in MEIS1, rs9357271 in BTBD9, and rs1026732 in MAP2K5/SKOR1 in 38 RLS families and 189 RLS patients/560 controls from the US for their association with RLS.

METHOD

Both family-based and population-based case-control association studies were carried out.

RESULTS

The family-based study showed that SNP rs1026732 in MAP2K5/SKOR1 was significantly associated with RLS (P=0.01). Case-control association studies showed significant association between all three variants and RLS (P=0.0001/OR=1.65, P=0.0021/OR=1.59, and P=0.0011/OR=1.55 for rs2300478, rs9357271, and rs1026732, respectively).

CONCLUSION

Variants in MEIS1, BTBD9, and MAP2K5/SKOR1 confer a significant risk of RLS in a US population.

Restless leg syndrome: is it a real problem?

Restless legs syndrome (RLS) is a common condition that is frequently unrecognized, misdiagnosed and poorly managed. It is characterized by uncomfortable sensations deep in the legs developing at rest that compel the person to move; symptoms are worst at night and sleep disturbance is common. RLS occurs in 7%-11% of the population in Western countries, and many such people experience troublesome symptoms. Primary RLS is familial in up to two thirds of patients. RLS may also be secondary to a number of conditions including iron deficiency, pregnancy and end-stage renal failure and, perhaps, neuropathy. Secondary RLS is most common in those presenting for the first time in later life. The pathogenesis of RLS probably involves the interplay of systemic or brain iron deficiency and impaired dopaminergic neurotransmission in the subcortex of the brain. RLS is very responsive to dopaminergic therapies. Rebound of RLS symptoms during the early morning and development of severe symptoms earlier in the day (augmentation) are problematic in those treated for a prolonged period with levodopa. Consequently, dopamine agonists have become first line treatment. Anti-convulsant medications and opioids are helpful in some patients. Correction of underlying problem wherever possible is important in the management of secondary RLS.

Prevalence and characteristics of restless legs syndrome (RLS) in the elderly and the relation of serum ferritin levels with disease severity: hospital-based study from Istanbul, Turkey

The RLS is an underdiagnosed condition, characterized by unpleasant sensations in the legs. Pathophysiological mechanisms may include iron deficiency as reflected by low serum ferritin levels and dopaminergic system dysfunction. The purpose of our study was to investigate the prevalence and characteristics of RLS in the elderly and the relation of serum ferritin levels with disease severity. Ambulatory 1012 (621 women, 391 men, mean age: 73.51 ± 7.12 years) consecutive patients above 65 years who admitted to our clinic for any reason were evaluated according to the International RLS Study Group (IRLSSG) criteria: 103 patients (74 women, 29 men, mean age: 72.43 ± 6.31) (10.18%) had RLS diagnosis. Only 9 of them had known RLS. The duration of symptoms was 4.80 ± 4.65 years and 27 patients (26.2%) had positive family history. The average of serum ferritin levels was 39.13 ± 23.74 ng/ml and 71 patients (68.9%) had serum ferritin levels ≤ 50 ng/ml. The disease severity was evaluated with IRLSSG rating scale. Patients were classified as severe-very severe group (n=49) and mild-moderate group (n=54). The ferritin levels of severe-very severe disease group were lower than those of mild-moderate disease group (26.01 ± 15.82 ng/ml versus 49.87 ± 23.24 ng/ml, p<0.001). Our data show that RLS is very common in the elderly and the disease is more severe in patients with lower ferritin levels.

Restless legs syndrome, periodic leg movements, and periodic limb movement disorder in children

The characteristic symptoms of restless legs syndrome (RLS) have been known for hundreds of years and were first reported in medicine in the 1600s. Clinicians must consider potential mimics, comorbid, and associated conditions when evaluating children with RLS symptoms. The traditional differentiation of RLS from periodic limb movement disorder (PLMD) is noted in children as well as adults. Because current pediatric RLS research is sparse, this article provides the most up-to-date evidence-based as well as consensus opinion-based information on the subject of childhood RLS and PLMD. Prevalence, pathophysiology, diagnosis, treatment, and clinical associations are discussed.

Profile of altered brain iron acquisition in restless legs syndrome

Restless legs syndrome is a neurological disorder characterized by an urgency to move the legs during periods of rest. Data from a variety of sources provide a compelling argument that the amount of iron in the brain is lower in individuals with restless legs syndrome compared with neurologically normal individuals. Moreover, a significant percentage of patients with restless legs syndrome are responsive to intravenous iron therapy. The mechanism underlying the decreased iron concentrations in restless legs syndrome brains is unknown. We hypothesize that the source of the brain iron deficit is at the blood-brain interface. Thus we analysed the expression of iron management proteins in the epithelial cells of the choroid plexus and the brain microvasculature in post-mortem tissues. The choroid plexus, obtained at autopsy, from 18 neurologically normal controls and 14 individuals who had primary restless legs syndrome was subjected to histochemical staining for iron and immunostaining for iron management proteins. Iron and heavy chain ferritin staining was reduced in the epithelial cells of choroid plexus in restless legs syndrome. Divalent metal transporter, ferroportin, transferrin and its receptor were upregulated in the choroid plexus in restless legs syndrome. Microvessels were isolated from the motor cortex of 11 restless legs syndrome and 14 control brains obtained at autopsy and quantitative immunoblot analyses was performed. Expression of heavy chain ferritin, transferrin and its receptor in the microvessels from restless legs syndrome was significantly decreased compared with the controls but divalent metal protein 1, ferroportin, prohepcidin, mitochondrial ferritin and light-chain ferritin remained unchanged. The presence of an iron regulatory protein was demonstrated in the brain microvasculature and the activity of this protein is decreased in restless legs syndrome; a finding similar to our earlier report in neuromelanin cells from the substantia nigra of restless legs syndrome brains. This study reveals that there are alterations in the iron management protein profile in restless legs syndrome compared with controls at the site of blood-brain interface suggesting fundamental differences in brain iron acquisition in individuals with restless legs syndrome. Furthermore, the decrease in transferrin receptor expression in the microvasculature in the presence of relative brain iron deficiency reported in restless legs syndrome brains may underlie the problems associated with brain iron acquisition in restless legs syndrome. The consistent finding of loss of iron regulatory protein activity in restless legs syndrome brain tissue further implicates this protein as a factor in the underlying cause of the iron deficiency in the restless legs syndrome brain. The data herein provide evidence for regulation of iron uptake and storage within brain microvessels that challenge the existing paradigm that the blood-brain barrier is merely a transport system.

Restless legs syndrome in Friedreich ataxia: a polysomnographic study

Friedreich ataxia (FA) is the most common type of hereditary ataxia. Frataxin deficiency due to a GAA expansion in the first intron of chromosome 9 results in intramitochondrial iron accumulation. On the basis of the patients' complaints about sleep disturbance and pathophysiological considerations, we systematically assessed sleep history and polysomnography in FA. We included 16 consecutive FA patients (11 men, 5 women; mean age, 35.4 ± 11.1 years) with a mean disease duration of 16.5 ± 7.0 years. All patients underwent a standardized protocol including a detailed sleep history and polysomnographic recordings. Eight out of 16 patients were diagnosed with restless legs syndrome (RLS). In seven patients, RLS onset was after the onset of FA. Interestingly, FA patients with RLS had significantly lower serum ferritin levels than FA patients without RLS (76.3 ± 56.0 μg/L vs. 176.3 ± 100.7 μg/L; P = 0.043 after correction for sex and age). Moreover, periodic leg movements in wakefulness (PLMW) indices were significantly higher in FA patients with RLS than FA patients without RLS (FA with RLS, 118.1 ± 50.7; FA without RLS, 65.6 ± 44.2; P = 0.028). There was an inverse correlation between serum ferritin levels and PLMW indices obtained in all FA patients (rho -0.538, P = 0.039). RLS is common in FA. Its frequency in this primarily spinal ataxia appears consistent with the concept of dysfunctional spinal sensorimotor integration in the pathophysiology of RLS. The finding that RLS is more frequent in the context of lower serum ferritin levels in FA is interesting, but requires further investigation in larger patient samples.

Restless legs syndrome during pregnancy in Brazilian women

OBJECTIVE

The objective of this study was to identify the prevalence of restless legs syndrome (RLS) among pregnant Brazilian women, with individual diagnostic clinical interviews during the trimesters of pregnancy, and to determine the severity.

METHODS

It was a cross-sectional study. We interviewed 524 pregnant women (18-45 years old) who came to the prenatal outpatient clinic to consult an obstetrician. We used a RLS clinical-diagnostic interview and the International RLS Study Group rating scale (IRLS).

RESULTS

The prevalence of RLS during pregnancy was 13.5% in our sample, among which 90.1% of the cases started with their symptoms during pregnancy. More than half of the patients (53.5%) presented severe or very severe symptoms and the largest proportion of them (15.2%) were in their third trimester. We did not observe any demographic differences among the trimesters for RLS prevalence and RLS severity.

CONCLUSION

RLS during pregnancy is more frequent than in the general population, such that more than half of the pregnant women with RLS present it severely or very severely. It occurs especially in the third trimester.

All the wrong moves: a clinical review of restless legs syndrome, periodic limb movements of sleep and wake, and periodic limb movement disorder

Restless legs syndrome, periodic limb movements in sleep, and periodic limb movement disorder are a group of conditions that merit awareness from the medical community. These disorders are commonly encountered yet are often confused and misdiagnosed by health care professionals. It is imperative that health care providers are able to recognize these conditions to accurately diagnose, manage, and appropriately refer patients.

Advances in the science of genomics in restless legs syndrome

Restless legs syndrome (RLS) is a sleep and movement disorder that affects up to 15% of the population across the lifespan. Many health care providers have doubted its validity as an illness and are uncertain as to the implications of health care outcomes. The cause of RLS is unknown. Common treatment options include dopaminergics, benzodiazepines, and opioids; however, the pharmacogenetic mechanisms of treatment are unknown. One of the greatest genetic discoveries in 2007 was the identification of genetic variance associated with RLS. There is, however, a lack of knowledge related to RLS and its genetic basis. Therefore, the purposes of this article are to (a) provide information about the science of clinical care related to RLS; (b) present a systematic review of the literature on the status of genetics/genomics of RLS, including the discovery of associated genetic variance; and (c) identify implications of the current state of the science for health care providers and biobehavioral researchers. With the continuing genetic discoveries in RLS, health care providers, specifically nurses who play a major role in research, genetic counseling, and education, need to understand the implications of this sleep and movement disorder for patients across the lifespan.

Up-regulation of striatal adenosine A(2A) receptors with iron deficiency in rats: effects on locomotion and cortico-striatal neurotransmission

Brain iron deficiency leads to altered dopaminergic function in experimental animals, which can provide a mechanistic explanation for iron deficiency-related human sensory-motor disorders, such as Restless Legs Syndrome (RLS). However, mechanisms linking both conditions have not been determined. Considering the strong modulation exerted by adenosine on dopamine signaling, one connection could involve changes in adenosine receptor expression or function. In the striatum, presynaptic A(2A) receptors are localized in glutamatergic terminals contacting GABAergic dynorphinergic neurons and their function can be analyzed by the ability of A(2A) receptor antagonists to block the motor output induced by cortical electrical stimulation. Postsynaptic A(2A) receptors are localized in the dendritic field of GABAergic enkephalinergic neurons and their function can be analyzed by studying the ability of A(2A) receptor antagonists to produce locomotor activity and to counteract striatal ERK1/2 phosphorylation induced by cortical electrical stimulation. Increased density of striatal A(2A) receptors was found in rats fed during 3 weeks with an iron-deficient diet during the post-weaning period. In iron-deficient rats, the selective A(2A) receptor antagonist MSX-3, at doses of 1 and 3 mg/kg, was more effective at blocking motor output induced by cortical electrical stimulation (presynaptic A(2A) receptor-mediated effect) and at enhancing locomotor activation and blocking striatal ERK phosphorylation induced by cortical electrical stimulation (postsynaptic A(2A) receptor-mediated effects). These results indicate that brain iron deficiency induces a functional up-regulation of both striatal pre- and postsynaptic A(2A) receptor, which could be involved in sensory-motor disorders associated with iron deficiency such as RLS.

No significance of the COMT val158met polymorphism in restless legs syndrome

The catechol-O-methyltransferase (COMT) val(158)met polymorphism, which codes for the substitution of valine (val) by methionine (met) leading to a reduced COMT activity in homo- or heterozygous individuals, is associated with individual pain sensitivity and dopaminergic responses in Parkinson's disease as well as with various chronic painful diseases. Recent investigations support the notion of an alteration of the medial pain pathway as well as of the descending inhibitory control system in restless legs syndrome (RLS), that both involve dopaminergic transmission as well. Thus, the distribution of the COMT val(158)met polymorphism was assessed in 298 RLS patients and compared with 135 healthy controls in relation to sex, age of onset and family history. The data revealed no significant differences in the distribution of the COMT val(158)met polymorphism in RLS patients compared with the control group, also when the heterozygous and the homozygous group containing the (158)met allele were combined. In addition, sex, age of onset and family history were not associated with the COMT val(158)met polymorphism in this German population of RLS patients. The present study adds to previous mostly negative investigations on the genetic determination of dopaminergic transmission in RLS, which have - so far - only detected an association of the MAO-A activity and RLS in females in a French-Canadian population. Further investigations assessing the different COMT haplotypes and experimental and clinical parameters are nevertheless warranted.

Mitochondrial ferritin in the substantia nigra in restless legs syndrome

Restless legs syndrome (RLS) is a neurological disorder that is thought to involve decreased iron availability in the brain. Iron is required for oxidative metabolism and plays a critical role in redox reactions in mitochondria. The recent discovery of mitochondrial ferritin (FtMt) provided the opportunity to identify a potential correlation between iron and mitochondrial function in RLS. Human substantia nigra (SN) and putamen autopsy samples from 8 RLS cases and 8 controls were analyzed. Mitochondrial ferritin levels in RLS SN tissue homogenate samples assessed by immunoblots had more FtMt than control samples (p < 0.01), whereas there were no significant differences in FtMt in the putamen samples. By immunohistochemistry, neuromelanin-containing neurons in the SN were the predominant cell type expressing FtMt. Staining in neurons in RLS samples was consistently greater than that in controls. Cytochrome c oxidase staining, which reflects numbers of mitochondria, showed a similar staining pattern to that of FtMt, whereas there was less immunostaining in the RLS cases for cytosolic H-ferritin. These results suggest that increased numbers of mitochondria in neurons in RLS and increased FtMt might contribute to insufficient cytosolic iron levels in RLS SN neurons; they are consistent with the hypothesis that energy insufficiency in these neurons may be involved in the pathogenesis of RLS.

Altered dopaminergic profile in the putamen and substantia nigra in restless leg syndrome

Restless leg syndrome (RLS) is a sensorimotor disorder. Clinical studies have implicated the dopaminergic system in RLS, while others have suggested that it is associated with insufficient levels of brain iron. To date, alterations in brain iron status have been demonstrated but, despite suggestions from the clinical literature, there have been no consistent findings documenting a dopaminergic abnormality in RLS brain tissue. In this study, the substantia nigra and putamen were obtained at autopsy from individuals with primary RLS and a neurologically normal control group. A quantitative profile of the dopaminergic system was obtained. Additional assays were performed on a catecholaminergic cell line and animal models of iron deficiency. RLS tissue, compared with controls, showed a significant decrease in D2R in the putamen that correlated with severity of the RLS. RLS also showed significant increases in tyrosine hydroxylase (TH) in the substantia nigra, compared with the controls, but not in the putamen. Both TH and phosphorylated (active) TH were significantly increased in both the substantia nigra and putamen. There were no significant differences in either the putamen or nigra for dopamine receptor 1, dopamine transporters or for VMAT. Significant increases in TH and phosphorylated TH were also seen in both the animal and cell models of iron insufficiency similar to that from the RLS autopsy data. For the first time, a clear indication of dopamine pathology in RLS is revealed in this autopsy study. The results suggest cellular regulation of dopamine production that closely matches the data from cellular and animal iron insufficiency models. The results are consistent with the hypothesis that a primary iron insufficiency produces a dopaminergic abnormality characterized as an overly activated dopaminergic system as part of the RLS pathology.

The dopaminergic neurons of the A11 system in RLS autopsy brains appear normal

Although the positive clinical benefits of levodopa have fostered the concept of an abnormality in the dopaminergic system in Restless Legs Syndrome (RLS), research into the nigro-striatal (PET/SPECT studies) or tubero-infundibular (i.e., prolactin secretion) dopaminergic pathways has shown limited positive results. Some research groups have focused on the A11 dopaminergic system in the hypothalamus as this is the primary source of descending dopaminergic input into the spinal cord, an area of the nervous system believed by some investigators to be involved in RLS symptom development. Some investigators have now proposed lesioning or toxin-inhibiting the A11 system as a model of RLS, even though there has been no clear clinical or autopsy data to suggest that RLS is a neurodegenerative disorder. In this study, the A11 cell bodies were identified in 6 RLS and 6 aged-matched control autopsy cases. Cells were stained for tyrosine hydroxylase (TH), and stereological measure of the individual TH (+) cell volume was made. Regional assessment of gliosis as assessed by immunostaining for glial fibrillary acidic protein (GFAP) was made in the surrounding tissue. General histological staining was also performed on the tissue. This study found no significant difference between RLS or control cases on any measure used: TH (+) cell volume, fractional GFAP staining, or general histological examination. Nor was there histological indication of any significant inflammation or concurrent ongoing pathology in these RLS cases. The findings do not support the concept of dramatic cell loss or of a neurodegenerative process in the A11 hypothalamic region of patients with RLS. However, that does not exclude the possibility that the A11 system is involved in RLS symptoms. Changes at the cellular level in dopaminergic metabolism or at the distal synapse with changes in receptors or transporters were not evaluated in this study.

Comparative study of the influence of Thy1 deficiency and dietary iron deficiency on dopaminergic profiles in the mouse striatum

Thy-1, a glycosyl-phosphatidylinositol (GPI)-linked integral membrane protein, may play a role in stabilizing synapses. Thy1 was identified in a gene expression analysis as iron responsive, and subsequent cell culture and animal models of iron deficiency expanded this finding to the protein. The importance of Thy1 in influencing neurotransmitter feedback mechanisms led to this study to determine the relative effects of Thy1 deficiency and dietary iron deficiency on the dopaminergic system in the mouse striatum. The model for this analysis was the Thy1 null mutant mouse in the presence or absence of dietary iron deficiency. The results revealed significant differences in dopaminergic profiles associated with Thy1 and iron deficiency and also a sex effect. For example, both iron deficiency and the absence of Thy1 are associated with increased dopamine in both sexes, but the dopamine transporter is increased in these experimental groups only in female mice. In male mice, the increase in dopamine transporter is found only in the Thy1 null mutants. Increases in vesicular monoamine transporter and phosphorylated tyrosine hydroxlyase are found only in iron-deficient mice. In contrast decreased release of dopamine from synaptosomes is found only in the Thy1 null mutant animals. In general, these results indicate that a loss of Thy1 can influence the dopaminergic profile in the striatum. Furthermore, the results reveal consistent differences in the dopaminergic profile in Thy1 knockout mice compared with iron-deficient mice, indicating that the effects of iron deficiency are not due only to a change in Thy1 expression.

The severity range of restless legs syndrome (RLS) and augmentation in a prospective patient cohort: association with ferritin levels

OBJECTIVES

The aim of the study was to prospectively examine all patients with a diagnosis of RLS consulting a sleep disorders clinic and to assess RLS severity and augmentation and their associations, including ferritin levels.

METHODS

Patients were stratified into patients with RLS as ancillary diagnosis, RLS sufferers without current augmentation and RLS sufferers with current augmentation. Work-up included RLS severity scales and blood biochemical variables including indices of iron metabolism.

RESULTS

In an 18-month period, 302 patients with RLS (183 women, 119 men; mean age, 59.1+/-13.7 years) were recruited. RLS was considered idiopathic in 291 patients (96.4%). Most patients (240, 79.5%) were RLS sufferers, whereas the remaining 62 (20.5%) had RLS as ancillary diagnosis. Nineteen out of 162 patients treated with dopaminergic agents (11.7%) had current augmentation. Almost one-third of all patients (31.1%) had ferritin levels <50microg/l. Patients with an ancillary diagnosis of RLS had higher ferritin levels than RLS sufferers without current augmentation. The lowest ferritin levels were present in RLS sufferers with current augmentation 132.8+/-98.0microg/l vs. 100.6+/-84.5microg/l vs. 55.8+/-43.6microg/l; p=0.002). Patients with augmentation did not differ from non-augmented patients regarding age, gender, RLS etiology, presence of previous augmentation, or any other documented comorbidity (p>0.05).

CONCLUSION

The severity spectrum of RLS in this clinical cohort ranged from the ancillary diagnosis of RLS to augmented RLS. There was an inverse correlation between RLS severity and ferritin levels. Patients with current augmentation had the lowest ferritin levels. Our data further strengthen a putative role of low iron stores as a potential aggravator of idiopathic RLS. Moreover, low ferritin might represent a potential biomarker of RLS augmentation under dopaminergic therapy.

Alpha-melanocyte stimulating hormone and adrenocorticotropic hormone: an alternative approach when thinking about restless legs syndrome?

Alpha-melanocyte stimulating hormone (alpha-MSH) and adrenocorticotropic hormone (ACTH) possess properties suggesting that they may be involved in the pathogenesis of restless legs syndrome (RLS). We sought to determine if alpha-MSH and ACTH when administered centrally in rat recapitulate features reminiscent of RLS: increased activity, sleep fragmentation, and periodic movements during sleep. Rats were instrumented with electroencephalography, electromyography, and intracerebral cannulae and recorded for the measurement of sleep, periodic movements, and behavior following intracerebroventricular administration of alpha-MSH, ACTH, or saline. Studied behavior included grooming, locomotion, and rearing during wake and limb movements during sleep. Vigilance states included active wake (AW), quiet wake (QW), slow wave sleep I (SWSI), slow wave sleep II (SWSII), and paradoxical sleep (PS). All rats received normal saline acting as their own controls. Different rats received alpha-MSH in doses of 0.05, 0.5, 1.0, 2.0, and 6.0 microg or ACTH in doses of 0.5, 1.0, and 2.0 microg. Administered alpha-MSH caused an increase in waking behavior and prolongation of sleep latency, while ACTH stimulated waking behavior and fragmented sleep, yielding more AW and less SWSII and PS. Both hormones increased periodic movements during sleep. When administered centrally in rat, alpha-MSH and ACTH stimulate motor activity in wake, cause changes in sleep architecture, and increase periodic movements in sleep. These melanocortin hormones may play a role in the pathogenesis of RLS.

Diminished iron concentrations increase adenosine A(2A) receptor levels in mouse striatum and cultured human neuroblastoma cells

Brain iron insufficiency has been implicated in several neurological disorders. The dopamine system is consistently altered in studies of iron deficiency in rodent models. Changes in striatal dopamine D(2) receptors are directly proportional to the degree of iron deficiency. In light of the unknown mechanism for the iron deficiency-dopamine connection and because of the known interplay between adenosinergic and dopaminergic systems in the striatum we examined the effects of iron deficiency on the adenosine system. We first attempted to assess whether there is a functional change in the levels of adenosine receptors in response to this low iron. Mice made iron-deficient by diet had an increase in the density of striatal adenosine A(2A) (A(2A)R) but not A(1) receptor (A(1)R) compared to mice on a normal diet. Between two inbred murine strains, which had 2-fold differences in their striatal iron concentrations under normal dietary conditions, the strain with the lower striatal iron had the highest striatal A(2A)R density. Treatment of SH-SY5Y (human neuroblastoma) cells with an iron chelator resulted in increased density of A(2A)R. In these cells, A(2A)R agonist-induced cyclic AMP production was enhanced in response to iron chelation, also demonstrating a functional upregulation of A(2A)R. A significant correlation (r(2)=0.79) was found between a primary marker of cellular iron status (transferrin receptor (TfR)) and A(2A)R protein density. In conclusion, the A(2A)R is increased across different iron-insufficient conditions. The relation between A(2A)R and cellular iron status may be an important pathway by which adenosine may alter the function of the dopaminergic system.

Restless legs syndrome: pathophysiology, diagnosis and treatment

Restless legs syndrome (RLS) is clinically defined by the presence of (i) an urge to move the legs with or without an actual paraesthesia; (ii) a worsening of symptoms with inactivity; (iii) improvement with activity; and (iv) a worsening of symptoms in the evening and at night. Patients may use a variety of semantic phrases to describe their symptoms but all must have an urge to move. Most people with RLS also have periodic limb movements during sleep, although this is not part of the clinical diagnostic criteria. RLS is very common. About 10% of all Caucasian populations have RLS, although it may be mild in the majority of cases. Women generally outnumber men by about 2:1. As a general rule, RLS severity worsens through the first seven to eight decades of life, but may actually lessen in old age. The aetiology of RLS is only partly understood. There is a strong genetic component, and several genetic linkages and three causative genes have been identified worldwide. Several medical conditions, including renal failure, systemic iron deficiency and pregnancy, and possibly neuropathy, essential tremor and some genetic ataxias, are also associated with high rates of RLS. In all cases to date, the actual CNS pathology of RLS demonstrates reduced iron stores, in a pattern that suggests that the homeostatic control of iron is altered, not just that there is not enough iron entering the brain. The relationship between reduced CNS iron levels and the clinical phenotype or treatment response to dopaminergics is not known but generates promising speculation. Treatment of RLS is usually rewarding. Most patients respond robustly to dopamine receptor agonists. Over time, response may lessen, or the patients may develop 'augmentation', whereby they have a worsening of symptoms, usually in the form of an earlier onset. Other treatment options include gabapentin, or similar antiepileptic drugs, and opioids. High-dose intravenous iron is a promising but still experimental approach.

Pathophysiology of restless legs syndrome: evidence for iron involvement

Neuroimaging, analysis of cerebrospinal fluid, and studies on postmortem tissue are generating data that support the concept that iron availability to the brain is a contributory process to, if not a cause of, restless legs syndrome. These data are reviewed and related to the dopaminergic system because of the use of dopamine agents in treating restless legs syndrome.

Restless legs syndrome in women: a review

Restless legs syndrome (RLS) is a neurological disorder with significant negative impact on sleep and quality of life, yet data suggest that it is frequently underdiagnosed. The clinical features, diagnosis, epidemiology, pathophysiology, and treatment options for RLS are reviewed and discussed, with particular emphasis on RLS in women. RLS is characterized by unpleasant sensations causing an urge to move the legs. RLS symptoms are exacerbated by rest, relieved by movement, and worse at night than during the day. The motor and sensory symptoms of RLS can have a negative impact on patients' sleep, resulting in a reduction in daytime functioning and overall quality of life. The prevalence of RLS is reported to increase with age and to be up to almost twice as high in women as in men. The explanation for this is unknown, although there is evidence that parity may be a factor. Diagnosis of RLS is made using four essential criteria based on the patient's report of sensorimotor symptoms. Several large, double-blind, placebo-controlled studies have demonstrated that dopamine agonists, such as ropinirole and pramipexole, are an efficacious first-line therapy for the treatment of RLS symptoms. As RLS is more prevalent in women, professionals working in the field of women's health need to be aware of this condition, its differential diagnosis, and the treatment options available. Accurate diagnosis is essential to facilitate appropriate management and treatment. Dopamine agonists have been shown to be an effective therapy for patients with moderate to severe symptoms of RLS.

Altered iron metabolism in lymphocytes from subjects with restless legs syndrome

OBJECTIVE

Studies using cerebrospinal fluid, magnetic resonance imaging, and autopsy tissue have implicated a primary role for brain iron insufficiency in restless legs syndrome (RLS). If the abnormalities of brain iron regulation reflect a basic disturbance of iron metabolism, then this might be expressed at least partially in some peripheral systems. Thus the study aim was to determine whether patients with RLS and control subjects show differences in lymphocyte iron regulator proteins.

METHODS

Fasting morning blood samples were used to obtain common serum measures of iron status and to determine lymphocyte iron management proteins. Twenty-four women with early-onset RLS and 25 control women without RLS symptoms were studied.

RESULTS

RLS and control subjects were matched for age, hemoglobin, and serum iron profile. However, transferrin receptor (TfR) and DMT1 (divalent metal transporter 1 protein) levels in lymphocytes were significantly higher for RLS patients than for controls. No significant differences in ferritin subtypes or transferrin levels were found. No significant correlations were found between lymphocyte and serum indices of iron status.

INTERPRETATION

RLS lymphocytes showed an increase in ferroportin, implying increased cellular iron excretion, in the face of increased iron need (increased TfR and DMT1). In the absence of changes in H-ferritin, the findings indicate a balance between input and output with no net iron change but probable overall increase in iron turnover. The lack of any significant correlation between serum and lymphocyte iron indices indicates that iron management proteins from lymphocytes are at a minimum an alternative and independent marker of cellular iron metabolism.

Iron, the substantia nigra and related neurological disorders

BACKGROUND

Iron status is higher in the substantia nigra than in other brain regions but can fluctuate as function of diet and genetics and disease. Of particular note is the compartmentalization of the iron-enrichment in this region; the pars reticulata contains higher levels of stainable iron as compared to the pars compacta. The latter area is where the dopaminergic neurons reside. How this compartmentalization impacts the interpretation of data that iron contributes to cell death as in Parkinson's disease or iron deficiency contributes to altered dopaminergic activity is unknown. Nonetheless, that iron can influence neuronal cell death and dopamine function is clear.

METHODS

The mechanisms by which iron may be managed in the substantia nigra, particularly in the neuromelanin cells where minimal levels of ferritin the iron storage protein have been detected are addressed. The current approaches to detect iron in the substantia nigra are also reviewed. In addition, the potential mechanisms by which iron enrichment may occur in the substantia nigra are explored.

GENERAL SIGNIFICANCE

This review attempts to provide a critical evaluation of the many avenues of exploration into the role of iron in one of the most iron-enriched and clinically investigated areas of the brain, the substantia nigra.

[Restless-legs syndrome]

Restless-legs syndrome (RLS) is a sensorimotor disorder, characterized by an irresistible urge to move the legs usually accompanied or caused by uncomfortable and unpleasant sensations. It begins or worsens during periods of rest or inactivity, is partially or totally relieved by movements and is exacerbated or occurs at night and in the evening. RLS sufferers represent 2 to 3% of the general population in Western countries. Supportive criteria include a family history, the presence of periodic-leg movements (PLM) when awake or asleep and a positive response to dopaminergic treatment. The RLS phenotypes include an early onset form, usually idiopathic with a familial history and a late onset form, usually secondary to peripheral neuropathy. Recently, an atypical RLS phenotype without PLM and l-DOPA resistant has been characterized. RLS can occur in childhood and should be distinguished from attention deficit/hyperactivity disorder, growing pains and sleep complaints in childhood. RLS should be included in the diagnosis of all patients consulting for sleep complaints or discomfort in the lower limbs. It should be differentiated from akathisia, that is, an urge to move the whole body without uncomfortable sensations. Polysomnographic studies and the suggested immobilization test can detect PLM. Furthermore, an l-DOPA challenge has recently been validated to support the diagnosis of RLS. RLS may cause severe-sleep disturbances, poor quality of life, depressive and anxious symptoms and may be a risk factor for cardiovascular disease. In most cases, RLS is idiopathic. It may also be secondary to iron deficiency, end-stage renal disease, pregnancy, peripheral neuropathy and drugs, such as antipsychotics and antidepressants. The small-fiber neuropathy can mimic RLS or even trigger it. RLS is associated with many neurological and sleep disorders including Parkinson's disease, but does not predispose to these diseases. The pathophysiology of RLS includes an altered brain-iron metabolism, a dopaminergic dysfunction, a probable role of pain control systems and a genetic susceptibility with nine loci and three polymorphisms in genes serving developmental functions. RLS treatment begins with the elimination of triggering factors and iron supplementation when deficient. Mild or intermittent RLS is usually treated with low doses of l-DOPA or codeine; the first-line treatment for moderate to severe RLS is dopaminergic agonists (pramipexole, ropinirole, rotigotine). In severe, refractory or neuropathy-associated RLS, antiepileptic (gabapentin, pregabalin) or opioid (oxycodone, tramadol) drugs can be used.

Sequential compression devices for treatment of restless legs syndrome

Restless legs syndrome (RLS) is a common disorder that presents with irresistible urges to move the legs and motor restlessness, worsening in the evening. RLS commonly causes insomnia and associated daytime symptoms. Treatment of first choice for RLS is usually medication, but medications are often ineffective or poorly tolerated. An effective nonpharmacologic therapy would be highly desirable. Here we review RLS and its treatment and present data from a pilot study on the effect of a novel treatment for this condition. The objective of this study was to determine the therapeutic effect of pneumatic sequential compression devices (SCDs) on RLS symptoms. We performed an uncontrolled, prospective interventional study using SCDs on a convenience sample of adults reliably diagnosed with RLS. Patients were asked to wear the SCD for an hour each evening before the usual time of onset of restless legs symptoms. Before and after 1-3 months of SCD therapy, patients completed validated questionnaires to assess RLS severity, daytime sleepiness, and impact of RLS on quality of life in the domains of social function, daily task function, sleep quality, and emotional well-being. Compliance with SCD therapy was measured using patient-recorded logs. Of 10 patients (7 women; age range, 37-80 yr; mean age, 56 yr), symptomatic for a mean of 68 months (range, 12-360 mo), 1 could not tolerate wearing the SCD and withdrew from the protocol after 3 days. The remaining 9 patients complied with therapy 58%-100% of nights (mean, 82%). Three patients experienced complete resolution of RLS and 6 patients had improvement of symptoms. Group severity score improved from 24/40 to 8/40 (p = 0.001). Epworth Sleepiness Scale score improved from 12/24 to 8/24 (p = 0.05). Every quality of life score improved: social function from 74% to 96% (p = 0.04), daily task function 63% to 80% (p = 0.05), sleep quality 27% to 63% (p = 0.003), and emotional well-being from 49% to 83% (p = 0.02). In this group of patients, wearing the SCD in the evening for an hour improved symptoms of RLS and improved quality of life, with complete resolution of symptoms in 3 of 10 patients.

Levodopa for idiopathic restless legs syndrome: Evidence-based review

Restless legs syndrome (RLS) is a sensory motor disorder characterized by a distressing urge to move the legs and sometimes also other parts of the body usually accompanied by a marked sense of discomfort or pain in the leg or other affected body part. The prevalence of RLS is estimated at 2.7 to 5% of adults and it is more common in women. The treatment of RLS with levodopa has been reported thus a systematic synthesis of evidence is necessary to evaluate the effectiveness and safety of levodopa for RLS. Systematic review of randomized or quasi-randomized, double blind trials on levodopa. Relief of restless legs symptoms marked on a validated scale, subjective sleep quality, sleep quality measured by night polysomnography and actigraphy, quality of life measured by subjective measures, adverse events associated with the treatments. Nine eligible clinical trials were included. The subjective analyses of these studies showed contradictory results, although the objective analyses showed that treatment group had a statistically significant improvement of periodic leg movement (PLM) index, favoring the treatment group. The most commonly adverse event seen was gastrointestinal symptoms. The short-term treatment with levodopa was demonstrated effective and safety for PLM, but there was only few trials assessing long-term treatment and the augmentation phenomenon in RLS. Further long-term randomized controlled trials using standard follow-up measurements as the International RLS Study Group Rating Scale are necessary.

Restless legs syndrome and Parkinson's disease: is there an etiologic link?

The etiologic link between restless legs syndrome (RLS) and Parkinson's disease (PD) has been debated. Since dopaminergic dysfunction and response to dopaminergic agents are consistent features in RLS and PD, some authors have suggested that these two diseases may share common pathophysiology. However, presently there is not enough evidence to suggest that the actual pathophysiologic mechanism in both diseases is identical. The nigrostriatal dopaminergic system is primarily involved in PD and it is possible that the extrastriatal dopaminergic system may be variably involved in those PD patients with RLS symptoms. Further clinical, imaging, pharmacologic, and genetic studies will be needed to address the many unanswered questions related to the link between RLS and PD.