Chronic encephalopathies induced by mercury or lead: aspects of underlying cellular and molecular mechanisms

Enzymatic reaction-based nanopore detection of zinc ions

We report a label-free nanopore sensor for the detection of Zn2+ ions. By taking advantage of the cleavage of a substrate peptide by zinc-dependent enzymes, nanomolar concentrations of Zn2+ ions could be detected within minutes. Furthermore, structurally similar transition metals such as Ni2+, Co2+, Hg2+, Cu2+, and Cd2+ did not interfere with their detection. The enzymatic reaction-based nanopore sensing strategy developed in this work may find potential applications in environmental monitoring and medical diagnosis.

Astrocytes As the Main Players in Primary Degenerative Disorders of the Human Central Nervous System

Along the last years it has been demonstrated that non-neural cells play a major role in the pathogenesis of the primary degenerative disorders (PDDs) of the human central nervous system. Among them, astrocytes coordinate and participate in many different and complex metabolic processes, in close interaction with neurons. Moreover, increasing experimental evidence hints an early astrocytic dysfunction in these diseases. In this mini review we summarize the astrocytic behavior in PDDs, with special consideration to the experimental observations where astrocytic pathology precedes the development of neuronal dysfunction. We also suggest a different approach that could be consider in human investigations in Alzheimer’s and Parkinson’s disease. We believe that the study of PDDs with human brain samples may hold the key of a paradigmatic physiopathological process in which astrocytes might be the main players.

Probing mercury(II)-DNA interactions by nanopore stochastic sensing

In this work, DNA-Hg(II) interactions were investigated by monitoring the translocation of DNA hairpins in a protein ion channel in the absence and presence of metal ions. Our experiments demonstrate that target-specific hairpin structures could be stabilized much more significantly by mercuric ions than by the stem length and the loop size of the hairpin due to the formation of Thymine-Hg(II)-Thymine complexes. In addition, the designed DNA probe allows the development of a highly sensitive nanopore sensor for Hg(2+) with a detection limit of 25 nM. Further, the sensor is specific, and other tested metal ions including Pb(2+), Cu(2+), Cd(2+), and so on with concentrations of up to 2 orders of magnitude greater than that of Hg(2+) would not interfere with the mercury detection.

Neuroimmunotoxicology: humoral assessment of neurotoxicity and autoimmune mechanisms

The interactions between the nervous and immune systems have been recognized in the development of neurodegenerative disease. This can be exploited through detection of the immune response to autoantigens in assessing the neurotoxicity of environmental chemicals. To test this hypothesis, the following questions were addressed. a) Are autoantibodies to nervous system (NS) antigens detected in populations exposed to environmental or occupational chemicals? In sera of male workers exposed to lead or mercury, autoantibodies, primarily IgG, to neuronal cytoskeletal proteins, neurofilaments (NFs), and myelin basic protein (MBP) were prevalent. These findings were confirmed in mice and rats exposed to either metal. b) Do autoantibodies to NS antigens relate to indices of exposure? In humans exposed to either metal, and similarly in exposed rats, titers of IgG against NFs and MBP significantly correlated with blood lead or urinary mercury, the typical indices of exposure. c) Do autoantibodies correlate with sensorimotor deficits? In workers exposed to lead or mercury, a significant correlation was observed between IgG titers and subclinical deficits. Doses of metals used in rat exposures were subclinical, suggesting that autoantibodies may be predictive of neurotoxicity. d) Is the detection indicative of nervous system pathology? In rats exposed to metals, histopathology indicated central nervous system (CNS) and peripheral nervous system (PNS) damage. In addition there was evidence of astrogliosis, which is indicative of neuronal damage in the CNS, and the presence of IgG concentrated along the blood-brain barrier, as indicated by immunostaining for antibodies. e) Are immune responses to NS antigens pathogenic? Immunoglobulin fractions from rat and human sera interfered with neuromuscular function. These studies suggest that the detection of autoantibodies to NS-specific antigens may be used to monitor the development of neurotoxicity to environmental chemicals and that immune mechanisms may be involved in the progression of neurodegeneration.

Lifetime exposure to environmental lead and children's intelligence at 11-13 years: the Port Pirie cohort study

OBJECTIVE

To examine the association between environmental exposure to lead and children's intelligence at age 11-13 years, and to assess the implications of exposure in the first seven years of life for later childhood development.

DESIGN

Prospective cohort study.

SUBJECTS

375 children born in or around the lead smelting town of Port Pirie, Australia, between 1979 and 1982.

MAIN OUTCOME MEASURE

Children's intelligence quotient (IQ) measured at 11-13 years of age.

RESULTS

IQ was inversely associated with both antenatal and postnatal blood lead concentrations. Verbal, performance, and full scale IQ were inversely related to blood lead concentration with no apparent threshold. Multivariate analyses indicated that after adjustment for a wide range of confounders, the postnatal blood lead concentrations (particularly within the age range 15 months to 7 years) exhibited inverse associations with IQ. Strong associations with IQ were observed for lifetime average blood lead concentrations at various ages. The expected mean full scale IQ declined by 3.0 points (95% confidence interval 0.07 to 5.93) for an increase in lifetime average blood lead concentration from 0.48 to 0.96 mumol/l (10 to 20 micrograms/dl).

CONCLUSION

Exposure to environmental lead during the first seven years of life is associated with cognitive deficits that seem to persist into later childhood.

Neurotoxicity induced by lead levels: an electrophysiological study

The object of the present study was to evaluate, with the aid of visual evoked potentials (VEPs), modifications induced in the optic nerve by lead, and to investigate the relationship between blood lead levels (PbB) and modification of the VEP. We studied a sample of 300 men with PbB values between 17 and 60 micrograms/100 ml. Our study demonstrates that alterations in the latency of the VEP are dependent on PbB levels, though there is not a directly proportional relationship.