Low arsenite concentrations induce cell proliferation via activation of VEGF signaling in human neuroblastoma SH-SY5Y cells

Arsenic widely contaminates the environment, especially in drinking water. Although it is a known carcinogen in humans, its carcinogenic mechanism has not yet been clarified. Here, we demonstrated that a low concentration of arsenite treatment induced proliferation of human neuroblastoma SH-SY5Y cells as indicated by increases in cell viability and BrdU incorporation. Additionally, arsenite increased VEGF expression and secretion. Inhibition of VEGF-induced signaling by SU4312, the inhibitor of VEGF receptor 2 kinase, and by treatment with anti-VEGF antibody blocked arsenite-induced increases in cell proliferation. Moreover, arsenite caused activation of ERK, a key signaling molecule involved in cell proliferation, and this activation was attenuated by SU4312, suggesting that ERK activation contributes to VEGF-mediated cell proliferation induced by arsenite. Collectively, the present study reveals that a mechanism underlying arsenic-induced cell proliferation may be through induction and activation of VEGF signaling, and this may subsequently contribute to tumor formation.     

Inhibition of paraquat-induced autophagy accelerates the apoptotic cell death in neuroblastoma SH-SY5Y cells.

Autophagy is a degradative mechanism involved in the recycling and turnover of cytoplasmic constituents from eukaryotic cells. This phenomenon of autophagy has been observed in neurons from patients with Parkinson's disease (PD), suggesting a functional role for autophagy in neuronal cell death. On the other hand, it has been demonstrated that exposure to pesticides can be a risk factor in the incidence of PD. In this sense, paraquat (PQ) (1,1'-dimethyl-4,4'-bipyridinium dichloride), a widely used herbicide that is structurally similar to the known dopaminergic neurotoxicant MPP(+) (1-methyl-4-phenyl-pyridine), has been suggested as a potential etiologic factor for the development of PD. The current study shows, for the first time, that low concentrations of PQ induce several characteristics of autophagy in human neuroblastoma SH-SY5Y cells. In this way, PQ induced the accumulation of autophagic vacuoles (AVs) in the cytoplasm and the recruitment of a LC3-GFP fusion protein to AVs. Furthermore, the cells treated with PQ showed an increase of the long-lived protein degradation which is blocked in the presence of the autophagy inhibitor 3-methyladenine and regulated by the mammalian target of rapamycin (mTOR) signaling. Finally, the cells succumbed to cell death with hallmarks of apoptosis such as phosphatidylserine exposure, caspase activation, and chromatin condensation. While caspase inhibition retarded cell death, autophagy inhibition accelerated the apoptotic cell death induced by PQ. Altogether, these findings show the relationship between autophagy and apoptotic cell death in human neuroblastoma cells treated with PQ.     

Diethylene glycol and its metabolites induce cell death in SH-SY5Y neuronal cells in vitro

Diethylene glycol (DEG) intoxication results in metabolic acidosis, renal and hepatic dysfunction, and late-stage neurotoxicity. Though the renal and hepatic toxicity of DEG and its metabolites 2-hydroxyethoxyacetic acid (2-HEAA) and diglycolic acid (DGA) have been well characterized, the resultant neurotoxicity has not. SH-SY5Y neuroblastoma cells were incubated with all 3 compounds at increasing concentrations for 24, 48, or 120 h. At all 3 time points, 50 mmol/L DGA and 100 mmol/L DEG showed significant Annexin V and propidium iodide (PI) staining with additional concentrations showing similar staining patterns at 24 h (100 mmol/L DGA) and 48 h (50 mmol/L DEG, 100 mmol/L DGA). Only the 200 mmol/L 2-HEAA concentration induced SH-SY5Y cell death. Interestingly at 24 and 48 h, 100 mmol/L DEG induced significant increases in apoptotic cell death markers, which progressed to necrosis at 120 h. Similar to DEG, 50 mmol/L DGA induced significant increases in SH-SY5Y cell apoptosis and necrosis markers at both 24 and 48 h. As expected, high DGA concentrations (100 mmol/L) at 120 h induced significant SH-SY5Y cell necrosis with no apoptosis detected. However, at 120 h lower DGA concentrations (20 mmol/L) significantly increased oligonucleosome formation alone and in combination with 2-HEAA or DEG. Taken together, these results indicate that DGA and DEG at threshold concentrations induce neurotoxicity in SH-SY5Y cells.     

Acrylonitrile induced apoptosis via oxidative stress in neuroblastoma SH-SY5Y cell

Acrylonitrile (ACN) is a chemical that is widely used in the production of plastics, acrylic fibers, synthetic rubbers and resins. It has been reported that ACN can cause oxidative stress, a condition which is well recognized as an apoptotic initiator; however, information regarding ACN-induced apoptosis is limited. This present study investigated whether ACN induces apoptosis in human neuroblastoma SH-SY5Y cells, and whether its apoptotic induction involves oxidative stress. The results showed that ACN caused activation of caspase-3, a key enzyme involved in apoptosis, in a dose- and time-dependent manner. Detection of sub-G1 apoptotic cell death and apoptotic nuclear condensation revealed that ACN caused an increase in the number of apoptotic cells indicating ACN induces apoptosis in SH-SY5Y cells. ACN dose- and time-dependently increased the level of proapoptotic protein, Bax. Pretreatment with N-acetylcysteine (NAC), an antioxidant, attenuated caspase-3 activation by ACN, as evidenced by a reduction in proteolysis of PARP, a known caspase-3 substrate, as well as in the number of sub-G1 apoptotic cells. Moreover, induction of Bax by ACN was abolished by NAC. Taken together, the results indicate that ACN induces apoptosis in SH-SY5Y cells via a mechanism involving generation of oxidative stress-mediated Bax induction.     

Suppression by phthalates of the calcium signaling of human nicotinic acetylcholine receptors in human neuroblastoma SH-SY5Y cells

Phthalates are widely used in industry and cause public concern since they have genomic estrogenic-like effects via estrogen receptors. We previously found that some phthalates have nongenomic effects, exerting inhibitory effects on the functional activities of nicotinic acetylcholine receptors (nAChRs) in bovine chromaffin cells. In this study, we investigated the effects of eight phthalates on the calcium signaling of human nAChR by using human neuroblastoma SH-SY5Y cells. All eight phthalates, with different potency, have inhibitory roles on the calcium signaling coupled with human nAChR, but not muscarinic acetylcholine receptors (mAChRs). For inhibition of human nAChR, the strongest to weakest potencies were observed as di-n-pentyl phthalate (DPP) → butyl benzyl phthalate (BBP) → di-n-butyl phthalate (DBP) → dicyclohexyl phthalate (DCHP) → di-n-hexyl phthalate (DHP) → di-(2-ethyl hexyl) phthalate (DEHP) → di-n-propyl phthalate (DPrP) → diethyl phthalate (DEP). The potencies of phthalates were associated with their structures such that the most effective ones had dialkyl group carbon numbers of C4 or C5, with shorter or longer numbers resulting in decreased potency. At as low as 0.1 μM, DPP, DBP, BBP, DCHP and DHP significantly inhibited the calcium signaling of human nAChR. The IC₅₀ of phthalates on human nAChR, ranging from 0.32 to 7.96 μM, were 10–50 lower than those for bovine nAChR. We suggest that some phthalates effectively inhibit the calcium signaling of human nAChR, and these nongenomic effects are cause for concern.     

Ursodeoxycholic acid suppresses mitochondria-dependent programmed cell death induced by sodium nitroprusside in SH-SY5Y cells

Although ursodeoxycholic acid (UDCA) and its highly water-soluble formula (Yoo's solution; YS) have been shown to prevent neuronal damage, the effects of UDCA or YS against Parkinson's disease (PD)-related dopaminergic cell death has not been studied. This study investigated the protective effects of UDCA and YS on sodium nitroprusside (SNP)-induced cytotoxicity in human dopaminergic SH-SY5Y cells. Both UDCA (50-200 μM) and YS (100-200 μM) dose-dependently prevented SNP (1mM)-induced cell death. Results showed that both UDCA and YS effectively attenuated the production of total reactive oxygen species (ROS), peroxynitrite (ONOO(-)) and nitric oxide (NO), and markedly inhibited the mitochondrial membrane potential (MMP) loss and intracellular reduced glutathione (GSH) depletion. SNP-induced programmed cell death events, such as nuclear fragmentation, caspase-3/7 and -9 activation, Bcl-2/Bax ratio decrease, and cytochrome c release, were significantly attenuated by both UDCA and YS. Furthermore, selective inhibitor of phosphatidylinositiol-3-kinase (PI3K), LY294002, and Akt/PKB inhibitor, triciribine, reversed the preventive effects of UDCA on the SNP-induced cytotoxicity and Bax translocation. These results suggest that UDCA can protect SH-SY5Y cells under programmed cell death process by regulating PI3K-Akt/PKB pathways.     

氧化应激在鱼藤素致SH-SY5Y细胞神经毒性中的作用

目的研究氧化应激与鱼藤素致神经毒性的相关性,为后续鱼藤素的结构改造和联合用药提供机制基础。方法将鱼藤素(1.56~100μmol·L-1)与SH-SY5Y细胞共孵育培养24~72 h,采用CCK-8法测定细胞存活率;比色法测定乳酸脱氢酶(lactate dehydrogenase,LDH)漏出量、丙二醛(malondialdehyde,MDA)含量、谷胱甘肽过氧化物酶(glutathione peroxidase,GPx)和超氧化物歧化酶(superoxide dismutase,SOD)的活力;流式细胞术检测活性氧(reactive oxygen species,ROS)含量;免疫印迹法检测细胞中MEK、EGF、RAS、CREB蛋白的表达情况。结果鱼藤素对SH-SY5Y细胞增殖有抑制作用,且呈浓度和时间依赖性(P<0.05)。鱼藤素损伤细胞后,LDH漏出量、MDA和ROS含量明显增加,GPx和SOD的活力下降(P<0.05)。同时MAPK/ERK信号通路中MEK、EGF、RAS、CREB蛋白水平出现不同程度的下调。结论鱼藤素致SH-SY5Y神经细胞的损伤与氧化应激密切相关,MAPK/ERK信号通路可能在其中起介导作用。     

Organophosphorus compound-induced apoptosis in SH-SY5Y human neuroblastoma cells

Organophosphorus (OP) compounds have been shown to be cytotoxic to SH-SY5Y human neuroblastoma cell cultures. The mechanisms involved in OP compound-induced cell death (apoptosis versus necrosis) were assessed morphologically by looking at nuclear fragmentation and budding using the fluorescent stain Hoechst 33342 (10 microgram/ml). Hoechst staining revealed significant paraoxon (1 mM), parathion (1 mM), phenyl saligenin phosphate (PSP, 10 and 100 microM), tri-ortho-tolyl phosphate (TOTP, 100 microM and 1 mM), and triphenyl phosphite (TPPi, 1 mM) induced time-dependent increases in traditional apoptosis (p < 0.05). In many cells, PSP and TOTP (1 mM) also induced nuclear condensation with little fragmentation or budding. Pretreatment with cyclosporin A (500 nM, 30 h) decreased apoptosis following 1 mM parathion and TOTP exposures. Apoptotic nuclear changes were verified by DNA gel electrophoresis. Activation of caspase-3, a cysteine aspartate protease, was also monitored. OP compounds induced significant time-dependent increases in caspase-3 activation following paraoxon (1 mM), parathion (100 microM, 1 mM), PSP (10 microM, 100 microM, 1 mM), TOTP (100 microM, 1 mM), and TPPi (1 mM) exposure (p < 0.05). Pretreatment with cyclosporin A (500 nM, 30 h) significantly decreased caspase-3 activation during extended incubations with paraoxon, parathion, and TPPi (p < 0.05). In addition, pretreatment with the caspase-3 inhibitor Ac-DEVD-CHO and the caspase-8 inhibitor Ac-IETD-CHO (25 microM, 8 h) significantly decreased caspase-3 activation following exposure to 1 mM PSP and parathion (p < 0.05). Pretreatment with the serine protease inhibitor phenylmethyl sulfonyl fluoride (PMSF; 1 mM, 8 h) also significantly decreased caspase activation following 1 mM PSP and TOTP exposures (p < 0.05). Alteration of OP compound-induced nuclear fragmentation or caspase-3 activation by pretreatment with cyclosporin A, Ac-IETD-CHO, or PMSF suggested that OP compound-induced cytotoxicity may be modulated through multiple sites, including mitochondrial permeability pores, receptor-mediated caspase pathways, or serine proteases.     

Diphenyl diselenide induces apoptotic cell death and modulates ERK1/2 phosphorylation in human neuroblastoma SH-SY5Y cells

Diphenyl diselenide (PhSe)₂ is a synthetic organoselenium compound displaying glutathione peroxidase-like activity. Protective and antioxidant potential of (PhSe)₂ have been extensively investigated in in vivo and in vitro studies. In spite of this, there is a lack of studies addressed to the investigation of potential cytotoxic effect and signaling pathways modulated by this compound. Herein, we aimed to analyze the effects of 24-h treatment with (PhSe)₂ on cell viability and a possible modulation of signaling pathways in human neuroblastoma cell line SH-SY5Y. For this purpose, cells were incubated with (PhSe)₂ (0.3–30 μM) for 24 h and cell viability, apoptotic cell death and modulation of MAPKs (ERK1/2 and p38^MAPK), and PKC substrates phosphorylation was determined. (PhSe)₂ treatment significantly decreased cell viability and increased the number of apoptotic cells with induction of PARP cleavage. An increase in ERK1/2 phosphorylation was observed at (PhSe)₂ 3 μM. In contrast, higher concentrations of the chalcogenide inhibited ERK1/2, p38^MAPK and PKC substrate phosphorylation. Pre-treatment with ERK1/2 inhibitor, U0126, increased cell susceptibility to (PhSe)₂. Together, these data indicate a cytotoxic potential of (PhSe)₂ in a neuronal cell line, which appears to be mediated by the ERK1/2 pathway.     

Rotenone-induced apoptosis is mediated by p38 and JNK MAP kinases in human dopaminergic SH-SY5Y cells.

Rotenone is a naturally derived pesticide that has recently been shown to evoke the behavioral and pathological symptoms of Parkinson's disease in animal models. Though rotenone is known to be an inhibitor of the mitochondrial complex I electron transport chain, little is known about downstream pathways leading to its toxicity. We used human dopaminergic SH-SY5Y cells to study mechanisms of rotenone-induced neuronal cell death. Our results suggest that rotenone, at nanomolar concentrations, induces apoptosis in SH-SY5Y cells that is caspase-dependent. Furthermore, rotenone treatment induces phosphorylation of c-Jun, the c-Jun N-terminal protein kinase (JNK), and the p38 mitogen activated protein (MAP) kinase, indicative of activation of the p38 and JNK pathways. Importantly, expression of dominant interfering constructs of the JNK or p38 pathways attenuated rotenone-induced apoptosis. These data suggest that rotenone induces apoptosis in the dopaminergic SH-SY5Y cells that requires activation of the JNK and p38 MAP kinases and caspases. These studies provide insights concerning the molecular mechanisms of rotenone-induced apoptosis in neuronal cells.     

Expression of CD38 in human neuroblastoma SH-SY5Y cells

Human CD38 antigen is a 42-45 kDa type II transmembrane glycoprotein with a short N-terminal cytoplasmic domain and a long C-terminal extracellular region. It is widely expressed in different cell types including thymocytes, activated T cells, and terminally differentiated B cells (plasma cells) and it is involved in cellular proliferation and adhesion. CD38 acts as an ectocyclase that converts NAD+ to the Ca2+ -releasing second messenger cyclic ADP-ribose (cADPR). It has been also demonstrated that increased extracellular levels of NAD+ and cADPR are involved in inflammatory diseases and in cellular damage, such as ischemia. In the present study, we have characterized the expression of CD38 in human neuroblastoma SH-SY5Y cell line. All-trans-retinoic acid (ATRA) treatment was used to induce cell differentiation. Our results indicate that: a) even if SH-SY5Y cells have a negative phenotype express CD38 at nuclear level, ATRA treatment does not influence this pattern; b) CD38 localizing to the nucleus may co-localize with p80-coilin positive nuclear-coiled bodies; c) purified nuclei, by Western blot determinations using anti-CD38 antibodies, display a band with a molecular mass of approximately 42 kDa; d) SH-SY5Y cells show nuclear ADP-ribosyl cyclase due to CD38 activity; e) the basal level of CD38 mRNA shows a time-dependent increase after treatment with ATRA. These results suggest that the presence of constitutive fully functional CD38 in the SH-SY5Y nucleus has some important implications for intracellular generation of cADP-ribose and subsequent nucleoplasmic calcium release.     

Tribromophenol induces the differentiation of SH-SY5Y human neuroblastoma cells in vitro

Tribromophenol is a pesticide with fungicide activity, presently used as a replacement of pentachlorophenol as a wood preservative, and as a flame retardant in electronic and electrotechnical devices. Retinoic acid differentiated and non-differentiated SH-SY5Y human neuroblastoma cell cultures were exposed to a range of concentrations of tribromophenol for 24, 48 and 72 h and the effects evaluated at morphological, basal cytotoxicity and biochemical levels. Neuroblastoma cell number, evaluated by quantification of total protein content, was increasingly inhibited in accordance with the concentration of tribromophenol and the exposure time period. According to the mean effective concentrations, differentiated cultures were nearly three times more sensitive than naive cells. Lysosomal function evaluated by the neutral red uptake was stimulated, particularly in non-differentiated cells. MTS metabolization was stimulated by all the treatments, with more potency at 24 h for differentiated cells. Acetylcholinesterase activity increased with the time of exposure in non-differentiated cells, while in differentiated cells the activity was doubled at 24 h. Morphological alterations were evident from 12.5 μ , showing hydropic degeneration and reduction in cell number, and from that concentration, piknosis and apoptotic bodies were observed. In conclusion, the main effects detected for tribromophenol were the induction of neuroblastoma cell differentiation, as expressed by the inhibition of cell growth and the increase in acetylcholinesterase activity with a critical cell concentration of 0.1 μ . Apoptosis was observed at high concentrations. The induction of cell differentiation and the special sensitivity of differentiated cells can explain some mechanisms involved in the embryotoxic and foetotoxic potential of tribromophenol.     

Morphine prevents peroxynitrite-induced death of human neuroblastoma SH-SY5Y cells through a direct scavenging action.

N-ethyl-2-(1-ethyl-2-hydroxy-2-nitrosohydrazino)-ethanamine (NOC12), a nitric oxide donor, 3-morpholinosydnonimine (SIN-1), a generator of peroxynitrite (ONOO-), and peroxynitrite induced cell death accompanied by DNA fragmentation in human neuroblastoma SH-SY5Y cell cultures. Morphine prevented the cell death induced by SIN-1 or peroxynitrite, but not that induced by NOC12. The protective effect of morphine was concentration-dependent (10-100 microM), but was not antagonized by naloxone. The selective ligands for opioid receptor subtypes, [D-Ala2, N-Me-Phe4, Gly-ol5]enkephalin (DAMGO, micro-opioid receptor agonist), [D-Pen2,5]enkephalin (DPDPE, delta-opioid receptor agonist) and trans-(+/-)-3,4-dichloro-N-methyl-N-(2-[1-pyrrolidinyl]-cyclohexyl)benze neacetamide (U-50488, kappa-opioid receptor agonist) even at the concentration of 100 microM did not prevent the cell death induced by SIN-1. From measurement of the absorbance spectrum of peroxynitrite, the decomposition of peroxynitrite in 0.25 M potassium phosphate buffer (pH 7.4) was very rapid and complete within seconds. However, the absorbance was very stable in the presence of morphine. In addition, morphine inhibited peroxynitrite-induced nitration of tyrosine in a concentration-dependent manner. These results indicate that morphine rapidly reacts with peroxynitrite. The present study showed that morphine prevented peroxynitrite-induced cell death through its direct scavenging action, suggesting that morphine can protect cells against damage caused by peroxynitrite.     

Oxidative stress-elicited autophagosome accumulation contributes to human neuroblastoma SH-SY5Y cell death induced by PBDE-47

Polybrominated diphenyl ethers, a ubiquitous persistent organic pollutant used as brominated flame retardants, is known to damage nervous system, however the underlying mechanism is still elusive. In this study, we used human neuroblastoma SH-SY5Y cells to explore the effects of PBDE-47 on autophagy and investigate the role of autophagy in PBDE-47-induced cell death. Results showed PBDE-47 could increase autophagic level (performation of cell ultrastructure with double membrane formation, MDC-positive cells raised, autophagy-related proteins LC3-II, Beclin1 and P62 increased) after cells exposed to PBDE-47. Then cells were exposed to PBDE-47 (1, 5, 10 μmol/L) respectively for 1, 3, 6, 9, 12, 18, 24 h, and the results showed that PBDE-47 increased the levels of LC3-II, Beclin1 and P62 in 5, 10 μmol/L (9, 12, 18, 24 h) PBDE-47 exposed groups. Furthermore, ROS scavenger N-Acetyl-l-cysteine (NAC), autophagic inhibitor 3-methyladenine (3-MA) and 5 μmol/L PBDE-47 treated for 9 h and 24 h were chosen for the follow-up research. Moreover, 3-MA significantly improved cell viability when cells exposed to 5 and 10 μmol/L PBDE-47, indicating that PBDE-47-induced autophagic cell death. Importantly, NAC could decrease PBDE-47-induced LC3-II, Beclin1 and P62 expression. We concluded that autophagosome accumulation mediated by oxidative stress may contribute to SH-SY5Y cell death induced by PBDE-47.     

Enhanced oxidative stress and aberrant mitochondrial biogenesis in human neuroblastoma SH-SY5Y cells during methamphetamine induced apoptosis

Methamphetamine (METH) is an abused drug that may cause psychiatric and neurotoxic damage, including degeneration of monoaminergic terminals and apoptosis of non-monoaminergic cells in the brain. The cellular and molecular mechanisms underlying these METH-induced neurotoxic effects remain to be clarified. In this study, we performed a time course assessment to investigate the effects of METH on intracellular oxidative stress and mitochondrial alterations in a human dopaminergic neuroblastoma SH-SY5Y cell line. We characterized that METH induces a temporal sequence of several cellular events including, firstly, a decrease in mitochondrial membrane potential within 1 h of the METH treatment, secondly, an extensive decline in mitochondrial membrane potential and increase in the level of reactive oxygen species (ROS) after 8 h of the treatment, thirdly, an increase in mitochondrial mass after the drug treatment for 24 h, and finally, a decrease in mtDNA copy number and mitochondrial proteins per mitochondrion as well as the occurrence of apoptosis after 48 h of the treatment. Importantly, vitamin E attenuated the METH-induced increases in intracellular ROS level and mitochondrial mass, and prevented METH-induced cell death. Our observations suggest that enhanced oxidative stress and aberrant mitochondrial biogenesis may play critical roles in METH-induced neurotoxic effects.     

Analysis of human Nav1.8 expressed in SH-SY5Y neuroblastoma cells

The tetrodotoxin-resistant voltage-gated sodium channel alpha-subunit Nav1.8 is expressed in nociceptors and has been implicated in chronic pain. Difficulties of heterologous expression have so far precluded analysis of the pharmacological properties of human Nav1.8. To address this we have introduced human Nav1.8 in neuroblastoma SH-SY5Y cells. Voltage-clamp analysis showed that human Nav1.8 generated an inward tetrodotoxin-resistant sodium current with an activating threshold around -50 mV, half maximal activation at -11+/-3 mV and a reversal potential of 67+/-4 mV. These properties closely match those of the endogenous rat tetrodotoxin-resistant sodium current in dorsal root ganglia suggesting that the expressed human channel is in a near physiological conformation. Human Nav1.8 was resistant to tetrodotoxin and activated by the pyrethroid toxin deltamethrin. Both voltage-activated and deltamethrin-activated human Nav1.8 were inhibited by the sodium channel blockers BIII 890 CL, NW-1029, and mexiletine. Inhibition of Nav1.8 by these compounds may underlie their known analgesic effects in animal models.     

Low-dose methylmercury-induced oxidative stress, cytotoxicity, and tau-hyperphosphorylation in human neuroblastoma (SH-SY5Y) cells

Acute neurotoxic effects of high-dose methylmercury (MeHg) in humans have been well documented in the scientific literature. However, low-dose effects are less well described. This study was designed to evaluate the effects of low-dose MeHg (<100 nM) on human brain cells in a tissue culture model. Neuroblastoma (NB) cells (SH-SY5Y) were used in the cell culture model to study low-dose effects of MeHg on cell growth, cell survival, reactive oxygen species (ROS), and the phosphorylation of tau protein, as a measure of potential markers of cellular events associated with tauopathies. When cells were incubated in culture with MeHg (50 and 100 nM), there were significant decreases in cell viability as well as significant increase in ROS generation as determined by fluorescent dye analysis (H(2)DCFDA). Furthermore, a concomitant decrease in glutathione levels to 25% of control was observed at both 50 and 100 nM MeHg. In addition, the level of phosphorylated tau was significantly increased after treatment at both 50 and 100 nM MeHg, compared with controls. Pretreatment of NB cells with the antioxidant, N-acetylcysteine (1.25 mM) and the calpain inhibitor, MDL-28170 (10 μM), significantly attenuated the effects of MeHg (50 and 100 nM) on cell viability as well as on tau phosphorylation. These results indicate that low-dose MeHg toxicity may be related to an induction of tau phosphorylation through an oxidative stress-dependent mechanism and that blockade of this pathway may attenuate the toxic effects of MeHg.     

Adiponectin protects human neuroblastoma SH-SY5Y cells against acetaldehyde-induced cytotoxicity

Acetaldehyde, an inhibitor of mitochondrial function, has been widely used as a neurotoxin because it elicits a severe Parkinson's disease-like syndrome with elevation of the intracellular reactive oxygen species (ROS) level and apoptosis. Adiponectin, secreted from adipose tissue, mediates systemic insulin sensitivity with liver and muscle as target organs. In this study, we investigated the protective effects of adiponectin on acetaldehyde-induced apoptosis in human neuroblastoma SH-SY5Y cells and attempted to examine its mechanism. Acetaldehyde-induced apoptosis was moderately reversed by adiponectin treatment. Our results suggest that the protective effects of adiponectin on acetaldehyde-induced apoptosis may be ascribed to ability to induce the expression of anti-oxidant enzymes and to regulate Bcl-2 and Bax expression. These data indicate that adiponectin may provide a useful therapeutic strategy for the prevention of progressive neurodegenerative disease such as Parkinson's disease.