Apoptosis signal-regulating kinase 1 mediates MPTP toxicity and regulates glial activation

Apoptosis signal-regulating kinase 1 (Ask1) deficiency alleviates MPP+-induced impairment of evoked dopamine release in the mouse hippocampus

The dopaminergic system is susceptible to dysfunction in numerous neurological diseases, including Parkinson's disease (PD). In addition to motor symptoms, some PD patients may experience non-motor symptoms, including cognitive and memory deficits. A possible explanation for their manifestation is a disturbed pattern of dopamine release in brain regions involved in learning and memory, such as the hippocampus. Therefore, investigating neuropathological alterations in dopamine release prior to neurodegeneration is imperative. This study aimed to characterize evoked hippocampal dopamine release and assess the impact of the neurotoxin MPP+ using a genetically encoded dopamine sensor and gene expression analysis. Additionally, considering the potential neuroprotective attributes demonstrated by apoptosis signal-regulating kinase 1 (Ask1) in various animal-disease-like models, the study also aimed to determine whether Ask1 knockdown restores MPP+-altered dopamine release in acute hippocampal slices. We applied variations of low- and high-frequency stimulation to evoke dopamine release within different hippocampal regions and discovered that acute application of MPP+ reduced the amount of dopamine released and hindered the recovery of dopamine release after repeated stimulation. In addition, we observed that Ask1 deficiency attenuated the detrimental effects of MPP+ on the recovery of dopamine release after repeated stimulation. RNA sequencing analysis indicated that genes associated with the synaptic pathways are involved in response to MPP+ exposure. Notably, Ask1 deficiency was found to downregulate the expression of Slc5a7, a gene encoding a sodium-dependent high-affinity choline transporter that regulates acetylcholine levels. Respective follow-up experiments indicated that Slc5a7 plays a role in Ask1 deficiency-mediated protection against MPP+ neurotoxicity. In addition, increasing acetylcholine levels using an acetylcholinesterase inhibitor could exacerbate the toxicity of MPP+. In conclusion, our data imply that the modulation of the dopamine-acetylcholine balance may be a crucial mechanism of action underlying the neuroprotective effects of Ask1 deficiency in PD.

Neuroprotective effects of GSK-343 in an in vivo model of MPTP-induced nigrostriatal degeneration

Parkinson's disease (PD) is characterized by the degeneration of dopaminergic nigrostriatal neurons, which causes disabling motor disorders. Scientific findings support the role of epigenetics mechanism in the development and progression of many neurodegenerative diseases, including PD. In this field, some studies highlighted an upregulation of Enhancer of zeste homolog 2 (EZH2) in the brains of PD patients, indicating the possible pathogenic role of this methyltransferase in PD. The aim of this study was to evaluate the neuroprotective effects of GSK-343, an EZH2 inhibitor, in an in vivo model of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced dopaminergic degeneration. Specifically, nigrostriatal degeneration was induced by MPTP intraperitoneal injection. GSK-343 was administered intraperitoneally daily at doses of 1 mg/kg, 5 mg/kg and 10 mg/kg, mice were killed 7 days after MPTP injection. Our results demonstrated that GSK-343 treatment significantly improved behavioral deficits and reduced the alteration of PD hallmarks. Furthermore, GSK-343 administration significantly attenuated the neuroinflammatory state through the modulation of canonical and non-canonical NF-κB/IκBα pathway as well as the cytokines expression and glia activation, also reducing the apoptosis process. In conclusion, the obtained results provide further evidence that epigenetic mechanisms play a pathogenic role in PD demonstrating that the inhibition of EZH2, mediated by GSK-343, could be considered a valuable pharmacological strategy for PD.

Signaling pathways in Parkinson's disease: molecular mechanisms and therapeutic interventions

Parkinson's disease (PD) is the second most common neurodegenerative disease worldwide, and its treatment remains a big challenge. The pathogenesis of PD may be related to environmental and genetic factors, and exposure to toxins and gene mutations may be the beginning of brain lesions. The identified mechanisms of PD include α-synuclein aggregation, oxidative stress, ferroptosis, mitochondrial dysfunction, neuroinflammation, and gut dysbiosis. The interactions among these molecular mechanisms complicate the pathogenesis of PD and pose great challenges to drug development. At the same time, the diagnosis and detection of PD are also one of obstacles to the treatment of PD due to its long latency and complex mechanism. Most conventional therapeutic interventions for PD possess limited effects and have serious side effects, heightening the need to develop novel treatments for this disease. In this review, we systematically summarized the pathogenesis, especially the molecular mechanisms of PD, the classical research models, clinical diagnostic criteria, and the reported drug therapy strategies, as well as the newly reported drug candidates in clinical trials. We also shed light on the components derived from medicinal plants that are newly identified for their effects in PD treatment, with the expectation to provide the summary and outlook for developing the next generation of drugs and preparations for PD therapy.

Natural Compounds Such as Hericium erinaceus and Coriolus versicolor Modulate Neuroinflammation, Oxidative Stress and Lipoxin A4 Expression in Rotenone-Induced Parkinson's Disease in Mice

BACKGROUND

A growing body of research suggests that oxidative stress and neuroinflammation are early pathogenic features of neurodegenerative disorders. In recent years, the vitagene system has emerged as a potential target, as it has been shown to have a high neuroprotective power. Therefore, the discovery of molecules capable of activating this system may represent a new therapeutic target to limit the deleterious consequences induced by oxidative stress and neuroinflammation, such as neurodegeneration. Lipoxins are derived from arachidonic acid, and their role in the resolution of systemic inflammation is well established; however, they have become increasingly involved in the regulation of neuroinflammatory and neurodegenerative processes. Our study aimed at activating the NF-E2-related factor 2 (Nrf2)/heme oxygenase 1 (HO-1) redox system and increasing lipoxin A4 for the modulation of antioxidant stress and neuroinflammation through the action of two fungi in a rotenone-induced Parkinson's model.

METHODS

During the experiment, mice received Hericium erinaceus, Coriolus versicolor or a combination of the two (200 mg/kg, orally) concomitantly with rotenone (5 mg/kg, orally) for 28 days.

RESULTS

The results obtained highlighted the ability of these two fungi and, in particular, their ability through their association to act on neuroinflammation through the nuclear factor-kB pathway and on oxidative stress through the Nrf2 pathway. This prevented dopaminergic neurons from undergoing apoptosis and prevented the alteration of typical Parkinson's disease (PD) markers and α-synuclein accumulation. The action of Hericium erinaceus and Coriolus versicolor was also able to limit the motor and non-motor alterations characteristic of PD.

CONCLUSIONS

Since these two mushrooms are subject to fewer regulations than traditional drugs, they could represent a promising nutraceutical choice for preventing PD.

Pre-clinical Studies Identifying Molecular Pathways of Neuroinflammation in Parkinson's Disease: A Systematic Review

Parkinson's disease (PD), the second most common neurodegenerative disorder, is characterized by neuroinflammation, formation of Lewy bodies, and progressive loss of dopaminergic neurons in the substantia nigra of the brain. In this review, we summarize evidence obtained by animal studies demonstrating neuroinflammation as one of the central pathogenetic mechanisms of PD. We also focus on the protein factors that initiate the development of PD and other neurodegenerative diseases. Our targeted literature search identified 40 pre-clinical in vivo and in vitro studies written in English. Nuclear factor kappa B (NF-kB) pathway is demonstrated as a common mechanism engaged by neurotoxins such as 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and 6-hydroxydopamine (6-OHDA), as well as the bacterial lipopolysaccharide (LPS). The α-synuclein protein, which plays a prominent role in PD neuropathology, may also contribute to neuroinflammation by activating mast cells. Meanwhile, 6-OHDA models of PD identify microsomal prostaglandin E synthase-1 (mPGES-1) as one of the contributors to neuroinflammatory processes in this model. Immune responses are used by the central nervous system to fight and remove pathogens; however, hyperactivated and prolonged immune responses can lead to a harmful neuroinflammatory state, which is one of the key mechanisms in the pathogenesis of PD.

Identification of Therapeutic Targets for Amyotrophic Lateral Sclerosis Using PandaOmics – An AI-Enabled Biological Target Discovery Platform

Amyotrophic lateral sclerosis (ALS) is a severe neurodegenerative disease with ill-defined pathogenesis, calling for urgent developments of new therapeutic regimens. Herein, we applied PandaOmics, an AI-driven target discovery platform, to analyze the expression profiles of central nervous system (CNS) samples (237 cases; 91 controls) from public datasets, and direct iPSC-derived motor neurons (diMNs) (135 cases; 31 controls) from Answer ALS. Seventeen high-confidence and eleven novel therapeutic targets were identified and will be released onto ALS.AI (http://als.ai/). Among the proposed targets screened in the c9ALS Drosophila model, we verified 8 unreported genes (KCNB2, KCNS3, ADRA2B, NR3C1, P2RY14, PPP3CB, PTPRC, and RARA) whose suppression strongly rescues eye neurodegeneration. Dysregulated pathways identified from CNS and diMN data characterize different stages of disease development. Altogether, our study provides new insights into ALS pathophysiology and demonstrates how AI speeds up the target discovery process, and opens up new opportunities for therapeutic interventions.

SUN11602, a bFGF mimetic, modulated neuroinflammation, apoptosis and calcium-binding proteins in an in vivo model of MPTP-induced nigrostriatal degeneration

Background

Parkinson’s disease (PD) is the second most frequent neurodegenerative disease. PD etiopathogenesis is multifactorial and not yet fully known, however, the scientific world advised the establishment of neuroinflammation among the possible risk factors. In this field, basic fibroblast growth factor/fibroblast growth factor receptor-1 (bFGF/FGFR1) could be a promising way to treat CNS-mediated inflammation; unfortunately, the use of bFGF as therapeutic agent is limited by its side effects. The novel synthetic compound SUN11602 exhibited neuroprotective activities like bFGF. With this perspective, this study aimed to evaluate the effect of SUN11602 administration in a murine model of MPTP-induced dopaminergic degeneration.

Methods

Specifically, nigrostriatal degeneration was induced by intraperitoneal injection of MPTP (80 mg/kg). SUN11602 (1 mg/kg, 2.5 mg/kg, and 5 mg/kg) was administered daily by oral gavage starting from 24 h after the first administration of MPTP. Mice were killed 7 days after MPTP induction.

Results

The results obtained showed that SUN11602 administration significantly reduced the alteration of PD hallmarks, attenuating the neuroinflammatory state via modulation of glial activation, NF-κB pathway, and cytokine overexpression. Furthermore, we demonstrated that SUN11602 treatment rebalanced Ca²⁺ overload in neurons by regulating Ca²⁺-binding proteins while inhibiting the apoptotic cascade.

Conclusion

Therefore, in the light of these findings, SUN11602 could be considered a valuable pharmacological strategy for PD.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-022-02457-3.

Recuperative effect of estrogen on rotenone-induced experimental model of Parkinson's disease in rats

Parkinson's disease (PD) is described as the loss of dopaminergic neurons located in the substantia nigra (SN) region of the brain and a progressive motor failure. Increased frequency of PD in women, especially after menopause, suggests the effect of estrogen. This view has been supported with empirical studies. Therefore, the effect of estrogen in an experimental model of Parkinson's disease induced by rotenone was investigated. A total of 32 female Wistar Albino rats were randomly assigned to four groups (control group, ovariectomy group, Parkinson's group, Parkinson's + estrogen group). The Parkinson's group received rotenone subcutanously at the dose of 2.5 mg/kg bw, on the 1st, 2nd, 3rd 4th, 6th, 9th, 12th, 15th, 18th, and 21st days animals in the Parkinson's + estrogen group received retonon as in the Parkinson's group and was additionally subcutaneously given estrogen (implant containing 0.5 mg 17 β-estradiol lasting for 21 days). The rats were subjected to rotarod, pole, and swimming tests at the end of the experiment for comparison of their motor activities, and then, histopathological and biochemical analyses were performed on the tissues that were extracted. The rotarod results revealed that Parkinson's group had the shortest time (32.33 ± 3.98 sn) than the groups of control (92.50 ± 12.60 s) ovariectomy (71.42 ± 10.58 s), and Parkinson's + estrogen (71.37 ± 9.26 s). The results of pole disclosed that return and landing time prolonged for Parkinson's group when compared with other groups (return time for control 2.98 ± 0.38 s, ovariectomy 3.02 ± 0.75 s, Parkinson 5.91 ± 0.33 s, Parkinson's + estrogen 3.48 ± 0.42 s and landing time for control 5.30 ± 0.59 s, ovariectomy 5.45 ± 0.73 s, Parkinson 9.80 ± 0.90 s, Parkinson's + estrogen 5.37 ± 1.02 s). Parkinson's group had longest (90.71 ± 12.56 s) swimming time to reach the target when compared with control (33.16 ± 8.68 s), ovariectomy (47.37 ± 12.19 s), and Parkinson's + estrogen (49.82 ± 5.78 s). Histopathological examination indicated a significant difference in tyrosine hydroxylase-stained cells (dopaminergic neurons and dopamine) between the Parkinson's + estrogen group and the Parkinson's group. The biochemical analyses of Caspas-3 activation in SN and striatum (STR) was significantly different between the Parkinson's + estrogen group and the Parkinson's group, but this difference was not observed in STR while evaluating Bcl-2. The results of this study suggested that estrogen may have a recuperative effect on PD.

Protective Role of Transduced Tat-Thioredoxin1 (Trx1) against Oxidative Stress-Induced Neuronal Cell Death via ASK1-MAPK Signal Pathway

Oxidative stress plays a crucial role in the development of neuronal disorders including brain ischemic injury. Thioredoxin 1 (Trx1), a 12 kDa oxidoreductase, has anti-oxidant and anti-apoptotic functions in various cells. It has been highly implicated in brain ischemic injury. However, the protective mechanism of Trx1 against hippocampal neuronal cell death is not identified yet. Using a cell permeable Tat-Trx1 protein, protective mechanism of Trx1 against hydrogen peroxide-induced cell death was examined using HT-22 cells and an ischemic animal model. Transduced Tat-Trx1 markedly inhibited intracellular ROS levels, DNA fragmentation, and cell death in H₂O₂-treatment HT-22 cells. Tat-Trx1 also significantly inhibited phosphorylation of ASK1 and MAPKs in signaling pathways of HT-22 cells. In addition, Tat-Trx1 regulated expression levels of Akt, NF-κB, and apoptosis related proteins. In an ischemia animal model, Tat-Trx1 markedly protected hippocampal neuronal cell death and reduced astrocytes and microglia activation. These findings indicate that transduced Tat-Trx1 might be a potential therapeutic agent for treating ischemic injury.

RIPK1 inhibitor ameliorates the MPP+/MPTP-induced Parkinson's disease through the ASK1/JNK signalling pathway

Receptor-interacting protein kinase 1 (RIPK1) is up-regulated in patients with neurodegenerative diseases. Our study aimed to explore the underlying mechanisms that involved in the neurotoxic function of RIPK1 in Parkinson's disease (PD). MPP+/MPTP-induced PD cellular and mice models were used in this study. The results showed that RIPK1 was high expressed and activated in MPP+-treated SH-SY5Y cells and MPTP-induced PD mice. Overexpression of RIPK1 facilitated cell apoptosis, necrosis, inflammation response, ROS production and mitochondrial dysfunction in MPP+- treated SH-SY5Y cells, while the RIPK1 inhibitor Nec-1s has an opposite effect. In addition, the Apoptosis-signaling kinase-1 (ASK1)/c-Jun N-terminal kinase (JNK) signalling pathway was activated during the overexpression of RIPK1, and inhibiting the ASK1/JNK signal by the ASK1 inhibitor partially reversed the decline of cell viability, the increase of cell apoptosis, necrosis and inflammation induced by RIPK1 overexpression in MPP+-treated SH-SY5Y cells. Further studies suggested that the inhibition of RIPK1 by Nec-1s largely alleviated the behavioural impairment in PD mice. Hence, our study indicated that the RIPK1 inhibitor Nec-1s has neuroprotective effects against PD through inactivating the ASK1/JNK signalling pathway.

Anti-inflammatory and Anti-oxidant Activity of Hidrox® in Rotenone-Induced Parkinson's Disease in Mice

BACKGROUND

In developed countries, the extension of human life is increasingly accompanied by a progressive increase in neurodegenerative diseases, most of which do not yet have effective therapy but only symptomatic treatments. In recent years, plant polyphenols have aroused considerable interest in the scientific community. The mechanisms currently hypothesized for the pathogenesis of Parkinson's disease (PD) are neuroinflammation, oxidative stress and apoptosis. Hydroxytyrosol (HT), the main component of Hidrox^® (HD), has been shown to have some of the highest free radical evacuation and anti-inflammatory activities. Here we wanted to study the role of HD on the neurobiological and behavioral alterations induced by rotenone.

METHODS

A study was conducted in which mice received HD (10 mg/kg, i.p.) concomitantly with rotenone (5 mg/kg, o.s.) for 28 days.

RESULTS

Locomotor activity, catalepsy, histological damage and several characteristic markers of the PD, such as the dopamine transporter (DAT) content, tyrosine hydroxylase (TH) and accumulation of α-synuclein, have been evaluated. Moreover, we observed the effects of HD on oxidative stress, neuroinflammation, apoptosis and inflammasomes. Taken together, the results obtained highlight HD's ability to reduce the loss of dopaminergic neurons and the damage associated with it by counteracting the three main mechanisms of PD pathogenesis.

CONCLUSION

HD is subject to fewer regulations than traditional drugs to improve patients' brain health and could represent a promising nutraceutical choice to prevent PD.

Apoptosis signal regulating kinase 1 deletion mitigates α-synuclein pre-formed fibril propagation in mice

α-Synuclein (α-Syn) is a key pathogenic protein in α-synucleinopathies including Parkinson disease and dementia with Lewy bodies. Accumulating evidence has shown that misfolded fibrillar α-Syn is transmitted from cell-to-cell, a phenomenon that correlates with clinical progression of the disease. We previously showed that deleting the MAP3 kinase apoptosis signal-regulating kinase 1 (ASK1), which is a central player linking oxidative stress with neuroinflammation, mitigates the phenotype of α-Syn transgenic mice. However, whether ASK1 impacts pathology and disease progression induced by recombinant α-Syn pre-formed fibrils (PFF) remains unknown. Here, we compared the neuropathological and behavioral phenotype of ASK1 knock-out mice with that of wild-type mice following intrastriatal injections of α-Syn PFF. At 6 months post-injections, ASK1 null mice exhibited reduced amount of phosphorylated α-Syn aggregates in the striatum and cortex, and less pronounced degeneration of the nigrostriatal pathway. Additionally, the neuroinflammatory reaction to α-Syn PFF injection and propagation seen in wild-type mice was attenuated in ASK1 knock-out animals. These neuropathological markers were associated with better behavioral performance. These data suggest that ASK1 plays an important role in pathological α-Syn fibril transmission and, consequently, may impact disease progression. These findings collectively support inhibiting ASK1 as a disease modifying therapeutic strategy for Parkinson disease and related α-synucleinopathies.

Apoptosis: Activation and Inhibition in Health and Disease

There are many types of cell death, each involving multiple and complex molecular events. Cell death can occur accidentally when exposed to extreme physical, chemical, or mechanical conditions, or it can also be regulated, which involves a genetically coded complex machinery to carry out the process. Apoptosis is an example of the latter. Apoptotic cell death can be triggered through different intracellular signalling pathways that lead to morphological changes and eventually cell death. This is a normal and biological process carried out during maturation, remodelling, growth, and development in tissues. To maintain tissue homeostasis, regulatory, and inhibitory mechanisms must control apoptosis. Paradoxically, these same pathways are utilized during infection by distinct intracellular microorganisms to evade recognition by the immune system and therefore survive, reproduce and develop. In cancer, neoplastic cells inhibit apoptosis, thus allowing their survival and increasing their capability to invade different tissues and organs. The purpose of this work is to review the generalities of the molecular mechanisms and signalling pathways involved in apoptosis induction and inhibition. Additionally, we compile the current evidence of apoptosis modulation during cancer and Leishmania infection as a model of apoptosis regulation by an intracellular microorganism.

2-Pentadecyl-2-Oxazoline Reduces Neuroinflammatory Environment in the MPTP Model of Parkinson Disease

Current pharmacological management of Parkinson disease (PD) does not provide for disease modification, but addresses only symptomatic features. Here, we explore a new approach to neuroprotection based on the use of 2-pentadecyl-2-oxazoline (PEA-OXA), the oxazoline derivative of the fatty acid amide signaling molecule palmitoylethanolamide (PEA), in an experimental model of PD. Daily oral treatment with PEA-OXA (10 mg/kg) significantly reduced behavioral impairments and neuronal cell degeneration of the dopaminergic tract induced by four intraperitoneal injections of the dopaminergic neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) on 8-week-old male C57 mice. Moreover, PEA-OXA treatment prevented dopamine depletion, increased tyrosine hydroxylase and dopamine transporter activities, and decreased α-synuclein aggregation in neurons. PEA-OXA treatment also diminished nuclear factor-κB traslocation, cyclooxygenase-2, and inducible nitric oxide synthase expression and through upregulation of the nuclear factor E2-related factor 2 pathway, induced activation of Mn-superoxide dismutase and heme oxygenase-1. Further, PEA-OXA modulated microglia and astrocyte activation and preserved microtubule-associated protein-2 alterations. In conclusion, pharmacological activation of nuclear factor E2-related factor 2 pathways with PEA-OXA may be effective in the future therapy of PD.

Cell Type-Specific Mechanisms in the Pathogenesis of Ischemic Stroke: The Role of Apoptosis Signal-Regulating Kinase 1

Stroke has become a more common disease worldwide. Despite great efforts to develop treatment, little is known about ischemic stroke. Cerebral ischemia activates multiple cascades of cell type-specific pathomechanisms. Ischemic brain injury consists of a complex series of cellular reactions in various cell types within the central nervous system (CNS) including platelets, endothelial cells, astrocytes, neutrophils, microglia/macrophages, and neurons. Diverse cellular changes after ischemic injury are likely to induce cell death and tissue damage in the brain. Since cells in the brain exhibit different functional roles at distinct time points after injury (acute/subacute/chronic phases), it is difficult to pinpoint genuine roles of cell types after brain injury. Many experimental studies have shown the association of apoptosis signal-regulating kinase 1 (ASK1) with cellular pathomechanisms after cerebral ischemia. Blockade of ASK1, by either pharmacological or genetic manipulation, leads to reduced ischemic brain injury and subsequent neuroprotective effects. In this review, we present the cell type-specific pathophysiology of the early phase of ischemic stroke, the role of ASK1 suggested by preclinical studies, and the potential use of ASK suppression, either by pharmacologic or genetic suppression, as a promising therapeutic option for ischemic stroke recovery.

N-palmitoylethanolamide Prevents Parkinsonian Phenotypes in Aged Mice

Parkinson's disease (PD) is a neurodegenerative disease characterized by degeneration of dopaminergic neurons. Aging is a major risk factor for idiopathic PD. Several prior studies examined the neuroprotective effects of palmitoylethanolamide (PEA), alone or combined with antioxidants, in a model of PD induced by the dopaminergic toxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Here, we analyzed the pretreatment effect of micronized PEA (PEAm) on neuroinflammation and neuronal cell death in the MPTP model. Male CD mice (21 months of age) were pre-treated for 60 days with PEAm. After this time, they received four intraperitoneal injections of MPTP over a 24-h period and were killed 7 days later. On the 8th day, brains were processed. Pretreatment with PEAm ameliorated behavioral deficits and the reductions in expression of tyrosine hydroxylase and dopamine transporter, while blunting the upregulation of α-synuclein and β3-tubulin in the substantia nigra after MPTP induction. Moreover, PEAm reduced proinflammatory cytokine expression and showed a pro-neurogenic effect in hippocampus. These findings propose this strategy as a valid approach to prevent neurodegenerative diseases associated with old age.

Regulation of ASK1 signaling by scaffold and adaptor proteins

The mitogen-activated protein kinase (MAPK) signaling pathway is a three-tiered kinase cascade where mitogen-activated protein kinase kinase kinases (MAP3Ks) lead to the activation of mitogen-activated protein kinase kinases (MAP2K), and ultimately MAPK proteins. MAPK signaling can promote a diverse set of biological outcomes, ranging from cell death to proliferation. There are multiple mechanisms which govern MAPK output, such as the duration and strength of the signal, cellular localization to upstream and downstream binding partners, pathway crosstalk and the binding to scaffold and adaptor molecules. This review will focus on scaffold and adaptor proteins that bind to and regulate apoptosis signal-regulating kinase 1 (ASK1), a MAP3K protein with a critical role in mediating stress response pathways.

Apoptosis signal-regulating kinase 1 inhibition attenuates cardiac hypertrophy and cardiorenal fibrosis induced by uremic toxins: Implications for cardiorenal syndrome

Intracellular accumulation of protein-bound uremic toxins in the setting of cardiorenal syndrome leads to adverse effects on cardiorenal cellular functions, where cardiac hypertrophy and cardiorenal fibrosis are the hallmarks. In this study, we sought to determine if Apoptosis Signal-Regulated Kinase 1 (ASK1), an upstream regulator of cellular stress response, mediates cardiac hypertrophy and cardiorenal fibrosis induced by indoxyl sulfate (IS) and p-cresol sulfate (PCS) in vitro, and whether ASK1 inhibition is beneficial to ameliorate these cellular effects. PCS augmented cardiac myocyte hypertrophy and fibroblast collagen synthesis (as determined by 3H-leucine and 3H-proline incorporation, respectively), similar to our previous finding with IS. IS and PCS also increased collagen synthesis of proximal tubular cells and renal mesangial cells. Pro-hypertrophic (α-skeletal muscle actin and β-MHC) and pro-fibrotic genes (TGF-β1 and ctgf) were induced by both IS and PCS. Western blot analyses revealed the activation of ASK1 and downstream mitogen activated protein kinases (MAPKs) (p38MAPK and ERK1/2) as well as nuclear factor-kappa B (NF-κB) by IS and PCS. ASK1, OAT1/3, ERK1/2 and p38MAPK inhibitors suppressed all these effects. In summary, IS and PCS exhibit pro-hypertrophic and pro-fibrotic properties, at least in part, via the activation of ASK1 and its downstream pathways. ASK1 inhibitor is an effective therapeutic agent to alleviate protein-bound uremic toxin-induced cardiac hypertrophy and cardiorenal fibrosis in vitro, and may be translated further for cardiorenal syndrome therapy.

CIB1 protects against MPTP-induced neurotoxicity through inhibiting ASK1

Calcium and integrin binding protein 1 (CIB1) is a calcium-binding protein that was initially identified as a binding partner of platelet integrin α_IIb. Although CIB1 has been shown to interact with multiple proteins, its biological function in the brain remains unclear. Here, we show that CIB1 negatively regulates degeneration of dopaminergic neurons in a mouse model of Parkinson's disease using 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Genetic deficiency of the CIB1 gene enhances MPTP-induced neurotoxicity in dopaminergic neurons in CIB1^-/- mice. Furthermore, RNAi-mediated depletion of CIB1 in primary dopaminergic neurons potentiated 1-methyl-4-phenyl pyrinidium (MPP⁺)-induced neuronal death. CIB1 physically associated with apoptosis signal-regulating kinase 1 (ASK1) and thereby inhibited the MPP⁺-induced stimulation of the ASK1-mediated signaling cascade. These findings suggest that CIB1 plays a protective role in MPTP/MPP⁺-induced neurotoxicity by blocking ASK1-mediated signaling.

Cytoprotective mechanisms of DJ-1 against oxidative stress through modulating ERK1/2 and ASK1 signal transduction

DJ-1 is a highly conserved multifunctional protein linked to both neurodegeneration and neoplasia. Among its various activities is an antioxidant property leading to cytoprotection under oxidative stress conditions. This is associated with the ability to modulate signal transduction events that determine how the cell regulates normal processes such as growth, senescence, apoptosis, and autophagy in order to adapt to environmental stimuli and stresses. Alterations in DJ-1 expression or function can disrupt homeostatic signaling networks and initiate cascades that play a role in the pathogenesis of conditions such as Parkinson's disease and cancer.

DJ-1 plays a major role in various signaling pathways. Related to its anti-oxidant properties, it mediates cell survival and proliferation by activating the extracellular signal-regulated kinase (ERK1/2) pathway and attenuates cell death signaling by inhibiting apoptosis signal-regulating kinase 1 (ASK1) activation. Here, we review the ways through which DJ-1 regulates these pathways, focusing on how its regulation of signal transduction contributes to cellular homeostasis and the pathologic states that result from their dysregulation.

The Neuroprotective Effect of Dimethyl Fumarate in an MPTP-Mouse Model of Parkinson's Disease: Involvement of Reactive Oxygen Species/Nuclear Factor-κB/Nuclear Transcription Factor Related to NF-E2

AIM

Oxidative stress plays a key role in Parkinson disease (PD), and nuclear transcription factor related to NF-E2 (Nrf-2) is involved in neuroprotection against PD. The aim of the present study was to investigate a role for nuclear factor-κB (NF-κB)/Nrf-2 in the neurotherapeutic action of dimethyl fumarate (DMF) in a mouse model of PD and in vitro in SHSY-5Y cells.

RESULTS

Daily oral gavage of DMF (10, 30, and 100 mg/kg) significantly reduced neuronal cell degeneration of the dopaminergic tract and behavioral impairments induced by four injections of the dopaminergic neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine. Moreover, treatment with DMF prevented dopamine depletion, increased tyrosine hydroxylase and dopamine transporter activities, and also reduced the number of α-synuclein-positive neurons. Furthermore, DMF treatment upregulated the Nrf-2 pathway, increased NeuN⁺/Nrf-2⁺ cell number in the striatum, induced activation of manganese superoxide dismutase and heme oxygenase-1, and regulated glutathione levels. Moreover, DMF reduced interleukin 1 levels, cyclooxygenase 2 activity, and nitrotyrosine neuronal nitrite oxide synthase expression. This treatment also modulated microglia activation, restored nerve growth factor levels, and preserved microtubule-associated protein 2 alterations. The protective effects of DMF treatment, via Nrf-2, were confirmed in in vitro studies, through inhibition of Nrf-2 by trigonelline.

INNOVATION

These findings demonstrate that DMF, both in a mouse model of PD and in vitro, provides, via regulation of the NF-κB/Nrf-2 pathway, novel cytoprotective modalities that further augment the natural antioxidant response in neurodegenerative and inflammatory disease models.

CONCLUSION

These results support the thesis that DMF may constitute a promising therapeutic target for the treatment of PD. Antioxid. Redox Signal. 27, 453-471.

ASK1 in neurodegeneration

Neurodegenerative diseases (NDDs) such as glaucoma, multiple sclerosis (MS), Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), and Huntington's disease (HD) are characterized by the progressive loss of neurons, causing irreversible damage to patients. Longer lifespans may be leading to an increase in the number of people affected by NDDs worldwide. Among the pathways strongly impacting the pathogenesis of NDDs, oxidative stress, a condition that occurs because of an imbalance in oxidant and antioxidant levels, has been known to play a vital role in the pathophysiology of NDDs. One of the molecules activated by oxidative stress is apoptosis signal-regulating kinase 1 (ASK1), which has been shown to play a role in NDDs. ASK1 activation is regulated by multiple steps, including oligomerization, phosphorylation, and protein-protein interactions. In the oxidative stress state, reactive oxygen species (ROS) induce the dissociation of thioredoxin, a protein regulating cellular reduction and oxidation (redox), from the N-terminal region of ASK1, and ASK1 is subsequently activated by the oligomerization and phosphorylation of a critical threonine residue, leading to cell death. Here, we review experimental evidence that links ASK1 signaling with the pathogenesis of several NDDs. We propose that ASK1 may be a new point of therapeutic intervention to prevent or treat NDDs.

Neuroprotective Effects of Temsirolimus in Animal Models of Parkinson's Disease

Parkinson's disease (PD) is a disorder caused by degeneration of dopaminergic neurons. At the moment, there is no cure. Recent studies have shown that autophagy may have a protective function against the advance of a number of neurodegenerative diseases. Temsirolimus is an analogue of rapamycin that induces autophagy by inhibiting mammalian target of rapamycin complex 1. For this purpose, in the present study we investigated the neuroprotective effects of temsirolimus (5 mg/kg intraperitoneal) on 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced (MPTP) neurotoxicity in in vivo model of PD. At the end of the experiment, brain tissues were processed for histological, immunohistochemical, Western blot, and immunofluorescent analysis. Treatment with temsirolimus significantly ameliorated behavioral deficits, increased the expression of specific markers of PD such as tyrosine hydroxylase, dopamine transporter, as well as decreased the upregulation of α-synuclein in the substantia nigra after MPTP induction. Furthermore, Western blot and immunohistochemistry analysis showed that temsirolimus administration significantly increased autophagy process. In fact, treatment with temsirolimus maintained high Beclin-1, p62, and microtubule-associated protein 1A/1B-light chain 3 expression and inhibited the p70S6K expression. In addition, we showed that temsirolimus has also anti-inflammatory properties as assessed by the significant inhibition of the expression of mitogen-activated protein kinases such as p-JNK, p-p38, and p-ERK, and the restored levels of neurotrophic factor expression such as BDNF and NT-3. On the basis of this evidence, we clearly demonstrate that temsirolimus is able to modulate both the autophagic process and the neuroinflammatory pathway involved in PD, actions which may underlie its neuroprotective effect.

Regulation of Signal Transduction by DJ-1

The ability of DJ-1 to modulate signal transduction has significant effects on how the cell regulates normal processes such as growth, senescence, apoptosis, and autophagy to adapt to changing environmental stimuli and stresses. Perturbations of DJ-1 levels or function can disrupt the equilibrium of homeostatic signaling networks and set off cascades that play a role in the pathogenesis of conditions such as cancer and Parkinson's disease.DJ-1 plays a major role in various pathways. It mediates cell survival and proliferation by activating the extracellular signal-regulated kinase (ERK1/2) pathway and the phosphatidylinositol-3-kinase (PI3K)/Akt pathway. It attenuates cell death signaling by inhibiting apoptosis signal-regulating kinase 1 (ASK1) activation as well as by inhibiting mitogen-activated protein kinase kinase kinase 1 (MEKK1/MAP3K1) activation of downstream apoptotic cascades. It also modulates autophagy through the ERK, Akt, or the JNK/Beclin1 pathways. In addition, DJ-1 regulates the transcription of genes essential for male reproductive function, such as spermatogenesis, by relaying nuclear receptor androgen receptor (AR) signaling. In this chapter, we summarize the ways that DJ-1 regulates these pathways, focusing on how its role in signal transduction contributes to cellular homeostasis and the pathologic states that result from dysregulation.

Dynamic Phosphorylation of Apoptosis Signal Regulating Kinase 1 (ASK1) in Response to Oxidative and Electrophilic Stress

Apoptosis signal-regulating kinase 1 (ASK1) is a critical cellular stress sensor that senses diverse reactive chemotypes and integrates these chemical signals into a single biological pathway response. It is unknown whether ASK1 senses all stressors in the same way or if unique stress-specific mechanisms detect distinct chemotypes. In order to answer this question, we treated ASK1-expressing cells with two distinct stress activators, H2O2 and 4-hydroxy-2-nonenal (HNE), and monitored the phosphorylation state of ASK1. Phosphorylation is an important regulator for the activity of ASK1, and we hypothesized that these two chemically distinct molecules may produce differences in the phosphorylation state of ASK1. Shotgun mass spectrometry and manual validation identified 12 distinct ASK1 phosphosites. Targeted parallel reaction monitoring assays were used to track the phosphorylation dynamics of each confirmed site in response to treatment. Eleven phosphosites exhibited dynamic response to one or both treatments. Six of these sites were identified in both H2O2- and HNE-treated cells, and four of these exhibited a consistent response between the two molecules. The results confirm that different chemotypes produce distinct phosphorylation patterns in concert with activation of a common MAPK pathway.

Thiol Oxidation by Diamide Leads to Dopaminergic Degeneration and Parkinsonism Phenotype in Mice: A Model for Parkinson's Disease

AIMS

This study investigates the role of thiol homeostasis disruption in Parkinson's disease (PD) pathogenesis using a novel animal model. A single unilateral administration of the thiol oxidant, diamide (1.45 μmol) into substantia nigra (SN) of mice leads to locomotor deficits and degeneration of dopaminergic (DA) neurons in SN pars compacta (SNpc).

RESULTS

Diamide-injected mice showed hemiparkinsonian behavior, measured as spontaneous contralateral body rotations, poor grip strength, and impaired locomotion on a rotarod. We observed a significant loss of DA neurons in ipsilateral but not contralateral SNpc and their striatal fibers. This was accompanied by increased Fluoro-Jade C-positive cells and a loss of NeuN-positive neurons, indicative of neurodegeneration. Importantly, diamide injection led to α-synuclein aggregation in ipsilateral SNpc, a hallmark of PD pathology not often seen in animal models of PD. On investigating putative mechanism(s) involved, we observed a loss of glutathione, which is essential for maintaining protein thiol homeostasis (PTH). Concomitantly, the redox-sensitive ASK1-p38 mitogen-activated protein kinase (MAPK) death signaling pathway was activated in the ipsilateral but not contralateral ventral midbrain through dissociation of ASK1-Trx1 complex. In Neuro-2a cells, diamide activated ASK1-p38 cascade through Trx1 oxidation, leading to cell death, which was abolished by ASK1 knockdown.

INNOVATION

Since diamide selectively disrupts PTH, DA neurons appear to be vulnerable to such perturbations and even a single insult with a thiol oxidant can result in long-lasting degeneration.

CONCLUSION

Identification of the role of PTH dysregulation in neurodegeneration, especially in early PD, not only facilitates an understanding of novel regulatory features of molecular signaling cascades but also may aid in developing disease-modifying strategies for PD. Antioxid. Redox Signal. 25, 252-267.

Assembly Dynamics and Stoichiometry of the Apoptosis Signal-regulating Kinase (ASK) Signalosome in Response to Electrophile Stress

Apoptosis signal-regulating kinase 1 (ASK1) is a key sensor kinase in the mitogen-activated protein kinase pathway that transduces cellular responses to oxidants and electrophiles. ASK1 is regulated by a large, dynamic multiprotein signalosome complex, potentially including over 90 reported ASK1-interacting proteins. We employed both shotgun and targeted mass spectrometry assays to catalogue the ASK1 protein-protein interactions in HEK-293 cells treated with the prototypical lipid electrophile 4-hydroxy-2-nonenal (HNE). Using both epitope-tagged overexpression and endogenous expression cell systems, we verified most of the previously reported ASK1 protein-protein interactions and identified 14 proteins that exhibited dynamic shifts in association with ASK1 in response to HNE stress. We used precise stable isotope dilution assays to quantify protein stoichiometry in the ASK signalosome complex and identified ASK2 at a 1:1 stoichiometric ratio with ASK1 and 14-3-3 proteins (YWHAQ, YWHAB, YWHAH, and YWHAE) collectively at a 0.5:1 ratio with ASK1 as the main components. Several other proteins, including ASK3, PARK7, PRDX1, and USP9X were detected with stoichiometries of 0.1:1 or less. These data support an ASK signalosome comprising a multimeric core complex of ASK1, ASK2, and 14-3-3 proteins, which dynamically engages other binding partners needed to mediate diverse stress-response signaling events. This study further demonstrates the value of combining global and targeted MS approaches to interrogate multiprotein complex composition and dynamics.

MPTP activates ASK1-p38 MAPK signaling pathway through TNF-dependent Trx1 oxidation in parkinsonism mouse model

Activation of apoptosis signal-regulating kinase 1 (ASK1)-p38 MAPK death signaling cascade is implicated in the death of dopaminergic neurons in substantia nigra in Parkinson's disease (PD). We investigated upstream activators of ASK1 using an MPTP mouse model of parkinsonism and assessed the temporal cascade of death signaling in ventral midbrain (VMB) and striatum (ST). MPTP selectively activated ASK1 and downstream p38 MAPK in a time-dependent manner in VMB alone. This occurred through selective protein thiol oxidation of the redox-sensitive thiol disulfide oxidoreductase, thioredoxin (Trx1), resulting in release of its inhibitory association with ASK1, while glutathione-S-transferase µ 1 (GSTM1) remained in reduced form in association with ASK1. Levels of tumor necrosis factor (TNF), a known activator of ASK1, increased early after MPTP in VMB. Protein covariation network analysis (PCNA) using protein states as nodes revealed TNF to be an important node regulating the ASK1 signaling cascade. In confirmation, blocking MPTP-mediated TNF signaling through intrathecal administration of TNF-neutralizing antibody prevented Trx1 oxidation and downstream ASK1-p38 MAPK activation. Averting an early increase in TNF, which leads to protein thiol oxidation resulting in activation of ASK1-p38 signaling, may be critical for neuroprotection in PD. Importantly, network analysis can help in understanding the cause/effect relationship within protein networks in complex disease states.

Cobalt Protoporphyrin Upregulates Cyclooxygenase-2 Expression Through a Heme Oxygenase-Independent Mechanism

Cobalt protoporphyrin (CoPP) is a potent HO-1 inducer and generally known to be an antioxidant in various cell types. Little is known about the CoPP-induced cyclooxygenase-2 (COX-2) expression and its downstream signaling in microglial cells. In current study, CoPP caused concentration- and time-dependent increases in COX-2 expression in microglial cells. Furthermore, activation of apoptosis signal-regulating kinase (ASK) 1/MAP kinase involved in CoPP-induced COX-2 expression in microglia. CoPP also induced P2X7 receptor activation, and treatment of P2X7 inhibitors effectively reduced CoPP-induced COX-2 expression. Protein inhibitor of activated STAT (PIAS) 1 is reported to be involved in modulating anti-inflammatory response through negative regulation of transcription factors. Interestingly, treatment with CoPP markedly induced PIAS1 degradation which is regulated by PI3K, Akt, and glycogen synthase kinase 3α/β (GSK3α/β) signaling pathways. These results suggest that CoPP induces COX-2 expression through activating P2X7 receptors and ASK1/MAP kinases as well as PIAS1 degradation signaling pathways. Our study provides a new insight into the regulatory effect of CoPP on neuroinflammation in microglial cells.

Neurotoxin mechanisms and processes relevant to Parkinson's disease: an update

The molecular mechanism responsible for degenerative process in the nigrostriatal dopaminergic system in Parkinson's disease (PD) remains unknown. One major advance in this field has been the discovery of several genes associated to familial PD, including alpha synuclein, parkin, LRRK2, etc., thereby providing important insight toward basic research approaches. There is an consensus in neurodegenerative research that mitochon dria dysfunction, protein degradation dysfunction, aggregation of alpha synuclein to neurotoxic oligomers, oxidative and endoplasmic reticulum stress, and neuroinflammation are involved in degeneration of the neuromelanin-containing dopaminergic neurons that are lost in the disease. An update of the mechanisms relating to neurotoxins that are used to produce preclinical models of Parkinson´s disease is presented. 6-Hydroxydopamine, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, and rotenone have been the most wisely used neurotoxins to delve into mechanisms involved in the loss of dopaminergic neurons containing neuromelanin. Neurotoxins generated from dopamine oxidation during neuromelanin formation are likewise reviewed, as this pathway replicates neurotoxin-induced cellular oxidative stress, inactivation of key proteins related to mitochondria and protein degradation dysfunction, and formation of neurotoxic aggregates of alpha synuclein. This survey of neurotoxin modeling-highlighting newer technologies and implicating a variety of processes and pathways related to mechanisms attending PD-is focused on research studies from 2012 to 2014.

Neuroinflammation in Parkinson's disease animal models: a cell stress response or a step in neurodegeneration?

The motor symptoms of Parkinson's disease are due to the progressive degeneration of dopaminergic neurons in the substantia nigra. Multiple neuroinflammatory processes are exacerbated in Parkinson's disease, including glial-mediated reactions, increased expression of proinflammatory substances, and lymphocytic infiltration, particularly in the substantia nigra. Neuroinflammation is also implicated in the neurodegeneration and consequent behavioral symptoms of many Parkinson's disease animal models, although it is not clear whether these features emulate pathogenic steps in the genuine disorder or if some inflammatory features provide protective stress responses. Here, we compare and summarize findings on neuroinflammatory responses and effects on behavior in a wide range of toxin-based, inflammatory and genetic Parkinson's disease animal models.

A cellular genetics approach identifies gene-drug interactions and pinpoints drug toxicity pathway nodes

New approaches to toxicity testing have incorporated high-throughput screening across a broad-range of in vitro assays to identify potential key events in response to chemical or drug treatment. To date, these approaches have primarily utilized repurposed drug discovery assays. In this study, we describe an approach that combines in vitro screening with genetic approaches for the experimental identification of genes and pathways involved in chemical or drug toxicity. Primary embryonic fibroblasts isolated from 32 genetically-characterized inbred mouse strains were treated in concentration-response format with 65 compounds, including pharmaceutical drugs, environmental chemicals, and compounds with known modes-of-action. Integrated cellular responses were measured at 24 and 72 h using high-content imaging and included cell loss, membrane permeability, mitochondrial function, and apoptosis. Genetic association analysis of cross-strain differences in the cellular responses resulted in a collection of candidate loci potentially underlying the variable strain response to each chemical. As a demonstration of the approach, one candidate gene involved in rotenone sensitivity, Cybb, was experimentally validated in vitro and in vivo. Pathway analysis on the combined list of candidate loci across all chemicals identified a number of over-connected nodes that may serve as core regulatory points in toxicity pathways.

Apoptosis signal-regulating kinase 1 modulates the phenotype of α-synuclein transgenic mice

α-Synuclein is a key pathogenic protein in α-synucleinopathies including Parkinson's disease, and its overexpression and aggregation in model systems are associated with a neuroinflammatory response and increased oxidative stress. Apoptosis signal-regulating kinase 1 (ASK1) is activated upon stress signaling events such as oxidative stress and is a central player linking oxidative stress with neuroinflammation. Here, we demonstrate that overexpression of human α-synuclein activates ASK1 in both PC12 cells and in the brains of α-synuclein transgenic mice. Deleting ASK1 in mice mitigates the neuronal damage and neuroinflammation induced by α-synuclein and improves performance of the animals on the rotarod. ASK1 deletion does not impact the aggregation profile or phosphorylation state of α-synuclein in the mouse brain. These results collectively implicate ASK1 in the cascade of events triggered by α-synuclein overexpression, likely because of the inflammatory response and oxidative stress that lead to ASK1 activation. These conclusions raise the possibility that potent antioxidants and anti-inflammatory agents may ameliorate the phenotype of α-synucleinopathies.

Intracerebral administration of ultrasound-induced dissolution of lipid-coated GDNF microbubbles provides neuroprotection in a rat model of Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disease characterized by loss of dopaminergic neurons in the substantia nigra. Neurotrophic factors, such as glial cell derived neurotrophic factor (GDNF), have been shown to provide a neuroprotective effect in PD rats. We have previously reported that ultrasound-induced lipid-coated GDNF microspheres, which release GDNF in a sustained manner after low frequency ultrasound stimulation, can reduce hypoxic-ischemic injury in neonatal rats. In the present study, we investigated whether lipid-coated GDNF microspheres can provide a neuroprotective effect in a rat model of PD. After a rat model of PD was produced by 6-hydroxydompamine (6-OHDA) injections, lipid-coated GDNF microspheres (1.5mg/kg) were injected into the striatum of PD rats. We found that GDNF levels were increased in the striatum of PD rats after lipid-coated GDNF microspheres administration following low frequency ultrasound stimulation (20kHz, 5min per day, daily for 4 weeks). Moreover, GDNF microspheres reduced apomorphine-induced rotations, and increased striatal dopamine and nigral tyrosine hydroxylase (TH) levels in PD rats. Additionally, GDNF microspheres reduced caspase-3, tumor necrosis factor-alpha, matrix metalloproteinase 9 (MMP-9) and OX-6 levels induced by 6-OHDA injections in PD rats. These data indicated that lipid-coated GDNF microspheres can provide a neuroprotective effect in PD rats.

Gene-environment interaction models to unmask susceptibility mechanisms in Parkinson's disease

Lipoxygenase (LOX) activity has been implicated in neurodegenerative disorders such as Alzheimer's disease, but its effects in Parkinson's disease (PD) pathogenesis are less understood. Gene-environment interaction models have utility in unmasking the impact of specific cellular pathways in toxicity that may not be observed using a solely genetic or toxicant disease model alone. To evaluate if distinct LOX isozymes selectively contribute to PD-related neurodegeneration, transgenic (i.e. 5-LOX and 12/15-LOX deficient) mice can be challenged with a toxin that mimics cell injury and death in the disorder. Here we describe the use of a neurotoxin, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), which produces a nigrostriatal lesion to elucidate the distinct contributions of LOX isozymes to neurodegeneration related to PD. The use of MPTP in mouse, and nonhuman primate, is well-established to recapitulate the nigrostriatal damage in PD. The extent of MPTP-induced lesioning is measured by HPLC analysis of dopamine and its metabolites and semi-quantitative Western blot analysis of striatum for tyrosine hydroxylase (TH), the rate-limiting enzyme for the synthesis of dopamine. To assess inflammatory markers, which may demonstrate LOX isozyme-selective sensitivity, glial fibrillary acidic protein (GFAP) and Iba-1 immunohistochemistry are performed on brain sections containing substantia nigra, and GFAP Western blot analysis is performed on striatal homogenates. This experimental approach can provide novel insights into gene-environment interactions underlying nigrostriatal degeneration and PD.

6-Shogaol, an active compound of ginger, protects dopaminergic neurons in Parkinson's disease models via anti-neuroinflammation

AIM

6-Shogaol [1-(4-hydroxy-methoxyphenyl)-4-decen-one], a pungent compound isolated from ginger, has shown various neurobiological and anti-inflammatory effects. The aim of this study was to examine the effects of 6-shogaol on neuroinflammatory-induced damage of dopaminergic (DA) neurons in Parkinson's disease (PD) models.

METHODS

Cultured rat mesencephalic cells were treated with 6-shogaol (0.001 and 0.01 μmol/L) for 1 h, then with MPP(+)(10 μmol/L) for another 23 h. The levels of TNF-α and NO in medium were analyzed spectrophotometrically. C57/BL mice were administered 6-shogaol (10 mg·kg(-1)·d(-1), po) for 3 d, and then MPTP (30 mg/kg, ip) for 5 d. Seven days after the last MPTP injection, behavioral testings were performed. The levels of tyrosine hydroxylase (TH) and macrophage antigen (MAC)-1 were determined with immunohistochemistry. The expression of iNOS and COX-2 was measured using RT PCR.

RESULTS

In MPP(+)-treated rat mesencephalic cultures, 6-shogaol significantly increased the number of TH-IR neurons and suppressed TNF-α and NO levels. In C57/BL mice, treatment with 6-shogaol reversed MPTP-induced changes in motor coordination and bradykinesia. Furthermore, 6-shogaol reversed MPTP-induced reductions in TH-positive cell number in the substantia nigra pars compacta (SNpc) and TH-IR fiber intensity in stratum (ST). Moreover, 6-shogaol significantly inhibited the MPTP-induced microglial activation and increases in the levels of TNF-α, NO, iNOS, and COX-2 in both SNpc and ST.

CONCLUSION

6-Shogaol exerts neuroprotective effects on DA neurons in in vitro and in vivo PD models.

Targeting caspase-3 as dual therapeutic benefits by RNAi facilitating brain-targeted nanoparticles in a rat model of Parkinson's disease

The activation of caspase-3 is an important hallmark in Parkinson’s disease. It could induce neuron death by apoptosis and microglia activation by inflammation. As a result, inhibition the activation of caspase-3 would exert synergistic dual effect in brain in order to prevent the progress of Parkinson’s disease. Silencing caspase-3 genes by RNA interference could inhibit the activation of caspase-3. We developed a brain-targeted gene delivery system based on non-viral gene vector, dendrigraft poly-L-lysines. A rabies virus glycoprotein peptide with 29 amino-acid linked to dendrigraft poly-L-lysines could render gene vectors the ability to get across the blood brain barrier by specific receptor mediated transcytosis. The resultant brain-targeted vector was complexed with caspase-3 short hairpin RNA coding plasmid DNA, yielding nanoparticles. In vivo imaging analysis indicated the targeted nanoparticles could accumulate in brain more efficiently than non-targeted ones. A multiple dosing regimen by weekly intravenous administration of the nanoparticles could reduce activated casapse-3 levels, significantly improve locomotor activity and rescue dopaminergic neuronal loss and in Parkinson’s disease rats’ brain. These results indicated the rabies virus glycoprotein peptide modified brain-targeted nanoparticles were promising gene delivery system for RNA interference to achieve anti-apoptotic and anti-inflammation synergistic therapeutic effects by down-regulation the expression and activation of caspase-3.

Solvents and Parkinson disease: a systematic review of toxicological and epidemiological evidence

Parkinson disease (PD) is a debilitating neurodegenerative motor disorder, with its motor symptoms largely attributable to loss of dopaminergic neurons in the substantia nigra. The causes of PD remain poorly understood, although environmental toxicants may play etiologic roles. Solvents are widespread neurotoxicants present in the workplace and ambient environment. Case reports of parkinsonism, including PD, have been associated with exposures to various solvents, most notably trichloroethylene (TCE). Animal toxicology studies have been conducted on various organic solvents, with some, including TCE, demonstrating potential for inducing nigral system damage. However, a confirmed animal model of solvent-induced PD has not been developed. Numerous epidemiologic studies have investigated potential links between solvents and PD, yielding mostly null or weak associations. An exception is a recent study of twins indicating possible etiologic relations with TCE and other chlorinated solvents, although findings were based on small numbers, and dose-response gradients were not observed. At present, there is no consistent evidence from either the toxicological or epidemiologic perspective that any specific solvent or class of solvents is a cause of PD. Future toxicological research that addresses mechanisms of nigral damage from TCE and its metabolites, with exposure routes and doses relevant to human exposures, is recommended. Improvements in epidemiologic research, especially with regard to quantitative characterization of long-term exposures to specific solvents, are needed to advance scientific knowledge on this topic.

The role of oxidative stress in Parkinson's disease

Oxidative stress plays an important role in the degeneration of dopaminergic neurons in Parkinson's disease (PD). Disruptions in the physiologic maintenance of the redox potential in neurons interfere with several biological processes, ultimately leading to cell death. Evidence has been developed for oxidative and nitrative damage to key cellular components in the PD substantia nigra. A number of sources and mechanisms for the generation of reactive oxygen species (ROS) are recognized including the metabolism of dopamine itself, mitochondrial dysfunction, iron, neuroinflammatory cells, calcium, and aging. PD causing gene products including DJ-1, PINK1, parkin, alpha-synuclein and LRRK2 also impact in complex ways mitochondrial function leading to exacerbation of ROS generation and susceptibility to oxidative stress. Additionally, cellular homeostatic processes including the ubiquitin-proteasome system and mitophagy are impacted by oxidative stress. It is apparent that the interplay between these various mechanisms contributes to neurodegeneration in PD as a feed forward scenario where primary insults lead to oxidative stress, which damages key cellular pathogenetic proteins that in turn cause more ROS production. Animal models of PD have yielded some insights into the molecular pathways of neuronal degeneration and highlighted previously unknown mechanisms by which oxidative stress contributes to PD. However, therapeutic attempts to target the general state of oxidative stress in clinical trials have failed to demonstrate an impact on disease progression. Recent knowledge gained about the specific mechanisms related to PD gene products that modulate ROS production and the response of neurons to stress may provide targeted new approaches towards neuroprotection.

Neuroprotective and anti-inflammatory properties of a coffee component in the MPTP model of Parkinson's disease

Consumption of coffee is associated with reduced risk of Parkinson's disease (PD), an effect that has largely been attributed to caffeine. However, coffee contains numerous components that may also be neuroprotective. One of these compounds is eicosanoyl-5-hydroxytryptamide (EHT), which ameliorates the phenotype of α-synuclein transgenic mice associated with decreased protein aggregation and phosphorylation, improved neuronal integrity and reduced neuroinflammation. Here, we sought to investigate if EHT has an effect in the MPTP model of PD. Mice fed a diet containing EHT for four weeks exhibited dose-dependent preservation of nigral dopaminergic neurons following MPTP challenge compared to animals given control feed. Reductions in striatal dopamine and tyrosine hydroxylase content were also less pronounced with EHT treatment. The neuroinflammatory response to MPTP was markedly attenuated, and indices of oxidative stress and JNK activation were significantly prevented with EHT. In cultured primary microglia and astrocytes, EHT had a direct anti-inflammatory effect demonstrated by repression of lipopolysaccharide-induced NFκB activation, iNOS induction, and nitric oxide production. EHT also exhibited a robust anti-oxidant activity in vitro. Additionally, in SH-SY5Y cells, MPP(+)-induced demethylation of phosphoprotein phosphatase 2A (PP2A), the master regulator of the cellular phosphoregulatory network, and cytotoxicity were ameliorated by EHT. These findings indicate that the neuroprotective effect of EHT against MPTP is through several mechanisms including its anti-inflammatory and antioxidant activities as well as its ability to modulate the methylation and hence activity of PP2A. Our data, therefore, reveal a strong beneficial effect of a novel component of coffee in multiple endpoints relevant to PD.

Zonisamide attenuates MPP+-induced oxidative toxicity through modulation of Ca2+ signaling and caspase-3 activity in neuronal PC12 cells

Parkinson's disease is an incurable progressive neurological condition caused by a degeneration of dopamine-producing cells characterized by motor and non-motor symptoms. The major mechanisms of the antiepileptic actions of ZNS are inhibition of voltage-gated Na(+) channel, T-type voltage-sensitive Ca(2+) channel, Ca(2+)-induced Ca(2+) releasing system, and neuronal depolarization-induced glutamate release; and enhancement of release of inhibitory neurotransmitters; however, the detailed mechanism of antiparkinsonian effects of ZNS remains to be clarified. We aimed to investigate to the effect of ZNS on the oxidative stress, cell viability, Ca(2+) signaling, and caspase activity that induced by the MPP(+) model of Parkinson's in neuronal PC12 cells. Neuronal PC12 cells were divided into four groups namely, control, ZNS, MPP(+), and ZNS+MPP(+) groups. The dose and duration of ZNS and MPP(+) were determined according to cell viability (MTT) analysis which used to assess the cell viability. The cells in ZNS, MPP(+), and ZNS+MPP(+) groups were incubated for 5 h with 100 μM ZNS, 10 h with 100 μM MPP(+), and 10 h with ZNS and MPP(+), respectively. Lipid peroxidation and cytosolic free Ca(2+) concentrations were higher in the MPP(+) group than in control although their levels were lower in ZNS and the ZNS+MPP(+) groups than in control. Reduced glutathione and glutathione peroxidase values were lower in the MPP(+) group although they were higher in the ZNS and the ZNS+MPP(+) groups than in control. Caspase-3 activity was lower in the ZNS group than in the MPP(+) group. In conclusion, ZNS induced modulator effects on the oxidative stress, intracellular Ca(2+), and the caspase-3 values in an experimental model of Parkinson disease.