Effects of bisphenol A on the metabolisms of active oxygen species in mouse tissues.

We investigated the modifications in endogenous antioxidant capacity, including superoxide dismutase (SOD), glutathione peroxidase (GPx), catalase, oxidative stress index, reduced glutathione (GSH), glutathione disulfide (GSSG), and thiobarbituric acid-reactive substance (TBARS) in the brain, liver, kidney, and testes of mice under bisphenol A (BPA), an endocrine disrupter, treated for 5 days. BPA was administrated intraperitoneally at doses of 25 and 50mg/kg/day. The TBARS levels were not affected by BPA administrations. The SOD activities increased and the catalase activities decreased in the liver after BPA administration. The GPx activity decreased in the kidney. The levels of GSH+GSSG increased in the brain, kidney, liver, and testes, while, the levels of GSH decreased in the testes. SOD converts superoxide into hydrogen peroxide, and catalase and GPx convert hydrogen peroxide into hydrogen oxide. Our results suggest that the injection of BPA induces overproduction of hydrogen peroxide in the mouse organs. Hydrogen peroxide is easily converted to hydroxy radical. The decrease of GSH and the increase of GSSG may be caused by the hydroxy radical. BPA may show its toxicity by increasing hydrogen peroxide.

Effects of magnetic fields on the accumulation of thiobarbituric acid reactive substances induced by iron salt and H(2)O(2) in mouse brain homogenates or phosphotidylcholine.

In this study, we examined the effects of magnetic fields (MFs) on the generation of thiobarbituric acid reactive substances (TBARS) in the mouse brain homogenates or phosphotidylcholine (PC) solution, incubated with FeCl(3) and/or H(2)O(2). Active oxygen species were generated and lipid peroxidation was induced in mouse brain homogenates by incubation with iron ions, resulting in the accumulation of TBARS. Lipid peroxidation was induced in PC by incubation with iron ions and H(2)O(2). Exposure to sinusoidal MFs (60 Hz, 0.2-1.2 mT), symmetric sawtooth-waveform MFs (50 Hz, 25-600 mT/s), rectangular MFs (1/0.4-1/16 Hz, 3.3 mT) and static MFs (1, 5-300 mT) had no effect on the accumulation of TBARS in brain homogenates induced by FeCl(3). In contrast, when the homogenates were incubated with FeCl(3) in static MFs (2-4 mT), the accumulation of TBARS was decreased. However, this inhibitory effect disappeared when EDTA was added to the homogenate and incubated with H(2)O(2). The accumulation of TBARS in PC solution incubated with FeCl(3) and H(2)O(2) was also inhibited by the static MF. These results indicate that only static MFs had an inhibitory effect on iron-induced lipid peroxidation and the effectiveness of this magnetic field on iron ion-induced active oxygen species generation is restricted to a so called 'window' of field intensity of 2-4 mT.

Activation of the bulbospinal serotonergic system during experimental tooth movement in the rat.

Experimental tooth movement is known to induce characteristic delayed and continuous nociception. Nociceptive somatic stimuli activate endogenous pain control systems such as descending monoaminergic pathways, which modulate the transmission of ascending sensory messages. To test the hypothesis that bulbospinal serotonergic pathways modulate subchronic nociception, we assayed the medulla at the level of the subnucleus caudalis and peri-aqueductal grey by high-performance liquid chromatography with electrochemical detection for the serotonin (5-hydroxytryptamine, 5-HT) and its metabolite (5-hydroxyindoleacetic acid, 5-HIAA) 24 hrs after the onset of experimental tooth movement. Experimental tooth movement significantly increased 5-HT and 5-HIAA levels, and 5-HIAA/5-HT, an index of serotonin turnover, in the medulla, and 5-HIAA level and 5-HIAA/5-HT in the peri-aqueductal grey, indicating that nociception induced by experimental tooth movement activates the bulbospinal serotonergic pathway.

Medullary monoamine levels during experimental tooth movement.

We investigated possible influence of nociception induced by experimental tooth movement on the medullary monoaminergic inhibitory systems. Forty-eight hours after the start of the experimental tooth movement, significant increases in dorsal serotonin (5-HT), dopamine (DA), norepinephrine (NE), 5-hydroxyindoleacetic acid (5-HIAA), and dihydroxyphenylacetic acid (DOPAC) levels were detected with ipsilateral dominance. These results suggest that the nociception induced by experimental tooth movement might be under modulation of serotonergic, noradrenergic, and dopaminergic systems.

Alternate magnetic fields potentiate monoamine oxidase activity in the brain.

Catecholamines and serotonin, which act as neurotransmitters and regulate blood circulation, are degraded by monoamine oxidase (MAO) [EC 1.4.3.4.] which exists two iso-enzymes named MAO-A and MAO-B. In this study, the effects of magnetic fields on MAO activity in the rat brain were examined. MAO-A activity was not changed in static magnetic fields (0.1-340 mT) or in 10-500 mT/s of alternate isosceles triangular magnetic fields (AITMF) (50 Hz). MAO-B activity was not changed in static magnetic fields (0.1-340 mT) and in 10, 34, 340, 95, 105, 110, and 340 mT/s of AITMF. However, it was increased to 114% in the 100 mT/s of AITMF. In 100 mT/s, Michaelis constant (K(m)) significantly decreased to 72%, suggesting that the affinity of the substrate to the enzyme also increased. These results indicate that only MAO-B was influenced by AITMF with 'active window' phenomenon, and suggest that AITMF might affect neural activity and hemodynamics by altering MAO-B.

Effects of an in vivo 60 Hz magnetic field on monoamine levels in mouse brain.

We studied the effects of electromagnetic fields (EMF) on mouse brain monoamine levels in models of (1) chronic exposure (7 days) of EMF (60 Hz, 10 Gauss) to mice in a vertical orientation, (2) prolonged chronic exposure (84 days) of EMF (60 Hz, 10 Gauss) to mice in a horizontal mode, (3) acute exposure (6 h) of EMF (60 Hz, 10 Gauss) to senescence accelerated mice (SAM-P8) at ages 1, 3, 6, 9 and 12 months in the horizontal mode, and (4) acute exposure (1 h) of EMF (60 Hz, 1, 3.3 and 10 Gauss) to restrained mice in the horizontal mode. No model except the restrained one changed their monoamine or metabolite levels by exposure to EMF. In the restrained group, dihydroxyphenylacetic acid (DOPAC) was significantly increased in the hippocampus (HP) and hypothalamus (HY), homovanillic acid (HVA) was significantly increased in HY, and 5-hydroxyindolacetic acid (5-HIAA) was significantly increased in HP and thalamus-midbrain (TM). None of these monoamine metabolite levels were changed when the mouse was restrained without EMF exposure. These results suggest that monoamine metabolism is influenced by EMF only when the exposure is in the same direction as the mouse position. Another possibility is that EMF enhances the restraint stress since stress is known to increase monoamine metabolism.

Continuous monitoring of nitric oxide release induced by cholecystokinin from the choledochal sphincter in guinea pigs.

BACKGROUND/AIMS: Many in vitro studies in the choledochoduodenal junction of the guinea pig have shown that cholecystokinin (CCK) contracts the sphincter of Oddi (SO). This study, using the choledochal sphincter of the guinea pig as the SO, evaluates the hypothesis that effects of CCK on the SO were mediated by nitric oxide (NO). METHODS: Spontaneous motility and effects of CCK on the choledochal sphincter were recorded using a constant-perfusion technique, and direct measurement of NO release using a specific NO sensor was performed at the same time. RESULTS: CCK-8 decreased the phasic wave amplitude of the choledochal sphincter, and increased NO release. N(G)-L-arginine-methyl-ester (L-NAME), an inhibitor of NO synthase, increased the spontaneous motility and converted the CCK-induced inhibitory response into an excitatory response. L-NAME also reduced NO release and abolished the increase of NO that had been caused by CCK-8. These effects were reduced by treatment with L-arginine (L-Arg). L-Arg application enhanced NO release, and recovered the increase of NO by CCK-8. CONCLUSION: These studies demonstrate that CCK relaxes the choledochal sphincter and this relaxant response is mediated by NO.

EPC-K1, a hydroxyl radical scavenger, prevents 6-hydroxydopamine-induced dopamine depletion in the mouse striatum by up-regulation of catalase activity.

We examined the effect of pretreatment with EPC-K1, a potent hydroxyl radical scavenger, on 6-hydroxydopamine (6-OHDA)-induced reduction of dopamine (DA) and its metabolites in the mouse striatum. EPC-K1 was mixed with diet (0.2%, wt/wt) for 1 or 2 weeks, and then 6-OHDA (60 microg in 2 microl of saline solution) was injected intracereberoventricularly. Mice continued to be fed EPC-K1-containing diet for another one week before they were sacrificed. The concentrations of DA and its metabolites in the striatum were measured by high performance liquid chromatography. 6-OHDA reduced the level of DA and its metabolites in the striatum. Pretreatment with EPC-K1 for 2 weeks, but not for 1 week, abrogated the neurotoxic effect of 6-OHDA on striatal concentrations of DA and its metabolites. Measurement of striatal concentrations of thiobarbituric acid reactive substances, glutathione, and malonaldehyde plus 4-hydroxynonenal, and the activities of superoxide dismutase and catalase in EPC-K1 treated mice showed an increase in catalase activity after 2 weeks of such treatment. No other changes in anti-oxidants levels were noted. Our results suggest that EPC-K1 counteracts the neurotoxicity of 6-OHDA by increasing catalase activities.

Dopamine D2 receptor-mediated antioxidant and neuroprotective effects of ropinirole, a dopamine agonist.

Recent information suggests that free radicals are closely involved in the pathogenesis and/or progression of Parkinson's disease (PD). High-dose levodopa therapy has been suggested to increase oxidative stress, thereby accelerating the progression of PD. Based on this viewpoint, free radical scavenging, antioxidant and neuroprotective agents which may prevent the progression of PD have recently attracted considerable attention. For example, ergot derivative dopamine (DA) agonists have been reported to scavenge free radicals in vitro and show a neuroprotective effect in vivo. Non-ergot DA agonists have also recently been used in the treatment of PD despite the lack of substantial evidence for any free radical scavenging activity or antioxidant activity. The present study was conducted to assess the in vitro free radical scavenging and antioxidant activities of ropinirole, a non-ergot DA agonist, as well as its glutathione (GSH), catalase and superoxide dismutase (SOD) activating effects and neuroprotective effect in vivo. Ropinirole scavenges free radicals and suppresses lipid peroxidation in vitro, but these activities are very weak, suggesting that the antioxidant effect of ropinirole observed in vitro may be a minor component of its neuroprotective effect in vivo. Administration of ropinirole for 7 days increased GSH, catalase and SOD activities in the striatum and protected striatal dopaminergic neurons against 6-hydroxydopamine (6-OHDA) in mice. Pre-treatment with sulpiride prevented ropinirole from enhancing striatal GSH, catalase and SOD activities and abolished the protection of dopaminergic neurons against 6-OHDA. Our findings indicate that activation of GSH, catalase and SOD mediated via DA D2 receptors may be the principal mechanism of neuroprotection by ropinirole.

Is low density lipoprotein apheresis effective for coronary artery disease?

Low density lipoprotein (LDL) apheresis is one type of therapy currently being used for coronary artery disease; however, there has been no study to compare the effectiveness of this therapy with the effectiveness of other treatments, such as coronary artery bypass grafting (CABG) and percutaneous transluminal coronary angioplasty (PTCA). In this study, we evaluated the clinical results of these three therapies to compare their individual effectiveness for the treatment of coronary artery disease. Forty-four patients with two vessel disease (plasma cholesterol levels > 250 mg/dl) were divided into three groups (L, LDL apheresis; C, CABG; I, PTCA). After 2 years' observation, the coronary artery findings were evaluated by quantitative coronary angiography (QCA), frequency of cardiac events, changes in plasma lipids, and subjective symptoms, and the cost was examined. The symptoms of patients in Groups C and I showed significant improvement when compared with those of Group L. In Group L, the frequency of cardiac events was low (L, 0%; P, 44%; C, 14%), and lipid reduction was marked (L, 48%; P, 13%; C, 14%); however, the cost of this therapy is much more than the other therapies. There was no difference in the minimal luminal diameter evaluated by QCA in the three groups. LDL apheresis may be a good strategy for coronary disease, if its cost can be improved.

Effects of kynurenine metabolites on the electrocorticographic activity in the rat.

We examined the effects of kynurenine metabolites administered into the right cerebroventricle (1 micromol) on the electrocorticogram (ECoG) of rats to establish the role of kynurenines on brain function. Kynurenine, anthranilic acid, quinaldic acid, xanthurenic acid or 8-hydroxyquinaldic acid showed no effect on ECoG throughout the recording period of 4 hours. 3-Hydroxykynurenine had a transient suppressive effect on the ECoG, while kynurenic acid caused a slight suppression of ECoG activity. 3-Hydroxyanthranilic acid (3-OH-An), a metabolite of 3-hydroxykynurenine, induced spike discharges with a long latency (60-230 min). 3-OH-An is thought to be metabolized to o-aminophenol, 3-methoxyanthranilic acid, quinolinic acid, 2-ketoadipic acid and picolinic acid. Among 3-OH-An metabolites, only o-aminophenol induced spike discharges several minutes after administration, lasting for 60 min. On the other hand, quinolinic acid suppressed ECoG, though 3-methoxyanthranilic acid, 2-ketoadipic acid and picolinic acid had no effects on ECoG. These electrocorticographic findings suggest that 3-OH-An may induce spike discharges after it is metabolized in the brain to o-aminophenol.

Melatonin inhibits iron-induced epileptic discharges in rats by suppressing peroxidation.

PURPOSE: Intracortical injection of iron ion induces recurrent seizures and epileptic discharges in the electrocorticogram. This observation may be used as a model of posttraumatic epilepsy. The involvement of iron-mediated oxygen free radical species and neuronal lipid peroxidation in iron-induced seizure has been suggested. Melatonin exerts free radical scavenging properties. In this study, we examined the protective effect of melatonin against iron-induced seizures. METHODS: We examined the protective effect of melatonin against in vitro iron-induced oxidative damage in homogenates from rat cerebral cortex, by measuring the concentration of thiobarbituric acid reactive substances (TBARS), as an index of oxidative damage. We also examined the effect of melatonin on the appearance of epileptic discharges in the EEG following injection of FeCl3 into the sensorimotor cortex in anesthetized rats, and by measuring the concentration of TBARS in the brain tissue. RESULTS: FeCl3 increased the concentration of TBARS in brain homogenates in a concentration-dependent manner, and melatonin reduced FeCl3-induced rise in TBARS in a dose-response fashion. Pretreatment with melatonin suppressed or delayed the development of FeCl3-induced epileptic discharges and decreased the concentration of TBARS in brain tissues. CONCLUSIONS: Our results suggest that iron ion generates oxygen free radical species that induce neuronal macromolecular peroxidation and seizure, and that melatonin inhibits iron-induced seizures by scavenging free radicals.

Initial cyclosporin A but not glucocorticoid treatment promotes recovery of striatal dopamine concentration in 6-hydroxydopamine lesioned mice.

We examined the effects of cyclosporin A (CsA) and glucocorticoid (GC; hydrocortisone sodium succinate) in a mouse model of experimental parkisonism. GC or CsA was administered 30 or 60 min, respectively, prior to intracerebroventricular injection of 6-hydroxydopamine, followed by injection of a similar dose of each drug 3 h later. CsA reduced the extent of depletion of striatal concentrations of dopamine (DA) and dihydroxyphenylacetic acid (DOPAC) associated with dopaminergic neuronal degeneration. GC reduced the extent of homovanillic acid (HVA) depletion in the same region. A combination treatment with CsA and GC did not produce a further enhancement of the recovery of striatal concentrations of monoamines observed with CsA only. Our findings demonstrated the beneficial effects of initial CsA treatment in experimental models of parkinsonism and further support the usefulness of CsA in the treatment of Parkinson's disease.

The effects of chronic administration of nimodipine on age-related changes in nitric oxide and its synthase in senescence-accelerated mouse brain.

The levels of nitric oxide (NO) and NO synthase (NOS) activities in the brain of young-adult (3 months old), aged (11 months old) and nimodipine-administered (11 months old) senescence-accelerated mouse (SAM), of which SAMP8 sub-strain is inferior in acquisition of learning and has a lower content in testosterone, were compared. Nimodipine, which is L-type calcium ion channel blocker and has memory-enhancing effects, was administered orally for 5 months. In the cerebral cortex of aged SAMP8, NOS activity was increased compared with that of young-adult SAMP8. Though nimodipine did not alter the contents of NO in any brain regions compared with those in aged SAMP8, nimodipine increased NOS activity in the aged cerebellum. Our data suggest that nimodipine may increase NOS activity through elevation of testosterone level, as testosterone increases NOS only in the cerebellum, although further work is clearly needed to ascertain effects of nimodipine on testosterone metabolism and maintenance in the acquisition of learning.

Pole test is a useful method for evaluating the mouse movement disorder caused by striatal dopamine depletion.

We evaluated the behavioral recovery of mice with 6-hydroxydopamine (6-OHDA)-induced lesions using a pole test. T(LA) (locomotor activity time) 1, 2, and 3 days after intracerebroventricular 6-OHDA injection (T(LA)(1-3D)) was correlated significantly with the levels of dopamine (DA), dihydroxyphenylacetic acid (DOPAC), and homovanillic acid (HVA) in the striatum 7 days after the injection of 6-OHDA, but 5-hydroxyindoleacetic acid (5-HIAA) and serotonin (5-HT) had no correlation with T(LA)(1-3D). The mice whose T(LA)(1-3D) was more than the median showed about 60% depletion of striatal DA and increased DA turnover, and recovered from movement disorders 4 days after injection. These results show that presynaptic neuroadaptations and behavioral recovery exist in this animal model. Thus, the pole test appears to be useful in predicting the extent of the lesion to select a mouse in which the receptive fields of the dopaminergic cells are denervated.

Chronic administration of Oren-gedoku-to (TJ15) inhibits ischemia-induced changes in brain indoleamine metabolism and muscarinic receptor binding in the Mongolian gerbil.

We examined the effect of Oren-gedoku-to (TJ15), which is a traditional herbal Kampo prescription used as an anti-cerebral apoplexy agent on these changes. Chronic pre- and post-ischemia TJ15 oral administration almost completely abolished the ischemia-induced muscarinic receptor reduction and 5-hydroxyindoleacetic acid level increase. These results suggest that TJ15 prevents cholinergic synaptic dysfunction and serotonergic presynaptic hyperactivity induced by transient ischemia.

Relationship between structure and inhibitory effect of arginine analogues on neuronal nitric oxide synthase activity.

Since nitric oxide (NO) is synthesized by nitric oxide synthase (NOS) from L-arginine (Arg) which has an amidino group in its molecule, we examined the effect of 29 kinds of Arg analogues on neuronal NOS (nNOS) activity in the rat brain. None of the Arg analogues acted as a substrate for nNOS. Diamidinocystamine, hirudonine, and guanethidine inhibited nNOS activity to 67.3%, 64.2% and 74.1%, respectively, but their inhibitory efficiency was lower than NG-monomethyl-L-arginine (to 36.5%) which is a well known NOS inhibitor. Dimethylguanidine and N-benzoylguanidine also significantly inhibited nNOS activity to 88.0% and 90.7%, respectively. Whereas almost all of the NOS inhibitors previously reported were synthesized by substituting the amidino nitrogen of Arg, none of these new inhibitors were substituted at this position. Furthermore, hirudonine, which is a naturally occurring compound, was thought to act as an agonist at polyamine binding site of the N-methyl-D-aspartate type of glutamate receptor complex. It is also interesting that guanethidine, an antihypertensive agent, inhibit nNOS activity. These new drugs are useful for the investigation not only of the chemical nature of nNOS but also of the physiologic function of NO.

Reduction in nitric oxide synthase activity with development of an epileptogenic focus induced by ferric chloride in the rat brain.

Intracortical injection of iron ion has been shown to induce recurrent seizures and epileptic discharges in electrocorticograms. The importance of the effects of NO on seizure control systems and their regulation is suggested. In this paper, we examined the changes in nitric oxide synthase (NOS) activity in the epileptogenic focus induced by intracortical injection of iron ion at 5 min, 10 min, 1 h, 3 h and 3 days. Iron ion significantly decreased NOS activity in the cortex at the injection site 5 min, 3 h and 3 days after injection. These results suggest that the formation of an epileptic focus induced by iron ion is accompanied by decreased NOS activity.

Cyclosporin A attenuates degeneration of dopaminergic neurons induced by 6-hydroxydopamine in the mouse brain.

To reveal new therapeutic strategies for Parkinson's disease (PD), we investigated the protective effect of an immunosuppressant, cyclosporin A (CsA), against 6-hydroxydopamine (6-OHDA)-induced injury of nigrostriatal dopamine neurons in mice. Seven days after induction of 6-OHDA lesion, dopamine (DA) and homovanillic acid (HVA) in the striatum were depleted by 60 and 50%, respectively, and repeated high dose CsA (20 mg/kg) treatment significantly protected against these depletions. HVA and dihydroxyphenylacetic acid (DOPAC) in the substantia nigra were depleted by 40%, and CsA significantly increased HVA and DOPAC in 6-OHDA-lesioned mice. Furthermore, CsA increased the [DOPAC + HVA]/DA ratio in the substantia nigra, indicating that DA metabolism was stimulated by CsA in 6-OHDA-lesioned mice. These results suggest that CsA is beneficial in reducing 6-OHDA-induced injury of nigrostriatal DA neurons, indicating the therapeutic potential of immunosuppressants in PD.