Aurintricarboxylic acid prevents NMDA-mediated excitotoxicity: evidence for its action as an NMDA receptor antagonist

Aurintricarboxylic acid inhibits protein synthesis independent, sanguinarine-induced apoptosis and oncosis

Sanguinarine, a benzophenanthridine alkaloid, has anticancer potential through induction of cell death. We previously demonstrated that sanguinarine treatment at a low concentration (1.5 microg/ml) induced apoptosis in K562 human erythroleukemia cells, and a high concentration (12.5 microg/ml) induced the morphology of blister formation or oncosis-blister cell death (BCD). Treatment of cells at an intermediate sanguinarine concentration (6.25 microg/ml) induced diffuse swelling or oncosis-diffuse cell swelling (DCS). To assess the underlying mechanism of sanguinarine-induced apoptosis and oncosis-BCD in K562 cells, we studied their response to pre-treatment with two chemical compounds: aurintricarboxylic acid (ATA) and cycloheximide (CHX). The pretreatment effects of both chemical compounds on apoptosis and oncosis-BCD were evaluated by measuring multiple parameters using quantitative morphology, electron microscopy, terminal deoxynucleotidyl transferase (TdT) end-labeling and annexin-V-binding. ATA, a DNA endonuclease inhibitor, efficiently prevented DNA nicking and inhibited apoptosis almost completely and oncosis-BCD by about 40%, while CHX, a protein synthesis inhibitor, failed to inhibit both apoptosis and oncosis-BCD. These results demonstrate, first, the importance of endonuclease in sanguinarine-induced apoptosis and to some extent in oncosis-BCD and, second, that this inhibition does not require de novo protein synthesis.

Inhibition of cytokine-induced JAK-STAT signalling pathways by an endonuclease inhibitor aurintricarboxylic acid

1. Inducible nitric oxide (iNOS) is thought to involve in host defence and tissue damage in inflammatory loci. In previous study, we have found that the endonuclease inhibitor aurintricarboxylic acid (ATA) can protect macrophages from cell death induced by bacterial lipopolysaccharide. This action is through the interruption with signalling pathways for NF-kappa B and AP-1 activation, and thus iNOS expression. In this study we have addressed the effects of ATA on JAK-STAT signalling pathways. 2. In murine RAW 264.7 macrophages, IFN-gamma-mediated NO production and iNOS expression were concentration-dependently reduced by the presence of 3-100 micro M ATA. 3. IFN-gamma-induced STAT1 activation, as assessed from its tyrosine phosphorylation, nuclear translocation, binding to specific DNA response element and evoked IRF-1 reporter gene assay, were concomitantly inhibited by ATA. However, ATA did not alter IFN-gamma binding to RAW 264.7 cells. 4. The activities of JAK1 and JAK2, the upstream kinases essential for STAT1 signalling in response to IFN-gamma, were also reduced by ATA. 5. Moreover, IL-4, IL-10, GM-CSF and M-CSF elicited tyrosine phosphorylation of STAT3, STAT5 and/or STAT6 in macrophages were diminished by the presence of ATA. 6. Taken together, we conclude that ATA can interfere JAK-STAT signalling pathways in response to cytokines. This action contributes to the inhibition of IFN-gamma-induced iNOS expression.

Dual regulation of NMDA receptor functions by direct protein-protein interactions with the dopamine D1 receptor

Dopamine D1-like receptors, composed of D1 and D5 receptors, have been documented to modulate glutamate-mediated fast excitatory synaptic neurotransmission. Here, we report that dopamine D1 receptors modulate NMDA glutamate receptor-mediated functions through direct protein-protein interactions. Two regions in the D1 receptor carboxyl tail can directly and selectively couple to NMDA glutamate receptor subunits NR1-1a and NR2A. While one interaction is involved in the inhibition of NMDA receptor-gated currents, the other is implicated in the attenuation of NMDA receptor-mediated excitotoxicity through a PI-3 kinase-dependent pathway.

Aurintricarboxylic acid protects against cell death caused by lipopolysaccharide in macrophages by decreasing inducible nitric-oxide synthase induction via IkappaB kinase, extracellular signal-regulated kinase, and p38 mitogen-activated protein kinase inhibition

To elucidate the mechanisms involved in cell protection by aurintricarboxylic acid (ATA), an endonuclease inhibitor, high nitric oxide (NO)-induced macrophage apoptosis was studied. In RAW 264.7 macrophages, a high level of NO production accompanied by cell apoptosis was apparent with lipopolysaccharide (LPS) treatment. Direct NO donor sodium nitroprusside (SNP) also dramatically induced cell death, with an EC(50) of 1 mM. Coincubation of ATA (1-500 microM) in LPS-stimulated RAW 264.7 cells resulted in a striking reduction of NO production and cell apoptosis, whereas only a partial cell protection was achieved in response to SNP. This suggests that abrogation of inducible nitric-oxide synthase (iNOS)-dependent NO production might contribute to ATA protection of LPS-treated cells. Immunoblotting and reverse transcription-polymerase chain reaction analysis revealed that ATA down-regulated iNOS protein through transcriptional inhibition of iNOS gene expression but was unrelated to iNOS protein stability. ATA not only inhibited nuclear factor-kappaB (NF-kappaB) activation through impairment of the targeting and degradation of IkappaBs but also reduced LPS-induced activator protein-1 (AP-1) activation. These actions of ATA were not caused by the influence on LPS binding to macrophage membrane. Kinase assays indicated that ATA inhibited IkappaB kinase (IKK), extracellular signal-regulated kinase (ERK), and p38 mitogen-activated protein kinase (MAPK) activity both in vivo and in vitro, suggesting a direct interaction between ATA and these signaling molecules. Taken together, these results provide novel action targets of ATA and indicate that ATA protection of macrophages from LPS-mediated cell death is primarily the result of its inhibition of NO production, which closely relates to the inactivation of NF-kappaB and AP-1 and inhibition of IKK, ERK and p38 MAPK.

Aurintricarboxylic acid promotes survival and regeneration of axotomised retinal ganglion cells in vivo

Aurintricarboxylic acid (ATA) has been used as an anti-apoptotic drug to counteract ischemic or cytotoxic injury to neurons. We investigated whether ATA has a neuroprotective effect on axotomized, adult retinal ganglion cells (RGC) as a model for traumatic neuronal cell death. A solution of ATA was injected into the vitreous body of rat eyes whose optic nerves had been cut. In controls, 14% of RGC survived 14 days after axotomy, whereas 44% of RGC survived after a single injection of ATA solution, and 59% survived when the injection was repeated after 7 days. A single injection of ATA 1 day after axotomy rescued 58% of RGC. However, injection of ATA 4 days after axotomy did not influence the survival of RGC, indicating that crucial, irreversible cascades of death are initiated prior to this point in time. The TUNEL technique was used to visualise apoptotic ganglion cells and revealed that 4 days after axotomy their number was significantly less in retinas whose optic nerves were axotomized and treated with ATA, than those of controls. As a consequence of neuroprotection, more RGC were recruited to regenerate into a peripheral nerve graft used to replace the cut optic nerve. In this paradigm, ATA-treated RGC extended significantly more axons within the graft than control RGC. This number could be increased by a second injection of ATA 7 days after axotomy. These data show that ATA is not only able to delay post-traumatic neuronal death but also enhances the extent of axonal regeneration in vivo.

Possible involvement of activator protein-1 DNA binding in mechanisms underlying ischemic tolerance in the CA1 subfield of gerbil hippocampus

Transcription factors are nuclear proteins with an ability to recognize particular nucleotide sequences on double stranded genomic DNAs and thereby modulate the activity of RNA polymerase II which is responsible for the formation of messenger RNAs in cell nuclei. Gel retardation electrophoresis revealed that transient forebrain ischemia for 5 min led to drastic potentiation of binding of a radiolabelled double-stranded oligonucleotide probe for the transcription factor activator protein-1, in the thalamus as well as the CA1 and CA3 subfields and the dentate gyrus of the hippocampus of the gerbils previously given ischemia for 2 min two days before, which is known to induce tolerance to subsequent severe ischemia in the CA1 subfield. By contrast, ischemia for 5 min resulted in prolonged potentiation of activator protein-1 binding in the vulnerable CA1 subfield of the gerbils with prior ischemia for 5 min 14 days before, which is shown to induce delayed death of the pyramidal neurons exclusively in this subfield. Similar prolongation was seen with activator protein-1 binding in the vulnerable thalamus but not in the resistant CA3 subfield and dentate gyrus of the gerbils with such repeated ischemia for 5 min. Limited proteolysis by Staphylococcus aureus V8 protease as well as supershift assays using antibodies against c-Fos and c-Jun proteins demonstrated the possible difference in constructive partner proteins of activator protein-1 among nuclear extracts of the CA1 subfield obtained from gerbils with single, tolerated and repeated ischemia. These results suggest that de novo protein synthesis may underlie molecular mechanisms associated with acquisition of the ischemic tolerance through modulation at the level of gene transcription by activator protein-1 composed of different constructive partner proteins in the CA1 subfield. Possible participation of glial cells in the modulation is also suggested in particular situations.

Aurintricarboxylic acid prevents GLUR2 mRNA down-regulation and delayed neurodegeneration in hippocampal CA1 neurons of gerbil after global ischemia

Aurintricarboxylic acid (ATA), an inhibitor of endonuclease activity and other protein-nucleic acid interactions, blocks apoptosis in several cell types and prevents delayed death of hippocampal pyramidal CA1 neurons induced by transient global ischemia. Global ischemia in rats and gerbils induces down-regulation of GluR2 mRNA and increased alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-induced Ca2+ influx in CA1 before neurodegeneration. This result and neuroprotection by antagonists of AMPA receptors suggests that formation of AMPA receptors lacking GluR2, and therefore Ca2+ permeable, leads to excessive Ca2+ influx in response to endogenous glutamate; the resulting delayed neuronal death in CA1 exhibits many characteristics of apoptosis. In this study, we examined the effects of ATA on expression of mRNAs encoding glutamate receptor subunits in gerbil hippocampus after global ischemia. Administration of ATA by injection into the right cerebral ventricle 1 h before (but not 6 h after) bilateral carotid occlusion prevented the ischemia-induced decrease in GluR2 mRNA expression and the delayed neurodegeneration. These findings suggest that ATA is neuroprotective in ischemia by blocking the transcriptional changes leading to down-regulation of GluR2, rather than by simply blocking endonucleases, which presumably act later after Ca2+ influx initiates apoptosis. Maintaining formation of Ca2+ impermeable, GluR2 containing AMPA receptors could prevent delayed death of CA1 neurons after transient global ischemia, and block of GluR2 down-regulation may provide a further strategy for neuroprotection.

Pretreatment with intraventricular aurintricarboxylic acid decreases infarct size by inhibiting apoptosis following transient global ischemia in gerbils

The goal of this study was to determine whether aurintricarboxylic acid (ATA), an endonuclease inhibitor known to inhibit apoptosis, could ameliorate cell damage in a gerbil model of transient ischemia. Transient ischemia was induced in gerbils by bilateral carotid artery occlusion for a period of 5 minutes. Four micrograms of ATA was administered intraventricularly 1 hour before ischemia, and the brains were assessed histologically 1 week later to quantitate cell loss in the vulnerable CA-1 subsector of the hippocampus. In a separate set of experiments, 4 microg of ATA was administered intraventricularly 1 hour before ischemia and the brains were assessed for evidence of DNA fragmentation by the TUNEL method. There was only a 16% cell loss compared with nonischemic controls in animals pretreated with ATA that was significantly less (p < 0.05) than the 48% cell loss in animals pretreated with saline alone. TUNEL-positive cells were first evident at 3 days and were still present at 7 days subsequent to ischemia. Maximal staining occurred at 4 days. Pretreatment with ATA virtually eliminated TUNEL staining at 4 days. These results support the hypothesis that the delayed cell death secondary to transient ischemia is, in part, apoptotic. Furthermore, ATA afforded significant neuronal protection and prevented DNA fragmentation.

Endonucleolytic DNA fragmentation is not required for apoptosis of cultured rat cerebellar granule neurons

Depolarizing concentrations of potassium (K+) promote maturation and survival of cerebellar granule neurons in vitro. Withdrawal of potassium from differentiated neurons induces morphological and biochemical features of apoptosis, including membrane blebbing, nuclear condensation, activation of caspases, and internucleosomal DNA fragmentation. Significant DNA fragmentation is detectable at 6 h after K+ withdrawal and slowly increases thereafter. Two observations indicate that endonucleolytic DNA degradation is neither required nor sufficient for K+ withdrawal-induced apoptosis in cerebellar granule neurons: (i) neurons are rescued from apoptosis by readdition of K+ up to 8 h after K+ withdrawal, when DNA fragmentation has already occurred. (ii) The endonuclease inhibitor, aurintricarboxylic acid, inhibits DNA fragmentation as assessed by quantitative DNA fluorometry, TUNEL staining, and DNA gel electrophoresis, but not cell death or chromatin condensation induced by K+ withdrawal.

Apoptosis in neurological disease

Enormous interest in cell death in the past several years has moved apoptosis to the forefront of scientific research. Apoptosis has been found to mediate cell deletion in tissue homeostasis, embryological development, and immunological functioning. It also occurs in pathological conditions, including cancer and acquired immunodeficiency syndrome, and is implicated in neurodegenerative diseases. Claims of neuronal apoptosis induced by various agents and conditions are published regularly, but in many instances the data are questionable because they are incomplete. This review presents a brief history of apoptosis and describes the evidence required before claims of apoptosis are made. Summaries and critiques of important investigations concerning the genetic and biochemical regulation of neuronal apoptosis are presented, as are other studies describing connections between apoptosis and neuronal cell death in physiological and pathological situations. There is a realization that apoptosis can be programmed and is distinguishable from necrotic cell death. Combining apoptosis with programmed cell death produces misleading terminology and confusion over these two forms of cell degeneration. Further investigations into neuronal apoptosis should focus on all of the criteria that the original investigators outlined 25 years ago, to clarify whether apoptosis and/or another form of cell death mediates neuronal degeneration in physiological settings and in neurological diseases such as Alzheimer's disease, Parkinson's disease, epilepsy, and ischemia/stroke.

Positive correlation between prolonged potentiation of binding of double-stranded oligonucleotide probe for the transcription factor AP1 and resistance to transient forebrain ischemia in gerbil hippocampus

Gel retardation electrophoresis revealed that binding of a radiolabelled double-stranded oligonucleotide probe for the nuclear transcription factor activator protein-1 was markedly potentiated in the CA1 and CA3 subfields and the dentate gyrus of the hippocampus of the gerbils with transient forebrain ischemia for 5 min, which is known to induce delayed death of pyramidal neurons exclusively in the CA1 subfield. The potentiation was transient in the vulnerable CA1 subfield, but persistent up to 18 h in the resistant CA3 subfield and dentate gyrus. However, no significant alteration was detected in endogenous levels of cyclic AMP response element binding protein phosphorylated at serine133 in these three different hippocampal structures 3 h after the reperfusion. On the other hand, hypothermia during ischemia which is known to protect the CA1 subfield against ischemic damages, led to a prolonged elevation of the activator protein-1 binding up to 9 h after the reperfusion in this vulnerable subfield at least in part through expression of c-Fos protein. Moreover, activator protein-1 binding was significantly elevated in the CA1 subfield up to 12 h after forebrain ischemia for 2 min which is shown not to induce marked damages to the vulnerable subfield. These results suggest that prolonged elevation of DNA binding activity of activator protein-1 may be responsible for molecular mechanisms underlying the unique vulnerability and/or resistance of particular subfields to a transient ischemic insult in the gerbil hippocampus.

Inhibition of spinal monosynaptic reflex in newborn rats by aurintricarboxylic acid

The effect of aurintricarboxylic acid (ATA), an inhibitor of nuclease, on glutamatergic synaptic transmission was examined electrophysiologically in the isolated spinal cords of newborn rats. Monosynaptic reflex (MSR) was depressed about 20%, 50 min after exposure to 100 microM of ATA. Pretreatment with APV, a N-methyl-D-aspartate (NMDA) type receptor antagonist, depressed MSR by about 10%, but additional application of ATA did not affect the MSR further. In contrast, the remaining MSR following treatment with DNQX, a non-NMDA type receptor antagonist, in the Mg2+-free medium was almost completely inhibited by addition of ATA. ATA depressed NMDA- but not D,L-alpha-amino-3-hydroxy-5-methyl-4-isoxalone propionic acid (AMPA)- or kainate-induced depolarization in the medium containing normal ionic composition. Thus it is concluded that the reduction of MSR by ATA is due to blockade of NMDA type but non-NMDA type glutamate receptors. The present study also confirmed the previous conclusion that Ia monosynaptic transmission in the spinal cord of the newborn rat is mediated by NMDA as well as non-NMDA type glutamate receptors.

Overexpression of glyceraldehyde-3-phosphate dehydrogenase is involved in low K+-induced apoptosis but not necrosis of cultured cerebellar granule cells

We have reported that overexpression of glyceraldehyde-3-phosphate dehydrogenase (GAPDH; EC 1.2.1.12) is involved in age-induced apoptosis of the cultured cerebellar granule cells that grow in a depolarizing concentration (25 mM) of KCI. The present study was undertaken to investigate whether GAPDH overexpression also occurs and participates in apoptosis of the cerebellar granule cells that result from switching the culturing conditions from high (25 mM) to low (5 mM) concentrations of KCl. We found that exposure of granule cells to low potassium (K+) for 24 hr induces not only apoptosis but also necrotic damage. The latter is supported by the morphological observations that a subpopulation of neurons showed cell swelling, extensive cytoplasmic vacuolization, damaged mitochondria, and apparently intact nuclei. Treatments with two antisense but not sense oligodeoxyribonucleotides directed against GAPDH attenuated low K+-induced neuronal death by approximately 50%. Morphological inspection revealed that GAPDH antisense oligonucleotides preferentially blocked low K+-induced apoptosis with little or no effect on necrotic damage. Similar to antisense oligonucleotides, actinomycin-D partially inhibited low K+-induced death of granule cells with a predominant effect on apoptosis. In contrast, cycloheximide almost completely blocked low K+-induced neuronal death and seemed to prevent both apoptotic and necrotic damage. The levels of GAPDH mRNA and protein were markedly increased in a time-dependent manner after low K+ exposure. The overexpression of GAPDH mRNA and protein was completely blocked by cycloheximide, actinomycin-D, and its antisense but not sense oligonucleotides. Taken together, these results lend credence to the view that exposure of cerebellar granule cells to low K+ induces both apoptosis and necrosis and that only the apoptotic component involves overexpression of GAPDH.

Tyrosine phosphorylation of ErbB4 is stimulated by aurintricarboxylic acid in human neuroblastoma SH-SY5Y cells

Aurintricarboxylic acid (ATA) has been reported to protect PC12 cells and cultured neuronal cells from serum starvation-induced cell death, and hippocampal neurons from N-methyl D-aspartate- or ischemia-induced cell death in vivo. We have found that ATA activated tyrosine phosphorylation cascade in PC12 cells as growth factors. Here, we report that ATA prevents cell death under serum starvation and induces tyrosine phosphorylation also in human neuroblastoma SH-SY5Y cells. Furthermore, it was found that erbB4, a member of epidermal growth factor receptor family, is tyrosine-phosphorylated in response to ATA. Both, erbB4 and its ligand, neu differentiation factor (NDF)/ heregulin family, have been reported to be expressed abundantly in nervous system. Thus, tyrosine phosphorylation of erbB4 might explain the neuro-protective activity of ATA.

Kainic acid induces apoptosis in neurons

Growing evidence suggests that non-N-methyl-D-aspartate receptor activation may contribute to neuronal death in both acute and chronic neurological diseases. The intracellular processes that mediate this form of neuronal death are poorly understood. We have previously characterized a model of kainic acid neurotoxicity using cerebellar granule cell neurons in vitro and we sought to determine the mechanism of kainic acid-induced neuronal degeneration. We found DNA laddering by agarose gel electrophoresis, cellular DNA fragmentation by in situ end labeling of DNA, and chromatin condensation using a fluorescent DNA intercalating dye, in cerebellar granule cells following exposure to kainic acid (100 microM). Aurintricarboxylic acid protected cerebellar granule cells from kainic acid-induced death. While the morphological and biochemical features of neuronal death induced by kainic acid resembled low K(+)-induced apoptosis in cerebellar granule cells, the time interval from the institution of the death promoting condition to neuronal death was shorter with kainic acid and did not require new protein or RNA synthesis. These results demonstrate that kainic acid receptor activation can induce transcription-independent apoptosis in neurons. This in vitro model should be useful in identifying the intracellular pathways that link kainic acid receptor activation with apoptosis.

Pathophysiology of oligodendroglial excitotoxicity

Oligodendrocyte-like cells (OLD) derived from the rat oligodendroglial precursor line, CG-4, express Ca(2+)-permeable non-methyl-D-aspartate glutamate receptor channels (GluR). Exposure to kainate, an L-glutamate analogue, markedly elevates OLC Ca2+ influx and cytosolic [Ca2+], and results in damage to both OLC plasma membrane and OLC nuclear DNA. Two observations indicate that kainate-induced OLC internucleosomal DNA nicking is not simply a delayed consequence of cell necrosis: 1) there is no temporal lag between onset of plasma membrane injury and of DNA nicking; and 2) aurintricarboxylic acid, an endonuclease inhibitor, blocks kainate-induced damage to the plasma membrane. N-acetyl-L-cysteine also inhibits OLC kainate injury, suggesting that reactive oxygen species participate in OLC excitotoxicity. Kainate-induced OLC Ca2+ influx and excitotoxicity are blocked by alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA), indicating that these kainate effects are mediated by AMPA-GluR. AMPA and L-glutamate fail to elicit OLC damage unless cyclothiazide, an AMPA-GluR desensitization blocker, is present. OLC express both the "flip" and "flop" forms of GluR2, GluR3, and GluR4 mRNAs, but neither flip nor flop GluR1 mRNA. These data, together with the restriction of the desensitization-blocking activity of cyclothiazide to GluR containing flip-encoded GluR subunits, and the sharply diminished Ca2+ permeability of GluR containing edited GluR2, suggest OLC excitotoxicity is mediated by AMPA-GluR that contain flip GluR3 and/or flip GluR4 protein subunits, but neither flip nor flop GluR2 protein subunits. Rapid desensitization of these GluR is likely to be important in protecting cells of the oligodendroglial lineage from excitotoxicity.

Kainate induces apoptosis in neurons

Growing evidence suggests that non-N-methyl-D-aspartate receptor activation may contribute to neuronal death in both acute and chronic neurological diseases. The intracellular processes that mediate this form of neuronal death are poorly understood. We have previously characterized a model of kainate neurotoxicity using cerebellar granule cell neurons in vitro and we sought to determine the mechanism of kainate-induced neurons degeneration. We found DNA, and chromatin condensation using a fluorescent DNA intercalating dye, in cerebellar granule cells following exposure to kainate (100 microM). Aurintricarboxylic acid protected cerebellar granule cells from kainate-induced death. While the morphological and biochemical features of neuronal death induced by kainate resembled low-K(+)-induced apoptosis in cerebellar granule cells; the time interval from the institution of the death-promoting condition to neuronal death was briefer with kainate and did not require new protein or RNA synthesis. These results demonstrate that kainate receptor activation can induce transcription-independent apoptosis in neurons. This in vitro model should be useful in identifying the intracellular pathways that link kainate receptor activation with apoptosis.

Attenuation of excitotoxic cell swelling and GABA release by the GABA transport inhibitor SKF 89976A

Acute excitotoxicity in the chick retina is characterized by cellular swelling and the subsequent selective release of GABA. In order to understand the source of GABA release, embryonic day 15 retina were incubated with 1 mM glutamate for 30 min in the presence or absence of the GABA transport inhibitor SKF 89976A (1-100 microM). SKF 89976A dose-dependently attentuated glutamate-induced GABA release (IC50, 39 microM). Histological examination of retina showed that SKF 89976A greatly reduced cellular swelling caused by glutamate exposure. Interaction of SKF 89976A with glutamate receptors was ruled out as a possible reason for protection vs acute glutamate excitotoxicity, since SKF 89976A had no effect on glutamate receptor-induced 22Na+ influx. In contrast, the NMDA antagonist, MK-801, significantly blocked glutamate-evoked 22NA+ uptake. These studies indicate that reversal of the GABA transporter contributes to the bulk of GABA release during acute excitotoxicity in retina. Further, a net effect of the presence of SKF 89976A during glutamate exposure is reduction in cellular swelling. It is not clear at present if attenuation of swelling is mediated specifically by an interaction with the GABA transporter or by a nonspecific or indirect effect of SKF 89976A.

Regulation of transforming growth factor-beta 1-mediated apoptosis in head and neck squamous cell carcinoma

The apoptotic cell death in Cal-27 cells induced by exposure to transforming growth factor-beta 1 was inhibited by the endonuclease inhibitor aurintricarboxylic acid (ATA) in a concentration-dependent fashion. In vitro studies of cytotoxicity, DNA fragmentation, and protein synthesis by Cal-27 cell lines were performed. Inhibition of cytotoxicity as well as endonucleolytic DNA cleavage was detected. ATA did not inhibit cytotoxicity either via transforming growth factor cell-surface-receptor alteration or by inhibition of macromolecular synthesis. ATA-sensitive events occurred late during treatment. These data suggest that endonucleolytic DNA cleavage is a mandatory event leading to cell death in this system.

Nuclear disintegration as a leading step of glutamate excitotoxicity in brain neurons

Recent studies on ischemic brain disease in vivo and glutamate excitotoxicity in vitro suggest that apoptosis may play a role in excitotoxic neuronal death. To examine the possible involvement of apoptosis in glutamate excitotoxicity, we studied an early process of morphological changes in rat cortical neurons exposed to 1 mM glutamate. Observations under Nomarski optics combined with a digital image processor revealed a rapid change in the nucleus followed by a cellular swelling. The nucleus increased in granularity and swelled in 5 min, then became liquefied in 30 min. The cell body swelled slowly in 15-45 min. These changes could be prevented by treatment of the neuron with MK-801 (dizocilpine maleate), a blocker of N-methyl-D-aspartate (NMDA) receptor-coupled ion channel. However, treatment of the neurons with N(G)-nitro-L-arginine (N-NORG), a nitric oxide synthase inhibitor, had no significant effect. Use of the in situ end-labeling technique for the demonstration of free 3'-hydroxyl ends revealed that DNA fragmentation took place within 1 hr after glutamate exposure. A change in intracellular Ca(2+) concentration was examined with fluo-3 under a confocal laser microscope. Application of 1 mM glutamate induced rapid Ca transients in the nucleus as well as in the cytoplasm. Both of these Ca responses were blocked by MK-801. These results indicate that glutamate excitotoxicity in the brain neuron does not fulfill morphological criteria of apoptosis, but suggest that the nuclear disintegration associated with DNA fragmentation is involved as a leading step in glutamate excitotoxicity.

Apoptosis induced by beta-N-oxalylamino-L-alanine on a motoneuron hybrid cell line

It has been suggested that beta-N-oxalylamino-L-alanine, a non-protein amino acid present in the Lathyrus Sativus seeds, may play a role in the etiopathogenesis of neurolathyrism, a toxic form of motor neuron disease clinically characterized by a severe spastic paraparesis. In order to investigate the mechanisms of beta-N-oxalylamino-L-alanine-mediated cell death, we studied the effect of this neurotoxin as well as other excitatory amino acids agonists on the growth and survival of motoneuron hybrid ventral spinal cord 4.1 cells. beta-N-oxalylamino-L-alanine was toxic to ventral spinal cord 4.1 cells in a concentration-dependent fashion (0.5-10 mM). Among the excitatory amino acids tested, only glutamate (1-10 mM), quisqualate (1 mM) and, with less extent, beta-N-methylamino-L-alanine (10 mM) induced a significant reduction of cell survival. The effect of Lathyrus Sativus neurotoxin was a slow process, becoming apparent only after 24-48 h of incubation. Interestingly, a mathematical analysis applied to the time course and dose curve of beta-N-oxalylamino-L-alanine toxicity suggested that even for very low concentrations of the amino acid it is theoretically possible to predict a time-dependent effect. The cell death was not blocked by antagonists of N-methyl-D-aspartate or non-N-methyl-D-aspartate receptors; aurintricarboxylic acid and alpha-tocopherol gave a partial protection; cysteine (1 mM) prevented the toxic effect of both Lathyrus Sativus neurotoxin and glutamate as well as quisqualate. Morphologically, in the presence of either beta-N-oxalylamino-L-alanine, glutamate or quisqualate, ventral spinal cord 4.1 cells showed apoptotic features also confirmed by ISEL technique and agarose gel electrophoresis of genomic DNA. Thus, our results suggest that in ventral spinal cord 4.1 motoneuron hybrid cells, in the absence of functional synaptic excitatory amino acid receptors, beta-N-oxalylamino-L-alanine induces cell degeneration through an apoptotic mechanism, possibly mediated by a block of cystine/glutamate Xc antiporter.

Ultrastructure of excitotoxic neuronal death in murine cortical culture

Ischemic and traumatic brain injury are likely to involve neuronal injury triggered by glutamate receptor overactivation. Although excitotoxic neuronal injury has been widely studied in the setting of primary culture, the extent to which these in vitro injury paradigms resemble in vivo ischemic injury morphologically has not previously been well studied. We studied glutamate receptor mediated neuronal death by transmission electron microscopy and light microscopy. Morphologic characteristics of neurons injured by 10 min exposure to 500 microM glutamate include rapid swelling of mitochondria and endoplasmic reticulum, and cytoplasmic and nuclear lucency. Both alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid and kainic acid caused vacuolation, dilatation of the endoplasmic reticulum, cytoplasmic condensation and random condensation of chromatin with preserved mitochondria. None of these injuries was ameliorated by cycloheximide or actinomycin D; all were significantly lessened by aurintricarboxylic acid. Gel electrophoresis showed no increase in DNA fragmentation over control. The morphologic changes seen with alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid and kainate are distinct from the changes induced by glutamate. Excitotoxic injury in this system due to high concentrations of glutamate resembles necrosis while the other agonists produce a different form of cell death which is neither necrosis nor apoptosis.

Carbamazepine induction of apoptosis in cultured cerebellar neurons: effects of N-methyl-D-aspartate, aurintricarboxylic acid and cycloheximide

We have previously demonstrated that carbamazepine (CBZ) at concentrations above the therapeutic range is toxic to cultured cerebellar granule cells. Here, we ask whether the effect of CBZ involves neuronal apoptosis or necrosis. Treatment of cultured cerebellar granule cells with CBZ for 3 days resulted in a concentration-dependent fragmentation of DNA revealed as a laddered pattern in agarose gel electrophoresis, a phenomenon characteristic of apoptosis. Pretreatment of cells with N-methyl-D-aspartate (NMDA) blocked CBZ-induced DNA fragmentation and neurotoxicity as assayed by loss of mitochondrial activity with MTT or by [3H]ouabain binding to Na+/K(+)-ATPase. Aurintricarboxylic acid (ATA), a polyanionic dye, also markedly suppressed DNA fragmentation and cell death detected by morphological examination. A considerable level of DNA ladder formation was detected in untreated cells and this basal DNA fragmentation was also blocked by NMDA and ATA. Moreover, NMDA and ATA prevented CBZ-induced chromatin condensation as revealed by DNA binding with the fluorescent dye Hoechst 33258. Pretreatment of cells with cycloheximide, a protein synthesis inhibitor, prevented CBZ-induced cell death detected morphologically and attenuated CBZ-induced neurotoxicity assessed by mitochondrial activity and [3H]ouabain binding assays. Taken together, our results suggest that CBZ-induces death of cerebellar granule cells by an apoptotic process that is sensitive to NMDA, ATA and cycloheximide.

Apoptotic DNA fragmentation in the rat cerebral cortex induced by permanent middle cerebral artery occlusion

Recent investigations have demonstrated internucleosomal DNA fragmentation in ischemic neuronal tissue. This type of fragmentation is characteristic of programmed cell death or apoptosis and suggests that neuronal death in stroke may be more complex than simple necrotic death. The present experiments provide a detailed examination of the regional localization and time course for apoptotic DNA fragmentation in the cerebral cortex following focal cerebral ischemia. Spontaneously hypertensive rats were subjected to permanent right middle cerebral artery occlusion and the cerebral cortices were examined for evidence of DNA fragmentation using electrophoretic, flow cytometric, and histological approaches. An electrophoretic examination of cortical DNA at 24 h after the occlusion indicated that the majority of nucleosomal ladders were in the transition zone or penumbra and the core of the infarction, with no fragmentation apparent in the contralateral normal cortex. A flow cytometric analysis of DNA fragmentation in intact cells revealed a similar pattern, with increased fragmentation observed in ischemic cortex vs. the contralateral cortex. Saggital sections taken 1.5 mm lateral to midline were collected from animals at 1, 4, and 24 h after the infarction and DNA fragmentation was examined histologically by terminal deoxynucleotidyl transferase mediated dUTP-biotin nick end labeling (TUNEL) staining. Quantitative analysis of these sections indicated that DNA fragmentation can be observed in the anterior and central area of the infarctions as soon as 1 h after the occlusion and that the extent and magnitude of the fragmentation increases at 4 and 24 h.(ABSTRACT TRUNCATED AT 250 WORDS)

A neuroprotective compound, aurin tricarboxylic acid, stimulates the tyrosine phosphorylation cascade in PC12 cells

Aurin tricarboxylic acid (ATA), a general nuclease inhibitor, was reported to prevent PC12 cells from cell death caused by serum starvation (1). In our study, ATA also protected PC12 cells, but not NIH3T3 cells, from serum-starved cell death. When we investigated the mechanism of action of ATA on these cells, ATA was found to increase tyrosine phosphorylation in PC12 cells, but not in NIH3T3 cells. Further investigation on tyrosine-phosphorylated proteins revealed that ATA, similar to nerve growth factor and epidermal growth factor, induced tyrosine phosphorylation of mitogen-activated protein kinases. Since the tyrosine phosphorylation of mitogen-activated protein kinases is thought to play an important role inn growth factor-dependent signal pathways, this finding suggests that the action of ATA on PC12 cells is mediated by tyrosine phosphorylation cascade, similar to growth factor signaling. In addition, we found that Shc proteins, phosphatidylinositol 3-kinase, and phospholipase C-gamma were also phosphorylated in ATA-treated PC12 cells. These key proteins in signal transduction pathways are known to associate with ligand-activated growth factor receptors and are phosphorylated on tyrosine. Thus, the phosphorylation of these three proteins by ATA stimulation supports the speculation that ATA activates a certain receptor tyrosine kinase.

The role of inducible transcription factors in apoptotic nerve cell death

Recent studies have shown that certain types of nerve cell death in the brain occur by an apoptotic mechanism. Researchers have demonstrated that moderate hypoxic-ischemic (HI) episodes and status epilepticus (SE) can cause DNA fragmentation as well as other morphological features of apoptosis in neurons destined to die, whereas more severe HI episodes lead to neuronal necrosis and infarction. Although somewhat controversial, some studies have demonstrated that protein synthesis inhibition prevents HI-and SE-induced nerve cell death in the brain, suggesting that apoptotic nerve cell death in the adult brain is de novo protein synthesis-dependent (i.e., programmed). The identity of the proteins involved in HI-and SE-induced apoptosis in the adult brain is unclear, although based upon studies in cell culture, a number of potential cell death and anti-apoptosis genes have been identified. In addition, a number of studies have demonstrated that inducible transcription factors (ITFs) are expressed for prolonged periods in neurons undergoing apoptotic death following HI and SE. These results suggest that prolonged expression of ITFs (in particular c-jun) may form part of the biological cascade that induces apoptosis in adult neurons. These various studies are critically discussed and in particular the role of inducible transcription factors in neuronal apoptosis is evaluated.

Mechanisms of delayed cell death following hypoxic-ischemic injury in the immature rat: evidence for apoptosis during selective neuronal loss

The mechanisms leading to delayed cell death following hypoxic-ischemic injury in the developing brain are unclear. We examined the possible roles of apoptosis and microglial activation in the 21-day-old rat brain following either mild (15 min) or severe (60 min) unilateral hypoxic-ischemic injury. The temporal and spatial patterns of DNA degradation were assessed using gel-electrophoresis and in-situ DNA end-labelling. Microglial activation, mitochondrial failure and cell death were examined using lectin histochemistry, 2,3,5,triphenyl-H-tetrazolium chloride (TTC) staining and acid fuchsin staining, respectively. Selective neuronal death produced by the 15 min injury was associated with the development of apoptotic morphology, DNA laddering and acidophilia from 3 days post-hypoxia. The 60 min injury accelerated this process with some cells showing signs of DNA degradation at 10 h post-hypoxia. However, in the cortex, which developed infarction after the 60 min injury, a different pattern of cell loss occurred. The DNA and mitochondria remained intact, and cells basophilic, until after 10 h post-hypoxia, then widespread necrosis developed by 24 hr. In contrast to regions of selective neuronal loss, DNA degradation was initially random (at 24 hr), with 180bp DNA ladders not detected until 3 days post-hypoxia. There was no morphological evidence of apoptosis. Microglial activation coincided with the onset of DNA degradation in regions of selective neuronal loss but not infarction, suggesting a possible role in selective neuronal death. The results suggest that cortical infarction, which was delayed for at least 10 h, was necrotic, and occurred independently of microglial activation and apoptosis. In contrast, selective neuronal death was apoptotic.

Hybridoma cell cultures continuously undergo apoptosis and reveal a novel 100 bp DNA fragment

This report represents an investigation into the nature of apoptosis in hybridoma cultures and its significance to their utilization in biotechnology. To this end DNA fragmentation and capillary electrophoresis of genomic DNA was studied during the culture of two hybridoma cell lines. This indicated that the phenomenon of apoptosis was always present even under normal culture conditions. Two DNA fragments not associated with the typical DNA fragmentation ladder were identified in the two hybridoma cultures: a previously unreported DNA fragment of about 100 bp and a large fragment which may correspond to one reported in the literature (Walker et al., 1993). The small fragment was identified as soon as the early exponential growth phase of culture, while the large fragment appeared only in the latter part of the growth curve when there was marked DNA fragmentation. In addition we present evidence that aurintricarboxylic acid, which inhibits apoptosis in neural cells, permits this process in hybridoma cells at levels below 100 microM. This unusual predisposition of hybridoma cultures to undergo apoptosis and their response to inhibitor of apoptosis may have important implications for approaches to the culture of hybridomas and their utilization for monoclonal production.

The effect of aurintricarboxylic acid, an endonuclease inhibitor, on ischemia/reperfusion damage in rat retina

Apoptosis is a form of cell death distinct from necrosis showing distinctive morphologic features and may require energy. It is under various control mechanisms and may involve an endonuclease, which cleavages genomic DNA in the internucleosomal linker regions. Previously, we reported that ischemic/reperfusion injury to rat retina induced endonuclease mediated apoptosis of retinal neurons. In this study, we examined the effect of aurintricarboxylic acid (ATA), an endonuclease inhibitor, on ischemia/reperfusion damage in rat retina in our established rat model. A single intraperitoneal injection of ATA at 2 mg/kg given immediately after 60 minutes of ischemia to the retina showed no observable effect. At 10 mg/kg, there was notable beneficial effect morphologically but not morphometrically. ATA at 100 mg/kg showed significant effect both morphologically and morphometrically. This observation is consistent with the hypothesis that endonuclease mediated apoptosis may be involved in retinal cell loss after ischemia/reperfusion insult.

Rapid potentiation of DNA binding activities of particular transcription factors with leucine-zipper motifs in discrete brain structures of the gerbil with transient forebrain ischemia

Binding of radiolabeled double stranded oligonucleotide probes for nuclear transcription factors with leucine-zipper motifs, such as activator protein-1 (AP1), cyclic AMP response element binding protein (CREB) and Myc, was unevenly distributed in gerbil brain in a manner peculiar to each factor. Among 3 different hippocampal subfields examined, the dentate gyrus had the highest basal DNA binding activities of AP1 with progressively less potent binding in the CA3 and CA1 subfields. Similarly, the dentate gyrus was highest in the basal binding of probes for both CREB and Myc among the 3 distinct hippocampal subregions. However, transient forebrain ischemia for 5 min induced more potent enhancement of the AP1 binding in the CA1 subfield 4 h after the insult than in the CA3 subfield and dentate gyrus. In contrast, the ischemic injury similarly tripled DNA binding activities of CREB without markedly affecting those of Myc in hippocampal CA1 and CA3 subfields. Binding of the probe for AP1 was also markedly potentiated following ischemia in the thalamus, caudate putamen, frontal cortex and cerebellar cortex in a rank order of decreasing magnitude, while the ischemic insult induced slight but statistically significant potentiation of both CREB and Myc binding in the thalamus without affecting that in other discrete brain regions. These results suggest that expression of AP1 may be a determinant of unique vulnerability and/or resistance to an ischemic insult in the gerbil hippocampus.

Delayed application of aurintricarboxylic acid reduces glutamate-induced cortical neuronal injury

The non-specific endonuclease inhibitor, aurintricarboxylic acid (ATA), attenuated glutamate-induced destruction of cultured cortical neurons. In part, this protective effect likely reflected the ability of ATA to produce a slowly developing block of N-methyl-D-aspartate receptor-mediated inward whole cell current or increase in intracellular free Ca2+. However, ATA also attenuated a high K(+)-induced increase in intracellular free Ca2+ in the presence of D-amino-phosphonovalerate, suggesting that ATA may have a more general effect on Ca2+ homeostasis. In addition, ATA attenuated glutamate neurotoxicity even if added up to 2 hr after completion of glutamate exposure, a time when glutamate antagonists or lipid peroxidation inhibitors are no longer neuroprotective. Involvement of apoptosis in this excitotoxic death is unlikely, as Southern blotting of genomic DNA revealed no evidence of fragmentation, and death was not prevented by inhibitors of RNA or protein synthesis. Most likely, ATA interferes with some key downstream consequences of excitotoxic glutamate receptor overactivation.

Internucleosomal DNA fragmentation in gerbil hippocampus following forebrain ischemia

Internucleosomal DNA fragmentation, the characteristics feature of programmed cell death, was demonstrated in gerbil hippocampus following 10 min of forebrain ischemia. Quantitative analysis revealed the presence of DNA fragments as early as 12 h after ischemia, reaching a maximum at 48 h. Measurable DNA fragmentation was still present in 3/3 subjects 96 h after the ischemic insult. In situ staining of hippocampus demonstrated pronounced DNA fragmentation that was localized in the CA1 region. The localization of fragmented DNA to the CA1 is consistent with the vulnerability of this layer to ischemic insult, and indicates that DNA fragmentation may be associated with the delayed loss of CA1 neurons in this model of forebrain ischemia.