7,8-Dihydroxy-4-methylcoumarin (Dhmc) is a precursor in the synthesis of derivatives of 4-methyl coumarin, which has excellent radical scavenging properties. In this study, we investigated whether Dhmc protects against oxidative stress and ischemic brain injury. We found that Dhmc protected against glutamate toxicity in hippocampal HT-22 cells in a concentration-dependent manner in vitro. Dhmc inhibited glutamate-induced glutathione depletion and generation of reactive oxygen species, suggesting that Dhmc has an antioxidant effect. In addition, Dhmc inhibited glutamate-induced depletion of hippocalcin, a protein that buffers intracellular calcium and prevents calcium-induced cell death. In our in vivo studies, Dhmc reduced infarct volume in neonatal rats when administered 4 h after cerebral hypoxia/ischemia injury and attenuated the hypoxia/ischemia injury-induced decrease of hippocalcin expression in neonatal rats. Taken together, these results suggest that Dhmc prevents glutamate-induced toxicity by scavenging free radicals and regulating hippocalcin expression. Dhmc may represent a promising agent in the treatment of acute and chronic neurological disorders induced by oxidative stress.

<p>Apoptosis is a genetically regulated cell death program, which shows distinct morphological characteristics. It takes place during neuronal development and in some neurodegenerative diseases. During apoptosis, the intracellular proteins are degraded by various caspases, cysteine aspartases, which are regulated by pro- and anti-apoptotic signals. This thesis elucidates the role of anti-apoptotic proteins in nerve cell survival and neurodegeneration. Studies have focused on Bcl-2 family members and Inhibitor of Apoptosis Proteins (IAP).</p><p>XIAP and RIAP-2 are IAP proteins, which are expressed by neurons in the central nervous system. Kainic acid, a glutamate receptor agonist that induces seizures, increased XIAP immunoreactivity in rat hippocampus, whereas RIAP-2 expression in the same time decreased in degenerating neurons. Both XIAP and RIAP-2 were absent in dying neurons indicating that these proteins have a protective role in kainic acid induced neurodegeneration.</p><p>NAIP, another IAP family member, was shown to interact with the calcium binding protein Hippocalcin using the yeast two-hybrid system and immunoprecipitation experiments. Hippocalcin-NAIP interaction increased motoneuron survival in caspase-3 independent and dependent manners.</p><p>The anti-apoptotic Bcl-2 proteins, Bcl-2 and Bcl-x, were studied using cultured neurons and human neuronal progenitor cells. In the progenitor cells, Bcl-2 overexpression enhanced cell survival and induced downregulation of Caspase-2 (ICH-1) and caspase-3 (YAMA/CPP32). These results suggest a novel mechanism for the action of Bcl-2.</p><p>Estrogen was shown to inhibit death of cultured dorsal root ganglion neurons (DRG) after nerve growth factor withdrawal. The hormone increased the levels of Bcl-x, which may explain the known neuroprotective function of estrogen.</p>

Apoptosis is a genetically regulated cell death program, which shows distinct morphological characteristics. It takes place during neuronal development and in some neurodegenerative diseases. During apoptosis, the intracellular proteins are degraded by various caspases, cysteine aspartases, which are regulated by pro- and anti-apoptotic signals. This thesis elucidates the role of anti-apoptotic proteins in nerve cell survival and neurodegeneration. Studies have focused on Bcl-2 family members and Inhibitor of Apoptosis Proteins (IAP). XIAP and RIAP-2 are IAP proteins, which are expressed by neurons in the central nervous system. Kainic acid, a glutamate receptor agonist that induces seizures, increased XIAP immunoreactivity in rat hippocampus, whereas RIAP-2 expression in the same time decreased in degenerating neurons. Both XIAP and RIAP-2 were absent in dying neurons indicating that these proteins have a protective role in kainic acid induced neurodegeneration. NAIP, another IAP family member, was shown to interact with the calcium binding protein Hippocalcin using the yeast two-hybrid system and immunoprecipitation experiments. Hippocalcin-NAIP interaction increased motoneuron survival in caspase-3 independent and dependent manners. The anti-apoptotic Bcl-2 proteins, Bcl-2 and Bcl-x, were studied using cultured neurons and human neuronal progenitor cells. In the progenitor cells, Bcl-2 overexpression enhanced cell survival and induced downregulation of Caspase-2 (ICH-1) and caspase-3 (YAMA/CPP32). These results suggest a novel mechanism for the action of Bcl-2. Estrogen was shown to inhibit death of cultured dorsal root ganglion neurons (DRG) after nerve growth factor withdrawal. The hormone increased the levels of Bcl-x, which may explain the known neuroprotective function of estrogen.