Mountain-cultivated ginseng protects against cognitive impairments in aged GPx-1 knockout mice via activation of Nrf2/ChAT/ERK signaling pathway.

Background: Escalating evidence shows that ginseng possesses an antiaging potential with cognitive enhancing activity. As mountain cultivated ginseng (MCG) is cultivated without agricultural chemicals, MCG has emerged as a popular herb medicine. However, little is known about the MCG-mediated pharmacological mechanism on brain aging. Methods: As we demonstrated that glutathione peroxidase (GPx) is important for enhancing memory function in the animal model of aging, we investigated the role of MCG as a GPx inducer using GPx-1 (a major type of GPx) knockout (KO) mice. We assessed whether MCG modulates redox and cholinergic parameters, and memory function in aged GPx-1 knockout KOmice. Results: Redox burden of aged GPx-1 KO mice was more evident than that of aged wild-type (WT) mice. Alteration of Nrf2 DNA binding activity appeared to be more evident than that of NFκB DNA binding activity in aged GPx-1 KO mice. Alteration in choline acetyltransferase (ChAT) activity was more evident than that in acetylcholine esterase activity. MCG significantly attenuated reductions in Nrf2 system and ChAT level. MCG significantly enhanced the co-localization of Nrf2-immunoreactivity and ChAT-immunoreactivity in the same cell population. Nrf2 inhibitor brusatol significantly counteracted MCG-mediated up-regulation in ChAT level and ChAT inhibition (by k252a) significantly reduced ERK phosphorylation by MCG, suggesting that MCG might require signal cascade of Nrf2/ChAT/ERK to enhance cognition. Conclusion: GPx-1 depletion might be a prerequisite for cognitive impairment in aged animals. MCG-mediated cognition enhancement might be associated with the activations of Nrf2, ChAT, and ERK signaling cascade.

Ulmus davidiana 60% edible ethanolic extract for prevention of pericyte apoptosis in diabetic retinopathy.

Diabetic retinopathy (DR) is a disease that causes visual deficiency owing to vascular leakage or abnormal angiogenesis. Pericyte apoptosis is considered one of the main causes of vascular leakage in diabetic retina, but there are few known therapeutic agents that prevent it. Ulmus davidiana is a safe natural product that has been used in traditional medicine and is attracting attention as a potential treatment for various diseases, but its effect on pericyte loss or vascular leakage in DR is not known at all. In the present study, we investigated on the effects of 60% edible ethanolic extract of U. davidiana (U60E) and catechin 7-O-ß-D-apiofuranoside (C7A), a compound of U. davidiana, on pericyte survival and endothelial permeability. U60E and C7A prevented pericyte apoptosis by inhibiting the activation of p38 and JNK induced by increased glucose and tumor necrosis factor alpha (TNF-α) levels in diabetic retina. Moreover, U60E and C7A reduced endothelial permeability by preventing pericyte apoptosis in co-cultures of pericytes and endothelial cells. These results suggest that U60E and C7A could be a potential therapeutic agent for reducing vascular leakage by preventing pericyte apoptosis in DR.

Esculetin and Fucoidan Attenuate Autophagy and Apoptosis Induced by Zinc Oxide Nanoparticles through Modulating Reactive Astrocyte and Proinflammatory Cytokines in the Rat Brain.

We examined the protective effects of esculetin and fucoidan against the neurotoxicity of ZnO NPs in rats. Ninety rats were divided into nine groups and pre-treated with esculetin or fucoidan 1 h before ZnO NP administration on a daily basis for 2 weeks. Serum and brain homogenates were examined by enzyme-linked immunosorbent assay (ELISA), and neurons, microglia, and astrocytes in the hippocampal region were examined with immunohistochemical analysis. The serum levels of interleukin-1-beta (IL-1ß), 3-nitrotyrosine (3-NT), superoxide dismutase (SOD), and 8-hydroxy-2'-deoxyguanosine (8-OHdG) were altered in the ZnO NP treatment groups. Brain IL-1ß and TNF-α levels were elevated after ZnO NP administration, and these effects were inhibited by esculetin and fucoidan. SOD, 8-OHdG, and acetylcholinesterase (AChE) levels in the brain were decreased after ZnO NP administration. The brain levels of beclin-1 and caspase-3 were elevated after ZnO NP treatment, and these effects were significantly ameliorated by esculetin and fucoidan. The number of reactive astrocytes measured by counting glial fibrillary acidic protein (GFAP)-positive cells, but not microglia, increased following ZnO NP treatment, and esculetin and fucoidan ameliorated the changes. Esculetin and fucoidan may be beneficial for preventing ZnO NP-mediated autophagy and apoptosis by the modulation of reactive astrocyte and proinflammatory cytokines in the rat brain.

Inhibitors of Lipoxygenase and Cyclooxygenase-2 Attenuate Trimethyltin-Induced Neurotoxicity through Regulating Oxidative Stress and Pro-Inflammatory Cytokines in Human Neuroblastoma SH-SY5Y Cells.

Trimethyltin (TMT) is an environmental neurotoxin that mediates dopaminergic neuronal injury in the brain. In this study, we characterized the toxic mechanism and possible protective compounds against TMT-induced neurotoxicity in human dopaminergic neuroblastoma SH-SY5Y cells. Antioxidants such as melatonin, N-acetylcysteine (NAC), α-tocopherol, and allopurinol alleviated TMT toxicity. Apoptosis induced by TMT was identified by altered expression of cleaved caspase-3, Bax, Bcl-2, and Bcl-xL through Western blot analysis. The iron chelator deferoxamine ameliorated the alteration of apoptosis-related proteins through TMT exposure. TMT also induced delayed ultrastructural necrotic features such as mitochondrial swelling and cytoplasmic membrane rupture; NAC reduced these necrotic injuries. Esculetin, meloxicam, celecoxib, and phenidone decreased TMT toxicity. Elevation of the pro-inflammatory cytokines IL-1ß, TNF-α, and NF-ĸB and reduction of the antioxidant enzymes catalase and glutathione peroxidase-1 (GPx-1) were induced by TMT and ameliorated by inhibitors of LOX and COX-2 enzymes. Both NMDA and non-NMDA antagonists attenuated TMT toxicity. The free calcium ion modulators nimodipine and BAPTA/AM contributed to neuronal survival against TMT toxicity. Inhibitors of the phosphoinositide 3-kinase/protein kinase B/mammalian target of rapamycin pathway, an autophagy regulator, decreased TMT toxicity. These results imply that TMT neurotoxicity is the chief participant in LOX- and COX-2-mediated apoptosis, partly via necrosis and autophagy in SH-SY5Y cells.

A 60% Edible Ethanolic Extract of Ulmus davidiana Inhibits Vascular Endothelial Growth Factor-Induced Angiogenesis.

As abnormal angiogenesis is associated with exacerbation of various diseases, precise control over angiogenesis is imperative. Vascular endothelial growth factor (VEGF), the most well-known angiogenic factor, binds to VEGF receptor (VEGFR), activates various signaling pathways, and mediates angiogenesis. Therefore, blocking the VEGF-induced angiogenic response-related signaling pathways may alleviate various disease symptoms through inhibition of angiogenesis. Ulmus davidiana is a safe natural product that has been traditionally consumed, but its effects on endothelial cells (ECs) and the underlying mechanism of action are unclear. In the present study, we focused on the effect of a 60% edible ethanolic extract of U. davidiana (U60E) on angiogenesis. U60E inhibited the VEGF-mediated proliferation, tube formation, and migration ability of ECs. Mechanistically, U60E inhibited endothelial nitric oxide synthase activation and nitric oxide production by blocking the protein kinase B signaling pathway activated by VEGF and consequently inhibiting proliferation, tube formation, and migration of ECs. These results suggest that U60E could be a potential and safe therapeutic agent capable of suppressing proangiogenic diseases by inhibiting VEGF-induced angiogenesis.

Glutathione Peroxidase-1 Knockout Facilitates Memory Impairment Induced by ß-Amyloid (1-42) in Mice via Inhibition of PKC ßII-Mediated ERK Signaling; Application with Glutathione Peroxidase-1 Gene-Encoded Adenovirus Vector.

A growing body evidence suggests that selenium (Se) deficiency is associated with an increased risk of developing Alzheimer's disease (AD). Se-dependent glutathione peroxidase-1 (GPx-1) of a major antioxidant enzyme, and the most abundant isoform of GPx in the brain. In the present study, we investigated whether GPx-1 is protective against memory impairments induced by beta-amyloid (Aß) (1-42) in mice. As the alteration of protein kinase C (PKC)-mediated ERK activation was recognized in the early stage of AD, we examined whether the GPx-1 gene modulates Aß (1-42)-induced changes in PKC and ERK levels. We observed that Aß (1-42) treatment (400 pmol, i.c.v.) significantly decreased PKC ßII expression in the hippocampus of mice. Aß (1-42)-induced neurotoxic changes [i.e., oxidative stress (i.e., reactive oxygen species, 4-hydroxy-2-noneal, and protein carbonyl), reduced PKC ßII and phospho-ERK expressions, and memory impairment under Y-maze and passive avoidance test] were more pronounced in GPx-1 knockout than in wild type mice. Importantly, exposure to a GPx-1 gene-encoded adenovirus vector (Adv-GPx-1) significantly increased GPx-1 mRNA and GPx activity in the hippocampus of GPx-1 knockout mice. Adv-GPx-1 exposure also significantly blocked the neurotoxic changes induced by Aß (1-42) in GPx-1 knockout mice. Treatment with ERK inhibitor U0126 did not significantly change Adv-GPx-1-mediated attenuation in PKC ßII expression. In contrast, treatment with PKC inhibitor chelerythrine (CHE) reversed Adv-GPx-1-mediated attenuation in ERK phosphorylation, suggesting that PKC ßII-mediated ERK signaling is important for Adv-GPx-1-mediated potentials against Aß (1-42) insult. Our results suggest that treatment with the antioxidant gene GPx-1 rescues Aß (1-42)-induced memory impairment via activating PKC ßII-mediated ERK signaling.

Zinc Oxide Nanoparticles Induce Autophagy and Apoptosis via Oxidative Injury and Pro-Inflammatory Cytokines in Primary Astrocyte Cultures.

The present study examined the potential toxic concentrations of zinc oxide nanoparticles (ZnO NPs) and associated autophagy and apoptosis-related injuries in primary neocortical astrocyte cultures. Concentrations of ZnO NPs ≥3 µg/mL induced significant toxicity in the astrocytes. At 24 h after exposure to the ZnO NPs, transmission electron microscopy revealed swelling of the endoplasmic reticulum (ER) and increased numbers of autophagolysosomes in the cultured astrocytes, and increased levels of LC3 (microtubule-associated protein 1 light chain 3)-mediated autophagy were identified by flow cytometry. Apoptosis induced by ZnO NP exposure was confirmed by the elevation of caspase-3/7 activity and 4',6'-diamidino-2-phenylindole (DAPI) staining. Significant (p < 0.05) changes in the levels of glutathione peroxidase, superoxide dismutase, tumor necrosis factor (TNF-α), and interleukin-6 were observed by enzyme-linked immunoassay (ELISA) assay following the exposure of astrocyte cultures to ZnO NPs. Phosphatidylinositol 3-kinase (PI3K)/mitogen-activated protein kinase (MAPK) dual activation was induced by ZnO NPs in a dose-dependent manner. Additionally, the Akt (protein kinase B) inhibitor BML257 and the mTOR (mammalian target of rapamycin) inhibitor rapamycin contributed to the survival of astrocytes. Inhibitors of cyclooxygenase-2 and lipoxygenase attenuated ZnO NP-induced toxicity. Calcium-modulating compounds, antioxidants, and zinc/iron chelators also decreased ZnO NP-induced toxicity. Together, these results suggest that ZnO NP-induced autophagy and apoptosis may be associated with oxidative stress and the inflammatory process in primary astrocyte cultures.

Zinc Oxide Nanoparticles Exhibit Both Cyclooxygenase- and Lipoxygenase-Mediated Apoptosis in Human Bone Marrow-Derived Mesenchymal Stem Cells.

Nanoparticles (NPs) have been recognized as both useful tools and potentially toxic materials in various industrial and medicinal fields. Previously, we found that zinc oxide (ZnO) NPs that are neurotoxic to human dopaminergic neuroblastoma SH-SY5Y cells are mediated by lipoxygenase (LOX), not cyclooxygenase-2 (COX-2). Here, we examined whether human bone marrow-derived mesenchymal stem cells (MSCs), which are different from neuroblastoma cells, might exhibit COX-2- and/or LOX-dependent cytotoxicity of ZnO NPs. Additionally, changes in annexin V expression, caspase-3/7 activity, and mitochondrial membrane potential (MMP) induced by ZnO NPs and ZnO were compared at 12 hr and 24 hr after exposure using flow cytometry. Cytotoxicity was measured based on lactate dehydrogenase activity and confirmed by trypan blue staining. Rescue studies were executed using zinc or iron chelators. ZnO NPs and ZnO showed similar dose-dependent and significant cytotoxic effects at concentrations ≥ 15 µg/mL, in accordance with annexin V expression, caspase-3/7 activity, and MMP results. Human MSCs exhibited both COX-2 and LOX-mediated cytotoxicity after exposure to ZnO NPs, which was different from human neuroblastoma cells. Zinc and iron chelators significantly attenuated ZnO NPs-induced toxicity. Conclusively, these results suggest that ZnO NPs exhibit both COX-2- and LOX-mediated apoptosis by the participation of mitochondrial dysfunction in human MSC cultures.

Benefits of hesperidin in central nervous system disorders: a review.

Citrus species contain significant amounts of flavonoids that possess antioxidant activities; furthermore, dietary citrus is not associated with adverse effects or cytotoxicity in healthy individuals. Hesperidin, which is an abundant flavanone glycoside in the peel of citrus fruits, possesses a variety of biological capabilities that include antioxidant and anti-inflammatory actions. Over the last few decades, many studies have been investigated the biological actions of hesperidin and its aglycone, hesperetin, as well as their underlying mechanisms. Due to the antioxidant effects of hesperidin and its derivatives, the cardioprotective and anti-cancer effects of these compounds have been widely reviewed. Although the biological activities of hesperidin in neurodegenerative diseases have been evaluated, its potential involvement in a variety of central nervous system (CNS) disorders, including autoimmune demyelinating disease, requires further investigation in terms of the underlying mechanisms. Thus, the present review will focus on the potential role of hesperidin in diverse models of CNS neuroinflammation, including experimental autoimmune encephalomyelitis, with special consideration given to its antioxidant and anti-inflammatory effects in neurodegenerative disease models. Additionally, current evidence provides information regarding the nutraceutical use of hesperidin to prevent various CNS disorders.

High-dose dextromethorphan produces myelinoid bodies in the hippocampus of rats.

Dextromethorphan (DM) administered at supra-antitussive doses produce psychotoxic and neurotoxic effects in humans. We administered DM (80 mg/kg) to rats intraperitoneally to determine the ultrastructural change induced by DM, because intraperitoneal route is sensitive for the behavioral responses. Treatment with DM resulted in mitochondrial dysfunction and formation of myelinoid bodies in the hippocampus. MK-801 [(+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine maleate] attenuated DM-induced cytosolic oxidative burdens. However, neither MK-801 nor naloxone affected DM-induced mitochondrial dysfunction and formation of myelinoid bodies, indicating that the neurotoxic mechanism needs to be further elucidated. Therefore, the spectrum of toxicological effects associated with DM need to be reassessed.

Protein kinase Cδ mediates trimethyltin-induced neurotoxicity in mice in vivo via inhibition of glutathione defense mechanism.

We investigated whether protein kinase C (PKC) is involved in trimethyltin (TMT)-induced neurotoxicity. TMT treatment (2.8 mg/kg, i.p.) significantly increased PKCδ expression out of PKC isozymes (i.e., α, ßI, ßII, δ, and ς) in the hippocampus of wild-type (WT) mice. Consistently, treatment with TMT resulted in significant increases in cleaved PKCδ expression. Genetic or pharmacological inhibition (PKCδ knockout or rottlerin) was less susceptible to TMT-induced seizures than WT mice. TMT treatment increased glutathione oxidation, lipid peroxidation, protein oxidation, and levels of reactive oxygen species. These effects were more pronounced in the WT mice than in PKCδ knockout mice. In addition, the ability of TMT to induce nuclear translocation of Nrf2, Nrf2 DNA-binding activity, and upregulation of γ-glutamylcysteine ligase was significantly increased in the PKCδ knockout mice and rottlerin (10 or 20 mg/kg, p.o. × 6)-treated WT mice. Furthermore, neuronal degeneration (as shown by nuclear chromatin clumping and TUNEL staining) in WT mice was most pronounced 2 days after TMT. At the same time, TMT-induced inhibition of phosphoinositol 3-kinase (PI3K)/Akt signaling was evident, thereby decreasing phospho-Bad, expression of Bcl-xL and Bcl-2, and the interaction between phospho-Bad and 14-3-3 protein, and increasing Bax expression and caspase-3 cleavage were observed. Rottlerin or PKCδ knockout significantly protected these changes in anti- and pro-apoptotic factors. Importantly, treatment of the PI3K inhibitor LY294002 (0.8 or 1.6 µg, i.c.v.) 4 h before TMT counteracted protective effects (i.e., Nrf-2-dependent glutathione induction and pro-survival phenomenon) of rottlerin. Therefore, our results suggest that down-regulation of PKCδ and up-regulations of Nrf2-dependent glutathione defense mechanism and PI3K/Akt signaling are critical for attenuating TMT neurotoxicity.

Zinc oxide nanoparticles induce lipoxygenase-mediated apoptosis and necrosis in human neuroblastoma SH-SY5Y cells.

Zinc oxide nanoparticles (ZnO NPs) are known to induce oxidative stress and modulate an inflammatory process in various cell types. Although the cytotoxic effects of ZnO NPs in various cell types have been evaluated, few neurotoxic surveys on ZnO NPs as well as rescue studies have been reported. This study was designed to examine the neurotoxic ZnO NP concentration according to exposure time and dose, and the mechanisms that underlie ZnO NP-induced neurotoxicity in the SH-SY5Y human neuroblastoma cell line. A significant reduction in neuronal viability as well as distinct morphological findings resulted from application of 15 µM ZnO NPs. Apoptotic injury-as measured by annexin V and caspase 3/7 activities-was significantly elevated at 12 h and 24 h, but not 6 h, after ZnO NP exposure. However, electron microscopy revealed typical necrotic characteristics, such as swelling or loss of cell organelles and rupture of the cytosolic or nuclear membrane at 12 h and 24 h after ZnO NP exposure. In rescue studies, the lipoxygenase (LOX) inhibitor esculetin attenuated ZnO NP-induced neuronal injury. The elevation of PI3 kinase (PI3K) and p-Akt/Akt activities induced by ZnO NP was significantly decreased by esculetin or LY294002. Allopurinol, N-acetyl-l-cysteine and α-tocopherol protected ZnO NP-induced cytotoxicity. Sodium nitroprusside (SNP)-induced neurotoxicity and ZnO NP-mediated NO overproduction were ameliorated by esculetin. Esculetin reduced the production of reactive oxygen species (ROS) and the depletion of antioxidant enzymes induced by ZnO NPs. The concentration of zinc from the dissolution of ZnO NPs increased in proportion to increases in the ZnO NPs concentration. These results suggest that ZnO NPs induce apoptosis via the PI3K/Akt/caspase-3/7 pathway and necrosis by LOX-mediated ROS production elevation.

Ceruloplasmin is an endogenous protectant against kainate neurotoxicity.

To determine the role of ceruloplasmin (Cp) in epileptic seizures, we used a kainate (KA) seizure animal model and examined hippocampal samples from epileptic patients. Treatment with KA resulted in a time-dependent decrease in Cp protein expression in the hippocampus of rats. Cp-positive cells were colocalized with neurons or reactive astrocytes in KA-treated rats and epileptic patient samples. KA-induced seizures, initial oxidative stress (i.e., hydroxyl radical formation, lipid peroxidation, protein oxidation, and synaptosomal reactive oxygen species), altered iron status (increasing Fe(2+) accumulation and L-ferritin-positive reactive microglial cells and decreasing H-ferritin-positive neurons), and impaired glutathione homeostasis and neurodegeneration (i.e., Fluoro-Nissl and Fluoro-Jade B staining analyses) were more pronounced in Cp antisense oligonucleotide (ASO)- than in Cp sense oligonucleotide-treated rats. Consistently, Cp ASO facilitated KA-induced lactate dehydrogenase (LDH) release, Fe(2+) accumulation, and glutathione loss in neuron-rich and mixed cultures. However, Cp ASO did not alter KA-induced LDH release or Fe(2+) accumulation in the astroglial culture, but did facilitate impairment in glutathione homeostasis in the same culture. Importantly, treatment with human Cp protein resulted in a significant attenuation against these neurotoxicities induced by Cp ASO. Our results suggest that Cp-mediated neuroprotection occurs via the inhibition of seizure-associated oxidative damage (including impairment in glutathione homeostasis), Fe(2+) accumulation, and alterations in ferritin immunoreactivity. Moreover, interactive modulation between neurons and glia was found to be important for Cp upregulation in the attenuation of epileptic damage in both animals and humans.

Ginsenoside Re protects methamphetamine-induced mitochondrial burdens and proapoptosis via genetic inhibition of protein kinase C δ in human neuroblastoma dopaminergic SH-SY5Y cell lines.

Recently, we have demonstrated that ginsenoside Re protects methamphetamine (MA)-induced dopaminergic toxicity in mice via genetic inhibition of PKCδ and attenuation of mitochondrial stress. In addition, we have reported that induction of mitochondrial glutathione peroxidase (GPx) is also important for neuroprotection mediated by ginsenoside Re. To extend our knowledge, we examined the effects of ginsenoside Re against MA toxicity in vitro condition using SH-SY5Y neuroblastoma cells. Treatment with ginsenoside Re resulted in significant attenuations against a decrease in the activity of GPx and an increase in the activity of superoxide dismutase (SOD) in the cytosolic and mitochondrial fraction. The changes in glutathione (GSH) paralleled those in GPx in the same experimental condition. Consistently, ginsenoside Re treatment exhibited significant protections against cytosolic and mitochondrial oxidative damage (i.e. lipid peroxidation and protein oxidation), mitochondrial translocation of PKCδ, mitochondrial dysfunction (mitochondrial transmembrane potential and intra-mitochondrial Ca(2+)), apoptotic events [i.e., cytochrome c release from mitochondria, cleavage of caspase-3 and poly(ADP-ribose)polymerase-1, nuclear condensation, terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL)-positive apoptotic cells], and a reduction in the tyrosine hydroxylase (TH) expression and TH activity induced by MA in SH-SY5Y neuroblastoma cells. These protective effects of ginsenoside Re were comparable to those of PKCδ antisense oligonucleotide (ASO). However, ginsenoside Re did not significantly provide additional protective effects mediated by genetic inhibition of PKCδ. Our results suggest that PKCδ is a specific target for ginsenoside Re-mediated protective activity against MA toxicity in SH-SY5Y neuroblastoma cells.

Ginsenoside Re rescues methamphetamine-induced oxidative damage, mitochondrial dysfunction, microglial activation, and dopaminergic degeneration by inhibiting the protein kinase Cδ gene.

Ginsenoside Re, one of the main constituents of Panax ginseng, possesses novel antioxidant and anti-inflammatory properties. However, the pharmacological mechanism of ginsenoside Re in dopaminergic degeneration remains elusive. We suggested that protein kinase C (PKC) δ mediates methamphetamine (MA)-induced dopaminergic toxicity. Treatment with ginsenoside Re significantly attenuated methamphetamine-induced dopaminergic degeneration in vivo by inhibiting impaired enzymatic antioxidant systems, mitochondrial oxidative stress, mitochondrial translocation of protein kinase Cδ, mitochondrial dysfunction, pro-inflammatory microglial activation, and apoptosis. These protective effects were comparable to those observed with genetic inhibition of PKCδ in PKCδ knockout (-/-) mice and with PKCδ antisense oligonucleotides, and ginsenoside Re did not provide any additional protective effects in the presence of PKCδ inhibition. Our results suggest that PKCδ is a critical target for ginsenoside Re-mediated protective activity in response to dopaminergic degeneration induced by MA.

Melatonin attenuates memory impairment induced by Klotho gene deficiency via interactive signaling between MT2 receptor, ERK, and Nrf2-related antioxidant potential.

BACKGROUND: We demonstrated that oxidative stress plays a crucial role in cognitive impairment in klotho mutant mice, a genetic model of aging. Since down-regulation of melatonin due to aging is well documented, we used this genetic model to determine whether the antioxidant property of melatonin affects memory impairment. METHODS: First, we examined the effects of melatonin on hippocampal oxidative parameters and the glutathione/oxidized glutathione (GSH/GSSG) ratio and memory dysfunction of klotho mutant mice. Second, we investigated whether a specific melatonin receptor is involved in the melatonin-mediated pharmacological response by application with melatonin receptor antagonists. Third, we examined phospho-extracellular-signal-regulated kinase (ERK) expression, nuclear factor erythroid 2-related factor 2 (Nrf2) nuclear translocation, Nrf2 DNA binding activity, and glutamate-cysteine ligase (GCL) mRNA expression. Finally, we examined effects of the ERK inhibitor SL327 in response to antioxidant efficacy and memory enhancement mediated by melatonin. RESULTS: Treatment with melatonin resulted in significant attenuations of oxidative damage, a decrease in the GSH/GSSG ratio, and a significant amelioration of memory impairment in this aging model. These effects of melatonin were significantly counteracted by the selective MT2 receptor antagonist 4-P-PDOT. Importantly, 4-P-PDOT or SL327 also counteracted melatonin-mediated attenuation in response to the decreases in phospho-ERK expression, Nrf2 nuclear translocation, Nrf2 DNA-binding activity, and GCL mRNA expression in the hippocampi of klotho mutant mice. SL327 also counteracted the up-regulation of the GSH/GSSG ratio and the memory enhancement mediated by melatonin in klotho mutant mice. CONCLUSIONS: Melatonin attenuates oxidative stress and the associated memory impairment induced by klotho deficiency via signaling interaction between the MT2 receptor and ERK- and Nrf2-related antioxidant potential.

Platelet-activating factor receptor knockout mice are protected from MPTP-induced dopaminergic degeneration.

Platelet-activating factor (PAF), a potent mediator of inflammatory and immune responses, plays various roles in neuronal functions. However, little is known about the role of PAF/platelet-activating factor receptor (PAF-R) in Parkinson's disease. Treatment with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) resulted in significant increases in PAF species in the striatum of wild-type mice. These increases paralleled PAF-R gene expression in wild-type mice. Although nuclear factor kappa B (NF-κB) DNA-binding activity was increased significantly in MPTP-treated wild-type mice, this increase was not significant in PAF-R antagonist ginkgolide B (GB)-treated mice or PAF-R knockout (PAF-R(-/-)) mice. Pyrrolidine dithiocarbamate (PDTC), an NF-κB inhibitor, significantly ameliorated the dopaminergic deficits induced by MPTP in wild-type mice. MPTP treatment significantly increased oxidative damage, the immunoreactivity of ionized calcium binding adaptor molecule 1 (Iba-1)-positive microglial cells, and microglial differentiation of the M1 type in the striatum of wild-type mice. Consistently, PDTC significantly attenuated MPTP-induced behavioral impairments in wild-type mice. However, dopaminergic deficits, oxidative damage, reactive microglial cells, and behavioral impairments induced by MPTP were not significantly observed in GB-treated mice or PAF-R(-/-) mice. PDTC did not significantly alter the attenuations evident in MPTP-treated PAF-R(-/-) mice, indicating that NF-κB is a critical target for neurotoxic modulation of PAF-R. We propose for the first time that PAF/PAF-R can mediate dopaminergic degeneration via an NF-κB-dependent signaling process.

Esculetin inhibits N-methyl-D-aspartate neurotoxicity via glutathione preservation in primary cortical cultures.

Recently, loss of endogenous glutathione during N-methyl-D-aspartate (NMDA) receptor-mediated excitotoxic injury, and the resultant overproduction of reactive oxygen species (ROS) through an arachidonic acid cascade process in brain, have been implicated in neuronal damage in various neurodegenerative diseases. Glutathione depletion induced by L-buthionine-(S,R)-sulfoximine (BSO), an inhibitor of glutathione synthesis, is known to cause arachidonic acid-mediated excitotoxicity in primary mixed cortical cultures. The aim of this study was to investigate whether esculetin (6,7-dihydroxycoumarin), an inhibitor of lipoxygenase, protects against neurotoxicity induced by NMDA or BSO. We observed that neurotoxicity induced by NMDA but not kainic acid was attenuated by esculetin. At the same concentration (100 µM), esculetin attenuated the (45)Ca(2+) uptake elevation induced by NMDA. Free radical-mediated neuronal injury induced by H(2)O(2) and xanthine/xanthine oxidase was concentration-dependently blocked by esculetin. Esculetin (1-30 µM) dose-dependently inhibited BSO-induced neuronal injury. In addition, arachidonate-induced neurotoxicity was completely blocked by esculetin. BSO also reduced glutathione peroxidase (GPx) activity, but did not change glutathione reductase (GR) activity 24 h after treatment. Esculetin dose-dependently increased GR activity, but did not alter GPx activity. These findings suggest that esculetin can contribute to the rescue of neuronal cells from NMDA neurotoxicity and that this protective effect occurs partly through NMDA receptor modulation and the sparing of glutathione depletion.

Amelioration of experimental autoimmune encephalomyelitis in Lewis rats treated with fucoidan.

We examined whether fucoidan affected the clinical symptoms of experimental autoimmune encephalomyelitis (EAE) in rats. EAE was induced in Lewis rats that were immunized with guinea-pig myelin basic protein (MBP) and complete Freund's adjuvant. Fucoidan (50 mg/kg, daily) was administered to rats with EAE intraperitoneally, either in the EAE induction phase from either 1 day before immunization to day 7 post-immunization (PI), or the effector phase from day 8 to 14 PI, to test which phase of rat EAE is affected by fucoidan treatment.The onset, severity and duration of EAE paralysis in the fucoidan-treated group in the days 8-14 PI-treated rats, but not in days -1-7 PI-treated rats, were significantly delayed, suppressed and reduced, respectively, compared with the vehicle-treated controls. Treatment with fucoidan reduced the encephalitogenic response and TNF-alpha production during EAE. Moreover, the clinical amelioration coincided with decreased infiltration of inflammatory cells in the EAE-affected spinal cord. The ameliorative effect of fucoidan on clinical paralysis in EAE-affected rats may be mediated, in part, by the suppression of the autoreactive T cell response and inflammatory cytokine production.

Potentiation of methamphetamine neurotoxicity by intrastriatal lipopolysaccharide administration.

Accumulated evidence has indicated that neuroinflammation is one of the important etiologic factors of Parkinson's disease (PD). Earlier studies have employed the inflammogen lipopolysaccharide (LPS) to induce inflammation of dopaminergic neurons. Methamphetamine (MA) dopaminergic toxicity similar to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) toxicity is frequently cited as a model of PD. In the present study, we examined whether striatal LPS exposure potentiates MA-induced dopaminergic toxicity. Combined treatment with LPS and MA significantly potentiates behavioral impairment and dopaminergic deficit. However, this combination did not significantly alter the other monoaminergic systems (e.g., serotonin, norepinephrine, and histamine). Consistently, microglial activation, labeled by F4/80 or Iba-1 in the nigrostriatal region was more pronounced with the combined treatment of LPS and MA compared to either treatment alone, but this combination did not significantly alter the microglial activation in other brain regions (e.g., hippocampus, dorsal raphe nuclei, and locus ceruleus). Furthermore, neuroinflammation, oxidative stress, and pro-apoptotic changes in the striatum were more accentuated with combined treatment of LPS and MA compared to either treatment alone. In addition, it is important that cytoplasmic accumulation of alpha-synuclein was observed in the substantia nigra of mice treated with LPS plus MA, and that L-Dopa treatment significantly attenuated behavioral changes and dopaminergic deficits induced by LPS plus MA. These results suggest that combined treatment of LPS with MA is a potential animal model for PD.