Metal concentrations in cerebrospinal fluid, blood, serum, plasma, hair, and nails in amyotrophic lateral sclerosis: A systematic review and meta-analysis.

BACKGROUND: Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease with progressive muscle wasting, paralysis, and respiratory failure. Whereas approximately 10-15 % of ALS cases are familial, the etiology of the remaining, sporadic ALS cases remains largely unknown. Environmental exposures have been suggested as causative factors for decades, and previous studies have found elevated concentrations of metals in ALS patients. PURPOSE: This meta-analysis aims to assess metal concentrations in body fluids and tissues of ALS patients. METHODS: We searched the MEDLINE and EMBASE databases on December 7th, 2022 for cross-sectional, case-control, and cohort studies which measure metal concentrations in whole blood, blood plasma, blood serum, cerebrospinal fluid (CSF), urine, erythrocytes, nail, and hair samples of ALS patients. Meta-analysis was then performed when three or more articles existed for a comparison. FINDINGS: Twenty-nine studies measuring 23 metals were included and 13 meta-analyses were performed from 4234 screened entries. The meta-analysis results showed elevated concentrations of lead and selenium. Lead, measured in whole blood in 6 studies, was significantly elevated by 2.88 µg/L (95 % CI: 0.83-4.93, p = 0.006) and lead, measured in CSF in 4 studies, was significantly elevated by 0.21 µg/L (95 % CI: 0.01 - 0.41, p = 0.04) in ALS patients when compared to controls. Selenium, measured in serum/plasma in 4 studies, was significantly elevated by 4.26 µg/L (95% CI: 0.73 - 7.79, p = 0.02) when compared to controls.Analyses of other metal concentrations showed no statistically significant difference between the groups. CONCLUSION: Lead has been discussed as a possible causative agent in ALS since 1850. Lead has been found in the spinal cord of ALS patients, and occupational exposure to lead is more common in ALS patients than in controls. Selenium in the form of neurotoxic selenite has been shown to geochemically correlate to ALS occurrence in Italy. Although no causal relationship can be established from the results of this meta-analysis, the findings suggest an involvement of lead and selenium in the pathophysiology of ALS. After a thorough meta-analysis of published studies on metal concentrations in ALS it can only be concluded that lead and selenium are elevated in ALS.

Elevated Levels of Selenium Species in Cerebrospinal Fluid of Amyotrophic Lateral Sclerosis Patients with Disease-Associated Gene Mutations.

BACKGROUND: Although an increasing role of genetic susceptibility has been recognized, the role of environmental risk factors in amyotrophic lateral sclerosis (ALS) etiology is largely uncertain; among neurotoxic chemicals, epidemiological and biological plausibility has been provided for pesticides, the heavy metal lead, the metalloid selenium, and other persistent organic pollutants. Selenium involvement in ALS has been suggested on the basis of epidemiological studies, in vitro investigations, and veterinary studies in which selenium induced a selective toxicity against motor neurons. OBJECTIVE: Hypothesizing a multistep pathogenic mechanism (genetic susceptibility and environmental exposure), we aimed to study selenium species in ALS patients carrying disease-associated gene mutations as compared to a series of hospital controls. METHODS: Using advanced analytical techniques, we determined selenium species in cerebrospinal fluid sampled at diagnosis in 9 ALS patients carrying different gene mutations (C9ORF72, SOD1, FUS, TARDBP, ATXN2, and TUBA4A) compared to 42 controls. RESULTS: In a patient with the tubulin-related TUBA4A mutation, we found highly elevated levels (in µg/L) of glutathione-peroxidase-bound selenium (32.8 vs. 1.0) as well as increased levels of selenoprotein-P-bound selenium (2.4 vs. 0.8), selenite (1.8 vs. 0.1), and selenate (0.9 vs. 0.1). In the remaining ALS patients, we detected elevated selenomethionine-bound selenium levels (0.38 vs. 0.06). CONCLUSIONS: Selenium compounds can impair tubulin synthesis and the cytoskeleton structure, as do tubulin-related gene mutations. The elevated selenium species levels in the TUBA4A patient may have a genetic etiology and/or represent a pathogenic pathway through which this mutation favors disease onset, though unmeasured confounding cannot be excluded. The elevated selenomethionine levels in the other patients are also of interest due to the toxicity of this nonphysiological selenium species. Our study is the first to assess selenium exposure in genetic ALS, suggesting an interaction between this environmental factor and genetics in triggering disease onset.

VEGF alleviates ALS-CSF induced cytoplasmic accumulations of TDP-43 and FUS/TLS in NSC-34 cells.

Cytoplasmic mislocalisation and aggregation of TDP-43 and FUS/TLS proteins in spinal motor neurons contribute to the pathogenesis of the highly fatal disorder amyotrophic lateral sclerosis (ALS). We investigated the neuroprotective effect of VEGF on expression of these proteins in the motor neuronal cell line NSC-34 modelled to reminisce sporadic form of ALS. We studied the expression of TDP-43 and FUS/TLS proteins after exposure to ALS-CSF and following VEGF supplementation by quantitative confocal microscopy and electron microscopy. ALS-CSF caused cytoplasmic overexpression of both the proteins and stress-granule formation in the cells. These alterations were alleviated by VEGF supplementation. The related ultrastructural changes like nuclear membrane dysmorphism and p-bodies associated changes were also reversed. However the protein expression did not completely translocate to the nucleus, as some cells continued to show to cytoplasmic mislocalisation. Thus, the present findings indicate that VEGF alleviates TDP43 and FUS pathology by complimenting its role in controlling apoptosis and reversing choline acetyl transferase expression. Hence, VEGF appears to target multiple pathogenic processes in the neurodegenerative cascade of ALS.

Brain-Derived Neurotrophic Factor Facilitates Functional Recovery from ALS-Cerebral Spinal Fluid-Induced Neurodegenerative Changes in the NSC-34 Motor Neuron Cell Line.

BACKGROUND: The survival of motor neurons is dependent upon neurotrophic factors both during childhood and adolescence and during adult life. In disease conditions, such as in patients with amyotrophic lateral sclerosis (ALS), the mRNA levels of trophic factors like brain-derived neurotrophic factor (BDNF), insulin-like growth factor-1 (IGF-1), fibroblast growth factor-2 (FGF-2), and vascular endothelial growth factor are downregulated. This was replicated in our in vivo experimental system following the injection of cerebral spinal fluid (CSF) of sporadic ALS (ALS-CSF) patients. OBJECTIVE: To evaluate the protective role of BDNF in a model of sporadic ALS patients. METHODS: The expressions of endogenous BDNF, its receptor TrkB, the enzyme choline acetyl transferase (ChAT), and phosphorylated neurofilaments were studied in NSC-34 cells. The calcium-buffering and proapoptotic effects were assessed by calbindin-D28K and caspase-3 expression, respectively. RESULTS: ALS-CSF considerably depleted the endogenous BDNF protein, while its effect on IGF-1 and FGF-2 was inconsequential; this indirectly indicates a key role for BDNF in supporting motor neuronal survival. The exogenous supplementation of BDNF reversed autocrine expression; however, it may not be completely receptor mediated, as the TrkB levels were not restored. BDNF completely revived ChAT expression. It may inhibit apoptosis by restoring Ca2+ homeostasis, since caspase-3 and calbindin-D28K expression was back to normal. The organellar ultrastructural changes were only partially reversed. CONCLUSION: Our study provides evidence that BDNF supplementation ameliorates most but not all degenerative changes. The incomplete revival at the ultrastructural level signifies the requirement of factors other than BDNF for near-total protection of motor neurons, and, to an extent, it explains why only a partial success is achieved in clinical trials with BDNF in ALS patients.

Evidence of endoplasmic reticular stress in the spinal motor neurons exposed to CSF from sporadic amyotrophic lateral sclerosis patients.

We have earlier reported that intrathecal injection of cerebrospinal fluid (CSF) from sporadic Amyotrophic Lateral Sclerosis patients (ALS-CSF) into neonatal rats and supplementation of rat spinal cord cultures with ALS-CSF induces motor neuron degeneration via aberrant neurofilament phosphorylation and Golgi apparatus fragmentation. Intracellular aggregates immunoreactive to ubiquitin, phosphorylated neurofilaments and choline acetyl transferase (ChAT) were prominently seen in NSC-34 cells exposed to ALS-CSF. Protein aggregation could cause stress on endoplasmic reticulum (ER) and may precede Golgi fragmentation. Here we assessed the effect of ALS-CSF on the expression of GRP-78 and caspase-12 proteins, the markers of ER stress responses, in NSC-34 cells and rat spinal cords by immunochemistry and immunoblotting. Both in vitro and in vivo, increased expression of these proteins accompanied elevated active caspase-12 levels. Apoptotic nuclei and nuclear translocation of caspase-12 were noted in some cells. In vitro, the occurrence of ER stress was supported by electron microscopic observations of numerous free polyribosomes and fragmented ER cisternae. Aggregated mSOD1 protein causes ER stress in familial ALS. ER stress is also reported in the autopsy samples of sporadic ALS. Thus our observation of ER stress may be linked to the protein aggregation, viz. phosphorylated neurofilaments and ChAT, reported earlier.

The advanced glycation end-product N epsilon-(carboxymethyl)lysine level is elevated in cerebrospinal fluid of patients with amyotrophic lateral sclerosis.

Oxidative stress is involved in the aetiopathogenesis of amyotrophic lateral sclerosis (ALS), a fatal degenerative disorder. To test whether oxidative stress in ALS is increased and confined to the central nervous system, we have measured the glycoxidation product N(epsilon)-(carboxymethyl)lysine (CML) in serum and cerebrospinal fluid (CSF) samples by means of a novel enzyme immunoassay. Significant increases of CSF/serum ratio of CML in ALS patients (n = 25) as compared to normal controls (n = 20, p = 0.001) and to Alzheimer disease patients (n = 9, p = 0.029) suggest intrathecal production of this glycoxidation product. Measurement of CML levels may provide a novel diagnostic tool and may supplement current monitoring strategies in interventional trials.