High oxygen atmosphere for neuronal cell culture with nerve growth factor. II. Survival and growth of clonal rat pheochromocytoma PC12h cells

Ondamtanggamibang protects neurons from oxidative stress with induction of heme oxygenase-1

Ondamtanggamibang (ODG) has been used as a remedy to treat psychological anxiety and depression in Oriental medicine. In this study, we found the protective effects of ODG against oxidative stress by induction of the antioxidative enzyme, heme oxygenase (HO)-1 in neuronal PC12 cells. Pretreatment with ODG extract protected neuronal cells from damage induced by H(2)O(2) and 6-hydroxydopamine (6-OHDA), but simultaneous treatment with ODG extract did not. ODG also inhibited the intracellular reactive oxygen species elevation by H(2)O(2) and 6-OHDA. ODG stimulation strongly induced the expression of HO-1 in PC12 cells. The protective effect of ODG extract on oxidative stress-induced damage was suppressed by HO inhibitor, zinc protoporphyrin IX (ZnPP-IX). Taken together, these data suggest that ODG treatment has potential protective effects in neuronal cells under oxidative stress.

Expression of cystatin C prevents oxidative stress-induced death in PC12 cells

Cystatin C, an inhibitor of cysteine proteinases, is suggested to be involved in oxidative stress-induced apoptosis of cultured CNS neurons and various neuronal diseases in vivo; however, little is known about its mechanism of action. To address the role cystatin C plays in oxidative stress-induced neuronal cell death, we established PC12 cell lines that stably expressed rat cystatin C. These cystatin C-expressing PC12 cells showed remarkable resistance to high (50%) oxygen atmosphere. This resistance correlate with expression levels of cystatin C, demonstrating that cystatin C has a protective effect on high oxygen-induced cell death. In contrast, in a normal (20%) oxygen atmosphere neither control nor cystatin C-expressing PC12 cells showed a significant change in the number of living cells, indicating that cystatin C does not play an important role in the regulation of cellular proliferation. Furthermore, the cystatin C-expressing cell line also resisted other oxidative stresses, including glutamate- and 13-L-hydroperoxylinoleic acid (LOOH)-induced cell death. These results demonstrate that cystatin C has protective effects against various oxidative stresses that induce cell death.

Role of mitochondria in neuronal cell death induced by oxidative stress; neuroprotection by Coenzyme Q10

Neuronal cells depend on mitochondrial oxidative phosphorylation for most of their energy needs and therefore are at a particular risk for oxidative stress. Mitochondria play an important role in energy production and oxidative stress-induced apoptosis. In the present study, we have demonstrated that external oxidative stress induces mitochondrial dysfunction leading to increased ROS generation and ultimately apoptotic cell death in neuronal cells. Furthermore, we have investigated the role of Coenzyme Q10 as a neuroprotective agent. Coenzyme Q10 is a component of the mitochondrial respiratory chain and a potent anti-oxidant. Our results indicate that total cellular ROS generation was inhibited by Coenzyme Q10. Further, pre-treatment with Coenzyme Q10 maintained mitochondrial membrane potential during oxidative stress and reduced the amount of mitochondrial ROS generation. Our study suggests that water-soluble Coenzyme Q10 acts by stabilizing the mitochondrial membrane when neuronal cells are subjected to oxidative stress. Therefore, Coenzyme Q10 has the potential to be used as a therapeutic intervention for neurodegenerative diseases.

Nerve growth factor protects against aluminum-mediated cell death

In the present study, we examined the effect of two salts of aluminum (Al), aluminum maltolate (Almal) and aluminum chloride (AlCl(3)), on the cell viability of PC12 cells in the absence and presence of nerve growth factor (NGF). A 72-h exposure of PC12 cells to Almal (300 microM) resulted in a marked increase of lactic dehydrogenase (LDH) release from the cells and a decrease of 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) activity. These results indicate that Almal induces a decrease in the cell viability. Under the same conditions, Almal also caused DNA ladder formation and chromatin condensation. In contrast, AlCl(3) did not showed an increased LDH release and a decreased MTT activity in the concentration range of the salt tested (0.1-1 mM). The extent of LDH release and MTT activity decrease induced by Almal treatment closely depended on the amount of Almal incorporated into the cells. An increase in the fluorescence intensity of 6-carboxy-2',7'-dichlorodihydrofluorescein diacetate, di(acetoxymethyl ester) (C-DCDHF-DA) which was loaded into the cell by Almal treatment and its prevention by pyrrolodine dithiocarbamate, a potent antioxidant, suggested that Almal-induced cell death partly proceeds via reactive oxygen species (ROS) production. NGF effectively inhibited the increase of LDH release and the decrease of MTT activity, as well as DNA fragmentation and chromatin condensation. However, NGF did not inhibit the increase of C-DCDHF-DA fluorescence in the cells induced by Almal treatment. From these results, it is suggested that ROS production associated with accumulation of Al is one possible important factor in the onset of Al neurotoxicity via apoptotic cell death and that NGF protects against cell degeneration associated with Al accumulation, but independently of ROS production.

Neuregulin rescues PC12-ErbB4 cells from cell death induced by H(2)O(2). Regulation of reactive oxygen species levels by phosphatidylinositol 3-kinase

Neuregulins (NRGs), a large family of transmembrane polypeptide growth factors, mediate various cellular responses depending on the cell type and receptor expression. We previously showed that NRG mediates survival of PC12-ErbB4 cells from apoptosis induced by serum deprivation or tumor necrosis factor-alpha treatment. In the present study we show that NRG induces a significant protective effect from H(2)O(2)-induced death. This effect of NRG is mediated by the phosphatidylinositol 3-kinase (PI3K)-signaling pathway since NRG failed to rescue cells from H(2)O(2) insult in the presence of the PI3K inhibitor, LY294002. Furthermore, the downstream effector of PI3K, protein kinase B/AKT, is activated by NRG in the presence of H(2)O(2), and protein kinase B/AKT activation is inhibited by LY294002. In addition, our results demonstrate that reactive oxygen species (ROS) elevation induced by H(2)O(2) is inhibited by NRG. LY294002, which blocks NRG-mediated rescue, increases ROS levels. Moreover, both H(2)O(2)-induced ROS elevation and cell death are reduced by expression of activated PI3K. These results suggest that PI3K-dependent pathways may regulate toxic levels of ROS generated by oxidative stress.

Brain-derived neurotropic factor prevents superoxide anion-induced death of PC12h cells stably expressing TrkB receptor via modulation of reactive oxygen species

In our previous report (Satoh et al., 1999. Regulation of reactive oxygen species by nerve growth factor but not by Bcl-2 as a novel mechanism of protection of PC12 cells from superoxide anion-induced death. J. Biochem. 125, 952-959), we reported that nerve growth factor (NGF) protected PC12 cells from superoxide anion (O2-)-induced cell death through a novel regulation of reactive oxygen species (ROS) which increased O2- and decreased hydrogen peroxide (H2O2), indicating that decreasing conversion from O2- to H2O2 is a critical process for the protection by NGF. In the present study, we performed a comparative study on protective mechanisms between NGF and brain-derived neurotrophic factor (BDNF) using TrkB-expressing PC12h cells. When compared with NGF, BDNF induced a weaker but significant protective effect on the cells from O2- induced death. BDNF did not seem to change the total amount of ROS in the cells treated with xanthine and xanthine oxidase. On the other hand, BDNF increased O2- and decreased H2O2- levels in the same cells, although not so strongly as NGF. These results suggest that decreasing conversion from O2- to H2O2 is also critical for the protection by BDNF, which is considered to play a central role in survival and differentiation of CNS neurons.

Oxygen toxicity induces apoptosis in neuronal cells

1. A high oxygen atmosphere induced apoptosis in cultured neuronal cells including PC12 cells and rat embryonic cortical, hippocampal, and basal forebrain neurons associated with DNA fragmentation and nuclear condensation. 2. The sensitivity of CNS neurons to a high-oxygen atmosphere was the following order; cortex > basal forebrain > hippocampus. 3. Cycloheximide and actinomycin-D inhibited the apoptosis, indicating that it depends on new macromolecular synthesis. In contrast, cultured postnatal CNS neurons were resistant to oxidative stress. 4. Neurotrophic factors such as nerve growth factor (NGF), fibroblast growth factor (FGF), and epidermal growth factor (EGF) blocked the apoptosis induced by a high-oxygen atmosphere.

Changes in mitochondrial membrane potential during oxidative stress-induced apoptosis in PC12 cells

We examined the effects of various types of oxidative stress on cell survival and on mitochondrial membrane potential (delta psi m) in PC12 cells transfected with BCL-2. Several types of oxidative stress such as exposure to hydrogen peroxide, 13-L-hydroperoxylinoleic acid, and xanthine + xanthine oxidase triggered apoptotic nuclear condensation and DNA fragmentation in normal PC12 cells. These types of oxidative stress induced significant increases in level of reactive oxygen species (ROS) before cell death. By contrast, BCL-2 prevented the apoptosis induced by these oxidative stresses. However, BCL-2 did not reduce ROS levels, indicating that it functions downstream of ROS generation. We measured delta psi m as a potential target of ROS during oxidative stress-induced cell death. Hydrogen peroxide, 13-L-hydroperoxylinoleic acid, and xanthine + xanthine oxidase induced a significant loss of delta psi m simultaneously with cell death. BCL-2 prevented the decrease in delta psi m as well as apoptosis induced by oxidative stress. These observations suggest that the oxidative stress triggers apoptosis associated with both increased generation of ROS and decreases in level of delta psi m and that BCL-2 prevents cell death as well as delta psi m but not ROS production.

The rescuing effect of nerve growth factor is the result of up-regulation of bcl-2 in hyperoxia-induced apoptosis of a subclone of pheochromocytoma cells, PC12h

The rat pheochromocytoma cell line PC12 is useful for studying neuronal cell differentiation since this cell line differentiates into neuron-like cells in response to nerve growth factor (NGF). We demonstrated that PC12h cells, a subclone of PC12 cells, died under hyperoxia (50% O2). This cell death did not occur in the presence of antioxidant reagents. In the dead cells, DNA fragmentation and chromatin condensation were observed, suggesting that hyperoxia-induced apoptosis via reactive oxygen species (ROS). NGF effectively suppressed this hyperoxia-induced apoptosis. Accordingly, the amounts of bcl-2, a proto-oncogene product, increased in the cells rescued from apoptosis by NGF. Furthermore, bcl-2 antisense oligonucleotide canceled this rescuing effect of NGF. The present findings indicate that NGF rescues PC12h cells from hyperoxia-induced apoptosis via up-regulation of bcl-2.

Generation of free radicals during lipid hydroperoxide-triggered apoptosis in PC12h cells

The compound 13-L-hydroperoxylinoleic acid (LOOH) triggered the death of clonal rat pheochromocytoma PC12h cells (LD50 = about 8 microM). LOOH induced nuclear condensation and DNA fragmentation, which was prevented by cycloheximide (a protein synthesis inhibitor) and NGF, indicating that LOOH triggered apoptosis in PC12h cells. LOOH produced reactive oxygen species (ROS) in PC12h cells in a time- and dose-dependent manner, as measured by flow cytometry using the ROS-specific fluorescent indicator, 6-carboxy-2,7-dichorodihydrofluorescein diacetate, di(acetoxymethyl ester) (C-DCDHF-DA). Antioxidants such as N,N'-diphenyl-p-phenylenediamine (DPPD), vitamin E and N-acetylcysteine, and a ferric iron chelator, deferoxamine, inhibited the LOOH-triggered apoptosis and simultaneously decreased the generation of ROS, whereas an inhibitor of glutathione synthesis, buthionine sulfoximine (BSO), enhanced the apoptosis and increased the generation of ROS. These results indicate that LOOH triggers the apoptosis of PC12h cells by increasing the production of ROS. A confocal analysis with the Ca(2+)-specific fluorescent indicator, fluo-3, demonstrated that LOOH at concentrations up to 200 microM, did not increase the intracellular Ca2+ concentration. These data indicate that LOOH induces apoptosis of PC12h cells through the enhanced production of ROS, not through increasing the permeability of Ca2+.

Protective role of nerve growth factor against postischemic dysfunction of sympathetic coronary innervation

BACKGROUND

Nerve growth factor (NGF) is produced rapidly in myocardium after brief myocardial ischemia. It contributes to the maintenance of neural integrity in several tissues. We examined the effect of exogenous and endogenous NGF on ischemia-induced dysfunction of cardiac sympathetic nerves.

METHODS AND RESULTS

In anesthetized dogs, bilateral stellate stimulation was performed, measuring changes in coronary vascular resistance (% delta CVR) before and after release of either a 7- or 15-minute occlusion of the left anterior descending coronary artery (LAD). NGF (10 ng.kg-1.min-1, n = 5) or vehicle (n = 6) was infused into the LAD in dogs during a 15-minute LAD occlusion. In separate experiments, antibody to NGF (anti-NGF, 2 ng.kg-1.min-1, n = 5) or vehicle (n = 6) was infused into dogs during a 7-minute LAD occlusion. After release of a 15-minute LAD occlusion, attenuation of the coronary constriction to stellate stimulation was seen in the vehicle group (30 +/- 3% to 15 +/- 1% increase in CVR, P < .05); however, no such reduction was seen in the group receiving NGF. A 7-minute LAD occlusion with reperfusion did not alter % delta CVR in the vehicle group (36 +/- 6% versus 37 +/- 7%, P = NS) but attenuated % delta CVR in the anti-NGF group (39 +/- 8% to 17 +/- 2%, P < .05).

CONCLUSIONS

We conclude that exogenously infused and endogenously released NGF protects against postischemic neural stunning of sympathetic cardiac innervation.

The neurotrophic action and signalling of epidermal growth factor

Epidermal growth factor (EGF) is a conventional mitogenic factor that stimulates the proliferation of various types of cells including epithelial cells and fibroblasts. EGF binds to and activates the EGF receptor (EGFR), which initiates intracellular signalling and subsequent effects. The EGFR is expressed in neurons of the cerebral cortex, cerebellum, and hippocampus in addition to other regions of the central nervous system (CNS). In addition, EGF is also expressed in various regions of the CNS. Therefore, EGF acts not only on mitotic cells, but also on postmitotic neurons. In fact, many studies have indicated that EGF has neurotrophic or neuromodulatory effects on various types of neurons in the CNS. For example, EGF acts directly on cultured cerebral cortical and cerebellar neurons, enhancing neurite outgrowth and survival. On the other hand, EGF also acts on other cell types, including septal cholinergic and mesencephalic dopaminergic neurons, indirectly through glial cells. Evidence of the effects of EGF on neurons in the CNS is accumulating, but the mechanisms of action remain essentially unknown. EGF-induced signalling in mitotic cells is better understood than that in postmitotic neurons. Studies of cloned pheochromocytoma PC12 cells and cultured cerebral cortical neurons have suggested that the EGF-induced neurotrophic actions are mediated by sustained activation of the EGFR and mitogen-activated protein kinase (MAPK) in response to EGF. The sustained intracellular signalling correlates with the decreased rate of EGFR down-regulation, which might determine the response of neuronal cells to EGF. It is likely that EGF is a multi-potent growth factor that acts upon various types of cells including mitotic cells and postmitotic neurons.

Oxygen-induced apoptosis in PC12 cells with special reference to the role of Bcl-2

We previously reported that PC12h cells are killed by a high oxygen atmosphere. In this study, we further characterized this oxygen-induced cell death and found apoptotic features, as follows. Firstly, chromatin condensation was observed in cells cultured in a 50% O2 atmosphere. Secondly, cycloheximide and cordycepin, protein and RNA synthesis inhibitors, respectively, prevented the oxygen-induced cell death in PC12h cells, suggesting that it is mediated by an intracellular death program. Thirdly, NGF, CPT-cAMP and depolarization by high potassium medium also effectively inhibited this apoptotic cell death in PC12h cells. The effect of high K+ is thought to be mediated by the influx of Ca2+ into cells through voltage-dependent Ca2+ channels, because nifedipine, an L-type Ca2+ channel blocker, inhibited the effect of high K+. In addition, since the oxygen-induced apoptosis was blocked by the antioxidant vitamin E, this oxygen toxicity is suggested to be mediated by reactive oxygen species. To further characterize this oxygen-induced apoptosis at the molecular level, we used PC12 cells overexpressing the proto-oncogene bcl-2. Although a large number of PC12 cells transfected with the control vector died in a 50% O2 atmosphere within 6 days, bcl-2-transfected PC12 cells survived and proliferated. These findings suggested that our system using PC12 cells will be a useful model with which to analyze the molecular mechanisms of apoptosis induced by oxidative stress in neuronal cells.

Survival factor-insensitive generation of reactive oxygen species induced by serum deprivation in neuronal cells

To investigate the involvement of reactive oxygen species (ROS) in neuronal apoptosis, we performed confocal and flow cytometric analysis with a ROS-specific fluorogen, 6-carboxy-2', 7'-dichorodihydrofluorescein diacetate, di(acetoxymethyl ester) (C-DCDHF-DA). Serum deprivation significantly increased the level of ROS in PC12 cells and rat cortical neurons. N,N'-diphenyl-p-phenylenediamine (DPPD), an antioxidant, reduced ROS production induced by serum deprivation and recovered cell survival. However, some survival factors such as nerve growth factor and Bcl-2, which prevented the apoptosis of PC12 cells, did not affect the up-regulation of ROS induced by serum deprivation. Epidermal growth factor which prevented the apoptosis of cortical neurons, did not affect the increase of ROS. These data suggest that survival factors rescue the serum deprivation induced apoptosis independently of ROS production.

Nerve growth factor and forskolin prevent H2O2-induced apoptosis in PC12 cells by glutathione independent mechanism

PC12 cells died by apoptosis at relatively low concentrations of H2O2, of which cytotoxicity was effectively suppressed by nerve growth factor (NGF), forskolin, and dbt-cAMP. Treatment with NGF or forskolin for 24 h increased the level of cellular antioxidant glutathione (GSH) by 1.6-2.0-fold. However, both NGF and forskolin protected cells against H2O2-stress even when cellular GSH was depleted by treatment with L-buthionine-(S,R)-sulfoximine (BSO). The GSH-independent protection effects of NGF and forskolin did not require new protein or RNA synthesis. Exogenous expression of an oncogenic ras suppressed apoptosis caused by H2O2 indicating that Ras protein also plays a role in suppressing apoptosis caused by oxidative radical stress.

NGF, BDNF and NT-5, but not NT-3 protect against MPP+ toxicity and oxidative stress in neonatal animals

A growing body of evidence suggests that neurotrophic factors can protect neurons against neuronal death. In the present study we examined whether systemic administration of members of the neurotrophin family, nerve growth factor (NGF), brain derived neurotrophic factor (BDNF), neurotrophin 3 (NT-3) and neurotrophin 5 (NT-5) and basic fibroblast growth factor (bFGF) could protect against 1-methyl-4-phenylpyridinium (MPP+) induced striatal damage in neonatal rats. Systemic administration of NGF, BDNF and NT-5 produced significant neuroprotective effects, whereas NT-3 was ineffective. Systemic administration of bFGF had significant neuroprotective effects as assessed by T2-weighted magnetic resonance imaging and measurements of n-acetylaspartate and lactate using chemical shift magnetic resonance imaging. Systemic administration of NGF, BDNF and bFGF, but not NT-3 attenuated MPP+ induced increases in hydroxyl radical generation as assessed by the conversion of salicylate to 2,3- or 2,5-dihydroxybenzoic acid (DHBA). These results show that systemic administration of several neurotrophins and bFGF can attenuate neuronal damage induced by chemical hypoxia in vivo by a mechanism which may involve attenuation of oxidative stress.

Epidermal growth factor prevents oxygen-triggered apoptosis and induces sustained signalling in cultured rat cerebral cortical neurons

Epidermal growth factor (EGF), a conventional mitogenic factor, acts as a neurotrophic factor on several types of neurons in the central nervous system. We found that EGF prevented the death of rat cerebral cortical neurons cultured in a 50% oxygen atmosphere. This high-oxygen-triggered cell death showed features of apoptotic cell death, which was blocked by inhibitors of RNA or protein synthesis. EGF prevented the oxygen-induced death of the cultured cortical neurons in a dose-dependent manner. Basic fibroblast growth factor (bFGF) also prevented this cell death, although there was no apparent additive effect of EGF and bFGF. Among the cultured cortical neurons, we observed neurons possessing the EGF receptor and cells expressing c-Fos protein in response to EGF. The cortical neurons were cultured in the presence of cytosine arabinoside, and the number of glial fibrillary acidic protein-positive astroglial cells was < 0.5% of that of the corresponding microtubule-associated protein 2-positive neurons. Therefore, the effect of EGF on the cultured cortical neurons is thought to be due to a direct action. We also examined EGF-induced signalling in the cultured cortical neurons. We found that EGF induced the sustained tyrosine phosphorylation of the EGF receptor and sustained the activation of mitogen-activated protein kinase in the cultured cortical neurons. We suggest that EGF may exert the survival effect through the prolonged activation of the EGF signalling.

Effect of exogenous nerve growth factor on neurotoxicity of and neuronal gene delivery by a herpes simplex amplicon vector in the rat brain

We have previously shown that local destruction of neural tissue by wild-type herpes simplex virus type 1 (HSV-1) is attenuated by intracerebral infusion of nerve growth factor (NGF). To investigate the effect of NGF on the extent of neurolysis and efficacy of neuronal gene transfer mediated by an HSV-1 amplicon vector system in vivo, rats were stereotaxically injected in the striatum with an amplicon preparation, pHSVlac. This amplicon contains the Escherichia coli lacZ gene under the transcriptional control of the HSV-1 immediate early 4/5 promoter and is packaged by an HSV-1 helper virus carrying a deletion in the immediate early 3 gene. Vector injection was followed by continuous intracerebral infusion of NGF-beta (total dose 5 micrograms) or vehicle solution over 7 days. Animals were sacrificed at the end of the 7-day infusion period for histological analysis of the brains. A distinct zone of inflammation and necrosis surrounded the injection site in all vector-inoculated animals. The volume of striatal tissue destruction was significantly smaller in NGF-treated animals (1.27 +/- 0.19 mm3; mean +/- SEM) than in the vehicle-treated controls (2.16 +/- 0.37 mm3; P < 0.05 by t-test). Immunohistochemical staining for HSV and beta-galactosidase (beta-Gal) in vehicle-treated animals revealed that many striatal cells harbored HSV antigens (3,678 +/- 636), but only a small number expressed the reporter gene at 7 days post-injection (294 +/- 60). NGF infusion did not significantly affect the number of HSV-immunoreactive cells (4,224 +/- 618), or the number of cells expressing beta-Gal (330 +/- 72) at this time.(ABSTRACT TRUNCATED AT 250 WORDS)

Apoptotic cell death occurs in hippocampal neurons cultured in a high oxygen atmosphere

When embryonic rat hippocampal neurons were cultured in a 50% oxygen atmosphere, neurons gradually died after 20 h in culture. This death pattern was found to be mediated by an intracellular active death program, so called apoptosis, as follows: (1) Cycloheximide and actinomycin-D, protein and RNA synthesis inhibitors, respectively, prevented cell death, indicating that cell death required new protein biosynthesis. (2) DNA fragmentation (called a "DNA ladder"), a specific biochemical marker of apoptosis, was detected during the course of cell death. (3) Depolarization with high K+ medium (26-50 mM) prevented cell death. This effect was suppressed by some dihydropyridine derivatives, L-type Ca channel blockers, such as nifedipine and nicardipine. These results indicate that increased levels of oxygen activate an apoptotic mechanism in the cultured hippocampal neurons, and suggest that neuronal activity may protect the neurons from oxygen-induced apoptosis.

Basic fibroblast growth factor rescues CNS neurons from cell death caused by high oxygen atmosphere in culture

In the present study, we cultured rat CNS neurons and tested the neurotrophic support provided by basic fibroblast growth factor (bFGF) to prevent the oxygen-induced neuronal cell death. When rat basal forebrain (septum and vertical limb of diagonal band of Broca) cells of embryonic day 20 were cultured in a serum-free medium containing 5 microM cytosine arabinoside in a 50% oxygen atmosphere, the neuronal cells, which were immunostained by an anti-microtubule-associated protein 2 (MAP2) antibody, gradually died after 1 day in culture. After 3.5 days in culture, only 2-5% of neuronal cells survived. This oxygen-induced cell death of cultured basal forebrain neurons was reversed by the addition of bFGF at a concentration of 100 ng/ml. This cell-saving effect was dose-dependent, and the ED50 value was 12 ng/ml. Nerve growth factor (NGF) and insulin-like growth factor II could not prevent cell death. The activity of choline acetyltransferase was also maintained when bFGF was present in the basal forebrain culture. Viable astroglial cells, which were immunostained by an anti-glial fibrillary acidic protein, accounted for a few percent of the total number of cells after 3 days in culture both with and without 100 ng/ml of bFGF. The survival-enhancing effect of bFGF was observed not only in basal forebrain neurons but also in neocortical and hippocampal neurons. However, the sensitivity to oxygen toxicity of cultured neurons from the 3 CNS regions varied greatly. The neocortical neurons were the most sensitive to oxidative stress, while the hippocampal neurons were the most resistant. These results suggest that bFGF plays an important role in saving neuronal cells from oxidative stress during their long life without division.

Growth of tumour cell lines in polymer capsules: ultrastructure of encapsulated PC12 cells

Recent studies indicate that polymer-encapsulated PC12 cells release sufficient amounts of dopamine to significantly alter behavioural paradigms in animals with unilateral lesions of dopaminergic midbrain neurons. Because cell fine structure provides a useful measure for assessment of storage function, exocytosis, metabolism, cell activity and cell viability, we examined the ultrastructure of PC12 cells grown in semi-permeable polymer capsules maintained in vitro or implanted into the forebrain of rats or guinea pigs. Encapsulated PC12 cells remained viable and continued to divide for the entire evaluation period of six months. Overall morphologies of encapsulated PC12 cells were similar in both environments and they resembled PC12 cells grown in monolayer cultures. In short-term cultures, encapsulated PC12 cells typically contained abundant quantities of chromaffin cell-like granules. The encapsulated cells had initially abundant microvilli on their surfaces which decline in frequency over time. After long-term enclosure for ten weeks or more, fewer secretory granules were detected in the cytoplasm of cells in capsules cultured in vitro and in brain-implanted capsules. Some cells in implanted capsules had long slender filipodia that were not present on PC12 cells in cultured capsules. The morphological changes of PC12 cells may correlate with altered growth conditions such as serum and oxygen concentrations, the presence or absence of growth factors in different environments, and with changes of cell interactions related to cell densities and build up of debris within the capsules over time. Since dopaminergic PC12 pheochromocytoma cells remain viable in semi-permeable polymer capsules for at least six months, such 'cell-capsules' could provide an alternative to dopamine-secreting embryonic neural grafts in dopamine replacement therapies.

High oxygen atmosphere for neuronal cell culture with nerve growth factor. I. Primary culture of basal forebrain cholinergic neurons from fetal and postnatal rats

Cholinergic neurons cultured from postnatal days 11-13 (P11-P13) rat basal forebrain showed better survival in the culture condition using a 50% O2 atmosphere with and without nerve growth factor (NGF) than in a low (10 or 20%) O2 atmosphere. Except for the culture at a low cell density, the beneficial effect of the highly oxidized culture condition was found in the culture from P3 neurons, but not from embryonic day 18 neurons. The survival of microtubule-associated protein 2 (MAP2)-positive neurons in culture from P3 basal forebrain regions was more enhanced in a 50% O2 atmosphere than in 20% and also 10% O2 atmosphere. The viable number of the MAP2-positive neurons in a 10% O2 condition was about half of that in a 20% condition. These results suggest that the response of the cultured neurons to an incubator O2 concentration changes during the neuronal development in CNS from fetal to postnatal stages.