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Neuroprotective MK801 is associated with nitric oxide synthase during hypoxia/reoxygenation in rat cortical cell
Hsueh-Meei Huang1, Chiung-Chyi Shen, Hsiu-Chung Ou
1Department of Education and Medical Research, Taichung Veterans General Hospital, Taichung, Taiwan, Republic of China. hhuang@burke.org
Abstract:
The neuroprotective effect of MK801 against hypoxia and/or reoxygenation-induced neuronal cell injury and its relationship to neuronal nitric oxide synthetase (nNOS) expression were examined in cultured rat cortical cells. Treatment of cortical neuronal cells with hypoxia (95% N(2)/5% CO(2)) for 2 h followed by reoxygenation for 24 h induced a release of lactate dehydrogenase (LDH) into the medium, and reduced the protein level of MAP-2 as well. MK801 attenuated the release of LDH and the reduction of the MAP-2 protein by hypoxia, suggesting a neuroprotective role of MK801. MK801 also diminished the number of nuclear condensation by hypoxia/reoxygenation. The NOS inhibitors 7-nitroindazole (7-NI) and N (G)-nitro-L-arginine methyl ester (L-NAME), as well as the Ca(2+) channel blocker nimodipine, reduced hypoxia-induced LDH, suggesting that nitric oxide (NO) and calcium homeostasis contribute to hypoxia and/or the reoxygenation-induced cell injury. The levels of nNOS immunoactivities and mRNA by RT-PCR were enhanced by hypoxia with time and, down regulated following 24 h reoxygenation after hypoxia, and were attenuated by MK801. In addition, the reduction of nNOS mRNA levels by hypoxia/reoxygenation was also diminished by MK801. Further delineation of the mechanisms of NO production and nNOS regulation are needed and may lead to additional strategies to protect neuronal cells against hypoxic/reoxygenation insults.
Insights
MK801 demonstrates neuroprotective effects against neuronal cell injury caused by hypoxia and reoxygenation. This protection is linked to the regulation of neuronal nitric oxide synthetase (nNOS) expression.
Area of Science:
- Neuroscience
- Cell Biology
- Pharmacology
Background:
- Hypoxia and reoxygenation induce neuronal cell injury, characterized by lactate dehydrogenase (LDH) release and reduced MAP-2 protein levels.
- Nitric oxide (NO) and calcium homeostasis are implicated in hypoxia/reoxygenation-induced neuronal damage.
- Neuronal nitric oxide synthetase (nNOS) expression is altered during hypoxic/reoxygenation insults.
Purpose of the Study:
- To investigate the neuroprotective effect of MK801 against hypoxia/reoxygenation-induced neuronal cell injury.
- To examine the relationship between MK801's neuroprotection and neuronal nitric oxide synthetase (nNOS) expression.
- To elucidate the roles of NO and calcium in hypoxic/reoxygenation injury.
Main Methods:
- Cultured rat cortical cells were subjected to hypoxia (2 h) followed by reoxygenation (24 h).
- MK801, NOS inhibitors (7-NI, L-NAME), and a calcium channel blocker (nimodipine) were used.
- Lactate dehydrogenase (LDH) release, MAP-2 protein levels, nuclear condensation, and nNOS mRNA/immunoactivity were measured.
Main Results:
- MK801 attenuated LDH release and MAP-2 reduction, indicating neuroprotection.
- MK801 reduced nuclear condensation caused by hypoxia/reoxygenation.
- NOS inhibitors and nimodipine reduced hypoxia-induced LDH release.
- Hypoxia increased nNOS expression, which was downregulated by reoxygenation but attenuated by MK801.
Conclusions:
- MK801 exhibits neuroprotective properties against hypoxia/reoxygenation injury in cultured cortical neurons.
- The neuroprotective mechanism of MK801 involves the modulation of nNOS expression and potentially calcium homeostasis.
- Further research into NO production and nNOS regulation may offer novel neuroprotective strategies.