Concentration-dependent effects of mercury and lead on Aß42: possible implications for Alzheimer's disease.

Mercury (Hg) and lead (Pb) are known to be toxic non-radioactive elements, with well-described neurotoxicology. Much evidence supports the implication of metals as potential risk cofactors in Alzheimer's disease (AD). Although the action mechanism of the two metals remains unclear, Hg and Pb toxicity in AD could depend on their ability to favour misfolding and aggregation of amyloid beta proteins (Aßs) that seem to have toxic properties, particularly in their aggregated state. In our study, we evaluated the effect of Hg and Pb both on the Aß42 ion channel incorporated in a planar lipid membrane made up of phosphatidylcholine containing 30% cholesterol and on the secondary structure of Aß42 in an aqueous environment. The effects of Hg and Pb on the Aß42 peptide were observed for its channel incorporated into a membrane as well as for the peptide in solution. A decreasing Aß42 channel frequency and the formation of large and amorphous aggregates in solution that are prone to precipitate were both dependent on metal concentration. These experimental data suggest that Hg and Pb interact directly with Aßs, strengthening the hypothesis that the two metals may be a risk factor in AD.

Clinical validation of REALQUALITY RQ-HPV Screen according to the international guidelines for human papillomavirus DNA test requirements for cervical screening.

BACKGROUND: According to international guidelines, HPV DNA tests represent a valid alternative to Pap Test for primary cervical cancer screening, provided that they guarantee balanced clinical sensitivity and specificity for cervical intraepithelial neoplasia grade 2 or more severe lesions. The aim of this study was to assess whether REALQUALITY RQ-HPV Screen, a new assay based on real time PCR that targets the E6-E7 region of 14 high-risk human papillomaviruses, meets the criteria for primary cervical cancer screening. METHODS: As required by guidelines, a non-inferiority test was conducted to compare the clinical performance of the test under evaluation with that of a clinically validated reference test (Hybrid Capture 2, HC2). The reproducibility of the device was assessed as well. The clinical samples used to test the hypothesis of non-inferiority and to asses reproducibility comprised 910 and 536 cervical specimens respectively. All specimens were originating from a population-based screening cohort. RESULTS: The study demonstrates that both the clinical sensitivity and specificity of REALQUALITY RQ-HPV Screen are non-inferior to those of HC2. In addition, an adequate intra- and inter-laboratory reproducibility has been reached by the test. CONCLUSIONS: REALQUALITY RQ-HPV Screen fulfils all the requirements of the international guidelines and can be considered clinically validated for primary cervical cancer screening purposes.

Heavy metals toxicity: effect of cadmium ions on amyloid beta protein 1-42. Possible implications for Alzheimer's disease.

Cadmium (Cd) is an environmental contaminant, highly toxic to humans. This biologically non-essential element accumulates in the body, especially in the kidney, liver, lung and brain and can induce several toxic effects, depending on the concentration and the exposure time. Cd has been linked to Alzheimer's disease (AD) as a probable risk factor, as it shows higher concentrations in brain tissues of AD patients than in healthy people, its implication in the formation of neurofibrillary tangles and in the aggregation process of amyloid beta peptides (AßPs). AßPs seem to have toxic properties, particularly in their aggregated state; insoluble AßP forms, such as small and large aggregates, protofibrils and fibrils, appear to be implicated in the pathogenesis of AD. In our study, we have evaluated the effect of Cd, at different concentrations, both on the AßP1-42 ion channel incorporated in a planar lipid membrane made up of phosphatidylcholine containing 30 % cholesterol and on the secondary structure of AßP1-42 in aqueous environment. Cadmium is able to interact with the AßP1-42 peptide by acting on the channel incorporated into the membrane as well as on the peptide in solution, both decreasing AßP1-42 channel frequency and in solution forming large and amorphous aggregates prone to precipitate. These experimental observations suggesting a toxic role for Cd strengthen the hypothesis that Cd may interact directly with AßPs and may be a risk factor in AD.

AßP1-42 incorporation and channel formation in planar lipid membranes: the role of cholesterol and its oxidation products.

Amyloid beta peptide (AßP) is a natural peptide, normally released into the cerebrospinal fluid (CSF), that plays a key role in Alzheimer's disease. The conversion of the peptide from a native soluble form to a non-native and often insoluble form, such as small and large aggregates, protofibrils and fibrils of AßP appears to be implicated in the pathogenesis of AD. Although the molecular mechanisms of AßP neurotoxicity are not fully understood, a large body of data suggests that the primary target of amyloid peptides is the cell membrane of neurons, that may modulate the structural and functional conversion of AßP into assemblies involved in pathological processes. In our study, we provide a systematic investigation of AßP1-42's ability to incorporate and form channel-like events in membranes of different lipid composition and focus on cholesterol and its oxidation products. We propose that cholesterol and its oxidation products can be considered neuroprotective factors because a) by favouring AßP1-42 insertion into membranes, the fibrillation/clearance balance shifts toward clearance; b) by shifting channel selectivity toward anions, the membrane potential is moved far from the threshold of membrane excitability, thus decreasing the influx of calcium into the cell.

Choline modulation of the aß p1-40 channel reconstituted into a model lipid membrane.

Nicotinic acetylcholine receptors (AChRs), implicated in memory and learning, in subjects affected by Alzheimer's disease result altered. Stimulation of α7-nAChRs inhibits amyloid plaques and increases ACh release. ß-amyloid peptide (AßP) forms ion channels in the cell and model phospholipid membranes that are retained responsible in Alzheimer disease. We tested if choline, precursor of ACh, could affect the AßP1-40 channels in oxidized cholesterol (OxCh) and in palmitoyl-oleoyl-phosphatidylcholine (POPC):Ch lipid bilayers. Choline concentrations of 5 × 10(-11) M-1.5 × 10(-8) M added to the cis- or trans-side of membrane quickly increased AßP1-40 ion channel frequency (events/min) and ion conductance in OxCh membranes, but not in POPC:Ch membranes. Circular Dichroism (CD) spectroscopy shows that after 24 and 48 hours of incubation with AßP1-40, choline stabilizes the random coil conformation of the peptide, making it less prone to fibrillate. These actions seem to be specific in that ACh is ineffective either in solution or on AßP1-40 channel incorporated into PLMs.