Manganese, selenium and other trace elements in spinal cord, liver and bone in motor neurone disease

Trace elements dyshomeostasis in liver and brain of weanling mice under altered dietary selenium conditions

BACKGROUND

A balanced diet containing selenium (Se) and other trace elements is essential for normal development and growth. Se has been recognized as an essential trace element; however, its interaction with other elements has not been fully investigated. In the present study, sodium (Na), magnesium (Mg), potassium (K), calcium (Ca), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), copper (Cu), zinc (Zn), Se and rubidium (Rb), were analysed in liver and brain regions under altered dietary Se intake in weanling mice to identify major discriminatory elements.

METHODS

The study investigated the effects of different levels of Se intake on the elemental composition in liver and brain tissues of weaned mice. After 24 weeks of feeding with Se adequate, deficient, and excess diets, elemental analysis was performed on the harvested tissues using Inductively coupled plasma mass spectrometry (ICP-MS). Statistical analysis that included analysis of covariance (ANCOVA), correlation coefficient analysis, principal component analysis, and partial least squares discriminant analysis were performed.

RESULTS

The ANCOVA showed statistically significant changes and correlations among the analysed elements under altered dietary Se status. The multivariate analysis showed differential changes in elements in liver and brain regions. The results suggest that long-term dietary Se alternations lead to dyshomeostasis in trace elements that are required in higher concentrations compared to Se. It was observed that changes in the Fe, Co, and Rb levels were similar in all the tissues studied, whereas the changes in Mg, Cr, and Mn levels were different among the tissues under altered dietary Se status. Additionally, the changes in Rb levels correlated with the dietary Se intake but had no relation with the tissue Se levels.

CONCLUSIONS

The findings suggest interactions between Mg, Cr, Mn, Fe, Co, and Se under altered Se status may impact cellular functions during postnatal development. However, the possible biological significance of alterations in Rb levels under different dietary Se paradigms needs to be further explored.

The study of levels from redox-active elements in cerebrospinal fluid of amyotrophic lateral sclerosis patients carrying disease-related gene mutations shows potential copper dyshomeostasis

Amyotrophic lateral sclerosis is a progressive neurodegenerative disease characterized by a loss of function of motor neurons. The etiology of this disorder is still largely unknown. Gene-environment interaction arises as a possible key factor in the development of amyotrophic lateral sclerosis. We assessed the levels of trace metals, copper (Cu), iron (Fe), and manganese (Mn), of 9 amyotrophic lateral sclerosis cases and 40 controls by measuring their content in cerebrospinal fluid. The following trace element species were quantified using ion chromatography-inductively coupled plasma mass spectrometry: univalent copper (Cu-I), divalent Cu (Cu-II), divalent Fe (Fe-II), trivalent Fe (Fe-III), divalent Mn (Mn-II), trivalent Mn (Mn-III), and also unidentified Mn species (Mn-unknown) were present in some samples. When computing the relative risks for amyotrophic lateral sclerosis through an unconditional logistic regression model, we observed a weak and imprecise positive association for iron (Fe III, adjusted odds ratio 1.48, 95% CI 0.46-4.76) and manganese (total-Mn and Mn-II; adjusted odds ratio 1.11, 95% CI 0.74-1.67, and 1.13, 95% CI 0.79-1.61, respectively). Increased risk for copper was found both in the crude analysis (odds ratio 1.14, 95% CI 0.99-1.31) and in multivariable analysis after adjusting for sex, age, and year of storage (1.09, 95% CI 0.90-1.32). Our results suggest a possible positive association between Cu and genetic amyotrophic lateral sclerosis, while they give little indication of involvement of Fe and Mn in disease, though some correlations found also for these elements deserve further investigation.

A novel hypothesis on metal dyshomeostasis and mitochondrial dysfunction in amyotrophic lateral sclerosis: Potential pathogenetic mechanism and therapeutic implications

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disorder characterized by motor dysfunctions resulting from the loss of upper (UMNs) and lower (LMNs) motor neurons. While ALS symptoms are coincidental with pathological changes in LMNs and UMNs, the causal relationship between the two is unclear. For example, research on the extra-motor symptoms associated with this condition suggests that an imbalance of metals, including copper, zinc, iron, and manganese, is initially induced in the sensory ganglia due to a malfunction of metal binding proteins and transporters. It is proposed that the resultant metal dyshomeostasis may promote mitochondrial dysfunction in the satellite glial cells of these sensory ganglia, causing sensory neuron disturbances and sensory symptoms. Sensory neuron hyperactivation can result in LMN impairments, while metal dyshomeostasis in spinal cord and brain stem parenchyma induces mitochondrial dysfunction in LMNs and UMNs. These events could prompt intracellular calcium dyshomeostasis, pathological TDP-43 formation, and reactive microglia with neuroinflammation, which in turn activate the apoptosis signaling pathways within the LMNs and UMNs. Our model suggests that the degeneration of LMNs and UMNs is incidental to the metal-induced changes in the spinal cord and brain stem. Over time psychiatric symptoms may appear as the metal dyshomeostasis and mitochondrial dysfunction affect other brain regions, including the reticular formation, hippocampus, and prefrontal cortex. It is proposed that metal dyshomeostasis in combination with mitochondrial dysfunction could be the underlying mechanism responsible for the initiation and progression of the pathological changes associated with both the motor and extra-motor symptoms of ALS.

Trace elements in ALS patients and their relationships with clinical severity

An exploratory study of trace elements in ALS and their relationships with clinical severity was detected. Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder that causes irreversible damage in humans, with the consequent loss of function of motoneurons (MNs), with a prognosis up to 5 years after diagnosis. Except to genetic rare cases it is not known the etiology of the disorder. Aim of our research is to investigate the possible role of heavy metals in the severity of the disease. In this study, by the use of plasma mass (ICP-MS), we have analyzed the content of essential and heavy metals such: Pb, Cd, Al, Hg, Mn, Fe, Cu, Zn, Se, Mg, and Ca, in blood, urine and hair of ALS patients and controls; moreover we divided the patients in two groups for disease severity and analyzed the difference among the groups, in order to study a possible involvement of metals in the severity of the damage. Our results suggest a protective role of Selenium, involved in protective antioxidant mechanisms, and a risk factor in the case of presence of Lead in blood. The levels of the other metals are not easy to interpret, because these may be due to life style and for essential metals a consequence of the disease condition, not a cause.

Blood levels of trace metals and amyotrophic lateral sclerosis

Some trace metals may increase risk of amyotrophic lateral sclerosis (ALS), whereas others may be beneficial. Our goal was to examine associations of ALS with blood levels of selenium (Se), zinc (Zn), copper (Cu), and manganese (Mn). We conducted a case-control study of 163 neurologist confirmed patients from the National Registry of Veterans with ALS and 229 frequency-matched veteran controls. We measured metal levels in blood using inductively coupled plasma mass spectrometry and estimated odds ratios (ORs) and 95% confidence intervals (CIs) for associations between ALS and a doubling of metal levels using unconditional logistic regression, adjusting for age, gender, and race/ethnicity. ALS was inversely associated with both Se (OR=0.4, 95% CI: 0.2-0.8) and Zn (OR=0.4, 95% CI: 0.2-0.8). Inverse associations with Se were stronger in patients with bulbar compared to spinal onset, worse function, longer diagnostic delay, and longer collection delay; inverse associations with Zn were stronger for those with worse function and longer collection delay. In contrast, ALS was positively associated with Cu (OR=3.4, 95% CI: 1.5-7.9). For Mn, no linear trend was evident (OR=0.9, 95% CI: 0.6-1.3, Ptrend=0.51). Associations of Se, Zn, Cu, and Mn with ALS were independent of one another. Adjustment for lead levels attenuated the positive association of ALS with Cu but did not change associations with Se, Zn, or Mn. In conclusion, Se and Zn were inversely associated with ALS, particularly among those with worse function, suggesting that supplementation with these metals may benefit such patients, while Cu was positively associated with ALS. Deficiencies of Se and Zn and excess Cu may have a role in ALS etiology.

Pathogenic Mechanisms in Sporadic Amyotrophic Lateral Sclerosis

In recognition of the 100th anniversary of Charcot’s death we have reviewed possible pathogenic mechanisms in amyotrophic lateral sclerosis (ALS). Advances in the last 5 years in molecular biology and genetics have identified mutations in the cytosolic dismutase (SODI) gene in some patients with familial ALS raising the possibility that oxidative stress may be involved in the pathogenesis. An excitotoxic pathogenesis has been implicated based on elevated plasma and CSF levels of amino acids and altered contents of amino acids in the nervous system of ALS patients and changes in the number of excitatory amino acid receptors. ALS sera containing antibodies to L-type calcium channels and the development of immune mediated lower and upper and lower motor neuron models have revitalized research efforts focusing on an immune basis for ALS. Other pathogenic mechanisms which have been the subject of recent research include elemental toxicity, apoptosis and programmed cell death and possibly a deficiency or abnormality in growth factors. Pathogenic processes for ALS must account for an increasing incidence of ALS, male preponderance, and the selective vulnerability of the corticomotoneuronal system.

Neutron activation analysis of scalp hair from ALS patients and residents in the Kii Peninsula, Japan

The aim of this study was to evaluate the accumulation of transition metals in the scalp hair of amyotrophic lateral sclerosis (ALS) patients in the Koza/Kozagawa/Kushimoto (K) area (K-ALS) in the Kii Peninsula, Japan. Metal contents were measured in the unpermed, undyed hair samples of 88 K-residents, 20 controls, 7 K-ALS patients, and 10 sporadic ALS patients using neutron activation analysis at the Research Reactor Institute, Kyoto University. A human hair standard and elemental standards were used as comparative standards. The contents of Zn, Mn, and V were higher, while that of S was lower in K-ALS patients than in the controls. The content of Mn in K-ALS patients negatively correlated with clinical durations. The content of Al was significantly higher in K-residents than in the controls, with 15.9 % of K-residents having high Mn contents over the 75th percentile of the controls. The contents of Zn, Mn, and V were high in the scalp hair of K-ALS patients and correlated with the content of Al. The accumulation of these transition metals may chronically increase metal-induced oxidative stress, which may, in turn, trigger the neuronal degeneration associated with K-ALS.

Selenium neurotoxicity in humans: bridging laboratory and epidemiologic studies

Selenium is a metalloid of considerable interest in the human from both a toxicological and a nutritional perspective, with a very narrow safe range of intake. Acute selenium intoxication is followed by adverse effects on the nervous system with special clinical relevance, while the neurotoxicity of long-term overexposure is less characterized and recognized. We aimed to address this issue from a public health perspective, focusing on both laboratory studies and the few epidemiologic human studies available, with emphasis on their methodological strengths and limitations. The frequently overlooked differences in toxicity and biological activity of selenium compounds are also outlined. In addition to lethargy, dizziness, motor weakness and paresthesias, an excess risk of amyotrophic lateral sclerosis is the effect on the nervous system which has been more consistently associated with chronic low-level selenium overexposure, particularly to its inorganic compounds. Additional research efforts are needed to better elucidate the neurotoxic effects exerted by selenium overexposure.

Cerebrospinal fluid of newly diagnosed amyotrophic lateral sclerosis patients exhibits abnormal levels of selenium species including elevated selenite

Exposure to selenium, and particularly to its inorganic forms, has been hypothesized as a risk factor for amyotrophic lateral sclerosis (ALS), a fast progressing motor neuron disease with poorly understood etiology. However, no information is known about levels of inorganic and some organic selenium species in the central nervous system of ALS patients, and recent observations suggest that peripheral biomarkers of exposure are unable to predict these levels for several Se species including the inorganic forms. Using a hospital-referred case-control series and advanced selenium speciation methods, we compared the chemical species of selenium in cerebrospinal fluid from 38 ALS patients to those of 38 reference neurological patients matched on age and gender. We found that higher concentrations of inorganic selenium in the form of selenite and of human serum albumin-bound selenium were associated with increased ALS risk (relative risks 3.9 (95% confidence interval 1.2-11.0) and 1.7 (1.0-2.9) for 0.1μg/L increase). Conversely, lower concentrations of selenoprotein P-bound selenium were associated with increased risk (relative risk 0.2 for 1μg/L increase, 95% confidence interval 0.04-0.8). The associations were stronger among cases age 50 years or older, who are postulated to have lower rates of genetic disease origin. These results suggest that excess selenite and human serum albumin bound-selenium and low levels of selenoprotein P-bound selenium in the central nervous system, which may be related, may play a role in ALS etiology.

Role of manganese in neurodegenerative diseases

Manganese (Mn) is an essential ubiquitous trace element that is required for normal growth, development and cellular homeostasis. Exposure to high Mn levels causes a clinical disease characterized by extrapyramidal symptom resembling idiopathic Parkinson's disease (IPD). The present review focuses on the role of various transporters in maintaining brain Mn homeostasis along with recent methodological advances in real-time measurements of intracellular Mn levels. We also provide an overview on the role for Mn in IPD, discussing the similarities (and differences) between manganism and IPD, and the relationship between α-synuclein and Mn-related protein aggregation, as well as mitochondrial dysfunction, Mn and PD. Additional sections of the review discuss the link between Mn and Huntington's disease (HD), with emphasis on huntingtin function and the potential role for altered Mn homeostasis and toxicity in HD. We conclude with a brief survey on the potential role of Mn in the etiologies of Alzheimer's disease (AD), amyotrophic lateral sclerosis (ALS) and prion disease. Where possible, we discuss the mechanistic commonalities inherent to Mn-induced neurotoxicity and neurodegenerative disorders.

Amyotrophic lateral sclerosis: possible role of environmental influences

This treatise briefly discusses the genetic features of ALS and reviews environmental exposures in sporadic ALS. At least 10 genetic foci are responsible for cases of familial motor neuron disease and more are yet to be discovered. Research into sporadic ALS suggests that abundant factors apparently participate in the disease process. A singular cause and unifying disease and nerve dysfunction in polyneuropathies, a multitude of genetic, toxic, autoimmune, infectious, and systematic processes seem to be at play. The ALS syndrome likely will not be dissimilar.

Plasma superoxide dismutase and glutathione peroxidase activity in sporadic amyotrophic lateral sclerosis

To determine the possible role of oxydative stress in the pathology of amyotrophic lateral sclerosis (SALS), we measured the plasma activities of superoxide dismutase (SOD) and glutathione peroxidase (GPX), together with GPX and malone dialdehyde (MDA, a marker of lipoperoxydation) plasma concentrations in a sample of 21 SALS patients and 7 normal control (NC) subjects. MDA concentration and SOD activity were significantly higher, whereas GPX activity was significantly lower in SALS patients than in NC. Increased MDA concentration provides indirect confirmation of excess lipoperoxydation. Increased plasma SOD activity might reflect the involvement of extra-cellular SOD (SOD3), a hitherto unreported finding in SALS. Impaired GPX activity, which has already been found in red blood cells and brain tissue of SALS patients, might play a part in the pathogenesis of this disease.

Essential trace element alterations in amyotrophic lateral sclerosis

Although trace elements have been implicated in the pathogenesis of amyotrophic lateral sclerosis (ALS) for a long time, new evidence has connected familial ALS with the metalloenzyme copper-zinc superoxide dismutase, thus reinforcing the study of their metabolism. This work presents the results of serum and cerebrospinal fluid levels of copper, zinc, manganese and magnesium, by atomic absorption spectrophotometry. Statistically significant decreased cerebrospinal fluid and serum copper levels were found in patients compared to the control group (20.25 +/- 7.09 vs. 30.86 +/- 16.02 SD micrograms/l and 913.21 +/- 165.55 vs. 1020.17 +/- 197.76 SD micrograms/l) while serum manganese levels were found to be increased in patients (3.59 +/- 0.89 SD micrograms/l) compared to controls (3.03 +/- 1.23 SD micrograms/l). Zinc and magnesium levels were unchanged. Our findings indicate an essential trace element imbalance in the disease.

Lead, cadmium, and selenium in the blood of patients with sporadic amyotrophic lateral sclerosis

We determined whole blood lead and cadmium levels, and serum selenium levels in patients with sporadic amyotrophic lateral sclerosis and age- and sex-matched controls. Disability due to the disease directly correlated with lead levels, and there was a strong inverse correlation with selenium concentrations. Lead and selenium concentrations tended to be similar in the cases and controls, both in the study population as a whole and after the removal from the analysis of the patients with the highest degree of disability. In the patients with limited disability, cadmium concentrations were higher than in the controls. Our findings lend limited support to a possible involvement of cadmium, but not lead, in the etiology of sporadic amyotrophic lateral sclerosis, and strongly suggest that short-term indicators of exposure are inadequate to investigate the relationship between selenium and the disease.

Analysis of trace elements in the central nerve tissues with inductively coupled plasma-mass spectrometry

To investigate the roles of various elements in neurological disorders, multi-element analysis of limited quantities of samples in the central nervous system is required. Inductively coupled plasma-mass spectrometry (ICP-MS) analysis suits this requirement, but spectral and non-spectral interferences are inevitable. We studied correction methods for the non-spectral interferences by analyzing signals of 21 elements in various concentrations of HNO3 as well as 5 major elements (Na, K, P, Ca, and Cl). Using internal standards, the interferences caused by the major elements were corrected, but the interferences caused by HNO3 were impossible to correct for the elements with high ionization potentials. Thus, we decided to use a standard addition method to correct these interferences. The spectral interferences on Mn and Fe rising from HNO3 or major elements were compared with the signals of samples. Although the interferences on Mn were negligible, those on Fe were considerable and careful blank subtraction were needed. We measured concentrations of elements in the spinal cord of 4 controls and a patient with amyotrophic lateral sclerosis (ALS) using the standard addition method. The concentrations of Mn, Se, Fe, and Zn in the controls were nearly the same as previously reported values, whereas Mn concentrations in the ALS patient were higher.

Absence of mutations in the Mn superoxide dismutase or catalase genes in familial amyotrophic lateral sclerosis

Familial amyotrophic lateral sclerosis (FALS) is an autosomal dominant, adult onset, neurological disorder caused by the degeneration of motor neurons of the cortex, brainstem and spinal cord. Recently, the defective gene in some FALS families was identified as the Cu/Zn superoxide dismutase (SOD1) gene. However, SOD1 mutations are present in approximately 20% of patients with FALS. We have tested the genes of two more free radical detoxifying enzymes, Mn superoxide dismutase (SOD2) and catalase by single strand conformation analysis (SSCA) for mutations in the remaining FALS cases. No mutations were found in the catalase enzyme in 73 unrelated FALS cases; mutations were not detected in the 66% of the SOD2 gene analyzed. FALS does not appear to be caused by mutations in the SOD2 nor the catalase genes.

Iron, selenium and glutathione peroxidase activity are elevated in sporadic motor neuron disease

Oxygen free radical damage is strongly implicated in the pathogenesis of familial motor neuron disease (MND) associated with mutation of the Cu/Zn superoxide dismutase gene, and may be relevant in sporadic MND. Selenium (Se) and iron (Fe) have important roles in free radical metabolism. Using neutron activation analysis we have demonstrated significant elevation of Se and Fe in lumbar spinal cord in MND cases (38) compared to controls (22). Analysis of enzymes involved in free radical scavenging showed a significant and specific increase in the activity of the selenoprotein enzyme glutathione peroxidase in MND spinal cord.

Mercury and selenium contents in amyotrophic lateral sclerosis in Hokkaido, the northernmost island of Japan

We evaluated the pathogenicity of mercury (Hg) and selenium (Se) which are supposed to be one of the risk factors in the development of amyotrophic lateral sclerosis (ALS). Hg and Se contents were measured in plasma, blood cells, scalp hair samples of 21 sporadic ALS patients and 36 controls, who included 19 patients with other neurological diseases, in Hokkaido, the northernmost island of Japan. Hg and Se levels in plasma and blood cells of ALS patients were significantly lower in advanced staged ALS patients than controls. Low Hg and Se contents in ALS, being correlated with their disabilities and nutritional conditions, would rather reflect the disease contracted states than the pathogenic roles in ALS.

Metallothionein immunoreactivity is increased in the spinal cord of patients with amyotrophic lateral sclerosis

Sections of the spinal cord from 10 patients with classic amyotrophic lateral sclerosis and from 10 control cases were examined by immunocytochemical methods to localize metallothionein. Metallothionein immunoreactivity was seen in the nucleus and cytoplasm of a subset of astrocytes, largely confined to the gray matter. Also, diffuse gray matter staining was observed, probably representing small glial fibers. Astrocytic metallothionein immunoreactivity (P less than 0.01) and strong gray matter matrix staining (P less than 0.03) was increased in the spinal cords from patients with amyotrophic lateral sclerosis. Although compatible with induction by metals, increased metallothionein expression in the spinal cords from patients with amyotrophic lateral sclerosis may also have resulted from inflammation or gliosis.