Effects of Ascorbic and Dehydroascorbic Acids on Apoptotic Cell Death in Hippocampal Slice Culture

Ascorbic acid (AA) and dehydroascorbic acid (DHA) are known to have protective effects in experimental central nerve system disorder models such as stroke, ischemia, and epileptic seizures. The present study was conducted to examine the protective effect of AA and DHA on kainic acid (KA) neurotoxicity using organotypic hippocampal slice cultures (OHSC). Protective effects of AA and DHA on KA-induced cell death were evaluated by analyzing caspase-3. In addition, to determine if the prooxidant effect of AA is related to iron, the effect of AA on cell death was examined using desferrioxamine (DFO), an iron chelator. After 12h-KA treatment, significant delayed neuronal death was detected in CA3 region, but not in CA1. The AA (500 micrometer) and DHA (100 and 500 micrometer) pretreatments significantly prevented cell death by inhibiting caspase-3 activation in CA3 region. In the concentration of 1,000 micrometer, however, AA pretreatment might have prooxidant effect, but AA-induced oxidative reaction is mainly not related to transition metal ions. These data showed that the pretreatments of intermediate-dose AA and DHA protected KA-induced neuronal damage in OHSCs and co-pretreatment of AA and DFO did not affect cell death except for a few cases. These data suggest that both AA and DHA pretreatment have antioxidant or prooxidant effect depending on doses treated on KA-induced neuronal injury and the possible prooxidant effect of AA may not depend on the Fenton reaction.

Effect of TrkA and p75NTR on the Survival of Neurons in the Cultured Organotypic Hippocampal Slice

BACKGROUND: Nerve growth factor (NGF) promotes the survival and differentiation of vertebrate neurons, and their actions are mediated by two classes of cell surface receptors: tyrosine kinase A receptor (TrkA) and p75 neurotrophic receptor (p75NTR). We evaluated the role of NGF receptors in neuronal survival and the physical interactions between them. METHODS: Organotypic hippocampal slices were obtained from 5 to 7-day-old rat pups and were grown for 14 days in vitro. The expression of the TrkA and p75NTR was evaluated by the western blot and immunohistochemical methods. The neuroprotective effect of NGF on the blocking of antibody-induced neuronal cell death was tested by the application of NGF (0, 50 and 150 ng/ml) to the culture media in the presence of 200 ng/ml of blocking antibodies against TrkA and p75NTR. Functional interactions between the two receptors were examined using the immunoprecipitation method. RESULTS: TrkA and p75NTR were co-expressed in the principal neurons of the hippocampal slice culture, and the expression level was increased time dependently until 14 days of culture. The blocking antibody against each receptor induced neuronal damage in time and dose-dependent manners. NFG delayed or prevented the blocking antibody from inducing neuronal damage. Results from the immunoprecipitation experiment showed physical interactions between the two NGF receptors. CONCLUSIONS: Our results indicate that the co-expressed NGF receptors, TrkA and p75NTR, might have protective roles in the survival of neuronal cells through the cooperative interactions between them.

Effects of electromagnetic stimulation on neurogenesis and neuronal proliferation in rat hippocampal slice culture / 소아과

PURPOSE: Transcranial electromagnetic stimulation(TMS) is a noninvasive method which stimulates the central nervous system through pulsed magnetic fields without direct effect on the neurons. Although the neurobiologic mechanisms of magnetic stimulation are unknown, the effects on the brain are variable according to the diverse stimulation protocols. This study aims to observe the effect of the magnetic stimulation with two different stimulation methods on the cultured hippocampal slices. METHODS: We obtained brains from 8-days-old Spague-Dawley rats and dissected the hippocampal tissue under the microscope. Then we chopped the tissue into 450 micrometer thickness slices and cultured the hippocampal tissue by Stoppini's method. We divided the inserts, which contained five healthy cultured hippocampal slices respectively, into magnetic stimulation groups and a control group. To compare the different effects according to the frequency of magnetic stimulation, stimulation was done every three days from five days in vitro at 0.67 Hz in the low stimulation group and at 50 Hz in the high stimulation group. After N-methyl-D-aspartate exposure to the hippocampal slices at 14 days in vitro, magnetic stimulation was done every three days in one and was not done in another group. To evaluate the neuronal activity after magnetic stimulation, the NeuN/beta-actin ratio was calculated after western blotting in each group. RESULTS: The expression of NeuN in the magnetic stimulation group was stronger than that of the control group, especially in the high frequency stimulation group. After N-methyl-D-aspartate exposure to hippocampal slices, the expression of NeuN in the magnetic stimulation group was similar to that of the control group, whereas the expression in the magnetic non-stimulation group was lower than that of the control group. CONCLUSION: We suggest that magnetic stimulation increases the neuronal activity in cultured hippocamal slices, in proportion to the stimulating frequency, and has a neuroprotective effect on neuronal damage.