Degeneration Of Neuronal Cells Research Articles

Syringin from Fraxinus rhynchophylla Hance inhibit the apoptotic neuronal cell death induced by Aβ25–35

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by progressive degeneration and loss of neuronal cells in the brain. β-Amyloid peptide (Aβ) is produced by proteolysis of amyloid precursor protein (APP), and its accumulation in the senile plaque is the major hallmark of AD pathogenesis [1, 2, 3]. Various experimental evidence support that Aβ plaque can induce neurotoxic effect on neuronal cells [4]. In the course of screening of anti-dementia agents from medicinal plants, the ethanolic extract of Fraxinus rhynchophylla Hance showed neuroprotective effect against Aβ25–35-induced cytotoxicity in cultured B103 cells. The extract was partitioned with dichloromethane (CH2Cl2), n-butanol (n-BuOH), and water, successively. The repeated chromatographic separation afforded an active compound, and its chemical structure was elucidated as syringin by 1H- and 13C-NMR and LC-MS. Its effects on apoptotic cell death were determined by MTT, H2DCF-DA and caspase-3 activity assay. As results, syringin significantly increased B103 cell viability up to 79.16% at 20µM in the presence of 12.5µM of Aβ25–35, and it remarkably decreased Aβ25–35-induced reactive oxygen species (ROS) generation up to 92.87% at the same concentration. In addition, the activity of caspase-3, an enzymatic major marker of apoptosis, was decreased up to 39.75% at 25µM. These results indicate that syringin and ethanolic extracts from Fraxinus rhynchophylla Hance could be a promising agent for anti-dementia.

Study of neuroprotection of donepezil, a therapy for Alzheimer's disease

Donepezil is a potent acetylcholinesterase inhibitor used for the treatment of Alzheimer's disease. Although acetylcholinesterase inhibitors are thought to be symptomatic treatment of Alzheimer's disease, it is not clear whether they are effective against progressive degeneration of neuronal cells. In this study, we investigated the neuroprotective effects of donepezil against ischemic damage, N-methyl- d-aspartate (NMDA) excitotoxicity, and amyloid-beta (Aβ) toxicity using rat brain primary cultured neurons. Lactate dehydrogenase (LDH) released into the culture medium was measured as a marker of neuronal cell damage. As an ischemic damage model, we used oxygen–glucose deprivation in rat cerebral cortex primary cultured neurons. Pretreatment with donepezil (0.1, 1 and 10 μM) significantly decreased LDH release in a concentration-dependent manner. However, other acetylcholinesterase inhibitors (galantamine, tacrine and rivastigmine) did not significantly decrease LDH release. In a NMDA excitotoxicity model, pretreatment with donepezil (0.1, 1 and 10 μM) decreased the LDH release in a concentration-dependent manner. In binding assay for glutamate receptors, donepezil at 100 μM only slightly inhibited binding to the glycine and polyamine sites on NMDA receptor complex. We further examined the effect of donepezil on Aβ (1–40)- and Aβ (1–42)-induced toxicity in primary cultures of rat septal neurons. Pretreatment with donepezil (0.1, 1 and 10 μM) significantly decreased LDH release induced by Aβs in a concentration-dependent manner. However, other acetylcholinesterase inhibitors (galantamine and tacrine) and NMDA receptor antagonists (memantine and dizocilpine (MK801)) did not significantly decrease LDH release. These results demonstrate that donepezil has protective effects against ischemic damage, glutamate excitotoxicity and Aβ toxicity to rat primary cultured neurons and these effects are not dependent on acetylcholinesterase inhibition and antagonism of NMDA receptors. Thus, donepezil is expected to have a protective effect against progressive degeneration of brain neuronal cells in ischemic cerebrovascular disease and Alzheimer's disease.

S100B in underweight and weight-recovered patients with anorexia nervosa

Anorexia nervosa (AN) commonly arises during adolescence, leading to interruptions of somatic and psychological development as well as to cortical atrophy and reductions of brain volume. While most brain changes shift towards normal with weight restoration, it is not certain whether they are related to the loss of brain cells, neuropil or merely due to fluid shifts. We measured S100B serum concentrations and psychometric characteristics in 34 patients with acute AN, 19 weight-recovered patients and 35 healthy control women (HCW). Plasma tryptophan and leptin levels were determined as markers for malnutrition and neuroendocrine adaptation to semi-starvation. Peripheral S100B concentrations of acute and former AN patients were not elevated and not statistically different from HCW. BMI, peripheral leptin levels and measures of psychopathology as well as executive cognitive functioning did not correlate with S100B. Plasma tryptophan was positively related to S100B. Our results are in line with our previous findings showing unaltered GFAP and NSE plasma levels in patients with acute AN. Together they do not support hypotheses comprising the degeneration of glial or neuronal cells to explain common signs of brain atrophy in patients with acute AN.

Synergistic Neurotoxic Effects of Arsenic and Dopamine in Human Dopaminergic Neuroblastoma SH-SY5Y Cells

Parkinson's disease is an environmentally influenced, neurodegenerative disease of unknown origin that is characterized by the progressive loss of dopaminergic neurons in the substantia nigra pars compacta of the brain. Arsenic is an environmental contaminant found naturally in ground water, industrial waste, and fertilizers. The initial goal of the present study was to determine if a mixture of arsenite (As(+3)) and dopamine (DA) could cause enhanced degeneration of dopaminergic neuronal cells. Additional goals were to determine the mechanism (apoptosis or necrosis) of As- and DA-induced cell death and if death could be attenuated by antioxidants. The cell culture model employed was the SH-SY5Y neuroblastoma cell line that has been shown to possess differentiated characteristics of dopaminergic neurons. The results demonstrated that a mixture of As(+3) and DA was synergistic in producing the death of the SH-SY5Y cells when compared with exposure to either agent alone. A mixture of 10muM As(+3) and 100muM DA produced almost a complete loss of cell viability over a 24-h period of exposure, whereas, each agent alone had minimal toxicity. It was shown that necrosis, and not apoptosis, was the mechanism of cell death produced by exposure of the SH-SY5Y cells to the mixture of As(+3) and DA. It was also demonstrated that the antioxidants, N-acetylcysteine, and Sulforaphane, attenuated the toxicity of the mixture of As(+3) and DA to the SH-SY5Y cells. This study provides initial evidence that As(+3) and DA synergistically can cause enhanced toxicity in cultured neuronal cells possessing dopaminergic differentiation.

Retinal Ischemia and Reperfusion Causes Capillary Degeneration: Similarities to Diabetes

Retinal neurons and vasculature interact with each other under normal conditions, and occlusion of the retinal vasculature can result in damage to retinal neurons. Whether damage to the neural retina will damage the vasculature, however, is less clear. This study was conducted to explore the relationship between vascular and nonvascular cells of the retina. The response of the retinal vasculature to an injury (ischemia and reperfusion; I/R) that is known to cause neuronal degeneration was studied. I/R injury to the retinas was induced in Lewis rats and C57BL/6J mice by elevating intraocular pressure (IOP), and reperfusion was established immediately afterward. Some rats were pretreated with aminoguanidine (AMG, 50 mg/Kg BW in drinking water) before the procedure. Poly(ADP-ribose) polymerase (PARP) activity and expression of inducible nitric oxide synthase (iNOS), and cycloxygenase-2 (COX-2) were measured by Western blot analysis, and levels of TNF-alpha and intercellular adhesion molecule (ICAM)-1 mRNA were measured by qPCR at 2 and 7 days after the procedure. Also at 2 and 7 days after the I/R injury, apoptosis of retinal neural cells (demonstrated by TUNEL assay), density of cells in the ganglion cell layer, and thickness of retinas were quantitated, and the number of TUNEL-positive capillary cells and degenerated capillaries were assessed. Retinal neurodegeneration and capillary degeneration were also examined in C57BL/6J mice 2, 5, 8, and 14 days after I/R injury. As expected, loss of cells in the retinal ganglion cell layer was apparent 2 days after I/R injury in the rat and mouse models. In contrast, the retinal vasculature had essentially no pathology at this time in either model. Surprisingly, the number of degenerated capillaries increased greatly by 7 to 8 days after the injury. Administration of aminoguanidine significantly inhibited the I/R-induced capillary degeneration as well as neurodegeneration in the rat model. Retinal I/R caused increased PARP activity (detected by poly(ADP-ribosy)lated proteins), as well as upregulation of iNOS, COX-2, TNF-alpha, and ICAM-1 levels in rats, consistent with an inflammatory process. Capillary degeneration is an unrecognized component of acutely elevated IOP and develops only after neurodegeneration is severe. Thus, this finding raises the possibility that damage to the neural retina contributes to capillary degeneration. Aminoguanidine, a nonspecific inhibitor of iNOS, inhibited I/R-induced degeneration of both neuronal and vascular cells of the retina. The model of retinal ischemia and reperfusion will be a useful tool for investigating the relationship between neuronal damage and vascular damage in glaucoma and other diseases such as diabetic retinopathy.

Expression and significance of nerve growth factor receptor p75 in rats' cathartic colonic wall

To investigate the expression of nerve growth factor receptor p75 in a normal and cathartic colon and its significance in the formation of the cathartic colon in rats. Sixty Sprague-Dawley rats were equally divided into normal control group, rhubarb group and phenolphthalein group. A model of the cathartic colon was constructed by gastric infusion with rhubarb or phenolphthalein in rats. The first dose of rhubarb and phenolphthalein was both 200 mg/kg/d and was increased by 200 mg/kg/d with each passing day. The last dose of rhubarb and phenolphthalein was 3200 mg/kg/d and 4200 mg/kg/d, respectively. The transit function of colon was measured by the Chinese ink expulsion test; the p75 in colon wall was determined by the immunohistochemical method. The transit speed was much slower in the cathartic colon group than that in the control group. The imprinted Chinese ink length and the ratio of imprinted length/total colon length in the rhubarb-induced cathartic colon was significantly shorter than that of the control group (77.38 +/- 8.42 vs 94.25 +/- 7.07 cm, P < 0.01). Those in the phenolphthalein-induced group (83.38 +/- 9.75 cm) were also significantly shorter than those of the control group but to a lesser degree (P < 0.05). p75 was abundantly expressed in the submucosal nerve plexus and weakly expressed in the myenteric plexus. The expression of p75 was much higher in the rhubarb-induced group. The expression was strongly positive in the submucosal nerve plexus, significantly higher than that in the controls (P < 0.01). In the myenteric plexus, p75 was also highly expressed (P < 0.05). In the case of the phenolphthalein-induced group, the expression of p75 was positive in the submucosal nerve plexus but was positive in the myenteric plexus of three rats only. The remaining rats were negative or weakly positive. This was not significantly different from that of the control group. The abnormal expression of p75 in cathartic colon probably has some effect on the degeneration or apoptosis of neuronal cells in the enteric nerve plexus, with a subsequent pathological change of the enteric nervous system, and thus leads to abnormalities in colonic dynamics. The kind of lesion is probably associated with long-term use of irritative cathartics.

Protective effects of EUK4010 on β‐amyloid(1–42) induced degeneration of neuronal cells

EUK4010 has been identified to exhibit an inhibitory effect on beta-amyloid (Abeta)(1-42)-induced loss of neuronal cell viability. Further studies demonstrated that EUK4010 attenuated the Abeta(1-42)-induced degeneration in both cultured rat hippocampal neurons and human neuroblastoma cells, as demonstrated by typical morphological changes, cell viability and the chip-based flow cytometric assay. Gene expression analysis using DNA microarray showed that the senescence marker calcium-binding protein, regucalcin (Rgn), GABA-A receptor pi subunit (Gabrp), the huntingtin binding protein, optineurin (Optn) and a semaphorin family plexin A3 similar protein (Plex-similar) changed their expression levels significantly in cultured neurons after Abeta(1-42) treatment. In this report, we have undertaken a chemical genetic approach to study the molecular basis of Abeta(1-42) effects on the neuronal degeneration. Our results demonstrate that EUK4010 completely blocked the Abeta(1-42)-induced up-regulation of GABA-A receptor pi subunit and the semaphorin family plexin A3 similar protein, and partially attenuated the down-regulation of senescence marker calcium-binding protein, regucalcin. These observations suggest that EUK4010 may prevent or reduce the Abeta toxicity by regulating the expression of genes involved in the Abeta induced neuronal degeneration. These genes may represent a promising target for the therapeutic drug development for Alzheimer's disease (AD) and other neurological disorders. Furthermore, EUK4010 and its analogues could potentially be developed as neuronal protective agents for the treatment of these diseases.

Cell Replacement Therapy in the Inner Ear

The mammalian inner ear is vulnerable to genetic disorders and aging, as well as to injuries caused by overstimulation, ototoxic drugs, and viral infections. Due to the poor regeneration of the sensory epithelium and the spiral ganglion neurons in the adult mammalian inner ear, cell replacement therapy strategies have been proposed to compensate for degeneration and loss of sensory and neuronal cells. Transplantation of stem cells and embryonic neurons into the inner ear has revealed that exogenous cells can survive, migrate, differentiate, and extend neuritic projections in the auditory system of adult mammals. These results suggest that cell replacement therapy could provide an effective future treatment alternative for hearing loss and other inner ear disorders.

Cloning and expression analysis of a Parkinson’s disease gene, uch-L1, and its promoter in zebrafish

Three genes, α-synuclein, parkin, and ubiquitin C-terminal hydrolase L1 (UCH-L1), have been associated with inherited forms of Parkinson’s disease (PD), although their in vivo functions have remained largely unknown. To develop an animal model for the molecular study of PD, we cloned zebrafish uch-L1 cDNA and its gene promoter. Sequence analysis revealed that the zebrafish Uch-L1 is highly homologous (79%) to the human UCH-L1, which is a member of the deubiquitinating enzymes. By whole-mount in situ hybridization, we examined the spatiotemporal expression of uch-L1 mRNA in developing zebrafish embryos. The uch-L1 mRNAs are detected in neuronal cells at the first day of embryo development. The expression domain of uch-L1 overlaps with that of tyrosine hydroxylase, a molecular marker for dopaminergic neurons, in the ventral diencephalon, an equivalent structure to the substantia nigra where PD progresses in human. To further analyze the tissue-specific regulation of uch-L1 gene expression, we also tested its gene promoter activity and showed a preferential neuronal expression in transient transgenic zebrafish embryos. These results suggest that uch-L1 may have an important role in the development of neuronal cells in early embryos as well as in the degeneration and disease of neuronal cells in late adult brain.

Neuroreplacement therapy and stem cell biology under disease conditions.

Recent advances in stem cell technology are expanding our ability to replace a variety of cells throughout the body. In the past, neurological diseases caused by the degeneration of neuronal cells were considered incurable because of a long-held 'truism'; neurons do not regenerate during adulthood. However, this statement has been challenged, and we have now found much evidence that the brain is indeed capable of regenerating neurons after maturing. Based on this new concept, researchers have shown neural differentiation of stem cells and recovery of function following transplantation of these cells into the brain. These results may promise a bright future for clinical applications of stem cell strategies in neurological diseases; however, we must consider the pathophysiological environments of individual diseases that may affect stem cell biology. Before we begin to develop clinical applications, we must consider environmental factors that have not been discussed in the current preclinical studies. Here, we study cases of Alzheimer's disease and schizophrenia and discuss the effects of environmental factors under disease conditions.

Protective effect of donepezil in a primary culture of rat cortical neurons exposed to oxygen–glucose deprivation

Donepezil hydrochloride (donepezil: (±)-2-[(1-benzylpiperidin-4-yl)methyl]-5,6-dimethoxy-indan-1-one monohydrochloride) is a potent acetylcholinesterase inhibitor used for treatment of Alzheimer's disease. Although acetylcholinesterase inhibitors are used as a symptomatic treatment for Alzheimer's disease, it is not clear whether or not they are effective against progressive degeneration of neuronal cells. In this study, we investigated the neuroprotective effects of donepezil and other acetylcholinesterase inhibitors used for treatment of Alzheimer's disease, i.e., galantamine, rivastigmine, and tacrine. As a neurodegenerative model, we used rat cortical neurons exposed to oxygen–glucose deprivation. Lactate dehydrogenase (LDH) released into the culture medium was measured as a marker of neuronal cell damage. First, the effects of donepezil (10 μM) on three different treatment schedules (from 12 h before to 24 h after oxygen–glucose deprivation (pre-12 h), from 1 h before to 24 h after oxygen–glucose deprivation (pre-1 h) and from 1 h after to 24 h after oxygen–glucose deprivation (post-1 h)) were compared. The pre-12-h treatment most effectively inhibited LDH release. The protective effect of donepezil was confirmed morphologically. Next, the effects of donepezil and the other three acetylcholinesterase inhibitors were compared under the pre-12-h treatment condition. Donepezil (0.1, 1, and 10 μM) significantly decreased LDH release in a concentration-dependent manner. However, galantamine (1, 10, and 100 μM), tacrine (0.1, 1, and 10 μM), and rivastigmine (0.1, 1, and 10 μM) did not significantly decrease LDH release. The neuroprotective effect of donepezil was not antagonized by scopolamine or mecamylamine. These results demonstrate that donepezil has a protective effect against oxygen–glucose deprivation-induced injury to rat primary cultured cerebral cortical neurons. Besides, it is suggested that this effect of donepezil is independent of muscarinic cholinergic system and nicotinic cholinergic system. Thus, donepezil is expected to have a protective effect against progressive degeneration of brain neuronal cells in ischemic cerebrovascular disease and Alzheimer's disease.

Activation of MAPK and CREB by GM1 induces survival of RGCs in the retina with axotomized nerve.

Neuronal cells undergo apoptosis when the supply of neurotrophic factor is limited by injury, trauma, or neurodegenerative disease. Ganglioside has both neuritogenic and neurotropic functions. Exogenously administered monosialoganglioside (GM1) has been shown to have a stimulatory effect on neurite outgrowth and to prevent degeneration of neuronal cells in the central nervous system. Even though GM1 has been shown to mimic, or have synergy with, neurotrophic factors, the neuroprotective mechanism of GM1 has not been well understood. In this study, optic nerve transection, or axotomy, was used as an in vivo model system for injury, to examine the protective mechanism of GM1 in injured retinal ganglion cells. GM1 was injected into the vitreous body before axotomy, and the protective effect of GM1 observed with regard to activation of mitogen-activated protein kinase (MAPK) and phosphorylation of cAMP-responsive element-binding (CREB) protein. Activation of MAPK and CREB were examined by Western blot analysis and immunohistochemistry, and the surviving retinal ganglion cells were counted after retrograde fluorescence labeling. GM1 inhibited the degeneration of axotomized retinal ganglion cells. In addition, GM1 enhanced the activation of MAPK and CREB with the treatment of GM1 in the retina with axotomized nerve. Treatment of MAPK inhibitor PD98059 with GM1 reduced the protective action of GM1 and prevented GM1-induced phosphorylation of CREB. GM1 protected the axotomized retinal ganglion cells (RGCs) from cell death after axotomy through the activation of MAPK and CREB.

Methylmercury-Mediated Down-Regulation of mtHSP70 and Phospholipase A2 mRNA Expression in Human Neuroblastoma NB-1 Cells Identified by cDNA Macroarray Analysis.

bCREST, Methylmercury (MeHg) is a well-known environmental pollutant that causes severe neurological damage, especially in the developing nervous system. When human neuroblastoma NB-1 cells were treated with MeHg at sublethal concentrations, down-regulation of two apoptosis-associated genes, mtHSP70 (GRP75/ PBP74/ mtHSP75 /HSPA9B/mortalin) and phospholipase A2 (PLA2), was identified using the cDNA macroarray technique. These observations were further confirmed by RT-PCR and Northern blotting experiments. Northern blotting data also demonstrated that only groups III and VI B of PLA2 were downregulated, while group IIE remained unchanged. These results suggest that the mtHSP70 and PLA2 may be involved in the MeHg-mediated degeneration of neuronal cells.

The Long-term Effect of Bilateral Inferior Colliculus Ablation on Auditory Brainstem Response in Awake Cats

In this study auditory brainstem responses (ABRs) were recorded repeatedly in three awake cats before and after bilateral aspiration of the inferior colliculi (ICs). All surgical procedures were performed under anaesthesia with Nembutal. Postoperative recordings were obtained 1 week, 3 months, 8 months and 13 months after bilateral aspiration of the ICs in order to study the long-term changes in ABRs. The P5 amplitude was markedly reduced only at 1 week after aspiration. P1 and P2 amplitudes were affected slightly at 3 months and 1 year, but those of P3 and P4 decreased significantly. After perfusion of these cats, histological examination of the brainstem revealed complete ablation of both ICs, neuronal loss in the nucleus of the lateral lemniscus and the superior olivary complex and preservation of the cochlear nucleus. Our results suggest that retrograde degeneration of neuronal cells of the brainstem, which project to the IC from the nucleus of the lateral lemniscus and superior olivary complex except the cochlear nucleus, affect the peak amplitudes of the ABR over the long-term.

High-density lipoprotein aggregated by oxidation induces degeneration of neuronal cells.

We have previously reported that high-density lipoprotein (HDL) exhibits antineuritogenic effects on chicken cerebral cells in culture. In the present study, we show the effects of HDLs, oxidized by UV irradiation or heating, on chicken cerebral neurons in culture. Both treatments produced several physical and chemical changes in the HDLs, i.e., formation of lipid peroxides, enlargement of HDL diameters, an increased exposure of the tryptophan groups of the apolipoprotein A-I to a more hydrophilic environment, formation of bityrosines, and cross-linking of apolipoprotein A-I. When these treatments were performed in the absence of EDTA, most of the modifications described above were more intense and HDLs formed a macroaggregate that displays a rosette-like structure. The aggregated HDLs produced neurodegeneration and death when added to both undifferentiated and differentiated cerebral neurons in culture. This process was accompanied by the disorganization of the cellular microtubular cytoskeleton and hyperphosphorylation of the microtubule-associated protein tau. Native HDL or HDLs treated in the presence of EDTA inhibited the neuritogenesis of undifferentiated neurons but did not show any significant effect on the differentiated neurons in culture. The effects on the cellular cytoskeleton and morphology of aggregated HDLs recall those of the fibrillar beta-amyloid peptide. The present results suggest that aggregated HDLs could participate in neurodegeneration associated with oxidative stress in the CNS.

Induction of the Serotonin1A Receptor in Neuronal Cells During Prolonged Stress and Degeneration

Neuronal migration in brain is followed by differentiation of committed neurons and simultaneous apoptosis of uncommitted preneuronal cells due to a limiting supply of trophic factors and nutrients. We have dissected differentiation and apoptosis by designing a simple in vitro model for this nutrient deprivation using engineered neuronal cell lines stably transfected with a promoterless segment (G-21) of the intronless human serotonin1A receptor (5-HT1A-R) gene. Despite the use of widely different heterologous promoters (cytomegalovirus and Rous sarcoma virus) for the stable expression of G-21, a dramatic increase in expression of the 5-HT(1A)-R (five- to 15-fold) and its mRNA was always observed during degeneration and apoptosis of nutrient-deprived neuronal cells. Involvement in this induction of a 170-bp 5'-end untranslated sequence (5'-UT) (tail end of the 500-bp natural promoter) of G-21 was confirmed by stable transfection of neuronal cells with an SV-40 promoter-driven construct harboring the 5'-UT and the reporter chloramphenicol acetyltransferase (CAT) cDNA. Presence of the 5'-UT resulted in a threefold increase in CAT expression during nutrient deprivation in randomly chosen clones. The induction was also observed in the endogenous 5-HT1A-R, expressed by embryonic day 16 mouse hippocampal neurons, subsequent to nutrient deprivation and onset of degeneration. A trophic role of the 5-HT1A-R has been suggested in earlier studies. Considering the example of protective heat shock proteins, which are induced during various types of stress, our results suggest that stressed neuronal cells undergoing degeneration and apoptosis synthesize increased levels of 5-HT1A-R as a final attempt to survive.

Alteration of transglutaminase activity in rat and human spinal cord after neuronal degeneration.

We measured the activity of transglutaminase (TG), a Ca(2+)-dependent enzyme and a biochemical marker of cell degeneration, in the adult rat spinal cord after unilateral occlusion of a branch of the dorsal spinal artery, and compared it to the enzyme activity in the tissue on the contralateral side without ischemic damage. The affected half of the spinal cord showed a significant rise in intrinsic (endogenous) TG activity one day after ischemic insult while no apparent morphological changes were observed in the tissue. However, the enzymic activity on the affected side gradually decreased to reach the level in the non-affected tissue, accompanying severe degeneration of neuronal cells at 7 days after the surgery, then it declined to nearly half the level in the intact tissue 30 days after the operation. We also determined the TG activity in transverse sections of the human spinal cord obtained at autopsy from 5 amyotrophic lateral sclerosis (ALS) and 9 non-ALS patients. TG activity in thoracic and lumbar cords was markedly low in ALS patients not only in ventral and lateral regions but also in the dorsal portion. These findings imply that the reduced TG activity in the ALS spinal cord is one of the characteristic features of the disease reflecting exhaustion of the enzyme in the tissue resulting from degeneration of the spinal neurons through cross-linkage of soluble intraneuronal cytoplasmic proteins.

The neurotoxic carboxy-terminal fragment of the Alzheimer amyloid precursor binds specifically to a neuronal cell surface molecule: pH dependence of the neurotoxicity and the binding

One of the hallmarks of Alzheimer's disease neurodegeneration is the accumulation of deposits of amyloid in neuritic plaques and in the cerebral vasculature. Recent studies have implicated carboxy-terminal fragments of the Alzheimer amyloid precursor protein (beta APP) in the processes of amyloidogenesis and neurodegeneration. In particular, the carboxy-terminal 104 amino acids of beta APP (beta APP-C104) have been shown to cause amyloid-like fibrils when expressed in non-neuronal cells and to cause the degeneration of neuronal cells. These data suggest that it may play a role in the development of the progressive neuropathology of Alzheimer's disease. We hypothesized that beta APP-C104 may cause the degeneration of neurons by interacting with a cell surface receptor. In the present report, we show that beta APP-C104 synthesized in vitro binds specifically and with high affinity to the surface of NGF-treated PC12 cells. Both the cell surface binding and the neurotoxicity of beta APP-C104 are pH dependent and are not inhibited by tachykinins. Mutational analysis suggests that both the binding and the neurotoxicity are dependent at least in part on the presence of a tyrosine residue that is a potential site of phosphorylation at the carboxy terminus of the fragment.

Chronic infusion of quinolinic acid in rat striatum: effects on discrete neuronal populations

The intrastriatal infusion of relatively low doses of quinolinic acid (Quin, 4–10 nmol/h) for 1 or 2 weeks induced time-dependent degeneration of neuronal cells. We examined the effects of these infusions on discrete cellular populations. The distribution of somatostatin (SOM)-positive neurons labelled by immunocytochemistry or by NADPH-diaphorase histochemistry and of cholinergic cells stained by acetylcholinesterase was quantified in the peripheral portion of the lesioned area. SOM-positive cells did not appear selectively spared by Quin infusion. The proportion of SOM- and NADPH-diaphorase-positive neurons killed by exposure to Quin was similar to or higher than the percentage of total neurons degenerated (from 30 to 85%). A selective sparing of cholinergic cells was observed in all conditions examined; perfusion of 6 nmol/h for a week induced 65% of cell death while not more than 30% of cholinergic neurons were killed. Thus, the neurochemical similarity between the degenerative effects of intrastriatal Quin and Huntington's disease (HD) did not appear confirmed by the chronic perfusion of low doses of Quin for SOM-positive neurons, whereas an analogy between Quin's effects and HD was suggested by the pattern of AChE staining.

Cholinotoxicity of the ethylcholine aziridinium ion in primary cultures from rat central nervous system

The cytotoxic effects of ethylcholine aziridinium ion (AF64A) were studied in primary cultures prepared from either whole brain, septum, or midbrain of fetal rats. AF64A, at concentrations up to 22.5 μM, significantly reduced the number of acetylcholinesterase-stained cells without affecting the number of dopaminergic neurons or their ability to take up and release [ 3H]dopamine. Many of the survived acetylcholinesterase-stained cells appeared with intact somata but damaged processes, indicating a retrograde degeneration starting at the nerve terminal. Higher concentrations of AF64A (22.5 μM), caused general toxicity which was expressed by degeneration of various neuronal and glial cells. Choline (500 μM), significantly protected the cells from AF64A induced cytotoxicity. The results are consistent with a previously described kinetic model, that predicted a dual action of AF64A: selective cholinotoxicity at low concentrations and non-selective cytotoxicity at higher concentrations.