Regulation of apolipoprotein E secretion in rat primary hippocampal astrocyte cultures

Apolipoprotein E isoforms may have differential effects on a number of pathological processes underlying Alzheimer's disease. Recent studies suggest that the amount, rather than the type, of apolipoprotein E may also be an important determinant for Alzheimer's disease. Therefore, understanding the regulated synthesis of apolipoprotein E is important for determining its role in Alzheimer's disease.We show here that in rat primary hippocampal astrocyte cultures, dibutyryl-cAMP increased apolipoprotein E secretion with time in a dose-dependent manner (to 177% at 48 h) and that retinoic acid potentiated this effect (to 298% at 48 h). Dibutyryl-cAMP also gave a rapid, albeit transient, increase of apolipoprotein E mRNA expression (to 200% at 1 h). In contrast, the protein kinase C activator phorbol 12-myristate 13-acetate decreased both apolipoprotein E secretion (to 59% at 48 h) and mRNA expression (to 22% at 1 h). Phorbol 12-myristate 13-acetate also reversed the effects of dibutyryl-cAMP. Apolipoprotein E secretion was also modulated by receptor agonists for the adenylyl cyclase/cAMP pathway. Isoproterenol (50 nM, a beta-adrenoceptor agonist) enhanced, while clonidine (250 nM, an alpha2-adrenoceptor agonist) decreased, secreted apolipoprotein E. We also analysed the effects of agonists for the phospholipase C/protein kinase C pathway. Arterenol (1 microM, an alpha1-adrenoceptor agonist) and serotonin (2.5 microM) enhanced, whereas carbachol (10 microM, an acetylcholine muscarinic receptor agonist) decreased secreted apolipoprotein E. The effects of these non-selective receptor agonists were modest, probably due to effects on different signalling pathways. Arterenol also potentiated the isoproterenol-mediated increase. We also show that phorbol 12-myristate 13-acetate and dibutyryl-cAMP have opposite effects on nerve growth factor, as compared to apolipoprotein E, secretion, suggesting that the results obtained were unlikely to be due to a general effect on protein synthesis.We conclude that astrocyte apolipoprotein E production can be regulated by factors that affect cAMP intracellular concentration or activate protein kinase C. Alterations in these signalling pathways in Alzheimer's disease brain may have consequences for apolipoprotein E secretion in this disorder.     

Galactosamine-induced cell death in primary cultures of rat hepatocytes.

Primary cultures of rat hepatocytes were exposed to 0.5 mM D-galactosamine. After 36 hours, only 10-20% of the original cells were viable, as assessed by trypan blue exclusion. In the absence of galactosamine, there was no loss of viability over this same period. The addition of 3 mM uridine to the culture medium completely prevented the cell death produced by galactosamine. Glucosamine had no effect on the viability of the hepatocytes. The extent of galactosamine-induced cell death was dependent upon the concentration of Ca++ ions in the culture medium. With the only source of Ca++ that added with the fetal calf serum, galactosamine had only a very slight effect on viability. With higher Ca++ than with the fetal calf serum, galactosamine had only a very slight effect on viability. With higher Ca++ concentrations, from 0.9 to 3.6 mM, the viability ranged from 75% to 31% 18 hours after treatment with galactosamine. The addition of 1.4 microM chlorpromazine to culture medium containing 1.8 mM Ca++ decreased the extent of the galactosamine-induced cell death. This protective effect was progressively reduced by raising the Ca++ concentration to 3.6 and 5.4 mM. Chlorpromazine given to intact rats 2 hours after treatment with 400 mg/kg galactosamine prevented the appearance of liver cell necrosis. At the same time, chlorpromazine prevented the increases in liver cell Ca++ content. These results indicate that many of the features of the effect of galactosamine on intact rat liver cells can be reproduced in primary cultures of these same cells. The data also support the hypothesis that a disturbance in intracellular Ca++ homeostasis leading to accumulations of these ions is causally related to the cell death produced by galactosamine.     

Stereoselective neuroprotection by novel 2,3-benzodiazepine non-competitive AMPA antagonist against non-NMDA receptor-mediated excitotoxicity in primary rat hippocampal cultures

Glutamate excitotoxicity has been implicated in a variety of acute and chronic neurodegenerative diseases but early phase clinical trials with competitive antagonists at both N-methyl-D-aspartate (NMDA)-receptors and alpha-amino-3-hydroxy-5-methyl-isoxazolepropionate (AMPA) receptors have been disappointing. A family of atypical 2,3 benzodiazepines, exemplified by GYKI 52466, have been described recently which function as non-competitive AMPA-receptor antagonists. We have investigated the neuroprotective efficacy of LY303070 and LY300164, two analogs of GYKI-52466, in an embryonic rat hippocampal culture model of non-NMDA receptor-mediated excitotoxicity using kainic acid (KA) as an agonist at the AMPA/KA receptor. Overnight treatment with 500 microM KA resulted in prominent neuronal excitotoxicity as assessed by lactate dehydrogenase efflux. LY300164 and LY303070 attenuated KA-excitotoxicity in a dose-dependent manner with IC50s of 4 and 2 microM, respectively. In contrast, their stereoisomers, LY300165 and LY303071 showed no neuroprotection at concentrations up to 25 microM. In addition, AMPA-mediated excitotoxicity in cyclothiazide pre-treated cultures was also completely blocked by LY303070. Finally, neuroprotection by this class of 2,3 benzodiazepines was not influenced by antagonism of the classical benzodiazepine receptor. LY303070 and LY300164 represent novel non-competitive AMPA-receptor antagonists which may offer unique advantages in the clinic over competitive AMPA-receptor antagonists.     

Protective effect of thymidine against cytostatic action of cyclic-AMP in mammalian cell cultures

Under the influence of 1 mM cyclic-adenosine-3,5-monophosphate (cyclic-AMP) the degree of survival and rate of reproduction of Chinese hamster cells in culture were reduced to 27 and 42% of the control level, respectively. Addition of 0.02 mM thymidine along with the cyclic-AMP almost completely abolished the cytostatic effect of the latter. Thymidine also prevented the cytostatic effect of noncyclic 5-AMP, but did not affect death of the cells due to the action of dibutyryl cyclic-AMP and theophylline. Thymidine did not prevent the inhibitory action of cyclic-AMP on a mutant line of mouse cells deficient in thymidine kinase. It is concluded that, in the concentrations used, the cytostatic action of exogenous cyclic-AMP on mammalian cells is the result of its splitting to 5-AMP in the culture medium, and that it acts by blocking one of the stages of TMP biosynthesis.Department of Genetics and Plant Breeding, Faculty of Biology, M. V. Lomonosov Moscow University. (Presented by Academician S. E. Severin.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 80, No. 7, pp. 93–95, July, 1975.     

The cytotoxic effect of fowlpox virus on primary human amniotic cell cultures

Summary This report describes a cytotoxic effect of fowlpox virus on human amnion cells. Changes began after 48 hours and were complete within a week following inoculation. The infective property and the cytotoxic property were compared. Suspensions which were cytotoxic nearly always contained at least 10³ PFU/ml. Titers of both properties fell to undetectable levels during 30 days in human amnion cell culture. Titers of both properties were reduced by centrifugation, filtration, heat, ultraviolet light, acid, chloroform, and ether. Exposure to ultraviolet light reduced infectivity more rapidly than cytotoxicity. Treatment with ultrasound regularly increased cytotoxicity titer; infectivity increased to a much smaller and less predictable degree. Cytotoxicity-neutralizing serum antibodies developed in guinea pigs inoculated with fowipox virus. Cytotoxicity was identical in normal and IDUR-treated human amnion cells, but no plaques appeared in IDUR-treated chick embryo cells. The data suggest a mechanism of cytotoxicity that requires contact between virus and cell that does not require assembly of infectious viral particles.This investigation was supported by research grant AI-01023 and by training grant AI-177 from the National Institute of Allergy and Infectious Diseases, U.S. Public Health Service.     

Protective effect of aripiprazole against glutamate cytotoxicity in dopaminergic neurons of rat mesencephalic cultures

Aripiprazole, a dopamine D₂ receptor partial agonist, is used to treat schizophrenia. Although aripiprazole has been reported to protect non-dopaminergic neurons, its effect on dopaminergic neurons has yet to be investigated. In the present study, we examined whether aripiprazole protected dopaminergic neurons against glutamate-induced cytotoxicity in rat mesencephalic cultures. Pretreatment with aripiprazole protected dopaminergic neurons in a concentration-dependent manner. The neuroprotective effect was not attenuated by sulpiride, a dopamine D₂ receptor antagonist, suggesting that the effect is independent of dopamine D₂ receptors. Aripiprazole reduced intracellular dopamine content in a concentration-dependent manner. In addition, its neuroprotective effect was partially inhibited when dopamine was added. These results suggest that aripiprazole protects dopaminergic neurons against glutamate cytotoxicity partly by reducing intracellular dopamine content.     

Short-term consequences of N-methyl-D-aspartate excitotoxicity in rat magnocellular nucleus basalis: effects on in vivo labelling of cholinergic neurons.

Cholinergic neurons of the basal forebrain form one of the neuron populations that are susceptible to excitotoxic injury. Whereas neuropharmacological studies have aimed at rescuing cholinergic neurons from acute excitotoxic attacks, the short-term temporal profile of excitotoxic damage to cholinergic nerve cells remains largely elusive. The effects of N-methyl-D-aspartate (NMDA) infusion on cytochemical markers of cholinergic neurons in rat magnocellular nucleus basalis were therefore determined 4, 24 and 48 h post-lesion. Additionally, the influence of excitotoxic damage on the efficacy of in vivo labelling of cholinergic neurons with carbocyanine 3-192IgG was investigated. Carbocyanine 3-192IgG was unilaterally injected in the lateral ventricle. Twenty-four hours later, NMDA (60 nM/microl) was infused in the right magnocellular nucleus basalis, while control lesions were performed contralaterally. Triple immunofluorescence labelling for carbocyanine 3-192IgG, NMDA receptor 2A and B subunits and choline-acetyltransferase (ChAT) was employed to determine temporal changes in NMDA receptor immunoreactivity on cholinergic neurons. The extent of neuronal degeneration was studied by staining with Fluoro-Jade. Moreover, changes in the numbers of ChAT or p75 low-affinity neurotrophin receptor immunoreactive neurons, and the degree of their co-labelling with carbocyanine 3-192IgG were determined in basal forebrain nuclei. The effects of NMDA-induced lesions on cortical projections of cholinergic nucleus basalis neurons were studied by acetylcholinesterase (AChE) histochemistry. Characteristic signs of cellular damage, as indicated by decreased immunoreactivity for NMDA receptors, ChAT and p75 low-affinity neurotrophin receptors, were already detected at the shortest post-lesion interval investigated. Fluoro-Jade at 4 h post-lesion only labelled the core of the excitotoxic lesion. Longer survival led to enhanced Fluoro-Jade staining, and to the decline of ChAT immunoreactivity reaching a maximum 24 h post-surgery. Significant loss of p75 low-affinity neurotrophin receptor immunoreactivity and of cortical AChE-positive projections only became apparent 48 h post-lesion. Carbocyanine 3-192IgG labelling in the ipsilateral basal forebrain exceeded that of the contralateral hemisphere at all time points investigated and progressively declined in the damaged magnocellular nucleus basalis up to 48 h after NMDA infusion.The present study indicates that excitotoxic lesion-induced alteration of cholinergic neuronal markers is a rapid and gradual process reaching its maximum 24 h post-surgery. Furthermore, in vivo labelling of cholinergic neurons may be applied to indicate neuronal survival under pathological conditions, and enable to follow their degeneration process under a variety of experimental conditions.     

Strychnine protection against excitotoxic cell death in primary cultures of rat cerebral cortex

Strychnine-insensitive glycine receptors are known to modulate the toxicity of excitatory amino acids via an allosteric action at the N-methyl-D-aspartate receptor complex. To elucidate whether strychnine-sensitive glycine receptors may also influence excitotoxicity, the effect of strychnine on the excitotoxic cell death was examined in primary cultures of the rat cerebral cortex. To exclude any interference at the N-methyl-D-aspartate receptor complex, cell death was evoked by kainic acid. The release of lactic dehydrogenase (LDH) into the culture medium was taken as a quantitative measure of cell death. Strychnine reduced the excitotoxic cell death in a concentration-dependent fashion. This finding indicates that glycine may modulate the vulnerability of cortical cells to excitotoxic insults not only via the strychnine-insensitive population of glycine receptors within the N-methyl-D-aspartate receptor-complex, but also via strychnine-sensitive receptor channels.     

The effect of hyaluronan on osteoblast proliferation and differentiation in rat calvarial-derived cell cultures

Hyaluronan (or hyaluronic acid, HA) is an essential component of extracellular matrices. It interacts with other macromolecules and plays a predominant role in tissue morphogenesis, cell migration, differentiation, and adhesion. The cell signaling functions of HA are mediated through the CD-44 receptor and are dependent upon the molecular weight of the polymer. We hypothesized that an HA of appropriate molecular weight alone in optimal concentration may induce osteoblast differentiation and bone formation. Enzyme-digested calvarial-derived mesenchymal cells from 2-day-old newborn rats were cultured with the addition of HA of three different molecular weights (2300, 900, and 60 kDa). We added, 0.5, 1.0, and 2.0 mg/mL HA for each molecular weight to the medium at the first plating of cells. After 7 to 20 days in culture, cell proliferation and differentiation were evaluated by measuring thymidine incorporation, alkaline phosphatase activity, and osteocalcin gene expression. The effects of HA on bone formation were examined by using Alizarin red staining for mineralization. The results showed that low molecular weight HA (60 kDa) significantly stimulated cell growth, increased osteocalcin mRNA expression in a dose-dependent manner, but showed no apparent effects on alkaline phosphatase activity and bone mineralization. On the other hand, high-weight HA (900 and 2,300 kDa) significantly increased all the parameters examined, particularly alkaline phosphatase activity, in a dose-dependent manner and stimulated cell mineralization to 126% and 119% of the controls, respectively, in the 1.0 mg/mL dose. Our findings suggest that HA has a molecular weight-specific and dose-specific mode of action that may enhance the osteogenic and osteoinductive properties of bone graft materials and substitutes due to its stimulatory effects on osteoblasts.     

Adipocyte development in primary rat cell cultures: a scanning electron microscopy study

This study utilized scanning electron microscopy (SEM) techniques to observe primary cultures of stromal-vascular (SV) cells derived from postnatal rat inguinal adipose tissue. Cells were grown on collagen-coated, fibronectin-coated, or uncoated glass coverslips. Coverslips were normally fixed in glutaraldehyde, osmium tetroxide, dehydrated, and critical-point-dried. Other coverslips were frozen in isopentane (cooled in LN2) and dried or fixed in Baker's formalin for demonstration of inosine diphosphatase (IDPase) by X-ray microprobe analysis (XRMA). Adipocyte morphologies were similar on all substrates. At 2 days of culture, actin cables were detected extending from developing adipocytes. No difference in actin cable structure, cellular shape, or lipid accumulation was observed among the different substrates. Some stromal cells did not accumulate lipid but proliferated into a multilayer by 9 days in culture. Inosine diphosphatase was detected in the Golgi apparatus of developing adipocytes utilizing the technique of XRMA. This study demonstrates the potential for using SEM and XRMA techniques to define morphological features and cytochemical markers of adipocytes in vitro and the response of primary cultured rat SV cells to other attachment substrates.     

Na-dependent Li-transport in primary nerve cell cultures

Primary cultures from chick embryonic brain were used to study the steady state distribution of lithium. The intra/extracellular Li+ ratio decreased by enhancing the external Na+ concentration. Ouabain did not influence this unequality. A phloretin-sensitive component was revealed in the Li uptake at low Na+ concentration. The findings might suggest the existence of a Na+-dependent Li+ countertransport system in these brain cell cultures.     

Isoform-specific effect of apolipoprotein E on endocytosis of beta-amyloid in cultures of neuroblastoma cells

Investigation of the interactions of nerve cells with human apolipoprotein E (apoE), beta-amyloid (Abeta), and their complex, which are known to be included in senile plaques, is necessary to clarify the functional role of apoE in the pathogenesis of Alzheimer's disease. Using flow cytometric analysis, we investigated the isoform-specific effects of apoE on the endocytosis of Abeta in cultured neuroblastoma cells. The level of internalized Abeta within the cells was dependent on the culture time and the kind of apoE isoform present. Both apoE3 and apoE4 enhanced the internalization of Abeta; however, no difference was observed between their effects. The internalized Abeta was hardly catabolized at all in the presence of apoE4, while rapid clearance of Abeta was observed in the presence of apoE3. Unlike apoE3 and apoE4, apoE2 had no effect on Abeta clearance from the media. The isoform-specific effects of apoE on the endocytosis of Abeta may be implicated in the development of Alzheimer's disease, and if so, each isoform of apoE would induce a different incidence of that disease.     

Cryopreservation of rat astrocytes from primary cultures

Summary A deep-freezing procedure that makes possible a reproducible recovery of astrocytes for subsequent culture, after several months of cryopreservation, is described. The use of undiluted fetal bovine serum containing 10% dimethyl sulfoxide resulted in very high cell viability and survival. A simple and easy three-step (2 h at –20° C, 4 h at –70° C and storage in liquid N₂ at –196° C) cooling procedure has been shown to be adequate to yield very high cell viabilities. Cell viability, after a freezing-thawing cycle was about 94 to 97%, comparable to that of the astrocyte suspension obtained from the primary culture before freezing (95 to 100%). Three well-accepted markers of the astrocyte differentiation were examined in 7-day astrocytes, both primary cultured and cultured after thawing: glial fibrillary acidic protein, and the glutamine synthetase, and buthyl-cholinesterase activities.     

谷氨酰胺减轻离体大鼠心脏内毒素性损伤

目的 研究谷氨酰胺抗大鼠离体心脏内毒素性损伤的作用。方法 健康SD雄性大鼠24只，随机分成3组：正常对照组，内毒素组，谷氨酰胺 内毒素组，在Langendorff装置上用K-H液对大鼠离体心脏行主动脉逆灌注。连续记录心肌细胞单相动作电位(MAP)、心肌收缩张力曲线；同时在相应的时点分别测定冠脉流出液中的一氧化氮(NO)含量、乳酸脱氢酶(LDH)和肌酸激酶(CK)的活性。结果谷氨酰胺可以减轻内毒素引起的心脏电活动的紊乱和收缩能力的损害，对内毒素引起的心肌细胞单相动作电位幅度减小及MAP D20延长、心肌张力降低、心率变慢等变化有明显的改善作用。谷氨酰胺对内毒素引起的冠脉流出液中一氧化氮含量的剧烈波动(先降低后快速升高)有明显的抑制作用，并且谷氨酰胺 内毒素组冠脉流出液中LDH和CK的活性明显低于内毒素组。结论 谷氨酰胺可以对抗内毒素性心肌损伤、改善心功能状态，其机制可能与其抑制内毒素诱导的一氧化氮的剧烈波动、减轻心肌损伤有关。     

Inhibition of nicotinic acetylcholine receptors by apolipoprotein E-derived peptides in rat hippocampal slices

Apolipoprotein E (ApoE) is a well-known genetic risk factor for Alzheimer's disease (AD). Dysfunctions in cholinergic signaling, and in particular in the function of neuronal nicotinic acetylcholine receptors (nAChRs), have also been linked with AD and cognition. To address whether there is a link between ApoE and nAChR function, we used electrophysiological techniques to test the effects of synthetic ApoE-mimetic peptides derived from the low-density lipoprotein receptor (LDLR) binding domain for the ability to modulate nAChR activity in hippocampal interneurons. ApoE(133-149) completely inhibited ACh-evoked responses in a dose-dependent manner, yielding an IC(50) value of 720+/-70 nM. A shorter peptide spanning residues 141-148 mimicked this effect while a second peptide spanning residues 133-140 was without effect, indicating that the arginine-rich domain is responsible for nAChR interaction. Inhibition of ACh-evoked responses was voltage-independent, and displayed partial receptor specificity as no effect on glycine- or GABA-evoked responses occurred. These results demonstrate that peptides derived from the LDLR binding domain of ApoE block the function of nAChRs in hippocampal slices, an interaction that may have implications for AD.     

Preparation of primary cell cultures from lamprey

The lamprey is an important model for studies of evolution and comparative biology. The ability to culture cells from lamprey tissues makes it possible to employ an in vitro approach to address basic questions in these areas. Methods are described for the initiation of cell cultures derived from tissues of adult and larval sea lamprey (Petromyzon marinus). Primary cultures initiated from gill, muscle, gut, brain, ovary, heart and kidney were viable for up to eight months and several of the cultures were propagated for multiple passages. Most cultures were initiated from tissue explants in basal nutrient medium supplemented with fetal bovine and trout sera on a culture surface treated with fibronectin and collagen. Variations of these culture conditions to meet the specific growth requirements of certain cell types are discussed.     

人参总甙抗四氯化碳损伤大鼠离体肝细胞的作用

本实验采用大鼠离体肝细胞原代培养２４ｈ并利用ＣＣｌ４造成急性细胞损伤模型，检定人参总甙（ＧＳＳＤ）对肝细胞损伤的影响。结果表明：ＧＳＳＤ可显著降低中毒肝细胞的脂质过氧化物水平。抑制肝细胞脂质过氧化，并降低谷丙转氨酶（ＧＰＴ）和谷草转氨酶（ＧＯＴ）水平，保护脂质膜。ＧＳＳＤ显著促进中毒肝细胞ＲＮＡ和ＤＮＡ的合成，超微结构观察证实ＧＳＳＤ能减轻ＣＣｌ４对肝细胞染色质，线粒体，内质网和核蛋白体的损害，结