Protective Potential of the Glutathione Peroxidase-1 Gene in Abnormal Behaviors Induced by Phencyclidine in Mice

A Kpna1-deficient psychotropic drug-induced schizophrenia model mouse for studying gene-environment interactions

KPNA1 is a mediator of nucleocytoplasmic transport that is abundantly expressed in the mammalian brain and regulates neuronal differentiation and synaptic function. De novo mutations in Kpna1 have been identified using genome-wide association studies in humans with schizophrenia; however, it remains unclear how KPNA1 contributes to schizophrenia pathogenesis. Recent studies have suggested a complex combination of genetic and environmental factors that are closely related to psychiatric disorders. Here, we found that subchronic administration of phencyclidine, a psychotropic drug, induced vulnerability and behavioral abnormalities consistent with the symptoms of schizophrenia in Kpna1-deficient mice. Microarray assessment revealed that the expression levels of dopamine d1/d2 receptors, an RNA editing enzyme, and a cytoplasmic dynein component were significantly altered in the nucleus accumbens brain region in a gene-environment (G × E) interaction-dependent manner. Our findings demonstrate that Kpna1-deficient mice may be useful as a G × E interaction mouse model for psychiatric disorders and for further investigation into the pathogenesis of such diseases and disorders.

Ginsenoside Re attenuates 8-OH-DPAT-induced serotonergic behaviors in mice via interactive modulation between PKCδ gene and Nrf2

It has been recognized that serotonergic blocker showed serious side effects, and that ginsenoside modulated serotonergic system with the safety. However, the effects of ginsenoside on serotonergic impairments remain to be clarified. Thus, we investigated ginsenoside Re (GRe), a major bioactive component in the mountain-cultivated ginseng on (±)-8-hydroxy-dipropylaminotetralin (8-OH-DPAT), a 5-HT_1A receptor agonist. In the present study, we observed that the treatment with GRe resulted in significant inhibition of protein kinase C δ (PKCδ) phosphorylation induced by the 5-HT_1A receptor agonist (±)-8-hydroxy-dipropylaminotetralin (8-OH-DPAT) in the hypothalamus of the wild-type (WT) mice. The inhibition of GRe was comparable with that of the PKCδ inhibitor rottlerin or the 5-HT_1A receptor antagonist WAY100635 (WAY). 8-OH-DPAT-induced significant reduction in nuclear factor erythroid-2-related factor 2 (Nrf2)-related system (i.e., Nrf2 DNA binding activity, γ-glutamylcysteine ligase modifier (GCLm) and γ-glutamylcysteine ligase catalytic (GCLc) mRNA expression, and glutathione (GSH)/oxidized glutathione (GSSG) ratio) was significantly attenuated by GRe, rottlerin, or WAY in WT mice. However, PKCδ gene knockout significantly protected the Nrf2-dependent system from 8-OH-DPAT insult in mice. Increases in 5-hydroxytryptophan (5-HT) turnover rate, overall serotonergic behavioral score, and hypothermia induced by 8-OH-DPAT were significantly attenuated by GRe, rottlerin, or WAY in WT mice. Consistently, PKCδ gene knockout significantly attenuated these parameters in mice. However, GRe or WAY did not provide any additional positive effects on the serotonergic protective potential mediated by PKCδ gene knockout in mice. Therefore, our results suggest that PKCδ is an important mediator for GRe-mediated protective activity against serotonergic impairments/oxidative burden caused by the 5-HT_1A receptor.

Ginsenoside Re mitigates memory impairments in aged GPx-1 KO mice by inhibiting the interplay between PAFR, NFκB, and microgliosis in the hippocampus

Ginsenoside Re (GRe) upregulates anti-aging klotho by mainly upregulating glutathione peroxidase-1 (GPx-1). However, the anti-aging mechanism of GPx-1 remains elusive. Here we investigated whether the GRe-mediated upregulation of GPx-1 modulates oxidative and proinflammatory insults. GPx-1 gene depletion altered redox homeostasis and platelet-activating factor receptor (PAFR) and nuclear factor kappa B (NFκB) expression, whereas the genetic overexpression of GPx-1 or GRe mitigated this phenomenon in aged mice. Importantly, the NFκB inhibitor pyrrolidine dithiocarbamate (PDTC) did not affect PAFR expression, while PAFR inhibition (i.e., PAFR knockout or ginkgolide B) significantly attenuated NFκB nuclear translocation, suggesting that PAFR could be an upstream molecule for NFκB activation. Iba-1-labeled microgliosis was more underlined in aged GPx-1 KO than in aged WT mice. Triple-labeling immunocytochemistry showed that PAFR and NFκB immunoreactivities were co-localized in Iba-1-positive populations in aged mice, indicating that microglia released these proteins. GRe inhibited triple-labeled immunoreactivity. The microglial inhibitor minocycline attenuated aging-related reduction in phospho-ERK. The effect of minocycline was comparable with that of GRe. GRe, ginkgolide B, PDTC, or minocycline also attenuated aging-evoked memory impairments. Therefore, GRe ameliorated aging-associated memory impairments in the absence of GPx-1 by inactivating oxidative insult, PAFR, NFkB, and microgliosis.

The critical role of nanoparticle sizes in the interactions between gold nanoparticles and ABC transporters in zebrafish embryos

Despite the increasing evidences for adenosine triphosphate-binding cassette (ABC transporters)-mediated efflux of nanoparticles, the universality of these phenomena and the determining factors for the process remained to be clarified. This paper aimed to systemically investigate the role of nanoparticle size in the interactions between adenosine triphosphate-binding cassette (ABC transporters) and gold nanoparticles (AuNPs, 3 nm, 19 nm, and 84 nm, named as Au-3, Au-19, and Au-84) in zebrafish embryos. The results showed that all the three AuNPs induced significant toxicity as reflected by delayed hatching of embryos, decreased glutathione (GSH) contents, and increased reactive oxygen species (ROS) levels. Under the hindrance of embryo chorions, smaller AuNPs could more easily accumulate in the embryos, causing higher toxicity. Addition of transporter inhibitors enhanced the accumulation and toxicity of Au-3 and Au-19, and these nanoparticles induced the expressions of abcc2 and abcb4, indicating a fact that Au-3 and Au-19 were the potential substrates of ABC transporters, but these phenomena were barely found for Au-84. On the contrary, Au-84 suppressed the gene expressions of various ABC transporters like abcc1, abcg5, and abcg8. With specific suppressors, transcription factors like nuclear factor-erythroid 2-related factor-2 (Nrf2) and pregnane X receptor (Pxr) were found to be important in the induction of ABC transporters by AuNPs. After all, these results revealed a vital role of nanoparticle sizes in the interactions between ABC transporters and AuNPs in zebrafish embryos, and the critical size could be around 19 nm. Such information would be beneficial in assessing the environmental risk of nanoparticles, as well as their interactions with other chemical toxicants.

BKM120 alters the migration of doublecortin-positive cells in the dentate gyrus of mice

BKM120 is an inhibitor of class I phosphoinositide 3-kinases and its anti-cancer effects have been demonstrated in various solid cancer models. BKM120 is highly brain permeable and has been reported to induce mood disturbances in clinical trials. Therefore, we examined whether BKM120 produces anxiety- and depression-like behaviors in mice, as with patients receiving BKM120 in clinical trials. In this study, repeated BKM120 treatment (2.0 or 5.0mg/kg, i.p., five times at 12-h interval) significantly induced anxiety- and depression-like behaviors in mice. Although abnormal changes in hippocampal neurogenesis have been suggested to, at least in part, associated with the pathogenesis of depression and anxiety, BKM120 did not affect the incorporation of 5-bromo-2'-deoxyuridine or the expression of doublecortin (DCX); however, it significantly enhanced the radial migration of DCX-positive cells in the dentate gyrus. BKM120-induced changes in migration were not accompanied by obvious neuronal damage in the hippocampus. Importantly, BKM120-induced anxiety- and depression-like behaviors were positively correlated with the extent of DCX-positive cell migration. Concomitantly, p-Akt expression was significantly decreased in the dentate gyrus. Moreover, the expression of p-c-Jun N-terminal kinase (JNK), p-DCX, and Ras homolog family member A (RhoA)-GTP decreased significantly, particularly in aberrantly migrated DCX-positive cells. Together, the results suggest that repeated BKM120 treatment enhances the radial migration of DCX-positive cells and induces anxiety- and depression-like behaviors by regulating the activity of Akt, JNK, DCX, and RhoA in the dentate gyrus. It also suggests that the altered migration of adult-born neurons in the dentate gyrus plays a role in mood disturbances.

Ouabain inhibitor rostafuroxin attenuates dextromethorphan-induced manic potential

Dextromethorphan (DM) abuse produces mania-like symptoms in humans. ERK/Akt signaling activation involved in manic potential can be attenuated by the inhibition of ouabain-like cardiac steroids. In this study, increased phosphorylations of ERK/Akt and hyperlocomotion induced by DM (30 mg/kg, i.p./day × 7) were significantly protected by the ouabain inhibitor rostafuroxin (ROSTA), suggesting that DM induces the manic potential. ROSTA significantly attenuated DM-induced protein kinase C δ (PKCδ) phosphorylation, GluN2B (i.e., MDA receptor subunit) expression, and phospho-PKCδ/GluN2B interaction. DM instantly upregulated the nuclear factor erythroid-2-related factor 2 (Nrf2)-dependent system. However, DM reduced Nrf2 nuclear translocation, Nrf2 DNA binding activity, γ-glutamylcysteine mRNA expression, and subsequent GSH/GSSG level and enhanced oxidative parameters following 1-h of administration. ROSTA, PKCδ inhibitor rottlerin, and GluN2B inhibitor traxoprodil significantly attenuated DM-induced alterations in Nrf2-related redox parameters and locomotor activity induced by DM in wild-type mice. Importantly, in PKCδ knockout mice, DM failed to alter the above parameters. Further, ROSTA and traxoprodil also failed to enhance PKCδ depletion effect, suggesting that PKCδ is a critical target for the anti-manic potential of ROSTA or GluN2B antagonism. Our results suggest that ROSTA inhibits DM-induced manic potential by attenuating ERK/Akt activation, GluN2B/PKCδ signalings, and Nrf2-dependent system.

Andrographolide improves PCP-induced schizophrenia-like behaviors through blocking interaction between NRF2 and KEAP1

Schizophrenia is one of the foremost psychological illness around the world, and recent evidence shows that inflammation and oxidative stress may play a critical role in the etiology of schizophrenia. Andrographolide is a diterpenoid lactone from Andrographis paniculate, which has shown anti-inflammation and anti-oxidative effects. In this study, we explored whether andrographolide can improve schizophrenia-like behaviors through its inhibition of inflammation and oxidative stress in Phencyclidine (PCP)-induced mouse model of schizophrenia. We found that abnormal behavioral including locomotor activity, forced swimming and novel object recognition were ameliorated following andrographolide administration (5 mg/kg and 10 mg/kg). Andrographolide inhibited PCP-induced production of inflammatory cytokines, decreased p-p65, p-IκBα, p-p38 and p-ERK1/2 in the prefrontal cortex. Andrographolide significantly declined the level of MDA and GSH, as well as elevated the activity of SOD, CAT and GCH-px. In addition, andrographolide increased expression of NRF-2, HO-1 and NQO-1, promoted nuclear translocation of NRF-2 through blocking the interaction between NRF-2 and KEAP1, which may be associated with directly binding to NRF-2. Furthermore, antioxidative effects and anti-schizophrenia-like behaviors of andrographolide were compromised by the application of NRF-2 inhibitor ML385. In conclusion, these results suggested that andrographolide improved oxidative stress and schizophrenia-like behaviors induced by PCP through increasing NRF-2 pathway.

GPx-1-encoded adenoviral vector attenuates dopaminergic impairments induced by methamphetamine in GPx-1 knockout mice through modulation of NF-κB transcription factor

We suggested that selenium-dependent glutathione peroxidase (GPx) plays a protective role against methamphetamine (MA)-induced dopaminergic toxicity. We focused on GPx-1, a major selenium-dependent enzyme and constructed a GPx-1 gene-encoded adenoviral vector (Ad-GPx-1) to delineate the role of GPx-1 in MA-induced dopaminergic neurotoxicity. Exposure to Ad-GPx-1 significantly induced GPx activity and GPx-1 protein levels in GPx-1-knockout (GPx-1-KO) mice. MA-induced dopaminergic impairments [i.e., hyperthermia; increased nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) DNA-binding activity; and decreased dopamine levels, TH activity, and behavioral activity] were more pronounced in GPx-1-KO mice than in WT mice. In contrast, exposure to Ad-GPx-1 significantly attenuated MA-induced dopaminergic loss in GPx-1-KO mice. The protective effect exerted by Ad-GPx-1 was comparable to that exerted by pyrrolidine dithiocarbamate (PDTC), an NF-κB inhibitor against MA insult. Consistently, GPx-1 overexpression significantly attenuated MA dopaminergic toxicity in mice. PDTC did not significantly impact the protective effect of GPx-1 overexpression, suggesting that interaction between NF-κB and GPx-1 is critical for dopaminergic protection. Thus, NF-κB is a potential therapeutic target for GPx-1-mediated dopaminergic protective activity. This study for the first time demonstrated that Ad-GPx-1 rescued dopaminergic toxicity in vivo following MA insult. Furthermore, GPx-1-associated therapeutic interventions may be important against dopaminergic toxicity.

Involvement of ABC transporters in the detoxification of non-substrate nanoparticles in lung and cervical cancer cells

This paper aimed to systemically investigate the role of adenosine triphosphate-binding cassette (ABC transporters) in the detoxification of non-substrate nanoparticles including titanium dioxide (n-TiO₂, 5-10 nm) and gold (AuNPs, 3 nm, 15 nm, and 80 nm, named as Au-3, Au-15 and Au-80) in human lung cancer (A549) and human cervical cancer (HeLa) cells. All these nanoparticles were of larger hydrophilic diameters than the channel sizes of ABC transporters, thus should not be the substrates of membrane proteins. After 24-h treatment, they induced significant cytotoxicity as reflected by the reduction in cell viability and glutathione (GSH) contents, as well as the increase in reactive oxygen species (ROS) level. At median-lethal concentrations (10 mg/L n-TiO₂, 2 mg/L Au-3, 5 mg/L Au-15, and 10 mg/L Au-80 for A549 cells; 20 mg/L n-TiO₂, 2 mg/L Au-3, 5 mg/L Au-15, and 10 mg/L Au-80 for Hela cells), all the nanoparticles significantly induced the gene expressions and activities of ABC transporters including P-glycoprotein (PGP) and multidrug resistance associated protein 1 (MRP1). Addition of transporter inhibitors enhanced the ROS levels produced by nanoparticles, but didn't alter their death-inducing effects and intracellular accumulations. With specific suppressors, transcription factors like nuclear factor-erythroid 2-related factor-2 (NRF2) and pregnane X receptor (PXR) were proved to be important in the induction of ABC transporters by nanoparticles. After all, this paper revealed a damage-dependent modulation of ABC transporters by non-substrate nanoparticles. The up-regulated ABC transporters could help in reducing the oxidative stress produced by nanoparticles. Such information should be useful in assessing the environmental risk of nanoparticles, as well as their interactions with other chemical toxicants or drugs.

Glutathione peroxidase-1 and neuromodulation: Novel potentials of an old enzyme

Glutathione peroxidase (GPx) acts in co-ordination with other signaling molecules to exert its own antioxidant role. We have demonstrated the protective effects of GPx,/GPx-1, a selenium-dependent enzyme, on various neurodegenerative disorders (i.e., Parkinson's disease, Alzheimer's disease, cerebral ischemia, and convulsive disorders). In addition, we summarized the recent findings indicating that GPx-1 might play a role as a neuromodulator in neuropsychiatric conditions, such as, stress, bipolar disorder, schizophrenia, and drug intoxication. In this review, we attempted to highlight the mechanistic scenarios mediated by the GPx/GPx-1 gene in impacting these neurodegenerative and neuropsychiatric disorders, and hope to provide new insights on the therapeutic interventions against these disorders.

An adenoviral vector encoded with the GPx-1 gene attenuates memory impairments induced by β-amyloid (1-42) in GPx-1 KO mice via activation of M1 mAChR-mediated signalling

In the present study, we examined whether glutathione peroxidase-1 (GPx-1), a major H₂O₂ scavenger in the brain, affects memory deficits induced by Aβ (1-42) in mice. Treatment with 400 pmol/5 μl Aβ (1-42) (i.c.v.) resulted in a reduction of GPx-1 expression in wild-type (WT) mice. An Aβ (1-42)-induced reduction in acetylcholine (ACh) level was observed in the hippocampus. Treatment with Aβ (1-42) consistently resulted in reduced expression and activity of choline acetyltransferase (ChAT) and in an increase in expression and activity of acetylcholinesterase (AChE). Upon examining each of the muscarinic acetylcholine receptors (mAChRs) and nicotinic AChRs, we noted that Aβ (1-42) treatment selectively reduced the levels of M1 mAChR. In addition, Aβ (1-42) induced a significant reduction in phospho-cAMP response element-binding protein (p-CREB) and brain-derived neurotrophic factor (BDNF) expression. The cholinergic impairments induced by Aβ (1-42) were more pronounced in GPx-1 knockout mice than in WT mice. Importantly, an adenoviral vector encoded with the GPx-1 gene (Ad-GPx-1) significantly rescued Aβ (1-42)-induced cholinergic impairments in GPx-1 knockout mice. In addition, M1 mAChR antagonist dicyclomine significantly counteracted Ad-GPx-1-mediated increases in p-CREB and BDNF expression, as well as memory-enhancing effects in GPx-1 knockout mice, thus indicating that M1 mAChR might be a critical mediator for the rescue effects of Ad-GPx-1. Combined, our results suggest that GPx-1 gene protected against Aβ (1-42)-induced memory impairments via activation of M1 mAChR-dependent CREB/BDNF signalling.

Glutathione peroxidase-1 knockout potentiates behavioral sensitization induced by cocaine in mice via σ-1 receptor-mediated ERK signaling: A comparison with the case of glutathione peroxidase-1 overexpressing transgenic mice

We demonstrated that the gene of glutathione peroxidase-1 (GPx-1), a major antioxidant enzyme, is a potential protectant against the neurotoxicity and conditioned place preference induced by cocaine. Because the sigma (σ)-1 receptor is implicated in cocaine-induced drug dependence, we investigated whether the GPx-1 gene modulates the σ-1 receptor in the behavioral sensitization induced by cocaine. Cocaine-induced behavioral sensitization was more pronounced in GPx-1 knockout (KO) than wild-type (WT) mice and was less pronounced in GPx-1 overexpressing transgenic (GPx-1 TG) than non-TG mice. Cocaine treatment significantly enhanced the oxidative burden and reduced the GSH levels in the striatum of WT, GPx-1 KO, and non-TG mice but not in that of GPx-1 TG mice. In addition, cocaine significantly increased the nuclear translocation, its DNA binding activity of nuclear factor erythroid-2-related factor 2 (Nrf2) as well as the mRNA expression of γ-glutamylcysteine (GCL). The genetic depletion of GPx-1 inhibited the Nrf2-related glutathione system, whereas the genetic overexpression of GPx-1 activated this system against behavioral sensitization. BD1047, a σ-1 receptor antagonist, and U0126, an ERK inhibitor significantly induced the Nrf2-related antioxidant potential against behavioral sensitization. Unlike BD1047, U0126 did not affect the cocaine-induced σ-1 receptor immunoreactivity, suggesting that the σ-1 receptor is an upstream molecule for ERK signaling. Importantly, BD1047 and U0126 failed to affect the σ-1 receptor immunoreactivity and ERK phosphorylation induced by cocaine in GPx-1 TG mice. Our results suggest that GPx-1 is a critical mediator for the attenuation of cocaine-induced behavioral sensitization via modulating σ-1 receptor-mediated ERK activation by the induction of the Nrf2-related system.

Glutathione Peroxidase-1 Knockout Facilitates Memory Impairment Induced by β-Amyloid (1-42) in Mice via Inhibition of PKC βII-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 (Aβ) (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 Aβ (1-42)-induced changes in PKC and ERK levels. We observed that Aβ (1-42) treatment (400 pmol, i.c.v.) significantly decreased PKC βII expression in the hippocampus of mice. Aβ (1-42)-induced neurotoxic changes [i.e., oxidative stress (i.e., reactive oxygen species, 4-hydroxy-2-noneal, and protein carbonyl), reduced PKC βII 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 Aβ (1-42) in GPx-1 knockout mice. Treatment with ERK inhibitor U0126 did not significantly change Adv-GPx-1-mediated attenuation in PKC βII expression. In contrast, treatment with PKC inhibitor chelerythrine (CHE) reversed Adv-GPx-1-mediated attenuation in ERK phosphorylation, suggesting that PKC βII-mediated ERK signaling is important for Adv-GPx-1-mediated potentials against Aβ (1-42) insult. Our results suggest that treatment with the antioxidant gene GPx-1 rescues Aβ (1-42)-induced memory impairment via activating PKC βII-mediated ERK signaling.

Oxidation-reduction mechanisms in psychiatric disorders: A novel target for pharmacological intervention

While neurotransmitter dysfunction represents a key component in mental illnesses, there is now a wide agreement for a central pathophysiological hub that includes hormones, neuroinflammation, redox mechanisms as well as oxidative stress. With respect to oxidation-reduction (redox) mechanisms, preclinical and clinical evidence suggests that an imbalance in the pro/anti-oxidative homeostasis toward the increased production of substances with oxidizing potential may contribute to the etiology and manifestation of different psychiatric disorders. The substantial and continous demand for energy renders the brain highly susceptible to disturbances in its energy supply, especially following exposure to stressful events, which may lead to overproduction of reactive oxygen and nitrogen species under conditions of perturbed antioxidant defenses. This will eventually induce different molecular alterations, including extensive protein and lipid peroxidation, increased blood-brain barrier permeability and neuroinflammation, which may contribute to the changes in brain function and morphology observed in mental illnesses. This view may also reconcile different key concepts for psychiatric disorders, such as the neurodevelopmental origin of these diseases, as well as the vulnerability of selective cellular populations that are critical for specific functional abnormalities. The possibility to pharmacologically modulate the redox system is receiving increasing interest as a novel therapeutic strategy to counteract the detrimental effects of the unbalance in brain oxidative mechanisms. This review will describe the main mechanisms and mediators of the redox system and will examine the alterations of oxidative stress found in animal models of psychiatric disorders as well as in patients suffering from mental illnesses, such as schizophrenia and major depressive disorder. In addition, it will discuss studies that examined the effects of psychotropic drugs, including antipsychotics and antidepressants, on the oxidative balance as well as studies that investigated the effectiveness of a direct modulation of oxidative mechanisms in counteracting the behavioral and functional alterations associated with psychiatric disorders, which supports the promising role of the redox system as a novel therapeutic target for the improved treatment of brain disorders.

Far-infrared Ray-mediated Antioxidant Potentials are Important for Attenuating Psychotoxic Disorders

Far-infrared ray (FIR) is an electromagnetic wave that produces various health benefits against pathophysiological conditions, such as diabetes mellitus, renocardiovascular disorders, stress, and depression etc. However, the therapeutic ap-plication on the FIR-mediated protective potentials remains to be further extended. To achieve better understanding on FIR-mediated therapeutic potentials, we summarized additional findings in the present study that exposure to FIR ameliorates stressful condition, memory impairments, drug dependence, and mitochondrial dysfunction in the central nervous system. In this review, we underlined that FIR requires modulations of janus kinase 2 / signal transducer and activator of transcription 3 (JAK2/STAT3), nuclear factor E2-related factor 2 (Nrf-2), muscarinic M1 acetylcholine receptor (M1 mAChR), dopamine D1 receptor, protein kinase C δ gene, and glutathione peroxidase-1 gene for exerting the protective potentials in response to neuropsychotoxic conditions

Indoleamine-2,3-dioxygenase-1 is a molecular target for the protective activity of mood stabilizers against mania-like behavior induced by d-amphetamine

It is recognized that d-amphetamine (AMPH)-induced hyperactivity is thought to be a valid animal model of mania. In the present study, we investigated whether a proinflammatory oxidative gene indoleamine-2,3-dioxygenase (IDO) is involved in AMPH-induced mitochondrial burden, and whether mood stabilizers (i.e., lithium and valproate) modulate IDO to protect against AMPH-induced mania-like behaviors. AMPH-induced IDO-1 expression was significantly greater than IDO-2 expression in the prefrontal cortex of wild type mice. IDO-1 expression was more pronounced in the mitochondria than in the cytosol. AMPH treatment activated intra-mitochondrial Ca²⁺ accumulation and mitochondrial oxidative burden, while inhibited mitochondrial membrane potential and activity of the mitochondrial complex (I > II), mitochondrial glutathione peroxidase, and superoxide dismutase, indicating that mitochondrial burden might be contributable to mania-like behaviors induced by AMPH. The behaviors were significantly attenuated by lithium, valproate, or IDO-1 knockout, but not in IDO-2 knockout mice. Lithium, valproate administration, or IDO-1 knockout significantly attenuated mitochondrial burden. Neither lithium nor valproate produced additive effects above the protective effects observed in IDO-1 KO in mice. Collectively, our results suggest that mood stabilizers attenuate AMPH-induced mania-like behaviors via attenuation of IDO-1-dependent mitochondrial stress, highlighting IDO-1 as a novel molecular target for the protective potential of mood stabilizers.

Selenoprotein W deficiency does not affect oxidative stress and insulin sensitivity in the skeletal muscle of high-fat diet-fed obese mice

Selenoprotein W (SelW) is a selenium-containing protein with a redox motif found abundantly in the skeletal muscle of rodents. Previous in vitro studies suggest that SelW plays an antioxidant role; however, relatively few in vivo studies have addressed the antioxidant role of SelW. Since oxidative stress is a causative factor for the development of insulin resistance in obese subjects, we hypothesized that if SelW plays a role as an antioxidant, SelW deficiency could aggravate the oxidative stress and insulin resistance caused by a high-fat diet. SelW deficiency did not affect insulin sensitivity and H₂O₂ levels in the skeletal muscle of control diet-fed mice. SelW levels in the skeletal muscle were decreased by high-fat diet feeding for 12 wk. High-fat diet induced obesity and insulin resistance and increased the levels of H₂O₂ and oxidative stress makers, which were not affected by SelW deficiency. High-fat diet feeding increased the expression of antioxidant enzymes; however, SelW deficiency did not affect the expression levels of antioxidants. These results suggest that SelW does not play a protective role against oxidative stress and insulin resistance in the skeletal muscle of high-fat diet-fed obese mice.

Glutathione peroxidase-1 gene rescues cocaine-induced conditioned place preference in mice by inhibiting σ-1 receptor expression

The aim of this study was to investigate whether the glutathione peroxidase-1 gene (GPx-1) affects cocaine-induced conditioned place preference (CPP) using a mouse model. Cocaine-induced CPP was accompanied by an increase in the level of σ-1 receptor in the nucleus accumbens (NAc). This phenomenon was more pronounced in the GPx-1 gene knockout (GPx-1 KO) than in wild type (WT) mice. In contrast, the CPP and expression of σ-1 receptor were much less pronounced in GPx-1-overexpressing transgenic (GPx-1 TG) mice than non-transgenic (non-TG) mice. Treatment of the mice with BD1047, a σ-1 receptor antagonist, significantly attenuated both cocaine-induced CPP and c-Fos-immunoreactivity (c-Fos-IR) in WT and GPx-1 KO mice, although the effects were more evident in the latter group. Despite the protective effects of BD1047 on cocaine-induced CPP and c-Fos in non-TG mice, there were no additional protective effects in cocaine-treated GPx-1 TG mice, indicating that the σ-1 receptor is a critical target for GPx-1-mediated psychoprotective activity. Overall, our results suggest that GPx-1 attenuates cocaine-induced CPP via inhibition of σ-1 receptor expression.

Clozapine attenuates mitochondrial burdens and abnormal behaviors elicited by phencyclidine in mice via inhibition of p47 phox; Possible involvements of phosphoinositide 3-kinase/Akt signaling

BACKGROUND

Oxidative stress and mitochondrial dysfunction have been implicated in the pathophysiology of schizophrenia.

AIMS

We investigated whether antipsychotic clozapine modulates nicotinamide adenine dinucleotide phosphate oxidase and mitochondrial burdens induced by phencyclidine in mice.

METHODS

We examined the effect of clozapine on nicotinamide adenine dinucleotide phosphate oxidase activation, mitochondrial burdens (i.e. oxidative stress and mitochondrial dysfunction), and activities of enzymatic antioxidant in the prefrontal cortex, and subsequent abnormal behaviors induced by repeated treatment with phencyclidine. p47 ^phox Knockout mice and LY294002, a phosphoinositide 3-kinase inhibitor, were employed to elucidate the pharmacological mechanism of clozapine.

RESULTS

Phencyclidine treatment resulted in an early increase nicotinamide adenine dinucleotide phosphate oxidase activity, membrane translocation of p47 ^phox, interaction between p-Akt and p47 ^phox, and mitochondrial burdens in wild-type mice. Although these increases returned to near control level four days post-phencyclidine, mitochondrial superoxide dismutase and glutathione peroxidase activities were decreased at that time. Clozapine, LY294002, or p47 ^phox knockout significantly ameliorated social withdrawal and recognition memory deficits produced by phencyclidine. Importantly, LY294002 did not significantly alter the effects of clozapine against abnormal behaviors and the interaction between p-Akt and p47 ^phox induced by phencyclidine. Furthermore, neither LY294002 nor clozapine exhibited any additive effects to the protection afforded by p47 ^phox knockout against phencyclidine insult.

CONCLUSION

Our results suggest that p47 ^phox gene mediates phencyclidine-induced mitochondrial burdens and abnormal behaviors, and that the interactive modulation between p47 ^phox and phosphoinositide 3-kinase/Akt is important for the understanding on the pharmacological mechanism of clozapine.

5-HT1A receptor agonist 8-OH-DPAT induces serotonergic behaviors in mice via interaction between PKCδ and p47phox

Serotonin syndrome is an adverse reaction due to increased serotonin (5-hydroxytryptophan: 5-HT) concentrations in the central nervous system (CNS). The full 5-HT_1A receptor (5-HT_1AR) agonist (±)-8-hydroxy-dipropylaminotetralin (8-OH-DPAT) has been recognized to elicit traditional serotonergic behaviors. Treatment with 8-OH-DPAT selectively increased PKCδ expression out of PKC isoforms and 5-HT turnover rate in the hypothalamus of wild-type mice. Treatment with 8-OH-DPAT resulted in oxidative burdens, co-immunoprecipitation of 5-HT_1AR and PKCδ, and phosphorylation and membrane translocation of p47phox. Importantly, p47phox also interacted with 5-HT_1AR or PKCδ in the presence of 8-OH-DPAT. Consistently, the interaction and oxidative burdens were attenuated by 5-HT_1AR antagonism (i.e., WAY100635), PKCδ inhibition (i.e., rottlerin and genetic depletion of PKCδ), or NADPH oxidase/p47phox inhibition (i.e., apocynin and genetic depletion of p47phox). However, WAY100635, apocynin, or rottlerin did not exhibit any additive effects against the protective effect by inhibition of PKCδ or p47phox. Furthermore, apocynin, rottlerin, or WAY100635 also significantly protected from pro-inflammatory/pro-apoptotic changes induced by 8-OH-DPAT. Therefore, we suggest that 8-OH-DPAT-induced serotonergic behaviors requires oxidative stress, pro-inflammatory, and pro-apoptotic changes, that PKCδ or p47phox mediates the serotonergic behaviors induced by 8-OH-DPAT, and that the inhibition of PKCδ-dependent p47phox activation is critical for protecting against serotonergic behaviors.

Vitamin A pretreatment protects NO-induced bovine mammary epithelial cells from oxidative stress by modulating Nrf2 and NF-κB signaling pathways

It is known that physiological overproduction of nitric oxide (NO) contributes to oxidative stress and inflammation. Our published studies indicated that vitamin A (VA) reduces NO-induced oxidative stress in bovine mammary epithelial cells (BMECs) by increasing antioxidant enzyme activities. However, the precise mechanism is unclear. The present study was conducted to examine the protective effects of VA on NO-induced damage to BMECs in vitro using diethylenetriamine nitric oxide (DETA-NO) as the NO donor and to explore the intracellular signaling mechanisms of VA that involve nuclear factor erythroid 2-related factor (Nrf2) and nuclear factor kappa-B (NF-κB). Subconfluent BMECs were divided into 10 treatment groups with 6 replicates per treatment and were cultured with dimethyl sulfoxide (DMSO, vehicle negative control) or 0, 0.05, 0.1, 0.2, 0.5, 1, 2, 3, or 4 μg/mL of VA for 24 h and then incubated in the absence or presence of DETA-NO (1,000 μmol/liter) and VA for an additional 6 h. The results showed that exposure to DETA alone decreased cell proliferation compared with the negative control. Pretreatment with VA promoted the proliferation of BMECs, increased the activities of antioxidative enzymes including selenoprotein glutathione peroxidase (GPx) and thioredoxin reductase (TrxR) and their gene and protein expression but decreased NO and interleukin 1 (IL-1) contents in a quadratic manner (P < 0.05). In addition, the expression of mRNA and protein of factors that are related to NF-κB or Nrf2 signaling pathways in BMECs were regulated by VA in a quadratic dose-dependent manner; VA at a concentration of 1 μg/mL exhibited the strongest effect. Together, these results suggest that VA promotes antioxidant functions of BMECs by regulating the synthesis of selenoproteins including GPx and TrxR and by reducing concentrations of IL-1 and NO in vitro by modulating Nrf2 and NF-κB signaling pathways.

Glutathione peroxidase-1 overexpressing transgenic mice are protected from neurotoxicity induced by microcystin-leucine-arginine

Although it has been well-recognized that microcystin-leucine-arginine (MCLR), the most common form of microcystins, induces neurotoxicity, little is currently known about the underlying mechanism for this neurotoxicity. Here, we found that MCLR (10 ng/μL/mouse, i.c.v.) induces significant neuronal loss in the hippocampus of mice. MCLR-induced neurotoxicity was accompanied by oxidative stress, as shown by a significant increase in the level of 4-hydroxynonenal, protein carbonyl, and reactive oxygen species (ROS). Superoxide dismutase-1 (SOD-1) activity was significantly increased, but glutathione peroxidase (GPx) level was significantly decreased following MCLR insult. In addition, MCLR significantly inhibited GSH/GSSG ratio, and significantly induced NFκB DNA binding activity. Because reduced activity of GPx appeared to be critical for the imbalance between activities of SODs and GPx, we utilized GPx-1 overexpressing transgenic mice to ascertain the role of GPx-1 in this neurotoxicity. Genetic overexpression of GPx-1 or NFκB inhibitor pyrrolidine dithiocarbamate (PDTC) significantly attenuated MCLR-induced hippocampal neuronal loss in mice. However, PDTC did not exert any additive effect on neuroprotection mediated by GPx-1 overexpression, indicating that NFκB is a neurotoxic target of MCLR. Combined, these results suggest that MCLR-induced neurotoxicity requires oxidative stress associated with failure in compensatory induction of GPx, possibly through activation of the transcription factor NFκB.

Procyanidin B2 mitigates behavioral impairment and protects myelin integrity in cuprizone-induced schizophrenia in mice

Numerous studies have suggested that neuropathological changes in schizophrenia may be related to damage to white matter or demyelination. Procyanidin B2, which is a constituent of many fruits such as grapes and strawberries, has various biological activities such as anti-inflammatory and anti-tumor activity, as has been reported. This study aimed to estimate the effects of procyanidin B2 on behavioral impairment and the protection of myelin integrity in a cuprizone-induced schizophrenia model. Mice were exposed to cuprizone (0.2% w/w in chow) for five weeks to induce schizophrenia-like behavioral changes and demyelination. Procyanidin B2 (20 or 100 mg kg⁻¹ day⁻¹) or vehicle was administered orally to mice after withdrawal from cuprizone. Behavioral impairment was detected with an open-field test, a rotarod test and a Morris water maze. Myelin integrity was assessed using LFB staining and MBP expression, including immunofluorescence and western blotting. In addition, enhancements in the expression of HO-1 and NQO1 suggested that procyanidin B2 may regulate oxidative homeostasis via promoting the translation of Nrf2 to the nucleus. Data indicated that procyanidin B2 could mitigate behavioral impairment and protect myelin integrity in the cuprizone-induced model via regulating oxidative stress by activating Nrf2 signaling.

Numerous studies have suggested that neuropathological changes in schizophrenia may be related to damage to white matter or demyelination.

Genetic overexpression of glutathione peroxidase-1 attenuates microcystin-leucine-arginine-induced memory impairment in mice

Microcystin-leucine-arginine (MCLR) is the most common form of microcystins, which are environmental toxins produced by cyanobacteria, and its hepatotoxicity has been well-documented. However, the neurotoxic potential of MCLR remains to be further elucidated. In the present study, we investigated whether intracerebroventricular (i.c.v.) infusion of MCLR induces mortality and neuronal loss in the hippocampus of mice. Because we found that MCLR impairs memory function in the hippocampus at a low dose (4 ng/μl/mouse, i.c.v.) without a significant neuronal loss, we focused on this dose for further analyses. Results showed that MCLR (4 ng/μl/mouse, i.c.v.) significantly increased oxidative stress (i.e., malondialdehyde, protein carbonyl, and synaptosomal ROS) in the hippocampus. In addition, MCLR significantly increased superoxide dismutase (SOD) activity without corresponding induction of glutathione peroxidase (GPx) activity, and thus led to significant decrease in the ratio of GPx/SODs activity. The GSH/GSSG ratio was also significantly reduced after MCLR treatment. GPx-1 overexpressing transgenic mice (GPx-1 Tg) were significantly protected from MCLR-induced memory impairment and oxidative stress. The DNA binding activity of nuclear factor erythroid-derived 2-related factor 2 (Nrf2) in these mice was significantly enhanced, and the ratios of GPx/SODs activity and GSH/GSSG returned to near control levels in the hippocampus. Importantly, memory function exhibited a significant positive correlation with the ratios of GPx/SODs activity and GSH/GSSG in the hippocampus of MCLR-treated non-transgenic (non-Tg)- and GPx-1 Tg-mice. Combined, our results suggest that MCLR induces oxidative stress and memory impairment without significant neuronal loss, and that GPx-1 gene constitutes an important protectant against MCLR-induced memory impairment and oxidative stress via maintaining antioxidant defense system homeostasis, possibly through the induction of Nrf2 transcription factor.

PKCδ Knockout Mice Are Protected from Dextromethorphan-Induced Serotonergic Behaviors in Mice: Involvements of Downregulation of 5-HT1A Receptor and Upregulation of Nrf2-Dependent GSH Synthesis

We investigated whether a specific serotonin (5-HT) receptor-mediated mechanism was involved in dextromethorphan (DM)-induced serotonergic behaviors. We firstly observed that the activation of 5-HT_1A receptor, but not 5-HT_2A receptor, contributed to DM-induced serotonergic behaviors in mice. We aimed to determine whether the upregulation of 5-HT_1A receptor induced by DM facilitates the specific induction of certain PKC isoform, because previous reports suggested that 5-HT_1A receptor activates protein kinase C (PKC). A high dose of DM (80 mg/kg, i.p.) induced a selective induction of PKCδ out of PKCα, PKCβI, PKCβII, PKCξ, and PKCδ in the hypothalamus of wild-type (WT) mice. More importantly, 5-HT_1A receptor co-immunoprecipitated PKCδ in the presence of DM. Consistently, rottlerin, a pharmacological inhibitor of PKCδ, or PKCδ knockout significantly protected against increases in 5-HT_1A receptor gene expression, 5-HT turnover rate, and serotonergic behaviors induced by DM. Treatment with DM resulted in an initial increase in nuclear factor erythroid-2-related factor 2 (Nrf2) nuclear translocation and DNA-binding activity, γ-glutamylcysteine (GCL) mRNA expression, and glutathione (GSH) level. This compensative induction was further potentiated by rottlerin or PKCδ knockout. However, GCL mRNA and GSH/GSSG levels were decreased 6 and 12 h post-DM. These decreases were attenuated by PKCδ inhibition. Our results suggest that interaction between 5-HT_1A receptor and PKCδ is critical for inducing DM-induced serotonergic behaviors and that inhibition of PKCδ attenuates the serotonergic behaviors via downregulation of 5-HT_1A receptor and upregulation of Nrf2-dependent GSH synthesis.

Blockade of platelet-activating factor receptor attenuates abnormal behaviors induced by phencyclidine in mice through down-regulation of NF-κB

Accumulating evidence suggests that neuroinflammation is one of the important etiologic factors of abusive and neuropsychiatric disorders. Platelet-activating factor (PAF) is potent proinflammatory lipid mediat1or and plays a pivotal role in neuroinflammatory disorders through the specific PAF receptor (PAF-R). Phencyclidine (PCP) induces a psychotomimetic state that closely resembles schizophrenia. Here, we investigated the role of PAF-R in the abnormal behaviors induced by PCP in mice. Repeated treatment with PCP resulted in a significant increase in PAF-R gene expression in the prefrontal cortex (PFC) and in the hippocampus. This increase was more pronounced in the PFC than hippocampus. Treatment with PCP resulted in a significant increase in nuclear translocation of the nuclear factor kappa beta (NF-κB) p65 and DNA binding activity, indicating that the proinflammatory molecule NF-κB was increased through up-regulation of PAF-R. Consistently, NF-κB activation was significantly protected by the PAF-R antagonist, ginkgolide B (Gink B), in PAF-R knockout mice and by the NF-κB inhibitor, pyrrolidine dithiocarbamate (PDTC). In addition, PCP-induced abnormal behaviors (i.e., reduced sociability, depression, cognitive impairment, and behavioral sensitization) were significantly attenuated by Gink B, in PAF-R knockout mice, and by PDTC. Importantly, PDTC did not significantly alter the attenuations observed in Gink B-treated mice or PAF-R knockout mice, indicating that NF-κB is a critical target for neuropsychotoxic modulation of PAF-R. Therefore, the results suggest that PAF-R mediates PCP-induced neuropsychotoxicity via a NF-κB-dependent mechanism, and that up-regulation of PAF-R may be associated with schizophrenia-like behavior in animal models.