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Neurotoxic Action (neurotoxic + action)

Distribution by Scientific Domains

Medical Sciences	50%

Selected Abstracts

Role of astrocytes in trimethyltin neurotoxicity

JOURNAL OF BIOCHEMICAL AND MOLECULAR TOXICOLOGY, Issue 5 2001
Palur G. Gunasekar
Abstract Although the neurotoxicity of trimethyltin (TMT) is well known, mechanisms are still not clear. Glia have been proposed to mediate the toxic action of TMT on nerve cells. Accordingly, the effects of TMT were tested in primary neuronal cultures from rat cerebellum and compared to effects in astrocytes and mixed cultures. Neuronal damage observed following TMT exposure was less in the presence of astrocytes and astrocytes alone were resistant to TMT. Thus, astrocytes have a protective effect against TMT-induced neurotoxicity. TMT caused an oxidative stress in granule cell cultures involving a variety of oxidative species ((O2),,, H2O2, NO), but astrocytes were less sensitive to TMT-induced oxidative species generation. Antioxidants, glutathione and 7-nitroindazole attenuated neuronal cell death induced by TMT. It appears that oxidative stress mediates a large part of the destructive action of TMT in neuronal cultures. The presence of astrocytes appears to modulate TMT-induced oxidative stress so that TMT causes only a small increase in lipid peroxidation in mouse brain after systemic administration. Thus, TMT induces a pronounced oxidative stress in cultured neurons, but when astrocytes are present, oxidative species play a lesser role in the neurotoxic action of TMT. © 2001 John Wiley & Sons, Inc. J Biochem Mol Toxicol 15:256,262, 2001 [source]

Key Factors in Alzheimer's Disease: ,-amyloid Precursor Protein Processing, Metabolism and Intraneuronal Transport

BRAIN PATHOLOGY, Issue 1 2001
Thomas A. Bayer
During the last years it has become evident that the ,-amyloid (A,) component of senile plaques may be the key molecule in the pathology of Alzheimer's disease (AD). The source and place of the neurotoxic action of A,, however, is still a matter of controversy. The precursor of the ,-amyloid peptide is the predominantly neuronal ,-amyloid precursor protein. We, and others, hypothesize that intraneuronal misregulation of APP leads to an accumulation of A, peptides in intracellular compartments. This accumulation impairs APP trafficking, which starts a cascade of pathological changes and causes the pyramidal neurons to degenerate. Enhanced A, secretion as a function of stressed neurons and remnants of degenerated neurons provide seeds for extracellular A, aggregates, which induce secondary degenerative events involving neighboring cells such as neurons, astroglia and macrophages/microglia. [source]

Dopamine activates Nrf2-regulated neuroprotective pathways in astrocytes and meningeal cells

JOURNAL OF NEUROCHEMISTRY, Issue 1 2007
Andy Y. Shih
Abstract The transcription factor Nrf2 controls inducible expression of multiple antioxidant/detoxification genes. We previously found that Nrf2 -/- mice have increased sensitivity to in vivo mitochondrial stress and ischemia. Although Nrf2 regulated these forms of neuronal toxicity, it was unclear which injury-triggered signal(s) led to Nrf2 activation in vivo. In this study, we use primary cultures to test the hypothesis that excessive dopamine release can act as an endogenous Nrf2-inducing signal. We cultured two cell types that show increased Nrf2 activity during ischemia in vivo, astrocytes and meningeal cells. Cultures were infected with an adenovirus reporter of Nrf2 transcriptional activity. Dopamine-induced Nrf2 activity in both cell types by generating oxidative stressors, H2O2 and dopamine-quinones. Nrf2 activation in meningeal cells was significantly higher than astrocytes. The effect of dopamine was blocked by antioxidants, and by over-expression of either dominant-negative Nrf2 or Keap1. Nrf2 induction was specific to oxidative stress caused by catecholaminergic neurotransmitters as epinephrine also induced Nrf2, but the monoamine serotonin had no significant effect. These in vitro results suggest Nrf2 activity in astrocytes and meningeal cells link the neurotoxic actions of dopamine to neuroprotective pathways that may potentially modulate ischemic injury and neurodegeneration. [source]

Gene Expression in Human Alcoholism: Microarray Analysis of Frontal Cortex

ALCOHOLISM, Issue 12 2000
Joanne M. Lewohl
Background: Changes in brain gene expression are thought to be responsible for the tolerance, dependence, and neurotoxicity produced by chronic alcohol abuse, but there has been no large scale study of gene expression in human alcoholism. Methods: RNA was extracted from postmortem samples of superior frontal cortex of alcoholics and nonalcoholics. Relative levels of RNA were determined by array techniques. We used both cDNA and oligonucleotide microarrays to provide coverage of a large number of genes and to allow cross-validation for those genes represented on both types of arrays. Results: Expression levels were determined for over 4000 genes and 163 of these were found to differ by 40% or more between alcoholics and nonalcoholics. Analysis of these changes revealed a selective reprogramming of gene expression in this brain region, particularly for myelin-related genes which were down-regulated in the alcoholic samples. In addition, cell cycle genes and several neuronal genes were changed in expression. Conclusions: These gene expression changes suggest a mechanism for the loss of cerebral white matter in alcoholics as well as alterations that may lead to the neurotoxic actions of ethanol. [source]