No abstract

N-Docosahexaenoyl dopamine exhibited antioxidant activity in the test with a stable oxygen radical galvinoxyl. This compound produced a dose-dependent protective effect on cultured granular cells from rat cerebellum under conditions of oxidative stress. N-Docosahexaenoyl dopamine decelerated the development of symptoms of Parkinson's disease in mice receiving neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine.

Floating retinal sections from 7-12-day-old rats form ball-shaped retinal bodies during roller culturing. Histological studies of serial sections of retinal bodies showed that their outer surface is formed by the retina completely retaining organotypic cytoarchitectonics. Some retinal bodies have laminar structure consisting of several layers of the retina. At the initial stages of culturing some retinal bodies contain a cavity, which later is completely obliterated due to the growth of axons of ganglion cells and migration of glial cells and fibroblasts. This study demonstrated the possibility of long-term survival, differentiation, and in vitro axonal regeneration of ganglion cells, the main retinal efferent neurons, which can provide the basis for investigation of pathology and drug correction of injuries and stimulation of regeneration of these cells in experimental glaucoma models.

Cortexin, a drug containing hydrolyzed brain peptides, has long been used in clinics, but the mechanisms of its action remain obscure. We have hypothesized that cortexin-related neuroprotection is associated with the ability of the drug to inhibit brain proteases. Cortexin effectively inhibited brain caspase-8, while its effects on caspase-1, -3, -9, cathepsin B and calpain were much less pronounced or absent. In addition, we isolated a peptide fraction from cortexin holding all the inhibitory capacity of the original drug, but with a much more simple composition. Both cortexin and its fraction prevented neuronal damage in a culture model of glutamate-induced cell death. Neuroprotective effect of Cortexin may be mediated by inhibition of the initiator caspase-8 in the brain.

The cysteine proteases caspase-3 and cathepsins are involved in both neuronal plasticity and neuropathology. Using primary neuroglial and glial cerebellar cultures, the pH dependence of cleavage of a synthetic caspase-3 substrate, Ac-DEVD-AMC, was studied. At acidic pH, cathepsin B cleaved Ac-DEVD, this activity being significantly higher than that of caspase-3 at pH 7.4. This activity is blocked by peptide inhibitors of both caspase-3 and cathepsin B. Substitution of culture medium for balanced salt solution stimulated cathepsin B secretion in both types of cultures. Ischemia (oxygen-glucose deprivation) significantly decreased secretion of cathepsin B activities into the culture medium.

The neuroprotective effects of synthesized lipophylic antioxidant from hindered phenol class (U-18) and hydrophylic antioxidative enzyme superoxide dismutase (SOD) were tested on long-term mouse hippocampal cell cultures exposed to hypoxia/reoxygenation. The application of U-18 to the cultures during 6-8 hr hypoxia followed by 16-18 hr reoxygenation in the absence of antioxidant significantly reduced neuronal death. Thus, lipophylic free radical scavenger may exert a delayed neuroprotective effect, probably owing to persistent incorporation into phospholipid membranes and prevention of their lipid peroxidation by means of prolonged intramembranous free radical quenching. On the other hand, the exposure of the cultures to U-18 during 15 hr hypoxia without subsequent reoxygenation also led to significant reduction of neuronal death compared with that observed without antioxidant. These findings suggest that free radical neuronal damage may occur under conditions of prolonged restricted oxygen access to the neurons. The hypoxic/posthypoxic neuronal injury significantly decreased in the cultures exposed to hydrophylic cytoplasmic enzyme SOD (300 U/ml). The neuroprotective effects of both lipophylic U-18 and hydrophylic SOD on the cultures exposed to hypoxia/reoxygenation might reflect the damaging free radical overproduction in different morphofunctional compartments of the nerve cell.

No abstract

In the model of induced neuronal resistance to the toxic effect of glutamate (deprivation of trophic factors), exosome secretion is demonstrated. Exosomes are secreted at the development of resistance during deprivation and at the first 24 h after preconditioning, as was shown by dot blot of extracellular fluid using anti-CD63 antibody. The autophagy inhibitor bafilomycin (0.01 μM) significantly reduces the quantity of the secreted exosomes at the stage of autophagy induction and at 24 h after induction. At the same time, inhibition of autophagy during the deprivation of trophic factors prevents the development of resistance, but inhibition of autophagy during the first 24 h after deprivation does not affect the development of resistance. We suggest that the long-term effects of preconditioning may be mediated by exosome secretion.