Increased nuclear factor-erythroid 2 p45-related factor 2 activity protects SH-SY5Y cells against oxidative damage

6-hydroxydopamine affects multiple pathways to induce cytotoxicity in differentiated LUHMES dopaminergic neurons

The debilitating effects of Parkinson's disease (PD) progress over time and are pathophysiologically characterized by the formation of Lewy bodies due to the accumulation of α-synuclein aggregates resulting in the death of dopaminergic neurons. In the present study, we determined cell death pathways activated by acute exposure to 6-hydroxydopamine (6-OHDA) in differentiated LUHMES cells empirically followed by a 24 h toxin free interval, henceforth termed as washout/recovery period. Acute 6-OHDA exposure led to morphological changes in LUHMES cells and resulted in significant loss of neurite length and neurite thickness. Generation of reactive oxygen species and loss of mitochondrial membrane potential in the neuronal processes were persistent even after the recovery period. Our results show that 6-OHDA exposure leads to significant reduction in expression of mitochondrial OXPHOS complexes I, II, and IV and activation of caspase mediated apoptotic cell death cascade as observed by enhanced protein expression of cleaved-PARP-1 and cleaved-Caspase-3. Immunofluorescence microscopy approach confirmed that cell death occurs independent of the AIF translocation to the nucleus. Our experimental model, led to a ∼5-fold lower α-synuclein monomer expression and, interestingly, resulted in loss of protein ubiquitination in whole cell lysates. Altogether, this work provides evidence of multiple pathways targeted by 6-OHDA in differentiated LUHMES cells and expands research avenues for addressing the knowledge gap regarding the effect of 6-OHDA in the ubiquitin proteasome system for PD therapies.

Efficacy of Sulforaphane in Neurodegenerative Diseases

Sulforaphane (SFN) is a phytocompound belonging to the isothiocyanate family. Although it was also found in seeds and mature plants, SFN is mainly present in sprouts of many cruciferous vegetables, including cabbage, broccoli, cauliflower, and Brussels sprouts. SFN is produced by the conversion of glucoraphanin through the enzyme myrosinase, which leads to the formation of this isothiocyanate. SFN is especially characterized by antioxidant, anti-inflammatory, and anti-apoptotic properties, and for this reason, it aroused the interest of researchers. The aim of this review is to summarize the experimental studies present on Pubmed that report the efficacy of SFN in the treatment of neurodegenerative disease, including Alzheimer’s disease (AD), Parkinson’s disease (PD), and multiple sclerosis (MS). Therefore, thanks to its beneficial effects, SFN could be useful as a supplement to counteracting neurodegenerative diseases.

Oxidative stress and related gene expression effects of cyfluthrin in human neuroblastoma SH-SY5Y cells: Protective effect of melatonin

This study was designed to assess oxidative stress induction in human neuroblastoma SH-SY5Y cells in response to cyfluthrin exposure. Cell viability MTT assay was carried out to assess cyfluthrin cytotoxicity; IC₃₀ and IC₅₀ values for cyfluthrin were calculated to be 4.81 ± 0.92 μM and 19.39 ± 3.44 μM, respectively. Cyfluthrin induced a significant increase in ROS generation, lipid peroxides measured as malondialdehyde (MDA) and nitric oxide (NO) production and a significant decrease in NQO1 activity. The antioxidant activity of melatonin (MEL), Trolox, N-acetylcysteine (NAC) and Sylibin against cyfluthrin-induced oxidative stress was examined. Cyfluthrin increased significantly gene expressions of apoptosis, proinflammation and oxidative stress (Bax, Bcl-2, Casp-3, BNIP3, AKT1, p53, APAF1, NFκB1, TNFα and Nrf2) mediators. In the most genes, the mRNA levels induced by cyfluthrin were partially reduced by MEL (1 μM). Cyfluthrin effects on gene expression profiling of oxidative stress pathway by Real-Time PCR array analysis showed that of the 84 genes examined, (fold change > 1.5) changes in mRNA levels were detected in 31 genes: 13 upregulated and 18 down-regulated. A fold change >3.0 fold was observed on upregulated CYBB, DUOX1, DUOX2, AOX1, BNIP3, HSPA1A, NOS2, and NQO1 genes. The greater fold change reversion (2.5 fold) by MEL (1 μM) was observed on cyfluthrin-upregulated CYBB, AOX1, BNIP3 and NOS2 genes. These results demonstrated that oxidative stress is a key element in cyfluthrin induced neurotoxicity as well as MEL may play a role in reducing cyfluthrin-induced oxidative stress.

Nrf2/ARE Pathway Modulation by Dietary Energy Regulation in Neurological Disorders

Nuclear factor erythroid 2-related factor 2 (Nrf2) regulates the expression of an array of enzymes with important detoxifying and antioxidant functions. Current findings support the role of high levels of oxidative stress in the pathogenesis of neurological disorders. Given the central role played by Nrf2 in counteracting oxidative damage, a number of studies have targeted the modulation of this transcription factor in order to confer neuroprotection. Nrf2 activity is tightly regulated by oxidative stress and energy-based stimuli. Thus, many dietary interventions based on energy intake regulation, such as dietary energy restriction (DER) or high-fat diet (HFD), modulate Nrf2 with consequences for a variety of cellular processes that affect brain health. DER, by either restricting calorie intake or meal frequency, activates Nrf2 thereby triggering its protective effects, whilst HFD inhibit this pathway, thereby exacerbating oxidative stress. Consequently, DER protocols can be valuable strategies in the management of central nervous system (CNS) disorders. Herein, we review current knowledge of the role of Nrf2 signaling in neurological diseases, namely Alzheimer’s disease, Parkinson’s disease, multiple sclerosis and cerebral ischemia, as well as the potential of energy intake regulation in the management of Nrf2 signaling.

Integrin linked kinase regulates the transcription of AQP2 by NFATC3

Two processes are associated with progressive loss of renal function: 1) decreased aquaporin-2 (AQP2) expression and urinary concentrating capacity (Nephrogenic Diabetes Insipidus, NDI); and 2) changes in extracellular matrix (ECM) composition, e.g. increased collagen I (Col I) deposition, characteristic of tubule-interstitial fibrosis. AQP2 expression is regulated by both the ECM-to-intracellular scaffold protein integrin-linked kinase (ILK) by NFATc/AP1 and other transcription factors. In the present work, we used in vivo and in vitro approaches to examine ILK participation in NFATc3/AP-1-mediated increases in AQP2 gene expression. Both NFATc3 knock-out mice and ILK conditional-knockdown mice (cKD-ILK) display symptoms of NDI (polyuria and reduced AQP2 expression). NFATc3 is upregulated in the renal medulla tubular cells of cKD-ILK mice but with reduced nuclear localization. Inner medullary collecting duct mIMCD3 cells were subjected to ILK depletion and transfected with reporter plasmids. Pharmacological activators or inhibitors determined the effect of ILK activity on NFATc/AP-1-dependent increases in transcription of AQP2. Finally, mIMCD3 cultured on Col I showed reduced activity of the ILK/GSK3β/NFATc/AQP2 axis, suggesting this pathway is a potential target for therapeutic treatment of NDI.

MicroRNA-7 activates Nrf2 pathway by targeting Keap1 expression

Nuclear factor E2-related factor 2 (Nrf2) is a key transcription factor that regulates the expression of a number of antioxidant and detoxifying genes that provide cellular protection against various stressors including reactive oxygen species (ROS). Nrf2 activity is tightly regulated by a cytoplasmic inhibitory protein called Kelch-like ECH-associated protein 1 (Keap1). The mechanism that controls Keap1 expression, however, remains poorly understood. In the present study, we demonstrate that microRNA-7 (miR-7), which is highly expressed in the brain, represses Keap1 expression by targeting the 3'-untranslated region (UTR) of its mRNA in human neuroblastoma cells, SH-SY5Y. Subsequently, this event results in an increased Nrf2 activity, as evidenced by an increase in the expression of its transcriptional targets, heme oxygenase 1 (HO-1) and glutamate-cysteine ligase modifier subunit (GCLM), and an enhanced nuclear localization of Nrf2. In addition, miR-7 decreases the intracellular hydroperoxides level and increases the level of reduced form of glutathione, indicative of oxidative stress relief. We also demonstrate that targeted repression of Keap1 and activation of Nrf2 pathway, in part, underlies the protective effects of miR-7 against 1-methyl-4-phenylpyridinium (MPP+)-induced toxicity in SH-SY5Y and differentiated human neural progenitor cells, ReNcell VM. These findings point to a new mechanism by which miR-7 exerts cytoprotective effects by regulating the Nrf2 pathway.

miRNA Influences in NRF2 Pathway Interactions within Cancer Models

The NRF2 transcription factor (nuclear factor-erythroid 2 p45-related factor 2) has been identified as a key molecular player in orchestrating adaptive cellular interactions following a wide spectrum of cellular stress conditions that could be either extracellular or intracellular. Dysregulation of the NRF2 system is implicated in various disease states, including inflammatory conditions. The NRF2 transcription factor is also known to permit cross talk with several other essential cellular signaling pathways. Recent literature has also elucidated the potential influences of miRNA activity over modulations of the NRF2 signalling network. Consequently, further delving into the knowledge regarding the extent of miRNA-induced epigenetic gene regulatory control on key elements of the NRF2 signalling pathway and its cross talk, particularly within the context of cancer models, can prove to be of high clinical importance. This is so since such miRNAs, once identified and validated, can be potentially exploited as novel drug targets for emerging translational medicine-based therapies.

6-OHDA-Induced Changes in Parkinson's Disease-Related Gene Expression are not Affected by the Overexpression of PGAM5 in In Vitro Differentiated Embryonic Mesencephalic Cells

LUHMES cells, a recently established line of immortalized embryonic mesencephalic cells, are the novel in vitro model for studying Parkinson's disease (PD) and dopaminergic neuron biology. Phosphoglyceromutase 5 (PGAM5) is a mitochondrial protein involved in mitophagy, mitochondria dynamics, and other processes important for PD pathogenesis. We tested the impact of lentiviral overexpression of PGAM5 protein in LUHMES cells on their differentiation and expression of 84 PD-related genes. LUHMES cells were transduced with PGAM5 or mock and treated with 100 μM 6-hydroxydopamine (6-OHDA), a model PD neurotoxin. Real-Time PCR analysis revealed that the treatment with 6-OHDA-induced changes in expression of 44 PD-related genes. PGAM5 transduction alone did not cause alternations in PD-related genes expression, nor it affected changes in gene expression mediated by 6-OHDA. The 6-OHDA-induced PD-related gene expression profile of LUHMES cells is presented for the first time and widely discussed.

Silencing of Hsp90 chaperone expression protects against 6-hydroxydopamine toxicity in PC12 cells

Parkinson's disease (PD) is the second most common age-related neurodegenerative disorder that has been shown to be associated with oxidative stress. This phenomenon occurs primarily via generation of 6-hydroxydopamine(6-OHDA) in catecholaminergic neurons leading to activation of apoptosis. The 90-kDa heat shock protein (Hsp90) functions as a chaperone in maintaining the functional stability and viability of cells under a transforming pressure. Since Hsp90 binds to inactive transcription factor heat shock factor-1 (HSF-1), inhibition of Hsp90 could activate HSF-1 and transcription of heat shock element containing genes subsequently, like Hsp70 as an anti-apoptotic factor. Our trial of silencing Hsp90 expression through transfection of Hsp90 siRNAs into neuronal PC12 cells being exposed to 6-OHDA resulted in the inhibition of pro-apoptotic factors, Bax, caspase-3, and PARP and upregulation of anti-apoptotic factor, Bcl2. In this manner,our data suggest a protective role for Hsp70 as it was observed to be induced upon Hsp90 knockdown. Furthermore, our results showed that Hsp90 silencing against 6-OHDA-induced oxidative stress may associate with upregulation of nuclear factor-erythroid 2-related factor 2. In summary, we found that silencing of Hsp90 expression leads to induction of cytoprotective pathways which can protect neurons against apoptosis in a PD model.

Therapeutic effect of hydrogen sulfide-releasing L-Dopa derivative ACS84 on 6-OHDA-induced Parkinson's disease rat model

Parkinson’s disease (PD), characterized by loss of dopaminergic neurons in the substantia nigra, is a neurodegenerative disorder of central nervous system. The present study was designed to investigate the therapeutic effect of ACS84, a hydrogen sulfide-releasing-L-Dopa derivative compound, in a 6-hydroxydopamine (6-OHDA)-induced PD model. ACS84 protected the SH-SY5Y cells against 6-OHDA-induced cell injury and oxidative stress. The protective effect resulted from stimulation of Nrf-2 nuclear translocation and promotion of anti-oxidant enzymes expression. In the 6-OHDA-induced PD rat model, intragastric administration of ACS84 relieved the movement dysfunction of the model animals. Immunofluorescence staining and High-performance liquid chromatography analysis showed that ACS84 alleviated the loss of tyrosine-hydroxylase positive neurons in the substantia nigra and the declined dopamine concentration in the injured striatums of the 6-OHDA-induced PD model. Moreover, ACS84 reversed the elevated malondialdehyde level and the decreased glutathione level in vivo. In conclusion, ACS84 may prevent neurodegeneration via the anti-oxidative mechanism and has potential therapeutic values for Parkinson’s disease.

Borneol alleviates oxidative stress via upregulation of Nrf2 and Bcl-2 in SH-SY5Y cells

CONTEXT

The β-amyloid (Aβ) peptide aggregation with accompanying oxidative stress plays the major role in the pathogenesis of Alzheimer's disease (AD). Some natural compounds, including borneol, shed promising light on AD treatment.

OBJECTIVE

The present study was designed to investigate the antioxidative, antiapoptotic effects, and neuroprotection of borneol in human neuroblastoma cells (SH-SY5Y).

MATERIALS AND METHODS

Oxidative stress was induced by administering 50 µM Aβ into SH-SY5Y cells. Neuroprotective effect of commercially available borneol was examined by determining cell viability with the MTT assay. Intracellular reactive oxygen species (ROS) generation was measured using a fluorometer with further examination of heme oxygenase-1 (HO-1) and nuclear factor-erythroid 2 p45-related factor 2 (Nrf2) expression. Apoptosis was examined by measuring the ratio of B-cell lymphoma 2 (Bcl-2)/Bcl-2-associated X protein (Bax).

RESULTS

Our data indicated that Aβ-induced cell cytotoxicity was inhibited by 100 µM of (-) and (+) borneol treatment. Treatment of borneol significantly decreased ROS generation (P < 0.01). The expression of HO-1 and nuclear translocation of Nrf2 were increased by Aβ treatment. This nuclear translocation of Nrf2 was further increased by administration of borneol. Compared with the Aβ treated group, the (+) borneol treated group significantly increased Bcl-2 expression with decreased expression of Bax.

DISCUSSION AND CONCLUSION

Borneol protected SH-SY5Y cells against Aβ-induced toxicity, exerted an antioxidative effect and suppressed apoptosis. It increases our knowledge about neuroprotective mechanism of borneol, and it is hopeful to be a candidate compound for developing therapeutic drug for the prevention and treatment of AD and other Aβ-related neurodegenerative diseases.

RETRACTED: S-allyl cysteine protects against 6-hydroxydopamine-induced neurotoxicity in the rat striatum: involvement of Nrf2 transcription factor activation and modulation of signaling kinase cascades

Pharmacological activation at the basal ganglia of the transcription factor Nrf2, guardian of redox homeostasis, holds a strong promise for the slow progression of Parkinson's disease (PD). However, a potent Nrf2 activator in the brain still must be found. In this study, we have investigated the potential use of the antioxidant compound S-allyl cysteine (SAC) in the activation of Nrf2 in 6-hydoxydopamine (6-OHDA)-intoxicated rats. In the rat striatum, SAC by itself promoted the Nrf2 dissociation of Keap-1, its nuclear translocation, the subsequent association with small MafK protein, and further binding of the Nrf2/MafK complex to ARE sequence, as well as the up-regulation of Nrf2-dependent genes encoding the antioxidant enzymes HO-1, NQO-1, GR, and SOD-1. In vivo and in vitro experiments to identify signaling pathways activated by SAC pointed to Akt as the most likely kinase participating in Nrf2 activation by SAC. In PC12 cells, SAC stimulated the activation of Akt and ERK1/2 and inhibited JNK1/2/3 activation. In the rat striatum, the SAC-induced activation of Nrf2 is likely to contribute to inhibit the toxic effects of 6-OHDA evidenced by phase 2 antioxidant enzymes up-regulation, glutathione recovery, and attenuation of reactive oxygen species (ROS), nitric oxide (NO), and lipid peroxides formation. These early protective effects correlated with the long-term preservation of the cellular redox status, the striatal dopamine (DA) and tyrosine hydroxylase (TH) levels, and the improvement of motor skills. Therefore, this study indicates that, in addition to direct scavenging actions, the activation of Nrf2 by SAC might confer neuroprotective responses through the modulation of kinase signaling pathways in rodent models of PD, and suggests that this antioxidant molecule may have a therapeutic value in this human pathology.

Activation of the Nrf2-ARE pathway by siRNA knockdown of Keap1 reduces oxidative stress and provides partial protection from MPTP-mediated neurotoxicity

Nuclear factor erythroid 2-related factor 2 (Nrf2) is a transcription factor that binds to the antioxidant response element, a cis-acting regulatory element that increases expression of detoxifying enzymes and antioxidant proteins. Kelch-like ECH associating protein 1 (Keap1) protein is a negative regulator of Nrf2. Previous work has shown that genetic overexpression of Nrf2 is protective in vitro and in vivo. To modulate the Nrf2-ARE system without overexpressing Nrf2, we used short interfering RNA (siRNA) directed against Keap1. Keap1 siRNA administration in primary astrocytes increased the levels of Nrf2-ARE driven genes and protected against oxidative stress. Moreover, Keap1 siRNA resulted in a persistent upregulation of the Nrf2-ARE pathway and protection against oxidative stress in primary astrocytes. Keap1 siRNA injected into the striatum was also modestly protective against MPTP-induced dopaminergic terminal damage. These data indicate that activation of endogenous intracellular levels of Nrf2 is sufficient to protect in models of oxidative stress and Parkinson's disease.

Induction of activation of the antioxidant response element and stabilization of Nrf2 by 3-(3-pyridylmethylidene)-2-indolinone (PMID) confers protection against oxidative stress-induced cell death

The antioxidant response elements (ARE) are a cis-acting enhancer sequence located in regulatory regions of antioxidant and detoxifying genes. Nuclear factor (erythroid-derived 2)-like 2 (Nrf2) is a member of the Cap 'n' Collar family of transcription factors that binds to the ARE and regulates the transcription of specific ARE-containing genes. Under oxidative stress, Nrf2/ARE induction is fundamental to defense against reactive oxygen species (ROS) and serves as a key factor in the protection against toxic xenobiotics. 3-(3-Pyridylmethylidene)-2-Indolinone (PMID) is a derivative of 2-indolinone compounds which act as protein kinase inhibitors and show anti-tumor activity. However, the role of PMID in the oxidative stress remains unknown. In the present study, we showed that PMID induced the activation of ARE-mediated transcription, increased the DNA-binding activity of Nrf2 and then up-regulated the expression of antioxidant genes such as HO-1, SOD, and NQO1. The level of Nrf2 protein was increased in cells treated with PMID by a post-transcriptional mechanism. Under CHX treatment, the stability of Nrf2 protein was enhanced by PMID with decreased turnover rate. We showed that PMID reduced the ubiquitination of Nrf2 and disrupted the Cullin3 (Cul3)-Keap1 interaction. Furthermore, cells treated with PMID showed resistance to cytotoxicity by H(2)O(2) and pro-oxidant 6-OHDA. PMID also up-regulated the antioxidant level in BALB/c mice. Taken together, the compound PMID induces the ARE-mediated gene expression through stabilization of Nrf2 protein and activation of Nrf2/ARE pathway and protects against oxidative stress-mediated cell death.

The Keap1-Nrf2 cell defense pathway--a promising therapeutic target?

By regulating the basal and inducible expression of an abundance of detoxification enzymes, antioxidant proteins, xenobiotic transporters and other stress response proteins, the Keap1-Nrf2 pathway plays a crucial role in determining the sensitivity of mammalian cells to chemical and oxidative insults that have the capacity to provoke cellular harm. This review highlights historical and recent advances in our understanding of the molecular mechanisms that regulate the activity of the Keap1-Nrf2 pathway. The important role of Nrf2 in protecting against the onset of specific diseases and drug-induced toxicities is also examined, alongside the emerging role of Nrf2 in promoting oncogenesis and chemotherapeutic drug resistance. A particular emphasis is placed on the potential for translation of this mechanistic understanding into clinical strategies that can improve human health, with consideration of the potential applications of targeting Nrf2 therapeutically.

The pesticide deltamethrin increases free radical production and promotes nuclear translocation of the stress response transcription factor Nrf2 in rat brain

The transcription factor NF-E2-related factor 2 (Nrf2) plays a critical role in the mammalian response to chemical and oxidative stress through induction of phase II detoxification enzymes and oxidative stress response proteins. We reported that Nrf2 expression was activated by deltamethrin (DM), a prototype of the widely used Parathyroid pesticides, in PC12 cells. However, no study has examined Nrf2 nuclear translocation and free radical production, two hallmarks of oxidative stress, in the mammalian brain in vivo. To this end, we examined translocation of Nrf2 and production of free radicals in rat brain exposed to DM. Indeed, DM initiated nuclear translocation of Nrf2 in a dose-dependent manner. Furthermore, Nrf2 translocation was accompanied by the expression of heme oxygenase-1 gene, an Nrf2-regulated gene linked to free radical production. Deltamethrin exposure promoted free radical formation in rat brain and reactive oxygen species generation in PC12 cells. Translocation of Nrf2 may be a response to DM-dependent induction of free radicals and DM may act as a mammalian neurotoxin by initiating oxidative stress.

The Nrf2/ARE Pathway: A Promising Target to Counteract Mitochondrial Dysfunction in Parkinson's Disease

Mitochondrial dysfunction is a prominent feature of various neurodegenerative diseases as strict regulation of integrated mitochondrial functions is essential for neuronal signaling, plasticity, and transmitter release. Many lines of evidence suggest that mitochondrial dysfunction plays a central role in the pathogenesis of Parkinson's disease (PD). Several PD-associated genes interface with mitochondrial dynamics regulating the structure and function of the mitochondrial network. Mitochondrial dysfunction can induce neuron death through a plethora of mechanisms. Both mitochondrial dysfunction and neuroinflammation, a common denominator of PD, lead to an increased production of reactive oxygen species, which are detrimental to neurons. The transcription factor nuclear factor E2-related factor 2 (Nrf2, NFE2L2) is an emerging target to counteract mitochondrial dysfunction and its consequences in PD. Nrf2 activates the antioxidant response element (ARE) pathway, including a battery of cytoprotective genes such as antioxidants and anti-inflammatory genes and several transcription factors involved in mitochondrial biogenesis. Here, the current knowledge about the role of mitochondrial dysfunction in PD, Nrf2/ARE stress-response mechanisms, and the evidence for specific links between this pathway and PD are summarized. The neuroprotection of nigral dopaminergic neurons by the activation of Nrf2 through several inducers in PD is also emphasized as a promising therapeutic approach.

Nutraceutical antioxidants as novel neuroprotective agents

A variety of antioxidant compounds derived from natural products (nutraceuticals) have demonstrated neuroprotective activity in either in vitro or in vivo models of neuronal cell death or neurodegeneration, respectively. These natural antioxidants fall into several distinct groups based on their chemical structures: (1) flavonoid polyphenols like epigallocatechin 3-gallate (EGCG) from green tea and quercetin from apples; (2) non-flavonoid polyphenols such as curcumin from tumeric and resveratrol from grapes; (3) phenolic acids or phenolic diterpenes such as rosmarinic acid or carnosic acid, respectively, both from rosemary; and (4) organosulfur compounds including the isothiocyanate, L-sulforaphane, from broccoli and the thiosulfonate allicin, from garlic. All of these compounds are generally considered to be antioxidants. They may be classified this way either because they directly scavenge free radicals or they indirectly increase endogenous cellular antioxidant defenses, for example, via activation of the nuclear factor erythroid-derived 2-related factor 2 (Nrf2) transcription factor pathway. Alternative mechanisms of action have also been suggested for the neuroprotective effects of these compounds such as modulation of signal transduction cascades or effects on gene expression. Here, we review the literature pertaining to these various classes of nutraceutical antioxidants and discuss their potential therapeutic value in neurodegenerative diseases.

Genome-wide microarray analysis of the differential neuroprotective effects of antioxidants in neuroblastoma cells overexpressing the familial Parkinson's disease alpha-synuclein A53T mutation

In Parkinson's disease substantia nigra neurons degenerate likely due to oxidative damage interacting with genetic risk factors. Here, SH-SY5Y cells expressing wild-type or A53T alpha-synuclein had increased sensitivity to methyl-4-phenylpyridinium iodide (MPP(+)), which induces mitochondrial dysfunction, and 6-hydroxydopamine (6-OHDA), which causes oxidative stress. Edaravone protected only against MPP(+), and EGCG ((-)-epigallocatechin-3-O-gallate) protected only against 6-OHDA. Thus genomic responses to MPP(+) and 6-OHDA in the presence of these antioxidants were analyzed using microarrays. Pathway analysis indicated that MPP(+) activated p53 (P < 0.001) while 6-OHDA induced the Nrf2 antioxidative stress response (P < 0.0001). EGCG was more effective at blocking 6-OHDA-mediated genomic responses, while edaravone was more effective against MPP(+). We identified 32 genes that responded to both toxins except in the presence of an effective anti-oxidant; eight are transcription factors and potentially constitute a stress-response transcriptional network. These data provide insights into the mechanisms of neurotoxicity and identifies genes that might mediate antioxidant efficacy.

Nrf2 activators provide neuroprotection against 6-hydroxydopamine toxicity in rat organotypic nigrostriatal cocultures

Oxidative stress and inflammation appear to play a critical role in the progression of Parkinson's disease. As a result, there has been growing interest in antioxidant pathways and how these pathways might be exploited to slow the progressive loss of dopamine neurons. One such pathway that has garnered attention recently is mediated by the transcription factor Nrf2 and is integral in orchestrating cells' antiinflammatory defense. Nrf2 controls the inducible expression of numerous antioxidant and phase 2 detoxification genes, such as glutathione S-transferase, heme oxygenase-1, and NAD(P)H:quinone oxidoreductase 1 (NQO1). Once activated, these genes work synergistically to maintain intracellular redox homeostasis. In this study, we test the hypothesis that Nrf2 activation can protect dopaminergic neurons against 6-hydroxydopamine (6-OHDA)-induced toxicity. Treatment of organotypic nigrostriatal cocultures with either tert-butylhydroquinone (tBHQ) or sulforaphane, known activators of Nrf2, mitigated dopaminergic cell loss. The observed protection appeared to be mediated, at least in part, by an increase in antioxidant activity. Simultaneous treatment of cultures with tBHQ and 6-OHDA increased NQO1 expression 17-fold compared with controls. Overall, these results suggest that Nrf2 may play an important role in cellular protection in neurodegenerative diseases and may be a viable therapeutic target in the future.

Multiple protective activities of neuroglobin in cultured neuronal cells exposed to hypoxia re-oxygenation injury

Oxidative stress is associated with the pathology of acute and chronic neurodegenerative disease. We have cloned a human neuroglobin (Nb) construct and over-expressed this protein in cultured human neuronal cells to assess whether Nb ameliorates the cellular response to experimental hypoxia-reoxygenation (H/R) injury. Parental cells transfected with a blank (pDEST40) vector responded to H/R injury with a significant decrease in cellular ATP at 5 and 24 h after insult. This was coupled with increases in the cytosolic Ca(2+), and the transition metals iron (Fe), copper (Cu), and zinc (Zn) within the cell body, as monitored simultaneously using X-ray fluorescence microprobe imaging. Parental cell viability decreased over the same time period with a approximately 4 to 5-fold increase in cell death (maximum approximately 25%) matched by an increase in caspase 3/7 activation (peaking at a 15-fold increase after 24 h) and condensation of beta-actin along axonal processes. Over-expression of Nb inhibited ATP loss and except for significant decreases in the sulfur (S), chlorine (Cl), potassium (K) and Ca(2+) contents, maintained cellular ion homeostasis after H/R insult. This resulted in increased cell viability, significantly diminished caspase activation and maintenance of the beta-actin cytoskeletal structure and receptor-mediated endocytosis. These data indicate that bolstering the cellular content of Nb inhibits neuronal cell dysfunction promoted by H/R insult through multiple protective actions including: (i) maintenance of cellular bioenergetics; (ii) inhibition of Ca(2+) influx; (iii) a reduction in cellular uptake of Fe, Cu and Zn at the expense of S, Cl and K; and (iv) an enhancement of cell viability through inhibiting necrosis and apoptosis.

The Nrf2-Keap1 defence pathway: role in protection against drug-induced toxicity

The metabolic biotransformation of xenobiotics to chemically reactive metabolites can, in some instances, underlie the pathogenesis of certain adverse drug reactions, due to the development of chemical or oxidative stress. In order to guard against such stresses, mammalian cells have evolved multi-faceted, highly-regulated defence systems, one of the most important being that which is regulated by the transcription factor Nrf2. Through regulating the expression of numerous cytoprotective genes, Nrf2 serves as a critical determinant of a cell's capacity to survive, or succumb, to a toxic insult. The aim of this review is to summarise our current understanding of the biochemistry that underlies the Nrf2 defence pathway, and highlight the important role of this transcription factor in the protection against drug-induced toxicity, primarily through the examination of recent investigations that have demonstrated an increased vulnerability to various toxins in animals lacking Nrf2.

Location, location, location: altered transcription factor trafficking in neurodegeneration

Neurons may be particularly sensitive to disruptions in transcription factor trafficking. Survival and injury signals must traverse dendrites or axons, in addition to soma, to affect nuclear transcriptional responses. Transcription factors exhibit continued nucleocytoplasmic shuttling; the predominant localization is regulated by binding to anchoring proteins that mask nuclear localization/export signals and/or target the factor for degradation. Two functional groups of karyopherins, importins and exportins, mediate RanGTPase-dependent transport through the nuclear pore. A growing number of recent studies, in Alzheimer, Parkinson, and Lewy body diseases, amyotrophic lateral sclerosis, and human immunodeficiency virus encephalitis, implicate aberrant cytoplasmic localization of transcription factors and their regulatory kinases in degenerating neurons. Potential mechanisms include impaired nuclear import, enhanced export, suppression of degradation, and sequestration in protein aggregates or organelles and may reflect unmasking of alternative cytoplasmic functions, both physiologic and pathologic. Some "nuclear" factors also function in mitochondria, and importins are also involved in axonal protein trafficking. Detrimental consequences of a decreased nuclear to cytoplasmic balance include suppression of neuroprotective transcription mediated by cAMP- and electrophile/antioxidant-response elements and gain of toxic cytoplasmic effects. Studying the pathophysiologic mechanisms regulating transcription factor localization should facilitate strategies to bypass deficits and restore adaptive neuroprotective transcriptional responses.

NF-E2 Related Factor 2 Activation and Heme Oxygenase-1 Induction by tert-Butylhydroquinone Protect against Deltamethrin-Mediated Oxidative Stress in PC12 Cells

Recent findings suggest that oxidative stress caused by pyrethroid pesticides could be closely involved in the neurotoxicity. tert-Butylhydroquinone ( tBHQ) is a known inducer of Nrf2-mediated transcription, and treatment of cells with tBHQ can confer protection against H 2O 2 and 6-hydroxydopamine (6-OHDA). In this study, we investigated the neuroprotective effect of tBHQ against deltamethrin (DM)-induced oxidative stress using rat PC12 adrenal pheochromocytoma cells. The pretreatment of PC12 cells with tBHQ significantly reduced DM-induced generation of reactive oxygen species (ROS) and increased intracellular ionized calcium ([Ca (2+)] i). We also observed that DM or tBHQ induced the expression of NF-E2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1), a Nrf2-regulated gene. In addition, the Nrf2 antioxidant responsive element (ARE) pathways activated by tBHQ caused a partial inhibition of the DM-induced Nrf2 and HO-1 expression. Altogether, our data clearly indicate that an activation of Nrf2/ARE pathways in PC12 cells by tBHQ treatment protects cells from DM-induced oxidative stress and regulates DM- mediated adaptive responses in PC12 cells via translocation of Nrf2.

Transcription factor Nrf2 activation by deltamethrin in PC12 cells: Involvement of ROS

Activation of transcription factor NF-E2-related factor 2 (Nrf2) is a key initiation step in the cellular protection against a broad range of chemical oxidative stresses. To gain insights into dopaminergic cell responses to pesticides, the present study was conducted to examine the effects of deltamethrin (DM), a prototype of widely used pyrithroid pesticides, on the activation and expression of Nrf2 in PC12 rat adrenal pheochromocytoma cells as a dopaminergic cell model. We found, for the first time, that DM enhanced cellular expression of Nrf2 at the transcriptional and protein levels and activated expression of Nrf2-regulated genes in these cells. In addition, DM exposure caused nuclear accumulation of Nrf2 in association with downstream activation of Nrf2-mediated oxidative response genes, such as heme oxygenase-l (HO-1) and gamma-glutamylcysteine synthetase catalytic heavy subunit (GCSh). Furthermore, when cells were pretreated with N-acetyl cysteine (NAC), a scavenger of reactive oxygen species (ROS), DM-induced Nrf2 signaling was suppressed. These results indicate that ROS is the mediator of nuclear Nrf2 accumulation. Taken together, these data clearly show that DM increases Nrf2 expression and activity and that ROS is one of the mediators of this process.

DJ-1, a cancer- and Parkinson's disease-associated protein, stabilizes the antioxidant transcriptional master regulator Nrf2

DJ-1/PARK7, a cancer- and Parkinson's disease (PD)-associated protein, protects cells from toxic stresses. However, the functional basis of this protection has remained elusive. We found that loss of DJ-1 leads to deficits in NQO1 [NAD(P)H quinone oxidoreductase 1], a detoxification enzyme. This deficit is attributed to a loss of Nrf2 (nuclear factor erythroid 2-related factor), a master regulator of antioxidant transcriptional responses. DJ-1 stabilizes Nrf2 by preventing association with its inhibitor protein, Keap1, and Nrf2's subsequent ubiquitination. Without intact DJ-1, Nrf2 protein is unstable, and transcriptional responses are thereby decreased both basally and after induction. This effect of DJ-1 on Nrf2 is present in both transformed lines and primary cells across human and mouse species. DJ-1's effect on Nrf2 and subsequent effects on antioxidant responses may explain how DJ-1 affects the etiology of both cancer and PD, which are seemingly disparate disorders. Furthermore, this DJ-1/Nrf2 functional axis presents a therapeutic target in cancer treatment and justifies DJ-1 as a tumor biomarker.

Oxidative stress in sepsis: a redox redux

Sepsis and sepsis syndrome are leading causes of mortality throughout the world. It is widely held that sepsis represents a dysregulated innate immune response to an offending pathogen. This immune response is often initiated via microbial products signaling through TLRs expressed on host immune cells. There is increasing evidence that this innate response can be dramatically influenced by the cellular redox state, and thus a better understanding of oxidative regulation of innate immunity could lead to new treatments for sepsis. In this issue of the JCI, Thimmulappa et al. show that nuclear factor-erythroid 2-related factor 2 (Nrf2), a member of the "cap'n'collar" family of basic region-leucine zipper transcription factors, which has previously been shown to be involved in the transcription of antioxidant gene expression in response to xenobiotic stress, is also a critical regulator of cellular oxidative stress in sepsis (see the related article beginning on page 984).