Increased DJ-1 expression under oxidative stress and in Alzheimer's disease brains

Knockdown of DJ-1 Exacerbates Neuron Apoptosis Induced by TgCtwh3 through the NF-κB Pathway

Mutations or loss of function of DJ-1 and Toxoplasma gondii (T. gondii) infection has been linked to neurodegenerative diseases, which are often caused by oxidative stress. However, the relationship between DJ-1 and T. gondii infection is not yet fully understood. Therefore, this study aimed to investigate the expression of DJ-1 in the hippocampus tissue of mice or in HT22 infected with T. gondii Chinese 1 genotype Wh3 strain (TgCtwh3) and the effect of DJ-1 knockdown on neuronal apoptosis induced by TgCtwh3 tachyzoite, as well as the underlying mechanism at the cellular and molecular level. Firstly, we detected DJ-1 protein expression and cell apoptosis in the hippocampal tissue of mice infected by TgCtwh3. Then, we examined DJ-1 expression and apoptosis in HT22 challenged with TgCtwh3. Finally, we evaluated the apoptosis in HT22 with DJ-1 knockdown which was infected with TgCtwh3 and assayed the expression of NF-κBp65 and p-NF-κBp65. Our results showed that DJ-1 expression was reduced and neurons underwent apoptosis in the hippocampus of mice infected with TgCtwh3 tachyzoites. Additionally, the knockdown of DJ-1 followed by infection with TgCtwh3 tachyzoites led to increased apoptosis in HT22 cells through the NF-κB signaling pathway. Therefore, this study suggests that DJ-1 is an important target for preventing apoptosis caused by T. gondii TgCtwh3.

DJ-1-mediated p62 degradation delays intervertebral disc degeneration by inhibiting apoptosis of nucleus pulposus cells

Intervertebral disc degeneration (IDD) is the most important pathological basis of degenerative spinal diseases, for which effective interventions are still lacking. Oxidative stress is considered to be one of the leading pathological mechanisms contributing to IDD. However, the exact role of DJ-1 as an essential member of the antioxidant defense system in IDD is still unclear. Therefore, the aim of this study was to investigate the role played by DJ-1 in IDD and to reveal its potential molecular mechanisms. Western blot and immunohistochemical staining assays were performed to detect the expression of DJ-1 in degenerative nucleus pulposus cells (NPCs). After overexpression of DJ-1 in NPCs by lentiviral transfection, DCFH-DA and MitoSOX fluorescent probes were used to evaluate the levels of reactive oxygen species (ROS); while western blot, TUNEL staining, and Caspase-3 activity were used to assess apoptosis. Immunofluorescence staining was used to demonstrate the relationship between DJ-1 and p62. After inhibition of lysosomal degradation function with chloroquine, p62 degradation and apoptosis in DJ-1 overexpressing NPCs were further examined. In vivo, we assessed the therapeutic effect of upregulated DJ-1 on IDD by X-ray, MRI and Safranin O-Fast green staining. The protein expression of DJ-1 was significantly decreased in degenerated NPCs, accompanied by increased apoptosis. However, overexpression of DJ-1 significantly inhibited the elevated ROS levels and apoptosis in NPCs under oxidative stress. Mechanistically, our results showed that upregulation of DJ-1 promoted p62 degradation via the autophagic lysosomal pathway and that the protective effect of DJ-1 on NPCs under oxidative stress was partially mediated by promoting lysosomal pathway degradation of p62. Moreover, intradiscal injection of adeno-associated virus for overexpression of DJ-1 mitigated the progression of IDD in rats. This study reveals that DJ-1 maintains the homeostasis of NPCs by promoting the degradation of p62 through the autophagic lysosomal pathway, suggesting that DJ-1 is a promising new target for IDD intervention.

LAR Downregulation Protects the Astrocytic U251 and Cocultured SH-SY5Y Cells in a Rotenone-Induced Parkinson's Disease Cell Model

Leukocyte common antigen-related protein tyrosine phosphatase (LAR) is a member of the protein tyrosine phosphatase family that serves as a key regulator of cellular survival. It is also involved in neurodevelopment and brain disorders. This study was designed to investigate the role of LAR in a cell-based model of Parkinson's disease (PD) in which U251 and SH-SY5Y cells were used as models of astrocytes and dopaminergic neurons, respectively. Cell viability, cell death, cell morphology, protein phosphorylation and expression, ATP levels, reactive oxygen species (ROS) generation, and mitochondrial membrane potential were analyzed in the wild-type (WT) and heterozygous LAR-knockout astrocytoma U251 cells to assess the cell state, signal transduction, and mitochondrial function. LAR downregulation showed a protective effect in rotenone-exposed U251 cells by increasing cell viability, reducing cell mortality, and restoring appropriate cellular morphology. LAR downregulation enhanced IGF-1R phosphorylation and downstream signal transduction as evidenced by increases in the Akt and GSK-3β phosphorylation, as well as the upregulation of NRF2 and HO-1. The downregulation of LAR also augmented DJ-1 levels in these cells. The enhanced Akt and GSK-3β phosphorylation contributed to a reduced Bax/Bcl2 ratio and suppressed apoptosis after rotenone exposure. Heterozygous LAR-knockout U251 cells exhibited higher mitochondrial function evidenced by increased mitochondrial membrane potential, ATP contents, and reduced ROS production compared to the WT cells following rotenone exposure. Further studies showed that the astrocytic protection mediated by the heterozygous knockout of LAR was associated with the activation of Akt. A specific Akt inhibitor, MK2206, reduced the cell viability, Akt and GSK3β phosphorylation, and HO-1 and NRF2 expression in U251 cells exposed to rotenone. Astrocytes provide structural and metabolic support to maintain neuronal health. Astrocytic glial cell-derived neurotrophic factor (GDNF) production is vital for dopaminergic neuron survival. Heterozygous LAR-knockout U251 cells produced higher amounts of GDNF than the WT cells. The SH-SY5Y cells cocultured with heterozygous LAR-knockout U251 cells exhibited greater viability than that of cells cocultured with WT U251 cells in response to rotenone. Together, these findings demonstrate that the heterozygous knockout of LAR in astrocytes can play a key role in protecting both astrocytic cells and cocultured neurons in a rotenone-induced cell-based model of PD. This neuroprotective effect is attributable to the augmentation of IGF1R-Akt-GDNF signaling and the maintenance of astrocytic mitochondrial function.

Fish Models for Exploring Mitochondrial Dysfunction Affecting Neurodegenerative Disorders

Neurodegenerative disorders are characterized by the progressive loss of neuronal structure or function, resulting in memory loss and movement disorders. Although the detailed pathogenic mechanism has not been elucidated, it is thought to be related to the loss of mitochondrial function in the process of aging. Animal models that mimic the pathology of a disease are essential for understanding human diseases. In recent years, small fish have become ideal vertebrate models for human disease due to their high genetic and histological homology to humans, ease of in vivo imaging, and ease of genetic manipulation. In this review, we first outline the impact of mitochondrial dysfunction on the progression of neurodegenerative diseases. Then, we highlight the advantages of small fish as model organisms, and present examples of previous studies regarding mitochondria-related neuronal disorders. Lastly, we discuss the applicability of the turquoise killifish, a unique model for aging research, as a model for neurodegenerative diseases. Small fish models are expected to advance our understanding of the mitochondrial function in vivo, the pathogenesis of neurodegenerative diseases, and be important tools for developing therapies to treat diseases.

Upregulation of DJ-1 in Dopaminergic Neurons by a Physically-Modified Saline: Implications for Parkinson's Disease

Parkinson's disease (PD) is the second most common neurodegenerative disorder in human and loss-of-functions DJ-1 mutations are associated with a familial form of early onset PD. Functionally, DJ-1 (PARK7), a neuroprotective protein, is known to support mitochondria and protect cells from oxidative stress. Mechanisms and agents by which the level of DJ-1 could be increased in the CNS are poorly described. RNS60 is a bioactive aqueous solution created by exposing normal saline to Taylor-Couette-Poiseuille flow under high oxygen pressure. Recently we have described neuroprotective, immunomodulatory and promyelinogenic properties of RNS60. Here we delineate that RNS60 is also capable of increasing the level of DJ-1 in mouse MN9D neuronal cells and primary dopaminergic neurons, highlighting another new neuroprotective effect of RNS60. While investigating the mechanism we found the presence of cAMP response element (CRE) in DJ-1 gene promoter and stimulation of CREB activation in neuronal cells by RNS60. Accordingly, RNS60 treatment increased the recruitment of CREB to the DJ-1 gene promoter in neuronal cells. Interestingly, RNS60 treatment also induced the enrollment of CREB-binding protein (CBP), but not the other histone acetyl transferase p300, to the promoter of DJ-1 gene. Moreover, knockdown of CREB by siRNA led to the inhibition of RNS60-mediated DJ-1 upregulation, indicating an important role of CREB in DJ-1 upregulation by RNS60. Together, these results indicate that RNS60 upregulates DJ-1 in neuronal cells via CREB-CBP pathway. It may be of benefit for PD and other neurodegenerative disorders.

Ubiquitin and Ubiquitin-like Proteins in Cancer, Neurodegenerative Disorders, and Heart Diseases

Post-translational modification (PTM) is an essential mechanism for enhancing the functional diversity of proteins and adjusting their signaling networks. The reversible conjugation of ubiquitin (Ub) and ubiquitin-like proteins (Ubls) to cellular proteins is among the most prevalent PTM, which modulates various cellular and physiological processes by altering the activity, stability, localization, trafficking, or interaction networks of its target molecules. The Ub/Ubl modification is tightly regulated as a multi-step enzymatic process by enzymes specific to this family. There is growing evidence that the dysregulation of Ub/Ubl modifications is associated with various diseases, providing new targets for drug development. In this review, we summarize the recent progress in understanding the roles and therapeutic targets of the Ub and Ubl systems in the onset and progression of human diseases, including cancer, neurodegenerative disorders, and heart diseases.

A Critical Review of Zebrafish Models of Parkinson's Disease

A wide variety of human diseases have been modelled in zebrafish, including various types of cancer, cardiovascular diseases and neurodegenerative diseases like Alzheimer’s and Parkinson’s. Recent reviews have summarized the currently available zebrafish models of Parkinson’s Disease, which include gene-based, chemically induced and chemogenetic ablation models. The present review updates the literature, critically evaluates each of the available models of Parkinson’s Disease in zebrafish and compares them with similar models in invertebrates and mammals to determine their advantages and disadvantages. We examine gene-based models, including ones linked to Early-Onset Parkinson’s Disease: PARKIN, PINK1, DJ-1, and SNCA; but we also examine LRRK2, which is linked to Late-Onset Parkinson’s Disease. We evaluate chemically induced models like MPTP, 6-OHDA, rotenone and paraquat, as well as chemogenetic ablation models like metronidazole-nitroreductase. The article also reviews the unique advantages of zebrafish, including the abundance of behavioural assays available to researchers and the efficiency of high-throughput screens. This offers a rare opportunity for assessing the potential therapeutic efficacy of pharmacological interventions. Zebrafish also are very amenable to genetic manipulation using a wide variety of techniques, which can be combined with an array of advanced microscopic imaging methods to enable in vivo visualization of cells and tissue. Taken together, these factors place zebrafish on the forefront of research as a versatile model for investigating disease states. The end goal of this review is to determine the benefits of using zebrafish in comparison to utilising other animals and to consider the limitations of zebrafish for investigating human disease.

DJ-1-Nrf2 axis is activated upon murine β-coronavirus infection in the CNS

Coronaviruses have emerged as alarming pathogens owing to their inherent ability of genetic variation and cross-species transmission. Coronavirus infection burdens the endoplasmic reticulum (ER.), causes reactive oxygen species production and induces host stress responses, including unfolded protein response (UPR) and antioxidant system. In this study, we have employed a neurotropic murine β-coronavirus (M-CoV) infection in the Central Nervous System (CNS) of experimental mice model to study the role of host stress responses mediated by interplay of DJ-1 and XBP1. DJ-1 is an antioxidant molecule with established functions in neurodegeneration. However, its regulation in virus-induced cellular stress response is less explored. Our study showed that M-CoV infection activated the glial cells and induced antioxidant and UPR genes during the acute stage when the viral titer peaks. As the virus particles decreased and acute neuroinflammation diminished at day ten p.i., a significant up-regulation in UPR responsive XBP1, antioxidant DJ-1, and downstream signaling molecules, including Nrf2, was recorded in the brain tissues. Additionally, preliminary in silico analysis of the binding between the DJ-1 promoter and a positively charged groove of XBP1 is also investigated, thus hinting at a mechanism behind the upregulation of DJ-1 during MHV-infection. The current study thus attempts to elucidate a novel interplay between the antioxidant system and UPR in the outcome of coronavirus infection.

Lamivudine improves cognitive decline in SAMP8 mice: Integrating in vivo pharmacological evaluation and network pharmacology

The reverse transcriptase inhibitors such as lamivudine (3TC) play important roles in anti‐ageing, but their effects on neurodegenerative diseases caused by ageing are not clear, especially on the functions of the nervous system such as cognition. In this study, we administered 3TC to senescence‐accelerated mouse prone 8 (SAMP8) mice by gastric perfusion (100 mg/kg) for 4 weeks. Our results showed that 3TC significantly improved the ageing status of SAMP8 mice, especially the decline of cognitive ability evaluated by the Morris water maze test. To further investigate the molecular mechanisms of improving the ageing status of SAMP8 mice by 3TC, the qPCR and tissue staining methods were used to study the brain tissues (i.e., hippocampus and cortex) of mice, while the network pharmacology analysis was applied to investigate the potential targets of 3TC. The results showed that the mRNA levels of genes related to long interspersed element‐1, type 1 interferon response, the senescence‐associated secretion phenotype and the Alzheimer's disease in the hippocampus and cortex of SAMP8 mice were increased due to senescence, but this trend was reversed partially by 3TC. Results of histological studies showed that 3TC reduced the death of hippocampal neurons, while the results of network pharmacology analysis indicated that 3TC may exert its influence through multiple pathways, including the oestrogen signalling and the PI3K/Akt and neuroactive ligand‐receptor interaction signalling pathways, which we have verified through in vitro experiments. These findings provide evidence for the therapeutic potential of 3TC in the treatment of neurodegenerative diseases.

Animal Models of Autosomal Recessive Parkinsonism

Parkinson’s disease (PD) is the most common neurodegenerative movement disorder. The neuropathological hallmark of the disease is the loss of dopamine neurons of the substantia nigra pars compacta. The clinical manifestations of PD are bradykinesia, rigidity, resting tremors and postural instability. PD patients often display non-motor symptoms such as depression, anxiety, weakness, sleep disturbances and cognitive disorders. Although, in 90% of cases, PD has a sporadic onset of unknown etiology, highly penetrant rare genetic mutations in many genes have been linked with typical familial PD. Understanding the mechanisms behind the DA neuron death in these Mendelian forms may help to illuminate the pathogenesis of DA neuron degeneration in the more common forms of PD. A key step in the identification of the molecular pathways underlying DA neuron death, and in the development of therapeutic strategies, is the creation and characterization of animal models that faithfully recapitulate the human disease. In this review, we outline the current status of PD modeling using mouse, rat and non-mammalian models, focusing on animal models for autosomal recessive PD.

DJ-1 in neurodegenerative diseases: Pathogenesis and clinical application

Neurodegenerative diseases (NDs) are one of the major health threats to human characterized by selective and progressive neuronal loss. The mechanisms of NDs are still not fully understood. The study of genetic defects and disease-related proteins offers us a window into the mystery of it, and the extension of knowledge indicates that different NDs share similar features, mechanisms, and even genetic or protein abnormalities. Among these findings, PARK7 and its production DJ-1 protein, which was initially found implicated in PD, have also been found altered in other NDs. PARK7 mutations, altered expression and posttranslational modification (PTM) cause DJ-1 abnormalities, which in turn lead to downstream mechanisms shared by most NDs, such as mitochondrial dysfunction, oxidative stress, protein aggregation, autophagy defects, and so on. The knowledge of DJ-1 derived from PD researches might apply to other NDs in both basic research and clinical application, and might yield novel insights into and alternative approaches for dealing with NDs.

Mitophagy and Oxidative Stress: The Role of Aging

Mitochondrial dysfunction is a hallmark of aging. Dysfunctional mitochondria are recognized and degraded by a selective type of macroautophagy, named mitophagy. One of the main factors contributing to aging is oxidative stress, and one of the early responses to excessive reactive oxygen species (ROS) production is the induction of mitophagy to remove damaged mitochondria. However, mitochondrial damage caused at least in part by chronic oxidative stress can accumulate, and autophagic and mitophagic pathways can become overwhelmed. The imbalance of the delicate equilibrium among mitophagy, ROS production and mitochondrial damage can start, drive, or accelerate the aging process, either in physiological aging, or in pathological age-related conditions, such as Alzheimer’s and Parkinson’s diseases. It remains to be determined which is the prime mover of this imbalance, i.e., whether it is the mitochondrial damage caused by ROS that initiates the dysregulation of mitophagy, thus activating a vicious circle that leads to the reduced ability to remove damaged mitochondria, or an alteration in the regulation of mitophagy leading to the excessive production of ROS by damaged mitochondria.

Genome-wide histone acetylation analysis reveals altered transcriptional regulation in the Parkinson's disease brain

BACKGROUND

Parkinson's disease (PD) is a complex, age-related neurodegenerative disorder of largely unknown etiology. PD is strongly associated with mitochondrial respiratory dysfunction, which can lead to epigenetic dysregulation and specifically altered histone acetylation. Nevertheless, and despite the emerging role of epigenetics in age-related brain disorders, the question of whether aberrant histone acetylation is involved in PD remains unresolved.

METHODS

We studied fresh-frozen brain tissue from two independent cohorts of individuals with idiopathic PD (n = 28) and neurologically healthy controls (n = 21). We performed comprehensive immunoblotting to identify histone sites with altered acetylation levels in PD, followed by chromatin immunoprecipitation sequencing (ChIP-seq). RNA sequencing data from the same individuals was used to assess the impact of altered histone acetylation on gene expression.

RESULTS

Immunoblotting analyses revealed increased acetylation at several histone sites in PD, with the most prominent change observed for H3K27, a marker of active promoters and enhancers. ChIP-seq analysis further indicated that H3K27 hyperacetylation in the PD brain is a genome-wide phenomenon with a strong predilection for genes implicated in the disease, including SNCA, PARK7, PRKN and MAPT. Integration of the ChIP-seq with transcriptomic data from the same individuals revealed that the correlation between promoter H3K27 acetylation and gene expression is attenuated in PD patients, suggesting that H3K27 acetylation may be decoupled from transcription in the PD brain. Strikingly, this decoupling was most pronounced among nuclear-encoded mitochondrial genes, corroborating the notion that impaired crosstalk between the nucleus and mitochondria is involved in the pathogenesis of PD. Our findings independently replicated in the two cohorts.

CONCLUSIONS

Our findings strongly suggest that aberrant histone acetylation and altered transcriptional regulation are involved in the pathophysiology of PD. We demonstrate that PD-associated genes are particularly prone to epigenetic dysregulation and identify novel epigenetic signatures associated with the disease.

Mechanism of N-acetylcysteine in alleviating diabetic myocardial ischemia reperfusion injury by regulating PTEN/Akt pathway through promoting DJ-1

Ischemic heart disease is the main cardiovascular complication of diabetes patients which is mainly caused by oxidative stress. DJ-1 is the key regulator for myocardial protection through inhibiting phosphatase and tensin homolog deleted on chromosome 10 (PTEN) and activating Akt (also known as PKB or protein kinase B). This research is to investigate whether the antioxidant N-acetylcysteine (NAC) could alleviate diabetic myocardial ischemia/reperfusion (I/R) injury by the protective molecule DJ-1. DJ-1 in rat myocardial H9c2 cells and cardiac tissue was respectively knocked down by siRNA and adeno-associated virus (AAV). From the present study, it could be found that compared with high glucose (HG)-normal (N)/DM group, hypoxia/reoxygenation (H/R) or I/R injury can aggravate oxidative stress injury and apoptosis rate of myocardial cells, inhibit the expression of Bcl-2, activate the BAX and cleaved caspase-3 (c-caspase-3) protein and PTEN/Akt pathway. However, in the groups of HG-N, DM, HG-N+I/R and DM+I/R, NAC can significantly reduce oxidative stress injury and apoptosis rate of myocytes, promote the Bcl-2 and DJ-1 molecules, inhibit BAX and c-caspase-3 protein and PTEN/Akt pathway. Compared with HG-N+I/R+NAC and DM+I/R+NAC groups, the oxidative stress injury, apoptosis rate of myocardial cells and heart tissues increased after the knockdown of DJ-1, the expression of Bcl-2 and DJ-1 were inhibited, the BAX and c-caspase-3 expression was increased, and PTEN/Akt pathway was activated. Taken together, the findings suggest that NAC can reduce I/R injury in diabetic myocardium by up-regulating the PTEN/Akt pathway through the level of DJ-1.

DJ-1 affects oxidative stress and pyroptosis in hippocampal neurons of Alzheimer's disease mouse model by regulating the Nrf2 pathway

Studies have confirmed that DJ-1 is associated with diseases associated with the nervous system, including Alzheimer's disease (AD). However, the role of DJ-1 in the pathogenesis of AD has not been clarified. To investigate the effect of DJ-1 on brain tissue damage and cognitive function in AD mice and its possible mechanism, 5XFAD transgenic mice were used as AD model mice and DJ-1 in the brain was overexpressed by transfection of a lentiviral containing a specific targeting DJ-1 gene into the bilateral hippocampus of mice. Following lentivirus infection, the Morris water maze test was performed to assess the cognitive function of the mice. When the behavioral evaluation was completed, the brain tissue of the mouse was examined. Pathological changes were observed by hematoxylin-eosin staining. The levels of relevant indicators were analyzed by reverse transcription-quantitative PCR, ELISA and western blotting. Bilateral hippocampal injection of a lentivirus containing DJ-1 significantly increased the expression of DJ-1 in the hippocampus of 5XFAD transgenic mice. Overexpression of DJ-1 in the brain could ameliorate brain tissue damage, β-amyloid protein (Aβ) deposition and cognitive function in 5XFAD mice. Compared with the sham group, the reactive oxygen species activity and malondialdehyde content in the brain tissue of DJ-1 overexpressing 5XFAD mice were significantly decreased, while the superoxide dismutase activity was significantly increased (P<0.05). In addition, DJ-1 overexpression decreased the expression of caspase-1 and the levels of interleukin (IL) 1β and IL-18 in the hippocampus while ameliorating the death of hippocampal neurons in 5XFAD mice and without affecting the expression of caspase-3. Overexpression of DJ-1 resulted in a significant decrease in nuclear factor erythroid 2-related factor 2 (Nrf2) protein expression in the cytoplasmic while significantly increasing the expression of Nrf2 in the nucleus. Simultaneously, DJ-1 overexpression in the brain inhibited the activation of nanoparticles activate the NLR pyrin domain containing 3 inflammatory bodies in brain tissue. Overexpression of DJ-1 in the brain could repair brain tissue damage, Aβ deposition and cognitive function in 5XFAD mice, and its mechanism may be associated with an inhibition of oxidative stress and neuronal pyroptosis by regulating the Nrf2 signaling pathway.

Inhibitor Kappa B Kinase β, Modulated by DJ-1/p-VHL, Reduces Phosphorylated Tau (p-Tau) Accumulation via Autophagy in Alzheimer's Disease Model

It has been demonstrated Inhibitor Kappa B Kinase β (IKKβ) facilitates autophagy, which in turn mediates p-Tau protein clearance. However, the specific regulatory mechanism in Alzheimer's disease (AD) remains unclear. Firstly, AD model was generated by the intracerebroventricular (ICV) injection of the Β-amyloid 1-42 (Aβ_1-42) peptide. Subsequently, mice were injected with shRNA adenoviral transduction particles designed to target DJ-1 or Aβ_1-42 or Aβ_1-42 + shNC or Aβ_1-42 + shRNA against DJ-1. shRNA against DJ-1 were injected into hippocampus of mice (8 × 10⁴ viral particles for each mice) for seven consecutive days. Immunohistochemistry was performed to detect the accumulation of Aβ in the hippocampus of mice, and Hematoxylin-Eosin (HE) staining assay was carried to detect pathological changes in the hippocampus of mice. Further, sh-IKKβ, shDJ-1, pcDNA-IKKβ and pcDNA-DJ-1 plasmids were transfected into HT-22 cells, MTT assay, TUNEL staining and Hoechst staining were performed to detect cell viability and apoptosis, respectively. Western blotting was carried to measure the relative expression of proteins. Findings indicated that Aβ_1-42 inhibited autophagy and up-regulated p-Tau protein expression; Overexpression of IKKβ and DJ-1 all rescued the autophagy inhibited by Aβ_1-42 and down-regulated p-Tau protein expression induced by Aβ_1-42; DJ-1 up-regulated IKKβ via p-VHL, further promoted autophagy and reduced the expression of p-Tau protein; DJ-1 knockdown inhibited autophagy and up-regulated p-Tau protein expression, resulting in delayed behavior in mice. In conclusion, IKKβ, modulated by DJ-1/p-VHL, reduces p-Tau accumulation via autophagy in AD's disease model. This study may provide theoretical basis for the treatment of AD.

DJ-1 plays a neuroprotective role in SH-SY5Y cells by modulating Nrf2 signaling in response to lidocaine-mediated oxidative stress and apoptosis

To investigate the effects of DJ-1 on lidocaine-induced cytotoxicity in neurons and the link with Nrf2 signaling, SH-SY5Y cells were treated with 1, 4, 8, and 16 mM lidocaine. Cell viability was measured by MTT assay, and apoptosis was measured by flow cytometry analysis. The mitochondrial membrane potential, reactive oxygen species (ROS) levels, lipid peroxidation (MDA), and GSH/GSSG ratio were determined with specific kits. Expression of DJ-1, Nrf2, and Nrf2 downstream signaling proteins (glutathione peroxidase [GPx], heme oxygenase-1 [HO-1], catalase [CAT], and glutathione reductase [GR]), was determined by western blot and qRT-PCR. The cell viability was dramatically decreased, while levels of apoptosis, ROS and Cys106-oxidized DJ-1 were significantly enhanced following treatment with lidocaine (concentration 4-16 mM), and increases were observed in a dose-dependent manner. After treatment with 8 mM lidocaine, DJ-1, and nuclear Nrf2, as well as antioxidative stress-related proteins, GPx, GR, HO-1, and CAT, were all significantly inhibited. Overexpression of DJ-1 suppressed lidocaine-induced apoptosis and oxidative stress in SH-SY5Y cells and activated Nrf2 signalling at the same time, and these effects were reversed by the inhibition of Nrf2. DJ-1 could protect SH-SY5Y cells from lidocaine-induced apoptosis through inhibition of oxidative stress via Nrf2 signaling.

DJ-1 Suppresses Cytoplasmic TDP-43 Aggregation in Oxidative Stress-Induced Cell Injury

DJ-1 (also called PARK7) is a multifunctional redox-sensitive protein that is protective against oxidative stress-induced cell death. TAR DNA-binding protein 43 (TDP-43) is a major protein component of pathological inclusions in amyotrophic lateral sclerosis and frontotemporal dementia. Reducing aberrant aggregation of TDP-43 is a potential approach to prevent cell death. To investigate whether DJ-1 might inhibit TDP-43 aggregation to exert a protective effect in oxidative stress-induced injury, we tested the protein level and subcellular localization of TDP-43 and DJ-1 in SH-SY5Y cells transfected with wild-type DJ-1, DJ-1 mutant (L166P) cDNA, or DJ-1 siRNA. We show that oxidative stress induced by paraquat leads to the formation of cytosolic TDP-43 aggregation in SH-SY5Y cells. DJ-1 overexpression decreases paraquat-induced cytoplasmic accumulation of TDP-43 in SH-SY5Y cells and protects against paraquat-induced cell death. Transfection of DJ-1 L166P mutant or DJ-1 siRNA leads to increased cytosolic aggregation of TDP-43 in paraquat-treated SH-SY5Y cells and promotes cell death. These data suggest that DJ-1 may protect against oxidative stress-induced cell death through the suppression of cytoplasmic TDP-43 aggregation.

Genetic analyses of early-onset Alzheimer's disease using next generation sequencing

Alzheimer’s disease (AD) is the most common type of neurodegenerative dementia, but the cause of AD remained poorly understood. Many mutations in the amyloid precursor protein (APP) and presenilin 1 and 2 (PSEN1 and PSEN2) have been reported as the pathogenic causes of early-onset AD (EOAD), which accounts for up to 5% of all AD cases. In this study, we screened familiar/de novo EOAD (n = 67) samples by next-generation sequencing (NGS) of a 50-gene panel, which included causative and possible pathogenic variants linked to neurodegenerative disorders. Remarkably, three missense mutations in PSEN1 (T119I, G209A, and G417A) and one known variant in PSEN2 (H169N) were discovered in 6% of the cases. Additionally, 67 missense mutations in susceptibility genes for late-onset AD were identified, which may be involved in cholesterol transport, inflammatory response, and β-amyloid modulation. We identified 70 additional novel and missense variants in other genes, such as MAPT, GRN, CSF1R, and PRNP, related to neurodegenerative diseases, which may represent overlapping clinical and neuropathological features with AD. Extensive genetic screening of Korean patients with EOAD identified multiple rare variants with potential roles in AD pathogenesis. This study suggests that individuals diagnosed with AD should be screened for other neurodegenerative disease-associated genes. Our findings expand the classic set of genes involved in neurodegenerative pathogenesis, which should be screened for in clinical trials. Main limitation of this study was the absence of functional assessment for possibly and probably pathogenic variants. Additional issues were that we could not perform studies on copy number variants, and we could not verify the segregation of mutations.

Modulation of Parkinson's Disease Associated Protein Rescues Alzheimer's Disease Degeneration

DJ-1, a causative gene product of an autosomal recessive familial form of Parkinson's disease (PD), plays roles in reducing oxidative stress and transcriptional regulation. Loss of its function is thought to result in the onset of PD. DJ-1 has been demonstrated to show general cytoprotective function mainly through antioxidant properties and possibly regulates the extent of stroke-induced damage and neurodegeneration in Alzheimer's disease (AD). The paper, "Effects of a DJ-1-Binding Compound on Spatial Learning and Memory Impairment in a Mouse Model of Alzheimer's Disease", by Kitamura et al. in this issue of Journal of Alzheimer's Disease reports that a DJ-1 modulator UCP0054278/compound B (comp-B), which has been previously shown to exhibit antioxidant and neuroprotective properties in PD models, can prevent neurodegenerative changes and cognitive dysfunction in an animal model of AD. Indeed, comp-B reduces not only α-synuclein but also insoluble Aβ42 levels, prevents the reductions in synaptophysin and drebrin, and rescues cognitive deficits in transgenic APdE9 mice model of AD. It is noteworthy that pharmacological modulation of a familial PD gene product is sufficient to modify biochemical phenotypes and cognitive performance in amyloid-based genetically driven mouse models of AD. Together with mixed pathology in the vast majority of the patients with late-onset dementia, these findings strongly suggest the existence of common pathogenesis of diverse neurodegenerative disorders. Anti-oxidative strategy such as DJ-1 modulation is one of the major candidates to address the common pathogenesis and should be assembled among multimodal or combinatory interventions against neurodegenerative disorders.

Zebrafish as an Animal Model for Drug Discovery in Parkinson's Disease and Other Movement Disorders: A Systematic Review

Movement disorders can be primarily divided into hypokinetic and hyperkinetic. Most of the hypokinetic syndromes are associated with the neurodegenerative disorder Parkinson’s disease (PD). By contrast, hyperkinetic syndromes encompass a broader array of diseases, including dystonia, essential tremor, or Huntington’s disease. The discovery of effective therapies for these disorders has been challenging and has also involved the development and characterization of accurate animal models for the screening of new drugs. Zebrafish constitutes an alternative vertebrate model for the study of movement disorders. The neuronal circuitries involved in movement in zebrafish are well characterized, and most of the associated molecular mechanisms are highly conserved. Particularly, zebrafish models of PD have contributed to a better understanding of the role of several genes implicated in the disease. Furthermore, zebrafish is a vertebrate model particularly suited for large-scale drug screenings. The relatively small size of zebrafish, optical transparency, and lifecycle, are key characteristics that facilitate the study of multiple compounds at the same time. Several transgenic, knockdown, and mutant zebrafish lines have been generated and characterized. Therefore, it is central to critically analyze these zebrafish lines and understand their suitability as models of movement disorders. Here, we revise the pathogenic mechanisms, phenotypes, and responsiveness to pharmacotherapies of zebrafish lines of the most common movement disorders. A systematic review of the literature was conducted by including all studies reporting the characterization of zebrafish models of the movement disorders selected from five bibliographic databases. A total of 63 studies were analyzed, and the most relevant data within the scope of this review were gathered. The majority (62%) of the studies were focused in the characterization of zebrafish models of PD. Overall, the zebrafish models included display conserved biochemical and neurobehavioral features of the phenomenology in humans. Nevertheless, in light of what is known for all animal models available, the use of zebrafish as a model for drug discovery requires further optimization. Future technological developments alongside with a deeper understanding of the molecular bases of these disorders should enable the development of novel zebrafish lines that can prove useful for drug discovery for movement disorders.

Insulin signaling pathway protects neuronal cell lines by Sirt3 mediated IRS2 activation

Cellular stress like ER and oxidative stress are the principle causative agents of various proteinopathies. Multifunctional protein PARK7/DJ-1 provides protection against cellular stress. Recently, insulin/IGF also has emerged as a neuro-protective molecule. However, it is not known whether DJ-1 and insulin/IGF complement each other for cellular protection in response to stress. In this study, we show for the first time, that in human and mouse neuronal cell lines, down regulation of DJ-1 for 48 h leads to compensatory upregulation of insulin/IGF signaling (IIS) pathway genes, namely, insulin receptor, insulin receptor substrate, and Akt under normal physiological conditions as well as in cellular stress conditions. Moreover, upon exogenous supply of insulin there is a marked increase in the IIS components both at gene and protein levels leading to down regulation and inactivation of GSK3β. By immunoprecipitation, it was observed that Sirt3 mediated deacetylation and activation of FoxO3a could not occur under DJ-1 downregulation. Transient DJ-1 downregulation also led to Akt mediated increased phosphorylation and nuclear exclusion of FoxO3a. When DJ-1 was downregulated increased interaction of Sirt3 with IRS2 was observed leading to its activation resulting in IIS upregulation. Thus, transient downregulation of DJ-1 leads to stimulation of IIS pathway by Sirt3 mediated IRS2 activation. Consequently, antiapoptotic program is triggered in neuronal cells via Akt-GSK3β-FoxO3a axis. © 2018 BioFactors, 44(3):224-236, 2018.

Effects of a DJ-1-Binding Compound on Spatial Learning and Memory Impairment in a Mouse Model of Alzheimer's Disease

Previously, DJ-1 modulator UCP0054278/comp-B was identified by virtual screening, where comp-B interacts with DJ-1 to produce antioxidant and neuroprotective responses in Parkinson's disease models. However, the effect of comp-B in an in vivo Alzheimer's disease (AD) model is yet undetermined. Thus, we examined the effect of comp-B on spatial learning, memory, and amyloid-β (Aβ) clearance in a transgenic mouse model of AD. We found that comp-B resolved the cognitive deficits, reduced insoluble Aβ42 levels, and prevented the degeneration of synaptic functions, thereby suggesting that comp-B may become a major compound for AD treatment.

New Developments in Genetic rat models of Parkinson's Disease

Preclinical research on Parkinson's disease has relied heavily on mouse and rat animal models. Initially, PD animal models were generated primarily by chemical neurotoxins that induce acute loss of dopaminergic neurons in the substantia nigra. On the discovery of genetic mutations causally linked to PD, mice were used more than rats to generate laboratory animals bearing PD-linked mutations because mutagenesis was more difficult in rats. Recent advances in technology for mammalian genome engineering and optimization of viral expression vectors have increased the use of genetic rat models of PD. Emerging research tools include "knockout" rats with disruption of genes in which mutations have been causally linked to PD, including LRRK2, α-synuclein, Parkin, PINK1, and DJ-1. Rats have also been increasingly used for transgenic and viral-mediated overexpression of genes relevant to PD, particularly α-synuclein. It may not be realistic to obtain a single animal model that completely reproduces every feature of a human disease as complex as PD. Nevertheless, compared with mice with the same mutations, many genetic rat animal models of PD better reproduce key aspects of PD including progressive loss of dopaminergic neurons in the substantia nigra, locomotor behavior deficits, and age-dependent formation of abnormal α-synuclein protein aggregates. Here we briefly review new developments in genetic rat models of PD that may have greater potential for identifying underlying mechanisms, for discovering novel therapeutic targets, and for developing greatly needed treatments to slow or halt disease progression. © 2018 International Parkinson and Movement Disorder Society.

The Role of Interleukin-18, Oxidative Stress and Metabolic Syndrome in Alzheimer's Disease

The role of interleukins (ILs) and oxidative stress (OS) in precipitating neurodegenerative diseases including sporadic Alzheimer's disease (AD), requires further clarification. In addition to neuropathological hallmarks-extracellular neuritic amyloid-β (Aβ) plaques, neurofibrillary tangles (NFT) containing hyperphosphorylated tau and neuronal loss-chronic inflammation, as well as oxidative and excitotoxic damage, are present in the AD brain. The pathological sequelae and the interaction of these events during the course of AD need further investigation. The brain is particularly sensitive to OS, due to the richness of its peroxidation-sensitive fatty acids, coupled with its high oxygen demand. At the same time, the brain lack robust antioxidant systems. Among the multiple mechanisms and triggers by which OS can accumulate, inflammatory cytokines can sustain oxidative and nitrosative stress, leading eventually to cellular damage. Understanding the consequences of inflammation and OS may clarify the initial events underlying AD, including in interaction with genetic factors. Inflammatory cytokines are potential inducers of aberrant gene expression through transcription factors. Susceptibility disorders for AD, including obesity, type-2 diabetes, cardiovascular diseases and metabolic syndrome have been linked to increases in the proinflammatory cytokine, IL-18, which also regulates multiple AD related proteins. The association of IL-18 with AD and AD-linked medical conditions are reviewed in the article. Such data indicates that an active lifestyle, coupled to a healthy diet can ameliorate inflammation and reduce the risk of sporadic AD.

Molecular Alterations in the Cerebellum of Sporadic Creutzfeldt-Jakob Disease Subtypes with DJ-1 as a Key Regulator of Oxidative Stress

Cerebellar damage and granular and Purkinje cell loss in sporadic Creutzfeldt-Jakob disease (sCJD) highlight a critical involvement of the cerebellum during symptomatic progression of the disease. In this project, global proteomic alterations in the cerebellum of brain from the two most prevalent subtypes (MM1 and VV2) of sCJD were studied. Two-dimensional gel electrophoresis (2DE) coupled mass spectrometric identification revealed 40 proteins in MM1 and 43 proteins in VV2 subtype to be differentially expressed. Of those, 12 proteins showed common differential expression in their expression between two subtypes. Differentially expressed proteins mainly belonged to (i) cell cycle, gene expression and cell death; (ii) cellular stress response/oxidative stress (OS) and (iii) signal transduction and synaptic functions, related molecular functions. We verified 10 differentially expressed proteins at transcriptional and translational level as well. Interestingly, protein deglycase DJ-1 (an antioxidative protein) showed an increase in its messenger RNA (mRNA) expression in both MM1 and VV2 subtypes but protein expression only in VV2 subtype in cerebellum of sCJD patients. Nuclear translocalization of DJ-1 confirmed its expressional alteration due to OS in sCJD. Downstream experiments showed the activation of nuclear factor erythroid-2 related factor 2 (Nrf2)/antioxidative response element (ARE) pathway. DJ-1 protein concentration was significantly increased during the clinical phase in cerebrospinal fluid of sCJD patients and also at presymptomatic and symptomatic stages in cerebellum of humanized PrP transgenic mice inoculated with sCJD (MM1 and VV2) brain. These results suggest the implication of oxidative stress during the pathophysiology of sCJD.

Oxidative stress: A major pathogenesis and potential therapeutic target of antioxidative agents in Parkinson's disease and Alzheimer's disease

Oxidative stress reflects an imbalance between the overproduction and incorporation of free radicals and the dynamic ability of a biosystem to detoxify reactive intermediates. Free radicals produced by oxidative stress are one of the common features in several experimental models of diseases. Free radicals affect both the structure and function of neural cells, and contribute to a wide range of neurodegenerative diseases, including Parkinson's disease and Alzheimer's disease. Although the precise mechanisms that result in the degeneration of neurons and the relevant pathological changes remain unclear, the crucial role of oxidative stress in the pathogenesis of neurodegenerative diseases is associated with several proteins (such as α-synuclein, DJ-1, Amyloid β and tau protein) and some signaling pathways (such as extracellular regulated protein kinases, phosphoinositide 3-kinase/Protein Kinase B pathway and extracellular signal-regulated kinases 1/2) that are tightly associated with the neural damage. In this review, we present evidence, gathered over the last decade, concerning a variety of pathogenic proteins, their important signaling pathways and pathogenic mechanisms associated with oxidative stress in Parkinson's disease and Alzheimer's disease. Proper control and regulation of these proteins' functions and the related signaling pathways may be a promising therapeutic approach to the patients. We also emphasizes antioxidative options, including some new neuroprotective agents that eliminate excess reactive oxygen species efficiently and have a certain therapeutic effect; however, controversy surrounds some of them in terms of the dose and length of therapy. These agents require further investigation by clinical application in patients suffering Parkinson's disease and Alzheimer's disease.

Three Dimensional Human Neuro-Spheroid Model of Alzheimer's Disease Based on Differentiated Induced Pluripotent Stem Cells

The testing of candidate drugs to slow progression of Alzheimer’s disease (AD) requires clinical trials that are lengthy and expensive. Efforts to model the biochemical milieu of the AD brain may be greatly facilitated by combining two cutting edge technologies to generate three-dimensional (3D) human neuro-spheroid from induced pluripotent stem cells (iPSC) derived from AD subjects. We created iPSC from blood cells of five AD patients and differentiated them into 3D human neuronal culture. We characterized neuronal markers of our 3D neurons by immunocytochemical staining to validate the differentiation status. To block the generation of pathologic amyloid β peptides (Aβ), the 3D-differentiated AD neurons were treated with inhibitors targeting β-secretase (BACE1) and γ-secretases. As predicted, both BACE1 and γ-secretase inhibitors dramatically decreased Aβ generation in iPSC-derived neural cells derived from all five AD patients, under standard two-dimensional (2D) differentiation conditions. However, BACE1 and γ-secretase inhibitors showed less potency in decreasing Aβ levels in neural cells differentiated under 3D culture conditions. Interestingly, in a single subject AD1, we found that BACE1 inhibitor treatment was not able to significantly reduce Aβ42 levels. To investigate underlying molecular mechanisms, we performed proteomic analysis of 3D AD human neuronal cultures including AD1. Proteomic analysis revealed specific reduction of several proteins that might contribute to a poor inhibition of BACE1 in subject AD1. To our knowledge, this is the first iPSC-differentiated 3D neuro-spheroid model derived from AD patients’ blood. Our results demonstrate that our 3D human neuro-spheroid model can be a physiologically relevant and valid model for testing efficacy of AD drug.

Loss of DJ-1 impairs antioxidant response by altered glutamine and serine metabolism

The oncogene DJ-1 has been originally identified as a suppressor of PTEN. Further on, loss-of-function mutations have been described as a causative factor in Parkinson's disease (PD). DJ-1 has an important function in cellular antioxidant responses, but its role in central metabolism of neurons is still elusive. We applied stable isotope assisted metabolic profiling to investigate the effect of a functional loss of DJ-1 and show that DJ-1 deficient neuronal cells exhibit decreased glutamine influx and reduced serine biosynthesis. By providing precursors for GSH synthesis, these two metabolic pathways are important contributors to cellular antioxidant response. Down-regulation of these pathways, as a result of loss of DJ-1 leads to an impaired antioxidant response. Furthermore, DJ-1 deficient mouse microglia showed a weak but constitutive pro-inflammatory activation. The combined effects of altered central metabolism and constitutive activation of glia cells raise the susceptibility of dopaminergic neurons towards degeneration in patients harboring mutated DJ-1. Our work reveals metabolic alterations leading to increased cellular instability and identifies potential new intervention points that can further be studied in the light of novel translational medicine approaches.

Characterization of Differentiated SH-SY5Y as Neuronal Screening Model Reveals Increased Oxidative Vulnerability

The immortalized and proliferative cell line SH-SY5Y is one of the most commonly used cell lines in neuroscience and neuroblastoma research. However, undifferentiated SH-SY5Y cells share few properties with mature neurons. In this study, we present an optimized neuronal differentiation protocol for SH-SY5Y that requires only two work steps and 6 days. After differentiation, the cells present increased levels of ATP and plasma membrane activity but reduced expression of energetic stress response genes. Differentiation results in reduced mitochondrial membrane potential and decreased robustness toward perturbations with 6-hydroxydopamine. We are convinced that the presented differentiation method will leverage genetic and chemical high-throughput screening projects targeting pathways that are involved in the selective vulnerability of neurons with high energetic stress levels.

DJ-1 links muscle ROS production with metabolic reprogramming and systemic energy homeostasis in mice

Reactive oxygen species (ROS) have been linked to a wide variety of pathologies, including obesity and diabetes, but ROS also act as endogenous signalling molecules, regulating numerous biological processes. DJ-1 is one of the most evolutionarily conserved proteins across species, and mutations in DJ-1 have been linked to some cases of Parkinson's disease. Here we show that DJ-1 maintains cellular metabolic homeostasis via modulating ROS levels in murine skeletal muscles, revealing a role of DJ-1 in maintaining efficient fuel utilization. We demonstrate that, in the absence of DJ-1, ROS uncouple mitochondrial respiration and activate AMP-activated protein kinase, which triggers Warburg-like metabolic reprogramming in muscle cells. Accordingly, DJ-1 knockout mice exhibit higher energy expenditure and are protected from obesity, insulin resistance and diabetes in the setting of fuel surplus. Our data suggest that promoting mitochondrial uncoupling may be a potential strategy for the treatment of obesity-associated metabolic disorders.

The protein DJ-1 is known to have antioxidant effects in cells. Here, the authors reveal that DJ-1 has a role in coupling mitochondrial respiration in skeletal muscles of mice, and show that absence of DJ-1 increases energy expenditure and protects mice from diet-induced obesity.

Induction of DJ-1 protects neuronal cells from isoflurane induced neurotoxicity

Oxidative stress, mitochondrial dysfunction and neuronal apoptosis are thought to be major contributors of Isoflurane toxicity. However, the underlying mechanisms remain largely to be determined. DJ-1, a protein that is involved in the response to various kinds of stress, has shown its neuroprotective effects. Whether DJ-1 has a neuroprotective effect against isoflurane-induced neurotoxocity is still unknown. In this study, we found that expression of DJ-1 is elevated in response to isoflurane treatment in human SH-SY5Y neuroblastoma cells. In order to clarify whether DJ-1 plays a potential role in isoflurane neurotoxicity or as a compensatory response for survival, we investigated the effects of DJ-1 silencing in isoflurane neurotoxicity. Our findings indicate that knockdown of DJ-1 promotes isoflurane-induced oxidative stress and mitochondrial dysfunction. Importantly, DJ-1 silencing was found to exacerbate isoflurane- induced apoptosis through modulation of mitochondria-dependent apoptosis pathways, thereby suggesting that induction of DJ-1 in response to isoflurane might act as a compensatory response for cell survival.

Interleukin-18 alters protein expressions of neurodegenerative diseases-linked proteins in human SH-SY5Y neuron-like cells

Chronic inflammation and oxidative stress (OS) are present in Alzheimer's disease (AD) brains in addition to neuronal loss, Amyloid-β (Aβ) plaques and hyperphosphorylated tau-protein neurofibrillary tangles (NFTs). Previously we showed that levels of the pro-inflammatory cytokine, interleukin-18 (IL-18), are elevated in post-mortem AD brains. IL-18 can modulate the tau kinases, Cdk5 and GSK3β, as well as Aβ-production. IL-18 levels are also increased in AD risk diseases, including type-2 diabetes and obesity. Here, we explored other IL-18 regulated proteins in neuron-like SH-SY5Y cells. Differentiated SH-SY5Y cells, incubated with IL-18 for 24, 48, or 72 h, were analyzed by two-dimensional gel electrophoresis (2D-DIGE). Specific altered protein spots were chosen and identified with mass spectrometry (MS) and verified by western immunoblotting (WIB). IL-18 had time-dependent effects on the SH-SY5Y proteome, modulating numerous protein levels/modifications. We concentrated on those related to OS (DDAH2, peroxiredoxins 2, 3, and 6, DJ-1, BLVRA), Aβ-degradation (MMP14, TIMP2), Aβ-aggregation (Septin-2), and modifications of axon growth and guidance associated, collapsin response mediator protein 2 (CRMP2). IL-18 significantly increased antioxidative enzymes, indicative of OS, and altered levels of glycolytic α- and γ-enolase and multifunctional 14-3-3γ and -ε, commonly affected in neurodegenerative diseases. MMP14, TIMP2, α-enolase and 14-3-3ε, indirectly involved in Aβ metabolism, as well as Septin-2 showed changes that increase Aβ levels. Increased 14-3-3γ may contribute to GSK3β driven tau hyperphosphorylation and CRMP2 Thr514 and Ser522 phosphorylation with the Thr555-site, a target for Rho kinase, showing time-dependent changes. IL-18 also increased caspase-1 levels and vacuolization of the cells. Although our SH-SY5Y cells were not aged, as neurons in AD, our work suggests that heightened or prolonged IL-18 levels can drive protein changes of known relevance to AD pathogenesis.

Zebrafish as a model system for mitochondrial biology and diseases

Animal models for studying human disease are essential to the continuing evolution of medicine. Rodent models are attractive for the obvious similarities in development and genetic makeup compared with humans, but have cost and technical limitations. The zebrafish (Danio rerio) represents an ideal alternative vertebrate model of human disease because of its high conservation of genetic information and physiological processes, inexpensive maintenance, and optical clarity facilitating direct observation. This review highlights recent advances in understanding genetic disease states associated with the dynamic organelle, the mitochondrion, using the zebrafish. Mitochondrial diseases that have been replicated in the zebrafish include those affecting the nervous and cardiovascular systems, as well as red blood cell function. Gene silencing techniques, including morpholino knockdown and transcription activator-like (TAL)-effector endonucleases, have been exploited to demonstrate how loss of function can induce human disease-like states in zebrafish. Moreover, modeling mitochondrial diseases has been facilitated greatly by the creation of transgenic fish with fluorescently labeled mitochondria for in vivo visualization of these structures. In addition, behavioral assays have been developed to examine changes in motor activity and sensory responses, particularly in larval stages. Zebrafish are poised to advance our understanding of the pathogenesis of human mitochondrial diseases beyond the current state of knowledge and provide a key tool in the development of novel therapeutic approaches to treat these conditions.

Altered expression of DJ-1 and PINK1 in sporadic ALS and in the SOD1(G93A) ALS mouse model

Mitochondrial dysfunction is an important mechanism in the pathogenesis of neurodegenerative diseases such as Parkinson disease and amyotrophic lateral sclerosis (ALS). DJ-1 and PTEN-induced putative kinase 1 (PINK1) are important proteins for the maintenance of mitochondrial function and protection against cell death. Mutations in the genes coding for these proteins cause familial forms of Parkinson disease. Recent studies have postulated that changes in the expression of both proteins are also involved in pathologic mechanisms in ALS mouse models. Here, we studied the mRNA and protein expression of PINK1 and DJ-1 in postmortem brain and spinal cord tissue and muscle biopsy samples from ALS patients and controls and in brain, spinal cord, and gastrocnemius muscle of SOD1(G93A) ALS mice at different disease stages. We found significant decreases of PINK1 and DJ-1 mRNA levels in muscle tissue of SOD1(G93A) mice. Together with the significant decrease of PINK1 mRNA levels in human ALS muscle tissue, statistically nonsignificant reduction of DJ-1 mRNA levels, and reduced immunostaining for PINK1 in human ALS muscle, the results suggest potential pathophysiologic roles for these proteins in both mutant SOD1 transgenic mice and in sporadic ALS(G93A).

DJ-1 modulates aggregation and pathogenesis in models of Huntington's disease

The oxidation-sensitive chaperone protein DJ-1 has been implicated in several human disorders including cancer and neurodegenerative diseases. During neurodegeneration associated with protein misfolding, such as that observed in Alzheimer's disease and Huntington's disease (HD), both oxidative stress and protein chaperones have been shown to modulate disease pathways. Therefore, we set out to investigate whether DJ-1 plays a role in HD. We found that DJ-1 expression and its oxidation state are abnormally increased in the human HD brain, as well as in mouse and cell models of HD. Furthermore, overexpression of DJ-1 conferred protection in vivo against neurodegeneration in yeast and Drosophila. Importantly, the DJ-1 protein directly interacted with an expanded fragment of huntingtin Exon 1 (httEx1) in test tube experiments and in cell models and accelerated polyglutamine aggregation and toxicity in an oxidation-sensitive manner. Our findings clearly establish DJ-1 as a potential therapeutic target for HD and provide the basis for further studies into the role of DJ-1 in protein misfolding diseases.

Knocking out DJ-1 attenuates astrocytes neuroprotection against 6-hydroxydopamine toxicity

Astrocytes are the most abundant glial cell type in the brain. Impairment in astrocyte functions can critically influence neuronal survival and leads to neurodegeneration. Parkinson's disease (PD) is a common neurodegenerative disorder, characterized by motor dysfunction that results from progressive neuronal loss. Astrocytic dysfunction was demonstrated in human samples and in experimental models of PD. Mutations in DJ-1 (PARK7) leading to loss of functional protein cause familial PD and enhance sensitivity to oxidative insults. Recently, an increase in DJ-1's expression was found in reactive astrocytes in various neurodegenerative disorders. Here we show that lack of DJ-1 attenuates astrocytes' ability to support neuronal cells, thereby leading to accelerated neuronal damage. DJ-1 knockout mice demonstrated increased vulnerability in vivo to 6-hydroxydopamine (6-OHDA) hemiparkinsonian PD model. Astrocytes isolated from DJ-1 knockout mice showed an inferior ability to protect human neuroblastoma cells against 6-OHDA insult both by co-culture and through their conditioned media, as compared to wild-type astrocytes. DJ-1 knockout astrocytes showed blunted ability to increase the expression of cellular protective mechanisms against oxidative stress mediated via Nrf-2 and HO-1 in response to exposure to 6-OHDA. These experiments demonstrated that lack of DJ-1 impairs astrocyte-mediated neuroprotection.

Dopaminergic neuronal loss and dopamine-dependent locomotor defects in Fbxo7-deficient zebrafish

Recessive mutations in the F-box only protein 7 gene (FBXO7) cause PARK15, a Mendelian form of early-onset, levodopa-responsive parkinsonism with severe loss of nigrostriatal dopaminergic neurons. However, the function of the protein encoded by FBXO7, and the pathogenesis of PARK15 remain unknown. No animal models of this disease exist. Here, we report the generation of a vertebrate model of PARK15 in zebrafish. We first show that the zebrafish Fbxo7 homolog protein (zFbxo7) is expressed abundantly in the normal zebrafish brain. Next, we used two zFbxo7-specific morpholinos (targeting protein translation and mRNA splicing, respectively), to knock down the zFbxo7 expression. The injection of either of these zFbxo7-specific morpholinos in the fish embryos induced a marked decrease in the zFbxo7 protein expression, and a range of developmental defects. Furthermore, whole-mount in situ mRNA hybridization showed abnormal patterning and significant decrease in the number of diencephalic tyrosine hydroxylase-expressing neurons, corresponding to the human nigrostriatal or ventral tegmental dopaminergic neurons. Of note, the number of the dopamine transporter-expressing neurons was much more severely depleted, suggesting dopaminergic dysfunctions earlier and larger than those due to neuronal loss. Last, the zFbxo7 morphants displayed severe locomotor disturbances (bradykinesia), which were dramatically improved by the dopaminergic agonist apomorphine. The severity of these morphological and behavioral abnormalities correlated with the severity of zFbxo7 protein deficiency. Moreover, the effects of the co-injection of zFbxo7- and p53-specific morpholinos were similar to those obtained with zFbxo7-specific morpholinos alone, supporting further the contention that the observed phenotypes were specifically due to the knock down of zFbxo7. In conclusion, this novel vertebrate model reproduces pathologic and behavioral hallmarks of human parkinsonism (dopaminergic neuronal loss and dopamine-dependent bradykinesia), representing therefore a valid tool for investigating the mechanisms of selective dopaminergic neuronal death, and screening for modifier genes and therapeutic compounds.

Involvement and interplay of Parkin, PINK1, and DJ1 in neurodegenerative and neuroinflammatory disorders

The involvement of parkin, PINK1, and DJ1 in mitochondrial dysfunction, oxidative injury, and impaired functioning of the ubiquitin-proteasome system (UPS) has been intensively investigated in light of Parkinson's disease (PD) pathogenesis. However, these pathological mechanisms are not restricted to PD, but are common denominators of various neurodegenerative and neuroinflammatory disorders. It is therefore conceivable that parkin, PINK1, and DJ1 are also linked to the pathogenesis of other neurological diseases, including Alzheimer's disease (AD) and multiple sclerosis (MS). The importance of these proteins in mechanisms underlying neurodegeneration is reflected by the neuroprotective properties of parkin, DJ1, and PINK1 in counteracting oxidative stress and improvement of mitochondrial and UPS functioning. This review provides a concise overview on the cellular functions of the E3 ubiquitin ligase parkin, the mitochondrial kinase PINK1, and the cytoprotective protein DJ1 and their involvement and interplay in processes underlying neurodegeneration in common neurological disorders.

Zebrafish Parla- and Parlb-deficiency affects dopaminergic neuron patterning and embryonic survival

Many genes associated with familial Parkinson's disease contribute to mitochondrial morphology and function. Some of these genes, for example, Pink1 and Parkin, are part of a common pathway. The presenilin-associated rhomboid-like (PARL) gene was recently linked to familial Parkinson's disease. The PARL gene product is found in the inner mitochondrial membrane and cleaves the optic atrophy 1 protein, involved in mitochondrial morphology and apoptosis. In Drosophila, the PARL-related rhomboid-7 gene acts upstream of pink1 and parkin. However, such a genetic relationship is still unknown in vertebrates. Here, we show that the zebrafish genome comprises two parl paralogs: parla and parlb. Morpholino-mediated loss of parla and/or parlb function resulted in mild neurodegeneration, as evidenced by a lower density of dopaminergic neurons. Patterning of dopaminergic neurons was also perturbed in the ventral diencephalon. Morphants exhibited extensive cell death throughout the entire body as well as increased larval mortality. The morphant phenotype could be rescued by injection of human PARL mRNA, but not catalytically inactive PARL, suggesting functional conservation between the human and zebrafish proteins. More importantly, the zebrafish pink1 mRNA as well as the human PINK1 mRNA, but not kinase-dead nor Parkinson's disease-linked mutant PINK1 mRNA, also rescued the morphant phenotype, providing evidence that Parl genes may function upstream of Pink1, as part of a conserved pathway in vertebrates.

Modeling neurodegeneration in zebrafish

The zebrafish, Danio rerio, has been established as an excellent vertebrate model for the study of developmental biology and gene function. It also has proven to be a valuable model to study human diseases. Here, we reviewed recent publications using zebrafish to study the pathology of human neurodegenerative diseases including Parkinson's, Huntington's, and Alzheimer's. These studies indicate that zebrafish genes and their human homologues have conserved functions with respect to the etiology of neurodegenerative diseases. The characteristics of the zebrafish and the experimental approaches to which it is amenable make this species a useful complement to other animal models for the study of pathologic mechanisms of neurodegenerative diseases and for the screening of compounds with therapeutic potential.

Proteomic analysis of pregnancy-related proteins from pig uterus endometrium during pregnancy

Many important molecular events associated with implantation and development occur within the female reproductive tract, especially within the uterus endometrium, during pregnancy periods. The endometrium includes the mucosal lining of the uterus, which provides a suitable site for implantation and development of a fertilized egg and fetus. To date, the molecular cascades in the uterus endometrium during pregnancy periods in pigs have not been elucidated fully. In this study, we compared the functional regulated proteins in the endometrium during pregnancy periods with those in non-pregnant conditions and investigated changes in expression patterns during pregnancy (days 40, 70, and 93) using two-dimensional gel electrophoresis (2-DE) and western blotting. The functional regulated proteins were identified and discovered from differentially expressed proteins in the uterus endometrium during pregnancy. We discovered 820 protein spots in a proteomic analysis of uterus endometrium tissues with 2-DE gels. We identified 63 of the 98 proteins regulated differentially among non-pregnant and pregnant tissues (matched and unmatched spots). Interestingly, 10 of these 63 proteins are development-, cytoskeleton- and chaperon-related proteins such as transferrin, protein DJ-1, transgelin, galectin-1, septin 2, stathmin 1, cofilin 1, fascin 1, heat shock protein (HSP) 90β and HSP 27. The specific expression patterns of these proteins in the endometrium during pregnancy were confirmed by western blotting. Our results suggest that the expressions of these genes involved in endometrium function and endometrium development from early to late gestation are associated with the regulation of endometrium development for maintaining pregnancy.

Sodium benzoate, a metabolite of cinnamon and a food additive, upregulates neuroprotective Parkinson disease protein DJ-1 in astrocytes and neurons

DJ-1 (PARK7) is a neuroprotective protein that protects cells from oxidative stress. Accordingly, loss-of-function DJ-1 mutations have been linked with a familial form of early onset Parkinson disease. Mechanisms by which DJ-1 level could be enriched in the CNS are poorly understood. Recently we have discovered anti-inflammatory activity of sodium benzoate (NaB), a metabolite of cinnamon and a widely-used food additive. Here we delineate that NaB is also capable of increasing the level of DJ-1 in primary mouse and human astrocytes and human neurons highlighting another novel neuroprotective effect of this compound. Reversal of DJ-1-inducing effect of NaB by mevalonate, farnesyl phosphate, but not cholesterol and ubiquinone, suggests that depletion of intermediates, but not end products, of the mevalonate pathway is involved in the induction of DJ-1 by NaB. Accordingly, either an inhibitor of p21(ras) farnesyl protein transferase (FPTI) or a dominant-negative mutant of p21(ras) alone was also able to increase the expression of DJ-1 in astrocytes suggesting an involvement of p21(ras) in DJ-1 expression. However, an inhibitor of geranyl geranyl transferase (GGTI) and a dominant-negative mutant of p21(rac) had no effect on the expression of DJ-1, indicating the specificity of the effect. Similarly lipopolysaccharide (LPS), an activator of small G proteins, also inhibited the expression of DJ-1, and NaB and FPTI, but not GGTI, abrogated LPS-mediated inhibition. Together, these results suggest that NaB upregulates DJ-1 via modulation of mevalonate metabolites and that p21(ras), but not p21(rac), is involved in the regulation of DJ-1.

Transgenic zebrafish models of neurodegenerative diseases

Since the introduction of the zebrafish as a model for the study of vertebrate developmental biology, an extensive array of techniques for its experimental manipulation and analysis has been developed. Recently it has become apparent that these powerful methodologies might be deployed in order to elucidate the pathogenesis of human neurodegenerative diseases and to identify candidate therapeutic approaches. In this article, we consider evidence that the zebrafish central nervous system provides an appropriate setting in which to model human neurological disease and we review techniques and resources available for generating transgenic models. We then examine recent publications showing that appropriate phenotypes can be provoked in the zebrafish through transgenic manipulations analogous to genetic abnormalities known to cause human tauopathies, polyglutamine diseases or motor neuron degenerations. These studies show proof of concept that findings in zebrafish models can be applicable to the pathogenic mechanisms underlying human diseases. Consequently, the prospects for providing novel insights into neurodegenerative diseases by exploiting transgenic zebrafish models and discovery-driven approaches seem favorable.

DJ-1 and prevention of oxidative stress in Parkinson's disease and other age-related disorders

Mutations in the PARK7/DJ-1 gene are rare causes of autosomal-recessive hereditary Parkinson's disease. Loss-of-function mutations lead to the characteristic selective neurodegeneration of nigrostriatal dopaminergic neurons, which accounts for parkinsonian symptoms. Originally identified as an oncogene, DJ-1 is a ubiquitous redox-responsive cytoprotective protein with diverse functions. In addition to cell-autonomous neuroprotective roles, DJ-1 may act in a transcellular manner, being up-regulated in reactive astrocytes in chronic neurodegenerative diseases as well as in stroke. Thus, DJ-1, particularly in its oxidized form, has been recognized as a biomarker for cancer and neurodegenerative diseases. The crystal structure of DJ-1 has been solved, allowing detailed investigations of the redox-reactive center of DJ-1. Structure-function studies revealed that DJ-1 may become activated in the presence of reactive oxygen species, under conditions of oxidative stress, but also as part of physiological receptor-mediated signal transduction. DJ-1 regulates redox signaling kinase pathways and acts as a transcriptional regulator of antioxidative gene batteries. Therefore, DJ-1 is an important redox-reactive signaling intermediate controlling oxidative stress after ischemia, upon neuroinflammation, and during age-related neurodegenerative processes. Augmenting DJ-1 activity might provide novel approaches to treating chronic neurodegenerative illnesses such as Parkinson's disease and acute damage such as stroke.