Aggregated and oligomeric amyloid beta-protein (Abeta) is known to exhibit neurotoxicity. However, the action of Abeta monomers on neurons is not fully understood. We have studied aggregation state-dependent actions of Abeta and found an oligomer-specific effect of Abeta on lipid metabolism in neurons (Michikawa et al., 2001). Here, we show a novel function of monomeric Abeta1-40, which is the major species found in physiological fluid, as a natural antioxidant molecule that prevents neuronal death caused by transition metal-induced oxidative damage. Monomeric Abeta1-40, which is demonstrated by SDS-PAGE after treatment with glutaraldehyde, protects neurons cultured in a medium containing 1.5 microm Fe(II) without antioxidant molecules. Metal ion chelators such as EDTA, CDTA (trans-1,2-diaminocyclohexane-N,N,N',N'-tetraacetic acid), and DTPA (diethylenetriamine-N,N,N',N",N"-penta-acetic acid, an iron-binding protein, transferrin, and antioxidant scavengers such as catalase, glutathione, and vitamin E also inhibit neuronal death under the same conditions. Monomeric Abeta1-40 inhibits neuronal death caused by Cu(II), Fe(II), and Fe(III) but does not protect neurons against H2O2-induced damage. Monomeric Abeta1-40 inhibits the reduction of Fe(III) induced by vitamin C and the generation of superoxides and prevents lipid peroxidation induced by Fe(II). Abeta1-42 remaining as a monomer also exhibits antioxidant and neuroprotective effects. In contrast, oligomeric and aggregated Abeta1-40 and Abeta1-42 lose their neuroprotective activity. These results indicate that monomeric Abeta protects neurons by quenching metal-inducible oxygen radical generation and thereby inhibiting neurotoxicity. Because aggregated Abeta is known to be an oxygen radical generator, our results provide a novel concept that the aggregation-dependent biological effects of Abeta are dualistic, being either an oxygen radical generator or its inhibitor.

Niemann-Pick type C1 (NPC1) disease is a fatal hereditary disorder characterized by a defect in cholesterol trafficking and progressive neurodegeneration. Although the NPC1 gene has been identified, the molecular mechanism responsible for neuronal dysfunction in brains of patients with NPC1 disease remains unknown. This study demonstrates that the amount of cholesterol within mitochondria membranes is significantly elevated in NPC1 mouse brains and neural cells. In addition, the mitochondrial membrane potential, the activity of ATP synthase, and henceforth the level of ATP are markedly decreased in NPC1 mouse brains and neurons. Importantly, reducing the level of cholesterol within mitochondrial membranes using methyl-␤-cyclodextrin can restore the activity of ATP synthase. Finally, NPC1 neurons show an impaired neurite outgrowth, which can be rescued by exogenous ATP. These results suggest that mitochondrial dysfunctions and subsequent ATP deficiency, which are induced by altered cholesterol metabolism in mitochondria, may be responsible for neuronal impairment in NPC1 disease.

The abnormal deposition of the amyloid ␤-protein (A␤) in the brain appears crucial to the pathogenesis of Alzheimer's disease (AD). Recent studies have suggested that highly amyloidogenic A␤ 1-42 is a cause of neuronal damage leading to AD pathogenesis and that monomeric A␤ 1-40 has less neurotoxicity than A␤ 1-42 . We found that mouse and human brain homogenates exhibit an enzyme activity converting A␤ 1-42 to A␤ 1-40 and that the major part of this converting activity is mediated by the angiotensin-converting enzyme (ACE).

A thermoresponsive substrate based on a triblock copolymer, poly(N-isopropylacrylamide)-block-poly[(R)-3-hydroxybutyrate]-block-poly(N-isopropylacrylamide) (PNIPAAm-PHB-PNIPAAm), co-coated with gelatin, was developed for the culture and non-enzymatic recovery of mouse embryonic stem cells. After culture, the cells could be detached by cooling at 4 degrees C for 20 min without trypsin digestion. The embryonic stem cells remained undifferentiated after culture on the gelatin/copolymer-coated surfaces, similar to standard culture techniques. Overall, the triblock copolymer coating was superior to the PNIPAAm homopolymer coating in terms of supporting better cell growth, being more stable, presenting a more homogeneous surface coating, and maintaining pluripotency of the embryonic stem cells.

The acquisition of neuronal type-specific morphogenesis is a central feature of neuronal differentiation and has important consequences for region-specific nervous system functions. Here, we report that the cell type-specific cholesterol profile determines the differential modulation of axon and dendrite outgrowths in hippocampal and cerebral cortical neurons in culture. The extent of axon and dendrite outgrowths is greater and the polarity formation occurs earlier in cortical neurons than in hippocampal neurons. The cholesterol concentrations in total homogenate and the lipid rafts from hippocampal neurons are significantly higher than those from cortical neurons. Cholesterol depletion by ␤-cyclodextrin markedly enhanced the neurite outgrowth and accelerated the establishment of neuronal polarity in hippocampal neurons, which were similarly observed in nontreated cortical neurons, whereas cholesterol loading had no effects. In contrast, both depletion and loading of cholesterol decreased the neurite outgrowths in cortical neurons. The stimulation of neurite outgrowth and polarity formation induced by cholesterol depletion was accompanied by an enhanced localization of Fyn, a Src kinase, in the lipid rafts of hippocampal neurons. A concomitant treatment with ␤-cyclodextrin and a Src family kinase inhibitor, PP2, specifically blocked axon outgrowth but not dendrite outgrowth (both of which were enhanced by ␤-cyclodextrin) in hippocampal neurons, suggesting that axon outgrowth modulated by cholesterol is induced in a Fyn-dependent manner. These results suggest that cellular cholesterol modulates axon and dendrite outgrowths and neuronal polarization under culture conditions and also that the difference in cholesterol profile between hippocampal and cortical neurons underlies the difference in neurite outgrowth between these two types of neurons.Neurons contain two types of processes, axons and dendrites, which are structurally and functionally distinct and play different roles in the maintenance of brain functions. There are studies showing the significant role of lipids in the formation of neuronal polarity; it has been shown that phospholipids regulate neurite outgrowth in cultured neurons (1) and that the correct distribution of axonal membrane proteins requires the formation of sphingomyelin/cholesterol-rich microdomains, lipid rafts, and the maturation of the axonal plasma membrane requires the up-regulation of sphingomyelin synthesis (2, 3). Cholesterol also plays a prominent role in raft-mediated trafficking and sorting, because cholesterol depletion by methyl-␤-cyclodextrin impedes trafficking from the trans-Golgi network to the apical membrane (4). It has been shown that cholesterol modulates dendrite outgrowth (5), that its deficiency enhances phosphorylation of tau and axonal depolymerization (6), and that axonal regeneration is dependent on local cholesterol reutilization in vivo (7). In addition, cholesterol supplied as glial lipoproteins stimulates the axon outgrowth of central nervous system neurons...

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Thirty-five multiparous Holstein cows averaging 550 ± 50 kg of body weight and in 2 to 4 parity were divided into three groups according to lactation stage (group A: nine cows from 4 to 1 weeks prepartum; group B: 11 cows from 1 to 30 days postpartum; group C: 15 cows from 30 to 100 days postpartum). Selenium concentration, malondialdehyde (MDA) level, glutathione peroxidase (GSH-Px) activity, thioredoxin reductase (TrxR) activity, and total antioxidant status (TAS) in serum were determined to evaluate selenium and antioxidant status in dairy cows at different stages of lactation. The results showed that mean serum selenium concentration, MDA level, and GSH-Px activity of cows in early lactation increased significantly (P < 0.05) when compared with cows in the dry period and peak lactation. Conversely, serum TrxR activity and TAS declined during this period (P < 0.05). The increase of serum MDA level during early lactation indicate that the reactive oxygen species, including lipid hydroperoxides, increase in this period, thus placing the cows at a greater risk of oxidative stress. The significant decrease in TrxR activity that is accompanied with a decrease in TAS during early lactation suggests that dairy cows have low antioxidant defense in this period and TrxR may be an important antioxidant defense mechanism in transition dairy cows.