Overexpression of heme oxygenase-1 protects dopaminergic neurons against 1-methyl-4-phenylpyridinium-induced neurotoxicity

Mitochondria in Multiple Sclerosis: Molecular Mechanisms of Pathogenesis

Mitochondria, the organelles that function as the powerhouse of the cell, have been increasingly linked to the pathogenesis of many neurological disorders, including multiple sclerosis (MS). MS is a chronic inflammatory demyelinating disease of the central nervous system (CNS) and a leading cause of neurological disability in young adults in the western world. Its etiology remains unknown, and while the inflammatory component of MS has been heavily investigated and targeted for therapeutic intervention, the failure of remyelination and the process of axonal degeneration are still poorly understood. Recent studies suggest a role of mitochondrial dysfunction in the neurodegenerative aspects of MS. This review is focused on mitochondrial functions under physiological conditions and the consequences of mitochondrial alterations in various CNS disorders. Moreover, we summarize recent findings linking mitochondrial dysfunction to MS and discuss novel therapeutic strategies targeting mitochondria-related pathways as well as emerging experimental approaches for modeling mitochondrial disease.

A Novel Perspective on the Biology of Bilirubin in Health and Disease

Unconjugated bilirubin (UCB) is known to be one of the most potent endogenous antioxidant substances. While hyperbilirubinemia has long been recognized as an ominous sign of liver dysfunction, recent data strongly indicate that mildly elevated bilirubin (BLB) levels can be protective against an array of diseases associated with increased oxidative stress. These clinical observations are supported by new discoveries relating to the role of BLB in immunosuppression and inhibition of protein phosphorylation, resulting in the modulation of intracellular signaling pathways in vascular biology and cancer, among others. Collectively, the evidence suggests that targeting BLB metabolism could be considered a potential therapeutic approach to ameliorate a variety of conditions.

Role of Nrf2/HO-1 system in development, oxidative stress response and diseases: an evolutionarily conserved mechanism

The multifunctional regulator nuclear factor erythroid 2-related factor (Nrf2) is considered not only as a cytoprotective factor regulating the expression of genes coding for anti-oxidant, anti-inflammatory and detoxifying proteins, but it is also a powerful modulator of species longevity. The vertebrate Nrf2 belongs to Cap 'n' Collar (Cnc) bZIP family of transcription factors and shares a high homology with SKN-1 from Caenorhabditis elegans or CncC found in Drosophila melanogaster. The major characteristics of Nrf2 are to some extent mimicked by Nrf2-dependent genes and their proteins including heme oxygenase-1 (HO-1), which besides removing toxic heme, produces biliverdin, iron ions and carbon monoxide. HO-1 and their products exert beneficial effects through the protection against oxidative injury, regulation of apoptosis, modulation of inflammation as well as contribution to angiogenesis. On the other hand, the disturbances in the proper HO-1 level are associated with the pathogenesis of some age-dependent disorders, including neurodegeneration, cancer or macular degeneration. This review summarizes our knowledge about Nrf2 and HO-1 across different phyla suggesting their conservative role as stress-protective and anti-aging factors.

Epalrestat Upregulates Heme Oxygenase-1, Superoxide Dismutase, and Catalase in Cells of the Nervous System

Heme oxygenase (HO)-1 has potent antioxidant and anti-inflammatory functions. Recent studies have shown that the upregulation of HO-1 is beneficial to counteract neuroinflammation, making HO-1 a new therapeutic target for neurological diseases. We have reported that epalrestat (EPS), which is currently used for the treatment of diabetic neuropathy, increases HO-1 levels through the activation of nuclear factor erythroid 2-related factor 2 (Nrf2) in bovine aortic endothelial cells. In this study, we tested the hypothesis that EPS upregulates HO-1 via Nrf2 activation in the component cells of the nervous system, by using rat Schwann cells and human SH-SY5Y cells. Treatment of Schwann cells with EPS at near-plasma concentration led to a dramatic increase in HO-1 levels. Nrf2 knockdown by small interfering RNA (siRNA) suppressed the EPS-induced HO-1 expression. EPS did not promote the intracellular accumulation of free ferrous ion and reactive oxygen species, by increasing ferritin via Nrf2 during HO-1 induction. Moreover, EPS stimulated the expression of superoxide dismutase 1 and catalase, which also are Nrf2 target gene products. It also markedly increased HO-1 levels in SH-SY5Y cells through the activation of Nrf2. We demonstrated for the first time that EPS upregulates HO-1, superoxide dismutase, and catalase by activating Nrf2. We suggest that EPS has the potential to prevent several neurological diseases.

Electroacupuncture inhibits pruritogen-induced spinal microglial activation in mice

In this study, we examined whether electroacupuncture (EA) represses pruritogen-induced microglial activation. Immunohistochemical studies revealed that a subcutaneous (s.c.) injection of the pruritogen 5'-guanidinonaltrindole (GNTI; 0.3mg/kg) to the back of the neck in mice induced acute expression of the ionized calcium-binding adaptor molecule 1 (Iba1) in both gray and white matter of the spinal cord, with the highest expression in the dorsal horn area. EA application (2Hz) to LI4 and LI11 attenuated GNTI-induced scratching behavior and repressed GNTI-induced Iba1 expression and Iba1 (+) microglia in the dorsal horn. In contrast, EA at the ST36 acupoint had no such effects. Confocal image analysis revealed co-expression of phosphorylated p38 and Iba1 in microglia with EA at the ST36 acupoint, but not at the LI4 or LI11 acupoints. In Western blot analysis, s.c. injection of GNTI to the back of the neck increased Iba1 and phospho-p38 expression in the spinal cord as compared with injection of saline, while EA at LI4 and LI11 reduced GNTI-induced expression of Iba1 and phospho-p38. These findings indicate that EA at LI4 and LI11, but not at ST36, reduces GNTI-induced microglial activation in the mouse spinal cord.

Hepatitis C virus infection: a risk factor for Parkinson's disease

Recent studies found that hepatitis C virus (HCV) may invade the central nervous system, and both HCV and Parkinson's disease (PD) have in common the overexpression of inflammatory biomarkers. We analysed data from a community-based integrated screening programme based on a total of 62,276 subjects. We used logistic regression models to investigate association between HCV infection and PD. The neurotoxicity of HCV was evaluated in the midbrain neuron-glia coculture system in rats. The cytokine/chemokine array was performed to measure the differences of amounts of cytokines released from midbrain in the presence and absence of HCV. The crude odds ratios (ORs) for having PD were 0.62 [95% confidence interval (CI), 0.48-0.81] and 1.91 (95% CI, 1.48-2.47) for hepatitis B virus (HBV) and HCV. After controlling for potential confounders, the association between HCV and PD remained statistically significant (adjusted OR = 1.39; 95% CI, 1.07-1.80), but not significantly different between HBV and PD. The HCV induced 60% dopaminergic neuron death in the midbrain neuron-glia coculture system in rats, similar to that of 1-methyl-4-phenylpyridinium (MPP(+) ) but not caused by HBV. This link was further supported by the finding that HCV infection may release the inflammatory cytokines, which may play a role in the pathogenesis of PD. In conclusion, our study demonstrated a significantly positive epidemiological association between HCV infection and PD and corroborated the dopaminergic toxicity of HCV similar to that of MPP(+) .

Preferential Heme Oxygenase-1 Activation in Striatal Astrocytes Antagonizes Dopaminergic Neuron Degeneration in MPTP-Intoxicated Mice

Parkinson's disease (PD) is characterized by the loss of dopaminergic neurons in the substantia nigra pars compacta (SNpc) accompanied by increased oxidative damage. Astrocytes, which are the most abundant glial cell types in the brain, possess higher antioxidant potential partially due to preferentially activated nuclear factor E2-related factor 2 genes. Heme oxygenase isoform 1 (HO-1) is crucial for the response to oxidative stress via the catabolism of heme to carbon monoxide, bilirubin, and iron. In the present study, we aimed to investigate astroglial expression of HO-1 in the SNpc, especially in the striatum of a subacute 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-intoxicated mouse model of PD, and to investigate the neuroprotective effects of intraventricularly administrated HO-1 activator cobalt protoporphyrin IX (CoPPIX). The results showed that HO-1 was faintly distributed in neurons but not astrocytes in the normal SNpc and striatum. MPTP triggered a robust HO-1 response in the astrocytes of the striatum after 1-day treatment, but the HO-1 levels declined dramatically at day 3 and were completely undetectable at day 5. Intraventricular administration of CoPPIX for 8 days could preferentially activate HO-1 in astrocytes in the striatum but not SNpc. The content of striatal dopamine and its derivatives was restored in the subacute MPTP models. CoPPIX also increased the number of dopaminergic neurons and the tyrosine hydroxylase levels in the SNpc. These results suggest that inadequate HO-1 in striatal astrocytes might contribute to the limited antioxidant defense and dopaminergic neuron degeneration in PD, and preferential HO-1 activation in striatal astrocytes might be neuroprotective. The study thus sheds light on the targeting of HO-1 in striatal astrocytes for PD therapeutics.

Moderate-Intensity Physical Exercise Protects Against Experimental 6-Hydroxydopamine-Induced Hemiparkinsonism Through Nrf2-Antioxidant Response Element Pathway

INTRODUCTION

Exercise improves the motor symptoms of patients with Parkinson disease in a palliative manner. Existing evidence demonstrates that exercise induces neuroprotection based on the neurotrophic properties. We investigated the effect of exercise on mitochondrial physiology and oxidative stress in an animal model of hemiparkinsonism.

METHODS

C57BL/6 mice completed a 6-week exercise program on a treadmill. We injected 6-hydroxydopamine (6-OHDA; 4 μg/2 μl) into the midstriatum. The animals progressively developed bradykinesia and R(-)-apomorphine-induced rotations that were attenuated by exercise. Transcriptional activation of protective genes is mediated by the antioxidant response element (ARE). Nuclear factor (erythroid-derived 2)-like 2 (Nrf2) binds to ARE. We investigated the Nrf2-ARE pathway in the striatum of animals.

RESULTS

Exercise protected 6-OHDA-induced loss of tyrosine hydroxylase immunolabeling and activated the Nrf2-ARE pathway in the nigrostriatal pathway. Exercise stimulated mitochondrial biogenesis in the striatum of animals that was more resistant to oxidant 6-OHDA and nitric oxide donor (±)-S-nitroso-N-acetylpenicillamine.

CONCLUSIONS

In mice, exercise activated Nrf2-ARE signaling in the nigrostriatal pathway that was protective against the development of hemiparkinsonism.

Effect of carbon monoxide on gene expression in cerebrocortical astrocytes: Validation of reference genes for quantitative real-time PCR

Quantitative real-time reverse transcription-polymerase chain reaction (qRT-PCR) is a widely used technique to characterize changes in gene expression in complex cellular and tissue processes, such as cytoprotection or inflammation. The accurate assessment of changes in gene expression depends on the selection of adequate internal reference gene(s). Carbon monoxide (CO) affects several metabolic pathways and de novo protein synthesis is crucial in the cellular responses to this gasotransmitter. Herein a selection of commonly used reference genes was analyzed to identify the most suitable internal control genes to evaluate the effect of CO on gene expression in cultured cerebrocortical astrocytes. The cells were exposed to CO by treatment with CORM-A1 (CO releasing molecule A1) and four different algorithms (geNorm, NormFinder, Delta Ct and BestKeeper) were applied to evaluate the stability of eight putative reference genes. Our results indicate that Gapdh (glyceraldehyde-3-phosphate dehydrogenase) together with Ppia (peptidylpropyl isomerase A) is the most suitable gene pair for normalization of qRT-PCR results under the experimental conditions used. Pgk1 (phosphoglycerate kinase 1), Hprt1 (hypoxanthine guanine phosphoribosyl transferase I), Sdha (Succinate Dehydrogenase Complex, Subunit A), Tbp (TATA box binding protein), Actg1 (actin gamma 1) and Rn18s (18S rRNA) genes presented less stable expression profiles in cultured cortical astrocytes exposed to CORM-A1 for up to 60 min. For validation, we analyzed the effect of CO on the expression of Bdnf and bcl-2. Different results were obtained, depending on the reference genes used. A significant increase in the expression of both genes was found when the results were normalized with Gapdh and Ppia, in contrast with the results obtained when the other genes were used as reference. These findings highlight the need for a proper and accurate selection of the reference genes used in the quantification of qRT-PCR results in studies on the effect of CO in gene expression.

PEP-1-HO-1 prevents MPTP-induced degeneration of dopaminergic neurons in a Parkinson's disease mouse model

Heme oxygenase-1 (HO-1) degrades heme to carbon dioxide, biliverdin, and Fe2+, which play important roles in various biochemical processes. In this study, we examined the protective function of HO-1 against oxidative stress in SH-SY5Y cells and in a Parkinson's disease mouse model. Western blot and fluorescence microscopy analysis demonstrated that PEP-1-HO-1, fused with a PEP-1 peptide can cross the cellular membranes of human neuroblastoma SH-SY5Y cells. In addition, the transduced PEP-1-HO-1 inhibited generation of reactive oxygen species (ROS) and cell death caused by 1-methyl-4-phenylpyridinium ion (MPP+). In contrast, HO-1, which has no ability to transduce into SH-SY5Y cells, failed to reduce MPP+-induced cellular toxicity and ROS production. Furthermore, intraperitoneal injected PEP-1-HO-1 crossed the blood-brain barrier in mouse brains. In a PD mouse model, PEP-1-HO-1 significantly protected against 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced toxicity and dopaminergic neuronal death. Therefore, PEP-1-HO-1 could be a useful agent in treating oxidative stress induced ailments including PD.

The neuroprotective effect of lovastatin on MPP(+)-induced neurotoxicity is not mediated by PON2

Parkinson's disease (PD) is a neurodegenerative disorder characterized by loss of the pigmented dopaminergic neurons in the substantia nigra pars compacta with subsequent striatal dopamine (DA) deficiency and increased lipid peroxidation. The etiology of the disease is still unclear and it is thought that PD may be caused by a combination of genetic and environmental factors. In the search of new pharmacological options, statins have been recognized for their potential application to treat PD, due to their antioxidant effect. The aim of this work is to contribute in the characterization of the neuroprotective effect of lovastatin in a model of PD induced by 1-methyl-4-phenylpyridinium (MPP(+)). Male Wistar rats (200-250 g) were randomly allocated into 4 groups and administered for 7 days with different pharmacological treatments. Lovastatin administration (5 mg/kg) diminished 40% of the apomorphine-induced circling behavior, prevented the striatal DA depletion and lipid peroxides formation by MPP(+) intrastriatal injection, as compared to the group of animals treated only with MPP(+). Lovastatin produced no change in paraoxonase-2 (PON2) activity. It is evident that lovastatin conferred neuroprotection against MPP(+)-induced protection but this effect was not associated with the induction of PON2 in the rat striatum.

Minocycline Rescues from Zinc-Induced Nigrostriatal Dopaminergic Neurodegeneration: Biochemical and Molecular Interventions

Accumulation of zinc (Zn) in dopaminergic neurons is implicated in Parkinson's disease (PD), and microglial activation plays a critical role in toxin-induced Parkinsonism. Oxidative stress is accused in Zn-induced dopaminergic neurodegeneration; however, its connection with microglial activation is still not known. This study was undertaken to elucidate the role and underlying mechanism of microglial activation in Zn-induced nigrostriatal dopaminergic neurodegeneration. Male Wistar rats were treated intraperitoneally with/without zinc sulphate (20 mg/kg) in the presence/absence of minocycline (30 mg/kg), a microglial activation inhibitor, for 2-12 weeks. While neurobehavioral and biochemical indexes of PD and number of dopaminergic neurons were reduced, the number of microglial cells was increased in the substantia nigra of the Zn-exposed animals. Similarly, Zn elevated lipid peroxidation (LPO) and activities of superoxide dismutase (SOD) and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase; however, catalase activity was reduced. Besides, Zn increased an association of NADPH oxidase subunit p67(phox) with membrane, cytochrome c release from the mitochondria and cleavage of pro-caspase 3. Zn attenuated the expression of tyrosine hydroxylase (TH) and vesicular monoamine transporter-2 (VMAT-2) while augmented the expression of dopamine transporter (DAT) and heme oxygenase-1 (HO-1). Minocycline alleviated Zn-induced behavioural impairments, loss of TH-positive neurons, activated microglial cells and biochemical indexes and modulated the expression of studied genes/proteins towards normalcy. The results demonstrate that minocycline reduces the number of activated microglial cells and oxidative stress, which rescue from Zn-induced changes in the expression of monoamine transporter and nigrostriatal dopaminergic neurodegeneration.

Increased bilirubin levels in de novo Parkinson's disease

BACKGROUND AND PURPOSE

Oxidative stress is a central pathogenic mechanism of Parkinson's disease (PD), and the heme oxygenase (HO) bilirubin pathway is one of the main mammalian antioxidative defences. Indeed, there is growing evidence of HO-bilirubin upregulation from early phases of PD. Our aim was to investigate bilirubin as a possible biomarker of PD diagnosis and progression.

METHODS

A cross-sectional case-control study was performed to evaluate differences in bilirubin levels between newly diagnosed, drug-naïve PD subjects and controls. Afterwards, PD subjects were included in a 2-year longitudinal study to evaluate disease progression in relation to baseline bilirubin levels.

RESULTS

Seventy-five de novo PD subjects were selected and matched with 75 controls by propensity score. Analysis of variance showed higher bilirubin levels in PD patients compared with controls (P < 0.001). Linear regression analysis failed to show a relationship between bilirubin and Unified Parkinson's Disease Rating Scale (UPDRS) part III (P = 0.283) at baseline evaluation. At 2-year follow-up, indirect relationships between bilirubin levels and UPDRS part III (P = 0.028) and between bilirubin levels and levodopa-equivalent daily dosage (P = 0.012) were found.

CONCLUSIONS

Parkinson's disease subjects showed higher levels of bilirubin compared with controls. Bilirubin increase might be due to HO overexpression as a compensatory response to oxidative stress occurring from early stages of PD.

Carbon monoxide and the CNS: challenges and achievements

Haem oxygenase (HO) and its product carbon monoxide (CO) are associated with cytoprotection and maintenance of homeostasis in several different organs and tissues. This review focuses upon the role of exogenous and endogenous CO (via HO activity and expression) in various CNS pathologies, based upon data from experimental models, as well as from some clinical data on human patients. The pathophysiological conditions reviewed are cerebral ischaemia, chronic neurodegenerative diseases (Alzheimer's and Parkinson's diseases), multiple sclerosis and pain. Among these pathophysiological conditions, a variety of cellular mechanisms and processes are considered, namely cytoprotection, cell death, inflammation, cell metabolism, cellular redox responses and vasomodulation, as well as the different targeted neural cells. Finally, novel potential methods and strategies for delivering exogenous CO as a drug are discussed, particularly approaches based upon CO-releasing molecules, their limitations and challenges. The diagnostic and prognostic value of HO expression in clinical use for brain pathologies is also addressed.

LC3 overexpression reduces Aβ neurotoxicity through increasing α7nAchR expression and autophagic activity in neurons and mice

Autophagy is an intracellular degradation pathway with dynamic interactions for eliminating damaged organelles and protein aggregates by lysosomal digestion. The EGFP-conjugated microtubule-associated protein 1 light chain 3 (EGFP-LC3) serves to monitor autophagic process. Extracellular β-amyloid peptide accumulation is reported as a major cause in Alzheimer's disease (AD) pathogenesis; large numbers of autophagic vacuoles accumulate in patients' brains. We previously demonstrated that extracellular Aβ (eAβ) induces strong autophagic response and α7nAChR acts as a carrier to bind with eAβ; which further inhibits Aβ-induced neurotoxicity via autophagic degradation. In the present study, we overexpressed LC3 in both neuroblastoma cells (SH-SY5Y/pEGFP-LC3) and mice (TgEGFP-LC3) to assess the effect of LC3 overexpression on Aβ neurotoxicity. SH-SY5Y/pEGFP-LC3 cells and primary cortical neuron cultures derived from E17 (embryonic day 17) TgEGFP-LC3 mice showed not only better resistance against Aβ neurotoxicity but also higher α7nAChR expression and autophagic activity than control. Administration of α-bungarotoxin (α-BTX) to block α7nAChR antagonized the neuroprotective action of SH-SY5Y/pECGF-LC3 cells, suggesting that eAβ binding with α7nAChR is an important step in Aβ detoxification. LC3 overexpression thus exerts neuroprotection through increasing α7nAChR expression for eAβ binding and further enhancing autophagic activity for Aβ clearance in vitro and in vivo.

Ginsenoside Rb1 prevents hypoxia-reoxygenation-induced apoptosis in H9c2 cardiomyocytes via an estrogen receptor-dependent crosstalk among the Akt, JNK, and ERK 1/2 pathways using a label-free quantitative proteomics analysis

Rb1 prevents H/R-induced apoptosis of H9c2 cells via an estrogen receptor-dependent crosstalk among the Akt, JNK, and ERK 1/2 pathways.

Neuroprotective effect of hemeoxygenase-1/glycogen synthase kinase-3β modulators in 3-nitropropionic acid-induced neurotoxicity in rats

The present study has been designed to explore the possible interaction between hemeoxygenase-1 (HO-1) and glycogen synthase kinase-3β (GSK-3β) pathway in 3-nitropropionic acid (3-NP)-induced neurotoxicity in rats. 3-NP produces neurotoxicity by inhibition of the mitochondrial complex II (enzyme succinate dehydrogenase) and by sensitizing the N-methyl-D-aspartate receptor. Recent studies have reported the therapeutic potential of HO-1/GSK-3β modulators in different neurodegenerative disorders. However, their exact role is yet to be explored. The present study is an attempt to investigate the effect of pharmacological modulation of HO-1/GSK-3β pathway against 3-NP-induced behavioral, biochemical and molecular alterations in rat. Behavioral observation, oxidative stress, pro-inflammatory [tumor necrosis factor-alpha (TNF-α) and interleukin-1 beta (IL-1β)], HO-1 and GSK-3β activity were evaluated post 3-NP treatment. Findings of the present study demonstrate a significant alteration in the locomotor activity, motor coordination, oxidative burden (increased lipid peroxidation, nitrite concentration and decreased endogenous antioxidants), pro-inflammatory mediators [TNF-α, IL-1β], HO-1 and GSK-3β activity in 3-NP-treated animals. Further, administration of hemin (10- and 30-mg/kg; i.p.) and lithium chloride (LiCl) (25- and 50-mg/kg; i.p.) prevented the alteration in body weight, motor impairments, oxidative stress and cellular markers. In addition, combined administration of hemin (10-mg/kg) and LiCl (25-mg/kg) showed synergistic effect on 3-NP-treated rats. Pretreatment with Tin (IV) protoporphyrin (40 μM/kg), HO-1 inhibitor reversed the beneficial effect of LiCl and hemin. Outcomes of the present study suggest that HO-1 and GSK-3β enzymes are involved in the pathophysiology of HD. The modulators of both the pathways might be used as adjuvants or prophylactic therapy for the treatment of HD-like symptoms.

Treadmill exercise activates Nrf2 antioxidant system to protect the nigrostriatal dopaminergic neurons from MPP+ toxicity

Exercise induces oxidative stress, which may activate adaptive antioxidant responses. Nuclear factor erythroid 2-related factor 2 (Nrf2) plays an important role in the defense of oxidative stress by regulating the expression of antioxidant enzymes, gamma-glutamylcysteine ligase (γGCL) and heme oxygenase-1 (HO-1). We investigated whether treadmill exercise protects dopaminergic neurons by regulating the Nrf2 antioxidant system in a 1-methyl-4-phenylpyridine (MPP(+))-induced parkinsonian rat model. We found that MPP(+) induced early decreases in total glutathione level and Nrf2/γGCLC (catalytic subunit of γGCL) expression, but late upregulation of HO-1 expression in association with loss of nigral dopaminergic neurons and downregulation of tyrosine hydroxylase and dopamine transporter expression in the striatum. Treadmill exercise for 4weeks induced upregulation of Nrf2 and γGCLC expression, and also prevented the MPP(+)-induced downregulation of Nrf2/γGCLC/glutathione, HO-1 upregulation, and nigrostriatal dopaminergic neurodegeneration. Moreover, the protective effect of exercise was blocked by the knockdown of Nrf2 using a lentivirus-carried shNrf2 delivery system. These results demonstrate an essential role of Nrf2 in the exercise-mediated protective effect that exercise enhances the nigrostriatal Nrf2 antioxidant defense capacity to protect dopaminergic neurons against the MPP(+)-induced toxicity.

Edaravone protected PC12 cells against MPP(+)-cytoxicity via inhibiting oxidative stress and up-regulating heme oxygenase-1 expression

Oxidative stress is involved in the pathogenesis of Parkinson's disease (PD). Edaravone has been shown to have a neuroprotective effect. In the present work, we investigated the effect of edaravone on 1-methyl-4-phenylpyridinium (MPP(+))-treated PC12 cells. Edaravone inhibited the decrease of cell viability and apoptosis induced by MPP(+) in PC12 cells. In addition, edaravone alleviated intracellular reactive oxygen species (ROS) production. MPP(+) induced heme oxygenase-1 (HO-1) expression, which was further enhanced by edaravone. The inhibitor of HO-1 zinc protoporphyrin-IX attenuated the neuroprotection of edaravone. So edaravone protected PC12 cells against MPP(+)-cytoxicity via inhibiting oxidative stress and up-regulating HO-1 expression. The data showed that edaravone was neuroprotective and could be potentially therapeutics for PD in future.

Antioxidant gene therapy against neuronal cell death

Oxidative stress is a common hallmark of neuronal cell death associated with neurodegenerative disorders such as Alzheimer's disease, Parkinson's disease, as well as brain stroke/ischemia and traumatic brain injury. Increased accumulation of reactive species of both oxygen (ROS) and nitrogen (RNS) has been implicated in mitochondrial dysfunction, energy impairment, alterations in metal homeostasis and accumulation of aggregated proteins observed in neurodegenerative disorders, which lead to the activation/modulation of cell death mechanisms that include apoptotic, necrotic and autophagic pathways. Thus, the design of novel antioxidant strategies to selectively target oxidative stress and redox imbalance might represent important therapeutic approaches against neurological disorders. This work reviews the evidence demonstrating the ability of genetically encoded antioxidant systems to selectively counteract neuronal cell loss in neurodegenerative diseases and ischemic brain damage. Because gene therapy approaches to treat inherited and acquired disorders offer many unique advantages over conventional therapeutic approaches, we discussed basic research/clinical evidence and the potential of virus-mediated gene delivery techniques for antioxidant gene therapy.

Silibinin attenuates MPP⁺-induced neurotoxicity in the substantia nigra in vivo

Parkinson's disease (PD) is characterized by degeneration of the nigrostriatal dopaminergic (DA) pathway. The cause of neuronal death in PD is largely unknown, but it is becoming clear that inflammation plays a significant role in the pathophysiology of PD. Silibinin is a major flavonoid in milk thistle which has an anti-inflammatory activity. We investigated whether silibinin could have neuroprotective effects on DA neurons in the 1-methyl-4-phenylpyridinium ion (MPP(+))-treated animal model of PD in vivo. To address this question, animals received intraperitoneal (i.p.) injections 10, 50, or 100 mg/kg of silibinin, starting 1 day before MPP(+) injection and continued daily until 6 days post-lesion for tyrosine hydroxylase (TH) staining, or until 1 hour prior to the MPP(+) injection to examine the expression levels of inflammatory proteins. Finally, their brains were harvested at the indicated time points for the analyses. Silibinin treatment with 10 mg/kg had no significantly neuroprotective effects in the substantia nigra (SN). However, 50 and 100 mg/kg of silibinin ameliorated the MPP(+)-induced neurotoxicity in the SN in a dose-dependent manner, and the increased levels of inflammatory molecules such as tumor necrosis factor-alpha (TNF-α), interleukin-1 beta (IL-1β) and inducible nitric oxide synthase (iNOS) by MPP(+) treatment were attenuated by treatment with 100 mg/kg of silibinin. These results indicate that silibinin could be a useful and beneficial natural product offering promise for the prevention of DA neuronal degeneration involved in PD.

Thrombomodulin domain 1 ameliorates diabetic nephropathy in mice via anti-NF-κB/NLRP3 inflammasome-mediated inflammation, enhancement of NRF2 antioxidant activity and inhibition of apoptosis

AIMS/HYPOTHESIS

Chronic inflammatory processes have been increasingly shown to be involved in the pathogenesis of diabetes and diabetic nephropathy. Recently, we demonstrated that a lectin-like domain of thrombomodulin (THBD), which is known as THBD domain 1 (THBDD1) and which acts independently of protein C activation, neutralised an inflammatory response in a mouse model of sepsis. Here, therapeutic effects of gene therapy with adeno-associated virus (AAV)-carried THBDD1 (AAV-THBDD1) were tested in a mouse model of type 2 diabetic nephropathy.

METHODS

To assess the therapeutic potential of THBDD1 and the mechanisms involved, we delivered AAV-THBDD1 (10(11) genome copies) into db/db mice and tested the effects of recombinant THBDD1 on conditionally immortalised podocytes.

RESULTS

A single dose of AAV-THBDD1 improved albuminuria, renal interstitial inflammation and glomerular sclerosis, as well as renal function in db/db mice. These effects were closely associated with: (1) inhibited activation of the nuclear factor κB (NF-κB) pathway and the NACHT, LRR and PYD domains-containing protein 3 (NLRP3) inflammasome; (2) promotion of nuclear factor (erythroid-derived 2)-like 2 (NRF2) nuclear translocation; and (3) suppression of mitochondria-derived apoptosis in the kidney of treated mice.

CONCLUSIONS/INTERPRETATION

AAV-THBDD1 gene therapy resulted in improvements in a model of diabetic nephropathy by suppressing the NF-κB-NLRP3 inflammasome-mediated inflammatory process, enhancing the NRF2 antioxidant pathway and inhibiting apoptosis in the kidney.

Resveratrol partially prevents rotenone-induced neurotoxicity in dopaminergic SH-SY5Y cells through induction of heme oxygenase-1 dependent autophagy

Parkinson disease (PD) is a complex neurodegenerative disorder characterized by a progressive loss of dopaminergic neurons. Mitochondrial dysfunction, oxidative stress or protein misfolding and aggregation may underlie this process. Autophagy is an intracellular catabolic mechanism responsible for protein degradation and recycling of damaged proteins and cytoplasmic organelles. Autophagic dysfunction may hasten the progression of neuronal degeneration. In this study, resveratrol promoted autophagic flux and protected dopaminergic neurons against rotenone-induced apoptosis. In an in vivo PD model, rotenone induced loss of dopaminergic neurons, increased oxidation of mitochondrial proteins and promoted autophagic vesicle development in brain tissue. The natural phytoalexin resveratrol prevented rotenone-induced neuronal apoptosis in vitro, and this pro-survival effect was abolished by an autophagic inhibitor. Although both rotenone and resveratrol promoted LC3-II accumulation, autophagic flux was inhibited by rotenone and augmented by resveratrol. Further, rotenone reduced heme oxygenase-1 (HO-1) expression, whereas resveratrol increased HO-1 expression. Pharmacological inhibition of HO-1 abolished resveratrol-mediated autophagy and neuroprotection. Notably, the effects of a pharmacological inducer of HO-1 were similar to those of resveratrol, and protected against rotenone-induced cell death in an autophagy-dependent manner, validating the hypothesis of HO-1 dependent autophagy in preventing neuronal death in the in vitro PD model. Collectively, our findings suggest that resveratrol induces HO-1 expression and prevents dopaminergic cell death by regulating autophagic flux; thus protecting against rotenone-induced neuronal apoptosis.

Management of the aging risk factor for Parkinson's disease

The aging risk factor for Parkinson's disease is described in terms of specific disease markers including mitochondrial and gene dysfunctions relevant to energy metabolism. This review details evidence for the ability of nutritional agents to manage these aging risk factors. The combination of alpha lipoic acid, acetyl-l-carnitine, coenzyme Q10, and melatonin supports energy metabolism via carbohydrate and fatty acid utilization, assists electron transport and adenosine triphosphate synthesis, counters oxidative and nitrosative stress, and raises defenses against protein misfolding, inflammatory stimuli, iron, and other endogenous or xenobiotic toxins. These effects are supported by gene expression via the antioxidant response element (ARE; Keap/Nrf2 pathway), and by peroxisome proliferator-activated receptor gamma co-activator 1 alpha (PGC-1 alpha), a transcription coactivator, which regulates gene expression for energy metabolism and mitochondrial biogenesis, and maintains the structural integrity of mitochondria. The effectiveness and synergies of the combination against disease risks are discussed in relation to gene action, dopamine cell loss, and the accumulation and spread of pathology via misfolded alpha-synuclein. In addition there are potential synergies to support a neurorestorative role via glial derived neurotrophic factor expression.

Mechanisms of Nrf2 protection in astrocytes as identified by quantitative proteomics and siRNA screening

The Nrf2 (NF-E2 related factor 2)-ARE (antioxidant response element) pathway controls a powerful array of endogenous cellular antioxidant systems and is an important pathway in the detoxification of reactive oxygen species (ROS) in the brain. Using a combination of quantitative proteomics and siRNA screening, we have identified novel protective mechanisms of the Nrf2-ARE pathway against oxidative stress in astrocytes. Studies from our lab and others have shown Nrf2 overexpression protects astrocytes from oxidative stress. However, the exact mechanisms by which Nrf2 elicits these effects are unknown. In this study, we show that induction of Nrf2 reduces levels of reactive oxygen species (ROS) produced by various oxidative stressors and results in robust cytoprotection. To identify the enzymes responsible for these effects, we used stable isotope labeling by amino acids in cell culture (SILAC) and quantitative shotgun proteomics to identify 72 Nrf2-regulated proteins in astrocytes. We hypothesized a subset of these proteins might play a critical role in Nrf2 protection. In order to identify these critical proteins, we used bioinformatics to narrow our target list of proteins and then systematically screened each candidate with siRNA to assess the role of each in Nrf2 protection. We screened each target against H2O2, tert-butyl hydroperoxide, and 4-hydroxynonenal and subsequently identified three enzymes-catalase, prostaglandin reductase-1, and peroxiredoxin-6-that are critical for Nrf2-mediated protection in astrocytes.

Protection of dopaminergic neurons by 5-lipoxygenase inhibitor

Neuroinflammation and oxidative stress are important factors that induce neurodegeneration in age-related neurological disorders. 5-Lipoxygenase (5-LOX) is the enzyme responsible for catalysing the synthesis of leukotriene or 5-HETE from arachidonic acid. 5-LOX is expressed in the central nervous system and may cause neurodegenerative disease. In this study, we investigated the effect of the pharmacological inhibition of 5-lipoxygenase on 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)/MPP(+)-induced dopaminergic neuronal death in midbrain neuron-glia co-cultures and in mice. It was found that 5-LOX was over-expressed in astrocytes after the injection of MPTP into C57BL6 mice. MK-886, a specific inhibitor of 5-LOX activating protein (FLAP), significantly increased [(3)H]-dopamine uptake, a functional indicator of the integrity of dopaminergic neurons, in midbrain cultures or the SH-SY5Y human dopaminergic cell line following MPP(+) treatment. In addition, LTB₄, one of 5-LOX's downstream products, was increased in the striatum and substantia nigra following MPTP injection in mice. LTB₄ but not LTD₄ and 5-HETE enhanced MPP(+)-induced neurotoxicity in primary midbrain cultures. MK-886 administration increased the number of tyrosine hydroxylase-positive neurons in the substantia nigra and the dopamine content in the striatum in MPTP-induced parkinsonian mice. Furthermore, the MPTP-induced upregulation of LTB₄ in the striatum and substantia nigra was antagonised by MK-886. These results suggest that 5-LOX inhibitors may be developed as novel neuroprotective agents and LTB₄ may play an important pathological role in Parkinson's disease.

Decursin Isolated from Angelica gigas Nakai Rescues PC12 Cells from Amyloid β-Protein-Induced Neurotoxicity through Nrf2-Mediated Upregulation of Heme Oxygenase-1: Potential Roles of MAPK

Decursin (D), purified from Angelica gigas Nakai, has been proven to exert neuroprotective property. Previous study revealed that D reduced A β 25 ‒ 35-induced cytotoxicity in PC12 cells. Our study explored the underlying mechanisms by which D mediates its therapeutic effects in vitro. Pretreatment of cells with D diminished intracellular generation of ROS in response to A β 25 ‒ 35. Western blot revealed that D significantly increased the expression and activity of HO-1, which was correlated with its protection against A β 25 ‒ 35-induced injury. Addition of ZnPP, an HO-1 competitive inhibitor, significantly attenuated its protective effect in A β 25 ‒ 35-treated cells, indicating the vital role of HO-1 resistance to oxidative injury. Moreover, D induced Nrf2 nuclear translocation, the upstream of HO-1 expression. While investigating the signaling pathways responsible for HO-1 induction, D activated ERK and dephosphorylated p38 in PC12 cells. Addition of U0126, a selective inhibitor of ERK, blocked D-induced Nrf2 activation and HO-1 induction and meanwhile reversed the protection of D against A β 25 ‒ 35-induced cell death. These findings suggest D augments cellular antioxidant defense capacity through both intrinsic free radical scavenging activity and activation of MAPK signal pathways that leads to Nrf2 activation, and subsequently HO-1 induction, thereby protecting the PC12 cells from A β 25 ‒ 35-induced oxidative cytotoxicity.

Increase of oxidative stress by a novel PINK1 mutation, P209A

Mutation in the human PTEN-induced protein kinase 1 (PINK1) gene is responsible for the second most common form of recessive Parkinson disease (PD). We have identified a single heterozygous PINK1 mutation, P209A, from a cohort of 68 patients with early onset PD. From age 31, this patient developed an asymmetric bradykinesia with rigidity that was L-DOPA responsive. An [(18)F]-fluorodopa PET scan showed reduced DOPA uptake in the bilateral basal ganglia. The H2O2-induced cell death, ROS production, and caspase-3 activation in SH-SY5Y cells were enhanced by the transfection of the PINK1 P209A mutant. The heme oxygenase-1 (HO-1) induction in response to H2O2 and MPP(+) treatment was impaired by the overexpression of the PINK1 P209A mutant. In addition, SOD2 induction after TNFα treatment was also inhibited by the PINK1 P209A mutation. Akt and ERK are involved in HO-1 induction after oxidative stress. The phosphorylation of Akt and ERK after exposure to H2O2 or MPP(+) was also inhibited in PINK1 P209A mutant cells compared with empty-vector-transfected cells. These results indicate a novel pathway by which the P209A defect in the PINK1 kinase domain inhibits oxidative stress-induced HO-1 and SOD2 induction, which may accelerate the neurodegeneration in PD with PINK1 defect.

Caffeic acid phenethyl ester protects nigral dopaminergic neurons via dual mechanisms involving haem oxygenase-1 and brain-derived neurotrophic factor

BACKGROUND AND PURPOSE

Caffeic acid phenethyl ester (CAPE) is a component of honey bee propolis that can induce expression of haem oxygenase-1 (HO-1). Because HO-1 induction has been suggested to protect dopaminergic neurons in the substantia nigra, we examined the effect of CAPE in experimental models of dopaminergic neurodegeneration.

EXPERIMENTAL APPROACH

Neuroprotective effect of CAPE was investigated in rat organotypic midbrain slice cultures and in vivo, using a mouse model of dopaminergic neurodegeneration induced by intranigral injection of LPS and intrastriatal injection of 6-hydroxydopamine.

KEY RESULTS

CAPE protected dopaminergic neurons in slice cultures from IFN-γ/LPS-induced injury. The effect of CAPE was inhibited by zinc protoporphyrin IX, an HO-1 inhibitor, and by neutralizing antibody against brain-derived neurotrophic factor (BDNF). A p38 MAPK inhibitor SB203580 prevented activation of NF-E2-related factor 2, attenuated increased expression of HO-1 and BDNF, and blocked the neuroprotective actions of CAPE. In the LPS-injected mouse model, daily intraperitoneal administration of CAPE protected dopaminergic neurons, up-regulated HO-1 and BDNF, and reduced the increase of activated microglia/macrophages. Neuroprotective effects of CAPE against LPS-induced injury was prevented by zinc protoporphyrin IX or anti-BDNF antibody. CAPE protected dopaminergic neurons and alleviated methamphetamine-induced rotational behaviour also in 6-hydroxydopamine hemiparkinsonian mice.

CONCLUSION AND IMPLICATIONS

CAPE is a novel type of neuroprotective agent whose actions are mediated by both HO-1 and BDNF. These findings may provide novel clues to develop neuroprotective agents for treatment of neurodegenerative disorders.

Resveratrol protects rats from Aβ-induced neurotoxicity by the reduction of iNOS expression and lipid peroxidation

Alzheimer disease (AD) is an age-dependent neurodegenerative disease characterized by the formation of β–amyloid (Aβ)-containing senile plaque. The disease could be induced by the administration of Aβ peptide, which was also known to upregulate inducible nitric oxide synthase (iNOS) and stimulate neuronal apoptosis. The present study is aimed to elucidate the cellular effect of resveratrol, a natural phytoestrogen with neuroprotective activities, on Aβ-induced hippocampal neuron loss and memory impairment. On adult Sprague-Dawley rats, we found the injection of Aβ could result in a significant impairment in spatial memory, a marked increase in the cellular level of iNOS and lipid peroxidation, and an apparent decrease in the expression of heme oxygenase-1 (HO-1). By combining the treatment with Aβ, resveratrol was able to confer a significant improvement in spatial memory, and protect animals from Aβ-induced neurotoxicity. These neurological protection effects of resveratrol were associated with a reduction in the cellular levels of iNOS and lipid peroxidation and an increase in the production of HO-1. Moreover, the similar neurological and cellular response were also observed when Aβ treatment was combined with the administration of a NOS inhibitor, N(G)-nitro-L-arginine methyl ester hydrochloride (L-NAME). These findings strongly implicate that iNOS is involved in the Aβ-induced lipid peroxidation and HO-1 downregulation, and resveratrol protects animals from Aβ-induced neurotoxicity by suppressing iNOS production.

Upregulation of heme oxygenase-1 by acteoside through ERK and PI3 K/Akt pathway confer neuroprotection against beta-amyloid-induced neurotoxicity

Our previous study has shown that acteoside, an antioxidative phenylethanoid glycoside, protect against beta-amyloid (Aβ)-induced cytotoxicity in vitro. However, the precise protective mechanisms remains unclear. Heme oxygenase-1 (HO-1) is a crucial factor in the response to oxidative injury, protecting neurons against Aβ-induced injury. In the present study we examined to determine whether acteoside upregulates HO-1 expression, and thereby protects PC12 cells against Aβ-induced cell death. It was revealed that acteoside is an activator of Nrf2 and inducer of HO-1 expression. We showed that acteoside increased HO-1 expression in vitro and in vivo. Acteoside treatment resulted in nuclear translocation of the transcription factor NF-E2-related factor 2 (Nrf2). Acteoside activated both ERK and PI3 K/Akt, and treatments with the specific ERK inhibitor PD98059, the PI3 K inhibitor LY294002, and the specific Nrf2 siRNA suppressed the acteoside-induced HO-1 expression. The HO-1 inhibitor ZnPP, PD98059, and LY294002 markedly abolished the neuroprotective effect of acteoside against Aβ-induced neurotoxicity. Taken together, these results demonstrate that acteoside is an activator of Nrf2 and inducer of HO-1 expression. We also showed that acteoside increased HO-1 expression through activation of ERK and PI3 K/Akt signal pathways in vitro. Upregulation of HO-1 by acteoside may involve in the neuroprotection against Aβ-induced neurotoxicity.

A polymorphism located at an ATG transcription start site of the heme oxygenase-2 gene is associated with classical Parkinson's disease

AIM

Oxidative stress and iron deposition is related to Parkinson's disease (PD). Heme oxygenase 2 (HMOX2) catalyzes the cleavage of the heme ring to form biliverdin with release of iron and carbon monoxide. This study aims to analyze variations in the HMOX2 gene in patients with PD.

MATERIALS AND METHODS

We mapped four single nucleotide polymorphisms (SNPs) and copy number variations of the HMOX2 gene in 691 patients with PD and 747 healthy individuals.

RESULTS

We identified a highly homogeneous association of the HMOX2 SNP rs2270363 homozygous G/G genotype with patients with classical PD phenotype compared with healthy individuals. We identified three patients with PD and two control individuals with a single copy of the HMOX2 gene. No individuals with zero or more than two gene copies were identified.

CONCLUSION

We describe for the first time, copy number variations in the HMOX2 gene and an association of the SNP rs2270363 with PD risk.

Dopamine and paraquat enhance α-synuclein-induced alterations in membrane conductance

We have previously demonstrated that α-synuclein overexpression increases the membrane conductance of dopaminergic-like cells. Although α-synuclein is thought to play a central role in the pathogenesis of several neurodegenerative diseases including Parkinson's disease, multiple system atrophy, and diffuse Lewy body disease, the mechanism of action is not completely understood. In this study, we sought to determine whether multiple factors act together with α-synuclein to engender cell vulnerability through an augmentation of membrane conductance. In this article, we employed a cell model that mimics dopaminergic neurons coupled with α-synuclein overexpression and oxidative stressors. We demonstrate an enhancement of α-synuclein-induced toxicity in the presence of combined treatment with dopamine and paraquat, two molecules known to incite oxidative stress. In addition, we show that combined dopamine and paraquat treatment increases the expression of heme oxygenase-1, an antioxidant response protein. Finally, we demonstrate for the first time that combined treatment of dopaminergic cells with paraquat and dopamine enhances α-synuclein-induced leak channel properties resulting in increased membrane conductance. Importantly, these increases are most robust when both paraquat and dopamine are present suggesting the need for multiple oxidative insults to augment α-synuclein-induced disruption of membrane integrity.

Manganese potentiates LPS-induced heme-oxygenase 1 in microglia but not dopaminergic cells: role in controlling microglial hydrogen peroxide and inflammatory cytokine output

Excessive manganese (Mn) exposure increases output of glial-derived inflammatory products, which may indirectly contribute to the neurotoxic effects of this essential metal. In microglia, Mn increases hydrogen peroxide (H(2)O(2)) release and potentiates lipopolysaccharide (LPS)-induced cytokines (TNF-α, IL-6) and nitric oxide (NO). Inducible heme-oxygenase (HO-1) plays a role in the regulation of inflammation and its expression is upregulated in response to oxidative stressors, including metals and LPS. Because Mn can oxidatively affect neurons both directly and indirectly, we investigated the effect of Mn exposure on the induction of HO-1 in resting and LPS-activated microglia (N9) and dopaminergic neurons (N27). In microglia, 24h exposure to Mn (up to 250 μM) had minimal effects on its own, but it markedly potentiated LPS (100 ng/ml)-induced HO-1 protein and mRNA. Inhibition of microglial HO-1 activity with two different inhibitors indicated that HO-1 is a positive regulator of the Mn-potentiated cytokine output and a negative regulator of the Mn-induced H(2)O(2) output. Mn enhancement of LPS-induced HO-1 does not appear to be dependent on H(2)O(2) or NO, as Mn+LPS-induced H(2)O(2) release was not greater than the increase induced by Mn alone and inhibition of iNOS did not change Mn potentiation of HO-1. However, because Mn exposure potentiated the LPS-induced nuclear expression of small Maf proteins, this may be one mechanism Mn uses to affect the expression of HO-1 in activated microglia. Finally, the potentiating effects of Mn on HO-1 appear to be glia-specific for Mn, LPS, or Mn+LPS did not induce HO-1 in N27 neuronal cells.

Protective Action of Neurotrophic Factors and Estrogen against Oxidative Stress-Mediated Neurodegeneration

Oxidative stress is involved in the pathogenesis of neurodegenerative disorders such as Alzheimer's disease, Parkinson's disease, and Huntington's disease. Low levels of reactive oxygen species (ROS) and reactive nitrogen species (RNS) are important for maintenance of neuronal function, though elevated levels lead to neuronal cell death. A complex series of events including excitotoxicity, Ca(2+) overload, and mitochondrial dysfunction contributes to oxidative stress-mediated neurodegeneration. As expected, many antioxidants like phytochemicals and vitamins are known to reduce oxidative toxicity. Additionally, growing evidence indicates that neurotrophic factors such as brain-derived neurotrophic factor (BDNF) and estrogens significantly prevent neuronal damage caused by oxidative stress. Here, we review and discuss recent studies addressing the protective mechanisms of neurotrophic factors and estrogen within this system.

Impairment of oxidative stress-induced heme oxygenase-1 expression by the defect of Parkinson-related gene of PINK1

Parkinson's disease (PD) is one of the most common neurodegenerative diseases. Mutation in the phosphatase and tensin homolog (PTEN)-induced putative kinase 1 (PINK1) gene causes an autosomal recessive form of PD. However, the etiology related to PINK1 is still not clear. Here, we examined the effect of PINK1 on heme oxygenase (HO)-1 induction in SH-SY5Y neuronal cells following H(2)O(2) or 1-methyl-4-phenylpyridinium (MPP(+)) treatment. The HO-1 induction in response to H(2)O(2) and MPP(+) treatment was impaired by the expression of recombinant PINK1 G309D mutant. PINK1 G309D mutation increased the apoptosis of SH-SY5Y cells following H(2)O(2) treatment and cell survival was rescued by the over-expression of HO-1 using adenovirus (Ad) infection. In addition, knockdown of tumor necrosis factor receptor-associated protein-1 (TRAP1), which is the substrate of PINK1 kinase, in SH-SY5Y cells also inhibited the expression of HO-1 in response to oxidative stress. The up-regulation of TRAP1 expression following H(2)O(2) treatment was inhibited by the expression of recombinant PINK1 G309D mutant. The H(2)O(2)-induced HO-1 induction was Akt- and ERK-dependent. The phosphorylation of ERK and Akt but not p38 was inhibited in cells expressing the PINK1 G309D mutant and knockdown of TRAP1. These results indicate a novel pathway by which the defect of PINK1 inhibits the oxidative stress-induced HO-1 production. Impairment of HO-1 production following oxidative stress may accelerate the dopaminergic neurodegeneration in Parkinson patients with PINK1 defect.

Dynamic changes of heme oxygenase-1 in the hippocampus of rats after acute carbon monoxide poisoning

Heme oxygenase-1 (HO-1), an inducible enzyme, degrades heme to carbon monoxide (CO), iron, and bilirubin. We have investigated the relationship among HO-1 protein expression, HO activity, and CO concentrations in the hippocampus of CO-exposed rats. Western blotting and immunohistochemistry revealed that the enzyme is predominantly localized in hippocampal CA1 and CA3 pyramidal cells and in granule cells of the dentate gyrus. HO enzyme activity was reduced immediately following CO exposure, while expression of HO-1 protein was consistently upregulated in a time-dependent manner. Local CO concentrations in hippocampus rose immediately following exposure, but the elevation was maintained for ~20 h despite the decline in blood carboxyhemoglobin levels toward baseline. We suggest that CO initially inhibits HO enzyme activity, whereas at later time points the inhibition is released and local CO generation is maintained by the activity of the endogenous HO enzyme. And the noninducible form of heme oxygenase, HO-2, was not altered following CO administration. Together these results indicate that the HO/CO pathway in the rat hippocampus is induced by acute CO exposure; local CO production may play a regulatory role in brain injury following CO poisoning.

Fibroblast growth factor 9 upregulates heme oxygenase-1 and gamma-glutamylcysteine synthetase expression to protect neurons from 1-methyl-4-phenylpyridinium toxicity

Oxidative stress and lower levels of trophic factors involved in nigrostriatal dopaminergic neurodegeneration are a hallmark of Parkinson disease. Our previous studies found that fibroblast growth factor 9 (FGF9) prevented 1-methyl-4-phenylpyridinium (MPP(+))-induced nigral dopaminergic neuron death and was involved in the neuroprotection of the antioxidant melatonin. However, the protective mechanisms mediated by FGF9 remain unclear. Herein, we explored whether FGF9 regulated the cellular antioxidant defense protecting dopaminergic neurons against MPP(+) intoxication. We found that FGF9 treatment alone induced a decrease in hydrogen peroxide (H(2)O(2)) level, an increase in glutathione content, and an upregulation of gamma-glutamylcysteine synthetase (gamma-GCS) and heme oxygenase 1 (HO-1) expression in primary cortical neurons but not in astrocytes. Simultaneous treatment with FGF9 and MPP(+) prevented MPP(+)-induced neuron death and H(2)O(2) overproduction but did not affect the FGF9-increased gamma-GCS and HO-1 protein expression. Inhibition of gamma-GCS or HO-1 prevented the inhibitory effect of FGF9 on MPP(+)-induced H(2)O(2) production and death in mesencephalic dopaminergic and cortical neurons. However, in the absence of MPP(+), the FGF9-induced H(2)O(2) reduction was blocked by HO-1 inhibitors, but not by gamma-GCS inhibitors. These results indicate that FGF9 upregulates gamma-GCS and HO-1 expression to protect cortical and dopaminergic neurons from MPP(+)-induced oxidative insult.