Iron is believed to contribute to the process of cell damage and death resulting from ischemic and traumatic insults by catalyzing the oxidation of protein and lipids. Exposure of cultured rat hippocampal neurons to iron (FeSO4) caused a dose-dependent reduction in neuronal survival, which was potentiated by ascorbate. Damage to neurons was associated with a significant level of oxygen radical in the culture medium. The iron chelator desferal prevented both the neuronal degeneration caused by FeSO4 and the production of oxygen radical, demonstrating that ionic iron was responsible for the cell damage. Iron neurotoxicity was associated with an elevation of [Ca2+]i and was attenuated by NMDA receptor antagonists. Since recent findings demonstrated neuroprotective effects of growth factors in cell culture and in vivo models of ischemia, we examined the effects of growth factors on iron-induced damage. Basic fibroblast growth factor (bFGF), nerve growth factor (NGF), and insulin-like growth factors (IGF-I and IGF-II) each protected neurons against iron-induced damage. Both rat hippocampal and human cortical neurons were protected by these growth factors. Taken together, the data suggest that the neuroprotective effects of growth factors against excitotoxic/ischemic insults may result, in part, from a prevention or attenuation of oxidative damage.
A series of tricyclic quinoxalinediones, 5,6-dihydro-1H-pyrrolo[1,2,3-de]quinoxaline-2,3-diones and 6,7-dihydro-1H,5H-pyrido[1,2,3-de]quinoxaline-2,3-diones, were synthesized and was evaluated for their affinity for the glycine binding site of the NMDA receptor using a [3H]-5,7-dichlorokynurenic acid binding assay. The six-membered ring-fused tricyclic quinoxalinedione 18g (Ki = 9.9 nM) displayed high affinity for the glycine site. The anilide derivative 20g (Ki = 2.6 nM) was 4-fold more potent than 18g and as potent as L-689,560, one of the most potent glycine antagonists so far prepared. Although the carboxylic acid derivative of the corresponding five-membered ring-fused tricyclic quinoxalinedione 18e (Ki = 7.3 nM) had affinity comparable to that of 18g, the anilide derivative 20e largely decreased in the affinity in contrast to 20g. Enantiomers 23g, 24g, 25g, and 26g were prepared and tested. Only the S enantiomer 25g (Ki = 0.96 nM) retained the affinity among the anilide derivatives, whereas both enantiomers 23g (Ki = 2.3 nM) and 24g (Ki = 9.6 nM) were active among the carboxylic acid derivatives. The origin of the high affinity of carboxylic acid derivatives such as 18e and 18g would be a charge-charge interaction between the anionic carboxylate residues of the compounds and the cationic proton-donor site in the receptor.
Brain-derived neurotrophic factor (BDNF) belongs to the neurotrophin family and has been shown to be a potent and effective trophic factor for motor neurons and other neurons of the peripheral and central nervous. Little is known, however, about the relationship between the efficacy and pharmacokinetics of s.c. administered BDNF. In this study, the efficacy of BDNF on motor neuron protection in sciatic or facial nerve axotomy models was examined and compared with the concommitant concentrations of BDNF in plasma. Delayed treatment (started at 1 week after surgery) of BDNF was also shown to retard choline acetyltransferase reduction in sciatic nerve axotomy models.
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