Near-Road Exposure and Impact of Air Pollution on Allergic Diseases in Elementary School Children: A Cross-Sectional Study

PURPOSE: The study aims to classify schools based on traffic pollutants and their complex sources, to assess the environment, to determine the state of allergic diseases among students using the International Study of Asthma and Allergies in children (ISAAC) questionnaire, and to assess their connection to air pollutants. MATERIALS AND METHODS: A total of seven schools were divided into three categories according to the characteristics of their surrounding environments: three schools in traffic-related zones, two schools in complex source zones I (urban), and two schools in complex source zones II (industrial complex). ISAAC questionnaires were administered and the 4404 completed questionnaires were analyzed. RESULTS: The frequency of asthma treatment during the past 12 months showed a significant increase (p<0.05) with exposure to NO2 [1.67, 95% confidence intervals (CIs) 1.03-2.71] in the complex source zones. The frequency of allergic rhinitis treatment during the past 12 months increased significantly with exposure to Black Carbon (1.60, 95% CIs 1.36-1.90) (p<0.001), SO2 (1.09, 95% CIs 1.01-1.17) (p<0.05), NO2 (1.18, 95% CIs 1.07-1.30) (p<0.01) for all subjects. CONCLUSION: In terms of supporting children's health, care, and prevention related to major spaces for children, such as school zones, spaces used in coming to and leaving school, playgrounds, and classrooms are essential to ensuring not only the safety of children from traffic accidents but also their protection from local traffic pollutants and various hazardous environmental factors.

Inhibitory Effect of Rotundarpene on Parkinsonian Neurotoxin 1-Methyl-4-Phenylpyridinium-Induced Apoptotic Cell Death

BACKGROUND: The extract and hemiterpene glycosides of Ilex Rotunda Thunb exert antioxidant and anti-inflammatory effects. The effect of rotundarpene on apoptosis in neuronal cells caused by the 1-methyl-4-phenylpyridinium (MPP⁺) has not been reported previously. METHODS: Using differentiated PC12 cells and human neuroblastoma SH-SY5Y cells, we investigated the effect of rotundarpene on MPP⁺-caused apoptosis in relation to the cell death process. RESULTS: MPP⁺-induced cell death was identified using the MTT and neutral red uptake tests. Apoptosis was induced by eliciting decreases in the cytosolic levels of Bid and Bcl-2 proteins, increases in the cytosolic levels of Bax and p53, disruption of the mitochondrial transmembrane potential, and the release of cytochrome c and the activation of caspase-8, -9, and -3 in differentiated PC12 cells and SH-SY5Y cells. Treatment with rotundarpene reduced the MPP⁺-induced changes in the levels of apoptosis-regulated proteins, formation of reactive oxygen species, depletion and oxidation of glutathione, and cell death in both PC12 and SH-SY5Y cells. CONCLUSIONS: Rotundarpene may reduce MPP⁺-induced apoptosis in neuronal cells by suppressing the activation of the mitochondria-mediated pathway and the caspase-8 and Bid pathways. Rotundarpene appears to act by inhibiting the production of reactive oxygen species and by the depletion and oxidation of glutathione.

Inhibitory Effect of Apocynin on Proteasome Inhibition-Induced Apoptosis in Differentiated PC12 Cells

BACKGROUND: The dysfunction of the proteasome system has been implicated in neuronal degeneration. Apocynin, a specific inhibitor for nicotinamide adenine dinucleotide phosphate oxidase, has anti-inflammatory and anti-oxidant effects. However, the effect of apocynin on the neuronal cell death induced by proteasome inhibition has not been studied. METHODS: Using differentiated PC12 cells, in the respect of cell death process the suppressive effect of apocynin on the proteasome inhibition-mediated apoptosis was examined. RESULTS: The proteasome inhibitors MG132 and MG115 induced a decrease in Bid and Bcl-2 protein levels, an increase in Bax and p53 levels, mitochondrial depolarization, efflux of cytochrome c into cytosol and increase in caspases (-8, -9 and -3) activities. Treatment with apocynin attenuated the proteasome inhibitor-induced changes in the apoptosis-related protein levels, formation of reactive oxygen species, glutathione (GSH) depletion and cell death. CONCLUSIONS: Apocynin may attenuate the proteasome inhibitor-mediated apoptosis in differentiated PC12 cells by inhibiting the activation of the mitochondria-mediated pathway and the caspase-8- and Bid-dependent pathways. The preventive effect of apocynin appears to be attributed to inhibition of the production of reactive oxygen species and the depletion of cellular GSH contents.

Inhibitory Effect of 3,4,5-Tricaffeoylquinic Acid on Parkinsonian Toxin 1-Methyl-4-phenylpyridinium-induced Apoptosis

BACKGROUND: 1-Methyl-4-phenylpyridinium (MPP+) causes a neuronal cell injury that is similar to the findings observed in Parkinson's disease. Caffeoylquinic acid derivatives have demonstrated anti-oxidant and anti-inflammatory effects. Nevertheless, the effect of 3,4,5-tricaffeoylquinic acid (3,4,5-triCQA) on the neuronal cell death due to exposure of parkinsonian toxin MPP+ remains unclear. METHODS: Using differentiated PC12 cells, the preventive effect of 3,4,5-triCQA on the MPP+-induced cell death in relation to apoptotic process was examined. RESULTS: MPP+ induced a decrease in Bid, Bcl-2 and survivin protein levels, increase in Bax levels, loss of the mitochondrial transmembrane potential, cytochrome c release, activation of caspases (-8, -9 and -3), cleavage of PARP-1, and an increase in the tumor suppressor p53 levels. 3,4,5-Tricaffeoylquinic acid attenuated the MPP+-induced changes in the apoptosis-related protein levels, formation of reactive oxygen species, depletion of GSH, nuclear damage and cell death. 3,4,5-Tricaffeoylquinic acid attenuated another parkinsonian neurotoxin rotenone-induced cell death. CONCLUSIONS: 3,4,5-Tricaffeoylquinic acid may attenuate the MPP+-induced apoptosis in PC12 cells by suppressing the activation of the mitochondrial pathway and the caspase-8- and Bid-dependent pathways. The preventive effect seems to be ascribed to its inhibitory effect on the formation of reactive oxygen species and depletion of GSH.

Taxifolin Glycoside Blocks Human ether-a-go-go Related Gene K+ Channels

Taxifolin glycoside is a new drug candidate for the treatment of atopic dermatitis (AD). Many drugs cause side effects such as long QT syndrome by blocking the human ether-a-go-go related gene (hERG) K+ channels. To determine whether taxifolin glycoside would block hERG K+ channels, we recorded hERG K+ currents using a whole-cell patch clamp technique. We found that taxifolin glycoside directly blocked hERG K+ current in a concentration-dependent manner (EC50=9.6+/-0.7 microM). The activation curve of hERG K+ channels was negatively shifted by taxifolin glycoside. In addition, taxifolin glycoside accelerated the activation time constant and reduced the onset of the inactivation time constant. These results suggest that taxifolin glycoside blocks hERG K+ channels that function by facilitating activation and inactivation process.

Corrigendum: Health Risks Assessments in Children for Phthalates Exposure Associated with Childcare Facilities and Indoor Playgrounds

In Table 6, the unit concentration of phthalates was not correctly indicated.

Inhibitory Effect of Flavonoid Luteolin on 6-Hydroxydopamine Cytotoxicity via Suppression of Apoptosis-Related Protein Activation

BACKGROUND: Flavonoid luteolin has been shown to exhibit cell protective effect. However, it is still uncertain whether the effect of luteolin on cellular toxicity of the parkinsonian toxin 6-hydroxydopamine is mediated by apoptosis-related protein activation. METHODS: In differentiated PC12 cells exposed to 6-hydroxydopamine in combination with luteolin, we observed the apoptosis-related protein activation, nuclear damage, formation of reactive oxygen species and cell death. RESULTS: 6-Hydroxydopamine caused apoptosis by inducing a decrease in Bid, Bcl-2, Bcl-xL and survivin levels, increase in Bax levels, cytochrome c release and activation of caspases. Treatment with luteolin reduced changes in the apoptosis-related protein levels, formation of reactive oxygen species, nuclear damage and cell death. CONCLUSIONS: Luteolin may reduce the 6-hydroxydopamine-induced apoptosis in differentiated PC12 cells by suppressing the activation of the caspase-8- and Bid-dependent pathways and the mitochondria-mediated apoptotic pathway, leading to caspase activation. The preventive effect of luteolin may be associated with its inhibitory effect on the production of reactive oxygen species. Luteolin may attenuate the oxidative stress and mitochondrial dysfunction-induced neuronal cell death take place in Parkinson's disease.

Effect of Extracellular Signal-Regulated Kinase Inhibition on Oxysterol 7-Ketocholesterol-Induced Apoptosis

BACKGROUND: Defects in mitochondrial function have been shown to participate in the induction of neuronal cell injury. The extracellular-signal-regulated kinase (ERK) signaling pathway plays a crucial role in almost all cell functions, including proliferation, differentiation, survival, and death. However, the effect of ERK inhibition on oxysterol-induced apoptosis remains uncertain. METHODS: This study assessed the effect of ERK inhibition on the apoptotic effect of 7-ketocholesterol. RESULTS: Treatment with 7-ketocholesterol increased phosphorylated-ERK1/2 levels in differentiated PC12 cells, while the total amount of ERK was not altered. 7-Ketocholesterol decreased Bid and Bcl-2 levels, increased Bax and p53 levels, and promoted cytochrome c release, which elicits the activation of caspases (-8, -9, and -3), nuclear damage, and cell death. ERK and farnesyltransferase inhibitors inhibited the 7-ketocholesterol-induced phosphorylation of ERK1/2, activation of apoptosis-related proteins, and cell death in PC12 cells. CONCLUSIONS: The ERK and farnesyltransferase inhibitors, which did not exhibit toxicity, may inhibit the 7-ketocholesterol toxicity on differentiated PC12 cells by suppressing the activation of the caspase-8-dependent pathway as well as activation of the mitochondria-mediated cell-death pathway, leading to the activation of caspases. The inhibition of ERK may confer a beneficial protective effect against the neuronal cell injury induced by cholesterol oxidation products.

Health Risks Assessment in Children for Phthalate Exposure Associated with Childcare Facilities and Indoor Playgrounds

OBJECTIVES: This study assessed the health risks for children exposed to phthalate through several pathways including house dust, surface wipes and hand wipes in child facilities and indoor playgrounds. METHODS: The indoor samples were collected from various children's facilities (40 playrooms, 42 daycare centers, 44 kindergartens, and 42 indoor-playgrounds) in both summer (Jul-Sep, 2007) and winter (Jan-Feb, 2008). Hazard index (HI) was estimated for the non-carcinogens and the examined phthalates were diethylhexyl phthalate (DEHP), diethyl phthalate (DEP), dibutyl-n-butyl phthalate (DnBP), and butylbenzyl phthalate (BBzP). The present study examined these four kinds of samples, i.e., indoor dust, surface wipes of product and hand wipes. RESULTS: Among the phthalates, the detection rates of DEHP were 98% in dust samples, 100% in surface wipe samples, and 95% in hand wipe samples. In this study, phthalate levels obtained from floor dust, product surface and children's hand wipe samples were similar to or slightly less compared to previous studies. The 50th and 95th percentile value of child-sensitive materials did not exceed 1 (HI) for all subjects in all facilities. CONCLUSIONS: For DEHP, DnBP and BBzP their detection rates through multi-routes were high and their risk based on health risk assessment was also observed to be acceptable. This study suggested that ingestion and dermal exposure could be the most important pathway of phthalates besides digestion through food.

Role of Casein Kinase 2 in Parkinsonian Toxin 1-Methyl-4-phenylpyridinium-induced Cell Death

BACKGROUND: Protein casein kinase 2 is involved in signal transduction, cell growth, and apoptosis. However, it has not been elucidated whether parkinsonian toxin 1-methyl-4-phenylpyridinium (MPP+)-induced neuronal cell death is mediated by a casein-kinase-2-mediated pathway. METHODS: We monitored apoptosis-related protein activation, changes in the level of casein kinase 2, nuclear damage, and apoptosis in differentiated PC12 cells exposed to MPP+ in combination with casein kinase 2 inhibitor. RESULTS: Casein kinase 2 inhibitors [4,5,6,7-tetrabromobenzotriazole (TBB), 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole, and apigenin] reduced MPP+- and rotenone-induced cell death in differentiated PC12 cells. TBB inhibited the MPP+-induced activation of apoptosis-related proteins (decreases in Bid and Bcl-2 levels, increase in Bax levels, cytochrome c release, and caspase-3 activation), increase in casein kinase 2 levels, and nuclear damage. CONCLUSIONS: Administering casein kinase 2 inhibitor TBB at concentrations that do not induce toxic effects may reduce MPP+-induced cell death in differentiated PC12 cells by suppressing the apoptosis-related protein activation that leads to cytochrome c release and subsequent activation of caspase-3. The results suggest that MPP+-induced cell death process is mediated by a casein kinase 2 pathway.

The Effects of Acer ginnala Leaves Extraction on the Atopic Dermatitis-like Skin Lesions in NC/Nga Mice / 대한피부과학회지

BACKGROUND: Atopic Dermatitis (AD) is a chronic relapsing inflammatory skin disease that is usually observed in patients with an individual or familial history of atopic diseases, and AD is precipitated by environmental factors, including mite antigens. AD is known to be generated by an imbalance of both Th1 and Th2 cytokines. However, the exact etiology of AD is unclear. The leaves of Acer ginnala (AGL) have been demonstrated to have an anti-oxidant effect. OBJECTIVE: We wanted to investigate the effect of AGL on AD-like skin lesions and the other factors related to an immune response. METHODS: The AGL was applied to the AD-like skin lesions on the backs of NC/Nga mice. The efficacy of AGL in the NC/Nga mice was evaluated by the changes of severity of the skin lesions (a modified SCORAD). Blood was collected from the retro-orbital area and the abdominal vena cava. The levels of eosinophils, immunoglobulin (Ig) E and Th2-related cytokines in the blood were measured. RESULTS: The topical application of AGL suppressed the development of AD-like skin lesions. The percent of blood eosinophils was decreased after treatment with AGL. The serum IgE and Th2-related cytokine levels were decreased after treatment with AGL compared with those treated with base cream (the vehicle treated AD group). The IL-4, IL-5 and IL-13 levels were lower than those of the vehicle treated AD group. CONCLUSION: The findings suggest that AGL may exert an inhibitory effect on atopic dermatitis.

Antitumor Effects of Camptothecin Combined with Conventional Anticancer Drugs on the Cervical and Uterine Squamous Cell Carcinoma Cell Line SiHa

Functional defects in mitochondria are involved in the induction of cell death in cancer cells. We assessed the toxic effect of camptothecin against the human cervical and uterine tumor cell line SiHa with respect to the mitochondria-mediated cell death process, and examined the combined effect of camptothecin and anticancer drugs. Camptothecin caused apoptosis in SiHa cells by inducing mitochondrial membrane permeability changes that lead to the loss of mitochondrial membrane potential, decreased Bcl-2 levels, cytochrome c release, caspase-3 activation, formation of reactive oxygen species and depletion of GSH. Combination of camptothecin with other anticancer drugs (carboplatin, paclitaxel, doxorubicin and mitomycin c) or signaling inhibitors (farnesyltransferase inhibitor and ERK inhibitor) did not enhance the camptothecin-induced cell death and caspase-3 activation. These results suggest that camptothecin may cause cell death in SiHa cells by inducing changes in mitochondrial membrane permeability, which leads to cytochrome c release and activation of caspase-3. This effect is also associated with increased formation of reactive oxygen species and depletion of GSH. Combination with other anticancer drugs (or signaling inhibitors) does not appear to increase the anti-tumor effect of camptothecin against SiHa cells, but rather may reduce it. Combination of camptothecin with other anticancer drugs does not seem to provide a benefit in the treatment of cervical and uterine cancer compared with camptothecin monotherapy.

Prostaglandin E2 Attenuates 7-Ketocholesterol Toxicity by Suppressing Changes in Mitochondria-Associated Cell Death Process

BACKGROUND: It has been shown that defects in mitochondrial function are involved in the induction of neuronal cell injury. Prostanoids such as prostaglandin E2 (PGE2) are thought to play an important role in inflammation and neurologic disorders. However, the effect of PGE2 on cholesterol-oxidation-product-induced neuronal cell injury remains uncertain. METHODS: The effect of PGE2 on toxicity of 7-ketocholesterol (7-KCS) was assessed in PC12 cells that were differentiated following treatment with nerve growth factor. The mitochondria-mediated apoptotic process was evaluated by examining the inhibitory effect of PGE2 on 7-KCS-induced toxicity. RESULTS: 7-KCS induced BID cleavage, increased the production of proapoptotic Bax protein, decreased antiapoptotic Bcl-2, increased p53, and promoted cytochrome c release in the cytosolic fraction, which subsequently elicited the activation of caspase-3, DNA fragmentation, and cell death. Treatment with PGE2 inhibited this 7-KCS-induced apoptotic process and cell death. CONCLUSIONS: The results show that PGE2 inhibits 7-KCS-induced toxicity in differentiated PC12 cells by suppressing the mitochondria-mediated apoptotic process. PGE2 may protect against cholesterol-oxidation-product-induced neuronal cell injury.

Glycyrrhizin Attenuates MPTP Neurotoxicity in Mouse and MPP+-Induced Cell Death in PC12 Cells

The present study examined the inhibitory effect of licorice compounds glycyrrhizin and a metabolite 18 beta-lycyrrhetinic acid on the neurotoxicity of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in the mouse and on the 1-methyl-4-phenylpyridinium (MPP+-induced cell death in differentiated PC12 cells. MPTP treatment increased the activities of total superoxide dismutase, catalase and glutathione peroxidase and the levels of malondialdehyde and carbonyls in the brain compared to control mouse brain. Co-administration of glycyrrhizin (16.8 mg/kg) attenuated the MPTP effect on the enzyme activities and formation of tissue peroxidation products. In vitro assay, licorice compounds attenuated the MPP+induced cell death and caspase-3 activation in PC12 cells. Glycyrrhizin up to 100 micrometer significantly attenuated the toxicity of MPP+ Meanwhile, 18beta-lycyrrhetinic acid showed a maximum inhibitory effect at 10 micrometer; beyond this concentration the inhibitory effect declined. Glycyrrhizin and 18beta-lycyrrhetinic acid attenuated the hydrogen peroxide- or nitrogen species-induced cell death. Results from this study indicate that glycyrrhizin may attenuate brain tissue damage in mice treated with MPTP through inhibitory effect on oxidative tissue damage. Glycyrrhizin and 18 beta-lycyrrhetinic acid may reduce the MPP+toxicity in PC12 cells by suppressing caspase-3 activation. The effect seems to be ascribed to the antioxidant effect.

Inhibitory Effect of Tyrphostin AG126 on Brain Synaptosomal Dysfunction Induced by Cholesterol Oxidation Products

BACKGROUND: Formation of cholesterol oxidation products is a suggested mechanism of neurodegenerative disorders. Neuronal cell death is mediated by an increased release of excitotoxic glutamate from the presynaptic nerve endings. Tyrosine-specific protein kinases modulate neurotransmitter release at the nerve terminals. Tyrphostin AG126 has anti-inflammatory and cytoprotective effects. However, it remains uncertain whether tyrphostin AG126 has a preventive effect on the alteration of nerve terminal function induced by cholesterol oxidation products. METHODS: The present study was performed to assess the effect of cholesterol oxidation products against nerve terminal function using synaptosomes isolated from rat cerebrum. We determined the preventive effect of tyrphostin AG126 against oxysterol toxicity by measuring the effects on the glutamate release, depolarization of the membrane potential, changes in Ca2+ levels, and Na+/K+-ATPase activity. RESULTS: Synaptosomes treated with 7-ketocholesterol or 25-hydroxycholesterol exhibited a sustained release of glutamate, depolarization of membrane potential, early rapid increase in cellular Ca2+ levels and decrease in Na+/K+-ATPase activity. Those responses were concentration-dependent. Treatment of tyrphostin AG126 interfered with alteration of synaptosomal functions and decrease in Na+/K+-ATPase activity induced by 7-ketocholesterol or 25-hydroxycholesterol. CONCLUSIONS: The results show that 7-ketocholesterol and 25-hydroxycholesterol seem to cause the release of glutamate by inducing depolarization of the membrane potential and early rapid increase in cellular Ca2+ levels and by inactivating Na+/K+-ATPase in the cerebral synaptosomes. Treatment of tyrphostin AG126 may prevent the oxysterol-induced nerve terminal dysfunction.

Inhibitory Effects of Valdecoxib on Sodium Currents in Sensory Neurons

BACKGROUND: Valdecoxib is a selective cyclooxygenase-2 (COX-2) inhibitor. It is effective in the treatment of rheumatoid arthritis, osteoarthritis, primary dysmenorrhea, and postoperative pain. Two kinds of sodium currents, tetrodotoxin-sensitive (TTX-S) and tetrodotoxin-resistant (TTX-R), are expressed in the dorsal root ganglia (DRG). Both sodium currents are implicated in the formation of normal and abnormal pain. METHODS: The effects of valdecoxib on sodium currents in rat DRG neurons were investigated using the whole-cell variation of the patch-clamp technique. RESULTS: Valdecoxib suppressed two types of sodium currents in a dose-dependent manner, without altering the activation and inactivation kinetics of either current type. It shifted the activation voltage toward a depolarizing direction and the steady-state inactivation voltage toward a hyperpolarizing direction, and suppressed resting channels to similar extents in both types of sodium currents. Valdecoxib slowed the recovery of both sodium currents from inactivation, and suppressed them in a frequency-dependent manner. CONCLUSIONS: The results suggest that valdecoxib may produce analgesic effects through the inhibition of sodium currents in sensory neurons as well as COX-2.

Inhibition of Oxidative Tissue Damage and Mitochondrial Dysfunction by Glycyrrhizin in the 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine Mouse Model of Parkinson's Disease

BACKGROUND: 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) produces an irreversible and severe parkinsonian-like syndrome. A licorice compound glycyrrhizin exerts a cytoprotective or anti-oxidant effect in various disease conditions, but its effect against the MPTP-induced brain tissue damage remains uncertain. The present study elucidates the protective effects of glycyrrhizin against brain tissue damage in the MPTP mouse model of Parkinson's disease. METHODS: We measured the activities of antioxidant enzymes and formation of tissue peroxidation products in the brains of MPTP-treated mice. We also performed an in vitro assay to examine the effects of 1-methyl-4-phenylpyridinium (MPP+) on the mitochondrial respiratory electron flow, membrane potential and cytochrome c release and measured the scavenging action of glycyrrhizin against reactive oxygen species. RESULTS: The MPTP treatment increased activities of total superoxide dismutase, catalase, and glutathione peroxidase and levels of malondialdehyde and carbonyls in the basal ganglia, diencephalon plus midbrain compared to the control mouse brain. Co-administration of glycyrrhizin (16.8 mg/kg = 20 micrometer) attenuated the MPTP effect on the enzyme activities and formation of tissue peroxidation products. Glycyrrhizin attenuated the 500 micrometer MPP+ -induced inhibition of electron flow, changes in the membrane potential and cytochrome c release in isolated brain mitochondria. Glycyrrhizin (1-50 micrometer) showed a scavenging action against superoxide radicals, hydrogen peroxide and hydroxyl radicals. CONCLUSIONS: Glycyrrhizin may prevent the toxicity of MPTP against brain tissue by suppressing mitochondrial damage and oxidative tissue damage. Glycyrrhizin seems to attenuate oxidative brain tissue damage occurring in Parkinson's disease through antioxidant action and prevention of mitochondrial dysfunction.

Developmental Differences in NMDA Neurototoxicity and the Expression of NMDA Receptor 2B Subunit of Rat Hippocampus

BACKGROUND: The developing brain has a distinctive set of characteristics that make it have different susceptibility to excitotoxins. Using primary tissue cultures of rat hippocampus, we investigated the developmental susceptibility to N-methyl-D-aspartic acid (NMDA)-induced cell death at various days in vitro in relation to the appearance of Bcl-2 protein and NMDA receptor 2B subunit. METHODS: Six, 12, and 18 days-in-vitro (DIV) hippocampal tissue cultures derived from 7-day-old Sprague-Dawley rat pups were used. Each group was treated with 100 micrometer NMDA in 5% CO2 incubator at 36 degrees C for 30 min. A western blot was then performed for the NeuN, Bcl-2 and NMDA receptor 2B subunit and propidium Iodide (PI) staining. RESULTS: The NeuN and Bcl-2 were most highly expressed in 12 DIV tissues. The reductions of the NeuN and Bcl-2 protein expressions by NMDA were significant at the 12 and the 18 DIV tissues, but less at 6 DIV tissues (p<0.05). The PI staining showed that the area of fluorescence of the 7 DIV tissues after NMDA exposure was less than the DIV 13 and 19 tissues. Without NMDA treatment, the NMDA receptor 2B subunit protein expressions at the 6 DIV tissues were highest and decreased with maturation. CONCLUSIONS: These results suggest that the immature tissues were more resistant to NMDA toxicity than the mature tissues, and further studies are needed to establish its relationship with the Bcl-2 protein and NMDA receptor 2B subunit.

Promoting Effect of Hydrogen Peroxide on 1-Methyl-4-phenylpyridinium-induced Mitochondrial Dysfunction and Cell Death in PC12 Cells

The promoting effect of hydrogen peroxide (H2O2) against the cytotoxicity of 1-methyl-4-phenylpyridinium (MPP+) in differentiated PC12 cells was assessed by measuring the effect on the mitochondrial membrane permeability. Treatment of PC12 cells with MPP+ resulted in the nuclear damage, decrease in the mitochondrial transmembrane potential, cytosolic accumulation of cytochrome c, activation of caspase-3, increase in the formation of reactive oxygen species (ROS) and depletion of GSH. Addition of H2O2 enhanced the MPP+-induced nuclear damage and cell death. Catalase, Carboxy-PTIO, Mn-TBAP, N-acetylcysteine, cyclosporin A and trifluoperazine inhibited the cytotoxic effect of MPP+ in the presence of H2O2. Addition of H2O2 promoted the change in the mitochondrial membrane permeability, ROS formation and decrease in GSH contents due to MPP+ in PC12 cells. The results show that the H2O2 treatment promotes the cytotoxicity of MPP+ against PC12 cells. H2O2 may enhance the MPP+-induced viability loss in PC12 cells by promoting the mitochondrial membrane permeability change, release of cytochrome c and subsequent activation of caspase-3, which is associated with the increased formation of ROS and depletion of GSH. The findings suggest that H2O2 as a promoting agent for the formation of mitochondrial permeability transition may enhance the neuronal cell injury caused by neurotoxins.

Monoamine Oxidase Inhibitors Attenuate Cytotoxicity of 1-Methyl-4-phenylpyridinium by Suppressing Mitochondrial Permeability Transition

Mitochondrial permeability transition has been shown to be involved in neuronal cell death. Mitochondrial monoamine oxidase (MAO)-B is considered to play a part in the progress of nigrostriatal cell death. The present study examined the effect of MAO inhibitors against the toxicity of 1-methyl-4-phenylpyridinium (MPP+) in relation to the mitochondrial permeability transition. Chlorgyline (a selective inhibitor of MAO-A), deprenyl (a selective inhibitor of MAO-B) and tranylcypromine (non-selective inhibitor of MAO) all prevented cell viability loss, cytochrome c release, caspase-3 activation, formation of reactive oxygen species and depletion of GSH in differentiated PC12 cells treated with 500 micrometer MPP+. The MAO inhibitors at 10 micrometer revealed a maximal inhibitory effect and beyond this concentration the inhibitory effect declined. On the basis of concentration, the inhibitory potency was tranylcypromine, deprenyl and chlorgyline order. The results suggest that chlorgyline, deprenyl and tranylcypromine attenuate the toxicity of MPP+ against PC12 cells by suppressing the mitochondrial permeability transition that seems to be mediated by oxidative stress.