A new Alamar Blue viability assay to rapidly quantify oligodendrocyte death

?-phenylpyruvate and glucose uptake in isolated mouse soleus muscle and cultured C2C12 muscle cells

Previous investigation demonstrated the potential of beta-phenylpyruvate at high concentration to cause hypoglycemia in mice totally deprived of insulin. For further elucidation of the glucose-lowering mechanism, glucose uptake, and quantity of glucose transporters (GLUT1 and GLUT4) in mouse soleus muscle and C2C12 muscle cell lines were investigated following incubation with beta-phenylpyruvate in various concentrations. A marked enhancement of glucose uptake was demonstrated that peaked at 0.5 and 1.0 mM beta-phenylpyruvate in soleus muscle (P<0.01) and C2C12 cells (P<0.001), respectively. Kinetic analysis in C2C12 cells showed a twofold increase in Vmax compared with controls (P<0.001). In addition, both GLUT1 and GLUT4 levels were increased following exposure to beta-phenylpyruvate. Our findings point to a peripheral hypoglycemic effect of beta-phenylpyruvate.

A rapid procedure to ascertain the antimicrobial efficacy of oral care formulations

A rapid method examining the antimicrobial efficacy of oral care formulations with alamar blue, an oxidation-reduction dye with fluorescent end-points, is described. Significant correlations between increasing viable plate counts of the oral bacteria Actinomyces viscosus, Streptococcus sanguis, Streptococcus mutans and Actinobacillus actinomycetemcomitans and increased alamar fluorescence were noted. Metabolically active bacteria reduced alamar with the reduced dye found in the cell-free filtrate. Insignificant alamar reductions were noted in the absence of bacteria or by spent culture supernatants. The efficacy of mouthrinses with clinically proven antiplaque agents such as chlorhexidine or cetylpyridinium chloride were determined by alamar blue. In a model system with A. viscosus, triclosan dentifrices demonstrate a dose-dependent effect on bacteria. Human salivary bacteria demonstrate increasing alamar fluorescence with increasing plate counts. A clinical study examined the effects of rinsing with chlorhexidine or cetylpyridinium chloride mouthrinses in comparison with a placebo mouthrinse and water on salivary bacteria. Rinsing with chlorhexidine resulted in the least number of bacteria by alamar and plate count methods. In summary, the current study demonstrates the utility of alamar blue to examine the antimicrobial effects of oral care formulations in laboratory and clinical studies.

Differentiation of hepatocellular carcinoma SMMC-7721 cell line induced by Chinese medicine recipe Weichangan

AIM

To observe the differentiation in hepatocellular carcinoma cell line induced by Chinese medicine recipe Weichangan.

METHODS

Weichangan, contrasted by the retinoic acid and distilled water, was made by using serum pharmacological method. The inhibition on the growth of SMMC-7721 cell line by Weichangan was observed through the method of MTT and Alamar Blue. Radioimmunoassay was applied to determine the concentration of a-fetoprotein and albumin secreted by the incubated cells. Western blot method was used to detect the mutant p53, p16 and p21 protein expression in SMMC-7721 cell line.

RESULTS

MTT assay showed both Weichangan and serum retinoic acid had inhibiting effect on the proliferation of human hepatocellular carcinoma SMMC-7721 cell line. Weichangan reached its maximal inhibition effect after 48 hours, while the effect of retinoic acid decreased gradually after 48 hours. Alamar Blue method showed that significant decrease was found in serum Weihangan after 16 hours compared with that in the control. After 32 hours, the decrease induced by Alamar Blue was more significant than that in cells incubated with serum Weichangan compared with those incubated in serum retinoic acid, indicating the gradual and durable action of Weichangan recipe. The decreased amount (11.4±1.4 mg/L vs 17.2±1.1 mg/L, P =0.036) of a-fetoprotein and increased amount (0.40±0.02 mg/L vs 0.29±0.01 mg/L, P =0.043) of albumin were found in the cells incubated in serum Weichangan. Western blot method showed decreased expression of p53 protein and increased expression of p16 and p21 protein in cells incubated in serum Weichangan.

CONCLUSION

The results suggest that Weichangan inhibits the growth of SMMC-7721 cell line and induces the differentiation in this hepatocellular carcinoma cell line. The effect on p53, p16 and p21 may be the mechanisms of Weichangan in inducing the differentiation of this cell lines.

L-cysteine increases glucose uptake in mouse soleus muscle and SH-SY5Y cells

Previous investigation demonstrated the potential of L-cysteine (L-Cys) at high concentrations to cause hypoglycemia in mice totally deprived of insulin. For further elucidation of the glucose-lowering mechanism, glucose uptake and quantity of glucose transporters (GLUTs 3 and 4) in mouse soleus muscle and C2C12 muscle cells, as well as in human SH-SY5Y neuroblastoma cells, were investigated. A marked enhancement of glucose uptake was demonstrated, peaking at 5.0 mM L-Cys in soleus muscle (P < 0.05) and SH-SY5Y cells (P < 0.001), respectively. In contrast, glucose uptake was not affected in the C2C12 muscle cells. Kinetic analysis of the SH-SY5Y glucose uptake showed a 2.5-fold increase in maximum transport velocity compared with controls (P < 0.001). In addition, both GLUT3 and GLUT4 levels were increased following exposure to L-Cys. Our findings point to a possible hypoglycemic effect of L-Cys.

Novel role of vitamin k in preventing oxidative injury to developing oligodendrocytes and neurons

Oxidative stress is believed to be the cause of cell death in multiple disorders of the brain, including perinatal hypoxia/ischemia. Glutamate, cystine deprivation, homocysteic acid, and the glutathione synthesis inhibitor buthionine sulfoximine all cause oxidative injury to immature neurons and oligodendrocytes by depleting intracellular glutathione. Although vitamin K is not a classical antioxidant, we report here the novel finding that vitamin K1 and K2 (menaquinone-4) potently inhibit glutathione depletion-mediated oxidative cell death in primary cultures of oligodendrocyte precursors and immature fetal cortical neurons with EC50 values of 30 nm and 2 nm, respectively. The mechanism by which vitamin K blocks oxidative injury is independent of its only known biological function as a cofactor for gamma-glutamylcarboxylase, an enzyme responsible for posttranslational modification of specific proteins. Neither oligodendrocytes nor neurons possess significant vitamin K-dependent carboxylase or epoxidase activity. Furthermore, the vitamin K antagonists warfarin and dicoumarol and the direct carboxylase inhibitor 2-chloro-vitamin K1 have no effect on the protective function of vitamin K against oxidative injury. Vitamin K does not prevent the depletion of intracellular glutathione caused by cystine deprivation but completely blocks free radical accumulation and cell death. The protective and potent efficacy of this naturally occurring vitamin, with no established clinical side effects, suggests a potential therapeutic application in preventing oxidative damage to undifferentiated oligodendrocytes in perinatal hypoxic/ischemic brain injury.

Differential lipid peroxidation, Mn superoxide, and bcl-2 expression contribute to the maturation-dependent vulnerability of oligodendrocytes to oxidative stress

To understand the basis of oligodendrocyte (OL) susceptibility to oxidative injury, purified rat OL cultures at different stages of maturation were exposed to nitric oxide (NO) donors with fast or slow kinetics of release and to tert-butyl-hydroperoxide, a membrane-permeant organic hydroperoxide. OL precursors (pre-OL) displayed the highest vulnerability to both oxygen or nitrogen reactive species, whereas mature OLs were uniquely vulnerable to long-lasting levels of NO. Cell death occurred by necrosis as well as apoptosis associated with increased caspase-3 activity and, only in the case of pre-OLs, with a decreased expression of the anti-apoptotic protein bcl-2. Pre-OLs were also more susceptible than mature OLs to lipid peroxidation, as measured by F2-isoprostane content in culture media. Finally, pre-OLs, but not mature OLs, expressed high levels of the mitochondrial scavenging enzyme Mn superoxide dismutase, suggesting that pre-OLs may efficiently convert anion superoxide into hydrogen peroxide and, paradoxically, be more predisposed than mature OLs to a toxic imbalance between hydrogen peroxide production and detoxification processes. These data suggest that susceptibility to lipid peroxidation, expression of the scavenging enzyme Mn superoxide dismutase and of the anti-apoptotic protein bcl-2, may contribute to the maturation-dependent vulnerability of OLs to oxidant injury.

Mature myelin basic protein-expressing oligodendrocytes are insensitive to kainate toxicity

We examined the vulnerability to excitotoxicity of rat oligodendrocytes in dissociated cell culture at different developmental stages. Mature oligodendrocytes that express myelin basic protein were resistant to excitotoxic injury produced by kainate, whereas earlier stages in the oligodendrocyte lineage were vulnerable to this insult. To test the hypothesis that the sensitivity of immature oligodendrocytes and the resistance of mature oligodendrocytes to kainate toxicity were due to differences in membrane responsiveness to kainate, we used whole-cell patch-clamp recording. Oligodendrocyte precursors in cultures vulnerable to kainate toxicity responded to 500 microM kainate with large inward currents, whereas mature myelin basic protein-expressing oligodendrocytes in cultures resistant to kainate toxicity showed no clear response to application of this agonist. We assayed expression of glutamate receptor subunits (GluR) -2, -4, -6, -7, and KA2 using immunoblot analysis and found that expression of all of these glutamate receptors was significantly down-regulated in mature oligodendrocytes. These results suggest a striking developmental regulation of glutamate receptors in oligodendrocytes and suggest that the vulnerability of oligodendrocytes to non- N-methyl-D-aspartate receptor-mediated excitotoxicity might be much greater in developing oligodendrocytes than after the completion of myelination.

Ceramide induces neuronal apoptosis through the caspase-9/caspase-3 pathway

C(2)-ceramide, a cell-permeable analog of ceramide, caused cell death in cultured rat cortical neuronal cells. C(2)-ceramide-induced neuronal loss was accompanied by upregulation of caspase-3 activity, measured by cleavage of its fluorogenic substrate Ac-DEVD-AMC. Similar results were obtained when cortical neuronal cultures were treated with sphingomyelinase, an enzyme responsible for ceramide formation in the cell. Morphological evaluation of C(2)-ceramide-treated cortical neurons showed nuclear condensation and fragmentation as visualized by Hoechst 33258 staining. Co-administration of the selective caspase-3 inhibitor z-DEVD-fmk or caspase-9 inhibitor z-LEHD-fmk significantly reduced C(2)-ceramide-induced cell death, while co-application of the caspase-8, inhibitor z-IETD-fmk, was without effect. Immunoblot analysis of protein extracts from C(2)-ceramide-treated cortical neuronal cultures revealed upregulation of active caspase-9 and caspase-3 protein levels, whereas presence of active caspase-8 immunoreactivity was undetectable in this system. Administration of C(2)-ceramide to SH-SY5Y human neuroblastoma cells also caused apoptotic cell death. Moreover, ceramide-induced cell death was significantly decreased in caspase-9 dominant-negative SH-SY5Y cells, while both caspase-8 dominant-negative cultures and mock-transfected cells showed equally high levels of cell death following C(2)-ceramide treatment. Taken together, these data suggest that neuronal death induced by ceramide may be linked to the caspase-9/caspase-3 regulated intrinsic pathway of cellular apoptosis.

The essential nutrient pyrroloquinoline quinone may act as a neuroprotectant by suppressing peroxynitrite formation

Pyrroloquinoline quinone (PQQ) is a redox active essential nutrient that can generate or scavenge superoxide depending on its microenvironment. PQQ has been shown previously to be neuroprotective in a rodent stroke model. Here we test whether PQQ interacts with reactive nitrogen species, known to be involved in the pathogenesis of stroke. Using rat forebrain neurons in culture, we determined that the toxicity of SIN-1 was mediated by peroxynitrite and that PQQ could block this toxic action. However, PQQ could not block the toxicity of peroxynitrite itself. Both SIN-1 and peroxynitrite caused ATP depletion, but only SIN-1 evoked ATP depletion was blocked by PQQ. In a cell-free system, PQQ blocked nitration of bovine serum albumin produced by SIN-1, but potentiated peroxynitrite-induced nitration. PQQ was unable to block ATP depletion and cell death induced by NO. donors (DEA/NO, DPT/NO and DETA/NO), indicating that it does not directly interact with nitric oxide, and suggesting that it acts as a superoxide scavenger. PQQ significantly potentiated cGMP accumulation evoked by SIN-1, similar to the effect of superoxide dismutase (SOD). However, unlike SOD, which potentiated neurotoxicity induced by SIN-1, PQQ blocked its toxicity, arguing against the possibility that PQQ functions simply as a SOD mimetic. Indeed, substantially less H2O2 was produced by the incubation of SIN-1 with PQQ, when compared to SOD. These results suggest that PQQ scavenges superoxide without forming toxic levels of H2O2. Therefore, the protective effect of PQQ on stroke might be due, at least in part, to the suppression of peroxynitrite formation.

Bromocriptine reverses P-glycoprotein-mediated multidrug resistance in tumor cells

One of the most important causes of anticancer treatment failure is the development of multidrug resistance (MDR). The main characteristics of tumor cells displaying the MDR phenomena are cross-resistance to structurally unrelated cytotoxic drugs having different mechanisms of action and the overexpression of the MDR1 gene, which encodes a transmembrane glycoprotein named P-glycoprotein (P-gp). This study evaluated whether bromocriptine, a D2 dopaminergic receptor agonist, influenced anticancer drug cytotoxicity and P-gp activity in a P-gp-expressing cell line compared to a non-expressing subline. The K(i) values for P-gp of cyclosporine and verapamil were 1.09 and 540 microM, respectively, and that of bromocriptine was 6.52 microM in a calcein-AM efflux assay using porcine kidney epithelial LLC-PK1 and L-MDR1 cells, overexpressing human P-gp. Bromocriptine at 10 microM reduced the IC50 of doxorubicin (DXR) in K562-DXR from 9000 to 270 ng/ml and that of vincristine (VCR) in K562-VCR from 700 to 0.30 ng/ml, whereas the IC50 values of DXR and VCR in the K562 subline were only marginally affected by these drugs. Bromocriptine restored the anticancer effect of DXR, VCR, vinblastine, vinorelbine and etoposide on MDR-tumor cells overexpressing P-gp. These observations suggest that bromocriptine has the potential to reverse tumor MDR involving the efflux protein P-gp in the clinical situation.

Gene expression profiling of the response to thermal injury in human cells

The genetic response of human cells to sublethal thermal injury was assessed by gene expression profiling, using macroarrays containing 588 complementary known genes. At 1, 4, 8, and 24 h following thermal injury, RNA was isolated, and a cDNA copy was generated incorporating (33)P and hybridized to Atlas arrays. About one-fifth of the genes on the membrane exhibited a significant elevation or depression in expression (>/=2-fold) by 4 h posttreatment. Genes for heat shock proteins (HSPs) were upregulated as well as genes for transcription factors, growth regulation, and DNA repair. Cluster analysis was performed to assess temporal relationships between expression of genes. Translation of mRNA for some expressed genes, including HSP70 and HSP40, was corroborated by Western blotting. Gene expression profiling can be used to determine information about gene responses to thermal injury by retinal pigment epithelium cells following sublethal injury. The induction of gene expression following thermal injury involves a number of genes not previously identified as related to the stress response.

High-glucose-induced metallothionein expression in endothelial cells: an endothelin-mediated mechanism

Vascular endothelial cells are constantly exposed to oxidative stress and must be protected by physiological responses. In diabetes mellitus, endothelial cell permeability is impaired and may be increased by high extracellular glucose concentrations. It has been postulated that metallothionein (MT) can protect endothelial cells from oxidative stress with its increased expression by cytokines, thrombin, and endothelin (ET)-1. In this study, we demonstrate that high glucose concentration can induce MT expression in endothelial cells through a distinct ET-dependent pathway. Exposure of human umbilical vein endothelial cells (HUVEC) to increasing concentrations of glucose resulted in a rapid dose-dependent increase in MT-2 and ET-1 mRNA expression. MT expression may be further augmented with addition of ET-1. Preincubation of the cells with the specific ET(B) antagonist BQ-788 blocked MT-2 mRNA expression more effectively than the ET(A) inhibitor TBC-11251. High glucose also increased immunoreactive MT protein expression and induced translocation of MT into the perinuclear area. Perinuclear localization of MT was related to high-glucose-induced reorganization of F-actin filaments. These results demonstrate that an increase in extracellular glucose in HUVEC can lead to a rapid dose-dependent increase in MT-2 mRNA expression and to perinuclear localization of MT protein with changes to the cytoskeleton. These effects are mediated via the ET receptor-dependent pathway.

Assessment of a simple, non-toxic Alamar blue cell survival assay to monitor tomato cell viability

The Alamar Blue (AB) assay, which incorporates a medox indicator that changes colour or fluorescence in response to metabolic activity, is commonly used to assess quantitatively the viability and/or proliferation of mammalian cells and micro-organisms. In this study the AB assay was adapted for the determination of the viability of plant cells. Cell suspension cultures of tomato, Lycopersicon esculentum, L., with differing viabilities, served as the experimental model for a comparison of the AB assay with the conventional 2,3,5-triphenyltetrazolium chloride (TTC) viability assay. The AB assay showed a sigmoidal relationship between cell viability and AB reduction (as quantified by spectrofluorometry or spectrophotometry), which was similar to that obtained using the TTC assay. Both assays detected a significant reduction in cell viability after 48 h exposure to virulent Ralstonia solanacearum (biovar III), while the TTC assay, in addition, revealed cell proliferation in control cells from 24 to 72 h. The TTC assay detected cell proliferation over a wider range of cell densities, while the AB assay was more rapid and versatile whilst being non-toxic and thus allowing subsequent cell analysis.

Recombinant human Fas ligand induces alveolar epithelial cell apoptosis and lung injury in rabbits

This study investigated whether recombinant human soluble Fas ligand (rh-sFasL) induces apoptosis of primary type II pneumocytes in vitro and lung injury in vivo. Type II cells isolated from normal rabbit lung expressed Fas on their surface and became apoptotic after an 18-h incubation with rh-sFasL. Fas expression in normal rabbit lungs was localized by immunohistochemistry to alveolar and airway epithelia and alveolar macrophages. The administration of 10 microg of rh-sFasL into the right lungs of rabbits resulted 24 h later in both significantly more bronchoalveolar lavage fluid total protein and significantly more tissue changes compared with those in the left lungs, which received rh-sFasL plus Fas:Ig (a fusion protein that binds and blocks sFasL). Tissue changes included thickening of the alveolar walls, neutrophilic infiltrates, apoptotic (terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling-positive) cells in the alveolar walls, and increased expression of interleukin-8 by alveolar macrophages (as determined by immunohistochemistry). We conclude that the alveolar epithelium of normal rabbits expresses Fas and that sFasL induces lung injury and inflammation in rabbits.

Monitoring of cell viability and cell growth in a hollow-fiber bioreactor by use of the dye Alamar Blue

We describe a method for monitoring cell proliferation in a small-scale hollow-fiber bioreactor (culture volume: 1 ml) by use of the Alamar Blue dye. Alamar Blue is a non-fluorescent compound, which yields a fluorescent product after reduction, e.g. by living cells. In contrast to the MTT-assay, the Alamar Blue assay does not lead to cell death. However, when not removed from the cells, the Alamar Blue dye shows a reversible, time- and concentration-dependent growth inhibition as observed for the leukemic cell lines CCRF-CEM, HL-60 and REH. When applied in the medium compartment of a hollow-fiber bioreactor system, the dye is delivered to the cells across the hollow-fiber membrane, reduced by the cells and released from the cell into the medium compartment back again. Thus, fluorescence intensity can be measured in medium samples reflecting growth of the cells in the cell compartment. This procedure offers several advantages. First, exposure of the cells to the dye can be reduced compared to conventional culture in plates. Second, handling steps are minimized since no sample of the cells needs to be taken for readout. Moreover, for the exchange of medium, a centrifugation step can be avoided and the cells can be cultivated further. Third, the method allows discriminating between cell densities of 10(5), 10(6) and 10(7) of proliferating HL-60 cells cultivated in the cell compartment of the bioreactor. Measurement of fluorescence in the medium compartment is more sensitive compared to glucose or lactate measurement for cell counts below 10(6) cells/ml, in particular. We conclude that the Alamar Blue-assay combined with a hollow-fiber bioreactor offers distinct advantages for the non-invasive monitoring of cell viability and proliferation in a closed system.

Increase in doxorubicin cytotoxicity by inhibition of P-glycoprotein activity with lomerizine

Acquired resistance to chemotherapy is a major problem during cancer treatment. One mechanism for drug resistance is overexpression of the MDR (multidrug resistance)1 gene encoding the transmembrane efflux pump, P-glycoprotein (P-gp). Calcium channel blockers such as verapamil, nifedipine and nicardipine have been shown to reverse cellular drug resistance by inhibiting P-gp drug efflux. This study evaluated whether a new calcium channel blocker, lomerizine, influenced doxorubicin (Dox) cytotoxicity and P-gp activity in a P-gp-expressing cell line compared to a non-expressing subline. Verapamil, and even more markedly, lomerizine, increased cellular uptake of calcein transported by P-gp in a P-gp-expressing erythroleukemia cell line, K562-Dox. Ten microM of lomerizine reduced the IC50 of doxorubicin in the K562-Dox from 60000 ng/ml to 800 ng/ml, whereas the IC50 of doxorubicin in the K562 subline was only marginally affected by these drugs. Lomerizine showed greater reduction in P-gp efflux than verapamil at an equimolar concentration. These results suggest that lomerizine has the clinical potential to reverse tumor MDR involving the efflux protein P-gp.

The uptake and metabolism of fructose-1,6-diphosphate in rat cardiomyocytes

Fructose-1,6-diphosphate (FDP) is a glycolytic intermediate which has been theorized to increase the metabolic activity of ischemic tissues. Here we examine the effects of externally applied FDP on cardiomyocyte uptake and metabolism. Adult rat cardiomyocytes were isolated and exposed to varying concentrations (0, 5, 25 and 50 mM) of FDP for either 1, 16 or 24 h of hypoxia (95% N2/5% CO2), each time period followed by a 1 h reoxygenation (95% air/5% CO2). The uptake of FDP by rat cardiomyocytes was more concentration-dependent than time-dependent. Furthermore, the uptake of FDP by the cardiomyocytes was similar in the hypoxia and normoxia treated cells. Alamar Blue, a redox indicator that is sensitive to metabolic activity, was used to monitor the effects of the FDP on cardiomyocyte metabolism. In the 1 h hypoxia or normoxia group, the 5, 10 and 25 mM FDP showed a significant increase in metabolism compared to the control cells. When the length of hypoxia was extended to 16 h, all doses of FDP were greater than control. And at the 24 h hypoxia or normoxia time period, only the 10, 25 and 50 mM FDP groups were greater than control. The results indicate a non-linear trend between the external concentration of FDP and the changes noted in metabolism. The findings from this study indicate that a narrow concentration range between 5-10 mM augments cardiomyocyte metabolism, but higher or lower doses may have little additional affect.

Effect of serine protease inhibitors on posttraumatic brain injury and neuronal apoptosis

N-Tosyl-l-phenylalanyl chloromethyl ketone (TPCK), an inhibitor of chymotrypsin-like serine protease (CSP), prevents DNA fragmentation and apoptotic cell death in certain blood cell lines and was reported to reduce hippocampal neuronal damage caused by cerebral ischemia. We examined the role of CSP on recovery after lateral fluid percussion-induced traumatic brain injury (TBI) in rats, as well as on cell survival in various in vitro models of neuronal cell death. TBI caused significant time-dependent upregulation of CSP activity, but not trypsin-like serine protease activity in injured cortex. Intracerebroventricular administration of TPCK to rats after TBI did not significantly affect deficits of spatial learning but exacerbated motor dysfunction after injury. Moreover, TPCK did not prevent apoptotic neuronal cell death caused by serum/K(+) deprivation or by application of staurosporine or etoposide in cultured rat cerebellar granule cells, rat cortical neurons, or in the human neuroblastoma SH-SY5Y cell line. Instead, at doses from 10 to 100 microM, TPCK was cytotoxic in all cultures tested. Similar results were obtained in cultures treated with another CSP inhibitor, 3,4-dichloroisocoumarin. Cell death caused by CSP inhibitors was neither caspase-dependent nor associated with oligonucleosomal DNA fragmentation. Taken together, these data do not support a neuroprotective role for CSP inhibitors. Rather, they suggest that CSPs may serve an endogenous neuroprotective role, possibly by modulating necrotic cell death.

NBN defined medium supports the development of O4+/O1- immunopanned pro-oligodendroglia

Maintenance of immunopanned cells in culture medium in the absence of serum or pre-conditioning by other neural cell types such as astrocytes can be problematic. Here we report the novel use of a chemically defined medium, which we refer to as NBN since it contains N-2 supplement, B-27 supplement, and N-acetyl-L-cysteine, for maintaining O4+/O1- immunopanned pro-oligodendroglia. Since we had previously characterized O4+/O1- immunopanned pro-oligodendroglia in astrocyte-conditioned basal defined medium (BDM; [24]), we compared their proliferation and differentiation in NBN medium or in NBN medium containing 40% NBN medium pre-conditioned by astrocytes. At 4 DIC in NBN, 23% of O4+ cells were BrdU+ while in conditioned NBN medium, 91% of O4+ cells were BrdU+. At 7 DIC in either medium, less than 25% of O4+ cells were BrdU+. O4+/O1- immunopanned pro-oligodendroglia cultured in NBN medium developed extensive processes and membranous expansions characteristic of mature oligodendroglia. At 4 DIC in NBN medium, approximately 100% of cells were O4+, 80% were O1+, and 54% were MBP+. By contrast, at 4 DIC in conditioned NBN, 87% of cells were O4+, 12% were O1+, and 2% were MBP+. At 7 DIC, there were no differences in the percentages of cells that expressed O4, O1, or MBP in either NBN or conditioned NBN. These results indicate that NBN defined medium supports the development of O4+/O1- immunopanned pro-oligodendroglia, and promotes more rapid maturation than conditioned NBN. The ability to maintain cells of the oligodendroglial lineage immunopanned at specific developmental stages in NBN defined medium should facilitate studies designed to identify effects of growth factors or toxins on oligodendroglia.

A microtiter trypan blue absorbance assay for the quantitative determination of excitotoxic neuronal injury in cell culture

An automated method for the determination of neuronal cell death using trypan blue is described. Following various excitotoxic insults, murine mixed cortical cell cultures are stained with trypan blue (0.05%; 15 min), followed by SDS (1%) lysis. The absorbance of the dye is measured spectrophotometrically at 590 nm using a microtiter plate reader. When compared to the biochemical lactate dehydrogenase assay, no statistical difference in the calculated levels of excitotoxic neuronal cell death was noted between the assays in any given paradigm. This method is fast and reliable. It eliminates the need for cell counting, thus allowing for high volume sample analysis with a minimum of sample error. Utility of this trypan blue absorbance spectrophotometric assay is likely to extend beyond the study of excitotoxic neuronal injury and should complement existing methods for measuring neuronal viability and cytotoxicity in cell culture.

Intracellular redox state determines whether nitric oxide is toxic or protective to rat oligodendrocytes in culture

We found that several nitric oxide donors had similar potency in killing mature and immature forms of oligodendrocytes (OLs). Because of the possibility of interaction of nitric oxide with intracellular thiols, we tested the effect of the nitrosonium ion donor S-nitrosylglutathione (SNOG) in OL cultures in the setting of cystine deprivation, which has been shown to cause intracellular glutathione depletion. Surprisingly, the presence of 200 microM SNOG completely protected OLs against the toxicity of cystine depletion. This protection appeared to be due to nitric oxide, because it could be blocked by hemoglobin and potentiated by inclusion of superoxide dismutase. We tested the effect of three additional NO* donors and found that protection was not seen with diethylamine NONOate, a donor with a half-life measured in minutes, but was seen with dipropylenetriamine NONOate and diethylaminetriamine NONOate, donors with half-lives measured in hours. This need for donors with longer half-lives for the protective effect suggested that NO* was required when intracellular thiol concentrations were falling, a process evolving over hours in medium depleted of cystine. These studies suggest a novel protective role for nitric oxide in oxidative stress injury and raise the possibility that intracerebral nitric oxide production might be a mechanism of defense against oxidative stress injury in OLs.