Phenidone attenuates oxygen/glucose deprivation-induced neurotoxicity by antioxidant and antiapoptotic action in mouse cortical cultures

Noradrenaline protects neurons against H2 O2 -induced death by increasing the supply of glutathione from astrocytes via β3 -adrenoceptor stimulation

Oxidative stress has been implicated in a variety of neurodegenerative disorders, such as Alzheimer's and Parkinson's disease. Astrocytes play a significant role in maintaining survival of neurons by supplying antioxidants such as glutathione (GSH) to neurons. Recently, we found that noradrenaline increased the intracellular GSH concentration in astrocytes via β₃ -adrenoceptor stimulation. These observations suggest that noradrenaline protects neurons from oxidative stress-induced death by increasing the supply of GSH from astrocytes to neurons via the stimulation of β₃ -adrenoceptor in astrocytes. In the present study, we examined the protective effect of noradrenaline against H₂ O₂ -induced neurotoxicity using two different mixed cultures: the mixed culture of human astrocytoma U-251 MG cells and human neuroblastoma SH-SY5Y cells, and the mouse primary cerebrum mixed culture of neurons and astrocytes. H₂ O₂ -induced neuronal cell death was significantly attenuated by pretreatment with noradrenaline in both mixed cultures but not in single culture of SH-SY5Y cells or in mouse cerebrum neuron-rich culture. The neuroprotective effect of noradrenaline was inhibited by SR59230A, a selective β₃ -adrenoceptor antagonist, and CL316243, a selective β₃ -adrenoceptor agonist, mimicked the neuroprotective effect of noradrenaline. DL-buthionine-[S,R]-sulfoximine, a GSH synthesis inhibitor, negated the neuroprotective effect of noradrenaline in both mixed cultures. MK571, which inhibits the export of GSH from astrocytes mediated by multidrug resistance-associated protein 1, also prevented the neuroprotective effect of noradrenaline. These results suggest that noradrenaline protects neurons against H₂ O₂ -induced death by increasing the supply of GSH from astrocytes via β₃ -adrenoceptor stimulation.

Nonsteroidal Anti-Inflammatory Therapy: A Journey Toward Safety

The efficacy of nonsteroidal anti-inflammatory drugs (NSAIDs) against inflammation, pain, and fever has been supporting their worldwide use in the treatment of painful conditions and chronic inflammatory diseases until today. However, the long-term therapy with NSAIDs was soon associated with high incidences of adverse events in the gastrointestinal tract. Therefore, the search for novel drugs with improved safety has begun with COX-2 selective inhibitors (coxibs) being straightaway developed and commercialized. Nevertheless, the excitement has fast turned to disappointment when diverse coxibs were withdrawn from the market due to cardiovascular toxicity. Such events have once again triggered the emergence of different strategies to overcome NSAIDs toxicity. Here, an integrative review is provided to address the breakthroughs of two main approaches: (i) the association of NSAIDs with protective mediators and (ii) the design of novel compounds to target downstream and/or multiple enzymes of the arachidonic acid cascade. To date, just one phosphatidylcholine-associated NSAID has already been approved for commercialization. Nevertheless, the preclinical and clinical data obtained so far indicate that both strategies may improve the safety of nonsteroidal anti-inflammatory therapy.

Role of oxidative stress in epileptic seizures

Oxidative stress resulting from excessive free-radical release is likely implicated in the initiation and progression of epilepsy. Therefore, antioxidant therapies aimed at reducing oxidative stress have received considerable attention in epilepsy treatment. However, much evidence suggests that oxidative stress does not always have the same pattern in all seizures models. Thus, this review provides an overview aimed at achieving a better understanding of this issue. We summarize work regarding seizure models (i.e., genetic rat models, kainic acid, pilocarpine, pentylenetetrazol, and trimethyltin), oxidative stress as an etiologic factor in epileptic seizures (i.e., impairment of antioxidant systems, mitochondrial dysfunction, involvement of redox-active metals, arachidonic acid pathway activation, and aging), and antioxidant strategies for seizure treatment. Combined, this review highlights pharmacological mechanisms associated with oxidative stress in epileptic seizures and the potential for neuroprotection in epilepsy that targets oxidative stress and is supported by effective antioxidant treatment.

Phenidone protects the nigral dopaminergic neurons from LPS-induced neurotoxicity

Anti-inflammatory drugs such as ibuprofen appear to prevent the development of Parkinson's disease (PD); however, long-term use has undesirable side-effects. A new strategy for anti-inflammatory drug therapy is using a dual inhibitor of COX and lipooxygenase (LOX). Here, we compared the dopaminergic neuroprotective property of phenidone (a dual COX and LOX inhibitor) with COX or LOX inhibitors including SC-560 (a COX-1 inhibitor), aspirin (a COX-1/2 inhibitor), meloxicam (a preferential COX-2 inhibitor), caffeic acid (a 5-LOX inhibitor), and esculetin (a 5, 12-LOX inhibitor) in our lipopolysaccharide (LPS)-induced PD animal model. Our results show that COX-2 and 5-LOX play a major role in LPS-induced dopaminergic neurotoxicity, as meloxicam and phenidone attenuated LPS-induced oxidative stress and meloxicam, phenidone, and caffeic acid attenuated dopaminergic neurodegeneration, while SC-560, aspirin, and esculetin did not. In addition, phenidone was superior in attenuating LPS-induced dopaminergic neurodegeneration and microglia activation, probably as a result of dual inhibition of COX-2 and LOX. Therefore, dual inhibition of COX and LOX with phenidone represents a promising new candidate for anti-inflammatory drug therapy, and may provide a novel therapeutic approach for inflammation-related neurodegenerative diseases including PD.

Catalpol protects rat pheochromocytoma cells against oxygen and glucose deprivation-induced injury

OBJECTIVES

Catalpol has been identified to have neuroprotective effect on gerbils subjected to transient global cerebral ischemia. However, the mechanism that catalpol prevents ischemia is still unclear. In the present study, PC12 cells, exposed to oxygen and glucose deprivation (OGD) followed by reperfusion, were used as an in vitro model of ischemia. The protective effects of catalpol were investigated in ischemic-induced apoptosis in PC12 cells.

METHODS

After OGD for 3 hours and reoxygenation for 18 hours, cell survival was quantified by the reduction of 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT). The activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-PX) were determined using commercially available kits. Caspase-3 assay was performed using caspase-3 assay kit. Microplate reader was used to detect the intensities of rhodamine123 (Rh123) and reactive oxygen species (ROS). The level of Bcl-2 protein was measured by flow cytometry.

RESULTS

Catalpol attenuated ischemia-induced apoptotic death via preventing the decrease in the level of Bcl-2 protein and the activities of SOD and GSH-PX, inhibiting the reduction of mitochondrial membrane potential and suppressing activation of caspase-3.

DISCUSSION

The results suggest that the catalpol has the potential to prevent ischemic-induced apoptosis.

Opuntia ficus-indica attenuates neuronal injury in in vitro and in vivo models of cerebral ischemia

We examined whether the methanol extract of Opuntia ficus-indica (MEOF) has a neuroprotective action against N-methyl-d-aspartate (NMDA)-, kainate (KA)-, and oxygen-glucose deprivation (OGD)-induced neuronal injury in cultured mouse cortical cells. We also evaluated the protective effect of MEOF in the hippocampal CA1 region against neuronal damage evoked by global ischemia in gerbils. Treatment of neuronal cultures with MEOF (30, 300, and 1000 microg/ml) inhibited NMDA (25 microM)-, KA (30 microM)-, and OGD (50 min)-induced neurotoxicity dose-dependently. The butanol fraction of Opuntia ficus-indica (300 microg/ml) significantly reduced NMDA (20 microM)-induced delayed neurotoxicity by 27%. Gerbils were treated with MEOF every 24h for 3 days (0.1, 1.0, and 4.0 g/kg, p.o.) or for 4 weeks (0.1 and 1.0 g/kg, p.o.), and ischemic injury was induced after the last dose. Neuronal cell damage in the hippocampal CA1 region was evaluated quantitatively at 5 days after the ischemic injury. When gerbils were given doses of 4.0 g/kg (3 days) and 1.0 g/kg (4 weeks), the neuronal damage in the hippocampal region was reduced by 32 and 36%, respectively. These results suggest that the preventive administration of Opuntia ficus-indica extracts may be helpful in alleviating the excitotoxic neuronal damage induced by global ischemia.

Actin redistribution underlies the sparing effect of mild hypothermia on dendritic spine morphology after in vitro ischemia

Brain hypothermia is at present the most effective neuroprotective treatment against brain ischemia in man. Ischemia induces a redistribution of proteins involved in synaptic functions, which is markedly diminished by therapeutic hypothermia (33 degrees C). Dendritic spines at excitatory synapses are motile and show both shape changes and rearrangement of synaptic proteins as a consequence of neuronal activity. We investigated the effect of reduced temperature (33 degrees C and 27 degrees C compared with 37 degrees C), on spine motility, length and morphology by studying the distribution of GFP-actin before, during and after induction of in vitro ischemia. Because high-concentration actin filaments are located inside spines, dissociated hippocampal neurons (7-11 DIV) from transgenic mice expressing GFP-actin were used in this study. The movement of the spines and the distribution of GFP-actin were recorded using time-lapse fluorescence microscopy. Under normal conditions rapid rearrangement of GFP-actin was seen in dendritic spines, indicating highly motile spines at 37 degrees C. Decreasing the incubation temperature to 33 degrees C or 27 degrees C, dramatically reduces actin dynamics (spine motility) by approximately 50% and 70%, respectively. In addition, the length of the spine shaft was reduced by 20%. We propose that decreasing the temperature from 37 degrees C to 33 degrees C during ischemia decreases the neuronal actin polymerization rate, which reduces spine calcium kinetics, disrupts detrimental cell signaling and protects neurons against damage.

Phenidone, a dual inhibitor of cyclooxygenases and lipoxygenases, ameliorates rat paralysis in experimental autoimmune encephalomyelitis by suppressing its target enzymes

This study examined whether phenidone, a dual inhibitor of cyclooxygenase (COX) and lipoxygenase (LOX), affects the clinical symptoms of experimental autoimmune encephalomyelitis (EAE) in the rat, and the expression of both COX-1/-2 and 5-LOX in EAE spinal cords. Oral phenidone (200 mg/kg) significantly suppressed the incidence and clinical severity of EAE paralysis. Western blot analysis showed that phenidone significantly inhibited the increases in COX-1/-2 and 5-LOX in the spinal cords of rats with EAE. This finding was paralleled by immunohistochemical observations. Overall, these findings suggest that COX-1/-2 and 5-LOX are important inflammatory mediators in the pathogenesis of EAE, and that the inhibition of both COX and LOX ameliorates the autoimmune disorder of the central nervous system.

Quercetin attenuates oxygen-glucose deprivation- and excitotoxin-induced neurotoxicity in primary cortical cell cultures

The possible role of quercetin, a naturally occurring plant flavonoid, in protecting against oxygen-glucose deprivation (OGD)-, excitotoxins-, and free radical-induced neuronal injury in mouse cortical cell cultures was investigated. Pre- and co-treatment with quercetin (100 microM) inhibited 50 min OGD-, 20 microM N-methyl-D-aspartate (NMDA)-, and 50 microM kainate-induced neurotoxicity by 36, 22, and 61%, respectively. Quercetin significantly ameliorated free radical-induced neuronal injury caused by buthionine sulfoximine, sodium nitroprusside, ZnCl(2), and FeCl(2). These results suggest that quercetin may contribute a neuroprotective action against ischemic neural injury, partially via antioxidant actions.

Incorporation of sodium channel blocking and free radical scavenging activities into a single drug, AM-36, results in profound inhibition of neuronal apoptosis

AM-36 is a novel neuroprotective agent incorporating both antioxidant and Na(+) channel blocking actions. In cerebral ischaemia, loss of cellular ion homeostasis due to Na(+) channel activation, together with increased reactive oxygen species (ROS) production, are thought to contribute to neuronal death. Since neuronal death in the penumbra of the ischaemic lesion is suggested to occur by apoptosis, we investigated the ability of AM-36, antioxidants and Na(+) channel antagonists to inhibit toxicity induced by the neurotoxin, veratridine in cultured cerebellar granule cells (CGC's). Veratridine (10 - 300 microM) concentration-dependently reduced cell viability of cultured CGC's. Under the experimental conditions employed, cell death induced by veratridine (100 microM) possessed the characteristics of apoptosis as assessed by morphology, TUNEL staining and DNA laddering on agarose gels. Neurotoxicity and apoptosis induced by veratridine (100 microM) were inhibited to a maximum of 50% by the antioxidants, U74500A (0.1 - 10 microM) and U83836E (0.03 - 10 microM), and to a maximum of 30% by the Na(+) channel blocker, dibucaine (0.1 - 100 microM). In contrast, AM-36 (0.01 - 10 microM) completely inhibited veratridine-induced toxicity ( IC(50) 1.7 (1.5 - 1.9) microM, 95% confidence intervals (CI) in parentheses) and concentration-dependently inhibited apoptosis. These findings suggest veratridine-induced toxicity and apoptosis are partially mediated by generation of ROS. AM-36, which combines both Na(+) channel blocking and antioxidant activity, provided superior neuroprotection compared with agents possessing only one of these actions. This bifunctional profile of activity may underlie the potent neuroprotective effects of AM-36 recently found in a stroke model in conscious rats.

Phenidone prevents kainate-induced neurotoxicity via antioxidant mechanisms

Acculmulating evidence indicates that a marked generation of oxygen free radicals derived from the metabolism of arachidonic acid causes neurodegeneration. Recently, we have demonstrated that the novel antioxidant actions mediated by phenidone, a dual inhibitor of cyclooxygenase/lipoxygenase pathways, may play a crucial role in preventing neuroexcitotoxicity in vitro [Neurosci. Lett. 272 (1999) 91], and that phenidone significantly attenuates kainic acid (KA)-induced seizures via inhibiting the synthesis of Fos-related antigen protein [Brain Res. 782 (1998) 337]. In order to extend our understanding of the pharmacological intervention of phenidone, we evaluated the antioxidant activity of this compound in vivo in the present study. In order to better understand the significance of a blockade of both the cyclooxygenase and lipoxygenase pathways, we studied the effects of aspirin (ASP; a non-selective inhibitor of cyclooxygenase), NS-398 (a selective inhibitor of cyclooxygenase-2), esculetin (an inhibitor of lipoxygenase) and phenidone on lipid peroxidation, protein oxidation, and glutathione (GSH) status in the rat hippocampus after KA administration. ASP (7.5 or 15 mg/kg), NS-398 (10 or 20 mg/kg), esculetin (5 or 10 mg/kg) or phenidone (25, 50 or 100 mg/kg) was administered orally five times every 12 h before the injection of KA (10 mg/kg, i.p.). The KA-induced toxic behavioral signs, oxidative stress (lipid peroxidation and protein oxidation), impairment of GSH status, and the loss of hippocampal neurons were dose-dependently attenuated by the phenidone, NS-398+esculetin, and ASP+esculetin. However, ASP, NS-398 and esculetin alone failed to protect against the neurotoxicities induced by KA. Therefore, the results suggest that protection by blockade of both cyclooxygenase and lipoxygenase pathways against KA-induced neuroexcitotoxicity is via antioxidant actions. However, a novel anticonvulsant/neuroprotective effect mediated by phenidone remains to be further characterized.