Pathological effects of glyoxalase I inhibition in SH-SY5Y neuroblastoma cells

In Alzheimer's disease (AD), in aging, and under conditions of oxidative stress, the levels of reactive carbonyl compounds continuously increase. Accumulating carbonyl levels might be caused by an impaired enzymatic detoxification system. The major dicarbonyl detoxifying system is the glyoxalase system, which removes methylglyoxal in order to minimize cellular impairment. Although a reduced activity of glyoxalase I was evident in aging brains, it is not known how raising the intracellular methylglyoxal level influences neuronal function and the phosphorylation pattern of tau protein, which is known to be abnormally hyperphosphorylated in AD. To simulate a reduced glyoxalase I activity, we applied an inhibitor of glyoxalase I, p-bromobenzylglutathione cyclopentyl diester (pBrBzGSCp(2)), to SH-SY5Y neuroblastoma cells to induce chronically elevated methylglyoxal concentrations. We have shown that 10 microM pBrBzGSCp(2) leads to a fourfold elevation of the methylglyoxal level after 24 hr. In addition, glyoxalase I inhibition leads to reduced cell viability, strongly retracted neuritis, increase in [Ca(2+)](i), and activation of caspase-3. However, pBrBzGSCp(2) did not lead to tau "hyper"-phosphorylation despite activation of p38 mitogen-activated protein kinase and c-Jun NH(2)-terminal kinase but rather activated protein phosphatases 2 and induced tau dephosphorylation at the Ser(202)/Thr(205) and Ser(396)/Ser(404) epitopes. Preincubation with the carbonyl scavenger aminoguanidine prevented tau dephosphorylation, indicating the specific effect of methylglyoxal. Also, pretreatment with the inhibitor okadaic acid prevented tau dephosphorylation, indicating that methylglyoxal activates PP-2A. In summary, our data suggest that a reduced glyoxalase I activity mimics some changes associated with neurodegeneration, such as neurite retraction and apoptotic cell death.     

Akt activity in presenilin 1 wild-type and mutation transfected human SH-SY5Y neuroblastoma cells after serum deprivation and high glucose stress.

The majority of early-onset familial Alzheimer disease cases are caused by mutations in the genes encoding presenilin 1 (PS1) and presenilin 2 (PS2). Presenilin mutations have been hypothesised to cause Alzheimer disease either by altering amyloid precursor protein metabolism or by increasing the vulnerability of neurons to undergo death by apoptosis. We showed previously that PS1 exon 9 deletion (PS1 DeltaE9) and L250S mutations predispose SH-SY5Y neuroblastoma cells to high glucose stress-induced apoptosis and that the anti-apoptotic effect of insulin-like growth factor I (IGF-I) is compromised by these mutations. The present study investigates whether the susceptibility of PS1 mutation transfected SH-SY5Y cells to undergo apoptosis is likely due to a downregulation of Akt/protein kinase B (Akt), a key intermediate in the phosphatidylinositol 3 (PI3)-kinase arm of the IGF-I signaling pathway. We used two methods to determine the regulation of Akt in response to the pro-apoptotic stimuli of serum deprivation and high glucose stress, as well as treatment with IGF-I. We also looked at the phosphorylatiom state of GSK-3beta at Ser9. Using a kinase assay with immunoprecipitated Akt, we detected an increased Akt activity in PS1 L250S cells at 1 hr after the combination of 20 mM glucose plus 10 nM IGF-I, when compared to the other cell types. This effect, however, was transient in that no mutation related differences were seen at either 6- or 24-hr post-treatment. Immunoblotting for Phospho-Akt as a ratio of total Akt, as well as for GSK-3beta phosphorylated at Ser9 revealed no apparent between cell type and treatment differences. This data strongly indicates that PS1 wt and mutant cells show no major differences in the pattern of Akt regulation after exposure to the pro-apoptotic stimuli of either serum deprivation or high glucose stress, or treatment with IGF-I. It is suggested that another component of IGF-I signaling is likely disrupted in these cells to increase their vulnerability to undergo death by apoptosis.     

Dihydroactinidiolide regulates Nrf2/HO-1 expression and inhibits caspase-3/Bax pathway to protect SH-SY5Y human neuroblastoma cells from oxidative stress induced neuronal apoptosis

Alzheimer’s disease (AD) etiology has been studied for a long time and it is found to be multifaceted involving the accumulation of amyloid β and tau protein. Oxidative stress is an early event in AD associated neurodegeneration provoking neuronal death through mitochondrial dysfunction and activation of caspase-3. Therefore we tested the efficacy of dihydroactinidiolide (DHAc), a monoterpene lactone against the oxidative load involved in AD like pathological conditions induced by sodium dithionite, glutamate, amyloid β and colchicine in SH-SY5Y cells. Some of the indicators of neurotoxicity like acetylcholinesterase activity, intracellular reactive oxygen species (ROS), nitrite content, lipid peroxidation, protein carbonylation, nuclear and membrane damage were found to be significantly high in the toxicant treated cells when compared to the control cells while DHAc pretreatment significantly restored the toxicant induced neuronal damage signatures. Caspase-3 activity was found to be increased in the toxicant treated cells while DHAc significantly reduced it. Western blotting and RT-PCR revealed that DHAc significantly increased anti-apoptotic Bcl-2 expression and mRNA levels of Nrf2 and HO-1. Therefore DHAc was found to protect SH-SY5Y cells from neurotoxicant induced oxidative stress and apoptosis by regulating cellular antioxidant defenses and apoptosis related genes.     

Ca(2+)-independent caspase-3 but not Ca(2+)-dependent caspase-2 activation induced by oxidative stress leads to SH-SY5Y human neuroblastoma cell apoptosis

Continuous and long-lasting exposure to tert-butylhydroperoxide (t-BOOH) increased the number of apoptotic SH-SY5Y human neuroblastoma cells both in the presence and in the absence of the intracellular Ca(2+) ion chelator 1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA). In addition, t-BOOH exposure induced activation of CPP32, as demonstrated by poly-(ADP-ribose) polymerase (PARP) cleavage, and of ICH-1L caspases. Exposure to t-BOOH also induced a time-dependent release of cytochrome c. Interestingly, in the presence of BAPTA, CPP32 activation still occurred, whereas ICH-1L activation was blocked. Ac-DEVD-CHO, an inhibitor of CPP32 activity, prevented the appearance of apoptotic cells, whereas the inhibitor of ICH-1L activity Z-VDVAD-FMK did not. Collectively, these findings demonstrate that in SH-SY5Y neuroblastoma cells exposure to continuous and long-lasting oxidative stress induced activation of caspase-3 that was independent of intracellular Ca(2+) ion concentration ([Ca(2+)](i)) elevation but led to cell apoptosis. In contrast, caspase-2 activation was dependent on [Ca(2+)](i) increase but did not result in apoptosis.     

The anti-parkinson drug, rasagiline, prevents apoptotic DNA damage induced by peroxynitrite in human dopaminergic neuroblastoma SH-SY5Y cells

Summary. Clinical trials for treatment of Parkinson's disease suggest that (−)deprenyl (selegiline), an inhibitor of type B monoamine oxidase, may slow the disease progression. However, the mechanism underlying protection of nigral dopamine neurons by selegiline remains an enigma. Recently, rasagiline, (R)(+)-N-propargyl-1-aminoindan, was reported to be neuroprotective by in vivo and in vitro experiments, which is another selective irreversible inhibitor of type B monoamine oxidase and not metabolized into amphetamine-like derivatives as in the case of selegiline. In this paper, the mechanism of the neuroprotection was examined using human dopaminergic neuroblastoma SH-SY5Y cells against apoptosis induced by peroxynitrite generated from SIN-1. After treatment with SIN-1, the apoptotic DNA damage in the cells was quantified by a single cell gel electrophoresis (comet) assay and by staining with Hoechst 33342. Change in mitochondrial membrane potential, Δψm, was measured by use of a fluorescent indicator, JC-1. Rasagiline reduced apoptosis with much more potency than selegiline, and the protection required 20 min pre-incubation before SIN-1 treatment. The protection by rasagiline was proved to be due to stabilization of mitochondrial membrane potential against the collapse induced by SIN-1, whereas rasagiline did not scavenge peroxynitrite directly. The studies on structure-activity relationship showed that a propargylamine group and a hydrophobic group with an adequate intermediate space were required for the protection. These results suggest that rasagiline may protect declining neurons through its anti-apoptotic activity in neurodegenerative diseases. Received June 26, 2001; accepted November 5, 2001     

Ca(2+) stores and capacitative Ca(2+) entry in human neuroblastoma (SH-SY5Y) cells expressing a familial Alzheimer's disease presenilin-1 mutation

Presenilins are involved in the proteolytic production of Alzheimer's amyloid peptides, but are also known to regulate Ca(2+) homeostasis in various cells types. In the present study, we examined intracellular Ca(2+) stores coupled to muscarinic receptors and capacitative Ca(2+) entry (CCE) in the human neuroblastoma SH-SY5Y cell line, and how these were modulated by over-expression of either wild-type presenilin 1 (PS1wt) or a mutant form of presenilin 1 (PS1 deltaE9) which predisposes to early-onset Alzheimer's disease. Ca(2+) stores discharged by application of 100 microM muscarine (in Ca(2+)-free perfusate) in PS1wt and PS1 DeltaE9 cells were significantly larger than those in control cells, as determined using Fura-2 microfluorimetry. Subsequent CCE, observed in the absence of muscarine when Ca(2+) was re-admitted to the perfusate, was unaffected in PS1wt cells, but significantly suppressed in PS1 deltaE9 cells. However, when Ca(2+) stores were fully depleted with thapsigargin, CCE was similar in all three cell groups. Western blots confirmed increased levels of PS1 in the transfected cells, but also demonstrated that the proportion of intact PS1 in the PS1 deltaE9 cells was far greater than in the other two cell groups. This study represents the first report of modulation of both Ca(2+) stores and CCE in a human, neurone-derived cell line, and indicates a distinct effect of the PS1 mutation deltaE9 over wild-type PS1.     

Specific up-regulation of GADD153/CHOP in 1-methyl-4-phenyl-pyridinium-treated SH-SY5Y cells

Growth arrest DNA damage-inducible 153 (GADD153) expression was increased in 1-methyl-4-phenyl-pyridinium (MPP(+))-treated human SH-SY5Y neuroblastoma cells as determined by gene microarray analysis. GADD153 expression increased after 24 hr of MPP(+) (1 mM) exposure and preceded activation of caspase 3. Comparison of GADD153 expression among cultures treated with other toxins whose primary mode of action is either via mitochondrial impairment (rotenone) or via oxidative stress (6-hydroxydopamine or hydrogen peroxide) showed that GADD153 was uniquely up-regulated by MPP(+). Together these data suggest that a cellular mechanism distinct from mitochondrial impairment or oxidative stress contributes significantly to the up-regulation of GADD153 by MPP(+) and that GADD153 may function as an inducer of apoptosis following MPP(+) exposure. Published 2002 Wiley-Liss, Inc.     

Low levels of Bax inhibitor-1 gene expression increase tunicamycin-induced apoptosis in human neuroblastoma SY5Y cells

A human SH-SY5Y neuroblastoma cell line with a low level of Bax inhibitor-1 expression was established by lentivirus-mediated RNA interference and fluorescence-activated cell sorting.In control SH-SY5Y cells,tunicamycin treatment induced endoplasmic reticulum stress-mediated apoptosis;however,after Bax inhibitor-1 gene knockdown,cell survival rates were significantly decreased and the degree of apoptosis was significantly increased following tunicamycin treatment.In addition,chromatin condensation and apparent apoptotic phenomena,such as marginalization and cytoplasmic vesicles,were observed.Our findings indicate that Bax inhibitor-1 can delay apoptosis induced by endoplasmic reticulum stress.     

1-Methyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline (salsolinol) is toxic to dopaminergic neuroblastoma SH-SY5Y cells via impairment of cellular energy metabolism

The endogenous neurotoxin 1-methyl-6,7-dihydroxy-1,2,3, 4-tetrahydroisoquinoline (salsolinol), which is structurally similar to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), has been reported to inhibit mitochondrial complex I (NADH-Q reductase) activity as does the MPTP metabolite 1-methyl-4-phenylpyridinium ion (MPP(+)). However, the mechanism of salsolinol leading to neuronal cell death is still unknown. Thus, we correlated indices of cellular energy production and cell viability in human dopaminergic neuroblastoma SH-SY5Y cells after exposure to salsolinol and compared these results with data obtained with MPP(+). Both toxins induce time and dose-dependent decrease in cell survival with IC(50) values of 34 microM and 94 microM after 72 h for salsolinol and MPP(+), respectively. Furthermore, salsolinol and MPP(+) produce a decrease of intracellular net ATP content with IC(50) values of 62 microM and 66 microM after 48 h, respectively. In contrast to MPP(+), salsolinol does not induce an increase of intracellular net NADH content. In addition, enhancing glycolysis by adding D-glucose to the culture medium protects the cells against MPP(+) but not salsolinol induced cellular ATP depletion and cytotoxicity. These results suggest that cell death induced by salsolinol is due to impairment of cellular energy supply, caused in particular by inhibition of mitochondrial complex II (succinate-Q reductase), but not complex I.     

Enantio-specific induction of apoptosis by an endogenous neurotoxin, N-methyl(R)salsolinol, in dopaminergic SH-SY5Y cells: suppression of apoptosis by N-(2-heptyl)-N-methylpropargylamine

Summary. Endogenous N-methyl(R)salsolinol, which caused parkinsonism in rats by injection in the striatum, was found to induce apoptosis in dopaminergic neuroblastoma SH-SY5Y cells. After 12-h incubation with 500 μM N-methyl(R)salsolinol, almost all the cells died with apoptosis and necrotic cell death was negligible. N-Methyl(R)salsolinol was much more potent to induce apoptosis than the (S)-enantiomer. The mechanism of apoptosis was studied in relation to changes in mitochondrial membrane potential, ΔΨm, using a fluorescent indicator, JC-1. Red fluorescence of J-aggregates representing hyperpolarized ΔΨm was found to decrease significantly within 60 min after incubation with N-methyl(R)salsolinol, but not by the (S)-enantiomer at the same concentration. It suggests that mitochondria may recognize the stereo-chemical structure of N-methyl(R)salsolinol. Aliphatic propargylamines, (R)-N-(2-heptyl)-N-methylpropargyl-amine and (R)-N-(2-heptyl)propargylamine, were found to prevent ΔΨm loss and subsequent apoptosis induced by N-methyl(R)salsolinol. These results suggest that mitochondria play a key role in the induction of apoptosis by the neurotoxin and the prevention by aliphatic propargylamines. Received April 4, 2000; accepted July 17, 2000     

Overexpression of aldehyde dehydrogenase 1A1 reduces oxidation‐induced toxicity in SH‐SY5Y neuroblastoma cells

Oxidative stress leading to lipid peroxidation is a problem in neurodegenerative diseases, because the brain is rich in polyunsaturated fatty acids and low in endogenous antioxidants. One of the most toxic byproducts of lipid peroxidation, 4‐hydroxynonenal (HNE), is implicated in oxidative stress‐induced damage in neurodegenerative diseases such as Alzheimer's disease (AD), Parkinson's disease (PD), and amyotrophic lateral sclerosis (ALS). In this study, the human neuroblastoma cell line SH‐SY5Y was used to test the protective effects of increasing the detoxification of HNE by overexpressing the HNE‐detoxifying enzyme aldehyde dehydrogenase 1A1 (ALDH1). Overexpression of ALDH1 in the SH‐SY5Y cells acts to reduce production of protein–HNE adducts and activation of caspase‐3. Our data suggest that detoxification of HNE could be therapeutic in preventing some of the toxic disruptions of the brain's redox systems found in many neurodegenerative diseases. © 2009 Wiley‐Liss, Inc.     

Activation of caspase‐6 and cleavage of caspase‐6 substrates is an early event in NMDA receptor–mediated excitotoxicity

Excitotoxicity, due to overstimulation of N‐methyl D‐aspartate receptors (NMDARs), has a pivotal role in many neurological disorders. However, NMDAR antagonists often cause side effects, and identifying more druggable therapeutic targets for NMDAR excitotoxicity is an important goal. Activation of caspases is a downstream effect of excitotoxicity that may be critically involved in NMDAR‐mediated cell death. Caspase‐6 (casp6) in particular has been shown to play a key role in the pathogenesis of stroke, Huntington disease, and Alzheimer disease. Using N‐methyl D‐aspartate (NMDA)‐induced excitotoxic injuries of primary rat neurons, we demonstrate that there is an early increase in caspase profiles after an excitotoxic event at the level of mRNA, protein, and activity. Casp6 is elevated and activated first, followed by caspase‐8 and caspase‐3. Similarly, known casp6 substrates huntingtin, as well as novel casp6 substrates serine/threonine kinase 3 and death domain‐associated protein, are cleaved in similar temporal patterns post NMDA. On the basis of these data, we propose that casp6 may be an initiator caspase in apoptotic cascades leading to neuronal death after an excitotoxic event and suggest casp6 as a potential therapeutic target for neurological disorders where NMDAR‐mediated excitotoxicity has been shown to play a role.     

Selective nitration of mitochondrial complex I by peroxynitrite: involvement in mitochondria dysfunction and cell death of dopaminergic SH-SY5Y cells

Summary. 3-Nitrotyrosine (3-NT) is a specific marker of protein nitration by peroxynitrite (ONOO⁻) produced from nitric oxide and superoxide. Increase in 3-NT containing protein (3-NT protein) was reported in brains from patients with some neurodegenerative disorders and aging. In this paper, intracellular localization of 3-NT protein was examined in dopaminergic SH-SY5Y cells using the selective antibody against protein-bound 3-NT. 3-NT protein was detected in plasma membrane/nucleus and mitochondria fractions, and interestingly in polypeptide composition of mitochondrial complex I. ONOO⁻-generating SIN-1 induced apoptotic cell death with concomitant increase in 3-NT protein and reduction in mitochondrial ATP synthesis. In addition, an inhibitor of proteasomes, carbobenzoxy-L-isoleucyl-γ-t-butyl-L-glutamyl-L-alanyl-L-leucinal, enhanced the effects of ONOO⁻. These results suggest that ONOO⁻ may induce mitochondrial dysfunction and cell death in neurons through nitration of mitochondrial complex I subunits. Received March 12, 2001; accepted September 26, 2001     

N-Propargylamine protects SH-SY5Y cells from apoptosis induced by an endogenous neurotoxin, N-methyl(R)salsolinol, through stabilization of mitochondrial membrane and induction of anti-apoptotic Bcl-2

Summary. Propargylamine derivatives, rasagiline and (–)deprenyl, are anti-Parkinson agents and protect neurons from cell death as shown by in vivo and in vitro experiments. The studies on the chemical structure-activity relationship proved that the propargyl moiety is essentially required for the neuroprotective function. In this paper, neuroprotective activity of free N-propargylamine was studied using SH-SY5Y cells expressing only type A monoamine oxidase (MAO) against apoptosis induced by an endogenous dopaminergic neurotoxin, N-methyl(R)salsolinol. N-Propargylamine prevented apoptosis, whereas N-methylpropargylamine and propiolaldehyde did not. N-Propargylamine stabilized mitochondrial membrane potential and induced anti-apoptotic Bcl-2 at 1 μM–10 nM. N-Propargylamine inhibited MAO-A in competition to substrate with the apparent K_i value of 28 μM, which was significantly higher than the concentration required for neuroprotection. It indicates that MAO inhibition is not prerequisite for the protective function of N-propargylamine. The anti-apoptotic function of N-propargylamine is discussed in terms of neuroprotection by propargylamines in neurodegenerative diseases, including Parkinson’s disease.     

Morphine dependence in human neuroblastoma SH-SY5Y cells is associated with adaptive changes in both the quantity and functional interaction of PGE1 receptors and stimulatory G proteins

Chronic exposure of all-trans-retinoic acid-differentiated SH-SY5Y cells to morphine (10 μM; 2 days) results in sensitization of adenylate cyclase as characterized by a significant increase in both PGE1 receptor-mediated as well as receptor-independent (NaF, 10 mM; forskolin, 100 μM) stimulation of effector activity. To investigate the underlying biochemical alterations, chronic opioid regulation of each of the components comprising the stimulatory PGE, receptor system was examined. On receptor level, chronic morphine treatment was found to reduce PGE₁ receptor number (B_max) by approximately 40%, whereas their affinity slightly increased. Binding experiments performed in the presence of GTPγS (100 μM) further indicate that the decrease in PGE1 receptor density is associated with a loss of functionally G protein-coupled receptors. On post-receptor level, chronic morphine treatment substantially increased the abundance and functional activity of stimulatory G proteins, as assessed by cholera toxin-catalyzed ADP-ribosylation of G_sα and S49 cyc⁻ reconstitution assays. No changes were found on the level of adenylate cyclase. Evaluation of the functional interaction between PGE₁ receptors and G_s in situ by application of a C-terminal anti-G_sα antibody revealed a more intense coupling efficiency between these two entities, since a significant higher amount of antibody (2.3-fold) was required in morphine dependent cell membranes to half-maximally attenuate PGE₁ receptor-stimulated adenylate cyclase activity. In addition, limitation of the amount of functionally available G_sα within the PGE₁ receptor/adenylate cyclase signal transduction cascade abolished the generation of a supersensitive adenylate cyclase response during the state of naloxone (100 μM)-precipitated withdrawal. These data demonstrate that in human neuroblastoma SH-SY5Y cells chronic morphine-induced sensitization of adenylate cyclase is associated with distinct quantitative and qualitative adaptations within the stimulatory adenylate cyclase-coupled PGE₁ receptor system. Thus, alterations in the functional activity of stimulatory receptor systems are suggested to contribute to the cellular mechanisms underlying opioid dependence.