Magnetite pollution nanoparticles in the human brain.

Biologically formed nanoparticles of the strongly magnetic mineral, magnetite, were first detected in the human brain over 20 y ago [Kirschvink JL, Kobayashi-Kirschvink A, Woodford BJ (1992) Proc Natl Acad Sci USA 89(16):7683-7687]. Magnetite can have potentially large impacts on the brain due to its unique combination of redox activity, surface charge, and strongly magnetic behavior. We used magnetic analyses and electron microscopy to identify the abundant presence in the brain of magnetite nanoparticles that are consistent with high-temperature formation, suggesting, therefore, an external, not internal, source. Comprising a separate nanoparticle population from the euhedral particles ascribed to endogenous sources, these brain magnetites are often found with other transition metal nanoparticles, and they display rounded crystal morphologies and fused surface textures, reflecting crystallization upon cooling from an initially heated, iron-bearing source material. Such high-temperature magnetite nanospheres are ubiquitous and abundant in airborne particulate matter pollution. They arise as combustion-derived, iron-rich particles, often associated with other transition metal particles, which condense and/or oxidize upon airborne release. Those magnetite pollutant particles which are <∼200 nm in diameter can enter the brain directly via the olfactory bulb. Their presence proves that externally sourced iron-bearing nanoparticles, rather than their soluble compounds, can be transported directly into the brain, where they may pose hazard to human health.

A longitudinal study on α-synuclein in blood plasma as a biomarker for Parkinson's disease.

There have been no longitudinal studies on α-synuclein as a potential biomarker for the progression of Parkinson's disease (PD). Here, blood plasma 'total α-synuclein' and 'Ser-129 phosphorylated α-synuclein' were assayed at 4-6 monthly intervals from a cohort of 189 newly-diagnosed patients with PD. For log-transformed data, plasma total α-synuclein levels increased with time for up to 20 yrs after the appearance of initial symptoms (p = 0.012), whereas phosphorylated α-synuclein remained constant over this same period. The mean level of phosphorylated α-synuclein, but not of total α-synuclein, was higher in the PD plasma samples taken at first visit than in single samples taken from a group of 91 healthy controls (p = 0.012). Overall, we conclude that the plasma level of phosphorylated α-synuclein has potential value as a diagnostic tool, whereas the level of total α-synuclein could act as a surrogate marker for the progression of PD.

Correlation of Aß oligomer levels in matched cerebrospinal fluid and serum samples.

We recently reported a newly developed enzyme-linked immunosorbent assay (ELISA) for high molecular weight amyloid-ß (Aß) oligomers in which the same Aß monoclonal antibody, BAN50, was used for both capture and detection in a single antibody sandwich enzyme linked immunosorbent assay (ELISA) system. Although our previous data have suggested that this assay will be useful for the early diagnosis of Alzheimer disease (AD) in cerebrospinal fluid (CSF) samples, the invasive CSF sampling procedure, with associated potential complications, limits use of these samples in routine clinical practice. In this study, we have demonstrated that our ELISA can detect signals in 60% of serum samples and in 80% of CSF samples obtained from non-demented subjects. Heterophilic antibodies that are reported to be a primary confounding factor in this type of ELISA system did not affect the signals obtained. Although the levels of serum Aß oligomers were unexpectedly high, suggesting the possible detection of non-pathological Aß complexes associated with serum carrier proteins, they did show a significant positive correlation with the levels obtained from matched CSF samples. This correlation between CSF and serum Aß oligomer levels implies that the levels of serum Aß oligomers measured with our ELISA might be useful as a marker for AD that reflects an intact system of Aß transport across the blood brain barrier.

TDP-43 pathological changes in early onset familial and sporadic Alzheimer's disease, late onset Alzheimer's disease and Down's syndrome: association with age, hippocampal sclerosis and clinical phenotype.

TDP-43 immunoreactive (TDP-43-ir) pathological changes were investigated in the temporal cortex and hippocampus of 11 patients with autosomal dominant familial forms of Alzheimer's disease (FAD), 169 patients with sporadic AD [85 with early onset disease (EOAD) (i.e before 65 years of age), and 84 with late onset after this age (LOAD)], 50 individuals with Down's Syndrome (DS) and 5 patients with primary hippocampal sclerosis (HS). TDP-43-ir pathological changes were present, overall, in 34/180 of AD cases. They were present in 1/11 (9%) FAD, and 9/85 (10%) EOAD patients but were significantly more common (p = 0.003) in LOAD where 24/84 (29%) patients showed such changes. There were no demographic differences, other than onset age, between AD patients with or without TDP-43-ir pathological changes. Double immunolabelling indicated that these TDP-43-ir inclusions were frequently ubiquitinated, but were only rarely AT8 (tau) immunoreactive. Only 3 elderly DS individuals and 4/5 cases of primary HS showed similar changes. Overall, 21.7% of AD cases and 6% DS cases showed hippocampal sclerosis (HS). However, only 9% FAD cases and 16% EOAD cases showed HS, but 29% LOAD cases showed HS. The proportion of EOAD cases with both TDP-43 pathology and HS tended to be greater than those in LOAD, where nearly half of all the cases with TDP-43 pathology did not show HS. The presence of TDP-43-ir changes in AD and DS may therefore be a secondary phenomenon, relating more to ageing than to AD itself. Nevertheless, a challenge to such an interpretation comes from the finding in AD of a strong relationship between TDP-43 pathology and cognitive phenotype. Patients with TDP-43 pathology were significantly more likely to present with an amnestic syndrome than those without (p < 0.0001), in keeping with pathological changes in medial temporal lobe structures. HS was also associated more commonly with an amnestic presentation (p < 0.005), but this association disappeared when TDP-43-positive cases were excluded from the analysis. TDP-43 may, after all, be integral to the pathology of AD, and to some extent determine the clinical phenotype present.

Phosphorylated α-synuclein can be detected in blood plasma and is potentially a useful biomarker for Parkinson's disease.

Parkinson's disease (PD) is characterized by the presence of Lewy bodies containing phosphorylated and aggregated α-synuclein (α-syn). α-Syn is present in human body fluids, including blood plasma, and is a potential biomarker for PD. Immunoassays for total and oligomeric forms of both normal and phosphorylated (at Ser-129) α-syn have been used to assay plasma samples from a longitudinal cohort of 32 patients with PD (sampled at mo 0, 1, 2, 3), as well as single plasma samples from a group of 30 healthy control participants. The levels of α-syn in plasma varied greatly between individuals, but were remarkably consistent over time within the same individual with PD. The mean level of phospho-α-syn was found to be higher (P=0.053) in the PD samples than the controls, whereas this was not the case for total α-syn (P=0.244), oligo-α-syn (P=0.221), or oligo-phospho-α-syn (P=0.181). Immunoblots of plasma revealed bands (at 21, 24, and 50-60 kDa) corresponding to phosphorylated α-syn. Thus, phosphorylated α-syn can be detected in blood plasma and shows more promise as a diagnostic marker than the nonphosphorylated protein. Longitudinal studies undertaken over a more extended time period will be required to determine whether α-syn can act as a marker of disease progression.

Plasma phosphorylated-TDP-43 protein levels correlate with brain pathology in frontotemporal lobar degeneration.

In the present study, we have correlated plasma TDP-43 levels, as measured by ELISA, with the presence of TDP-43 pathological changes in the brains of 28 patients with frontotemporal lobar degeneration (FTLD) (14 with FTLD-TDP and 14 with FTLD-tau) and 24 patients with pathologically confirmed AD (8 with, and 16 without, TDP-43 pathological changes). Western blotting revealed full-length TDP-43, including a phosphorylated form, and a phosphorylated C-terminal fragment, in all samples examined. Both ELISA and immunohistochemistry were performed using phospho-dependent and phospho-independent TDP-43 antibodies for detection of phosphorylated and total TDP-43, respectively. Over all 52 cases, plasma levels of TDP-43, and scores of brain TDP-43 pathology, determined using TDP-43 phospho-dependent antibody correlated with the equivalent measure determined using the TDP phospho-independent antibody. In FTLD, but not AD, TDP-43 plasma levels correlated significantly with the pathology score when using the TDP-43 phospho-dependent antibody, but a similar correlation was not seen in either FTLD or AD using the TDP-43 phospho-independent antibody. With the TDP-43 phospho-independent antibody, there were no significant differences in median plasma TDP-43 levels between FTLD, or AD, patients with or without TDP-43 pathology. Using TDP-43 phospho-dependent antibody, median plasma TDP-43 levels were greater in patients with, than in those without, TDP-43 pathology for FTLD patients, though not significantly so, but not for AD patients. Present assays for TDP-43 do not differentiate between FTLD, or AD, patients with or without TDP-43 pathological changes in their brains. However, the levels of phosphorylated TDP-43 in plasma do correlate with the extent of TDP-43 brain pathology in FTLD, and therefore might be a useful surrogate marker for tracking changes in TDP-43 brain pathology during the course of this disease.

Increased TDP-43 protein in cerebrospinal fluid of patients with amyotrophic lateral sclerosis.

There is mounting pathological, biochemical and genetic evidence that the metabolism and aggregation of the 43-kDa transactive response (TAR)-DNA-binding protein (TDP-43) play a crucial role in the pathogenesis of sporadic and some forms of familial amyotrophic lateral sclerosis (ALS). Recently, it was reported using an ELISA system that elevated levels of TDP-43 were detected in plasma samples from patients with Alzheimer's disease and frontotemporal dementia, compared to healthy controls. To determine whether quantification of TDP-43 in cerebrospinal fluid (CSF) is potentially informative in the diagnosis of ALS, we measured the concentration, by a similar ELISA method, of TDP-43 in CSF from 30 patients with ALS (diagnosed according to the revised El Escorial criteria) and 29 age-matched control patients without any neurodegenerative disease. We found that, as a group, the ALS patients had significantly higher levels of TDP-43 in their CSF than the age-matched controls (6.92 +/- 3.71 ng/ml in ALS versus 5.31 +/- 0.94 ng/ml in controls, p < 0.05), with levels of TDP-43 in CSF elevated beyond 95% upper confidence level for the control group in six (20%) of the patients with sporadic ALS. All the six patients with higher levels of CSF TDP-43 were examined within 10 months of the onset of illness. The patients examined within 10 months of onset showed significantly higher levels of CSF TDP-43 (8.24 +/- 4.72 ng/ml) than those examined after 11 months or more of onset (5.41 +/- 0.66 ng/ml, p < 0.05). These results suggest that the levels of TDP-43 in CSF may increase in the early stage of ALS. We also confirmed the existence of the TDP-43 protein in CSF from some patients with ALS, and a control subject, by western blotting of proteins immunocaptured from the CSF samples. Raised TDP-43 levels in the CSF may preempt the formation of TDP-43 pathology in the central nervous system, or correlate with early-stage TDP-43 pathology, and accordingly be a biomarker for the early stage of ALS.

TDP-43 protein in plasma may index TDP-43 brain pathology in Alzheimer's disease and frontotemporal lobar degeneration.

Autopsy studies have shown that about 55% of patients with frontotemporal lobar degeneration (FTLD) and 25% of patients with Alzheimer's disease (AD) harbour TDP-43 immunoreactive pathological changes in their brains. Using ELISA, we investigated whether we could detect the presence, or increased amounts, of TDP-43 in plasma of patients with FTLD and AD compared to normal control subjects. We detected elevated levels of TDP-43 protein in plasma of 46% patients with FTLD with clinical frontotemporal dementia (FTD) and 22% patients with AD, compared to 8% of control subjects. The proportions of patients with FTD and AD showing raised plasma TDP-43 levels correspond closely to those proportions known from autopsy studies to contain TDP-43 pathological changes in their brains. Raised TDP-43 plasma levels may thereby index TDP-43 pathology within the brain. Plasma TDP-43 levels may be a biomarker that can provide a laboratory test capable of identifying the presence of TDP-43 brain pathology in neurodegenerative disease during life. It may help to distinguish those cases of FTLD with ubiquitin/TDP-43 pathology in their brains from those with tauopathy. As a predictive test, plasma TDP-43 level may have great practical value in directing therapeutic strategies aimed at preventing or removing tau or TDP-43 pathological changes from the brain in FTLD and AD.