Polyhalogenated aromatic hydrocarbons (PAHs) are highly persistent environmental contaminants that pose a potential risk to human health. 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is the prototypical representative of these widely dispersed pollutants and one of the most potent toxins and tumor promoters known to man. TCDD exposure in experimental animals results in an array of tissue and species-specific responses, including the following: dermal toxicity, immunotoxicity, hepatoxicity, carcinogenicity, teratogenicity, and neurobehavioral, endocrine, and metabolic alterations. 1)Recent studies have demonstrated that oxidative stress occurs in various tissues of TCDD-treated animals and is considered an important mechanism in the toxicity of TCDD. 2,3)Oxidative stress following TCDD exposure in laboratory animals has been demonstrated to increase the production of reactive oxygen species, lipid peroxidation, DNA and membrane damage, and possible enzyme inhibition. [2][3][4] Chitooligosaccharides are known to be biologically active compounds.5) Chitohexaose and its N-peracetylated derivative were shown to inhibit the growth of murine cancer cells.6) N-Acetylchitohexose protected against Candida albicans infection and increased the activities of macrophages, T lymphocytes, and natural killer cells in tumor-bearing mice. 5)The current authors previously demonstrated the effects of chitosan oligosaccharide on enzymes for cancer chemoprevention 7) and various chemical mutagens. 8,9) In this study, the effects of two types of chitosan oligosaccharides, chitosan oligosaccharide I (1-kDaϽMWϽ3-kDa) and chitosan oligosaccharide II (3-kDaϽMWϽ5-kDa), on the oxidative stress resulting from exposure to TCDD were investigated in mice. MATERIALS AND METHODS MaterialsWater soluble chitosan oligosaccharides were prepared from 1% chitosan by an ultrafiltration membrane reactor system (Millipore Minitan system; molecular weight cut-off 5000, 3000, and 1000 membrane) which recycles a chitosanase (derived from Bacillus pumilus BN-262).Animals and Treatments Five-week-old male ICR mice were purchased from the Dae-Han Laboratory Animal Research Center (Eumsung, Korea). The animals were housed ten per cage. After a one-week acclimation period, chitosan oligosaccharide I, chitosan oligosaccharide II, or the vehicle alone were administered for 14 consecutive days (intragastric application at doses of 500 mg/kg). A single dose of 25 mg TCDD/kg was administered by oral gavage with corn oil as the vehicle on day 8. At the end of the application regimen, the mice were killed by cervical dislocation. The livers were perfused with a cold 0.15 M KCl buffer (pH 7.0) and homogenized in 0.25 M sucrose. Microsomes and the cytosol fractions were prepared from liver homogenates by differential centrifugation.Determination of Lipid Peroxidation Microsomal malondialdehyde (MDA) production was used as an index of lipid peroxidation. Microsomes (300 mg/ml) were incubated at 37°C for 60 min with 0.4 mM FeSO 4 and 0.2 mM ascorbic acid in 0.1 M Tris-HCl buff...

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Local protein synthesis in neuronal dendrites is important for site-specific regulation of synaptic plasticity. In this study, we investigated whether translation initiation factors (eIFs) are present at the postsynaptic sites. High resolution confocal microscopy showed that the eIF4E and eIF4G (which bind the 5'-terminal mRNA cap), eIF5 (which is important during the 3' direction scanning to find an initiation codon), eIF6 (which mediates upregulation of translation by external stimuli), and eIF5A (which mediate translation upregulation under adverse conditions) were localized to the postsynaptic sites. Immunoblot and detergent extraction experiments also indicated that these eIFs were present in the synapse in association with the postsynaptic density (PSD). Our data provide evidence for the strategic positioning of eIFs at the postsynaptic site for initiation of translation in diverse situations.

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stress by free radicals is a major cause of neuronal cell death. Excitotoxicity in hypoxia/ischemia causes an increase in reactive oxygen species (ROS) and a loss of mitochondrial membrane potential (MMP), resulting in dysfunction of the mitochondria and cell death. Pinelliae Rhizoma (PR) is a traditional medicine for incipient stroke. We investigated the effects of PR Water-Extract on the modulation of ROS and MMP in a hypoxic model using cultured rat cortical cells. PR Water-Extract was added to the culture medium at various concentrations (0.25～5, 5.0 µg/ml) on day in vitro 12(DIV12), given a hypoxic shock (2% O2/5% CO2, 37 o C, 3 hr), and cell viability was assessed on DIV15 by Lactate Dehydrogenase Assay (LDH assays). PR Water-Extract showed a statistically significant effect on neuroprotection (10～15% increase in viability; p<0.01) at 1.0 and 2.5 µg/ml in normoxia and hypoxia. Measurement of ROS production by H2DCF-DA stainings showed that PR Water-Extract efficiently reduced the number and intensity of ROS-producing neurons, especially at 1 hr post shock and DIV15. When MMP was measured by JC-1 stainings, PR Water-Extract efficiently maintained high-energy charged mitochondria. These results indicate that PR Water-Extract protects neurons in hypoxia by preventing ROS production and preserving the cellular energy level.