Overexpression of DJ-1/PARK7, the Parkinson's disease-related protein, improves mitochondrial function via Akt phosphorylation on threonine 308 in dopaminergic neuron-like cells

The role of neuron-like cell lines and primary neuron cell models in unraveling the complexity of neurodegenerative diseases: a comprehensive review

Neurodegenerative diseases (NDs) are characterized by the progressive loss of neurons. As to developing effective therapeutic interventions, it is crucial to understand the underlying mechanisms of NDs. Cellular models have become invaluable tools for studying the complex pathogenesis of NDs, offering insights into disease mechanisms, determining potential therapeutic targets, and aiding in drug discovery. This review provides a comprehensive overview of various cellular models used in ND research, focusing on Alzheimer's disease, Parkinson's disease, Huntington's disease, and amyotrophic lateral sclerosis. Cell lines, such as SH-SY5Y and PC12 cells, have emerged as valuable tools due to their ease of use, reproducibility, and scalability. Additionally, co-culture models, involving the growth of distinct cell types like neurons and astrocytes together, are highlighted for simulating brain interactions and microenvironment. While cell lines cannot fully replicate the complexity of the human brain, they provide a scalable method for examining important aspects of neurodegenerative diseases. Advancements in cell line technologies, including the incorporation of patient-specific genetic variants and improved co-culture models, hold promise for enhancing our understanding and expediting the development of effective treatments. Integrating multiple cellular models and advanced technologies offers the potential for significant progress in unraveling the intricacies of these debilitating diseases and improving patient outcomes.

N-homocysteinylation of DJ-1 promotes neurodegeneration in Parkinson's disease

DJ-1, also known as Parkinson's disease protein 7 (Park7), is a multifunctional protein that regulates oxidative stress and mitochondrial function. Dysfunction of DJ-1 is implicated in the pathogenesis of Parkinson's disease (PD). Hyperhomocysteinemia is associated with an increased risk of PD. Here we show that homocysteine thiolactone (HTL), a reactive thioester of homocysteine (Hcy), covalently modifies DJ-1 on the lysine 182 (K182) residue in an age-dependent manner. The N-homocysteinylation (N-hcy) of DJ-1 abolishes its neuroprotective effect against oxidative stress and mitochondrial dysfunction, exacerbating cell toxicity. Blocking the N-hcy of DJ-1 restores its protective effect. These results indicate that the N-hcy of DJ-1 abolishes its neuroprotective effect and promotes the progression of PD. Inhibiting the N-hcy of DJ-1 may exert neuroprotective effect against PD.

Neuron-secreted NLGN3 ameliorates ischemic brain injury via activating Gαi1/3-Akt signaling

We here tested the potential activity and the underlying mechanisms of neuroligin-3 (NLGN3) against ischemia-reperfusion-induced neuronal cell injury. In SH-SY5Y neuronal cells and primary murine cortical neurons, NLGN3 activated Akt-mTOR and Erk signalings, and inhibited oxygen and glucose deprivation (OGD)/re-oxygenation (OGD/R)-induced cytotoxicity. Akt activation was required for NLGN3-induced neuroprotection. Gαi1/3 mediated NLGN3-induced downstream signaling activation. NLGN3-induced Akt-S6K1 activation was largely inhibited by Gαi1/3 silencing or knockout. Significantly, NLGN3-induced neuroprotection against OGD/R was almost abolished by Gαi1/3 silencing or knockout. In vivo, the middle cerebral artery occlusion (MCAO) procedure induced NLGN3 cleavage and secretion, and increased its expression and Akt activation in mouse brain tissues. ADAM10 (A Disintegrin and Metalloproteinase 10) inhibition blocked MCAO-induced NLGN3 cleavage and secretion, exacerbating ischemic brain injury in mice. Neuronal silencing of NLGN3 or Gαi1/3 in mice also inhibited Akt activation and intensified MCAO-induced ischemic brain injury. Conversely, neuronal overexpression of NLGN3 increased Akt activation and alleviated MCAO-induced ischemic brain injury. Together, NLGN3 activates Gαi1/3-Akt signaling to protect neuronal cells from ischemia-reperfusion injury.

Neuroprotective compounds from marine invertebrates

Background

Neuroinflammation is a key pathological feature of a wide variety of neurological disorders, including Parkinson’s, multiple sclerosis, Alzheimer’s, and Huntington’s disease. While current treatments for these disorders are primarily symptomatic, there is a growing interest in developing new therapeutics that target the underlying neuroinflammatory processes.

Main body

Marine invertebrates, such as coral, sea urchins, starfish, sponges, and sea cucumbers, have been found to contain a wide variety of biologically active compounds that have demonstrated potential therapeutic properties. These compounds are known to target various key proteins and pathways in neuroinflammation, including 6-hydroxydopamine (OHDH), caspase-3 and caspase-9, p-Akt, p-ERK, p-P38, acetylcholinesterase (AChE), amyloid-β (Aβ), HSF-1, α-synuclein, cellular prion protein, advanced glycation end products (AGEs), paraquat (PQ), and mitochondria DJ-1.

Short conclusion

This review focuses on the current state of research on the neuroprotective effects of compounds found in marine invertebrates and the potential therapeutic implications of these findings for treating neuroinflammatory disorders. We also discussed the challenges and limitations of using marine-based compounds as therapeutics, such as sourcing and sustainability concerns, and the need for more preclinical and clinical studies to establish their efficacy and safety.

Graphical abstract

Mangiferin, a natural glucoxilxanthone, inhibits mitochondrial dynamin-related protein 1 and relieves aberrant mitophagic proteins in mice model of Parkinson's disease

BACKGROUND

Parkinson's disease (PD) is the second most common neurodegenerative disease featured to mitochondrial dysfunction in neuronal cells. Dynamin-related protein 1 (Drp1) is an important regulator of mitochondrial fission and subsequent mitophagy. Mangiferin (MGF) is a glucosyl xanthone mainly derived from Mangifera indica L., possessing multifaceted properties, e.g., antioxidant, anti-inflammatory, and enhancement of cognitive ability. Besides, it can cross the blood-brain barrier, thereby exerting a neuroprotective effect. However, so far, MGF's effect in balancing mitochondrial homeostasis via regulation of Drp1 level and mitophagic pathway in PD remains rarely reported.

PURPOSE

We aimed to investigate the neuroprotective effect of MGF against 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of PD and examine the possible mechanisms.

METHODS

We utilized C57BL/6 mice exposed to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP); Behavioral parameters, containing the open field test, balance beam, pole test, and rotarod test, assessed the locomotor activity; immunohistochemistry assessed the number of TH-positive neurons; transmission electron microscopy detected ultrastructural mitochondrial morphology in the dopaminergic neuron; complex I enzymatic activity microplate assay kit measured the mitochondrial complex I activity; ATP determination kit measured ATP levels in mitochondria isolated from cells or striatal tissues; western blot measured the levels of Drp1 and mitophagic proteins.

RESULTS

We observed that MGF could mitigate motor deficiency and improve the expression of tyrosine hydroxylase in the substantia nigra of MPTP-induced PD mice. Furthermore, MGF not only ameliorated mitochondrial ultrastructure, but also improved mitochondrial ATP content. Within mitochondria, MGF could reduce Drp1 expression and reverse the expressions of mitophagic proteins, including PINK1, Parkin, NIX, BNIP3, FUNDC1, and p62.

CONCLUSION

Present study indicates that MGF benefits mitochondrial networks by recovering mitochondrial ultrastructure and ATP contents, reducing mitochondrial Drp1, and modulating mitophagic proteins in the MPTP-induced PD mice model, which revealed a novel acting mechanism of MGF in PD's treatment.

Precise control of mitophagy through ubiquitin proteasome system and deubiquitin proteases and their dysfunction in Parkinson's disease

Parkinson’s disease (PD) is one of the most common neurodegenerative diseases in the elderly population and is caused by the loss of dopaminergic neurons. PD has been predominantly attributed to mitochondrial dysfunction. The structural alteration of α-synuclein triggers toxic oligomer formation in the neurons, which greatly contributes to PD. In this article, we discuss the role of several familial PD-related proteins, such as α-synuclein, DJ-1, LRRK2, PINK1, and parkin in mitophagy, which entails a selective degradation of mitochondria via autophagy. Defective changes in mitochondrial dynamics and their biochemical and functional interaction induce the formation of toxic α-synuclein-containing protein aggregates in PD. In addition, these gene products play an essential role in ubiquitin proteasome system (UPS)-mediated proteolysis as well as mitophagy. Interestingly, a few deubiquitinating enzymes (DUBs) additionally modulate these two pathways negatively or positively. Based on these findings, we summarize the close relationship between several DUBs and the precise modulation of mitophagy. For example, the USP8, USP10, and USP15, among many DUBs are reported to specifically regulate the K48- or K63-linked de-ubiquitination reactions of several target proteins associated with the mitophagic process, in turn upregulating the mitophagy and protecting neuronal cells from α-synuclein-derived toxicity. In contrast, USP30 inhibits mitophagy by opposing parkin-mediated ubiquitination of target proteins. Furthermore, the association between these changes and PD pathogenesis will be discussed. Taken together, although the functional roles of several PD-related genes have yet to be fully understood, they are substantially associated with mitochondrial quality control as well as UPS. Therefore, a better understanding of their relationship provides valuable therapeutic clues for appropriate management strategies.

Precise control of mitophagy through ubiquitin proteasome system and deubiquitin proteases and their dysfunction in Parkinson's disease

Parkinson's disease (PD) is one of the most common neurodegenerative diseases in the elderly population and is caused by the loss of dopaminergic neurons. PD has been predominantly attributed to mitochondrial dysfunction. The structural alteration of α-synuclein triggers toxic oligomer formation in the neurons, which greatly contributes to PD. In this article, we discuss the role of several familial PD-related proteins, such as α-synuclein, DJ-1, LRRK2, PINK1, and parkin in mitophagy, which entails a selective degradation of mitochondria via autophagy. Defective changes in mitochondrial dynamics and their biochemical and functional interaction induce the formation of toxic α-synucleincontaining protein aggregates in PD. In addition, these gene products play an essential role in ubiquitin proteasome system (UPS)-mediated proteolysis as well as mitophagy. Interestingly, a few deubiquitinating enzymes (DUBs) additionally modulate these two pathways negatively or positively. Based on these findings, we summarize the close relationship between several DUBs and the precise modulation of mitophagy. For example, the USP8, USP10, and USP15, among many DUBs are reported to specifically regulate the K48- or K63-linked de-ubiquitination reactions of several target proteins associated with the mitophagic process, in turn upregulating the mitophagy and protecting neuronal cells from α-synuclein-derived toxicity. In contrast, USP30 inhibits mitophagy by opposing parkin-mediated ubiquitination of target proteins. Furthermore, the association between these changes and PD pathogenesis will be discussed. Taken together, although the functional roles of several PD-related genes have yet to be fully understood, they are substantially associated with mitochondrial quality control as well as UPS. Therefore, a better understanding of their relationship provides valuable therapeutic clues for appropriate management strategies. [BMB Reports 2021; 54(12): 592-600].

Inhibition of dynamin-related protein 1 ameliorates the mitochondrial ultrastructure via PINK1 and Parkin in the mice model of Parkinson's disease

Parkinson's disease (PD) is the prevalent neurodegenerative disorder characterized by the degeneration of the nigrostriatal neurons. Dynamin-related protein 1 (Drp1) is a key regulator mediating mitochondrial fission and affecting mitophagy in neurons. It has been reported that the inhibition of Drp1 may be beneficial to PD. However, the role of Drp1 and mitophagy in PD remains elusive. Therefore, in this research, we investigated the role of Drp1 and the underlying mechanisms in the mice model of PD. We used the dynasore, a GTPase inhibitor, to inhibit the expression of Drp1. We found that inhibition of Drp1 could ameliorate the motor deficits and the expression of tyrosine hydroxylase in the mice of the PD model. But Drp1 inhibition did not affect mitochondria number and morphological parameters. Moreover, suppression of Drp1 up-regulated the mitochondrial expressions of PINK1 and Parkin while not affected the expressions of NIX and BNIP3. Conclusively, our findings suggest that the inhibition of Drp1 ameliorated the mitochondrial ultrastructure at least via regulating PINK1 and Parkin in the mice of the PD model. This study also implicates that inhibition of Drp1 might impact mitophagy and recover mitochondrial homeostasis in 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.

Neuroprotective effect of apigenin against cerebral ischemia/reperfusion injury

Objective

The therapeutic efficacy of apigenin in PC12 cells and rats remains uncertain. The aim of this study was to investigate the neuroprotective effects of apigenin against cerebral ischemia/reperfusion injury, both in vitro and in vivo.

Methods

We first treated PC12 cells with cobalt chloride (CoCl₂) to create a model of oxidative stress injury. Cell viability was then determined using a multifunctional microplate reader. In addition, reactive oxygen species (ROS) levels, apoptosis, and mitochondrial membrane potentials (MMPs) were examined using high-content cytometer analysis. The efficacy of apigenin treatment was also analyzed in a rat middle cerebral artery occlusion (MCAO) model using TTC staining and neurological deficit scores.

Results

The half-inhibitory concentration of CoCl₂ was 1.2 mM. Pretreatment with 10 µg ⋅ mL⁻¹ apigenin significantly enhanced cell viability, reduced ROS levels, alleviated apoptosis, and improved MMP in PC12 cells with CoCl₂-induced injury in vitro. In addition, apigenin treatment in vivo significantly improved neurological deficit scores and reduced infarct areas in MCAO rats. These results suggest that the neuroprotective mechanisms of apigenin may be related to mitochondrial activation.

Conclusions

Apigenin had excellent neuroprotective effects for the treatment of cerebral ischemia/reperfusion injury in vitro and in vivo.

Lycium barbarum Polysaccharide Ameliorates Heat-Stress-Induced Impairment of Primary Sertoli Cells and the Blood-Testis Barrier in Rat via Androgen Receptor and Akt Phosphorylation

Male infertility induced by heat stress has been attracting more and more attention. Heat stress not only causes apoptosis of spermatocytes but also has adverse effects on Sertoli cells, further damaging spermatogenesis. Lycium barbarum polysaccharide (LBP) is the main bioactive component of Lycium barbarum, which has a protective effect on male reproduction, but its mechanism is still unclear. In this study, our results proved that LBP blocked the inhibitory effect on the proliferation activity of Sertoli cells after heat stress, reversed the dedifferentiation of Sertoli cells induced by heat stress, and ameliorated the structural integrity of the blood-testis barrier. In addition, it increased the expression of the androgen receptor and activated Akt signaling pathway to resist heat-stress-induced injury of Sertoli cells.

Mitophagy, a Form of Selective Autophagy, Plays an Essential Role in Mitochondrial Dynamics of Parkinson's Disease

Parkinson's disease (PD) is a severe neurodegenerative disorder caused by the progressive loss of dopaminergic neurons in the substantia nigra and affects millions of people. Currently, mitochondrial dysfunction is considered as a central role in the pathogenesis of both sporadic and familial forms of PD. Mitophagy, a process that selectively targets damaged or redundant mitochondria to the lysosome for elimination via the autophagy devices, is crucial in preserving mitochondrial health. So far, aberrant mitophagy has been observed in the postmortem of PD patients and genetic or toxin-induced models of PD. Except for mitochondrial dysfunction, mitophagy is involved in regulating several other PD-related pathological mechanisms as well, e.g., oxidative stress and calcium imbalance. So far, the mitophagy mechanisms induced by PD-related proteins, PINK1 and Parkin, have been studied widely, and several other PD-associated genes, e.g., DJ-1, LRRK2, and alpha-synuclein, have been discovered to participate in the regulation of mitophagy as well, which further strengthens the link between mitophagy and PD. Thus, in this view, we reviewed mitophagy pathways in belief and discussed the interactions between mitophagy and several PD's pathological mechanisms and how PD-related genes modulate the mitophagy process.

Epigenetic regulation of apoptosis via the PARK7 interactome in peripheral blood mononuclear cells donated by tuberculosis patients vs. healthy controls and the response to treatment: A systems biology approach

AIMS

The aims of our study were to determine for the first time differentially expressed genes (DEGs) and enriched molecular pathways involving the PARK7 interactome in PBMCs donated from tuberculosis patients.

METHODS

Data on a previously reconstructed PARK7 interactome (Vavougios et al., 2017) from datasets GDS4966 (Case-Control) and GDS4781 (Treatment Series) were retrieved from the Gene Expression Omnibus (GEO) repository. Gene Enrichment analysis was performed via the STRING algorithm and the GeneTrail2 software.

RESULTS

17 and 22 PARK7 interactores were determined as DEGs in the active TB vs HD and Treatment Series subset analyses, correspondingly, associated with significantly enriched pathways (FDR <0.05) involving p53 and PTEN mediated, stress responsive apoptosis regulation pathways. The treatment subset was characterized by the emergence of an additional layer of transcriptional regulation mediated by polycomb proteins among others, as well as TLR-mediated and cytokine survival signaling. Finally, the enrichment of a Parkinson's disease signature including PARK7 interactors was determined by its differential regulation both in the exploratory analyses (FDR = 0.024), as well as the confirmatory analyses (FDR = 1.81e^-243).

CONCLUSIONS

Our in silico analysis revealed for the first time the role of PARK7's interactome in regulating the epigenetics of the PBMC lifecycle and Mtb symbiosis.

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.

Update on the association between alpha-synuclein and tau with mitochondrial dysfunction: Implications for Parkinson's disease

The critical role of mitochondrial dysfunction in the pathological mechanisms of neurodegenerative disorders, particularly Parkinson's disease (PD), is well established. Compelling evidence indicates that Parkinson's proteins (e.g., α-synuclein, Parkin, PINK1, DJ-1, and LRRK2) are associated with mitochondrial dysfunction and oxidative stress in PD. Significantly, there is a possible central role of alpha-synuclein (α-Syn) in the occurrence of mitochondrial dysfunction and oxidative stress by the mediation of different signaling pathways. Also, tau, traditionally considered as the main component of neurofibrillary tangles, aggregates and amplifies the neurotoxic effects on mitochondria by interacting with α-Syn. Moreover, oxidative stress caused by mitochondrial dysfunction favors assembly of both α-Syn and tau and also plays a key role in the formation of protein aggregates. In this review, we provide an overview of the relationship between these two pathological proteins and mitochondrial dysfunction in PD, and also summarize the underlying mechanisms in the interplay of α-Syn aggregation and phosphorylated tau targeting the mitochondria, to find new strategies to prevent PD processing.

The Parkinson's disease gene PINK1 activates Akt via PINK1 kinase-dependent regulation of the phospholipid PI(3,4,5)P3

Akt signalling is central to cell survival, metabolism, protein and lipid homeostasis, and is impaired in Parkinson's disease (PD). Akt activation is reduced in the brain in PD, and by many PD-causing genes, including PINK1 This study investigated the mechanisms by which PINK1 regulates Akt signalling. Our results reveal for the first time that PINK1 constitutively activates Akt in a PINK1-kinase dependent manner in the absence of growth factors, and enhances Akt activation in normal growth medium. In PINK1-modified MEFs, agonist-induced Akt signalling failed in the absence of PINK1, due to PINK1 kinase-dependent increases in PI(3,4,5)P₃ at both plasma membrane and Golgi being significantly impaired. In the absence of PINK1, PI(3,4,5)P₃ levels did not increase in the Golgi, and there was significant Golgi fragmentation, a recognised characteristic of PD neuropathology. PINK1 kinase activity protected the Golgi from fragmentation in an Akt-dependent fashion. This study demonstrates a new role for PINK1 as a primary upstream activator of Akt via PINK1 kinase-dependent regulation of its primary activator PI(3,4,5)P₃, providing novel mechanistic information on how loss of PINK1 impairs Akt signalling in PD.This article has an associated First Person interview with the first author of the paper.

SC79, a novel Akt activator, protects dopaminergic neuronal cells from MPP+ and rotenone

In pathogenesis of Parkinson's disease (PD), mitochondrial dysfunction causes substantial reactive oxygen species (ROS) production and oxidative stress, leading to dopaminergic (DA) neuronal cell death. Mitochondrial toxins, including MPP⁺ (1-methyl-4-phenylpyridinium ion) and rotenone, induce oxidative injury in cultured DA neuronal cells. The current study tested the potential effect of SC79, a first-in-class small-molecule Akt activator, against the process. In SH-SY5Y cells and primary murine DA neurons, SC79 significantly attenuated MPP⁺- and rotenone-induced viability reduction, cell death, and apoptosis. SC79 activated Akt signaling in DA neuronal cells. Akt inhibition (by LY294002 and MK-2206) or CRISPR-Cas9-mediated Akt1 knockout completely abolished SC79-induced DA neuroprotection against MPP⁺. Further studies demonstrated that SC79 attenuated MPP⁺- and rotenone-induced ROS production, mitochondrial depolarization, and lipid peroxidation in SH-SY5Y cells and primary DA neurons. Moreover, upregulation of Nrf2-dependent genes (HO1 and NQO1) and Nrf2 protein stabilization were detected in SC79-treated SH-SY5Y cells and primary DA neurons. Together we show that SC79 protects DA neuronal cells from mitochondrial toxins possibly via activation of Akt-Nrf2 signaling.

RNAi-mediated knockdown of DJ-1 leads to mitochondrial dysfunction via Akt/GSK-3ß and JNK signaling pathways in dopaminergic neuron-like cells

Deletions or some mutations in the gene encoding the multifunctional protein, DJ-1, have been considered to be linked with autosomal recessive early onset Parkinson's disease (PD). Current emerging evidence suggests that DJ-1 is involved in the protection against oxidative stress-induced mitochondrial damage. However, the exact molecular mechanisms underlying this are not completely clear. The aim of this study was to investigate the effects of DJ-1 on the Akt pathway, nuclear factor erythroid 2-related factor (Nrf2), and c-Jun N-terminal kinase (JNK) with regard to modulating mitochondrial function. Here we showed that knockdown of DJ-1 resulted in mitochondrial dysfunction, including a decrease in active mitochondrial mass, complex I deficits, and inhibition of cellular adenosine 5'-triphosphate (ATP) content in the dopaminergic neuron-like cells PC12 and SH-SY5Y. Additionally, loss of DJ-1 impaired Akt signaling, and reduced nuclear translocation of Nrf2, thereby inhibiting activity of Nrf2-regulated downstream antioxidant enzymes such as heme oxygenase-1 and NAD(P)H quinone oxidoreductase 1. Moreover, DJ-1 knockdown also led to a significant increase in the mitochondrial reactive oxygen species, and then promoted the activation of JNK pathways. Furthermore, oxidative stress and mitochondrial dysfunction induced by knockdown of DJ-1 were blocked by a JNK inhibitor, which confirmed the important role of JNK activation in mitochondrial dysfunction. In conclusion, the present study indicates that DJ-1 knockdown leads to mitochondrial dysfunction in dopaminergic neuron-like cells, at least in part, through suppressing the Akt/GSK3β pathway and impairing the oxidative stress response, as well as through the subsequent increased JNK activation in dopaminergic neuron-like cells.

Natrium Benzoate Alleviates Neuronal Apoptosis via the DJ-1-Related Anti-oxidative Stress Pathway Involving Akt Phosphorylation in a Rat Model of Traumatic Spinal Cord Injury

This study aimed to explore the neuroprotective effects and mechanisms of natrium benzoate (NaB) and DJ-1 in attenuating reactive oxygen species (ROS)-induced neuronal apoptosis in traumatic spinal cord injury (t-SCI) in rats. T-SCI was induced by clip compression. The protein expression and neuronal apoptosis was evaluated by Western blotting, double immunofluorescence staining and transmission electron microscope (TEM). ROS level, spinal cord water content (SCWC) and Evans blue (EB) extravasation was also examined. Locomotor function was evaluated by Basso, Beattie, and Bresnahan (BBB) and inclined plane test (IPT) scores. We found that DJ-1 is expressed in spinal cord neurons and increased after t-SCI. At 24 h post-injury, the levels of DJ-1, p-Akt, SOD2, ROS, p-p38 MAPK/p38 MAPK ratio, and CC-3 increased, while the Bcl-2/Bax ratio decreased. NaB upregulated DJ-1, p-Akt, and SOD2, decreased ROS, p-p38 MAPK/p38 MAPK ratio, and CC-3, and increased the Bcl-2/Bax ratio, which were reversed by DJ-1 siRNA. The proportion of CC-3- and TUNEL-positive neurons also increased after t-SCI and was reduced by NaB. These effects were reversed by MK2206. Moreover, the level of oxDJ-1 increased after t-SCI, which was decreased by DJ-1 siRNA, NaB or the combination of them. NaB also reduced mitochondrial vacuolization, SCWC and EB extravasation, and improved locomotor function assessed by the BBB and IPT scores. In conclusion, NaB increased DJ-1, and thus reduced ROS and ROS-induced neuronal apoptosis by promoting Akt phosphorylation in t-SCI rats. NaB shows potential as a therapeutic agent for t-SCI, with DJ-1 as its main target.

Da-Bu-Yin-Wan Improves the Ameliorative Effect of DJ-1 on Mitochondrial Dysfunction Through Augmenting the Akt Phosphorylation in a Cellular Model of Parkinson's Disease

Da-Bu-Yin-Wan (DBYW) is recorded originally in China over six centuries ago, and it is used to treat Parkinson’s disease (PD) clinically in recent decades. DJ-1 is a homodimeric protein linked to early-onset PD, and found in the mitochondria. In addition, DJ-1 could protect the cells by regulating gene transcription and modulating the Akt signal pathways. Therefore, in this research, we aimed to investigate the ameliorative effect of DBYW on mitochondria in the view of the DJ-1 and Akt signaling. Rat adrenal pheochromocytoma cell line PC-12 was transfected with the plasmid pcDNA3-Flag-DJ-1 (pDJ-1). Subsequently, PC-12 cells were exposed to the PD-related mitochondrial toxin (1-methyl-4-phenylpyridinium) without/with the DBYW. After transfected with the plasmid pDJ-1, the 1-methyl-4-phenylpyridinium-induced toxicity was decreased, and the DJ-1 expression in protein level was increased. DJ-1 overexpression not only increased the mitochondrial mass, but also improved the total ATP content. Moreover, Akt phosphorylation was augmented by DJ-1 overexpression. Additionally, DBYW enhanced the above effects. Conclusively, these findings indicate that DBYW promotes the ameliorative effects of DJ-1 on mitochondrial dysfunction at least through augmenting the Akt phosphorylation in 1-methyl-4-phenylpyridinium-treated PC-12 cells.

δ-Opioid Receptor Activation Attenuates Hypoxia/MPP+-Induced Downregulation of PINK1: a Novel Mechanism of Neuroprotection Against Parkinsonian Injury

There is emerging evidence suggesting that neurotoxic insults and hypoxic/ischemic injury are underlying causes of Parkinson's disease (PD). Since PTEN-induced kinase 1 (PINK1) dysfunction is involved in the molecular genesis of PD and since our recent studies have demonstrated that the δ-opioid receptor (DOR) induced neuroprotection against hypoxic and 1-methyl-4-phenyl-pyridimium (MPP⁺) insults, we sought to explore whether DOR protects neuronal cells from hypoxic and/or MPP⁺ injury via the regulation of PINK1-related pathways. Using highly differentiated rat PC12 cells exposed to either severe hypoxia (0.5-1% O₂) for 24-48 h or varying concentrations of MPP⁺, we found that both hypoxic and MPP⁺ stress reduced the level of PINK1 expression, while incubation with the specific DOR agonist UFP-512 reversed this reduction and protected the cells from hypoxia and/or MPP⁺-induced injury. However, the DOR-mediated cytoprotection largely disappeared after knocking down PINK1 by PINK1 small interfering RNA. Moreover, we examined several important signaling molecules related to cell survival and apoptosis and found that DOR activation attenuated the hypoxic and/or MPP⁺-induced reduction in phosphorylated Akt and inhibited the activation of cleaved caspase-3, whereas PINK1 knockdown largely deprived the cell of the DOR-induced effects. Our novel data suggests a unique mechanism underlying DOR-mediated cytoprotection against hypoxic and MPP⁺ stress via a PINK1-mediated regulation of signaling.

Cellular and Molecular Basis of Neurodegeneration in Parkinson Disease

It has been 200 years since Parkinson disease (PD) was described by Dr. Parkinson in 1817. The disease is the second most common neurodegenerative disease characterized by a progressive loss of dopaminergic neurons in the substantia nigra pars compacta. Although the pathogenesis of PD is still unknown, the research findings from scientists are conducive to understand the pathological mechanisms. It is well accepted that both genetic and environmental factors contribute to the onset of PD. In this review, we summarize the mutations of main seven genes (α-synuclein, LRRK2, PINK1, Parkin, DJ-1, VPS35 and GBA1) linked to PD, discuss the potential mechanisms for the loss of dopaminergic neurons (dopamine metabolism, mitochondrial dysfunction, endoplasmic reticulum stress, impaired autophagy, and deregulation of immunity) in PD, and expect the development direction for treatment of PD.

Cellular and Molecular Basis of Neurodegeneration in Parkinson Disease

It has been 200 years since Parkinson disease (PD) was described by Dr. Parkinson in 1817. The disease is the second most common neurodegenerative disease characterized by a progressive loss of dopaminergic neurons in the substantia nigra pars compacta. Although the pathogenesis of PD is still unknown, the research findings from scientists are conducive to understand the pathological mechanisms. It is well accepted that both genetic and environmental factors contribute to the onset of PD. In this review, we summarize the mutations of main seven genes (α-synuclein, LRRK2, PINK1, Parkin, DJ-1, VPS35 and GBA1) linked to PD, discuss the potential mechanisms for the loss of dopaminergic neurons (dopamine metabolism, mitochondrial dysfunction, endoplasmic reticulum stress, impaired autophagy, and deregulation of immunity) in PD, and expect the development direction for treatment of PD.

Computer-Aided Design and Synthesis of 1-{4-[(3,4-Dihydroxybenzylidene)amino]phenyl}-5-oxopyrrolidine-3-carboxylic Acid as an Nrf2 Enhancer

The design and synthesis of a novel nuclear factor erythroid 2-related factor 2 (Nrf2) enhancer is reported. Using a structure-based virtual screening approach, several commercially available compounds were identified as having high probability to interact with the Nrf2-binding pocket in the Kelch-like ECH-associated protein 1 (Keap1). Keap1 is an adaptor protein that recruits Nrf2 to a cullin-3-dependent ubiquitin ligase complex. The identified compounds were tested against rat pheochromocytoma PC-12 cells for their cytoprotective activity, and one compound (SKT359126) demonstrated an Nrf2-mediated cell-protective effect. Based on the structure of SKT359126, 23 novel derivatives were synthesized and evaluated. Of the screened derivatives, 1-{4-[(3,4-dihydroxybenzylidene)amino]phenyl}-5-oxopyrrolidine-3-carboxylic acid demonstrated better activity than the parent molecules in activating the Nrf2 transduction pathway in a dose- and time-dependent manner. This compound represents a promising starting point for the development of therapeutics for the treatment of oxidative-stress-related diseases.

Identification of potential therapeutic compounds for Parkinson's disease using Drosophila and human cell models

Parkinson's disease (PD) is the second most common neurodegenerative disorder after Alzheimer's disease. It is caused by a loss of dopaminergic neurons in the substantia nigra pars compacta, leading to a decrease in dopamine levels in the striatum and thus producing movement impairment. Major physiological causes of neurodegeneration in PD are oxidative stress (OS) and mitochondrial dysfunction; these pathophysiological changes can be caused by both genetic and environmental factors. Although most PD cases are sporadic, it has been shown that 5-10% of them are familial forms caused by mutations in certain genes. One of these genes is the DJ-1 oncogene, which is involved in an early-onset recessive PD form. Currently, PD is an incurable disease for which existing therapies are not sufficiently effective to counteract or delay the progression of the disease. Therefore, the discovery of alternative drugs for the treatment of PD is essential. In this study we used a Drosophila PD model to identify candidate compounds with therapeutic potential for this disease. These flies carry a loss-of-function mutation in the DJ-1β gene, the Drosophila ortholog of human DJ-1, and show locomotor defects reflected by a reduced climbing ability. A pilot modifier chemical screen was performed, and several candidate compounds were identified based on their ability to improve locomotor activity of PD model flies. We demonstrated that some of them were also able to reduce OS levels in these flies. To validate the compounds identified in the Drosophila screen, a human cell PD model was generated by knocking down DJ-1 function in SH-SY5Y neuroblastoma cells. Our results showed that some of the compounds were also able to increase the viability of the DJ-1-deficient cells subjected to OS, thus supporting the use of Drosophila for PD drug discovery. Interestingly, some of them have been previously proposed as alternative therapies for PD or tested in clinical trials and others are first suggested in this study as potential drugs for the treatment of this disease.

Proteomic Analysis of Mitochondria-Enriched Fraction Isolated from the Frontal Cortex and Hippocampus of Apolipoprotein E Knockout Mice Treated with Alda-1, an Activator of Mitochondrial Aldehyde Dehydrogenase (ALDH2)

The role of different genotypes of apolipoprotein E (apoE) in the etiology of Alzheimer’s disease is widely recognized. It has been shown that altered functioning of apoE may promote 4-hydroxynonenal modification of mitochondrial proteins, which may result in mitochondrial dysfunction, aggravation of oxidative stress, and neurodegeneration. Mitochondrial aldehyde dehydrogenase (ALDH2) is an enzyme considered to perform protective function in mitochondria by the detoxification of the end products of lipid peroxidation, such as 4-hydroxynonenal and other reactive aldehydes. The goal of our study was to apply a differential proteomics approach in concert with molecular and morphological techniques to elucidate the changes in the frontal cortex and hippocampus of apolipoprotein E knockout (apoE^−/−) mice upon treatment with Alda-1—a small molecular weight activator of ALDH2. Despite the lack of significant morphological changes in the brain of apoE^−/− mice as compared to age-matched wild type animals, the proteomic and molecular approach revealed many changes in the expression of genes and proteins, indicating the impairment of energy metabolism, neuroplasticity, and neurogenesis in brains of apoE^−/− mice. Importantly, prolonged treatment of apoE^−/− mice with Alda-1 led to the beneficial changes in the expression of genes and proteins related to neuroplasticity and mitochondrial function. The pattern of alterations implies mitoprotective action of Alda-1, however, the accurate functional consequences of the revealed changes require further research.

Protective effects of DJ-1 medicated Akt phosphorylation on mitochondrial function are promoted by Da-Bu-Yin-Wan in 1-methyl-4-phenylpyridinium-treated human neuroblastoma SH-SY5Y cells

ETHNOPHARMACOLOGICAL RELEVANCE

Da-Bu-Yin-Wan (DBYW), a historically traditional Chinese medicine formula, was originally defined over 600 years ago. In recent decades, DBYW was clinically employed to treat Parkinson's disease (PD).

AIM OF THE STUDY

To explore the underlying mechanism of DBYW on mitochondrial function, we investigated the effect of DBYW on mitochondrial function from the perspectives of DJ-1 and Akt signaling.

MATERIALS AND METHODS

Human derived neuroblastoma SH-SY5Y cells were transiently transfected with the plasmid pcDNA3-Flag-DJ-1 aimed to overexpress the DJ-1 protein. Transfected cells were treated with 1-methyl-4-phenylpyridinium (MPP(+)), a PD-related mitochondrial complex I inhibitor, in the absence and presence of DBYW. The cell viability was assessed by Cell Counting Kit-8 assay. The protein expressions of DJ-1 and Akt signaling were examined by western blotting. The mitochondrial mass was evaluated by confocal fluorescence microscopy. The mitochondrial complex I activity and cellular ATP content were measured by commercial kits.

RESULTS

Transfection with pcDNA3-Flag-DJ-1 decreased the MPP(+)-induced toxicity and overexpressed the DJ-1. In DJ-1 overexpressed cells, the mitochondrial mass was raised, mitochondrial complex I activity was improved, and cellular ATP content was increased. In addition, overexpression of DJ-1 augmented the Akt phosphorylation on threonine 308 and serine 473. Moreover, DBYW promoted the above effects in DJ-1 expressed cells.

CONCLUSIONS

These data suggest that DJ-1 protects the mitochondrial function by medicating Akt phosphorylation in MPP(+)-treated SH-SY5Y cells. Moreover, DBYW enhances the protective effect of DJ-1 medicated Akt phosphorylation on mitochondrial function.