Lead, cadmium and mercury in cerebrospinal fluid and risk of amyotrophic lateral sclerosis: A case-control study.

Exposure to neurotoxic chemicals such as pesticides, selenium, and heavy metals have been suggested to play a role in the etiology of amyotrophic lateral sclerosis (ALS). We assessed exposure to lead, cadmium, and mercury in 38 ALS patients (16 men and 22 females) and 38 hospital-admitted controls by using their cerebrospinal fluid (CSF) content as biomarker. We determined CSF heavy metal levels with inductively coupled plasma sector field mass spectrometry, according to a methodology specifically developed for this biological matrix. ALS patients had higher median values for Pb (155 vs. 132ng/L) but lower levels for Cd (36 vs. 72ng/L) and Hg (196 vs. 217ng/L). In the highest tertile of exposure, ALS odds ratio was 1.39 (95% CI 0.48-4.25) for Pb, 0.29 (0.08-1.04) for Cd and 3.03 (0.52-17.55) for Hg; however, no dose-response relation emerged. Results were substantially confirmed after conducting various sensitivity analyses, and after stratification for age and sex. Though interpretation of these results is limited by the statistical imprecision of the estimates, and by the possibility that CSF heavy metal content may not reflect long-term antecedent exposure, they do not lend support to a role of the heavy metals cadmium, lead and mercury in ALS etiology.

Cellular uptake of lead in the blood-cerebrospinal fluid barrier: Novel roles of Connexin 43 hemichannel and its down-regulations via Erk phosphorylation.

As the structural basis of blood-cerebrospinal fluid barrier (BCB), epithelial cells in the choroid plexus (CP) are targets for lead (Pb). Pb is known to accumulate in the CP; however, the mechanism of Pb uptake in the choroidal epithelial cells remains unknown. Recently, hemichannels of Connexin 43 (Cx43), the most ubiquitously expressed gap junction proteins in the CP, were found to be important pathways for many substances. This study was designed to investigate the roles of Cx43 in Pb uptake in the epithelial cells. Autometallography was used to outline Pb's subcellular location, and the characteristics of Pb transport into CP cells, including concentration- and time-dependence were analyzed by atomic absorption spectroscopy. Knockdown/overexpression of Cx43 with transient siRNA/plasmids transfections before Pb exposure diminished/increased the Pb accumulation. In the Z310 cell-based doxycycline-inducible Cx43 expression cell line (iZCx43), doxycycline induced a significant increase (3-fold) in Pb uptake, corresponding to the increased Cx43 levels. Activation of Cx43 hemichannels by reduced serum conditions caused an increase of Pb concentrations. Cx43-induced Pb uptake was attenuated after blockage of Cx43 hemichannels with its inhibitor, carbenoxolone. Additionally, down-regulation of Cx43 protein levels by Pb exposure paralleled cellular Pb concentrations in the time study. Concomitantly, expressions of phosphor-Src and phosphor-Erk were both significantly increased by Pb. However, inactivation of Erk, not Src pathway, reversed Pb-induced downregulation of Cx43. Taken together, these data establish that Pb can accumulate in the BCB and validate the role of Cx43 hemichannel in Pb uptake and its regulations through Erk phosphorylation.

Increased ß-amyloid deposition in Tg-SWDI transgenic mouse brain following in vivo lead exposure.

Previous studies in humans and animals have suggested a possible association between lead (Pb) exposure and the etiology of Alzheimer's disease (AD). Animals acutely exposed to Pb display an over-expressed amyloid precursor protein (APP) and the ensuing accumulation of beta-amyloid (Aß) in brain extracellular spaces. This study was designed to examine whether in vivo Pb exposure increased brain concentrations of Aß, resulting in amyloid plaque deposition in brain tissues. Human Tg-SWDI APP transgenic mice, which genetically over-express amyloid plaques at age of 2-3 months, received oral gavages of 50mg/kg Pb acetate once daily for 6 weeks; a control group of the same mouse strain received the same molar concentration of Na acetate. ELISA results revealed a significant increase of Aß in the CSF, brain cortex and hippocampus. Immunohistochemistry displayed a detectable increase of amyloid plaques in brains of Pb-exposed animals. Neurobehavioral test using Morris water maze showed an impaired spatial learning ability in Pb-treated mice, but not in C57BL/6 wild type mice with the same age. In vitro studies further uncovered that Pb facilitated Aß fibril formation. Moreover, the synchrotron X-ray fluorescent studies demonstrated a high level of Pb present in amyloid plaques in mice exposed to Pb in vivo. Taken together, these data indicate that Pb exposure with ensuing elevated Aß level in mouse brains appears to be associated with the amyloid plaques formation. Pb apparently facilitates Aß fibril formation and participates in deposition of amyloid plaques.

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.

Selective removal of lead and bromide from a hazardous industrial solid waste using Limited Acid Demand and Separation Factor at ambient conditions.

A detailed methodology is described for the selective removal of lead and bromide content from an industrial toxic solid waste, containing also large quantities of iron. Limited Acid Demand (LAD) was examined in order to avoid the co-dissolution of undesirable constituents. The Separation Factor (SF), which is the concentration ratio of dissolved constituents in the resulting leaching solution after the application of extraction stage, can describe the selective release of lead against iron, according to the variation of major leaching parameters (i.e. the molarity of used acid and the liquid to solid (L/S) ratio). A general equation, describing the overall leaching process was obtained, containing a specific "inhibition constant" and indicating that when the initial stoichiometry of leaching procedure and the applied L/S ratio are known, then the removal of lead can be predicted.

Transthyretin, thyroxine, and retinol-binding protein in human cerebrospinal fluid: effect of lead exposure.

Transthyretin (TTR), synthesized by the choroid plexus, is proposed to have a role in transport of thyroid hormones in the brain. Our previous studies in animals suggest that sequestration of lead (Pb) in the choroid plexus may lead to a marked decrease in TTR levels in the cerebrospinal fluid (CSF). The objectives of this study were to establish in humans whether TTR and thyroxine (T(4)) are correlated in the CSF, and whether CSF levels of Pb are associated with those of TTR, T(4), and/or retinol-binding protein (RBP). Eighty-two paired CSF and blood/serum samples were collected from patients undergoing clinical diagnosis of CSF chemistry. Results showed that the mean value of CSF concentrations for TTR was 3.33 +/- 1.60 microg/mg of CSF proteins (mean +/- SD, n = 82), for total T(4) (TT(4)) was 1.56 +/- 1.68 ng/mg (n = 82), for RBP was 0.34 +/- 0.19 microg/mg (n = 82), and for Pb was 0.53 +/- 0.69 microg/dl (n = 61 for those above the detection limit). Linear regression analyses revealed that CSF TTR levels were positively associated with those of CSF TT(4) (r = 0.33, p < 0.005). CSF TTR concentrations, however, were inversely associated with CSF Pb concentrations (r = -0.29, p < 0.05). There was an inverse, albeit weak, correlation between CSF TT(4) and CSF Pb concentrations (r = -0.22, p = 0.09). The concentrations of TTR, TT(4), and Pb in the CSF did not vary as the function of their levels in blood or serum, but RBP concentrations in the CSF did correlate to those of serum (r = 0.39, p < 0.0005). Unlike TTR, CSF RBP concentrations were not influenced by PB: These human data are consistent with our earlier observations in animals, which suggest that TTR is required for thyroxine transport in the CSF and that Pb exposure is likely associated with diminished TTR levels in the CSF.

Determination of cerebrospinal fluid and serum lead levels in patients with amyotrophic lateral sclerosis and other neurological diseases.

In a total of 62 samples of cerebrospinal fluid (CSF) and an equal number of serum samples obtained from 16 patients suffering from amyotrophic lateral sclerosis, 22 patients suffering from miscellaneous neurological diseases, and 24 controls, lead was measured by atomic absorption spectrophotometry. No statistical difference in lead concentration was found between the above three groups.

High accuracy (stable isotope dilution) measurements of lead in serum and cerebrospinal fluid.

The concentration of lead in blood, serum, cerebrospinal fluid, and urine was measured in patients with neurological disease and in control subjects including cases of plumbism. A plot of blood lead versus serum lead resembles the familiar curves of blood lead versus either free erythrocyte porphyrin or urinary delta-aminolaevulinic acid in that serum lead is constant up to a blood lead concentration of 40 micrograms/dl (2 mumol/l) and rises steeply thereafter. The serum lead concentrations yield renal clearances in the range 5-22 ml/min in agreement with values obtained with radiolead on man and predicted from animal studies. The lead content of cerebrospinal fluid is consistently less than that of serum, averaging 50% of the serum concentration for blood leads of less than 20 micrograms/dl (1 mumol/l) but rising to 80-90% in cases of plumbism. Patients with motor neurone disease could not be distinguished from those with other neurological diseases on the basis of the lead content of their serum or cerebrospinal fluid.

Lead in cerebrospinal fluid and its relationship to plasma lead in humans.

Lead levels in whole blood, plasma and cerebrospinal fluid (CSF) were determined in 18 patients suffering from Amyotrophic Lateral Sclerosis (ALS) and in 21 subjects hospitalized for neurological investigations. No significant differences were found for blood, plasma and CSF lead concentration between the ALS group and the other patient group. The plasma lead-CSF lead mean ratio was greater than 1 in both groups, while in subjects with a slight degree of blood-CSF barrier impairment a significant decrease of the ratio was demonstrated. A significant relationship between plasma lead and CSF lead levels (r = 0.405; p less than 0.01), but not between whole blood lead and CSF lead levels, was established. Lead levels in CSF were also age-related (r = 0.485; p less than 0.05) in the group of patients not suffering from ALS. In subjects with normal blood-brain barrier permeability, lead in plasma is a good indicator of CSF lead concentration.

Lead concentrations in blood, plasma, erythrocytes, and cerebrospinal fluid in amyotrophic lateral sclerosis.

The purpose of the investigation was to elucidate the repeatedly discussed relationship between chronic lead intoxication and ALS. The following mean lead concentrations were determined in 9 patients with ALS: 8.65 +/- 3,91 micrograms/100 ml in the blood, 0.97 +/- 0.78 microgram/100 ml in the plasma, 19.15 +/- 5.0 micrograms/100 ml in the erythrocytes, and 0.89 +/- 0.44 microgram/100 ml in the cerebrospinal fluid. These values did not differ appreciably from the controls with 7.91 +/- 3.83 micrograms/100 ml (n = 14) in the blood, 1.13 +/- 0.46 microgram/100 ml (n = 10) in the plasma, 18.96 +/- 12.63 micrograms/100 ml (n = 10) in the erythrocytes, and 0.85 +/- 0.91 microgram/100 ml (n = 15) in the cerebrospinal fluid. These findings do not support the assumption of lead poisoning as a pathogenetic factor in ALS.

Abnormal distribution of lead in amyotrophic lateral sclerosis--reestimation of lead in the cerebrospinal fluid.

The lead concentration in CSF was determined by flameless atomic absorption spectrophotometry in 16 ALS patients and 22 control cases. The mean values were 0.69 +/- 0.55 (ALS) and 0.41 +/- 0.37 (controls), P < 0.01. This confirms our earlier findings of raised CSF lead levels in ALS but the present values are lower than previously reported for both ALS patients and controls.

Adenoviral meningoencephalitis in a patient with lead toxicity.

Adenovirus type 12 was recovered from the CSF of a 36-year-old woman with adenoviral meningoencephalitis and lead toxicity. The serum level of lead was 199 micrograms/dL and the CSF level was 7 micrograms/dL. After therapy with edetate disodium calcium (Calcium Disodium Versenate), she had an uneventful recovery. The possibility of exacerbation of lead poisoning with encephalopathy due to adenovirus type 12 meningoencephalitis is raised.

Abnormal tissue distribution of lead in amyotrophic lateral sclerosis.

The lead content of cerebrospinal fluid (CSF) was found to be significantly elevated in 12 patients with amyotrophic lateral sclerosis, when compared to 28 control subjects having non-degenerative neurological disorders. The difference could not be explained as being merely secondary to blood-CSF barrier damage. A hypothetical model of the pathogenesis of the disease is advanced and the results are discussed in relation to this model.