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PubMed1997

Human cells lack the inducible tolerance to arsenite seen in hamster cells.

Chinese hamster V79 cells and their arsenite-resistant variants were found to have an arsenite- and antimonite-inducible tolerance mechanism which protects against the subsequent cytotoxic effects of arsenate, arsenate and antimonite. Inducible tolerance requires de novo mRNA and protein synthesis, and is independent of the heat shock response. In contrast, we report that the arsenite hypersensitive variant line As/S27D lacks the inducible tolerance response. Numerous attempts were made to detect an inducible tolerance response to arsenite in a variety of human cells. An assay based on Neutral red uptake was used in order to study inducible tolerance in cells with poor clonability. Neither normal diploid cells nor human tumor cells of different origins were found to elicit an inducible tolerance response to arsenite. This finding may help to explain why rodents do not develop tumors after exposure to arsenite, while humans do. In addition, all human cell lines tested were much more sensitive to arsenite compared to Chinese hamster cells. Human keratinocytes were especially sensitive. In general, human cells resemble arsenic hypersensitive Chinese hamster As/R27D cells, which have lost a protective mechanism found in wild-type Chinese hamster cells.

Animals↗
PubMed2002

Evaluation of neuronal cell death by laser scanning cytometry.

We developed a method in which laser scanning cytometry (LSC) is applied to evaluate cell viability. Neuronal cell death induced by glutamic acid, serum potassium deprivation and 3-nitropropionic acid was studied in cerebellar granule cells by neutral red assay (NR) and LSC, using propidium iodide (PI) as fluorescent dye. PI labeled the nuclei of dead neurons and increased fluorescence was measured using a laser scanning cytometer. Similar levels of damage for each injury were detected by NR or LSC. The protocol presented here, provides a fast and sensitive assay for the analysis of neuronal viability using LSC, and can be used to study new neuroprotective drugs in neuronal cell cultures.

Animals↗
PubMed2001

Cyclodiene organochlorine insecticide-induced alterations in the sulfur-redox cycle in CHO-K1 cells.

The effect of the cyclodiene organochlorine pesticides aldrin, dieldrin and endosulfan was assessed on CHO-K1 cultures at fractions of their lethal doses, determined by the neutral red (NRI) incorporation assay (NRI6.25, NRI12.5 and NRI25). Glutathione peroxidase, reductase and S-transferase, and total and oxidised glutathione were evaluated along the standard growth curve of the cultures. After a 24-h incubation with each insecticide, glutathione peroxidase incurred a large increase, while glutathione reductase and S-transferase activities were slightly higher than untreated controls. Unlike oxidised glutathione, the content of total glutathione declined significantly after exposure to cyclodiene insecticides. Changes in cell membrane integrity were assessed by the lactate dehydrogenase (LDH) release assay and lipid peroxidation for a wide range of pesticide concentrations. Membrane leakage and peroxide production were significantly enhanced at concentrations of aldrin and as low as 12.5 microg/ml, whereas dieldrin and endosulfan increased membrane fragility at much higher concentrations.

Aldrin↗
PubMed1994

Extent and rate of proton release by photosynthetic water oxidation in thylakoids: electrostatic relaxation versus chemical production.

The detailed chemical mechanism of the four steps of photosynthetic oxidation of two molecules of water to yield molecular oxygen plus four protons is under contention. The observed release of protons is a composite of the chemical production and more indirect reactions such as electrostatically induced shifts of acid/base equilibria of peripheral amino acids. In thylakoids we studied the extent and the rate (at microsecond time resolution) of proton release and uptake by each of the four oxidation steps. The pattern of net proton release in thylakoids varied drastically (between 0.3 and 2 H+/e-) as a function of pH. It differed substantially from the pH-dependent patterns of PSII-enriched membrane fragments and core particles, but the stepped progression toward release of dioxygen (the Kok parameter triple) was about the same. This implied an electrostatic origin of this variation and, within the observed limits, a lack of (inhibitory) feedback of the uncompensated charge on the electron transfer from the catalytic Mn cluster to TyrZ+. The rate of rapid proton transfer to the amphiphilic, surface-adsorbed indicator neutral red was proportional to its concentration. The shortest half-transfer time was 12 microseconds, substantially shorter than the time for electron transfer from Mn to TyrZ+ at any oxidation step. Rapid deprotonation thus occurred at the level of TyrZ+. By rapid deprotonation acts the four light-driven oxidation steps S0-->S1-->S2-->S3-->S4 created between 3.4 (at pH 7.4) and 4.5 (pH 6.3) bases per photosystem II.(ABSTRACT TRUNCATED AT 250 WORDS)

Electricity↗
PubMedDate not supplied

On-line monitoring of adhesion and proliferation of cultured hepatoma cells using optical waveguide lightmode spectroscopy (OWLS).

Monitoring of cell adhesion, cell spreading, and cell proliferation opens attractive perspectives in the on-line control of monolayer cell cultures in toxicity tests, in bioreactors as used for the serial production of skin grafts, or in extracorporeal liver devices. In this study the hepatoma Hep G2 cell adhesion and proliferation was monitored using an integrated optical method, optical waveguide lightmode spectroscopy (OWLS). This method is based upon refractive index measurements within a 100-nm thin layer above a Si(Ti)O(2) surface on which the cells were cultured and exposed to cytotoxic and cytostatic agents. The OWLS signal was proportional to cell density during the spreading period (4 h), and in long-term experiments (46 h) the OWLS signal correlated on a logarithmic scale with cell density. After administration of the protein synthesis inhibitor cycloheximide (4 microg/mL) to fully spread hepatoma cells, cell growth was arrested and change of the OWLS signal became noticeable within 6 h after drug administration. For exposure to increasing concentrations of the anticancer drug cyclophosphamide (2.5-20 mM) a concentration-dependent reduction of the OWLS signal was found. For cycloheximide and cyclophospamide the OWLS signal was also confirmed by cell viability measurements using the neutral red assay, the thiazolylblue tetrazoliumbromide assay, total protein measurements, and cell morphology. It was demonstrated that the OWLS signal detects minor changes in cell adhesion, which serve as indicators of metabolic state and growth behavior. OWLS is thus a quantitative tool to characterize impaired cell growth mediated by culture medium, by extracellular matrix, or after exposure to a toxin.

Bioreactors↗
PubMed2003

Epigenetic toxicity of hydroxylated biphenyls and hydroxylated polychlorinated biphenyls on normal rat liver epithelial cells.

2-Biphenylol, 3-biphenylol, 2,2'-biphenyldiol, 3,3'-biphenyldiol, 3-chloro-2-biphenylol, and 4,4'-dichloro-3-biphenylol were evaluated using the scrape-loading/dye transfer (SL/ DT) technique to determine in vitro gap junctional intercellular communication (GJIC) in a normal rat liver epithelial cell line as a measure of the epigenetic toxicity. Cytotoxicity was determined using the neutral red uptake assay. A dose range of 0-300 microM was examined. Only 3,3'-biphenyldiol and 4,4'-dichloro-3-biphenylol induced cytotoxicity within the tested dose ranges. Noncytotoxic doses were selected for evaluation of epigenetic toxicity. 4,4'-Dichloro-3-biphenylol was most inhibitory to GJIC at the lowest dose. The cytotoxicity and GJIC inhibitory effects observed for 4,4'-dichloro-3-biphenylol might be, although not exclusively, a consequence of the lipophilic nature of this chemical. 3-Chloro-2-biphenylol was least inhibitory to GJIC. 3-Chloro-2-biphenylol was less inhibitory to GJIC than 2-biphenylol because of the presence of the chlorine functional group, which appears to attenuate the toxic effect of the ortho-hydroxyl group. Although cells were capable of complete recovery of GJIC after removal of each of the chemicals, only with 2,2'-biphenyldiol and 4,4,'-dichloro-3-biphenylol did the cells demonstrate partial recovery without removal of the chemical. The more noncoplanar conformation of 2,2'-biphenyldiol and 2-biphenylol might explain their more inhibitory behavior in comparison to 3,3'-biphenyldiol and 3-biphenylol, respectively.

Animals↗
PubMed2004

Do arsenosugars pose a risk to human health? The comparative toxicities of a trivalent and pentavalent arsenosugar.

Seafood frequently contains high concentrations of arsenic (approximately 10-100 mg/kg dry weight). In marine algae (seaweed), this arsenic occurs predominantly as ribose derivatives known collectively as arsenosugars. Although it is clear that arsenosugars are not acutely toxic, there is a possibility of arsenosugars having slight chronic toxicity. In general, trivalent arsenicals are more toxic than their pentavalent counterparts, so in this work we examine the hypothesis that trivalent arsenosugars might be significantly more toxic than pentavalent arsenosugars in vitro. We compared the in vitro toxicity of (R)-2,3-dihydroxypropyl-5-deoxy-5-dimethylarsinoyl-beta-D-riboside, a pentavalent arsenosugar, to that of its trivalent counterpart, (R)-2,3-dihydroxypropyl-5-deoxy-5-dimethylarsino-beta-D-riboside. The trivalent arsenosugar nicked plasmid DNA, whereas the pentavalent arsenosugar did not. The trivalent arsenosugar was more cytotoxic (IC50 = 200 microM, 48 h exposure) than its pentavalent counterpart (IC50 > 6000 microM, 48 h exposure) in normal human epidermal keratinocytes in vitro as determined via the neutral red uptake assay. However, both the trivalent and the pentavalent arsenosugars were significantly less toxic than MMA(III), DMA(III), and arsenate. Neither the pentavalent arsenosugar nor the trivalent arsenosugar were mutagenic in Salmonella TA104. The trivalent arsenosugar was readily formed by reaction of the pentavalent arsenosugar with thiol compounds, including, cysteine, glutathione, and dithioerythritol. This work suggests that the reduction of pentavalent arsenosugars to trivalent arsenosugars in biology might have environmental consequences, especially because seaweed consumption is a significant environmental source for human exposure to arsenicals.

Arsenates↗
PubMed1996

Energy of the Photosubstitutionally Reactive Excited State of Pentaammine(pyridine)ruthenium(II).

The photosensitized aquation of pentaammine(pyridine)ruthenium(II) by several dyes has been studied under conditions where only the sensitizers absorb light. The ratio of the quantum yields for ammine and pyridine substitution was the same as that for direct photoaquation. Sensitization was effective with singlet sensitizers Rhodamine-B (17 452 cm(-)(1)) and Safranine-T (17 690 cm(-)(1)), as well as the triplet sensitizer biacetyl (19 000 cm(-)(1)), but no reaction was observed with Neutral-Red (16 900 cm(-)(1)). The results indicate that the excited state precursor of the observed photosubstitution in the complex lies in the energy range between 17 000 and 17 700 cm(-)(1).

Journal Article↗
PubMedDate not supplied

Detection of local polarity of alpha-lactalbumin by N-terminal specific labeling with a new tailor-made fluorescent probe.

To detect the local polarity such as the N-terminal domain of a protein molecule, 3-(4-chloro-6-hydrazino-1,3,5-triazinylamino)-7-(dimethylamino)-2-methylphenazine has been designed and synthesized as a polarity-sensitive fluorescent probe by using an s-triazine ring as a backbone, neutral red and hydrazine as a polarity-sensitive fluorophore, and a labeling group, respectively. The fluorescence properties of the probe have been characterized. The probe has the following features: (1) stable in various solvents; (2) the long-wavelength emission of >550 nm that can avoid the interferences of the background fluorescence shorter than 500 nm from common biomacromolecules; and (3) the maximum emission wavelength (lambda(em)) sensitive to solvent polarity only but not to pH and temperature. The hydrazino group in such a probe reacts readily with an active carbonyl produced by transamination of a protein molecule, leading to N-terminal specific attachment of the fluorophore and thereby allowing the monitoring of local polarity. With this probe, the polarity of the N-terminal domain in both native and heat-denatured alpha-lactalbumin has been first determined, which corresponds to that with a dielectric constant of about 16, and the hydrophobic core near the N-terminus is found to be conservative for heating. The present strategy may provide a general method to study the local environmental changes of a protein molecule under different denaturation conditions.

Fluorescent Dyes↗
PubMed1995

1H NMR spectroscopic studies on the reactions of haloalkylamines with bicarbonate ions: formation of N-carbamates and 2-oxazolidones in cell culture media and blood plasma.

1H NMR spectroscopic methods have been applied to compare the in vitro reactivity of the renal papillary nephrotoxin 2-bromoethanamine (BEA) with those of selected halide-substituted nephrotoxic analogues, 2-chloroethanamine (CEA), 2-fluoroethanamine (FEA), and 1-phenyl-2-iodoethanamine (PIEA). The primary 1H NMR-detectable transformation during a 24 h incubation of confluent Madin Darby canine kidney (MDCK) cells with BEA, CEA, and FEA (at concentrations up to the IC50 determined by neutral red uptake) was the appearance in cell culture media of 2-oxazolidone (OX). Additional novel signals assigned as FEA carbamate (N-carbamoyl-2-fluoroethanamine) were observed in media collected following incubation of cells with FEA. We propose that N-carbamate intermediates are formed from the spontaneous reaction of these haloalkylamines with HCO(3-)-buffered growth media and that OX is formed from the carbamate via elimination of the hydrogen halide. Further 1H NMR experiments, conducted for up to 8 h at 25 degrees C on 5 mM solutions of BEA, CEA, and FEA in 2H2O containing a 20-fold excess of HCO3- at pH 7.6, demonstrated a time-dependent decrease in the concentration of the free haloalkylamines accompanied by the production of N-carbamate intermediates and OX. Under these pseudo-first-order reaction conditions, the formation of OX from BEA was complete within approximately 6 h. In similar reaction conditions OX formation from CEA (24 h after initiation) had reached 54% of its final equilibrium concentration. Equivalent experiments demonstrated that PIEA was almost completely converted to 4-phenyl-2-oxazolidinone (PHOX) within 2 h. These observations reveal the strong disposition of this series of haloalkylamines toward reaction with HCO3- and indicate that the compounds in this family may exist only transiently as free amines in vivo, where there will virtually always be excess HCO3-. The physiological relevance of the in vitro findings is further indicated by the NMR-detectable conversion of BEA to OX and also an alkylating aziridine (AZ) moiety in rat plasma containing BEA. The ability to form carbamoylated species and OX (or PHOX) may mediate the toxicity of this series of haloalkylamines and hence is potentially of considerable significance.

Animals↗
PubMed2005

Dynamic monitoring of cytotoxicity on microelectronic sensors.

A real-time cell electronic sensing (RT-CES) system was used for label-free, dynamic measurement of cell responses to cytotoxicants. Cells were grown onto the surfaces of microelectronic sensors, which are comprised of circle-on-line electrode arrays and are integrated into the bottom surfaces of the microtiter plate. Changes in cell status such as cell number, viability, morphology, and adherence were monitored and quantified by detecting sensor electrical impedance. For cell quantification and viability measurement, the data generated on the RT-CES system correlated well with those from the colorimetric (MTT) assay. For cytotoxicity assessment, cells growing on microelectronic sensors were treated with different cytotoxicants, such as arsenic, mercury, and sodium dichromate. The dynamic responses of the cells to the toxicants were continuously monitored by the RT-CES system. On the basis of the IC50 values, the RT-CES system displays an equal sensitivity to the neutral red uptake assay at specific time points. Furthermore, because the RT-CES system provides real-time information regarding the state of cell morphology and adhesion in addition to cell number, we were able to discern a previously unreported effect of arsenic on NIH 3T3 cells prior to cell death. Also, using the RT-CES system, we were able to monitor cytotoxicity effects that occur within a minute of compound addition. Taken together, the RT-CES system allows for real-time, continuous monitoring and quantitative recording of the whole assay process and provides new insight into the cell-toxicant interaction.

Animals↗
PubMed2006

Involvement of semiquinone radicals in the in vitro cytotoxicity of cigarette mainstream smoke.

Free radicals in cigarette smoke have attracted a great deal of attention because they are hypothesized to be responsible in part for several of the pathologies related to smoking. Hydroquinone, catechol, and their methyl-substituted derivatives are abundant in the particulate phase of cigarette smoke, and they are known precursors of semiquinone radicals. In this study, the in vitro cytotoxicity of these dihydroxybenzenes was determined using the neutral red uptake (NRU) assay, and their radical-forming capacity was determined by electron paramagnetic resonance (EPR). All of the dihydroxybenzenes studied were found to generate appreciable amounts of semiquinone radicals when dissolved in the cell culture medium employed in the NRU assay. Hydroquinone exhibited by far the highest capacity to form semiquinone radicals at physiological pH, even though it is not the most cytotoxic dihydroxybenzene. Methyl-substituted dihydroxybenzenes were found to be more cytotoxic than either hydroquinone or catechol. The formation of semiquinone radicals via auto-oxidation of the dihydroxybenzenes was found to be dependent on the reduction potential of the corresponding quinone/semiquinone radical redox couple. The capacity to generate semiquinone radicals was found to be insufficient to explain the variance in the cytotoxicity among the dihydroxybenzenes in our study; consequently, other mechanisms of toxicity must also be involved. The observed interactions between 2,6-dimethylhydroquinone and hydroquinone in the cytotoxicity assay and EPR analysis suggest that care needs to be taken when the bioactivity of cigarette smoke constituents is evaluated, i.e., the effect of the cigarette smoke complex matrix on the activity of the single constituent studied must be taken into consideration.

Animals↗
PubMed1998

Isolation, purification and partial characterization of chloragocytes from the earthworm species Lumbricus terrestris.

Chloragocytes were isolated from the earthworm species Lumbricus terrestris. After mechanical dissociation and sedimentation through Percoll, a highly purified fraction of viable chloragocytes was obtained. The isolated chloragocytes accumulated the vital dye neutral red and reduced the tetrazolium dye MTT, thereby indicating cellular integrity. Time of flight flow cytometric analyses revealed a main population of large and highly granulated cells in the 30-33 microm size range. Hydrolase measurements showed that beta-D-N-acetyl-glucosaminidase and acid phosphatase exhibited the highest activities (146.6 and 24.9 mU/mg of protein, respectively), possibly indicating a major role for these 2 hydrolases in the physiological function of chloragocytes. In contrast, other acid hydrolases such as beta-D-galactosidase and beta-D-glucuronidase had specific activities of respectively 26 and 182 times lower than the glucosaminidase. The specific activity of the membrane-bound alkaline phosphatase was comparable to that of its acid counterpart (18.9 vs. 24.9 mU/mg of protein, respectively) and this level of activity may show an important trans-membrane activity in chloragocytes. The cytoplasmic and mitochondrial enzyme isocitrate dehydrogenase had a level of activity comparable to that of the exclusively cytoplasmic enzyme lactate dehydrogenase (6.6 vs. 8.1 mIU/mg of protein, respectively). When L. terrestris chloragocyte homogenates were separated on Percoll, results showed that hydrolases and dehydrogenases were mainly associated with the lighter materials that remained above the Percoll layer. Nonetheless, the detection of significant proportions (15-25%) of the total recovered activity of acid phosphatase and beta-galactosidase in the enriched chloragosome fraction supports the notion that some chloragosomes may be 'lysosome-like' organelles.

Animals↗
PubMed1998

In vitro cytotoxicity testing of chitosan-containing polyelectrolyte complexes.

Two chitosan-containing polyelectrolyte complexes, chitosan-poly(acrylic acid) and chitosan-poly(styrenesulphonate), were synthesized by polymerizing acrylic acid and sodium styrenesulphonate in the presence of chitosan and chitosan hydrochloride, respectively. The complexes were studied by optical microscopy and tested for cytotoxicity by the Neutral Red uptake, Kenacid Blue R-Binding and 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyl tetrazolium bromide assays. The optical microscopy confirmed the differences in crystallinity and structure already found for the two polycomplexes by other characterization techniques. The cytoxicity tests showed different influences on the cell activity by the extracts of the two polyelectrolyte complexes. Such results were discussed and correlated to the different structures of the two materials.

Journal Article↗
PubMed1998

Differential cytotoxicity of trace metals in cisplatin-sensitive and -resistant human ovarian cancer cells.

Cellular resistance of cisplatin is related to various factors such as membrane transformations, changes in cellular transport systems, and an increased efflux of cisplatin by the tumor cells. Deficiencies of one or more trace metals can affect normal physiological functions, leading to altered enzymatic activities and a reduction in immune responses. This in vitro investigation was undertaken to study and determine the differential cytotoxicity of certain trace metals in human ovarian cancer cells that were sensitive and resistant to cisplatin. Standard cytotoxicity assays were performed using the neutral red assay. In general, the cisplatin-resistant cells exhibited an increased resistance to the externally supplied trace metals. For both cell lines the rank order of cytotoxicity from greatest to least with the non-essential metals was Cd2+ > Bi3+, and for the macrometals, Ca2+ > K+ > Mg2+. The transition metals and selenium exhibited a slight difference between the two cell lines with respect to the order of cytotoxicity. The cisplatin-sensitive cells had a rank order of V5+ > Se6+ > Cu2+ > Zn2+ > Fe3+, from greatest to least toxicity. The cisplatin-resistant cells had a rank order of Cu2+ > V5+ > Se6+ > Zn2+ > Fe3+. Since trace metals have various functions in maintaining normal health, these results provide key baseline cytotoxicity data and show that, in general, cytotoxic resistance to the trace metals tested followed a pattern similar to cellular cisplatin resistance.

Antineoplastic Agents↗
PubMed2001

The glutathione peroxidase homologous gene from Chlamydomonas reinhardtii is transcriptionally up-regulated by singlet oxygen.

The glutathione peroxidase homologous gene (Gpxh gene) in Chlamydomonas reinhardtii is up-regulated under oxidative stress conditions. The Gpxh gene showed a remarkably strong and fast induction by the singlet oxygen-generating photosensitizers neutral red, methylene blue and rose Bengal. The Gpxh mRNA levels strongly increased, albeit much more slowly, upon exposure to the organic hydroperoxides tert-butyl hydroperoxide (t-BOOH) and cumene hydroperoxide. In contrast, the Gpxh mRNA levels were only weakly induced by exposure to the superoxide-generating compound paraquat and by hydrogen peroxide. A comparison of the Gpxh mRNA levels with those of the heat shock protein HSP70A and the iron superoxide dismutase gene showed qualitative and quantitative differences for the three genes under oxidative stress conditions tested. The Gpxh gene is specifically induced by singlet-oxygen photosensitizers and the relative induction by other compounds is much weaker for Gpxh than for the other genes investigated. Using Gpxh promoter fusions with the arylsulfatase reporter gene, we have shown that the Gpxh was transcriptionally up-regulated by singlet-oxygen photosensitizers. It is also shown that the Gpxh promoter contains a region between 104 and 179 bp upstream of the transcription start that is responsible for the mRNA up-regulation upon exposure to 1O2 but not t-BOOH. Within this region a regulatory sequence homologous to the mammalian cAMP response element (CRE) and activator protein 1 (AP-1) binding site was identified within a 16 bp palindrome.

Algal Proteins↗
PubMed2001

Studies on cytotoxic effect of nickel ions on three cultured fibroblasts.

Cytotoxicity of Ni ions on three fibroblasts such as L929, Balb/3T3 clone A31 and MC3T3-E1 were examined by cell count (CC) and Neutral Red assay (NR). Three cells were incubated for 6 days in 1 ml DME medium containing Ni ions which ranged from 0 to 2 mM/l. The results clarified that Ni ions had dose-dependent cytotoxicity. L929 possessed the largest TC50 values (the amount of Ni ion that caused 50% cell death or 50% cell viability) of 0.12 mM/l (CC) and 0.32 mM/l (NR), and Balb/3T3 clone A31 had the least values of 0.05 mM/l (CC) and 0.09 mM/l (NR), whilst MC3T3-E1 had the intermediate values of 0.08 mM/l (CC) and 0.15 mM/l (NR). The dissolution of Ni ions from Ni-containing metallic restorations must be lower than these concentration levels so that body tissues might not be severely damaged.

Journal Article↗
PubMed2001

Evaluation of the neurotoxic activity of typical and atypical neuroleptics: relevance to iatrogenic extrapyramidal symptoms.

Typical neuroleptic therapy often results in extrapyramidal symptoms (EPS) and tardive dyskinesia (TD). Recent reports reveal neurotoxic activity in some neuroleptics. We hypothesized that neurotoxicity might be implicated in EPS. This study aims to evaluate the neurotoxic activity of typical and atypical neuroleptics and to determine the possible role of neurotoxicity in neuroleptic-induced EPS. Perphenazine, haloperidol, clozapine, sulpiride, and risperidone (10-100 microM) were administered, either alone or combined with dopamine, to primary mouse neuronal or intact brain culture and to a human neuroblastoma (NB) cell line (SK-N-SH). Cell viability (measured by neutral red and alamar blue), DNA fragmentation (flow cytometry-NB) were determined. Neuroblastoma: perphenazine, clozapine, and haloperidol (100 microM) decreased viability by 87, 43, and 34% respectively. Sulpiride and risperidone were not toxic. At 10 microM, toxicity decreased markedly. Dopamine (125 microM) potentiated the perphenazine-induced toxicity. Flow cytometry of NB cells treated with perphenazine (2.5-40 microM) showed an increase (perphenazine 20 microM, 40 microM, 48 h) in fragmented DNA (74.7% and 95.0% vs. 8.7% in controls). Lower concentrations increased the G1 phase and decreased S phase in the cell cycle. In primary neurons, perphenazine, haloperidol, and clozapine, but not risperidone and sulpiride, induced a significant neurotoxic effect, which, in intact brain culture, was absent (haloperidol and clozapine) or lowered (perphenazine). Dopamine (0.5 mM) did not modify the effect of the drugs in the primary cultures. Neuroleptics possess differential neurotoxic activity with higher sensitivity of neoplasm tissue (NB compared to primary cultures). The order of toxicity was perphenazine > haloperidol = clozapine:sulpiride and risperidone were not toxic. Neurotoxicity is independent of dopamine and is associated with cell cycle arrest and apoptosis. With the exception of clozapine, neurotoxicity seems relevant to neuroleptic-induced EPS and TD.

Animals↗