Mechanism of cellular 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) reduction

Hydrogen sulfide enhances reducing activity in neurons: neurotrophic role of H2S in the brain?

Hydrogen sulfide (H2S) can enzymatically be produced from cysteine in the brain. H2S functions as a synaptic modulator as well as a neuroprotectant from oxidative stress in the brain. Here we show that H2S specifically enhances the reducing activity in neurons and mouse neuroblastoma Neuro2a cells. An inhibitor of protein tyrosine kinase, genistein, suppresses the effect of H2S, suggesting that tyrosine kinase may be involved in the enhancement of reducing activity by H2S. The H2S-specific enhancement of the reducing activity in neurons may lead to a neurotrophic role in the brain.

[Protection of Tianshen Yizhi Recipe against low expression of nicotinic receptor and neurotoxicity induced by beta-amyloid peptide]

OBJECTIVE

To investigate the inhibition effects of Tianshen Yizhi Recipe (TSYZR), a compound traditional Chinese herbal medicine, on decreased expression of nicotinic acetylcholine receptor (nAChR) and the neurotoxicity as well as lipid peroxidation induced by beta-amyloid peptide (Abeta) in human SH-SY5Y neuroblastoma cells.

METHODS

The SH-SY5Y cells were treated by a certain concentration of TSYZR, and then exposed to Abeta(25-35). Methyl thiazolyl tetrazolium reduction assay was carried out to understand the influences of the drugs on cellular viability. Expressions of nAChR subunits (alpha3 and alpha7) at protein and mRNA levels were detected by Western-blotting and reverse transcription polymerase chain reaction, respectively. Lipid peroxidation was measured by thiobarbituric acid to observe the capacity of antioxidant of the drugs.

RESULTS

TSYZR at a safe concentration could increase alpha7 protein in the cells, inhibit decreased expressions of alpha3 and alpha7 nAChR subunit proteins, prevent lower expression of alpha7 mRNA in SH-SY5Y cells induced by Abeta, reduce the neurotoxicity and lipid peroxidation resulting from Abeta, but had no significant effect on the lower expression of alpha3 mRNA.

CONCLUSIONS

TSYZR can up-regulate the expression of alpha7 nAChR subunit protein and prevent decreased expressions of nAChRs and neurotoxicity as well as lipid peroxidation induced by Abeta. This drug may play an important therapeutic role in treatment of Alzheimer disease.

Down-regulation of the progesterone receptor by the methylation of progesterone receptor gene in endometrial cancer cells

Progesterone plays an important role in the regulation of normal endometrium function by binding to progesterone receptor (PR). In endometrial cancer, however, PR is always down-regulated. Previous reports showed that methylation in the promoter region of the PR gene may be responsible for PRB isoform repression. However, the CpG islands in the exon region of the PR gene are much richer and longer than in the promoter region. We hypothesize that methylation in the exon region may also take part in the down-regulation of the PR gene. The methylation status of the first exon of the PR gene in endometrial cell cultures was investigated. Aberrant methylation patterns were observed in the first exon of PR gene, and the methylation density is correlated with the differentiation of different types of endometrial cancer cells. DNA methyltransferase (DNMT) and histone deacetylase inhibitor 5-aza-2'-deoxycytidine (ADC), as well as trichostatin A (TSA), which reverses PR gene expression, were also studied. A combination of ADC and TSA resulted in synergistic effects in inducing PR expression, down-regulation of DNMT1 and DNMT3A, and could also have antigrowth effect on endometrial cancer cells by inducing apoptosis.

Mechanism of guanosine-induced neuroprotection in rat hippocampal slices submitted to oxygen-glucose deprivation

Guanine derivates have been implicated in many relevant extracellular roles, such as modulation of glutamate transmission, protecting neurons against excitotoxic damage. Guanine derivatives are spontaneously released to the extracellular space from cultured astrocytes during oxygen-glucose deprivation (OGD) and may act as trophic factors, glutamate receptors blockers or glutamate transport modulators, thus promoting neuroprotection. The aim of this study was to evaluate the mechanisms involved in the neuroprotective role of the nucleoside guanosine in rat hippocampal slices submitted to OGD, identifying a putative extracellular binding site and the intracellular signaling pathways related to guanosine-induced neuroprotection. Cell damage to hippocampal slices submitted to 15 min of OGD followed by 2 h of reperfusion was decreased by the addition of guanosine (100 microM) or guanosine-5'-monophosphate (GMP, 100 microM). The neuroprotective effect of guanosine was not altered by the addition of adenosine receptor antagonists, nucleosides transport inhibitor, glutamate receptor antagonists, glutamate transport inhibitors, and a non-selective Na(+) and Ca(2+) channel blocker. However, in a Ca(2+)-free medium (by adding EGTA), guanosine was ineffective. Nifedipine (a Ca(2+) channel blocker) increased the neuroprotective effect of guanosine and 4-aminopyridine, a K(+) channel blocker, reversed the neuroprotective effect of guanosine. Evaluation of the intracellular signaling pathways associated with guanosine-induced neuroprotection showed the involvement of PKA, PKC, MEK and PI-3 K pathways, but not CaMKII. Therefore, this study shows guanosine is acting via K(+) channels activation, depending on extracellular Ca(2+) levels and via modulation of the PKA, PKC, MEK and/or PI-3 K pathways.

Aggregation and fibrillation of bovine serum albumin

The all-alpha helix multi-domain protein bovine serum albumin (BSA) aggregates at elevated temperatures. Here we show that these thermal aggregates have amyloid properties. They bind the fibril-specific dyes Thioflavin T and Congo Red, show elongated although somewhat worm-like morphology and characteristic amyloid X-ray fiber diffraction peaks. Fibrillation occurs over minutes to hours without a lag phase, is independent of seeding and shows only moderate concentration dependence, suggesting intramolecular aggregation nuclei. Nevertheless, multi-exponential increases in dye-binding signal and changes in morphology suggest the existence of different aggregate species. Although beta-sheet content increases from 0 to ca. 40% upon aggregation, the aggregates retain significant amounts of alpha-helix structure, and lack a protease-resistant core. Thus BSA is able to form well-ordered beta-sheet rich aggregates which nevertheless do not possess the same structural rigidity as classical fibrils. The aggregates do not permeabilize synthetic membranes and are not cytotoxic. The ease with which a multidomain all-alpha helix protein can form higher-order beta-sheet structure, while retaining significant amounts of alpha-helix, highlights the universality of the fibrillation mechanism. However, the presence of non-beta-sheet structure may influence the final fibrillar structure and could be a key component in aggregated BSA's lack of cytotoxicity.

Intracellular cholesterol changes induced by translocator protein (18 kDa) TSPO/PBR ligands

One of the main functions of the translocator protein (18 kDa) or TSPO, previously known as peripheral-type benzodiazepine receptor, is the regulation of cholesterol import into mitochondria for steroid biosynthesis. In this paper we show that TSPO ligands induce changes in the distribution of intracellular cholesterol in astrocytes and fibroblasts. NBD-cholesterol, a fluorescent analog of cholesterol, was rapidly removed from membranes and accumulated into lipid droplets. This change was followed by a block of cholesterol esterification, but not by modification of intracellular cholesterol synthesis. NBD-cholesterol droplets were in part released in the medium, and increased cholesterol efflux was observed in [(3)H]cholesterol-prelabeled cells. TSPO ligands also induced a prominent shrinkage and depolarization of mitochondria and depletion of acidic vesicles with cytoplasmic acidification. Consistent with NBD-cholesterol changes, MTT assay showed enhanced accumulation of formazan into lipid droplets and inhibition of formazan exocytosis after treatment with TSPO ligands. The effects of specific TSPO ligands PK 11195 and Ro5-4864 were reproduced by diazepam, which binds with high affinity both TSPO and central benzodiazepine receptors, but not by clonazepam, which binds exclusively to GABA receptor, and other amphiphilic substances such as DIDS and propranolol. All these effects and the parallel immunocytochemical detection of TSPO in potentially steroidogenic cells (astrocytes) and non-steroidogenic cells (fibroblasts) suggest that TSPO is involved in the regulation and trafficking of intracellular cholesterol by means of mechanisms not necessarily related to steroid biosynthesis.

Morroniside and loganin extracted from Cornus officinalis have protective effects on rat mesangial cell proliferation exposed to advanced glycation end products by preventing oxidative stress

Advanced glycation end products (AGE) are involved in the alterations of renal mesangial cell (MCs) growth, a feature of early stages of diabetic nephropathy (DN). We postulate that morroniside and loganin, 2 components extracted from Cornus officinalis, may ameliorate the detrimental effects of AGE-induced MCs proliferation by preventing oxidative stress. Rat MCs cultured in AGE milieu were treated with morroniside and loganin. Results showed that morroniside and loganin inhibited AGE-induced MC proliferation as measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) method. Fluorescence microscopy revealed that the morroniside and loganin improved the morphological changes of MCs. Flow cytometric analysis showed that morroniside and loganin inhibited the cell cycle of rat MCs. Furthermore, the level of reactive oxygen species was significantly reduced, and the activities of superoxide dismutase and glutathione peroxidase were markedly increased, whereas the level of malondialdehyde was not significantly reduced. These results suggest that morroniside and loganin regulate MC growth by preventing oxidative stress. Thus, this study provides a molecular basis for the use of morroniside and loganin in the early stages of DN.

Prolonged hemiplegic episodes in children due to mutations in ATP1A2

BACKGROUND

Familial hemiplegic migraine (FHM) is an unusual migraine syndrome characterised by recurrent transient attacks of unilateral weakness or paralysis as part of the migraine aura. Genetically and clinically heterogeneous, FHM1 is caused by mutations in CACNA1A and FHM2 by mutations in ATP1A2.

AIM

Three children with prolonged hemiplegia were tested for mutations in CACNA1A or ATP1A2.

METHODS

Mutations in CACNA1A and ATP1A2 were screened for by denaturing high performance liquid chromatography and confirmed by sequencing. Expression studies were performed to characterise the functional consequences of these mutations.

RESULTS

No mutation was found in the FHM1 gene while three mutations were identified in the FHM2 gene. All three mutations were missense: two were novel and one was de novo; none was found in controls. Functional studies in HeLa cells showed complete loss of mutant pump function without interfering with the wild-type pump, consistent with haploinsufficiency.

CONCLUSION

We identified novel disease causing mutations in the FHM2 gene. Genetic screening for FHM should be considered in a child with prolonged hemiplegia even if there is no prior history or family history of migraine or hemiplegic episodes.

Cytotoxicity of partial-stabilized cement

Partial-stabilized cement (PSC) is a kind of modified calcium silicate cement used for root-end surgery. Minor transition metal elements Co, Cr, and Zn were added for enhancing the setting property of to PSC. In our previous study, minor transition metal additions greatly improved the setting property of PSC. However, the concern of metal toxicity was raised, as the material would be used in the human body. In this study, we evaluated the cytotoxicity of PSC in comparison with mineral trioxide aggregate (MTA), which is one of the commercialized materials used for dental root-end filling. Primary osteoblast cell was used as the target cell. Cell proliferation, cytotoxicity, viability, function, and senescence were analyzed. The cytotoxicity of the PSC-Zn group (PSC with Zn addition) was similar to that of MTA. PSC-Zn is not only nontoxic at the cellular level but also has adequate mechanical property, which makes it a potential root-end filling material for apical surgery.

Aryl radical involvement in amiodarone-induced pulmonary toxicity: Investigation of protection by spin-trapping nitrones

Amiodarone (AM), an antidysrrhythmic drug, can produce serious adverse effects, including potentially fatal AM-induced pulmonary toxicity (AIPT). AM-induced cytotoxicity and pulmonary fibrosis are well recognized, but poorly understood mechanistically. The hypothesis of aryl radical involvement in AM toxicity was tested in non-biological and biological systems. Photolysis of anaerobic aqueous solutions of AM, or N-desethylamiodarone (DEA) resulted in the formation of an aryl radical, as determined by spin-trapping and electron paramagnetic resonance (EPR) spectroscopy experiments. The non-iodinated AM analogue, didesiodoamiodarone (DDIA), did not form aryl radicals under identical conditions. The toxic susceptibility of human lung epithelioid HPL1A cells to AM, DEA, and DDIA showed time- and concentration-dependence. DEA had a more rapid and potent toxic effect (LC(50)=8 microM) than AM (LC(50)=146 microM), whereas DDIA cytotoxicity was intermediate (LC(50)=26 microM) suggesting a minor contribution of the iodine atoms. Incubation of human lung epithelial cells with the spin-trapping nitrones alpha-phenyl-N-t-butylnitrone (PBN, 10 mM) or alpha-(4-pyridyl N-oxide)-N-t-butylnitrone (POBN, 5.0 mM) did not significantly protect against AM, DEA, or DDIA cytotoxicity. Intratracheal administration of AM to hamsters produced pulmonary fibrosis at day 21, which was not prevented by 4 days of treatment with 150 mg/kg/day PBN or 164 mg/kg/day POBN. However, the body weight loss in AM-treated animals was counteracted by PBN. These results suggest that, although AM can generate an aryl radical photochemically, its in vivo formation may not be a major contributor to AM toxicity, and that spin-trapping reagents do not halt the onset of AM toxicity.

Influence of medium type and serum on MTT reduction by flavonoids in the absence of cells

The MTT (3-(4, 5-dimethylthiazolyl-2)-2, 5-diphenyltetrazolium bromide) assay is widely accepted as a simple and reproducible method for determining cell proliferation or cytotoxicity in vitro. In this study, we show that the flavonoids quercetin, rutin and luteolin but not apigenin can reduce MTT in the absence of live cells in the following order: quercetin >> rutin > luteolin > apigenin. Moreover, this reduction can be influenced by medium type and serum. The final concentrations of the flavonoids used were 200, 100, 50, 25 and 12.5 mug/mL. MTT reduction in Dulbecco's Modified Eagle's Medium (DMEM) is statistically higher than those in RPMI 1640 and F12 media, which are generally similar. Particularly for luteolin, MTT reduction is considerably higher with serum than without serum. In the case of quercetin at 50 mug/mL, a serum concentration of even only 0.01% is sufficient to significantly enhance MTT reduction versus that at 0% (P < 0.05). Serum at concentrations ranging from 0% to 5% also dose-dependently affects the pattern of formazan crystal formation. In the presence of 0.156-5% serum, the formazan crystals gradually change from being small, numerous and scattered to being large, few and clumpy. The authors hypothesize that flavonoid structure, nutrient concentration in the culture medium as well as serum components directly affect MTT reduction by flavonoids in the absence of cells.

Melatonin prevents glutamate-induced oxytosis in the HT22 mouse hippocampal cell line through an antioxidant effect specifically targeting mitochondria

The pineal hormone melatonin has neuroprotective effects in a large number of models of neurodegeneration. Melatonin crosses the blood-brain barrier, shows a decrease in its nocturnal peaks in blood with age that has been associated with the development of neurodegenerative disorders, and has been shown to be harmless at high concentrations. These properties make melatonin a potential therapeutic agent against neurodegenerative disorders but the pathways involved in such neuroprotective effects remain unknown. In the present report we study the intracellular pathways implicated in the complete neuroprotection provided by melatonin against glutamate-induced oxytosis in the HT22 mouse hippocampal cell line. Our results strongly suggest that melatonin prevents oxytosis through a direct antioxidant effect specifically targeted at the mitochondria. Firstly, none of the described transducers of melatonin signalling seems to be implicated in the neuroprotection provided by this indole. Secondly, melatonin does not prevent cytosolic GSH depletion-dependent increase in reactive oxygen species (ROS), but it totally prevents mitochondrial ROS production despite the fact that the latter is much higher than the former. And finally, there is a high correlation between the concentration at which melatonin and closely related indoles exert a direct antioxidant effect in vitro and a neuroprotective effect against glutamate-induced oxytosis.

Functional screening revisited in the postgenomic era

Functional screening can reveal a hidden function of a gene. cDNA library-based functional screening has flourished in various fields of biology so far, such as cancer biology, developmental biology and neuroscience. In the postgenomic era, however, various sequence database and public full-length cDNA resources are available, which now allow us to perform more straightforward, gene-oriented screening. Furthermore, the advent of RNA interference techniques has made it possible to perform effective loss-of-function screening. Gene-based functional screening is able to bridge the gap between genes and biological phenomena and raise important biological questions which should be tackled by integration of 'omic' datasets. These possible roles of functional screening will become more and more important in modern molecular biology moving toward the system level understanding of living organisms.

Pyruvate modifies glycolytic and oxidative metabolism of rat embryonic spinal cord astrocyte cell lines and prevents their spontaneous transformation

This study aimed to provide detailed data on mitochondrial respiration of normal astrocyte cell lines derived from rat embryonic spinal cord. Astrocytes in early passages (EP), cultured without pyruvate for more than 35 passages, defined here as late passages (LP), undergo spontaneous transformation. To study initial steps in cell transformation, EP data were compared with those of LP cells. LP cells had reduced glycolysis, fewer mitochondria and extremely low oxidative rates, resulting from a dysfunction of complexes I and II + III of the respiratory chain. Treatment of EP cells with pyruvate until they were, by definition, LP cultures prevented transformation of these cells. Pyruvate-treated EP cells had more mitochondria than normal cells but slightly lower respiratory rates. The increase of mitochondrial content thus appears to act as a compensatory effect to maintain oxidative phosphorylation in these LP 'non-transformed' cells, in which mitochondrial function is reduced. However, pyruvate treatment of transformed LP cells during additional passages did not significantly restore their oxidative metabolism. These data highlight changes accompanying spontaneous astrocyte transformation and suggest potential targets for the control of astrocyte proliferation and reaction to various insults to the central nervous system.

Measuring the lifetime of singlet oxygen in a single cell: addressing the issue of cell viability

Singlet molecular oxygen, O(2)(a(1)Delta(g)), has been detected from single neurons and HeLa cells in time-resolved optical experiments by its 1270 nm phosphorescence (a(1)Delta(g)--> X(3)Sigma(-)(g)) upon irradiation of a photosensitizer incorporated into the cell. The cells were maintained in a buffered medium and their viability was assessed by live/dead assays. To facilitate the detection of singlet oxygen, intracellular H(2)O was replaced with D(2)O by an osmotic de- and rehydration process. The effect of this insult on the cells was likewise assessed. The data indicate that, in the complicated transition from a "live" to "dead" cell, the majority of our cells have the metabolic activity and morphology characteristic of a live cell. Quenching experiments demonstrate that the singlet oxygen lifetime in our cells is principally determined by interactions with intracellular water and not by interactions with other cell constituents. The data indicate that in a viable, metabolically-functioning, and H(2)O-containing cell, the lifetime of singlet oxygen is approximately 3 micros. This is consistent with our previous reports, and confirms that the singlet oxygen lifetime in a cell is much longer than hitherto believed. This implies that, in a cell, singlet oxygen is best characterized as a selective rather than reactive intermediate. This is important when considering roles played by singlet oxygen as a signaling agent and as a component in events that result in cell death. The data reported herein also demonstrate that spatially-resolved optical probes can be used to monitor selected events in the light-induced, singlet-oxygen-mediated death of a single cell.

Congo red and protein aggregation in neurodegenerative diseases

Congo red is a commonly used histological dye for amyloid detection. The specificity of this staining results from Congo red's affinity for binding to fibril proteins enriched in beta-sheet conformation. Unexpectedly, recent investigations indicate that the dye also possesses the capacity to interfere with processes of protein misfolding and aggregation, stabilizing native protein monomers or partially folded intermediates, while reducing concentration of more toxic protein oligomers. Inhibitory effects of Congo red upon amyloid toxicity may also range from blockade of channel formation and interference with glycosaminoglycans binding or immune functions, to the modulation of gene expression. Particularly, Congo red exhibits ameliorative effect in models of neurodegenerative disorders, such as Alzheimer's, Parkinson's, Huntington's and prion diseases. Another interesting application of Congo red analogues is the development of imaging probes. Based on their small molecular size and penetrability through blood-brain barrier, Congo red congeners can be used for both antemortem and in vivo visualization and quantification of brain amyloids. Therefore, understanding mechanisms involved in dye-amyloidal fibril binding and inhibition of aggregation will provide instructive guides for the design of future compounds, potentially useful for monitoring and treating neurodegenerative diseases.

Cell-penetrating proline-rich peptidomimetics

Cell-penetrating peptides (CPPs) offer potential as delivery agents for the cellular administration of drugs. However, the pharmacological utility of CPPs that are derived from natural amino acids is limited by their rapid metabolic degradation, low membrane permeability, and toxicity. Various peptidomimetics able to overcome these problems have been described, including peptides formed by D-amino acids and beta-peptides. This chapter summarizes the synthesis of gamma-proline-derived peptides and polyproline dendrimers for drug delivery applications, and includes descriptions of several modifications in the gamma-peptides (mimicking the side chains of the alpha-amino acids) or modulating the dendrimer surface. 5(6)-Carboxyfluorescein labeling of the aforementioned peptidomimetics for use in cell translocation studies is also described. Furthermore, different protocols for the study of the drug delivery capabilities of these compounds are reviewed, including enzymatic stability studies, cellular uptake measurements by plate fluorimetry and flow cytometry, confocal laser scanning microscopy, and cytotoxicity assays.

Combining the rapid MTT formazan exocytosis assay and the MC65 protection assay led to the discovery of carbazole analogs as small molecule inhibitors of Abeta oligomer-induced cytotoxicity

The discovery of small molecule inhibitors of cytotoxicity induced by amyloid-beta (Abeta) oligomers, either applied extracellularly or accumulated intraneuronally, is an important goal of drug development for Alzheimer's disease (AD), but has been limited by the lack of efficient screening methods. Here we describe our approach using two cell-based methods. The first method takes advantage of the unique ability of extracellularly applied Abeta oligomers to rapidly induce the exocytosis of formazan formed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT). We employed a short protocol to quantify this toxicity, and quickly identified two novel inhibitors, code-named CP2 and A5, from two compound libraries. A second independent screen of the same libraries using our previously published MC65 protection assay, which identifies inhibitors of toxicity related to intracellular Abeta oligomers, also selected the same two leads, suggesting that both assays select for the same anti-Abeta oligomer properties displayed by these compounds. We further demonstrated that A5 attenuated the progressive aggregation of existing Abeta oligomers, reduced the level of intracellular Abeta oligomers, and prevented the Abeta oligomer-induced death of primary cortical neurons, effects similar to those demonstrated by CP2. Our results suggest that, when combined, the two methods would generate fewer false results and give a high likelihood of identifying leads that show promises in ameliorating Abeta oligomer-induced toxicities within both intraneuronal and extracellular sites. Both assays are simple, suitable for rapid screening of a large number of medicinal libraries, and amenable for automation.

Establishment of a novel intervertebral disc/endplate culture model: analysis of an ex vivo in vitro whole-organ rabbit culture system

STUDY DESIGN

Ex vivo in vitro study evaluating a novel intervertebral disc/endplate culture system.

OBJECTIVES

To establish a whole-organ intervertebral disc culture model for the study of disc degeneration in vitro, including the characterization of basic cell and organ function.

SUMMARY OF BACKGROUND DATA

With current in vivo models for the study of disc and endplate degeneration, it remains difficult to investigate the complex disc metabolism and signaling cascades. In contrast, more controlled but simplified in vitro systems using isolated cells or disc fragments are difficult to culture due to the unconstrained conditions, with often-observed cell death or cell dedifferentiation. Therefore, there is a demand for a controlled culture model with preserved cell function that offers the possibility to investigate disc and endplate pathologies in a structurally intact organ.

METHODS

Naturally constrained intervertebral disc/endplate units from rabbits were cultured in multi-well plates. Cell viability, metabolic activity, matrix composition, and matrix gene expression profile were monitored using the Live/Dead cell viability test (Invitrogen, Basel, Switzerland), tetrazolium salt reduction (WST-8), proteoglycan and deoxyribonucleic acid quantification assays, and quantitative polymerase chain reaction.

RESULTS

Viability and organ integrity were preserved for at least 4 weeks, while proteoglycan and deoxyribonucleic acid content decreased slightly, and matrix genes exhibited a degenerative profile with up-regulation of type I collagen and suppression of collagen type II and aggrecan genes. Additionally, cell metabolic activity was reduced to one third of the initial value.

CONCLUSIONS

Naturally constrained intervertebral rabbit discs could be cultured for several weeks without losing cell viability. Structural integrity and matrix composition were retained. However, the organ responded to the artificial environment with a degenerative gene expression pattern and decreased metabolic rate. Therefore, the described system serves as a promising in vitro model to study disc degeneration in a whole organ.

Mild surfection of neural cells, especially motoneurons, in primary culture and cell lines

Of all cell types, motoneurons (MNs), are possibly the most difficult to maintain in culture, since their development and survival is conditioned by many factors that are still in the course of identification. This may also be the reason why they are difficult to transfect. We succeed to transfect these fragile cells with lipoplex [DOTAP:PC (10:1)-pGFP]-precoated coverslips. Here, we report that this original method, also termed 'surfection' does not perturbate MN development and survival while giving important transfection yield (15%). Lipofectamine 2000 and other well-known auxiliary lipids (DOPE, Chol) give lower surfection yields. The use of (DOTAP:PC)-based lipid vector also can be extended to several neural and non-neural cell lines with appreciable transfection yield such as a glial cell line (GCL) derived from rat spinal cord (65%), HeLa S3 (60%), COS-7 (30%) and HEK 293 cells (20%). The efficiency of DOTAP:PC (10:1) and Lipofectamine 2000 vectors in our surfection method are compared on standard HeLa S3 cell lines. Lipofectamine 2000 (72%) is slightly better than DOTAP:PC (10:1) (60%). However, the surfection method improved the efficiency of Lipofectamine 2000 itself (72%) as compared to the classical (62%) approach. In summary we have developed an original standard surfection protocol for both MN primary cultures and cell lines, thus simplifying laboratory practice; moreover, Lipofectamine 2000 used in this surfection method is more efficient for the cell lines than the manufacturer-recommended method. We emphasize that our method particularly spares fragile cells like MNs from injure and therefore, might be applied to other fragile cell type in primary cultures.

Sense and sensibility: the use of cell death biomarker assays in high-throughput anticancer drug screening and monitoring treatment responses

Cell-based screening allows identification of biologically active compounds, for example, potential anticancer drugs. In this review, various screening assays are discussed in terms of what they measure and how this affects interpretation and relevance. High-throughput (HT) assays of viability based on the reduction of exogenous substrates do not always reflect viability or cell number levels. Membrane integrity assays can be used for HT quantification of cell death, but are non-specific as to the death mode. Several HT assays monitor end point apoptosis. Screening libraries at a single concentration (micromolar) can prevent detection of potent apoptosis inducers, as high concentrations may induce mainly necrosis. Using monolayer cultures limits the significance of cell-based screening as the properties of monolayer cells differ from tumours in vivo. Spheroid cultures are more physiological, but are impractical for screening by conventional methods. The authors have developed an assay quantifying accumulation of a caspase-cleaved protein specific for epithelial cells. It provides an integrated measure of apoptosis in two- and three-dimensional cultures and can be used as a blood biomarker assay for tumour apoptosis in vivo.

The formation of bioactive amyloid species by prion proteins in vitro and in cells

Amyloid proteins are a group of proteins that can polymerize into cross beta-sheeted amyloid species. We have found that enhancing cellular 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) formazan exocytosis is a common property of bioactive amyloid species formed from all of the amyloid proteins tested to date. In this report, we show that the infectious amyloid species of the prion protein HET-s of the filamentous fungus Podospora anserina, like other amyloidogenic proteins, also enhances MTT formazan exocytosis. More strikingly, cellular MTT formazan exocytosis revealed the formation of bioactive amyloid species in prion-infected mouse N2a neuroblastoma cells. These findings suggest that cellular MTT formazan exocytosis can be useful for studying the roles of bioactive amyloid species in prion infectivity and prion-induced neurodegeneration.

Reduction of 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide inner salt (XTT) is dependent on CaFRE10 ferric reductase for Candida albicans grown in unbuffered media

The reduction of 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide inner salt (XTT) and other tetrazolium salts is widely used as an assay for bacterial, fungal and mammalian cell viability, but the genes encoding the reductase activities have not been defined. Here, it was shown that XTT and plasma membrane ferric reductase activities were 10-40-fold greater in Candida albicans than in Saccharomyces cerevisiae. XTT reductase activity was induced fivefold in C. albicans grown in low-iron conditions compared with iron-replete conditions, and for cells grown in unbuffered (pH 4.0-4.4) medium, XTT reductase activity was largely dependent on CaFRE10. XTT reductase activity of C. albicans grown in medium buffered to pH 6.8 was independent of CaFRE10 but, nonetheless, was upregulated in cells deprived of iron. Reduction of 2-(4,5-dimethyl-2-thiazolyl)-3,5-diphenyl-2H-tetrazolium bromide (MTT), a membrane-permeable tetrazolium salt, occurred at an intracellular location and was independent of CaFRE10. However, MTT activity was induced by iron deprivation in C. albicans but not in S. cerevisiae. C. albicans possessed multiple iron- and pH-regulated reductase activities capable of reducing tetrazolium salts, but, when grown in unbuffered medium, CaFRE10 was required for XTT reductase activity.

Recovery after short-term bilirubin exposure in human NT2-N neurons

We used human NT2-N neurons to investigate delayed effects of short-term exposure to unconjugated bilirubin (UCB). Cell viability was evaluated with MTT reduction assays and nuclear morphology. A 6-h exposure to 1, 5, or 25 microM UCB and serum deprivation (SED) significantly diminished MTT reduction. 96 h after rescue of neurons with removal of UCB and re-incubation in the original serum-containing medium, delayed effects were evident as recovery (1 microM UCB), intermediate cell death (5 microM UCB), or near complete cell death (25 microM UCB). The impact of 6 h of SED alone appeared to be modest in rescued neurons. In this model, co-treatment with the specific caspase-3 inhibitor, zDEVD.FMK (100 microM), or the pancaspase inhibitor zVAD.FMK (100 microM) did not improve viability in rescued neurons exposed to 5 microM UCB, while treatment with the NMDA receptor antagonist MK-801 (1 microM) enhanced the number of undamaged nuclei (86 +/- 14% versus 50 +/- 12%, P = 0.001). MK-801 had, however, no impact on MTT reduction. In a different model with a 102-h continuous exposure to UCB and SED, we found a significant additional toxic impact of serum deprivation. Separate experiments suggested that this was a result of late caspase-mediated toxicity. We conclude that UCB-mediated effects may be reversible in this model. Blockade of excitotoxic mechanisms, but not caspase activity may prevent delayed cell death.

The use of a fluorescence-based oxygen uptake assay in the analysis of cytotoxicity

Cellular oxygen uptake is an informative parameter of cellular function but is not measured routinely in the analysis of cytotoxicity. Here we have evaluated the ability of a fluorescence-based oxygen uptake assay to assess the metabolic activity of common adherent cells including HepG2, LLC-PK1, Hek293T, C2C12, H-4-II-E, and primary rat hepatocytes. The assay employs water-soluble phosphorescent oxygen probes, analysed in standard 96-well plates on a conventional fluorescence plate reader. Using this respirometric method, cellular responses to known toxicants were examined and results compared to those obtained using established cell viability assays such as MTT, LDH and CyQuant. Respirometric analysis successfully detected these cytotoxic insults with responses being influenced by both mode of toxicity and the biochemical characteristics of the individual cell line. Results indicate that the oxygen uptake assay was more sensitive to the impairment of mitochondrial function than the other assays used. In conjunction with assays analysing other biomarkers of cytotoxicity, a more detailed picture of cell response to drug treatment can be obtained.

Diazoxide protects against methylmalonate-induced neuronal toxicity

Methylmalonic acidemia is an inherited metabolic disorder that leads to brain damage associated to the accumulation of methylmalonic acid (MMA) and impairment of energy metabolism. We demonstrate here that treatment with diazoxide, an agonist of mitochondrial ATP-sensitive K(+) channels (mitoK(ATP)), can prevent death promoted by treatment with MMA in PC12 cells and freshly prepared rat brain slices. This diazoxide effect was reversed by 5-hydroxydecanoate, a mitoK(ATP) antagonist, confirming it occurs due to the activity of this channel. Diazoxide was not capable of preventing inner membrane potential loss promoted by MMA and Ca(2+) in isolated mitochondria, indicating it does not directly prevent mitochondrial damage. Furthermore, diazoxide did not prevent respiratory inhibition in cells treated with MMA. Interestingly, we found that the mitochondrial inner membrane potential within intact cells treated with MMA was maintained in part by the reverse activity of ATP synthase (ATP hydrolysis) and that diazoxide prevented the formation of the membrane potential in the presence of MMA, in a manner sensitive to 5-hydroxydecanoate. Furthermore, the effects of diazoxide on cell survival after treatment with MMA were similar to those of ATP synthase inhibitor oligomycin and adenine nucleotide translocator inhibitor atractyloside. These results indicate that diazoxide prevents PC12 cell death promoted by MMA by decreasing mitochondrial ATP hydrolysis. These results uncover new potential neuroprotective effects of mitoK(ATP) agonists under situations in which oxidative phosphorylation is inhibited.

Effects of natural prenylated flavones in the phenotypical ER (+) MCF-7 and ER (−) MDA-MB-231 human breast cancer cells

The effect of seven natural prenylated flavones in DNA synthesis of two human breast cancer cell lines, the estrogen-dependent ER (+) MCF-7 and the estrogen-independent ER (-) MDA-MB-231 cells, was evaluated. Flavones with an isopentenyl group at C-8 and a ring linking C-3 and C-2' presented a biphasic effect in DNA synthesis of ER (+) MCF-7 and displayed a stimulation at low concentrations (0.02-0.78 microM) whilst at higher concentrations (> 3.12 microM) inhibition was observed. No stimulation was observed in ER (-) MDA-MB-231. In contrast, all the flavones exhibited an antiproliferative effect in both ER (-) and ER (+). Curiously, the inhibition of DNA synthesis was accompanied by a high capacity of these cells to reduce MTT, which was concurrent with the appearance of an intense intracytoplasmic vacuolization. The accumulation of the formazan product in these vacuoles could justify the enhancements of MTT reduction. The characterization of these vacuoles with the autophagic marker monodansylcadaverine (MDC) is consistent with autophagic vacuoles, which led to the suggestion that these flavones could induce autophagy in both ER (+) and ER (-) breast cancer cell lines.

Mutations in amyloid precursor protein and presenilin-1 genes increase the basal oxidative stress in murine neuronal cells and lead to increased sensitivity to oxidative stress mediated by amyloid beta-peptide (1-42), HO and kainic acid: implications for Alzheimer's disease

Oxidative stress is observed in Alzheimer's disease (AD) brain, including protein oxidation and lipid peroxidation. One of the major pathological hallmarks of AD is the brain deposition of amyloid beta-peptide (Abeta). This 42-mer peptide is derived from the beta-amyloid precursor protein (APP) and is associated with oxidative stress in vitro and in vivo. Mutations in the PS-1 and APP genes, which increase production of the highly amyloidogenic amyloid beta-peptide (Abeta42), are the major causes of early onset familial AD. Several lines of evidence suggest that enhanced oxidative stress, inflammation, and apoptosis play important roles in the pathogenesis of AD. In the present study, primary neuronal cultures from knock-in mice expressing mutant human PS-1 and APP were compared with those from wild-type mice, in the presence or absence of various oxidizing agents, viz, Abeta(1-42), H2O2 and kainic acid (KA). APP/PS-1 double mutant neurons displayed a significant basal increase in oxidative stress as measured by protein oxidation, lipid peroxidation, and 3-nitrotyrosine when compared with the wild-type neurons (p < 0.0005). Elevated levels of human APP, PS-1 and Abeta(1-42) were found in APP/PS-1 cultures compared with wild-type neurons. APP/PS-1 double mutant neuron cultures exhibited increased vulnerability to oxidative stress, mitochondrial dysfunction and apoptosis induced by Abeta(1-42), H2O2 and KA compared with wild-type neuronal cultures. The results are consonant with the hypothesis that Abeta(1-42)-associated oxidative stress and increased vulnerability to oxidative stress may contribute significantly to neuronal apoptosis and death in familial early onset AD.

Evaluation of antiviral activity of phenolic compounds and derivatives against rabies virus

Human rabies is a viral disease with a great impact on public health, mainly on account of its fatal course in the majority of cases. Despite the well-established prophylaxis by immunization, rabies is believed to be responsible for 40,000-70,000 human deaths per year, mostly in endemic areas. Palliative support and experimental protocols to avoid death have been employed with no expressive results, with the exception of a recent human case of recovery from rabies. No antiviral drugs are currently available to fight against this infection. In combination with the prophylaxis, an antiviral drug would be useful for human rabies treatment, providing enhanced protection against the encephalitis caused by the virus. Phenolic compounds are derived from the secondary plant metabolism, although they can also be obtained by synthetic processes. Many studies have shown a great range of pharmacological effects for these substances, including vasodilatation, antiallergenic, antiinflammatory and antiviral properties, among others. In this study, the potential in-vitro anti-rabies activity of 24 synthetic phenolic compounds was evaluated using McCoy cells and PV rabies strain. The cytotoxicity (CC50) was assayed by the MTT method and the antiviral activity (IC50) was estimated by the inhibition of viral cytopathic effects. Isoprinosine and ketamine were used as positive controls. The tested compounds showed selectivity indices (SI=CC50/IC50) ranging from 1.0 to 3.9. Six phenolic compounds failed to inhibit the cytopathic effect to any degree, and four showed SI > or = 3.0. According to these results, some probable structure-activity relationships are suggested. It was observed that the presence of free hydroxyl and ether groups influenced the anti-rabies activity. However, additional studies are required to establish these relationships.

Influence of cholesterol and lovastatin on alpha-form of secreted amyloid precursor protein and expression of alpha7 nicotinic receptor on astrocytes

The influence of cholesterol and the lovastatin (cholesterol-lowering drug) on secretion of alpha-secretase cleavage product of amyloid precursor protein (APP) and expression of nicotinic acetylcholine receptors (nAChRs) was investigated in human HTB-15 astrocytes. The results showed that exposure of cholesterol to astrocytes inhibited the secretion of alpha-form of secreted APP (alphaAPPs) and reduced cell viability, while lovastatin enhanced the alpha-secretase processing on astrocytes; cholesterol treatment decreased expression of alpha7 nAChR, whereas lovastatin induced an up-regulation of the receptor; the increase in alphaAPPs resulted from lovastatin was partially inhibited by the alpha7 nAChR antagonists, alpha-bungarotoxin or methyllycaconitine; cholesterol or lovastatin did not influence either whole APP level or expression of alpha4 nAChR. We suggest that high dose of cholesterol may inhibit both the activity of alpha-secretase in APP metabolic processing and the expression of alpha7 nAChR, while lovastatin may stimulate alpha-secretase cleavage processing that might be regulated by alpha7 nAChR.

Inhibition of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) endocytosis by ouabain in human endothelial cells

3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) uptake and reduction is widely used to evaluate cell proliferation and viability. MTT is taken up by the cells through endocytosis. We find that ouabain (1-200 nM) inhibits MTT reduction in human umbilical vein endothelial cells (HUVEC) without affecting cell viability. Ouabain does not inhibit MTT reduction when cell lysates substituted for the intact cells. Disruption of caveolae by cholesterol depletion, completely prevents the effect of ouabain. Treatment of HUVEC with Src inhibitor 4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine partially abrogates the inhibitory effect of ouabain. The data suggest that ouabain interaction with caveolar Na/K-ATPase inhibits MTT endocytosis through the activation of signaling proteins such as Src kinase.

A study of the cytotoxicity of branched-chain phytanic acid with mitochondria and rat brain astrocytes

Phytanic acid, a saturated fatty acid of 20-carbon-atoms with isoprenoic structure, is formed from the phytol-side chain of chlorophyll in ruminants. Degradation of phytanic acid is blocked in Refsum disease by several enzymatic defects of peroxisomal degradation of branched-chain fatty acids. Refsum disease is an inherited neurological disorder progressively developing from early childhood to adultness. Clinical signs are attributed to toxicity of phytanic acid, which accumulates to unusually high levels in the tissue and serum of patients suffering from untreated Refsum disease. We report here that hippocampal astrocytes isolated from rat brain, which were exposed to phytanic acid (50 microM) die within a few hours. In situ depolarization of mitochondria and an increase of cytosolic Ca2+ precede cell death. Therefore, we also investigated the influence of phytanic acid on physiology of mitochondria isolated from rat brain. Mitochondria become functionally impaired by phytanic acid, as indicated by uncoupling (resting state), inhibition of the electron transport (state 3), stimulation of ROS-generation, decline of Ca2+ loading and severe release of cytochrome c. Thus, phytanic acid seems to initiate astrocyte cell death by activating the mitochondrial route of apoptosis.

In vitro cytotoxicity of polycyclic aromatic hydrocarbon residues arising through repeated fish fried oil in human hepatoma Hep G2 cell line

Repeated frying of vegetarian and non-vegetarian foods in edible oil is a common practice round the globe. Our studies suggest that repeated fish fried oil (RFFO) generates polycyclic aromatic hydrocarbons (PAHs), which may lead to hazardous effect on human health. In order to understand the mechanism of toxicity of RFFO extracts containing a mixture of PAHs, the in vitro cytotoxicity assays in human hepatoma cell line, Hep G2 was undertaken. In addition to RFFO extract, benzo(a)pyrene (BP) and chrysene were used as prototype compounds for heavy and light PAHs, respectively. Doses of BP and chrysene were made in such a way, that it could represent the appropriate content of heavy and light PAHs found in the RFFO extract. Out of total content of PAHs (1240.4 microg/kg) in RFFO, major composition is of light PAHs (854.8 microg/kg) while heavy PAHs showed the concentration of 385.7 microg/kg. Treatment of cells with 1 microg/ml RFFO extract for 48 h showed significant induction in ethoxyresorufin-O-deethylase (EROD) activity. Exposure of cells to higher doses of RFFO extract (10-100 microg/ml) for 24, 48 and 72 h caused 3.5-5.2, 4.3-8.5 and 1.8-2.3-fold enhancement in EROD activity, respectively. Further, RFFO extract caused a dose dependent increase (2.1-3.5-fold) in aryl hydrocarbon hydroxylase (AHH) activity at 48 h. Induction of EROD and AHH activity in Hep G2 cells was found to be relatively more following BP or chrysene treatment as compared to RFFO extract. RFFO extract did not cause any significant effect on cell viability at 1 microg/ml and 10 microg/ml. However, at 100 microg/ml concentration RFFO extract significantly decreased the cell viability at 24, 48 and 72 h. Exposure of 10 microg/ml RFFO extract reduced the colony forming ability (CFA) of Hep G2 cells with maximum decrease of 33.5% at 72 h. However, exposure of cells to RFFO extract at highest concentration of assay (100 microg/ml) reduced CFA (35-52%) at 24, 48 and 72 h. RFFO extract (1-100 microg/ml) had no significant effect on growth inhibition of cell up to 48 h of exposure. However, exposure of RFFO extract at all doses showed significant growth inhibition (20-25%) at 72 h. In conclusion, the results suggest that RFFO extract has substantial cytotoxic potential through the metabolic activation process of PAHs generated per se.

Respirometric Screening Technology for ADME-Tox studies

Analysis of mitochondrial dysfunction is of particular importance in drug development, as it has been implicated in many common diseases and therapeutic treatments. Here, the markers of mitochondrial function and toxicity are reviewed, as well as current methods of assessment, with particular emphasis on oxygen respirometry. Fluorescence-based Respirometric Screening Technology (RST) allows convenient high-throughput analysis of oxygen consumption by cells, isolated mitochondria, enzymes, tissues and organisms, and is, therefore, of high value for such studies and general absorption, distribution, metabolism and excretion and toxicology studies. Various RST assay formats are described and specific applications are discussed. Consideration is also given to the future potential of this analytical approach.

Comparative study of endoplasmic reticulum stress-induced neuronal death in rat cultured hippocampal and cerebellar granule neurons

In this study, experiments were performed to characterize further the pathways responsible for neuronal death induced by endoplasmic reticulum (ER) stress in cultured hippocampal neurons (HPN) and cerebellar granule neurons (CGN) using tunicamycin (TM) and amyloid beta-peptide (Abeta). Exposure of HPN to Abeta or TM resulted in a time-dependent increase in the expression of 78-kDa glucose-regulated protein (GRP78) and caspase-12, an ER-resident caspase. In contrast, in CGN, although a drastic increase in the expression of GRP78 was found as was the case in HPN, no up-regulation of caspase-12 was detected. These results were consistent with immunohistochemical results that there were far lower number of caspase-12-positive cells in the cerebellum than in the cerebral cortex and hippocampus, and that caspase-12-positive cells were not identified in the external granule cell layer of the cerebellum of P7 rats. In CGN, a significant increase in the expression of C/EBP homologous protein (CHOP) protein was detected after exposure to Abeta or TM, whereas no such an increase in the protein expression was observed in HPN. In addition, S-allyl-L-cysteine (SAC), an organosulfur compound purified from aged garlic extract, protected neurons against TM-induced neurotoxicity in HPN but not in CGN, as in the case of Abeta-induced neurotoxicity. These results suggest that the pathway responsible for neuronal death induced by Abeta and TM in HPN differs from that in CGN, and that a caspase-12-dependent pathway is involved in HPN while a CHOP-dependent pathway is involved in CGN in ER stress-induced neuronal death.

Apoptosis-inducing factor triggered by poly(ADP-ribose) polymerase and Bid mediates neuronal cell death after oxygen-glucose deprivation and focal cerebral ischemia

Delayed neuronal cell death occurring hours after reperfusion is a hallmark of ischemic stroke and a primary target for neuroprotective strategies. In the present study, we investigated whether apoptosis-inducing factor (AIF), a caspase-independent proapoptotic protein, is responsible for neuronal cell death after glutamate toxicity and oxygen-glucose deprivation (OGD) in vitro and after experimental stroke in vivo. AIF translocated to the nucleus in which it colocalized with DNA fragmentation and nuclear apoptotic morphology after exposure to glutamate or OGD in cultured neurons or after transient middle cerebral artery occlusion (MCAo) in mice. Small inhibitory RNA-mediated downregulation of AIF reduced glutamate- and OGD-induced neuronal apoptosis by 37 and 60%, respectively (p < 0.01). Moreover, Harlequin mutant mice, which express AIF at low levels (approximately 20% of wild-type mice), displayed smaller infarct volumes (-43%; p < 0.03) and showed dramatically reduced cell death in the ischemic penumbra after 45 min of MCAo compared with wild-type littermates. Inhibition of poly(ADP-ribose) polymerase and Bid reduced nuclear AIF translocation. These results provide the first evidence for a causal role of AIF in ischemic neuronal cell death. Therefore, caspase-independent cell death signaling may provide a promising novel target for therapeutic interventions in cerebrovascular diseases.

EGCG protects HT-22 cells against glutamate-induced oxidative stress

(-)-Epigallocatechin-3-gallate (EGCG) is a major polyphenol in green tea. Many health promoting effects of EGCG have been reported based on its antioxidative and gene modulation properties, but no study has demonstrated a protective effect of EGCG against glutamate-induced neuronal damage. Excessive glutamate stimulation on neuronal cells leads to accumulation of reactive oxygen species (ROS) which ultimately contribute to cell death in stroke, trauma and other neurodegenerative disorders. In this study, mouse hippocampal cell line, HT-22, was used to determine the effect of EGCG on glutamate neurotoxicity. It was found that EGCG protected HT-22 cells against glutamate neurotoxicity when administered 10 h after glutamate incubation. The protective action of EGCG is mainly due to its antioxidative effect.

A bioactive collagen-β tricalcium phosphate scaffold for tissue engineering

Collagen-phosphate composites (COL/β-TCP) are novel materials that have the potential to be used as bone analogues. The aim of our study was to develop a porous bioactive material composed of type I collagen, the main bone protein and tricalcium phosphate, the mineral phase of natural bone, and investigate their in vitro biocompatibility in a human dermal fibroblast culture system. In order to obtain the bioactive materials, type I collagen was isolated from bovine tendon and characterized by physicochemical methods. β-TCP was obtained from calcium carbonate by thermal decomposition at 900 °C temperature. The powder was examined with X-ray diffraction. Two variants of COL/β-TCP scaffolds (P1 and P2) were prepared and examined by scanning electron microscopy. Our results revealed a microporous structure with small white aggregates of β-TCP, non-homogenous scattered in the collagen framework without any preferential orientation. The biocompatibility of the obtained scaffolds was tested by biochemical and histological methods on human fibroblast cultures. Both materials acted as good subtrates for human dermal fibroblast proliferation and migration.

Rotenone-like action of the branched-chain phytanic acid induces oxidative stress in mitochondria

Phytanic acid (Phyt) increase is associated with the hereditary neurodegenerative Refsum disease. To elucidate the still unclear toxicity of Phyt, mitochondria from brain and heart of adult rats were exposed to free Phyt. Phyt at low micromolar concentrations (maximally: 100 nmol/mg of protein) enhances superoxide (O(2)(.))(2) generation. Phyt induces O(2)(.) in state 3 (phosphorylating), as well as in state 4 (resting). Phyt stimulates O(2)(.) generation when the respiratory chain is fed with electrons derived from oxidation of glutamate/malate, pyruvate/malate, or succinate in the presence of rotenone. With succinate alone, Phyt suppresses O(2)(.) generation caused by reverse electron transport from succinate to complex I. The enhanced O(2)(.) generation by Phyt in state 4 is in contrast to the mild uncoupling concept. In this concept uncoupling by nonesterified fatty acids should abolish O(2)(.) generation. Stimulation of O(2)(.) generation by Phyt is paralleled by inhibition of the electron transport within the respiratory chain or electron leakage from the respiratory chain. The interference of Phyt with the electron transport was demonstrated by inhibition of state 3- and p-trifluoromethoxyphenylhydrazone (FCCP)-dependent respiration, inactivation of the NADH-ubiquinone oxidoreductase complex in permeabilized mitochondria, decrease in reduction of the synthetic electron acceptor 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide in state 4, and increase of the mitochondrial NAD(P)H level in FCCP-uncoupled mitochondria. Thus, we suggest that complex I is the main site of Phyt-stimulated O(2)(.) generation. Furthermore, inactivation of aconitase and oxidation of the mitochondrial glutathione pool show that enhanced O(2)(.) generation with chronic exposure to Phyt causes oxidative damage.

Synergistic protection of a general caspase inhibitor and MK-801 in bilirubin-induced cell death in human NT2-N neurons

Unconjugated bilirubin (UCB) induces both apoptosis and necrosis in neurons. To investigate the role of caspases and excitotoxicity in UCB-induced cell death, we exposed NT2-N neurons to 5 microM UCB (a concentration known to induce apoptosis) or 2 microM staurosporine (positive apoptosis control) and investigated the effects of treatments with the specific caspase-3 inhibitor, zDEVD.FMK (20 and 100 microM), or the general caspase inhibitor, zVAD.FMK (20 and 100 microM), and/or the N-methyl-D-aspartate (NMDA) receptor antagonist MK-801 (10 microM) during a 24- or 48-h exposure. UCB increased caspase-3 activity 2.3-fold after 6 h. Despite this, treatment with zDEVD.FMK did not prevent cell death. zVAD.FMK enhanced neuronal survival by reducing apoptotic nuclear fragmentation, while MK-801 enhanced survival by reducing apoptotic nuclear condensation; both without affecting the MTT assays. Combined treatment reduced both apoptotic morphologies (without affecting necrosis), and this effect was also reflected in the MTT assays [corrected] We conclude that NMDA receptor-mediated pathways and caspase-mediated pathways are involved in UCB-induced cell death in human NT2-N neurons. Concomitant inhibition of both pathways results in synergistic protection.

Acetyl-L-carnitine-induced up-regulation of heat shock proteins protects cortical neurons against amyloid-beta peptide 1–42-mediated oxidative stress and neurotoxicity: Implications for Alzheimer's disease

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by loss of memory and cognition and by senile plaques and neurofibrillary tangles in brain. Amyloid-beta peptide, particularly the 42-amino-acid peptide (Abeta(1-42)), is a principal component of senile plaques and is thought to be central to the pathogenesis of the disease. The AD brain is under significant oxidative stress, and Abeta(1-42) peptide is known to cause oxidative stress in vitro and in vivo. Acetyl-L-carnitine (ALCAR) is an endogenous mitochondrial membrane compound that helps to maintain mitochondrial bioenergetics and lowers the increased oxidative stress associated with aging. Glutathione (GSH) is an important endogenous antioxidant, and its levels have been shown to decrease with aging. Administration of ALCAR increases cellular levels of GSH in rat astrocytes. In the current study, we investigated whether ALCAR plays a protective role in cortical neuronal cells against Abeta(1-42)-mediated oxidative stress and neurotoxicity. Decreased cell survival in neuronal cultures treated with Abeta(1-42) correlated with an increase in protein oxidation (protein carbonyl, 3-nitrotyrosine) and lipid peroxidation (4-hydroxy-2-nonenal) formation. Pretreatment of primary cortical neuronal cultures with ALCAR significantly attenuated Abeta(1-42)-induced cytotoxicity, protein oxidation, lipid peroxidation, and apoptosis in a dose-dependent manner. Addition of ALCAR to neurons also led to an elevated cellular GSH and heat shock proteins (HSPs) levels compared with untreated control cells. Our results suggest that ALCAR exerts protective effects against Abeta(1-42) toxicity and oxidative stress in part by up-regulating the levels of GSH and HSPs. This evidence supports the pharmacological potential of acetyl carnitine in the management of Abeta(1-42)-induced oxidative stress and neurotoxicity. Therefore, ALCAR may be useful as a possible therapeutic strategy for patients with AD.

Glutathione peroxidase 4 protects cortical neurons from oxidative injury and amyloid toxicity

Polyunsaturated fatty acids (PUFA) in membrane lipids are prone to attack by reactive oxygen species (ROS), and the resulting lipid peroxidation can cause injury and death of cells. Glutathione peroxidase 4 (Gpx4) is an antioxidant defense enzyme that can directly detoxify lipid hydroperoxides generated by ROS. Overexpression of Gpx4 has been shown to be protective against oxidative damage in several cell lines. We examined in this study the stress response of neurons with increased expression of Gpx4, because neurons are especially vulnerable to oxidative injury as a result of their high content of PUFA. Our results show that primary culture cortical neurons derived from Gpx4 transgenic mice, which had increased expression of Gpx4, had increased cell survival and reduced level of apoptosis after exposure to t-butyl hydroperoxide and hydrogen peroxide. We also studied the protective role of Gpx4 against beta-amyloid toxicity, because beta-amyloid-induced neural toxicity is believed to be mediated through lipid peroxidation. Primary culture cortical neurons from Gpx4 transgenic mice had significantly less cell toxicity than their wild-type counterparts after exposure to Abeta25-35 and Abeta1-40 peptides, and apoptosis induced by Abeta25-35 was attenuated in neurons from Gpx4 transgenic mice. Our data demonstrate that overexpression of Gpx4 protects neurons against oxidative injury and beta-amyloid-induced cytotoxicity.

Cytotrophoblast differentiation in the first trimester of pregnancy: evidence for separate progenitors of extravillous trophoblasts and syncytiotrophoblast

It is commonly accepted that a single pool of villous cytotrophoblasts are precursors of both syncytiotrophoblast and extravillous trophoblasts during the first trimester. Here we present evidence that these two trophoblast subpopulations arise from separate progenitors that have different survival characteristics when studied in villous explant cultures. Dual staining with chloromethylfluorescin diacetate and ethidium bromide revealed degeneration of the syncytiotrophoblast by non-apoptotic mechanisms within 4 h of culture. The syncytiotrophoblast had regenerated within 48 h but at this point the vast majority of the cytotrophoblast and cells of the mesenchymal core were dead. Despite this extensive cytotrophoblast death, explants are able to produce extravillous trophoblast outgrowth for up to 3 weeks in culture. We believe that the villous cytotrophoblasts in the tips of anchoring villi are resistant to the factors that cause the death of the majority of villous cytotrophoblasts in culture. We speculate that as early as 8 weeks of gestation there are two separate villous cytotrophoblast populations, one committed to differentiate into syncytiotrophoblast and the second committed to the extravillous differentiation pathway.

Regulation of p53 by activated protein kinase C-delta during nitric oxide-induced dopaminergic cell death

Selective cell death of dopaminergic neurons in the substantia nigra is the major cause of Parkinson disease. Current evidence suggests that this cell death could be mediated by nitric oxide by-products such as nitrate and peroxynitrite. Because protein kinase C (PKC)-delta is implicated in apoptosis of various cell types, we studied its roles and activation mechanisms in nitric oxide (NO)-induced apoptosis of SN4741 dopaminergic cells. When cells were treated with sodium nitroprusside (SNP), a NO donor, endogenous PKC-delta was nitrated and activated. Immunoprecipitation revealed that p53 co-immunoprecipitated with PKC-delta and was phosphorylated at the 15th serine residue in SNP-treated cells. An in vitro kinase assay revealed that p53 was directly phosphorylated by SNP-activated PKC-delta. The p53 Ser-15 phosphorylation was suppressed in SNP-treated cells when the NO-mediated activation of PKC-delta was inhibited by rottlerin or (-)-epigallocatechin gallate. Within 3 h of p53 phosphorylation, its protein levels increased because of decreased ubiquitin-dependent proteosomal proteolysis, whereas the protein levels of MDM2, ubiquitin-protein isopeptide ligase, were down-regulated in a p53 phosphorylation-dependent fashion. Taken together, these results demonstrate that nitration-mediated activation of PKC-delta induces the phosphorylation of the Ser-15 residue in p53, which increases its protein stability, thereby contributing to the nitric oxide-mediated apoptosis-like cell death pathway. These findings may be expanded to provide new insight into the cellular mechanisms of Parkinson disease.

Fluorescence based oxygen uptake analysis in the study of metabolic responses to apoptosis induction

Mitochondrial activity has been shown to be centrally involved in the progression of apoptosis. The electron transport chain is a major player in this process and oxygen uptake analysis provides detailed information on its activity. Here we examined the ability of a fluorescence based oxygen uptake assay to inform on cellular responses to apoptosis induction. HL60 cells treated with camptothecin and UV light were used as a model and the ability of the assay to detect dose and time dependent decreases in respiratory activity analysed. The data obtained were compared to more specific markers of apoptosis including annexin V binding, and caspase-3 activity. Reductions in oxygen uptake rates were seen at lower doses than increases in annexin V binding or mitochondrial membrane potential depolarisation. These reductions were observed earlier than detectable caspase-3 activity and were unaffected by pre-treatment with the caspase-3 inhibitor benzyloxycarbonyl-Val-Ala-Asp-fluoro-methylketone (zVADfmk).

Dilinoleoyl-phosphatidylethanolamine from Hericium erinaceum protects against ER stress-dependent Neuro2a cell death via protein kinase C pathway

In many types of neurodegeneration, neuronal cell death is induced by endoplasmic reticulum (ER) stress. Hence, natural products able to reduce ER stress are candidates for use in the attenuation of neuronal cell death and, hence, in the reduction of the damage, which occurs in neurodegenerative disease. In this study, we investigated ER stress-reducing natural products from an edible mushroom, Hericium erinaceum. As a result of screening by cell viability assay on the protein glycosylation inhibitor tunicamycin-induced (i.e., ER stress-dependent) cell death, we found that dilinoleoyl-phosphatidylethanolamine (DLPE) was one of the molecules effective at reducing ER stress-dependent cell death in the mouse neuroblastoma cell line Neuro2a cells. A purified DLPE, commercially available, also exhibited a reducing effect on this ER stress-dependent cell death. Therefore, we concluded that DLPE has potential as a protective molecule in ER stress-induced cell death. From the structure of DLPE, it was hypothesized that it might activate protein kinase C (PKC). The activity of PKC-epsilon, a novel-type PKC, was increased by adding DLPE, and PKC-gamma, a conventional-type PKC, was activated on the coaddition of diolein and DLPE, as shown by in vitro enzyme activity analysis. The protecting activity of DLPE was attenuated in the presence of a PKC inhibitor GF109203X but not completely diminished. Therefore, DLPE can protect neuronal cells from ER stress-induced cell death, at least in part by the PKC pathway.