The role of metallobiology and amyloid-ß peptides in Alzheimer's disease.

The biggest risk factor for Alzheimer's disease is the process of ageing, but the mechanisms that lead to the manifestation of the disease remain to be elucidated. Why age triggers the disease is unclear but an emerging theme is the inability for a cell to efficiently maintain many key processes such as energy production, repair, and regenerative mechanisms. Metal ions are essential to the metabolic function of every cell. This review will explore the role and reported changes in metal ions in Alzheimer disease, particularly the brain, blood and cerebral spinal fluid, emphasizing how iron, copper and zinc may be involved through the interactions with amyloid precursor protein, the proteolytically cleaved peptide amyloid-beta (Aß), and other related metalloproteins. Finally, we explore the monomeric makeup of possible Aß dimers, what a dimeric Aß species from Alzheimer's disease brain tissue is likely to be composed of, and discuss how metals may influence Aß production and toxicity via a copper catalyzed dityrosine cross-link.

The Association of Essential Metals with APOE Genotype in Alzheimer's Disease.

BACKGROUND: The major confirmed genetic risk factor for late-onset, sporadic Alzheimer's disease (AD) is variant ɛ4 of apolipoprotein E gene (APOE). It is proposed that ApoE, a protein involved in transport of cholesterol to neurons can cause neurodegeneration in AD through interaction with metals. Previous studies mostly associated copper, iron, zinc, and calcium with ApoE4-mediated toxicity. OBJECTIVE: To test the association of essential metals with APOE genotype. METHODS: We compared plasma and cerebrospinal fluid (CSF) levels of copper, zinc, iron, sodium, magnesium, calcium, cobalt, molybdenum, manganese, boron, and chromium, and CSF ferritin levels among AD, mild cognitive impairment (MCI) patients, and healthy controls (HC) with different APOE genotype. RESULTS: Sodium, copper, and magnesium levels were increased in carriers of ɛ4 allele. Additionally, the increase in sodium, calcium and cobalt plasma levels was observed in carriers of ɛ4/ɛx genotype. The decrease in boron plasma levels was observed in carriers of ɛ4 allele and ɛ4/ɛ4 genotype. Additionally, CSF zinc levels as well as plasma sodium levels were increased in AD patients compared to HC. CONCLUSION: These results indicate that the molecular underpinnings of association of essential metals and metalloids with APOE should be further tested and clarified in vivo and in vitro.

Cerebrospinal Fluid Metals and the Association with Cerebral Small Vessel Disease.

BACKGROUND: Brain metal homeostasis is essential for brain health, and deregulation can result in oxidative stress on the brain parenchyma. OBJECTIVE: Our objective in this study was to focus on two hemorrhagic MRI manifestations of small vessel disease [cerebral microbleeds (CMBs) and cortical superficial siderosis (cSS)] and associations with cerebrospinal fluid (CSF) iron levels. In addition, we aimed to analyze CSF biomarkers for dementia and associations with CSF metal levels. METHODS: This is a cross-sectional study of 196 patients who underwent memory clinic investigation, including brain MRI. CSF was collected and analyzed for metals, amyloid-ß (Aß) 42, total tau (T-tau), and phosphorylated tau (P-tau), and CSF/serum albumin ratios. Statistical analyses were performed using generalized linear models. RESULTS: No significant difference was found between CSF metal levels across diagnostic groups. Higher iron and copper levels were associated with higher CSF levels of Aß42, T-tau, P-tau, and CSF/serum albumin ratios (p < 0.05). Zinc was associated with higher CSF/serum albumin ratios. There was no significant association between CMBs or cSS and CSF iron levels. An increase in CSF iron with the number of CMBs was seen in APOEɛ4 carriers. CONCLUSION: CSF iron levels are elevated with cerebral microbleeds in APOEɛ4 carriers, with no other association seen with hemorrhagic markers of small vessel disease. The association of elevated CSF iron and copper with tau could represent findings of increased neurodegeneration in these patients.

Zinc concentration in serum and cerebrospinal fluid simultaneously decrease in children with febrile seizure: findings from a prospective study in Bangladesh.

OBJECTIVE: Since the underlying mechanisms of febrile seizure (FS) having multi-factorial aetiology yet remains unclear, we conducted this prospectively designed cross-sectional study to determine if there was any simultaneous change in zinc (Zn) concentration (conc.) in serum and cerebrospinal fluid (CSF) among the FS children in comparison to their matched non-seizure febrile (NSF) peers. METHODS: Zn concentration (level) in both serum (intravenous blood) and CSF (lumber puncture: LP) of 50 children with FS and 30 NSF peers (serving as control) were measured employing graphite furnace atomic absorbance spectrophotometer. Data were analysed to compare Zn level between two groups using appropriate statistical tools employing SPSS/Windows 12.0. RESULTS: Mean Zn conc. in both serum and CSF was less in FS children (464.60 +/- 64.57 and 46.28 +/- 7.46, respectively) than their matched NSF peers (749.33 +/- 73.19 microg/L and 111.28 +/- 19.11 microg/L, respectively) showing significant differences both in serum (p < 0.001) and CSF (p < 0.001). None of serum or CSF-Zn differed significantly with age, degree and duration of fever between FS and NSF peers. CSF-Zn among these children showed an upward trend in LP specimen taken beyond 12 h following FS episodes. CONCLUSION AND RECOMMENDATION: Serum and CSF-Zn simultaneously decreased in FS children in comparison to their matched NSF peers. Further prospectively designed multicentral studies are recommended to conduct in geographically diverse regions involving larger sample to confirm or refute our findings. It remains crucial in standardizing/strengthening national seizure prevention protocol with adequate Zn supplementation.

Species fractionation in a case-control study concerning Parkinson's disease: Cu-amino acids discriminate CSF of PD from controls.

BACKGROUND: Parkinson's disease is affecting about 1% of the population above 65 years. Improvements in medicine support prolonged lifetime which increases the total concentration of humans affected by the disease. It is suggested that occupational and environmental exposure to metals like iron (Fe), manganese (Mn), copper (Cu) and zinc (Zn) can influence the risk for Parkinson's disease. These metals play a key role as cofactors in many enzymes and proteins. METHODS: In this case-control study, we investigated the Mn-, Fe-, Cu- and Zn-species in cerebrospinal fluid (CSF) by size-exclusion chromatography hyphenated to inductively coupled plasma mass spectrometry (SEC-ICP-MS) and the total concentration of these metals by inductively coupled plasma sector field mass spectrometry (ICP-sf-MS). RESULTS: The investigation of total metal concentration and speciation provided only minor changes, but it produced strong significance for a number of ratios. The analysis revealed a strong change in the ratio between total concentration of Fe and the amino acid-fraction of Cu. This could be observed when analyzing both the respective element concentrations of the fraction (which also depends on individual variation of the total element concentration) as well as when being expressed as percentage of total concentration (normalization) which more clearly shows changes of distribution pattern independent of individual variation of total element concentrations. CONCLUSION: Speciation analysis, therefore, is a powerful technique to investigate changes in a case-control study where ratios of different species play an important role.

Separation of proteins including metallothionein in cerebrospinal fluid by size exclusion HPLC and determination of trace elements by HR-ICP-MS.

A method to study the protein binding patterns of trace elements in human cerebrospinal fluid (CSF) is described. Proteins in CSF samples were separated by size exclusion chromatography combined with high performance liquid chromatography (SEC-HPLC). The column was calibrated to separate proteins in the molecular weight range 6-70 kDa. Fractions were then analyzed off-line for trace elements using high resolution inductively coupled plasma mass spectrometry (HR-ICP-MS). We were able to accurately determine more than 10 elements of clinical interest in the CSF fractions. Results are presented for Cd, Mn, Fe, Pb, Cu and Zn. The total concentrations of 16 trace elements in human plasma and CSF are also presented. The method was able to differentiate the relative contribution of metallothionein and other proteins towards metal binding in human CSF.

Significance of Low Nanomolar Concentration of Zn2+ in Artificial Cerebrospinal Fluid.

Much less attention has been paid to Zn2+ in artificial cerebrospinal fluid (ACSF), i.e., extracellular medium, used for in vitro slice experiments than divalent cations such as Ca2+. Approximately 2 mM Ca2+ is added to conventional ACSF from essentiality of Ca2+ signaling in neurons and glial cells. However, no Zn2+ is added to it, even though the importance of Zn2+ signaling in them is recognizing. On the other hand, synaptic Zn2+ homeostasis is changed during brain slice preparation. Therefore, it is possible that not only neuronal excitation but also synaptic plasticity such as long-term potentiation is modified in ACSF without Zn2+, in which original physiology might not appear. The basal (static) levels of intracellular (cytosolic) Zn2+ and Ca2+ are not significantly different between brain slices prepared with conventional ACSF without Zn2+ and pretreated with ACSF containing 20 nM ZnCl2 for 1 h. In the case of mossy fiber excitation, however, presynaptic activity assessed with FM 4-64 is significantly suppressed in the stratum lucidum of brain slices pretreated with ACSF containing Zn2+, indicating that hippocampal excitability is enhanced in brain slices prepared with ACSF without Zn2+. The evidence suggests that low nanomolar concentration of Zn2+ is necessary for ACSF. Furthermore, exogenous Zn2+ has opposite effect on LTP induction between in vitro and in vivo experiments. It is required to pay attention to extracellular Zn2+ concentration to understand synaptic function precisely.

Decreased circulating Zinc levels in Parkinson's disease: a meta-analysis study.

There is no consensus on the involvement of zinc (Zn) dysfunctions in Parkinson's Disease (PD). We performed a meta-analysis to evaluate whether circulating Zn levels in the serum, plasma, and cerebrospinal fluid (CSF) are altered in PD. Twenty-three published studies were selected by searching the databases of PubMed and China National Knowledge Infrastructure (CNKI). A total of 803 PD patients and 796 controls, 342 PD patients and 392 controls, and 135 PD patients and 93 controls were included to study Zn levels in the serum, plasma, and CSF, respectively. Our meta-analysis showed that the serum Zn levels were significantly lower in PD patients compared with health controls (SMD = -0.59; 95% CI [-1.06, -0.12]; P = 0.014). A reduced Zn levels in PD patients were found when serum and plasma studies were analyzed together (SMD = -0.60, 95% CI [-0.98; -0.22]; p = 0.002). PD patients had a tendency toward reduced CSF Zn levels compared with health controls (SMD = -0.50; 95% CI [-1.76, 0.76]; P = 0.439), but no statistical significance was obtained and this data did not allow conclusions due to a small sample size of CSF studies. This study suggests that reduced Zn levels in the serum and plasma are associated with an increased risk for PD.

[Determination of trace elements in cerebrospinal fluid (CSF) of patients suffering cerebrovascular disease by atomic absorption spectrometry].

The contents of some trace elements such as zinc, copper, iron and cadmium in cerebrospinal fluid (CSF) of normal persons and the patients who suffered cerebral hemorrhage or infarction were determined directly by atomic absorption spectrometry. The method is simple and convenient with a recovery ratio by standard addition being 97.6% to 104.8%, and a relative standard deviation (RSD) is lower than 5%. The test showed that except for the content copper lower than normal, the patients suffering cerebrovascular disease have much higher contents of zinc, iron and cadmium. The result provides useful data for studying the relation between the contents of these trace elements and cerebrovascular disease, as well as diagnosing, treating and preventing this disease.

Negative correlation between CSF zinc level and anxiety in male Chinese subjects.

Zinc is crucial for brain development and psychiatric regulation. In the present study, we investigated the relationship between cerebrospinal fluid (CSF) zinc level and anxiety in a group of male Chinese subjects. Results demonstrated that zinc levels had no considerable interindividual variations, ranging from 8.37 to 16.83µm. Correlation analyses revealed that CSF Zinc levels were positively correlated with education years (r=0.225, p=0.024) and negatively correlated with SAS scores (r=-0.287, p=0.004), but not associated with age or BMI. In conclusion, this present study suggests that CSF zinc level is associated with anxiety.

Zinc in Alzheimer's Disease: A Meta-Analysis of Serum, Plasma, and Cerebrospinal Fluid Studies.

To evaluate whether zinc levels in serum, plasma, and cerebrospinal fluid are altered in Alzheimer's disease (AD), we performed meta-analyses of 27 studies on the topic published from 1983 to 2014. The subjects' sample obtained by merging studies was a pooled total of 777 AD subjects and 1,728 controls for serum zinc studies, 287 AD subjects and 166 controls for plasma zinc, and of 292 AD subjects and 179 controls for CSF zinc. The main result of this meta-analysis is the very high heterogeneity among the studies either in demographic terms or in methodological approaches. Although we considered these effects in our analyses, the heterogeneity persisted and it has to be taken into account in the interpretation of the results. Our meta-analysis indicated that serum zinc appears significantly decreased in AD patients compared with healthy controls, and this result is confirmed when serum and plasma studies were analyzed together. If we considered the age-matched studies, the meta-analysis carried out on only six studies showed no significant difference in zinc levels between AD and healthy controls (SMD =-0.55, 95% CI (-1.18; 0.09); p = 0.094; I2 = 91%). In the light of these findings, we speculated about the possibility that the decreases observed could indicate a possible dietary zinc deficiency and we suggested that the possible involvement of zinc alterations in AD may have an interplay with copper metabolism.

Cerebrospinal fluid zinc concentrations in ex-heroin addicts and patients with schizophrenia: some preliminary observations.

Mean CSF zinc concentration was lower in a group of ex-heroin addicts than in groups of normal controls and neuroleptic-treated schizophrenic patients, but values were generally within the normal range of CSF zinc concentrations. There were no significant differences in mean CSF zinc concentrations between groups of drug-free schizophrenic patients, schizophrenic patients on neuroleptics, and normal controls. CSF zinc concentration may be influenced by differences in racial composition and related dietary and other habits of the groups studied.

Cerebrospinal fluid trace element content in dementia: clinical, radiologic, and pathologic correlations.

Using inductively coupled argon plasma emission spectroscopy, we measured 19 trace elements in cerebrospinal fluid of 265 patients who were undergoing diagnostic lumbar puncture. Thirty-three patients had Alzheimer-type dementia (ATD); 16 patients had other dementing illnesses; and 20 had no neurologic disease. There were seven cases of autopsy-proven Alzheimer's disease (AD) and eight autopsy controls. We found elevated CSF silicon in 24% of ATD and 71% of AD patients. We found no relationship between CSF aluminum, arsenic, lead, or manganese and ATD, AD, or other dementing illnesses.

Opening the blood-brain barrier to zinc.

Sheep with guide tubes implanted over the brain lateral ventricles, in order to facilitate episodic sampling of cerebrospinal fluid (CSF), were used to determine the effects of increasing cranial blood osmolality or electroconvulsive shock (ECS) on the permeability of the blood-brain barrier (BBB) to zinc. Zinc acetate solution (1 mg Zn/ml) was infused intravenously (i.v.) at 1.0 ml/min for 30 min and then continuously at 0.125 ml/min. This infusion increased plasma total zinc concentration (pZn) approximately 10-fold without altering CSF zinc concentration (CSFZn). After 1.5-3.5 h, 4 M NaCl was infused at 5-10 ml/min for 10 min into one carotid artery with the other carotid artery occluded, or the animals were anaesthetized and given an ECS (140 V, 2 s). Paired samples of blood and CSF were collected before and after these treatments. Results were: (i) CSFZn was approximately one tenth of pZn; (ii) zinc administered i.v. was almost completely excluded from the CSF; (iii) increased cranial blood osmolality or ECS increased CSFZn in all experiments, but the time course and extent of the rise were variable. CSFZn reached the concentrations of zinc in normal sheep plasma in some experiments; (iv) CSFZn subsequently fell towards the low values of zinc in normal CSF; (v) the animals suffered no evident ill-effects from either procedure. The procedures may, therefore, be used for reversible opening of the BBB to particles such as zinc in conscious or anaesthetized sheep with no troublesome sequelae.

65Zn localization in rat brain after intracerebroventricular injection of 65Zn-histidine.

Previous studies have shown that 65Zn uptake in the brain expressed relative to plasma 65Zn level is enhanced by histidine infusion into the blood vessel. To study the effect of histidine on zinc uptake in the brain parenchyma via the CSF, the brains of rats injected intracerebroventricularly with 65Zn-His were subjected to autoradiography. Six days after injection, the radioactivity from 65Zn-His was distributed in the major part of the brain parenchyma higher than that from 65ZnCl(2), and relatively concentrated in the hippocampal formation, globus pallidus and hypothalamus. The radioactivity of the aqueduct was also higher in the 65Zn-His group, indicating that CSF clearance of the 65Zn-His group may be lower than that of the 65ZnCl(2) group. These results suggest an enhancement by histidine on zinc uptake in the brain parenchyma via the CSF.

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.

Copper, zinc and iron levels in the cerebrospinal fluid of copper poisoned sheep.

Copper, zinc and iron levels were measured in cerebrospinal fluid (CSF) of normal and copper poisoned sheep. Copper values were within the range recorded for humans but zinc levels were six to 20 times and iron levels were 20 to 30 times higher than values reported for humans. The amount of copper, zinc and iron in the CSF did not increase in sheep dosed with copper and hence it is unlikely that the level of copper in the CSF is related to the changes in the nervous system that have been reported in copper poisoned sheep.

Manganese, copper, and zinc in cerebrospinal fluid from patients with multiple sclerosis.

The concentrations of manganese, copper, and zinc in cerebrospinal fluid (CSF) from patients with multiple sclerosis (MS) and patients with no known neurological disease (control group) were measured. Manganese and copper levels were determined by two different analytical methods: atomic absorption spectrometry (AAS) and high-resolution inductively coupled plasma-mass spectrometry (HR-ICP-MS), whereas zinc levels were determined by HR-ICP-MS only. Manganese levels (mean+/-SEM) were significantly decreased in the CSF of MS patients (1.07+/-0.13 microg/L, ICP-MS; 1.08+/-0.11 microg/L, AAS) compared to the levels in the control group (1.78+/-0.26 microg/L, ICP-MS; 1.51+/-0.17 microg/L, AAS). Copper levels were significantly elevated in the CSF of MS patients (10.90+/-1.11 microg/L; ICP-MS, 11.53+/-0.83 microg/L, AAS) compared to the levels in the control group (8.67+/-0.49 microg/L, ICP-MS; 9.10+/-0.62 microg/L, AAS). There were no significant differences between the CSF zinc levels of MS and control patients. The physiological basis for the differences in manganese and copper concentrations between MS patients and controls is unknown, but could be related to alterations in the manganese- containing enzyme glutamine synthetase and the copper-containing enzyme cytochrome oxidase.

Changes of CSF-Cu and -Zn in children with acute lymphoblastic leukemia.

In 20 Dutch children with acute lymphoblastic leukemia (ALL), Cu and Zn levels in cerebrospinal fluid (CSF) were studied during standard treatment (Protocol ALL-BFM-86/SNWLK-ALL-VII). CSF-Cu in 10 controls was 0.04 +/- 0.02 mumol/L, lower compared to values in adults. At the moment of diagnosis, CSF-Cu values were higher, 0.06 +/- 0.03 mumol/L, and during maintenance therapy lower, 0.01 +/- 0.01 mumol/L. Children with central nervous system (CNS) involvement ALL as judged by CAT Scan and EEG--in addition to cytology--showed lower CSF-Cu values compared to children without. CSF-Zn values were also measured. CSF-Zn was 0.05 mumol/L and did not vary. Cu/Zn molar ratios were increased at the onset of treatment, and decreased during maintenance therapy. The changes in CSF-Cu may follow the natural course of the disease or may relate to the success of treatment, reflecting a decrease of leukemia activity. Another explanation concerns a risk of CNS damage by low CSF-Cu causing neuron dysfunction. Conditions necessary for the interpretation of these results into a clinical strategy for followup study are outlined.