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

Exploring Liraglutide in Lithium-Pilocarpine-Induced Temporal Lobe Epilepsy Model in Rats: Impact on Inflammation, Mitochondrial Function, and Behavior

Background/Objectives: Glucagon-like peptide-1 receptor agonists such as liraglutide are known for their neuroprotective effects in neurodegenerative disorders, but their role in temporal lobe epilepsy (TLE) remains unclear. We aimed to investigate the effects of liraglutide on several biological processes, including inflammation, antioxidant defense mechanisms, mitochondrial dynamics, and function, as well as cognitive and behavioral changes in the TLE model. Methods: Low-dose, repeated intraperitoneal injections of lithium chloride-pilocarpine hydrochloride were used to induce status epilepticus (SE) in order to develop TLE in rats. Fifty-six male Sprague Dawley rats were subjected and allocated to the groups. The effects of liraglutide on inflammatory markers (NLRP3, Caspase-1, and IL-1β), antioxidant pathways (Nrf-2 and p-Nrf-2), and mitochondrial dynamics proteins (Pink1, Mfn2, and Drp1) were evaluated in hippocampal tissues via a Western blot. Mitochondrial function in peripheral blood mononuclear cells (PBMCs) was examined using flow cytometry. Cognitive-behavioral outcomes were assessed using the open-field, elevated plus maze, and Morris water maze tests. Results: Our results showed that liraglutide modulates NLRP3-mediated inflammation, reduces oxidative stress, and triggers antioxidative pathways through Nrf2 in SE-induced rats. Moreover, liraglutide treatment restored Pink1, Mfn2, and Drp1 levels in SE-induced rats. Liraglutide treatment also altered the mitochondrial function of PBMCs in both healthy and epileptic rats. This suggests that treatment can modulate mitochondrial dynamics and functions in the brain and periphery. Furthermore, in the behavioral aspect, liraglutide reversed the movement-enhancing effect of epilepsy. Conclusions: This research underscores the potential of GLP-1RAs as a possibly promising therapeutic strategy for TLE.

Investigation of the therapeutic effect of melatonin on deltamethrin applied mouse primary hepatocyte culture

OBJECTIVE

In recent years, it has been known that the melatonin hormone, secreted from the pineal gland, possesses significant antioxidant activity. This study explores the therapeutic effect of melatonin on the deleterious effects of deltamethrin, a pyrethroid pesticide extensively used worldwide, including in Türkiye, on mouse liver cells.

METHODS

Hepatocytes from Balb/C mice were isolated using a two-stage perfusion method, resulting in over 85% live hepatocytes. The isolated cells were cultured with different doses of deltamethrin (1 and 10 µM) and melatonin (100 µM) for 24 and 48 hours. At the conclusion of the culture period, hepatocytes were extracted at the 24th and 48th hours, and Malondialdehyde (MDA), Total Antioxidant Capacity (TAC), Total Oxidation Status (TOS), and DNA damages (8-hydroxy-2'-deoxyguanosine (8-OHdG)) were examined.

RESULTS

While an increase in MDA, TOS, and DNA damage was observed in the deltamethrin-administered groups of hepatocytes, a decrease in TAC level was noted. It was determined that the applied deltamethrin had no effect on cell viability throughout the application period.

CONCLUSION

Furthermore, it was observed that melatonin, when administered concurrently with deltamethrin, reduced the toxic effect of deltamethrin. This study suggests that melatonin has a protective effect against deltamethrin-induced damage in mouse hepatocyte cells.

Advances in Nrf2 Signaling Pathway by Targeted Nanostructured-Based Drug Delivery Systems

Nanotechnology has gained significant interest in various applications, including sensors and therapeutic agents for targeted disease sites. Several pathological consequences, including cancer, Alzheimer's disease, autoimmune diseases, and many others, are mostly driven by inflammation and Nrf2, and its negative regulator, the E3 ligase adaptor Kelch-like ECH-associated protein 1 (Keap1), plays a crucial role in maintaining redox status, the expression of antioxidant genes, and the inflammatory response. Interestingly, tuning the Nrf2/antioxidant response element (ARE) system can affect immune-metabolic mechanisms. Although many phytochemicals and synthetic drugs exhibited potential therapeutic activities, poor aqueous solubility, low bioavailability, poor tissue penetration, and, consequently, poor specific drug targeting, limit their practical use in clinical applications. Also, the therapeutic use of Nrf2 modulators is hampered in clinical applications by the absence of efficient formulation techniques. Therefore, we should explore the engineering of nanotechnology to modulate the inflammatory response via the Nrf2 signaling pathway. This review will initially examine the role of the Nrf2 signaling pathway in inflammation and oxidative stress-related pathologies. Subsequently, we will also review how custom-designed nanoscale materials encapsulating the Nrf2 activators can interact with biological systems and how this interaction can impact the Nrf2 signaling pathway and its potential outcomes, emphasizing inflammation.

Protective effect of nebivolol on rat ovary exposed to deltamethrin toxicity

PURPOSE

We aimed to investigate the antioxidant activity of nebivolol against possible damage to the ovarian tissue due to the application of deltamethrin as a toxic agent, by evaluating histopathological proliferating cell nuclear antigen (PCNA) and tumor necrosis factor-alpha (TNF-α) signal molecules immunohistochemically.

METHODS

The animals were divided into three groups as control, deltamethrin and deltamethrin + nebivolol groups. Vaginal smears were taken after the animals were mated and detected on the first day of pregnancy. After the sixth day, deltamethrin (0.5 mL of 30 mg/kg BW undiluted ULV), and 2 mL of sterile nebivolol solution were administered intraperitoneally every day for 6-21 periods. After routine histopathological follow-up, the ovarian tissue was stained with hematoxylin and eosin stain.

RESULTS

Control group showed normal histology of ovarium. In deltamethrin group, hyperplasic cells, degenerative follicles, pyknotic nuclei, inflammation and hemorrhagic areas were observed. Nebivolol treatment restored these pathologies. Deltamethrin treatment increased TNF-α and PCNA reaction. However, nebivolol decreased the expression.

CONCLUSIONS

It was thought that deltamethrin toxicity adversely affected follicle development by inducing degeneration and apoptotic process in preantral and antra follicle cells, and nebivolol administration might reduce inflammation and slow down the apoptotic signal in the nuclear phase and regulate reorganization.

Chronic exposure to low-dose deltamethrin can lead to colon tissue injury through PRDX1 inactivation-induced mitochondrial oxidative stress injury and gut microbial dysbiosis

OBJECTIVE

To date, it is unclear whether deltamethrin (DLM) intake causes damage to colon tissue. Hence, in this study, we aimed to clarify the effect of long-term exposure to low-dose DLM on colon tissues, and its potential mechanisms.

METHODS

Mice were treated with DLM (0.2 mg/kg/day) or DLM combined with N-acetyl-l-cysteine (NAC) (50 mg/kg/day) for 8 weeks. Human colon cancer cells (HCT-116) were treated with DLM (0, 25, 50, or 100 µM), NAC (2 mM), or overexpression plasmids targeting peroxiredoxin 1 (PRDX1) for 48 h. DLM was detected using a DLM rapid detection card. Colon injury was evaluated using haematoxylin and eosin staining and transmission electron microscopy. Apoptosis was determined using immunofluorescence staining (IF), western blotting (WB) and flow cytometry (FC) assays. MitoTracker, JC-1, and glutathione (GSH) detection were used to detect mitochondrial oxidative stress. Intestinal flora were identified by 16 S rDNA sequencing.

RESULTS

DLM accumulation was detected in the colon tissue and faeces of mice following long-term intragastric administration. Interestingly, our results showed that, even at a low dose, long-term intake of DLM resulted in severe weight loss and decreased the disease activity index scores and colon length. The results of IF, WB, and FC showed that DLM induced apoptosis in the colon tissue and cells. MitoTracker, JC-1, and GSH assays showed that DLM increased mitochondrial stress in colonic epithelial cells. Mechanistic studies have shown that increased mitochondrial stress and apoptosis are mediated by PRDX1 inhibition. Further experiments showed that PRDX1 overexpression significantly reduced DLM-induced oxidative stress injury and apoptosis. In addition, we observed that chronic exposure to DLM altered the composition of the intestinal flora in mice, including an increase in Odoribacter and Bacteroides and a decrease in Lactobacillus. The gut microbial richness decreased after DLM exposure in mice. Supplementation with NAC both in vivo and in vitro alleviated DLM-induced oxidative stress injury, colonic epithelial cell apoptosis, and gut microbial dysbiosis.

CONCLUSION

Chronic exposure to DLM, even at small doses, can cause damage to the colon tissue, which cannot be ignored. The production and use of pesticides such as DLM should be strictly regulated during agricultural production.

Neuroprotective Effects of Phenolic Antioxidant Tert-butylhydroquinone (tBHQ) in Brain Diseases

Human life and health are gravely threatened by brain diseases. The onset and progression of the illnesses are influenced by a variety of factors, including pathogenic causes, environmental factors, mental issues, etc. According to scientific studies, neuroinflammation and oxidative stress play a significant role in the development and incidence of brain diseases by producing pro-inflammatory cytokines and oxidative tissue damage to induce inflammation and apoptosis. Neuroinflammation, oxidative stress, and oxidative stress-related changes are inseparable factors in the etiology of several brain diseases. Numerous neurodegenerative diseases have undergone substantial research into the therapeutic alternatives that target oxidative stress, the function of oxidative stress, and the possible therapeutic use of antioxidants. Formerly, tBHQ is a synthetic phenolic antioxidant, which has been widely used as a food additive. According to recent researches, tBHQ can suppress the processes that lead to neuroinflammation and oxidative stress, which offers a fresh approach to treating brain diseases. In order to achieve the goal of decreasing inflammation and apoptosis, tBHQ is a specialized nuclear factor erythroid 2-related factor (Nrf2) activator that decreases oxidative stress and enhances antioxidant status by upregulating the Nrf2 gene and reducing nuclear factor kappa-B (NF-κB) activity. This article reviews the effects of tBHQ on neuroinflammation and oxidative stress in recent years and looks into how tBHQ inhibits neuroinflammation and oxidative stress through human, animal, and cell experiments to play a neuroprotective role in Alzheimer's disease (AD), stroke, depression, and Parkinson's disease (PD). It is anticipated that this article will be useful as a reference for upcoming research and the creation of drugs to treat brain diseases.

Klotho alleviates NLRP3 inflammasome-mediated neuroinflammation in a temporal lobe epilepsy rat model by activating the Nrf2 signaling pathway

Neuroinflammation not only contributes to epileptogenesis and neurodegeneration, but is also associated with cognitive impairment. Nod-like receptor family pyrin domain containing 3 (NLRP3) inflammasome-mediated neuroinflammation is positively correlated with progression of temporal lobe epilepsy (TLE) and cognitive impairment. Recent studies have shown that the anti-aging protein, klotho, exerts anti-neuroinflammation effects and enhances cognition in neurodegenerative disorders. In the present study, we investigated the role and underlying mechanism of klotho action in NLRP3 inflammasome-mediated neuroinflammation in a TLE model. Specifically, we first injected an adeno-associated viral (AAV)-mediated overexpression of klotho (AAV-KL) into the bilateral hippocampus of rats. After 3 weeks, rats were intraperitoneally injected with lithium-chloride pilocarpine (LiCl-Pilo) to generate a TLE model. Results showed that klotho was significantly downregulated six weeks after TLE, while AAV-mediated klotho overexpression substantially attenuated TLE-induced hippocampal neuronal injury and cognitive impairment. Interestingly, klotho overexpression significantly alleviated expression of NLRP3, IL-1β, and caspase-1 proteins, but up-regulated activation of nuclear factor erythroid 2-related factor 2 (Nrf2). However, treatment with Nrf2 inhibitor ML385 significantly reversed klotho's beneficial effects, including alleviated neuroinflammation, attenuated neuronal injury, and improved cognitive function. Taken together, these results indicated that klotho alleviated NLRP3 inflammasome-mediated neuroinflammation by activating the Nrf2 signaling pathway in the TLE rat model, suggesting that this the anti-aging protein could be a novel and promising therapeutic agent for managing TLE-associated cognitive impairment.

Attenuation of Pancreatic Cancer In Vitro and In Vivo via Modulation of Nrf2 and NF-κB Signaling Pathways by Natural Compounds

Pancreatic cancer is a disease in which deregulation of signaling pathways plays a key role, thus searching for their novel modulators is a promising therapeutic strategy. Hence, in this study, the effect of phytochemical combinations on the canonical and non-canonical activation of Nrf2 and its interaction with the NF-κB pathway was evaluated in extensively proliferating pancreatic cancer cell line, PSN-1, in comparison to non-cancerous MS1 cells. The activation of Nrf2 and NF-κB, expression of their target genes, and effect on cell survival were assessed in PSN-1 cells. The tumor burden was evaluated in mice carrying xenografts. PSN-1 cells were more sensitive to the tested compounds as compared to the MS1 cell line. Combination of xanthohumol and phenethyl isothiocyanate was more effective than single compounds at decreasing the canonical and non-canonical activation of Nrf2 in PSN-1 cancer cells. Decreased activation of NF-κB, and subsequent reduced cytosolic COX-2 and nuclear STAT3 level indicated their anti-inflammatory and pro-apoptotic activities. In vivo studies showed the partial response in groups treated with xanthohumol or the combination of xanthohumol and phenethyl isothiocyanate. Overall, these results suggest that the combination of xanthohumol and phenethyl isothiocyanate may be a promising therapeutic candidate against pancreatic cancer.

Systematic Review of Calcium Channels and Intracellular Calcium Signaling: Relevance to Pesticide Neurotoxicity

Pesticides of different chemical classes exert their toxic effects on the nervous system by acting on the different regulatory mechanisms of calcium (Ca2+) homeostasis. Pesticides have been shown to alter Ca2+ homeostasis, mainly by increasing its intracellular concentration above physiological levels. The pesticide-induced Ca2+ overload occurs through two main mechanisms: the entry of Ca2+ from the extracellular medium through the different types of Ca2+ channels present in the plasma membrane or its release into the cytoplasm from intracellular stocks, mainly from the endoplasmic reticulum. It has also been observed that intracellular increases in the Ca2+ concentrations are maintained over time, because pesticides inhibit the enzymes involved in reducing its levels. Thus, the alteration of Ca2+ levels can lead to the activation of various signaling pathways that generate oxidative stress, neuroinflammation and, finally, neuronal death. In this review, we also discuss some proposed strategies to counteract the detrimental effects of pesticides on Ca2+ homeostasis.

Pharmacological Modulation of Nrf2/HO-1 Signaling Pathway as a Therapeutic Target of Parkinson's Disease

Parkinson’s disease (PD) is a complex neurodegenerative disorder featuring both motor and nonmotor symptoms associated with a progressive loss of dopaminergic neurons in the substantia nigra pars compacta. Oxidative stress (OS) has been implicated in the pathogenesis of PD. Genetic and environmental factors can produce OS, which has been implicated as a core contributor to the initiation and progression of PD through the degeneration of dopaminergic neurons. The transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) orchestrates activation of multiple protective genes, including heme oxygenase-1 (HO-1), which protects cells from OS. Nrf2 has also been shown to exert anti-inflammatory effects and modulate both mitochondrial function and biogenesis. Recently, a series of studies have reported that different bioactive compounds were shown to be able to activate Nrf2/antioxidant response element (ARE) and can ameliorate PD-associated neurotoxin, both in animal models and in tissue culture. In this review, we briefly overview the sources of OS and the association between OS and the pathogenesis of PD. Then, we provided a concise overview of Nrf2/ARE pathway and delineated the role played by activation of Nrf2/HO-1 in PD. At last, we expand our discussion to the neuroprotective effects of pharmacological modulation of Nrf2/HO-1 by bioactive compounds and the potential application of Nrf2 activators for the treatment of PD. This review suggests that pharmacological modulation of Nrf2/HO-1 signaling pathway by bioactive compounds is a therapeutic target of PD.

Epigenetics in neurodegenerative disorders induced by pesticides

Neurodegenerative diseases are becoming major socio-economic burdens. However, most of them still have no effective treatment. Growing evidence indicates excess exposure to pesticides are involved in the development of various forms of neurodegenerative and neurological diseases through trigger epigenetic changes and inducing disruption of the epigenome. This review summaries studies on epigenetics alterations in nervous systems in relation to different kinds of pesticides, highlighting potential mechanism in the etiology, precision prevention and target therapy of various neurodegenerative diseases. In addition, the current gaps in research and future areas for study were also discussed.

Neurotoxicity of a pyrethroid pesticide deltamethrin is associated with the imbalance in proteolytic systems caused by mitophagy activation and proteasome inhibition

Pyrethroids are one of the most commonly used classes of synthetic pesticides in the world. Recent laboratory and epidemiological evidence suggested that pyrethroids have potential adverse effects in the mammalian brain; however, the underlying mechanisms of the neurotoxic effects of pyrethroids have not been fully elucidated. In the present study, we investigated the mechanisms of effects of a type II pyrethroid deltamethrin (DM) in a neuronal cell model focusing on the proteolytic function, including autophagy and the ubiquitin-proteasome system. We confirmed that a micromolar concentration of DM dose-dependently decreased the cell viability and induced apoptotic cell death. Our results showed that DM enhanced autophagy in association with an accumulation of autophagosomes and increase in the levels of autophagy markers LC3-II/LC3-I ratio and p62 which were much elevated in the presence of lysosomal inhibitors bafilomycin A1 and chloroquine. We also found that DM caused a dysfunction of mitochondria with a decrease of mitochondrial membrane potential and mitochondrial DNA copy number as well as colocalization with autophagosomes. Moreover, a decrease in the activities of three major proteasomal enzymes and an accumulation of ubiquitinated proteins were observed by the exposure to DM. Transcriptome analysis revealed that up-regulated genes supported the activation of autophagy with induction of cellular stress responses including oxidative stress and endoplasmic reticulum stress, while down-regulated genes related to the cell cycle and DNA replication. These findings provide novel insights into the neurotoxicity of DM which underlie the imbalance in proteolytic function caused by mitophagy activation and proteasome inhibition.

Astragaloside IV, a saponin from Astragalus membranaceus var. mongholicus, induces expressions of heme recycle proteins via signaling of Nrf2/ARE in cultured macrophages

ETHNOPHARMACOLOGICAL RELEVANCE

In traditional Chinese medicine (TCM) theory, "Qi" is classified as energetic essence supporting the life activities in human. "Blood" is categorized as nourishing essence and circulating in the body. "Blood" and "Qi" have an intimate relationship. Astragali Radix (AR; root of Astragalus membranaceus (Fisch.) Bge. Var. mongholicus (Bge.) Hsiao) has a broad spectrum of application for "Qi-Blood" enrichment. Astragaloside IV, a major saponin in AR, has therapeutic functions in erythropoietic, cardiovascular and immune systems. However, the efficacy of astragaloside IV in erythrophagocytosis has not been elucidated.

AIM OF THE STUDY

The possible functions of astragaloside IV in heme iron recycling during erythrophagocytosis in cultured macrophage were elucidated.

METHODS

The translational and transcriptional expressions of heme recycling enzymes were determined after incubating of astragaloside IV for 24 h in cultured macrophage.

RESULTS

In astragaloside IV-treated macrophage, the expressions, both RNA and protein levels, of regulators of heme recycling, e.g. heme oxygenase-1 (HO-1), ferroportin (FPN), biliverdin reductase A and B (BVRA, BVRB), were markedly induced in dose-dependent manners. In parallel, the transcriptional activity of antioxidant response element, cloned within an expression vector as pARE-Luc and transfected in cultured macrophages, was markedly induced after a challenge with astragaloside IV in a dose-dependent manner. Moreover, the translocation of Nrf2, a transcriptional factor in regulating expression of heme recycling protein, was induced by astragaloside IV, leading to an enrichment at nucleus fraction.

CONCLUSION

Astragaloside IV shed lights in enhancing the expression of heme recycle proteins via Nrf2/ARE signaling pathway.

An Overview of Nrf2 Signaling Pathway and Its Role in Inflammation

Inflammation is a key driver in many pathological conditions such as allergy, cancer, Alzheimer’s disease, and many others, and the current state of available drugs prompted researchers to explore new therapeutic targets. In this context, accumulating evidence indicates that the transcription factor Nrf2 plays a pivotal role controlling the expression of antioxidant genes that ultimately exert anti-inflammatory functions. Nrf2 and its principal negative regulator, the E3 ligase adaptor Kelch-like ECH- associated protein 1 (Keap1), play a central role in the maintenance of intracellular redox homeostasis and regulation of inflammation. Interestingly, Nrf2 is proved to contribute to the regulation of the heme oxygenase-1 (HO-1) axis, which is a potent anti-inflammatory target. Recent studies showed a connection between the Nrf2/antioxidant response element (ARE) system and the expression of inflammatory mediators, NF-κB pathway and macrophage metabolism. This suggests a new strategy for designing chemical agents as modulators of Nrf2 dependent pathways to target the immune response. Therefore, the present review will examine the relationship between Nrf2 signaling and the inflammation as well as possible approaches for the therapeutic modulation of this pathway.

Redox toxicology of environmental chemicals causing oxidative stress

Living organisms are surrounded with heavy metals such as methylmercury, manganese, cobalt, cadmium, arsenic, as well as pesticides such as deltamethrin and paraquat, or atmospheric pollutants such as quinone. Extensive studies have demonstrated a strong link between environmental pollutants and human health. Redox toxicity is proposed as one of the main mechanisms of chemical-induced pathology in humans. Acting as both a sensor of oxidative stress and a positive regulator of antioxidants, the nuclear factor erythroid 2-related factor 2 (NRF2) has attracted recent attention. However, the role NRF2 plays in environmental pollutant-induced toxicity has not been systematically addressed. Here, we characterize NRF2 function in response to various pollutants, such as metals, pesticides and atmospheric quinones. NRF2 related signaling pathways and epigenetic regulations are also reviewed.

Nrf2 activation protects auditory hair cells from cisplatin-induced ototoxicity independent on mitochondrial ROS production

Cisplatin is a well-known and commonly used chemotherapeutic agent. However, cisplatin-induced ototoxicity limits its clinical use. Previous studies have shown an important role of reactive oxygen species (ROS) accumulation in the pathogenesis of cisplatin-induced ototoxicity. In many cell types, the transcription factor, nuclear factor erythroid 2-related factor 2 (Nrf2) and antioxidant response element (ARE) protect against oxidative stress by suppressing ROS. Here our results showed that cisplatin injury reduced Nrf2 expression and inhibited Nrf2 translocation in HEI-OC1 cells and Nrf2 activator tert-butylhydroquinone (TBHQ) rescued hair cells from cisplatin induced apoptosis by suppressing the total cellular ROS accumulation. Moreover, we found that decreased ROS accumulation induced by TBHQ didn't depend on mitochondrial derived ROS production, indicating that Nrf2 activation alleviated cisplatin induced oxidative stress and apoptosis through mitochondrial-independent ROS production. Therefore, we provide a potential strategy of prevention and treatment for cisplatin-induced ototoxicity by Nrf2 activation. In conclusion, Nrf2 activation protects auditory hair cells from cisplatin-induced ototoxicity through suppressing the total cellular ROS levels which arise from sources other than mitochondria.

Deltamethrin exposure induces oxidative stress and affects meiotic maturation in mouse oocyte

Pyrethroid insecticides are commonly used as insecticides and considered to be less toxic to mammals, but may still impair the reproduction of animals and humans. The aim of this research was to evaluate the tendency of deltamethrin induced oxidative stress and its effects on meiosis, apoptosis and autophagy of mouse oocytes in vitro maturation after deltamethrin exposure. Especially, the maturation rate of oocytes decreased significantly after 14 h exposure of deltamethrin in concentration-dependent manners, which was manifested as abnormal spindle morphology and DNA double strand breaks. Oxidative stress was found in mouse oocytes exposed to deltamethrin, as shown by changes in the expression of CAT and SOD2. Our results also show that deltamethrin affects the quality of oocytes by causing abnormal mitochondrial distribution and by decreasing mitochondrial membrane potential. The apoptosis of oocyte regulated by the expression of Bax and Bcl-2 protein was obviously affected by deltamethrin. Compared with the control group, the expression of key regulatory factors in the autophagy pathway, LC3, Atg12, Atg14, and Beclin, increased in the experimental group. In summary, these results revealed that deltamethrin might inhibit the maturation of mouse oocytes and adversely affect the survival of oocytes.

Deltamethrin toxicity: A review of oxidative stress and metabolism

Deltamethrin is widely used worldwide due to its valuable insecticidal activity against pests and parasites. Increasing evidence has shown that deltamethrin causes varying degrees of toxicity. Moreover, oxidative stress and metabolism are highly correlated with toxicity. For the first time, this review systematically summarizes the deltamethrin toxicity mechanism from the perspective of oxidative stress, including deltamethrin-mediated oxidative damage, antioxidant status, oxidative signaling pathways and modulatory effects of antagonists, synergists and placebos on oxidative stress. Further, deltamethrin metabolism, including metabolites, metabolic enzymes and pathways and deltamethrin metabolite toxicity are discussed. This review will shed new light on deltamethrin toxicity mechanisms and provide effective strategies to ensure pest control and prevention of human and animal poisoning.

Evaluation of Nrf2 with Exposure to Nanoparticles

Transcription factor Nrf2, nuclear factor (erythroid-derived 2)-like 2, is considered a master regulator of redox homeostasis and plays a central role in antioxidant and anti-inflammatory defence. It has been largely reported that oxidative stress is implicated in nanoparticle-induced toxicity with the involvement of Nrf2. Several basic methods for Nrf2 evaluation with exposure to nanoparticles are described in this chapter including real-time reverse transcription-polymerase chain reaction (RT-PCR), western blotting, immunofluorescence staining, electrophoretic mobility shift assay, DNase I footprinting, dimethylsulfate footprinting, protein pulse-chase analysis, and tert-butylhydroquinone treatment.

Paraquat and MPTP induce neurodegeneration and alteration in the expression profile of microRNAs: the role of transcription factor Nrf2

Both transcription factors (TFs) and microRNAs (miRNAs) can exert a widespread impact on gene expression. In the present study, we investigated the role of Nrf2 in paraquat-induced intracorporeal neurodegeneration and miRNA expression by exposing Nrf2 wild-type and knockout mice to paraquat (PQ) or 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Exposure to 10 mg/kg PQ or 30 mg/kg MPTP caused damage to nerve cells in the substantia nigra (SN) in both Nrf2 (+/+) and Nrf2 (−/−) ICR mice, which included cell morphological changes, detectable apoptosis and a significant reduction in the number of dopaminergic (DA) neurons. When mice were exposed to the same PQ dose of 10 mg/kg, significant fewer tyrosine hydroxylase (TH)-positive DA neurons were observed in the Nrf2 (−/−) mice than that in the Nrf2 (+/+) mice. Both Nrf2 deficiency and PQ or MPTP exposure could alter miRNA expression profile in the SN, suggesting the potential involvement of Nrf2 in the PQ-induced or MPTP-induced miRNA expression alteration. The expression of miR-380-3p was altered by the Nrf2-MPTP interaction effect. miR-380-3p/Sp3-mRNA pathway is likely part of the mechanism of MPTP-induced neurodegeneration. Collectively, our results corroborated the protective role of Nrf2 and also demonstrated the essential interaction of Nrf2 with miRNAs in intracorporal neurodegeneration induced by neurotoxicants.

The gene expression regulators Nrf2 and small regulatory RNA molecule miR-380-3p protect nerve cells from damage caused by neurotoxins. Huangyuan Li, at Fujian Medical University, China, and colleagues examined the effects of paraquat and MPTP (1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine), two chemicals known to induce parkinsonism, in mice lacking Nrf2, a key mediator of antioxidant and anti-inflammatory responses. They found that after MPTP or paraquat exposure, the extent of neuronal loss in the substantia nigra was greater in mice lacking Nrf2 than in wild-type controls. Moreover, Nrf2 deficiency prevented an upregulation of miR-380-3p following MPTP exposure. These findings implicate miR-380-3p in the mechanism through which Nrf2 protects the brain from Parkinson’s disease-related cell death and opens new avenues of investigation for developing more effective neuroprotective therapies.

4-Hydroperoxy-2-decenoic acid ethyl ester protects against 6-hydroxydopamine-induced cell death via activation of Nrf2-ARE and eIF2α-ATF4 pathways

Parkinson's disease (PD) is a neurodegenerative disorder characterized by progressive degeneration of dopaminergic neurons in the substantia nigra. Oxidative stress has been reported to be closely related to the pathogenesis and worsening of symptoms of PD. One therapeutic strategy is to alleviate neuronal injuries caused by oxidative stress. In this study, we investigated protective effects of royal jelly (RJ) fatty acids and their derivatives on oxidative stress-induced cell death using human neuroblastoma SH-SY5Y cells. 4-Hydroperoxy-2-decenoic acid ethyl ester (HPO-DAEE), a synthesized RJ fatty acid derivative, markedly induced antioxidant enzymes such as heme oxygenase-1 (HO-1). Pretreatment with HPO-DAEE protected against 6-hydroxydopamine (6-OHDA)-induced cell death. NF-E2-related factor 2 (Nrf2), a master regulator of antioxidative responses, plays a key role in the acquisition of resistance to oxidative stress. HPO-DAEE elicited nuclear accumulation of Nrf2 and activated antioxidant response element (ARE), a cis-activating regulatory element, indicating that HPO-DAEE induced expression of antioxidant genes through Nrf2-ARE signaling. Recently, the activating transcription factor-4 (ATF4) has been shown to cooperate with Nrf2 and modulate antioxidant gene expression. We also found that HPO-DAEE promoted phosphorylation of eukaryotic initiation factor 2α (eIF2α), which is an upstream effector of ATF4, and subsequent nuclear accumulation of ATF4. The eIF2α phosphatase inhibitor, salubrinal, augmented HPO-DAEE-induced HO-1 expression and protection against 6-OHDA-induced cell death. These results indicate that HPO-DAEE activates both the Nrf2-ARE and eIF2α-ATF4 pathways. Moreover, ROS generation occurred upon treatment of SH-SY5Y cells with HPO-DAEE, and the antioxidants N-acetylcysteine and glutathione suppressed HPO-DAEE-induced activation of the Nrf2-ARE and eIF2α-ATF4 pathways. Therefore, sublethal oxidative stress caused by HPO-DAEE is likely to activate both these pathways. Taken together, we conclude that HPO-DAEE elicits adaptive responses to oxidative stress through cooperative activation of the Nrf2-ARE and eIF2α-ATF4 pathways.

Fenofibrate exerts protective effects against gentamicin-induced toxicity in cochlear hair cells by activating antioxidant enzymes

Fenofibrate, an activator of peroxisome proliferator-activated receptors (PPARs), has been shown to protect the kidneys and brain cells from oxidative stress; however, its role in preventing hearing loss has not been reported to date, at least to the best of our knowledge. In this study, we demonstrated the protective effects of fenofibrate against gentamicin (GM)-induced ototoxicity. We found that the auditory brainstem response threshold which was increased by GM was significantly reduced by pre-treatment with fenofibrate in rats. In cochlear explants, the disruption of hair cell layers by GM was also markedly attenuated by pre-treatment with fenofibrate. In addition, fenofibrate almost completely abolished GM-induced reactive oxygen species generation, which seemed to be mediated at least in part by the restoration of the expression of PPAR-α-dependent antioxidant enzymes, including catalase and superoxide dismutase (SOD)-1. Of note, fenofibrate markedly increased the expression of heme oxygenase-1 (HO-1) which was also induced to a certain degree by GM alone. The induced expression of HO-1 by fenofibrate appeared to be essential for mediating the protective effects of fenofibrate, as the inhibition of HO-1 activity significantly diminished the protective effects of fenofibrate against the GM-mediated death of sensory hair cells in cochlea explant culture, as well as in zebrafish neuromasts. These results suggest that fenofibrate protects sensory hair cells from GM-induced toxicity by upregulating PPAR-α-dependent antioxidant enzymes, including HO-1. Our results provide insight into the preventive therapy for hearing loss caused by aminoglycoside antibiotics.

The History, Status, Gaps, and Future Directions of Neurotoxicology in China

BACKGROUND

Rapid economic development in China has produced serious ecological, environmental, and health problems. Neurotoxicity has been recognized as a major public health problem. The Chinese government, research institutes, and scientists conducted extensive studies concerning the source, characteristics, and mechanisms of neurotoxicants.

OBJECTIVES

This paper presents, for the first time, a comprehensive history and review of major sources of neurotoxicants, national bodies/legislation engaged, and major neurotoxicology research in China.

METHODS

Peer-reviewed research and pollution studies by Chinese scientists from 1991 to 2015 were examined. PubMed, Web of Science and Chinese National Knowledge Infrastructure (CNKI) were the major search tools.

RESULTS

The central problem is an increased exposure to neurotoxicants from air and water, food contamination, e-waste recycling, and manufacturing of household products. China formulated an institutional framework and standards system for management of major neurotoxicants. Basic and applied research was initiated, and international cooperation was achieved. The annual number of peer-reviewed neurotoxicology papers from Chinese authors increased almost 30-fold since 2001.

CONCLUSIONS

Despite extensive efforts, neurotoxicity remains a significant public health problem. This provides great challenges and opportunities. We identified 10 significant areas that require major educational, environmental, governmental, and research efforts, as well as attention to public awareness. For example, there is a need to increase efforts to utilize new in vivo and in vitro models, determine the potential neurotoxicity and mechanisms involved in newly emerging pollutants, and examine the effects and mechanisms of mixtures. In the future, we anticipate working with scientists worldwide to accomplish these goals and eliminate, prevent and treat neurotoxicity.

CITATION

Cai T, Luo W, Ruan D, Wu YJ, Fox DA, Chen J. 2016. The history, status, gaps, and future directions of neurotoxicology in China. Environ Health Perspect 124:722-732; http://dx.doi.org/10.1289/ehp.1409566.

Vitamin E attenuates neurotoxicity induced by deltamethrin in rats

Background

The safety of Deltamethrin (DM) has been raised as a point of concern. The current investigation was envisaged to explore the responsiveness of oxidative stress parameters, DNA fragmentation and expression levels of TP53, cycloxygenase 2 (COX2) and cytochrome p4502E1 (CYP2E1) as toxicological endpoint in rats treated with DM. as well as attention was provided to the neuroprotective effect of vitamin E (VE).

Methods

Four different groups of rats were used in this study, group I served as control, group II received DM (0.6 mg/kg BW), group III received both DM plus VE and finally group IV received VE only (200 mg/kg BW). The treatment regimen was extending for one month for all groups and the brain tissues were collected for further analysis.

Results

The obtained results showed a highly statistically significant increase in lipid peroxidation (LPO) content, nitric oxide concentration, and DNA fragmentation percentage and expression level of CYP2E1, TP53 and COX2 genes, in addition statistical significant reduction in total antioxidant capacity in DM treated group as compared to control were detected. Oral administration of VE attenuated the neurotoxic effects of DM through improvement of oxidative status, DNA fragmentation percentage and suppressing the expression level of CYP2E1, TP53 and COX2 genes.

Conclusion

From this study we concluded that VE supplementation has beneficial impacts on DM neurotoxicity in rats through its antioxidant and antiapoptotic properties.

Transcriptional responses in Atlantic salmon (Salmo salar) exposed to deltamethrin, alone or in combination with azamethiphos

Recently, Atlantic salmon (Salmo salar) fish farmers have applied a combination of deltamethrin and azamethiphos in high-concentration and short-duration immersion treatment to improve protection against sea-lice (Lepeophtheirus sp.). In this work we aimed to study the effects of deltamethrin, alone or in combination with azamethiphos, on the transcription of stress and detoxification marker genes. Atlantic salmon kept at 12°C (one group was also kept at 4-5°C) were treated with deltamethrin alone or in combination with azamethiphos for a total of 40min, and gill and liver tissue harvested for transcriptional analysis 2 and 24h post treatment. No lethality was observed during the experiment. The result showed that deltamethrin, alone or in combination with azamethiphos, affected the transcriptional levels of several oxidative stress markers, including MnSOD (SOD2) and HSP70 (HSPA8) in the liver, and GPX1, CAT, MnSOD, HSP70 and GSTP1 in the gills. Significant responses for CASP3B, BCLX, IGFBP1B and ATP1A1 (Na-K-ATPase a1b) by some of the treatments suggest that the pharmaceutical drugs may affect apoptosis, growth and ion regulation mechanisms. In fish kept at 4-5°C, different effects were observed, suggesting a temperature-dependent response. In conclusion, the observed responses indicate that short-term exposure to deltamethrin has a profound effect on transcription of the evaluated markers in gills and liver of fish. Co-treatment with azamethiphos appears to have small mitigating effects on the transcriptional response caused by deltamethrin exposure alone.

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.

Light modulation, not choroidal vasomotor action, is a regulator of refractive compensation to signed optical blur

BACKGROUND AND PURPOSE

The nitric oxide system has two proposed sites and mechanisms of action within the ocular growth/refractive compensation platform-neuromodulatory effects on retinal physiology, and vascular/smooth muscle effects in the choroid. The relative contribution of these mechanisms are tested here with drugs that perturb the nitric oxide system and with slow flicker modulation of the ON and OFF pathways of the retina.

EXPERIMENTAL APPROACH

Intravitreal injection of saline or 900 nmol N(G) -nitro-L-arginine methyl ester or L-arginine in saline was followed by monocular defocus with ±10 D lens (or no lens), from days 5-9 under standard diurnal (SD) or daytime 1 Hz ramped flicker conditions. Biometric, electrophysiological and histological analyses were conducted.

KEY RESULTS

After 4 days of SD conditions, both drugs enhanced electroretinogram (ERG) b-wave cf. d-wave amplitudes compared with saline and reduced refractive compensation to -10 D lenses. Under flicker conditions compensation to +10 D lenses was suppressed. Choroidal thinning was observed in the drug, no lens groups under SD conditions, whereas choroidal thickening was seen in most groups under flicker conditions, irrespective of refractive outcomes.

CONCLUSIONS AND IMPLICATIONS

As choroidal thickness was not predictive of final refractive compensation across any of the variables of drug, defocus sign or light condition, it is unlikely that choroidal thickness is a primary mechanism underlying refractive compensation across the range of parameters of this study. Rather, the changes in refractive compensation observed under these particular drug and light conditions are more likely due to a neuromodulatory action on retinal ON and OFF pathways.

Antioxidant protection: A promising therapeutic intervention in neurodegenerative disease

Oxidative stress has been consistently linked to ageing-related neurodegenerative diseases. Neurodegenerative diseases are characterized by progressive dysfunction and death of neurons. Oxidative stress is associated with dysfunction of the mitochondria and endoplasmic reticulum, inducing apoptosis and protein misfolding in neurons. Decreased activities of antioxidant enzymes like SOD, catalase, glutathione, glutathione peroxidase in neurodegenerative states signifies role of reduced antioxidant potential in neurodegeneration. Among the cellular pathways conferring protection against oxidative stress, a key role is played by vitagenes, which include Hsp70, heme oxygenase-1, thioredoxin and sirtuins. Cellular signalling pathways and molecular mechanisms that mediate hormetic responses typically involve antioxidant enzymes and transcription factors such as Nrf-2 and NFκB. Vitagenes, either individually or by acting in concert, contribute to counteract the ROS mediated damage. In this review the importance of oxidative stress and the potential use of antioxidants in the prevention and treatment of neurodegenerative disorders are discussed.

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.

Glutathione biosynthesis via activation of the nuclear factor E2-related factor 2 (Nrf2)--antioxidant-response element (ARE) pathway is essential for neuroprotective effects of sulforaphane and 6-(methylsulfinyl) hexyl isothiocyanate

Oxidative stress plays pivotal roles in aging, neurodegenerative disease, and pathological conditions such as ischemia. We investigated the effect of sulforaphane and 6-(methysulfinyl) hexyl isothiocyanate (6-HITC), a naturally occurring isothiocyanate, on oxidative stress-induced cytotoxicity using primary neuronal cultures of rat striatum. Pretreatment with sulforaphane and 6-HITC significantly protected against H(2)O(2)- and paraquat-induced cytotoxicity in a concentration-dependent manner. Sulforaphane and 6-HITC induced the translocation of nuclear factor E2-related factor 2 (Nrf2) into the nucleus and increased the expression of γ-glutamylcysteine synthetase (γ-GCS), a rate-limiting enzyme in glutathione synthesis, and the intracellular glutathione content. Treatment with reduced glutathione (GSH) and N-acetyl-L-cysteine, a substance for glutathione synthesis, significantly prevented the cytotoxicity induced by H(2)O(2) and paraquat. Moreover, exposure to L-buthionine-sulfoximine, an irreversible inhibitor of γ-GCS, suppressed the protective effects of sulforaphane and 6-HITC. In contrast, sulforaphane and 6-HITC increased heme oxygenase-1 (HO-1) expression in neurons. However, zinc-protophorphyrin IX, a competitive inhibitor of HO-1, did not influence the protective effects of sulforaphane and 6-HITC. These results suggest that sulforaphane and 6-HITC prevent oxidative stress-induced cytotoxicity in rat striatal cultures by raising the intracellular glutathione content via an increase in γ-GCS expression induced by the activation of the Nrf2-antioxidant response element pathway.

Dietary supplementation with tBHQ, an Nrf2 stabilizer molecule, confers neuroprotection against apoptosis in amyloid β-injected rat

Nuclear factor erythroid 2-related factor 2 (Nrf2) coordinates the up-regulation of cytoprotective genes via the antioxidant response element (ARE). There is significant evidence that oxidative stress is a critical event in the pathogenesis of AD. Considering the protective role of Nrf2 against oxidative injury, we studied to determine whether in vivo toxicity of amyloid β (Aβ) can be attenuated by tBHQ, an Nrf2 stabilizer, Using an Aβ injection model. We demonstrated that pre-activation of endogenous Nrf2 by tBHQ attenuated Aβ-induced caspase-3 expression. tBHQ enhanced GSH, decreased MDA level, and inhibited NF-κB. This investigation provides the first documentation of tBHQ's neuroprotective effect through decrease of Aβ accumulation in rat brain. Our results show the involvement of Hsp-70 in this protective effect. In summary tBHQ treatment for 1 week prior to Aβ injection protected against the oxidative damage, apoptosis and Aβ accumulation in rats.

Nrf2-ARE stress response mechanism: a control point in oxidative stress-mediated dysfunctions and chronic inflammatory diseases

Nrf2, a redox sensitive transcription factor, plays a pivotal role in redox homeostasis during oxidative stress. Nrf2 is sequestered in cytosol by an inhibitory protein Keap1 which causes its proteasomal degradation. In response to electrophilic and oxidative stress, Nrf2 is activated, translocates to nucleus, binds to antioxidant response element (ARE), thus upregulates a battery of antioxidant and detoxifying genes. This function of Nrf2 can be significant in the treatment of diseases, such as cancer, neurodegenerative, cardiovascular and pulmonary complications, where oxidative stress causes Nrf2 derangement. Nrf2 upregulating potential of phytochemicals has been explored, in facilitating cure for various ailments while, in cancer cells, Nrf2 upregulation causes chemoresistance. Therefore, Nrf2 emerges as a key regulator in oxidative stress-mediated diseases and Nrf2 silencing can open avenues in cancer treatment. This review summarizes Nrf2-ARE stress response mechanism and its role as a control point in oxidative stress-induced cellular dysfunctions including chronic inflammatory diseases.

Upregulation of transcription factor NRF2-mediated oxidative stress response pathway in rat brain under short-term chronic hypobaric hypoxia

Exposure to high altitude (and thus hypobaric hypoxia) induces electrophysiological, metabolic, and morphological modifications in the brain leading to several neurological clinical syndromes. Despite the known fact that hypoxia episodes in brain are a common factor for many neuropathologies, limited information is available on the underlying cellular and molecular mechanisms. In this study, we investigated the temporal effect of short-term (0-12 h) chronic hypobaric hypoxia on global gene expression of rat brain followed by detailed canonical pathway analysis and regulatory network identification. Our analysis revealed significant alteration of 33, 17, 53, 81, and 296 genes (p < 0.05, <1.5-fold) after 0.5, 1, 3, 6, and 12 h of hypoxia, respectively. Biological processes like regulation, metabolic, and transport pathways are temporally activated along with anti- and proinflammatory signaling networks like PI3K/AKT, NF-κB, ERK/MAPK, IL-6 and IL-8 signaling. Irrespective of exposure durations, nuclear factor (erythroid-derived 2)-like 2 (NRF2)-mediated oxidative stress response pathway and genes were detected at all time points suggesting activation of NRF2-ARE antioxidant defense system. The results were further validated by assessing the expression levels of selected genes in temporal as well as brain regions with quantitative RT-PCR and western blot. In conclusion, our whole brain approach with temporal monitoring of gene expression patterns during hypobaric hypoxia has resulted in (1) deciphering sequence of pathways and signaling networks activated during onset of hypoxia, and (2) elucidation of NRF2-orchestrated antioxidant response as a major intrinsic defense mechanism. The results of this study will aid in better understanding and management of hypoxia-induced brain pathologies.

Tert-butylhydroquinone induces mitochondrial oxidative stress causing Nrf2 activation

Tert-butylhydroquinone (tBHQ), the major metabolite of butylated hydroxyanisole, induces an antioxidant response through the redox-sensitive transcription factor, nuclear factor-E2-related factor-2 (Nrf2). However, the mechanism by which tBHQ induces Nrf2 activity is not entirely understood. Here, we show that tBHQ preferentially alters the redox status in the mitochondrial compartment in HeLa cells. HeLa cells treated with tBHQ showed a preferential oxidation of mitochondrial thioredoxin-2 (Trx2), while cellular glutathione and cytosolic thioredoxin-1 were not affected. Preferential mitochondrial oxidation by tBHQ was supported by detection of reactive oxygen species (ROS) specific to this compartment. To determine the role of Trx2 in regulating downstream effects of tBHQ, HeLa cells were transiently transfected with an empty, Trx2, or C93S (Cys93Ser) Trx2 dominant-negative mutant expression vector. Overexpression of Trx2 decreased basal mitochondrial ROS production, whereas expression of C93S Trx2 enhanced it. In addition, under untreated conditions, expression of C93S Trx2 led to an increase in the basal activities of Nrf2. With tBHQ treatments, Trx2 overexpression suppressed Nrf2 accumulation and activity, whereas expression of C93S Trx2 had no effect on the degree of inducibility or Nrf2 accumulation but did increase the overall activity of Nrf2. Quantitative polymerase chain reaction analysis of Nrf2-regulated gene expression corroborate Trx2 control of tBHQ-mediated Nrf2 activation. These data show a compartment-specific effect where tBHQ-induced Nrf2 signaling is mediated by Trx2 and suggest that antioxidant status in various compartments would provide different levels of control of redox signaling.

Rottlerin induces heme oxygenase-1 (HO-1) up-regulation through reactive oxygen species (ROS) dependent and PKC delta-independent pathway in human colon cancer HT29 cells

Heme oxygenase-1 (HO-1) is a cytoprotective enzyme activated by its substrate heme and diverse stimuli. The induction of HO-1 gene expression is one of the important events in cellular response to pro-oxidative and pro-inflammatory insults. In this study, the effect of rottlerin, a putative PKC delta inhibitor, on HO-1 expression in HT29 human colon cancer cells was investigated. Rottlerin-induced HO-1 at both protein and mRNA levels in a dose- and time-dependent manner. Rottlerin-mediated HO-1 induction was abrogated in the presence of N-acetylcysteine (NAC) or glutathione (GSH). Rottlerin induced nuclear translocation of NF-E2-related factor 2 (Nrf2) and increased antioxidant response element (ARE)-driven transcriptional activity. Additionally, rottlerin activated p38 mitogen-activated protein kinase (MAPK) and ERK. The pharmacological inhibition of ERK and p38 MAPK inhibited rottlerin-induced HO-1 up-regulation. However, suppression of protein kinase C delta (PKC delta) expression by siRNA or overexpression of WT-PKC delta did not abrogate the rottlerin-mediated induction of HO-1. These results suggest that rottlerin induces up-regulation of HO-1 via PKC delta-independent pathway. Taken together, the present study identified rottlerin as a novel inducer of HO-1 expression and identified the mechanisms involved in this process.

Methamphetamine induces dopamine D1 receptor-dependent endoplasmic reticulum stress-related molecular events in the rat striatum

Methamphetamine (METH) is an illicit toxic psychostimulant which is widely abused. Its toxic effects depend on the release of excessive levels of dopamine (DA) that activates striatal DA receptors. Inhibition of DA-mediated neurotransmission by the DA D1 receptor antagonist, SCH23390, protects against METH-induced neuronal apoptosis. The initial purpose of the present study was to investigate, using microarray analyses, the influence of SCH23390 on transcriptional responses in the rat striatum caused by a single METH injection at 2 and 4 hours after drug administration. We identified 545 out of a total of 22,227 genes as METH-responsive. These include genes which are involved in apoptotic pathways, endoplasmic reticulum (ER) stress, and in transcription regulation, among others. Of these, a total of 172 genes showed SCH23390-induced inhibition of METH-mediated changes. Among these SCH23390-responsive genes were several genes that are regulated during ER stress, namely ATF3, HSP27, Hmox1, HSP40, and CHOP/Gadd153. The secondary goal of the study was to investigate the role of DA D1 receptor stimulation on the expression of genes that participate in ER stress-mediated molecular events. We thus used quantitative PCR to confirm changes in the METH-responsive ER genes identified by the microarray analyses. We also measured the expression of these genes and of ATF4, ATF6, BiP/GRP78, and of GADD34 over a more extended time course. SCH23390 attenuated or blocked METH-induced increases in the expression of the majority of these genes. Western blot analysis revealed METH-induced increases in the expression of the antioxidant protein, Hmox1, which lasted for about 24 hours after the METH injection. Additionally, METH caused DA D1 receptor-dependent transit of the Hmox1 regulator protein, Nrf2, from cytosolic into nuclear fractions where the protein exerts its regulatory functions. When taken together, these findings indicate that SCH23390 can provide protection against neuronal apoptosis by inhibiting METH-mediated DA D1 receptor-mediated ER stress in the rat striatum. Our data also suggest that METH-induced toxicity might be a useful model to dissect molecular mechanisms involved in ER stress-dependent events in the rodent brain.

Nrf2-induced antioxidant protection: a promising target to counteract ROS-mediated damage in neurodegenerative disease?

Neurodegenerative diseases share various pathological features, such as accumulation of aberrant protein aggregates, microglial activation, and mitochondrial dysfunction. These pathological processes are associated with generation of reactive oxygen species (ROS), which cause oxidative stress and subsequent damage to essential molecules, such as lipids, proteins, and DNA. Hence, enhanced ROS production and oxidative injury play a cardinal role in the onset and progression of neurodegenerative disorders. To maintain a proper redox balance, the central nervous system is endowed with an antioxidant defense mechanism consisting of endogenous antioxidant enzymes. Expression of most antioxidant enzymes is tightly controlled by the antioxidant response element (ARE) and is activated by nuclear factor E2-related factor 2 (Nrf2). In past years reports have highlighted the protective effects of Nrf2 activation in reducing oxidative stress in both in vitro and in vivo models of neurodegenerative disorders. Here we provide an overview of the involvement of ROS-induced oxidative damage in Alzheimer's disease, Parkinson's disease, and Huntington's disease and we discuss the potential therapeutic effects of antioxidant enzymes and compounds that activate the Nrf2-ARE pathway.